JPS6334673B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a vertical line correction device that can be used in a projection television receiver.

Conventional configurations and their problems In projection television receivers, trapezoidal distortion occurs due to the angle between the projection optical axis and the screen, and pincushion distortion occurs depending on the projection distance. Therefore, in practical use, it is necessary to correct the trapezoidal distortion and pincushion distortion.

FIG. 1 shows a conventional raster correction circuit including left and right pincushion distortion correction circuits and a trapezoidal distortion correction circuit. To correct left and right pincushion distortion (hereinafter referred to as side pink distortion), it is best to increase the horizontal deflection force at the center of the raster. In addition, for trapezoidal distortion, a trapezoidal distortion correction signal (vertical sawtooth voltage) may be applied to the horizontal deflection coil. In FIG. 1, reference numeral 1 denotes an integrating circuit which converts a vertical sawtooth wave signal from a vertical output circuit (not shown) into a vertical parabolic wave voltage and applies it to the base of a transistor 2. The transistor 2 inverts and amplifies the parabolic wave voltage, and then supplies it to the side pink coupling volume 3. The vertical parabolic wave voltage supplied to the side pincushion volume 3 is amplitude-adjusted here, and the DC voltage adjusted by the horizontal amplitude volume 4 is added to the base of the transistor 5. After being inverted and amplified by transistor 5, the vertical parabolic voltage is applied to the base of transistor 6. The internal resistance of transistor 6 therefore varies parabolically with vertical rate and also with DC voltage from the horizontal amplitude volume. This vertical parabolic wave voltage is supplied to a horizontal output circuit 7 including a diode modulator type raster correction circuit to modulate the horizontal polarized current. This diode modulator type circuit has the advantage that the collector pulse of the horizontal output transistor 71 is always constant and that the secondary side of the flyback transformer 8 is not subject to fluctuations due to raster correction.

Further, a circuit consisting of transistors 91, 92, 93 and a volume 94 is a trapezoidal distortion correction circuit 9.
By adjusting the volume 94, a trapezoidal distortion correction voltage (vertical sawtooth voltage) of desired amplitude and polarity can be obtained. By moving the movable terminal of the volume 94 from the midpoint to either side, a vertical sawtooth voltage is obtained, and the obtained vertical sawtooth voltage is supplied to the base of the transistor 6 through the transistor 5, and therefore the transistor at this time A voltage having a waveform as shown in the circle in FIG. 1 is applied to the base of 6.

As described above, according to the circuit configuration shown in FIG. 1, side pink cushion correction and trapezoidal correction are possible. The solid line in FIG. 2 indicates the trapezoidal distortion that occurs when the projection television receiver is placed on the floor. In order to create a distortion-free raster as shown by the broken line, the vertical sawtooth voltage shown in FIG. 3a is applied to both ends of the capacitor 72 forming the horizontal output circuit 7, as described above. Here, since the capacitor 72 functions as a filter to prevent the horizontal signal component from flowing to the modulation signal generation circuit, the capacitor 72 cannot be made much smaller than that value. As a result, even if a vertical sawtooth voltage as shown by the broken line in Figure 3a is applied, the capacitor 7
The charging time constant of 2 becomes large, and the waveform becomes sluggish as shown by the solid line. This appears on the projected screen as a curve at the top of the screen, as shown in Figure 3b.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned problems, and aims to perform vertical line correction without bending at the top of the screen.

Configuration of the Invention The vertical line correction device according to the present invention performs vertical line correction by further adding a rectangular wave voltage during a vertical retrace period to a vertical sawtooth wave voltage for trapezoidal correction.
The capacitor is instantly charged by the rectangular wave during the vertical retrace period. This eliminates the dullness of the sawtooth waveform, making it possible to obtain a vertical line correction device without bending in the upper part of the image.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 4, elements and circuits that perform the same functions as those in FIG. 1 are given the same numbers.
The differences in FIG. 4 from FIG. 1 are transistors 101 and 102 for inversion amplification, collector resistor 103 of each transistor 101, emitter resistor 104, collector resistor 105 of transistor 102, and variable width adjustment. A rectangular wave amplification output circuit 10 is provided, which is composed of a resistor 106 and a diode 107 for preventing backflow, and amplifies a rectangular wave having a pulse width of one vertical retrace period V _BLK and supplies the amplified rectangular wave to the horizontal output circuit 7. be.

A rectangular wave having a pulse width V _BLK of one vertical period is input to the base of the transistor 101 , inverted and amplified, and then supplied to the base of the transistor 102 . The square wave is further inverted and amplified by the transistor 102, and the collector of the transistor 102 has a +
A square wave with a level of _B3 is output. The amplitude of this rectangular wave is appropriately adjusted by a variable resistor 106, and the wave is passed through a diode 107 for preventing backflow.
It is supplied to the horizontal output circuit 7 together with a vertical sawtooth voltage for trapezoidal correction and a vertical parabolic voltage for side pink cushion correction. As a result, the capacitor 72 in the horizontal output circuit 7 is instantly charged, so that the sawtooth wave is no longer rounded and the curve at the top of the image can be corrected to become a straight line.

Effects of the Invention According to the present invention, by applying a rectangular wave having a pulse width of one vertical retrace period to the horizontal output circuit together with a vertical sawtooth voltage, etc., the screen can be By correcting the curvature at the top, a screen with straight vertical lines can be obtained, and the effect is extremely large.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional vertical line correction device, Fig. 2 is a raster diagram for explaining the problem when the projector is placed on the floor, and Fig. 3 a and b are the same as Fig. 1. A diagram to explain the problems with the device,
FIG. 4 is a circuit diagram of a vertical line correction device in one embodiment of the present invention. 1...Integrator circuit, 3...Side pink tension volume, 4...Horizontal amplitude volume, 7...
Horizontal output circuit, 9... Keystone correction circuit, 9... Keystone correction volume, 10... Rectangular wave output circuit.

Claims (1)

[Claims] 1. A horizontal output circuit equipped with a diode modulator-type raster correction circuit including a capacitor for a horizontal signal component filter is provided, and a vertical sawtooth wave voltage for trapezoidal distortion correction is created to perform the raster correction. A rectangular wave output circuit configured to supply the voltage to the circuit and outputting a rectangular wave voltage having a pulse width of one vertical blanking period is provided, and the rectangular wave voltage is supplied to the raster correction circuit together with the vertical sawtooth voltage. A vertical line distortion correction device configured to modulate a horizontal deflection current by the vertical sawtooth voltage and the rectangular wave voltage. 2. The vertical line correction device according to claim 1, wherein the rectangular wave output circuit includes means for adjusting the amplitude of the rectangular wave.