JPS5815995B2 - TV program - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION When displaying an image on a television receiver, the beam current increases in areas with high brightness, which increases the beam spot size and inevitably reduces sharpness.

For example, as shown in Figure 1A, when a video signal changes between the black level and the white level with relatively steep rises and falls, it will not fall from the point a where the white level rises or from the white level. At point C, as shown in Figure B, the spot size of the beam is as large as that at the point halfway between the white levels, and as a result, the light-emitting area expands in the horizontal direction. The edges become blurred and the sharpness decreases.

When trying to project a bright rectangular area as shown by the broken line 1 in Figure 2A using a so-called window signal, the spot size of the beam increases even at the edges in the horizontal direction as described above, and Since the spot size of the beam increases even at the edge of the direction, the actual light emitting area spreads both horizontally and vertically, as shown by solid line 2, and the outline becomes blurred. .

The present invention modulates the scanning speed of the electron beam on the screen to control the amount of light emission in the portion where the level of the video signal changes, and in the bright level portion of the video signal.
As shown in Figure 3, by making the beam spot on the screen flattened in the direction perpendicular to the scanning direction, images can be projected with sufficient sharpness in both the horizontal and vertical directions. It was made so that it could be done.

Hereinafter, referring to a case in which an example of the method of the present invention is applied to a color television receiver, the explanation will be given with respect to FIG. 4 and subsequent figures.

FIG. 4 shows an example of the method of the present invention, in which a received color television signal is supplied to a video detection circuit 13 through a tuner 11 and a video intermediate frequency amplification circuit 12, and the detected output from this is sent to a pre-stage amplification section 14. , a luminance signal Y is supplied to an image amplification circuit 17 consisting of a delay line 15 and a post-intensification section 16.

Take out. And this luminance signal Y.

is supplied to a circuit that forms a signal for modulating the scanning speed of the beam and a signal for controlling the shape of the beam spot.

In the example shown in the figure, two delay lines 1 with equal delay amounts τ
8 and 19 and the subtractor 20 constitute a signal forming circuit for scanning speed modulation, and the delay lines 18 and 19 and the minimum value extraction circuit 21 constitute a circuit for forming a signal for controlling the shape of the beam spot. This is the case.

That is, the original luminance signal Y.

is delayed by τ in the delay line 18 to obtain the signal Y. This is further delayed by τ in the delay line 19 to obtain the signal ¥2, and the subtracter 20 returns the original luminance signal Y.

A signal ¥2 delayed by 2τ is subtracted from this to obtain a scanning speed modulation signal SV.

Here, the delay amount τ is as shown in FIG. 5A, for example. As shown in , the luminance signal Y.

is equal to the rise time or fall time when the level changes from black level to white level or vice versa.

In practice, τ may be selected to be approximately 0.1μ.

Therefore, the scanning speed modulation signal SV is as shown in FIG. 5B.

Signal Y.

The part corresponding to the rising edge of signal Y becomes a positive pulse.

A negative polarity pulse is obtained at a location corresponding to the rising edge of .

On the other hand, the minimum value extraction circuit 21 connects the power supply terminal 22 to ground through the collectors of transistors 23, 24 and 25, and further through resistors 26, 27 and 28, respectively, and connects the power supply terminal 22 to ground through the resistor 29. A signal Y is connected to the emitters of transistors 23, 24 and 25 through diodes 30, 31 and 32, respectively.

, Yl and Y2 to the bases of transistors 23, 24 and 25, respectively.

Therefore, the emitters of transistors 23, 24 and 25 have a signal Y.

, ¥1 and ¥2 are obtained, respectively, and 1 and ``signal Y'' are obtained at the connection point 33 between the resistor 29 and the diodes 30 to 32, as shown in FIG. 5B.

, ¥1, and ¥2, a signal Es is obtained in which the smallest value is extracted.

This signal Es is then taken out as a signal for controlling the shape of the beam spot.

On the other hand, the color television signal obtained from the front-stage amplification section 14 of the video amplification circuit 17 is supplied to the band amplification device 34 to extract the carrier color signal, which is then supplied to the color demodulation circuit 35 to reproduce red and blue signals. Each color difference signal is obtained and sent to the matrix circuit 36.
supply and also delays.

The luminance signal ¥1 obtained from the line 18 is sent to the matrix circuit 3.
6 to obtain red, green and blue color signals from the circuit 36.

These color signals are then sent to amplifiers 37B, 37, respectively.
G and 37B to each cathode of the color cathode ray tube 38 to density-modulate the red, green, and blue electron beams.

Then, with the signal SV obtained from the above-mentioned subtracter 20, the tube 3
The scanning speed of each beam is modulated on the screen of tube 8, and the shape of each beam spot on the screen of tube 38 is controlled by a signal voltage ES obtained from terminal 33.

Specifically, for example, two deflection electrode plates 39 and 40 are provided in the high-pressure part of the tube 38 in a horizontal direction, and the signal SV is transmitted through an amplifier 41 to one of the deflection electrodes. It is supplied to the plate 39.

In this case, it is necessary to supply high voltage to the deflection electrode plates 39 and 40, so the high voltage obtained at the terminal 42 is directly supplied to the deflection electrode plate 40 as shown in the figure. In contrast, the signal SV is supplied through a resistor 43 with a high resistance value of about 100Ω, and the signal SV is 50Ω. It is supplied through a capacitor 44 having a capacitance of about F.

For example, the focus electrode 45, i.e., the fourth grid electrode in the case of a unipotential type electron gun, and the third grid electrode in the case of a pi potential type electron gun, are electrodes facing each other in the vertical direction. 45A and 45B,
It is divided into a total of four electrodes, electrodes 45C and 45D facing each other in the horizontal direction, to form a four-electrode lens; the signal voltage ES is taken out through an amplifier 46, and superimposed on a focus voltage of a constant potential to be applied to the electrodes. 45C and 45D and electrode 45
A and 45B, so that the electrodes 45C and 45D sides are positive.

Therefore, each beam is deflected by the horizontal and vertical deflection means, and is also deflected horizontally by the signal Sv, and due to the deflection by the signal SV, at the times corresponding to the rising and falling edges of the signal is modulated as shown by curve 47 in FIG.

In other words, the scanning speed becomes faster just before the signal Y starts to rise, then becomes slower in the middle of the rise of the signal Y, and after the signal Y completely rises, the scanning speed becomes faster. returns to normal.

Then, the scanning speed slows down just before the signal ¥1 starts to fall, conversely becomes faster in the middle of the falling of the signal Y0, and after the signal Y0 completely falls, the scanning speed slows down. returns to normal.

Therefore, when the scanning speed of the beam is not modulated by the signal Sv, the amount of light emitted at the position on the screen corresponding to the signal ¥1 changes as shown by the curve 48, whereas the beam scanning speed is When modulating the scanning speed of the screen, the amount of light emitted is kept low at positions on the screen where the scanning speed is fast, and the amount of light emitted is increased at positions where the scanning speed is slow. The amount of light emitted at the position changes as shown by curve 4i.

That is, by modulating the scanning speed, the amount of light emission changes sharply at positions on the screen corresponding to the rising and falling edges of the signal ¥1.

Follow C horizontal sharpness. will improve.

On the other hand, as is clear from FIG. 4, the signal voltages Es and S are positive in the bright level portion of the luminance signal ¥1 for density modulating the electron beam, so the horizontal direction as shown in FIG. The potential of focus electrodes 45C and 45D becomes higher than the potential of focus electrodes 45A and 45B in the vertical direction, so that the electric field is distorted and astigmatism occurs as shown by the arrows in the figure, and each electron beam is As shown in FIG. 8, the lens is in a so-called "just-focus" or '-scrap state with respect to the screen 50, and in the horizontal direction, as shown in FIG. 9, it is in a so-called under-focus state with respect to the screen 50. As shown in FIG. 3, the beam spot has a collapsed shape in the vertical direction, that is, in the direction perpendicular to the scanning direction.

This is equivalent to the pot having a smaller diameter.

Therefore, the sharpness in the vertical direction is improved.

Therefore, according to the method of the present invention, when a so-called window signal is used to display a rectangular bright area as indicated by the broken line 1 in FIG.

At the horizontal edges, the scanning speed of the beam on the screen is modulated as described above to control the amount of light emitted on the screen, and at the vertical edges, the beam spot is moved vertically as shown in the figure. Since the shape is flattened, the light-emitting part does not widen in both the horizontal and vertical directions, and its outline is flat in both the horizontal and vertical directions, as shown by the solid line 3 in Figure 2B. A sharp image can be obtained.

By the way, if you only control the scanning speed of the beam on the screen as described above, but do not control the shape of the beam spot, the sharpness will change in the horizontal direction, as shown by the solid line 4 in Figure 2C. Improved but not vertically.

In addition, the beam spot is flattened in the horizontal direction, that is, the scanning direction, where the level of the video signal changes, and the beam spot is flattened in the vertical direction at the bright level of the video signal, as described above. However, in this case, the corners would protrude outward as shown by the solid line 5 in the second diagram, and the corners would protrude outward as shown in the second diagram E. When attempting to project a diagonal band, there is an inconvenience that the width of the band becomes wider.

Note that the specific configurations of the circuit for forming the signal for changing the scanning speed and the circuit for forming the signal for controlling the shape of the beam spot can be changed in various ways other than those shown in the figure.

Moreover, various changes can be made as specific means for changing the shape of the beam spot, such as incorporating an electrode forming a cylindrical lens in any part of the electron gun.

It goes without saying that the present invention can also be applied to a black and white television receiver.

[Brief explanation of drawings]

Figures 1 to 3 are diagrams for explaining the present invention, Figure 4 is a system diagram of an example of the method of the present invention, Figure 4 is a waveform diagram for explaining the method, and Figures 6 to 10 are diagrams for explaining the present invention. It is a figure for the explanation. 17 is an image amplification circuit, 18 and 19 are delay lines, 20 is a subtracter, 21 is a minimum value extraction circuit, 38 is a color cathode ray tube,
39 and 40 are electrostatic deflection plates, and 45 is a focus electrode.

Claims (1)

[Claims] 1 Obtain a scanning speed modulation signal that changes according to the change in level near the part where the level changes based on the video signal, and use this scanning speed modulation signal to adjust the horizontal direction of the electron beam on the screen of the cathode ray tube. Means for modulating the scanning speed of the electron beam and controlling the shape of the spot of the electron beam on the screen of the cathode ray tube is disposed near the electron gun of the cathode ray tube, and the video signal is transmitted through an amplifier. In addition to the means for controlling the shape of the spot, the spot of the electron beam on the screen is made into a substantially elliptical shape crushed in a direction perpendicular to the horizontal scanning direction in a bright portion of the video signal. A method for improving the sharpness of television images, characterized by: