JP2012220598A - Projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projector without pixel shift and with excellent resolution performance.SOLUTION: A reflective light modulating device 25b is disposed so as to reflect G light with a polarization selection element 32g, reflective light modulating devices 25a and 25c are disposed so as to transmit R light and B light through polarization selection elements 32r and 32b respectively, and toroidal lenses 28b and 28r are disposed for R light and B light.

Description

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

  Conventionally, a polarizing beam splitter formed of a multilayer interference film on a glass surface is generally used for a polarizing element applied to a projector using a reflective liquid crystal element as a spatial light modulation element. In recent years, a wire grid type PBS (polarizing plate) has been developed as an alternative to this, and it has begun to be installed in an optical engine of a projector, and a proposal of this wire grid polarizing element or a projector using the same has been made (Patent Literature). 1).

JP 2008-139389 A

When a wire grid type PBS is used as a polarization beam splitter (PBS), the polarization separation plane is inclined 45 degrees with respect to the incident direction of the light beam and arranged in the optical path.
When the light modulated by the reflective liquid crystal element is polarized and separated by the wire grid type PBS thus arranged, it is generally arranged and used so that the modulated image light is reflected.

  However, in the configuration in which the image light is arranged to be reflected by the wire grid type PBS in this way, when the image light modulated by the three reflective liquid crystal elements is synthesized on the screen and projected in full color, 3 Although it is necessary to adjust the position of the color image with high accuracy, there has been a problem that pixel displacement easily occurs due to deformation of the polarization separation surface of the wire grid type PBS.

  On the other hand, when the wire grid type PBS is used so as to transmit the image light modulated by the reflective liquid crystal element, the glass substrate of the wire grid type PBS is arranged at 45 degrees in the air with respect to the incident direction of the modulated light. Therefore, there is a problem that a large astigmatism occurs when the image light passes through the wire grid type PBS, and the resolution performance of the projected image on the screen by the projection lens is greatly deteriorated.

  In order to solve this problem, as shown in Patent Document 1, a proposal has been made to arrange a cylindrical lens for correcting this astigmatism on the exit surface of the color synthesis prism. However, since the three colors of light are corrected after being synthesized, chromatic aberration cannot be corrected.

  An object of the present invention is to provide a projector capable of correcting chromatic aberration while suppressing deterioration in resolution of an image projected on a screen and reducing pixel shift.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  In order to solve the above problems, a projector according to the present invention includes a light source, a color separation light guide optical system that separates a light beam from the light source into first, second, and third color lights having different wavelength bands, and Of the light from the first, second, and third reflective light modulators, the first, second, and third reflective light modulators that modulate the second and third color lights according to the image information, respectively. First, second, and third polarization selection elements that selectively pass light projected as light, and an astigmatism correction lens through which image light from the second and third polarization selection elements passes, A synthesis optical system that synthesizes the image light of the first, second, and third color lights; and a projection optical system that projects the image light that has passed through the synthesis optical system. The second reflection type light modulation device is arranged so as to be reflected by the polarization selection element, and the first and third color light images are arranged. Characterized in that the light and the first and third reflective light modulation device to transmit the first and third polarization selective element placed.

  According to the projector, since the second reflection type light modulation device is arranged so that the image light from the second reflection type light modulation device is reflected by the second polarization selection element, an image of the second color light is obtained. Light can produce a projected image with good resolution performance without causing astigmatism. In addition, since the first and third reflective light modulators are arranged so that the image light from the first and third reflective light modulators passes through the first and third polarization selection elements, It is possible to easily adjust the positions of the first and third reflective light modulators so that pixel displacement does not occur with reference to the second reflective light modulator. Furthermore, since the astigmatism correction lens is disposed in the optical path through which the image light from the first and third polarization selection elements passes, it is possible to correct astigmatism and chromatic aberration.

  In the projector, the first color light and the third color light are red light and blue light, and the second color light modulated by the second reflective light modulation device arranged so that the image light is reflected by the second polarization selection element. Is preferably green light.

  According to the above projector, since the green image light is reflected by the polarization selection element, no astigmatism occurs in the green image light, and thus other astigmatism correction lenses are used. Resolution performance is improved compared to the optical path. Since green light has higher visibility than red light and blue light, it is possible to obtain an effect of improving the overall resolution performance.

  Furthermore, the astigmatism correction lens includes an astigmatism correction lens that transmits image light from the first polarization selection element and an astigmatism correction lens that transmits image light from the third polarization selection element. It is preferable that they have different shapes.

  According to the projector, the astigmatism correction lens through which the image light of the first color light having different shapes passes and the astigmatism correction lens through which the second color light passes have different influences on the respective color lights. In addition to the astigmatism correction effect, a chromatic aberration correction effect can be obtained, and the resolution performance of the projected image can be improved and the pixel shift can be improved at the same time.

  Furthermore, in the projector, it is preferable that the astigmatism correction lens is any one of a toroidal lens, a cylindrical lens, and a free-form surface lens.

  According to the projector, an astigmatism correction effect can be obtained by the effects of the toroidal lens, the cylindrical lens, and the free-form surface lens, and the resolution performance of the projected image can be improved. By making the curvature of the toroidal lens through which the image light of the first color light passes different from the curvature of the toroidal lens through which the second color light passes, chromatic aberration correction can be easily performed.

  Further, in the projector, the first, second and third polarization selection elements are preferably flat plate-shaped optical elements provided with a birefringent structure.

  Here, a flat optical element provided with a birefringent structure means a polarizing element utilizing structural birefringence, specifically, a wire grid type PBS (polarizing plate), a laminated photonic crystal polarization. Including plates. A wire grid type PBS (polarizing plate) or the like has high stability with respect to the usage environment such as temperature, and can improve reliability at a relatively low cost.

It is a figure explaining the structure of the optical system of the projector which concerns on 1st Embodiment.

(First embodiment)
FIG. 1 is a diagram illustrating the configuration of the optical system of the projector according to the first embodiment of the invention.

  The projector 10 includes a light source device 21 that generates light source light, a color separation light guide optical system 23 that separates the light source light emitted from the light source device 21 into three colors of RGB, and emission from the color separation light guide optical system 23. The light modulation device 25 illuminated by the illumination light of each color, the cross dichroic prism 27 that combines the image light of each color emitted from the light modulation device 25, and the image light that has passed through the cross dichroic prism 27 is screened (not shown) And a projection lens 29 which is a projection optical system for projecting to the projector. Among these, the light source device 21, the color separation light guide optical system 23, the light modulation device 25, and the cross dichroic prism 27 are image forming devices that form image light to be projected onto the screen.

  In the projector 10 described above, the light source device 21 that is a light source includes a light source lamp 21a, a concave lens 21b, a pair of fly-eye optical systems 21d and 21e, a polarization conversion member 21g, and a superimposing lens 21i. Among these, the light source lamp 21a is composed of, for example, a high-pressure mercury lamp, and includes a concave mirror that collects the light source light and emits it forward. The concave lens 21b has a role of collimating the light source light from the light source lamp 21a. When the concave mirror of the light source lamp 21a is a paraboloid, the concave lens 21b can be omitted. The pair of fly-eye optical systems 21d and 21e is composed of a plurality of element lenses arranged in a matrix, and the light source light from the light source lamp 21a passing through the concave lens 21b is divided by these element lenses to be individually condensed and diverged. Let The polarization conversion member 21g converts the light source light emitted from the fly-eye optical system 21e into, for example, only the S-polarized component perpendicular to the paper surface of FIG. The superimposing lens 21i appropriately superimposes the illumination light having passed through the polarization conversion member 21g as a whole, thereby enabling superimposing illumination on the light modulation devices of the respective colors provided in the light modulation device 25. In other words, the illumination light that has passed through both the fly-eye optical systems 21d and 21e and the superimposing lens 21i passes through the color separation light guide optical system 23 described in detail below, and is reflected light modulation of each color provided in the light modulation device 25. The devices 25a, 25b, and 25c are uniformly superimposed and illuminated.

The color separation light guide optical system 23 includes a cross dichroic mirror 23a, a dichroic mirror plate 23b, and reflection mirrors 23j and 23k, and first, second and third color lights (red (R) light, The light is separated into green (G) light and blue (B) light) and guided to the corresponding optical path of the light modulator 25. The cross dichroic mirror 23a is a first dichroic that reflects light in a wavelength range corresponding to red (R) light and green (G) light and transmits light in a wavelength range corresponding to blue (B) light among incident light. And a second dichroic mirror that transmits light in a wavelength range corresponding to red (R) light and green (G) light and reflects light in a wavelength range corresponding to blue (B) light among the incident light. Part 31b. The dichroic mirror plate 23b transmits incident red (R) light and reflects green (G) light.
In the color separation light guide optical system 23, the substantially white light source light from the light source device 21 enters the cross dichroic mirror 23a. The red (R) light reflected by one of the first dichroic mirrors 31a constituting the cross dichroic mirror 23a is reflected by the reflection mirror 23j, passes through the dichroic mirror plate 23b, and remains as S-polarized light, for example. The light is incident on a polarization selection element 32 r which is a reflection type polarizing plate provided at 25.

  On the other hand, the blue (B) light reflected by the other second dichroic mirror portion 31b constituting the cross dichroic mirror 23a is reflected by the reflection mirror 23k and is provided in the light modulation device 25, for example, as S-polarized light. The light enters the polarization selection element 32b which is a reflective polarizing plate.

  Further, the green (G) light reflected by the first dichroic mirror unit 31 a is reflected by the reflection mirror 23 j and reflected by the dichroic mirror plate 23 b, and enters the half-wave plate 26 provided in the light modulator 25. To do.

  The light modulation device 25 is the first, second, and third reflection type modulation devices 25a, 25b, and 25c as reflection type spatial light modulation elements, a half-wave plate 26, and a reflection type polarizing plate. 1, second and third polarization selection elements 32 r, 32 g, and 32 b, and cleanup polarizing plates 34 r, 34 g, and 34 b that are first, second, and third polarizing plates.

  Each of the reflection type light modulation devices 25a to 25c is a non-light-emitting reflection type light modulation device that modulates the spatial intensity distribution of the incident illumination light, and each of the three color lights that have entered the reflection type light modulation devices 25a to 25c. Light (red (R) light, green (G) light, blue (B) light) is modulated according to a drive signal or an image signal input as an electrical signal to each of the reflection type light modulation devices 25a to 25c. . At that time, the polarization selection elements 32r, 32g, and 32b adjust the polarization direction of the illumination light incident on the respective reflection type light modulation devices 25a, 25b, and 25c, and also from the reflection type light modulation devices 25a, 25b, and 25c. Component light having a predetermined polarization direction is extracted as image light from the emitted modulated light. At this time, the clean-up polarizing plates 34r, 34g, and 34b can increase the extinction ratio on the exit side of the polarization selection elements 32r, 32g, and 32b, thereby improving the contrast of the image light.

  The S knitted light guided to the red (R) optical path OP1 by the color separation light guide optical system 23 is reflected by the polarization selection element 32r and illuminates the reflective light modulation device 25a. The reflection type light modulation device 25a reflects light modulated according to image information. Thereafter, the red (R) light modulated by the reflective light modulation device 25a is incident on the polarization selection element 32r again, and the P-polarized component of the modulated red (R) light is transmitted as image light. The S-polarized light component which is non-image light is reflected. This image light is in a state in which large astigmatism is generated when it passes through the substrate of the polarization selection element 32r. The red (R) light as the image light transmitted through the polarization selection element 32r has its remaining S-polarized component removed by the cleanup polarizing plate 34r and is incident on the cross dichroic prim.

  The S knitted light guided to the blue (B) optical path OP3 by the color separation light guide optical system 23 is reflected by the polarization selection element 32b and illuminates the reflective light modulation device 25c. The reflection type light modulation device 25c reflects light modulated according to image information. Thereafter, the blue (B) light modulated by the reflective light modulator 25b is incident on the polarization selection element 32b again, and the P-polarized component of the modulated blue (B) light is transmitted as image light. The S-polarized light component which is non-image light is reflected. As with the red (R) light, the blue (B) light image light is in a state in which a large amount of astigmatism occurs when it passes through the substrate of the polarization selection element 32b. The blue (B) light as the image light transmitted through the polarization selection element 32b is removed by the cleanup polarizing plate 34b, and the remaining S-polarized light component is incident on the cross dichroic prim.

  The S-shaped light guided to the green (G) optical path OP2 by the color separation light guide optical system 23 passes through the half-wave plate 26, rotates the polarization vibration direction by 90 degrees, and becomes P-polarized light. The light passes through the polarization selection element 32g, which is a plate, and illuminates the reflective light modulation device 25b. The reflection type light modulation device 25b reflects light modulated according to image information. Thereafter, the green (G) light modulated by the reflective light modulator 25b is incident on the polarization selection element 32g again, and reflects the S-polarized light component of the modulated green (G) light as image light, and the others. The P-polarized light component that is non-image light is transmitted. Unlike the red (R) light and the blue (B) light, the green (G) image light does not pass through the substrate of the polarization selection element 32g, so that astigmatism does not occur. The green (G) light as the image light reflected from the polarization selection element 32g has its remaining P-polarized light component removed by the cleanup polarizing plate 34g and is incident on the cross dichroic prim.

  The cross dichroic prism 27 is a photosynthetic member, has a substantially square shape in plan view in which four right-angle prisms are bonded together, and a pair of first and second crosses in an X shape at the interface where the right-angle prisms are bonded together. Two dielectric multilayer films 27a and 27b are formed. One first dielectric multilayer film 27a reflects red (R) light, and the other second dielectric multilayer film 27b reflects blue (B) light. The cross dichroic prism 27 reflects the red (R) light from the reflection type light modulation device 25a by the first dielectric multilayer film 27a and emits it to the left in the traveling direction, and the green (G) from the reflection type light modulation device 25b. ) Light travels straight through and exits through the first and second dielectric multilayer films 27a and 27b, and the blue (B) light from the reflective light modulator 25c is reflected by the second dielectric multilayer film 27b and travels in the traveling direction. Inject to the right.

Here, toroidal lenses 28r and 28b are arranged on the incident surfaces of the cross dichroic prism 27 according to the respective color lights as astigmatism correction lenses for correcting astigmatism generated by the polarization selection elements 32r and 32b. Therefore, astigmatism is favorably corrected by the toroidal lenses 28r and 28b. For example, a toroidal lens 28r is formed on the surface of the cross dichroic prism 27 where the red (R) light is incident, and a toroidal lens 28b is formed on the surface of the blue (B) light.
Red (R) light, green (G) light, and blue (B) light image light superimposed by the cross dichroic prism 27 is incident on the projection lens 29.

  The projection lens 29 projects the color image light synthesized by the cross dichroic prism 27 on a screen (not shown) at a desired magnification. That is, a color moving image or a color still image with a desired magnification corresponding to the drive signal or image signal input to each of the reflection type light modulation devices 25a to 25c is projected on the screen.

  At this time, the curvature of the toroidal lenses 28r and 28b of the cross dichroic prism 27 is changed corresponding to each of red (R) light and blue (B) light. That is, the toroidal lenses 28r and 28b have different curvatures. As a result, it is possible to correct the astigmatism of the image light of red (R) light and blue (B) light and at the same time correct the chromatic aberration of the projection lens 29.

In the projector 10 described above, the image light of red (R) light and blue (B) light is transmitted through the polarization selection elements 32r and 32b, so that astigmatism occurs but the glass substrates of the polarization selection elements 32r and 32b. The influence of the deformation such as warpage on the pixel shift is very small. On the other hand, since the image light of green (G) light reflects the polarization selection element 32g, astigmatism does not occur and good resolution performance can be obtained.
According to the present embodiment, since the green (G) light image light is reflected by the polarization selection element 32g, no astigmatism occurs in the green (G) light image light. This improves the resolution performance compared to other red (R) light and blue (B) image light using an astigmatism correction lens. Since green (G) light has higher visibility than red (R) light and blue (B) light, it is possible to obtain an effect of improving the overall resolution performance.

Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and can be implemented in various modes without departing from the gist thereof. Such modifications are also possible.
In the present embodiment, the wire selection type PBS (polarizing plate) has been described as an example of the polarization selection elements 32r, 32g, and 32b, but is not limited thereto. The polarization conversion elements 2r, 32g, and 32b are flat-plate optical elements provided with a birefringence structure, and mean polarization elements using structural birefringence. Specifically, in addition to a wire grid type PBS (polarizing plate), a laminated photonic crystal polarizing plate is included. A wire grid type PBS (polarizing plate) or the like has high stability with respect to the usage environment such as temperature, and can improve reliability at a relatively low cost.

  In this embodiment, the toroidal lenses 28r and 28b have been described as being formed on the incident surface of the cross dichroic prism 27, but the present invention is not limited to this. The toroidal lenses 28r and 28b can be formed separately from the cross dichroic prism 27, and can be arranged in the corresponding optical paths between the polarization selection elements 32r and 32b and the cross dichroic prism 27, respectively. In that case, the toroidal lenses 28r and 28b and the cross dichroic prism 27 can be arranged apart from each other, or the toroidal lenses 28r and 28b and the cross dichroic prism 27 can be bonded and fixed.

  In this embodiment, an example in which a toroidal lens is applied as an astigmatism correction lens has been described. However, the present invention is not limited to this. Cylindrical lens as an astigmatism correction lens. A free-form surface lens or the like can also be applied.

  In the projector 10 of the above embodiment, the light source device 21 is configured by the light source lamp 21a, the concave lens 21b, the pair of fly-eye optical systems 21d and 21e, the polarization conversion member 21g, and the superimposing lens 21i. 21d and 21e, the polarization conversion member 21g, and the like can be omitted, and the light source lamp 21a can be replaced with another light source such as an ultrahigh pressure mercury lamp, a metal halide lamp, or an LED (light emitting diode).

  In the projector 10 of the above embodiment, the fly-eye optical systems 21d and 21e and the superimposing lens 21i are provided so that the reflective light modulators 25a, 25b, and 25c of the respective colors are illuminated with uniform brightness in the respective planes. However, an integrator rod optical system can be used instead.

  The projector 10 according to the above embodiment can be used not only as a front type projector that projects from the direction of observing the screen, but also as a rear type projector that projects from the side opposite to the direction of observing the screen.

  DESCRIPTION OF SYMBOLS 10 ... Projector, 21 ... Light source device, 23 ... Color separation light guide optical system, 23a ... Cross dichroic mirror, 23b ... Dichroic mirror plate, 23j, 23k ... Reflection mirror, 25 ... Light modulation device, 25a, 25b, 25c ... Reflection 27: Cross dichroic prism, 27a, 27b ... Dielectric multilayer film, 28r, 28b ... Toroidal lens, 29 ... Projection lens, 31a, 31b ... Dichroic mirror part, 32r, 32g, 32b ... Polarization selection element, 34r, 34g, 34b ... cleanup polarizing plates.

Claims (5)

A light source;
A color separation light-guiding optical system that separates a light beam from the light source into first, second, and third color lights having different wavelength bands;
First, second, and third reflective light modulators that modulate the first, second, and third color lights, respectively, according to image information;
First, second, and third polarization selection elements that selectively pass light projected as image light out of light from the first, second, and third reflective light modulation devices;
An astigmatism correction lens through which image light from the first and third polarization selection elements passes,
A combining optical system that combines the image light of the first, second, and third color lights;
A projection optical system for projecting image light that has passed through the synthetic optical system;
With
Disposing the second reflective light modulation device so as to reflect the image light of the second color light by the second polarization selection element;
The projector according to claim 1, wherein the first and third reflective light modulators are arranged so that the image light of the first and third color lights is transmitted through the first and third polarization selection elements. The first color light and the third color light are red light and blue light,
The projector according to claim 1, wherein the second color light modulated by the second reflective light modulation device arranged so that image light is reflected by the second polarization selection element is green light.   The astigmatism correction lens includes an astigmatism correction lens that transmits image light from the first polarization selection element, and an astigmatism correction lens that transmits image light from the third polarization selection element. The projector according to claim 1, wherein the projectors have different shapes.   The projector according to claim 1, wherein the astigmatism correction lens is any one of a toroidal lens, a cylindrical lens, and a free-form surface lens.   5. The projector according to claim 1, wherein each of the first, second, and third polarization selection elements is a flat optical element provided with a birefringent structure.

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