JP2006047967A - Projection display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection display apparatus capable of projecting an image of high definition by setting the axial chromatic aberration of a projection imaging lens as the large one. <P>SOLUTION: A white light emitted from a light source 111 is homogenized by an integrator optical system 112, also, transmitted through a color polarizer 113 to be turned into an R light and a G light of a P polarized light, and transmitted through a color polarizer 118 to be turned into a G light of an S polarized light and an R light of a P polarized light. These R light and G light are subjected to light modulation in a reflection type spatial light modulation element for G 161 and a reflection type spatial light modulation element for R 162 arranged at unequal distances from a polarization split surface 131 of a polarizing beam splitter 103, and emitted from the projection lens 130 having the axial chromatic aberration corresponding to the unequal distances. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a projection display device using a reflective spatial light modulator.

  The color projection display device decomposes R (red), G (green), and B (blue) color lights related to the three primary colors from white light and leads them to the corresponding spatial light modulation elements. Color light modulated according to the video signal is synthesized and projected to display a color video on the screen.

  A method using a reflective spatial light modulation element as a color projection display device is advantageous for high resolution, but tends to have a complicated optical configuration. That is, a projection display device to which a reflective spatial light modulator is applied needs a polarization beam splitter to separate incident light that irradiates the spatial light modulator and reflected light modulated by the spatial light modulator. It is to do. In order to realize high contrast, it is usually necessary to operate two or more polarization beam splitters on one spatial light modulator, which complicates the optical configuration of the reflection type projection display device. . Various configurations have been proposed to solve this problem (see, for example, Patent Document 1).

JP 2001-174755 A

  By the way, as proposed in the above-mentioned Patent Document 1, in order to reduce the size of a color projection display device using a reflective spatial light modulation element, one polarized light among a plurality of polarizing beam splitters to be actuated is used. It is necessary to adopt a configuration in which two spatial light modulation elements are arranged with respect to the beam splitter.

  In the polarization beam splitter in which the two reflective spatial light modulation elements are arranged, two color lights corresponding to the respective color lights are incident with their polarization states being 90 degrees different from each other. Separated by the polarization separation plane. That is, the two color lights incident on the polarization beam splitter are separated depending on whether they are transmitted or reflected in accordance with the polarization state, and are incident on the reflective spatial light modulator.

  Considering general characteristics on the polarization separation surface of this polarization beam splitter, it is difficult to achieve total transmission, that is, transmission of 100%, and some reflection occurs. Attention is now focused on the color light that is incident on the corresponding reflective spatial light modulation element through the polarization separation surface of the polarization beam splitter, out of the two color light incident thereon. The colored light is transmitted through the polarization splitting surface and incident on the corresponding reflective spatial light modulator, and is modulated by the image signal corresponding to the colored light in the spatial light modulator, that is, the polarization state is changed and reflected. .

  The reflected modulated light is incident on the polarization separation surface again, but since the polarization state is changed, it is reflected by the polarization separation surface and emitted to the polarization beam splitter that combines the color lights, and is passed through the projection lens to the screen. Projected on top.

  Of the focused color light, the light reflected by the slight reflection described above is incident on a reflective spatial light modulation element corresponding to one color light different from the focused color light. The light reflected by the slight reflection is further reflected by this spatial light modulation element and is incident on the polarization separation surface again, but here the polarization state has not changed and the color light is synthesized through the polarization separation surface. Is output to a polarizing beam splitter and projected onto a screen via a projection lens.

  Usually, in a projection display device, in order to make the focal point of an image projected on a screen uniform with each color light, the distance from the screen to each reflective spatial light modulator is uniform, and the axis of the projection lens The upper chromatic aberration is set to be minimum for each color light. Therefore, the focused color light reflected by the reflective spatial light modulation element corresponding to the focused color light and the reflected reflected by the reflective spatial light modulation element corresponding to one color light different from the focused color light There was a problem that the colored light interfered with the projected screen to form interference fringes.

  The present invention has been made in view of the above points, and an object thereof is to provide a projection display device that can reduce interference fringes in a projected image and project a high-quality image.

In order to solve the above-mentioned problems, the present invention comprises means described in the following 1) to 2).
That is,
1) In the projection display device (300),
A light source (111) that emits indefinitely polarized light;
First to third reflective spatial light modulators (161, 162, 163) for optically modulating three primary color lights obtained by color-separating the indefinitely polarized light;
The indefinitely polarized light emitted from the light source (111) is converted into a first color component light having a first polarization plane and another polarization plane having a polarization plane that is 90 degrees different from the first polarization plane. First wavelength-selective polarization conversion means (113) that separates and emits the second and third color component lights having a second polarization plane;
A first polarization separation that splits an optical path between the first color component light and the second and third color component lights when a light beam transmitted through the first wavelength selective polarization conversion means (113) is incident. An element (102);
The second and third color component lights are incident from the first polarization separation element (102), and the polarization plane of the second color component light and the polarization plane of the third color component light are orthogonal to each other. Second wavelength selective polarization conversion means (118) emitting as a state;
A polarization separation surface (131) on which the second and third color component lights are incident from the second wavelength-selective polarization conversion means (118), and the polarization separation surface (131) Color component light is transmitted and is incident on the second reflective spatial light modulator (162) installed at a first distance from the polarization separation surface (131), and the third color. The component light is reflected and is incident on the third reflective spatial light modulator (161) installed at a second distance different from the first distance with respect to the polarization separation surface (131). A second polarization separation element (103);
A polarization beam combining element (105) that receives the modulated light modulated by the first to third reflective spatial light modulation elements (161, 162, 163), and synthesizes and emits these modulated lights;
A projection lens (130) provided with axial chromatic aberration according to the difference between the first distance and the second distance;
A projection display device (300) characterized by comprising:
2) The projection display device (300) according to 1), wherein the axial chromatic aberration ΔL of the projection lens (130) has a relationship of 20 μm <ΔL = | fb1-fb2 | ≦ 70 μm. .
However, the back focus distance of the projection lens (130) with respect to the center wavelength λ1 of the second color component light incident on the second reflective spatial light modulator (162) is fb1, and the third reflective space. The back focus distance of the projection lens (130) with respect to the center wavelength λ2 of the third color component light incident on the light modulation element (161) is denoted by fb2.

  According to the projection display device of the present invention, each reflective spatial light modulator configured to arrange two reflective spatial light modulators with respect to one polarization beam splitter, a screen, By arranging reflective spatial light modulation elements so that the distance between them is different and providing axial chromatic aberration of the projection imaging lens according to the difference in distance, interference fringes of the image projected on the screen are reduced. It is possible to provide a projection display device that can project a high-quality image. This is particularly effective for improving the image quality of dark images.

  Hereinafter, the best mode for carrying out the invention of the projection display device according to the present invention will be described with reference to preferred embodiments.

FIG. 1 is a schematic plan view illustrating an optical configuration of a projection display device applied to the first embodiment.
A color separation / synthesis optical system 290 surrounded by a broken line includes first, second, and third polarization beam splitters 102, 103, and 104 that function as cubic or prismatic polarization separation elements, and a fourth that functions as a polarization composition element. The polarization beam splitter 105 is arranged so that its polarization separation surfaces 121, 131, 141, 151 as a whole are substantially X-shaped. Further, a color polarizer having a function of rotating the polarization planes of the R light and the G light by 90 degrees on the light transmitting surface (upper side surface of the first polarization beam splitter) on the incident side of the first polarization beam splitter 102. 113, a color polarizer 118 having a function of rotating the polarization plane of the G light by 90 ° is provided between the first and second polarization beam splitters 102 and 103. Further, a color polarizer 124 having a function of rotating the polarization plane of the R light by 90 ° is provided between the second and fourth polarizing beam splitters 103 and 105, and between the third and fourth polarizing beam splitters 104 and 105. Includes a color polarizer 115 having a function of rotating the polarization plane of the B light by 90 °.

The projection display device 300 applied to the first embodiment operates as follows.
Unfixed polarized white light emitted from the light source 111 enters the integrator optical system 112. Then, the white light is made uniform and aligned with the S-polarized light and enters the color polarizer 113. Since the color polarizer 113 is a wavelength-selective polarization conversion means that rotates the planes of polarization of the R light and the G light by 90 °, the S polarization associated with the R light and the G light transmitted through the color polarizer 113 is converted to P polarization. Converted. Further, since the color polarizer 113 has no effect on the B light, they remain S-polarized light.
Hereinafter, the transition of the optical path and the plane of polarization of each color light will be described individually.

  First, the P-polarized G light transmitted through the color polarizer 113 passes through the polarization separation surface 121 of the first polarization beam splitter 102 and enters the color polarizer 118. Since the color polarizer 118 is a wavelength-selective polarization conversion unit that rotates the polarization plane of the G light by 90 °, the P-polarized light related to the G light transmitted through the color polarizer 118 is converted into S-polarized light. The S-polarized G light transmitted through the color polarizer 118 is incident on the second polarization beam splitter 103, reflected by the polarization separation surface 131 of the second polarization beam splitter 103, and emitted from the light-transmitting surface 103a. Is incident on the reflective spatial light modulator 161. Then, the reflection type spatial light modulation element 161 receives light modulation according to the video signal corresponding to G and reflects the light.

  The P-polarized component of the G light generated by the light modulation travels straight through the polarization separation surface 131 of the second polarization beam splitter 103 and enters the color polarizer 124. Since the color polarizer 124 is a wavelength-selective polarization conversion unit that rotates the polarization plane of the R light by 90 °, it does not act on the G light and the P-polarized component of the G light goes straight through as it is P-polarized. Then, the light enters the fourth polarizing beam splitter 105. Then, the light travels straight through the polarization separation surface 151 of the fourth polarization beam splitter 105 and exits from the light transmission surface 105 c of the fourth polarization beam splitter 105.

  Next, the R light will be described. The P-polarized R light transmitted through the color polarizer 113 travels straight through the polarization separation surface 121 of the first polarization beam splitter 102 and enters the color polarizer 118. Since the color polarizer 118 is a wavelength-selective polarization conversion unit that rotates the polarization plane of the G light by 90 °, the color polarizer 118 does not act on the R light, and the R light remains P-polarized and the second polarizing beam splitter 103. Is incident on. The P-polarized R light incident on the second polarization beam splitter 103 travels straight through the polarization separation surface 131 of the second polarization beam splitter 103 and exits from the light transmission surface 103b to be reflected in R-type spatial light. The light enters the modulation element 162. Then, the reflection type spatial light modulation element 162 receives the light modulation corresponding to the video signal corresponding to R and is reflected.

  The S-polarized component of the R light generated by the light modulation is reflected by the polarization separation surface 131 of the second polarization beam splitter 103 and enters the color polarizer 124. Since the color polarizer 124 is a wavelength-selective polarization conversion unit that rotates the polarization plane of the R light by 90 °, the S-polarized component of the R light is converted into P-polarized light and enters the fourth polarizing beam splitter 105. To do. Then, the light travels straight through the polarization separation surface 151 of the fourth polarization beam splitter 105 and exits from the light transmission surface 105 c of the fourth polarization beam splitter 105.

  Next, the B light will be described. Since the color polarizer 113 has no effect on the B light, the B light remains as S-polarized light. Therefore, the S-polarized B light transmitted through the color polarizing filter 16 is polarized by the first polarization beam splitter 102. The light is reflected by the separation surface 121 and enters the third polarization beam splitter 104.

  The S-polarized B light is reflected by the polarization separation surface 141 of the third polarization beam splitter 104, exits from the light transmitting surface 104 d, and enters the B-type reflective spatial light modulator 163. Then, the reflection type spatial light modulation element 162 receives light modulation according to the video signal corresponding to B and is reflected.

  The P-polarized component of the B light generated by the light modulation is transmitted through the polarization separation surface 141 of the third polarization beam splitter 104 and enters the color polarizer 115. As described above, the color polarizer 115 is a wavelength-selective polarization conversion unit that rotates the polarization plane of the B light by 90 °, so that the P-polarized component of the B light is converted into the S-polarized light, and the fourth polarizing beam splitter. 105 is incident. Then, the light is reflected by the polarization separation surface 151 of the fourth polarization beam splitter 105 and is emitted from the light transmission surface 105 c of the fourth polarization beam splitter 105.

  In this way, the R light, G light, and B light emitted from the translucent surface 105c of the fourth polarizing beam splitter 105 expands the color image on a screen (not shown) via the projection lens 130 arranged in the subsequent stage. indicate.

  Here, the generation of interference fringes, which is a problem in the conventional optical system, will be described with reference to FIG. This figure is an enlarged view of the arrangement of the second polarizing beam splitter 103, the reflective spatial light modulator 161 for G light, and the reflective spatial light modulator 162 for R light. As described in the problem to be solved by the above-described invention, a configuration in which two reflective spatial light modulation elements are arranged with respect to one polarization beam splitter, and a polarization separation surface of the polarization beam splitter is provided. Since the interference light fringes are generated in the color light reflected and reflected by the polarization separation surface, the P-polarized light incident on the second polarization beam splitter 103 is transmitted. R light becomes a problem.

  For the sake of explanation, symbols R, Rmi, Rmo, Rsi, and Rso are attached to each R light in the figure. The R light incident on the second polarization beam splitter 103 is incident as P-polarized light R as described above. Then, the light travels straight through the polarization separation surface 131 of the second polarization beam splitter 103, becomes Rmi, exits from the light transmission surface 103b, and enters the R-compatible reflective spatial light modulator 162.

However, due to the general characteristics of the polarization separation surface of the polarization beam splitter, a part of the incident R light R is reflected by the polarization separation surface 131 and emitted from the light transmission surface 103a of the second polarization beam splitter 103, so that it corresponds to G. R-light Rsi is incident on the reflective spatial light modulator 161.
The R light Rsi is reflected by the reflective spatial light modulation element 161 corresponding to G and becomes R light Rso. Since the R light Rso is P-polarized light, it travels straight through the polarization separation surface 131 and enters the fourth polarization beam splitter 105. Then, the light travels straight through the polarization separation surface 151 of the fourth polarization beam splitter 105 and exits from the light transmission surface 105 c of the fourth polarization beam splitter 105.

  On the other hand, the R light Rmi that travels straight through the polarization separation surface 131 of the second polarization beam splitter 103, exits from the light transmission surface 103b, and enters the R-compatible reflective spatial light modulator 162 is reflected by the reflective spatial light modulation. The element 162 receives light modulation corresponding to the video signal corresponding to R and is reflected. The S polarization component Rmo of the R light generated by the light modulation is reflected by the polarization separation surface 131 of the second polarization beam splitter 103 and enters the color polarizer 124. In the color polarizer 124, the S-polarized component of the R light is converted into P-polarized light and enters the fourth polarizing beam splitter 105. Then, the light travels straight through the polarization separation surface 151 of the fourth polarization beam splitter 105 and exits from the light transmission surface 105 c of the fourth polarization beam splitter 105.

  These R light Rmi and R light Rmo emitted from the light transmitting surface 105c of the fourth polarizing beam splitter 105 interfere with each other on the screen via the projection lens 123 to form interference fringes. This interference fringe is a dark screen in which the level of the R light Rmo is small and the R light Rmo and the R light Rmi are at the same level, and between the polarization separation surface 131 and the G-compatible reflective spatial light modulator 161. When the distance Lg and the distance Lr between the polarization separation surface 131 and the R-compatible reflective spatial light modulation element 162 coincide with each other, the distance Lg becomes most noticeable.

  In general, a projection display device has a configuration in which the distance from the screen to each color reflection type spatial light modulation element is made uniform in order to make the focus of the image projected on the screen uniform with each color light. That is, the distance Lg between the polarization separation surface 131 and the G-compatible reflective spatial light modulator 161 and the distance Lr between the polarization separation surface 131 and the R-compatible reflective spatial light modulator 162 are made to coincide with each other. Yes.

  Therefore, an optical arrangement and a projection lens 130 that improve the arrangement relation will be described. The distance Lg between the polarization separation surface 131 and the reflective spatial light modulation element 161 corresponding to G and the distance Lr between the polarization separation surface 131 and the reflective spatial light modulation element 162 corresponding to R are respectively different from each other in the G correspondence. A corresponding reflective spatial light modulator 161 and an R compatible reflective spatial light modulator 162 are provided.

  However, the distance Lg between the polarization separation surface 131 and the G-compatible reflective spatial light modulator 161 and the distance Lr between the polarization separation surface 131 and the R-compatible reflective spatial light modulator 162 are different from each other at positions G. When the corresponding reflective spatial light modulator 161 and the corresponding reflective spatial light modulator 162 are installed, the focus on the screen is naturally shifted between the R light and the G light.

  Therefore, each of the G-corresponding G positions is located at a position where the distance Lr between the polarization separating surface 131 and the R-compatible reflective spatial light modulator 162 is larger than the distance Lg between the polarization separating surface 131 and the G-compatible reflective spatial light modulator 161. The reflection type spatial light modulation element 161 and the reflection type spatial light modulation element 162 corresponding to R are installed, and the axial chromatic aberration of the R region is large in the projection lens 130, and the focus position of the G region and the focus position of the R region can be different. Thus, axial chromatic aberration is given.

  That is, an axis corresponding to the difference between the distance Lr between the polarization separation surface 131 and the R-compatible reflective spatial light modulator 162 and the distance Lg between the polarization separation surface 131 and the G-compatible reflective spatial light modulator 161. Upper chromatic aberration is imparted to the projection lens 130. 3A shows an example of spherical aberration, and FIG. 3B shows an example of astigmatism. The spherical aberration and astigmatism shown in FIGS. 4A and 4B indicate the amount of aberration generated on the incident side of the projection lens 130 when an image is projected onto the screen. The horizontal axis represents the magnitude of aberration, which is the amount of aberration, and the unit is μm. The vertical axis in the spherical aberration shown in FIG. 5A is the height of the light ray incident on the projection lens 130, and the distance from the optical axis (distance from the center) of the projection lens 130 is normalized to 1 as the maximum value. It expresses. The vertical axis in astigmatism shown in FIG. 4B is from the lens optical axis (distance from the center) of the projection lens 130 at the position of the reflective spatial light modulator disposed at the back focus position of the projection lens 130, respectively. The maximum value is normalized to 1 and expressed.

  The spherical aberration and astigmatism shown in FIGS. 4A and 4B are each 0 on the vertical axis and the value on the optical axis of the projection lens 130 is the axial chromatic aberration. The difference between the aberration in the green region and the aberration in the red region between the colors means that the back focus position is different, and this difference in aberration is the difference between the back focus position in the green region and the back focus in the red region. This corresponds to the difference in distance from the position. From the figure, it can be seen that the axial chromatic aberration in the red region is large and there is a difference of about 67 μm between the focus position in the green region and the focus position in the red region. Accordingly, the difference between the distance Lr between the polarization separation surface 131 and the R-compatible reflective spatial light modulator 162 and the distance Lg between the polarization separation surface 131 and the G-compatible reflective spatial light modulator 161 is also about 67 μm. It is installed.

  In the figure, G indicates the aberration of the light wavelength of 0.54607 μm, and R indicates the aberration of the light wavelength of 0.630 μm. Astigmatism S indicates a sagittal ray, T indicates an aberration of a tangential ray, SR indicates an aberration of a sagittal ray of R light, SG indicates an aberration of a sagittal ray of G light, and TR indicates an aberration of a tangential ray of R light. Aberration, TG, indicates the aberration of tangential rays of G light.

The difference between the distance Lr between the polarization separation surface 131 and the R-compatible reflective spatial light modulator 162 and the distance Lg between the polarization separation surface 131 and the G-compatible reflective spatial light modulator 161 is the projection. This corresponds to the difference between the back focus distance for each of the R-compatible reflective spatial light modulators 162 of the lens 130 and the back focus distance for the G-compatible reflective spatial light modulator 161.
This is because, when the image is in focus on the screen, the reflective spatial light modulator corresponding to each color is at the position of the back focus distance of the projection lens 130.

Therefore, when the axial chromatic aberration of the projection lens 130 is ΔL, the lower limit value of ΔL, that is, the distance Lg between the polarization separation surface 131 and the G-type reflective spatial light modulator 161, and the polarization separation surface 131 and R correspondence. The lower limit value of the difference from the distance Lr to the reflective spatial light modulator 162 is a value that does not generate interference fringes from the condition of coherence distance, and manufacturing errors of the respective polarization beam splitter and projection lens 130 are taken into consideration. And a value exceeding 20 μm. More preferably, the value is 30 μm or more.
The coherence distance is generally expressed as λ0 ² / Δλ, where λ0 is the center wavelength of light that generates interference fringes and Δλ is the spread of the spectrum. If λ0 = 0.6 μm and Δλ = 0.018 μm, then λ0 ² / Δλ = 20 μm, which is preferably larger than this value.

The upper limit value of ΔL may be set based on the axial chromatic aberration condition of the projection lens 130. However, when white light is divided and combined into three colors of G / B / R, each color of G / B / R is a single color. If the axial chromatic aberration of the projection lens 130 is excessive because it is not light but has some spectral spread, the color light will be blurred and the desired imaging performance cannot be obtained. Therefore, the inventor has obtained a result that an upper limit value of ΔL is preferably 70 μm so that the axial chromatic aberration of the projection lens 130 is not excessive.
As described above, the value of the longitudinal chromatic aberration of the projection lens 130 is desirably 20 μm to 70 μm, and more desirably 30 μm to 70 μm.

  As described above, in the projection display device using the reflective spatial light modulator, each reflective spatial light modulator configured to arrange two reflective spatial light modulators with respect to one polarization beam splitter. A reflective spatial light modulation element is arranged so that the distance between the spatial light modulation element and the screen is different, and an axial chromatic aberration of the projection imaging lens is provided according to the difference in the distance, so that the polarization beam splitter has P The interference fringes of the colored light that is incident in the polarization state, reflected and emitted in the S polarization state are made inconspicuous, and the image quality of the dark image can be remarkably improved.

  The configuration of the optical system according to the first embodiment is the same as that of the conventional example, and can be realized without adding new components. Furthermore, there is no need to change the adjustment method.

  Next, the optical configuration of the projection display device applied to the second embodiment will be described with reference to FIG. This figure is a schematic plan view showing the optical configuration of the projection display device applied to the second embodiment, and the same components as those in the first embodiment are given the same numbers.

FIG. 4 is a schematic plan view showing an optical configuration of a projection display device applied to the second embodiment.
A color separation / synthesis optical system 290 surrounded by a broken line includes first, second, and third polarization beam splitters 102, 103, and 104 that function as cubic or prismatic polarization separation elements, and a fourth that functions as a polarization composition element. The polarization beam splitter 105 is arranged so that its polarization separation surfaces 121, 131, 141, 151 as a whole are substantially X-shaped. Further, a color polarizer having a function of rotating the polarization planes of the R light and the G light by 90 degrees on the light transmitting surface (upper side surface of the first polarization beam splitter) on the incident side of the first polarization beam splitter 102. 113, a color polarizer 118 having a function of rotating the polarization plane of the G light by 90 ° is provided between the first and second polarization beam splitters 102 and 103. Further, a color polarizer 124 having a function of rotating the polarization plane of the R light by 90 ° is provided between the second and fourth polarizing beam splitters 103 and 105, and between the third and fourth polarizing beam splitters 104 and 105. Includes a color polarizer 115 having a function of rotating the polarization plane of the B light by 90 °.

The projection display device 301 applied to the second embodiment operates as follows.
Unfixed polarized white light emitted from the light source 111 enters the integrator optical system 112. Then, the white light is made uniform and aligned with the S-polarized light and enters the color polarizer 113. Since the color polarizer 113 is a wavelength-selective polarization conversion means that rotates the planes of polarization of the R light and the G light by 90 °, the S polarization associated with the R light and the G light transmitted through the color polarizer 113 is converted to P polarization. Converted. Further, since the color polarizer 113 has no effect on the B light, they remain S-polarized light.
Hereinafter, the transition of the optical path and the plane of polarization of each color light will be described individually.

  First, the P-polarized G light transmitted through the color polarizer 113 passes through the polarization separation surface 121 of the first polarization beam splitter 102 and enters the color polarizer 118. Since the color polarizer 118 is a wavelength-selective polarization conversion unit that rotates the polarization plane of the G light by 90 °, the P-polarized light related to the G light transmitted through the color polarizer 118 is converted into S-polarized light. The S-polarized G light transmitted through the color polarizer 118 is incident on the second polarization beam splitter 103, reflected by the polarization separation surface 131 of the second polarization beam splitter 103, and emitted from the light-transmitting surface 103a. Is incident on the reflective spatial light modulator 161. Then, the reflection type spatial light modulation element 161 receives light modulation according to the video signal corresponding to G and reflects the light.

  The P-polarized component of the G light generated by the light modulation travels straight through the polarization separation surface 131 of the second polarization beam splitter 103 and enters the color polarizer 124. Since the color polarizer 124 is a wavelength-selective polarization conversion means that rotates the polarization plane of the R light by 90 °, it does not act on the G light and the P-polarized component of the G light goes straight through as it is P-polarized. Then, the light enters the fourth polarizing beam splitter 105. Then, the light travels straight through the polarization separation surface 151 of the fourth polarization beam splitter 105 and exits from the light transmission surface 105 c of the fourth polarization beam splitter 105.

  Next, the R light will be described. The P-polarized R light transmitted through the color polarizer 113 travels straight through the polarization separation surface 121 of the first polarization beam splitter 102 and enters the color polarizer 118. Since the color polarizer 118 is a wavelength-selective polarization conversion unit that rotates the polarization plane of the G light by 90 °, the color polarizer 118 does not act on the R light, and the R light remains P-polarized and the second polarizing beam splitter 103. Is incident on. The P-polarized R light incident on the second polarization beam splitter 103 travels straight through the polarization separation surface 131 of the second polarization beam splitter 103 and exits from the light transmission surface 103b to be reflected in R-type spatial light. The light enters the modulation element 162. Then, the reflection type spatial light modulation element 162 receives the light modulation corresponding to the video signal corresponding to R and is reflected.

  The S-polarized component of the R light generated by the light modulation is reflected by the polarization separation surface 131 of the second polarization beam splitter 103 and enters the color polarizer 124. Since the color polarizer 124 is a wavelength-selective polarization conversion unit that rotates the polarization plane of the R light by 90 °, the S-polarized component of the R light is converted into P-polarized light and enters the fourth polarizing beam splitter 105. To do. Then, the light travels straight through the polarization separation surface 151 of the fourth polarization beam splitter 105 and exits from the light transmission surface 105 c of the fourth polarization beam splitter 105.

  Next, the B light will be described. Since the color polarizer 113 has no effect on the B light, the B light remains as S-polarized light. Therefore, the S-polarized B light transmitted through the color polarizing filter 16 is polarized by the first polarization beam splitter 102. The light is reflected by the separation surface 121 and enters the third polarization beam splitter 104.

  The S-polarized B light is reflected by the polarization separation surface 141 of the third polarization beam splitter 104, exits from the light transmitting surface 104 d, and enters the B-type reflective spatial light modulator 163. Then, the reflection type spatial light modulation element 162 receives light modulation according to the video signal corresponding to B and is reflected.

  The P-polarized component of the B light generated by the light modulation is transmitted through the polarization separation surface 141 of the third polarization beam splitter 104 and enters the color polarizer 115. As described above, the color polarizer 115 is a wavelength-selective polarization conversion unit that rotates the polarization plane of the B light by 90 °, so that the P-polarized component of the B light is converted into the S-polarized light, and the fourth polarizing beam splitter. 105 is incident. Then, the light is reflected by the polarization separation surface 151 of the fourth polarization beam splitter 105 and is emitted from the light transmission surface 105 c of the fourth polarization beam splitter 105.

  In this way, the R light, G light, and B light emitted from the translucent surface 105c of the fourth polarizing beam splitter 105 expands the color image on a screen (not shown) via the projection lens 123 arranged in the subsequent stage. indicate.

The principle of generation of interference fringes, which is a problem in the conventional optical system, is as described with reference to FIG.
In Example 2, as shown in FIG. 4, the distance Lr between the polarization separation surface 131 and the R-type reflective spatial light modulator 162 is equal to the distance Lg between the polarization separation surface 131 and the G-type reflective spatial light modulator 161. A reflective spatial light modulation element 161 corresponding to G and a reflective spatial light modulation element 162 corresponding to R are respectively installed at larger positions, and the axial chromatic aberration of the R region corresponding to the difference between the distance Lr and the distance Lg is set. The applied chromatic aberration plate 126 was placed in the gap between the light transmitting surface 105 c of the fourth polarizing beam splitter 105 and the projection lens 123. However, these differences need to be set within a range where the focus of the image on the screen is not blurred. Table 1 shows an example of the chromatic aberration plate 126.

However, the numbers in Table 1 are
On-axis chromatic aberration of chromatic aberration plate: ΔI = | t / n1−t / n2 |
nd: refractive index of glass substrate used for chromatic aberration plate 126 νd: Abbe number of glass substrate used for chromatic aberration plate 126 t: thickness of glass substrate used for chromatic aberration plate 126 n1: center wavelength corresponding to second reflective liquid crystal element 162 Refractive index at λ1 n2: Refractive index at the center wavelength λ2 corresponding to the third reflective liquid crystal element 163.

  Examples 1 to 3 shown in Table 1 show that the axial chromatic aberration in the red region is large, and there are differences of about 51 μm, about 55 μm, and about 57 μm between the back focus position in the green region and the back focus position in the red region, respectively. Yes. Accordingly, the difference between the distance Lr between the polarization separation surface 131 and the R-compatible reflective spatial light modulation element 162 and the distance Lg between the polarization separation surface 131 and the G-compatible reflective spatial light modulation element 161 is also about 51 μm. , About 55 μm, about 57 μm.

The difference between the distance Lr between the polarization separation surface 131 and the R-compatible reflective spatial light modulator 162 and the distance Lg between the polarization separation surface 131 and the G-compatible reflective spatial light modulator 161 is the projection. This corresponds to the difference between the back focus distance for each of the R-compatible reflective spatial light modulators 162 of the lens 123 and the back focus distance for the G-compatible reflective spatial light modulator 161.
This is because, when the image is in focus on the screen, the reflective spatial light modulator corresponding to each color is at the position of the back focus distance of the projection lens 130.

Accordingly, when the axial chromatic aberration of the chromatic aberration plate is ΔI, the lower limit value of ΔI, that is, the distance Lg between the polarization separation surface 131 and the G-type reflective spatial light modulator 161, and the polarization separation surface 131 and the R correspondence The lower limit value of the difference from the distance Lr to the reflective spatial light modulator 162 is a value that does not generate interference fringes from the coherent distance condition, and also considers manufacturing errors of the respective polarization beam splitter and chromatic aberration plate 126. And a value exceeding 20 μm. More preferably, the value is 30 μm or more.
The coherence distance is generally expressed as λ0 ² / Δλ, where λ0 is the center wavelength of light that generates interference fringes and Δλ is the spread of the spectrum. If λ0 = 0.6 μm and Δλ = 0.018 μm, then λ0 ² / Δλ = 20 μm, which is preferably larger than this value.

The upper limit value of ΔI may be set based on the axial chromatic aberration condition of the chromatic aberration plate 126. When white light is divided and combined into three colors of G / B / R, each G / B / R color is a single color. If the longitudinal chromatic aberration of the chromatic aberration plate 126 is excessive because it is not light but has a certain spectral spread, blurring occurs in each color light and the desired imaging performance cannot be obtained. For this reason, the inventor obtained from experiments that the upper limit value of ΔL is desirably 70 μm so that the longitudinal chromatic aberration of the chromatic aberration plate 126 is not excessive.
As described above, the axial chromatic aberration value of the chromatic aberration plate 126 is desirably 20 μm to 70 μm, and more desirably 30 μm to 70 μm.

  As described above, in the projection display device using the reflective spatial light modulator, each reflective spatial light modulator configured to arrange two reflective spatial light modulators with respect to one polarization beam splitter. A reflective spatial light modulation element is arranged so that the distance between the spatial light modulation element and the screen is different, and a chromatic aberration plate is provided in accordance with the difference in the distance, so that it enters the polarization beam splitter in a P-polarized state. In addition, the interference fringes of the colored light reflected and emitted in the S-polarized state are made inconspicuous, and the image quality of a dark image can be remarkably improved.

  In the above description, a chromatic aberration plate is provided. However, a desired axial chromatic aberration is obtained by a polarizing beam splitter disposed between the projection lens and a reflective spatial light modulation element corresponding to colored light in which interference fringes are generated. The axial chromatic aberration of the polarization beam splitter and the chromatic aberration plate may be added to obtain a desired axial chromatic aberration.

  Further, the configuration of the optical system according to the second embodiment can be realized by adding a chromatic aberration plate to the same configuration as the conventional example, so that it is not necessary to change the structure of the optical system or change the adjustment method. A projection display device capable of projecting a quality image can be realized.

In the description of each of the above-described embodiments, the interference fringes of red light have been described based on the color arrangement of the optical system of the configuration example. However, in the projection display device using the reflective spatial light modulation element, one polarization beam splitter is used. This is a problem that can occur with colored light that is configured by arranging two reflective spatial light modulators, enters the polarization beam splitter in the P-polarized state, is reflected in the S-polarized state, and is emitted. You may comprise so that the interference fringe of blue light or green light may be reduced.
In the description of each of the above-described embodiments, the two color light beams out of the white light emitted from the light source are applied to the polarization beam splitter in which two reflective spatial light modulation elements are arranged. The polarizing beam splitter arranged in the previous stage is configured to pass through and enter, but it may be configured to be reflected by the polarizing beam splitter arranged in the previous stage.
The present invention is not limited to the embodiments described above.

1 is a schematic configuration diagram of an optical system of a projection display device applied to Example 1. FIG. It is a block diagram for demonstrating in detail the optical system used as the problem in the projection display apparatus applied to each Example. 2 shows an example of chromatic aberration of a projection lens applied to Example 1. FIG. It is a schematic block diagram of the optical system of the projection display apparatus applied to Example 2. FIG.

Explanation of symbols

111 ... Light source 112 ... Integrator optical system 113, 115, 118, 124 ... Color polarizers 102, 103, 104, 105 ... Polarizing beam splitters 121, 131, 141, 151 ... Polarization separating surfaces 123, 130 ... Projection lens 126 ... Chromatic aberration Plates 161, 162, 163... Reflective spatial light modulators

Claims (2)

In the projection display device,
A light source that emits indefinitely polarized light;
First to third reflective spatial light modulators for optically modulating three primary color lights obtained by color-separating the indefinitely polarized light;
The indefinitely polarized light emitted from the light source is converted into a first color component light having a first polarization plane and a second polarization plane having a plane of polarization different from the first polarization plane by 90 degrees. A first wavelength-selective polarization conversion means for separating and emitting the second and third color component lights having a polarization plane of
A first polarization separation element that receives a light beam that has passed through the first wavelength-selective polarization conversion unit and branches an optical path between the first color component light and the second and third color component lights;
The second and third color component lights are incident from the first polarization separation element, and the polarization plane of the second color component light and the polarization plane of the third color component light are emitted so as to be orthogonal to each other. Second wavelength-selective polarization conversion means,
A polarization separation surface on which the second and third color component lights are incident from the second wavelength-selective polarization conversion means, and the polarization separation surface transmits the second color component light, and The light is incident on the second reflective spatial light modulator disposed at a first distance with respect to the polarization separation surface, and the third color component light is reflected so that the light is reflected on the polarization separation surface. A second polarization separation element that is incident on the third reflective spatial light modulation element installed at a second distance different from the first distance;
A polarization beam combining element that receives the modulated light modulated by the first to third reflective spatial light modulation elements and synthesizes and emits the modulated light; and
A projection lens provided with axial chromatic aberration according to the difference between the first distance and the second distance;
A projection display device comprising: 2. The projection display device according to claim 1, wherein the axial chromatic aberration ΔL of the projection lens is configured to have a relationship of 20 μm <ΔL = | fb1−fb2 | ≦ 70 μm.
However, the back focus distance of the projection lens with respect to the center wavelength λ1 of the second color component light incident on the second reflective spatial light modulator is fb1, and the incident light is incident on the third reflective spatial light modulator. The back focus distance of the projection lens with respect to the center wavelength λ2 of the third color component light is assumed to be fb2.

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