JPS635854B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides three different colors of light.
The present invention relates to a projection type color receiver that displays color images by projecting them using two projection tubes, and particularly aims to obtain high-resolution images.

As shown in FIG. 1, the general principle of construction of a projection type color receiver is that projection tubes 1, 2, and 3 equipped with optical magnifying lenses project images onto a screen 4.
A color image is obtained by projecting optical images of three colors: red, green, and blue, and combining the three colors on a screen.

FIG. 2 is a cross-sectional view showing the main parts of the projection tubes 1, 2, and 3 used in the projection color receiver in more detail, in which 5 is an electron gun, 6 is an electromagnetic focus unit, 7 is a convergence coil, 8 is a deflection coil, 9 is a spherical reflection lens, 10 is a fluorescent target, and 11 is a Schmitt correction lens.

Electrons generated from the cathode of the electron gun 5 are accelerated by the accelerating electrode of the electron gun 5, focused by the magnetic field type electron lens made by the electromagnetic focus unit 6, and further deflected by the deflection coil 8, so that they are directed onto the fluorescent surface target. Projects a monochromatic image on the screen. This monochromatic image is enlarged and projected by a spherical reflection lens 9 and a Schmidt correction lens 11, and is formed on the screen 4 as an enlarged image.

By the way, when a color image is obtained by projecting red, green, and blue lights onto the screen 4 from different projection tubes, a color shift occurs between the three colors. In order to correct this, the image on the fluorescent surface target 10 is geometrically corrected by the convergence coil 7 shown in FIG.

FIG. 3 shows the configuration of this conventionally used convergence correction circuit.

7-1, 7-2, and 7-3 indicate convergence coils for three red, green, and blue projection tubes, each of which is equipped with a horizontal correction coil and a vertical correction coil.

As a convergence adjustment method, red and blue images are differentially corrected in the horizontal direction by the correction circuit R/B-H12 and superimposed, and the correction circuit R/B-V
13, the images are differentially corrected and superimposed in the vertical direction. Now match the red image and blue image,
Next, the correction circuit G-H14 and the correction circuit G-V15
The green image is corrected independently in the horizontal and vertical directions, and the green image is made to match the previously superimposed red and blue images.

Generally, in a projection type color receiver, the image obtained by the fluorescent surface target 10 is magnified through an optical lens system, so in order to obtain a high-resolution image, a high-precision optical lens system is required. It is required to project a bright and high resolution image onto the phosphor surface target 10. For this purpose, as shown in FIG. 2, an electromagnetic focus unit 6 is used, which can be used as an electron focusing lens and can be made into a large-diameter lens in order to reduce aberrations as much as possible. A focus coil is wound around the axis of the projection tube in this unit, forming an electron focusing lens larger than the diameter of the projection tube. Note that this electromagnetic focus unit can also be constructed from a permanent magnet without using a coil.

By the way, the diameter D of the electron beam spot on the fluorescent surface target 10 is expressed by the following formula, ignoring aberrations.

D=m×d (where m: electron lens magnification d: diameter of cathode front crossover image) Therefore, as another means of reducing the electron beam spot diameter in order to obtain a high-resolution image, the electron lens magnification There are ways to lower this.

The electron lens magnification is determined by the distance a between the cathode front crossover point and the electron lens, as shown in Figure 2.
and the distance b between the fluorescent surface target and the electron lens, b/a. Therefore, it is necessary to attach the electromagnetic focus unit 6 as close to the fluorescent surface target 10 as possible. However, in order to focus the electron beam without causing aberrations, the electron lens must be formed before the convergence coil 7 and the deflection coil 8, and is subject to positional restrictions.

In order to solve the above-mentioned conventional problems, the present invention improves the convergence correction adjustment method,
This aims to obtain high-resolution images by reducing the magnification of the electronic lens. The implementation configuration of the present invention will be described below with reference to FIGS. 4, 5, and 6.

By the way, in FIG. 1, projection tubes 1 and 3 project a red image and a blue image, and projection tube 2 projects a green image to obtain a color image on the screen. As is clear, it is placed in the center with respect to the screen, and the red and blue images are shifted in opposite directions with the green image at the center. Therefore, in this example,
As shown in FIG. 5, the correction circuit R-H16, R-V
17. Using G-H18 and G-V19, apply correction current to convergence coils 7-1 and 7-3 to move the red image and blue image independently in the horizontal and vertical directions, and superimpose them on the green image. This is to adjust the convergence. By adopting such a convergence adjustment method, there is no need to provide a convergence coil in the green projection tube 2, and the electromagnetic focus unit 6 is installed at a position immediately in front of the deflection coil 8, as shown in FIG. Therefore, the lens magnification becomes b/
It can be lowered from a to b'/a'.

By using the configuration in which the convergence is adjusted independently for red and blue and superimposed on green as in the above embodiment, the conventional convergence coil 7-2 can be removed from the projection tube 2 for green, and therefore The electromagnetic focus unit 6 of the green projection tube 2 can be mounted closer to the fluorescent surface than the other two color projection tubes, and as a result, the electronic lens magnification of the green projection tube 2 can be lowered. . That is, the diameter of the beam spot on the fluorescent surface target 10 is reduced and a high-resolution image can be obtained.

Here, FIG. 6 shows the relative luminous efficiency characteristics of the human eye. As can be seen from this characteristic, the human eye has high visibility for green, and therefore, as in this embodiment, it is possible to lower the electronic lens magnification of the green projection tube 2 and increase the resolution of the green image. Accordingly, the substantial sharpness of the color image can be improved.

As described above, the present invention includes a configuration in which red and blue projection tubes independently adjust the convergence of red and blue images, and a green projection tube in which the electronic lens magnification is set low. The object of the present invention is to provide an excellent projection-type color receiver that can improve sharpness and obtain high-resolution images.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the main parts of a general projection type color receiver, Fig. 2 is a sectional view showing a conventional projection tube and connecting parts, Fig. 3 is a block diagram showing a conventional convergence circuit section, and Fig. 4 is a block diagram showing a conventional projection tube and connecting parts. The figure is a cross-sectional view showing a projection tube and network components used in an embodiment of the present invention, and FIG. 5 is a configuration diagram showing a convergence circuit section of this embodiment.
FIG. 6 is a specific luminous efficiency characteristic diagram. 5... Electron gun, 6... Electromagnetic focus unit, 7
-1... Convergence coil for "red", 7-3...
Convergence coil for "Blue", 8...Deflection coil,
10... Fluorescent surface target, 16... Correction circuit R-
H, 17... Correction circuit R-V, 18... Correction circuit G-
H, 19...Correction circuit G-V.

Claims (1)

[Claims] 1. Mount an electromagnetic focus unit, a convergence coil, and a deflection yoke in order from the electron gun to the neck of the red and blue projection tubes, and attach the electromagnetic focus unit and deflection yoke to the neck in order from the electron gun side. The electromagnetic focus unit of the green projection tube is installed closer to the fluorescent surface of the projection tube than the red and blue projection tubes. A projection type color receiver characterized in that the electronic lens magnification is set lower than the electronic lens magnification of the red and blue projection tubes.