JPH09138369A - Optical device, optical correcting method and projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce adverse effect exerted on resolution by astigmatism caused at a color synthesizing optical system. SOLUTION: A projecting lens is constituted of a first lens group 71 and second lens groups 64, 65 and 66; a color synthesizing optical system is constituted of a transparent plate 67, dichroic mirrors 68 and 69, and a plane mirror 70; the second lens groups 64, 65 and 66 are arranged between the color synthesizing optical system and polarizing beam splitters 52, 53 and 54; and the flat surface of the plate 67, a flat surface including the normal of the color synthesizing surface of the mirrors 68 and 69, and the optical axis of the projecting lens, and a flat surface including the normal of the polarizing separation surfaces of the beam splitters 52, 53 and 54 and the optical axis of the projecting lens cross at a right angle with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device, an optical correction method and a projection type display device which can be used for, for example, a device for enlarging and projecting an optical image formed on a light valve on a screen.

[0002]

2. Description of the Related Art In order to obtain a large-screen image, a method of forming an optical image corresponding to an image signal on a light valve, irradiating the optical image with light, and enlarging and projecting the image on a screen by a projection lens is well known. Have been. Recently, attention has been paid to a projection display device using a liquid crystal panel as a light valve.

In order to increase the resolution of the projected image,
For example, Ledebuhr et al. Have proposed in US Pat. No. 4,836,649 a method of using a reflective light valve capable of increasing the number of pixels without decreasing the pixel aperture ratio of a liquid crystal panel. In the case of a reflective light valve, it is not necessary to place a switching element between pixel electrodes, so the pixel pitch can be made smaller and the density can be easily increased. To be

An example of the basic structure of the reflection type light valve and its operating principle will be described below with reference to FIG. A photoconductive layer 3, a light reflection layer 4, and a liquid crystal layer 5 as a light modulation layer are sandwiched between two transparent electrodes 2 and 6 formed on two glass substrates 1 and 7, and two transparent electrodes 2 are provided. , 6 is applied with a voltage. The writing light 8 from the image source enters the photoconductive layer 3 from the glass substrate 1 side. On the other hand, the reading light 9 enters the liquid crystal layer 5 from the glass substrate 7 side. The applied voltage of the liquid crystal layer 5 changes according to the written image formed on the photoconductive layer 3 to modulate the read light 9. The modulated read light 9 is reflected by the light reflection layer 4 and then projected as a projection image on a screen (not shown). As the material of the light modulation layer, ferroelectric liquid crystal, nematic liquid crystal, or the like can be used.

Next, in order to obtain a full-color, high-luminance, high-resolution projected image, an example of the configuration of a projection type display device using three reflection type light valves for red, green and blue is shown in FIG. Show. The near-parallel light emitted from the light source 11 passes through a cold mirror 12 that transmits ultraviolet light and infrared light and reflects visible light, and then dichroic mirrors 13 and 14,
The color separation optical system including the plane mirror 15 separates the light into three primary colors of green, blue, and red. The three primary color lights are plane mirrors 16,
Reference numerals 17 and 18 respectively enter the corresponding polarization beam splitters 19, 20, and 21 to separate the reflected S-polarized light component and the transmitted P-polarized light component, and the S-polarized light component is read out as a corresponding reflection type light valve 22, 23, 2
4 respectively. Reflective light valves 22, 2
Reference numerals 3 and 24 are for modulating the readout light by utilizing the birefringence of the liquid crystal, and have the structure shown in FIG. Writing light from an image source 25, 26, 27 such as a CRT is imaged on the photoconductive layers of the reflection type light valves 22, 23, 24 by the writing lenses 28, 29, 30, and an applied voltage corresponding to the written image. Therefore, the birefringence of the liquid crystal layer changes. That is, when linearly polarized light having a predetermined polarization direction enters as read light, reflected light becomes elliptically polarized light. Therefore, the S-polarized component is reflected by the reflective light valve 22,
A part of the light is converted into a P-polarized component by 23 and 24 and is incident on the polarization beam splitters 19, 20 and 21 again. The P-polarized component contained in the reflected light is the polarization beam splitter 1
After passing through 9, 20, and 21, dichroic mirror 3
The color synthesizing optical system consisting of 1, 32 and a plane mirror 33 combines them into one and enters the projection lens 34, and the S-polarized component is reflected by the polarization beam splitters 19, 20, 21 and advances toward the light source 11. In this way, the optical image formed as a change in birefringence on the liquid crystal layers of the reflective light valves 22, 23, 24 is enlarged and projected on the screen (not shown) by the projection lens 34.

[0006]

In the configuration shown in FIG. 13, the number of the projection lens 34 is one, and compared with the case where three projection lenses are used, the convergence adjustment and the color uniformity of the projection image of the three primary colors, and the This is advantageous in terms of compactness of the set. However, a color combining optical system for combining the reflected light from the three light valves into one is required, and the color combining surfaces of the dichroic mirrors 31 and 32 used in this case are as follows.
The projection lens 34 is arranged obliquely with respect to the optical axis. If a plane-parallel plate (dichroic mirror) having a specific thickness that is obliquely inclined is in the optical path of the imaging optical system, astigmatism occurs, which causes a significant deterioration in the resolution of the projected image.

Therefore, the dichroic mirrors 31, 32 are provided.
The following two methods are conceivable as means for reducing or eliminating the astigmatism that occurs in 1.

A) The substrate thickness of the dichroic mirror is reduced.

B) A dichroic prism that does not generate astigmatism is used.

Since the color synthesizing optical system is arranged between the light valve and the projection lens, it is necessary to consider it as a part of the projection optical system. In this case, particularly the reflecting surface of the dichroic mirror is required to have high surface accuracy. This becomes more difficult as the substrate thickness is reduced. In particular, when displaying a high-definition projection image such as high-definition, the substrate thickness must be at least 1.5 mm or more to satisfy the surface accuracy required for the reflecting surface of the dichroic mirror. Therefore, the method a) has a limit, and it is difficult to reduce the adverse effect of astigmatism on the resolution.

In the method b), two glass prisms are used as the dichroic prism, a color combining surface is formed on the joint surface, and the refractive index of the dichroic mirror substrate is placed in a transparent container having the dichroic mirror disposed therein. A method of filling a liquid having the same refractive index as the above and forming a prism shape as a whole can be considered. However, the former becomes very expensive and the weight becomes heavier. In the latter, the optical path length occupied by the liquid in the color combining optical path is very long, so that the focal point shift of the projected image due to the temperature dependence of the liquid refractive index is prevented. There was a problem that it was difficult to hire in each case because it cannot be ignored.

The present invention takes these problems of the prior art into consideration,
Provided are an optical device and an optical correction method capable of correcting astigmatism generated in a color synthesizing optical system more satisfactorily than in the past, and by using this optical device, it is possible to further improve the optical system and the optical correction method. It is an object of the present invention to provide a projection type display device capable of displaying a projection image having a resolution.

[0013]

According to a first aspect of the present invention, there is provided an image forming means for forming an optical image, a second lens means for transmitting light from the image forming means, and a second lens means. Of the flat plate member for transmitting and / or reflecting the light, and a first lens means for entering and emitting the light from the flat plate member, wherein the flat plate member is provided on the optical axis of the first lens means. The optical device is obliquely arranged, and the degree of astigmatism caused by the flat plate member is smaller than the degree caused by the absence of the second lens means.

According to a sixth aspect of the present invention, the image forming means for forming an optical image and the first and second polarization components orthogonal to each other reflect the first polarization component and the second polarization component. A polarization separation means having a polarization selection characteristic for transmitting light, a flat plate member for transmitting and / or reflecting light, and a lens means for making the light from the flat plate member incident and to emit the light are arranged in this order. The face plate member is obliquely arranged with respect to the optical axis of the lens means, and the polarization separating means is obliquely arranged with respect to the optical axis of the lens means, on which a film having the polarization selection characteristic is formed. A transparent substrate having a predetermined thickness, and a plane including a normal to the plane of the flat plate member on which the transmission and / or reflection is performed and the optical axis of the lens means; and the film forming surface of the transparent substrate. The normal to and the lens means An optical device comprising a plane containing the optical axes are orthogonal to each other.

The present invention according to claim 11 is the image forming means for forming an optical image, the second lens means for transmitting the light from the image forming means, and the light for transmitting the light from the second lens means. Alternatively, a plane plate member for reflecting the light and a first lens unit for entering and emitting light from the plane plate member are provided, and the plane plate member is arranged obliquely with respect to the optical axis of the first lens unit. An optical correction method for an optical device,
The first lens means receives light from the flat plate member and projects the optical image, and the second lens means is disposed between the flat plate member and the image forming means, and the flat plate member is provided. The degree of astigmatism caused by the member is the second
It is an optical correction method that adjusts the magnification of the second lens so that it becomes smaller than the degree that occurs when there is no lens.

According to a twelfth aspect of the present invention, image forming means for forming an optical image, polarized light separating means of a predetermined thickness for transmitting or reflecting light according to a polarization component of the light, and transmitting and / or reflecting light. A plane plate member having a predetermined thickness and a lens means for entering and emitting light from the plane plate member are provided in this order, and the plane plate member is arranged obliquely with respect to the optical axis of the lens means. An optical correction method for an optical device,
The plane including the normal line to the plane plate member and the optical axis of the lens means and the plane including the normal line to the polarization separating means and the optical axis of the lens means are orthogonal to each other, and are generated by the plane plate member. This is an optical correction method that adjusts the relationship between the plate thickness of the plane plate member and the plate thickness of the transparent substrate so that astigmatism and astigmatism generated by the polarization splitting means are mutually corrected.

According to a thirteenth aspect of the present invention, a plurality of image forming means for forming an optical image as a change in birefringence and a polarization component provided for each of the image forming means and having polarization planes orthogonal to each other are separated. Polarization separating means, a second lens provided for each polarization separating means for transmitting the light from the polarization separating means, and one light from each of the polarization separating means.
A color synthesizing means for synthesizing the two and a first lens for emitting and emitting the light emitted from the color synthesizing means, respectively, in this order, and each polarization separating means is provided on the optical axis of the first lens. A parallel-plane transparent substrate obliquely arranged with respect to the transparent substrate, a dielectric multi-layer film having polarization selectivity is formed on the transparent substrate, and the color synthesizing means includes an optical axis of the first lens. It is configured to include a plurality of dichroic mirrors formed a dielectric multilayer film having wavelength selectivity on a transparent substrate of parallel planes arranged obliquely with respect to,
A plane including the normal line of the dielectric multilayer film forming surface of each of the dichroic mirrors and the optical axis of the first lens and / or the second lens, and a normal line of the dielectric multilayer film forming surface of each of the polarization separating means. An optical device in which a plane including the optical axes of the first lens and / or the second lens is orthogonal to each other.

According to a nineteenth aspect of the present invention, there is provided a light source which emits light containing color components of three primary colors, a color separation means which decomposes the emitted light of the light source into three primary color lights, and three of the color separation means.
Three front polarizers to which each of the two output lights respectively enter, a polarization beam splitter provided for each of the front polarizers, which transmits or reflects light from the front polarizer, A reflection type light valve, which is provided for each polarization beam splitter and forms an optical image based on light from a predetermined image source and optical writing means, and a color for combining the light from each polarization beam splitter into one. A second lens provided between the polarizing beam splitter and the color synthesizing means in correspondence with the polarized beam splitter; and a second lens for entering and emitting light emitted from the color synthesizing means. 1 lens, the image source generates image light to be incident corresponding to the reflection type light valve, and the optical writing unit converts the image light from the image source to the reflection type light. valve To form, each polarizing beam splitter has a polarization separation mirror dielectric multilayer film is formed with the polarization selectivity on a parallel plane transparent substrate, and,
The respective polarization beam splitters are arranged between the reflection type light valve and the second lens, and the color synthesizing means includes two dichroic mirrors and one optical correction plate having antireflection treatment on both surfaces. And one plane mirror, and the color synthesizing means is disposed between the first lens and the second lens, and the polarization splitting surface of the polarization splitting mirror and the two The color combining surface of the two dichroic mirrors and the antireflection surface of the optical correction plate are respectively arranged obliquely with respect to the optical axis of the first lens, and the normal line of the polarization separation surface of the polarization separation mirror. A plane including the optical axis of the first lens and / or the second lens, a color combining surface of the two dichroic mirrors, and a normal line of an antireflection surface of the optical correction plate and the first
The projection display device is arranged so as to be orthogonal to a plane including the lens and / or the optical axis of the second lens.

According to a twenty-seventh aspect of the present invention, a light source that emits light containing color components of three primary colors, a color separation means that decomposes the emitted light of the light source into three primary color lights, and three of the color separation means.
Provided between the three light valves to which each of the two output lights individually enter, color combining means for combining the light emitted from the light valves into one, and between the light valves and the color combining means. A second lens, and a first lens that emits light emitted from the color synthesizing unit and emits the light. The color synthesizing unit includes a first dichroic mirror, a second dichroic mirror, and a single dichroic mirror. The second lens is a projection display device arranged between the first dichroic mirror and the second dichroic mirror.

According to the present invention, the image forming means forms an optical image, the second lens means transmits the light from the image forming means, and the plane plate member transmits the light from the second lens means. Are transmitted and / or reflected, and the first lens means makes the light from the plane plate member incident and emits it. Further, the plane plate member is arranged obliquely with respect to the optical axis of the first lens means, and the degree of astigmatism generated based on the plane plate member is set in the case where the second lens means is not provided. It is small compared to the above-mentioned degree.

According to a sixth aspect of the present invention, the image forming means forms an optical image, and the polarization separating means reflects the first polarization component of the first and second polarization components orthogonal to each other, The plane plate member transmits and / or reflects light having a polarization selection characteristic of transmitting the second polarization component, and the lens means allows the light from the plane plate member to enter and exit. The plane plate member is arranged obliquely with respect to the optical axis of the lens means, and the polarization separation means is formed with a film having the polarization selection characteristic with respect to the optical axis of the lens means. A plane having a transparent substrate of a predetermined thickness arranged obliquely, the plane including a normal to the plane of the plane plate member on which the transmission and / or reflection is performed, and the optical axis of the lens means; A normal line to the film formation surface and a plane including the optical axis of the lens means are orthogonal to each other.

According to the present invention, astigmatism can be corrected more satisfactorily than in the conventional case, and the light source emits light containing color components of the three primary colors, and the color separation means is provided. The light emitted from the light source is decomposed into three primary color lights,
One front polarizer makes each of the three output lights of the color separation means incident individually, and a polarization beam splitter separates the light from the front polarizer provided for each of the front polarizers. Transmitting or reflecting, a reflection type light valve is provided for each of the polarization beam splitter, forms an optical image based on light from a predetermined image source and optical writing means,
The color synthesizing means outputs the light from each of the polarization beam splitters to 1
And a second lens is provided between the polarization beam splitter and the color synthesizing means in correspondence with the polarization beam splitter, and the first lens enters the light emitted from the color synthesizing means. And emit. Then, the image source generates image light to be incident corresponding to the reflection type light valve, and the optical writing unit forms the image light from the image source on the reflection type light valve. Each of the polarization beam splitters has a polarization separation mirror in which a dielectric multilayer film having polarization selectivity is formed on a transparent substrate having parallel planes, and each polarization beam splitter has the reflection type light valve. And the second lens, and the color combining unit includes two dichroic mirrors,
It is composed of one optical correction plate having antireflection treatment on both sides and one plane mirror, and the color synthesizing means is arranged between the first lens and the second lens. The polarization splitting surface of the polarization splitting mirror, the color combining surface of the two dichroic mirrors, and the antireflection surface of the optical correction plate are respectively arranged obliquely with respect to the optical axis of the first lens, and A normal to the polarization splitting surface of the polarization splitting mirror and the first lens and / or the second lens.
A plane including an optical axis of the lens, a color combining surface of the two dichroic mirrors, a normal line of an antireflection surface of the optical correction plate, and an optical axis of the first lens and / or the second lens. The planes are arranged so as to be orthogonal to each other.

According to the 27th aspect of the present invention, the light source emits light containing color components of three primary colors, the color separation means decomposes the emitted light of the light source into three primary color lights, and three light valves are provided. The three output lights of the color separation means are individually made incident, the color combining means combines the light emitted from the respective light valves into one, and the second lens combines the light valves and the color combining means. A first lens provided in between makes the emitted light from the color synthesizing unit incident and emits it. The color synthesizing means includes a first dichroic mirror, a second dichroic mirror, and one plane mirror, and the second lens includes the first dichroic mirror and the first dichroic mirror. It is arranged between the second dichroic mirrors.

With the above configuration, for example, astigmatism generated in the color combining optical system can be corrected well, and the projection optical system can be made compact. Therefore, in the projection type display device using the optical device of the present invention, a projection image with a very high resolution can be displayed even if it is configured by one projection lens having a color synthesizing optical system.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the accompanying drawings.

Dichroic mirror as color synthesizing means
Astigmatism due to
If the converging light is transmitted through the parallel flat plate P that is inclined for
The boundary surface between the transparent plate P and the medium (air in this case)
The plane including the line and the principal ray O of the convergent light is the incident surface, and
A ray lying in a plane perpendicular to the plane of incidence of is a sagittal ray S,
A ray lying in a plane parallel to the plane of incidence is meridional
Let the ray M be the sagittal ray S that has passed through the transparent plate P.
Point where each meridional ray M intersects with the principal ray O
Is Q_S, Q_MIt is caused by different things. or,
Point Q in this case _SAnd point Q_MThe interval between and is called the astigmatic difference
You.

As shown in FIG. 2A, when two parallel plane transparent plates P1 and P2 whose incident surfaces are orthogonal to each other are arranged, a sagittal ray and a meridional ray defined by the transparent plates P1 and P2, respectively. Replace each other and also act so as to cancel out astigmatism. When there is no lens system having power between the transparent plate P1 and the transparent plate P2, astigmatism can be corrected by making the inclination angle with respect to the optical axis, the plate thickness, and the refractive index of the transparent plate the same.

However, when a transparent plate for correcting astigmatism is added between the projection lens as the projection means and the light valve as the image forming means in addition to the dichroic mirror as the color synthesizing means, the projection is performed. The lens is required to have a very long back focus.

Therefore, as shown in FIG. 2B, the projection lens is composed of a first lens unit L1 and a second lens unit L2 having a long air gap, and a first lens unit L1 and a second lens unit L2. A color synthesizing optical system is arranged between the second lens group L2 and the light valve LV so as to correct astigmatism generated in the parallel flat plate P1 which is a dichroic mirror of the color synthesizing optical system. By disposing the transparent plate P2 having a parallel plane, it is possible to realize a projection lens having a small lens outer diameter while realizing a substantially long back focus (a distance from the first lens unit L1 to the light valve LV).

In this case, the transparent plate P2 for correcting astigmatism generated in the color combining optical system and the transparent plate P1 of the color combining optical system.
Since the second lens unit L2 having a power is disposed between and, the astigmatic difference d ₁ ′ generated in the color combining optical system is expressed by the following equation.

[0031]

(Equation 6)

Here, m is the virtual image magnification of the second lens unit L2, and d ₁ is the astigmatic difference generated in the color combining optical system when the second lens unit L2 is not provided.

Therefore, assuming that the astigmatic difference generated in the transparent plate P2 arranged between the second lens unit L2 and the light valve LV is d ₂ , the transparent plate P1 and the transparent plate P2 for correcting astigmatism. With respect to the relationship, the mutual plate thicknesses may be set so as to satisfy the following conditions.

[0034]

(Equation 7)

Further, the optical device of the present invention uses the polarization beam splitter as the polarization separation means having the functions of the polarizer and the analyzer, and the polarization beam splitter is provided between the second lens group and the image plane. And a transparent plate of a parallel plane forming a polarization separation surface is arranged so as to correct the astigmatism generated in the color combining optical system. By doing so, the polarization beam splitter can have a polarization separation function and an astigmatism correction function at the same time.

[0036] Incidentally, (6) a color synthesizing optical system as seen from the transparent plate P1 astigmatism generated in (dichroic mirror) d ₁ 'is astigmatic if the second lens group L2 is not astigmatism d ₁ Compared with, it is possible to reduce by the square of the virtual image magnification m by the second lens group having positive power. With respect to this point as well, a specific embodiment will be described later.

Specific embodiments of the projection display device using the optical device of the present invention will be described below with reference to the configuration diagram shown in FIG.

The second lens groups 64, 65 and 66 are cemented with the corresponding polarization beam splitters 52, 53 and 54, respectively. Further, the first lens group 71 and the second lens groups 64, 65, 66 constitute a projection lens, and the optical system from the polarization beam splitters 52, 53, 54 to the first lens group 71 includes a reflection type light valve 55. , 56, 57 will be referred to as a projection optical system for projecting the optical image on the screen.

The light emitted from the light source 41 emits light containing color components of three primary colors. The cold mirror 42 reflects visible light,
It transmits infrared light. Only the visible light of the radiated light from the light source 41 is reflected by the cold mirror 42, and the color separation optical system including the three dichroic mirrors 43, 44 and 45 sequentially decomposes the light into three primary color lights of green, blue and red. To be done. Each primary color light is transmitted to the front polarizer 46,
It is incident on 47 and 48, and both are emitted as substantially linearly polarized light. The primary color lights that have become substantially linearly polarized light enter the polarization beam splitters 52, 53, 54 through the mirrors 49, 50, 51 as readout light, and are reflected by the reflection type light valve 55,
It is reflected to the 56, 57 side. Reflective light valve 55,
56 and 57 have the same basic structure as that shown in FIG.

On the other hand, the images formed on the CRTs 58, 59, 60 are written by the writing lenses 61, 6 as writing light.
Reflective light valves 55, 5 corresponding to 2, 63
An image is formed on the photoconductive layers of 6, 57. The liquid crystal layer, which is a light modulation layer, modulates the incident linearly polarized read-out light into elliptically polarized light in accordance with the image formed on the photoconductive layer. The modulated read light is reflected by the light valves 55, 56, 57.
Reflected by the light reflection layer of the second lens group 6 and again enters the polarization beam splitters 52, 53, 54, and the reflected polarized component proceeds to the light source 41 side, and the transmitted polarized component is the second lens group 6
It is incident on 5, 66 and 67.

Light emitted from the second lens group 65, 66, 67 is transmitted through the transparent plate 67, dichroic mirrors 68, 69, and
The combined light is combined into one light by the color combining optical system in which the flat mirror 70 and the plane mirror 70 are combined.
Incident on 1. Three reflective light valves 55, 56,
The optical image on 57 is the first lens group 71 and the second lens group 6
4, 65, 66 enlarges and projects it on the screen at a distant position.

The transparent plate 67 is inserted in order to make the astigmatic differences generated in the color combining optical systems of the three primary color lights the same. Thereby, there is an effect that the plate thickness of each transparent plate of the three polarization beam splitters 52, 53, and 54 can be made the same.

Polarizing beam splitters 52, 53, 54,
Second lens group 64, 65, 66, transparent plate 67, dichroic mirrors 68, 69, mirror 70, first lens group 7
It is recommended to store all 1s in one lens barrel. In this case,
The projection optical system from the polarization beam splitters 52, 53, 54 to the first lens group 71 can be assembled accurately.

Next, the detailed structure of the polarization beam splitter will be described with reference to FIG. Polarizing beam splitter 5
2, 53, 54 and the second lens groups 64, 65, 66 are shown in FIG.
The polarization beam splitters 52, 53, 54 and the second lens groups 64, 65, 66 shown in FIG.

A liquid 85 is filled in the space of the container constituted by the frame 81, the transparent plates 82 and 83, and the polarization separation mirror 84. The polarization separation mirror 84 is a dielectric multilayer film deposited on a transparent glass substrate, and the surface of the dielectric multilayer film serving as the polarization separation surface is brought into close contact with the surrounding liquid 85 to exhibit polarization separation performance.

The liquid 85 used for the polarization beam splitters 52, 53, 54 is required to be transparent, have uniform optical characteristics, have a low freezing point, have a high boiling point, and be inexpensive. In the present embodiment, 55 wt% of ethylene glycol, 30 wt% of diethylene glycol, and 1 of glycerin are used as the liquid that substantially satisfies the above conditions.
A 5% by weight mixed solution of three kinds is used. The three-type mixed liquid has good optical performance, and has a freezing point of −52 ° C. and a boiling point of + 198 ° C., and thus can be used without problems in the environment in which the projection display device of the present embodiment is used. Further, the cost is low, and the weight and the cost are overwhelmingly advantageous as compared with the case where the glass prism is used.

As the liquid, other liquids containing ethylene glycol as a main component and different mixing ratios of the above-mentioned three kinds of liquids, pure ethylene glycol, or ethylene glycol aqueous solution may be used. However, it should be noted that when the material of the frame body 91 is aluminum, aluminum oxide may be precipitated due to the reaction of aluminum and water and the liquid may gradually become cloudy. Further, as the liquid, a material which is liquid at the time of assembly but becomes solid or gel after the assembly is completed (for example, gel transparent silicone resin KE1051 manufactured by Shin-Etsu Chemical Co., Ltd.) may be used.

The polarization-selective mirror 84 is formed by vapor-depositing a dielectric multilayer film in which low-refractive index film layers and high-refractive index film layers are alternately laminated on a glass substrate and has a maximum transmittance of P-polarized light. A type that utilizes the interference effect of the Brewster angle and the dielectric multilayer film is adopted. In this type of polarization splitting mirror, when the refractive index of the external medium is n _M , the refractive index of the low refractive index layer is n _L , and the refractive index of the high refractive index layer is n _H , the optimum incident angle θ _M of the light beam is Required by.

[0049]

(Equation 8)

If the condition of (Equation 8) is satisfied, the reflectance of S-polarized light can be increased by increasing the number of dielectric multilayer films while keeping the transmittance of P-polarized light at 100%.

The polarization separation mirror 84 of the present embodiment uses magnesium fluoride (refractive index 1.39) as a low refractive index film,
Titanium dioxide (refractive index 2.30) is used as the high refractive index film, and since the liquids 86, 87, 88 have a refractive index of 1.44 (Equation 8), the optimum ray incident angle is 55.6 °. Become. Therefore, the polarization selective mirror 84 is arranged so as to be inclined so that the angle formed with the optical axis of the projection optical system is 34.4 °. The dielectric multilayer film has a 13-layer structure, and each film thickness of the dielectric multilayer film is set so that the reflectance peak of S-polarized light becomes the center wavelength of each of the incident three primary color lights.

As described above, the reflectance is related to the number of layers of the dielectric multilayer film, and the center wavelength of the reflection wavelength is related to each film thickness of the dielectric multilayer film.

There are the following two configurations for broadening the reflection wavelength band.

That is, in the first configuration, the polarization separation mirror 84 has a first dielectric multilayer film and a second dielectric multilayer film having different reflection wavelength bands of the S-polarized component formed on both surfaces of the glass substrate. With this configuration, the reflection wavelength band of S-polarized light can be broadened as a whole. By doing this,
Good polarization separation performance can be exhibited even when the wavelength band of the light incident on the polarization beam splitters 52, 53, 54 is wide.

In the second configuration, the polarization separation mirror 84 widens the wavelength band for reflecting S-polarized light as the refractive index difference between the low refractive index layer and the high refractive index layer forming the dielectric multilayer film increases. be able to. Polarization separation mirror 8 of the present embodiment
In No. 4, magnesium fluoride, which is the lowest refractive index material that can be used as a transparent and highly durable material, and titanium dioxide, which is the highest refractive index material, are used to widen the reflection wavelength band of the S-polarized component as much as possible. However, a thin film material having another refractive index may be used. For example, silicon dioxide (refractive index 1.46), dialuminum trioxide (refractive index 1.62), etc. as the low refractive index layer, zinc sulfide (refractive index 2.30), cerium dioxide ( Refractive index 2.
30), zirconium dioxide (refractive index 2.05), ditantalum pentoxide (refractive index 2.10), hafnium dioxide (refractive index 2.00) and the like can be used. However,
Even in that case, the arrangement angle of the polarization separation mirror 84 is (Equation 8).
It is necessary to set so as to satisfy the condition of.

As shown in FIG. 4, the S-polarized light 86 vertically incident on the transparent plate 82 passes through the liquid 85 and is incident on the polarization separation mirror 84 at an angle of 55.6 °. Polarization separation mirror 8
The S-polarized light 87 reflected by 4 passes through the liquid 85 and is emitted from the transparent plate 83 to the reflective light valve side. The light reflected by the reflective light valve passes through the transparent plate 83 and the liquid 85 again and enters the polarization separation mirror 84. The P-polarized light 88 modulated by the reflection type light valve sequentially passes through the polarization separation mirror 84, the liquid 85, and the second lens group 88, goes to the first lens group 71 side shown in FIG. 3, and the unmodulated S-polarized light is generated. It is reflected by the polarization separation mirror 84 again to the transparent substrate 82 side.

In the structure shown in FIG. 3, the antireflection surface of the transparent plate 67 and the color combining surfaces of the dichroic mirrors 68 and 69 forming the color combining optical system as shown in FIG. The plane including the line and the optical axis of the projection optical system and the plane including the normal line of the polarization splitting surfaces of the polarization beam splitters 52, 53, and 54 and the optical axis of the projection optical system are arranged so as to be orthogonal to each other. There is. By doing so, the astigmatism generated in the transparent plate 67 and the dichroic mirrors 68 and 69,
Astigmatisms generated in the polarization beam splitters 52, 53, 54 act so as to cancel each other out. The greatest feature of the configuration of the present embodiment is that the polarization beam splitter 5
A refractive index difference is provided between a glass substrate serving as a polarization separation mirror of 2, 53, 54 and a liquid serving as a medium, and the polarization beam splitters 52, 53, 54 function as a polarizer and an analyzer, and color combination. It also has a function of correcting astigmatism that occurs in the optical system.

The principle of astigmatism generation and the amount of astigmatic difference will be described below with reference to the model diagrams shown in FIGS. 5 (a) and 5 (b).

FIG. 5A shows the case where the convergent light is obliquely incident on the boundary plane A having a refractive index difference. A ray traveling from the incident medium toward the point Q is refracted at the point B on the boundary plane A. Assuming that the refractive index of the incident side medium is n, the refractive index of the outgoing side medium is n ′, the incident angle is θ, and the refraction angle is θ ′, from Snell's law,

[0060]

(Equation 9)

The following relationship holds.

The sagittal paraxial ray in the incident side medium is the point Q.
It can be considered that it is on the surface of a cone formed by rotating the straight line BQ around the straight line NQ as the central axis and N is the leg of the perpendicular line dropped from the boundary plane A to the boundary plane A. Therefore, the sagittal paraxial image point Q _S should exist on the straight line NQ.

From the relationship between ΔBNQ and ΔBNQ _S ,

[0064]

(Equation 10)

The following relationship holds. (Equation 9), (Equation 10)
From the above, the following equation is obtained as an equation representing the position of the sagittal paraxial image point Q _S.

[0066]

[Equation 11]

On the other hand, in order to obtain the meridional paraxial image point, point B'on the boundary surface A from the incident side medium to the point Q.
Consider an incident ray that is incident on. Point B'is slightly apart from point B. The incident angle of the incident ray incident on the point B ′ is θ
Let + δθ and the refraction angle be θ ′ + δθ ′. △ BB'Q
Applying the triangular sine law to and ΔBB′Q _M ,

[0068]

(Equation 12)

[0069]

(Equation 13)

The following relationship holds. (Equation 12), (Equation 1)
From 3),

[0071]

[Equation 14]

Is obtained. If both δθ and δθ ′ are very small, (Equation 14) becomes

[0073]

(Equation 15)

Is obtained. Differentiating both sides of (Equation 9) by θ gives the following.

[0075]

(Equation 16)

From (Equation 15) and (Equation 16), δθ ′ / δ
When θ is deleted, the following equation is obtained as an equation representing the position of the meridional paraxial image point Q _M.

[0077]

[Equation 17]

From the comparison of (Equation 11) and (Equation 17), when a ray obliquely enters the boundary plane having a difference in refractive index, the sagittal paraxial image point Q _S and the meridional paraxial image point Q _M do not match. I understand.

Next, as shown in FIG. 5 (b), consider a case where the transparent plate P having a parallel plane is arranged obliquely with respect to the optical axis. When the thickness of the transparent plate P is t and the refractive index is n, the transparent plate P
Let n ′ be the refractive index of the external medium.

Let Q be a paraxial image point when there is no transparent plate P, B be an incident point when a light ray traveling along the optical axis is incident on the transparent plate P, and C be an exit point. Point Q due to plane of incidence of transparent plate P
Let Q _{S1 be} the sagittal paraxial image point, Q _{M1 be} the meridional paraxial image point, Q _{S2 be} the sagittal paraxial image point corresponding to the point Q _S1 on the exit side plane, and Q _M2 be the meridional paraxial image point. .

The following equations are established by (Equation 11) and (Equation 17).

[0082]

(Equation 18)

[0083]

[Equation 19]

[0084]

(Equation 20)

[0085]

(Equation 21)

Using the thickness t of the transparent plate P and the incident angle θ of the light rays,

[0087]

(Equation 22)

It can be expressed as Also, from FIG. 5 (b),

[0089]

(Equation 23)

[0090]

(Equation 24)

[Equation 18], (Equation 19), (Equation 2)
Substituting (2) into (Equation 23) and (Equation 24) and substituting the results into (Equation 20) and (Equation 21), the following equation is obtained.

[0092]

(Equation 25)

[0093]

(Equation 26)

From (Equation 25) and (Equation 26), the paraxial image points Q _S2 and Q _M2 corresponding to the paraxial image point Q when the transparent plate P is obliquely arranged with respect to the optical axis are obtained. You can If the transparent plate P is not perpendicular to the optical axis, points Q _S2 and Q _M2
It can be understood that astigmatism is generated because the values do not match.

If the distance between the sagittal paraxial image point Q _S2 and the meridional paraxial image point Q _M2 is d,

[0096]

[Equation 27]

[Equation 25] and (Equation 26) are replaced by (Equation 2)
By substituting it in (7) and eliminating θ ′ by using (Equation 9), the astigmatic difference d can be obtained by the following equation.

[0098]

[Equation 28]

When the medium is air, the refractive index n'is 1
And (Equation 28) can be expressed as the following equation.

[0100]

(Equation 29)

The configuration shown in FIG. 3 has the transparent plate 67 and the dichroic mirror 6 as shown in the model diagram of FIG. 2B.
The astigmatism is corrected by disposing 8, 69, the second lens groups 64, 65, 66, and the polarization beam splitters 52, 53, 54, respectively. In this placement method,
In particular, the effect of the second lens groups 64, 65, 66 will be described with reference to the schematic view of the projection optical system shown in FIG.

If the reflection type light valve 91 shown in FIG. 6 corresponds to the reflection type light valve 56 shown in FIG. 3, the polarization beam splitter 92 shown in FIG.
The second lens group 93 and the plane-parallel plates 94, 95, 96 forming the color combining optical system are respectively the polarization beam splitter 53, the transparent plate 67, the dichroic mirror 69, and
Corresponds to 68. The first lens group 97 shown in FIG.
Corresponds to the first lens group 71 in FIG.

The reflected light from the reflective light valve 91 is
The polarization beam splitter 92, the second lens group 93, the dichroic mirrors forming the color combining optical system, the transparent plate, or the plane parallel plates 94, 95, 96 serving as plane mirrors, the first
It passes through each of the lens groups 97 and is projected on a screen (not shown).

A solid line 98 is a light beam when the second lens group 93 is used, and a broken line 99 is a light beam when the second lens group 93 is not provided.

Since the projection display apparatus according to the present embodiment uses the reflection type light valve 91 and the polarization beam splitter 92 using the multilayer film as the polarizer and the analyzer, the projection type display device particularly in the periphery of the projection image is used. The contrast depends on the incident angle of the light beam that enters the polarization beam splitter 92.
Therefore, the light passing through the polarization beam splitter 92 is preferably close to telecentric.

Further, as shown in FIG. 3, in order to make the entire apparatus compact, the reflection type light valves 55, 56, 5 are used.
It is desirable that the optical axes from 7 to CRTs 58, 59 and 60 are parallel, that is, the polarization splitting surfaces of the polarization beam splitters 52, 53 and 54 are parallel to each other. For that purpose, as shown in FIG. 6, a polarization beam splitter 92 having both a polarization separation function and an astigmatism correction function between the first lens group 97 and the reflection type light valve 91, and at least three color combining optical systems. A space for arranging the plane-parallel plates is required. In this case, the back focus of the projection lens is required to be very long. In the present embodiment, the effective display area of the reflective light valve 91 is diagonal 2.
5 inches (aspect ratio 3: 4), a projection lens focal length of about 78 mm, and an F number of 4.0 are used, and the back focus is at least 320 mm in terms of the air optical path length.
As mentioned above, 350 mm or more is desirable. If the projection lens is configured by only the first lens group 97, the light emitted from the polarization beam splitter 92 proceeds as shown by a broken line 99, and the reflection type light valve side lens of the projection lens and the color combining optical system are configured. Parallel plane plates 94 and 9
A large diameter is required for 5,96. Therefore, the projection lens and the color synthesizing optical system are very expensive, and the projection lens is heavy.

Therefore, the second lens group 9 having a positive power.
If 3 is arranged at a position sufficiently separated from the first lens group 97 and the entire projection lens is composed of two groups having a long space, the light travels as shown by the solid line 98, and the entire projection optical system is made compact. it can. The second lens group 93 may be used by cutting the periphery into a rectangular shape according to the effective area of the light emitted from the polarization beam splitter 98, using plastic as the material.

By thus disposing the second lens group 93 between the plane-parallel plates 94, 95, 96 and the polarization beam splitter 92, the compactness and telecentricity of the entire apparatus and the correction of astigmatism are achieved. The functions of can be satisfied at the same time. This configuration is used in the polarization beam splitter 92.
It is similarly effective for the optical device in the case of arranging a parallel plane transparent plate having only a function of correcting astigmatism instead of.

Next, the second lens group 64 having power,
Astigmatism generated in the transparent plate 67 and the dichroic mirrors 68 and 69 when 65 and 66 are arranged will be described with reference to the model diagram shown in FIG. 7. The light rays are considered to travel from the screen side to the reflective light valve side.

The parallel plane transparent plate P in FIG. 7 includes a transparent plate 67, dichroic mirrors 68 and 69, and a lens L in FIG.
Corresponds to the second lens group 64, 65, 66.

The focal length of the lens L is f, the sagittal paraxial image point in the absence of the lens L is Q _aS , the meridional paraxial image point is Q _aM , the astigmatic difference is d ₁ , and the sagittal near the principal plane of the lens L. Letting the distance to the axial image point Q _{aS be} a, the sagittal magnification m _S and the meridional magnification m _M of the virtual image by the lens L can be expressed by the following equations.

[0112]

[Equation 30]

[0113]

(Equation 31)

When the sagittal paraxial image point when the lens L is arranged is Q _bS , the meridional paraxial image point is Q _bM , and the astigmatic difference is d ₁ ′, the sagittal paraxial image from the principal plane of the lens L is shown. _Let b _{S be} the distance to the point Q _bS and b _M be the distance to the meridional paraxial image point Q _bM.

[0115]

(Equation 32)

[0116]

[Equation 33]

[0117]

(Equation 34)

Is obtained. (Equation 30), (Equation 31), (Equation 3)
2), (Equation 33), and (Equation 34), the astigmatic difference d'can be expressed by the following equation.

[0119]

(Equation 35)

(Equation 35) can be approximated as follows if d ₁ is sufficiently smaller than f and a.

[0121]

[Equation 36]

Therefore, from (Equation 28) and (Equation 36), the astigmatic difference d ₁ ′ of the transparent plate P in FIG. 7 is obtained by determining the thickness of the transparent plate P as t ₁ , the refractive index as n ₁ , and the refraction of the medium. When the ratio is n ₁ ′ and the angle of incidence of the light beam on the transparent plate P is θ ₁ , it can be calculated by the following equation.

[0123]

(37)

On the other hand, the astigmatic difference d ₂ generated by the polarization beam splitters 52, 53 and 54 shown in FIG. 3 is as follows: the plate thickness of the polarization separation mirror substrate is t ₂ , the refractive index of the substrate is n ₂ , the liquid refraction is Assuming that the ratio is n ₂ ′ and the incident angle of light rays from the liquid to the polarization splitting surface is θ ₂ , the following equation is obtained from (Equation 28).

[0125]

(38)

Since the astigmatic difference d ₂ is the value in the liquid, the astigmatic difference d ₂ 'in the air after being emitted from the polarization beam splitters 52, 53, 54 is d ₂ ' = d ₂ /
From the relationship of n ₂ ', the following equation is obtained.

[0127]

[Equation 39]

Therefore, from (Equation 37) and (Equation 39), the projection optical system shown in FIG. 3 can correct astigmatism by satisfying the following equation.

[0129]

(Equation 40)

From (Equation 37) and (Equation 39), the plate thickness t ₁ ,
It is understood that the relationship of t ₂ should satisfy the condition of the following equation.

[0131]

[Equation 41]

In the structure shown in FIG. 3, the transparent plate 67 and the dichroic mirrors 68 and 69 of the color combining optical system and the polarization splitting mirror substrate of the polarization beam splitter have the same refractive index. Is used, and n
_{Since 1} = n ₂ , and the medium of the transparent plate 67 and the dichroic mirrors 68 and 69 is air, n ₁ ′ = 1, and therefore (Formula 41) is

[0133]

(Equation 42)

Is obtained.

The above-mentioned concept of astigmatism and the correction condition of astigmatism have been described with reference to a ray passing on or near the optical axis of the projection optical system. As the light passes and has a larger angle with the optical axis, the strict astigmatism is slightly different from that near the optical axis. But,
The basic idea and tendency of astigmatism that occurs when light having imaging performance is transmitted through a parallel flat transparent plate that is inclined with respect to the optical axis is the same. When it is relatively thin, it does not make a big difference compared to the vicinity of the optical axis. Therefore, the astigmatism correction condition has a sufficiently large effect for improving the resolution of the entire effective area of the projection image projected by the projection type display as shown in FIG.

All the values of the refractive index are values at the e-line (546.07 nm) which is near the center wavelength of visible light. The refractive index has wavelength dispersion characteristics, and the refractive index is slightly different depending on the wavelength. Strictly speaking, it may be optimized according to the respective conditions of the three primary color lights of red, blue and green. However, even if the e-line, which is the green light having the highest luminosity factor in visible light and dominantly affects the resolution of the projected image, is used as a reference, there is no particular problem in the astigmatism correction effect.

In the present embodiment, the second lens groups 64, 6
The focal length f of 5, 66 is 240 mm, the distance a from the principal plane of the second lens group to the sagittal paraxial image point in the absence of the second lens groups 64, 65, 66 is 110 mm. The sagittal magnification m _S is about 0.686. Further, the refractive index n ₁ of each of the transparent plate 67, the dichroic mirrors 68, 69 substrate, and the polarization separation mirror substrates of the polarization beam splitters 52, 53, 54 is 1.52, and the liquid refraction of the polarization beam splitters 52, 53, 54 is refracted. The ratio n ₂ is 1.44, the incident angle θ ₁ of light rays from the medium (air) side to the transparent plate 67 and the dichroic mirrors 68, 69 is 45 °, and the polarization separation mirror 84 of the polarization beam splitters 52, 53, 54 from the liquid side. The incident angle θ ₂ of the light ray incident on is 55.6.
A °, a t ₂ / t ₁ is 0.668 from equation (42).

Here, the surface accuracy of the light reflecting surfaces of the dichroic mirrors 68 and 69 and the plane mirror 70 shown in FIG.
This has a great influence on the resolution performance of the projection optical system, and this surface accuracy is greatly influenced by the board thickness condition of the substrate. When displaying high-resolution projected images such as high-definition video, the surface accuracy of each reflective surface is either concave or convex with respect to an ideal flat surface (infinite radius of curvature). The radius of curvature is required to be at least ± 2λ (λ is the center wavelength of incident light) or less, and preferably ± λ or less.

If the substrate is thin, the surface accuracy is likely to deteriorate due to the stress when the dielectric multilayer film is vapor-deposited and the pressure of the peripheral mechanical parts when the dielectric multilayer film is assembled and fixed in the apparatus. The dichroic mirrors 68 and 69 and the plane mirror 7 of this embodiment
0 effective area is at least 80mm x 60m
In order to satisfy the above condition of surface accuracy even after polishing the surface, a substrate thickness of at least 1.5 mm or more, preferably 2 mm or more is required. Of these, the plane mirror 70 is a surface mirror and a substrate having a sufficient thickness can be used, so there is no problem. However, if the substrates are too thick, the dichroic mirrors 68 and 69 pass a position away from the optical axis of the projection optical system. It becomes difficult to correct the astigmatism of the light beam. Therefore, the substrate thickness is at least 3.0 mm or less, preferably 2.5 m
m or less is desirable.

From the above, the dichroic mirror 6
The substrate thickness of 8, 69 is preferably 1.5 mm or more and 3.0 mm or less. In addition, the polarization beam splitters 52, 53, 54
Is a reflection type light valve 55 in the optical path of the projection optical system.
Since only light from 56 and 57 is transmitted, it can be considered that there is almost no influence of resolution deterioration due to the surface accuracy of the polarization separation mirror substrate.

Therefore, in the present embodiment, the thickness t ₁ of the transparent plate 67 and the dichroic mirrors 68, 69 is set to about 2.0 m.
and the thickness t ₂ of the polarization separation mirror substrate is set to about 1.3 mm from the calculation result of (Expression 42). By doing so, astigmatism of the entire projection optical system can be corrected well, and a high-resolution projection image can be displayed.

In the above description, the transparent plate 6 of the color combining optical system is used.
7, the astigmatism generated by the dichroic mirrors 68, 69 is corrected by the virtual image magnification m of the second lens group (64, 65, 66).
And the astigmatism is reduced by the astigmatism generated by the polarization separation mirror 84 of the polarization beam splitter (52, 53, 54). Said.

What is different from the above embodiment is that the second lens group is not provided and the astigmatism generated in the color combining optical system is canceled by the astigmatism generated in the polarization separation mirror 84. It is a concrete example of the case of configuring.

That is, this case corresponds to the case where m _s = 1 in the above (Formula 42). Therefore, in the above-described embodiment in which the virtual image magnification of the second lens group is m _s = 0.686, t ₂ / t ₁ = 0.668 was derived, but here, (Formula 42) is t ₂ / T ₁ = 0.668 /
The value is 0.686 ² = 1.419.

From this, if t ₁ = 2.0 mm, then t ₂ = 2.839 mm. In this case, the thickness of the polarization separation substrate of the polarization beam splitter is 2.84 m.
m.

The structure of the illumination optical system in the structure shown in FIG. 3 will be described below with reference to FIG. Although not shown in the configuration diagram of FIG. 3, when relay lenses 105 and 106 are arranged as shown in FIG. 8 in the optical path until the emitted light from the light source 41 illuminates the reflection type light valves 55, 56 and 57. Good. The reflective light valve 107 is the same as the reflective light valves 55, 56 and 57 shown in FIG. First relay lens 105 and second relay lens 1
06 between the dichroic mirror 4 shown in FIG.
The color separation optical system composed of 3, 44 and 45, the front polarizers 46, 47 and 48, and the plane mirrors 49, 50 and 51 are arranged, and between the second relay lens 106 and the reflection type light valve 108. Is a polarization beam splitter 52, 53, 54
Is arranged. The light source 41 is a lamp 101 and an ellipsoidal mirror 10.
2, the lamp 101 is a xenon lamp, and emits light containing color components of three primary colors. Elliptical mirror 10
Reference numeral 2 is made of glass, and its reflection surface is coated with an aluminum thin film layer. The light-reflecting surface may be a vapor-deposited multilayer film that transmits infrared light and reflects visible light.

The radiated light from the lamp 101 is reflected by the elliptical mirror 102, the infrared light is removed by the cold mirror 103, and the infrared light is condensed at the second focal point 104 of the elliptical mirror 102. Second
After passing through the focal point 104, the light that has become divergent light is converted by the first relay lens 104 into light that is nearly parallel.
Since the dichroic mirror using the dielectric multilayer film has a characteristic that the spectral performance changes depending on the incident angle dependence of the light beam, it is desirable that the light passing through the dichroic mirror be as parallel as possible. The light that is nearly parallel is collected again by the second relay lens 106 and illuminates the reflective light valve 107. The relay lenses 105 and 106 form the lamp 10 imaged at the second focal point 103 of the ellipsoidal mirror 102.
The image of No. 1 has a role of efficiently illuminating the image of No. 1 at a magnifying power corresponding to the effective display area of the reflective light valve 107.

In FIG. 8, the first relay lens 105 is used.
Although it is configured to have two sheets, it may have one sheet or three or more sheets. The second relay lens 106 is provided between the color separation optical system shown in FIG. 3 and the front polarizers 46, 47, 48.
Alternatively, it may be arranged between the front polarizers 46, 47 and 48 and the plane mirrors 49, 50 and 51 leading to the polarization beam splitter. Furthermore, in the present embodiment, the xenon lamp is used as the lamp 101, but a metal halide lamp, a halogen lamp or the like may be used instead.

The detailed structure of the front polarizers 46, 47 and 48 will be described below with reference to FIG.

A V-shaped groove is formed inside the frame body 111, and the ends of the polarization selective mirrors 114 and 115 are inserted into the groove so that the respective cross sections are V-shaped. There is. A liquid 116 is filled in the space of a container constituted by the frame 111, the entrance window 112 and the exit window 113 made of a glass substrate, and the polarization separation mirrors 114 and 115. The multilayer structure of the liquid material and the polarization separation mirrors 114 and 115 is the same as that of the polarization beam splitters 52, 53 and 5 shown in FIG.
I am using the same one as in 4.

As shown in FIG. 9, the front polarizers 46, 4 are
The natural light 117 that is vertically incident on the light beams 7 and 48 is transmitted through the incident window 112 and the liquid 116, respectively, and then the polarization separation mirror 114.
Is incident at an angle of 55.6 °. Polarization separation mirror 114
Therefore, the natural light 117 becomes S-polarized component 118 and P, respectively.
The P-polarized component 119 is separated into the polarized component 119, passes through the liquid 116, and then exits from the exit window 113, and the S-polarized component 118b enters the inner wall of the frame 111, respectively.

In order to ensure the compactness of the front polarizers 46, 47, 48, the number of polarization separating mirrors 114, 115 is two, and they are arranged symmetrically in a V shape with respect to the optical axis. The V-shaped apex may be arranged toward the light source side so that the unnecessary S-polarized component reflected by the polarization separation mirrors 114 and 115 does not proceed to the emission window 113 side.
In the case of one polarization separation mirror, not only the size in the optical axis direction becomes large, but also when the light obliquely enters the front polarizer, the incident angle dependence becomes asymmetrical, and this effect affects the projected image. The problem arises that it is easy to appear in. Further, three or more polarization separation mirrors may be arranged in a zigzag shape, but in the case of an odd number of polarization separation mirrors, the arrangement of the polarization separation mirrors is asymmetric with respect to the optical axis. preferable. Further, the S-polarized light component, which is unnecessary light, may be reflected by the polarization splitting mirror and then enter adjacent polarization beam splitters, and a part of the multiple reflected light may travel to the exit window side. This unnecessary polarization component is the polarization beam splitters 52, 53, 54 and the reflection type light valves 55, 5 shown in FIG.
Note that reaching 6, 57 may cause a significant deterioration in the contrast performance of the projected image. As described above, it is understood that the front polarizer having the configuration shown in FIG. 9 can efficiently extract light close to linearly polarized light.

The positional relationship between the front polarizer and the polarization beam splitter is such that P polarized light emitted from the front polarizer is reflected as S polarized light by the polarization beam splitter.
In general, the incident light is spread over a certain angle range around the optical axis, and the wavelength of the incident light is not a single wavelength. Therefore, the reflectance of S-polarized light is less than that of the polarization splitting mirror even under the use conditions of the incident light. 100% by increasing the number of dielectric multilayer films
Is relatively easy to approach, while it is difficult to approach the transmittance of P-polarized light to 100%. Therefore, it is preferable to take out P-polarized light in the front polarizer that needs to cut unnecessary polarization components. In order to efficiently guide the linearly polarized light incident on the polarization beam splitter to the reflection type light valve side, and in the case of black display, it is necessary to cut the readout light reflected from the reflection type light valve with the polarization beam splitter. The polarization component incident on the polarization beam splitter is preferably S-polarized light. By doing so, a high-contrast projection image can be displayed.

The projection type display device of the present invention shown in FIG.
Since the second lens group 64, 65, 66 is used, the projection beam system is compact but the polarization beam splitter 5
It has the performance that the telecentricity of the light passing through 2, 53, 54 is good. Therefore, the principal ray incident on the polarization splitting surface of the polarization beam splitter is substantially parallel to the optical axis of the projection optical system, and the polarization splitting performance hardly deteriorates due to the incident angle of the light ray on the polarization splitting surface. Therefore, it is possible to display a high-quality projected image without the problem of contrast deterioration or nonuniformity of the projected image caused by the deterioration of the polarization separation performance.

Further, in the configuration shown in FIG. 3, since the number of projection lenses is substantially one, color shading does not occur. In addition, from the light source 41 to each reflective light valve 5
Since the illumination light path lengths up to 5, 56, 57 are the same for the three colors and the screen centers of the reflection type light valves 55, 56, 57 are located on the optical axis of the projection lens, the occurrence of color unevenness is small.

In this embodiment, three CRTs, a writing lens, a reflection type light valve, a polarization beam splitter, and a second lens group are arranged in the horizontal direction of the CRT screen, but in the vertical direction of the CRT screen. You may arrange.

Further, in this embodiment, CR is used as the image source.
Although T is used, for example, a transmissive TFT liquid crystal panel is used, which is illuminated by a light source such as a metal halide lamp from the rear, and an optical image formed on the liquid crystal panel according to a video signal is written by a writing lens by a reflection type light. It may be configured to form an image on the photoconductive layer of the bulb. Further, as the writing optical system, an optical fiber bar used as an image guide may be used instead of the writing lens.

Another embodiment of the present invention will be described below.

FIG. 10 is a block diagram of the projection optical system in the projection type display device shown in FIG. 3 when only the structure of the color combining optical system is different.

The color synthesizing optical system comprises flat mirrors 130, 13
3 and dichroic mirrors 131 and 132.

The light from the reflective light valve 121 passes through the polarization beam splitter 124 and the second lens group 127, then passes through the two dichroic mirrors 131 and 132, and enters the first lens group 134. In addition, the light from the reflection type light valve 122 is transmitted through the polarization beam splitter 12
5. After passing through the second lens group 128, the light is reflected by the plane mirror 130 and the dichroic mirror 131 in which the transparent plate of the parallel plane is joined to the surface mirror, and the dichroic mirror 1
The light passes through 32 and enters the first lens group 134. Further, the light from the reflective light valve 123 passes through the polarization beam splitter 126 and the second lens group 129, is reflected by the back surface of the plane mirror 133 of the front surface mirror and the dichroic mirror 132, and enters the first lens group 134. .

The reflecting surfaces of the plane mirrors 130 and 133 and the color combining surfaces of the dichroic mirrors 131 and 132 are both inclined by 45 ° with respect to the optical axis of the projection optical system. The substrates of the dichroic mirrors 131 and 132 and the transparent plate joined to the reflecting surface of the plane mirror 130 are the same as those of the various substrates shown in FIG.

In the color synthesizing optical system of the projection optical system shown in FIG. 10, the reflecting surfaces of the plane mirror 130 and the dichroic mirror 132 are effectively back-reflected, so that the three reflecting light valves 121, 122, 123 are respectively driven. The conditions for correcting the astigmatism of the emitted light are the same.

Considering the conditional expression (Equation 40) and the surface accuracy of the reflecting surfaces of the dichroic mirrors 131 and 132, the polarization separation mirrors of the polarization beam splitters 124, 125 and 126 have a substrate thickness t ₂ of 2 mm and a plane mirror 130. The substrate thickness of the transparent plate joined to the reflecting surface of 0.75 mm is 0.75 mm, and the substrate thickness of the dichroic mirrors 131 and 132 is 1.5 respectively.
mm, and the total plate thickness t ₁ of the plane parallel plates for each color in the color combining optical system is set to 3.0 mm.

In this case, the substrate thicknesses t ₁ and t ₂ in (Equation 41) are values represented by the following equations, respectively.

[0166]

[Equation 43]

[0167]

[Equation 44]

Here, i is the number of planes that pass through the plane-parallel plate of the color combining optical system, and j is the number of parallel planes provided to correct the astigmatism generated in the color combining optical system. In the case of back surface reflection, it is considered that the light is transmitted through two parallel plane plates for each reflection.

In the embodiment shown in FIG. 10, j is 1 for each optical path from the reflection type light valves 121, 122 and 123, but for i, the optical path from the reflection type light valve 121 is. 2, the optical path from the reflective light valve 122 is 3, reflective light valve 123
The optical path from is 2.

As described above, in the embodiment shown in FIG. 10, the color synthesizing optical system is used in the case where the light ray is transmitted through the plurality of parallel plane plates and the back reflection is used which is the same condition as the case where the light ray is transmitted twice. Although configured, the idea of astigmatism correction,
The basic expression of the correction condition (Equation 40) can be applied as it is.

In the above embodiment, the reflection type light valve which modulates the polarization state of the reading light in the liquid crystal layer according to the image written in the photoconductive layer is used as the light valve, but other types of liquid crystal panel or Any reflective type that forms an optical image as a change in birefringence, such as one using an electro-optic crystal, can be used as a light valve.

Further, the concept and method of astigmatism correction of the present invention are based on the optical characteristics of a transmission type light valve or a light valve of a scattering, diffraction or light deflection type as a light modulation type. Any application that forms an optical image as a change can be applied.

An embodiment of a projection type apparatus constructed by using a transmission type light valve will be described below with reference to FIG.

Transmission type light valves 150, 151, 15
Reference numeral 2 is a TFT liquid crystal cell using twisted nematic liquid crystal as a light modulating material, and a polarizer and a polarizing plate used as an analyzer are arranged in front of and behind the TFT liquid crystal cell.

The light emitted from the light source 141 absorbs or reflects ultraviolet light and infrared light, and transmits only visible light.
After passing through the V-IR cut filter 142 and the plane mirror 143, it is separated into three primary color lights of red, green and blue by a color separation optical system composed of dichroic mirrors 144 and 145 and a plane mirror 146. The lights of the three primary colors sequentially enter the corresponding field lenses 147, 148, 149 and the transmission type light valves 150, 151, 152.

The color combining optical system is composed of a plane mirror 153 and dichroic mirrors 154 and 155. The projection lens is the second lens group 15 having positive power.
6, 157 and the first lens group 158. Further, the reflecting surface of the plane mirror 153 and the color combining surface of the dichroic mirrors 154 and 155 are both arranged at an angle of 45 ° with respect to the optical axis of the projection lens.

The lights emitted from the light valves 150, 151, 152 are combined into one by the color combining optical system and enlarged and projected on the screen by the projection lens.

As described above, the plane mirror 153 and the dichroic mirrors 154 and 15 which constitute the color combining optical system.
The light reflecting surface of No. 5 is required to have high surface accuracy, and the surface accuracy is greatly influenced by the substrate thickness. In particular, the closer the position of the reflecting surface is to the principal point of the projection lens, the greater the effect of this surface accuracy on the resolution of the projected image. That is, the condition of the surface accuracy of the light reflecting surface of the dichroic mirror 155 becomes stricter than that of the plane mirror 153 and the dichroic mirror 154.

Therefore, in the configuration shown in FIG. 11, the second lens group 156, 1 located at a position apart from the first lens group 158.
57 are arranged between the plane mirror 153, the dichroic mirror 154 and the dichroic mirror 155, respectively. By doing so, as can be seen from (Equation 36), the astigmatic difference generated in the dichroic mirror 155 on the light valve 150, 151, 152 side is the second
Compared with the case where the lens group 156 is not provided, it can be reduced by the square of the virtual image magnification by the second lens group having positive power. Therefore, the substrate thickness of the dichroic mirror 155 can be made thicker than in the case where the second lens group 156 is not provided, and the reflecting surface of the dichroic mirror 155 can have high surface accuracy without increasing astigmatism. .

The embodiment shown in FIG. 11 does not completely correct the astigmatism generated in the color synthesizing optical system on the paraxial axis of the projection optical system, but the astigmatism of the optical device of the present invention. Is the same, and the effect of using the second lens group 156 is great.

In the optical path passing through the second lens group 157, the light emitted from the light valve 152 is changed to the plane mirror 15.
3. Since it is only reflected by the dichroic mirror 155, there is no factor that causes astigmatism. Therefore,
The second lens group 157 does not exhibit the effect of reducing astigmatism. However, since the first lens group 158 and the second lens groups 156 and 157 are a lens system that integrally have an imaging performance, the second lens group 157 is necessary in terms of imaging performance.

Also in the configuration of FIG. 11, a plane including the normal line of the parallel plane and the optical axis of the projection lens and the dichroic mirror 154 are provided between the light valves 150, 151 and 152 and the first lens group 158. , 155, the astigmatism may be corrected by providing a space for arranging transparent plates such that planes including the normal line of the color combining surface and the optical axis of the projection lens are orthogonal to each other.

In the embodiment shown in FIG. 11, a transmissive light valve is used, but the same applies to the case where a reflective light valve is used as long as it uses a projection optical system having a color combining optical system. The effect of is obtained.

As described above, according to the present invention, it is possible to satisfactorily correct the astigmatism generated in the color synthesizing optical system, and the projection optical system can be made compact. Therefore, by using the optical device of the present invention in a projection display device,
Even in the case of a projection optical system having a color synthesizing optical system and configured with one projection lens, it is possible to display a projected image with a very high resolution, which is a great effect.

In the above-described embodiment, in order to obtain a full-color projection image, a projection display device using three light valves for red, green, and blue, or an optical device used for such a device. Although the correction method has been described, the present invention is not limited to this, and may be, for example, an optical device that forms and outputs an optical image of monochromatic light, or an optical correction method used in such an optical device.

Further, in the above-mentioned embodiment, the second lens group as the second lens means of the present invention and the polarization splitting mirror as the transparent substrate of the polarization splitting means of the present invention are provided, and the flat plate member of the present invention is provided. As a result, the astigmatism generated in the dichroic mirror of the color synthesizing optical system is reduced (or the surface precision of the dichroic mirror is increased without increasing the astigmatism), and the astigmatism is reduced. Projection-type display device when correcting so as to cancel each other, or
The optical correction method used in such a device has been described. However, the invention is not limited to this, and for example, an apparatus having a configuration in which the transparent substrate of the polarization splitting means is not provided and the second lens means is provided, or an optical correction method used in an apparatus having such a configuration may be used. In this case, as can be seen from (Equation 36) above, for example,
Astigmatism generated by the transparent plate 67 and the dichroic mirrors 68, 69 of the color combining optical system shown in FIG. 3 can be reduced by the square of the virtual image magnification m of the second lens group (64, 65, 66). Exert the effect of saying. Alternatively, as another effect, the substrate thickness of the dichroic mirror can be further increased without increasing the astigmatism, compared with the case where the second lens group is not provided. It also has the effect that the reflective surface of can be made highly precise.

Further, in the above-mentioned embodiment, the case where the polarized light separating means of the present invention has the transparent substrate having the predetermined thickness, on which the film having the polarization selection characteristic is formed, is explained.
Not limited to this, for example, the polarization separation means may include a thin film having polarization selection characteristics, and both sides of the thin film may be held by prism-shaped members. Even in this case, for example, the transparent plate 67 of the color combining optical system shown in FIG.
The astigmatism generated in the dichroic mirrors 68, 69 can be reduced by the square of the virtual image magnification m of the second lens group (64, 65, 66).

As is apparent from the above, the advantage of the optical device according to the optical correction method of the present invention is that the astigmatism generated in the color combining optical system can be corrected well, and the projection optical system can be made compact. is there. Therefore, the projection display device using the optical device of the present invention can display a projection image with a very high resolution even when it is configured with one projection lens having a color combining optical system.

[0189]

As is apparent from the above description, the present invention has an advantage that astigmatism can be corrected more satisfactorily than in the conventional case. Further, the present invention has an advantage that a projected image with a higher resolution can be displayed as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating astigmatism according to an embodiment of the present invention.

FIG. 2A is a schematic configuration diagram illustrating an astigmatism correction method in which transparent plates P1 and P2 having two parallel planes whose incident surfaces are orthogonal to each other are arranged in the present embodiment. FIG. The first lens unit L1 in the form of
A plane-parallel transparent plate P1 serving as a dichroic mirror of the color combining optical system, a second lens group L2, and a plane-parallel transparent plate P2 for correcting astigmatism generated in the transparent plate P1.
And a light valve LV are arranged in order to explain an astigmatism correction method.

FIG. 3 is a perspective view showing a configuration of an embodiment of a projection display device of the present invention.

FIG. 4 is a cross-sectional view showing the configuration of the polarization beam splitter of this embodiment.

5A is an explanatory view for explaining the principle of astigmatism when convergent light is obliquely incident on the boundary plane A having a refractive index difference in the present embodiment. FIG. Explanatory diagram for explaining the principle of astigmatism when the transparent plate P having parallel planes is obliquely arranged with respect to the optical axis in the embodiment.

FIG. 6 is a schematic configuration diagram of a projection optical system according to an embodiment of an optical device of the present invention.

FIG. 7 is an explanatory diagram illustrating an astigmatic difference amount according to the present embodiment.

FIG. 8 is a schematic configuration diagram of an illumination optical system according to an embodiment of an optical device of the present invention.

FIG. 9 is a sectional view showing a configuration of a front polarizer of an embodiment of the optical device of the present invention.

FIG. 10 is a schematic configuration diagram of a projection optical system of an optical device according to another embodiment of the present invention.

FIG. 11 is a schematic configuration diagram of an optical device according to another embodiment of the present invention.

FIG. 12 is a schematic sectional view showing the basic structure of a reflective light valve.

FIG. 13 is a perspective view showing a configuration example of a conventional optical device.

[Explanation of symbols]

41 light source 43,44,45,68,69 dichroic mirror 46,47,48 pre-deflector 49,50,51,70 plane mirror 52,53,54,92 polarization beam splitter 55,56,57,91 reflection type Light valve 58, 59, 60 CRT 61, 62, 63 Writing lens L2, 64, 65, 66, 93 Second lens group P, P1, P2, 67, 94, 95, 96 Transparent plate L1, 71, 97 First Lens group

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H04N 5/74 H04N 5/74 A

Claims (27)

[Claims] 1. An image forming unit for forming an optical image, a second lens unit for transmitting light from the image forming unit, and a flat plate member for transmitting and / or reflecting light from the second lens unit. A first lens means for entering and emitting light from the plane plate member, wherein the plane plate member is arranged obliquely with respect to an optical axis of the first lens means, The optical device is characterized in that the degree of astigmatism caused by the above is smaller than the degree caused by the case where the second lens means is not provided. 2. A polarization separation means having a polarization selection characteristic of reflecting the first polarization component and transmitting the second polarization component of the first and second polarization components orthogonal to each other, and the image forming means. Provided between the second lens means, the image forming means is a reflection type means for modulating the deflection direction of light, wherein the first polarization component of the light from the light source is reflected by the polarization separation means, The reflected first polarization component is incident on the image forming means, and the image forming means uses the incident first polarization component as the second polarization component in accordance with predetermined image light or a predetermined image signal. 2. The optical device according to claim 1, wherein the polarized light is modulated and made incident on the polarized light separating means again, and the incident second polarized light component is transmitted by the polarized light separating means. 3. The optical device according to claim 2, wherein the polarized light separating means includes a thin film having the polarization selection characteristic, and both sides of the thin film are held by prism-shaped members. 4. The polarized light separating means has a transparent substrate of a predetermined thickness, which is formed obliquely with respect to the optical axis of the first lens means, on which a film having the polarization selecting characteristic is formed. A plane including the normal to the surface of the face plate member where the transmission and / or reflection is performed and the optical axis of the first or second lens means, the normal to the film forming surface of the transparent substrate, and the first or The optical device according to claim 2, wherein a plane including the optical axis of the second lens means is orthogonal to each other. 5. The transmission type which forms the optical image by controlling the transmitted light according to an image signal when the image forming means obtains the light incident from the light source and transmits the light. The optical device according to claim 1, wherein the optical device is a means. 6. An image forming means for forming an optical image, and the first of the first and second polarization components orthogonal to each other,
A polarization separation means having a polarization selection characteristic of reflecting a polarization component and transmitting the second polarization component, a flat plate member for transmitting and / or reflecting light, and entering and emitting light from the flat plate member. Lens means in this order, the plane plate member is arranged obliquely with respect to the optical axis of the lens means, the polarization separation means, a film having the polarization selection characteristics is formed, A transparent substrate having a predetermined thickness is arranged obliquely with respect to the optical axis of the lens means, and includes a normal to the surface of the plane plate member on which the transmission and / or reflection is performed and the optical axis of the lens means. A plane,
An optical device, wherein a normal line to the film forming surface of the transparent substrate and a plane including an optical axis of the lens means are orthogonal to each other. 7. The image forming means is a reflection type means for modulating the deflection direction of light, wherein the first polarized component of the light from the light source is reflected by the polarized light separating means, and the reflected first Of the first polarization component is incident on the image forming unit, and the first polarization component incident on the image forming unit is changed to the second polarization component.
The polarized light component is modulated according to a predetermined image light or a predetermined image signal and is made incident again on the polarized light separating means, and the incident second polarized light component is transmitted by the polarized light separating means. Item 7. The optical device according to item 6. 8. The plate thickness of the transparent substrate and the plate of the plane plate member so that the astigmatism caused by the transparent substrate and the astigmatism caused by the plane plate member substantially cancel each other out. The optical device according to claim 4 or 7, wherein the relationship with the thickness is adjusted. Wherein said flat plate member is a transparent substrate having a thickness t _1, the relationship between the thickness t ₂ of the transparent substrate of the polarization separating means, claims, characterized by satisfying the following expression 8. The optical device according to item 8. (Equation 1) Here, n ₁ is the refractive index of the flat plate member, n ₁ ′ is the refractive index of the medium of the flat plate member, and θ ₁ is the light beam on the optical axis of the lens means that enters the flat plate member from the medium. The incident angle, n ₂ is the refractive index of the transparent substrate of the polarization splitting means, n ₂ ′
Is the refractive index of the medium of the polarization splitting means, and θ ₂ is the angle of incidence of the light beam on the optical axis of the lens means that enters the polarization splitting surface of the polarization splitting means from the medium. 10. The plate thickness t ₁ and / or the plate thickness t ₂ is represented by the following formula when a plurality of the flat plate members and / or the transparent substrates of the polarization splitting means are provided. The optical device according to claim 9, wherein: (Equation 2) (Equation 3) However, t _1i (i = 1, 2, 3, ...) Is each plate thickness of the i-th plane plate member of the plurality of plane plate members,
t _2j (j = 1, 2, 3, ...) Is the thickness of each of the j-th transparent substrates of the plurality of transparent substrates. 11. An image forming unit for forming an optical image, a second lens unit for transmitting light from the image forming unit, and a flat plate member for transmitting and / or reflecting light from the second lens unit. A first lens means for entering and emitting light from the plane plate member, wherein the plane plate member is arranged obliquely with respect to the optical axis of the first lens means. Wherein the first lens means receives the light from the flat plate member and projects the optical image, and the second lens means is arranged between the flat plate member and the image forming means, The optical system is characterized in that the magnification of the second lens is adjusted so that the degree of astigmatism caused by the flat plate member is smaller than the degree caused by the absence of the second lens. Correction method. 12. An image forming means for forming an optical image, a polarized light separating means having a predetermined thickness for transmitting or reflecting in accordance with a polarization component of light, and a flat plate member having a predetermined thickness for transmitting and / or reflecting light. In the optical correction method of the optical device, the flat plate member is provided in this order with a lens unit for entering and emitting light, and the flat plate member is arranged obliquely with respect to the optical axis of the lens unit. Wherein a plane including a normal line to the plane plate member and an optical axis of the lens means and a plane including a normal line to the polarization splitting means and an optical axis of the lens means are orthogonal to each other, and the plane plate The relationship between the plate thickness of the flat plate member and the plate thickness of the transparent substrate is adjusted so that the astigmatism caused by the member and the astigmatism caused by the polarized light separating means are mutually corrected. Optical correction method. 13. A plurality of image forming means for forming an optical image as a change in birefringence, a polarization separating means provided for each of the image forming means for separating polarization components whose polarization planes are orthogonal to each other, and A second lens which is provided for each polarized light separating means and transmits light from the polarized light separating means, a color synthesizing means for synthesizing light from the respective polarized light separating means into one, and a color synthesizing means from the color synthesizing means. And a first lens that emits and outputs outgoing light, respectively, in this order, and each of the polarization separating means has a parallel-plane transparent substrate obliquely arranged with respect to the optical axis of the first lens. , A dielectric multilayer film having polarization selectivity is formed on the transparent substrate, and the color synthesizing unit is arranged on a transparent substrate of a parallel plane arranged obliquely with respect to the optical axis of the first lens. Shape dielectric multilayer film with wavelength selectivity A plurality of dichroic mirrors formed, and a plane including the normal line of the dielectric multilayer film formation surface of each dichroic mirror and the optical axis of the first lens and / or the second lens, An optical device in which a normal line of the dielectric multilayer film forming surface of each of the polarization separating means and a plane including the optical axis of the first lens and / or the second lens are orthogonal to each other. 14. The plate thickness t _{1 of the} transparent substrate of the one or more dichroic mirrors and the plate thickness t _{2 of the} transparent substrate of the polarization splitting means satisfy the following conditions. The optical device according to claim 13. (Equation 4) Where m _S is the virtual image magnification at the sagittal paraxial image point of the second lens, n ₁ is the refractive index of the transparent substrate of the dichroic mirror, n ₁ ′ is the refractive index of the medium of the dichroic mirror, and θ ₁ is the above The incident angle of the ray on the optical axis of the first lens or the second lens entering the dichroic mirror from the medium, n ₂ is the refractive index of the transparent substrate of the polarization splitting means, and n ₂ ′ is the polarization splitting means. Refractive index of medium, θ ₂
Is the incident angle of the light beam on the optical axis of the first lens or the second lens which is incident on the polarization splitting surface of the polarization splitting means from the medium. 15. The optical device according to claim 14, wherein the plate thickness of the transparent substrate of the dichroic mirror is 1.5 mm or more and 3.0 mm or less. 16. The polarized light separating means adheres a liquid or a solid having a refractive index different from that of the transparent substrate on which the dielectric multilayer film having the polarization selectivity is formed, to both surfaces of the transparent substrate. 14. The optical device according to claim 13, wherein the optical device has a prism shape as a whole. 17. The color synthesizing means includes two of the dichroic mirrors), one optical correction plate, and one plane mirror, and the two dichroic mirrors, the optical correction plate, and the plane mirror include: 14. The optical device according to claim 13, wherein the respective planes are parallel to each other. 18. The optical device according to claim 17, wherein the two dichroic mirrors and the optical correction plate have the same plate thickness. 19. A light source that emits light containing color components of three primary colors, a color separation unit that decomposes the emitted light of the light source into three primary color lights, and each of three output lights of the color separation unit. Three pre-polarizers that are incident normally, a polarization beam splitter that is provided for each of the front polarizers that transmits or reflects light from the front polarizer, and that is provided for each of the polarization beam splitters. A reflective light valve that forms an optical image based on light from a predetermined image source and optical writing means, color combining means that combines the light from the polarization beam splitters into one, and the polarization beam Between the splitter and the color combining means,
A second lens provided corresponding to the polarized beam splitter, and a first lens for entering and emitting the light emitted from the color combining unit are provided, and the image source corresponds to the reflective light valve. To generate image light for incidence, and the optical writing means forms the image light from the image source on the reflection type light valve, and each of the polarization beam splitters is a transparent substrate of parallel planes. A polarization separation mirror on which a dielectric multilayer film having polarization selectivity is formed, and each polarization beam splitter is arranged between the reflection type light valve and the second lens; The synthesizing means is composed of two dichroic mirrors, one optical correction plate having antireflection treatment on both surfaces, and one plane mirror, and the color synthesizing means is the first lens The polarization splitting surface of the polarization splitting mirror, the color combining surface of the two dichroic mirrors, and the antireflection surface of the optical correction plate, which are disposed between the second lens and the second lens, are respectively arranged with respect to the optical axis of the first lens. And a plane including the normal line of the polarization splitting surface of the polarization splitting mirror and the optical axis of the first lens and / or the second lens, and the color combination of the two dichroic mirrors. A projection surface, and a normal line of the antireflection surface of the optical correction plate and a plane including the optical axis of the first lens and / or the second lens are arranged to be orthogonal to each other. Type display device. 20. The two dichroic mirrors,
20. The projection display device according to claim 19, wherein the optical correction plates have the same plate thickness. 21. The plate thickness t ₁ of each of the two dichroic mirrors and the optical correction plate, and the plate thickness t _{2 of the} transparent substrate forming the polarization separation surface of the polarization beam splitter.
Is characterized in that the following conditions are satisfied:
9. The projection display device according to item 9. (Equation 5) Where m _S is the virtual image magnification of the second lens at the sagittal paraxial image point, n ₁ is the refractive index of the two dichroic mirror substrates and the optical correction plate, and n ₁ ′ is the two dichroic mirrors and the optical Refractive index of compensator medium, θ ₁
Is the angle of incidence of the rays on the optical axis of the first lens or the second lens that enters the two dichroic mirrors and the optical correction plate from the medium, n ₂ is the refractive index of the transparent substrate of the polarization splitting mirror, n ₂ ′ is the refractive index of the medium of the polarization splitting mirror of the polarization beam splitter, θ ₂ is the ray on the optical axis of the first lens or the second lens which is incident from the medium to the polarization splitting surface of the polarization splitting mirror. Angle of incidence. 22. The plate thicknesses of the two dichroic mirrors and the optical correction plate are each 1.5 m.
3. The thickness is m or more and 3.0 mm or less.
2. The projection display device according to 1. 23. Each of the polarization beam splitters includes a frame body, a plurality of transparent substrates serving as an entrance window and an exit window, and a polarization separation mirror having a polarization separation surface, and the frame body and the plurality of polarization beam splitting mirrors. 20. The projection display device according to claim 19, which is a transparent prism body in which a transparent liquid (85) is filled in a container formed of a transparent substrate and the polarization separation mirror. 24. The projection display device according to claim 23, wherein a main component of the transparent liquid is ethylene glycol. 25. The projection display device according to claim 23, wherein a refractive index of the transparent substrate on which a polarization splitting surface of the polarization splitting mirror is formed and a refractive index of the transparent liquid are different from each other. . 26. The projection display device according to claim 19, wherein the polarization splitting planes of the polarization splitting mirrors of the three polarization beam splitters are parallel to each other. 27. A light source that emits light containing color components of three primary colors, a color separation unit that decomposes the emitted light of the light source into three primary color lights, and three output lights of the color separation units, respectively. Three light valves that are incident on the light valve, a color combining unit that combines the light emitted from the light valves into one, and a second lens that is provided between the light valve and the color combining unit, A first lens for entering and emitting light emitted from the color synthesizing means, wherein the color synthesizing means includes a first dichroic mirror and a second lens.
A dichroic mirror and a plane mirror, wherein the second lens is arranged between the first dichroic mirror and the second dichroic mirror. Display device.