JPH10197703A - Projecting device for projection television - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the contrast of an image while increasing the color purity of three-tube type projection television and to eliminate color irregularity, and to eliminate variation in absorption characteristics of unnecessary light with temperature and to obtain stable characteristics by improving a projection lens which is used for the projecting device. SOLUTION: Red, green, and blue three-tube CRT images are projected on a screen by a projection lens consisting of a meniscus lens 3 arranged in its front and a lens group R which is arranged in front of the meniscus lens 3 and includes lenses; and a light absorbing substance which absorbs light of a sideband of light emission characteristics of a green CRT is added to the lens R1 which is arranged most closely to the meniscus lens 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called three-tube type projection television for projecting images of three projection tubes of red, green and blue onto a screen by a projection lens, and to an improvement of the projection tube device.

[0002]

2. Description of the Related Art Conventionally, there is a projection television as described above, for example, as shown in FIG. This apparatus comprises three CRT projection tubes 10R, 10R for red, green and blue.
G and 10B are projected onto the respective projection lenses 20R, 20G and 20.
B is projected onto the back of the screen 30 and synthesized so that an enlarged color image can be viewed on the front of the screen 30, and is called a so-called rear projection television.

[0003] By the way, CRT projection tubes 10R, 10G,
Each of the 10B emission colors has its own characteristics, especially the green CR
As shown by the solid line A in FIG. 5, the emission characteristics of the T projection tube 10G have sidebands around 580 nm and 625 nm on the red wavelength band side. This sideband reduces the color purity of green,
The color of the green CRT projection tube 10G is yellowish green,
When combined with red and blue with the same light emission characteristics, the color balance of the image deteriorates. For this reason, conventionally, a dichroic filter having characteristics as shown by a dashed line B in FIG. 5 is coated on the lens inside the projection lens 20G to increase the color purity of the green image.

However, when the dichroic filter is used as described above, the extra light cut by the filter is reflected from the projection lens 20G to the CRT projection tube 10G side, and the front glass of the CRT projection tube 10G is illuminated and the image is formed. There is a problem that the contrast is reduced.
In addition, the dichroic filter has an angle dependence on an incident light beam, and the filter characteristic changes depending on a difference in the incident angle of the light beam on the lens surface, causing color unevenness of a screen screen.

A sealed space is formed on the front panel side of the projection tube, and a light-transmissive liquid refrigerant is sealed in the space to cool the heat generated from the front panel. As an example, there has been proposed an apparatus in which a dye that absorbs light other than the main wavelength generated by a phosphor is dissolved to absorb unnecessary light from, for example, a green projection tube (Japanese Utility Model Application No. 56-68233 (Japanese Utility Model Application Publication No. Kaisho 57-18095
No. 7) microfilm).

However, in such a configuration, the temperature of the liquid refrigerant rises due to the heat generated from the front panel, and the dye is heated to deteriorate the light absorbing property, and the dye flows due to convection generated in the liquid refrigerant. In addition, the absorption characteristics of unnecessary light fluctuate, and a sufficient absorption effect cannot be obtained.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a three-tube projection television, which improves a projection lens used in a projection apparatus, improves image contrast while increasing color purity, and eliminates color unevenness. Aim. It is another object of the present invention to obtain stable characteristics without changing the absorption characteristics of unnecessary light with temperature.

[0008]

According to the projection apparatus for a projection television of the present invention, images of three red, green and blue projection tubes are formed by a meniscus lens disposed in front of each of the projection tubes and the meniscus lens of the meniscus lens. In a projection television projection apparatus used for a three-tube projection television, which is configured to project on a screen by a projection lens configured with a lens group including a plurality of lenses disposed on the front surface, the projection device for the green projection tube A light-absorbing substance that absorbs light in a sideband in light emission characteristics is added to a lens arranged at a position closest to a meniscus lens among a plurality of lenses arranged in front of the green projection tube. It is characterized by.

[0009]

FIG. 1 is an assembled side view showing a projection device according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of the projection device. The same three projection devices are provided in red, green and blue. It forms three color images, respectively, and is used for, for example, a rear projection television. In the drawing, reference numeral 1 denotes a CRT projection tube having a front glass 1a having a flat surface, 2 denotes an aluminum die-cast coupler having a plurality of fins 21 around it,
Reference numeral 3 denotes a plastic meniscus lens which constitutes a projection lens together with a plurality of lens groups R and mainly corrects field curvature, and an image projected on the front glass 1a of the CRT projection tube 1 passes through a coupler 2. Meniscus lens 3
And is projected on a screen (not shown) by the lens group R.

In the coupler 2, a circular opening 2a for fitting the meniscus lens 3 is formed at the center thereof, and a side wall surrounding a substantially rectangular space is formed on the CRT projection tube 1 side of the opening 2a. 22 are formed. The opening formed by the side wall portion 22 on the side of the CRT projection tube 1 has substantially the same shape as the surface of the front glass 1a.

Then, the CRT projection tube 1 and the coupler 2
The packing 4 is arranged between the front glass 1 a and the periphery of the opening of the side wall 22 and is fixed by the mounting frame 5. Also,
The meniscus lens 3 is provided with a packing 6 and has an opening 2a.
, And screwed to the coupler 2 by the lens fixing frame 7.

A portion sealed by the CRT projection tube 1, the meniscus lens 3 and the side wall 22 is filled with a cooling liquid.
The front glass 1a is cooled by the cooling liquid, and the front glass 1a and the meniscus lens 3 are optically coupled. The heat of the cooling liquid is transmitted to the coupler 2 and the fins 21 and radiated. A pressure regulating chamber 23 for keeping the pressure of the coolant constant is formed in a part of the side wall 22 of the coupler 2.

The projection device of this embodiment projects a green image, and the emission characteristics of the CRT projection tube 1 are as shown by a solid line A in FIG. In the projection lens disposed in front of the green projection tube, a lens R1 disposed at a position closest to the meniscus lens 3 among the plurality of lens groups R is indicated by a dashed line C in FIG. A light-absorbing substance having an absorption characteristic is added, and light transmitted through the lens R1 is light in which a green sideband is cut.

Therefore, the green image obtained by this projector has high color purity, and the light in the sideband is absorbed by the light absorbing substance added to the lens R1 on the CRT projection tube 1 side. Therefore, it is possible to reduce the reflection of unnecessary light in the lens unit R.
Even if slightly unnecessary light enters the lens group R and is reflected in the lens group R due to the absorption characteristic of the CRT, the reflected light is absorbed by the lens R1.
Unnecessary light is not reflected to the side, and the contrast of the image is improved.

[0015]

As described above, according to the projection device for a projection television of the present invention, the light absorbing substance that absorbs the light in the sideband in the emission characteristic of the green projection tube is disposed in front of the projection tube. Of the multiple lenses that were added, the lens was added to the lens located closest to the meniscus lens, and this light absorbing material absorbed sideband light to reduce reflected light, so color purity was improved. It is possible to improve the contrast of the image while increasing the color and to eliminate color unevenness. Also, stable characteristics can be obtained without the light absorption characteristics fluctuating with temperature.

[Brief description of the drawings]

FIG. 1 is an assembled side view showing a projection device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the same device.

FIG. 3 shows absorption characteristics of a light absorbing substance and green C in an example.
It is a figure showing the light emission characteristic of a RT projection tube.

FIG. 4 is a diagram showing an example of a conventional three-tube projection television.

FIG. 5 is a diagram showing absorption characteristics of a conventional dichroic filter and light emission characteristics of a green CRT projection tube.

[Brief description of reference numerals]

 1 CRT projection tube R lens group R1 lens 3 meniscus lens

Claims (1)

[Claims] 1. A lens group including a meniscus lens disposed on the front of each projection tube, and a plurality of lenses disposed on the front of the meniscus lens. A projection device for a projection television used in a three-tube projection television configured to project on a screen by using a projection lens composed of: a light-absorbing material that absorbs sideband light in the emission characteristics of the green projection tube. Is added to a lens disposed at a position closest to the meniscus lens among a plurality of lenses disposed in front of the green projection tube.