JP3858548B2 - Optical engine and liquid crystal projector using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display technique using three reflective liquid crystal display elements, and more particularly to a technique using a polarization beam splitter prism in at least a part of a color separation / synthesis optical system for separating and synthesizing video light of three primary colors.
[0002]
[Prior art]
As a liquid crystal projector using this type of reflective liquid crystal display element, for example, there is a description in JP-A-10-312034.
[0003]
In addition, as a liquid crystal projector using a polarization rotation element that rotates only polarized light in a specific wavelength range, for example, United States Patent No. COLOR POLARIZERS FOR POLARIZING AN ADDITIVE COLOR SPECTRUM ALONG A FIRST AXIS AND IT'S COMPLIMENT ALONG A SECOND AXIS described in 5, 751, 384.
[0004]
FIG. 10 is a schematic top view of a liquid crystal projector optical system including a light source, a polarizing beam splitter prism, three reflective liquid crystal display elements, and a color separation optical system (also serving as a color synthesis optical system) according to the former disclosure. . Hereinafter, an optical system as a related technique and a liquid crystal projector using the same will be described in detail with reference to FIG.
[0005]
The light source 81 is a white light source such as a high-pressure mercury lamp or a xenon lamp, and emitted light is converted into substantially parallel light 82 by a reflector. The substantially parallel light 82 is composed of an R light component 82R, a G light component 82G, and a B light component 82B, and is rectified by the polarization conversion element 83 into light having only a wavefront perpendicular to the paper surface. Here, the polarization conversion element is an optical element having an action of rectifying non-polarized substantially parallel light having no specific polarization plane into a specific polarization plane. For the sake of simplification of description, light having only a wavefront perpendicular to the paper surface will be denoted as S-polarized light, and light having only a wavefront horizontal to the paper surface will be denoted as P-polarized light.
[0006]
The S-polarized light emitted from the polarization conversion element 83 passes through the polarizing plate 83a arranged in a direction in which only the S-polarized light is transmitted, and becomes R S-polarized light 84R, G S-polarized light 84G, and B S-polarized light 84B. Next, the S-polarized light of the three primary colors incident on the polarization beam splitter prism 85 is reflected by the splitter surface 85a (a multilayer thin film having a property of reflecting only the S-polarized light) and enters the color separation / combination prism 86.
[0007]
The color separation / combination prism 86 has a configuration in which the right-angled surfaces of the four right-angle prisms are bonded to each other with an adhesive, and an R reflecting dichroic mirror 86R and a B reflecting dichroic mirror 86B are deposited on the bonded surfaces. Here, the R reflecting dichroic mirror 86R is a multilayer thin film that reflects only R light and transmits G light and B light. The B reflecting dichroic mirror 86B is a multilayer thin film having the property of reflecting only B light and transmitting R light and G light.
[0008]
The substantially parallel S-polarized light 84R, 84G, and 84B incident on the color separation / combination prism 86 go straight only through the G S-polarized light 84G, the R S-polarized light 84R goes to the R reflecting dichroic mirror 86R, and the B S-polarized light 84B goes to B. The light is reflected by the reflective dichroic mirror 86B and enters the reflective liquid crystal display elements 87R, 87G, 87B corresponding to the respective colors. Each pixel of the reflective liquid crystal display element is converted to P-polarized light when it is brightly displayed, and is reflected as S-polarized light when it is darkly displayed. In FIG. 7, only light to be displayed brightly is plotted. When the reflected substantially parallel light is displayed brightly, it becomes R P-polarized light 88R, G P-polarized light 88G, and B P-polarized light 88B, and is synthesized into white light by the color separation / combination prism 86, and is again polarized. The light enters the splitter 85. The P-polarized light that is brightly displayed here passes through the splitter surface 85a, is enlarged and projected by the projection lens 90, becomes P-polarized video light 91, and enters the screen or the like. S-polarized light, which is light to be displayed dark, passes through the color separation / combination prism 86 for all three colors, and is then reflected by the splitter surface 85a of the polarization beam splitter prism 85 and does not reach the projection lens 90.
[0009]
However, since it is difficult to make the polarization separation performance of the polarization beam splitter prism 85 reflect 100% of the S-polarized light, a part of the S-polarized light that is originally darkly displayed is the splitter surface of the polarization beam splitter 85. 85a is transmitted, and the contrast of the image deteriorates. Therefore, by arranging the polarizing plate 89 at an angle that transmits only the P-polarized light between the polarizing beam splitter prism 85 and the projection lens 90, the S-polarized light is absorbed and an image with high contrast can be obtained.
[0010]
Although FIG. 7 shows a configuration in which the light incident on the reflective liquid crystal display element is S-polarized light, and among the reflected light, light that is brightly displayed is P-polarized light, the actual configuration of the light source 81 and the projection lens 90 is described. A configuration in which incident light is P-polarized light and reflected light for bright display is S-polarized light can be easily considered by changing the position.
[0011]
According to the latter disclosure document United States Patent Nos. 5, 751, and 384, when manufacturing a polarization rotation element, the polarization of only light in a specific wavelength region is rotated by laminating phase difference plates having different rotation angles. It becomes possible. FIG. 3 shows an example of the configuration of the polarization rotation element according to the latter disclosure document, FIG. 4 shows the wavelength characteristics of the polarization rotation element. FIG. As shown in FIG. 4, the polarization rotation element according to the present disclosure has a property of rotating only the light having a wavelength of about 500 nm or more and not rotating the polarization of light having a wavelength of 500 nm or less. Here, the wavelength band for rotating the polarized light can be controlled by changing the configuration of the phase difference plate to be laminated.
[0012]
FIG. 10 is a schematic top view of a liquid crystal projector color synthesis optical system according to the present disclosure.
[0013]
Hereinafter, the liquid crystal projector optical system as the related art will be described in detail with reference to FIG.
[0014]
FIG. 10 shows a color synthesis optical system of a liquid crystal projector according to the present disclosure, and a light source, a color separation optical system, and a projection lens are omitted. In FIG. 10, 96 and 99 are polarization rotation elements that rotate the polarization of light in a specific wavelength range according to the present disclosure, 96 is a property that rotates the polarization of G light, and 99 is a property that rotates the polarization of B light. have.
[0015]
The image light emitted from the image display elements 93R, 93G, and 93B of the three primary colors of R, G, and B is P-polarized light 94B for B image light, S-polarized light 94R for R image light, and P-polarized light 94G for G image light. It consists of The S-polarized video light 94R emitted from the R image display element 93R and the P-polarized video light 94G emitted from the G image display element 93G are incident on the polarization beam splitter prism 95 from different surfaces. Here, the R S-polarized light 94R is reflected by the splitter surface 95a, the G P-polarized light 94G is transmitted through the splitter surface 95a, and the R light is combined into one image light having S-polarized light and the G light is combined with P-polarized light. Is done. Next, the image light is incident on a polarization rotation element 96 that rotates the polarization of only the G light, the S polarization 94R of R does not change and becomes the S polarization 97R, the polarization of the G P polarization 94G rotates, and the S polarization of G By becoming 97G, both RG are converted into image light having an S-polarized component. Both the R S-polarized light 97R and the G S-polarized light 97G are incident on the polarization beam splitter prism 98 and reflected by the splitter surface 98a.
[0016]
On the other hand, the video light 94B having B P-polarized light emitted from the B image display element 93B enters the polarization beam splitter prism 98 and passes through the splitter surface 98a. In this way, RGB image light is synthesized, and R and G light becomes image light having S-polarized light and B light becomes P-polarized light. Then, this image light is incident on a polarization rotation element 99 that rotates only the polarization of the B light, and the S polarization 97R of R and the S polarization 97G of G do not change to become the S polarization 100R of R and the S polarization 100G of G, Only the B P-polarized light 94 </ b> B rotates and becomes B S-polarized light 100 </ b> B, so that all of the light is converted into image light having an S-polarized component and is enlarged and projected by the projection lens 101. As described above, according to the technique according to the present disclosure, it is possible to perform color synthesis using the polarization beam splitter prism instead of the dichroic mirror.
[0017]
Here, FIG. 11 shows a schematic top view of the optical system when a reflective liquid crystal display element is applied to the known optical system shown in FIG.
[0018]
Hereinafter, this known optical system will be described in detail with reference to FIG.
[0019]
Light emitted from the light source 110 that generates R and G light is converted into substantially parallel light 111 by a reflector, and becomes R light 111R and G light 111G. The R light 111R and the G light 111G pass through the polarization conversion element 112 and are both converted to light having P polarization, and then the R light 111R is converted into R P by the polarization rotation element 113 that rotates only the G light. The polarized light 114R and the G light 111G are converted into G S-polarized light 114G. The R P-polarized light 114R and the G S-polarized light 114G are incident on the polarization beam splitter prism 115, the R P-polarized light 114R travels straight by the splitter surface 115a, and the G S-polarized light 114G is reflected. , 116G. Here, the light to be displayed brightly is reflected as R-polarized light 117R as S-polarized light, and G-polarized light as P-polarized light 117G, and enters the polarization beam splitter prism 115 again. On the splitter surface 115a of the polarizing beam splitter prism 115, the R S-polarized light 117R is reflected, and the G P-polarized light 117G travels straight, thereby synthesizing two video lights. The image light with R being S-polarized light and G being P-polarized light is incident on the polarization rotating element 118 that rotates only the G-light polarized light, and the S-polarized light 117R of R does not change to become the S-polarized light 119R of G. The polarization of the P-polarized light 117G is rotated to become the S-polarized light 119G of G. Then, both R and G become S-polarized light and enter the polarizing beam splitter prism 120, and are reflected by the splitter surface 120a.
[0020]
On the other hand, the B light 126 </ b> B emitted from the light source 125 that generates the B light is converted into the B S-polarized light 128 </ b> B by the polarization conversion element 127 and is incident on the polarization beam splitter prism 120. Next, the B S-polarized light 129B reflected by the splitter surface 120a is incident on the B reflective liquid crystal display element 130B. The light to be displayed brightly becomes P-polarized light 131B and is incident again on the polarizing beam splitter prism 120. Since it is P-polarized light this time, it passes through the splitter surface 120a and goes straight. Thus, the image light combined with white light having components of B-polarized light, R-light, and G-light S-polarized light is incident on the polarization rotation element 122 that rotates only the polarized light of B light, and the P-polarized light 131B of B The polarized light is rotated to become B S-polarized light 132B, and R S-polarized light 119R and G S-polarized light 119G are not changed, and become 121R and 121G, all of which become image light having S-polarized components, and are enlarged and projected by the projection lens 124. Is done. In addition, the light (reflected light having the same polarization as the incident light) converted to image light to be darkly displayed by the reflective liquid crystal display elements 116R, 116G, and 130B is transmitted to the light source by the polarization beam splitter prisms 115 and 120. Thus, the projection lens 124 is not reached. However, since it is difficult to make the separation performance of the polarizing beam splitter prism 100% reflected or transmitted for both S-polarized light and P-polarized light, part of the image light that is originally displayed darkly reaches the projection lens. As a result, the contrast of the image is deteriorated. Therefore, in order to improve the image contrast, it is necessary to dispose the polarizing plate 123 between the polarization rotation element 122 and the projection lens 124.
[0021]
In addition, the arrangement of RGB colors in the present disclosure is not limited to this configuration, and it is apparent that similar performance can be obtained with other arrangements.
[0022]
[Problems to be solved by the invention]
However, the technique disclosed in Japanese Unexamined Patent Publication No. 10-312034 of the former disclosure document is advantageous for reducing the size of the set, but it is difficult to achieve both high contrast and high brightness of the image. The dichroic mirror used in the present disclosure generally has a property that the wavelength reflection characteristics are greatly different depending on S-polarized light and P-polarized light.
[0023]
FIG. 13 shows an example of the transmittance when light enters from one surface of the color separation / combination prism. The horizontal axis of the graph in FIG. 13 indicates the wavelength of light, and the vertical axis indicates the transmittance. As shown in FIG. 13, the wavelength band of G light transmittance is narrower for S-polarized light and wider for P-polarized light. The opposite is true for R light and B light. Here, in the liquid crystal projector used in the present disclosure, the light corresponding to the signal to be brightly displayed is S-polarized light for the incident light to the reflective liquid crystal display element, and P-polarized light for the reflected light. The wavelength characteristics at the time of synthesis will be different. For example, light having a wavelength of 580 nm is reflected by an R reflective dichroic mirror upon incidence and is incident on an R reflective liquid crystal display element, but after being reflected, becomes P-polarized light, passes through an R reflective dichroic mirror and a B reflective dichroic mirror, The light enters the reflective liquid crystal display element B and becomes stray light, and the contrast of the image is remarkably deteriorated. In order to prevent this stray light, light in the vicinity of the wavelength of 580 nm and the wavelength of 500 nm must be cut in advance with a color filter or the like, resulting in a decrease in the light utilization rate. Similarly, the stray light of the G light is generated even when the incident light is P-polarized light. As described above, the conventional liquid crystal projector has a problem that it is difficult to achieve both high contrast and high luminance.
[0024]
Further, in the technique disclosed in the latter disclosed document, United States Patent No. 5,751,384, the problem of the color separation / synthesis optical system using the reflective liquid crystal display element is not considered.
[0025]
In an optical system that uses a reflective liquid crystal display element and makes the incident light and outgoing light have different polarizations, a part of the incident light and the outgoing light pass through the same optical path, and further, a color separation optical system and color synthesis optics Since at least a part of the system is shared, there is a problem that it is difficult to improve the contrast of an image by installing a polarizing plate immediately after the reflective liquid crystal display element. The problem of the optical system using the element is not considered.
[0026]
In an optical system that combines RGB image light with a polarization beam splitter prism as shown in FIG. 12, the combined image light has S-polarized light and P-polarized light, and therefore a polarizing plate for improving contrast is installed. In addition, it is necessary to install a polarization rotation element that rotates polarized light only at a specific wavelength before the polarizing plate. However, the polarization rotator having wavelength selectivity has a gap of 10 nm to 30 nm or more between the wavelength range where the polarization is completely rotated by 90 degrees and the wavelength range where the polarization is not rotated. The rotation angle changes slowly and has the characteristic of becoming elliptically polarized light. Since the elliptically polarized light in this transient region significantly deteriorates the contrast of the image, it is necessary to cut the light in this transient region with a filter or the like in order to improve the contrast of the image. There is a problem that the use efficiency decreases.
[0027]
Further, in a three-plate type projection apparatus that generally uses a white light source and one projection lens and performs color separation and synthesis of the three primary colors of RGB, it is projected that the optical distances from the projection lens to the three display elements are the same. In order to obtain the focusing performance of the lens, it is necessary to shorten the optical distance between the projection lens and the display element and shorten the back focus of the projection lens. Further, in order to reduce the color unevenness of the image, it is desirable that the optical distance from the light source to the three display elements is also substantially the same, and in order to increase the brightness of the image, from the light source to the display element. It is desirable to shorten the distance. In particular, in an optical system using a reflective display element, incident light and outgoing light partially pass through the same optical path, which makes it difficult to achieve both of them. Issues are not taken into account.
[0028]
Accordingly, an object of the present invention is to propose an optical engine having a high light utilization rate and a high image contrast in a liquid crystal projector optical engine using a reflective liquid crystal display element, and a liquid crystal projector using the same.
[0029]
Another object of the present invention is to reduce the color unevenness by making the distance from the light source to the three reflective liquid crystal display elements of RGB substantially equal, and to keep the distance between the reflective liquid crystal display element and the projection lens at an equal distance. Another object of the present invention is to propose a small and lightweight liquid crystal projector optical engine having excellent focusing performance and a flat liquid crystal projector using the same, shortening the back focus of the projection lens.
[0030]
[Means for Solving the Problems]
  To achieve the above objectiveIn the present invention, a light source that emits light, a polarization conversion element that unifies the polarization of the light, and light that has been polarized by the polarization conversion element are separated into three colors of R, G, and B. A dichroic mirror that separates light of the first color of R, G, and B from light emitted from the light source; and three reflective liquid crystal display elements arranged corresponding to the three colors; A first polarizing beam splitter prism disposed substantially immediately before a reflective surface of a reflective liquid crystal display element corresponding to the first color light; and an incident surface on which light from which the first color light is separated is incident. The light incident from the incident surface is separated into the light of the second color and the light of the third color, and the first of the light reflected by the reflective liquid crystal display elements arranged corresponding to the respective colors. Separating and combining surface for combining light of two colors and light of the third color, and emitting the combined light A second polarization beam splitter prism having an exit surface, and a first wavelength selective polarization rotation element that is disposed on the entrance surface and that rotates the polarization of the second color light or the third color light. A second wavelength-selective polarization rotation element that is disposed on the exit surface and rotates the polarization of the second color light or the third color light; and the light from the first polarization beam splitter prism. A dichroic mirror prism that synthesizes the light from the second wavelength-selective polarization rotation element and a projection lens that projects the light synthesized by the dichroic mirror prism are configured.
[0031]
A polarization conversion element is arranged so that the illumination light emitted from the white light source has the same polarization direction for all of R, G, and B, and the G light is first separated from the RB light by the color separation optical system. .
[0032]
Then, a polarization rotation element that rotates the polarized light in the specific wavelength region is disposed in the separated RB optical path, and the polarization directions of the R and B illumination light are converted into polarized light that intersects each other at an angle of about 90 degrees. The beam splitter prism is used to separate RB light. The polarizing beam splitter prism is configured to have a function of synthesizing the RB image light reflected by the reflective liquid crystal display element. At this time, the R light and the B light separated from the G light are rotated in the polarization direction by a polarization rotation element that rotates the polarization direction in a specific wavelength region, and enter the polarization beam splitter prism. The polarization rotator is configured such that the characteristics change with a band of about 510 to 580 nm, which is the G light region. The R light and B light having different polarization directions are separated by the polarization beam splitter, are incident on the respective reflection type liquid crystal display elements, are reflected and again enter the polarization beam splitter prism, and are synthesized again at the same time as an image is obtained.
[0033]
With this configuration, two color images can be obtained simultaneously with one polarizing beam splitter prism, and a compact and lightweight optical engine can be designed. In addition, a polarization rotation element that rotates polarized light in a specific wavelength region can be arranged in an optical path through which R and B light passes, and G light that is a wavelength in the transient region of the polarization rotation element passes through another optical path. As a result, it is possible to obtain an image with high contrast without cutting light in a transitional region.
[0047]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0048]
FIG. 1 is a schematic top view of a liquid crystal projector optical system according to a first embodiment of the present invention.
[0049]
FIG. 2 shows a graph of the polarization rotation characteristics of the polarization rotation elements 9 and 16 that rotate the wavelength of only the B light used in this embodiment. The horizontal axis of the graph represents the wavelength of light, and the vertical axis represents the polarization rotation angle. As shown in FIG. 2, the polarization rotating element used in this embodiment has an intermediate point for rotating the polarized light at a wavelength of about 550 nm.
[0050]
Hereinafter, a first embodiment of the present invention will be described in detail with reference to FIG.
[0051]
White light emitted from the light source 1 is converted into substantially parallel light 2 by the reflector. The substantially parallel light 2 is composed of a component 2R of R light, a component 2G of G light, and a component 2B of B light, and is converted into S-polarized light by the polarization conversion element 3, and S-polarized light 4R of R, S-polarized light 4G of G, B becomes S-polarized light 4B.
[0052]
The R S-polarized light 4R and the B S-polarized light 4B incident on the reflective RB transmissive dichroic mirror 5 are transmitted through the dichroic mirror surface, then transmitted through the polarizing plate 7, and the P-polarized light component is absorbed. B becomes S-polarized light 8B. Incidentally, the reason why the polarizing plate 7 is disposed at this position is that the polarization rectification by the polarization conversion element 3 is not sufficient, and the incident light 4R, 4G, 4B includes a part of the P-polarized light and deteriorates the contrast of the image. This is to make it happen. A higher contrast can be obtained by absorbing the P-polarized light by the polarizing plate 7.
[0053]
The R S-polarized light 8R and the B S-polarized light 8B enter the polarization rotation element 9 for rotating the polarization of the B light, and the S polarization of the R does not change and becomes the S polarization 10R of the R, and the S polarization of the B Becomes a P-polarized light 10B of B. The R S-polarized light 10R incident on the polarization beam splitter prism 11 is reflected by the splitter surface 11a, becomes R S-polarized light 12R, and enters the reflective liquid crystal display element 13R. Here, light that is displayed brightly by the reflective liquid crystal display element 13R is reflected as R P-polarized light 14R, and light that is displayed dark is reflected as R S-polarized light. In FIG. 1, R, G, and B are all omitted for light that is displayed darkly. Light P to be displayed brightly, R P-polarized light 14R, is incident on the polarization beam splitter prism 11 again, and is now P-polarized light, so that it passes through the splitter surface 11a and becomes R P-polarized light 15R.
[0054]
On the other hand, the B P-polarized light 10B that has passed through the polarization rotating element 9 that rotates the polarization of the B light is incident on the polarization beam splitter prism 11, passes through the splitter surface 11a, and becomes the B S-polarized light 12B. Incident on the liquid crystal display element 13B. Here, light to be displayed brightly by the B reflective liquid crystal display element 13B is reflected as S-polarized light B of B, and light to be displayed dark is reflected as B P-polarized light. The brightly displayed light, B S-polarized light 14B, is incident on the polarization beam splitter 11 again, and this time it is S-polarized light. Therefore, the light is reflected by the splitter surface 11a, becomes B S-polarized light 15B, and is combined with R P-polarized light 15R. Is done.
[0055]
The combined R P-polarized light 15R and B S-polarized light 15B are incident on the polarization rotation element 16 for rotating the polarization of the B light, and the R P-polarized light 15R remains unchanged as the R P-polarized light 19R. The polarized light of the B S-polarized light 15B rotates and becomes the B P-polarized light 19B. The R P-polarized light 19R and the B P-polarized light 19B that are both P-polarized light are incident on the polarizing beam splitter prism 20, transmitted through the splitter surface 20a, the R P-polarized light 21R, and the B P-polarized light 21B. Become. At this time, since the S-polarized light that causes dark display of both the RB light is reflected, the contrast of both the R and B lights is further improved.
[0056]
As for the G light, the G light 2 G emitted from the light source 1 is converted into S-polarized light 4 G by the polarization conversion element 3, then reflected by the G-reflecting RB transmission dichroic mirror 5, and reflected on the polarizing plate 25. Incident light, the P-polarized light component is almost completely cut to become S-polarized light G of G, and enters the polarization beam splitter 27. The G S-polarized light 26G incident on the polarization beam splitter 27 is reflected by the splitter surface 27a to become the G S-polarized light 28G and enters the G reflective liquid crystal display element 29G. The light to be displayed brightly is reflected as G P-polarized light 30G and enters the polarization beam splitter 27 again. Since it is P-polarized light this time, it passes through the splitter surface 27a and becomes G P-polarized light 31G. Here, the G P-polarized light 31G is incident on the polarization rotation element 34 and the polarized light is rotated to become G S-polarized light 35G.
[0057]
The G S-polarized light 35G is incident on the polarization beam splitter prism 20 and is reflected by the splitter surface 20a to become G S-polarized light 36G, which is combined with the R P-polarized light 21R and the B P-polarized light 21B. The combined image light has components of R and B for P-polarized light and G for S-polarized light, and is enlarged and projected on a screen or the like by the projection lens 24.
[0058]
In this embodiment, a black paint is applied to the upper and lower surfaces of each prism. With this configuration, internal reflection inside the polarizing beam splitter prism or dichroic mirror prism can be reduced, and high contrast can be obtained.
[0059]
According to the present embodiment, with respect to the contrast characteristics of the image, the G image light 31G reflected by the G reflective liquid crystal display element 29G is sufficiently reflected by the splitter surface 27a of the polarization beam splitter prism 27 to sufficiently reflect the light. Therefore, the contrast is high. In addition, the image light of R is reflected by the splitter surfaces 11a and 20a of the polarizing beam splitter prisms 11 and 20 so as to be darkly displayed, so that a good contrast can be obtained. Further, the B image light can be made high contrast by the splitter surface 20 a of the polarization beam splitter prism 20.
[0060]
Further, in this embodiment, even when the polarization rotation elements 9 and 16 for rotating the polarization of the B light have the characteristics as shown in FIG. 2, the R light and the B light passing through the wavelength in the transient region of the wavelength rotation angle. Therefore, a high image contrast can be obtained after passing through the polarizing plate 18. Further, since the polarization rotator 16 is used, it is not necessary to cut off the light between the R light and the G light, and the light between the G light and the B light in order to improve the contrast of the image, and a high light utilization rate can be obtained. it can.
[0061]
Further, according to the present embodiment, the distances from the polarization conversion element 3 to the reflective liquid crystal display elements 13R, 29G, and 13B can be made substantially equal, and an image with little color unevenness can be obtained. The distance from the polarization conversion element 3 to the reflective liquid crystal display element and the distance from the reflective liquid crystal display element to the projection lens 24 are both about 2.5 times the length of the horizontal side of the reflective liquid crystal display element. Thus, the back focus of the projection lens can be shortened, the entire optical system can be reduced in size and weight, and the light utilization efficiency can be improved at the same time.
[0062]
FIG. 3 is a schematic top view of the liquid crystal projector optical system according to the second embodiment of the present invention. The second embodiment of the present invention is different from the first embodiment of the present invention in that the polarization beam splitter 20 is replaced with a dichroic mirror prism 39 except for the polarization rotation element 16 in the optical path of R and B image light. It is a thing. The dichroic mirror surface 39a of the dichroic mirror prism 39 is a multilayer thin film having the property of reflecting light in the G wavelength region and transmitting light in the RB wavelength region.
[0063]
The action of the optical system of the present embodiment with respect to the R light and the B light is the same as that of the first embodiment before exiting from the polarization beam splitter prism 11.
[0064]
The R P-polarized light 15R and the B S-polarized light 15B synthesized by the polarization beam splitter prism 11 are incident on the polarization rotation element 16 for rotating the polarization of the B light, and the R P-polarized light 15R is not changed. P polarized light 19R, and the B S polarized light 15B rotates and becomes B P polarized light 19B. The R P-polarized light 19R and the B P-polarized light 19B, both of which are P-polarized light, enter the dichroic prism 39, pass through the dichroic surface 39a, and become R P-polarized light 41R and B P-polarized light 41B. At this time, since the S-polarized light that causes dark display of both the R and B lights is reflected, the contrast of both the R and B lights is improved.
[0065]
Further, the action of G on the video light 31 </ b> G is the same as that of the first embodiment until it is emitted from the polarization beam splitter 27, and thereafter enters the dichroic mirror prism 39.
[0066]
The G P-polarized light 31G incident on the dichroic mirror prism 39 is reflected by the dichroic mirror surface 39a to become the G P-polarized light 41G, and is combined with the R P-polarized light 41R and the B P-polarized light 41B. The combined video light has P-polarized components for both RGB and is enlarged and projected on a screen or the like by the projection lens 24.
[0067]
According to the present embodiment, the same effect as that of the first embodiment can be obtained, and the polarization rotating element 34 can be omitted, and the apparatus can be simplified.
[0068]
In this embodiment, the same effect can be obtained even if the dichroic mirror prism 39 is replaced with a dichroic mirror. In addition, since an inclined film or the like can be freely set in the dichroic mirror 5 and the dichroic film of the dichroic mirror for synthesis or the dichroic mirror, an image with high uniform color purity can be obtained.
FIG. 4 is a schematic top view of the liquid crystal projector optical system according to the third embodiment of the present invention.
[0069]
The third embodiment of the present invention is different from the second embodiment of the present invention in that the positions of the R and B liquid crystal display elements 13R and 13B are changed, and the polarizing plate 7 on the R and B illumination light incident surfaces is changed. The polarizing plate 46 is changed to the polarizing plate 46 dedicated to the B light, and the polarization rotating elements 9 and 16 for rotating the polarization of the B light are changed to the polarization rotating elements 42 and 43 for rotating the polarization of the R light.
[0070]
FIG. 5 is a graph showing the wavelength transmittance characteristics of the polarizing plate exclusively for B light used in this example and the wavelength transmittance characteristics of the polarizing plate for the entire wavelength region. As shown in FIG. 5, the polarizing plate for exclusive use of B light used in this embodiment works as a polarizing plate for light in the B wavelength range, but for the light in the R wavelength range, the absorption axis. , The transmission axis is transmitted and does not work as a polarizing plate.
[0071]
The action of the optical system of this embodiment with respect to R light and B light is the same as that of the second embodiment before entering the polarizing plate 46 dedicated to B light and after entering the dichroic prism 39.
[0072]
The B S-polarized light 4B that has passed through the G-reflecting RB transmitting dichroic mirror 5 is absorbed by the B-light-only polarizing plate 46 to become a B S-polarized light 8B. The B S-polarized light 8B passes through the polarization rotation element 42 for rotating the polarization of the R light, becomes the B S-polarized light 10B, and enters the polarization beam splitter prism 11. The B S-polarized light 10B reflected by the splitter surface 11a of the polarization beam splitter prism 11 becomes the B S-polarized light 12B and enters the B reflective liquid crystal display element 13B. The B light reflected by the B reflective liquid crystal display element 13B becomes B P-polarized light 14B and is incident on the polarization beam splitter prism 11 again when displaying brightly. The B P-polarized light 14B passes through the splitter surface 11a. At this time, since the S-polarized light to be displayed darkly is reflected by the splitter surface 11a, the B image light can have a high contrast. Here, the B P-polarized light 14B passes through the polarization rotation element 43 for rotating the polarization of the R light, becomes the B P-polarized light 17B, and enters the dichroic mirror prism 39.
[0073]
The R S-polarized light 4R transmitted through the G-reflecting RB transmitting dichroic mirror 5 is transmitted through the polarizing plate 46 dedicated to the B light, is transmitted through the polarization rotating element 42 for rotating the polarization of the R light, and is the R P-polarized light 10R. And enters the polarization beam splitter prism 11. The R P-polarized light 10R is transmitted through the splitter surface 11a. At this time, the S S-polarized component of R is reflected by the splitter surface 11a and becomes the R P-polarized light 12R that does not substantially contain the S-polarized component. The light enters the display element 13R. The R image light reflected by the R reflective liquid crystal display element 13 </ b> R becomes R S-polarized light 14 </ b> R and is incident on the polarization beam splitter prism 11 again when being displayed brightly. The R S-polarized light 14R reflected by the splitter surface 11a enters the polarization rotation element 43 for rotating the polarization of the R light, becomes the R P-polarized light 17R, and enters the dichroic mirror prism 39. The R image light incident on the dichroic prism 39 is reflected by the dichroic surface 39a as S-polarized light to be displayed dark, and is emitted from the dichroic prism 39 as R-polarized light 21R having high contrast.
[0074]
The action of the optical system of this embodiment on G light is substantially the same as that of the second embodiment.
[0075]
According to the present embodiment, substantially the same effect as that of the second embodiment of the present invention can be obtained, and the polarizing plate for the illumination light incident side for R and B can be used as a polarizing plate for B. High brightness can be achieved.
[0076]
FIG. 6 is a schematic top view of a liquid crystal projector optical system according to the fourth embodiment of the present invention.
[0077]
  The fourth embodiment of the present invention is different from the first embodiment of the present invention in that a polarization beam splitter prism 11, a polarization rotation element 16, a polarization beam splitter prism 20, a polarization rotation element 34, and a polarization beam splitter 27 are provided. To each otherPastedIt is a combination.
[0078]
The action of the optical system of this embodiment with respect to R, G, and B light is the same as that of the first embodiment.
[0079]
Further, the polarizing beam splitters 11 and 27 of this embodiment are smaller in size than the polarizing beam splitter 20. Thereby, the configuration of the entire optical system can be reduced in a state in which the image light emitted from the reflective liquid crystal display element is not vignetted on the prism side surface.
[0080]
Further, according to the configuration of the present embodiment, the chamfered portion 49 is provided in the optical element 20 such as a polarizing beam splitter prism, and this support member is provided here, or an optical member such as the dichroic mirror 5 and the polarizing plates 7 and 25. By providing the supporting portion, it is possible to easily hold and position the optical member, shorten the assembling time during mass production, and further reduce the cost of the projection display apparatus.
[0081]
According to this embodiment, substantially the same effect as that of the first embodiment of the present invention can be obtained, the configuration of the entire optical system can be reduced in size, the assembling time in mass production can be shortened, and a projection type image can be obtained. The cost of the entire display device can also be reduced.
[0082]
FIG. 7 is a schematic top view of a liquid crystal projector optical system according to the fifth embodiment of the present invention.
[0083]
The embodiment of FIG. 7 shows the entire apparatus of a reflective three-plate liquid crystal projector in which the reflective liquid crystal display elements 13R, 29G, and 13B are made to correspond to R, G, and B of the three primary colors.
[0084]
Hereinafter, the fifth embodiment of the present invention will be described in detail with reference to FIG.
[0085]
The light source 1 in FIG. 7 is a white light source such as an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, a mercury xenon lamp, or a halogen lamp.
[0086]
The white illumination light emitted from the light source 1 is converted into substantially parallel light by the reflector 1 a having an elliptical surface, a paraboloidal surface, or an aspherical reflecting surface, and is incident on the first array lens 150. The first array lens 150 is constituted by a plurality of condensing lenses provided in a rectangular frame having a size substantially equal to the exit aperture of the reflector 1a, and the substantially parallel light is placed on the second array lens 151 by a plurality of secondary light sources. Focus as an image. The second array lens 151 has substantially the same outer size as the first array lens, is configured by the same number of condensing lenses, and is disposed in the vicinity where the plurality of secondary light source images are formed. The individual condenser lenses of the second array lens 151 have the effect of forming the individual lens images of the first array lens 150 on the liquid crystal display elements 13R, 29G, and 13B.
[0087]
The white illumination light that has passed through the second array lens 151 has a width that is approximately ½ of the width of each lens, which is arranged to match the lateral pitch of each lens of the second array lens 151. Incident to the row of rhombus prisms. The reflecting surface of the prism is provided with a polarizing beam splitter 152, and incident light is separated into P-polarized light and S-polarized light by the polarizing beam splitter 152. The P-polarized light passes through the polarization beam splitter 152 as it is, and the polarization direction is rotated by 90 ° by the polarization rotating element 153 provided on the exit surface of the prism, and is emitted as S-polarized light. On the other hand, the S-polarized light is reflected by the polarizing beam splitter 152, is reflected once again in the original optical axis direction in the adjacent rhomboid prism, and then emitted as S-polarized light.
[0088]
Illumination light is converted into light having S polarization by the rhomboid prism and the polarization rotation element 153.
[0089]
Here, in the projection type liquid crystal display device using the conventional reflection type liquid crystal display element, only the polarized light in one direction of S-polarization or P-polarization can be used by the combination of the incident side polarizing plate and the reflection liquid crystal display element. It is about half. However, by using the polarization beam splitter 152 and the polarization rotation element 153, the polarization direction of illumination light having a random polarization component emitted from the light source 1 can be aligned and incident on the reflective liquid crystal display element 13, which is ideal. Specifically, the brightness twice as high as that of the conventional projection type liquid crystal display device can be obtained.
[0090]
The first and second array lenses 150 and 151 separate the illumination light emitted from the reflector 1 a by the first array lens 150, and the individual array images are again superimposed on the liquid crystal display element 13 by the second array lens 151. By combining them, a uniform image quality can be obtained with little brightness unevenness at the center, periphery, etc. of the screen.
[0091]
The S-polarized component illumination light emitted from the polarization beam splitter 152 enters the condenser lens 154. The condenser lens 154 has one or a plurality of components, has a positive refractive power, and has a function of further condensing the illumination light. The illumination light transmitted through the condenser lens 154 is bent in the optical axis direction by the mirrors 155 and 156 and enters the condenser lens 157. This condenser lens 157 makes the incident angle of the principal ray of the illumination light incident on the peripheral portion of the reflective liquid crystal display element 13 substantially perpendicular to the polarization beam splitter prism, and eliminates color unevenness caused by the angle dependency of the polarization beam splitter prism. Reduce.
[0092]
Next, the illumination light is incident on the G transmission RB reflection dichroic mirror 158. In this embodiment, the G transmissive RB reflecting dichroic mirror 158 has the same effect even if it is a dichroic mirror prism. Illumination light is divided into G light, R light, and B light by a G transmission RB reflection dichroic mirror 158, and is transmitted through the polarizing plates 25 and 7 and then incident on the polarization beam splitters 27 and 11 dedicated to colors. To do. The G light travels straight and enters the polarization beam splitter prism 27 dedicated to G. At this time, since the incident light is S-polarized light, it is reflected by the reflection surface of the polarizing beam splitter and enters the G-use reflective liquid crystal display element 29G. Further, the B light and the R light are transmitted through the polarizing plate 7, and then pass through the polarization rotation element 9 that rotates the polarization direction of only the light in the B light wavelength region, and the polarization of the B light is converted from S-polarized light to P-polarized light. Then, it is incident on the polarization beam splitter prism 11 dedicated to R and B. Here, the B light travels straight through the RB-dedicated polarization beam splitter 11 and enters the B-use reflective liquid crystal display element 13B. On the other hand, the R light remains as S-polarized light and is reflected by the reflection surface of the R and B-dedicated polarization beam splitter 11 and then enters the R reflective liquid crystal display element 13R.
[0093]
The above arrangement example is one specific example, and the present embodiment is not limited to this. R may be converted to P-polarized light, and the positions of the R and B reflective liquid crystal display elements may be interchanged. Separately, the positions of the R and B reflective liquid crystal display elements 13R and 13B and the polarizing beam splitter 11 and the G reflective liquid crystal display element 29G and the polarizing beam splitter prism 27 are switched, and the like. Even when the optical system shown in FIG. 4 is used, the effect of the present embodiment can be obtained.
[0094]
The incident illumination light is then converted into image light whose polarization has been rotated in accordance with the image signal by the reflective image display element 13 for each color, and is again incident on the polarization beam splitters 11 and 27 for each color, and S is reflected on the reflection surface. Polarized light is reflected and P-polarized light is transmitted.
[0095]
Each of the reflective image display elements 13R, 39G, and 13B is provided with a number of liquid crystal display units corresponding to the pixels to be displayed (for example, 1024 pixels in the horizontal direction and 768 pixels in the vertical direction and 3 colors). Then, according to a signal driven from the outside, each angle of polarization rotation of each pixel changes, and light that is orthogonal to the incident polarization direction is reflected by the polarization beam splitters 11 and 27 for light to be displayed brightly. Image light is emitted toward the projection lens 24. When the display is dark, the reflected light has the same polarization direction as that of the incident light and is returned to the light source side along the incident light path.
[0096]
Thereafter, the RGB light components that have become image light are synthesized again by the G-transmitting RB reflecting dichroic mirror prism 159, and pass through the projection lens 24 such as a zoom lens to reach the screen. Images formed on the reflective liquid crystal display elements 13R, 29G, and 13B by the projection lens 24 are enlarged and projected on a screen to function as a display device. In the reflective liquid crystal display device using the three reflective liquid crystal display elements, a power source 160 drives a lamp, a panel, and the like.
[0097]
Therefore, the configuration using two polarization beam splitters dedicated to G and RB according to the present invention can achieve a reduction in size and weight, and further, can control color purity, improve color unevenness, and improve performance at the same time. Therefore, a compact, high-brightness, high-quality projection-type image display device can be realized.
[0098]
Further, the projection display apparatus of the present invention has a transmission efficiency or a reflection efficiency of the P-polarized light with respect to the light of a specific wavelength band incident on the polarization beam splitter disposed almost immediately before the reflective liquid crystal display element, S A configuration in which a film for exclusive use in a limited wavelength region is applied so that the transmission efficiency or reflection efficiency of polarized light takes a peak value, for example, an optimum dielectric multilayer film for exclusive use for G light in the wavelength band from about 500 nm to about 600 nm. G-polarized polarization beam splitter 27 with an optimal dielectric multilayer film for exclusive use of R light and B light in two or more wavelength bands from near 400 nm to near 500 nm and from near 600 nm to near 700 nm. The RB beam splitter 11 can be used, the dielectric multilayer film can be easily formed, and the transmission efficiency and the reflection efficiency as well as the above-described light detection efficiency are also conventional. Better than. Therefore, it is possible to provide a reflective liquid crystal display device that achieves both high-precision color reproducibility, high brightness, and high-efficiency contrast. Furthermore, by adding an inclined film to the dichroic film in some cases, it is possible to provide an image with higher uniformity and high color purity.
[0099]
In addition, the projection display device of the present invention has a configuration in which the polarizing plates 25 and 7 are installed after separating the G light and the R and B lights and before entering the polarizing beam splitter prisms 11 and 27. For this reason, it is easy to provide a color filter or dichroic filters 161 and 162 for correcting the color purity of G light and R light on the light incident surface of the polarizing plate, thereby achieving both high monochromatic color purity and high light utilization rate. I can do it.
[0100]
FIG. 8 is a schematic top view of a liquid crystal projector optical system according to the sixth embodiment of the present invention. The seventh embodiment of the present invention is different from the fifth embodiment of the present invention in that there are three condenser lenses 157, 163R, 163G, and 163B, and the installation positions are the reflective liquid crystal display element 13 and the polarization beam splitter prism. 27,11. Further, the dichroic thin film of the color separation dichroic mirror is an inclined thin film.
[0101]
In this embodiment, the reflective liquid crystal display element 13 and the condenser lens 163 are integrated. However, when the reflective liquid crystal display element 13 and the condenser lens 163 are installed apart from each other, or the condenser lens 163 is installed upside down, the polarizing beam splitter prisms 27 and 11 The same effect can be obtained when they are integrated.
[0102]
The action of the optical system of this embodiment with respect to R, G, and B light is substantially the same as that of the fifth embodiment. Further, in this embodiment, the position of the condenser lens is set almost immediately before the reflective liquid crystal display element, so that the internal reflection in the polarization beam splitters 27 and 11 and the dichroic mirror prism 159 is reduced, and the image quality with higher contrast is increased. It is the structure which can obtain a simple image.
[0103]
Further, in this embodiment, since the chief ray angle of the illumination light corresponding to the peripheral portion of the screen incident on the dichroic mirror is not parallel to the chief ray corresponding to the center of the screen, color unevenness occurs in the horizontal direction of the image. Although it is easy, an image with little color unevenness can be obtained by using a dichroic thin film as an inclined thin film.
[0104]
In this embodiment, the first synthetic focus of the condenser lens 163 is set in the vicinity of the diaphragm surface of the projection lens 24, the central axis of the condenser lens 163 is made coincident with the center of the reflective liquid crystal display element 13, and the projection lens. By decentering the central axis of 24 upward with respect to the center of the panel, the projected image can be decentered upward with respect to the projector set, and a good image with little difference in luminance between the image center and the peripheral portion can be obtained.
[0105]
FIG. 9 is a schematic top view of a liquid crystal projector optical system according to a seventh embodiment of the present invention. The seventh embodiment of the present invention is different from the sixth embodiment of the present invention in that a condenser lens 164 is provided and the combined focal length of the condenser lens 165 and the condenser lens 164 is the same as that of the sixth embodiment. The condenser lens 163 is set to be substantially the same.
[0106]
The action of the optical system of this embodiment on R, G, and B light is substantially the same as that of the sixth embodiment. In this embodiment, by dividing the condenser lens into two, it is possible to design the power of the condenser lens 165 to be smaller, and to reduce the focus deterioration of the image. In addition, since the angle of the principal ray passing through the polarization beam splitter prisms 11 and 27 can be made smaller, the occurrence of color unevenness can be made smaller.
[0107]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain an optical engine for a liquid crystal projector having a high light utilization rate and a high image contrast, and a liquid crystal projector using the same.
[0108]
Further, according to the present invention, it is possible to obtain an optical engine and a liquid crystal projector for a liquid crystal projector that are small and light, have little color unevenness in an image, and have good focusing performance.
[Brief description of the drawings]
FIG. 1 is a top view of a liquid crystal projector optical system according to a first embodiment of the present invention.
FIG. 2 is a graph showing the wavelength characteristics of a polarization rotator used for the liquid crystal projector optical system of the first embodiment of the present invention, for rotating the polarization of B light.
FIG. 3 is a top view of a liquid crystal projector optical system according to a second embodiment of the present invention.
FIG. 4 is a top view of a liquid crystal projector optical system according to a third embodiment of the present invention.
FIG. 5 is a graph showing the transmittance of a polarizing plate used in the liquid crystal projector optical system according to the first embodiment of the present invention and having polarization absorption characteristics for B light.
FIG. 6 is a top view of a liquid crystal projector optical system according to a fourth embodiment of the present invention.
FIG. 7 is a top view of a liquid crystal projector optical system according to a fifth embodiment of the present invention.
FIG. 8 is a top view of a liquid crystal projector optical system according to a sixth embodiment of the present invention.
FIG. 9 is a top view of a liquid crystal projector optical system according to a seventh embodiment of the present invention.
FIG. 10 is a top view of a conventional reflective liquid crystal projector optical system.
FIG. 11 is a top view of a conventional liquid crystal projector combining optical system.
FIG. 12 is a top view of a conventional reflective liquid crystal projector optical system.
FIG. 13 is a graph showing wavelength transmittance characteristics of a polarizing beam splitter prism.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Light source, 3 ... Polarization conversion element, 5 ... G reflection RB transmission dichroic mirror, 7 ... Polarizing plate, 9 ... Polarization rotation element which rotates only polarized light of B light, 11 ... Polarization beam splitter, 13R ... R reflection type A liquid crystal display element, a reflective liquid crystal display element of 13B... B, a polarization rotating element for rotating the polarization of only B light, a polarizing plate having a property of absorbing the polarization of only B light, a polarization beam splitter, 24 ... projection lens, 25 ... polarizing plate, 27 ... polarization beam splitter, 29G ... G reflective liquid crystal display element, 34 ... polarization rotation element, 39 ... dichroic mirror prism, 42 ... polarization rotation that rotates only the polarization of R light Element: 43... Polarization rotating element for rotating only polarized light of R light, 46... Polarizing plate, 49... Chamfered portion, 83 a. Color separation / combination prism, 86R ... R reflective dichroic mirror, 86B ... B reflective dichroic mirror, 87R ... R reflective liquid crystal display element, 87G ... G reflective liquid crystal display element, 87B ... B reflective liquid crystal display element, 89 ... Polarizing plate, 90 ... Projection lens, 93R ... R image display element, 93G ... G image display element, 93B ... B image display element, 95 ... Polarizing beam splitter prism, 96 ... Rotating polarized light of only G light Polarization rotator, 98... Polarization beam splitter, 99... Polarization rotation element that rotates polarization of only B light, 101... Projection lens, 110... RG light source, 112. Polarization rotating element, 115... Polarization beam splitter prism, 116 R... R reflective liquid crystal display element, 116 G... G reflective liquid crystal display element. 117R ... R P-polarized light, 117G ... G S-polarized light, 118 ... polarization rotating element that rotates only G light polarization, 120 ... polarization beam splitter prism, 122 ... polarization rotating element that rotates only B light polarization, 123: Polarizing plate, 124: Projection lens, 125 ... B light source, 127 ... Polarization conversion element, 130B ... B reflective liquid crystal display element.

Claims (26)

A light source that emits light;
A polarization conversion element for unifying the polarization of the light;
In order to separate the light whose polarization is unified by the polarization conversion element into three colors of R, G, and B, the light of the first color of the R, G, and B is separated from the light emitted from the light source. A dichroic mirror,
Three reflective liquid crystal display elements arranged corresponding to the three colors;
A first polarizing beam splitter prism disposed substantially immediately before the reflecting surface of the reflective liquid crystal display element corresponding to the first color light;
Separating incident light from which the light of the first color is incident, separating light incident from the incident surface into light of the second color and light of the third color, and corresponding to each of the colors Of the light reflected by the reflective liquid crystal display element disposed in a second position, a second combining surface for combining the light of the second color and the light of the third color, and an output surface for emitting the combined light. A polarizing beam splitter prism;
A first wavelength-selective polarization rotation element that is disposed on the incident surface and rotates the polarization of the light of the second color or the light of the third color;
A second wavelength-selective polarization rotation element that is disposed on the exit surface and rotates the polarization of the light of the second color or the light of the third color;
A dichroic mirror prism that combines light from the first polarization beam splitter prism and light from the second wavelength-selective polarization rotation element;
An optical engine having a projection lens that projects light synthesized by the dichroic mirror prism. A light source that emits light;
A polarization conversion element for unifying the polarization of the light;
In order to separate the light whose polarization is unified by the polarization conversion element into three colors of R, G, and B, the light of the first color of the R, G, and B is separated from the light emitted from the light source. A dichroic mirror,
Three reflective liquid crystal display elements arranged corresponding to the three colors;
A first polarizing beam splitter prism disposed substantially immediately before the reflecting surface of the reflective liquid crystal display element corresponding to the first color light;
Separating incident light from which the light of the first color is incident, separating light incident from the incident surface into light of the second color and light of the third color, and corresponding to each of the colors Of the light reflected by the reflective liquid crystal display element disposed in a second position, a second combining surface for combining the light of the second color and the light of the third color, and an output surface for emitting the combined light. A polarizing beam splitter prism;
A first wavelength-selective polarization rotation element that is disposed on the incident surface and rotates the polarization of the light of the second color or the light of the third color;
A second wavelength-selective polarization rotation element that is disposed on the exit surface and rotates the polarization of the light of the second color or the light of the third color;
A third polarizing beam splitter prism that combines light from the first polarizing beam splitter prism and light from the second wavelength selective polarization rotation element;
An optical engine having a projection lens that projects the light combined by the third polarization beam splitter prism. The two reflective liquid crystal display elements corresponding to the second color light and the third color light are arranged so as to be substantially adjacent to each other and at an angle of about 90 degrees,
3. The second polarizing beam splitter prism according to claim 1, wherein the second polarizing beam splitter prism is disposed substantially immediately before both reflecting surfaces of the two reflective liquid crystal display elements. Optical engine. 4. The light emitted from the first and second polarizing beam splitter prisms is incident from two surfaces of the dichroic mirror prism or the third polarizing beam splitter prism, respectively. The optical engine according to any one of the above. The first color is G,
5. The optical engine according to claim 4, wherein the polarization direction of the G light incident on the third polarization beam splitter prism or the dichroic mirror prism is substantially orthogonal to the polarization direction of the R and B light. The first color is G,
3. The device according to claim 1, wherein the first and second wavelength-selective polarization rotation elements rotate the polarization direction of either R or B light by approximately 90 degrees. 4. The optical engine described in 1. The said 1st and 2nd wavelength selective polarization rotation element rotates a polarization | polarized-light with respect to the light of the wavelength band near 400 nm-500 nm, or the wavelength band near 600 nm-700 nm, It is characterized by the above-mentioned. Optical engine. In the first and second wavelength selective polarization rotation elements, the polarization directions of light having a wavelength band of 400 nm to 500 nm and light having a wavelength band of 600 nm to 700 nm incident in the same polarization direction are substantially orthogonal to each other. The optical engine according to any one of claims 6 to 7, wherein the polarization of any one of the lights is rotated. The first color is G,
5. The optical engine according to claim 1, wherein the first polarization beam splitter prism has a peak value of transmission efficiency or reflection efficiency with respect to G. 6. The first color is G,
5. The optical device according to claim 1, wherein the second polarization beam splitter prism has a peak value of transmission efficiency or reflection efficiency with respect to R or B light. 6. engine. 3. The optical device according to claim 1, wherein the second wavelength-selective polarization rotation element and the third polarization beam splitter prism are bonded together to form an integrated body. engine. The first wavelength-selective polarization rotation element, the second polarization beam splitter prism, the second wavelength-selective polarization rotation element, and the dichroic mirror prism are bonded together to form an integral body. The optical engine according to any one of claims 1, 4, and 5. The dichroic mirror separates G light and R and B light, and rectifies polarized light before the first polarizing beam splitter prism and before the second polarizing beam splitter prism. The optical engine according to claim 1, further comprising an element for performing the operation. The optical engine according to claim 13, wherein the element for rectifying the polarized light is a polarizing plate. 15. The optical engine according to claim 13, further comprising a filter for adjusting color purity of light on a light incident side of an element for rectifying each of the polarized lights. The optical engine according to claim 15, wherein the filter for adjusting the color purity of the light is a color filter or a dichroic filter. The first color is G,
The reflective liquid crystal display element corresponding to the R light is disposed on a surface opposite to the incident surface,
The reflective liquid crystal display element corresponding to the light of B is disposed on the surface opposite to the emission surface,
The optical engine according to claim 13, wherein a polarizing plate corresponding to the B light is disposed on the incident surface. The optical engine is
A principal ray of light incident on the first polarizing beam splitter prism is incident substantially vertically on the peripheral portion of the three reflective liquid crystal display elements, and between the light source and the first polarizing beam splitter prism The optical engine according to claim 1, further comprising a condenser lens disposed therebetween. The optical engine according to claim 18, wherein the condenser lens is disposed on a reflective surface side of the three reflective liquid crystal display elements. The condenser lens is arranged such that a central axis of the condenser lens substantially coincides with a central axis of each of the three reflective liquid crystal display elements, and is decentered with respect to the central axis of the projection lens. The optical engine according to claim 19. 20. The optical engine according to claim 19, wherein the dichroic reflective thin films of the dichroic mirror and the dichroic mirror prism are inclined thin films whose reflection wavelength characteristics are changed by changing the film thickness in a certain direction. 3. The optical engine according to claim 2, wherein a size of the third polarizing beam splitter prism is larger than sizes of the first polarizing beam splitter prism and the second polarizing beam splitter prism. The optical engine according to claim 22, wherein the third polarizing beam splitter prism has a chamfered portion. 2. The optical engine according to claim 1, wherein black paint is applied to both upper and lower surfaces of the first polarizing beam splitter prism, the second polarizing beam splitter prism, and the dichroic mirror prism. 3. The optical engine according to claim 2, wherein black paint is applied to both upper and lower surfaces of the first polarizing beam splitter prism, the second polarizing beam splitter prism, and the third polarizing beam splitter prism. An optical engine according to any one of claims 1 to 25;
A liquid crystal projector comprising a drive circuit for driving the three reflective liquid crystal display elements.

Images