JP2009229804A - Optical component, optical unit and display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical component that performs optical compensation with high precision even with simple constitution, and to provide an optical unit and a display. <P>SOLUTION: The optical component includes: reflection type optical modulating elements 11R, 11G and 11B; and an optical compensating element 14 disposed on light incidence/projection sides of the reflection type optical modulating elements 11R, 11G and 11B. The optical compensating element 14 is disposed obliquely in a direction wherein a phase difference of liquid crystal is canceled to a plane perpendicular to a light axis. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical component, an optical unit, and a display device that include a reflective light modulation element that modulates and reflects incident light with liquid crystal.

  Conventionally, a display device (projection-type image display device) including an illumination device, a light modulation element illuminated by the illumination device, and a projection lens that forms an image of the light modulation element has been proposed. Among these, discharge lamps are used as light sources, and transmissive liquid crystal elements and DMDs (digital micromirror devices) are often used as image modulation elements. Various improvements have been made in both devices and optical systems. Yes. Furthermore, in recent years, a projection type image display apparatus using a reflective liquid crystal element with higher resolution has been put into practical use.

  Here, 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 corresponds to each color. Illuminate the light modulation element. Then, after being modulated by the light modulation element, each color modulated light is synthesized by a color synthesizing means such as a cross prism and projected onto a screen by a projection lens.

  FIG. 16 is a schematic diagram illustrating a schematic structure of the projection type image display apparatus. In this projection type image display device, the light emitting portion of the light source 1 such as an ultra high pressure mercury lamp is disposed at the focal position of the reflector, and the light emitted from the light source 1 is reflected by the reflector to become substantially parallel light. The light enters the first integrator lens 2 and the second integrator lens 3. These integrator lenses 2 and 3 have an effect of making the illuminance of light incident on the reflective light modulation elements 11R, 11G, and 11B, which are liquid crystal display devices, uniform.

  The light beams emitted from the integrator lenses 2 and 3 enter the polarization beam splitter 4 where they are polarized into light having a predetermined polarization direction. The light emitted from the polarization beam splitter 4 enters the condenser lens 5 and is condensed. The white light emitted from the condenser lens 5 is separated by the dichroic mirror 6.

  For example, the dichroic mirror 6 transmits light in the red wavelength band, and reflects light in the green wavelength band and the blue wavelength band. The transmitted light in the red wavelength band passes through the reflection mirror 8 and the field lens 9 and then enters the reflection polarizer 10 to illuminate the reflection light modulator 11R.

  On the other hand, the light reflected by the dichroic mirror 6 enters the dichroic mirror 7. Here, light in the blue wavelength band is transmitted and light in the green wavelength band is reflected. The separated light beams are incident on the field lens 9 and the reflective polarizer 10 to illuminate the reflective light modulation elements 11G and 11B.

  Each color light light-modulated by the reflection-type light modulation elements 11G and 11B is incident on the reflection-type polarizer 10 again, and depending on the degree of modulation, part of the light is transmitted and returned to the direction of the light source 1 and part of the light is reflected. The light enters the color synthesis prism 12. The color synthesizing prism 12 is configured to transmit light in the green wavelength band and reflect light in the red and blue wavelength bands, and the light beams of the respective colors are combined and incident on the projection lens 13 and expanded to a predetermined magnification. The image is displayed on a screen (not shown).

  In recent years, in a projection type image projection apparatus, an optical compensation technique using a phase difference element is used to improve contrast characteristics and viewing angle characteristics. For example, in the black luminance correction in the vertically aligned liquid crystal, the liquid crystal molecules are vertically distributed in the non-voltage applied state (black state) in the vertically aligned liquid crystal. Does not cause birefringence. For this reason, the polarization of the light beam that has entered the reflective polarizer and has been converted into the predetermined linearly polarized light is not disturbed, but is incident on and transmitted through the reflective polarizer again, and light does not leak to the screen.

  However, birefringence occurs with light incident on the reflective light modulation element at a predetermined angle, so that the light beam incident on the reflective light modulation element as linearly polarized light becomes elliptically polarized light. Part of the light incident on the polarizer reaches the screen and causes a deterioration in contrast.

  Furthermore, it has been proposed that the liquid crystal molecules be tilted at a predetermined angle (pretilt angle) with respect to the surface of the reflective light modulation element in order to suppress the light distribution disturbance of the liquid crystal molecules due to the transverse electric field and to improve the response speed of the liquid crystal molecules. In this case, the light beam perpendicularly incident on the reflective light modulation element is also disturbed in the polarization state due to birefringence, which causes deterioration of contrast.

  Therefore, various methods have been proposed as a method for compensating for the polarization disturbance described above and realizing an optimum polarization state. For example, a single crystal having birefringence, for example, a method of performing phase difference compensation by placing an optical compensation element such as crystal or sapphire in parallel with the surface of the reflective light modulation element, or a compound film such as a polymer film or a liquid crystal polymer. A method of performing phase difference compensation by placing an organic material having refraction in parallel with the surface of the reflective light modulation element is also considered (see, for example, Patent Documents 1 and 2).

JP 2005-172984 A JP 2007-101864 A

  However, when using a method of processing a single crystal as an optical compensation element, it is necessary to cut out at a predetermined angle with respect to the crystal axis, particularly when trying to compensate in consideration of the pretilt angle of the liquid crystal. (Crystal) is very impractical because it requires very high accuracy for cutting and polishing. Further, if compensation is to be made including a pretilt angle of liquid crystal molecules using a polymer film, it is necessary to assemble a biaxial retardation film or a plurality of retardation films. Although this method can be handled relatively easily, it is difficult to optically compensate at a wide viewing angle. Further, when the liquid crystal polymer is used as a material, there is a problem that the manufacturing process is difficult although the degree of freedom in design is high.

  Therefore, an object of the present invention is to provide an optical component, an optical unit, and a display device that can perform optical compensation with high accuracy even with a simple configuration.

  The present invention is an optical component that includes a reflection type light modulation element that modulates and reflects incident light by liquid crystal and an optical compensation element that is disposed on the light incident / exit side of the reflection type light modulation element. The liquid crystal is arranged so as to be inclined with respect to a plane perpendicular to the axis of light so as to cancel the phase difference of the liquid crystal.

  In the present invention, the phase difference caused by the pretilt angle of the liquid crystal can be compensated by tilting the optical compensation element having the same characteristics as the liquid crystal and having the opposite sign with respect to the plane perpendicular to the optical axis. The tilt angle of the optical compensation element is determined according to the pretilt angle of the liquid crystal, and is, for example, greater than 0 degrees and less than or equal to about 8 degrees.

  Further, this optical compensation element is also arranged so as to rotate in the direction of canceling the phase difference of the liquid crystal around the light axis. Here, an optical compensation element having an in-plane phase difference is used.

  Further, the present invention is an optical unit that divides light emitted from a light source into a plurality of colors, guides the light to a reflective light modulation element corresponding to each color, and synthesizes the light modulated by each reflective light modulation element. In other words, the optical compensation element disposed on the light incident / exit side of the light modulation element is disposed so as to be inclined in a direction that cancels the phase difference of the liquid crystal with respect to a plane perpendicular to the light axis.

  In the present invention, an optical unit that can compensate for a phase difference caused by a pretilt angle of the liquid crystal by tilting an optical compensation element having the same characteristics as the liquid crystal and having an opposite sign with respect to a plane perpendicular to the optical axis can be provided. It becomes like this. The tilt angle of the optical compensation element is determined according to the pretilt angle of the liquid crystal, and is, for example, greater than 0 degrees and less than or equal to about 8 degrees.

  Further, this optical compensation element is also arranged so as to rotate in the direction of canceling the phase difference of the liquid crystal around the light axis. Here, an optical compensation element having an in-plane phase difference is used. The rotation angle of the optical compensation element is, for example, between -5 degrees and 5 degrees.

  The present invention also splits the light emitted from the light source and the light emitted from the light source into a plurality of colors, guides the light to a reflective light modulation element corresponding to each color, and synthesizes the light modulated by each reflective light modulation element. The display device includes an optical unit and a projection optical system that projects the light synthesized by the optical unit. The optical unit includes an optical compensation element on a light incident / exit side of the light modulation element. The liquid crystal is arranged so as to be inclined with respect to a plane perpendicular to the axis of light so as to cancel the phase difference of the liquid crystal.

  According to the present invention, it is possible to provide a display device capable of compensating for the phase difference caused by the pretilt angle of the liquid crystal by tilting the optical compensation element having the same characteristics and the opposite sign as the liquid crystal with respect to the plane perpendicular to the optical axis. It becomes like this. The tilt angle of the optical compensation element is determined according to the pretilt angle of the liquid crystal, and is, for example, greater than 0 degrees and less than or equal to about 8 degrees.

  Further, this optical compensation element is also arranged so as to rotate in the direction of canceling the phase difference of the liquid crystal around the light axis. The rotation angle of the optical compensation element is, for example, between -5 degrees and 5 degrees. Here, an optical compensation element having an in-plane phase difference is used.

  According to the present invention, in an optical component, an optical unit, and a display device using a reflection type light modulation element made of a vertical alignment type liquid crystal, the phase difference of a light beam is controlled with a simple configuration in which the optical compensation element is simply tilted. Thus, the contrast in image display can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Overall configuration of display device>
FIG. 1 is a schematic diagram illustrating the configuration of the display device according to the present embodiment. The display device of the present embodiment is mainly applied as a projection type image display device, and includes a light source 1 such as an ultra-high pressure mercury lamp, and a reflection type light modulation element that modulates light illuminated and illuminated by the light from the light source 1. 11R, 11G, and 11B, a reflective polarizer 10 that realizes a predetermined polarization state, and a projection lens 13 are provided. Between the reflective polarizer 10 and the reflective light modulators 11R, 11G, and 11B, An optical compensation element 14 which is a main configuration is provided.

  Among these, the optical component of the present invention is constituted by the reflection type light modulation elements 11R, 11G, and 11B and the optical compensation element 14, and the optical unit of the present invention spectrally divides the light emitted from the light source 1 into a plurality of colors. An optical system, a reflection-type light modulation element 11R, 11G, 11B corresponding to each color, an optical system for combining the light modulated by each reflection-type light modulation element 11R, 11G, 11B, and an optical compensation element 14. (In this embodiment, the configuration other than the light source 1 in FIG. 1 is an optical unit.)

  The light emitting part of the light source 1 is arranged at the focal position of the reflector, and the light emitted from the light source 1 is reflected by the reflector to become substantially parallel light, and the first fly-eye lens 2 and the second fly-eye lens. 3 is incident. The first fly-eye lens 2 and the second fly-eye lens 3 have the effect of making the illuminance of light incident on the reflection-type light modulation elements 11R, 11G, and 11B later uniform. The light beams emitted from the first and second fly-eye lenses 2 and 3 enter the polarization beam splitter 4 where they are polarized into light having a predetermined polarization direction.

  The light emitted from the polarization beam splitter 4 enters the condenser lens 5 and is condensed. The white light emitted from the condenser lens 5 is separated into each color by a plurality of types of dichroic mirrors 6 arranged in the subsequent stage. For example, the dichroic mirror 6 transmits light in the red wavelength band, and reflects light in the green wavelength band and the blue wavelength band. The transmitted light in the red wavelength band passes through the reflection mirror 8 and the field lens 9 and then enters the reflection polarizer 10 to illuminate the reflection light modulator 11R.

  On the other hand, the light reflected by the dichroic mirror 6 enters the dichroic mirror 7. Here, light in the blue wavelength band is transmitted and light in the green wavelength band is reflected. The light in the green wavelength band reflected by the dichroic mirror 7 enters the field lens 10 and the reflective polarizer 10 and irradiates the reflective light modulation element 11G. Further, the light in the blue wavelength band transmitted through the dichroic mirror 7 is incident on the field lens 9 and the reflective polarizer 10 to illuminate the reflective light modulation element 11B.

  In the present embodiment, liquid crystal elements are used as the reflective light modulation elements 11R, 11G, and 11B, and in particular, a liquid crystal panel using a vertical alignment type liquid crystal is applied. Each color light light-modulated by the reflection-type light modulation elements 11R, 11G, and 11B corresponding to each color is incident on the reflection-type polarizer 10 again, and a part of the light is transmitted and returned to the light source 1 depending on the degree of modulation. A part of the light is reflected and enters the color synthesis prism 12.

  The color synthesizing prism 12 is configured to transmit light in the green wavelength band and reflect light in the red and blue wavelength bands, and the light beams of the respective colors are combined and incident on the projection lens 13 and expanded to a predetermined magnification. The image is displayed on a screen (not shown).

  Here, when there is no optical element having birefringence between the reflection type light modulation elements 11R, 11G, and 11B corresponding to each color and the reflection type polarizer 10, a slight amount of liquid crystal molecules is present even during black display. The polarization state changes depending on the phase difference, and an elliptically polarized component is generated. Therefore, a problem such as a decrease in contrast occurs. Therefore, in the present embodiment, the plate-shaped optical compensation element 14 is disposed between the reflective light modulation elements 11R, 11G, and 11B and the reflective polarizer 10.

  The optical compensation element 14 is arranged in parallel to the same plane as the reflective light modulation elements 11R, 11G, and 11B, so that the phase difference caused by the liquid crystal molecules can be canceled out.

  Further, in the present embodiment, the optical compensation element 14 is disposed in a state inclined at a predetermined angle with respect to a plane perpendicular to the light axis (optical axis), that is, the plane of the reflection type light modulation elements 11R, 11G, and 11B. ing. This tilt can cancel the phase difference caused by the pretilt angle among the phase differences of the liquid crystal. The tilt angle of the optical compensation element 14 is determined according to the pretilt angle of the liquid crystal, and is, for example, greater than 0 degree and less than about 8 degrees.

  In the present embodiment, an optical compensation element 14 having an in-plane phase difference is used as necessary, and the optical compensation element 14 is arranged rotated by a predetermined angle around the optical axis. By this rotation, the phase difference of the liquid crystal can be canceled out. The rotation angle of the optical compensation element 14 is, for example, between -5 degrees and 5 degrees. The optical compensation element 14 having an in-plane retardation may be a layer using an inorganic material laminated structure in addition to the case of using an organic material having birefringence such as a polymer film or a liquid crystal polymer.

  In order to tilt or rotate the optical compensation element 14, the positioning frame member of the optical compensation element 14 is used so that the optical compensation element 14 is fixedly attached to a preset tilt angle or rotation angle, or the optical compensation element with respect to the positioning frame material is used. You may use the mechanism which enables adjustment of the inclination angle of 14 and a rotation angle.

  In the display device of the present embodiment shown in FIG. 1, all the optical compensation elements 14 corresponding to the reflection type light modulation elements 11R, 11G, and 11B of the respective colors are arranged so as to be tilted or rotated. The optical compensation element 14 corresponding to at least one of the colors may be arranged so as to be tilted or rotated.

<Optical unit>
FIG. 2 is a diagram illustrating the appearance of the optical unit. The optical unit 1000U according to the present embodiment includes an optical system that splits light emitted from a light source into a plurality of colors, reflective light modulation elements 11R, 11G, and 11B corresponding to each color, and each reflective light modulation element 11R. , 11G, 11B, and an optical system for synthesizing the light modulated by 11B and 11B. The optical compensation element 14 is packaged as a single member. In the present embodiment, optical components other than the light source shown in FIG. 1 are incorporated in the package in a state where the optical axes are aligned.

  In this optical unit, in this embodiment, the optical compensation element 14 disposed on the light incident / exit side of the reflective light modulators 11R, 11G, and 11B is a surface perpendicular to the optical axis, that is, the reflective light modulator 11R, It arrange | positions in the state inclined by the predetermined angle with respect to the plane of 11G and 11B. This tilt can cancel the phase difference caused by the pretilt angle among the phase differences of the liquid crystal. The tilt angle of the optical compensation element 14 is determined according to the pretilt angle of the liquid crystal, and is, for example, greater than 0 degree and less than about 8 degrees.

  In the optical unit of the present embodiment, an optical compensation element 14 having an in-plane phase difference is used as necessary, and the optical compensation element 14 is arranged with a predetermined angle rotated around the optical axis. By this rotation, the phase difference of the liquid crystal can be canceled out. The rotation angle of the optical compensation element 14 is, for example, between -5 degrees and 5 degrees. The optical compensation element 14 having an in-plane retardation may be a layer using an inorganic material laminated structure in addition to the case of using an organic material having birefringence such as a polymer film or a liquid crystal polymer.

  By using such an optical unit, it is possible to easily commercialize the display device simply by incorporating the optical unit into the housing of the display device when the display device is configured.

<Optical parts>
The optical component according to the present embodiment includes a reflection type light modulation element and an optical compensation element, a tilt adjustment mechanism that can tilt the optical compensation element at a predetermined angle with respect to the reflection type light modulation element, and a surface that can adjust the rotation angle. An internal rotation amount (phase difference amount) adjusting mechanism is provided. The optical component is applied to the display device and the optical unit described above. It should be noted that the present invention can be applied to an optical device that requires optical compensation accuracy even if it is not a display device.

  FIG. 3 is a schematic diagram illustrating the configuration of the optical component according to the present embodiment. The optical component of the present embodiment includes a reflective light modulation element 11 (corresponding to at least one of the reflective light modulation elements 11R, 11G, and 11B in FIG. 1) that modulates and reflects incident light by liquid crystal, and a reflective type. And an optical compensation element 14 disposed on the light incident / exit side of the light modulation element 11, and the optical compensation element 14 is inclined with respect to a plane perpendicular to the light axis to cancel the phase difference of the liquid crystal. Has been. Thus, the optical compensation element 14 is disposed at an inclination, so that the phase difference (birefringence) caused by the liquid crystal of the reflective light modulation element 11 can be canceled. Therefore, an image with high contrast can be displayed by applying the optical component of the present embodiment to a display device.

  Here, an operation capable of canceling the birefringence caused by the liquid crystal of the reflective light modulation element 11 by the optical compensation element 14 in the present embodiment and displaying an image with high contrast will be described.

  In the optical component of this embodiment, a vertical alignment type liquid crystal is used as the liquid crystal of the reflective light modulation element 11. When a liquid crystal having an optical axis in a direction perpendicular to the surface of the reflection type light modulation element 11 is considered, a phase difference is not given to a light ray incident perpendicularly to the surface of the reflection type light modulation element 11.

  However, a phase difference occurs with respect to a light beam incident from an oblique direction, resulting in light leakage during black display and a decrease in contrast. In order to eliminate the phase difference generated with respect to the oblique light beam, a phase difference element having the same characteristics as the liquid crystal and having the opposite sign may be disposed between the reflection type light modulation element 11 and the reflection type polarizer 10.

  If the liquid crystal has an optical axis in a direction perpendicular to the surface of the reflection type light modulation element 11 and has an ideal positive uniaxial characteristic, the phase difference element (optical compensation element) to be arranged has a reflection type light modulation on the optical axis. A negative uniaxial birefringent element having a direction perpendicular to the surface of the element 11 may be used as the optical compensation element 14. Further, from an actual macro viewpoint, even if a biaxial birefringence element is used as the optical compensation element 14, a sufficient optical compensation effect can be expected.

  Here, in general, in the vertical alignment liquid crystal, in order to guide the driving direction of the liquid crystal molecules to a predetermined direction when a driving voltage is applied, the alignment treatment is performed in advance, and even in a state where no voltage is applied, The optical axis of the liquid crystal molecules has an inclination angle (pretilt angle) with respect to the normal of the reflective light modulation element 11. In this case, ideally, if the optical axis of the optical compensation element 14 having the negative one axis described above is also tilted to be equal to the pretilt angle of the liquid crystal molecules, no phase difference is generated regardless of whether the incidence is normal or oblique. Alternatively, the phase difference can be made very small, and the contrast ratio of the image displayed as a result can be increased. In practice, a sufficient optical compensation effect can also be obtained by tilting the biaxial birefringent element.

  In the present embodiment, as the optical compensation element 14 used for the optical component, a mechanical component that is installed at a certain angle θ with respect to the reflective liquid crystal element 11 and performs tilt adjustment and in-plane rotation amount (phase difference amount) adjustment. It has. The optical compensation element 14 is tilted and rotated with respect to the surface of the reflective light modulation element 11 by the tilt adjustment and the in-plane rotation amount (phase difference amount) adjustment mechanism, thereby generating a phase difference corresponding to the pretilt angle of the liquid crystal molecules. Can be canceled out.

  The tilt angle amount of the optical compensation element 14 is determined according to the desired performance depending on the liquid crystal molecule alignment direction of the reflective light modulation element 11. Specifically, for example, it is greater than 0 degree and less than or equal to about 8 degrees. On the other hand, as the tilt angle of the optical compensation element 14 increases, the amount of astigmatism increases, and image quality may be degraded. If the degree of astigmatism with respect to the focal depth is sufficiently small in the calculation, the influence of the tilt angle of the optical compensation element 14 can be ignored. Therefore, in order to provide optical correction for the image quality deterioration on the incident side of the color synthesizing prism 12, a structure that adds a structure of a transparent base material to reduce the amount of astigmatism generated by the optical compensation element 14 is provided in the optical system. You may make it take in.

  FIG. 4 is a schematic perspective view for explaining an inclination in the arrangement of the optical compensation elements. 4 shows the positional relationship between one set of the reflection type light modulation element 11, the reflection type polarizer 10, and the optical compensation element 14 in FIG. The x, y, and z axes shown in the figure are based on the surface of the reflection type light modulation element 11, and the axis along one direction of the surface of the reflection type light modulation element 11 is the x axis. The axis perpendicular to the x axis along the surface of the element 11 is the y axis, and the axis perpendicular to the surface of the reflective light modulation element 11, that is, the optical axis is the z axis.

  The optical compensation element 14 is disposed between the reflective light modulation element 11 and the reflective polarizer 10 that are disposed at predetermined intervals along the z-axis direction. In the arrangement of the optical compensation element 14 shown in FIG. 4, the optical compensation element 14 is arranged at an angle θ with respect to the surface of the reflective light modulation element 11, that is, a plane parallel to the xy plane. In other words, the optical compensation element 14 is arranged in a state inclined by an angle θ with the y axis as the rotation center. The tilt angle θ is an amount corresponding to the pretilt angle of the liquid crystal molecules of the reflective light modulation element 11, thereby making it possible to cancel the phase difference caused by the pretilt angle of the liquid crystal.

  FIG. 5 is a schematic perspective view illustrating rotation (part 1) in the arrangement of the optical compensation elements. 5 also shows the positional relationship between one set of the reflection type light modulation element 11, the reflection type polarizer 10, and the optical compensation element 14 in FIG. The x, y, and z axes shown in the figure are also the same as those in FIG. 4. The axis along one direction of the surface of the reflective light modulator 11 is the x axis, and the x axis is along the surface of the reflective light modulator 11. An axis orthogonal to the y-axis and an axis perpendicular to the surface of the reflective light modulation element 11, that is, the optical axis is the z-axis.

  The optical compensation element 14 is disposed between the reflective light modulation element 11 and the reflective polarizer 10 that are disposed at predetermined intervals along the z-axis direction. In the arrangement of the optical compensation element 14 shown in FIG. 5, the optical compensation element 14 is arranged at an angle θ with respect to the surface of the reflective light modulation element 11, that is, a plane parallel to the xy plane. In other words, the optical compensation element 14 is arranged in a state inclined by an angle θ with the y axis as the rotation center.

  Further, the optical compensation element 14 shown in FIG. 5 is arranged in a state of being rotated by an angle Φ with an axis perpendicular to the plane of the optical compensation element 14 as a rotation center axis (see the lower diagram of FIG. 5). In other words, the optical compensation element 14 is inclined at an angle θ with respect to the surface (xy plane) of the reflective light modulation element 11 and is rotated by an angle Φ along the plane of the optical compensation element 14. Yes.

  The inclination angle θ is an amount corresponding to the pretilt angle of the liquid crystal molecules of the reflective light modulation element 11. Further, the rotation angle Φ is an amount corresponding to the interpolation for canceling the liquid crystal phase difference by the tilt angle θ. The rotation angle Φ is, for example, between −5 degrees and 5 degrees. By providing the optical compensation element 14 with such an inclination angle θ and a rotation angle Φ, the vertical phase difference amount of the optical compensation element 14 can be more precisely canceled with respect to the phase difference amount of the liquid crystal. There is an effect.

  FIG. 6 is a schematic perspective view illustrating rotation (part 2) in the arrangement of the optical compensation elements. 6 also shows the positional relationship between one set of the reflective light modulation element 11, the reflective polarizer 10, and the optical compensation element 14 in FIG. The x, y, and z axes shown in the figure are also the same as those in FIG. 4. The axis along one direction of the surface of the reflective light modulator 11 is the x axis, and the x axis is along the surface of the reflective light modulator 11. An axis orthogonal to the y-axis and an axis perpendicular to the surface of the reflective light modulation element 11, that is, the optical axis is the z-axis.

  The optical compensation element 14 is disposed between the reflective light modulation element 11 and the reflective polarizer 10 that are disposed at predetermined intervals along the z-axis direction. In the arrangement of the optical compensation element 14 shown in FIG. 6, the optical compensation element 14 is arranged at an angle θ with respect to the surface of the reflective light modulation element 11, that is, a plane parallel to the xy plane. In other words, the optical compensation element 14 is arranged in a state inclined by an angle θ with the y axis as the rotation center.

  Furthermore, the optical compensation element 14 shown in FIG. 6 is arranged in a state of being rotated by an angle γ with the z-axis that is the optical axis as the rotation center axis (see the lower diagram in FIG. 6). That is, the optical compensation element 14 is inclined at an angle θ with respect to the surface (xy plane) of the reflective light modulation element 11 and along the surface (xy plane) of the reflective light modulation element 11. It is arranged with an angle γ rotation.

  The inclination angle θ is an amount corresponding to the pretilt angle of the liquid crystal molecules of the reflective light modulation element 11. The rotation angle γ is an amount corresponding to the interpolation for canceling the liquid crystal phase difference by the tilt angle θ. The rotation angle γ is, for example, between −5 degrees and 5 degrees. By arranging the optical compensation element 14 with such an inclination angle θ and a rotation angle γ, the vertical phase difference amount of the optical compensation element 14 can be more precisely canceled with respect to the phase difference amount of the liquid crystal. There is an effect. Here, in the adjustment at the rotation angle θ, since the cross-sectional shape of the incident light beam on the surface of the optical compensation element 14 is a constant shape, the area of the cross-sectional shape does not change due to the angle, and the image quality when the angle is adjusted No change is required.

  Note that the rotation of the optical compensation element 14 as necessary may be either the rotation angle Φ shown in FIG. 5 or the rotation angle γ shown in FIG. 6, but both the rotation angle Φ and the rotation angle γ are rotated. May be combined. This makes it possible to perform further highly accurate phase difference cancellation interpolation.

  Next, the relationship between the tilt direction of the liquid crystal molecules and the tilt of the optical compensation element will be described with reference to FIG. First, the direction unit vector k extending in the direction in which the liquid crystal molecules of the reflective light modulator 11 are tilted, the plane P including the grid plane of the reflective polarizer 10, and the plane Q on which the reflective light modulator 11 is installed. Define The state in which the projection component of the direction unit vector k is in the first quadrant and the fourth quadrant of the plane Q is called “state A”, the second quadrant, and the third quadrant.

  8 to 11 are schematic perspective views showing the positional relationship between the liquid crystal alignment direction of the reflective light modulation element and the grid of the reflective polarizing element. In each figure, the vertical direction in the figure is the z-axis direction, and the reflection type light modulation element 11 is arranged along the xy plane with the origin of each axis of x, y, z as the center, and z so as to face this. The optical compensation element 14 and the reflective polarizer 10 are arranged with a predetermined interval in the axial direction.

  Each of FIGS. 8 to 11 shows a direction unit vector k extending in the direction in which the liquid crystal molecules are tilted. 8 and 9 show “state A” in which the projection component of the direction unit vector k is in the first quadrant and the fourth quadrant of the plane Q (the plane of the reflective light modulation element 11). 10 and 11 show “state B” in which the projection component of the direction unit vector k is in the second quadrant and the third quadrant of the plane Q.

  The inventors of the present application have contrasts R (red), G (green), and B (blue) when the inclination angle θ of the optical compensation element 14 is changed in each of the “state A” and “state B” states. Each color was measured. The measurement was performed for two types of cases where the pretilt angle of the liquid crystal molecules is large and small.

  12 and 13 show changes in contrast (absolute value) with respect to the tilt angle θ of the optical compensation element. FIG. 12 shows a case where the pretilt angle of the liquid crystal is large, and FIG. 13 shows a case where the pretilt angle of the liquid crystal is small. ing. 14 and 15 are normalized values of contrast for each of FIGS. 12 and 13. In each figure, the white plot is “state A” and the black plot is “state B”, and each of the RGB colors is shown.

  According to this measurement result, when the tilt angle θ of the optical compensation element is 0 degree, that is, compared with the case where the reflection type light modulation element and the optical compensation element are arranged in parallel, the pre-tilt Regardless of the size of the angle, the contrast increases in both the “state A” and “state B” (see FIGS. 14 and 15).

  Further, considering each color of RGB, the B (blue) and G (green) contrasts are higher in the “state A” than in the “state B” regardless of whether the pretilt angle is large or small. On the other hand, the contrast of R (red) is higher in “state B” than in “state A” whether the pretilt angle is large or small (see FIGS. 12 and 13).

  Further, when the tilt angle θ of the optical compensation element is changed, the tilt angle at which the contrast becomes a maximum value is smaller in “State A” than in “State B”. Therefore, since the maximum contrast can be obtained at a smaller tilt angle in the “state A”, the amount of astigmatism generated by tilting the optical compensation element is lighter and the image quality is significantly degraded. There will be nothing.

  The above-described contrast measurement was performed using two types of samples, ie, a sample having a large pretilt angle of the reflection type light modulation element, and a sample having a small pretilt angle. In contrast, “Contrast B” has higher contrast than “State B”, and the inclination angle that gives the maximum contrast value for all the colors of RGB is smaller in “State A” than in “State B”.

  That is, it is understood that “state A” is more suitable for image quality deterioration factors such as astigmatism when considering the pretilt angle variation of the liquid crystal molecules of the reflective light modulation element. Further, an image projection apparatus having at least one set of such “state A” relationships can further increase contrast compared to a conventional image projection apparatus.

  In the embodiment described above, an example using a light source that emits white light is shown. However, the present invention is not limited to this, and a monochromatic light source such as an LED (Light Emitting Diode) or a laser, Or even a combination of them can be applied. In this embodiment, an example in which a reflective polarizing element is used as a polarizer has been described. However, an absorbing polarizing element or PBS (polarizing beam splitter) may be used.

<Implementation effect>
In order to cancel out the phase difference generated by the reflective light modulation element during black display, at least the front incident light has a predetermined phase difference between the reflective polarizer and the reflective light modulation element. The optical element (optical compensation element) characterized by canceling the phase difference of the liquid crystal by tilting the optical element (optical compensation element) at a certain angle with respect to the reflective light modulation element, and the tilt adjusting mechanism and the in-plane rotation amount (position) An optical system characterized by having a (phase difference amount) adjusting mechanism makes it possible to realize a projection display device with high contrast and high brightness.

  An optical component, an optical module, and a display device that are excellent in heat resistance, light resistance, and mass productivity can be provided by using a laminated structure of inorganic materials as a retardation layer for optical compensation in an optical compensation element. It becomes possible.

It is a schematic diagram explaining the structure of the display apparatus which concerns on this embodiment. It is a figure explaining the external appearance of an optical unit. It is a schematic diagram explaining the structure of the optical component which concerns on this embodiment. It is a model perspective view explaining the inclination in arrangement | positioning of an optical compensation element. It is a model perspective view explaining the rotation (the 1) in arrangement | positioning of an optical compensation element. It is a model perspective view explaining the rotation (the 2) in arrangement | positioning of an optical compensation element. It is a model perspective view explaining the relationship between the direction in which a liquid crystal molecule is tilted, and the inclination of an optical compensation element. It is a model perspective view (the 1) which shows the relationship between the liquid crystal orientation direction of a reflective light modulation element, and the position of the grid of a reflective polarizing element. It is a model perspective view (the 2) which shows the relationship between the liquid crystal orientation direction of a reflective light modulation element, and the position of the grid of a reflective polarizing element. It is a model perspective view (the 3) which shows the relationship between the liquid crystal orientation direction of a reflection type light modulation element, and the position of the grid of a reflection type polarizing element. It is a model perspective view (the 4) which shows the relationship between the liquid crystal orientation direction of a reflective light modulation element, and the position of the grid of a reflective polarizing element. It is a figure (pretilt angle large) which shows the change of contrast (absolute value) with respect to inclination-angle (theta) of an optical compensation element. It is a figure (pretilt angle small) which shows the change of contrast (absolute value) with respect to inclination-angle (theta) of an optical compensation element. It is a figure (pretilt angle large) which shows the change of contrast (normalization) with respect to inclination-angle (theta) of an optical compensation element. It is a figure (pre-tilt angle small) which shows the change of contrast (normalization) with respect to inclination-angle (theta) of an optical compensation element. It is a schematic diagram explaining the schematic structure of the conventional projection type image display apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... 1st integrator lens, 3 ... 2nd integrator lens, 4 ... Polarizing beam splitter, 5 ... Condenser lens, 6 ... Dichroic mirror, 7 ... Dichroic mirror, 8 ... Reflection mirror, 9 ... Field lens DESCRIPTION OF SYMBOLS 10 ... Reflective type polarizer, 11 (11R, 11G, 11B) ... Reflective type light modulation element, 12 ... Color synthesis prism, 13 ... Projection lens, 14 ... Optical compensation element

Claims (9)

A reflective light modulation element that modulates and reflects incident light by liquid crystal; and
In an optical component comprising an optical compensation element disposed on the light incident / exit side of the light modulation element,
The optical component, wherein the optical compensation element is arranged to be inclined in a direction that cancels a phase difference of the liquid crystal with respect to a plane perpendicular to the light axis. 2. The optical component according to claim 1, wherein the optical compensation element is arranged to rotate in a direction that cancels a phase difference of the liquid crystal about the light axis. The optical component according to claim 1, wherein the optical compensation element has an in-plane phase difference. In an optical unit that splits light emitted from a light source into a plurality of colors, guides the light to a reflective light modulation element corresponding to each color, and synthesizes the light modulated by each reflective light modulation element.
The optical compensation element disposed on the light incident / exit side of the reflective light modulation element is disposed to be inclined in a direction that cancels the phase difference of the liquid crystal with respect to a plane perpendicular to the light axis. Optical unit to be used. The optical unit according to claim 4, wherein the optical compensation element is arranged to rotate in a direction that cancels a phase difference of the liquid crystal about the light axis. The optical unit according to claim 4, wherein the optical compensation element has an in-plane phase difference. A light source;
An optical unit that divides the light emitted from the light source into a plurality of colors, guides the light to a reflective light modulation element corresponding to each color, and synthesizes the light modulated by each reflective light modulation element;
In a display device comprising a projection optical system for projecting light synthesized by the optical unit,
The optical unit is
An optical compensation element is provided on the light incident / exit side of the reflective light modulation element,
The display device, wherein the optical compensation element is disposed to be inclined in a direction that cancels a phase difference of the liquid crystal with respect to a plane perpendicular to the light axis. The display device according to claim 7, wherein the optical compensation element is arranged so as to rotate in a direction that cancels a phase difference of the liquid crystal about the axis of the light. The display device according to claim 7, wherein the optical compensation element has an in-plane phase difference.

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