JP2952904B2 - Projection display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type liquid crystal display device that uses a plurality of liquid crystal light valves for image formation and performs image display by projecting.

2. Description of the Related Art Conventionally, a projection type liquid crystal display device using a plurality of liquid crystal light valves has been used to separate white light of a projection light source into three primary colors.
By using a combination of two dichroic mirrors, the three primary colors are extracted by reflecting blue light and green light at an incident angle of 45 degrees and transmitting the remaining red light, and modulating, combining, and projecting to display an image.

[Problems to be Solved by the Invention] However, in the above-described conventional technology, the projection light source does not become an ideal point light source, and tends to diffuse even when condensed. Since the light does not enter at 45 degrees, color unevenness occurs in both reflection and transmission depending on the incident angle due to the angle dependence of the dichroic mirror. There is a problem that the color light having the color unevenness is modulated by the liquid crystal light valve and synthesized by the dichroic prism, and the color unevenness is displayed as it is on the screen.

Therefore, the present invention solves such a problem,
An object of the present invention is to provide a projection-type liquid crystal display device that displays a high-quality image without color unevenness on a screen.

[Means for Solving the Problems] A projection display apparatus according to the present invention includes a light source, a reflector that reflects light from the light source, and a color separation unit that separates the light reflected by the reflector into three color lights. And 3 for modulating the color lights separated by the color separation means, respectively.
A projection type display device comprising: two modulation units; a color combination unit that combines the three colors of light modulated by the modulation unit; and a projection unit that projects the light combined by the color combination unit. The color separation unit is separated by a first dichroic mirror that separates three color lights emitted from the light source into a first color light and second and third color lights, and is separated by the first dichroic mirror. A second dichroic mirror that separates the second and third color lights into the second color light and the third color light, wherein the color synthesizing unit is arranged along a bonding surface of the four prisms. A first reflection surface for reflecting the first color light and a second reflection surface for reflecting the third color light, wherein the reflector converts the light from the light source from several degrees to several degrees. The dichroic with a diffusion angle of 10 degrees And the first dichroic mirror adjusts the wavelength selection characteristics of S-polarized light from a large incident angle portion to a small incident angle portion in accordance with the diffusion angle of the light emitted from the reflector. The wavelength selection characteristic is continuously changed, and the second dichroic mirror adjusts the wavelength of P-polarized light from a portion having a large incident angle to a portion having a small incident angle in accordance with the diffusion angle of light emitted from the reflector. The wavelength selection characteristic is continuously changed so as to make the characteristics uniform, and the first color light of S polarization is reflected by the color synthesizing means, the third color light of S polarization is reflected, and The second color light is transmitted and combined.

[Effect] Light from a light source having a tendency to diffuse is used for dichroic surfaces having continuously different wavelength selection characteristics from a portion having a large incident angle to a portion having a small incident angle, and the wavelength characteristics of reflected light and emitted light are aligned. By doing so, it becomes possible to make color light without color unevenness incident on the modulating means.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a projection type liquid crystal display device of the present invention.

White light emitted from a light source 1 such as a halogen lamp, a xenon lamp, or a metal halide lamp is condensed by a parabolic reflector 2, enters a heat ray cut filter 3, becomes visible light only, and enters a dichroic mirror system. Here, the light may be condensed by using an elliptical mirror or a combination of a spherical mirror and a condensing lens as the light collecting means. However, here, since the light source 1 is not a point light source, it does not become perfect parallel light, and the light intensity in the diffusion direction is large.

The light thus collected is incident on a color-separating dichroic mirror system. The color separation dichroic mirror system includes a blue reflection dichroic mirror 4, a green reflection dichroic mirror 5, and a reflection mirror 6.

FIG. 2 (a) is a wavelength characteristic diagram of the blue reflection dichroic mirror 4, wherein the solid line indicates the central portion, the dotted line indicates the optical path A, and the dashed line indicates the S-polarized light characteristic of the optical path B. FIG. 2 (b) is a wavelength characteristic diagram of the green reflection dichroic mirror 5, in which the solid line indicates the central portion, the dotted line indicates the optical path A, and the dashed line indicates the P-polarized light characteristic in the optical path B. The horizontal axis represents the wavelength, the vertical axis represents the transmittance, and the incident angle is a characteristic of 45 degrees. Hereinafter, when the wavelength is represented by a numerical value, the numerical value of the transmittance is 50%.

In this color separation, as described above, the light from the light source 1 is not parallel light but has a characteristic of a tendency to diffuse. Therefore, in the optical path A and the optical path B in the optical path diagram of FIG. 45
And the incident angle at the optical path B becomes larger than 45 degrees. FIG. 3A is a characteristic diagram showing the angle dependency of a general blue reflecting dichroic mirror (500 [nm]), and FIG. 3 (b) is a general green reflecting dichroic mirror (590 [nm]). FIG. 4 is a characteristic diagram illustrating the angle dependence of the graph. As can be seen from this figure, the wavelength selection characteristic changes when the incident angle changes. The reflected light shifts to the short wavelength side when the incident angle increases, and shifts to the long wavelength side when the incident angle decreases. The transmitted light corresponds to the reflected light and shifts respectively. In other words, regarding green light, yellowish green light enters the green modulation liquid crystal light valve 7G on the optical path A side, and blue-greenish green light enters on the optical path B side.

In the present invention, considering the light flux emitted from the light source 1 at an angle and the angle dependency of the dichroic mirror,
A dichroic mirror in which the wavelength selection characteristic is continuously changed from the optical path A to the optical path B is used. (See FIG. 2A and FIG. 2B.) Therefore, the wavelength characteristics of the reflected light and the transmitted light in the optical path A and the optical path B become substantially equal.

In this embodiment, when the diffusion angle is ± 5 degrees, the wavelength selection characteristics of the blue reflection dichroic mirror 4 are continuously 505 [nm] in the optical path A and 495 [nm] in the optical path B. By controlling and using the dichroic mirror 5 so that the green reflection dichroic mirror 5 is 588 [nm] in the optical path A and 569 [nm] in the optical path B, color unevenness on the screen is minimized. Further, the chromaticity of the three primary colors displayed on the screen is substantially determined by the wavelength characteristic at the center of the dichroic mirror. Blue light has a wavelength region of approximately 500 nm or less, green light has a wavelength region of approximately 510 [nm] to 580 [nm], and red light has a wavelength region of approximately 590 [nm] or more. Note that the diffusion angle of the light emitted from the light source 1 differs depending on the lamp and the reflector, and is several to ten and several degrees.
If the wavelength selectivity of the dichroic mirror (wavelength characteristic from the optical path A to the optical path B) is optimally selected according to the diffusion angle from the light source, color unevenness can be eliminated even with any light source 1. is there.

Such a dichroic mirror is created by partially changing the distance from the deposition source, that is, by setting the deposition source so as to be oblique to the deposition source and performing deposition. Therefore, when the distance from the evaporation source changes, the film thickness changes, and by continuously controlling the film thickness, the wavelength selection characteristics also change continuously.

Thus, color light without color unevenness enters the modulated liquid crystal light valve of each color. The color-separated color lights are changed in direction by the reflection mirror 6 and are respectively incident on the liquid crystal light valves 7R, 7G, 7B for color modulation.

The liquid crystal light valves 7R, 7G, and 7B for modulating each color use an active matrix liquid crystal panel, apply a signal voltage for each color, and control the transmittance for each color according to the magnitude of the voltage to form an image. Here, since the liquid crystal light valves 7R, 7G, and 7B perform the function of a shutter that controls the transmittance of incident light, the transmittance is varied not only by an active matrix liquid crystal panel or a time-division driving liquid crystal panel, but also by a signal voltage. Any liquid crystal panel may be used. Further, it is possible to replace the valve with a valve whose transmittance can be controlled by a mechanical type, an electromagnetic type, or the like.

Since the liquid crystal light valves 7R, 7G, and 7B are in a normally black mode (transmit when a voltage is applied), a polarizing element (not shown) having the same polarization axis is used on the light incident side and the light emitting side. I have. The blue modulation liquid crystal light valve 7B and the red modulation liquid crystal light valve 7R correspond to S-polarized light (parallel to the drawing), and the green modulation liquid crystal light valve 7G corresponds to P-polarization (vertical to the drawing). . This is to minimize color light attenuation and display a bright image without overlapping the wavelength separation characteristics of the color separation dichroic mirror system with the wavelength synthesis characteristics of the color synthesis dichroic prism 8.

Each color light modulated by the liquid crystal light valves 7R, 7G, 7B enters the dichroic prism 8, is synthesized, and is enlarged and projected on the screen by the projection lens 11 to display a color image.

The dichroic prism 8 used as a means for synthesizing images is configured so that the red reflecting surface 9 and the blue reflecting surface 10 are orthogonal to each other. This is obtained by depositing a dielectric multilayer film on both sides of a right-angle prism with a right angle interposed therebetween.

The spectral characteristics of the red reflection surface 9 are such that the S-polarized component transmits the blue wavelength region, reflects the red wavelength region, and transmits the P-polarized blue-green wavelength region (the solid line in FIG. In the S-polarization characteristic, the broken line is the P-polarization characteristic). Blue reflective surface
The spectral characteristics of 10 are such that the red wavelength region of the S-polarized component is transmitted, the blue wavelength region is reflected, and the yellow wavelength region of the P-polarized component is transmitted. , And the two-dot chain line is the P polarization characteristic).

The projection lens 11 can display a bright image by using a lens having a small F value.

The present invention is effective for all projection-type liquid crystal display devices that separate white light into three primary colors, respectively modulate, combine, and project.Even if the order of color separation is changed, the mode of the liquid crystal panel is changed, It goes without saying that, regardless of whether the polarization characteristic is S-polarized light or P-polarized light, the present invention enables image display without color unevenness. Further, the present invention is effective in a color synthesis method using a dichroic mirror in addition to a dichroic prism in color synthesis.

In another embodiment, as a means for image synthesis,
The image may be directly synthesized on a screen using three projection lenses 11. (When used in the present invention for a color separation system of an optical system shown in the 1989 National Congress of the Institute of Television Engineers, pp.81-82.) The present invention is very effective for a color separation system in, for example, volumes pp. 79-82 and the 5th volume of the Transactions of the Institute of Electronics, Information and Communication Engineers Autumn Meeting, pp. 28, 33.

[Effects of the Invention] As described above, according to the present invention, color separation without color unevenness is performed by performing color separation using a dichroic surface in which wavelength selection characteristics are continuously changed according to an incident angle. This makes it possible to display high-quality images without color unevenness on the screen.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of the projection type liquid crystal display device of the present invention. (The optical paths of the optical path A and the optical path B are also shown at the same time.) FIG. 2A is a wavelength characteristic diagram of the blue reflecting dichroic mirror, and FIG. 2B is a wavelength characteristic diagram of the green reflecting dichroic mirror. FIG. 3A is a characteristic diagram showing the angle dependency of the blue reflecting dichroic mirror, and FIG. 3B is a characteristic diagram showing the angle dependency of the green reflecting dichroic mirror. FIG. 4 is a wavelength characteristic diagram of a red reflecting surface and a blue reflecting surface of the dichroic prism. DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Parabolic reflector 3 ... Heat ray cut filter 4 ... Blue reflection dichroic mirror 5 ... Green reflection dichroic mirror 6 ... Reflection mirror 7R ... Red modulation liquid crystal light valve 7G ... Green modulation liquid crystal light valve 7B Blue light modulation liquid crystal light valve 8 Dichroic primum 9 Red reflective surface 10 Blue reflective surface 11 Projection lens

Claims (1)

(57) [Claims] A light source, a reflector for reflecting light from the light source, a color separating unit for separating the light reflected by the reflector into three color lights, and a color light separated by the color separating unit. A projection display apparatus comprising: three modulating units that modulate light; a color synthesizing unit that synthesizes three colors of light modulated by the modulating unit; and a projection unit that projects the light synthesized by the color synthesizing unit. The color separation means includes: a first dichroic mirror that separates three color lights emitted from the light source into a first color light and second and third color lights; and a first dichroic mirror. A second dichroic mirror for separating the separated second and third color lights into the second color light and the third color light, wherein the color synthesizing unit is configured by attaching four prisms. Along with the mating surface, a first reflection surface that reflects the first color light and a second reflection surface that reflects the third color light are formed, and the reflector controls light from the light source. The light is emitted toward the dichroic mirror at a diffusion angle of several degrees to several tens degrees, and the first dichroic mirror corresponds to the diffusion angle of the light emitted from the reflector, and the angle of incidence is changed from a large part to a small part. The wavelength selection characteristics are continuously changed so that the wavelength selection characteristics of the S-polarized light up to the same, and the second dichroic mirror has an incident angle corresponding to the diffusion angle of the light emitted from the reflector. The wavelength selection characteristics are continuously changed so that the wavelength selection characteristics of the P-polarized light from the large part to the small part are uniform, and the first color light of the S-polarized light is reflected by the color combining means. , The S-polarized third color light is reflected, and the P-polarized second color light is transmitted and combined.