JPH05268494A - Picture quality correction circuit - Google Patents

Abstract

PURPOSE:To reduce effectively a fog of a moving picture whose resolution is deteriorated in comparison with that of a still picture by selecting an amplitude of a speed modulation signal to a speed modulation coil with an output signal of a moving area detection circuit. CONSTITUTION:A video signal is fed to a base of a transistor(TR) Q9 via speed modulation signal synthesis use combined resistors R1, R2 and its amplitude is changed by a SW1 controlled to be turned on for a still picture and turned off for a moving picture by an output signal of a moving area detection circuit as shown in an output signal waveform. The degree of the change is set depending on a ratio of a resistance of a resistor R6 to the resistance of the resistors R1, R2. As a result, the amplitude of the speed modulation signal outputted from an emitter of the TR Q9 for a moving picture is larger than that for a still picture and the moving picture is subjected to larger speed modulation than the still picture. Thus, a trailing and a leading of the signal is corrected steeply and a fog of a video image is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image quality correction circuit used in a television receiver.

[0002]

2. Description of the Related Art Various methods have been put to practical use for an image quality correction circuit used in a television receiver. Among these, as one for correcting the image quality by emphasizing the contour of the image, 1) A method of creating a velocity modulation signal from a video signal, thereby applying a modulation current to a velocity modulation coil to emphasize the outline of an apparent image, (2) Creating an aperture compensation signal from a video signal, and the original video signal Conventionally, two methods, that is, a method of emphasizing the contour of an image by superimposing them, are generally used. An example of the circuit is shown in FIG. Here, the speed modulation signal indicated by (H) generated from the video signal input from the base of the transistor Q1 is the transistor Q1.
An output signal from the emitter of 9 and an aperture-compensated video signal of (F) in which the original video signal (A) is superimposed on the aperture-compensated signal of (E) is output from the collector of the transistor Q5. The amplitude and width of these velocity modulation signal and aperture compensation signal are the circuit constant and DL1.
And DL2 can be set by the delay amount of the delay element. The process in which the contour of the image is emphasized by the velocity modulation signal is shown in FIG. In the figure, the video signal of a) is apparently subjected to velocity modulation so that the rising edge and the falling edge are steep and the contour is emphasized as shown in d).

As described above, the image quality can be corrected by emphasizing the contour of the image. However, since excessive correction impairs the image quality of a fine portion of the image, the correction amount is included in the original video signal. Must be set according to the highest frequency However, in some high-definition television transmission methods, the highest frequency of reproduced images, that is, the resolution, differs between still images and moving images. An example of this transmission method is shown in FIG. In this example, the original image input signal is initially sampled in the encoder, and then it is detected whether or not the sample signal is in the moving region and each signal in the moving region and the still region is passed through a separate filter and then the The compression of the transmission frequency band is realized by performing sampling. Also, the decoder detects whether or not the received sample signal belongs to the moving region, and if it is the moving region, it is interpolated within the frame (the missing signal is interpolated from the surrounding signals). Inter-frame interpolation (a missing signal is interpolated by the previous frame signal) and output. FIG. 6 shows the outline of the signal processing when the original image is a still image, and FIG. 7 shows the case where the original image is a moving image.
In these figures, FIG. 6 g) and FIG. 7 d) are the reproduction maximum frequency signals of still images and moving images, respectively, and the former has twice the resolution of the latter. Therefore, in a high-definition television receiver compatible with this type of transmission system, the image quality correction amount has conventionally been set so as not to impair the image quality of a still image.

[0004]

As described above, when the image quality correction amount is set to a level that does not impair the image quality of a still image, there is a problem that image quality deterioration (image blurring) due to a difference in resolution is noticeable in a moving image. there were. The present invention provides an image quality correction circuit for reducing the difference in image quality between a still image and a moving image in a high definition television receiver.

[0005]

The image quality correction circuit of the present invention is characterized in that the image quality correction amount for a still image and the image quality correction amount for a moving image are switched by a signal from a moving region detection circuit.

[0006]

According to the image quality correction circuit of the present invention, blurring of a moving image can be easily reduced.

[0007]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit in which a capacitor C1, a resistor R6 and a switch SW1 are added to a part of the speed modulation signal output circuit of the conventional image quality correction circuit of FIG. 9 and also the input signal waveform and the output signal waveform are shown. .. In this circuit, the video signal is applied to the base of the transistor Q9 via the speed-modulation-signal synthesizing coupling resistors R1 and R2. SW that is controlled to ON during drawing and OFF during moving image
It can be changed by 1. Here, the degree of the change can be set by the ratio of the resistance value of R6 to the resistance values of R1 and R2. As a result, the amplitude of the velocity modulation signal output from the emitter of the transistor Q9 is larger in the moving image than in the still image, and the moving image is subjected to the larger velocity modulation than the still image. Apparent video signal waveforms at this time are shown in FIGS. 10A is an input waveform of a still image, and b) is an apparent signal waveform when it is subjected to velocity modulation. 11 (a) is an input waveform of a moving image, and b) is an apparent signal waveform when it is subjected to the same velocity modulation as in the case of a still image, that is, when SW1 is not switched, and it shows a rising portion and a rising portion of the signal. The correction of the falling part is not sufficient. c) is an apparent signal waveform when SW1 is switched to increase the amplitude of the speed modulation signal and b) a higher speed modulation is applied, and the rising and falling parts of the signal are steeper as compared to b). Is corrected to reduce the blurring of the image.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a circuit in which a capacitor C2, a resistor R7 and a switch SW2 are added to a part of the video signal output circuit of the conventional image quality correction circuit of FIG. 9 and also shows an input signal waveform and an output signal waveform. The emitter of the transistor Q4 has coupling resistors R3, R4 for synthesizing aperture compensation signals.
An aperture compensation signal is added via R5, but its amplitude can be changed by SW2, which is controlled to be ON for a still image and OFF for a moving image by the output signal of the motion area detection circuit as shown in the output signal waveform in the figure. You can Here, the degree of change is R with respect to the resistance values of R3, R4 and R5.
It can be set by the ratio of the resistance values of 7. As a result, as shown in the output signal waveform in FIG. 5F, a larger aperture compensation signal is added to the video signal of the moving image than the video signal of the still image, and the contour portion of the moving image is emphasized, so that blurring of the image is reduced. To be done.

(Embodiment 3) FIG. 3 shows a circuit in which SW3 is added to a part of the speed modulation signal output circuit of the conventional image quality correction circuit shown in FIG. A delayed video signal is added to the base of the transistor Q8, and the amount of delay can be changed by SW2 that is switched between 1 for still image and 2 for moving image by the output signal of the moving region detection circuit. Outputs a velocity modulation signal having different pulse widths for a still image and a moving image. As a result, the moving image and the still image are subjected to velocity modulation for different periods, and the apparent video signal waveforms at that time are as shown in FIGS. 10 and 11.
10A is an input waveform of a still image, and b) is an apparent signal waveform when it is subjected to velocity modulation. FIG. 11A shows an input waveform of a moving image, and b) shows a waveform when it is subjected to velocity modulation for the same period as a still image, that is, SW3.
Is an apparent signal waveform when is at a position of 1, and the correction of the rising portion and the falling portion of the signal is not sufficient.
d) is an apparent signal waveform when SW3 is switched to the position of 2 and speed modulation is applied for a longer period than b).
Compared with the above, the rising portion and the falling portion of the signal are sharply corrected and the blur of the image is reduced.

(Embodiment 4) FIG. 4 is a method for selecting the output of an image quality correction circuit which outputs different speed modulation signals and aperture-compensated video signals for the same input signal by the output signal of the moving area detection circuit. It is a block diagram of. According to this method, it is possible to set the optimum velocity modulation signal amplitude and aperture compensation amount for moving images and still images,
Blurring of a moving image can be reduced without deteriorating the image quality of a still image.

[0013]

As described above, according to the image quality correction circuit of the present invention, in a television receiver for reproducing a moving image and a still image having different maximum frequencies of video signals, a moving image having a resolution lower than that of the still image. Image blur can be effectively reduced.

[Brief description of drawings]

FIG. 1 is a speed modulation signal output circuit of an image quality correction circuit according to a first embodiment of the present invention.

FIG. 2 is a video signal output circuit of an image quality correction circuit according to a second embodiment of the present invention.

FIG. 3 is a speed modulation signal output circuit of an image quality correction circuit according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of an image quality correction circuit according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram of an example of a transmission system of a high definition television.

6 is a process of still image signal processing in the system example of FIG.

7 is a process of moving image signal processing in the system example of FIG.

FIG. 8 shows an example of a conventional image quality correction circuit and signal waveforms of various parts.

FIG. 9 is an explanatory diagram of image contour correction using a velocity modulation signal.

FIG. 10 is a signal waveform of a still image and an apparent signal waveform when it is velocity-modulated.

FIG. 11 is a signal waveform of a moving image and an apparent signal waveform when it is velocity-modulated.

[Explanation of symbols]

Q1 Q2 Q3 Q6 Q7 Transistor for aperture compensation signal synthesis Q8 Q9 Transistor for velocity modulation signal synthesis and output DL1 DL2 Video signal delay element R1 R2 Coupling resistor for velocity modulation signal synthesis R3 R4 R5 Coupling resistor for aperture compensation signal synthesis R6 Velocity Modulation signal amplitude switching resistor R7 Aperture compensation signal amplitude switching resistor SW1 Velocity modulation signal amplitude switching switch SW2 Aperture compensation signal amplitude switching switch SW3 Velocity modulation signal pulse width switching switch SW4 SW5 Image quality correction circuit output selection switch

Claims (4)

[Claims] 1. An image quality correction circuit for switching the amplitude of a velocity modulation signal to a velocity modulation coil according to an output signal of a moving region detection circuit. 2. An image quality correction circuit for switching the amplitude of an aperture compensation signal according to an output signal of a moving area detection circuit. 3. An image quality correction circuit for switching a pulse width of a velocity modulation signal to a velocity modulation coil according to an output signal of a moving region detection circuit. 4. One of two image quality correction circuits that outputs different speed modulation signals and aperture-compensated video signals for the same input signal is selected and output by the output signal of the motion area detection circuit. Image quality correction circuit.