JP2643893B2 - 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 which irradiates an optical image formed on a light valve with illumination light and projects it on a screen by a projection lens.

[0002]

2. Description of the Related Art In order to display an image on a large screen, an optical image corresponding to an image signal is formed as a change in optical characteristics on a relatively small light valve, and this optical image is irradiated with illumination light and a projection lens is formed. Conventionally, a method of enlarging and projecting the image on a screen is 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 light output increases as the light source increases,
If a high-resolution light valve is used, a projection display device with high resolution and high light output can be realized even if its display area is small. Recently, a method of using a liquid crystal panel as a light valve has attracted attention (for example,
(SID86 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 then enter the color separation means 5. The color separation means 5 is configured by arranging a plate-type red reflection dichroic mirror 6 and a two-part plate-type blue reflection dichroic mirror 7, 8 at 90 ° intersection.

The red light exiting the color separation means 5 passes through the plane mirrors 9 and 10, the green light goes straight on as it is, and the blue light passes through the plane mirrors 11 and 12 to the corresponding liquid crystal panels. 13, 14, and 15 are incident. LCD panel 1
Optical images are formed at 3, 14, and 15 as changes in transmittance according to the respective video signals. Liquid crystal panel 13, 1
The output lights from 4 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 on a screen (not shown) by a telecentric projection lens 17. The light combining means 16 includes four right-angle prisms 1.
This is a prism type dichroic mirror in which 8, 19, 20, and 21 are bonded, and a red reflective multilayer film is deposited on bonding surfaces 22 and 23, and a blue reflective multilayer film is deposited on bonding surfaces 24 and 25.

The projection type display device shown in FIG. 6 has a single projection lens, so that the screen size or the projection lens 1
The feature is that the distance from 7 to the screen can be easily changed.

[0006]

In the configuration shown in FIG. 6, the multilayer films 22, 23, 24,
The 25 spectral characteristics have a reflection band where the reflectance is at a high level and a transmission band where the transmittance is at a high level. The wavelength at which the reflectance and the transmittance are 50% between the two bands is expressed as a cutoff wavelength. However, it may be considered that the internal loss of the multilayer film is almost nil.

In the wavelength range of several tens of nm near the cutoff wavelength, since the reflectance and the transmittance continuously increase or decrease, the red and blue light valves 13 and 15 are used.
Even if light emitted from the light enters, a part of the light is transmitted without being efficiently reflected. Similarly, the green light valve 14
Some of the light emitted from the light is reflected without being transmitted efficiently. Therefore, the effective band for efficiently combining the respective color lights in the light combining means 16 is the multilayer films 22 and 23, respectively.
The band is narrower than the band determined by the cutoff wavelengths 24 and 25. At this time, light near the cutoff wavelength is not effectively used, and there is a problem that the light use efficiency of the light combining means 16 is reduced.

Further, since the luminous body of the lamp 1 is not a perfect point light source but has a finite size, the light emitted from the condenser lens 2 travels while spreading, and
Light incident on 23, 24, 25 has a certain range of incident angles. In general, since the multilayer film has a property that the cutoff wavelength shifts according to the incident angle, the band for each color light of the light combining unit becomes narrower, and the brightness and color uniformity of the projected image are reduced. There's a problem.

The present invention has been made in view of the above points, and provides a projection type display device which improves the light use efficiency of a photosynthesis unit, thereby providing a large light output, and having good brightness and uniform color. It is intended to be.

[0010]

In order to solve the above-mentioned problems, a projection display device according to the present invention comprises: a red light emitting linearly polarized light spatially modulated in which an optical image is formed according to a video signal; Green, blue light valves, illumination means for irradiating the corresponding color light to the red, green, blue light valves, and a prism type dichroic mirror in which red and blue reflective multilayer films are crossed in an X shape. A light combining means for combining the light emitted from the light valves 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 emitted from the light valve goes straight through the light synthesizing means and enters the projection lens.The red reflective multilayer film and the blue reflective multilayer film bring the S-polarized cutoff wavelength closer to the green wavelength band, and Morphism multilayer film is less than 560nm or more 540nm cutoff wavelength of the S polarized light, the red reflecting multilayered film cutoff wavelength of the P polarized light is more than 620 nm 64
0 nm or less, the blue reflective multilayer film has an S-polarized cutoff wavelength of 510 nm or more and 540 nm or less, the blue reflective multilayer film has a P-polarized cutoff wavelength of 440 nm or more and 470 nm or less, and the green light valve. And the light emitted from the red and blue light valves is incident on the red and blue reflection multilayer films as S-polarized light. It is. It is preferable to use a metal halide lamp as a light source of the lighting means.

[0011]

According to the above construction, the effective band for the red, green and blue lights of the light synthesizing means is sufficiently wider than the band of each color light incident, so that the light emitted from each light valve is efficiently synthesized. 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 light combining means becomes narrower, the effective band when there is no shift becomes wider than the band of incident color light. As a result, it is possible to improve a reduction in light use efficiency and a reduction in uniformity of color and brightness in a projected image.

[0012] Further, even if a metal halide lamp having a longer luminous body length than a xenon lamp or a halogen lamp is used as a light source, a projection image with high uniformity in color and brightness can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a projection display device according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows the structure of an optical system according to an embodiment of the present invention. Reference numeral 30 denotes a light source, 38 denotes color separation means, 39, 40, 41, and 42 denote plane mirrors, and 43 and 4.
Reference numerals 4 and 45 denote light valves, 46 denotes a light synthesizing unit, and 47 denotes a projection lens. The light source 30, the color separation means 38 and the plane mirrors 39, 40, 41, 42 constitute illumination means. In addition, the configuration shown in FIG.
The configuration is the same as that of the conventional example shown in FIG. However, the red reflection multilayer film 51 of the photosynthesis means 46,
The characteristics of 52 and the characteristics of the blue reflective multilayer films 53 and 54 are the same. If the light beam ideally emitted from the light source 30 is completely parallel to the optical axis 37, the multilayer films 51, 52, 5
The incident angle of the light incident on 3, 54 is 45 degrees.

The light source 30 includes a lamp 31 and a condenser lens 32.
, A concave mirror 33, and a heat ray absorbing filter 34, and the lamp 31 uses a metal halide lamp,
It emits light containing three primary color components, green and blue. Lamp 3
The light radiated from 1 is converted by the condenser lens 32 and the concave mirror 33 into light that is nearly parallel. Strictly speaking, the lamp 31
The light emitted from the center 36 of the luminous body 35
From the optical axis 37 in parallel. Light emitted from the condenser lens 32 is subjected to removal of infrared rays by the heat ray absorption filter 34.

The output light of the light source 30 is incident on the color separation means 38, and the red reflection dichroic mirror 48 which crosses at 90 degrees.
And blue reflecting dichroic mirrors 49 and 50,
Decomposed into red, green and blue light. The spectral energy distribution of each separated color light is determined by the spectral energy distribution of the light beam emitted from the lamp 31 and the spectral characteristics of the red and blue reflection dichroic mirrors 48, 49, and 50. The red light leaving the color separation means 38 passes through the plane mirrors 39 and 40, the green light goes straight on, and the blue light passes through the plane mirrors 41 and 42.
Through the corresponding light valves 43, 44, respectively.
45.

The output lights from the light valves 43, 44 and 45 are combined into one by the light combining means 46, and a color image is combined substantially at the position of the light valve 44. This color image is enlarged and projected by a projection lens 47 on a screen (not shown).

The light valves 43, 44, and 45 are transmissive liquid crystal panels, having polarizing plates on the incident side and the outgoing side.
An optical image is formed as a change in transmittance according to a video signal. The polarization axes of the exit-side polarizers of the red and blue light valves 43 and 45 are perpendicular to the plane of the paper, and the green light valve 44 is
Are set parallel to the paper surface. Therefore, the light emitted from each light valve is linearly polarized light, and the light emitted from the red and blue light valves 43 and 45 enters the multilayer films 51, 52, 53 and 54 as S-polarized light, and the green light The light emitted from the valve 44 enters as P-polarized light. The polarization axis of the incident side polarizer of each light valve is
An arbitrary direction is taken depending on the characteristics of the liquid crystal panel. FIG. 2 shows an example of a spectral energy distribution of light emitted from the green light valve 44, and FIG. 3 shows an example of a spectral energy distribution of light emitted from the red and blue light valves 43 and 45, respectively. According to these configurations, the light combining means 46 emits light from the light valves 43, 44, 45.
The band of each color light incident on the
00 nm, green light ranges from 500 nm to 580 nm, and blue light ranges from 400 nm to 500 nm.

The light combining means 46 is a prism type dichroic mirror characterized in that the cutoff wavelengths of the S-polarized light of the red reflection and blue reflection multilayer films 51, 52, 53, 54 are very close in the green wavelength band. It is composed of In general, in a prism type dichroic mirror, if the material constituting the prism and the material and configuration of the multilayer film are appropriately selected, the cut-off wavelength of the P-polarized light of the red reflective multilayer film becomes longer than the cut-off wavelength of the S-polarized light. About 80nm on the side
Shift. Similarly, the cut-off wavelength of the P-polarized light incident on the blue reflective multilayer film is about 7 from the cut-off wavelength of the S-polarized light incident to the shorter wavelength side.
It is shifted by 0 nm. FIG. 4 shows the spectral reflectance characteristics of the red reflective multilayer films 51 and 52 of the light combining means 46. The solid line indicates the characteristic of P-polarized light incidence, and the broken line indicates the characteristic of S-polarized light incidence. The cutoff wavelength is 540 nm for S-polarized light incidence and 620 for P-polarized light incidence.
nm. Similarly (FIG. 5) shows blue reflective multilayer films 53 and 54.
Shows the spectral reflectance characteristics of The cut-off wavelength is 530 nm for S-polarized light incidence and 460 nm for P-polarized light incidence. Here, the value obtained by subtracting the reflectance from 100% may be considered as the transmittance, and the incident angles are both 45 degrees.

From the above configuration, when expressed using a cutoff wavelength, the light combining means 46 reflects light in the wavelength range of 540 nm to 700 nm for S-polarized incident red light and 460 nm for P-polarized incident green light. From 620
The light in the wavelength range of 400 nm is transmitted, and the light in the wavelength range of 400 nm to 530 nm is reflected with respect to blue light of S-polarized light incidence. Therefore, the effective band of the light synthesizing means 46 is sufficiently wider than the band of each color light to be incident, each color light can be efficiently synthesized, and high light use efficiency can be obtained.

The multilayer films 51, 52, 53, 54
When the incident angle of light changes from 45 degrees to ± 5 degrees, the cutoff wavelength shifts by about ± 25 nm. As a result, the effective band for each color light of the light synthesizing unit 46 may be narrowed. However, since the effective band when there is no shift is sufficiently wider than the band of each incident color light, the light use efficiency is reduced and the projected image quality is reduced. The decrease in brightness and color uniformity is very small. The above is remarkable when a lamp having a long luminous body length such as a metal halide lamp is used as the light source 30, and the above-described effects can reduce the deterioration of the image quality of the projected image and improve the light use efficiency. Furthermore, metal halide lamps are convenient because they have a longer life 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. 1, the light source 30, the color separation unit 38, and the plane mirrors 39, 40, 41, 42 constitute the illumination unit, but the red, green, and blue light valves 4 are used.
Any configuration may be used as long as the three, 44, and 45 are irradiated with three primary color lights. For example, a plurality of light sources can be used. A color filter such as a dichroic filter can be used as a means for obtaining the three primary colors. Regardless of the configuration of the illumination means, the light emitted from the green light valve 44 will
6, the light emitted from the red and blue light valves 43 and 45 is bent by the light combining means 46 so that each color light is incident on the projection lens 47. If the structure shown in FIG. Similar effects can be obtained.

[0023]

As described above, according to the present invention, the spectral characteristics of the prism type dichroic mirror constituting the light synthesizing means are optimally set, the polarization direction of the light emitted from the light valve is appropriately selected, and the light synthesis is performed. Since the cut-off wavelength of each multilayer film of the means is sufficiently separated from the band of light emitted from each of the red, green, and blue light valves, each color light can be efficiently combined into one, and projected. Deterioration of image quality can be reduced. As a result, it is possible to provide a projection display device which has good brightness and color uniformity of a projected image and high light output, and has a very great effect.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a configuration of a projection display device according to an embodiment of the present invention.

FIG. 2 is a graph showing an example of a spectral energy distribution of light emitted from a green light valve.

FIG. 3 is a graph showing an example of a spectral energy distribution of light emitted from red and blue light valves.

FIG. 4 is a graph showing spectral characteristics of a red reflective multilayer film of the photosynthesis unit shown in FIG.

FIG. 5 is a graph showing the spectral characteristics of the blue reflective multilayer film of the photosynthesis unit shown in FIG.

FIG. 6 is a schematic configuration diagram showing a configuration of a conventional projection display device.

[Explanation of symbols]

 Reference Signs List 30 light source 38 color separation means 39, 40, 41, 42 folding mirrors 43, 44, 45 light valve 46 photosynthesis means 47 projection lens

Claims (2)

(57) [Claims] 1. A red, green, and blue light valve from which an optical image is formed in accordance with a video signal and spatially modulated linearly polarized light is emitted, and the corresponding color light is divided into the red, green, and blue light valves. An illuminating means for irradiating the light valve; a light synthesizing means for synthesizing light emitted from each of the light valves into a prism type dichroic mirror in which red and blue reflective multilayer films are crossed in an X-shape; A projection lens that receives light emitted from the light combining means and projects an optical image of the light valve on a screen, and light emitted from the green light valve travels straight through the light combining means and enters the projection lens. The red reflective multilayer film and the blue reflective multilayer film make the cut-off wavelength of the S-polarized light close to the green wavelength band, and the red reflective multilayer film has a cut-off wavelength of the S-polarized light of 540 nm or more and 560 nm or less. Ri, the red reflecting multilayered film is less than 640nm cutoff wavelength above 620nm P-polarized light,
The blue reflective multilayer film has an S-polarized cutoff wavelength of 510n.
m or more and 540 nm or less, the blue reflective multilayer film has a P-polarized light cutoff wavelength of 440 nm or more and 470 nm or less, and light emitted from the green light valve is P-polarized light and enters the red and blue reflective multilayer films. A projection display device wherein light emitted from the red and blue light valves is incident on the red reflection and blue reflection multilayer films as S-polarized light. 2. The projection type display device according to claim 1, wherein a metal halide lamp is used as a light source.