JPS581593B2 - TV program - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for improving the sharpness of television images.

In television receivers, as shown in Figure 1, the larger the cand current (beam current), the smaller the focus voltage and the wider the difference from the high voltage, the smaller the beam spot size and the sharper the beam. Images can be projected.

In order to do this, as shown in FIG. 2, a video signal for density modulating the beam may be superimposed on a DC voltage with its polarity reversed and supplied to the focus electrode.

However, in this case, it is necessary to ensure that the pedestal level shown by the chain line in the figure does not change even if the level of the signal used to perform dynamic focusing changes, and for this reason, this signal must contain a DC component. However, it is quite difficult to superimpose such a wideband signal including a DC component on a DC voltage, and the power loss is also large.

The signal for dynamic focusing needs to have an amplitude of about 200 to 300 volts, which is sufficiently larger than that of the signal for density modulating the beam, which is also difficult.

Furthermore, when the electron gun is of the pi-potential type, the focus DC voltage is as high as 4 to 5 KV, making it even more difficult.

In consideration of these points, the present invention improves the sharpness by superimposing only the alternating current component on the direct current voltage to perform dynamic focusing.

In general, whether an image is sharp or not depends on whether the outline of the image is clear. If this is done, the sharpness of the image will be significantly improved.

In such a portion, the signal level changes greatly between the black level and the white level.

In the present invention, focusing on such points, AC voltage for focus correction is obtained in the portion where the level changes based on the video signal and in minute sections before and after that, and this is superimposed on the DC voltage. is supplied to the focus electrode to perform dynamic focusing.

For example, as shown in FIG. 4, if two cascaded delay lines 3 and 4 each having a delay amount τ are connected to the video signal source 5 via an appropriate impedance, the input of the delay line 3 When the signal on the side is E1, a signal E2 delayed by τ is obtained at the output side of the delay line 3, and a signal E3 delayed by 2τ from the signal E1 is obtained at the output side of the delay line 4.

By the way, in the contour part 1 and line part 2 mentioned above, the signal originally changes in a rectangular waveform between the black level and the white level, but because the high frequency components are attenuated due to the frequency characteristics of the transmission system of the receiver, the signal changes. It slows down and changes into an almost trapezoidal wave shape.

Therefore, if the above-mentioned delay amount τ is selected to be equal to the rise or fall time of the signal that changes in a trapezoidal waveform, when the signal level changes in this way, each of the above-mentioned signals E1
, E2 and E3 are as shown in FIG. 5A.

Therefore, if we obtain the signals E and +E3 as shown in Fig. 5B, and further obtain this signal, this becomes the alternating current obtained at the rising and falling portions of the original signal E1, as shown in Fig. 5C. It becomes a signal.

Then, if this AC signal EA is superimposed on a DC voltage and supplied to the focus electrode, and the delayed signal E2 is supplied to the picture tube to density-modulate the beam, the signal EA becomes positive at the rising edge of the signal E2. Since the focus voltage changes rapidly from the state to the negative state, the focus voltage changes as explained in FIG. 1 with respect to the change in the beam current, and the signal E2
Since the signal EA rapidly changes from a negative state to a positive state during the falling portion of , the focal voltage also changes in response to changes in the beam current in the manner described in FIG. 1.

Therefore, the beam spot size is minimized at the rising and falling portions of the video signal E2, that is, at the contour portion 1 described above, and the sharpness of the image is improved.

As mentioned above, in line part 2, when the time span during which the video signal is at the white level is small, the AC signal EA for correction is the sixth
The waveform shown in the figure is almost the same as the video signal with the polarity reversed, so the beam spot size is minimized over the entire width of line part 2, and line part 2
is clearly displayed.

Specifically, in order to obtain the above-mentioned focus correction AC signal EA, superimpose it on a DC voltage, and supply it to the focus electrode, a circuit configuration as shown in FIG. 7, for example, may be used.

That is, in the figure, 6 is a delay line having a delay amount τ so that signal reflection occurs, and this is connected between the collector of the transistor and the base of the transistor 8.

Then connect the collector of transistor 7 to another transistor 9.
The collector of this transistor 9 and the emitter of transistor 8 are connected via a resistor 10.

Further, the collector of the transistor 9 is connected to the base of the transistor 1, and the resonant circuit 14 consisting of the primary side of the transformer 12 and the capacitor 3 is connected to the collector side of the transistor 1, and the terminal 15 from which high voltage can be obtained is connected to the resistor 1.
6 to 18, and connect the secondary side of the transformer 12 to 50
It is connected to a connection point P between resistors 16 and 17 via a capacitor 9 having a capacitance of about pF.

According to this configuration, when the original video signal E1 is supplied to the base of the transistor 7, a signal of 1E1 appears at the collector of the transistor, and since the output end of the delay line 6 is open, the signal is reflected. A signal -E3, which is obtained by delaying E, by 2τ, appears.

That is, a signal of -(E1+E3) is obtained at the collector of the transistor and therefore at the base of the transistor 9.

On the other hand, at the emitter of the transistor 8, a signal -E2 obtained by delaying the signal -E1 by τ is obtained.

Therefore, at the collector of transistor 9 -(E1+
E3) Signal E1+E3 and signal -E which are inverted signals
2 are added with a predetermined level relationship, resulting in the above result.

This signal EA is amplified by the AC amplifier having the transistor 1 shown in the figure, but the frequency response of this signal EA is determined by the delay amount τ of the delay line 6. For example, when As shown in the figure, the signal EA can be efficiently amplified by setting the resonant frequency of the resonant circuit 14 to 2.5 MHz and by adjusting the resistance value of the tamping resistor 20 to an appropriate amplification bandwidth.

Therefore, if the electron gun of the picture tube is of the pi-potential type, for example, if a DC voltage of, for example, 5KV is obtained at the connection point P of the resistors 16 and 17, the AC signal EA obtained on the secondary side of the transformer 12 will be is boosted to an appropriate level and superimposed on this 5KV DC voltage by the capacitor 9. Therefore, if the voltage obtained at this point P is supplied to the focus electrode, that is, the third grid electrode in this case, the above-mentioned dynamics can be achieved. Focus can be performed.

In addition, if the electron gun of the picture tube is a unipotential type, P
It is sufficient to obtain a DC voltage corresponding to the voltage at the point, superimpose the AC signal EA on this voltage, and supply it to the fourth grid electrode.

Sharpness can be further improved by performing so-called aperture correction at the same time as performing the Quinaminck focus as described above.

In other words, the Takagi component of the signal that originally changes in a rectangular waveform between the black level and the white level is attenuated as described above, resulting in the signal shown in FIG. 9A.
This signal E changes into an almost trapezoidal waveform as shown in the figure.

By differentiating twice and inverting the phase, a correction signal EB as shown in figure B is obtained.
and convert this into the original signal E.

In addition to this, a video signal EC with steep rises and falls as shown in FIG.

If only this aperture correction is used, the beam current will increase at the peak of the signal and the beam spot size will become larger, reducing the correction effect by half. For example, in a portion where the spot size of the beam is not expected to increase, the spot size is narrowed down and made smaller by dynamic focusing, so that the effect of aperture correction is further demonstrated.

In this case, since the aperture correction signal EB has the opposite polarity to the focus correction signal EA, the above-mentioned beam is density-modulated with the focus correction signal EA reversed in polarity and set to an appropriate level. This superimposed signal is then supplied to the picture tube to density-modulate the beam.

Specifically, as shown in FIG. 10, in the circuit of FIG. 7, the resistor 10 is made into a variable resistor, the aperture correction signal EA is taken out from the movable element, and this signal is converted to the delayed signal E2 with an appropriate polarity. All you have to do is add it to

The method of the invention can be further advantageously combined with a device that improves sharpness by modulating the scanning speed of the beam across the screen.

That is, this method obtains a scanning speed modulation signal corresponding to the change in the level of the video signal at a portion where the level changes, and supplies this to a horizontal deflection means provided separately from the horizontal and vertical deflection means. It modulates the scanning speed of the beam on the screen of the picture tube, that is, the video signal E as shown in FIG.

Assuming that the rise or fall time when the signal E undergoes the largest level change between the black level and the white level is 2t, the signal E is input to the subtracter 21 as shown in FIG. 12, for example.

From this signal E. By subtracting the signal Eβ delayed by 2t in the delay lines 22 and 23, each having a delay amount of t, the signal E is obtained as shown in FIG. 11B.

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

At a portion corresponding to the fall of , a negative pulse signal E2 is obtained, which is supplied, for example, between two electrostatic deflection plates disposed horizontally opposite to each other in the high voltage section of the electron gun.

On the other hand, in this case signal E.

A signal Eα delayed by t in the delay line 22 is extracted and supplied to the picture tube to density-modulate the beam.

In practice, t may be selected to be about 0.1 μsec.

In this way, the beam is density-modulated by the delayed video signal Eα, while the beam is deflected by the horizontal/vertical deflection means and also horizontally deflected by the scanning speed modulation signal EV. At times corresponding to the rise and fall of Eα, the scanning speed of the beam on the screen is modulated as shown by curve 24 in FIG. 13.

That is, the scanning speed becomes faster just before the signal Eα starts to rise, then becomes slower in the middle of the rise of the signal Eα, and after the signal Eα completely rises, the scanning speed returns to normal. Return to state.

Then, the scanning speed becomes slow just before the signal Eα starts to fall, conversely becomes faster in the middle of the fall of the signal Eα, and after the signal Eα completely falls, the scanning speed returns to normal. Return to state.

Therefore, when the scanning speed of the beam is not modulated by the signal EV, the amount of light emitted at the position on the screen corresponding to the signal Eα changes as shown by the curve 25, whereas the signal E
When the scanning speed of the beam is modulated in this way, 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, thereby corresponding to the signal Eα. The amount of light emitted at a position on the screen changes as shown by a curve 26.

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

Therefore, if this method of modulating the scanning speed and the above-mentioned dynamic focus method are combined, the sharpness can be further improved.

The present invention can also be applied to color television images; in this case, it is sufficient to obtain the AC signal EA for focus correction based on the luminance signal, and the signal E for scanning speed modulation can also be applied to this luminance signal. You can get it based on this.

According to the above-mentioned apparatus of the present invention, an AC signal for focus correction is obtained at a portion where the level changes based on the video signal, and this is superimposed on a DC voltage and supplied to the focus electrode to perform dynamic focusing. Since there is no DC component in the signal for dynamic focus, it can be easily superimposed on the DC voltage, and there is less power loss.Also, when superimposing this signal on the DC voltage, it is easy to use a transformer to superimpose this signal on the DC voltage. Can be boosted.

Moreover, by performing Quinamink Focus using such a signal, the sharpness can be greatly improved at the rising and falling portions of the signal where sharpness is most required, and an image with sufficient sharpness can be obtained as a whole. be able to.

5 Brief explanation of the drawings Fig. 1 is a curve diagram showing the relationship between cathode current and optimal focus voltage, Fig. 2 is a waveform diagram to explain the dynamic focus, and Fig. 3 is a diagram to explain the image. FIG. 4 is a theoretical connection diagram of an example of a method for forming an AC signal for focus correction in the device of the present invention, FIGS. 5 and 6 are waveform diagrams for explaining the method, and FIG. A specific connection diagram of an example of the inventive device, FIG. 8 is a curve diagram for explaining the same, FIG. 9 is a waveform diagram for explaining aperture correction, and FIG. 10 is a specific example of the pond of the inventive device. Connection diagram, Figure 11 is a waveform diagram for explaining when modulating the beam scanning speed, Figure 12 is
The figure is a connection diagram of an example of a method of forming a signal for scanning speed modulation, and FIG. 13 is a curve diagram for explaining the state of light emission on the screen when the scanning speed of the beam is modulated.

3, 4, and 6 are delay lines, and EA is an AC signal for focus correction.

Claims (1)

[Claims] 1 Based on the video signal, an AC signal for focus correction is generated that changes in accordance with the amount of change in the portion where the level changes and in the minute sections before and after that, and returns to a constant voltage in the portion where the video signal does not change. This is amplified to a predetermined amplitude via an AC amplifier, and this amplified AC signal for focus correction is supplied to the focus electrode of the picture tube, and the focus correction described above is applied to the DC voltage originally supplied to this focus electrode. An apparatus for improving the sharpness of a television image, wherein a focus electrode of the picture tube is controlled by a signal superimposed with an alternating current signal.