JPH10142691A - Projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a light loss without causing any deterioration in resolution of a projected image. SOLUTION: In S polarized light beams which are emitted from a light source 1 so as to be polarized and separated in a polarization beam splitter 2, a G light beam is reflected by means of a dichroic mirror 3 provided with a G light reflecting characteristic so as to be separated firstly, and color separation of a B light beam and an R light beam, which are transmitted through the dichroic mirror 3, into an R light beam and a B light beam is carried out in a dichroic prism 4. The respective color separated color light beams are modulated by means of reflection type light valves 5R, 5G, 5B so as to be reflected, and through the inverse path, color synthesis of these light beams is carried out by means of the mirror 3 and the prism 4. The color synthesized light beam is detected by means of the polarized beam splitter 2 and is projected by means of a projection lens 10. The prism 4 transmits an S polarized light beam in the short wavelength side wavelength area as against the wavelength existing in the G light wavelength area while reflects an S polarized light beam in the long wavelength side wavelength area. The prism 4 transmits a P polarized light beam in the short wavelength side wavelength area as against the wavelength existing in the G light wavelength area while reflects a P polarized light beam in the long wavelength side wavelength area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a reflective light valve for R, B, and G light to modulate each color light incident on the light valve according to each color signal. The present invention relates to a projection type display device that obtains a full-color projection image by performing an operation, reflecting the modulated light of each color light, performing color synthesis, and analyzing and projecting the modulated light.

[0002]

2. Description of the Related Art Light from a light source is reflected by a plurality of dichroic films.
Light, G light, and B light are color-separated into three primary colors, and the respective color lights are made incident on reflection-type liquid crystal light valves arranged for each color.
As a conventional example of a projection type display device that reflects and emits light including modulated light by a signal for each color light, performs color synthesis with the dichroic film, and projects the color synthesized light on a screen with a projection lens. A projection display device shown in FIG. 1 of Japanese Patent Publication No. 5-82793 is known. FIG.
FIG. 1 shows a configuration diagram of this conventional projection type display device, and the projection type display device will be briefly described with reference to FIG.

In this projection display device, light emitted from a light source comprising a lamp 20 and an elliptical mirror 21 is converted into substantially parallel light by a collimating lens 22, and then only an opening 23a of a light shielding plate 23 and visible light are emitted. Is incident on the polarization beam splitter 16 via a filter 24 that transmits light. The light source light incident on the polarization beam splitter 16 is polarized and separated by the polarization beam splitter 16 into a reflected S-polarized light l _S and a transmitted and discarded P-polarized light l _P. The S-polarized light l _{S that} has been polarized and separated is converted into a B light (blue light) l _SB , an R light (red light) l _SR , and a G light (green light) by a B light reflecting dichroic prism 17 and an R light reflecting dichroic prism 18. Each color light is separated into 1 _SG , and each color light is incident on each color light reflection type light valve 1B, 1G, 1R.
The modulated light modulated by each image signal in each color light valve 1B, 1G, 1R exits each color light reflection type light valve 1B, 1G, 1R as reflected light, and proceeds to dichroic prisms 17, 18 in reverse. The light is then combined by the dichroic prisms 17 and 18, and the combined light enters the polarization beam splitter 16 again, where only the signal component (P-polarized light) is detected, transmitted through the polarization beam splitter 16, emitted, and projected. At 25, it is projected on a screen 26. The dichroic prism 1
Reference numerals 7 and 18 constitute a color separation / synthesis optical system that performs color separation and color synthesis. In FIG. 11, reference numeral 19 denotes an optical path match glass.

[0004]

However, in the above-mentioned conventional projection type display apparatus, as described below, there is a problem that the loss of light is large, the amount of projection light is reduced, and the color balance is not good. Occurs.

[0005] The dichroic characteristics of a dichroic prism generally vary greatly depending on the polarization. FIG. 9 shows that an S-polarized light and a P-polarized light are applied to an R-light reflecting dichroic prism as used in the conventional projection display device.
An example of dichroic characteristics of the dichroic prism when polarized light enters the dichroic film at an incident angle of 45 degrees is shown. In FIG. 9, the vertical axis indicates the transmittance, and the horizontal axis indicates the wavelength. In the example shown in FIG. 9, with respect to the P-polarized light, the light in the wavelength region on the shorter wavelength side is substantially reflected at about 500 nm as a boundary, and the light in the wavelength region on the longer wavelength side is substantially transmitted. About 5 for polarized light
With a boundary of 80 nm, light in the shorter wavelength region is substantially reflected, and light in the longer wavelength region is substantially transmitted. As described above, the difference between the transmission / reflection boundary wavelength (about 500 nm) for P-polarized light and the transmission / reflection boundary wavelength (about 580 nm) for S-polarized light is large, and the dichroic characteristics of P-polarized light and S-polarized light are greatly different.

In the conventional projection display device, the light actually projected is light that is modulated by the light valves 1R, 1G, and 1B into the other polarized light (P-polarized light) different from the incident polarized light (S-polarized light). Therefore, the two dichroic prisms 17 and 18 used as a color separation / synthesis optical system for performing color separation and color synthesis perform color separation in accordance with dichroic characteristics regarding S-polarized light and perform color synthesis in accordance with dichroic characteristics regarding P-polarized light. Will be. Therefore, as described above, the two dichroic prisms 1
The dichroic characteristics of the dichroic prisms 7 and 18 differ greatly between the P-polarized light and the S-polarized light.
Loss of light projected and synthesized by reciprocating the colors 7 and 18 increases, and the color balance deteriorates. The amount of the projected light depends on the dichroic characteristics (S
This is because it is determined by the so-called product of the dichroic characteristic of the polarized light and the dichroic characteristic of the return (the dichroic characteristic of the P-polarized light).

Incidentally, in order to obtain dichroic characteristics in which the difference between P-polarized light and S-polarized light is as small as possible, instead of using a dichroic prism, for example, a dichroic mirror having a dichroic film formed on a glass plate member is used. I just need. As an example of the dichroic characteristic of the dichroic mirror, as shown in FIG. 9, a dichroic mirror formed with a dichroic film having the same dichroic film as the dichroic prism having the dichroic characteristics is formed. The characteristics are shown in FIG. In FIG.
The vertical axis indicates transmittance, and the horizontal axis indicates wavelength. In the example shown in FIG.
When the transmission / reflection boundary wavelength for P-polarized light is about 500 nm, S
The transmission / reflection boundary wavelength for the polarized light is about 520 nm, the deviation between the two is considerably reduced, and the characteristics are greatly improved.

Therefore, in the above-mentioned conventional projection display device, if two dichroic mirrors are used instead of the two dichroic prisms 17 and 18 as the color separation / synthesis optical system, the loss of light is reduced, and the projection light is reduced. A decrease in the amount of light can be prevented, and the color balance can be improved. . However, since the dichroic mirror has, for example, a structure in which a dichroic film is formed on a thin glass plate member, if it is arranged obliquely with respect to the optical axis, astigmatism will occur and the resolution of the projected image will be reduced. Problem arises. The dichroic prism, unlike the dichroic mirror, hardly causes the above-mentioned aberration and hardly lowers the resolution of the projected image.

As described above, conventionally, it has not been possible to improve the color balance by suppressing the loss of light and preventing the light quantity of the projected light from being reduced without lowering the resolution of the projected image.

In a conventional projection display device,
There was a problem that the contrast of the projected image did not improve. That is, the reflected light emitted from each light valve without being modulated by each color signal in the light valve is S
In the case of polarized light, these lights are color-synthesized by a color separation / synthesis optical system and return to the light source side as they are when reaching the polarization beam splitter, and a black projected image should be achieved on the screen. There is a problem that the black state cannot be achieved and the contrast of the projected image is reduced.

[0011] This problem is caused by the following mechanism. When the linearly polarized light generated by passing through the polarizing beam splitter enters the dichroic film of the color separation / synthesis optical system, the S direction and the P direction of the transmitted light and the reflected light are the normal vector n of the dichroic film. (The direction vector S of the S-polarized light is expressed as vector S = vector n × vector T). When the linearly polarized light enters without being included in the plane formed by the normal line of the dichroic film and the traveling direction of the incident light, the linearly polarized light is decomposed into an S-polarized component and a P-polarized component. Since a phase difference is generated between the P-polarized component and the P-polarized component, the polarization state changes, and the light generally becomes elliptically polarized light. For this reason, when the light is analyzed by the polarizing beam splitter, unnecessary polarized light components are superimposed on the screen, and go around to the screen side, so that the black state of the projected image on the screen is deteriorated.

The present invention has been made in view of such circumstances, and suppresses light loss and prevents a decrease in the amount of projected light without deteriorating the resolution of a projected image, thereby improving color balance. It is an object of the present invention to provide a projection display device capable of performing the above-described operations.

Another object of the present invention is to provide a projection display device having good contrast without changing the polarization state.

[0014]

According to a first aspect of the present invention, there is provided a projection display apparatus comprising: a polarizing beam splitter; a color separation / synthesis optical system;
And a third reflective light valve, and a projection optical system, wherein the polarizing beam splitter separates the light from the light source into first and second polarized lights, and the color separation / synthesis optical system includes the first and second polarized light beams. Is separated into G light, B light and R light, and the first, second and third reflective light valves
Light, B light, and R light, respectively, and the color separation / synthesis optical system performs color synthesis on the respective color lights modulated by the first, second, and third reflective light valves, respectively, and the polarization beam splitter includes: In the projection display device, the color separation / combination optical system detects light that is color-combined by the color separation / synthesis optical system, and the projection optical system projects the light detected by the polarization beam splitter. A dichroic mirror that color-separates the first polarized light into the G light, the B light, and light including the R light; and a light that includes the B light and the R light color-separated by the dichroic mirror. A dichroic prism that separates the light into the B light and the R light. The dichroic mirror (1) substantially transmits or reflects S-polarized light in a wavelength region on the short wavelength side with respect to the first transmission / reflection boundary wavelength near the boundary wavelength between G light and B light; Substantially transmitting or reflecting S-polarized light in a wavelength region on the longer wavelength side with respect to the second transmission / reflection boundary wavelength near the boundary wavelength between the light and the R light; (3) the first transmission / reflection boundary wavelength S-polarized light in a wavelength range between the second transmission and reflection boundary wavelength is substantially reflected or transmitted, and (4) a short wavelength with respect to the third transmission and reflection boundary wavelength near the boundary wavelength between G light and B light. (5) substantially transmitting or reflecting the P-polarized light in the wavelength region on the side, and (5) converting the P-polarized light in the wavelength region on the longer wavelength side to the fourth transmission / reflection boundary wavelength near the boundary wavelength between the G light and the R light. Substantially transmitting or reflecting,
(6) It has a dichroic characteristic of reflecting or transmitting P-polarized light in a wavelength range between the third transmission / reflection boundary wavelength and the fourth transmission / reflection boundary wavelength. The dichroic prism (1) substantially transmits or reflects S-polarized light in a wavelength region on the short wavelength side with respect to the fifth transmission / reflection boundary wavelength;
(2) substantially reflecting or transmitting the S-polarized light in the wavelength region on the long wavelength side with respect to the fifth transmission / reflection boundary wavelength; and (3) P in the short wavelength region with respect to the sixth transmission / reflection boundary wavelength. (4) substantially transmitting or reflecting polarized light; (4) substantially reflecting or transmitting P-polarized light in a wavelength region on a longer wavelength side with respect to the sixth transmission / reflection boundary wavelength; and (5) fifth transmission. A reflection boundary wavelength and the sixth transmission / reflection boundary wavelength are a wavelength near the first transmission / reflection boundary wavelength or near the third transmission / reflection boundary wavelength and a wavelength near the second transmission / reflection boundary wavelength or the fourth transmission / reflection boundary wavelength. And has a dichroic characteristic existing in a wavelength range between the wavelengths near the transmission / reflection boundary wavelength.

In the first aspect, the dichroic mirror may have any of the following dichroic characteristics. That is, the dichroic mirror has (1) G light and B light as first dichroic characteristics.
(2) substantially transmitting S-polarized light in a wavelength region on the short wavelength side with respect to the first transmission / reflection boundary wavelength near the boundary wavelength with light;
Substantially transmitting S-polarized light in a wavelength region on the longer wavelength side with respect to the second transmission / reflection boundary wavelength near the boundary wavelength between the G light and the R light; and (3) the first transmission / reflection boundary wavelength and the second transmission / reflection boundary wavelength. (4) a wavelength on the short wavelength side with respect to the third transmission / reflection boundary wavelength near the boundary wavelength between G light and B light. (5) substantially transmits the P-polarized light in the wavelength region on the longer wavelength side with respect to the fourth transmission / reflection boundary wavelength near the boundary wavelength between the G light and the R light. (6) P in a wavelength range between the third transmission / reflection boundary wavelength and the fourth transmission / reflection boundary wavelength.
It may have dichroic characteristics that reflect polarized light. This dichroic characteristic is a so-called G light reflection characteristic. Further, the dichroic mirror has, as a second dichroic characteristic, (1) substantially S-polarized light in a wavelength region on the short wavelength side with respect to the first transmission / reflection boundary wavelength near the boundary wavelength between G light and B light. And (2) substantially reflects S-polarized light in a wavelength region on the longer wavelength side with respect to a second transmission / reflection boundary wavelength near the boundary wavelength between G light and R light, and (3) the first transmission. (4) substantially transmitting S-polarized light in a wavelength range between a reflection boundary wavelength and the second transmission reflection boundary wavelength;
P-polarized light in a wavelength region on the short wavelength side with respect to the third transmission / reflection boundary wavelength near the boundary wavelength between G light and B light is substantially reflected, and (5) near the boundary wavelength between G light and R light. P-polarized light in a wavelength region on the long wavelength side with respect to the fourth transmission / reflection boundary wavelength is substantially reflected, and (6) a wavelength between the third transmission / reflection boundary wavelength and the fourth transmission / reflection boundary wavelength. It may have a dichroic characteristic that transmits P-polarized light in the region. This dichroic characteristic is a so-called G light transmission characteristic.

In the first aspect, the dichroic prism has any one of the following dichroic characteristics even when the dichroic mirror has any one of the two types of dichroic characteristics described above. It may be. That is, the dichroic prism has, as first dichroic characteristics, (1) substantially transmitting S-polarized light in a wavelength region on the short wavelength side with respect to the fifth transmission / reflection boundary wavelength, and (2) the fifth transmission. (3) substantially reflecting S-polarized light in a wavelength region on the long wavelength side with respect to the reflection boundary wavelength, and (3) substantially transmitting P-polarized light in a wavelength region on the short wavelength side with respect to the sixth transmission / reflection boundary wavelength; 4) The sixth
(5) the fifth transmission / reflection boundary wavelength and the sixth transmission / reflection boundary wavelength correspond to the first transmission. A dichroic that exists in a wavelength range between a wavelength near a reflection boundary wavelength or near the third transmission / reflection boundary wavelength and a wavelength near the second transmission / reflection boundary wavelength or near the fourth transmission / reflection boundary wavelength. It may have characteristics. Also,
The dichroic prism has, as second dichroic characteristics, (1) substantially reflects S-polarized light in a wavelength region on the short wavelength side with respect to the fifth transmission / reflection boundary wavelength, and (2) the fifth transmission / reflection boundary. (3) substantially transmitting the S-polarized light in the wavelength region on the long wavelength side with respect to the wavelength, (3) substantially reflecting the P-polarized light in the wavelength region on the short wavelength side with respect to the sixth transmission / reflection boundary wavelength; P-polarized light in a wavelength region on the long wavelength side with respect to the sixth transmission / reflection boundary wavelength is substantially transmitted, and (5) the fifth transmission / reflection boundary wavelength and the sixth transmission / reflection boundary wavelength are different from each other. Exists in a wavelength range between a wavelength near the first transmission / reflection boundary wavelength or near the third transmission / reflection boundary wavelength and a wavelength near the second transmission / reflection boundary wavelength or near the fourth transmission / reflection boundary wavelength. May have dichroic characteristics.

According to the first aspect, there is provided a dichroic mirror which has an advantage that a difference in dichroic characteristics between S-polarized light and P-polarized light is small, although the resolution is easily reduced.
A dichroic prism having an advantage that a difference in dichroic characteristics between the S-polarized light and the P-polarized light is large, but a reduction in resolution is hardly caused, is skillfully combined. Loss is suppressed, and a decrease in the amount of projection light is prevented, thereby improving the color balance.

That is, in the first aspect, of one of the polarized lights separated by the polarization beam splitter,
The G light is first reflected or transmitted by a dichroic mirror having a G light reflection characteristic or a G light transmission characteristic to be separated, and the B light and the R light transmitted or reflected by the dichroic mirror are separated.
The light including light is converted to R light and B light by a dichroic prism having transmission / reflection boundary wavelengths (the fifth transmission / reflection boundary wavelength and the sixth transmission / reflection boundary wavelength) substantially in the G light wavelength region.
It is separated into light and color. As a result, with respect to the G light, the color separation and the color synthesis are performed with the characteristic that the difference between the P-polarized light and the S-polarized light of the dichroic mirror is small. In the dichroic prism, there is a large difference in the characteristics between the P-polarized light and the S-polarized light. However, since the wavelength region where the characteristic difference is large exists substantially in the G light wavelength region, the R light reflected and transmitted by the dichroic prism. And B light are not substantially affected by the difference. Therefore, according to the first aspect, the loss of light is suppressed, the decrease in the amount of projection light is prevented, and the color balance is improved. In addition, since the dichroic prism is used instead of one dichroic mirror as the color separation / synthesis optical system instead of using two dichroic mirrors, the reduction in the resolution of the projected image is sufficiently small. Can be suppressed.

In the first aspect, since the color separation / synthesis optical system is composed of a dichroic mirror and a dichroic prism, the dichroic prism is more resistant to environmental changes than the dichroic mirror. It is more resistant to environmental changes than when two dichroic mirrors are used as the optical system.

The projection type display device according to a second aspect of the present invention is the projection type display device according to the first aspect, wherein the dichroic prism is provided between the dichroic prism and the second reflection type light valve. A first trimming filter that cuts light in the wavelength region on the G light side, which has a small amount of light, of the B light emitted from the dichroic prism after being color-separated by the dichroic prism, and the dichroic prism and the third reflective light A second trimming filter is arranged between the bulb and the second trimming filter that cuts light in the wavelength region on the G-light side where the amount of light is small among the R lights that have been separated by the dichroic prism and emitted from the dichroic prism. is there.

When the color is separated by the dichroic film, the rise or fall of the transmittance or the reflectance with respect to the wavelength in the vicinity of the transmission / reflection boundary wavelength does not become perpendicular to the wavelength axis but rises or falls gently. Has characteristics. That is, it has a so-called base field, which overlaps between adjacent color light areas, and lowers the color purity of each separated light in color separation. In the second aspect, the first trimming filter cuts light (corresponding to the base) in the wavelength region on the G light side with a small amount of light out of the B light emitted from the dichroic prism, and performs the second trimming. The filter cuts out the light in the wavelength region on the G light side where the amount of light is small (corresponding to the skirt) out of the R light emitted from the dichroic prism, thereby improving the color purity of the projected image.

A projection display according to a third aspect of the present invention is the projection display according to the first or second aspect, wherein the polarization splitting film of the polarizing beam splitter, the dichroic film of the dichroic mirror, and the dichroic film. The dichroic films of the prism are arranged substantially parallel to each other.

If the polarization splitting film of the polarizing beam splitter, the dichroic film of the dichroic mirror and the dichroic film of the dichroic prism are not arranged parallel to each other, the P-polarization direction and the S-polarization direction defined for each film are different. As a result, unnecessary polarized components superimposed on the light finally analyzed by the polarizing beam splitter via these films are increased, and the black state of the projected image on the screen is deteriorated and the projection is performed. The contrast of the image is reduced. In this regard, according to the third aspect, since the respective films are arranged substantially in parallel, the P-polarized light direction and the S-polarized light direction defined for each film substantially coincide with each other. Unnecessary polarization components superimposed on the light detected by the polarization beam splitter are reduced, and the contrast of the projected image is improved.

The projection display apparatus according to a fourth aspect of the present invention is the projection display apparatus according to the third aspect, wherein the dichroic prism and the dichroic prism are disposed between the dichroic mirror and the first reflective light valve. Between the second reflective light valve and between the dichroic prism and the third reflective light valve, the fast axis or the slow axis is perpendicular to the optical axis and the dichroic axis is The first, second, and third quarter-wave plates are respectively arranged so as to be substantially included in a plane defined by a normal vector of a mirror and a dichroic film of the dichroic prism and the optical axis. is there.

When the first, second and third quarter-wave plates are arranged as in the fourth embodiment, unnecessary polarized light superimposed on light finally detected by the polarizing beam splitter is superimposed. The components are eliminated, which is more preferable. If such a quarter-wave plate is not arranged, even if the films are arranged substantially in parallel, there is little unnecessary polarization component superimposed on the light finally analyzed by the polarization beam splitter. Will also remain.
That is, the light incident on the polarization beam splitter is emitted from the polarization splitting film of the polarization beam splitter and travels through the dichroic film of the dichroic mirror and the dichroic prism when entering the reflection type light valve through the dichroic film. The light beam includes a light beam whose direction is different from the traveling direction of the light beam when the light beam is reflected by the reflection type light valve and returns along the reverse path. Therefore, the P-polarization direction and the S-polarization direction of each film when the light beam travels from the polarization beam splitter to the reflection type light valve, and the film thickness when the light beam is reflected by the reflection type light valve and returns to the polarization beam splitter. Are shifted from the P polarization direction and the S polarization direction. Therefore, even if the respective films are arranged substantially in parallel, the fourth
Unless a quarter-wave plate is arranged as in the embodiment, unnecessary polarized components superimposed on light finally detected by the polarization beam splitter will still remain. In this regard, according to the fourth aspect, the light incident on the polarizing beam splitter is transmitted through each film and before being incident on the reflective light valve, and after being reflected by the reflective light valve. Since the light passes through the quarter-wave plate twice before passing through each film, the quarter-wave plate acts as a half-wave plate, and the polarization plane of the light is The rotation is compensated for. For this reason, unnecessary light components superimposed on the light finally detected by the polarizing beam splitter are eliminated, and the contrast of the projected image is further improved, which is more preferable.

A projection display apparatus according to a fifth aspect of the present invention includes a polarizing beam splitter, a color separation / synthesis optical system, first, second, and third reflective light valves, and a projection optical system. The polarizing beam splitter separates the light from the light source into first and second polarized lights, and the color separation / synthesis optical system converts the first polarized light into first, second, and third colored lights. Decomposing, the first, second and third reflective light valves modulate the first, second and third color lights, respectively;
The color separation / synthesis optical system performs color synthesis of each color light modulated by the first, second, and third reflection type light valves, and the polarization beam splitter performs light synthesis by the color separation / synthesis optical system. And the projection optical system projects the light detected by the polarizing beam splitter. In the projection display device, the color separation / synthesis optical system converts the first polarized light into the first colored light. A dichroic mirror that separates the light into light including the second and third color lights, and the light including the second and third color lights separated by the dichroic mirror into the second color light and the second color light. A dichroic prism that separates color light into three color lights, a polarization splitting film of the polarization beam splitter, a dichroic film of the dichroic mirror, and the dichroic film. The dichroic film of Kkupurizumu are those substantially parallel each other.

According to the fifth aspect, similarly to the third aspect described above, since the respective films are arranged substantially in parallel with each other, the light is finally superimposed on the light detected by the polarization beam splitter. Unnecessary polarization components are reduced, and the contrast of the projected image is improved.

A projection display according to a sixth aspect of the present invention is the projection display according to the fifth aspect, wherein the dichroic prism and the dichroic prism are disposed between the dichroic mirror and the first reflective light valve. Between the second reflective light valve and between the dichroic prism and the third reflective light valve, the fast axis or the slow axis is perpendicular to the optical axis and the dichroic axis is The first, second, and third quarter-wave plates are respectively arranged so as to be substantially included in a plane defined by a normal vector of a mirror and a dichroic film of the dichroic prism and the optical axis. is there.

According to the sixth aspect, similarly to the fourth aspect, the light finally detected by the polarization beam splitter has no unnecessary polarization components superimposed thereon, and the contrast of the projected image is reduced. Is further improved.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a projection type display device according to the present invention will be described in detail with reference to the drawings.

(First Embodiment) First, the first embodiment of the present invention will be described.
The projection type display device according to the embodiment will be described with reference to FIGS.

FIG. 1 is a perspective view showing a schematic configuration of the projection type display device according to the present embodiment. For simplicity of description, an X axis, a Y axis, and a Z axis that are orthogonal to each other are defined as shown in the figure (the same applies to FIGS. 4, 5, 6, and 10 described later).

In the projection type display device according to the present embodiment,
The light source 1 includes a lamp (not shown) and a concave mirror such as an elliptical mirror disposed on the back of the lamp. The light source light emitted from the light source 1 passes through an infrared light absorption filter and an ultraviolet light absorption filter (not shown), further forms a substantially parallel light beam through a shaping optical system (not shown), and travels in the −Y direction. 2 is incident. The polarization beam splitter 2 is disposed so that the plane of the polarization separation film 2p is a plane orthogonal to the XY plane and forms 45 degrees with respect to the Y axis (that is, with respect to the incident optical axis). The light that has entered the polarization beam splitter 2 is transmitted through the polarization separation film 2p, is emitted from the polarization beam splitter 2 in the −Y direction and is discarded, and the P-polarized light is reflected by the polarization separation film 2p and is polarized light splitter. 2 is separated into S-polarized light emitted in the X direction.

The S-polarized light emitted from the polarizing beam splitter 2 in the X direction enters the dichroic mirror 3.
The dichroic mirror 3 is on one side (incident side) of the glass plate.
And a dichroic film is formed, and the dichroic film is arranged so as to be parallel to the polarization splitting film 2p of the polarization beam splitter 2. In the present embodiment, the dichroic mirror 3 basically has a dichroic characteristic that reflects only G light and transmits B light and R light, that is, a so-called G light reflection characteristic.
The characteristics of the dichroic mirror 3 will be described later in detail with reference to FIG.

The G light of the light incident on the dichroic mirror 3 in the X direction is reflected by the dichroic mirror 3, travels in the −Y direction, and is incident on the reflection light valve 5G for G light. Of the light incident on the dichroic mirror 3, the light including the R light and the B light passes through the dichroic mirror 3, travels in the X direction, and enters the dichroic prism 4.

The dichroic prism 4 has, for example, a structure in which a dichroic film 4d is sandwiched between two triangular prisms. The dichroic film 4d is parallel to the polarization splitting film 2p of the polarizing beam splitter 2 and the dichroic film of the dichroic mirror 3. It is arranged so that it becomes. In the present embodiment, the dichroic prism 4
Basically has a dichroic characteristic of reflecting R light and transmitting B light. The characteristics of the dichroic prism 4 will be described later in detail with reference to FIG.

The R light out of the light including the R light and the B light incident on the dichroic prism 4 in the X direction is reflected by the dichroic film 4d of the dichroic prism 4, travels in the −Y direction, and is a reflection type light. The light is incident on the valve 5R. Among the light including the R light and the B light incident on the dichroic prism 4 in the X direction, the B light passes through the dichroic film 4d of the dichroic prism 4, travels in the X direction, and is incident on the reflection type light valve 5B. You.

As described above, the S-polarized light polarized and separated by the polarization beam splitter 2 is separated into G light, R light, and B light by the color separation / combination optical system including the dichroic mirror 3 and the dichroic prism 4. Is done.

Each of the S-polarized light beams incident on the reflection type light valves 5G, 5R, 5B is modulated by the reflection type light valves 5G, 5R, 5B, respectively, and the modulated light of each color light travels in the opposite direction to that at the time of incidence. And each dichroic mirror 3
Then, the process returns to the dichroic prism 4. In the present embodiment, an electric writing type reflective light valve is used as the reflective light valve 5G, 5R, 5B. Basically, the electric write type reflection type light valve converts the polarization direction of the reflected and emitted light at a location that is electrically selected based on each color signal into a polarization direction different from the incident light, and reflects and reflects the polarization at the unselected location. It has the function of keeping the polarization direction of the emitted light the same as that of the incident light. Light valve 5
In the modulated light modulated by the respective color signals emitted from G, 5R, and 5B, P-polarized light (signal component) at an electrically selected portion and S-polarized light at an unselected portion are mixed.

The modulated light of the R light reflected and emitted from the light valve 5R travels in the Y direction, reenters the dichroic prism 4, is reflected by the dichroic prism 4d of the dichroic prism 4, and travels in the -X direction. I do. The modulated light of the B light reflected and emitted from the light valve 5B travels in the −X direction, is incident on the dichroic prism 4 again, passes through the dichroic prism 4d of the dichroic prism 4, and travels in the −X direction as it is. Therefore, the modulated light of the R light and the modulated light of the B light are color-combined by the dichroic prism 4, and the color-combined light is emitted from the dichroic prism 4 in the −X direction. The color-combined light passes through the dichroic mirror 3 and proceeds in the −X direction as it is. On the other hand, the modulated light of the G light reflected and emitted from the light valve 5G is Y light.
The light travels in the dichroic mirror 3 again in the direction, is reflected by the dichroic mirror 3, and travels in the −X direction. As a result, the modulated light of the G light is color-combined with the color combined light of the modulated light of the R light and the modulated light of the B light, and three-color combining is achieved.

As described above, the modulated light of each color light (including the P-polarized light as the signal component and the S-polarized light which is not the signal component) is converted by the color separation / synthesis optical system including the dichroic mirror 3 and the dichroic prism 4. Are combined.

The three-color combined light travels in the −X direction and is incident on the polarization beam splitter 2, and only the P-polarized light (signal component) of the three-color combined light is the polarization separation film 2 p of the polarization beam splitter 2. And travels in the −X direction (that is,
The S-polarized light of the three-color combined light is reflected by the polarization splitting film 2p of the polarization beam splitter 2 and discarded in the Y direction. That is, the three-color combined light is detected by the polarizing beam splitter 2, and the detected light (P-polarized light) is projected on a screen (not shown) by the projection lens 10.

The above is the basic configuration of the projection type display device according to the present embodiment.

Next, an example of the dichroic characteristics of the dichroic mirror 3 and the dichroic prism 4 which are the color separation / synthesis optical systems according to the present embodiment, and the color separation and color synthesis achieved thereby will be described with reference to FIG. This will be described in detail.

FIG. 2A schematically (qualitatively) shows the characteristics of the dichroic mirror 3, in which the vertical axis indicates transmittance, the horizontal axis indicates wavelength, and the dotted line indicates dichroic light for S-polarized light. The characteristics and the solid line show the dichroic characteristics for the P-polarized light. In the actual dichroic characteristics, for example, as shown in FIG. 9, at a predetermined wavelength, transmission and reflection may be reversed like noise, but such a portion is omitted in FIG. 2 (a). (The same applies to FIGS. 2 (b), 3 (a), and 3 (b) described later).

As shown in FIG. 2A, the dichroic mirror 3 (1) has a first wavelength near the boundary wavelength between G light and B light.
In the wavelength region on the short wavelength side with respect to the transmission / reflection boundary wavelength λ1
(2) substantially transmitting S-polarized light in a wavelength region on the longer wavelength side with respect to the second transmission / reflection boundary wavelength λ2 near the boundary wavelength between G light and R light; 3) substantially reflects S-polarized light in a wavelength range between the first transmission / reflection boundary wavelength λ1 and the second transmission / reflection boundary wavelength λ2, and (4) the vicinity of the boundary wavelength between G light and B light. Substantially transmitting P-polarized light in a wavelength region on the short wavelength side with respect to the third transmission / reflection boundary wavelength λ3;
(5) substantially transmitting P-polarized light in a wavelength region on the long wavelength side with respect to the fourth transmission / reflection boundary wavelength λ4 near the boundary wavelength between G light and R light; and (6) third transmission / reflection boundary wavelength λ3 and 4th
Has a dichroic characteristic of reflecting P-polarized light in a wavelength range between the transmission and reflection boundary wavelength λ4.

As can be seen from FIG. 2A, in the dichroic mirror 3, the difference between the dichroic characteristic of the S-polarized light and the dichroic characteristic of the P-polarized light is small. In this example, the first transmission / reflection boundary wavelength λ1 is slightly smaller than the third transmission / reflection boundary wavelength λ3, and the second transmission / reflection boundary wavelength λ2 is slightly larger than the fourth transmission / reflection boundary wavelength λ4. That is, the reflection wavelength range of the S-polarized light is wider than the reflection wavelength range of the P-polarized light.

FIG. 2B shows a dichroic prism 4.
Is a diagram schematically (qualitatively) showing the characteristics of the above, wherein the vertical axis represents the transmittance, the horizontal axis represents the wavelength, the dotted line represents the dichroic characteristic for S-polarized light, and the solid line represents the dichroic characteristic for P-polarized light. I have.

As shown in FIG. 2B, the dichroic prism 4 substantially transmits S-polarized light in a wavelength region on the short wavelength side with respect to the fifth transmission / reflection boundary wavelength λ5, and (2) the fifth S-polarized light in the wavelength region on the long wavelength side with respect to the transmission / reflection boundary wavelength λ5 is substantially reflected, and (3) P-polarized light in the short wavelength region with respect to the sixth transmission / reflection boundary wavelength λ6 is substantially transmitted. (4) substantially reflecting the P-polarized light in the wavelength region on the long wavelength side with respect to the sixth transmission / reflection boundary wavelength λ6;
The fifth transmissive / reflective boundary wavelength λ5 and the sixth transmissive / reflective boundary wavelength λ6 include a wavelength near the first transmissive / reflective boundary wavelength λ1 or near the third transmissive / reflective boundary wavelength λ3, and a second transmissive / reflective boundary wavelength λ2. It has a dichroic characteristic that exists in the wavelength range between the vicinity and the wavelength near the fourth transmission / reflection boundary wavelength λ4.

As can be seen from FIG. 2B, in the dichroic prism 4, the difference between the dichroic characteristic of the S-polarized light and the dichroic characteristic of the P-polarized light is large.
In this example, the sixth transmission / reflection boundary wavelength λ6 is considerably larger than the fifth transmission / reflection boundary wavelength λ5.

In this example, the fifth transmission / reflection boundary wavelength λ5 is slightly larger than the third transmission / reflection boundary wavelength 3. Further, the sixth transmission / reflection boundary wavelength λ6 is considerably larger than the first transmission / reflection boundary wavelength λ1, and is slightly smaller than the fourth transmission / reflection boundary wavelength λ4.

FIG. 2C shows the relationship between the quantity of light and the wavelength of light (corresponding to G light) reflected by the dichroic mirror 3 and incident on the light valve 5G in accordance with the characteristics of the S-polarized light shown in FIG. Show the relationship. In FIG. 2C, the vertical axis indicates the light amount, and the horizontal axis indicates the wavelength (the same applies to FIGS. 2 (d) to 2 (j) and FIGS. 3 (c) to 3 (j) described later. ).

FIG. 2D shows that the light passes through the dichroic mirror 3 in accordance with the characteristic relating to the S-polarized light shown in FIG. 2A and then transmits through the dichroic prism 4 according to the characteristic relating to the S-polarized light shown in FIG. Light valve 5
The relationship between the amount of light and the wavelength of light incident on B (corresponding to B light) is shown.

FIG. 2E shows that the light passes through the dichroic mirror 3 in accordance with the characteristics relating to the S-polarized light shown in FIG. 2A and is reflected by the dichroic prism 4 according to the characteristics relating to the S-polarized light shown in FIG. The relationship between the light quantity and the wavelength of the light (corresponding to the R light) that is incident on the light valve 5R is shown.

FIG. 2 (f) shows that after all the incident light (all light for convenience of explanation, hereinafter the same) is modulated into P-polarized light and reflected by the light valve 5G, FIG.
7A shows the relationship between the amount of light and the wavelength of light (corresponding to G light) reflected by the dichroic mirror 3 and incident on the polarization beam splitter 2 in accordance with the characteristics of the P-polarized light shown in FIG.

FIG. 2 (g) shows that after all the incident light is modulated by the light valve 5B into P-polarized light and reflected,
FIG. 2B shows the relationship between the amount of light and the wavelength of light (corresponding to B light) transmitted through the dichroic prism 4 in accordance with the characteristics of the P-polarized light shown in FIG.

FIG. 2H shows that after all the incident light is modulated into P-polarized light and reflected by the light valve 5R,
2B shows the relationship between the amount of light and the wavelength of light (corresponding to R light) reflected by the dichroic prism 4 in accordance with the characteristics of the P-polarized light in FIG.

FIG. 2 (i) shows a dichroic prism 4
Light that is synthesized at and enters the dichroic mirror 3,
That is, the relationship between the light amount and the wavelength of the combined light of the light shown in FIG. 2G and the light shown in FIG.

FIG. 2 (j) shows light (three-color combined light) which is color-combined by the dichroic mirror 3 and enters the polarization beam splitter, ie, the light shown in FIG. 2 (f) and FIG.
6 shows the relationship between the light quantity and the wavelength of the combined light with the light shown in (i).

Although the dichroic prism 4 has a large difference in dichroic characteristics between the S-polarized light and the P-polarized light as shown in FIG. 2B, as can be seen from FIG. The wavelength width (the wavelength range between the transmissive / reflective boundary wavelength λ1 and the transmissive / reflective boundary wavelength λ3, which corresponds to the smaller characteristic between the S-polarized light and the P-polarized light in the dichroic mirror 3 shown in FIG. And a wavelength range between the transmission / reflection boundary wavelength λ4 and the transmission / reflection boundary wavelength λ2)
The three-color combined light passes through the polarizing beam splitter 2 and is projected by the projection lens 10. Therefore, light in a wavelength range substantially coincident with the incident light is projected, and light loss is suppressed.

In the example described above, as shown in FIGS. 2A and 2B, the transmission / reflection boundary wavelengths λ5 and λ6
Exist in the wavelength range between the transmission / reflection boundary wavelength λ3 and the transmission / reflection boundary wavelength λ4. For example, the transmission / reflection boundary wavelength λ5 is changed to the wavelength range between the transmission / reflection boundary wavelength λ1 and the transmission / reflection boundary wavelength λ3. And the transmission / reflection boundary wavelength λ6 is different from the transmission / reflection boundary wavelength λ4 and the transmission / reflection boundary wavelength λ2
It can be seen from similar considerations that even in these cases, the same three-color combined light as the three-color combined light shown in FIG. 2J can be obtained.

Next, another example of the dichroic characteristics of the dichroic mirror 3 and the dichroic prism 4 which are the color separation / synthesis optical systems according to the present embodiment, and the color separation and color synthesis achieved thereby with reference to FIG. And will be described in detail. In this example, the characteristics of the dichroic mirror 3 are the same as those of the example shown in FIG. 2, but the characteristics of the dichroic prism 4 are different.

FIG. 3A is a diagram schematically showing the characteristics of the dichroic mirror 3, in which the vertical axis shows the transmittance, the horizontal axis shows the wavelength, the dotted line shows the dichroic characteristic for S-polarized light, and the solid line shows the P 9 shows dichroic characteristics for polarized light. This dichroic characteristic is the same as the dichroic characteristic shown in FIG.

FIG. 3B shows a dichroic prism 4.
Is a diagram schematically (qualitatively) showing the characteristics of the above, wherein the vertical axis represents the transmittance, the horizontal axis represents the wavelength, the dotted line represents the dichroic characteristic for S-polarized light, and the solid line represents the dichroic characteristic for P-polarized light. I have.

As shown in FIG. 3B, the dichroic prism 4 substantially converts the S-polarized light in the wavelength region on the short wavelength side to the fifth transmission / reflection boundary wavelength λ5 similarly to the characteristic of FIG. 2B. (2) Fifth transmission / reflection boundary wavelength λ5
(3) substantially reflects P-polarized light in a wavelength region on the short wavelength side with respect to the sixth transmission / reflection boundary wavelength λ6; P-polarized light in a wavelength region on the longer wavelength side with respect to the sixth transmission / reflection boundary wavelength λ6 is substantially reflected, and (5) the fifth transmission / reflection boundary wavelength λ5 and the sixth transmission / reflection boundary wavelength λ6 are equal to the first transmission / reflection boundary wavelength λ6. A wavelength near the transmission / reflection boundary wavelength λ1 or near the third transmission / reflection boundary wavelength λ3, and a wavelength near the second transmission / reflection boundary wavelength λ2 or the fourth wavelength.
Has a dichroic characteristic which exists in a wavelength range between the transmission and reflection boundary wavelength λ4 and the wavelength near the boundary wavelength λ4.

However, in this example, unlike the example shown in FIG. 2B, the fifth transmission / reflection boundary wavelength λ5 is slightly smaller than the first transmission / reflection boundary wavelength λ1, and the fifth transmission / reflection boundary wavelength λ5 is The wavelength is near the first transmission / reflection boundary wavelength λ1, and is on the short wavelength side of the first transmission / reflection boundary wavelength λ1. The sixth transmission / reflection boundary wavelength λ6 is a wavelength substantially at the center between the third transmission / reflection boundary wavelength λ3 and the fourth transmission / reflection boundary wavelength λ4. That is, in this example,
The dichroic prism 4 is an example in which the fifth transmission / reflection boundary wavelength λ6 and the sixth transmission / reflection boundary wavelength are largely shifted to the shorter wavelength side as compared with the characteristics shown in FIG.

FIGS. 3 (c) to 3 (j) correspond to FIG.
(C) to (j) respectively. As can be understood from FIG. 3 (j), in this example, as compared with the case of FIG. 2 (j), the three colors correspond to the shift of the transmission / reflection boundary wavelength λ5 to the shorter wavelength side than the transmission / reflection boundary wavelength λ1. The wavelength range of the B light in the combined light is narrowed. However, when the transmission / reflection boundary wavelength λ5 is a wavelength near the transmission / reflection boundary wavelength λ1, the shift amount is small, and light loss is suppressed as compared with the above-described conventional projection display device.

In the example described above, the transmission / reflection boundary wavelength λ5 is shifted to a shorter wavelength side than the transmission / reflection boundary wavelength λ1, as shown in FIGS. 3 (a) and 3 (b).
For example, the transmission / reflection boundary wavelength λ6 is changed to the transmission / reflection boundary wavelength λ2.
When the wavelength shifts to a longer wavelength side, the wavelength range of the R light in the three-color combined light is narrowed from the same consideration. Even in this case, if the transmission / reflection boundary wavelength λ6 is a wavelength near the transmission / reflection boundary wavelength λ2, the shift amount is small, and light loss is suppressed as compared with the above-described conventional projection display device.

As described above, according to the present embodiment, light loss is suppressed despite the large difference in dichroic characteristics between S-polarized light and P-polarized light in dichroic prism 4. In this embodiment, two dichroic mirrors are not used as the color separation / synthesis optical system, but the dichroic prism 4 is used instead of one of the dichroic mirrors. The reduction in resolution can be kept sufficiently small.

That is, according to the present embodiment, the dichroic mirror 3 has an advantage that the resolution is easily reduced but the difference in dichroic characteristics between the S-polarized light and the P-polarized light is small. The dichroic prism 4, which has the advantage that the difference in characteristics is large but does not easily cause a decrease in resolution, is skillfully combined with
Thus, the loss of light is suppressed, the light amount of the projected light is prevented from lowering, and the color balance is improved without causing a significant reduction in the resolution of the projected image.

The dichroic film 4d of the dichroic prism 4 originally has the purpose of separating the R light and the B light. However, as described above, the dichroic film 4d reflects only the R light and transmits only the B light, or In order to transmit only the R light and reflect only the B light, it is not necessary to set the transmission / reflection boundary wavelength at the boundary between the R light and the G light and the boundary between the G light and the B light. What is necessary is just to set the boundary wavelength of the transmission and reflection of the S-polarized light and the P-polarized light in the region, and there is also an effect that the manufacture of the dichroic prism 4 becomes ready.

Further, according to the present embodiment, the polarization splitting film 2p of the polarization beam splitter 2, the dichroic film of the dichroic mirror 3, and the dichroic prism 4
Since the dichroic films d are arranged substantially parallel to each other, the contrast of the projected image is improved. This will be described in connection with a third embodiment described later.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
The projection type display device according to the embodiment will be described with reference to FIG.

FIG. 4 is a perspective view showing a schematic configuration of a projection type display device according to the second embodiment of the present invention. In addition,
4, elements that are the same as or correspond to elements in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted.

The difference between the projection type display device according to the present embodiment and the projection type display device according to the first embodiment shown in FIG. 1 is that the R light and the B light which have been separated by the dichroic prism 4 are separated. The only difference is that a trimming filter 6R for R light and a trimming filter 6B for B light are respectively arranged near each surface of the dichroic prism 4 that emits light. In the present embodiment, a short wavelength cut filter is used as the trimming filter 6R, and a long wavelength cut filter is used as the trimming filter 6B. As shown in FIGS. 2 and 3, normally, when color separation is performed by the dichroic film of the dichroic mirror 3 or the dichroic prism 4, the rise or fall of the transmittance or the reflectance with respect to the wavelength near the transmission / reflection boundary wavelength. Are not perpendicular to the wavelength axis, but have the characteristic of rising or falling gently. That is, it has a so-called base field, which overlaps between adjacent color light areas, and lowers the color purity of each separated light in color separation. According to the present embodiment, of the B light emitted from the dichroic prism 4, the light in the wavelength region on the G light side with a small amount of light (corresponding to the skirt) is cut by the trimming filter 6 B, and the trimming filter 6 R Of the R light emitted from the dichroic prism 4, light in the wavelength region on the G light side where the amount of light is small (corresponding to the base).
Is cut, so that in addition to the same advantages as in the first embodiment, the advantage that the color purity of the projected image is improved can be obtained.

Note that the trimming filters 6R and 6B are
As shown in FIG. 4, since the filters 6R and 6B can be arranged perpendicular to the optical axis, there is no problem of increasing the size of the device.

(Third Embodiment) Next, the third embodiment of the present invention will be described.
The projection type display device according to the embodiment will be described with reference to FIGS.

FIG. 5 is a perspective view showing a schematic configuration of a projection type display device according to a third embodiment of the present invention. FIG.
FIG. 7 is an explanatory diagram for explaining functions of quarter-wave plates 7R, 7G, and 7B, and is a ray diagram corresponding to FIG. FIG.
FIG. 6 is a diagram illustrating a state of polarization in each optical path in FIG. 5. 5 and 6, the same or corresponding elements as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

The point that the projection type display device according to the present embodiment is different from the projection type display device according to the second embodiment shown in FIG. 4 described above, as shown in FIG. 5, is a reflection type light valve 5R for each color light. , 5G, and 5B just before the quarter-wave plates 7R, 7G, and 7B, respectively. The quarter-wave plates 7R, 7G, 7B are arranged perpendicular to the optical axis. Further, the 板 wavelength plates 7R and 7G have their fast axes X
１ ／ wavelength plate is arranged such that the fast axis is in the Y direction. That is, 1 /
The four-wavelength plates 7R, 7G, and 7B have a fast axis or a slow axis whose dichroic mirror 3 and dichroic prism 4
Are arranged so as to be included in the plane defined by the normal vector of the dichroic film and the optical axis.

Not all rays emitted from the light source 1 travel parallel to the optical axis, but some rays travel at a predetermined angle to the optical axis and enter the polarizing beam splitter 2. Now, FIG. 6 shows one of the rays as T1. In FIG. 6, the light source 1 is omitted.

The light beam T incident on the polarization beam splitter 2
1 is polarized and separated by the polarization splitting film 2p of the polarization beam splitter 2, becomes S-polarized light, travels as a light beam having a predetermined angle to the optical axis, and enters the dichroic mirror 3 and the dichroic prism 4. Now, consider only the light beam incident on the light valve 5B, that is, the B light component. The B light transmitted through the dichroic mirror 3 is
Quarter-wave plate 7B transmitted through dichroic prism 4
Then, the light enters the light valve 5B, is reflected by the light valve 5B according to the reflection law, passes through the dichroic prism 4 and the dichroic mirror 3, and is analyzed by the polarization beam splitter 2.

FIG. 7 is a view showing each optical path of the ray T1 in FIG.
And the polarization state in the YZ plane viewed in the −X direction of FIG. The T1 light beam reflected and emitted by the polarization beam splitter 2 is S-polarized light having a vibration direction S1 in the S1 direction shown in FIG. 7, and is slightly inclined with respect to the Z axis. This is because the normal direction of the polarization separation film 2p of the polarization beam splitter 2 and the light beam T1
This is because the S1 direction is determined according to the direction in which. Since the dichroic film of the dichroic mirror 3 and the polarization splitting film 2p of the polarization beam splitter 2 are parallel to each other, when the polarized light passes through the dichroic mirror 3, the polarized light still maintains the S polarization for the dichroic mirror 3. Pass this as it is. The state of this polarization is as shown in FIG. Dichroic prism 4
The same applies to the light beam T1 that has passed through the dichroic prism, and passes through the dichroic film of the dichroic prism while maintaining the S-polarized light. The polarization direction is the same as that of FIG. 7 as shown in FIG. Is transmitted through the quarter-wave plate 7B having the optical axis arranged in the Y direction, reflected by the light valve 5B, and further divided by 1/4.
The light passes through the wave plate 7B. This light is １ ／ wavelength plate 7B
Is transmitted twice, which means that the light has passed through the half-wave plate, and when the polarization direction is not converted by the light valve 5B, the oscillation direction of the polarization is Z as shown in S4 in FIG. 7 will be inclined by the same angle with respect to the axis in the direction opposite to the inclination shown in FIG. This direction is perpendicular to the plane formed by the traveling direction of the light beam after reflection from the light valve 5B and the normal of the dichroic film of the dichroic prism 4 (that is, the S-polarization of the reflected light with respect to the dichroic prism 4). Direction), which is the direction shown in S4 of FIG.

Assuming that there is no quarter-wave plate 7B, the polarization direction of the light beam at the point shown in FIG. 6 is the same as the direction indicated by the arrows in FIG. in this case,
Since the S polarization direction of the dichroic prism 4 is S5 in FIG. 7 (the same as S4 in FIG. 7), the vibration direction S
4 ′ (= S5 ′) is a direction s parallel to S5 shown in FIG.
5 '(S-polarized direction with respect to dichroic prism 4)
And a direction p5 ′ perpendicular to it (dichroic prism 4
In the P polarization direction). Dichroic film 4p of dichroic prism 4
Is composed of a dielectric film, and generally generates a phase shift between the P-polarized component and the S-polarized component. Therefore, the dichroic prism is separated by the polarization beam splitter 2 and then reflected by the light valve 5B. When the linearly polarized light that has been kept until the light enters the dichroic prism 4 passes through the dichroic prism 4, it becomes elliptically polarized light at the position shown in FIG. The same applies when this light passes through the dichroic mirror 3, so that when returning to the polarizing beam splitter 2, the polarization state no longer changes greatly from linearly polarized light.

On the other hand, in the present embodiment, as described above, by reciprocating the quarter-wave plate 7B, FIG.
Since the polarization direction of the light beam at the point is changed to the S4 direction, such polarization disturbance to the dichroic prism 4 and the dichroic mirror 3 is eliminated, and the light reflected by the light valve 5B keeps the linear polarization. The light enters the polarization beam splitter 2 again. FIG. 6 at this time
Is the same as the direction of the S component with respect to the plane of the polarization splitting film 2p of the polarization beam splitter 2, since the polarization direction S6 of the light beam at the position (2) is the same as that of the polarization splitting film 2p of the polarization beam splitter 2. All of the light is reflected and complete analysis is achieved, so that a so-called black state can be achieved, and the contrast of the projected image is improved. If the quarter-wave plate 7B is not disposed, the component s6 ′ shown in FIG. 7 is reflected by the polarization splitting film 2p, but the component p6 ′ is transmitted through the polarization splitting film 2p and passes through a screen (not shown). In this case, the contrast is reduced.

Up to now, the transmitted light (B light) transmitted through the dichroic mirror 3 and the dichroic prism 4 has been discussed.
However, the case of reflection by the dichroic mirror 3 and the dichroic prism 4 can be considered in the same manner. Similarly, the １ ／ wavelength plates 7G and 7R are set to the phase advance immediately before the reflection type light valves 5G and 5R. The axis is in the X direction or Z
By arranging in the direction, the contrast of the projected image is improved.

The above is the description of the improvement of the contrast by the quarter-wave plates 7R, 7G, 7B. In order to achieve such improvement of the contrast, the polarization separation film 2p of the polarization beam splitter and the dichroic of the dichroic mirror 3 are required. The film and the dichroic film 4d of the dichroic prism 4 are arranged substantially in parallel with each other, and furthermore, at the front of the light valves 5R, 5G, and 5B, perpendicular to the optical axis.
In addition, it is necessary to arrange such that the fast axis or the slow axis is parallel to the X axis or the Z axis.

However, unlike the first and second embodiments described above, the polarization splitting film 2 of the polarization beam splitter 2 can be provided without providing the quarter-wave plates 7R, 7G, 7B.
If p, the dichroic film of the dichroic mirror 3 and the dichroic film 4d of the dichroic prism 4 are arranged substantially parallel to each other, the contrast of the projected image can be much improved as compared with the case where these are not parallel. In other words, if they are not parallel to each other, the S direction with respect to the polarization beam splitter 2 can be obtained both when the light exits from the polarization beam splitter 2 and reaches the light valve 7B and when the polarization beam splitter 2 returns from the light valve 7B. Since the S direction with respect to the dichroic mirror 3 and the S direction with respect to the dichroic prism 4 are different from each other, each time the light passes through each of them, it deviates from linearly polarized light, and finally the polarization state when returning to the polarization beam splitter 2 is linear. This is a remarkably large change from the polarized light. On the other hand, if these are parallel to each other, as can be seen from (1) to (5) in FIG. 7, linear polarization is maintained at least from the emission of the polarization beam splitter 2 to the light valve 7B. 5, the amount of change in the polarization state with respect to the linearly polarized light when returning to the polarization beam splitter 2 is reduced, and although not as large as in the embodiment shown in FIG. 5, the contrast of the projected image can be improved.

As described above, according to this embodiment, the same advantages as those of the above-described second embodiment can be obtained, and the polarization of light caused by the incident angle of the light beam entering the polarization beam splitter can be obtained. It is possible to suppress the inclination of the direction and the disturbance of the polarization due to the dichroic mirror and the dichroic film in the dichroic prism, thereby obtaining an advantage that the contrast of the projected image can be further improved.

(Fourth Embodiment) In the first to third embodiments, the dichroic mirror 3 has a G light reflection characteristic (reflects only G light and transmits light including R light and B light). Characteristic), and the dichroic mirror 3
Is guided to the light valve 5G for G light, and the light transmitted through the dichroic mirror 3 is separated into R light and B light by the dichroic prism 4 and guided to the light valves 5R and 5B for each color light. Had a configuration.

However, the present invention is not limited to such a configuration, and the dichroic mirror 3 is provided with a G light transmission characteristic (a characteristic of transmitting only G light and reflecting light including R light and B light). May be provided.

FIG. 10 shows a dichroic mirror 3 according to a fourth embodiment of the present invention, in which a G light transmission characteristic (for example, a dichroic characteristic shown in FIG. FIG. 1 is a perspective view showing a schematic configuration of a projection display device using a device having ()). The projection display device according to the fourth embodiment corresponds to the projection display device according to the first embodiment shown in FIG. 1 using a dichroic mirror 3 having a G light reflection characteristic. In FIG. 10,
Elements that are the same as or correspond to the elements in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted.

It is apparent that the present embodiment also provides the same advantages as the first embodiment.

Although not shown in the drawing, in the configuration shown in FIG. 10, trimming filters 6R and 6B are arranged near the respective exit end faces of the dichroic prism 4 in the same manner as in FIGS. 4 and 5. It is needless to say that quarter-wave plates 7R, 7G, 7B may be arranged immediately before the light valves 5R, 5G, 5B for the respective color lights as in the case of FIG.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments.

For example, in each of the above-described embodiments, the dichroic prism 4 is replaced with the one shown in FIG.
2B, the dichroic prism 4 has the dichroic characteristics shown in FIG.
It may have a dichroic characteristic in which the transmittance and the reflectance are inverted from the dichroic characteristic shown in (b).

[0096]

As described above, according to the present invention,
It is possible to provide a projection type display device having a good color balance by suppressing light loss and preventing a decrease in the amount of projection light without causing a decrease in resolution of a projected image.

Further, according to the present invention, it is possible to provide a projection display device having good contrast of a projected image.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of a projection display device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of characteristics relating to color separation and color synthesis of the projection display device according to the first embodiment.

FIG. 3 is a diagram illustrating another example of characteristics relating to color separation and color synthesis of the projection display device according to the first embodiment.

FIG. 4 is a perspective view showing a schematic configuration of a projection display according to a second embodiment of the present invention.

FIG. 5 is a perspective view showing a schematic configuration of a projection display device according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a state of obliquely incident light rays in the projection display apparatus according to the third embodiment.

FIG. 7 is a view showing a state of polarization in each optical path in FIG. 6;

FIG. 8 is a diagram illustrating an example of dichroic characteristics of a dichroic mirror.

FIG. 9 is a diagram illustrating an example of dichroic characteristics of a dichroic prism.

FIG. 10 is a perspective view illustrating a schematic configuration of a projection display device according to a fourth embodiment of the present invention.

FIG. 11 is a configuration diagram illustrating an example of a conventional projection display device.

[Explanation of symbols]

 Reference Signs List 1 light source 2 polarizing beam splitter 3 dichroic mirror 4 dichroic prism 5R, 5G, 5B reflection type light valve 6R, 6B trimming filter 7R, 7G, 7B quarter wavelength plate 10 projection lens

Claims (6)

[Claims] 1. A polarizing beam splitter, a color separation / synthesis optical system, first, second and third reflective light valves,
A projection optical system, wherein the polarization beam splitter polarization-separates light from a light source into first and second polarization lights, and the color separation / synthesis optical system converts the first polarization light into G light, B light and The light is separated into R light, and the first, second and third reflective light valves are used to separate the G light, B light.
The color separation / combination optical system modulates the light and the R light, respectively, and the color separation / combination optical system performs color synthesis on the respective color lights modulated by the first, second, and third reflection type light valves, respectively, and the polarization beam splitter performs the color separation. In a projection display device, the color separation / combination optical system detects the light color-combined by the combination optical system, and the projection optical system projects the light detected by the polarization beam splitter. A dichroic mirror for color-separating the polarized light into the G light and the light including the B light and the R light, and converting the light including the B light and the R light color-separated by the dichroic mirror to the B light.
A dichroic prism for color separation into light and the R light, wherein the dichroic mirror has: (1) a wavelength on a short wavelength side with respect to a first transmission / reflection boundary wavelength near a boundary wavelength between G light and B light. Substantially transmitting or reflecting S-polarized light in the region;
(3) substantially transmitting or reflecting S-polarized light in a wavelength region on the longer wavelength side with respect to the second transmission / reflection boundary wavelength near the boundary wavelength between G light and R light; S-polarized light in a wavelength range between the second transmission and reflection boundary wavelength is substantially reflected or transmitted, and (4) a short wavelength with respect to the third transmission and reflection boundary wavelength near the boundary wavelength between G light and B light. P-polarized light in the wavelength region on the wavelength side is substantially transmitted or reflected.
Substantially transmitting or reflecting P-polarized light in a wavelength region on the longer wavelength side with respect to a fourth transmission / reflection boundary wavelength near the boundary wavelength with light; (6) the third transmission / reflection boundary wavelength and the fourth The dichroic prism has a dichroic property of reflecting or transmitting P-polarized light in a wavelength range between the transmission and reflection boundary wavelengths. (2) substantially transmitting or reflecting polarized light; (2) substantially transmitting or reflecting S-polarized light in a wavelength region on a longer wavelength side with respect to the fifth transmission / reflection boundary wavelength; and (3) sixth transmission / reflection. Substantially transmitting or reflecting P-polarized light in the wavelength region on the short wavelength side with respect to the boundary wavelength,
(4) substantially reflecting or transmitting P-polarized light in a wavelength region on the long wavelength side with respect to the sixth transmission / reflection boundary wavelength; and (5) the fifth transmission / reflection boundary wavelength and the sixth transmission / reflection boundary. The wavelength is near the first transmission / reflection boundary wavelength or the third transmission / reflection boundary wavelength;
Having a dichroic characteristic, which exists in a wavelength range between the wavelength near the transmission / reflection boundary wavelength and the wavelength near the second transmission / reflection boundary wavelength or the wavelength near the fourth transmission / reflection boundary wavelength, Projection display device. 2. The dichroic prism and the second dichroic prism.
A first trimming filter that cuts light in the wavelength region on the G light side, which has a small amount of light, of the B light that has been color-separated by the dichroic prism and emitted from the dichroic prism, R, which is disposed between the dichroic prism and the third reflective light valve, is separated by the dichroic prism and emitted from the dichroic prism.
2. The projection display device according to claim 1, further comprising a second trimming filter for cutting light in a wavelength region on the G light side having a small amount of light. 3. The polarizing beam splitter, a dichroic film of the dichroic mirror, and a dichroic film of the dichroic prism are arranged substantially parallel to each other. Projection display device. 4. The method according to claim 1, further comprising: a step between the dichroic mirror and the first reflective light valve, a step between the dichroic prism and the second reflective light valve, and a step between the dichroic prism and the third reflective light valve. In between, the optical axis is perpendicular to the optical axis, and its fast axis or slow axis is substantially in a plane formed by a normal vector of the dichroic film of the dichroic mirror and the dichroic film and the optical axis. 4. The projection display device according to claim 3, wherein the first, second, and third quarter-wave plates are arranged so as to be included. 5. A polarizing beam splitter, a color separation / synthesis optical system, first, second and third reflection type light valves,
A projection optical system, wherein the polarization beam splitter polarizes and separates light from the light source into first and second polarization lights, and the color separation / synthesis optical system converts the first polarization light into first, second, and Color separation into a third color light,
The first, second, and third reflective light valves modulate the first, second, and third color lights, respectively, and the color separation / synthesis optical system includes the first, second, and third reflective light valves. Each color light modulated by the light valve is color-combined, the polarization beam splitter detects the color-combined light by the color separation / combination optical system, and the projection optical system is detected by the polarization beam splitter. In a projection type display device that projects light, the color separation / synthesis optical system converts the first polarized light into the first polarized light.
A dichroic mirror that separates the color light into light including the second and third color lights, and the light including the second and third color lights separated by the dichroic mirror as the second color light. A dichroic prism that separates the light into the third color light, and a polarization separation film of the polarization beam splitter, a dichroic film of the dichroic mirror, and a dichroic film of the dichroic prism are arranged substantially parallel to each other. Characteristic projection display device. 6. The method according to claim 1, further comprising: a step between the dichroic mirror and the first reflective light valve, a step between the dichroic prism and the second reflective light valve, and a step between the dichroic prism and the third reflective light valve. In between, the optical axis is perpendicular to the optical axis, and its fast axis or slow axis is substantially in a plane formed by a normal vector of the dichroic film of the dichroic mirror and the dichroic film and the optical axis. 6. The projection display device according to claim 5, wherein the first, second, and third quarter-wave plates are arranged so as to be included.