JPH01302385A - Projection type display - Google Patents

Abstract

PURPOSE:To prevent the lowering of a light utilizing efficiency and the lowering of uniformities of a color and a brightness in a projected image when an effective band is made into a narrow band by sufficiently widening the effective band to red, green and blue lights of a light synthesizing means in comparison with the band of each color light made incident efficiently synthesizing lights emitted from respective light valves. CONSTITUTION:The spectral characteristic of a prism type dichroic mirror to compose a light synthesizing means 46 is set optimum, the polarizing directions of the lights emitted from light valves 43-45 are properly selected, and the cut-off wavelengths of respective multilayer films 51-54 of the light synthesizing means 46 are sufficiently separated from the bands of the lights emitted from respective light valves 43-45 of the red, green and blue. Consequently, respective color lights can be efficiently synthesized into one, and the deterioration of the picture quality of the projected image can be reduced. Thus, a projection type display can be obtained in which the uniformities of the brightness and color of the projected image are satisfactory and, moreover, a light output is large.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a projection display device that irradiates an optical image formed on a light valve with illumination light and projects it onto a screen using a projection lens.

Conventional technology In order to display images on a large screen, an optical image is formed in a relatively small light valve according to the image signal as changes in optical characteristics, and this optical image is irradiated with illumination light and projected onto a screen using a projection lens. A method of enlarging and projecting an image upward has been well known.

In this type of projection display device, the resolution of the projected image is almost determined by the resolution of the light valve, and the stronger the light source, the greater the light output. A projection display device with high resolution and high light output can be realized. Also, recently,
A method of using a liquid crystal panel as a light valve is attracting attention (for example, 5ID86 Digest, page 375).

An example of a conventional configuration of such a projection display device is shown in FIG.

The lamp 1 emits light containing red, green, and blue color components, and the light emitted from the lamp 1 is converted into nearly parallel light by a condenser lens 2 and a concave mirror 3, and transmitted through a heat ray absorption filter 4. Thereafter, the light enters the color separation means 5. The color separation means 5 is composed of a flat plate type red reflective dichroic mirror 6 and a flat plate type blue reflective dichroic mirror 7.8 which are divided into two parts and are arranged to cross each other at 90 degrees.

The red light coming out of the color separation means 5 passes through the plane mirror 9, 10, the green light goes straight, and the blue light passes through the plane mirror 1.
). 12, the respective corresponding liquid crystal panels 13.
14.Injected on 15th. Optical images are formed on the liquid crystal panels 13, 14, and 15 as changes in transmittance according to the respective video signals. The output lights from the liquid crystal panels 13, 14, and 15 are combined into one by the light combining means 16 to form a color image substantially at the position of the green liquid crystal panel 14.

This color image is enlarged and projected onto a screen (not shown) by a telescopic projection lens 17. The light synthesis means 16 includes four right angle prisms 18.19.20.2
It is a prism type gicchroic mirror in which 1 is bonded to the bonding surface 22.23, and a red reflective multilayer film is bonded to the bonding surface 24.2.
5, a blue reflective multilayer film is deposited.

The projection type display device shown in FIG. 6 has a feature that the screen size or the distance from the projection lens I7 to the screen can be easily changed because it has one projection lens.

Problems to be Solved by the Invention In the configuration shown in FIG. 6, the spectral characteristics of the multilayer film 22, 23, 24, 25 of the photosynthesis means 16 have a reflection band at a high level of reflectance and a high level of transmittance. It has a certain transmission band. The wavelength at which the reflectance and transmittance are 50% between the above two bands is expressed as the cutoff wavelength. However, it may be considered that the multilayer film has almost no internal loss.

In the wavelength range of several tens of I1) near the above-mentioned cutoff wavelength, the reflectance and transmittance continuously increase or decrease, so that the light emitted from the red'' and blue light valves 13.15 is incident. Similarly, a portion of the light emitted from the green light valve 14 is also reflected without being efficiently transmitted. The effective bands for efficiently synthesizing each color light are multilayer films 22, 231, and 24, respectively.
．． The band is narrower than the band determined by the cutoff wavelength of 25. At this time, there is a problem that the light near the cutoff wavelength is not used effectively, and the light usage efficiency of the photosynthesizing means I6 becomes low.

In addition, since the light emitting body in the lamp l is not a complete point light source but has a finite size, the light emitted from the condenser lens 2 travels while spreading, and the multilayer film 22, 23, 24...
The light incident on 25 has a range of angles of incidence. in general,
Since the multilayer film has the property that the cutoff wavelength shifts depending on the angle of incidence, the band for each color light of the light synthesis means becomes narrower, which causes the problem that the brightness and color uniformity of the projected image decreases. be.

The present invention has been made in view of the above points, and an object of the present invention is to improve the light utilization efficiency of a photosynthesis means, thereby providing a projection type display device with a large light output and good brightness and color uniformity. It is said that

Means for Solving the Problems In order to solve the above problems, the projection display device of the present invention includes:
Red, green, and blue light valves that form optical images in response to video signals and emit spatially modulated linearly polarized light;
an illumination means for irradiating each of the red, green, and blue light valves with corresponding colored lights; and a prism-type guichroic mirror in which red reflective and blue reflective multilayer films are crossed in an X-shape, the light valves each comprising: a light combining means for combining light emitted from the light valve into one, and a projection lens for receiving the light emitted from the light combining means and projecting an optical image of the light valve onto a screen, the light emitting from the light valve recorded previously. passes straight through the light combining means and enters the projection lens, the red reflective multilayer film has a cutoff wavelength of S-polarized light of 540 nm or more and 560 nm or less, and the blue reflective multilayer film has a cutoff wavelength of S-polarized light of 510 nm or more. 540 nm or less, the light emitted from the light valve of the previous recording is P-polarized light and enters the red reflective and blue reflective multilayer films, and the light emitted from the red and blue light pulps is S-polarized light and enters the red reflective and blue reflective multilayer films. The light is made incident on a reflective multilayer film. Note that it is preferable to use a metal halide lamp as the light source of the illumination means.

Effect: According to the above configuration, the effective bands of the light combining means for red, green, and blue lights are sufficiently wider than the bands of each incident color light, so that the lights emitted from each light valve are efficiently combined. Furthermore, even if the cutoff wavelength shifts depending on the angle of incidence of light on each multilayer film and the effective band of the photosynthesizing means becomes narrow, the effective band when it does not shift becomes broader than the band of incident colored light. Therefore, it is possible to improve the reduction in light utilization efficiency and the reduction in uniformity of color and brightness in the projected image.

Further, due to the above effect, even if a metal halide lamp, which has a longer light emitting body than a xenon lamp or a halogen lamp, is used as a light source, a projected image with high uniformity in color and brightness can be obtained.

Embodiment An embodiment of a projection type display device according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows the configuration of an optical system in an embodiment of the present invention, in which 30 is a light source, 38 is color separation means, 39.40
．． 4, 42 is a plane mirror, 43, 44, 45 are light valves, 46 is a light combining means, and 47 is a projection lens.

Light R30 and color separation means 38 and plane mirror 39.40
．． 41 and 42 constitute the illumination means. The configuration shown in FIG. 1 is the same as that of the conventional example shown in FIG. 6, except for the lamp 31 of the light source 30.

However, the characteristics of the red reflective multilayer films 51 and 52 and the characteristics of the blue reflective multilayer films 53 and 54 of the light combining means 46 are the same. Ideally, if the light beam emitted from the light source 30 is completely parallel to the optical axis 37, the multilayer film 51, 52, 53, 54
The angle of incidence of light entering the is 45 degrees.

The light source 30 includes a lamp 31, a condensing lens 32, and a concave mirror 3.
3 and a heat ray absorption filter 34.
1 uses a metal halide lamp and emits light containing the three primary color components of red, green, and blue. Light emitted from the lamp 31 is converted into nearly parallel light by a condenser lens 32 and a concave mirror 33. Strictly speaking, the light rays emitted from the center 36 of the light emitter 35 of the lamp 31 are emitted from the condenser lens 32 in parallel to the optical axis 37.

Infrared rays of the light emitted from the condensing lens 32 are removed by a heat ray absorption filter 34.

The output light from the light source 30 enters the color separation means 38, and is separated into red, green, and blue light by a red reflective dichroic mirror 48 and a blue reflective dichroic mirror 49, 50 which intersect at 90 degrees. The spectral energy distribution of each separated color light is the spectral energy distribution of the luminous flux emitted from the lamp 31, and the red reflection and blue reflection dichroic mirrors 48, 49.
It is determined by the spectral characteristics of 50. Red light exiting the color separation means 38 passes through plane mirrors 39, 40, green lights go straight, and blue lights pass through plane mirrors 41, 42, respectively, to the corresponding light pulps 43, 44, . 45.

The output lights from the light valves 43, 44, and 45 are combined into one by a light combining means 46 to essentially create a color image of the light pulp 44. This color image is enlarged and projected onto a screen (not shown) by a projection lens 47.

The Light Pulp 43, 44, and 45 are transmissive liquid crystal panels that have polarizing plates on the incident side and the output side, and form an optical image as a change in transmittance according to a video signal. The polarizing axes of the polarizing plates on the output side of the red and blue light pulps 43 and 45 are set perpendicular to the plane of the paper, and the polarizing axes of the polarizing plates on the output side of the green light valve 44 are set parallel to the plane of the paper. Therefore,
The emitted light of each light pulp is linearly polarized light, and the multilayer film 51
．． 52, 53, and 54, the light emitted from the red and blue light pulps 43.45 enters as S-polarized light, and the light emitted from the green light valve 44 enters as P-polarized light. The polarization axis of the incident-side polarizing plate of each light valve is set in an arbitrary direction depending on the characteristics of the liquid crystal panel. Figure 2 shows an example of the spectral energy distribution of light emitted from the green light valve 44, and Figure 3 shows the red and blue light valves 43.4.
An example of the spectral energy distribution of light emitted from 5 is shown. According to these configurations, the light valve 43.4
The bands of each color light emitted from 4.45 and incident on the light combining means 46 are from 580 nm to 700 nm for red light, from 500 nm to 580 nm for green light, and from 400 nm to 500 nm for blue light.

The light synthesizing means 46 includes red reflective and blue reflective multilayer films 51 and 52.
．． It is composed of a prism-type gicchroic mirror characterized in that the cutoff wavelengths of S-polarized light of 53 and 54 are very close to each other in the green wavelength band.

In general, in a prism-type gicroic mirror, if the material constituting the prism and the material and structure of the multilayer film are appropriately selected, the cutoff wavelength of the P-polarized light incident on the red reflective multilayer film can be changed from the cutoff wavelength of the S-polarized light incident. Approximately 80 on the long wavelength side
It shifts by nm. Similarly, the cutoff wavelength of the P-polarized light incident on the blue reflective multilayer film is shifted from the cutoff wavelength of the S-polarized light incident to the shorter wavelength side by about 70 nm.

FIG. 4 shows the spectral reflectance characteristics of the red reflective multilayer films 51 and 52 of the photosynthesis means 46. The solid line represents the characteristic when P-polarized light is incident, and the broken line represents the characteristic when S-polarized light is incident. The cutoff wavelength is 540 nm for S-polarized light incidence and 620 nm for P-polarized light incidence. Similarly, FIG. 5 shows the spectral reflectance characteristics of the blue reflective multilayer films 53 and 54. The cutoff wavelength is 530 nm for S-polarized light incident.
P-polarized light incidence is 460 nm. Here, the value obtained by subtracting the reflectance from 100% may be considered to be the transmittance, and the incident angle is 45 degrees in both cases.

From the above configuration, the light combining means 46 is expressed using a cutoff wavelength of 540 nm for S-polarized incident red light.
Reflects light in the wavelength range from m to 700 nm, transmits light in the wavelength range from 460r+m to 62Or+m for green light with P-polarized incidence, and transmits light in the wavelength range of 460r+m to 62Or+m with respect to S-polarized incident blue light.
Reflects light in the wavelength range of 00 nm to 530 nm.

Therefore, the effective band of the light combining means 46 is sufficiently wider than the band of each incident color light, and each color light can be efficiently combined, resulting in high light utilization efficiency.

In addition, the multilayer film 5152, 53, 54 has a light incident angle of 4
When changing from 5 degrees to ±5 degrees, the cutoff wavelength is ±25 nm.
shift in degree. As a result, the effective band for each color light of the light combining means 46 may be narrowed, but since the effective band without shifting is sufficiently wide compared to the band of each incident color light, the light utilization efficiency may be reduced or the projected image may be There is very little reduction in brightness and color uniformity. The above problem occurs significantly when a lamp with a long light emitting body length, such as a metal halide lamp, is used as the light source 30, and the above effects can reduce the deterioration of the image quality of the projected image and improve the light utilization efficiency. Furthermore, metal halide lamps are advantageous because they have a longer lifespan and higher efficiency than xenon lamps and halogen lamps.

Next, another embodiment of the present invention will be described.

In the configuration shown in FIG.
8 and a plane mirror 39, 40, 41, 42 were used to construct the illumination means, and red, green, and blue light valves 43, 44
．． Any structure may be used as long as it irradiates light of three primary colors onto the light source 45. For example, it is also possible to use multiple light sources. In addition, as a means of obtaining colored light of the three primary colors,
It is also possible to use a color filter such as a dichroic ink filter. Regardless of the configuration of the lighting means,
The light emitted from the green light valve 44 goes straight through the light combining means 46 , and the light emitted from the red and blue light valves 43 , 45 is bent by the light combining means 46 and passes through the projection lens 47 .
If the structure is such that each color light is incident on the light source, the same effect as the structure shown in FIG. 1 can be obtained.

Effects of the Invention As described above, according to the present invention, the spectral characteristics of the prism-type gicroic mirror constituting the photosynthesis means are set optimally, the polarization direction of the light emitted from the light valve is appropriately selected, and the photosynthesis is performed. Since the cutoff wavelength of each multilayer film of the means is set sufficiently apart from the band of light emitted from each of the red, green, and blue light valves, each color light is efficiently divided into one.
Therefore, it is possible to reduce the deterioration of the image quality of the projected image. As a result, it is possible to provide a projection type display device with good brightness and color uniformity of projected images and high light output, which has a very large effect.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing the configuration of a projection display device according to an embodiment of the present invention, FIG. 2 is a graph showing an example of the spectral energy distribution of light emitted from a green light valve, and FIG.
The figure is a graph showing an example of the spectral energy distribution of light emitted from the red and blue light valves, FIG. 4 is a graph showing the spectral characteristics of the red reflective multilayer film of the photosynthesis means shown in FIG. 1,
FIG. 5 is a graph showing the spectral characteristics of the blue reflective multilayer film of the photosynthesis means shown in FIG. 1, and FIG. 6 is a schematic diagram showing the structure of a conventional projection display device. 30... Light source, 38... Color separation means,
39.40.41.42... folding mirror,
43.44.45...Light bulb, 46...
...Photosynthesis means, 47...Projection lens. Name of agent: Patent attorney Toshio Nakao

Claims (2)

[Claims] (1) Red, green, and blue light valves from which an optical image is formed according to a video signal and spatially modulated linearly polarized light is emitted; an illumination means for irradiating the light to the light source; a light synthesis means that is a prism-type dichroic mirror in which red reflective and blue reflective multilayer films are crossed in an X-shape and that combines the lights emitted from each of the light valves into one; a projection lens that receives light emitted from the means and projects an optical image of the light valve onto a screen; the light emitted from the green light valve passes straight through the light combining means and enters the projection lens; The red reflective multilayer film has a cutoff wavelength of 540 for S-polarized light.
nm or more and 560 nm or less, and the blue reflective multilayer film is S
The cutoff wavelength of polarized light is 510 nm or more and 540 nm or less, the light emitted from the green light valve is P-polarized and enters the red reflective and blue reflective multilayer films, and the light emitted from the red and blue light valves is P-polarized light. A projection type display device in which S-polarized light is incident on the red reflective and blue reflective multilayer films. (2) Claim (1) in which a metal halide lamp is used as the light source
) projection type display device.