JP2002122810A - Optical engine and video display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten and equalize an optical distance, to reduce the deviation of pixel convergence and to realize high contrast in the optical system of a video display device using a display element. SOLUTION: A color separating and synthesizing optical system is provided with 1st and 2nd dichroic optical devices and two polarizing beam splitters. The 1st dichroic optical device and the two polarizing beam splitters form a 1st path for color-separating incident light from a light source side and radiating it toward the display element, and the two polarizing beam splitters and the 2nd dichroic optical device form a 2nd path for synthesizing the reflected light from the display element and emitting it to a projection optical system side. Then, the 1st dichroic optical device separates the incident light RGB into the light B and the light RG in the 1st path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical engine such as a color separation / synthesis optical system in an image display technique for forming an image by irradiating a light from a light source side to a display element by color separation.

[0002]

2. Description of the Related Art As a prior art of this kind, there is one described in, for example, US Pat. No. 5,751,384. FIG. 4 shows a configuration example when a reflection type display element is combined with the technique described in the patent specification as a conventional example. In this configuration, the RG light and the B light are made to enter two separate polarizing beam splitter prisms from separate light source units, irradiate the reflective liquid crystal display elements provided on each side thereof, and reflect the reflected light of the display elements. Is combined with one of the two polarizing beam splitter prisms and emitted to the projection lens side. A polarization rotation element (retarder) is provided between the two polarization beam splitter prisms to rotate the polarization of R light of the reflected light from the display element side. In FIG. 4, light emitted from a first light source 110 that generates R and G light is converted into substantially parallel light 111 by a reflector, and R light 111R and G light
It becomes light 111G. After the R light 111R and the G light 111G are both converted to P-polarized light by the polarization conversion element 112, the polarization direction of the G light is rotated by the polarization rotation element 113 to be changed to S-polarized light 114G. On the other hand, the R light 111R passes through the polarization rotation element 113 as P-polarized light. The R light P-polarized light 114R and the G light S-polarized light 114G that have exited the polarization rotator 113 are incident on a first polarization beam splitter prism 115, and the R light P-polarized light 114R travels straight on a splitter surface 115a. And S-polarized light of G light 11
4G is reflected, and each of the reflective liquid crystal display elements 116
R, incident on 116G. In each of the display elements,
R image light is S-polarized light 117R, G image light is P-polarized light 11
Reflected as 7G, polarizing beam splitter prism 1
15 again. Polarizing beam splitter prism 1
On the 15 splitter surface 115a, the R S-polarized light 117
R is reflected, and G P-polarized light 117G goes straight. As a result, the two image lights are combined in the polarizing beam splitter prism 115. The composite image light of the S-polarized light R light and the P-polarized light G light is incident on the wavelength-selective polarization rotating element 118, where only the G light is rotated in the polarization direction to produce the S-polarized light 119G. Becomes R S-polarized light 117
R is emitted as S-polarized light 119R without changing the polarization direction. The R and G light converted to the S-polarized light enter the second polarizing beam splitter prism 120, are reflected by the splitter surface 120a, and are emitted to the projection lens 124 side. On the other hand, the B light 126 emitted from the second light source 125
B is converted into B S-polarized light 128B by the polarization conversion element 127.
And enters the second polarizing beam splitter prism 120. The polarizing beam splitter prism 1
The B S-polarized light 129B reflected by the 20 splitter surface 120a enters the reflective liquid crystal display element 130B corresponding to the B light. The display element converts the image light into P-polarized light 13 of B light.
The light is reflected as 1B, and is incident on the second polarizing beam splitter prism 120 again. P-polarized light 131 of the B light
B transmits through the splitter surface 120a and
Go straight to 4 side. In this manner, the image light, which is white light, in which the B light is P-polarized light and the R light and G light are S-polarized light, is incident on the polarization rotating element 122 for rotating the polarization of only the B light.
All of the GB light is converted into S-polarized light image light, and the projection lens 12
4 is enlarged and projected. The reflected light converted into image light to be displayed dark by the reflective liquid crystal display elements 116R, 116G and 130B is guided toward the light source by the polarizing beam splitter prisms 115 and 120. The polarizing plate 123 is provided to prevent a part of the reflected light from reaching the projection lens and deteriorating the contrast of an image.

[0003]

SUMMARY OF THE INVENTION In view of the above prior art, the problems of the present invention are as follows: (1) In order to secure the focusing performance of the projection lens system, the optical distance from each display element to the projection lens system must be mutually different. (2) optical distances from the light source to each display element are substantially equal and short to reduce color unevenness of the image and increase luminance;
(3) A configuration in which the pixel convergence deviation of each display element is suppressed, (4) A configuration capable of reducing the size and weight, and the like. An object of the present invention is to provide a technique capable of solving the above problems.

[0004]

In order to solve the above-mentioned problems, the present invention provides: (1) light from a light source side is color-separated and applied to a display element, and reflected light from the display element is synthesized. An optical engine for a video display device having a color separation / combination optical system configured to emit light to the projection optical system side, wherein the color separation / combination optical system includes first and second dichroic optical elements, and the display element includes: The first dichroic optical element and the two polarizing beam splitters color-separate incident light from the light source side to the display element. Forming a first path for irradiation, wherein the two polarizing beam splitters and the second dichroic optical element combine reflected light from the display element and emit the reflected light to the projection optical system side; Forming a second path, In the first path, the first dichroic optical element is RGB.
The configuration is such that incident light is color-separated into B light and RG light. (2) For a video display device provided with a color separation / combination optical system configured to irradiate light from a light source side to a display element after separating the color and irradiate the display element with the reflected light from the display element. In the optical engine, the color separation / combination optical system includes first and second dichroic optical elements, and first and second polarization beam splitters each having the display element disposed on a side surface, The first and second dichroic optical elements are disposed substantially diagonally to each other such that the respective dichroic reflection films are substantially on an extension of each other, and the first and second polarizing beam splitters are also disposed at respective positions. A configuration in which the polarizing beam splitter films are disposed substantially diagonally to each other so as to be substantially on an extension of each other, and the first dichroic optical element color-separates the RGB incident light into B light and RG light. I do. (3) For a video display device equipped with a color separation / combination optical system configured to irradiate light from a light source side to a display element after separating the color and irradiate the display element with reflected light from the display element. In the optical engine of the above, the color separation / synthesis optical system includes a first and a second two dichroic optical elements, two polarization beam splitters having the display element arranged on a side surface, and a polarization rotation element. A first path through which the first dichroic optical element, the two polarization beam splitters, and the polarization rotation element separate the color of incident light from the light source side and irradiate the display element with the light. The two polarizing beam splitters and the second dichroic optical element form a second path for combining reflected light from the display element and emitting the reflected light to the projection optical system side, In one path, the first dichroic Click optical element is color separation of RGB incident light into B light and RG light, the polarization rotating element is configured such that so as to rotate the G light out of the RG incident light. (4) In the above (1), (2) or (3), the first dichroic optical element is a dichroic mirror, and the second dichroic optical element is a dichroic prism. (5) In the above (1), (2) or (3), the second dichroic optical element has a property of transmitting P-polarized B light, reflecting S-polarized G light and P-polarized R light. It is assumed to have a configuration. (6) In the above (1), (2) or (3), the polarizing beam splitter is formed in a prism shape, and is coupled to the second dichroic optical element in a close contact state. (7) In the above (1), (2) or (3), the second dichroic optical element is a dichroic prism having a larger configuration than the polarizing beam splitter. (8) In the above (1), (2) or (3), the second dichroic optical element is formed integrally with the polarizing beam splitter. (9) In any one of the above (1) to (8), the display element is constituted by three liquid crystal panels. (10) A video display device comprising the optical engine according to any one of the above (1) to (9) and a drive circuit for driving the engine. The dichroic reflection surface of the first dichroic optical element has such characteristics that S-polarized light is reflected in a wide band, and the reflection wavelength range is narrow for P-polarized light. Therefore, the dichroic reflecting surface reflects almost all of the G light including the B light region for the S polarized light,
For P-polarized light, B light including the G light region is transmitted, and R light is transmitted.
It reflects almost all of the light. The configuration in which the size of the second dichroic optical element is made larger than the size of the polarizing beam splitter prevents or reduces blurring of image light inside the prism. Further, the configuration in which the second dichroic optical element and the polarizing beam splitter are integrated reduces internal reflection of the prism.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. In the first embodiment, the color separation / combination optical system is configured by using two dichroic optical elements, a dichroic mirror and a dichroic prism, two polarization beam splitter prisms, and a polarization rotation element. A mirror, the two polarization beam splitters, and the polarization rotator form a path for color-separating the incident light from the light source side and irradiating the display element with the light; the two polarization beam splitters and the dichroic; A prism forms a path for combining reflected light from the display element and emitting the reflected light to the projection optical system side. The dichroic mirror color-separates the RGB incident light into B light and RG light. Is the RG
The G light of the incident light is rotated. The dichroic mirror and the dichroic prism are arranged at substantially diagonal positions so that the respective dichroic reflection films are substantially on the extension of each other, and the two polarization beam splitters are also arranged at the respective polarization beam splitter films. The dichroic prism and the two polarization beam splitters are arranged at substantially diagonal positions to each other so as to lie substantially on an extension of the dichroic film and the splitter film in a positional relationship such that the dichroic film and the splitter film are orthogonal to each other. They are joined in close contact.

In FIG. 1, 1 is a light source and 3 is white light.
A polarization conversion element that converts polarized light, 5 is a dichroic mirror that transmits B light and reflects R light and G light, 6 is a polarizing plate, and 7 rotates the polarized light for G light and turns S polarized light into P polarized light. A polarization rotating element to be changed, 8 and 21 are polarization beam splitter prisms, 14 is a dichroic prism for synthesis, and 9R, 11G and 22B are display elements such as reflective liquid crystal panels. The dichroic mirror 5 emits B light, RG
The light is separated, the polarizing beam splitter prism 8 separates and combines the R light and the G light, and the combining dichroic prism 14 combines the B image light and the RG image light. The size of the combining dichroic prism 14 is made larger than the size of the polarizing beam splitter prisms 8 and 21, and the image light emitted from each display element passes through the polarizing beam splitter prisms 8 and 21 and enters the combining dichroic prism 14. In such a case, the internal side surface is designed so that no or little jolts occur. The polarizing plate 6
Is for increasing the contrast of an image by absorbing P-polarized light partially contained in the incident light 4R, 4G, and 4B. The white light emitted from the light source 1 is an R light component 2R,
It comprises a G light component 2G and a B light component 2B. The white light is converted into S-polarized light by the polarization conversion element 3, and the S light of R
The polarized lights 4R, 4G become S polarized light 4G, and B become S polarized light 4B, and enter the dichroic mirror 5. In the dichroic mirror 5, the B S-polarized light 4B passes through the dichroic surface, and the R S-polarized light 4R and the G S-polarized light 4G
Is reflected by the dichroic surface. S-polarized light 4B transmitted through the dichroic surface of the dichroic mirror 5
Is incident on the polarizing beam splitter prism 21, is reflected on the splitter surface 21a, and is irradiated on the display element 22B. In the display element 22B, the light is modulated in accordance with the image signal and emitted as image light (P-polarized light B image light). The light passes through the polarizing beam splitter prism 21 again and enters the synthesizing dichroic prism 14. On the other hand, R reflected on the dichroic surface of the dichroic mirror 5
The S-polarized light 4R and the G S-polarized light 4G pass through the polarizing plate 6 and the polarization rotating element 7 and enter the polarization beam splitter prism 8. The G S-polarized light 4G is converted into P-polarized light when passing through the polarization rotating element 7, and thus enters the polarization beam splitter prism 8 as the P-polarized light 12G. R S incident on the polarizing beam splitter prism 8
The polarized light 4R is reflected on the splitter surface 8a and then applied to the display element 9R, and the G P-polarized light 12G is transmitted through the splitter surface 8a and applied to the display element 11G. In each of the display elements 9R and 11G, the irradiated polarized light is modulated in accordance with an image signal, and emitted as respective image light, that is, R image light of P polarized light and G image light of S polarized light. The light passes through the polarizing beam splitter prism 8 and is incident on the dichroic prism 14 for synthesis.
In the combining dichroic prism 14, the B image light of the P-polarized light, the R image light of the P-polarized light, and the G image light of the S-polarized light are combined and emitted to the projection lens system 16 side. .

FIG. 2 shows the transmission wavelength characteristics of the dichroic film of the dichroic prism 14 for synthesis in the first embodiment. In the characteristics of FIG. 2, the horizontal axis is the wavelength of light,
The vertical axis represents the transmittance. For S-polarized light, it transmits B region light (wavelength approximately 400 to 500 nm), R region light (wavelength approximately 600 to 700 nm) and G region light (wavelength approximately 500 to 500 nm).
600 nm), and for P-polarized light, transmits B-region light and G-region light and reflects R-region light. In the first embodiment, B light and R light are P-polarized light and G light is S-polarized light.
The R light and the G light are reflected.

According to the first embodiment, (1) since the optical distances from each display element to the projection lens system are substantially equal and short, the back focus of the projection lens can be shortened and the focusing performance can be improved. (2) Since the optical distances from the light source to each display element are substantially equal and short, it is possible to reduce the color unevenness of the image and increase the brightness. (3) A component such as a wavelength-selective polarization rotator is provided between the synthesizing dichroic prism 14 and the polarization beam splitters 8 and 21 because of the configuration for first separating the B light from the white light from the light source side. No need. (4) As a result of (3), the combining dichroic prism 14 and the two polarizing beam splitters 8,
21 can be bonded to each other in close contact with each other. Therefore, both mechanically and optically, the bonding between the two can be enhanced, the resistance to temperature changes and external forces is increased, and optical obstruction factors are eliminated to prevent or reduce convergence deviation. be able to. Further, reflection at the prism entrance / exit surface can be reduced, and image contrast can be improved. (5) G light and B light can be combined with each other without loss, and the light utilization can be improved and a bright screen can be formed. (6) Since the size of the dichroic prism 14 for synthesis is larger than each of the two polarization beam splitters 8 and 21, the dichroic prism for synthesis 1
4 can be suppressed, and as a result, the contrast can be increased. Further, a bright screen can be formed by increasing the light utilization rate. (7) The optical engine and the device using it can be reduced in size and weight.

FIG. 3 shows a second embodiment of the present invention. The second embodiment is different from the first embodiment in that the mutually contacting portions of the polarizing beam splitter prism and the synthesizing dichroic prism are integrated, and a new integrated member 3 is formed.
1, 32. Here, a dichroic mirror is deposited on the joint surface 31a of the integrated member 31 and the integrated member 32. Further, a polarizing beam splitter film is deposited on a joining surface 33a between the polarizing beam splitter prism piece 33 and the integrated member 31 and on a joining surface 34a between the polarizing beam splitter prism piece 34 and the integrated member 32. Further, the integrated members 31 and 32 are configured to have dimensions larger than those of the polarizing beam splitter prism pieces 33 and 34. According to the second embodiment,
In addition to the same effects as in the first embodiment, the number of prism pieces can be reduced to four pieces, and a simpler configuration can be achieved. It is also possible to reduce the internal reflection of the prism, thereby improving the contrast of the image.

[0010]

According to the present invention, it is possible to provide an optical engine and an image display device which have a high light utilization rate and can achieve a high contrast. Further, according to the present invention, it is possible to provide a technique which has a small convergence deviation, a small color unevenness of an image, and a good focus performance. Further, the size and weight can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an example of optical characteristics of a dichroic prism used in the first embodiment of the present invention.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light source, 3 ... Polarization conversion element, 5 ... Dichroic mirror, 6, 20 ... Polarizer, 7 ... Polarization rotation element,
8, 21 ... polarizing beam splitter prism, 9R, 11
G, 22B: display element, 14: dichroic prism, 16: projection lens, 31, 32: integrated member,
33, 34: polarizing beam splitter prism pieces.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Takuya Shomei 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Digital Media System Division of Hitachi, Ltd. (72) Inventor Tsutomu Nakajima Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa 292 F-term in Hitachi Digital Media Systems Division (Reference) 2H042 CA06 CA14 CA17 2H049 BA05 BA07 BA43 BB03 BC22 2H099 AA11 BA09 CA02 CA11 DA05

Claims (10)

[Claims] An image display having a color separation / combination optical system configured to irradiate light from a light source side to a display element after irradiating the display element with light, combine reflected light from the display element, and emit the combined light to a projection optical system side. In the optical engine for an apparatus, the color separation / synthesis optical system includes first and second dichroic optical elements, and two polarization beam splitters each including the display element arranged on a side surface. The first dichroic optical element and the two polarization beam splitters form a first path for color-separating the incident light from the light source side and irradiating the display element with the light. The second dichroic optical element forms a second path for synthesizing the reflected light from the display element and outputting the combined light to the projection optical system, and the first dichroic in the first path. Optical element converts RGB incident light to B light An optical engine characterized in that it is configured to separate colors into light and RG light. 2. An image display comprising a color separation / combination optical system configured to irradiate light from a light source side to a display element after irradiating the display element with light, combine reflected light from the display element, and emit the combined light to a projection optical system side. In an optical engine for an apparatus, the color separation / synthesis optical system includes first and second dichroic optical elements, and first and second polarization beam splitters having the display elements arranged on side surfaces. The first and second dichroic optical elements are disposed at substantially diagonal positions so that the respective dichroic reflection films are substantially on the extension of each other, and the first and second polarization beam splitters are also provided. The respective polarizing beam splitter films are disposed substantially diagonally to each other so as to be substantially on an extension of each other, and the first dichroic optical element converts the RGB incident light into B light and R light.
An optical engine, wherein color separation into G light is performed. 3. An image display having a color separation / combination optical system configured to irradiate light from a light source side to a display element after irradiating the display element with light, and to combine reflected light from the display element and emit the combined light to a projection optical system side. In an optical engine for an apparatus, the color separation / synthesis optical system includes a first and a second two dichroic optical elements, and the display element is disposed on a side surface.
The first dichroic optical element, the two polarization beam splitters, and the polarization rotator, color-separate incident light from the light source side. A first method for irradiating the display element
And the two polarization beam splitters and the second dichroic optical element form a second path for combining reflected light from the display element and emitting the reflected light to the projection optical system side, In the first path, the first dichroic optical element color-separates the RGB incident light into B light and RG light, and the polarization rotation element rotates the G light among the RG incident light. An optical engine, characterized in that: 4. The device according to claim 1, wherein the first dichroic optical element is a dichroic mirror, and the second dichroic optical element is a dichroic prism.
An optical engine according to claim 1. 5. The device according to claim 1, wherein the second dichroic optical element is
4. The optical engine according to claim 1, wherein the optical engine has a characteristic of transmitting polarized B light, and reflecting S polarized G light and P polarized R light. 6. The optical engine according to claim 1, wherein the polarizing beam splitter is formed in a prism shape, and is coupled to the second dichroic optical element in a tight contact state. 7. The optical engine according to claim 1, wherein said second dichroic optical element is a dichroic prism having a larger size configuration than said polarizing beam splitter. 8. The optical engine according to claim 1, wherein said second dichroic optical element is formed integrally with said polarizing beam splitter. 9. The optical engine according to claim 1, wherein said display element comprises three liquid crystal panels. 10. An image display device comprising: the optical engine according to claim 1; and a drive circuit for driving the engine.