JPH07152026A - Projection type display device - Google Patents

Abstract

PURPOSE:To provide a projection type liquid crystal display device capable of adjusting the intensity of respective color light beams. CONSTITUTION:This projection type display device is provided with a light source, color separation means 1 and 2 separating a light beam from the light source to three primary colors, three transmission type liquid crystal light valves 4 modulating the respective color light beams separated by the color separation means 1 and 2, color synthesis means 1 and 2 synthesizing the respective color light beams modulated by the light valves 4, and a projection optical means projecting the light beam synthesized by the synthesis means 1 and 2. In the device, the light valve 14 has a polarizing means and the direction of the axis of polarization of the polarizing means is adjusted for every primary color in order to adjust the intensity of three primary colors.

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 Mifu, SID'75 Tigest, P.I. 24, SID '72 digest, p. 62,
Optronics (1985) NO. 4, P. 73, the 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 device, is expensive, and is not sufficient in terms of life and light utilization efficiency.

Therefore, the present invention solves such a problem, and an object of the present invention is to provide a compact projection type power display device having excellent contrast and high utilization efficiency of light from a light source. . 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]

A projection type display apparatus of the present invention modulates a light source, a color separation means for separating light from the light source into three primary colors, and each color light separated by the color separation means. Projection type including three transmissive liquid crystal light valves, color synthesizing means for synthesizing each color light modulated by each transmissive liquid crystal light valve, and projection optical means for projecting the light synthesized by the color synthesizing means In the display device, each of the transmissive liquid crystal light valves has a polarizing means, and the direction of the polarization axis of the polarizing means is adjusted for each primary color in order to adjust the intensities of the three primary colors. And

[0007]

1 shows the illumination structure of a full-color projection type 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. Reference numeral 3 is a mirror for bending the direction of the light beam. Reference numeral 4 is a transmissive light valve that forms an image corresponding to red, green, and blue. Here, a liquid crystal panel driven by an active matrix (thin film transistor matrix or the like) 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, or the like can be adopted. 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 condensed 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 colored light is reflected by the mirror 3.
The direction is bent by and enters the transmissive light valve 4. The light-halve surface is coated with an antireflection coating to effectively transmit 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 bulb forms an image corresponding to each color of light. In this case, red, green, and blue video signals 18 were supplied to each liquid crystal panel to form a monochromatic drawing image.

[0010]

[Table 1]

The liquid crystal panel uses a twisted nematic (hereinafter referred to as 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 imaging position deviates from the optical axis or a trapezoidal image is formed. The tilt angle of the light valve can be determined in consideration of the characteristics of the projection lens and the image forming range, but in the TN liquid crystal mode used here, the range of 0 to 30 ° was practical.

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 in the column direction of the TFT,
The Y-side shift register performs 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. For details of the drive and the liquid crystal panel, see Nikkei Electronics, No. 351, 1984 (1984). 211 or SI
D'83 DIGEST, P.I. It is based on what was described in 156.

The liquid crystal panels of the respective colors are aligned so that the displayed images match on the screen.

R. G. When the three primary colors B are combined and full-color display is performed, 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 pitches of the respective colors are equal, by regularly displacing approximately half surface elements, it is possible to achieve a higher resolution change than a monochromatic panel.

As is clear from FIG. 1, the R panel image and the B panel image have a left-right mirror image relationship with the G panel image.

The dichroic mirror of the present invention only needs to have a separating / combining function of colored light, but the polarization of the reflection of the dielectric thin film always occurs. That is, in FIG. 1, red light and blue light have many vertical polarization components, and edge light has many horizontal polarization components. Therefore, in the electro-optical effect mode using a polarizing plate, it may be necessary to appropriately adjust the direction of the polarizing plate. For example, in the case of using the TN (90 ° twisted nematic liquid crystal) liquid crystal display mode, in order to use the luminous flux most effectively, the transmission axis of the incident side polarization plate of the R panel and the B panel is set to be vertical in FIG. The transmission axis of the panel should be horizontal.

Further, in the present invention, white balance adjustment, that is, intensity adjustment of each color is performed by setting the orientation of the polarizing plate.

The color light thus image-modulated by the transmissive light valve is incident on the dichroic mirror group again. As shown in FIG. 1, the red, green, and blue lights are reversibly combined, and projected and imaged on the screen 9 by the projection lens 6.

For the dichroic mirror, arrangements other than those shown in FIG. 1 can be used. 4 and 5 are examples of the configuration.
In the case of FIGS. 4 and 5, the dichroic mirror. Light valve. A projection optical system is arranged. 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. Blue light and green light are different. 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, in the case of FIGS. 4 and 5, 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 as in FIG. .

Further, as shown in FIGS. 2, 3, 4, and 5, the present system requires only one projection lens, and it is not necessary to adjust the convergence between color images when changing the projection magnification or the projection distance. There are also advantages.

Next, the effect of this embodiment will be described. The light source light is separated into a plurality of color lights by the first dichroic mirror group. Next, an image is formed by the transmissive 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, a moving image can be displayed by adopting an image display panel using the electro-optical effect. An electro-optical material such as liquid crystal or PLZT can be used as the light valve. In any case, as compared with the CRT optical writing type reflective light valve and the oil film type light valve, it has a thin plate-like compact shape, and the degree of freedom in the configuration of the entire device increases, and the system can be compactly configured.

Next, the image-modulated color light is combined by the second dichroic mirror group. At this time, the second dichroic mirror group has a performance substantially equal to the wavelength characteristic characteristic of the first dichroic mirror group, and reversibly combines the separated color lights. For example, in contrast to the first dichroic mirror group that separates white light into red, green, and blue, the second dichroic mirror group has substantially the same red, green, and blue color separation characteristics as the first dichroic mirror group. And reversibly synthesizes red, green, and blue image color lights. If all light valves are transparent, the combined light will be a ray color. As for 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 polarization component, which is required in the above-mentioned conventional technique, is not necessary.

In this way, the light from the light source is separated into the colored light and modulated,
Since they are combined, a plurality of light sources corresponding to the respective colored lights are unnecessary, and a single light source is sufficient.

The color image light thus combined forms an image on the screen by the projection lens.

Since a plurality of color lights are combined, the images corresponding to the respective colors are accurately arranged. For example, when full-color display is performed using light of three primary colors of red, green, and blue, the respective primary color images are converged and synthesized with each other.

The first dichroic mirror and the second dichroic mirror
By combining two dichroic mirrors having different color light separation characteristics in a cross shape, it becomes possible to shorten 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 light valve on the transmission side makes the wavelength dependence of the extinction ratio of the transmitted color light coincide with the dominant wavelength of the color light, thereby improving the contrast of the image obtained by combining and projecting these. For example, the peak of the wavelength-transmittance curve due to the retardance of the twisted nematic liquid crystal mode is matched with the dominant wavelength of each color light. The dichroic ratio peak of the guest-host liquid crystal mode dichroic dye is made to coincide with the dominant wavelength of each color light.
Etc. Table 1 summarizes the major modes and wavelength dependence. That is, in the light bulb of the present invention, the thickness and pigments used, which are parameters of 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 both light valves.
It is tilted 5 degrees. That is, it means that the light valve surface is inclined to obtain a larger extinction ratio with respect to the incident light angle dependency of the extinction ratio of the transmissive light valve. Examples of the light valve mode having an incident light angle dependency include the TN liquid crystal mode, guest-host mode, and refraction mode shown in Table 1.

Although the TN liquid crystal panel is used as the transmissive light valve in the above, the light valve mode shown in Table 1 can of course be used. In addition, a light valve mode other than Table 1, for example, a switching phenomenon of a scattering state or a transparent state (a liquid crystal driving scattering mode or the like) or a liquid crystal storage type water surface mode can be used. Furthermore, the present invention is not limited to liquid crystals, and any transmission type light valve can be applied without problems. For example, the electro-optical effect of a translucent ceramic such as PLZT, electrochromic, or electrophoretic can be used. Further, although an example of separating and synthesizing three colors of red, green, and blue has been described here, two colors or more colors are also effective.

[0036]

As described above, according to the present invention, the light source, and the color separation means for separating the light from the light source into the three primary colors,
Three transmissive liquid crystal light valves for modulating the respective color lights separated by the color separating means, a color synthesizing means for synthesizing the respective color lights modulated by the respective transmissive liquid crystal light valves, and a synthesizing means by the color synthesizing means. In the projection type display device, the transmission type liquid crystal light valve has a polarization means, and the polarization axes of the polarization means of the polarization means are adjusted to adjust the intensities of the three primary colors. By adjusting the direction for each primary color, the following remarkable effects can be achieved.

(A) By adopting the transmissive liquid crystal light valve, the influence of the reflected light on the surface of the light valve, which has been a problem in the reflective light valve, can be reduced and the contrast of the projected image can be improved.

(B) The transmissive liquid crystal light valve has a thin plate-like compact shape and can be projected by a single light source. Moreover, since a single projection optical means is required, the conventional projection type display is possible. The entire device can be made significantly smaller than the device.

(C) Even if the color balance of the projected light on the screen changes, the color balance can be adjusted and the color balance between the three primary colors can be compensated, so that the color reproducibility can be improved and You can reduce the machine difference in.

[Brief description of 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 type display device using the illumination structure of FIG.

FIG. 3 is a configuration diagram of a projection type display device using a tilted light valve.

FIG. 4 is a plan view layout diagram according to the present invention.

FIG. 5 is a plan view showing a cross-shaped dichroic mirror according to the present invention.

FIG. 6 is a circuit diagram illustrating driving of the 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

[Procedure amendment]

[Submission date] August 8, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

Further, in the present invention, the color balance adjustment , that is, the intensity adjustment of each color is performed by setting the orientation of the polarizing plate.

Claims (1)

[Claims] 1. A light source, color separation means for separating light from the light source into three primary colors, three transmissive liquid crystal light valves for modulating each color light separated by the color separation means, and each transmissive type. In a projection type display device comprising a color synthesizing means for synthesizing each color light modulated by a liquid crystal light valve and a projection optical means for projecting the light synthesized by the color synthesizing means,
Each of the transmissive liquid crystal light valves has a polarizing means, and the direction of the polarization axis of the polarizing means is adjusted for each primary color in order to adjust the intensities of the three primary colors respectively. Display device.