JP2011128569A - Image projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image projection device which obtains high contrast by a simple constitution using a reflecting liquid crystal panel. <P>SOLUTION: The image projection device includes: a color separation element; a wavelength selecting phase plate; first, second and third reflective image display elements; first and second beam splitters having polarizing effects; a combination prism; and a projection lens. The second polarizing beam splitter has an optical film surface having a polarizing effect as a first optical film surface, and the combination prism has an optical film surface having a color combination effect as a second optical film surface. A first cross section is defined as a cross section parallel to a line normal to an entrance and exit surface of the second reflective image display element and a line normal to the first optical film surface. A second cross section is defined as a cross section parallel to a line normal to an exit surface of the combination prism and a line normal to the second optical film surface. The first cross section and the second cross section are perpendicular to each other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical system used in an image projection apparatus using a reflective image display element, and more particularly to a color separation / synthesis optical system.

  As an optical system in which the color separation / synthesis optical system is miniaturized in an image projection apparatus using three reflective image display elements, the color separation / synthesis optical systems shown in Patent Document 1 and Patent Document 2 are known. The color separation / synthesis optical system is an optical system that analyzes and combines three colors of light with two polarization beam splitters. According to this, the optical system can be reduced in size.

JP 2002-122810 A JP 2004-020621 A

However, in the color separation / synthesis optical system described in Patent Document 1 or Patent Document 2, it is necessary to dispose an optical element having a light detection function such as a polarizing plate in order to improve contrast, and the number of optical elements to be disposed increases. . Therefore, in the conventional configuration, it is difficult to achieve both a simple configuration and a high contrast.
Accordingly, an object of the present invention is to obtain high contrast with a simple configuration.

A color separation element that separates light from the light source into first color light, second color light, and third color light;
A wavelength-selective phase plate that rotates the polarization direction of either the second color light or the third color light by 90 °;
A first reflective image display element that modulates and reflects the first color light;
A second reflective image display element that modulates and reflects the second color light;
A third reflective image display element that modulates and reflects the third color light;
A first polarizing beam splitter for analyzing the first color light modulated by the first reflective image display element;
A second polarizing beam splitter for analyzing the second color light and the third color light modulated by the second reflective image display element and the third reflective image display element;
The first color light, the second color light, and the third color light analyzed by the first polarization beam splitter and the second polarization beam splitter are combined to generate at least one color light of the second color light or the third color light. A synthetic prism having the function of analyzing
In an image projection apparatus having a projection lens that projects the first color light, the second color light, and the third color light synthesized by the synthesis prism,
The optical film surface having the polarization action of the second polarizing beam splitter is the first optical film surface,
The optical film surface having the color combining function of the combining prism is a second optical film surface,
A cross section parallel to the normal line of the incident / exit surface of the second reflective image display element and the normal line of the first optical film surface is defined as a first cross section,
A cross section parallel to the normal of the exit surface of the synthetic prism and the normal of the second optical film surface is defined as a second cross section,
The image projection apparatus, wherein the first cross section and the second cross section are orthogonal to each other.

  According to the present invention, it is possible to provide an image projection apparatus capable of obtaining high contrast with a simple configuration.

Illumination optical system according to Embodiment 1 Color separation / synthesis optical system according to Embodiment 1 Film characteristics of second polarizing beam splitter and combining prism according to embodiment 1 Color separation / synthesis optical system according to Embodiment 2

(Embodiment 1)
1 and 2 show an illumination optical system and a color separation / synthesis optical system of the image projection apparatus of the present embodiment. In FIG. 1, 2 is a lamp unit (light source unit), 3 is a first fly-eye lens, 4 is a second fly-eye lens, 5 is a PS conversion element (polarization conversion element), and 6 is a condenser lens. The lamp unit 2 to the condenser lens 6 are used as the illumination optical system 1. The same applies to the embodiments described below. Reference numeral 7 denotes a color separation / synthesis optical system.

  2, 8 is a projection lens (projection optical system), 11 is a dichroic mirror (color separation element), 12 is a first mirror, 13 is a first field lens, and 14 is a first polarization beam splitter. 15 is a G-band reflective liquid crystal panel (first reflective image display element), 16 is a second mirror, 17 is a wavelength selective phase plate, 18 is a second field lens, and 19 is a second polarization. It is a beam splitter. Reference numeral 20 denotes a B-band reflective liquid crystal panel (second reflective image display element), 21 denotes an R-band reflective liquid crystal panel (third reflective image display element), and 22 denotes a composite prism. Reference numeral 14A denotes an optical film surface (third optical film surface) having a polarizing action of the first polarizing beam splitter 14, and 19A denotes an optical film surface having a polarizing action of the second polarizing beam splitter 19 (first optical film surface). ), 22A indicates an optical film surface (second optical film surface) having a polarizing action of the synthetic prism. In the present specification, red band light, green band light, and blue band light, which are the respective color lights, are represented as R, G, and B, respectively. The reflective image display elements for R, G, and B are referred to as an R liquid crystal panel, a G liquid crystal panel, and a B liquid crystal panel, respectively. Hereinafter, the x axis represents the long side direction of the B liquid crystal panel, the y axis represents the short side direction of the B liquid crystal panel, and the z axis represents the optical axis of the projection lens. The coordinate axes are shown in the lower right of FIG. The color separation / synthesis optical system 7 (color separation / synthesis system) is an optical system having optical elements from the dichroic mirror 11 to the synthesis prism 22. A first mirror 12 (first reflecting portion) is provided between the dichroic mirror 11 and the first polarizing beam splitter 14, and a second mirror 16 (between the dichroic mirror 11 and the second polarizing beam splitter 19 is provided. The second reflection part) is arranged. In the first mirror 12 and the second mirror 16, the green band light (first color light) and the red and blue band light (second and third color lights) separated by the dichroic mirror 11 are substantially parallel to each other. To reflect in the y direction.

  Hereinafter, a cross section parallel to the normal line of the optical film surface 14A and the normal line of the incident / exit surface of the G liquid crystal panel 15 is referred to as an A cross section (xy cross section, third cross section). A cross section parallel to the normal line of the optical film surface 19A and the normal line of the incident / exit surface of the B liquid crystal panel 20 is defined as a B cross section (yz cross section, first cross section). A cross section parallel to the normal line of the optical film surface 22A and the normal line of the exit surface of the combining prism 22 is defined as a C cross section (xz cross section, second cross section). In the present embodiment, the A cross section, the B cross section, and the C cross section are configured to be orthogonal to each other. With this configuration, the separation surface separated by the dichroic mirror 11 (the surface including the optical axis of the illumination optical system and the normal line of the dichroic mirror) and the synthesis surface synthesized by the synthesis prism 22 (G liquid crystal panel method) And the plane including the normal line of the B liquid crystal panel) are different planes.

  In the first embodiment, the long side 15L of the G liquid crystal panel 15 is parallel to one side 14L orthogonal to the xy section, the long side 20L of the B liquid crystal panel 20 and the long side 21L of the R liquid crystal panel 21 are orthogonal to the yz section. It is parallel to the side 19L.

  The light flux from the lamp unit 2 is divided into a plurality of light fluxes by the first fly-eye lens 3, and each split light flux is condensed in the vicinity of the second fly-eye lens 4 and the PS conversion element 5 to form an image of the light source. make. The first and second fly-eye lenses 3 and 4 are configured by arranging a plurality of lenses in a two-dimensional direction. The PS conversion element 5 converts each divided light beam emitted from the second fly-eye lens 4 into linearly polarized light. In this embodiment, it is aligned with S-polarized light. The S-polarized light emitted from the PS conversion element 5 is converged by the condenser lens 6 and illuminates the B, G, and R liquid crystal panels 20, 15, and 21 via the color separation / synthesis optical system 7.

  The dichroic mirror 11 transmits the B band light and the R band light of the S polarized light transmitted through the condenser lens 6, reflects the G band light, and transmits the G band light (first color light) and the B band light (second color light). ) And R band light (third color light). The G-band S-polarized light reflected by the dichroic mirror 11 is reflected by the first mirror 12. The light reflected by the first mirror 12 passes through the first field lens 13 disposed on the incident surface side of the first polarization beam splitter, is reflected by the first polarization beam splitter 14, and is reflected on the G liquid crystal panel. 15 is incident. The image light from the G liquid crystal panel 15 passes through the first polarization beam splitter 14, is further reflected by the combining prism 22, and is projected onto a screen (not shown) by the projection lens 8. The image light represents light modulated by the liquid crystal panel, and the image light in this embodiment is light whose polarization is rotated by 90 ° on the liquid crystal panel and is directed toward the projection lens. The unmodulated light is reflected by the first polarization beam splitter 14 and returned to the light source side.

  The synthesizing prism 22 having a color synthesizing function is a prism having an optical film surface that transmits B-band light, reflects G-band light, transmits R-band light image light, and reflects R-band light non-image light. is there. Non-image light is light whose polarization direction is orthogonal to image light.

  On the other hand, the B band and the R band transmitted through the dichroic mirror 11 are reflected by the second mirror 16. The wavelength selective phase plate 17 rotates only the polarization direction of the R band by 90 degrees. The B-band light and the R-band light are transmitted through the second field lens 18 disposed on the incident surface side of the second polarization beam splitter, and the B-band light that is S-polarized light is transmitted by the second polarization beam splitter 19. The R band light that is reflected and is P-polarized light passes through the second polarization beam splitter 19. Then, the B-band light and the R-band light emitted from the second polarizing beam splitter 19 are condensed on the B liquid crystal panel 20 and the R liquid crystal panel 21, respectively. The R band polarized light (S polarized light) reflected and modulated by the R liquid crystal panel 21 is reflected by the second polarization beam splitter 19. The B-band image light reflected and modulated by the B liquid crystal panel 20 passes through the second polarization beam splitter 19. Thereafter, the B-band image light and the R-band image light are transmitted through the combining prism 22 and projected onto the screen by the projection lens 8. That is, the image light from the G liquid crystal panel 15 is analyzed by the first polarization beam splitter 14, and the image light from the B liquid crystal panel 20 is analyzed by the second polarization beam splitter 19. Image light from the R liquid crystal panel is analyzed by the second polarizing beam splitter 19 and the combining prism 22.

  FIGS. 3A and 3B show the reflection angle characteristics of the second polarizing beam splitter 19 for the non-image light (P-polarized light) in the R band and the image light (S-polarized light) in the R band of the combining prism 22. The transmission angle characteristic is shown. The representative wavelength of light in the R band in the graphs shown in FIGS. 3A and 3B is 610 (nm).

  FIG. 3A shows the reflection angle characteristics of the R-band light of the second polarizing beam splitter 19 with respect to non-image light (P-polarized light). The horizontal axis represents the incident angle (degree) of the light beam with respect to the optical film surface 19A, and the vertical axis represents the reflectance (%) of P-polarized light. The higher the reflectivity, the greater the leakage light and the lower the contrast. Since the reflectance increases as the incident angle of the second polarizing beam splitter 19 with respect to the optical film surface 19A deviates from 45 °, leakage light increases. Leakage light is light that partially travels toward the projection lens when the drive panel is driven so that all pixels display black. In other words, it is the light that is emitted from the R liquid crystal panel 21 and is reflected among the P-polarized light that should originally pass through the optical film surface 19A of the second polarizing beam splitter 19.

  The R-band light reflected from the second polarization beam splitter 19 has a larger change in the incident angle with respect to the optical film surface 19A when the incident angle in the y direction is changed than in the x direction. Therefore, the second polarization beam splitter 19 can obtain high light detection performance even for incident light having a large incident angle in the x direction.

  FIG. 3B shows the transmission angle characteristic of the S-polarized light of the R band light with respect to the combining prism 22. The horizontal axis represents the incident angle (degree) of the light beam with respect to the optical film surface 22A, and the vertical axis represents the reflectance (%) of P-polarized light.

  In addition, the R-band light transmitted through the combining prism 22 has a larger incident angle change with respect to the optical film surface 22A when the incident angle in the x direction changes than when the incident angle in the y direction in the figure changes. Therefore, the synthesis prism 22 can obtain high light detection performance even for incident light having a large incident angle in the y direction.

  In the image projection apparatus of the present embodiment, the polarizing beam splitter 19 and the combining prism 22 are arranged in view of the characteristics of the optical film surface having the polarization action shown in FIGS. 3 (a) and 3 (b). That is, the degree of polarization is not increased by an optical element such as a polarizing plate, but the directions in which the analyzing performance of each analyzer (for example, the polarizing beam splitter 19 and the combining prism 22) is good are arranged so as to be orthogonal to each other. High contrast can be realized with a simple configuration.

  More specifically, high light detection performance can be obtained with respect to light beams having a large angle in the x and y directions entering and exiting the R liquid crystal panel 21, so that leakage light of R band light can be efficiently reduced. And the contrast can be improved.

  As another effect, the arrangement direction of the synthetic prism 22 and the dichroic mirror 11 can be shifted in the vertical direction (y direction). Accordingly, the optical elements (for example, the combining prism 22 and the dichroic mirror 11) can be arranged close to each other in the xz plane without worrying about interference between the optical elements when viewed from the y-axis direction. That is, the arrangement intervals of the optical elements can be narrowed compared to the case where the optical elements constituting the color separation / synthesis optical system are arranged in the xz plane. Thereby, since each color light can be synthesize | combined in the place where the breadth of the light beam radiate | emitted from the liquid crystal panel is less, the synthetic | combination prism 22 can be reduced in size. In addition, since the color separation / synthesis optical system can be reduced as a whole, the back focus of the projection lens 8 can be shortened.

  In the present embodiment, the leakage light reduction of the R band light has been described. However, the leakage light can be efficiently reduced with respect to the optical paths of the B and G band light, and a high contrast can be obtained.

(Embodiment 2)
FIG. 4 shows a color separation / synthesis optical system of the image projection apparatus of this embodiment. In the figure, 30 is a color separation / synthesis optical system, 31 is a dichroic mirror, 32 is a first mirror, 33 is a first field lens, 34 is a first polarization beam splitter, and 35 is a G liquid crystal panel. 36 is a second mirror, 37 is a wavelength selective phase plate, 38 is a second field lens, 39 is a second polarizing beam splitter, 40 is a B liquid crystal panel, 41 is an R liquid crystal panel, 42 is a combining prism, 43 Indicates a projection lens. The color separation / synthesis optical system 30 is an optical system having optical elements from the dichroic mirror 31 to the synthesis prism 42 having a color synthesis function. The combining prism 42 reflects G light and transmits B and R light. A first mirror 32 (first reflecting portion) is provided between the dichroic mirror 31 and the first polarizing beam splitter 34, and a second mirror 36 (between the dichroic mirror 31 and the second polarizing beam splitter 39). The second reflection part) is arranged. In the first mirror 32 and the second mirror 36, the green band light (first color light) and the red and blue band light (second and third color lights) separated by the dichroic mirror 31 are substantially parallel to each other. Is reflected in the -x direction. The −x direction is the direction opposite to the arrow direction of the x axis in the figure.

  A cross section parallel to the normal line of the optical film surface 34A and the incident / exit surface of the G liquid crystal panel 35 is defined as an xy cross section, and a cross section parallel to the optical film surface 39A and the normal line of the incident / exit surface of the B liquid crystal panel 40 is defined as an xz cross section. A section parallel to the normal line of the optical film surface 42A and the exit surface of the combining prism 42 is defined as a yz section. The xy cross section, the xz cross section, and the yz cross section are orthogonal to each other. The coordinate axes are shown in the lower right of FIG.

  In the second embodiment, the long side 35L of the G liquid crystal panel 35 is perpendicular to one side 34L orthogonal to the xy cross section, the long side 40L of the B liquid crystal panel 40 and the long side 41L of the R liquid crystal panel 41 are one side orthogonal to the xz cross section. It is the structure arrange | positioned perpendicularly to 39L.

  In the present invention, in view of the incident angle characteristics of the polarizing beam splitter, it is possible to realize high contrast by arranging the directions in which the detection performance of the two polarizing beam splitters is orthogonal to each other. In addition, since it is not necessary to insert an optical element such as a polarizing plate, it is possible to provide an image projection apparatus having a simpler structure.

  As another effect, the arrangement direction of the synthetic prism 42 and the dichroic mirror 31 can be shifted in the vertical direction (x direction). Thereby, each optical element (for example, the synthetic prism 42 and the dichroic mirror 31) can be placed close to the yz plane without worrying about interference between the optical elements when viewed from the x-axis direction. That is, the arrangement interval of the optical elements can be narrowed compared to the case where the optical elements constituting the color separation / synthesis optical system are arranged in the yz plane. Thereby, since each color light can be synthesize | combined in the place where the breadth of the light beam radiate | emitted from the liquid crystal panel is less, a synthetic | combination prism can be reduced in size. Further, since the color separation / synthesis optical system can be reduced as a whole, the back focus of the projection lens 43 can be shortened.

DESCRIPTION OF SYMBOLS 8 Projection lens 11 Dichroic mirror 14 1st polarizing beam splitter 15 G band reflective liquid crystal panel 19 2nd polarizing beam splitter 20 B band reflective liquid crystal panel 21 R band reflective liquid crystal panel 22 Synthetic prism

Claims (6)

A color separation element that separates light from the light source into first color light, second color light, and third color light;
A wavelength-selective phase plate that rotates the polarization direction of either the second color light or the third color light by 90 °;
A first reflective image display element that modulates and reflects the first color light;
A second reflective image display element that modulates and reflects the second color light;
A third reflective image display element that modulates and reflects the third color light;
A first polarizing beam splitter for analyzing the first color light modulated by the first reflective image display element;
A second polarizing beam splitter for analyzing the second color light and the third color light modulated by the second reflective image display element and the third reflective image display element;
The first color light, the second color light, and the third color light analyzed by the first polarization beam splitter and the second polarization beam splitter are combined, and at least one of the second color light and the third color light is combined. A synthetic prism having the function of analyzing color light;
In the image projection apparatus having a projection lens that projects the first color light, the second color light, and the third color light synthesized by the synthesis prism,
The optical film surface having the polarization action of the second polarizing beam splitter is the first optical film surface,
The optical film surface having the color combining function of the combining prism is a second optical film surface,
A cross section parallel to the normal line of the incident / exit surface of the second reflective image display element and the normal line of the first optical film surface is defined as a first cross section,
A cross section parallel to the normal of the exit surface of the synthetic prism and the normal of the second optical film surface is defined as a second cross section,
The image projection apparatus, wherein the first cross section and the second cross section are orthogonal to each other. The optical film surface having the polarization action of the first polarizing beam splitter is a third optical film surface,
A cross section parallel to the normal line of the incident / exit surface of the first reflective image display element and the normal line of the third optical film surface is defined as a third cross section,
The image projection apparatus according to claim 1, wherein the second cross section and the third cross section are orthogonal to each other. A color separation element that separates light from the light source into first color light, second color light, and third color light;
A wavelength-selective phase plate that rotates the polarization direction of either the second color light or the third color light by 90 °;
A first reflective image display element that modulates and reflects the first color light;
A second reflective image display element that modulates and reflects the second color light;
A third reflective image display element that modulates and reflects the third color light;
A first polarizing beam splitter for analyzing the first color light modulated by the first reflective image display element;
A second polarizing beam splitter for analyzing the second color light and the third color light modulated by the second reflective image display element and the third reflective image display element;
A combining prism having an operation of combining the first color light, the second color light, and the third color light detected by the first polarizing beam splitter and the second polarizing beam splitter, and detecting the first color light;
In the image projection apparatus having a projection lens that projects the first color light, the second color light, and the third color light synthesized by the synthesis prism,
The optical film surface having the polarization action of the first polarizing beam splitter is defined as a first optical film surface,
The optical film surface having the color combining function of the combining prism is a second optical film surface,
A cross section parallel to a normal line of the incident / exit surface of the first reflective image display element and a normal line of the first optical film surface is defined as a first cross section,
A cross section parallel to the normal of the exit surface of the synthetic prism and the normal of the second optical film surface is defined as a second cross section,
The image projection apparatus, wherein the first cross section and the second cross section are orthogonal to each other. The optical film surface having the polarization action of the second polarizing beam splitter is a third optical film surface,
A cross section parallel to the normal line of the incident / exit surface of the second reflective image display element and the normal line of the third optical film surface is defined as a third cross section,
The image projection apparatus according to claim 2, wherein the second cross section and the third cross section are orthogonal to each other. A first reflector between the color separation element and the first polarization beam splitter;
A second reflecting portion between the color separation element and the second polarizing beam splitter;
The first color light and the second and third color lights are reflected so as to be parallel by the first reflection unit and the second reflection unit, respectively. The image projection apparatus described. In order to illuminate the first, second, and third reflective image display elements, the color separation / combination optics separates the light from the light source into three color lights, and synthesizes the separated light again to guide it to the projection optical system. In the system,
A color separation element that separates light from the light source into first color light, second color light, and third color light;
A wavelength-selective phase plate that rotates the polarization direction of either the second color light or the third color light by 90 °;
A first polarizing beam splitter for analyzing the first color light modulated by the first reflective image display element;
A second polarizing beam splitter for analyzing the second color light and the third color light modulated by the second reflective image display element and the third reflective image display element;
The first color light, the second color light, and the third color light analyzed by the first polarization beam splitter and the second polarization beam splitter are combined to generate at least one color light of the second color light or the third color light. And a synthetic prism having an action of analyzing
The optical film surface having the polarization action of the second polarizing beam splitter is the first optical film surface,
The optical film surface having the color combining function of the combining prism is a second optical film surface,
A cross section parallel to the normal line of the incident / exit surface of the second reflective image display element and the normal line of the first optical film surface is defined as a first cross section,
A cross section parallel to the normal of the exit surface of the synthetic prism and the normal of the second optical film surface is defined as a second cross section,
A color separation / synthesis optical system, wherein the first cross section and the second cross section are orthogonal to each other.

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