JPS597261B2 - TV Jiyounga Zouno Sen-Aid Kaizen Cairo - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION When displaying an image on a television receiver, the beam current of the picture tube increases in areas with high brightness, resulting in a decrease in sharpness due to the large beam spot size.

In particular, in the horizontal contour portion 1 as shown in FIG. 1A and the line portion 2 as shown in FIG. 1B, the original video signal is
As shown in Figure A, there is a sharp change between the black level and the white level, but due to the frequency characteristics of the receiver's transmission system, the high-frequency components are attenuated, so the signal becomes sloppy and horizontal as shown in Figure B. The directional sharpness is further reduced. Therefore, as a method of compensating for the decrease in sharpness, a second differential signal SB as shown in FIG. 2B is obtained from the video signal 50 shown in FIG. There is a method of obtaining a video signal Sc with steep upper and lower edges and supplying it to a picture tube. However, in this method, since the beam current is increased more at the peak of the signal, the beam spot size is larger, resulting in less improvement in sharpness. Another method is to supply the video signal 50 shown in FIG. 3A to the picture tube as it is, differentiate this video signal 50 to obtain a signal SA shown in FIG. There is a method in which the horizontal deflection magnetic field is corrected as shown in Figure C by supplying it to a separately provided auxiliary deflection coil, thereby modulating the scanning speed of the beam on the screen as shown in Figure D.

According to this method, the scanning speed of the beam increases in the section Ta, and the amount of light emitted at the corresponding point on the screen decreases.
In section Tb, the scanning speed of the beam is slow and the amount of light emitted at the corresponding point on the screen increases, so considering the spot size of the beam, the amount of light emitted in the horizontal direction on the screen is as shown in Figure 3E. horizontal sharpness is improved. However, as is clear from the figure, this method has the disadvantage that the width of the light-emitting portion on the screen does not correspond to the time width of the video signal 50 and becomes narrow.

In view of this point, the present invention improves (V) sharpness by modulating the scanning speed of the electron beam on the screen of the cathode ray tube. This eliminates the drawbacks of the method shown in the figure.

Hereinafter, a specific example of this will be explained with reference to FIG. 4 and subsequent figures. FIG. 4 shows an example in which the scanning speed modulation signal is superimposed on the horizontal deflection signal and supplied to the horizontal deflection coil.
The electron beam is supplied to the cathode of the cathode ray tube 6 through the electron beam to density-modulate the electron beam.

On the other hand, the video signal SO from the first video amplifier 4 (Fig. 6,
A) in FIG. 1 is supplied to the differentiating circuit 7 for differentiation, and the differentiated signal SA (B in FIG. 6, FIG. r) is supplied to the synthesizer 8,
Further, this differential signal SA is supplied to the polarization circuit 9, and the polarity of the portion of the signal SA corresponding to the falling edge of the video signal SOl is inverted, resulting in a signal SD having the same polarity (FIGS. 6 and 7). C) is further supplied to the differentiating circuit 10 for differentiation, and the differentiated signal SE (D in FIGS. 6 and 7) is supplied to the synthesizer 8 to be combined with the differentiated signal SA. From vessel 8, 2
The polarity is different between the rising edge b and the falling edge of the video signal SO, and the positions of the positive and negative peaks are shifted to the lower level side of the video signal SO than those of the differential signal SA, and the amplitude is different from that of the video signal SO. Signal SF that changes depending on the level of signal SO
(E in Fig. 6, Fig. r) 2 is obtained.

This signal SF is then supplied to the correction circuit 11 composed of a non-linear circuit to obtain a signal SG (F in Figs. 6 and 7) whose amplitude is almost constant regardless of the level of the video signal SO. It is supplied to the synthesizer 12 as a scanning speed modulation signal.
On the other hand, the output of the video three-image detection circuit 3 is transferred to the synchronization signal separation circuit 13.
The horizontal synchronizing signal is supplied to the horizontal deflection and high voltage generation circuit 14 to obtain a horizontal deflection signal and a high voltage output, and the horizontal deflection signal is supplied to the combiner 12 to generate a correction circuit. A scanning speed modulation signal SG of 11 degrees is superimposed on this, the superimposed signal is supplied as a horizontal deflection current to the horizontal deflection coil of the main deflection means 15, a high voltage output is supplied to the anode of the cathode ray tube 6, and A vertical synchronization signal is supplied to the vertical deflection circuit 16 to obtain a vertical deflection signal, which is then supplied to the vertical deflection coil of the main deflection means 15. Therefore, the horizontal deflection current is as shown by line 17 in Figure 8, and at the beginning of the rising edge of the video signal SO, the scanning speed of the beam suddenly increases, which corresponds to the rising edge v period. The beam reaches the midpoint of the width W, during which time the amount of light emitted is suppressed, and when the beam reaches the halfway point, the scanning speed of the beam suddenly slows down and the amount of light emitted suddenly increases.On the other hand, on the falling side of the video signal SO, this As a result, the amount of light emitted changes in the horizontal direction on the screen as shown by line 18, and the sharpness is improved and the width of the light emitted portion changes from the rise of the video signal SO. This corresponds to the time width from the midpoint to the midpoint of the falling edge, and does not become narrow as in the method shown in FIG.

In addition, the correction circuit 11 generates a scanning speed modulation signal SG (7
) Since the amplitude is kept almost constant regardless of the level of the video signal SO, the state of change in scanning speed is constant regardless of the level of the video signal SO. The following improvements will be made. Fifth
In the example shown in the figure, the main deflection means 15 does not superimpose the scanning speed modulation signal SG obtained from the correction circuit 11 on the horizontal deflection signal.
This is a case where the scanning speed is modulated by supplying the light to another deflecting means 19.

This deflection means 19 can be purchased with two electrostatic deflection plates disposed horizontally opposite each other in the neck of the tube 6 on the front side of the main deflection means 15, and a scanning It is sufficient to supply the speed modulation signal SG. ．． Alternatively, the deflection means 19 may be constituted by a coil, through which a current based on the scanning speed modulation signal SG may be passed. Alternatively, the deflection means 19 may be provided by specially purchasing, for example, a focusing electrode of the electron gun in the neck portion of the tube 6.

FIG. 9 shows an example of this, in which a cathode 20, a suppression electrode 21, an acceleration electrode 22, a first anode 23, a focusing electrode 24, and a second anode 25 are arranged in sequence on the same axis. Then, the focusing electrode 24 is divided so that it has a shape similar to that of a single cylindrical body cut in the middle by a plane that is perpendicular to the horizontal plane but diagonal to the tube axis. A focused voltage of zero to several KV is supplied to each of the electrode parts 24A and 24B, and a focused voltage of zero to several KV is supplied to each of the electrode parts 24A and 24B.
In between, the above-mentioned scanning speed modulation signal SG is supplied. In this way, a horizontal electric field is generated by the signal SG at the position of the focusing electrode 24, and this deflects the beam 26 in the horizontal direction, so that the beam falls on the screen as described above. The scanning speed is modulated. As described above, according to the present invention, the sharpness can be improved and the narrowing of the width of the light emitting portion can be suppressed.

In addition, when a correction circuit (such as a non-linear circuit) is provided, the amplitude of the scanning speed modulation signal can be made almost constant regardless of the level of the video signal. This has the advantage that the correction works properly. The present invention can also be applied to the case where a color image is displayed on a color television receiver; in this case, the scanning speed modulation signal may be formed from the luminance signal as described above.

[Brief explanation of drawings]

Figures 1 to 3 are diagrams for explaining the present invention, Figures 4 and 5 are system diagrams of an example of the sharpness improvement circuit according to the present invention, and Figures 6 to 8 are diagrams for explaining the invention. FIG. 9 is a sectional view of the electron gun section when the focusing electrode is used as the scanning speed modulation deflection means. 3 is a video detection circuit, 4 and 5 are first and second video amplifiers, 6 is a cathode ray tube, 7 and 10 are differentiating circuits, 9 is a polarization circuit, 11 is a correction circuit, 13 is a synchronization signal separation circuit, 14
15 is a horizontal deflection and high voltage generation circuit; 15 is a main deflection means; 16 is a horizontal deflection and high voltage generation circuit;
is a vertical deflection circuit, and 19 is another deflection means.

Claims (1)

[Claims] 1. An input terminal to which an input video signal is supplied; a circuit that applies the video signal from the input terminal to the picture tube; a circuit for obtaining a corresponding first signal;
a circuit for obtaining a second signal corresponding to a waveform obtained by making the first signal the same polarity and further differentiating the same; and a circuit for synthesizing the first signal and the second signal to obtain a differentiated waveform of the input video signal. A circuit for obtaining a signal for scanning speed modulation, which is a corresponding signal and whose peak position is corrected to shift to the lower level side of the input video signal, and a control signal provided to and applied to the picture tube to control the image reception. means for modulating the scanning speed of the electron beam on the screen of the tube, wherein the signal for modulating the scanning speed is applied as the control signal to the means for modulating the scanning speed. Image sharpness improvement circuit.