JPH11271893A - Projection display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection display device capable of obtaining a clear image with high contrast with a simple constitution, and also which is made compact and whose efficiency is improved. SOLUTION: The device is provided with a dichroic mirror 101 for separating a luminous flux into luminous fluxes having B, G and R component wavelength areas respectively, a dichromic polarized beam splitter 201 for transmitting the luminous flux having the B component wavelength area and the luminous flux having the G component wavelength area, and reflection type liquid crystal display elements 301 and 303 for separately modulating and reflecting the transmitted luminous fluxes, and the dichroic polarized beam splitter 201 is constituted so as to transmit the luminous flux from the element 301, but, to reflect the luminous flux from the element 303, and then, to synthesize respective luminous fluxes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection display device using a reflection type liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, in a so-called projection display device, for example, as described in Japanese Patent Application Laid-Open No. 2-74903, a color-separated illumination light is transmitted from a polarizing beam splitter, a liquid crystal display element and a cross dichroic prism. An optical system configured to be synthesized by a color synthesis system is used. Further, as described in Japanese Patent Application Laid-Open No. 8-122772 as a conventional technique, an optical system having a configuration of three reflective liquid crystal display elements, a polarizing beam splitter and two dichroic mirrors is used. Alternatively, as described in Japanese Patent Application Laid-Open No. 8-122772, an optical system including three reflective liquid crystal display elements and one polarizing beam splitter is disclosed.

[0003]

However, the cost of an optical system using the above-mentioned cross dichroic prism increases because the cross dichroic prism is expensive. In the optical system having the three reflective liquid crystal display elements, the polarizing beam splitter, and the two dichroic mirrors, at least two dichroic mirrors are required between the polarizing beam splitter and the reflective liquid crystal display element. Therefore, the lens back between the projection lens and the reflection type liquid crystal display element becomes long, and the F number of the projection lens becomes large, resulting in darkness.

In an optical system having a structure as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 8-122772, unpolarized light is made incident on a polarizing beam splitter. Flares come out. Further, since the P-polarized light of the green component and the S-polarized light of the red and blue components are discarded without being used for image formation, the efficiency of the light source is poor. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a compact and efficient projection display device capable of obtaining a high-contrast and beautiful image with a simple configuration at a low cost.

[0005]

In order to achieve the above object, according to the present invention, a first dichroic reflecting surface for separating a light beam into light beams of first and second wavelength ranges, and first and second dichroic reflecting surfaces thereof are provided. A dichroic polarization beam splitter that allows each of the light beams in the wavelength range to enter from different directions and transmits the light beams, and first and second reflective liquid crystal display elements that respectively modulate and reflect any of the transmitted light beams. A configuration in which the dichroic polarizing beam splitter transmits a light beam from the first reflective liquid crystal display device, reflects a light beam from the second reflective liquid crystal display device, and combines the respective light beams. I do.

Alternatively, a first dichroic reflecting surface for separating a light beam into light beams of first and second wavelength ranges,
And a dichroic polarization beam splitter that causes each of the light beams in the second wavelength range to enter and reflect from different directions, and a first and a second reflective liquid crystal display that modulates and reflects one of the reflected light beams, respectively. The dichroic polarization beam splitter reflects a light beam from the first reflective liquid crystal display device, transmits a light beam from the second reflective liquid crystal display device, and separates each light beam. It is configured to be synthesized.

[0007] The dichroic polarizing beam splitter functions to separate a light beam having a predetermined polarization plane into a light beam that is transmitted and a light beam that is reflected according to a wavelength range.

In addition, the light flux in the first wavelength range separated by the first dichroic reflection surface is transmitted or reflected and made incident on the dichroic polarization beam splitter, and the combined light from the dichroic polarization beam splitter is transmitted therefrom. A configuration is provided with a polarizing beam splitter that transmits or reflects and transmits. However, this polarization beam splitter has the same meaning as the following second polarization beam splitter.

Further, a third light beam in the second wavelength band separated by the first dichroic reflecting surface is further converted into a third light beam.
A second dichroic reflecting surface for separating the light beam in the third wavelength band, and a first dichroic reflecting surface for reflecting the separated light beam in the third wavelength region.
, And a third reflective liquid crystal display element that modulates and reflects the reflected light beam, wherein the light beam from the third reflective liquid crystal display device is the first polarized beam splitter. And a second polarizing beam splitter that combines the transmitted light beam and the light beam combined by the dichroic polarizing beam splitter.

In addition, a polarizing plate for adjusting the polarization planes of the light beams in the first and second wavelength ranges is provided in front of the dichroic polarizing beam splitter. Also,
The light beam is a polarized light beam. Then, a light source and a polarization converter for aligning the polarization direction of the light beam from the light source to a predetermined polarization plane are provided, and the light beam from the polarization converter is incident on the first dichroic reflection surface.

Further, the light beam in the third wavelength range is equal to the second light beam.
And a wavelength plate for rotating the polarization plane of the light beam in the third wavelength range immediately before the light beam enters the polarization beam splitter.

The light beam in the third wavelength range is red,
It is assumed that the light beam is a light beam in the red wavelength range among the light beams of the three primary colors of green and blue. Then, the light flux in the second wavelength range, from which the light flux in the third wavelength range is separated, is a light flux in the green wavelength range of the three primary colors of red, green, and blue. Further, the light flux in the first wavelength range is a light flux in the blue wavelength range among the light fluxes of the three primary colors of red, green and blue.

Further, a band-pass filter corresponding to the wavelength range of a light beam incident on each of the first to third reflective liquid crystal display elements is provided on the front surface of each of the first to third reflective liquid crystal display elements.
Further, a configuration is provided that includes a projection optical system that projects a light beam from the first to third reflective liquid crystal display elements that are combined.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing a first embodiment of the present invention. In the figure,
1 is a white light source, 2 is disposed so as to surround the white light source 1, and a reflector that reflects light from the white light source 1 is provided, 3 is disposed beside the white light source 1 and keeps the light from the white light source 1 constant. Is a polarization converter that converts the light into polarized light. In the present embodiment, an example is shown in which a mirror, a prism, and the like, which will be described later, are used after being converted into P-polarized light.

The polarization converter 3 includes a polarization beam splitter 4 that reflects an S-polarized component indicated by a dashed arrow S and transmits it while transmitting a P-polarized component indicated by a solid arrow P.
A half-wave plate 5 that rotates the polarization plane of the transmitted S-polarized component to P-polarized light. The above is the illumination optical system. Although not shown, an integrator optical system is generally added in order to eliminate unevenness in illumination by the illumination optical system.

Further, 101 and 102 are dichroic mirrors, 201 and 203 are dichroic polarization beam splitters, 202 is a polarization beam splitter, and are indicated by oblique lines.
01 to 303 are reflection type liquid crystal display elements, 401 is a reflection mirror, 501 to 503 and 507 shown by stripe patterns are polarizing plates, 601 to 603 are shown by dot patterns, band pass filters, plain 701 is a half-wave plate, Reference numeral 6 denotes a relay optical system for correcting an optical path length.

As shown in FIG. 1, the illumination light (white light flux) in which the direct light from the white light source 1 and the reflected light from the reflector 2 are mixed is transmitted through the polarization converter 3 while the P-polarized light component is transmitted and the S-polarized light component is transmitted. After being converted into P-polarized light, the light reaches the dichroic mirror 101. Here, only the blue (B) component of the P-polarized white light beam is transmitted, and the other green (G) and red (R) components are reflected.

B transmitted through the dichroic mirror 101
The component is reflected by the reflection mirror 401, passes through the relay optical system 6, is further reflected by the two reflection mirrors 401, and has its polarization direction adjusted by the polarizing plate 503 before reaching the dichroic polarization beam splitter 203. Here, the B component, which is P-polarized light, is transmitted, further transmitted through the dichroic polarization beam splitter 201, and the wavelength range is adjusted by the band-pass filter 601 to illuminate each pixel on the reflective liquid crystal display element 301.

In the reflection type liquid crystal display element 301, the pixels used for screen display are turned on at each time point, and the P-polarized light of the B component light beam incident thereon is converted into S-polarized light and reflected, and the unused pixels are reflected. When turned off, the light is reflected with P polarization. The B component reflected by the reflection type liquid crystal display element 301 is again transmitted to the dichroic polarization beam splitter 201.
Reach Here, the B component, which is S-polarized light, is transmitted, and subsequently reflected by the dichroic polarization beam splitter 203.

On the other hand, the G and R components reflected by the dichroic mirror 101 are combined with the dichroic mirror 102
Reach Here, the R component that is P-polarized light is transmitted, and the G component that is also P-polarized light is reflected, and both are separated.
The R component, which is P-polarized light, has its polarization plane rotated by a half-wave plate 701 to become S-polarized light, the polarization direction of which is adjusted by a polarizing plate 502, and the polarization beam splitter 20.
After being reflected at 2 and having its wavelength range adjusted by the bandpass filter 602, each pixel on the reflective liquid crystal display element 302 is illuminated.

Here, at each time point, the pixels used for screen display are turned ON, the S-polarized light of the R component light beam incident thereon is converted into P-polarized light and reflected, and the unused pixels are turned OFF and the S-polarized light is turned off. Reflect as it is. The R component reflected by the reflection type liquid crystal display element 302 reaches the polarization beam splitter 202 again. Here, only the P component of the R component is transmitted, and the plane of polarization is rotated by the half-wave plate 701 to become S polarized light, and transmitted through the dichroic polarization beam splitter 203.

The G component, which is P-polarized light, separated by the dichroic mirror 102 reaches the dichroic polarization beam splitter 201 after the polarization direction is adjusted by the polarizing plate 501. Here, the G component, which is P-polarized light, is transmitted, the wavelength range is adjusted by the bandpass filter 603, and then each pixel on the reflective liquid crystal display element 303 is illuminated.

In the reflection type liquid crystal display element 303, the pixels used for screen display are turned ON at each time point, and the P-polarized light of the G component light beam incident thereon is converted into S-polarized light and reflected, and the unused pixels are reflected. When turned off, the light is reflected with P polarization. The G component reflected by the reflection type liquid crystal display element 303 is again transmitted to the dichroic polarization beam splitter 201.
Reach Here, the G component, which is S-polarized light, is reflected, and further reflected by the dichroic polarization beam splitter 203.

Finally, R, G,
The B component is synthesized by the dichroic polarizing beam splitter 203, and after the three primary colors are synthesized, the polarizing plate 5
07, the polarization direction is adjusted and guided to a projection optical system (not shown).

FIG. 2 is a diagram schematically showing a second embodiment of the present invention. In the figure, 1 is a white light source, 2 is disposed so as to surround the white light source 1, and a reflector that reflects light from the white light source 1 is disposed 3 beside the white light source 1; This is a polarization converter that converts the light into a certain polarization light. In the present embodiment,
An example in which the light is converted into S-polarized light and used is shown.

The polarization converter 3 reflects the S-polarized light component indicated by the dashed arrow S while allowing it to pass through, and transmits the P-polarized light component indicated by the solid-line arrow P;
A half-wave plate 5 which rotates the plane of polarization of the transmitted P-polarized component to S-polarized light. The above is the illumination optical system. Although not shown, an integrator optical system is generally added in order to eliminate unevenness in illumination by the illumination optical system.

Also, 101 and 102 are dichroic mirrors, 204 is a dichroic polarization beam splitter,
Reference numerals 202 and 205 denote polarization beam splitters, indicated by hatching.
01 to 303 are reflection type liquid crystal display elements, 401 is a reflection mirror, 502 and 504 to 506 indicated by stripe patterns are polarizing plates, 601 to 603 are indicated by dot patterns, band pass filters, 701 is a half-wave plate, Reference numeral 6 denotes a relay optical system for correcting an optical path length.

As shown in FIG. 2, the illumination light (white light flux) in which the direct light from the white light source 1 and the reflected light from the reflector 2 are mixed passes through the polarization converter 3 while passing the S-polarized light component and the P-polarized light component. After being converted into S-polarized light, the light reaches the dichroic mirror 101. Here, only the blue (B) component of the S-polarized white light flux is transmitted, and the other green (G) and red (R) components are reflected.

B transmitted through the dichroic mirror 101
The component is reflected by the reflection mirror 401, passes through the relay optical system 6, and is further reflected by the reflection mirror 401.
After the polarization direction is adjusted by the polarizing plate 505, the light reaches the polarization beam splitter 205. Here, B which is S-polarized light
The component is reflected, further reflected by the dichroic polarizing beam splitter 204, and the wavelength range is adjusted by the band-pass filter 601.
1 illuminate each pixel.

In the reflection type liquid crystal display element 301, the pixels used for screen display are turned ON at each time point, and the S-polarized light of the B-component light beam incident thereon is converted into P-polarized light and reflected. When turned off, the light is reflected with S-polarized light. The B component reflected by the reflection type liquid crystal display element 301 is again transmitted to the dichroic polarization beam splitter 204.
Reach Here, the B component, which is P-polarized light, is reflected, and subsequently passes through the polarizing beam splitter 205.

On the other hand, the G and R components reflected by the dichroic mirror 101 are combined with the dichroic mirror 102
Reach Here, the R component that is S-polarized light is transmitted, and the G component that is also S-polarized light is reflected, and both are separated.
The R component, which is S-polarized light, has its polarization direction adjusted by a polarizing plate 502, is reflected by a polarization beam splitter 202, has its wavelength range adjusted by a bandpass filter 602, and has a reflection type liquid crystal display element 302. Illuminate each pixel above.

Here, at each time point, the pixels used for screen display are turned ON, the S-polarized light of the R component light beam incident thereon is converted into P-polarized light and reflected, and the unused pixels are turned OFF and the S-polarized light is turned off. Reflect as it is. The R component reflected by the reflection type liquid crystal display element 302 reaches the polarization beam splitter 202 again. Here, only the P component of the R component is transmitted, the polarization direction is adjusted by the polarizing plate 506, and the polarization plane is rotated by the half-wave plate 701 to become S polarized light, which is reflected by the polarization beam splitter 205.

The G component, which is S-polarized light, separated by the dichroic mirror 102 reaches the dichroic polarization beam splitter 204 after the polarization direction is adjusted by the polarizing plate 504. Here, the G component, which is S-polarized light, is reflected, the wavelength range is adjusted by the band-pass filter 603, and then the pixels on the reflective liquid crystal display element 303 are illuminated.

In the reflection type liquid crystal display element 303, the pixels used for the screen display are turned on at each point in time, and the S-polarized light of the G component light beam incident thereon is converted into P-polarized light and reflected. When turned off, the light is reflected with S-polarized light. The G component reflected by the reflection type liquid crystal display element 303 is again transmitted to the dichroic polarization beam splitter 204.
Reach Here, the G component that is P-polarized light is transmitted, and further transmitted through the polarization beam splitter 205.

Finally, the G and B components which are P-polarized light and S
The R component, which is polarized light, is synthesized by the polarization beam splitter 205, and after the three primary colors are synthesized, is guided to a projection optical system (not shown). In each of the first and second embodiments, the lens back from the projection optical system to the reflective liquid crystal display element for each color component is configured to be the same.

FIG. 3 is a diagram showing the transmittance characteristics of the polarization beam splitter of the present invention in the wavelength range of each color component, and (a) to (e) show the characteristics of the polarization beam splitters 201 to 205, respectively. I have. In the figure,
The broken line represents P-polarized light, and the solid line represents S-polarized light. FIG.
As shown in the figure, the dichroic polarizing beam splitter 2
01 indicates that almost 100% of light in the wavelength range of the B component and G component is transmitted for P-polarized light, almost 100% of light in the wavelength range of the B component is transmitted for S-polarized light, and It has a characteristic of reflecting almost 100%.

As shown in FIG. 2B, the polarization beam splitter 202 transmits almost 100% of the light in the wavelength range of the G component and the R component for the P-polarized light, and transmits the G component and the R component for the S-polarized light. It has the property of reflecting almost 100% of light in the wavelength range of the component.

As shown in FIG. 3C, the dichroic polarization beam splitter 203 converts the light in the wavelength ranges of the B, G, and R components for P-polarized light to almost 100%.
It has the property of transmitting S-polarized light, transmitting almost 100% of light in the wavelength range of the R component, and reflecting almost 100% of light in the wavelength range of G and B components.

As shown in FIG. 3D, the dichroic polarization beam splitter 204 transmits almost 100% of the light in the wavelength range of the G component for P-polarized light, and almost 100% of the light in the wavelength range of the B component. %, And the S-polarized light has a characteristic of reflecting almost 100% of light in the wavelength range of the B component and the G component.

As shown in FIG. 3E, the polarization beam splitter 205 transmits almost 100% of the B component, G component, and R component wavelengths for P-polarized light, and transmits B light for S-polarized light. It has a characteristic of reflecting almost 100% of light in the wavelength range of the component, the G component, and the R component.

Each of the above-mentioned polarizing beam splitters uses a prism type polarizer called a MacNile type polarizer. The characteristics of each of the above polarizing beam splitters can be obtained by alternately stacking two types of layers having different refractive indexes.

FIGS. 4 and 5 show the transmittance characteristics (film characteristics).
It is a graph which shows the specific example of. First, FIG. 4 shows characteristics corresponding to the dichroic polarization beam splitter 201. In FIG. 4, a broken line represents P-polarized light, and a solid line represents S-polarized light. This is because, as shown in Table 1 below, 1 is sandwiched between glass prisms (0th and 18th layers).
Seven coating films are provided with respective refractive indexes and optical thicknesses nd / λ ₀ . Note that the reference wavelength λ ₀ is
865.8356 nm.

<Table 1> [Layer] [Refractive index] [Optical film thickness (nd / λ ₀ )] 18 1.62 17 1.62 0.125 16 2.05 0.214 15 1.385 0. 393 14 2.05 0.178 13 1.385 0.307 12 2.05 0.255 11 1.385 0.262 10 2.05 0.183 9 1.385 0.391 8 2.05 0.183 7 1.385 0.262 6 2.05 0.255 5 1.385 0.307 4 2.05 0.179 3 1.385 0.393 2 2.05 0.214 1 1.62 0.125 0 1.62

Next, FIG. 5 shows a characteristic corresponding to the dichroic polarization beam splitter 203. In FIG. 5, a broken line indicates P-polarized light, and a solid line indicates S-polarized light. As shown in Table 2 below, 17 coating films sandwiched between glass prisms (0th and 18th layers) were provided with respective refractive indexes and optical thicknesses nd / λ _0. It is. Note that the reference wavelength λ ₀ is 650.959.
5 nm.

<Table 2> [Layer] [Refractive index] [Optical film thickness (nd / λ ₀ )] 18 1.62 17 1.62 0.125 16 2.05 0.249 15 1.385 0. 270 14 2.05 0.133 13 1.385 0.314 12 2.05 0.240 11 1.385 0.345 10 2.05 0.199 9 1.385 0.236 8 2.05 0.199 7 1.385 0.345 6 2.05 0.240 5 1.385 0.314 4 2.05 0.133 3 1.385 0.270 2 2.05 0.249 1 1.62 0.1250 1.62

[0046]

As described above, according to the present invention,
With a simple configuration, a high-contrast and beautiful image can be obtained, and a compact and efficient projection display device can be provided at low cost.

In particular, according to the first or second aspect, it is not necessary to use an expensive optical component such as a cross dichroic prism, so that the cost can be reduced and the so-called lens back can be shortened. The projection optical system can be made bright.

According to the third aspect, it is possible to realize a low-cost and simple configuration in separation and synthesis of each wavelength range.

According to the fourth aspect, it is possible to realize a low-cost and simple configuration in separation and synthesis of three wavelength ranges.

According to the fifth or sixth aspect, it is possible to prevent both the S and P polarized lights from entering the dichroic polarization beam splitter, and furthermore, to adjust the polarization direction to suppress the influence of flare.

Further, according to the seventh aspect, the effect of flare can be similarly suppressed, and the efficiency of the light source can be increased.

Further, according to the eighth aspect, the polarization planes of the light beams serving as the projection light can be aligned and adjusted collectively.

According to the ninth to eleventh aspects, an optical path configuration according to the luminosity factor in the wavelength range is provided.
A configuration having as high an image performance as possible can be obtained.

Further, according to the twelfth aspect, it is possible to prevent light beams in unnecessary wavelength ranges from entering each reflection type liquid crystal display element, thereby improving image performance.

According to the thirteenth aspect, the basic configuration of the projection display device can be established.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a second embodiment of the present invention.

FIG. 3 is a diagram illustrating transmittance characteristics of a polarizing beam splitter.

FIG. 4 is a graph showing a specific example of transmittance characteristics (film characteristics).

FIG. 5 is a graph showing a specific example of transmittance characteristics (film characteristics).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 White light source 2 Reflector 3 Polarization converter 4 Polarization beam splitter 5 1/2 wavelength plate 101,102 Dichroic mirror 201,203,204 Dichroic polarization beam splitter 202,205 Polarization beam splitter 301-303 Reflection type liquid crystal display element 401 Reflection mirror 501-507 Polarizing plate 601-603 Bandpass filter 701 1/2 wavelength plate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03B 21/00 G03B 21/00 D

Claims (13)

[Claims] A first dichroic reflecting surface for separating a light beam into light beams in first and second wavelength ranges;
A dichroic polarization beam splitter that allows each of the light beams in the wavelength range to enter and transmit from different directions, and first and second reflective liquid crystal display elements that respectively modulate and reflect any of the transmitted light beams. The dichroic polarizing beam splitter transmits the light beam from the first reflective liquid crystal display element, reflects the light beam from the second reflective liquid crystal display element, and combines the respective light beams. A projection display device. 2. A first dichroic reflecting surface for separating a light beam into light beams in first and second wavelength ranges, and said first and second dichroic reflecting surfaces.
A dichroic polarization beam splitter that makes each of the light beams in the wavelength range incident from different directions and reflects them, and first and second reflective liquid crystal display elements that respectively modulate and reflect any one of the reflected light beams. The dichroic polarization beam splitter reflects the light beam from the first reflective liquid crystal display device, transmits the light beam from the second reflective liquid crystal display device, and combines the respective light beams. A projection display device characterized by the above-mentioned. 3. The light beam of the first wavelength range separated by the first dichroic reflection surface is transmitted or reflected and is incident on the dichroic polarization beam splitter, and the combined light from the dichroic polarization beam splitter is 3. A polarizing beam splitter for transmitting or reflecting and passing therethrough.
3. The projection display device according to 1. 4. A second dichroic reflecting surface that further separates a light beam in a third wavelength band from the light beam in the second wavelength band separated by the first dichroic reflecting surface, and the separated third dichroic reflecting surface. A first polarizing beam splitter that reflects a light beam in a wavelength range of: and a third reflective liquid crystal display element that modulates and reflects the reflected light beam. 2. The light beam of claim 1, further comprising a second polarizing beam splitter for transmitting the transmitted light beam and a light beam synthesized by the dichroic polarizing beam splitter. Or the projection display device according to claim 2. 5. The apparatus according to claim 1, wherein a polarizing plate for adjusting a polarization plane of each of the light beams in the first and second wavelength ranges is provided in front of the dichroic polarizing beam splitter.
The projection display device according to claim 4. 6. The projection display device according to claim 1, wherein the light beam is a polarized light beam. 7. A light source comprising: a light source; and a polarization converter for aligning a polarization direction of a light beam from the light source to a predetermined polarization plane, wherein the light beam from the polarization converter is incident on the first dichroic reflection surface. The projection display device according to any one of claims 1 to 6, wherein 8. A wave plate for rotating the polarization plane of the light beam in the third wavelength range immediately before the light beam in the third wavelength region enters the second polarization beam splitter. The projection display device according to claim 4. 9. The light beam of the third wavelength band is a light beam of a red wavelength region among light beams of three primary colors of red, green, and blue. 3. The projection display device according to 1. 10. The light beam in the second wavelength region, from which the light beam in the third wavelength region is separated, is a light beam in the green wavelength region among the light beams of the three primary colors red, green, and blue. The projection display device according to any one of claims 3 to 8, wherein: 11. The luminous flux in the first wavelength range is red, green,
9. The projection display device according to claim 3, wherein the light beam is a light beam in a blue wavelength range among light beams of three primary colors of blue. 12. A band-pass filter corresponding to a wavelength range of a light beam incident on each of the first to third reflection-type liquid crystal display elements is provided on a front surface of each of the first to third reflection-type liquid crystal display elements. Item 12. The projection display device according to any one of Items 11. 13. The projection optical system according to claim 3, further comprising a projection optical system configured to project a light beam from the first to third reflection-type liquid crystal display elements combined. Projection display device.