JPS63135090A - Picture quality correction circuit - Google Patents

Abstract

PURPOSE:To sufficiently correct picture quality at a bright picture without deteriorating the S/N at a dark picture by providing a DC gain control circuit superimposing a video signal onto a DC gain control signal to apply gain control of a picture quality correction signal. CONSTITUTION:The picture quality correction signal 10 is subjected to amplitude change by a DA gain control section 5 and the result is fed to a synthesis circuit 7, where the signal is synthesized with the original video signal 9 and the level of the picture quality correction signal is changed dynamically by superimposing the video signal 9 onto the DC gain control signal 6 via a superimposing circuit 12 at a gain control terminal of the DC gain control section 5. Thus, the picture quality correction signal is increased as the picture is brighter and the correction signal is decreased with the darker picture so as to correct the picture quality sufficiently at a brighter screen without deteriorating the S/N at the dark screen.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to image quality correction of a television receiver.

[Conventional technology]

FIG. 3 shows, for example, an image quality correction circuit of a model currently in production, and FIG. 4 shows the signal waveforms of each part of the image quality correction circuit.

In this Figure 3, 1 is the composite signal and 2 is the Y/
C (luminance signal/chroma signal) separation circuit, which includes buffer transistors Tr+, ) transistors Try to Tra.
, a delay circuit 2a (hereinafter referred to as an IH play line) for one horizontal period is the main component.

Further, 3 is a Y/C separated chroma signal, 9 is a Y/C separated video signal amplified by a transistor Tr, 4
is an image quality correction signal generation circuit mainly consisting of transistors Tr, -Trs.

The image quality correction signal 10 output from the image quality correction signal generation circuit 4 is sent to the gain control section 5 to the thermal synthesis circuit 7, and the DC gain control section 5 performs gain control using the DC gain control signal 6. It looks like this.

On the other hand, the Y/C separated video signal 9 is connected to a resistor Ra,
Synthesis circuit 7 via play circuit 11 with capacitor C0
The synthesis circuit 7 synthesizes the output of the play circuit 11 and the image quality correction signal whose gain has been controlled by the DC gain control section 5 to obtain a video signal output 8 whose image quality has been corrected. .

Of the waveforms in Figure 4 (al to Figure 4 fal), Figure 4 (
a) is a composite signal, Fig. 4 (bl is a Y/C separated video signal, Fig. 4 (C1 is a video signal waveform when a rectangular wave is input as a composite signal l, Fig. 4 f)
d) is an image quality correction signal when a rectangular wave is input to the composite input, and +el in FIG. 4 is a video signal whose image quality has been corrected.

Next, the operation will be explained. A composite signal 1 shown in FIG. 4 fa+ is input to a Y/C separation circuit 2, and the video signal separated therein is input to the bases of transistors Trg and Trs via a buffer transistor Tr+.

Further, the above-mentioned component shift signal is input to the base of the transistor Tra through the IH play line 2a with a delay of one inch. And the transistor Trz.

Tr, , Tr, a Y/C separated chroma signal 3 appears at the collector of the transistor Try, and a Y/C separated chroma signal 3 appears at the collector of the transistor Trs.
The separated video signal (FIG. 2(b)) is output.

Here, when a rectangular wave is input as the composite signal 1 shown in FIG.
The video signal output appearing at the collector of the transistor Tr5 passes through the transistor Tr5, and the video signal 9 has the waveform shown in FIG. 4 (C1).The video signal shown in FIG. Trh
1 parallel between the emitter of the transistor Tr11 and the base of the transistor Tr11.

Furthermore, by differentiating between the emitter of the transistor Trt and the base of the transistor Trs,
An image quality correction signal 10 (FIG. 4(d)) is obtained from the video signal of the two machines. The level of this image quality correction signal 10 is controlled by the DC gain control No. 1 6 in the DC gain control section 5, and is input to the video signal synthesis circuit section 7.

Also, the video signal 9 output from the transistor Trs
(FIG. 4(C)), the image quality correction signal 10 is passed through the play circuit 11 in order to synchronize with the image quality correction signal 10.
The signal is input to the synthesis circuit 7. This image quality correction signal 10 (
A video signal output 8 (FIG. 4(e)) whose image quality has been corrected by combining with FIG. 4(d)) is obtained.

[Problem that the invention seeks to solve]

Since the conventional image quality correction circuit is configured as described above, correction is applied regardless of the brightness or darkness of the screen.

This is a bright signal as shown in Figure 5 (Figure 5(a)).
The signal for performing image quality correction on the signal (Fig. 5 Yamaguchi), and the ratio of the correction signal to the total signal is not very large, but if the image quality correction is performed on the dark signal (Fig. 5 (C)), it becomes Fig. 5 + d). The ratio of the correction signal to the total signal becomes large. This causes S/H deterioration on dark screens.

This invention was made in order to solve such problems, and an object of the present invention is to obtain an image quality correction circuit that can sufficiently correct the image quality on bright screens without deteriorating the S/N on dark screens. do.

[Means for solving problems]

The image quality correction circuit according to the present invention is provided with a DC gain control circuit that superimposes a video signal on the DC gain control signal to control the gain of the image quality correction signal.

[For production]

In this invention, the image quality correction signal is dynamically changed by superimposing a video signal on the DC gain control signal applied to the DC gain control circuit,
For signals with a high average image quality level, the DC control voltage increases and the image quality correction signal is further amplified. For signals with a low average image quality level, the DC control voltage decreases and reduces the gain of the image quality correction signal, increasing the correction for bright screens and increasing the correction for dark screens. Reduce correction.

〔Example〕

Embodiments of the image quality correction circuit of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of one embodiment.

In FIG. 1, parts that are the same as those in FIG. 3 are given the same reference numerals to avoid duplication, and parts that are different from those in FIG. 3 will be mainly described.

In this Figure 1, as is clear from comparison with Figure 3,
A superimposing circuit 12 is newly added to the circuit configuration shown in FIG. 3.

That is, the superimposition circuit 12 is configured to superimpose the video signal 9 appearing at the emitter of the transistor Trs on the DC gain control signal 6 and apply it to the gain control terminal of the DC gain control circuit 5.

The output of this DC gain control section 5 is output to a synthesis circuit 7, and the synthesis circuit 7 receives the video signal 9 appearing at the emitter of the transistor Trs through a resistor R1 and a play circuit 11.
A composite signal of this video signal and the output of the DC gain control circuit 5 is taken out as a video signal output 8 whose image quality has been corrected. The other configurations are the same as in FIG. 3.

With this configuration, when the same composite signal 1 as shown in FIG. 4 111 is input, the third
Similarly to the conventional circuit shown in the figure, the emitter of the transistor Tr5 takes out the same video signal 9 as shown in FIG. Added.

Further, this video signal 9 passes through the transistors Tr, -Tr of the image quality correction signal generation circuit 4, and an image quality correction signal 10 as shown in FIG. 4 111 is obtained. 5 is input.

On the other hand, the video signal 9 and the DC gain control signal 6 are applied to a superimposition circuit 12, where the video signal 9 is superimposed on the DC gain control signal 6.

As a result, the level of the DC gain control signal 6 changes according to the amplitude of the video signal 9. This video signal is applied to the gain control terminal of the DC gain control section 5 on which the video signal is superimposed.

In the DC gain control unit 5, the image quality correction signal 10 is changed in amplitude by the DC gain control unit 5 and sent to a synthesis circuit 7, where it is synthesized with the original video signal 9. By superimposing the video signal 9 on the DC gain control signal 6 via the superimposition circuit 12 at the gain control terminal of the image quality correction signal level, it is possible to dynamically change the image quality correction signal level.

In this embodiment, since the circuit increases the gain as the control voltage becomes higher, the effect can be obtained by manually inputting the video signal without inverting it.

By doing this, as shown in Fig. 2 (as shown in Ml, the brighter the screen, the larger the image quality correction signal is, as shown in Fig. 2).
By reducing the correction signal for a dark screen such as , it is possible to sufficiently correct the image quality for a bright screen without deteriorating the S/N ratio for the dark screen.

〔Effect of the invention〕

As explained above, this invention superimposes a video signal on the DC gain control signal and dynamically changes the level of the image quality correction signal in addition to the DC gain control circuit, which degrades the S/N on dark screens. The image quality can be sufficiently corrected on a bright screen without the need for

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the image quality correction circuit of the present invention.
FIG. 2(a), middle of FIG. 2) is a waveform diagram for explaining the operation of the image quality correction circuit same as above, FIG. 3 is a circuit diagram of a conventional image quality correction circuit, and FIG. ) and the fifth
Figures (a) to 5 (d+ are waveform diagrams of various parts for explaining the operation of the image quality correction circuit in Figure 3. 2... Y/C separation circuit, 4... Image quality correction signal generation Circuit, 5... DC gain control section, 7... Synthesis circuit, 11... Play circuit, 12... Superimposition circuit. In addition, the same reference numerals in the figures indicate the same or equivalent parts. Agent: Oiwa MasuoFigure 2Figure 4Figure 5

Claims (1)

[Claims] A luminance signal/chroma signal separation circuit that separates a composite signal into a video signal and a chroma signal; an image quality correction signal generation circuit that generates an image quality correction signal from the separated video signal; a circuit for outputting a gain control signal, a gain control means for controlling the gain of the image quality correction signal by the gain control signal, and a delayed signal of the image quality correction signal and the video signal whose level is controlled by the gain control means; An image quality correction circuit comprising a synthesis circuit that synthesizes the signals and outputs a video signal whose image quality has been corrected.