JP2563892B2 - Projection display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type display device using a transmissive light valve for forming a plurality of images.

[0002]

2. Description of the Related Art A conventional projection display device is disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 58-150937, which discloses an image formed by three reflective light valves as a polarization beam splitter and It was synthesized by a dichroic mirror and projected on the screen.
Further, there is one disclosed in Japanese Patent Application Laid-Open No. 60-179723, which was filed before the application of the present invention and subsequently published, which is a dichroic mirror for an image formed by three transmissive light valves. It was synthesized by and projected on the screen.

[0003]

However, Japanese Patent Application Laid-Open No.
Since the light valve is disclosed in JP-A-150937, reflection of unmodulated light on the surface of the light valve causes a decrease in contrast, and secondly, separation of incident light and emitted light is performed. Therefore, the polarization beam splitter is indispensable and the optical system is complicated. Further, the light valve is a large-scale device because it is controlled by the light of the cathode ray tube (CRT). In addition, JP-A-60-
Although the one disclosed in Japanese Patent No. 179723 does not have the above-mentioned problem, since the dichroic optical elements of the color separating means and the color synthesizing means are both arranged at right angles, they are reflected by the dichroic optical element of the color separating means. After being separated, the two color lights emitted from the color separation means are emitted in opposite directions and are projected on both sides to form a large-scale optical system. Further, since the optical unit is arranged in a plane and the dichroic optical elements of the color separating means and the color synthesizing means are arranged at right angles, the distance from the light source to the light valve and the optical distance from the light source to the projection optical means are increased. There is a problem that the target distance is different for each primary color light, and the color unevenness is large.

An object of the present invention is to solve the above problems and to provide a compact projection type display device having high contrast and less color unevenness.

[0005]

A projection type display device according to the present invention comprises a light source, a color separation means for separating light from the light source, and a plurality of transmission type for modulating each color light separated by the color separation means. In a projection type display device provided with a liquid crystal light valve, a color synthesizing unit for synthesizing each color light modulated by each transmissive liquid crystal light valve, and a projection optical unit for projecting the light synthesized by the color synthesizing unit, The transmissive liquid crystal light valve has a polarization means, and adjusts the direction of the polarization axis of the polarization means according to each color light to perform white balance adjustment.

[0006]

In the present invention, the light from the light source is separated into a plurality of color lights by the color separation means. Next, an image is formed by a transmissive liquid crystal light valve corresponding to color light, and the color light is modulated. As a result of using a transmissive liquid crystal light valve,
The influence of the reflected light on the surface of the light valve can be removed from the projected light, and the contrast of the projected image is improved. In addition, an image display panel using the electro-optical effect of liquid crystal is adopted, and a moving image can be displayed. Other than that, an electro-optic crystal such as PLZT can be used, but in any case, it is a thin plate-like compact shape that controls the transmission of light, compared to a CRT optical writing type reflective light valve, and the entire device can be used. It can be made compact. Next, the modulated color lights are combined by the color combining means.

In this way, the light from the light source is separated into a plurality of color lights,
Since they are modulated and combined, a light source corresponding to each color light is unnecessary, and a single light source is sufficient. And the combined color light is
An image is formed on the screen by the projection lens.

The present invention operates as described above, but focusing on the characteristic point of the present invention, the transmissive liquid crystal light valve is provided with the respective polarization means, and the direction of the polarization axis of the polarization means is changed according to each color light. To adjust the white balance. Therefore, even if the color balance reproduced on the screen changes due to the reflection characteristics of the screen or the external irradiation environment, the color balance reproduced on the screen can be easily adjusted by adjusting the color balance of the projected light. The color reproducibility can be improved. Also,
Even if the color balance is different for each color light due to the variation of the optical system that occurs between products, the color balance can be easily compensated, so that the machine difference (variation) of the color reproducibility between products can be reduced. be able to.

[0009]

1 shows the illumination structure of a full-color projection type display device according to the present invention. Two dichroic mirrors (B mirrors) 1 that reflect blue light and two dichroic mirrors (R mirrors) 2 that reflect red light are arranged as shown in the figure, and these perform separation and combination of incident light beams. ing. 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, it is used for a liquid crystal panel driven by an active matrix (thin film transistor matrix or the like). Reference numeral 5 is a condenser lens, 6 is a projection lens, and 7 is a light source. Koehler illumination, critical illumination, or the like can be adopted in the illumination system of the embodiment of FIG.

The dichroic mirror (B mirror) 1 and the dichroic mirror (R mirror) 2 arranged on the side of the light source 7 in FIG. 1 constitute the color separation means of the present invention, and they are mutually separated as shown in the drawing. Are arranged in parallel with. Further, the dichroic mirror (B mirror) 1 and the dichroic mirror (R mirror) 2 arranged on the side of the projection lens 6 in FIG. 1 constitute the color combining means of the present invention,
These are also arranged in parallel with each other. The dichroic mirror (B mirror) 1 and the dichroic mirror (R mirror) 2 that form the color separating unit and the color synthesizing unit are all arranged in parallel with each other. Further, the optical systems are arranged so that the optical distances from the light source 7 to the transmissive light valves 4 are equal to each other, and the optical distances from the transmissive light valves 4 to the projection lens 6 are also equal to each other. The optical system is located at. Further, as shown in FIG. 1, all the optical elements from the light source 7 to the projection lens 6 are arranged in a plane.

Next, the operation will be described. As shown in FIG. 1, the light source 7 emits white light (for example, a halogen lamp) and is condensed by the condenser lens 5. The white light incident on the dichroic mirror 2 is decomposed into red (R) light and other colored light, and red (R) is reflected by the dichroic mirror 2 and then further reflected by the mirror 3 to enter the transmissive light valve 4. . When the other colored light transmitted through the dichroic mirror 2 is incident on the dichroic mirror 1, the blue (R) light is reflected by the dichroic mirror x and then further reflected by the mirror 3 to enter the transmissive light valve 4. At this time, green (G) from the dichroic mirror 1.
Light is transmitted, and also reflected by the mirror 3 to enter the transmissive light valve 4. The transmissive light valve 4 is arranged at a position where an image is formed on the screen of the projection lens 6. The transmissive light valve 4 forms an image corresponding to each color light. In this case, red, green, and blue video signals are supplied to each liquid crystal panel to form a monochromatic moving image. For details of drive and liquid crystal panel, see Nikkei Electronics No. 351 (19).
84) P.I. It is based on what was described in 211. Also,
The liquid crystal panels of each color are aligned so that the displayed images match on the screen.

The dichroic mirrors 1 and 2 only need to have a separating / combining function of colored light, but the reflection of the dielectric thin film always causes a polarization action. In the embodiment of FIG. 1, red light and blue light have many vertical polarization components, and green 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, when the TN (90 ° twisted nematic liquid crystal) liquid crystal display mode is used, in order to use the luminous flux most effectively, the transmission axes of the incident side polarization plates of the R panel and the B panel are set to be vertical in FIG. The transmission axis of the G panel should be horizontal. In addition, white balance adjustment, that is, intensity adjustment of each color can be performed by setting the orientation of the polarizing plate.

The color light thus image-modulated by the transmissive light valve 4 is again dichroic mirrors 1 and 2.
Incident on. As shown in FIG. 1, red, green, and blue lights are reversibly combined, and the combined light is projected by a projection lens 6 onto a screen (not shown) to form an image.

In the embodiment shown in FIG. 1, only one projection lens 6 is required as shown in the drawing, and when changing the projection magnification or the projection distance, there is an advantage that the convergence adjustment between the color images is unnecessary. . By the way, although the liquid crystal panel is used as the transmissive light valve in the above-described embodiments, a light transmissive ceramic such as PLZT can be used as long as it is a light valve using the electro-optical effect.

[0015]

As described above, according to the present invention, a light source, a color separation means for separating light from the light source, a plurality of transmission type liquid crystal light valves for modulating each color light separated by the color separation means, A transmission type liquid crystal light valve for a projection type display device provided with a color synthesizing means for synthesizing each color light modulated by each transmissive liquid crystal light valve and a projection optical means for projecting the light synthesized by the color synthesizing means Has a polarizing means and adjusts the direction of the polarization axis of the polarizing means according to each color light to perform white balance adjustment, and therefore the following excellent effects are obtained.

A) The influence of the reflected light on the surface of the light valve can be removed from the projected light, and the contrast of the displayed image is high. b) A polarization mirror for separating the optical paths of the light incident on the light valve and the light emitted from the light valve according to the difference in the polarization state is unnecessary, and the optical system is simplified. c) It is possible to reversibly perform color separation and color synthesis regardless of whether light from a light source is polarized light or non-polarized light. For example, various light valves such as liquid crystals and crystals utilizing electro-optical effect. Can be used. d) Since the polarization axis of the polarizing means provided in the light valve is adjusted according to each color light and the white balance is adjusted, the color balance reproduced on the screen changes depending on the reflection characteristics of the screen and the external irradiation environment. However, by adjusting the color balance of the projected light, the color balance reproduced on the screen can be easily optimized and the color reproducibility can be improved. In addition, even if the color balance differs for each color light due to the variation of the optical system that occurs between products, the color balance can be easily compensated, and therefore, the machine difference (variation) of the color reproducibility between products can be reduced. Can be made smaller.

[Brief description of drawings]

FIG. 1 is a diagram showing an illumination structure of a full-color projection display device according to an embodiment of the present invention.

[Explanation of symbols]

 1 …… Red reflection dichroic mirror 2 …… Blue reflection dichroic mirror 3 …… Mirror 4 …… Transmissive light valve 5 …… Condenser lens 6 …… Projection lens 7 …… Light source

Claims (1)

(57) [Claims] And 1. A light source, color separating means for separating the light from said light source, the respective color lights separated by the color separating means modulation
Provided that a plurality of transmission-type liquid crystal light valves, a color synthesizing means for synthesizing the modulated respective color light by respective transmission type liquid crystal light valve, and a projection optical means for projecting the light synthesized by the color synthesizing means in the projection type display device, pre-Symbol
Each transmissive liquid crystal light valve has a polarization means,
The direction of the polarization axis of the means is adjusted according to each color light and the white
A projection-type display device characterized by performing balance adjustment .