JPH10319344A - Projection display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the light transmissivity characteristic of a dichroic mirror surface suitable for color separation and color synthesis by using a prism where a specified incident angle is set as a color separation and synthesis means and making light P polarized light by a color separation optical system. SOLUTION: The color separation and synthesis means is provided with the prism having the 1st dichroic mirror surface 42 where the incident angle θ1 of the optical axis of a projection lens to the normal line of a mirror surface is 20 deg. to 30 deg. and the 2nd dichroic mirror surface 43 where the incident angle θ2 is 30 deg. to 35 deg., and either polarized light is the P poarized light with respect to the 1st and the 2nd dichroic mirror surfaces 42 and 43. Thus, the light transmissivity characteristic of the dichroic mirror surface suitable for the color separation and the color synthesis is obtained. By using a V-shaped prism 41 for the color separation and synthesis means 32, the reference incident angles θ1 and θ2 are set to be smaller than 45 deg., and the excellent spectral characteristic is obtained. When the incident angle θ1 is smaller than 20 deg., a prism constituting body 38 gets long along the path of the light, so that the device can not be miniaturized.

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 which irradiates an image formed on a light valve with illumination light and enlarges and projects the image on a screen by a projection lens.

[0002]

2. Description of the Related Art Projection display devices using display devices such as liquid crystal displays are widely known. Since such a projection display device can realize a large-screen image without increasing the size of the liquid crystal display itself,
In principle, it is possible to enlarge the display image without limit.

In a conventional projection display device, an optical image is formed by irradiating a small light valve formed of a liquid crystal display with illumination light. The formed optical image is enlarged by the operation of the projection lens and projected on a screen. In forming an optical image, the light valve modulates and outputs illumination light in accordance with a received video signal. For example, an active matrix light valve is widely used as such a light valve.

[0004] For example, SID95 digest PP235
238 discloses a projection display device using a reflection type light valve. According to the reflection-type light valve, even if the resolution is increased with the same light valve size, the aperture ratio of the light valve does not decrease, so that a small-sized projection display device with high brightness and high resolution can be realized. .

As a reflection type light valve, a polymer dispersed liquid crystal which forms an optical image based on a change in light scattering characteristics,
Examples include a homeotropic mode liquid crystal and a hybrid aligned nematic (hereinafter abbreviated as “HAN”) mode liquid crystal that form an optical image based on a change in birefringence. When using a liquid crystal that forms an optical image based on the change in birefringence, the use of polarized light reduces the light use efficiency in principle compared to a polymer dispersed liquid crystal, but is superior to a polymer dispersed liquid crystal. High contrast performance is obtained.

FIG. 10 shows an example of a conventional projection type color display device using a liquid crystal for forming an optical image based on a change in birefringence as a reflection type light valve. Light from a lamp 1 as a light source is condensed by a concave mirror 2 and then converted into a substantially parallel light beam by a condenser lens 3. The substantially parallel light is split by the polarizing beam splitter 4 into P-polarized light and S-polarized light whose polarization planes are orthogonal to each other. The separated P-polarized light passes through the polarization beam splitter 4 and is supplied to the color separation / synthesis optical system 7.

In the color separation / combination optical system 7, the P-polarized light is separated into red, green, and blue color lights by the operation of the two dichroic mirrors 5, 6. The separated color lights are reflected by active matrix type reflection type liquid crystal light valves 8, 9, 10.
Incident on. The reflective liquid crystal light valves 8, 9, 10
P-polarized light is modulated into S-polarized light by birefringence according to an applied voltage based on a video signal, and output. Each color light converted into the S-polarized light is synthesized by the color separation / synthesis optical system 7 to generate an original image. The generated original image is reflected by the polarizing beam splitter 4 and then projected on a screen (not shown) through the projection lens 11. As a result, a small projection display device with high brightness and high resolution is realized.

In constructing the color separation / synthesis optical system, in addition to a plate-type dichroic mirror shown in FIG. 10, an X-shaped dichroic prism in which four prisms are bonded (see Japanese Patent Publication No. 6-72987), ,
A compound prism having two dichroic mirror surfaces and a total reflection surface (see JP-A-63-31892).
May be used.

As shown in FIG. 11, an X-shaped dichroic prism 12 includes a red reflecting dichroic mirror surface 13 and a blue reflecting dichroic mirror surface 14 having a reference incident angle of 45 °. The green light transmitted through the two dichroic mirror surfaces 13 and 14 goes straight and is irradiated on the green light valve 9.

As shown in FIG. 12, the compound prism has a red reflecting dichroic mirror surface 15 having a reference incident angle of 13 °.
And a blue reflection dichroic mirror surface 16 having a reference incident angle of 22.5 °. The first total reflection surface 17 is formed by the air layer 19, and the red light reflected by the red reflection dichroic mirror surface 15 is guided to the red light valve 8 by the first total reflection surface 17. The blue light reflected by the blue reflection dichroic mirror surface 16 is reflected by the total reflection surface 18.
Is led to the light valve 10 for blue.

[0011]

For example, when a plate type dichroic mirror is used in a color separation / combination optical system,
A problem of convergence shift, which means a shift in the superposition of the red, green, and blue projected images, occurs. The convergence shift occurs because an astigmatic difference is generated due to the rotation of the dichroic mirror not being rotationally symmetric with respect to the optical axis of the projection lens. If the thickness of the dichroic mirror is reduced, the astigmatism difference can be reduced, but the flatness is reduced and the surface of the dichroic mirror is distorted. As a result, it is not possible to avoid the problem of the focus shift and the convergence shift of the projected image.

Therefore, if a prism is used as the color separation / synthesis optical system, the flatness of the dichroic mirror surface can be maintained with high accuracy, and no astigmatic difference occurs. Therefore, it is possible to obtain a high-resolution projection image without a focus shift or a convergence shift.

For example, consider the case where an X-shaped dichroic prism is used in a color separation / combination optical system. FIGS. 13A and 13B show transmittance characteristics of a red reflecting dichroic mirror surface and a blue reflecting dichroic mirror surface of an X-shaped dichroic prism, respectively. When observing FIGS. 13A and 13B, the transmittance at the reflection wavelength in P-polarized light is as high as about 10%, the transmittance at the transmission wavelength in S-polarized light is less than 100%, and the transmittance curve of the band is obtained. It can be seen that the slope width (wavelength bandwidth of the transmittance curve inclined in the range of 10% to 90% transmittance) is large. Therefore, if the transmittance at the transmission wavelength is increased or the transmittance at the reflection wavelength approaches zero, the light use efficiency can be further increased.

If the wavelength width of each color light can be sharply extracted by narrowing the inclination width, the color reproducibility can be further improved. 14 and FIG.
Fig. 3 shows a state in which the transmittance characteristics of the red reflecting dichroic mirror surface and the blue reflecting dichroic mirror surface change due to the shift of the incident angle. It can be seen that a shift in the incident angle with respect to the 45 ° reference incident angle results in a large shift in the transmittance curve. In particular, in the case of P-polarized light, the transmittance in the reflection wavelength band changes or the bandwidth of the reflection wavelength band changes. If such a shift can be avoided as much as possible, it is possible to improve the color unevenness of the projected image.

By the way, in the X-shaped dichroic prism, the incident angle of the spectrum with respect to the dichroic mirror surface is fixed at 45 ° in the process of color separation and the process of color synthesis. Therefore, as shown in FIG. 13, the cut-off wavelength band of P-polarized light (wavelength band of 50% transmittance).
And a large deviation between the S-polarized light and the cut-off wavelength band of S-polarized light, the spectral characteristics are different between the color separation process and the color synthesis process, resulting in a reduction in light use efficiency.

Therefore, it is conceivable to make the incident angle of P-polarized light different from the incident angle of S-polarized light by using different prisms in the process of color separation and the process of color synthesis.
However, if different optical systems are used in the process of color separation and the process of color synthesis as described above, the size and cost of the projection display device will increase.

Therefore, if the above-described composite prism is used in the color separation / synthesis optical system, the reference incident angle can be made smaller than 45 °, and the deterioration of the spectral characteristics which is a problem in the X-shaped dichroic prism does not occur. However, in this composite prism, when the air layer 19 is thick, the astigmatism that occurs degrades the resolution of the projected image. If the layer thickness of the air layer 19 is not uniform, the light entrance surface of the prism and the light exit The decrease in the parallelism of the surface causes the resolution of the projected image to deteriorate. In order to make the air layer 19 sufficiently thin or to establish the parallelism of the prism interface on both sides of the air layer 19 with high accuracy, it is necessary to improve the assembly accuracy of the prism, resulting in a significant increase in cost. Becomes

Furthermore, in the conventional projection display device,
When unnecessary light is incident on the light valve, there has been a problem that the contrast of the light valve is lowered and the modulation characteristic is deteriorated due to an increase in temperature. Therefore, it is necessary to reduce unnecessary light incidence on the light valve.

In view of the above-mentioned problems, the present invention provides a small-sized, low-cost projection display device that uses a reflection-type light valve to enhance light use efficiency, has good color reproducibility of a projected image, and has no color unevenness. The purpose is to provide.

[0020]

Means for Solving the Problems In order to solve the above problems, the present invention has taken the following means. That is, claim 1
The invention described in (1) is an illumination unit that outputs illumination light, a first polarization separation unit that separates two polarized light beams whose polarization directions are orthogonal to each other, and separates one polarized light beam from the polarized light separation unit into each color light beam. And a color separation / combination means for combining each color light, a reflective light valve for forming an optical image corresponding to a video signal using each color-separated color light, and a projection lens for enlarging and projecting the optical image. The color separation / combination means includes a first dichroic mirror surface having an incident angle θ1 formed by the optical axis of the projection lens with respect to a normal line of the mirror surface of 20 ° to 30 °, and an incident angle θ2 of 30 °. A prism having at least a second dichroic mirror surface of 35 ° is provided, and the one polarized light is P-polarized with respect to the first and second dichroic mirror surfaces.

According to this configuration, light transmittance characteristics of the dichroic mirror surface suitable for color separation and color synthesis can be obtained as compared with the conventional X-shaped dichroic prism. As a result, it is possible to realize a small-sized and low-cost projection display device having high light use efficiency, good color reproducibility of a projected image and no color unevenness.

According to a second aspect of the present invention, in the first aspect, the illuminating means comprises a light source, a concave mirror for condensing light emitted from the light source, and a plurality of lenses. And a second lens array plate which is composed of a plurality of lenses and into which light from the lenses of the first lens array plate converges and enters. According to this configuration, light is superimposed on the reflective light valve, and is uniformly illuminated on the reflective light valve.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the light from the illuminating means is polarized orthogonally between the illuminating means and the first polarization splitting means. Second polarized light separating means for separating the two polarized lights into
A configuration is adopted in which polarization rotating means for rotating the polarization direction of one polarized light from the second polarization separating means is arranged. According to this configuration, by the action of the polarization rotating means,
Light use efficiency can be improved.

According to a fourth aspect of the present invention, in the first aspect, a convex lens is disposed between the color separation / synthesis optical unit and the reflective light valve. take. According to this configuration, it is possible to improve color reproducibility and color unevenness of the projected image.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the angle between the optical axis and the principal ray of the projection lens is 3 ° or less in terms of an air medium. The configuration is a telecentric projection lens.
According to this configuration, it is possible to further improve the color unevenness caused by the incident angle dependence of the dichroic mirror surface.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the color separation / synthesis means and the reflection type light valve are arranged in close contact with each other. According to this configuration, the convergence adjusting mechanism of the three reflective light valves is not required, and the projection display device can be further reduced in size, which leads to low misconvergence and low cost.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the first dichroic mirror is configured to reflect green light and transmit blue light and red light. take. According to this configuration, a V-shaped prism having good spectral characteristics can be realized.

According to an eighth aspect of the present invention, in the first aspect, the first dichroic mirror reflects blue light and the second dichroic mirror reflects green light. Take. According to this configuration, since the manufacturing tolerance of the dichroic film is loose, such a V-shaped prism can be easily obtained.

According to a ninth aspect of the present invention, in any one of the first to eighth aspects of the present invention, a color filter is arranged between the color separation / combination means and the reflection type light valve. take. According to this configuration, color unevenness and color reproducibility can be improved.

[0030]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a configuration of a projection display apparatus according to a first embodiment of the present invention. The projection display device 30 includes an illumination unit 31 that outputs illumination light, and a light valve group 32 that forms an optical image by modulating the illumination light in accordance with a video signal. Light valve group 3
2 is a reflective light valve for red light 33 that forms an optical image based on red light, a reflective light valve for green light that forms an optical image based on green light, and an optical image based on blue light. Reflection light valve 35 for blue light forming
It is composed of Each reflection type light valve 33, 34,
Reference numeral 35 includes an active matrix type liquid crystal layer using a homeotropic liquid crystal or a HAN mode liquid crystal, and a reflection film.

Each of the reflection type light valves 33, 34, 35 has red,
Green and blue light are emitted. Each reflective light valve 3
The red, green, and blue color lights emitted from 3, 34, and 35 are combined by a color separation / combination unit 36 to form an original image. The formed original image is enlarged and projected through the projection lens 37.

The color separating / synthesizing means 36 has the same refractive index 3
It has a V-shaped prism 41 constituted by two prism components 38, 39, 40. A first dichroic mirror surface 42 having a reference incident angle θ1 for reflecting green light is formed of a dielectric multilayer film on a joint surface between the two prism members 38 and 39. Two prism structures 39, 4
A second dichroic mirror surface 43 having a reference angle of incidence θ2 for reflecting blue light is formed of a dielectric multilayer film on the bonding surface of zero. In this V-shaped prism 41, 2
The two dichroic mirror surfaces 42 and 43 intersect in a V-shape. The reference angle of incidence refers to the angle of the optical axis of the projection lens 37 with respect to the normal to the mirror surface.

The color separation / combination means 36 includes the polarization separation means 4
At 5, P-polarized light is provided which is separated from the illumination light. The polarization separation means 45 is constituted by a prism type polarization beam splitter 47 having a polarization separation film 46. The polarization separation film 46 is formed of a dielectric multilayer film, and the incident angle is 4
It is set to 5 °. Therefore, the P-polarized light entering at an incident angle of 45 ° passes through the polarization separation film 46, and
The S-polarized light entering at an incident angle of 45 ° is reflected from the polarization separation film 46 at an emission angle of 45 °.

The illumination means 31 includes a light source 50 and the light source 5.
Elliptical mirror 51 as a concave mirror for condensing emitted light from zero
And The convergent light reflected from the ellipsoidal mirror 51 is U
It passes through a VIR cut filter 52. Infrared rays and ultraviolet rays are removed by the UVIR cut filter 52. U
The convergent light that has passed through the VIR cut filter 52 enters a first lens array plate 53 composed of a plurality of lenses. The first lens array plate 53 divides the incident convergent light into a large number of light beams by the function of each lens.
As the light source 50, for example, a metal halide lamp or a xenon lamp is used.

The illuminating means 31 is provided with a second lens array plate 54 composed of a plurality of lenses. Second
A light beam from the corresponding lens of the first lens array plate 53 converges and enters each lens of the lens array plate 54. The focal length of each lens of the first lens array plate 53 is set substantially equal to the distance from the total reflection mirror 55 to the corresponding lens of the second lens array plate 54. By the function of the second lens array plate 54, the opening surfaces of the lenses of the first lens array plate 53 and the reflection type light valves 33, 34, 35
Is almost conjugate with the surface of. Many light beams emitted from the second lens array plate 54 are reflected by the reflection type light valves 33, 3
4 and 35 are superimposed on the reflective light valves 33 and 3
It is evenly illuminated on 4,35.

Next, the projection type display device 3 according to the first embodiment.
The operation of 0 will be described. When the power of the projection display device 30 is turned on, a large number of parallel light beams emitted from the illumination means 31 enter the polarization separation means 45. In the polarization separation means 45, the P-polarized light of each light beam is transmitted and travels straight, and the S-polarized light of each light beam is reflected. The P-polarized light that has traveled straight enters the color separation / combination unit 32.

The P-polarized light that has entered the color separation / combination means 32 enters the first dichroic mirror surface 42. The first dichroic mirror surface 42 reflects green light from P-polarized light having an incident angle θ1. The reflected green light is reflected by the total reflection surface 44 and guided to the green light reflective light valve 34. The P-polarized light from which the green light has been separated subsequently enters the second dichroic mirror surface 43. The second dichroic mirror surface 43 reflects blue light from the P-polarized light at the incident angle θ2 and guides the blue light to the blue light reflective light valve 35. P transmitted through the first and second dichroic mirror surfaces 42 and 43
The polarized light reaches the reflective light valve 33 for red light.

Each of the reflection type light valves 33, 34, 35,
Is applied with a voltage according to the RGB video signal. This applied voltage changes the birefringence of the liquid crystal. Each color light incident on the reflection type light valves 33, 34, 35 passes through the liquid crystal, is reflected by the reflection film, and transmits the liquid crystal again. In the process of transmitting the liquid crystal, P-polarized light is converted into S-polarized light by the action of birefringence. An optical image is formed by the S-polarized light. The S-polarized light of each color light from each of the reflection type light valves 33, 34, 35 is synthesized by the V-shaped prism 41 to form an original image.

The S-polarized light emitted from the color separation / combination means 36 enters the polarization separation means 45. In the polarization separation means 45,
P-polarized light is transmitted and goes straight, and S-polarized light is reflected. The reflected S-polarized light enters the projection lens 37. Projection lens 3
Reference numeral 7 enlarges the original image formed by the S-polarized light and projects it on a screen (not shown). A full-color enlarged image is projected on the screen. On the other hand, the P-polarized light whose polarization state is maintained by the reflection type light valves 33, 34, and 35 passes through the polarization separation unit 45 and returns to the illumination unit 31 side.

As described above, since the V-shaped prism 41 is used for the color separation / combination means 32, the reference incident angles θ1, θ2
Can be set smaller than 45 °, and good spectral characteristics can be obtained. The reference incident angle θ1 may be 20 ° or more and 30 ° or less, and the reference incident angle θ2 may be 30 ° or more and 35 ° or less. If the reference angle of incidence θ1 is smaller than 20 °, the prism structure 38 becomes longer along the light path, so that the V-shaped prism 41 becomes larger and the size of the projection display device 30 cannot be reduced. If the reference angle of incidence θ1 exceeds 30 °, the spectral characteristics of the dichroic prism having the reference angle of incidence of 45 ° become close to the above, and the problem described in the related art occurs. If the two prism components 39 and 40 have the same shape, the productivity of the V-shaped prism 41 can be improved and the cost can be reduced. In this case, a relationship of θ1 = 90 ° −2θ2 is established between the reference incident angle θ1 and the reference incident angle θ2.

Assume that the reference incident angle θ1 is set to 26 ° and the reference incident angle θ2 is set to 32 °. FIG.
(A) and (b) respectively show the spectral transmittance characteristics of the green reflecting first dichroic mirror surface 42 and the blue reflecting second dichroic mirror surface 43 in this case. As is apparent from a comparison between FIG. 2 and FIG. 13, the difference between the cut-off wavelength band of the P-polarized light and the cut-off wavelength band of the S-polarized light is greatly improved. Therefore, the spectral characteristics are similar between the color separation process and the color synthesis process, and the light use efficiency does not decrease. In addition, since the transmittance of the reflection wavelength of the P-polarized light is reduced, the light use efficiency is improved.
Since the inclination width of the transmittance curve is narrow, the wavelength band of the color light can be extracted sharply, and as a result, a projected image with good color reproducibility can be displayed.

Further, the spectral characteristics of the green reflection shown in FIG. 2A are different from the spectral characteristics of the blue reflection and the red reflection at the same incident angle, in the cut-off wavelength band of the P-polarized light and the cut-off wavelength band of the S-polarized light. It has been clarified that the divergence from is small. Therefore, by making the first dichroic mirror surface 42 reflect green, the first dichroic mirror surface 4
2 can be made sufficiently small. In this case, since green light does not enter the second dichroic mirror surface 43, if the cutoff wavelength of the second dichroic mirror surface 43 is set to about 540 nm, which is an intermediate wavelength between the red wavelength band and the blue wavelength band, Even if the reference incident angle θ1 is larger than the reference incident angle θ2, it is possible to avoid an increase in the divergence width of the cutoff wavelength band between the S-polarized light and the P-polarized light and an increase in the influence of the incident angle dependence.

FIGS. 3A and 3B show the green reflection first.
The incident angle dependence of the dichroic mirror surface 42 on the P-polarized light and the S-polarized light is shown. In comparison with the characteristic at the reference incident angle θ1, the characteristic at the reference incident angle θ1 ± 5 ° (converted angle in the air medium) is shown. Similarly, FIGS. 4A and 4B similarly show the incident angle dependence of the P-polarized light and the S-polarized light of the blue reflecting second dichroic mirror surface 43. In each case, the incident angle dependency is reduced as compared with the spectral characteristics shown in FIGS. For this reason, it is possible to display a projection image with less color unevenness.

Here, the configuration of the projection optical system including the projection lens 37, the V-shaped prism 41, and the polarization beam splitter 47 will be described in further detail. FIG. 5 shows a principal ray and a ray bundle from points A and B on the reflection type light valve 33, which are transmitted through the V-shaped prism 41, reflected by the polarization beam splitter 47, and reach the projection lens 37. . The shift angle formed by the principal ray and the optical axis is α, and the emission angles formed by each principal ray and the second dichroic mirror surface 43 are φA and φB, respectively.

As is clear from FIG. 5, when the deviation angle α is not 0, the emission angle φA <θ1 is satisfied on the point A side of the reflection type light valve 33. On the other hand, on the point B side of the reflection type light valve 33, the emission angle φB> θ1 is established. Therefore, the angle of incidence on the first dichroic mirror surface 42 varies depending on the location, and this causes color unevenness in the projected image due to the dependency of the dichroic mirror surface on the angle of incidence. Therefore, as shown in FIG. 3 and FIG. 4, in the case where the incident angle dependence is still a little with respect to the dichroic mirror surface, the shift angle α is reduced, that is, the telecentricity of the projection lens is increased. Thereby, color unevenness of the projected image can be reduced. For example, shift angle α ≦ 3 ° (converted angle in air medium)
If the telecentricity is realized, it is possible to sufficiently reduce the color unevenness of the projected image.

As is apparent from FIG. 2, the reflection wavelength band of the P-polarized light is narrower than the reflection wavelength band of the S-polarized light. Therefore, if P-polarized light is used in the process of color separation, it is possible to sufficiently reduce the incidence of unnecessary light on the reflective light valves 33, 34, and 35, as compared with the case of using S-polarized light. As a result, it is possible to reduce the deterioration of the modulation characteristics of the light valve due to the incidence of unnecessary light, that is, it is possible to improve the quality of the projected image. In addition, if the shift angle α is not equal to zero as described above, the incident angle dependency of the S-polarized light has an influence. Since the band is narrowed, the influence of the wavelength shift in the S-polarized light is reduced, and as a result, the color unevenness of the projected image is suppressed.

Further, according to the V-shaped prism 41, since the compound prism shown in FIG. 12 does not have an air layer, the resolution does not deteriorate when an air layer exists. Therefore, the productivity of the prism can be improved and the cost can be reduced as compared with the composite prism which requires the assembly accuracy of the air layer.

In order to further improve the color unevenness and color reproducibility of the projected image, an interference film type or absorption type color filter is provided between the reflection type light valves 33, 34, 35 and the V-shaped prism 41, respectively. It may be arranged. Further, when joining the prism components 38 to 40 of the V-shaped prism 41 to each other, the reflection type light valves 33, 34, 35 are integrated by tightly joining to the end face of the V-shaped prism 41 after alignment. May be done. In such a case, the convergence adjusting mechanism of the three reflective light valves 33, 34, 35 becomes unnecessary, and the projection display device 30 can be further reduced in size, leading to low misconvergence and low cost.

FIG. 6 shows the configuration of a projection display device 60 according to a second embodiment of the present invention. In the second embodiment, V
-Shaped prism 41 and three reflective light valves 33, 3
Plano-convex lenses 61 to 63 whose plane sides face the light valve side are arranged between the light-emitting elements 4 and 35, respectively. Note that components having the same functions as in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof will be omitted.

According to the configuration of the second embodiment, the color light emitted from the color separation / combination means 36 is converted into the plano-convex lenses 61-61.
After passing through 63, the light enters the reflection type light valves 33, 34, 35, and the reflection type light valves 33, 34, 3
The reflected light from 5 enters the color separation / combination means again through the plano-convex lenses 61-63. Therefore, since the plano-convex lenses 61 to 63 converge each color light, the effective beam area of the V-shaped prism 41 and the polarizing beam splitter 47 can be reduced, and as a result, the V-shaped prism 41 and the polarizing beam splitter 47 can be downsized, and the back focus of the projection lens 37 can be shortened. Therefore, the size of the projection display device 60 is further reduced. The downsizing of the V-shaped prism 41, the polarizing beam splitter 47 and the projection lens 37 also reduces the manufacturing cost.

When convergent light is used in the color combining optical system 36, the telecentricity of the projection lens 37 is reduced, and the quality of color unevenness of the projected image is slightly reduced. In such a case, the plano-convex lenses 61 to 63 and the reflection type light valves 33 to
35, or between the plano-convex lenses 61 to 63 and the V-shaped prism 41, an interference film type or absorption type color filter may be arranged. By disposing the color filters, color unevenness and color reproducibility are improved.

FIG. 7 shows the configuration of a projection display device 70 according to a third embodiment of the present invention. In the third embodiment, in addition to the above-described polarization beam splitter 47, the polarization separation unit 45 includes a first polarization separation sub-unit 71 for separating P-polarized light and S-polarized light from illumination light, and a first polarization separation sub-unit 71. And a polarization rotation unit 72 for rotating the polarization plane of the separated S-polarized light and outputting it as P-polarized light. An auxiliary lens 73 is disposed between the polarization rotation unit 72 and the polarization beam splitter 47. Here, the aforementioned polarization beam splitter 47
Corresponds to a second polarization separation sub-means according to the present invention. Note that components having the same functions as those of the above-described first or second embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 8, the first polarization separation sub-means 71 is configured as a polarization beam splitter array plate 77 in which a plurality of prism type polarization beam splitter bodies 76 having a polarization separation film 75 are joined. In the polarization beam splitter array plate 77, a half-wave plate 78 as a polarization rotation unit 72 made of a resin film is adhered to every other polarization beam splitter body 76.

According to this configuration, a large number of light beams split by the second lens array plate 54 are incident on the minute polarizing beam splitter 76 while converging. In each polarization beam splitter 76, P-polarized light is transmitted and S-polarized light is reflected. The reflected S-polarized light enters the adjacent polarizing beam splitter body 76 and is reflected again by the polarization splitting film 75. The reflected S-polarized light is converted into P-polarized light by the half-wave plate 78 and emitted. At this time, the P-polarized light transmitted through the polarizing beam splitter 76 is
8 does not pass through. Therefore, the auxiliary lens 73
, P-polarized light that makes full use of the illumination light is guided. By utilizing S-polarized light, the light use efficiency can be improved.

FIG. 9 shows the configuration of a projection display device 80 according to a fourth embodiment of the present invention. In the fourth embodiment,
In addition to the configuration of the third embodiment, the V-shaped prism 41
And three reflective light valves 33, 34, 35 between plano-convex lenses 61-61 with the flat side facing the light valve side
63 is arranged. Note that components having the same functions as those of the above-described first to third embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

According to the configuration of the fourth embodiment, in addition to the effects obtained by the third embodiment, effects similar to those of the second embodiment can be obtained. That is, since the plano-convex lenses 61 to 63 converge each color light, the area of the effective luminous flux of the V-shaped prism 41 and the polarization beam splitter 47 can be reduced.
The character-shaped prism 41 and the polarization beam splitter 47 can be reduced in size, and the back focus of the projection lens 37 can be shortened. Also in this case, the second
As in the embodiment, an interference film type or absorption type color filter is provided between the plano-convex lenses 61 to 63 and the reflection type light valves 33 to 35 or between the plano-convex lenses 61 to 63 and the V-shaped prism 41. It may be arranged.

In the above-described embodiment, the green dichroic mirror is used as the first dichroic mirror surface 42 and the blue dichroic mirror is used as the second dichroic mirror surface 43. And a green reflecting dichroic mirror may be used for the second dichroic mirror surface 43. If a green reflecting dichroic mirror is used for the first dichroic mirror surface 42, the cutoff wavelength will be two points on the short wavelength side and the long wavelength side, and the manufacturing tolerance will be strict. Only when the dichroic film is formed, the manufacturing tolerance is reduced, and the cost of the V-shaped prism 41 can be reduced.

[0058]

As described above, the projection type display apparatus of the present invention uses a prism having a predetermined reference incident angle as a color separation / synthesis means and uses a color separation optical system to generate P-polarized light. Light transmittance characteristics of a dichroic mirror surface suitable for color separation and color synthesis can be obtained as compared with a letter-shaped dichroic prism. As a result, it is possible to realize a small-sized and low-cost projection display device having high light use efficiency, good color reproducibility of a projected image and no color unevenness.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a projection display device according to a first embodiment of the present invention.

FIG. 2A is a graph showing a spectral transmittance characteristic of a green reflecting dichroic mirror surface at an incident angle θ1. (B) A graph showing a spectral transmittance characteristic of a blue reflection dichroic mirror surface at an incident angle θ2.

FIG. 3A is a graph showing an incident angle dependence of a spectral transmittance characteristic of a first dichroic mirror surface with respect to P-polarized light. (B) A graph showing the incident angle dependence of the spectral transmittance characteristic of the first dichroic mirror surface with respect to S-polarized light.

FIG. 4A is a graph showing an incident angle dependence of a spectral transmittance characteristic of a second dichroic mirror surface with respect to P-polarized light. (B) A graph showing the incident angle dependence of the spectral transmittance characteristic of the second dichroic mirror surface with respect to S-polarized light.

FIG. 5 is a configuration diagram showing a projection optical system in detail.

FIG. 6 is a configuration diagram of a projection display device according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram of a projection display device according to a third embodiment of the present invention.

FIG. 8 is a detailed configuration diagram of a first polarization separation sub-means.

FIG. 9 is a configuration diagram of a projection display device according to a fourth embodiment of the present invention.

FIG. 10 is a diagram showing a schematic configuration of a conventional projection display device.

FIG. 11 is a diagram illustrating an X-shaped dichroic prism used in a conventional color separation / synthesis optical system.

FIG. 12 is a diagram showing a compound prism used in a conventional color separation / synthesis optical system.

FIG. 13A is a graph showing a spectral transmittance characteristic of a red reflecting dichroic mirror in an X-shaped dichroic prism. (B) A graph showing the spectral transmittance characteristics of a blue reflection dichroic mirror in an X-shaped dichroic prism.

FIG. 14A is a graph showing the incident angle dependence of the spectral transmittance characteristic of the red reflection dichroic mirror surface for P-polarized light. (B) A graph showing the incident angle dependence of the spectral transmittance characteristic of the red reflection dichroic mirror surface for S-polarized light.

FIG. 15A is a graph showing the incident angle dependence of spectral transmittance characteristics of a blue reflection dichroic mirror surface with respect to P-polarized light. (B) A graph showing the incident angle dependence of the spectral transmittance characteristic of the blue reflection dichroic mirror surface for S-polarized light.

[Explanation of symbols]

 30, 60, 70, 80 Projection display device 31 Illumination means 32 Color separation / combination means 33-35 Reflection type light valve 37 Projection lens 41 V-shaped prism 42 First dichroic mirror surface 43 Second dichroic mirror surface 45 Polarization separation means 46 Polarization Separation Film 47 Polarization Beam Splitter 50 Light Source 51 Concave Mirror 53 First Lens Array Plate 54 Second Lens Array Plate 61-63 Plano-Convex Lens as Convex Lens 71 First Polarization Separation Sub Means 72 Polarization Rotating Means 77 Polarization Beam Splitter Array Plate 78 1/2 wavelength plate as polarization rotating means

Claims (9)

[Claims] An illumination unit that outputs illumination light; a first polarization separation unit that separates two polarization lights having orthogonal polarization directions; and one polarization light from the polarization separation unit is separated into each color light. A color separating / combining means for combining each color light, a reflection type light valve for forming an optical image corresponding to a video signal using each color separated color light, and a projection lens for enlarging and projecting the optical image. The color separation / combination means, the incident angle θ formed by the optical axis of the projection lens with respect to the normal to the mirror surface.
A prism having at least a first dichroic mirror surface whose 1 is 20 ° to 30 ° and a second dichroic mirror surface whose incident angle θ2 is 30 ° to 35 °;
The one-polarized light is P-polarized with respect to the first and second dichroic mirror surfaces. 2. The illumination means includes: a light source; a concave mirror for condensing light emitted from the light source; a first lens array plate including a plurality of lenses and dividing the light from the concave mirror into a large number of light fluxes; 2. The projection display device according to claim 1, further comprising a second lens array plate that includes a plurality of lenses and into which light from the lenses of the first lens array plate converges and enters. 3. 3. A second polarized light separating means for separating light from the illuminating means into two polarized lights having polarization directions orthogonal to each other, between the illuminating means and the first polarized light separating means. 3. The projection display device according to claim 1, further comprising a polarization rotation unit configured to rotate a polarization direction of the one polarized light from the polarization separation unit. 4. The projection display device according to claim 1, wherein a convex lens is disposed between the color separation / synthesis optical unit and the reflection type light valve. 5. The projection display device according to claim 1, wherein the projection lens is a telecentric projection lens in which an angle between an optical axis and a principal ray is 3 ° or less in air medium conversion. . 6. The projection type display device according to claim 1, wherein the color separation / combination means and the reflection type light valve are arranged in close contact with each other. 7. The projection display device according to claim 1, wherein the first dichroic mirror reflects green light and transmits blue light and red light. 8. The projection display according to claim 1, wherein the first dichroic mirror reflects blue light, and the second dichroic mirror reflects green light. 9. The projection display device according to claim 1, wherein a color filter is arranged between the color separation / combination means and the reflection type light valve.