JPS6053950B2 - television receiver - 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, which increases the beam spot size and reduces sharpness.

In particular, in the horizontal ring part 1 as shown in Figure 1A and the line part 2 as shown in Figure 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 because the frequency characteristics of the receiver's transmission system attenuate the high-frequency components, the signal becomes distorted as shown in Figure B. Horizontal sharpness is further reduced. Therefore, as a method of compensating for the decrease in sharpness, the video signal 50 shown in FIG.
A second-order differential signal SB as shown in C in the same figure is obtained, and this is added to the signal 50 to obtain a video signal Sc with steep rises and falls as shown in D in the same figure, which is supplied to the picture tube. There is a way. However, in this method, the beam current increases more at the peak of the signal, so the beam spot size becomes larger, so the sharpness is not improved as much.

As another method, the video signal 50 shown in FIG. 3A is supplied as is to the picture tube, and this video signal 50 is differentiated 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, in section Ta, the scanning speed of the beam becomes faster and the amount of light emitted at the corresponding point on the screen decreases, and in section 'L, the scanning speed of the beam becomes slower and the amount of light emitted at the corresponding point on the screen decreases. Since the amount of light emitted increases, taking into account the spot size of the beam, the amount of light emitted i in the horizontal direction on the screen changes as shown in Figure 3E, and the sharpness in the horizontal direction is improved.However, when using this method, teeth,
As is clear from the figure, the width of the light emitting part on the screen is the video signal S.

It has the disadvantage that it does not correspond to the time width of , and becomes narrow. In view of this point, there is a method that eliminates the drawbacks of the method shown in FIG. 3 by correcting the waveform of the video signal. As shown in FIG. 4, the video signal SO (5th
For example, the differential signal SA (FIG. A) is differentiated by the differential signal generating circuit 12 to obtain the differential signal SA (FIG. B), which is then double-wave rectified by the rectifying circuit 13, which is a video signal correction signal generating circuit. The polarity of the portion of the signal SA corresponding to the falling edge of the video signal SO is inverted to obtain a signal SD (C in the same figure), and the synthesizer 14 combines this signal SD with respect to the original video signal SO. After combining, the original video signal S is obtained.

A video output signal Sp (D in the same figure) in which the width of the white signal is made wider than that of the video output signal Sp is obtained, and this video output signal Sp is supplied to the control electrode of the picture tube 16, for example, the cathode 17, to density-modulate the electron beam. . Further, the video output signal S2 or the original video signal SO is differentiated by a differentiating circuit 15 using a scanning speed modulation circuit, for example, to obtain a differential signal Sv (E in the same figure), and this is used as a signal for scanning speed modulation to the picture tube 16. For example, the electron beam is supplied to a scanning speed modulating deflection means 19 provided separately from the horizontal and vertical deflection means 18 to modulate the scanning speed of the electron beam on the screen of the picture tube 16. The scanning speed modulation deflection means 19 includes two electrostatic deflection sheets in the neck of the tube 16 on the front side of the deflection means 18. The facing plates may be arranged to face each other in the horizontal direction. According to this method, the horizontal luminescence distribution on the screen is shown in Figure 5F.
As shown by line 5, the width of the light emitting part is within the rising edge of the original video signal SO. It corresponds to the time from the midpoint to the midpoint of the fall, and does not become narrow as in the method shown in FIG.

By the way, in this case, the level of the scanning speed modulation signal Sv is the video output signal S, and therefore the video signal S.

When the level of the video signal SO is low, the level of the scanning speed modulation signal Sv also becomes low. Therefore, when the level of the video signal SO is low, the scanning speed is not modulated much, that is, the scanning speed does not change significantly, and even in such a case, the original video output signal Sp is used as the video output signal Sp, as described above. If a white signal whose width is widened by the same amount as the video signal SO is obtained, there is the problem that the width of the light-emitting portion becomes too large.
To prevent this, the video signal S. The level of the scanning speed modulation signal may be kept constant regardless of the level of the scanning speed modulation signal. One possible method for this purpose is to supply the differential signal Sv obtained from the differential circuit 15 described above to the limiter.

However, in this case, the output signal of the limiter becomes a rectangular waveform, and it is necessary to supply this signal again to a filter or the like for waveform shaping, resulting in a complicated configuration. As another method, as shown in FIG.
One possible method is to supply it to a certain level.

However, in this case, even if the peak level of the differential signal Sv is detected and the gain is controlled according to that level, there will be a delay in the control, so it is not practical to keep the peak level constant from time to time. In view of this point, the present invention provides a video signal S.

When the level of is small, in addition to this, the level of the correction signal for widening the width of the white signal is made smaller than the value proportional to the level of the video signal SO. For this reason, in the present invention, as shown in FIG. The signal SE obtained from the linear circuit 22 is synthesized to obtain the video output signal Sp.

Here, as shown in FIG. 8, the nonlinear circuit 22 is a circuit in which the ratio of the output voltage to the input voltage increases as the input voltage increases.

Such a non-linear circuit 22 can be easily constructed from a diode 23 and a resistor 24, as shown in FIG. That is, the larger the input voltage, the smaller the impedance of the diode 23, so the resistance 24 and the diode 2
The voltage division ratio determined by 3 becomes large, and the ratio of the output voltage to the input voltage becomes large. In this way, the video signal S
. When the level of the scanning speed modulation signal Sv is small, and therefore the scanning speed modulation signal Sv is also small and the scanning speed is not strongly modulated, the width of the white signal in the video output signal Sp is not widened that much, so the width of the light emitting part becomes large. There's no such thing as too much. That is, FIGS. 14 and 15 show when the level of the video signal SO is large and when it is small, and the level of the differential signal SA obtained from the differentiating circuit 12 and the level of the signal SD obtained from the rectifier circuit 13 are shown in FIGS. is the video signal S.

It is approximately proportional to the level of However, the level of the signal SE obtained from the nonlinear circuit 22 is
It is not proportional to the level of the video signal SO, and the ratio of the level of the signal SE to the level of the video signal SO becomes smaller as the level of the video signal SO becomes smaller, as shown in FIG. Therefore, the width of the video output signal Sp obtained from the synthesizer 14 does not become very large when the level of the video signal SO is low. What is indicated by a chain line S''P in FIG. 15 is a signal S.
This is the video output signal when the signal is directly combined with the video signal SO without passing through the non-linear circuit 22. When the level of the scanning speed modulation signal Sv is low, the width of the white signal in the video output signal Sp is not widened as much, so the width of the light emitting portion does not become too large. As shown in FIG. 9, since the non-linear circuit 22 can be composed of a diode and a resistor, one circuit can serve as both the rectifier circuit 13 and the non-linear circuit 22.

FIG. 10 shows an example of this case. Reference numeral 25 denotes a polarization circuit that serves both functions, and is composed of a polarity inversion circuit 26, diodes 27 and 28, and a resistor 29.

As in the example of FIG. 11, the differential signal Sv obtained from the differentiating circuit 15 is further supplied to the non-linear circuit 31, and the signal Svc obtained thereby is sent to the scanning speed modulation deflection means 19 as a scanning speed modulation signal. It may also be supplied.

In this case, the nonlinear circuit 31 is a circuit in which the ratio of the output voltage to the input voltage increases as the input voltage decreases, as shown in FIG. 12, contrary to the nonlinear circuit 22.

In this way, as shown in FIGS. 14 and 15, the level of the scanning speed modulation signal SvO does not differ as much as the level of the video signal SO, that is, even when the level of the video signal SO is small, the scanning speed Since the level of the modulation signal SvO is not so reduced and the modulation of the scanning speed is not weakened so much, the video signal S.

The same luminescence distribution can be obtained whether the level of is large or small. The scanning speed modulation deflection means 19 can also be constructed by specially forming, for example, a focusing electrode of the electron gun of the picture tube 16, as shown in FIG.

That is, FIG. 13 shows the electron gun inside the neck of the tube 16, in which a cathode 40, a control electrode 41, an accelerating electrode 42, a first anode 43, a focusing electrode 44 and a second anode 45 are sequentially arranged on the same axis. Arranged.

The focusing electrode 44 is divided into two electrode parts 44A and 44A, each having a shape similar to that of a single cylindrical body cut by a plane that is orthogonal to the horizontal plane at the middle part and diagonal to the tube axis. 44B, and a focused voltage of zero V to several KV is supplied to each of the electrode parts 44A and 44B, and superimposed on this, both electrode parts 44A and 4
The above-mentioned scanning speed modulation signals Sv to Svc are supplied between 4B and 4B. Therefore, a horizontal electric field is generated by the signals Sv to SvO at the location of the focusing electrode 44, which deflects the beam 46 horizontally and modulates the scanning speed of the beam 46 on the screen. Alternatively, the horizontal deflection coil may also be used as the deflection means for scanning speed modulation, and a combination of the above-mentioned scanning speed modulation signal and the horizontal deflection signal may be supplied thereto.

As described above, according to the present invention, the width of the light emitting portion can be appropriately regulated to improve sharpness regardless of the level of the video signal.

Note that the present invention can also be applied to a color television receiver, and in this case, the luminance signal may be treated as the above-mentioned video signal.

[Brief explanation of drawings]

Figures 1 to 3 are diagrams for explaining the present invention, Figure 4 is a system diagram showing one method for explaining the invention, Figure 5 is a waveform diagram for explaining the invention, and Figure 6 is a diagram for explaining the invention. is a system diagram showing another method for explaining this invention, FIG. 7 is a system diagram of an example of this invention, FIG. 8 is a diagram showing the characteristics of the nonlinear circuit, and FIG.
The figure is a connection diagram of an example of a non-linear circuit, Figure 10 is a connection diagram of a specific example of this invention, Figure 11 is a system diagram of another example of this invention, and Figure 12 is a characteristic of another non-linear circuit. Figure 1 showing
Figure 3 is a cross-sectional view of an example of a deflection means for scanning speed modulation;
15 and 15 are waveform diagrams for explaining the present invention. 11 is a video amplifier, 12 and 15 are differentiating circuits, 13 is a rectifier circuit, 16 is a picture tube, and 22 and 31 are nonlinear circuits.

Claims (1)

[Claims] 1 A differential signal generation circuit extracts this differential component from the original video signal, inverts the negative polarity component of this output and adds it to this positive polarity component, and generates the same polarity at the rising and falling parts of the video signal. a correction signal generation circuit for obtaining a correction signal; a signal adder for adding this output to the original video signal via a non-linearity circuit to obtain a signal with an expanded white signal; A signal supply path for supplying the control electrode of the picture tube and the input terminal of the scanning velocity modulation circuit, and a scanning velocity modulation deflection that is driven by the output of the scanning velocity modulation circuit and modulates the scanning velocity of the electron beam on the screen of the picture tube. 2. A television receiver, characterized in that the non-linearity circuit is selected such that the ratio of the output voltage to the input voltage increases as the input voltage increases.