JPS63122368A - Picture quality adjusting device - Google Patents

Abstract

PURPOSE:To constantly obtain a proper picture quality automatically to various types of video signals by feeding back the signal component of the prescribed frequency band of a video signal to add as a contour signal of a constantly fixed amplitude. CONSTITUTION:The noise of the contour signal from a subtraction circuit 11 is removed in a noise removing circuit 13 and it is supplied to a gain control circuit 15. An amplitude detecting circuit 12 detects the amplitude of the contour signal from the gain control circuit 15. A comparator 14 compares a detecting signal with a reference potential to control the gain control circuit 15 by the comparison signal and controls so as to output the contour signal of the constantly fixed amplitude from the gain control circuit 15. In the entire gain control of the gain control circuit 15, the contour signal of the constantly fixed amplitude from the gain control circuit 15 in which the gain is controlled by a gain control signal from an input terminal 19 is added to the delayed video signal from a delay circuit 8 in an addition circuit 16 and the picture quality adjusted video signal is outputted from an output terminal 17.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a horizontal image quality adjustment device suitable for a television receiver.

2. Description of the Related Art In a conventional television receiver, since the electron beam in the picture tube has a finite size, the high-frequency components of the optical output signal on the screen are reduced. It is necessary to compensate for this deterioration of high frequency components. Further, by adding appropriate preshoot and overshoot to the step response waveform of the signal, the sharpness of the image can be substantially improved. To achieve this, the characteristics are designed to emphasize the high-frequency components, but depending on the noise when receiving the 1-weak electric field signal or the viewer's preference, the overall frequency characteristics may be designed to be variable as shown in Figure 9. many.

FIG. 7 shows two sides of the image quality adjustment circuit, and FIG. 8 shows its waveforms. The video signal shown in FIG. 8a is input to the input terminal 1 in FIG. 7, and the video signal is converted into two parts as shown in FIG. A second derivative waveform is obtained. Therefore, at the position of terminal 4, the sliding terminal of variable resistor VR with an intermediate terminal has a step response waveform with preshoot and overshoot as shown in FIG. 8C, that is, a sharp state as shown in FIG. 9. At the position of the terminal 6, the response waveform is free from waveform distortion, that is, the normal state shown in FIG. 9, and at the position of the terminal 6, due to the effect of the capacitor 6□, there is a response with a gradual rise, that is, the video signal is in the soft state shown in FIG. is output to output terminal 3.

The sharpness of the image can be improved by variably adjusting the amount of preshoot and overshoot given to the video signal in one image quality adjustment circuit, as shown in FIG. 9, which shows the overall frequency characteristics.

Problems to be Solved by the Invention However, in the conventional image quality adjustment circuit, the frequency characteristic changes to a specific frequency f as shown in FIG. 9 in accordance with the adjustment of the image quality. The frequency band emphasized by image quality adjustment is f. For example, when a wideband video signal is input, appropriate image quality adjustment can be performed for the narrowband video signal, but the wideband video signal is emphasized by the image quality adjustment. Since the frequency band of the video signal is too low compared to the band of the video signal, the image quality adjustment may not be appropriate.

In other words, in an image quality adjustment circuit that improves image quality by emphasizing a predetermined frequency band of a video signal, in order to obtain appropriate image quality, the frequency band to be emphasized and the gain must be changed depending on the band of each video signal. However, in conventional image quality adjustment circuits, the frequency band to be emphasized is fixed and only the gain can be adjusted manually, so it is not possible to always obtain appropriate image quality depending on the frequency band of the video signal. There was a drawback that there was no

In view of this point, the present invention provides an image quality adjustment device that can always automatically obtain appropriate image quality even for various video signals.

Means for Solving the Problems The present invention provides extraction means for extracting signal components in a predetermined frequency band of a video signal, means for detecting the amplitude of the extracted contour signal, and comparing the detection signal with a reference potential. an image quality adjustment device comprising: a comparison means for controlling the gain of the contour signal from the extraction means using the comparison signal; and an addition means for adding the contour signal from the gain control means and the video signal. It is.

Operation The present invention extracts a signal component in a predetermined frequency band of a video signal using the above-described configuration, and converts this extracted signal, that is, a contour signal, into a contour signal with a constant amplitude through gain control using a feedback loop, and adds the signal to the video signal. By doing so, it is possible to always automatically obtain appropriate image quality for various video signals.

Embodiment FIG. 1 shows a block diagram of an image quality adjustment device according to a first embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining its operation. In FIG. 1, 8.9 is a delay circuit for delaying a video signal, 10.11 is an addition circuit and a subtraction circuit for creating a contour signal from the delayed signal, and 1
3 is a noise removal circuit for removing noise in the contour signal, 12 is an amplitude detection circuit for detecting the amplitude of the contour signal, 14 is a comparator for comparing the detection signal with the reference potential X, and 16 is the comparison circuit. A gain control circuit 16 controls the gain of the contour signal using a signal, and 16 is an addition circuit for adding the gain-controlled contour signal and the video signal.

The operation of the image quality adjustment device of this embodiment configured as described above will be described below. The video signal shown in FIG. 2a is input to the input terminal 7, and the signal is supplied to the delay circuit 8 having a delay time of 2, and a signal delayed by 2 is obtained from the delay circuit 8 as shown in FIG. It will be done. The output from the delay circuit 8 is also supplied to the delay circuit 9, and as shown in FIG. 2C, a signal delayed by 2τ with respect to the input video signal shown in FIG. 2a is obtained from the delay circuit 9. By adding the video signal from the input terminal 7 shown in FIG. 2a and the signal delayed by 2τ from the delay circuit 9 shown in FIG. The signal shown in FIG. 2d is output. The signal delayed by τ from the delay circuit 8 shown in FIG. 2S and the added output from the adder circuit 10 shown in FIG. A contour signal on which is superimposed is output. Figure 2 θ
The contour signal from the subtraction circuit 11 shown in FIG.
Noise is removed in step 3, and a noise-free contour signal is output as shown in FIG. 2f. The signal from the noise removal circuit 13 is supplied to a gain control circuit 16. Amplitude detection circuit 1
Reference numeral 2 is composed of, for example, a peak detection circuit that detects the amplitude of the contour signal from the gain control circuit 16, and detects a potential corresponding to the amplitude of the contour signal. The comparator 14 compares the detection signal with a reference potential, and controls the gain control circuit 16 using this comparison signal so that a contour signal of constant amplitude is always output from the gain control circuit 16. Further, the overall gain control of the gain control circuit 15 is controlled by the gain control signal from the input terminal 19.The contour signal of constant amplitude from the gain control circuit 16 is processed by the adder circuit 16 with a delay shown in FIG. By adding the video signal delayed by τ from the circuit 8, a video signal whose image quality has been adjusted as shown in FIG. 2g is outputted from the output terminal 17.

In order to explain in more detail, the resolution characteristic diagram shown in FIG. 3 will be used. The contour signal is transmitted through two delay circuits 8 and 9 having a delay time τ.
However, in order to know the resolution characteristics in the horizontal direction, if we consider the number of resolution lines in the horizontal direction as the repetition of a sine wave within the horizontal effective scanning period, we can say that the input signal is
When C1n is Kin = sfn 2πm(t+τ).

The output E from the delay circuit 8 is Abuse, = m2πmτ The output E2 from the delay circuit 9 is 1c2=picture 2πrrL(t−τ).

m is the number of repetitions of the sine wave within the horizontal effective scanning section.

At this time, the contour signal EH is = (1-2πmτ) sin2πmt...
・・・・・・・・・(1) is obtained, and the response of (1-CO52π涌τ) can be seen to have a comb-shaped frequency characteristic as shown in Figure 3.11 Frequency f2 becomes f2 = 0 .

Next, in order to explain the operation in detail, the waveform diagram in FIG. 4 and the frequency characteristic diagram in FIG. 6 will be used.

When a signal with a fast pulse response as shown in FIG. 4a, that is, a video signal including high-frequency components, is supplied to the input terminal 7 in FIG. The frequency components are as shown in Figure 3. This contour signal is subjected to noise removal by a noise removal circuit 13 by clipping signals below a certain level. Thereafter, the amplitude of the contour signal is kept constant at V by the automatic gain control circuit 18 of the feedback loop composed of the amplitude detection circuit 12, the comparator 14, and the gain control circuit 15. A contour signal is output from the gain control circuit 16. The contour signal shown in FIG. 4A and the input video signal shown in FIG.

Next, when a signal with a slow pulse response as shown in FIG. 4d, that is, a video signal that does not even include high-frequency components, is supplied to the input terminal 7 in FIG. 1, the resolution characteristics of the contour signal created by the image quality adjustment device are , for example, becomes a frequency component of f, which is lower than the frequency of f shown in FIG. Therefore, as shown in FIG. 3, the amplitude of the contour signal has a gain of 2 for the frequency component f, but a gain of 1 for the frequency component f3.

Further, the noise removal level in the noise removal circuit 13 is V.

It is. The noise-removed contour signal from the noise removal circuit 13 is sent to the amplitude detection circuit 12 and the comparator 14 as described above.
．． Automatic gain control circuit 18 composed of gain control circuit 16
As a result, the amplitude of the contour signal is maintained at V, and the low-frequency contour signal shown in FIG. 4 is output from the gain control circuit 16. The contour signal shown in FIG. 4e and the input video signal shown in FIG. 4d are added by an adder 16, and a video signal whose image quality has been adjusted is outputted from an output terminal 17 as shown in FIG. 4f.

Therefore, when a video signal including high frequency components as shown in FIG. 4a is supplied, the frequency to be emphasized is set to high < f as shown in FIG. 6, and as shown in FIG. 4C. You can adjust the image quality to suit the input signal. Furthermore, when a video signal that does not include high frequency components as shown in Figure 4d is supplied, the emphasized frequency is set to low (f) and the noise removal level is also controlled as shown in Figure 5. As shown in FIG. 4r, image quality adjustment with good S/H suitable for the input signal can be performed.

As described above, according to this embodiment, a signal component of a predetermined frequency of an input video signal is extracted, and this contour signal is always made into a constant amplitude contour signal by gain control by the feeder loop, and is added to the video signal. By doing so, appropriate image quality can always be automatically obtained for various video signals.

FIG. 6 is a block diagram of an image quality adjustment circuit showing a second embodiment of the present invention. In the same figure, 8 and 9 are delay circuits, 1
0.16 is an addition open circuit, 11 is a subtraction circuit, 13 is a noise removal circuit, 12 is an amplitude detection circuit, 14 is a comparator, and 16 is a gain control circuit, which is the same as the configuration shown in FIG. The difference from the configuration shown in FIG. 1 is that an average value detection circuit 20 is provided after the noise removal circuit 13 to detect the average value level of the amplitude of the contour signal, and this average value level and the reference potential ICo of the comparator 14 are are added by the adding circuit 21 and the comparator 21
The point is that it is provided so that it can be supplied to

The operation of the image quality adjustment circuit of the second embodiment configured as described above will be explained below. Noise removal circuit 13
The noise-clipped contour signal is supplied to an average value detection circuit 20, and the average level of one contour signal is detected. The average level signal is supplied to an adder circuit 21,
Reference potential X.

is added. The addition output from the addition circuit 21 is supplied to the comparator 14, where gain control is performed using the same feedback loop as described above.

As described above, according to this embodiment, the reference potential X of the comparator 14. and the average value level of the contour signal from the average value detection circuit 20 are added in the addition circuit 21 and supplied to the comparator 14. Thereafter, by providing gain control by feedback loose, the average value level of the contour signal is added. Since the gain of the contour signal can be controlled using the method, amplitude fluctuations and boost frequency fluctuations of the contour signal at the time of rapid changes in the video signal band can be suppressed, and appropriate image quality can always be automatically obtained.

It goes without saying that in the second embodiment, by controlling the response speed of the average value detection circuit 20, the response speed of the contour signal gain control can be changed. Furthermore, by controlling the addition ratio of the reference potential 1co in the adding circuit 21 and the average value level from the average value detection circuit 2o,
It goes without saying that the gain control range of the contour signal can be changed.

As described in detail, according to the present invention, optimal image quality adjustment can be automatically performed even for input video signals with different frequency bands without requiring boost frequency and image quality adjustment. , its practical effects are great.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an image quality adjustment device according to an embodiment of the present invention, Fig. 2 is an operation waveform diagram of the embodiment, Fig. 6 is a frequency characteristic diagram of the embodiment, and Fig. 6 is a detailed explanation of the invention. FIG. 9 is a frequency characteristic diagram for explaining the operation. 8.9...Delay circuit, 10,16.21...
... Addition circuit, 11 ... Subtraction circuit, 13 ...
... Noise removal circuit, 12 ... Amplitude detection circuit, 14 ... Comparator, 15 ... Gain control circuit, 2o ... Average value detection circuit. Name of agent: Patent attorney Toshio Nakao and one other person Hitomi
(Figure 2, Figure 3, Figure 4, Figure 5, Figure 7, Figure 8, Figure 9,

Claims (2)

[Claims] (1) Extraction means for extracting signal components in a predetermined frequency band of a video signal, noise removal means for removing noise from the contour signal from the extraction means, and amplitude for detecting the amplitude of the contour signal from the noise removal means. a detection means; a comparison means for comparing the detection signal from the amplitude detection means with a reference potential;
It is characterized by comprising: gain control means for controlling the gain of the contour signal from the noise removal means using the signal from the comparison means; and addition means for adding the contour signal from the gain control means and the video signal. Image quality adjustment device. (2) average value detection means for detecting the average level of the contour signal from the noise removal means; addition means for adding the detection signal and the reference potential; and a reference input terminal of the comparison means for outputting the output of the addition means. 2. The image quality adjustment device according to claim 1, wherein: