JPH09185014A - Projection display device - Google Patents

Abstract

A projection-type liquid crystal display device capable of compensating the incident light angle dependency of a light valve is provided. SOLUTION: In order to compensate the incident light angle dependency of the light valve, the light transmission direction of the color light transmitted through the light valve is 0 to 45 ° with respect to the normal line of the incident surface of each light valve.
Arrange to tilt.

Description

Detailed Description of the Invention

[0001]

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.

[0002]

2. Description of the Related Art A conventional light valve type projection drawing color display device is disclosed in Japanese Patent Application Laid-Open No. 58-150937 (US Pat.
34680, 334682),
Synthetic projection of a single color image by a reflection type light valve and dichroic mirror, SID'75 Tgest, P.I. 24, SID '72 digest, P.E. 62,
Optronics (1985) NO. 4, p. 73, an oil film light valve system, and the like.

[0003]

In the former reflection type light valve system, since it is a reflection type light valve, the contrast is lowered due to the light reflected on the surface. Second
Since the light valve is addressed by the light of the cathode ray tube (CRT), it becomes a large-scale device. Thirdly, the dichroic mirror is required to have not only color separation characteristics but also excellent polarization separation characteristics for separating incident light and emitted light.

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 which has high color reproducibility on the screen and has a small difference in color reproducibility among products.

[0006]

The projection type display device of the present invention includes an illuminating means for generating color lights of three primary colors, a plurality of light valves for modulating each color light generated by the illuminating means, and each light. In a projection type display device comprising a color synthesizing means for synthesizing each color light modulated by a valve and a projection optical means for projecting the light synthesized by the color synthesizing means, each light valve is reduced to a light incident surface. It is characterized by having a reflective coating.

[0007]

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,
It is a transmissive light valve that forms images 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. Reference numeral 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.

[0010]

[Table 1]

The liquid crystal panel uses a twisted nematic (TN) liquid crystal mode. From the wavelength dependence shown in Table 1, when the nematic liquid crystal of Δn = 1.5 is used to match 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 7.1 μm, and the liquid crystal layer thickness of the blue light valve was 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 with respect 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 drive, the video signal (18) is 1 field (1F)
Inversion is performed by the polarity inversion circuit (10) every time. Synchronous control circuit is VCO (11), loop filter
(12), a phase comparator (13) and a frequency divider (14). Y clock. Data and 1F signal are generated. The liquid crystal panel (4) has an X side shift register (1
5) Thereby, the transmission gate (17) for distributing the video signal to each pixel and the Y side shift register (16) are connected.

The X-side shift register is arranged in the TFT column direction,
The Y-side shift register performs an address in the row direction.

As a result, the pixel voltage corresponding to the video signal is applied to the TFT liquid crystal pixel, 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.I. 156.

The liquid crystal panels of each color are aligned so that the displayed image matches on the screen.

When the three primary colors of R, G, and B are combined to perform full-color display, misconvergence causes color misregistration or display as a color ghost. Especially when a matrix panel is used, it is desired to perform the alignment within the pixel pitch. Further, when the surface element pitch of each color is the same, by regularly displacing about half a pixel, it is possible to achieve a higher resolution change than that of a monochrome panel.

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 luminous 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 transmissive light valve in this manner 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.
In the case of FIGS. 4 and 5, the dichroic mirror, the light valve, and the 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) of FIG. 4,
(2) is a simple system that does not need to be formed in a cross shape. Mirror (3) for bending colored light
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 characteristic of the system of FIG. 5 is that the optical 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. In addition, 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 ray direction is increased. be able to.

Further, the position of the light valve (4) for each color light must be at an image forming position which is optically equidistant to the projection lens 6 for each color in the case of FIGS. 4 and 5 as in FIG.

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 surface of the light valve, which cannot be avoided by the reflective light valve, can be removed 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 lights are combined by the second dichroic mirror group. At this time, the second dichroic mirror group has a performance substantially equal to the wavelength-dividing capability of the first dichroic mirror group, and reversibly combines the separated color lights. For example, with respect to a first dichroic mirror group that divides white light into red, green, and blue,
The dichroic mirror group has red, green, and blue color light separation characteristics substantially equal to those of the first dichroic mirror group.
It reversibly combines red, green, and blue image light. 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.

As described above, the light from the light source is separated into color lights,
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, 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.

Also, 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 reduce the optical path length from the light beam 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.

The transmission type light valve makes the wavelength dependence of the extinction ratio coincide with the main wavelength of the color light with respect to the transmitted color light, thereby improving the contrast of an image projected by combining them. 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 major modes and wavelength dependence. That is, in the light valve of the present invention, parameters such as thickness and pigments used in the light valve configuration are changed so that the dominant wavelength of each color light matches the wavelength-dependent characteristics of Table 1.

Further, in the transmissive light valve, the light transmission direction of the transmitted color light is 0 to 4 with respect to the normal line of 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 an incident light angle dependency include the TN liquid crystal mode, guest-host mode, and birefringence mode shown in Table 1.

Although the TN liquid crystal panel is used as the transmissive light valve in the above, the light valve modes shown in Table 1 can of course be used. Further, light valve modes other than those in Table 1, for example, switching phenomenon of scattering state-transparent state (dynamic scattering mode of liquid crystal, etc.) and memory-type display mode of 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.

[0036]

As described above, according to the present invention, the illumination means for generating the color lights of the three primary colors, the plurality of light valves for modulating the respective color lights generated by the illumination means, and the light valves for modulation are provided. In a projection type display device provided with a color synthesizing means for synthesizing each color light and a projection optical means for projecting the light synthesized by the color synthesizing means, each light valve has a light-incident surface provided with an antireflection coating. As a result, it is possible to suppress reflection on the light incident surface of the light valve on which strong colored light is incident for forming a projected image. Therefore, it is possible to suppress the light loss on the light valve incident surface and increase the light incident on the light valve. Therefore, by effectively utilizing the light from the light source for the projection image, the projection image can be made brighter. it can.

[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 layout diagram 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.

[Explanation of symbols]

 1 ... Red reflective tyroic mirror 2 ... Blue reflective tyroic mirror 3 ... Mira 1 ... Transmissive light valve 5 ... Condenser lens 6 ... Projection lens 7 ... Light source 9 ... Screen

Claims (1)

[Claims] 1. A lighting unit for generating color lights of three primary colors, a plurality of light valves for modulating each color light generated by the lighting unit, and a color synthesizing unit for synthesizing each color light modulated by each light valve. And a projection optical means for projecting the light combined by the color combining means, wherein each light valve has a light-incident surface provided with antireflection coating. Type display device.