JP2006039135A - Optical device and projection type image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To project a high-contrast and high-quality video with simple constitution. <P>SOLUTION: The reflection type projector 10 is equipped with a polarizing beam splitter 23, a 1/4 wavelength plate 24, a retardation plate 24 making a phase difference in accordance with the angle of incident light to an optical axis in incident light, and a reflection type liquid crystal element 26 changing the polarization direction of the incident light according to an image signal and reflecting the light. The light separation surface 23a of the PBS 23 is set to be perpendicular to a plane formed by an X axis - a Z axis and has the angle of 45° to the X axis and a Y axis, and the optic axis of the 1/4 wavelength plate 24 is set to be perpendicular to the Y axis and also perpendicular to the optical axis, and the optic axis of the retardation plate 25 is parallel with the optical axis. Furthermore, the retardation plate 25 is set so that a refractive index n<SB>o</SB>to a normal light beam may be larger than a refractive index n<SB>e</SB>to an abnormal light beam. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical device used for, for example, a reflective liquid crystal projector and a projection image display device such as, for example, a reflective liquid crystal projector.

  Conventionally, an illumination device, a light modulation element that modulates irradiated light according to an image signal, a separation optical system that irradiates the light modulation element with light emitted from the illumination device, and an image of the light modulation element A projection-type image display device including a projection optical system that forms an image is proposed (see, for example, Patent Document 1).

  In general, a projection-type image display apparatus uses a discharge lamp as a light source, and a transmissive liquid crystal element, a DMD (Digital Micromirror Device), or the like is often used as an image modulation element. Furthermore, in recent years, a projection type image display apparatus using a reflective liquid crystal element having a higher resolution as a light modulation element has been put into practical use.

  The projection type image display device has a light source that emits white light, and the white light from the light source is separated into three colors of red, green, and blue by a dichroic mirror, and each color is converted into a corresponding light modulation element. Illuminate. The light modulation element modulates irradiation light in accordance with red, green, and blue video signals. Then, after being modulated by the light modulation element, it is synthesized by a color synthesizing means such as a cross prism and projected on a screen by a projection lens.

  When a reflective liquid crystal element is used as the light modulation element, polarized light is used. In this case, the light emitted from the light source is converted into unidirectional polarized light using a polarization conversion element, and then separated into three colors and incident on a reflective liquid crystal element corresponding to each color. . FIG. 32 is a schematic diagram showing a device configuration in the vicinity of a liquid crystal element in a conventional projection image display apparatus using a reflective liquid crystal element.

  As shown in FIG. 32, the conventional projection type image display apparatus 110 includes a polarization beam splitter (PBS) 111, a reflective liquid crystal element 112, and a linear polarizer 113.

  With the polarization conversion element described above, it is difficult to obtain high PS conversion characteristics over the entire visible region and for a wide incident angle. Therefore, in the conventional projection-type image display device 110, the light is transmitted through the linear polarizer 113 again, so that the light beam has a higher degree of polarization and enters the PBS 111. Most of the light beam incident on the PBS 111 is reflected and enters the reflective liquid crystal element 112. When displaying white, it is converted into P-polarized light, re-enters the PBS 111 and passes through as it is, and forms an image on the screen through the projection lens. On the other hand, in the case of black, it is re-incident on the PBS 111 while being S-polarized light and reflected, and returns to the original optical path.

  Incidentally, the projection type image display apparatus 110 using such a conventional reflective liquid crystal element has the following problems.

  As shown in FIG. 33, incident light incident on the PBS 111 has an angle with respect to the optical axis x as well as light parallel to the optical axis x. Therefore, light that is not parallel to the optical axis z (light having an angle with respect to the optical axis z) is emitted from the PBS 111.

  When the angle Θ (polar angle) formed with the optical axis z increases, the light beam emitted from the PBS 111 is reflected by the reflective liquid crystal element 112 and returns to the PBS 111, so that the polarization direction of linearly polarized light is an ideal direction. It will rotate from. Therefore, in the case of black, it should re-enter the PBS 111 with the S-polarized light and return to the original optical path after being reflected by the PBS 111. However, the P-polarized light is included by the amount of rotation from the ideal direction when re-entering. That portion is transmitted and projected onto the screen. Therefore, the contrast of the projected image has been reduced.

  As a method for solving such a problem, an optical compensation method in which a quarter wavelength plate 114 is provided between a PBS 111 and a reflective liquid crystal element 112 as shown in FIG. 34 has been proposed (see Patent Document 1). .) In this optical compensation method, the ¼ wavelength plate 114 is arranged so that the fast axis or the slow axis is perpendicular to a plane including the optical axis x incident on the PBS 111 and the reflected optical axis z from the PBS 111. ing.

  In this way, the polarization direction of a number of light beams reflected by the reflective liquid crystal element 112 becomes the ideal polarization direction of S-polarized light, and the contrast is not deteriorated.

  Specifically, the angle (polar angle) formed between the light beam reflected as the S-polarized component by the PBS 111 and the Z-axis direction is Θ, and the angle (azimuth angle) formed between the projection of the light beam on the XY plane and the X-axis is Φ. (See FIG. 33), a light beam satisfying Φ = 0 °, 90 °, 270 °, 360 ° is reflected as an ideal S-polarized component after being reflected by an image modulation element that does not exhibit birefringence. Since it re-enters the PBS 111, the contrast is not deteriorated.

  However, in this method, a light beam having another azimuth angle Φ, for example, a light beam of Φ = 45 degrees, is not only an ideal S wave polarization component but also a P polarization component when re-entering the PBS 111. Will also exist. That is, it is not possible to optimally compensate for all the light beams having the azimuth angle Φ, and therefore, it is a factor that deteriorates the contrast of the projected image.

Japanese Patent Publication No. 7-38050

  An object of the present invention is to solve these problems and to realize an optical device and a projection-type image display device that can provide high-definition images with high contrast.

An optical device according to the present invention includes a polarization beam splitter having a light separation surface that reflects polarized light in a predetermined direction and transmits polarized light in a direction orthogonal to the reflected polarization direction, and light reflected or transmitted by the polarized beam splitter. The quarter wave plate arranged at the incident position and the position where the light reflected or transmitted by the polarizing beam splitter is incident, and a phase difference corresponding to the angle of the incident light with respect to the optical axis is incident. A three-dimensional space represented by coordinates of the X, Y, and Z axes, the X axis being the direction perpendicular to the plane of incidence of the polarizing beam splitter, and the Z axis being When the light beam parallel to the X axis is parallel to the light beam reflected by the light separation surface of the polarization beam splitter and the Y axis is the direction perpendicular to the X axis and the Z axis, the light separation of the polarization beam splitter is performed. The plane is the X axis-Z axis The optical axis of the quarter wave plate is parallel to the Y axis, and the optical axis of the retardation plate is parallel to the optical axis. is a further, the phase difference plate, than the refractive index n _o for the ordinary ray, and wherein the refractive index n _e for extraordinary ray is large.

An optical device according to the present invention includes a polarization beam splitter having a light separation surface that reflects polarized light in a predetermined direction and transmits polarized light in a direction orthogonal to the reflected polarization direction, and light reflected or transmitted by the polarized beam splitter. The quarter wave plate arranged at the incident position and the position where the light reflected or transmitted by the polarizing beam splitter is incident, and a phase difference corresponding to the angle of the incident light with respect to the optical axis is incident. A three-dimensional space represented by coordinates of the X-axis, Y-axis, and Z-axis, the X-axis being a direction perpendicular to the incident surface of the polarizing beam splitter, and the Z-axis being When the light beam parallel to the X axis is parallel to the light beam reflected by the light separation surface of the polarization beam splitter and the Y axis is the direction perpendicular to the X axis and the Z axis, the light separation of the polarization beam splitter is performed. The plane is the X axis-Z axis The optical axis of the quarter wave plate is perpendicular to the plane and has a predetermined angle with respect to the X axis and the Z axis, the optical axis of the quarter wave plate is perpendicular to the Y axis and the optical axis, and the optical axis of the retardation plate is , is parallel to the optical axis, further, the phase difference plate, wherein the refractive index n _o for the ordinary ray than the refractive index n _e for extraordinary ray is large.

A projection-type image display apparatus according to the present invention includes a light emitting means for emitting light, and a polarization beam splitter having a light separation surface that reflects an S-polarized component of incident light and transmits a P-polarized component of incident light. A quarter-wave plate disposed at a position where the light reflected or transmitted by the polarizing beam splitter is incident, and a position at which a light reflected or transmitted by the polarizing beam splitter is incident. A phase difference plate that generates a phase difference corresponding to the angle of incident light with respect to the incident light, a light modulation unit that changes the polarization direction of the incident light according to an image signal, and reflects the incident light; A projection optical system for projecting the emitted light to the outside, and the light emitted from the light emitting means reflects or transmits the light separation surface of the polarizing beam splitter, and the quarter wavelength plate and the retardation plate Transmitted light modulation The light irradiated on the stage and reflected by the light modulation means passes through the quarter-wave plate and the phase difference plate, passes or reflects the light separation surface of the polarization beam splitter, and enters the irradiation means. The three-dimensional space is represented by the coordinates of the X axis, Y axis, and Z axis. The X axis is the direction perpendicular to the incident surface of the polarization beam splitter, and the Z axis is a light beam parallel to the X axis. When the direction parallel to the light beam reflected by the separation surface and the Y axis is the direction perpendicular to the X axis and the Z axis, the light separation surface of the polarizing beam splitter is perpendicular to the plane formed by the X axis and the Z axis. And having a predetermined angle with respect to the X axis and the Z axis, the optical axis of the quarter wave plate is parallel to the Y axis, and the optical axis of the retardation plate is parallel to the optical axis, further, the phase difference plate, than the refractive index n _o for the ordinary ray, the refractive index for extraordinary ray _e which are characterized by large.

A projection-type image display apparatus according to the present invention includes a light emitting means for emitting light, and a polarization beam splitter having a light separation surface that reflects an S-polarized component of incident light and transmits a P-polarized component of incident light. A quarter-wave plate disposed at a position where the light reflected or transmitted by the polarizing beam splitter is incident, and a position at which a light reflected or transmitted by the polarizing beam splitter is incident. A phase difference plate that generates a phase difference corresponding to the angle of incident light with respect to the incident light, a light modulation unit that changes the polarization direction of the incident light according to an image signal, and reflects the incident light; A projection optical system for projecting the emitted light to the outside, and the light emitted from the light emitting means reflects or transmits the light separation surface of the polarizing beam splitter, and the quarter wavelength plate and the retardation plate Transmitted light modulation The light emitted to the stage and emitted from the light modulation means is transmitted through the quarter-wave plate and the phase difference plate, is transmitted or reflected through the light separation surface of the polarization beam splitter, and is incident on the irradiation means. The three-dimensional space is represented by the coordinates of the X axis, Y axis, and Z axis. The X axis is the direction perpendicular to the incident surface of the polarization beam splitter, and the Z axis is a light beam parallel to the X axis. When the direction parallel to the light beam reflected by the separation surface and the Y axis is the direction perpendicular to the X axis and the Z axis, the light separation surface of the polarizing beam splitter is perpendicular to the plane formed by the X axis and the Z axis. And the optical axis of the quarter-wave plate is perpendicular to the Y axis and perpendicular to the optical axis, and the optical axis of the retardation plate is an optical axis. is parallel to, further, the phase difference plate, pairs ordinary ray than the refractive index n _e for extraordinary ray Characterized in that that refractive index n _o is large.

A projection-type image display apparatus according to the present invention includes a light emitting means for emitting light, and a polarization beam splitter having a light separation surface that reflects an S-polarized component of incident light and transmits a P-polarized component of incident light. A quarter-wave plate disposed at a position where the light reflected or transmitted by the polarizing beam splitter is incident, and a position at which a light reflected or transmitted by the polarizing beam splitter is incident. A phase difference plate that generates a phase difference corresponding to the angle of incident light with respect to the incident light, a light modulation unit that changes the polarization direction of the incident light according to an image signal, and reflects the incident light; A projection optical system for projecting the emitted light to the outside, and the light emitted from the light emitting means reflects or transmits the light separation surface of the polarizing beam splitter, and the quarter wavelength plate and the retardation plate Transmitted light modulation The light irradiated on the stage and reflected by the light modulation means passes through the quarter-wave plate and the phase difference plate, passes or reflects the light separation surface of the polarization beam splitter, and enters the irradiation means. The three-dimensional space is represented by the coordinates of the X axis, Y axis, and Z axis. The X axis is the direction perpendicular to the incident surface of the polarization beam splitter, and the Z axis is a light beam parallel to the X axis. When the direction parallel to the light beam reflected by the separation surface and the Y axis is the direction perpendicular to the X axis and the Z axis, the light separation surface of the polarizing beam splitter is perpendicular to the plane formed by the X axis and the Z axis. And having a predetermined angle with respect to the X axis and the Z axis, the optical axis of the quarter wave plate is parallel to the Y axis, and the optical axis of the retardation plate is parallel to the optical axis, The light modulating means is a VA (Vrtically Aligned) reflective liquid crystal element, and Feedboard, rather than the refractive index n _e for extraordinary ray, wherein the refractive index n _o for the ordinary ray is large.

A projection-type image display apparatus according to the present invention includes a light emitting means for emitting light, and a polarization beam splitter having a light separation surface that reflects an S-polarized component of incident light and transmits a P-polarized component of incident light. A quarter-wave plate disposed at a position where the light reflected or transmitted by the polarizing beam splitter is incident, and a position at which a light reflected or transmitted by the polarizing beam splitter is incident. A phase difference plate that generates a phase difference corresponding to the angle of incident light with respect to the incident light, a light modulation unit that changes the polarization direction of the incident light according to an image signal, and reflects the incident light; A projection optical system for projecting the emitted light to the outside, and the light emitted from the light emitting means reflects or transmits the light separation surface of the polarizing beam splitter, and the quarter wavelength plate and the retardation plate Transmitted light modulation The light irradiated on the stage and reflected by the light modulation means passes through the quarter-wave plate and the phase difference plate, passes or reflects the light separation surface of the polarization beam splitter, and enters the irradiation means. The three-dimensional space is represented by the coordinates of the X axis, Y axis, and Z axis. The X axis is the direction perpendicular to the incident surface of the polarization beam splitter, and the Z axis is a light beam parallel to the X axis. When the direction parallel to the light beam reflected by the separation surface and the Y axis is the direction perpendicular to the X axis and the Z axis, the light separation surface of the polarizing beam splitter is perpendicular to the plane formed by the X axis and the Z axis. And the optical axis of the quarter-wave plate is perpendicular to the Y axis and perpendicular to the optical axis, and the optical axis of the retardation plate is an optical axis. The light modulation means is a VA (Vrtically Aligned) reflective liquid crystal element, Luo, the phase difference plate, than the refractive index n _e for extraordinary ray, wherein the refractive index n _o for the ordinary ray is large.

In the optical device and the projection-type image display device according to the present invention, the three-dimensional space is represented by coordinates of the X axis, the Y axis, and the Z axis, the X axis is a direction perpendicular to the incident surface of the polarization beam splitter, and the Z axis is When the light beam parallel to the X axis is parallel to the light beam reflected by the light separation surface of the polarization beam splitter and the Y axis is the direction perpendicular to the X axis and the Z axis, the light separation of the polarization beam splitter is performed. The surface is perpendicular to the plane formed by the X-axis and the Z-axis, has a predetermined angle with respect to the X-axis and the Z-axis, the optical axis of the quarter-wave plate is parallel to the Y-axis, and the optical axis of the retardation plate was parallel to the optical axis, further, the phase difference plate, to increase the refractive index n _e for extraordinary ray than the refractive index n _o for the ordinary ray.

In the optical apparatus and the projection-type image display apparatus according to the present invention, the three-dimensional space is represented by the coordinates of the X axis, the Y axis, and the Z axis, and the X axis is a direction perpendicular to the incident surface of the polarization beam splitter, Z When the axis is a direction parallel to the light beam parallel to the X-axis and reflected by the light separation surface of the polarization beam splitter, and the Y-axis is a direction perpendicular to the X-axis and the Z-axis, The light separation surface is perpendicular to the plane formed by the X-axis and the Z-axis and has a predetermined angle with respect to the X-axis and the Z-axis. and then, a parallel to the optical axis of the optical axes of the retardation plate, further, the phase difference plate, to increase the refractive index n _o for the ordinary ray than the refractive index n _e for extraordinary ray.

In the projection type image display apparatus according to the present invention, the three-dimensional space is represented by the coordinates of the X axis, the Y axis, and the Z axis, the X axis is the direction perpendicular to the incident surface of the polarization beam splitter, and the Z axis is the X axis. Is parallel to the light beam reflected by the light separation surface of the polarization beam splitter, and the Y axis is a direction perpendicular to the X axis and Z axis, the light separation surface of the polarization beam splitter is: It has a predetermined angle with respect to the X-axis and the Z-axis and is perpendicular to the plane formed by the X-axis and the Z-axis, the optical axis of the quarter-wave plate is parallel to the Y-axis, and parallel to the axis, the light modulating means is a reflection-type liquid crystal device VA (Vrtically Aligned) mode, further increasing the refractive index n _o for the ordinary ray than the refractive index n _e of the phase difference plate for the extraordinary ray.

In the projection type image display apparatus according to the present invention, the three-dimensional space is represented by the coordinates of the X axis, the Y axis, and the Z axis, the X axis is the direction perpendicular to the incident surface of the polarization beam splitter, and the Z axis is the X axis. Is parallel to the light beam reflected by the light separation surface of the polarization beam splitter, and the Y axis is a direction perpendicular to the X axis and Z axis, the light separation surface of the polarization beam splitter is: The X-axis and Z-axis are perpendicular to the plane and have a predetermined angle with respect to the X-axis and Z-axis, and the optical axis of the quarter-wave plate is perpendicular to the Y-axis and perpendicular to the optical axis. and parallel to the optical axis of the optical axis, the light modulating means is a reflection-type liquid crystal device VA (Vrtically Aligned) mode, further increasing the refractive index n _o for the ordinary ray than the refractive index n _e of the phase difference plate for extraordinary ray To do.

  As a result, the optical device and the projection-type image display device according to the present invention can project a high-quality image with high contrast.

  Hereinafter, embodiments of the present invention will be described.

First Embodiment As a first embodiment, a projection type image display device (hereinafter simply referred to as a reflection type projector) to which the present invention is applied will be described.

(overall structure)
FIG. 1 is a schematic diagram showing the configuration of a reflective projector 10 to which the present invention is applied.

  The reflective projector 10 includes a lamp 11, an integrator lens 12, a PS conversion element 13, a condenser lens 14, a first dichroic mirror 15, a second dichroic mirror 16, a mirror 17, and an R polarization. An optical system 18 -R, a G polarizing optical system 18 -G, a B polarizing optical system 18 -B, a color synthesis prism 19, and a projection lens 20 are provided.

  The lamp 11 is an irradiation light source for white light, and is, for example, a halogen lamp, a xenon lamp, a metal halide lamp, an ultrahigh pressure mercury lamp, or the like. In the lamp 11, an ellipse or rectangular reflector 11b is disposed on the rear side of the optical path in order to efficiently emit the light beam from the light source 11a. The white light beam emitted from the lamp 11 is incident on the pair of integrator lenses 12.

  The pair of integrator lenses 12 make the spatial distribution of the light flux uniform with respect to the incident light from the lamp 11. The light beam that has passed through the integrator lens 12 enters the PS conversion element 13.

  The PS conversion element 13 converts the light transmitted through the integrator lens 12 into polarized light aligned in one direction. The light beam that has passed through the PS conversion element 13 passes through the condenser lens 14 and enters the first dichroic mirror 15.

  The first dichroic mirror 15 transmits light (R) in the red wavelength band and reflects light (G, B) in the blue and green wavelength bands. The reflected blue and green wavelength band light (G, B) is further incident on the second dichroic mirror 16. The second dichroic mirror 16 reflects the green wavelength band light (G) and transmits the blue wavelength band light (B).

  The red wavelength band light transmitted by the first dichroic mirror 15 is reflected by the mirror 17 and then enters the R polarization optical system 18 -R. The light in the green wavelength band reflected by the second dichroic mirror 16 is incident on the G polarization optical system 18-G. The light in the blue wavelength band transmitted by the second dichroic mirror 16 is incident on the B polarization optical system 18-B.

  The red (R) signal of the video signal is input to the R polarization optical system 18-R. The R polarization optical system 18-R emits a light beam in which an image corresponding to the R component of the image is formed by spatially modulating the incident red wavelength band light according to the R signal.

  A green (G) signal among the video signals is input to the G polarization optical system 18-G. The G polarization optical system 18-G emits a light beam in which an image corresponding to the G component of the video signal is formed by spatially modulating light in the green wavelength band according to the G signal.

  The blue B (B) signal of the video signal is input to the B polarization optical system 18-B. The B polarization optical system 18-B emits a light beam in which an image corresponding to the B component of the video signal is formed by spatially modulating light in the blue wavelength band according to the B signal.

  All the light emitted from the R polarizing optical system 18 -R, the G polarizing optical system 18 -G, and the B polarizing optical system 18 -B is incident on the color combining prism 19. The color combining prism 19 combines the red component light, the green component light, and the blue component light into one light beam, and emits the combined light beam.

  The combined light emitted from the color combining prism 19 enters the projection lens 20. The projection lens 20 enlarges the incident combined light, projects it on a screen (not shown), and forms an image on the screen.

(Configuration of polarization optical system 18)
Next, the internal configurations of the R polarizing optical system 18-R, the G polarizing optical system 18-G, and the B polarizing optical system 18-B will be described.

  The R polarizing optical system 18-R, the G polarizing optical system 18-G, and the B polarizing optical system 18-B all have the same configuration. Hereinafter, when these are described together, they are referred to as a polarization optical system 18.

  Further, when describing the arrangement of each component in the polarization optical system 18, the position and direction of the three-dimensional space are defined using coordinate axes represented by the X, Y, and Z axes orthogonal to each other. Specifically, the direction of the incident light beam to the polarization optical system 18 is taken as the X axis, and the direction of the outgoing light beam from the polarization optical system 18 (direction perpendicular to the X direction) is perpendicular to the Z axis, the X axis, and the Z axis. The axis is the Y axis.

  FIG. 2 is a diagram showing a configuration in the polarization optical system 18.

  As shown in FIG. 2, the polarization optical system 18 includes a field lens 21, a linear polarizer 22, a polarization beam splitter (PBS) 23, a ¼ wavelength plate 24, a phase difference plate 25, a reflection type image modulation. An element 26 is provided.

  A light beam in the red, green, or blue wavelength band separated by the first dichroic mirror 15 and the second dichroic mirror 16 is incident on the polarization optical system 18.

  A red wavelength band or green and blue wavelength band beams separated by the first dichroic mirror 15 and the second dichroic mirror 16 are incident on the field lens 21. The field lens 21 is arranged so that the optical axis is parallel to the X axis. The field lens 21 divides the incident light flux into a divergent bundle and irradiates the linear polarizer 22. A divergent light beam is a light beam whose width increases as it travels along the optical path.

  The linear polarizer 22 is an element having a flat plate shape, and is a device that emits only polarized light in one direction among incident light beams. The linear polarizer 22 transmits polarized light in one direction, which is S-polarized light, to the PBS 23 and transmits other polarized light. The linear polarizer 22 is a reflective polarizer or an absorptive polarizer that transmits polarized light in one direction and absorbs other polarized light. Further, as the reflective polarizer, for example, a wire grid polarizer that is put into practical use by MOTTEK may be used.

  The flat linear polarizer 22 is disposed perpendicular to a plane formed by the X axis and the Z axis (a plane perpendicular to the Y axis, hereinafter referred to as a Z-X plane) and perpendicular to the optical axis X. It is inclined at an acute angle with respect to a flat surface in the opposite direction (minus direction) to the separation surface of PBS 23. With this arrangement, the linear polarizer 22 increases the proportion of light rays incident on the PBS 23 as S-polarized light.

  The PBS 23 is a polarized light separating element having a polarization separation surface (separation surface) 23a that reflects S-polarized light and transmits P-polarized light. The PS separation surface 23a is arranged perpendicular to the Z-X plane and 45 with respect to a plane formed by the Y-axis and the Z-axis (a plane perpendicular to the X-axis, hereinafter referred to as the Y-Z plane). Tilt to an angle of °.

  Light passing through the field lens 21 and the linear polarizer 22 is incident on the PS separation surface 23a. The PS separation surface 23a is disposed so as to totally reflect polarized light in one direction transmitted from the linear polarizer 22. That is, the arrangement relationship between the linear polarizer 22 and the PS separation surface 23a is set so that the unidirectional polarized light transmitted from the linear polarizer 22 is S-polarized light. In other words, the direction of the absorption axis of the linear polarizer 22 is set so that the transmitted light is incident on the PS separation surface 23a as S-polarized light.

  The quarter-wave plate 24 is an optical element that changes the phase difference of polarized light that vibrates in directions perpendicular to each other when transmitting light, by a quarter wavelength. The quarter-wave plate 24 is disposed in parallel to the XY plane at a position where light that has passed through the field lens 21 and the linear polarizer 22 and reflected by the PS separation surface 23a is incident (that is, 1). The quarter-wave plate 24 is provided so that its optical axis is parallel to the Z-axis). The quarter wavelength plate 24 is arranged so that the optical axis is parallel to the Y axis. The optical axis is the direction axis that minimizes the difference in refractive index between ordinary and extraordinary rays of light traveling in that direction.

  The phase difference plate 25 is an optical element that changes the phase difference of the light according to the angle between the incident direction and the optical axis when transmitting the light. The phase difference plate 25 does not cause a phase difference with respect to light incident in parallel to the optical axis. The phase difference plate 25 is disposed parallel to the XY plane at a position where light that has passed through the field lens 21 and the linear polarizer 22 and reflected by the PS separation surface 23a is incident (that is, the phase difference plate). 25 is provided such that its optical axis is parallel to the Z-axis).

  The phase difference plate 25 is disposed such that the optical axis is parallel to the Z axis. Further, the phase difference plate 25 has a relationship of no <ne, where the refractive index is no for ordinary light and the refractive index is ne for extraordinary light. Therefore, the phase difference plate 25 does not produce a phase difference with respect to a light beam incident in parallel to the Z axis. When a light beam having an angle with respect to the Z axis is incident, the phase difference plate 25 generates a phase difference according to the incident angle. Cause it to occur.

  The light that has passed through the field lens 21 and the linear polarizer 22 and reflected from the PS separation surface 23 a passes through the quarter-wave plate 24 and the phase difference plate 25, and is then applied to the reflective image modulation element 26.

  The reflective image modulation element 26 is composed of, for example, a VA (Vrtically Aligned) type reflective liquid crystal element. S-polarized light reflected by the PBS 23 is incident on the reflective image modulation element 26. The reflection-type image modulation element 26 receives color signals (R signal, G signal, and B signal among video signals), and spatially modulates incident S-polarized light according to the input color signals. As a result of spatial modulation of incident light (S-polarized light) according to the video signal, S-polarized light is converted to P-polarized light and reflected in the bright part (white part) of the image, and in the dark part (black part) of the image. S-polarized light is reflected as S-polarized light.

  The light passing path of the polarizing optical system 18 having the above optical configuration is as follows.

  The light enters the polarizing optical system 18 from a direction parallel to the X axis.

  Incident light is made into a divergent light beam by the field lens 21, and then passes through the linear polarizer 22 and is irradiated onto the PS separation surface 23a. The PS separation surface 23a is converted into linearly polarized light by the linear polarizer 22 and is incident as almost S-polarized light.

  The PS separation surface 23a reflects incident light as S-polarized light. The S-polarized light reflected by the PS separation surface 23 a passes through the quarter-wave plate 24 and the phase difference plate 25 and is applied to the reflective image modulation element 26.

  The reflective image modulation element 26 performs spatial modulation on the incident S-polarized light in the polarization direction corresponding to the image signal level. Specifically, in the bright part (white part) of the image, the S-polarized light is converted to P-polarized light, and in the dark part (black part) of the image, the S-polarized light is reflected as S-polarized light. Modulation is performed according to the signal level.

  The light reflected from the reflective image modulation element 26 passes through the phase difference plate 25 and the quarter wavelength plate 24 and is incident again on the PS separation surface 23a. The PS separation surface 23a transmits the P-polarized component of the incident light again and reflects the S-polarized component.

  Then, the polarization optical system 18 emits light (P-polarized light) that has been reflected from the reflective image modulation element 26 and then transmitted through the PBS 23 to the color synthesis prism 19.

  As described above, in the polarization optical system 18, in the bright portion (white portion) of the image, the reflective image modulation element 26 converts the incident light (S-polarized light) into P-polarized light and reflects it, and then enters the PBS 23 again and remains as it is. The light passes through and forms an image on the screen via the color synthesis prism 19 and the projection lens 20. On the other hand, in the dark part (black part) of the image, the reflection-type image modulation element 26 is incident again on the PBS 23 as S-polarized light and reflected, and returns to the original optical path.

  Therefore, from the polarization optical system 18, an image in which light and dark are formed according to the video signal is formed in the outgoing light. That is, the R polarization optical system 18-R emits red component video light of the video signal, and the G polarization optical system 18-G emits green component video light of the video signal, The B polarization optical system 18-B emits light of the blue component image of the image signal. For this reason, an image of light corresponding to the video signal is projected on the screen.

(1/4 wavelength plate and phase difference plate)
The quarter wavelength plate 24 and the phase difference plate 25 are provided to improve the contrast of the projected image. Hereinafter, functions of the quarter wavelength plate 24 and the phase difference plate 25 will be described.

  In the following description, it is assumed that the reflective image modulation element 26 has no birefringence or is very small unless otherwise mentioned. Further, in the following description of the functions of the quarter-wave plate 24 and the retardation plate 25, as shown in FIG. 3, the light beam that has passed through the linear polarizer 22 and reflected by the PS separation surface 23a is formed by the Z-axis. Let Θ be the angle (polar angle), and Φ be the angle (azimuth angle) between the projection of the light beam that has passed through the linear polarizer 22 and reflected by the PS separation surface 23a onto the XY plane and the X axis.

  In the following description of the functions of the quarter-wave plate 24 and the phase difference plate 25, as shown in FIG. 4, Φ> 0 degree and Φ = 45 degree light beam (L1), and Θ> 0 degree Φ As an example, there are four rays: a ray (L2) of 135 degrees, a ray (L3) of Φ = 225 degrees with Θ> 0 degrees, and a light beam (L4) of Φ = 315 degrees with Θ> 0 degrees. I will explain. FIG. 4 shows each light beam when the PS separation surface is viewed from the direction of Z> 0, and the four arrows drawn in FIG. 4 pass through the linear polarizer 22 to perform PS separation. Of the reflected light rays reflected by the surface 23a, the polarization direction of the light beam (L1) with Θ> 0 degrees and Φ = 45 degrees, the polarization direction of the light beam (L2) with Θ> 0 degrees and Φ = 135 degrees, Θ> The polarization direction of the light beam (L3) at 0 ° and Φ = 225 °, and the traveling direction of the light beam (L4) at Φ> 0 ° and Φ = 315 ° are shown.

  First, a case where black (dark state) is displayed in a state where the quarter wavelength plate 24 and the phase difference plate 25 are not present will be considered.

  When displaying black (dark state) without the quarter wave plate 24 and the phase difference plate 25, the S-polarized component of the light beam incident on the PBS 23 reflects the PBS 23 to the reflection type image modulation element 26. Head to. Then, the light is reflected by the reflection-type image modulation element 26, travels again to the PBS 23, and is reflected again by the PBS 23, thereby returning to the light source side (direction x <0 in FIG. 2).

  However, even with the ideal PBS 23 that transmits all the P-polarized components and reflects all the S-polarized components, if light that is not parallel to the optical axis is incident, it is projected when it is black (dark state). There is a component that is transmitted in the lens side (Z <0) direction, which lowers the contrast.

  FIG. 5 schematically shows the optical path (S-polarized light) of the light beam L1. FIG. 6 schematically shows the PBS 23 of FIG. 5 and the S-polarized component of the incident light projected onto the XY plane. As shown in FIGS. 5 and 6, when light that is not parallel to the optical axis is incident, the S polarization direction with respect to the PS separation surface 23 a is different between the first incidence and the second incidence on the PBS 23. .

FIG. 7 shows light rays L1 to L4 obtained by projecting the angle component of S-polarized light with respect to the PS separation surface 23a onto the XY plane. 7A shows L1 (Φ = 45 degrees), FIG. 7B shows L2 (Φ = 135 degrees), FIG. 7C shows L3 (Φ = 225 degrees), and FIG. (D) shows L4 (Φ = 315 degrees). In FIG. 7, θ _{si First} (i = 1, 2, 3, 4) is the projection of the S-polarized component on the XY plane when it enters the PBS 23 for the first time for each of the light beams L1 to L4. And the angle between the Y axis. In FIG. 7, θ _{si Second} (i = 1, 2, 3, 4) is an S-polarized component when each of the light beams L1 to L4 is reflected by the reflective image modulation element 26 and then re-enters the PBS 23. Represents the angle between the projection onto the XY plane and the Y axis.

  With reference to FIG. 7 as described above, the relationship of polarization between the first incident and the second incident on the PBS 23 will be considered. For simplicity, the refraction and surface reflection at the interface of the PBS 23 are not considered here.

As shown in FIG. 7, the angle component of S-polarized light changes between the first incidence and the second incidence on the PBS 23, as shown in FIG. The Y axis is symmetrically reversed in the first incident and the second incident on the PBS 23. Further, depending on the azimuth angle Φ of the light beam, θ _{si First} (i = 1, 2, 3, 4) and θ _{si Second} (i = 1, 2, 3, 4) have different magnitude relationships, and L1 For each ray of ~ L4
θ _S 1 _First <θ _S 1 _Second (Φ = 45 degrees)
θ _S 2 _First > θ _S 2 _Second (Φ = 135 degrees)
θ _S 3 _First > θ _S 3 _Second (Φ = 225 degrees)
θ _s 4 _First <θ _s 4 _Second (Φ = 315 degrees)
The relationship is established.

For reference, FIG. 8 shows a change in the direction of the S-polarized light component depending on the azimuth angle Φ when the polar angle Θ of the light beam is 10 degrees. In this case, as shown in FIG.
θ _S 1 _First = 6.3 degrees (−X axis direction) θ _S 1 _Second = 8.1 degrees (+ X axis direction)
θ _S 2 _First = 8.1 degrees (−X axis direction) θ _S 2 _Second = 6.3 degrees (+ X axis direction)
θ _S 3 _First = 8.1 degrees (+ X-axis direction) θ _S 3 _Second = 6.3 degrees (−X-axis direction)
θ _s 4 _First = 6.3 degrees (+ X axis direction) θ _s 4 _Second = 8.1 degrees (−X axis direction)
Thus, it can be seen that the relationship shown above is satisfied.

  When entering the PBS 23 (first time), the S-polarized component of the incident light is reflected, and then the light beam is reflected by the reflective image modulation element 26 and again enters the PBS 23 (second time). At this time, as shown in FIG. 7, the direction of the S-polarized component is different when it is incident on the PBS 23 for the first time and when it is incident for the second time. And the light beam is transmitted in the direction of the projection lens (Z <0). The phenomenon described above applies not only to the light beams having the azimuth angles indicated by L1 to L4 in FIG. 4 but also to all light beams other than the direction of Φ = 0 and 180 degrees.

  The above is the reason that the contrast is lowered.

  In order to prevent image deterioration due to the above-described factors, the polarization state of the light beam determined by the first reflection of the PBS 23 is changed, and the polarization state at the second incidence is changed with respect to the PS separation surface 23a. It suffices to match or approach the S polarization component.

  Therefore, in the polarizing optical system 18 of the reflective projector 10, a quarter wavelength plate 24 having an optical axis in the Y-axis direction and an optical axis in the Z-axis direction are provided between the PBS 23 and the reflective image modulation element 26. A retardation plate 25 satisfying no <ne (no: refractive index for ordinary light, ne: refractive index for extraordinary light) is provided to improve the reduction in contrast.

  Hereinafter, the change in the polarization state by the configuration in which the quarter wavelength plate 24 and the phase difference plate 25 are provided will be described for the light beams L1 to L4.

  9A shows a position (Z1) of the light beam L1 (Φ = 45 degrees) before the first incidence of the quarter-wave plate 24 (Z1) → the position after the first transmission of the quarter-wave plate 24 ( Z2) → 1/4 wavelength plate 24 before the second incident position (Z3) → 1/4 wavelength plate 24 after the second transmission position (Z4) shows the change in polarization state at each position. Is. The slow axis and the fast axis shown in FIG. 9A represent those viewed from the light beam L1, and therefore, the slow axis of the phase difference plate 25 is 45 with respect to the X axis of the light beam. The direction is inclined.

  FIG. 9B is a plan view of a part of the transition of the polarization state of FIG. 9A represented by a Poincare sphere. Similar to FIG. 9A, the light beam L1 (azimuth angle Φ = 45) is obtained. (Degree) polarization direction change. In FIG. 9B, -S1 is linearly polarized light directed in the Y-axis direction, + S2 and -S2 are linearly polarized light directed in the direction of 45 degrees with respect to the Y-axis as shown in the figure, and + S3 and -S3 are respectively Represents clockwise circularly polarized light and counterclockwise circularly polarized light.

  For example, the slow axis direction of the quarter-wave plate in FIG. 9A is strict due to the fact that the polar angle Θ of the light beam is not 0, such as actually having a slight inclination with respect to the Y axis direction. However, it is not an amount that causes a problem in at least the following description.

As shown in FIG. 9C, the orientation of the polarization axis of the light beam L1 reflected by the PS separation surface 23a is a direction inclined by θ1 _Initial on the −X axis side with respect to the Y axis. This polarization state coincides with the projection of the S-polarized component on the PS separation surface 23a onto the XY plane, and is linearly polarized light as shown by the position of Z1 in FIGS. 9A and 9B. .

  When the light beam emitted from the PS separation surface 23a passes through the quarter-wave plate 24 having the slow axis in the Y-axis direction, an elliptical shape is obtained as shown by the position Z2 in FIGS. 9A and 9B. It becomes polarized light. Thereafter, the light passes through the retardation plate 25 whose slow axis is inclined 45 degrees to the X axis side with respect to the Y axis twice. After passing through the retardation plate 25 twice, it is converted into elliptically polarized light as shown by the position of Z3 on FIGS. 9 (A) and 9 (B). The phase difference plate 25 is transmitted by two reciprocations by being reflected by the reflection type image modulation element 26, but is shown collectively in FIGS. 9A and 9B.

The light beam that has passed through the retardation plate 25 twice passes through the quarter wavelength plate 24 whose slow axis is in the Y-axis direction again. The light beam that has been transmitted through the quarter-wave plate 24 again is converted into linearly polarized light as indicated by the position of Z4 in FIGS. 9A and 9B. That is, as shown in FIG. 9C, the direction of the polarization axis of the light beam L1 incident again on the PS separation surface 23a is a direction inclined by θ1 _Final on the X axis side with respect to the Y axis.

That is, by providing the ¼ wavelength plate 24 and the phase difference plate 25, the light emitted from the PBS 23 with the polarization axis of θ1 _Initial is converted into the θ1 _Final and the light is incident on the PBS 23 again.

Here, the relationship θ1 _Initial <θ1 _Final is established (see FIG. 9C). Further, | θ1 _Final −θ1 _Initial | is determined by the phase difference generated in the process from the incident position (Z2) to the phase difference plate 25 for the first time to the emission position (Z3) for the second phase difference plate 25. If the phase difference is large, | θ1 _Final −θ1 _Initial | becomes large. If there is no phase difference, θ1 _Final = θ1 _Initial , that is, the polarization direction is symmetric with respect to the Y-axis direction.

  10A, 10B, and 10C illustrate changes in the polarization state at each position of the light beam L2 (azimuth angle φ = 135 degrees), as in FIG. 9, and FIGS. FIGS. 12B and 12C illustrate changes in the polarization state at each position of the light beam L3 (azimuth angle φ = 225 degrees). FIGS. 12A, 12B, and 12C illustrate the light beam L4 ( The change of the polarization state at each position of the azimuth angle (φ = 315 degrees) is illustrated.

To summarize the changes in the polarization state shown in FIGS. 9 to 12, between the PBS 23 and the reflective image modulation element 26, the ¼ wavelength plate 24 whose slow axis with respect to vertical incidence is in the Y-axis direction, and the optical axis. Is installed in the Z direction so that no <ne (no: refractive index for ordinary rays, ne: refractive index for extraordinary rays), and after the first reflection of PBS 23 and the second incidence of PBS 23. The previous state of linear polarization changes symmetrically in the opposite direction with respect to all rays from L1 to L4. Further, the amount of change is set to θ1 _Initial , θ2 _Initial , θ3 _Initial , and θ4 _Initial , respectively, as the projection components of the polarization axis after the first reflection of the PBS 23 onto the XY plane, and the polarization immediately before entering the PBS 23 again. If the projected components of the axis onto the XY plane are θ1 _Final , θ2 _Final , θ3 _Final , and θ4 _Final , the following relationships are established (FIG. 9C, FIG. 10C, FIG. 11). C), see FIG.
θ1 _Initial <θ1 _Final
θ2 _Initial > θ2 _Final
θ3 _Initial > θ3 _Final
θ4 _Initial <θ4 _Final

  The state of the change in the polarization direction when first reflected by the PBS 23 and the change in the polarization direction when re-entering the PBS 23 is in agreement with the S-polarization state when the PBS 23 is incident for the second time shown in FIG. . Therefore, by setting an appropriate phase difference with respect to the phase difference plate 25, the polarization direction of the light beam and the S-polarized component at the time of PBS incident again are closer.

  By providing the quarter wavelength plate 24 and the phase difference plate 25 as described above, light leaking to the screen when displaying black is reduced, so that a high-definition image with high contrast can be realized.

  Next, the phase difference of the phase difference plate 25 will be examined.

  FIG. 13 shows the relationship between Δn × d of the phase difference plate 25 and the relative value of the contrast ratio. FIG. 13 shows changes in a plurality of contrast ratios obtained by changing the refractive index of the PBS 23, the refractive index of the quarter-wave plate, and the refractive index of the retardation plate in various practical ranges. . Here, Δn represents a refractive index difference with respect to a light beam perpendicularly incident on the optical axis of the retardation plate 25, and d represents a thickness of the retardation plate 25 in the Z-axis direction. The wavelength of light was 550 nm. As shown in FIG. 13, even when each condition is changed, when the phase difference (Δn × d) of the phase difference plate 25 is in the range of ± 50 nm centered around 140 nm, the contrast is high. It can be seen that there is a maximum value.

  Since the highest quality image can be projected when the contrast is maximum, the refractive index difference with respect to the light incident perpendicularly to the optical axis of the retardation plate 25 is Δn, and the thickness of the retardation plate (distance in the Z-axis direction) is When d, it is understood that Δn × d of the phase difference plate 25 is desirably set in a range of 0.16 × λ <Δn × d <0.35 × λ. Here, λ represents the wavelength of light incident on the retardation plate 25.

  More specifically, the refractive index of the PBS 23 is about 1.84, the refractive index of the quarter-wave plate 24 is about 1.62, the refractive index n of the phase difference plate 25 is 1.55, and Δn is 0.1. When the wavelength is about 550 nm, the contrast becomes maximum when the thickness d of the retardation plate is about 14.5 μm.

  However, how much the thickness d of the phase difference plate 25 is made depends on the refractive index of the PBS 23, the wavelength of the light beam, and the like. Qualitatively, in the case of the phase difference plate 25 having the same Δn, the refractive index of the PBS 23 is smaller, and the longer the wavelength, the larger the thickness d of the optimum phase difference plate.

  In the reflective projector 10 according to the first embodiment, the PBS 23, the quarter wavelength plate 24, and the phase difference plate 25 are disposed separately. However, any combination or all of these may be optically integrated without disposing them separately. By integrating optically, surface reflection is reduced, and contrast can be further improved. In addition, the quarter-wave plate 24 and the retardation plate 25 may be arranged such that the quarter-wave plate 24 and the retardation plate 25 are interchanged. For example, the PBS 23 and the quarter wavelength plate 24 may be optically integrated, or the PBS 23 and the phase difference plate 25 may be optically integrated. Further, the quarter wavelength plate 24 and the phase difference plate 25 may be optically integrated, or all of the PBS 23, the quarter wavelength plate 24, and the phase difference plate 25 may be optically integrated. .

Second Embodiment Next, a reflective projector according to a second embodiment will be described.

  The reflective projector according to the second embodiment includes a polarizing optical system 18 (R polarizing optical system 18-R, G polarizing optical system 18-) of the reflective projector 10 according to the first embodiment shown in FIG. The polarization optical system 18-B) for G and B is replaced with a polarization optical system 30 having another configuration. The configuration other than the polarizing optical system 30 is the same as that of the reflective projector 10 shown in FIG. Hereinafter, in describing the reflective projector according to the second embodiment, only the polarization optical system 30 will be described, and detailed description of other components will be omitted.

  In the description of the polarizing optical system 30, members having the same configurations as those used in the polarizing optical system 18 of the first embodiment are denoted by the same reference numerals in the drawings, and the detailed description thereof will be omitted. Description is omitted.

  Similarly to the first embodiment, in the second embodiment, the position and direction of the three-dimensional space are defined by using the coordinate axes represented by the X axis, the Y axis, and the Z axis, and the constituent members Will be explained. Similarly, the angle (polar angle) between the light beam that has passed through the linear polarizer 22 and reflected by the PS separation surface 23a and the Z axis is Θ, and the light beam that has passed through the linear polarizer 22 and reflected by the PS separation surface 23a. The angle (azimuth angle) formed by the projection onto the XY plane and the X axis is Φ.

  In the following description, it is assumed that the reflective image modulation element 26 has no birefringence or is very small unless otherwise mentioned.

(Configuration of polarization optical system 30)
FIG. 14 is a diagram showing a configuration in the polarization optical system 30.

  As shown in FIG. 14, the polarization optical system 30 includes a field lens 21, a linear polarizer 22, a polarization beam splitter (PBS) 23, a ¼ wavelength plate 31, a phase difference plate 32, and a reflection type image modulation. An element 26 is provided.

  The quarter-wave plate 31 is an optical element that changes the phase difference of polarized light that vibrates in directions perpendicular to each other when the light is transmitted. The quarter-wave plate 31 is disposed in parallel to the XY plane at a position where light that has passed through the field lens 21 and the linear polarizer 22 and reflected by the PS separation surface 23a is incident (that is, 1). The quarter-wave plate 31 is provided so that its optical axis is parallel to the Z-axis). The quarter wavelength plate 31 is arranged so that the optical axis is parallel to the X axis.

  The phase difference plate 32 is an optical element that changes the phase of the light according to the angle between the incident direction and the optical axis when transmitting the light. The phase difference plate 32 does not change the phase with respect to light incident parallel to the optical axis. The phase difference plate 32 is arranged in parallel to the XY plane at a position where light that has passed through the field lens 21 and the linear polarizer 22 and reflected by the PS separation surface 23a is incident (that is, the phase difference plate). 32 is provided such that its optical axis is parallel to the Z-axis).

  The phase difference plate 32 is disposed so that the optical axis is parallel to the Z axis. Further, the phase difference plate 32 is assumed to have a relationship of no> ne when the refractive index is no for ordinary light and the refractive index is ne for extraordinary light. Therefore, the phase difference plate 32 does not produce a phase difference with respect to a light beam incident parallel to the Z axis, and when a light beam having an angle with respect to the Z axis is incident, the phase difference plate 32 generates a phase difference according to the incident angle. Cause it to occur.

  The light that has passed through the field lens 21 and the linear polarizer 22 and reflected from the PS separation surface 23 a passes through the quarter-wave plate 31 and the phase difference plate 32, and is then applied to the reflective image modulation element 26.

  The light passing path of the polarizing optical system 30 having the optical configuration as described above is as follows.

  The light enters the polarizing optical system 30 from a direction parallel to the X axis.

  Incident light is made into a divergent light beam by the field lens 21, and then passes through the linear polarizer 22 and is irradiated onto the PS separation surface 23a. The PS separation surface 23a is converted into linearly polarized light by the linear polarizer 22 and is incident as almost S-polarized light. The PS separation surface 23a reflects incident light as S-polarized light. The S-polarized light reflected by the PS separation surface 23 a passes through the quarter-wave plate 31 and the phase difference plate 32 and is applied to the reflective image modulation element 26.

  The reflective image modulation element 26 performs spatial modulation on the incident S-polarized light in the polarization direction corresponding to the image signal level.

  The light reflected from the reflective image modulation element 26 passes through the phase difference plate 32 and the quarter-wave plate 31 and is incident again on the PS separation surface 23a. The PS separation surface 23a transmits the P-polarized component of the incident light again and reflects the S-polarized component. Then, the polarization optical system 30 emits light (P-polarized light) that has been reflected from the reflective image modulation element 26 and then transmitted through the PBS 23 to the color synthesis prism 19.

  As described above, in the polarization optical system 30, in the bright part (white part) of the image, the reflection type image modulation element 26 converts the incident light (S-polarized light) into P-polarized light and reflects it. The light is transmitted and an image is formed on the screen through the color synthesis prism 19 and the projection lens. On the other hand, in the dark part (black part) of the image, the reflection-type image modulation element 26 is incident again on the PBS 23 as S-polarized light and reflected, and returns to the original optical path.

(1/4 wavelength plate 31 and phase difference plate 32)
The quarter wavelength plate 31 and the phase difference plate 32 are provided to improve the contrast of the projected image, similarly to the quarter wavelength plate 24 and the phase difference plate 25 of the first embodiment. Is. Hereinafter, the quarter wavelength plate 31 and the phase difference plate 32 will be described.

  In order to prevent image deterioration, the polarization state of the light beam determined by the first reflection of the PBS 23 is changed, and the polarization state at the second incidence is made to coincide with the S polarization component with respect to the PS separation surface 23a. Or close.

Therefore, in the polarizing optical system 30 of the reflective projector, a quarter wavelength plate 31 having an optical axis in the X- axis direction and a no having an optical axis in the Z-axis direction between the PBS 23 and the reflective image modulation element 26. A phase difference plate 32 having> ne (no: refractive index for ordinary light, ne: refractive index for extraordinary light) is provided to improve the reduction in contrast.

  Hereinafter, the change in the polarization state by the configuration in which the quarter wavelength plate 31 and the phase difference plate 32 are provided will be described for the light beam of L1 (Φ = 45 degrees).

  15A shows a position (Z1) before the first incidence of the quarter wavelength plate 31 in the light beam L1 (Φ = 45 degrees) → the position after the first transmission of the quarter wavelength plate 31 ( Z2) → 1/4 wavelength plate 31 before the second incidence (Z3) → 1/4 wavelength plate 31 after the second transmission position (Z4) shows the change in polarization state at each position. Is.

  FIG. 15B is a plan view of a part of the transition of the polarization state of FIG. 15A represented by a Poincare sphere. Similar to FIG. 15A, the light beam L1 (azimuth angle Φ = 45) is obtained. (Degree) polarization direction change.

As shown in FIG. 15C, the orientation of the polarization axis of the light beam L1 reflected by the PS separation surface 23a is a direction inclined by θ1 _Initial on the −X axis side with respect to the Y axis. This polarization state coincides with the projection of the S-polarized component on the PS separation surface 23a onto the XY plane, and is linearly polarized light as indicated by the position Z1 in FIGS. 15A and 15B. .

  When the light beam emitted from the PS separation surface 23a passes through the quarter-wave plate 31 having a slow axis in the X-axis direction, an elliptical shape is obtained as shown by the position Z2 in FIGS. 15A and 15B. It becomes polarized light. Thereafter, the light passes through the phase difference plate 32 whose slow axis is inclined 45 degrees to the X axis side with respect to the Y axis. After passing through the retardation plate 32 twice, it is converted to elliptically polarized light as shown by the position of Z3 on FIGS. 15 (A) and 15 (B).

The light beam that has passed through the retardation plate 32 twice passes through the quarter-wave plate 31 whose slow axis is in the Y-axis direction again. The light beam that has been transmitted through the quarter-wave plate 31 again is converted into linearly polarized light as shown by the position of Z4 in FIGS. 15 (A) and 15 (B). That is, as shown in FIG. 15C, the direction of the polarization axis of the light beam L1 incident again on the PS separation surface 23a is a direction inclined by θ1 _Final on the X axis side with respect to the Y axis.

That is, by providing the quarter wavelength plate 31 and the phase difference plate 32, the light emitted from the PBS 23 with the polarization axis θ1 _Initial is converted into the θ1 _Final polarization axis and reentered into the PBS 23.

Here, the relationship θ1 _Initial <θ1 _Final is established (see FIG. 15C). Further, | θ1 _Final −θ1 _Initial | is determined by the phase difference generated in the process from the incident position (Z2) to the phase difference plate 32 for the first time to the emission position (Z3) for the second phase difference plate 32. If the phase difference is large, | θ1 _Final −θ1 _Initial | becomes large. If there is no phase difference, θ1 _Final = θ1 _Initial , that is, the polarization direction is symmetric with respect to the Y-axis direction.

Similarly, the polarization state at each position of the light beam L2 (azimuth angle φ = 135 degrees), the change in the polarization state at each position of the light beam L3 (azimuth angle φ = 225 degrees), and the light beam L4 (azimuth angle φ = 315 degrees). ), The quarter-wave plate 31 whose slow axis with respect to vertical incidence is in the X-axis direction and the optical axis is Z between the PBS 23 and the reflective image modulation element 26. By installing a phase difference plate 32 that indicates no> ne (no: refractive index for ordinary light, ne: refractive index for extraordinary light) in the direction, it is reflected after the first reflection of PBS 23 and before the second incidence of PBS 23. The state of the linear polarization changes in the opposite direction symmetrically with respect to the Y axis for all the light beams from L1 to L4. The amount of change is set to θ1 _Initial , θ2 _Initial , θ3 _Initial , and θ4 _Initial , respectively, as the projection components of the polarization axis after the first reflection on the PBS 23 onto the XY plane. Assuming that the projection components onto the XY plane are θ1 _Final , θ2 _Final , θ3 _Final , and θ4 _Final , respectively, the following relationship is established as in the first embodiment.
θ1 _Initial <θ1 _Final
θ2 _Initial > θ2 _Final
θ3 _Initial > θ3 _Final
θ4 _Initial <θ4 _Final

  The state of the change in the polarization direction when it is first reflected by the PBS 23 and the change in the polarization direction when it is incident again on the PBS 23 coincides with the S polarization state when the PBS 23 is incident on the second time shown in FIG. . Therefore, by setting an appropriate phase difference for the phase difference plate 32, the polarization direction of the light beam and the S-polarized component at the time of PBS 23 re-incidence become closer.

  By providing the quarter-wave plate 31 and the phase difference plate 32 as described above, light leaking to the screen when displaying black is reduced, so that a high-definition image with high contrast can be realized.

  Next, the phase difference set for the phase difference plate 32 will be discussed.

  In the reflective projector of the second embodiment, the relationship between Δn × d of the phase difference plate 32 and the relative value of the contrast ratio is the same as that of the first embodiment shown in FIG.

  Accordingly, when the light wavelength is 550 nm, even when each condition is changed, the phase difference (Δn × d) of the retardation plate 32 is in the range of ± 50 nm centered around 140 nm. There is a value that maximizes the contrast. Therefore, when the refractive index difference with respect to light incident perpendicularly to the optical axis of the retardation plate 32 is Δn and the thickness of the retardation plate (distance in the Z-axis direction) is d, the retardation plate 32 is 0 .16 × λ <Δn × d <0.35 × λ is desirable. Here, λ represents the wavelength of light incident on the phase difference plate 32.

  Note that the thickness d of the phase difference plate 32 depends on the refractive index of the PBS 23, the wavelength of the light beam, and the like. Qualitatively, in the case of the phase difference plate 32 having the same Δn, the refractive index of the PBS 23 is smaller, and the longer the wavelength, the greater the thickness d of the optimum phase difference plate.

  Further, the PBS 23, the quarter-wave plate 31 and the phase difference plate 32 are arranged separately, but any combination or all of these may be optically integrated in the first embodiment. It is the same. Also, the quarter-wave plate 31 and the retardation plate 32 may be replaced by the quarter-wave plate 31 and the retardation plate 32.

Third Embodiment Next, a reflective projector according to a third embodiment will be described.

  In describing the reflective projector according to the third embodiment, members having the same configurations as those used in the first embodiment or the second embodiment are denoted by the same reference numerals in the drawings. The detailed description is omitted.

  Similarly to the first embodiment, in the third embodiment, the position and direction of the three-dimensional space are defined using the coordinate axes represented by the X axis, the Y axis, and the Z axis, and the constituent members Will be explained.

(overall structure)
FIG. 16 is a schematic diagram showing the configuration of a reflective projector 40 to which the present invention is applied.

  The reflective projector 40 includes a lamp 11, an integrator lens 12, a PS conversion element 13, a condenser lens 14, a field lens 41, a linear polarizer 42, a specific wavelength band polarization conversion element 43, and a polarization beam splitter ( PBS) 44, R light modulation optical system 45 -R, G and B light modulation optical systems 45 -G and B, a combining optical system 46, and the projection lens 20.

  The white light beam emitted from the lamp 11 is incident on the pair of integrator lenses 12. The light beam that has passed through the integrator lens 12 enters the PS conversion element 13. The light beam that has passed through the PS conversion element 13 passes through the condenser lens 14 and enters the field lens 41.

  A light beam emitted from the condenser lens 14 is incident on the field lens 41. The field lens 41 is disposed so that the optical axis is parallel to the X axis. The field lens 41 divides the incident light beam into a divergent bundle and irradiates the linear polarizer 42.

  The linear polarizer 42 is an element having a flat plate shape, and is a device that emits only polarized light in one direction among incident light beams. The linear polarizer 22 transmits polarized light in one direction that is S-polarized light to the PBS 44 and transmits other polarized light. The linear polarizer 42 is a reflective polarizer or an absorptive polarizer that transmits polarized light in one direction and absorbs other polarized light. Further, as the reflective polarizer, for example, a wire grid polarizer that is put into practical use by MOTTEK may be used.

  The light beam transmitted through the linear polarizer 42 enters the specific wavelength band polarization conversion element 43.

  The specific wavelength band polarization conversion element 43 does not act on light in the green and blue wavelength bands, and rotates the polarization axis in the red wavelength band by 90 degrees. The light beam that has passed through the specific wavelength band polarization conversion element 43 enters the PBS 44.

  The PBS 44 is a polarized light separating element having a polarization separation surface (separation surface) 44a that reflects S-polarized light and transmits P-polarized light. The PS separation surface 44a is arranged perpendicular to the Z-X plane and 45 with respect to a plane formed by the Y-axis and the Z-axis (a plane perpendicular to the X-axis, hereinafter referred to as the Y-Z plane). Tilt to an angle of °.

  Light that has passed through the specific wavelength band polarization conversion element 43 is incident on the PS separation surface 44a. The PS separation surface 44a is arranged so that polarized light in one direction transmitted from the linear polarizer 42 is converted to S-polarized light. The light passing through the specific wavelength band polarization conversion element 43 has the polarization direction of the light of only the red wavelength band rotated by 90 degrees. Accordingly, the PBS 44 reflects green and blue light beams (S-polarized light) and transmits red light beams (P-polarized light).

  The blue and green light fluxes (S-polarized light) reflected by the PBS 44 are incident on the G and B light modulation optical systems 45-G and B. The red wavelength band light beam (P-polarized light) transmitted through the PBS 44 is incident on the R light modulation optical system 45-R.

  The G and B light modulation optical systems 45 -G and B include a quarter-wave plate 47, a phase difference plate 48, and a blue and green reflection type image modulation element 49.

  The blue and green light fluxes reflected by the PBS 44 are transmitted through the quarter-wave plate 47 and the phase difference plate 48 and enter the blue and green reflective image modulation element 49. The blue / green reflective image modulation element 49 receives a composite signal of the blue (B) and green (G) signals of the video signal. The blue and green reflective image modulation element 49 spatially modulates the incident S-polarized light in accordance with the input composite signal. Specifically, as a result of spatial modulation of incident light (S-polarized light) according to the video signal, in the bright part (white part) of the image, S-polarized light is converted to P-polarized light and reflected, and the dark part of the image In (black part), the S-polarized light is reflected as it is. The light reflected from the blue and green reflective image modulation elements 49 passes through the phase difference plate 48 and the quarter-wave plate 47 and is incident again on the PS separation surface 44a. The PS separation surface 44a transmits the P-polarized component of the incident light again and reflects the S-polarized component.

  The R light modulation optical system 45 -R includes a ¼ wavelength plate 50, a phase difference plate 51, and a red reflection type image modulation element 52.

  The light beam in the red wavelength band transmitted through the PBS 44 passes through the ¼ wavelength plate 50 and the phase difference plate 51 and enters the red reflection type image modulation element 52. The red reflection type image modulation element 52 receives a red (R) signal of the video signal. The red reflection type image modulation element 52 spatially modulates the incident P-polarized light in accordance with the input red (R) signal. Specifically, as a result of spatially modulating incident light (P-polarized light) according to the video signal, P-polarized light is converted to S-polarized light and reflected in a bright part (white part) of the image, and a dark part of the image In (black part), P-polarized light is reflected as P-polarized light. The light reflected from the red reflection-type image modulation element 52 passes through the phase difference plate 51 and the quarter-wave plate 50 and is incident again on the PS separation surface 44a. The PS separation surface 44a reflects the S-polarized component of the incident light again and transmits the P-polarized component.

  Blue and green light fluxes emitted from the G and B light modulation optical systems 45-G and B and transmitted through the PBS 44, and a red wavelength band emitted from the R light modulation optical system 45-R and reflected from the PBS 44 Are incident on the combining optical system 46.

  The combining optical system 46 includes an optical compensation plate 53, a specific wavelength band polarization conversion element 54, and a linear polarizer 55. The light beam incident on the combining optical system 46 sequentially passes through the optical compensation plate 53, the specific wavelength band polarization conversion element 54, and the linear polarizer 55. The optical compensator 53 aligns the polarization axes of the light beams in the green and blue wavelength bands with the transmission axis of the linear polarizer 55, and aligns the polarization axes of the light beams in the red wavelength band with the absorption axis of the linear polarizer 55. The specific wavelength band polarization conversion element 54 does not act on the light in the green and blue wavelength bands, and rotates the polarization axis in the red wavelength band by 90 degrees. By the action of the optical compensation plate 53 and the specific wavelength band polarization conversion element 54, the polarization axis of the light beam transmitted through the linear polarizer 55 is aligned with the transmission axis.

  The light beam that has passed through the linear polarizer 55 passes through the projection lens 20 and forms an image on a screen (not shown).

Here, in the reflective projector 40, the positional relationship of the field lens 41, the linear polarizer 42, the PBS 44, the quarter wavelength plate 47, the phase difference plate 48, and the blue and green reflective image modulation elements 49 is shown in FIG. 2 is the same as the arrangement relationship of the field lens 21, the linear polarizer 22, the PBS 23, the quarter wavelength plate 24, the phase difference plate 25, and the reflective image modulation element 26 of the first embodiment shown in FIG. Or the same arrangement relationship of the field lens 21, the linear polarizer 22, the PBS 23, the quarter wave plate 31, the phase difference plate 32, and the reflective image modulation element 46 of the second embodiment shown in FIG. For this reason, in the reflective projector 40, the contrast of the projection image generated by the optical system existing at the position where the PBS 44 is reflected and re-entered can be improved. .

  Further, in the reflection type projector 40, an optical system (hereinafter referred to as a PBS transmission side) composed of a quarter wavelength plate 50, a phase difference plate 51, and a reflection type image modulation element 52 that exist at positions where the PBS 44 is transmitted and re-entered. The contrast of the projected image generated by the optical system is improved.

(PBS transmission side optical system)
Hereinafter, the PBS transmission side optical system will be described.

  In the following description of the PBS transmission side optical system, the angle (polar angle) formed between the light beam transmitted through the PBS 44 and the X axis is Θ, the projection of the light beam transmitted through the PBS onto the YZ plane, and the Z axis Let Φ be the angle (azimuth angle) formed by.

  First, consider a case where black (dark state) is displayed in the PBS transmission side optical system portion without the quarter wavelength plate 50 and the phase difference plate 51. When displaying black (dark state) without the quarter-wave plate 50 and the phase difference plate 51, the P-polarized component of the light beam incident on the PBS 44 is transmitted through the PBS 44 to the reflection type image modulation element 52. Head to. Then, the light is reflected by the reflective image modulation element 52, travels again to the PBS 44, and is transmitted again by the PBS 44, thereby returning to the light source side (x <0 direction in FIG. 16). However, even an ideal PBS 44 that transmits all the P-polarized components and reflects all the S-polarized components, there is a component that reflects in the direction of the projection lens (Z <0). This reflection component reduces the contrast.

  FIG. 17A schematically shows an optical path (P-polarized light) of the light beam L5. FIG. 17B schematically shows a projection of the PBS 44 of FIG. 17A and the P-polarized component of incident light on the YZ plane.

  As shown in FIG. 17, when light that is not parallel to the optical axis is incident, the P-polarization direction with respect to the PS separation surface 44a differs between the first incidence and the second incidence on the PBS 44.

FIG. 18 shows light rays L5 to L6 that are obtained by projecting the S-polarized angle component with respect to the PS separation surface 44a onto the YZ plane when only the PBS transmission side optical system portion is extracted. . 18A shows L5 (Φ = 45 degrees), FIG. 18B shows L6 (Φ = 135 degrees), FIG. 18C shows L7 (Φ = 225 degrees), and FIG. (D) shows L8 (Φ = 315 degrees). 18 in _{θ s i First (i = 5,6,7,8} ) for each of the rays of L5 to L8, projection to Y-Z plane of the P polarization components as they enter the first time in PBS44 And the angle between the Z axis. 17 in _{θ s i Second (i = 5,6,7,8} ) for each of the rays of L5 to L8, P-polarized light component at the time of re-entering the PBS44 after being reflected by the reflection type image modulation element 52 Represents the angle between the projection onto the YZ plane and the Z axis.

As shown in FIG. 18, the angle component of the P-polarized light changes between the first incidence and the second incidence on the PBS 44, and shows the opposite direction with respect to the Z axis. Further, the azimuth angle of the light ray [Phi, the magnitude relation between _{θ s i First (i = 5,6,7,8} ) and _{θ s i Second (i = 5,6,7,8} ) are different, L5 to L8 For each ray of
θ _S 5 _First <θ _S 5 _Second (Φ = 45 degrees)
θ _S 6 _First > θ _S 6 _Second (Φ = 135 degrees)
θ _S 7 _First > θ _S 7 _Second (Φ = 225 degrees)
θ _s 8 _First <θ _s 8 _Second (Φ = 315 degrees)

  When entering the PBS 44 (first time), the P-polarized component of the incident light is transmitted, and then the light beam is reflected by the reflective image modulation element 26 and again enters the PBS 44 (second time). At this time, as shown in FIG. 18, the direction of the P-polarized component is different between the first incident on the PBS 44 and the second incident on the PBS 44. Therefore, the S-polarized component is incident on the PBS 44 for the second time. The light beam is reflected in the direction of the projection lens (Z <0). The phenomenon described above applies not only to the light beams having the azimuth angles indicated by L5 to L8 but also to all light beams other than the direction of Φ = 0, 180 degrees.

  This is the reason why the contrast is lowered in the PBS transmission side optical system.

  In order to prevent image degradation due to the above-described factors, the polarization state of the light beam determined by the first transmission through the PBS 44 is changed, and the polarization state at the second incidence is changed with respect to the PS separation surface 44a. It is sufficient to match or approach the P-polarized light component.

  Therefore, in the polarization optical system 18 of the reflective projector 40, as shown in FIG. 19, a quarter wavelength plate 50 having an optical axis in the Y-axis direction between the PBS 44 and the reflective image modulation element 52, and the X A retardation plate 51 having an optical axis in the axial direction and no <ne (no: refractive index for ordinary light, ne: refractive index for extraordinary light) is provided to improve the reduction in contrast.

  Hereinafter, the change in the polarization state by the configuration in which the quarter wavelength plate 50 and the phase difference plate 51 are provided will be described for the light beams L5 to L8.

  20A, 20B, and 20C illustrate changes in the polarization state at each position of the light beam L5 (azimuth angle φ = 45 degrees), as in FIG. 9, and FIGS. FIGS. 22B and 22C illustrate changes in the polarization state at each position of the light beam L6 (azimuth angle φ = 135 degrees). FIGS. 22A, 22B, and 22C illustrate the light beam L7 ( The change of the polarization state at each position (X1, X2, X3, X4) at the azimuth angle φ = 225 degrees is illustrated. FIGS. 23A, 23B, and 23C show the light beam L8 (azimuth angle φ). (= 315 degrees) illustrates the change in polarization state at each position.

20 to 23, the change of the polarization state shown in FIGS. 20 to 23 is summarized as follows. Between the PBS 44 and the reflective image modulation element 52, the ¼ wavelength plate 50 whose slow axis with respect to vertical incidence is in the Y-axis direction, and the optical axis. Is installed in the X direction so that no <ne (no: refractive index for ordinary rays, ne: refractive index for extraordinary rays), and after the first reflection of PBS 44 and the second incidence of PBS 44. The state of the previous linearly polarized light changes in the opposite direction symmetrically with respect to the Z axis for all the light beams from L5 to L8. Further, the amount of change is set to θ1 _Initial , θ2 _Initial , θ3 _Initial , and θ4 _Initial , respectively, as the projection components of the polarization axis after the first reflection of the PBS 44 onto the YZ plane, and the polarization immediately before entering the PBS 44 again. If the projected components of the axis onto the YZ plane are θ1 _Final , θ2 _Final , θ3 _Final , and θ4 _Final , the following relationships are established (FIGS. 20C, 21C, and 22). C), see FIG.
θ5 _Initial <θ5 _Final
θ6 _Initial > θ6 _Final
θ7 _Initial > θ7 _Final
θ8 _Initial <θ8 _Final

  The state of the change in the polarization direction when first reflected by the PBS 44 and the change in the polarization direction when re-entering the PBS 44 coincides with the S polarization state when the PBS 44 is incident for the second time shown in FIG. . Therefore, by setting an appropriate phase difference with respect to the phase difference plate 51, the polarization direction of the light beam and the S polarization component at the time of PBS 44 re-incidence become closer.

  By providing the quarter wavelength plate 50 and the phase difference plate 51 as described above, light leaking to the screen when displaying black is reduced, so that an image with high contrast and high quality can be realized.

  Further, in order to change the polarization state of the light beam determined by the first transmission through the PBS 44 and make the polarization state at the second incidence coincide with the P polarization component with respect to the PS separation surface 44a, the second embodiment described above is used. Similarly to the embodiment, as shown in FIG. 24, a quarter-wave plate 50 having an optical axis in the Z-axis direction and a no having an optical axis in the X-axis direction between the PBS 44 and the reflective image modulation element 52. Contrast can also be lowered by providing a retardation plate 51 that satisfies> ne (no: refractive index for ordinary light, ne: refractive index for extraordinary light).

  Next, the phase difference set for the phase difference plate 51 will be discussed.

  In the reflection type projector 40 of the third embodiment, when the relationship between Δn × d of the phase difference plate 32 and the relative value of the contrast ratio is measured, the relationship is similar to the relationship of the first embodiment shown in FIG. Become.

  Therefore, when the wavelength of light is 550 nm, there is a value at which the contrast is maximum around ± 50 nm, centering around 140 nm. Therefore, when the refractive index difference with respect to the light incident perpendicularly to the optical axis of the retardation plate 51 is Δn and the thickness of the retardation plate (distance in the Z-axis direction) is d, the retardation plate 51 is 0 .16 × λ <Δn × d <0.35 × λ is desirable. Here, λ represents the wavelength of light incident on the retardation plate 51.

  Further, the PBS 44, the quarter-wave plate 50, and the phase difference plate 51 are arranged separately, but any combination or all of these may be optically integrated in the first embodiment. It is the same. In addition, the quarter-wave plate 50 and the retardation plate 51 may be arranged such that the quarter-wave plate 50 and the retardation plate 51 are interchanged.

Fourth Embodiment Next, a reflection type projector according to a fourth embodiment will be described.

  FIG. 25A and FIG. 25B are configuration diagrams of the main part of the liquid crystal projector of the fourth embodiment.

  As shown in FIGS. 25A and 25B, the liquid crystal projector of the fourth embodiment includes the retardation plates 25, 32, 48, 51 of the first to third embodiments, and a reflection type. Between the image modulation elements 26, 49 and 52, an optical compensator 70 having an action of canceling the birefringence at the time of black display of the TN reflection type liquid crystal element is provided.

  Note that, among the components of the liquid crystal projector of the fifth embodiment, the components other than the optical compensation plate 70 are the same as those of the first to third embodiments, so detailed description thereof will be omitted. .

  In the fourth embodiment, TN-type reflective liquid crystal elements are used as the reflective image modulation elements 26, 49, and 52.

  The optical compensator 70 uses a negative uniaxial retardation film such as a discotic liquid crystal compound, and uses, for example, a Fujifilm wide-view film.

  When the TN liquid crystal is used as the reflection type image modulation elements 26, 49, and 52, and it is used together with the discotic liquid crystal compound, birefringence at the time of reflection by the liquid crystal is canceled or reduced, approximately Can be considered.

When a VA-type reflective liquid crystal element is used as the reflective image modulation elements 26, 49, 52, the difference in refractive index of the liquid crystal element (difference between the major axis and the minor axis of the birefringent ellipsoid) is Δn _LC , and the liquid crystal If the phase thickness is d _LC , the refractive index difference (difference between the major axis and minor axis of the birefringent ellipsoid) of the optical compensator 70 is Δn _OC , and the thickness of the optical compensator is d _OC , then Δn _LC · d _LC = A retardation film satisfying Δn _op · d _OC and having negative uniaxiality with the same optical axis direction may be used. As a result, birefringence at the time of reflection by the liquid crystal is canceled or becomes extremely small, and can be regarded as an approximately simple reflecting surface.

  As described above, by using the optical compensator 70, the quarter-wave plates 24, 31, 47, 50 and the retardation plate 25 are used regardless of the birefringence of the reflective image modulation elements 26, 49, 52. , 32, 48, and 51 show the same operation as the case.

Fifth Embodiment Next, a reflective projector according to a fifth embodiment will be described.

  FIGS. 26A and 26B are configuration diagrams of the main part of the liquid crystal projector of the fifth embodiment.

  The liquid crystal projector of the fifth embodiment includes a retardation plate 71 as shown in FIGS. 26 (A) and 26 (B).

  Of the components of the liquid crystal projector of the fifth embodiment, the components excluding the retardation plate 71 are the retardation plates of the first embodiment (FIG. 1) or the third embodiment of FIG. The configuration is the same as those other than 24 and 51. Therefore, in the fourth embodiment, detailed description of the constituent elements excluding the phase difference plate 71 is omitted.

  The phase difference plate 71 is an optical element that changes the phase difference of the light according to the angle between the incident direction and the optical axis when transmitting the light. The phase difference plate 71 does not cause a phase difference with respect to light incident in parallel to the optical axis. The phase difference plate 71 is provided at a position where light that has reflected the PBS 23 and passed through the quarter-wave plate 24 or light that has passed through the PBS 44 and passed through the quarter-wave plate 50 is incident vertically. ing. Further, the phase difference plate 71 is assumed to have a relationship of no> ne, where the refractive index is no for ordinary light and the refractive index is ne for extraordinary light.

  Here, in the liquid crystal projector of the fifth embodiment, VA reflection type liquid crystal elements are used as the reflection type image modulation elements 26 and 52. The VA reflection type polarizing element has a relatively small pretilt angle representing the orientation direction with respect to the normal line of the glass substrate, for example, 10 degrees or less.

In general, in the case of a vertically aligned liquid crystal, birefringence occurs when a light beam having an angle with respect to the alignment direction of the liquid crystal is incident. As a method for preventing this, as shown in the fourth embodiment, it is conceivable to use a phase difference plate (optical compensation plate 70 in FIG. 25) having the same optical axis direction and having negative uniaxiality. In this case, sapphire crystal, discotic liquid crystal, optical film, etc. are used as the material of the retardation plate. The difference in refractive index between ordinary light and extraordinary light with respect to light incident perpendicularly to the optical axis of the liquid crystal element is Δn _LC , the thickness of the liquid crystal phase is d _LC , and ordinary light with respect to light incident perpendicularly to the optical axis of the optical compensation plate 70. And the extraordinary light refractive index difference is Δn _OC , and the thickness of the optical compensator 70 is d _OC , the effect of birefringence of the reflective liquid crystal element can be prevented by Δn _LC · d _LC = Δn _op · d _OC be able to.

On the other hand, in the fifth embodiment, as shown in FIG. 27A, Δn _LC · d _LC > Δn _op · d _OC and no> ne (no: refractive index with respect to ordinary light, ne: abnormal A phase difference plate 71 having a refractive index with respect to a light beam is provided.

  As a result, between the PBS 23 and the reflection type image modulation element 26, as shown in FIG. 27B, the quarter wavelength plate 24 having the optical axis in the Y-axis direction and the optical axis in the Z-axis direction are used. , Substantially the same operation as when there is the phase difference plate 25 satisfying no <ne (the same configuration as in the first embodiment).

  Further, between the PBS 44 and the reflective image modulation element 52, as shown in FIG. 27B, a quarter wavelength plate 50 having an optical axis in the Y-axis direction, an optical axis in the X-axis direction, The operation is almost the same as in the case where there is the phase difference plate 51 (the same configuration as in FIG. 19 of the third embodiment) where no <ne.

As described in the first embodiment, the phase difference plates 25 and 51 are
0.16λ <Δn × d <0.35λ
It is preferable to satisfy the relationship. Here, Δn is a refractive index difference with respect to light incident perpendicularly to the optical axes of the retardation plates 25 and 51, and d is a thickness of the retardation plates 25 and 51 (distance in the Z-axis direction or X-axis direction). .

Therefore, in the fifth embodiment, the retardation film 71 and the reflective liquid crystal elements 26 and 52 are:
0.16λ <Δn _LC · d _LC −Δn _op · d _OC <0.35λ
It is preferable to satisfy.

Sixth Embodiment Next, a reflective projector according to a sixth embodiment will be described.

  FIG. 28A and FIG. 28B are configuration diagrams of a main part of a liquid crystal projector of the sixth embodiment.

  The liquid crystal projector of the sixth embodiment includes a retardation plate 72 as shown in FIGS. 28 (A) and 28 (B).

  Of the components of the liquid crystal projector of the sixth embodiment, the components other than the retardation plate 72 are the retardation plates of the second embodiment (FIG. 14) or the third embodiment of FIG. The configuration is the same as that other than 31 and 51. Therefore, in the fourth embodiment, detailed description of the components other than the phase difference plate 72 is omitted.

  The phase difference plate 72 is an optical element that changes the phase difference of the light according to the angle between the incident direction and the optical axis when transmitting the light. The phase difference plate 72 does not cause a phase difference with respect to light incident parallel to the optical axis. The phase difference plate 72 is provided at a position where light that has reflected the PBS 23 and passed through the quarter-wave plate 32 or light that has passed through the PBS 44 and passed through the quarter-wave plate 50 is incident vertically. ing. Further, the phase difference plate 72 has a relationship of no> ne, where the refractive index is no for ordinary light and the refractive index is ne for extraordinary light.

  Here, in the liquid crystal projector according to the sixth embodiment, VA reflection type liquid crystal elements are used as the reflection type image modulation elements 26 and 52. The VA reflection type polarizing element has a relatively small pretilt angle representing the orientation direction with respect to the normal line of the glass substrate, for example, 10 degrees or less.

In general, in the case of a vertically aligned liquid crystal, birefringence occurs when a light beam having an angle with respect to the alignment direction of the liquid crystal is incident. As a method for preventing this, Δn _LC · d _LC = Δn _op · d An optical compensation plate 70 (FIG. 25) having an _OC condition may be provided.

In contrast, in the sixth embodiment, as shown in FIG. 29A, Δn _LC · d _LC <Δn _op · d _OC , where no> ne (no: refractive index with respect to ordinary light, ne: abnormal) A phase difference plate 72 to be a refractive index for a light beam) is installed.

  As a result, between the PBS 23 and the reflective image modulation element 26, as shown in FIG. 29B, the quarter wavelength plate 31 having the optical axis in the X-axis direction and the optical axis in the Z-axis direction are used. , No> ne, the same effect as in the case where there is the phase difference plate 32 (the same configuration as in the second embodiment) is exhibited.

Further, between the PBS 44 and the reflective image modulation element 52, as shown in FIG. 29B, a quarter wavelength plate 50 having an optical axis in the Z direction, an optical axis in the X axis direction, and no. The operation is almost the same as in the case where there is the phase difference plate 51 satisfying> ne (the same configuration as in FIG. 24 of the third embodiment).
As described in the first embodiment, the phase difference plates 31 and 51 are
0.16λ <Δn × d <0.35λ
It is preferable to satisfy the relationship. Here, Δn is a refractive index difference with respect to light incident perpendicularly to the optical axes of the phase difference plates 31 and 51, and d is a thickness of the phase difference plates 31 and 51 (distance in the Z-axis direction or X-axis direction). .

Therefore, in the sixth embodiment, the retardation film 72 and the reflective liquid crystal elements 26 and 52 are:
0.16λ <Δn _op · d _OC −Δn _LC · d _LC <0.35λ
It is preferable to satisfy.

Seventh Embodiment Next, a reflective projector according to a seventh embodiment will be described.

  FIGS. 30A and 30B are configuration diagrams of a main part of a liquid crystal projector according to the seventh embodiment.

  The liquid crystal projector of the seventh embodiment includes a biaxial retardation plate 73 as shown in FIGS. 30 (A) and 30 (B).

  Of the constituent elements of the liquid crystal projector of the seventh embodiment, the constituent elements other than the biaxial retardation plate 73 are the same as those in the first embodiment (FIG. 1) or the third embodiment shown in FIG. The configuration is the same as the configuration other than the phase difference plates 24 and 51. Therefore, in the seventh embodiment, detailed description of the constituent elements excluding the biaxial retardation film 73 is omitted.

  The biaxial phase difference plate 73 is a flat plate shape, and is a biaxial phase difference plate in which two optical axes that cause a phase difference exist in the in-plane direction of the main surface and in the vertical direction of the main surface. The biaxial retardation plate 73 is positioned at a position where light that has reflected the PBS 23 and passed through the quarter-wave plate 32 or light that has passed through the PBS 44 and passed through the quarter-wave plate 50 is vertically incident. Is provided.

  In the seventh embodiment, VA reflection type liquid crystal elements are used as the reflection type image modulation elements 26 and 52. Note that, as shown in FIG. 31, in the VA reflective polarizing element, the pretilt angle representing the optical axis of the liquid crystal molecules with respect to the normal line of the glass substrate is θtilt.

The biaxial retardation film 73, the refractive index of the two orthogonal directions _n x in the main _{surface, n y (n x> n} y), the refractive index in the thickness direction of the biaxial retardation film 73 _{n z,} LCD The refractive index difference between ordinary light and extraordinary light incident perpendicularly to the optical axis of the element is Δn _LC , the thickness of the reflection type image modulation elements 26 and 52 is d _LC , and the thickness of the biaxial retardation plate 73 is d _OC. Then, the biaxial retardation film 73 has the conditions as shown in the following formulas (11) and (12).
_{(N x -n y) · d} OC ≧ Δn LC · d LC · sin 2 (θ tilt) ... (11)
_{(N x -n Z) · d} OC = Δn LC · d LC -C (C> 0) ... (12)

Further, the direction of the slow axis with respect to the light perpendicularly incident on the biaxial retardation plate 73 and the direction of the slow axis with respect to the light perpendicularly incident on the reflection type image modulation elements 26 and 52 are orthogonalized.
By setting left side = right side to equation (11), it is possible to cancel the phase difference in the in-plane direction.

  If the left side is greater than the right side, even if there is an optical variation or unevenness of the biaxial retardation plate 73 itself, a voltage is applied to the reflective image modulation elements 26 and 52 to thereby display black images. The pretilt angle of the liquid crystal molecules can be adjusted, and a high-quality image with high contrast can be easily provided.

  In the equation (12), when C = 0, it is possible to cancel the phase difference in the optical axis direction and cancel the influence of the birefringence of the liquid crystal on the light beam.

  However, in the seventh embodiment, C> 0. Accordingly, the biaxial retardation plate 73 and the VA reflection type image modulation elements 26 and 52 have an optical axis approximately in the optical axis direction, and ne> no (no: refractive index with respect to the normal line, ne: abnormal. It can be regarded as almost equivalent to the phase difference plates 25 and 51 that are (refractive index to light).

As described in the first embodiment, the phase difference plates 25 and 51 are
0.16λ <Δn × d <0.35λ
It is preferable to satisfy the relationship. Here, Δn is a refractive index difference with respect to light incident perpendicularly to the optical axes of the retardation plates 25 and 51, and d is a thickness (distance in the Z-axis direction) of the retardation plates 25 and 51.

Therefore, in the seventh embodiment, the retardation film 73 and the reflective liquid crystal elements 26 and 52 are:
0.16λ <C <0.35λ (where C = Δn _LC · d _LC − (n _x −n _Z ) · d _OC )
It is preferable to satisfy.

Further, the refractive index of the PBSs 23 and 44 is about 1.84, the refractive index of the quarter-wave plates 24 and 50 is about 1.62, and the maximum refractive index of extraordinary light of the projection type image modulation elements 26 and 52 is 1.63. When the refractive index of ordinary light is 1.49 and the pretilt angle is 15 degrees, the contrast becomes maximum near C = 140 nm. The retardation value of the retardation plate 73 at that time is
(N _x n _y ) · d _OC ≧ 2 nm
(N _x n _Z ) · d _OC ≈ 80 nm
The degree is appropriate.

  In the seventh embodiment, the PBSs 23 and 44, the quarter-wave plates 24 and 50, and the biaxial retardation plate 73 are provided separately. However, if the PBSs 23 and 44 and the quarter-wave plates 24 and 50 are fixed, the surface reflection is reduced, thereby realizing an illumination device with higher contrast. Similarly, the PBSs 23 and 44, the quarter wave plates 24 and 50, and the biaxial retardation plate 73 may be fixed. As a more optimal method, the PBSs 23 and 44 and the quarter-wave plates 24 and 50 are fixed, and the biaxial retardation plate 73 is parallel to the XY plane (or YZ plane). It is preferable to have a mechanism that rotates while maintaining. By doing this, even if the direction of the optical axis of the quarter-wave plates 24 and 50 is deviated from the target direction due to the influence of manufacturing error, the biaxial retardation plate 73 is rotated to make it more Conditions with high contrast can be easily realized.

(Other)
As described above, an example in which the present invention is applied to a reflective liquid crystal projector has been described. However, the present invention can be applied not only to a reflection type liquid crystal projector but also to any apparatus as long as it is an optical system that separates S-polarized light and P-polarized light.

  In the above embodiment, the angle between the incident / exiting surface and the reflecting surface of the polarizing beam splitter is 45 degrees, but the present invention is not limited to this, and a polarizing beam splitter other than 45 degrees may be used. .

  Further, most of the quarter-wave plate and the retardation plate have a structure obtained by stretching a polymer material or a structure using a crystal having birefringence such as quartz. However, in the present invention, a quarter wavelength plate and a retardation plate having a structure composed of a plurality of dielectric multilayer films having different refractive indexes, or a structure in which the refractive index is periodically changed continuously by hologram exposure or the like are used. May be.

It is a block diagram of the optical system of the reflection type liquid crystal projector of 1st Embodiment. It is a block diagram of the principal part of 1st Embodiment. It is the figure which showed the light ray and the polar angle and azimuth which were reflected by the beam splitter. It is a figure which shows the polarization direction of each light ray when the PS separation surface of a beam splitter is seen from the direction of Z> 0. It is the figure which showed the optical path of the light which reflects a beam splitter. It is the figure which showed typically what projected the S polarization component of the incident light of the beam splitter of FIG. 5 on XY plane. It is a figure which shows the angle when the S polarization with respect to PS separation surface of a beam splitter is projected on XY plane about the light ray L1-light ray L4. It is the figure which showed the angle | corner showing the angle when the S polarization | polarized-light with respect to PS separation surface of a beam splitter is projected on XY plane about the light ray whose polar angle is 10 degree | times. For the light beam L1 (Φ = 45 degrees), the position of the 1/4 wavelength plate before the first incidence (Z1), the position after the first transmission of the 1/4 wavelength plate (Z2), and the position of the 1/4 wavelength plate It is the figure before the 2nd incidence (Z3)-> It is the figure which showed the change of the polarization state in each position of the position after the 2nd transmission of a quarter wavelength plate. For the light beam L2 (Φ = 135 degrees), the position of the quarter-wave plate before the first incidence (Z1), the position after the first transmission of the quarter-wave plate (Z2), and the position of the quarter-wave plate It is the figure before the 2nd incidence (Z3)-> It is the figure which showed the change of the polarization state in each position of the position after the 2nd transmission of a quarter wavelength plate. For the light beam L3 (Φ = 225 degrees), the position of the 1/4 wavelength plate before the first incidence (Z1), the position after the first transmission of the 1/4 wavelength plate (Z2), and the position of the 1/4 wavelength plate It is the figure before the 2nd incidence (Z3)-> It is the figure which showed the change of the polarization state in each position of the position after the 2nd transmission of a quarter wavelength plate. For the light beam L4 (Φ = 315 degrees), the position of the quarter-wave plate before the first incidence (Z1), the position after the first transmission of the quarter-wave plate (Z2), and the position of the quarter-wave plate It is the figure before the 2nd incidence (Z3)-> It is the figure which showed the change of the polarization state in each position of the position after the 2nd transmission of a quarter wavelength plate. It is the figure which showed the relationship between (DELTA) n * d of a phase difference plate, and the relative value of contrast ratio. It is a block diagram of the principal part of the reflection type liquid crystal projector of 2nd Embodiment. For the light beam L1 (Φ = 45 degrees) of the second embodiment, the position of the quarter-wave plate before the first incidence (Z1) and the position after the first transmission of the quarter-wave plate (Z2) It is the figure which showed the change of the polarization state in each position of the position (Z3) before the 2nd incidence of the 1/4 wavelength plate-> the position after the 2nd transmission of the 1/4 wavelength plate. It is a block diagram of the optical system of the reflective liquid crystal projector of 3rd Embodiment. (A) is a figure which shows the optical path of the light which permeate | transmits a beam splitter, (B) is what projected the P polarization component of the incident light of the beam splitter of (A) on the YZ plane typically. FIG. It is a figure which shows the angle when the P polarization | polarized-light with respect to PS separation surface of a beam splitter is projected on the YZ plane about the light ray L5-light ray L8. It is a block diagram of the principal part of 3rd Embodiment. For the light beam L5 (Φ = 45 degrees), the position of the 1/4 wavelength plate before the first incidence (Z1), the position after the first transmission of the 1/4 wavelength plate (Z2), and the position of the 1/4 wavelength plate It is the figure before the 2nd incidence (Z3)-> It is the figure which showed the change of the polarization state in each position of the position after the 2nd transmission of a quarter wavelength plate. For the light beam L6 (Φ = 135 degrees), the position of the quarter-wave plate before the first incidence (Z1), the position after the first transmission of the quarter-wave plate (Z2), and the position of the quarter-wave plate It is the figure before the 2nd incidence (Z3)-> It is the figure which showed the change of the polarization state in each position of the position after the 2nd transmission of a quarter wavelength plate. For the light beam L7 (Φ = 225 degrees), the position of the quarter-wave plate before the first incidence (Z1), the position after the first transmission of the quarter-wave plate (Z2), and the position of the quarter-wave plate It is the figure before the 2nd incidence (Z3)-> It is the figure which showed the change of the polarization state in each position of the position after the 2nd transmission of a quarter wavelength plate. For the light beam L8 (Φ = 315 degrees), the position of the 1/4 wavelength plate before the first incidence (Z1), the position after the first transmission of the 1/4 wavelength plate (Z2), and the position of the 1/4 wavelength plate It is the figure before the 2nd incidence (Z3)-> It is the figure which showed the change of the polarization state in each position of the position after the 2nd transmission of a quarter wavelength plate. It is a block diagram of the principal part of the other structural example of 3rd Embodiment. It is a principal part block diagram of the reflection type liquid crystal projector for demonstrating 4th Embodiment. It is a principal part block diagram of the reflection type liquid crystal projector for demonstrating 5th Embodiment. It is a figure for demonstrating the phase difference plate of 5th Embodiment. It is a principal part block diagram of the reflection type liquid crystal projector for demonstrating 6th Embodiment. It is a figure for demonstrating the phase difference plate of 7th Embodiment. It is a principal part block diagram of the reflection type liquid crystal projector for demonstrating 7th Embodiment. It is a figure which shows the pretilt angle showing the optical axis of a liquid crystal molecule. It is a schematic diagram which shows the device structure of the liquid crystal element vicinity in the conventional projection type image display apparatus. It is a figure which shows the reflected light path of the beam splitter in the conventional projection type image display apparatus. It is a figure for demonstrating the optical compensation method which provides a quarter wavelength plate between PBS and a reflection type liquid crystal element.

Explanation of symbols

  10, 40 Reflective projector, 24, 31, 47, 50 1/4 wavelength plate, 25, 32, 48, 51 Retardation plate, 26, 49, 52 Reflective image modulator

Claims (37)

A polarization beam splitter having a light separation surface that reflects polarized light in a predetermined direction and transmits polarized light in a direction orthogonal to the reflected polarization direction;
A quarter-wave plate disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident;
A phase difference plate that is disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident, and that generates a phase difference corresponding to the angle of the incident light with respect to the optical axis, with respect to the incident light;
The three-dimensional space is represented by the coordinates of the X, Y, and Z axes. The X axis is the direction perpendicular to the incident surface of the polarization beam splitter, the Z axis is parallel to the X axis, and the light beam is separated by the polarization beam splitter. When the direction parallel to the light beam reflected by the surface and the Y-axis is the direction perpendicular to the X-axis and the Z-axis, the light separation surface of the polarization beam splitter is perpendicular to the plane formed by the X-axis and the Z-axis. Having a predetermined angle with respect to the X axis and the Z axis;
The optical axis of the quarter wave plate is parallel to the Y axis,
The optical axis of the retardation plate is parallel to the optical axis,
Further, the phase difference plate, than the refractive index n _o for ordinary ray, optical apparatus, wherein the refractive index n _e for extraordinary ray is large. The retardation plate has the following formula (1) when Δn is a refractive index difference between an ordinary ray and an extraordinary ray with respect to light incident perpendicularly to the optical axis, d is a thickness, and λ is a wavelength of incident light. The optical device according to claim 1, wherein the optical device is satisfied.
0.16 × λ <Δn × d <0.35 × λ (1) The optical apparatus according to claim 1, wherein any two or all of the polarizing beam splitter, the quarter-wave plate, and the retardation plate are optically integrated. The quarter-wave plate and / or the retardation plate have a structure composed of a plurality of dielectric multilayer films having different refractive indexes, or a structure in which the refractive index is periodically and continuously changed. Item 4. The optical device according to Item 1. A polarization beam splitter having a light separation surface that reflects polarized light in a predetermined direction and transmits polarized light in a direction orthogonal to the reflected polarization direction;
A quarter-wave plate disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident;
A phase difference plate that is disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident, and that generates a phase difference corresponding to the angle of the incident light with respect to the optical axis, with respect to the incident light;
The three-dimensional space is represented by the coordinates of the X, Y, and Z axes. The X axis is the direction perpendicular to the incident surface of the polarization beam splitter, the Z axis is parallel to the X axis, and the light beam is separated by the polarization beam splitter. When the direction parallel to the light beam reflected by the surface and the Y-axis is the direction perpendicular to the X-axis and the Z-axis, the light separation surface of the polarization beam splitter is perpendicular to the plane formed by the X-axis and the Z-axis. Having a predetermined angle with respect to the X axis and the Z axis;
The optical axis of the ¼ wavelength plate is perpendicular to the Y axis and perpendicular to the optical axis,
The optical axis of the retardation plate is parallel to the optical axis,
Further, the phase difference plate, an optical device, wherein the refractive index n _o for the ordinary ray than the refractive index n _e for extraordinary ray is large. The retardation plate has the following formula (2), where Δn is the refractive index difference between the ordinary ray and extraordinary ray with respect to the light incident perpendicular to the optical axis, d is the thickness, and λ is the wavelength of the incident light. The optical device according to claim 5, wherein the optical device is satisfied.
0.16 × λ <Δn × d <0.35 × λ (2) The optical apparatus according to claim 5, wherein any two or all of the polarizing beam splitter, the quarter-wave plate, and the retardation plate are optically integrated. The quarter-wave plate and / or the retardation plate have a structure composed of a plurality of dielectric multilayer films having different refractive indexes, or a structure in which the refractive index is periodically and continuously changed. Item 6. The optical device according to Item 5. A light emitting means for emitting light;
A polarizing beam splitter having a light separation surface that reflects an S-polarized component of incident light and transmits a P-polarized component of incident light;
A quarter-wave plate disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident;
A phase difference plate that is disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident, and that causes a phase difference corresponding to an angle of incident light with respect to an optical axis, to the incident light;
A light modulation means for reflecting the direction of polarization of incident light according to an image signal and reflecting it;
A projection optical system for projecting incident light to the outside,
The light emitted from the light emitting means reflects or transmits the light separation surface of the polarizing beam splitter, passes through the quarter wavelength plate and the phase difference plate, and is irradiated to the light modulating means.
The light reflected by the light modulation means is transmitted through the quarter-wave plate and the phase difference plate, is transmitted or reflected through the light separation surface of the polarization beam splitter, and is incident on the irradiation means.
The three-dimensional space is represented by the coordinates of the X, Y, and Z axes. The X axis is the direction perpendicular to the incident surface of the polarization beam splitter, the Z axis is parallel to the X axis, and the light beam is separated by the polarization beam splitter. When the direction parallel to the light beam reflected by the surface and the Y-axis is the direction perpendicular to the X-axis and the Z-axis, the light separation surface of the polarization beam splitter is perpendicular to the plane formed by the X-axis and the Z-axis. Having a predetermined angle with respect to the X axis and the Z axis;
The optical axis of the quarter wave plate is parallel to the Y axis,
The optical axis of the retardation plate is parallel to the optical axis,
Further, the phase difference plate, than the refractive index n _o for the ordinary ray, the projection type image display apparatus characterized by a large refractive index n _e for extraordinary ray. The retardation plate has the following formula (3), where Δn is the refractive index difference between the ordinary ray and extraordinary ray with respect to the light incident perpendicular to the optical axis, d is the thickness, and λ is the wavelength of the incident light. The projection type image display device according to claim 9, wherein:
0.16 × λ <Δn × d <0.35 × λ (3) The projection image display apparatus according to claim 9, wherein any two or all of the polarizing beam splitter, the quarter-wave plate, and the retardation plate are optically integrated. The quarter-wave plate and / or the retardation plate have a structure composed of a plurality of dielectric multilayer films having different refractive indexes, or a structure in which the refractive index is periodically and continuously changed. Item 10. A projection type image display device according to Item 9. A light emitting means for emitting light;
A polarizing beam splitter having a light separation surface that reflects an S-polarized component of incident light and transmits a P-polarized component of incident light;
A quarter-wave plate disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident;
A phase difference plate that is disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident, and that causes a phase difference corresponding to an angle of incident light with respect to an optical axis, to the incident light;
A light modulation means for reflecting the direction of polarization of incident light according to an image signal and reflecting it;
A projection optical system for projecting incident light to the outside,
The light emitted from the light emitting means reflects or transmits the light separation surface of the polarizing beam splitter, passes through the quarter wavelength plate and the phase difference plate, and is irradiated to the light modulating means.
The light emitted from the light modulation means is transmitted through the quarter-wave plate and the phase difference plate, is transmitted or reflected by the light separation surface of the polarization beam splitter, and is incident on the irradiation means.
The three-dimensional space is represented by the coordinates of the X, Y, and Z axes. The X axis is the direction perpendicular to the incident surface of the polarization beam splitter, the Z axis is parallel to the X axis, and the light beam is separated by the polarization beam splitter. When the direction parallel to the light beam reflected by the surface and the Y-axis is the direction perpendicular to the X-axis and the Z-axis, the light separation surface of the polarization beam splitter is perpendicular to the plane formed by the X-axis and the Z-axis. Having a predetermined angle with respect to the X axis and the Z axis;
The optical axis of the ¼ wavelength plate is perpendicular to the Y axis and perpendicular to the optical axis,
The optical axis of the retardation plate is parallel to the optical axis,
Further, the phase difference plate, a projection type image display apparatus, wherein the refractive index n _o for the ordinary ray than the refractive index n _e for extraordinary ray is large. The retardation plate is expressed by the following formula (4), where Δn is a refractive index difference between an ordinary ray and an extraordinary ray with respect to light incident perpendicularly to the optical axis, d is a thickness, and λ is a wavelength of incident light. The projection type image display device according to claim 13, wherein:
0.16 × λ <Δn × d <0.35 × λ (4) The projection image display apparatus according to claim 13, wherein any two or all of the polarizing beam splitter, the quarter-wave plate, and the retardation plate are optically integrated. The quarter-wave plate and / or the retardation plate have a structure composed of a plurality of dielectric multilayer films having different refractive indexes, or a structure in which the refractive index is periodically and continuously changed. Item 14. A projection type image display device according to Item 13. A light emitting means for emitting light;
A polarizing beam splitter having a light separation surface that reflects an S-polarized component of incident light and transmits a P-polarized component of incident light;
A quarter-wave plate disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident;
A phase difference plate that is disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident, and that causes a phase difference corresponding to an angle of incident light with respect to an optical axis, to the incident light;
A light modulation means for reflecting the direction of polarization of incident light according to an image signal and reflecting it;
A projection optical system for projecting incident light to the outside,
The light emitted from the light emitting means reflects or transmits the light separation surface of the polarizing beam splitter, passes through the quarter wavelength plate and the phase difference plate, and is irradiated to the light modulating means.
The light reflected by the light modulation means is transmitted through the quarter-wave plate and the phase difference plate, is transmitted or reflected through the light separation surface of the polarization beam splitter, and is incident on the irradiation means.
The three-dimensional space is represented by the coordinates of the X, Y, and Z axes. The X axis is the direction perpendicular to the incident surface of the polarization beam splitter, the Z axis is parallel to the X axis, and the light beam is separated by the polarization beam splitter. When the direction parallel to the light beam reflected by the surface and the Y-axis is the direction perpendicular to the X-axis and the Z-axis, the light separation surface of the polarization beam splitter is perpendicular to the plane formed by the X-axis and the Z-axis. Having a predetermined angle with respect to the X axis and the Z axis;
The optical axis of the quarter wave plate is parallel to the Y axis,
When the optical action of the retardation plate and the optical modulation element is combined, the direction of the combined optical axis is the optical axis direction and exhibits positive uniaxiality. Type image display device. 18. The projection type according to claim 17, wherein a retardation of a combination of optical actions of the retardation plate and the optical modulation element is larger than 0.16 × λ and smaller than 0.35 × λ. Image display device.
Note that λ is the wavelength of light. The light modulating means is a VA (Vrtically Aligned) reflective liquid crystal element,
The optical axis of the retardation plate is parallel to the optical axis,
The retardation plate, than the refractive index n _e for extraordinary ray, projection type image display apparatus according to claim 17, wherein the refractive index n _o is greater for the ordinary ray. The refractive index difference between ordinary and extraordinary rays with respect to light incident perpendicular to the optical axis of the reflective liquid crystal element is Δn _LC , the thickness of the liquid crystal layer of the reflective liquid crystal element is d _LC , and the retardation plate When the refractive index difference between the ordinary ray and the extraordinary ray with respect to the light incident perpendicularly to the optical axis is Δn _OC and the thickness of the retardation plate is d _OC , the relationship of the following formula (5A) is satisfied. The projection type image display apparatus according to claim 19.
Δn _LC × d _LC > Δn _OC × d _OC (5A) The projection type image display device according to claim 20, wherein the phase difference plate satisfies a relationship of the following formula (5B).
0.16 × λ <Δn _LC × d _LC −Δn _OC × d _OC <0.35 × λ (5B)
Note that λ is the wavelength of light. The quarter-wave plate and / or the retardation plate have a structure composed of a plurality of dielectric multilayer films having different refractive indexes, or a structure in which the refractive index is periodically and continuously changed. Item 18. A projection type image display device according to Item 17. The optical apparatus according to claim 17, wherein any two or all of the polarizing beam splitter, the quarter-wave plate, and the retardation plate are optically integrated. A light emitting means for emitting light;
A polarizing beam splitter having a light separation surface that reflects an S-polarized component of incident light and transmits a P-polarized component of incident light;
A quarter-wave plate disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident;
A phase difference plate that is disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident, and that causes a phase difference corresponding to an angle of incident light with respect to an optical axis, to the incident light;
A light modulation means for reflecting the direction of polarization of incident light according to an image signal and reflecting it;
A projection optical system for projecting incident light to the outside,
The light emitted from the light emitting means reflects or transmits the light separation surface of the polarizing beam splitter, passes through the quarter wavelength plate and the phase difference plate, and is irradiated to the light modulating means.
The light reflected by the light modulation means is transmitted through the quarter-wave plate and the phase difference plate, is transmitted or reflected through the light separation surface of the polarization beam splitter, and is incident on the irradiation means.
The three-dimensional space is represented by the coordinates of the X, Y, and Z axes. The X axis is the direction perpendicular to the incident surface of the polarization beam splitter, the Z axis is parallel to the X axis, and the light beam is separated by the polarization beam splitter. When the direction parallel to the light beam reflected by the surface and the Y-axis is the direction perpendicular to the X-axis and the Z-axis, the light separation surface of the polarization beam splitter is perpendicular to the plane formed by the X-axis and the Z-axis. Having a predetermined angle with respect to the X axis and the Z axis;
The optical axis of the ¼ wavelength plate is perpendicular to the Y axis and perpendicular to the optical axis,
When the optical action of the retardation plate and the optical modulation element is combined, the direction of the combined optical axis is the optical axis direction and exhibits negative uniaxiality. Type image display device. 25. The projection type according to claim 24, wherein a retardation of a combination of optical actions of the retardation plate and the optical modulation element is larger than 0.16 × λ and smaller than 0.35 × λ. Image display device.
Note that λ is the wavelength of light. The light modulating means is a VA (Vrtically Aligned) reflective liquid crystal element,
The optical axis of the retardation plate is parallel to the optical axis,
The retardation plate, than the refractive index n _e for extraordinary ray, projection type image display apparatus according to claim 24, wherein the refractive index n _o is greater for the ordinary ray. The refractive index difference between ordinary and extraordinary rays with respect to light incident perpendicular to the optical axis of the reflective liquid crystal element is Δn _LC , the thickness of the liquid crystal layer of the reflective liquid crystal element is d _LC , and the retardation plate When the refractive index difference between an ordinary ray and an extraordinary ray with respect to light incident perpendicularly to the optical axis is Δn _OC , and the thickness of the retardation plate is d _OC , the relationship of the following formula (6A) is satisfied. 27. The projection type image display apparatus according to claim 26.
Δn _LC × d _LC <Δn _OC × d _OC (6A) The projection type image display device according to claim 27, wherein the phase difference plate satisfies a relationship of the following formula (6B).
0.16 × λ <Δn _OC × d _OC −Δn _LC × d _LC <0.35 × λ (6B)
Note that λ is the wavelength of light. The quarter-wave plate and / or the retardation plate have a structure composed of a plurality of dielectric multilayer films having different refractive indexes, or a structure in which the refractive index is periodically and continuously changed. Item 25. A projection type image display device according to Item 24. The optical apparatus according to claim 24, wherein any two or all of the polarizing beam splitter, the quarter-wave plate, and the retardation plate are optically integrated. A light emitting means for emitting light;
A polarizing beam splitter having a light separation surface that reflects the S-polarized component of incident light and transmits the P-polarized component of incident light;
A quarter-wave plate disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident;
A phase difference plate that is disposed at a position where light reflected or transmitted by the polarizing beam splitter is incident, and that causes a phase difference corresponding to an angle of incident light with respect to an optical axis, to the incident light;
A reflective liquid crystal element of a VA (Vrtically Aligned) system that reflects and changes the direction of polarization of incident light according to an image signal;
A projection optical system for projecting incident light to the outside,
The light emitted from the light emitting means reflects or transmits the light separation surface of the polarizing beam splitter, passes through the quarter-wave plate and the phase difference plate, and is applied to the reflective liquid crystal element.
The light emitted from the reflective liquid crystal element is transmitted through the quarter-wave plate and retardation plate, is transmitted or reflected through the light separation surface of the polarizing beam splitter, and is incident on the irradiation unit.
The three-dimensional space is represented by the coordinates of the X, Y, and Z axes. The X axis is the direction perpendicular to the plane of incidence of the polarizing beam splitter, and the Z axis is parallel to the X axis. When the direction parallel to the light beam reflected by the surface and the Y-axis is the direction perpendicular to the X-axis and the Z-axis, the light separation surface of the polarizing beam splitter is perpendicular to the plane formed by the X-axis and the Z-axis. Having a predetermined angle with respect to the X axis and the Z axis;
The optical axis of the ¼ wavelength plate is perpendicular to the Y axis and perpendicular to the optical axis,
The retardation plate is a flat plate,
Two orthogonal directions of the refractive indices n _x in the major surface of the retardation _{plate, n y (n x> n} y), the refractive index in the thickness direction n _z, perpendicular to the optical axis of the reflective liquid crystal device The refractive index difference between ordinary light and extraordinary light of incident light is Δn _LC , the thickness of the reflective liquid crystal element is d _LC , the thickness of the retardation plate is d _OC , and the normal line of the glass substrate of the reflective liquid crystal element When the pretilt angle representing the optical axis of the liquid crystal molecules with respect to is θ _tilt , the retardation plate satisfies the condition of the following formula (7).
_{(N x -n Z) · d} OC = Δn LC · d LC -C ... (7)
In Expression (8), C is a positive constant. The projection type image display device according to claim 31, wherein the retardation plate satisfies a condition of the following formula (8).
_{(N x -n y) · d} OC ≧ Δn LC · d LC · sin 2 (θ tilt) ... (8) The direction of the slow axis with respect to the light perpendicularly incident on the retardation plate and the direction of the slow axis with respect to the light perpendicularly incident on the reflective liquid crystal element are orthogonal to each other. Projection type image display device. 34. The projection type image display device according to claim 33, wherein C in the formula (8) satisfies the relationship of the following formula (9).
0.16 × λ <C <0.35 × λ (9)
In equation (9), λ is the wavelength of light. 32. The optical device according to claim 31, wherein any two or all of the polarizing beam splitter, the quarter-wave plate, and the retardation plate are optically integrated. 36. The optical apparatus according to claim 35, further comprising a rotating unit that rotates the retardation plate in an in-plane direction of the main surface. The quarter-wave plate and / or the retardation plate have a structure composed of a plurality of dielectric multilayer films having different refractive indexes, or a structure in which the refractive index is periodically and continuously changed. Item 32. The projection type image display device according to Item 31.

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