JPH0650367B2 - Projection display device - Google Patents

Description

The present invention relates to a projection type display device using a plurality of transmissive light valves for image formation.

[Prior Art] As a conventional projection type display device, for example, JP-A-58-150.
There is one disclosed in Japanese Patent No. 937, but this is 3
The image formed by the reflection type light valve is combined by the polarization beam splitter and dichroic mirror,
It was projected on the screen. Further, JP-A-60-1 filed before the application of the present invention and subsequently published.
There is one disclosed in Japanese Patent Publication No. 79723, which is one in which images formed by three transmissive light valves are combined by a dichroic mirror and projected on a screen.

[Problems to be Solved by the Invention] However, the one disclosed in Japanese Patent Application Laid-Open No. 58-150937 is the first because the light valve is a reflection type.
Secondly, the reflection of unmodulated light on the surface of the light valve causes a reduction in contrast, and secondly, a polarization beam splitter is indispensable for separating incident light and emitted light, and the optical system was complicated. Also, the light valve is a cathode ray tube (CRT).
It was a large-scale device because it was controlled by the light.

Further, the one disclosed in Japanese Patent Laid-Open No. 60-179723 does not have the above-mentioned problems, but first, the wavelength selection characteristics of the dichroic mirror of the color separating means and the dichroic mirror of the color synthesizing means are completely matched. However, due to the variation in the color separation / synthesis characteristics, the overlap between the color separation and the color synthesis is shifted, and as a result, the color-separated primary color light is not reversibly color-synthesized as it is The efficiency and color reproducibility deteriorate, and secondly, the number of parts is large,
Maintaining high assembly precision is difficult, long-term reliability is low due to vibration and heat history, and the optical system cannot be simplified.
There was also a limit to miniaturization of the device.

The present invention has solved such a problem,
An object of the present invention is to provide a compact projection-type display device that has good light utilization efficiency and color reproducibility, high contrast, a simplified optical system, and a small number of parts.

[Means for Solving the Problems] A projection display apparatus according to the present invention includes a color separation unit that separates light from a single light source into three primary colors, and three transmissive light valves that modulate each primary color from the color separation unit. A color synthesizing means for synthesizing the primary color light modulated by each transmissive light valve,
In the projection type display device having the projection optical means for projecting the color-combined light, the color separating means and the color combining means are constituted by the same optical means. That is, the color separating means and the color synthesizing means have different wavelength selection characteristics,
First and second dichroic optical elements arranged in a cross shape, and a first transmissive light in three transmissive light valves by further reflecting the first primary color reflected by the first dichroic optical element. A first mirror group for making the light incident on the first dichroic optical element again via the bulb;
The second primary color reflected by the second dichroic optical element is further reflected and is incident on the second dichroic optical element again through the second transmissive light valve in the three transmissive light valves. The third primary color transmitted through the mirror group and the first and second dichroic optical elements is reflected, and the first and second dichroic are again transmitted through the third transmissive light valve in the three transmissive light valves. And a third mirror group which is made incident on the optical element, and an incident position from the single light source to the first and second dichroic optical elements, and an incident position from the first, second and third mirror groups. And each entry location includes an intersection of the first dichroic optical element and the second dichroic optical element.

[Operation] In the present invention, the light source light is incident on the position including the intersection of the first dichroic optical element and the second dichroic optical element, and is separated into a plurality of color lights by these dichroic optical elements. Next, the separated color lights are guided by the first to third mirror groups and enter the transmissive light valve. An image is formed by a transmission type light valve corresponding to each color light, and the color light is modulated. As a result of using the transmissive 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.

The colored lights are then combined by the first and second dichroic optical elements. At this time, the first and second dichroic optical elements first perform color separation and then perform color combination. Therefore, the red, green, and blue image color lights can be combined completely reversibly with respect to the red, green, and blue color light splitting properties. As for the function of the dichroic optical element, only the separation of the color light is sufficient, and the performance of limiting the polarization component, which is required in the above-mentioned conventional technique, is not necessary.

In this way, since the light source light is separated into color lights, modulated, and combined, a light source corresponding to each color light is unnecessary, and a single light source is sufficient.

Next, the combined color light is projected on the screen by the projection lens to form an image.

The present invention operates as described above, but particularly focusing on the characteristics of the present invention, the color separating means and the color synthesizing means are constituted by the same optical means. Therefore, firstly, the dichroic mirror and the color of the color separating means are combined. The wavelength selection characteristics of the dichroic mirror of the synthesizing means can be perfectly matched, the color-separated primary color light is reversibly color-synthesized as it is, and there is no variation in color separation characteristics and color synthesis characteristics depending on the parts, and light utilization is possible. Good efficiency and color reproducibility. Therefore, the screen is bright and the image quality is high. Secondly, the number of parts can be reduced, the assembling accuracy is high, the long-term reliability is not impaired by vibration or heat history, the optical system can be simplified, and the device can be made compact.

〔Example〕

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. 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 the projection optical system. Only green is drawn for simplicity. Further, the illumination system and the image forming system are not strictly described. As the illumination system, Koehler illumination, critical 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. 1, 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 decomposed into red (R), green (G), and blue (B) light by the dichroic mirrors. The separated color light is bent by the mirror 3 and enters the transmissive light valve 4. Light valve is screen 9
It is placed at a position where an image is formed 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 were 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 (1984) P.
It is based on what was described in 211.

In addition, the liquid crystal panels of each color are aligned so that the displayed images match on the screen. Therefore, in 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 only needs to have a separating / combining function of the colored light, but the dielectric thin film always has a polarization effect. That is, in 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, 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, R in FIG.
The transmission axes of the incident side polarization plates of the panels B and
The transmission axis of the 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 image-modulated by the transmissive 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 and imaged on the screen 9 by the projection lens 6.

Further, as shown in FIGS. 2 and 3, there is an advantage that only one projection lens is required, and when the projection magnification or the projection distance is changed, the convergence adjustment between the color images is unnecessary.

Although the liquid crystal panel is used as the transmissive light valve in the above, if the light valve uses the electro-optical effect, the PL
A translucent ceramic such as ZT can also be used.
Further, here, an example of separating and synthesizing three colors of red, green and blue is given, but two colors or more colors are also effective.

〔The invention's effect〕

As described above, the projection type display apparatus of the present invention includes a color separation unit that separates light from a single light source into three primary colors, three light valves that modulate each primary color from the color separation unit, and each light. It has a color synthesizing means for color synthesizing the primary color light modulated by the bulb, and a projection optical means for projecting the color-synthesized light, wherein the color separating means and the color synthesizing means are respectively composed of two types of dichroic optical elements. In such a projection type display device, since the color separating means and the color synthesizing means are configured by the same optical means, the following effects are obtained.

a) Since the color separation characteristics and the color composition characteristics are completely the same,
The color-separated primary color light is reversibly color-synthesized as it is, resulting in a bright screen and good color reproducibility.

b) The number of parts is reduced, the assembly accuracy is high, the long-term reliability is high, the optical system is simplified, and the device can be made compact.

Further, the projection type display device of the present invention is characterized in that, in such a projection type display device, the two types of dichroic optical elements of the color synthesizing means are arranged in a cross shape, and therefore the following effects are obtained. Have.

c) The distance from the light valve to the lens is short, the screen is bright, the degree of freedom of the enlargement ratio is increased, and a more compact optical system can be configured.

Furthermore, the projection type display device of the present invention is characterized in that, in the above-mentioned projection type display device, the distance from the light source to the light valve and the distance from the light source to the projection optical means are substantially equal for each primary color light. Therefore, it has the following effects.

d) The size of the light flux at the position of the light valve is substantially the same for each primary color light, and the size of the light flux at the position of the projection optical means is substantially the same for each primary color light. That is, the in-plane intensity distribution of the light illuminating the light valve is the same for each primary color light, and the in-plane intensity distribution of the light projected by the projection optical means is also the same for each primary color light, so an image display without color unevenness is possible. It will be possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an illumination structure 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. 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 9 ... Screen

Claims (1)

[Claims] 1. A color separation means for separating light from a single light source into three primary colors, three transmissive light valves for modulating each primary color from the color separation means, and each transmissive light valve. In a projection type display device having a color synthesizing unit for synthesizing primary color light and a projection optical unit for projecting the color-synthesized light, the color separating unit and the color synthesizing unit have different wavelength selection characteristics. First and second dichroic optical elements arranged in a cross shape, and further reflecting the first primary color reflected by the first dichroic optical element to provide a third dichroic optical element in the three transmissive light valves. 1 through the transmissive light valve.
And a second transmissive light valve in the three transmissive light valves by further reflecting the second primary color reflected by the second dichroic optical element. Again through the second
Second mirror group for making the dichroic optical element incident on the third dichroic optical element, and third transmissive light in the three transmissive light valves by reflecting the third primary color transmitted through the first and second dichroic optical elements. A third mirror group for making the light incident on the first and second dichroic optical elements again via a valve, and an incident position from a single light source on the first and second dichroic optical elements, and Different from the incident positions from the first, second and third mirror groups, and each of the incident positions includes an intersection of the first dichroic optical element and the second dichroic optical element. Characteristic projection display device.