JP2842419B2 - Projection display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type color display device using a plurality of image forming light valves. 2. Description of the Related Art A conventional light valve type projection type color display device is disclosed in Japanese Patent Application Laid-Open No. 58-150937 (US Pat.
No. 34680, 334682), a monochromatic image is synthesized and projected by a reflection type light valve and a dichroic mirror, SID '75 Digest, p. 24, SID '72 digest, P.E. 6
2, Optronics (1985) No. 4, p. 73, an oil film light valve system, and the like. [0003] The reflection type light valve system of the former type is firstly a reflection type light valve, which causes a decrease in contrast due to light reflected on the surface. Second
Since the light valve is addressed by light from a cathode ray tube (CRT), the device becomes a large-scale device. Third, the dichroic mirror has been required to have excellent polarization separation characteristics for separating incident light and output light in addition to color separation characteristics. The latter oil film light valve system requires a large-scale apparatus and is expensive, and is not sufficient in terms of life and light use efficiency. Accordingly, the present invention is to solve such a problem, and an object of the present invention is to provide a compact projection type color display device which is excellent in contrast and has a high light source light use efficiency. . Another object of the present invention is to provide a projection type display device having high color reproducibility on a screen and having little difference in color reproducibility between products. SUMMARY OF THE INVENTION The present invention provides a light source, a separating means for separating light from the light source into a plurality of color lights, and a corresponding one of the plurality of color lights separated by the separating means. A plurality of transmissive light valves that respectively modulate the color light; a combining unit that combines the color lights modulated by the plurality of transmissive light valves; and a projection optical unit that projects the light combined by the combining unit. In the projection display device, the plurality of transmission light valves transmit a normal line of a light incident surface of each light valve through the light valves so as to increase an extinction ratio having an incident light angle dependency. The optical axis of the projection optical unit is set so as to be inclined by 0 to 45 ° with respect to the light transmission direction of each color light, and along the emission direction of the light combined by the combining unit. Features . A light source; separating means for separating the light from the light source into a plurality of color lights; and a plurality of transmissive liquid crystal lights for respectively modulating the corresponding one of the plurality of color lights separated by the separating means. A projection type display device comprising: a valve; a combining unit configured to combine the color lights modulated by the plurality of transmission-type liquid crystal light valves; and a projection optical unit configured to project the light combined by the combining unit. The plurality of transmissive liquid crystal light valves have a liquid crystal panel of a twisted nematic liquid crystal mode, and normalize the light incident surface of each light valve so as to increase the extinction ratio having incident light angle dependence. It is set to be inclined by 0 to 30 ° with respect to the light transmission direction of each color light passing through the bulb,
Along the emission direction of the light combined by the combining means,
The optical axis of the projection optical means is set. FIG. 1 shows an illumination structure of a full-color projection display device according to the present invention. A dichroic mirror (B mirror) 1 that reflects blue light and a dichroic mirror (R mirror) 2 that reflects red light are combined in a cross shape to separate and combine incident light beams. 3
Is a mirror for bending the direction of the light beam. 4 is red,
This is a transmission type light valve that forms an image corresponding to green and blue. Here, a liquid crystal panel driven by an active matrix (such as a thin film transistor matrix) is used. FIG. 2 is an overall configuration diagram including a projection optical system. Only green is drawn for simplicity. As the illumination system, Koehler illumination, critical illumination, telecentric illumination, and the like can be employed. 5 is a condenser lens, 6 is a projection lens, 7 is a light source, and 9 is a screen. Next, the operation will be described. As shown in FIG. 2, the light source 7 emits white light (for example, a halogen lamp) and is collected by the condenser lens 5. The white light 8 incident on the dichroic mirrors 1 and 2 is red (R), green (G),
Decomposed into blue (B) light. The separated color light is reflected by the mirror 3
And the light enters the transmission type light valve 4. The light valve surface is provided with an anti-reflection coating to effectively transmit the incident light. The light valve is placed at a position where an image is formed on the screen 9 by the projection lens 6. The light valve forms an image corresponding to each color light. In this case, red, green and blue video signals 18 were supplied to each liquid crystal panel to form a monochromatic figure image. [Table 1] The liquid crystal panel uses a twisted nematic (TN) liquid crystal mode. From the wavelength dependence shown in Table 1, using a nematic liquid crystal with Δn = 1.5 and adjusting to the second peak, the liquid crystal layer thickness of the red light valve is 8.4 μm, and the liquid crystal layer thickness of the green light valve is Was set to 7.1 μm, and the liquid crystal layer thickness of the blue light valve was set to 5.8 μm. The thickness of each liquid crystal layer is determined in consideration of the steady temperature after irradiation with the projection light. Since the TN liquid crystal mode has an incident light angle dependency of the extinction ratio, it is more effective to arrange the incident light at an angle to the normal to the light valve surface as shown in FIG. However, in this case, since the projection lens deviates from the optical axis, the image forming position deviates from the optical axis, or a trapezoidal image is formed. The tilt angle of the light valve is determined in consideration of the characteristics of the projection lens and the image forming range, but in the case of the TN liquid crystal mode used here, the range of 0 to 30 ° was practical. Here, the driving of the TFT liquid crystal panel will be briefly described with reference to FIG. Since the liquid crystal panel requires AC driving, the video signal (18) is one field (1F)
Each time the polarity is inverted by the polarity inversion circuit (10). Synchronous control circuit is VCO (11), loop filter
(12), a phase comparator (13), and a frequency divider (14). Y clock. Generate data and 1F signals. The liquid crystal panel (4) has an X-side shift register (1
5) The transmission gate (17) and the Y-side shift register (16) for distributing the video signal to each pixel are connected. The X-side shift register has a TFT column direction,
The Y-side shift register performs an address in the row direction. As a result, a pixel voltage corresponding to the video signal is applied to the TFT liquid crystal pixels, and pixel display can be performed. Details of the driving and the liquid crystal panel are described in Nikkei Electronics, No. 351 (1984) p. 211 or SI
D'83 DIgest, P.E. 156. The liquid crystal panels of each color are aligned so that the displayed image matches on the screen. When full-color display is performed by combining the three primary colors of R, G, and B, if misconvergence occurs, a color shift or color ghost is displayed. In particular, when a matrix panel is used, alignment at a pixel pitch or less is desired. Further, when the surface element pitches of the respective colors are equal to each other, a high resolution change can be made higher than that of a monochromatic panel by regularly displacing about half a pixel. As is apparent from FIG. 1, the R panel image and the B panel image are in a left-right mirror image relationship with the G panel image. The dichroic mirror of the present invention only needs to have a function of separating and synthesizing color light, but the reflection of the dielectric thin film necessarily produces a polarizing action. That is, in FIG. 1, red light and blue light have many polarization components in the vertical direction, and green light has many polarization components in the horizontal direction. For this reason, in the electro-optical effect mode using a polarizing plate, the direction of the polarizing plate may need to be appropriately adjusted in some cases. For example, when the TN (90 ° twisted nematic liquid crystal) liquid crystal display mode is used, in order to use the light flux most effectively, in FIG. The transmission axis of the panel should be horizontal. In the present invention, white balance adjustment, that is, intensity adjustment of each color is performed by setting the azimuth of the polarizing plate. The color light image-modulated by the transmission type light valve in this way enters the dichroic mirror group again. As shown in FIG. 1, red, green, and blue lights are reversibly combined and projected on a screen 9 by a projection lens 6 to form an image. The arrangement of the dichroic mirror other than that shown in FIG. 1 can be used. 4 and 5 show examples of the configuration.
4 and 5, a dichroic mirror, a light valve, and a projection optical system are arranged on the same plane. Therefore, a thinner system can be configured as compared with the example of FIG. The dichroic mirror (1) shown in FIG.
(2) is a simple system that does not need to be configured in a cross shape. Mirror for bending color light (3)
Are also arranged on the same plane as the dichroic mirror. As in the case of FIG. 1, (5) is a condenser lens,
(4) is a light valve and (6) is a projection lens. FIG. 5 shows a cross-shaped dichroic mirror used in the case of FIG. 1 arranged in a plane. The feature of the system of FIG. 5 is that the light path length between the light valve (4), the light source (7) and the condenser lens (5) is red light and green light. It is different for blue light and green light. Further, since red light and blue light reflected by the dichroic mirrors (1) and (2) have many polarization components perpendicular to the paper surface, the reflection efficiency at the mirror (3) for changing the light beam direction is increased. be able to. The position of the light valve (4) for each color light must be at an imaging position optically equidistant with respect to the projection lens 6 for each color in the case of FIGS. As shown in FIGS. 2, 3, 4, and 5, the present system requires only one projection lens, and does not require convergence adjustment between the color images when changing the projection magnification or the projection distance. There are advantages too. Next, the effect of this embodiment will be described. The light source light is split into a plurality of color lights by a first dichroic mirror group. Next, an image is formed by a transmission type light valve corresponding to the color light, and the color light undergoes image modulation.
As a result of using the transmissive light valve, the influence of the reflected light on the light valve surface which cannot be avoided in the reflective light valve can be eliminated from the projected light, and the contrast of the projected image is improved. In addition, moving images can be displayed by employing an image display panel using an electro-optic effect. An electro-optic material such as liquid crystal or PLZT can be used for the light valve. In any case, as compared with a CRT light writing type reflective light valve or an oil film type light valve, it is a thin and compact shape, the degree of freedom in the configuration of the entire apparatus is increased, and a compact system can be configured. Next, the image-modulated color light is synthesized by the second dichroic mirror group. At this time, the second dichroic mirror group has performance substantially equal to the wavelength separation performance of the first dichroic mirror group, and reversibly combines the separated color lights. For example, while the first dichroic mirror group separates white light into red, green, and blue light, the second dichroic mirror group has substantially the same red, green, and blue color light separation characteristics as the first dichroic mirror group. And reversibly synthesizes red, green, and blue image color lights. If all the light valves are transmitted, the combined light will have a light color.
As the function of the dichroic mirror of the present invention, only the separation of the color light is sufficient, and the performance of separating the polarized light component required in the above-described prior art is unnecessary. In this way, the light source light is separated into color lights, modulated,
Since the light sources are combined, a plurality of light sources corresponding to the respective color lights are not required, and a single light source is sufficient. The color image light synthesized in this way forms an image on a screen by the projection lens. Since a plurality of color lights are combined, the images corresponding to each color are accurately arranged. For example, when performing full-color display using three primary colors of red, green, and blue, the respective primary color images are converged and combined. The first dichroic mirror, the second
By combining two dichroic mirrors having different color light separation characteristics in a cross shape, it has become possible to shorten the optical path length from the light valve to the light valve and from the light valve to the projection optical system. Furthermore, by arranging these dichroic mirrors on a plane,
A thin and compact system can be configured. In the transmission type light valve, the wavelength dependence of the extinction ratio is made to match the main wavelength of the color light with respect to the transmitted color light, and the contrast of an image projected by combining them is improved. For example, the peak of the wavelength-transmittance curve due to the retardance of the twisted nematic liquid crystal mode is matched with the main wavelength of each color light. The peak of the dichroic ratio of the dichroic dye in the guest-host liquid crystal mode coincides with the main wavelength of each color light.
Etc. Table 1 summarizes the main modes and the wavelength dependence. That is, in the light valve of the present invention, the parameters of the light valve configuration such as the thickness and the pigment used are changed so that the main wavelength of each color light matches the wavelength-dependent characteristics shown in Table 1. In the transmission type light valve, the light transmission direction of the transmitted color light is 0 to 4 with respect to the normal to the light valve surface.
It is leaning 5 ゜. In other words, it means that the light valve surface is inclined to obtain a larger extinction ratio with respect to the incident light angle dependence of the extinction ratio of the transmission type light valve. Examples of the light valve mode having the incident light angle dependence include a TN liquid crystal mode, a guest-host mode, and a birefringence mode shown in Table 1. In the above, the TN liquid crystal panel is used as the transmission type light valve. However, the light valve modes shown in Table 1 can of course be used. Further, light valve modes other than those in Table 1, such as a switching phenomenon of a scattering state and a transparent state (dynamic scattering mode of a liquid crystal, etc.), and a storage type display mode of a liquid crystal can be used. Further, the present invention is not limited to the liquid crystal and can be applied without any problem as long as it is a transmission type light valve. For example, an electro-optic effect of a translucent ceramic such as PLZT, electrochromic, electrophoretic, or the like can be used. Further, here, the embodiment of the three-color separation / combination of red, green and blue is described, but it is also effective to use two or more colors. As described above, according to the present invention, a plurality of transmissive light valves each modulating a corresponding one of a plurality of color lights separated from a light source light, and a plurality of transmissive light valves are provided. A projection display apparatus comprising: a combining unit configured to combine the color lights modulated by the light valves, and a projection optical unit configured to project the light combined by the combining unit. In order to increase the dependent extinction ratio, the normal to the light incident surface of each light valve is set so as to be inclined by 0 to 45 ° with respect to the light transmission direction of each color light passing through the light valve. Alternatively, when the transmissive light valve is a transmissive liquid crystal light valve having a liquid crystal panel of a twisted nematic liquid crystal mode, the normal of the light incident surface of each light valve is set to the light valve. Is set at an angle of 0 to 30 ° with respect to the light transmission direction of each color light passing through, and the optical axis of the projection optical unit is set along the emission direction of the light combined by the combining unit. Therefore, the following remarkable effects can be obtained. (A) By employing a transmissive liquid crystal light valve, the influence of reflected light on the light valve surface, which has been a problem with a reflective light valve, can be reduced, and the contrast of a projected image can be improved. (B) If the extinction ratio of the light valve has an incident light angle dependence, a sufficient extinction ratio (contrast) of transmitted light cannot be obtained even when color light is incident perpendicularly to the incident surface. The normal of the light incident surface of each light valve is set to 0 to the light transmission direction of each color light passing through the light valve.
The extinction ratio can be increased by setting the angle to 45 ° or setting the angle to 0 ° to 30 ° in the case of a transmission type liquid crystal light valve having a liquid crystal panel of a twisted nematic type liquid crystal mode. As a result, a sufficient contrast of the projected image can be obtained. Further, since the extinction ratio of each light valve is increased instead of a specific light valve, it is possible to reduce color unevenness in a projected image. (C) The optical axis of the projection optical means is set along the emission direction of the light obtained by combining the color light, despite being arranged obliquely with respect to the color light passing through the transmission type light valve. Further, it is possible to provide a novel projection type display device which can form a projection image on a screen which is arranged at an oblique angle with respect to the optical axis of the projection optical means, which has not existed conventionally. (D) Further, although the transmission type light valve is arranged obliquely with respect to the transmitted color light, the optical axis of the projection optical means is set along the emission direction of the light obtained by combining the color lights. Although the projected image becomes trapezoidal and the image is distorted, the inclination angle of the light valve is 0 to 45 ° or 0 to 3 °.
Since the angle is kept within the range of 0 °, it is possible to reduce the image shift, reduce the blur of the projected image, and suppress the trapezoid.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illumination structure diagram showing an example of a full-color projection display device according to the present invention. FIG. 2 is a configuration diagram of a projection display device using the illumination structure of FIG. FIG. 3 is a configuration diagram of a projection display device using an inclined light valve. FIG. 4 is a plan view showing a configuration according to the present invention. FIG. 5 is a configuration diagram of a cross-shaped dichroic mirror according to the present invention, which is arranged in a plane. FIG. 6 is a circuit diagram illustrating driving of a light valve used in the embodiment. [Description of Signs] 1 ... Red-reflective tychroic mirror 2 ... Blue-reflective tychroic mirror 3 ... Mirror 1-4 ... Transmissive light valve 5 ... Condenser lens 6 ... Projection lens 7 ... Light source 9 ... Screen

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G02B 27/18 G02F 1/13 505 G03B 21/00 H04N 9/31

Claims (1)

(57) [Claims] A light source, a separating unit that separates light from the light source into a plurality of color lights, a plurality of transmissive light valves that respectively modulate corresponding color lights of the plurality of color lights separated by the separating unit, A projection type display device including a combining unit that combines the color lights modulated by the transmission type light valves, and a projection optical unit that projects the light combined by the combination unit, wherein the plurality of transmission type light valves are In order to increase the extinction ratio having the incident light angle dependency, the normal of the light incident surface of each light valve is inclined by 0 to 45 ° with respect to the light transmission direction of each color light passing through the light valve. Along the emission direction of the light combined by the combining means,
A projection display device, wherein an optical axis of the projection optical unit is set. 2. A light source; a separating unit that separates light from the light source into a plurality of color lights; a plurality of transmissive liquid crystal light valves that respectively modulate a corresponding one of the plurality of color lights separated by the separating unit; A projection type display device comprising: a combining unit that combines the color lights modulated by the transmission type liquid crystal light valves, and a projection optical unit that projects the light combined by the combination unit. The light valve has a liquid crystal panel of a twisted nematic type liquid crystal mode, and a normal line of a light incident surface of each light valve is passed through the light valve so as to increase an extinction ratio having an incident light angle dependency. Is set to be inclined by 0 to 30 ° with respect to the light ray transmission direction of the color light, and along the emission direction of the light combined by the combining means,
A projection display device, wherein an optical axis of the projection optical unit is set.