JP3191292B2 - Projection display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection display device that enlarges and projects an image formed by a reflection type light valve by a projection lens.

[Prior Art] Conventionally, a technique as described in JP-A-63-228887 and shown in FIG. 5 has been known. In FIG. 5, light emitted from a light source (29) is converted into a parallel light beam by a collimator lens (30), and separated into three primary colors of R, G, and B by a dichroic prism (31). The R component is a mirror (3
2) and (33) enter the PBS (34), the B component enters the PBS (37) via the mirrors (35) and (36), and the G component goes straight to the PBS (38). Each color light incident on each PBS is linearly polarized and incident on a reflection type liquid crystal light valve (39), (40), (41), and the polarization plane of the incident light is independently modulated for each pixel. Is reflected. The reflected light from the reflective liquid crystal light valves (39), (40), (41) is synthesized by a dichroic mirror (42),
The image is enlarged and projected on the screen (44) by the projection lens (43).

[Problems to be Solved by the Invention] However, in the conventional technique, as is apparent from FIG. 5, the number of optical components is very large and complicated, so that the optical system is large and expensive. In particular, the PBSs (34), (37), and (38) are very expensive due to the need for wideband performance, and arranging three of them is fatally costly. Further, since the optical path length of G from the light source (29) to the reflection type liquid crystal light valve (41) is shorter than that of R and B, a difference occurs in the divergence ratio of G light and R and B light. That causes color unevenness on the screen (44).

The projection display device of the present invention solves the above-described problems, and an object of the invention is to provide a low-cost projection display device that realizes a projection image without color unevenness.

Means for Solving the Problems The present invention separates light from a light source into two types of polarized light components, and synthesizes light modulated by the three reflective light valves. A first component that separates a first color light component from one of the two component light components separated by the polarization separating / combining means;
A first reflection type light valve that modulates the color light separated by the first color light separation unit, and the other of the two types of polarization component light separated by the polarization separation / combination unit. A second color light separating means for separating the second color light from the polarized light component, a second reflection type light valve for modulating the second color light separated by the second color light separating means, A third color light separation unit that separates the third color light from the other polarization component light after the second color light is separated by the second color light separation unit, and a third color light separation unit that separates the third color light. A third reflective light valve that modulates the third color light.

[Operation] The greatest advantage of the reflection type light valve used in the projection display device of the present invention is that the aperture ratio can be increased as compared with the transmission type light valve. Accordingly, a light valve having a smaller pixel density and a higher pixel density than a transmissive light valve can be realized, and is also useful as a light valve compatible with high vision. In addition, as a result of increasing the aperture ratio and reducing the size of the light valve, it is also possible to reduce the size of the display device and increase the light use efficiency. In addition, since the pixel electrode has a structure that shields the pixel switch from light, it is possible to prevent functional deterioration of the pixel switch element due to photoconduction.

Its configuration is simple compared to the prior art,
In particular, a single PBS greatly contributes to a reduction in the price of the display device. Also, if the R, G, B light valves are arranged at the same optical distance from the light source, each of the R, G, B color lights will reach their respective light valves in almost the same diverging state, suppressing color unevenness. Can be.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a conceptual diagram of a reflective projection type liquid crystal display device. Light emitted from the light source (1) is incident on the PBS (2) and is linearly polarized, and the reflected light is incident on the reflective liquid crystal light valve (3). The liquid crystal light valve (3) independently modulates the polarization plane of the incident light for each picture element and reflects it. The reflected light from the liquid crystal light valve (3) enters the PBS (2) again and is separated into transmitted light and reflected light according to the degree of modulation, and the transmitted light is screened by the projection lens (4). (5) An image is formed thereon.

FIG. 2 is a sectional view of a reflective liquid crystal light valve of the present invention. A liquid crystal layer (11) is sandwiched between a counter substrate (7) including a transparent electrode (6) and a reflective substrate (10) including a reflective electrode (8) and a pixel switch element (9). The picture element switch element (9) is composed of a source (12), a gate (13), and a drain (14), and the drain (14) is connected to a reflective electrode (8) in a contact hole (16) via an insulating layer (15). ) And connected. In this configuration, light incident from the counter substrate (7) side passes through the transparent electrode (6), undergoes polarization plane modulation by the liquid crystal layer (11), is reflected by the reflective electrode (8), and is again The light is emitted to the outside of the substrate (7). In order to prevent the function of the pixel switch element (9) from deteriorating due to light conduction at this time, the pixel switch element (9) has a structure that is shielded from this light by the reflective electrode (8).

FIG. 3 is a configuration diagram of an optical system in a reference example of the projection display apparatus of the present invention. The light emitted from the light source (1) is PBS
The light is linearly polarized by (2), S-polarized light is reflected, and P-polarized light is transmitted. The transmitted P-polarized light is separated into three primary colors of R, G and B by dichroic mirrors (17) and (18).
Light is incident on three liquid crystal light valves (19), (20), and (21) having the arrangement shown in the figure. The correspondence between the liquid crystal light valves (19), (20), (21) and the three primary colors R, G, B
It can be appropriately selected by adjusting the wavelength selection characteristics of the dichroic mirrors (17) and (18). Each color light incident on the liquid crystal light valves (19), (20), and (21) is reflected by the reflective electrode after independently modulating the polarization plane for each picture element, and is reflected by the dichroic mirror (17),
Synthesized by (18). Next, this combined light is PBS
The light entering (2) is separated into transmitted light and reflected light depending on the degree of modulation of the polarization plane. At this time, the transmitted light returns to the light source (1), and the reflected light enters the projection lens (22) and is enlarged and projected on the screen (5). Therefore, each liquid crystal light valve can be arranged at an optically equal distance from the light source. In addition, only the P-polarized light is used as the irradiation light in common to the three liquid crystal light valves for R, G, and B. In addition,
By arranging the dichroic mirrors (17) and (18) and the liquid crystal light valves (19), (20) and (21) on the reflection side of the PBS (2), only S-polarized light is used as irradiation light in the same manner as described above. It is also possible to use.

FIG. 4 is a configuration diagram of an optical system in an embodiment using both P-polarized light and S-polarized light as irradiation light. Light emitted from the light source (1) is linearly polarized by the PBS (2), and P-polarized light is transmitted and S-polarized light is reflected. Reflected S
The polarized light undergoes wavelength selection by the dichroic mirror (23), and then enters a reflective liquid crystal light valve (24). Here, for example, if the liquid crystal light valve (24) is for R, the dichroic mirror (23) has the property of transmitting R light and reflecting G and B light. At this time, the reflected G and B lights are reflected by the PBS (2) and return to the light source (1) again. On the other hand, the P-polarized light transmitted through PBS (2) is
The wavelength is selected by the dichroic mirror (25),
For example, G light is reflected, R and B light is transmitted, and the reflected G light is incident on a reflection type liquid crystal light valve (26). The R and B lights transmitted through the dichroic mirror (25) enter the dichroic mirror (27) and reflect, for example, the R light and transmit the B light. At this time, the reflected R light passes through the dichroic mirror (25) and the PBS (2) and returns to the light source (1), and the transmitted B light enters the reflection type liquid crystal light valve (28). Each color light incident on the liquid crystal light valves (24), (26) and (28) is reflected by the reflective electrode after its polarization plane is independently modulated for each picture element. The reflected light of each color is incident on the PBS (2), and the reflected light from the liquid crystal light valve (24) is transmitted through the P-polarized light according to the degree of the modulation, is incident on the projection lens (29), and is S-polarized. Is reflected back to the light source (1). The liquid crystal light valve (2
The reflected light from (6) and (28) transmits the P-polarized light and returns to the light source (1) according to the degree of the modulation, and the S-polarized light is reflected and enters the projection lens (29). Each color light thus incident on the projection lens (29) is enlarged and projected on the screen (5) by the projection lens (29). Therefore, also in this embodiment, each liquid crystal light valve can be disposed at an optically equal distance from the light source. Note that, similarly to the reference example in FIG. 3, in this embodiment, the liquid crystal light valve and the R, G, B
It goes without saying that the correspondence between the primary colors and the correspondence between the P, S polarized light as the irradiation light and the liquid crystal light valve can be freely selected as appropriate.

[Effect of the Invention] As described above, the projection type display device of the present invention has a 3
Since the light valves can be optically arranged at the same distance from the light source, it is possible to prevent color unevenness on the screen due to the difference in the divergence state of each color light on the optical path. In addition, since it has a simple configuration using a reflection-type light valve and a single PBS, a low-cost projection display device is realized, and the possibility of realizing a high-vision projection display device is high.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a reflection type projection type liquid crystal display device, and FIG.
FIG. 3 is a sectional view of a reflection type liquid crystal light valve of the present invention.
FIG. 1 is a configuration diagram of an optical system in a reference example of a projection type display device of the present invention, FIG. 4 is a configuration diagram of an optical system in an example of a projection type liquid crystal display device of the present invention, and FIG. It is a block diagram of the optical system of the reflection type projection type liquid crystal display device which is. (1) Light source (2) Polarizing beam splitter (3) Liquid crystal light valve (4) Projection lens (5) Screen (6) Transparent electrode (7) Counter substrate ( 8) Reflective electrode (9) Pixel switch element (10) Reflective substrate (11) Liquid crystal layer (15) Insulating layer (17), (18), (23), (25) ), (27)… dichroic mirror (19), (20), (21), (24), (26), (28)
LCD light valve

Claims (2)

(57) [Claims] 1. A polarization separation / combination means for separating light from a light source into two kinds of polarization component lights and combining light modulated by the three reflection-type light valves; A first color light separation unit that separates the first color light from one of the two types of separated polarization component light; and a first color light that modulates the color light separated by the first color light separation unit. A reflection type light valve; a second color light separation unit that separates a second color light from the other polarization component light of the two types of polarization component light separated by the polarization separation / synthesis unit; A second reflection type light valve that modulates the second color light separated by the color light separation unit; and the other polarization component light after the second color light is separated by the second color light separation unit. From the third color light Projection display device of the third color light separating means for separating, characterized by having a third reflective light valves for modulating the separated third color light by the third color light separation means. 2. The reflection type light valve according to claim 1, wherein the reflection type light valve is a reflection type liquid crystal light valve including a matrix-shaped pixel and a switch element for switching and controlling the pixel. A liquid crystal is interposed therebetween, and the switch element is shielded from light by the reflective electrode.