JPS61269575A - Projection type television receiver - Google Patents

Abstract

PURPOSE:To eliminate trapezoidal distortion on a screw by displaying a raster on a screen of a projection CRT to give the trapezoidal distortion, applying a DC current to a vertical deflection yoke and moving the position of raster in the vertical direction. CONSTITUTION:The raster is displayed on the screen of a projection cathoderay tube so as to have trapezoidal distortion. The position of the raster is moved in the vertical direction to connect a series circuit comprising resistors R1, R2 to a vertical deflection yoke DY and while a switch SW1 is connected in parallel with the resistor R2, a switch SW2 is provided to select DC power supplies V1, V2 and power supplies V1, V2 and a common contact of the switch SW2 is connected to the end opposite to the connecting point of the resistor R2 to the resistor R1 and the switches SW1, SW2 are interlocked together. Thus, the correcting direction of the position of raster is changed by changing over the switches SW1, SW2 to display the raster fully on the CRT effective screen.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is a projection type that enlarges and projects red, green, and blue images on a cathode ray tube (hereinafter abbreviated as CRT) using a lens to obtain a large screen image. Regarding color television receivers.

BACKGROUND ART As shown in FIG. Since there is an angle φ between the center line of the screen 2 and the center line of the screen 2, the projection distances M and B of the upper and lower parts of the screen 2 are different, and therefore the projected image on the screen 2 causes trapezoidal distortion. In order to eliminate this trapezoidal distortion on the screen 2, as shown in FIG. 3, the raster on the CRT tube surface is made to have trapezoidal distortion by turning the trapezoid upside down in advance. In addition, in Figure 2, 3
is a CRT, 4 is a magnifying lens with constant magnification, and the third
In the figure, M indicates the effective screen of the CRT 3, and B and C indicate rasters having trapezoidal distortion.

Problems to be Solved by the Invention As described above, by imparting trapezoidal distortion to the CRT in advance and displaying raster images, it is possible to eliminate distortion on the screen. However, in this case.

In order to correct the above trapezoidal distortion, the dimensions C2D above and below the vertical center line of raster B on the CRT tube surface are 0<D.
are different from each other, resulting in a vertically unbalanced raster. If one attempts to use the third vane star to fill the CRT's effective screen under such conditions, a problem arises in which the image is missing at the bottom of the raster.

Therefore, conventionally, the entire raster has been made smaller than the CRT effective screen. However, if the raster is made smaller in this way, due to the current density (μm/CJ) that determines the lifetime of the phosphor, the CRT
It is necessary to lower the beam current. When the CRT beam current is lowered, the light output of the cathode ray tube decreases, and the screen 2
There was a problem with the upper raster becoming dark.

The present invention solves the above-mentioned conventional problems, and can eliminate trapezoidal distortion on the screen and (i
It is an object of the present invention to provide a device capable of displaying raster images on the entire RT effective screen.

Means for Solving the Problems In order to solve the above problems, the projection type color television receiver of the present invention is configured to supply a vertical deflection current including a direct current to the vertical deflection yoke to determine the raster position. It is characterized by being configured so that it can be varied in the vertical direction. Further, the present invention is configured so that the amount of correction can be changed to obtain a desired raster position in either the ceiling hanging type or the floor standing type.

According to the projection type color television receiver of the present invention, since the raster position can be varied in the vertical direction, it is possible to increase the size of the test 1cRT to the full effective screen and still project the raster at the center of the CRT screen. It is possible to obtain bright images with large light output. Of course, trapezoidal distortion of the raster on the screen does not occur.

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1, 3, and 4. FIG. 1 shows the configuration of the output section of a vertical deflection circuit, which is a main part of an embodiment of the present invention. In Figure 1a, Q+ and Q2 are vertical output transistors with class 8 push-pull configuration, C1 is a DC cut capacitor, DY is a vertical deflection coil, R1 and R2 are resistors connected in series with each other, and DC cut capacitor 6 It is connected in parallel to both ends of the penodenser C1. A switch sw, 6, is connected to both ends of this resistor R2 so that the resistor R2 is short-circuited and is still connected in series with the resistor R1. By flowing a direct current through this resistor R1 or a series circuit of resistors R1 and R2, the raster position can be moved in the vertical direction by ΔI. In addition, switch s
If the switch sw is connected to two contacts I and only the resistor R1 is used, the raster movement amount ΔX can be made larger than when the switch sw is connected to one contact y and the resistor R+10Rz is used.

As shown in Figure 2, this projection television receiver can be used by hanging it on the ceiling or by installing it on the floor, but the top and bottom and left and right sides of the image are reversed between the ceiling hanging version and the floor version. do. Therefore, the directions of ΔI are also opposite to each other. For this usage, as shown in Figure 1, linear power supplies vl and v2 with different polarities are provided, and this DC power supply v11 is used.
It is connected to the vertical deflection yoke DY via the v2k switch SW2 and the resistor R5. The correction direction of ΔX can be changed by selecting DC power supply V+lV2 with the switch SW2 and supplying DC 6 vane currents with different polarities to the vertical deflection yoke DY.

In addition, in this example, the angle φ is
Since the values are different, that is, the correction amounts ΔX are different, it is necessary to perform position correction according to each.

The circuit shown in FIG. 1C satisfies this requirement.

This circuit is basically a combination of the circuits shown in Figure 1a and b, connecting the series circuit of resistors R1 and R2 to the vertical deflection yoke D.
Y, and a switch SW1 is connected in parallel to this resistor R2, while a DC power source v1. v2 and this DC power supply v
1. A switch SW2 for selecting v2 is provided, the common contact of this switch SW2 is connected to the end of the resistor R2 opposite to the end connected to the resistor R1, and this switch SW1
．． sw2 are configured to interlock with each other. Therefore, according to the configuration of FIG. 1C, the switches sw1. sw2
You can change the correction direction of the raster position by switching , and also adjust the correction amount ΔI according to each specification.
can be obtained.

7 Vane By the way, in an actual television receiver, as shown in Figure 4, the center of the video signal's Rask deflection range and the transmitted effective signal (actual video range) B are shifted, so the actual effective If the position of the raster (effective video signal) is corrected by half Δy of the deviation Δy between the center of the video signal and the center of deflection, then the value of the resistor that supplies DC current for either direction of raster correction is By adjusting .DELTA.W/2f.DELTA.X, it is possible to cancel the difference by .DELTA.W/2f.DELTA.X, and .DELTA.X is substantially corrected only in the other direction. Therefore, in this case, the circuit shown in FIG. 1a may be used. Note that, for the sake of simplicity, FIG. 4 is shown with the raster distortion correction set to zero. By correcting Δy/2 in this manner, the amount of correction by the centering magnet, which is a correction element for aligning the center of the image with the center of the cathode ray tube screen, can be reduced.

This is because when the amount of correction of the centering magnet exceeds a certain limit, the spot diameter of the electron beam increases, resulting in a problem in that the focus quality of the image deteriorates and the image quality deteriorates. It is possible to prevent problems such as smoke and improve image quality.

Effects of the Invention As described above, according to the present invention, a raster with trapezoidal distortion can be projected at the center of a CRT screen by superimposing a direct current on the vertical deflection current and supplying it to the vertical deflection yoke. In addition, it is possible to enlarge the image to the full extent of the effective screen of (ljRT), and it is possible to improve the brightness of the image.

[Brief explanation of drawings]

Figures 1a, b, and O are circuit diagrams of essential parts of a projection type television receiver according to an embodiment of the present invention, Figure R2 is a side view showing an example of installation of a projection type television receiver, and Figures 3 and 3 are FIG. 4 is a front view showing the state of the screen for explaining the operation of the receiver of the present invention. Q+, Q2... Vertical quadrantis (ri, cl
・Old: DC cut capacitor, DY...
Vertical deflection yoke, R,, R2... Resistor, SWl
······switch.

Claims (2)

[Claims] (1) A raster is projected on the screen of a projection cathode ray tube with trapezoidal distortion, and a direct current is supplied to a vertical deflection yoke so that the position of this raster can be moved in the vertical direction. Projection type television receiver. (2) The projection television receiver according to claim 1, which is configured to be able to adjust the amount of correction of the raster position.