JPS62219790A - Screen for projection type television receiver - Google Patents

Abstract

PURPOSE:To reduce the deviation of the beam light of a CRT, and to prevent deterioration in picture quality, by arranging optical detecting elements respectively at respective center parts of four sides; an upper, a lower, a right, and a left sides. CONSTITUTION:In a projection type television receiver main body 2, each one CRT for an R, a G, and a B are provided, and three colors of the R, the G, and the B display a color picture projected on a screen 1. Photodetecting elements 3A-3D are mounted at the center parts of four sides of a frame body 11 on the screen 1. The inside of dotted line in figure is a display area for a character and a graphic, etc., and the outside of it is a raster part, and the raster is expanded to almost the outside of the outer frame 11, and the optical detecting elements 3A-3D are arranged just the outside of a video display area. At a narrow range including the photodetecting elements 3A-3D of a part enclosed with dotted line and the outer frame 11, brightness points, or short luminescence lines of the three colors R, G, and B are projected, and by changing a projection timing, and a detecting timing at the photodetecting elements 3A-3D, the deviation at the center of the beam light in the CRT can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a halo screen used in a projection television receiver.

Conventionally, in projection television receivers, in order to keep the screen rask size constant, expansion and contraction of the screen rask size is detected, and the detection output is fed back to the control circuit and deflection circuit to adjust the desired screen rask size. No technology has been developed to achieve this goal, and therefore there is no example of a light detection section being provided around the screen (particularly on the outer periphery), and even if a detection element were provided, it would have to be a separate detection element for each of the 83 colors, R and G. It is expected that three color filters will be used.

Problems to be Solved by the Invention Therefore, in the screen of a conventional projection type television receiver, since the screen does not have a detection element for CRT beam light, when the rask size expands or contracts, the image quality deteriorates. Even if a detection element is provided, a filter is required, and detection elements for three colors are required, which is disadvantageous in terms of structure and cost.

The present invention aims to solve the above-mentioned problems and provides a screen on which photodetecting elements can be arranged at low cost.

Means for Solving the Problems In the present invention, photodetecting elements are arranged on the outer periphery of the screen (top, bottom, right, left, and right), and the photodetecting elements are placed at the outermost part of the raster so as not to interfere with the display of the screen. It is characterized by being attached to the frame of the screen.

Therefore, according to the present invention, by detecting the deviation of the beam light of the CRT with a photodetection element, feeding it back to the receiver side including the CRT drive unit, and changing the convergence, the deviation of the beam light of the jRT is reduced. This makes it possible to prevent deterioration of image quality.

EXAMPLE An example of the present invention is shown in FIG. In the figure, 1 is a screen equipped with a detection element of the present invention, and 2 is the main body side of a projection television receiver. This projection television receiver main body 2 has 861 R, G, and 861 CRTs.
Three colors, G and H, are projected onto the screen 1 to display a color image.

A beam shift detection signal from the CRT is projected from the CRT of the projection television receiver body 2 onto the screen 1, and is detected by the photodetecting elements 3A to 3D, which do not have monochromatic filters. 3 at the outer periphery of the screen.
Eliminate color shift. For example, photodetecting elements 3A to 3
The detection signal detected at D controls the horizontal and vertical amplitude control circuits to keep the rask size constant.

Now, the outer periphery of the screen 1 is shown enlarged in FIG. The shaded area 11 is the outer frame of the screen 1, and the photodetecting elements 3M to 3D are attached to the center of each of its four sides by slightly recessing the outer frame 11 as shown in the figure. The area inside the broken line in the figure is a display area for images such as characters 1 and figures, and the area outside is a part of the raster, and the raster is extended to the outside of the outer frame 11 in FIG. 2, for example. By arranging the photodetecting elements 3A to 3D just outside the image display area, blanking is normally performed with only the lasque, and nothing is displayed outside this display area. R, G are applied to a narrow area surrounded by the broken line and the outer frame 11, including the photodetecting elements 3M to 3D.

Bright spots of three colors in B (for 3 people, 3G) or short bright lines (
3B and 3D), the projection timing is changed, and the shift of the center of the CRT beam light is detected based on the detection timing of the photodetecting elements 3B and 3D.

In this way, the drift of the CRT beam light can be detected without affecting the display screen.

Effects of the Invention As described above, according to the present invention, changes in CRT beam light projected onto a screen can be detected without affecting the display screen, and can be used for control.

[Brief explanation of drawings]

FIG. 1 is a conceptual block diagram of a projection television receiver including a screen according to an embodiment of the present invention, and FIG. 2 is a front view of the same screen. DESCRIPTION OF SYMBOLS 1...Screen, 2...Projection type television receiver main body, 3A to 3D...Photodetection element, 11...Outer frame of screen. Name of agent: Patent attorney Toshio Nakao (1st person)
figure

Claims (2)

[Claims] (1) In a screen for a television receiver on which the image on the cathode ray tube surface is magnified and projected by a lens,
A screen for a projection television receiver, characterized in that photodetecting elements are arranged near the center of each of the four sides, top, bottom, left and right. (2) A projection television receiver according to claim 1, characterized in that a photodetector element having no monochromatic filter is provided for the beam output light of the cathode ray tube in three colors R, G, and B. screen.