JPH09261509A - Speed modulation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit with which the degradation of picture quality can be prevented by operating a speed modulation circuit corresponding to a noise produced in a TV receiver when an RF input electric field is lowered by providing a video input level detection circuit and a variable amplifier circuit. SOLUTION: When remarkable video amplitude is inputted to a differentiation circuit like a studio program, this amplitude is simultaneously inputted to an input level detection circuit 7 as well. A variable amplifier circuit 3 is controlled corresponding to this input level and operated so as to decrease the amplification gain of the variable amplifier circuit 3 in the case of large input amplitude but operated so as to increase the amplification gain of the variable amplifier circuit 3 in the case of small amplitude. As a result, concerning an image like the studio program, the effect of the speed modulation circuit is lowered but in any other video signal, the effect of the speed modulation circuit is improved and natural picture quality can be provided. When the speed modulation circuit is operated, the noise on the screen is made much more conspicuous. In this case, the operation of the variable amplifier circuit is stopped by operating an RF input detection circuit and the speed modulation circuit is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed modulation circuit for a television receiver.

[0002]

2. Description of the Related Art Conventionally, as a speed modulation circuit, for example, one described in Japanese Patent Laid-Open No. 63-164765 is known. FIG. 3 shows a speed modulation circuit of a conventional television receiver.

Reference numeral 41 is a video input terminal, 42 is a differentiating circuit, 43 is a video amplifying circuit, 44 is an output circuit, and 45 is a velocity modulation coil.

[0004]

In the conventional speed modulation circuit described above, an operation proportional to the amplitude of the input video signal is performed, and a current flows through the speed modulation coil. Therefore, when the amplitude of the video signal is large, its effect is large,
If the amplitude of the video signal is small, the effect becomes small, and the sharpening of the contour of the video changes depending on the amplitude of the input video signal, and the natural image quality is impaired.

Further, when the RF input electric field decreases, the noise component contained in the video signal increases, the speed modulation circuit operates due to the noise component, and the image quality is impaired.

It is an object of the present invention to prevent the image quality from deteriorating due to the operation of the speed modulation circuit due to the noise generated in the television receiver when the RF input electric field is lowered.

[0007]

In order to solve this problem, the present invention provides (1) a configuration including a video signal input level detection circuit and a variable amplification circuit. (2) An RF input electric field in addition to the configuration of (1). Configuration with addition of detection circuit (3) Configuration with circuit for detecting noise level of video signal

(4) A configuration in which the RF input electric field detection circuit and the noise level detection circuit signal of the video signal are combined. It is what it was.

With the above arrangement, it is possible to eliminate an unnatural image quality feeling due to the speed modulation circuit.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a velocity modulation for causing a differential current synthesized from an image signal to flow in a velocity modulation coil of a cathode ray tube to modulate a scanning velocity to sharpen an outline of an image. And a video input level detection circuit that detects the video signal level input to the speed modulation circuit, lowers the gain of the speed modulation circuit when the input level is high, and increases the gain of the speed modulation circuit when the input level is low. , A speed modulator having a variable amplifier circuit,
When a certain constant electric field input is reached, the speed modulation operation is stopped, and the unnatural image quality of the speed modulation circuit can be eliminated.

Further, the invention according to claim 2 of the present invention is a velocity modulation circuit for flowing a differential current synthesized from an image signal to a velocity modulation coil of a cathode ray tube to modulate a scanning velocity to sharpen an outline of an image. , A circuit for detecting an input electric field from RF is used, and when the electric field input from RF becomes a certain electric field or less, a speed modulation circuit device having a circuit for stopping the speed modulation circuit is provided. When the electric field input of is reached, the speed modulation is stopped.

According to a third aspect of the present invention, in a speed modulation circuit for applying a differential current synthesized from a video signal to a speed modulation coil of a cathode ray tube to modulate a scanning speed to sharpen an edge of an image, Detect the noise component of the signal,
When the noise component exceeds a certain ratio, the velocity modulation device has a circuit that stops the velocity modulation circuit. When the noise level reaches a certain level or more, the velocity modulation operation is stopped.

According to a fourth aspect of the present invention, in a speed modulation circuit for applying a differential current synthesized from a video signal to a speed modulation coil of a cathode ray tube to modulate a scanning speed to sharpen an outline of a video, Detect the noise component of the signal,
When the noise component exceeds a certain ratio, and
When the electric field input from RF becomes a certain electric field or less, the detection signals are combined and the speed modulation device is provided with a circuit for stopping the speed modulation circuit, which is unnatural due to the operation of the speed modulation. It has the effect of eliminating the image quality and providing a more natural image quality to the user.

The speed modulation circuit according to the embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows the first aspect of the present invention.
2 is a block diagram of the speed modulation circuit in FIG. In FIG. 1, reference numeral 1 is a video input terminal, 2 is a differentiation circuit, 3 is a variable amplification circuit, 4 is an amplification circuit, 5 is an output circuit, 6 is a speed modulation coil, and 7 is an input level detection circuit.

The operation of the speed modulation circuit of the television receiver configured as described above will be described.

For example, when a large image amplitude such as a studio program is input to the differentiating circuit 2, it is also input to the input level detecting circuit 7. The variable amplifier circuit 3 is controlled in accordance with this input level, and when the input amplitude is large, the amplification gain of the variable amplifier circuit is reduced, and when the input amplitude is small, the amplification gain of the variable amplifier circuit is increased.

As a result, the effect of the speed modulation circuit is reduced in the case of a video such as a studio program, and the effect of the speed modulation circuit is increased in the case of a video signal which is not so that a natural image quality can be obtained.

(Embodiment 1) Next, an embodiment of the present invention will be described with reference to FIG.

(Embodiment 2) FIG. 2 shows the second aspect of the present invention.
2 is a block diagram of a speed modulation circuit of the television receiver in FIG. In FIG. 2, reference numeral 21 is a video input terminal, 22 is a differentiation circuit, 23 is a variable amplification circuit, 24 is an amplification circuit, 25 is an output circuit, 26 is a speed modulation coil, 27 is an input level detection circuit, and 28 is an RF input detection. A circuit, 29 is an RF input detection signal terminal.

The operation of the speed modulation circuit of the television receiver configured as described above will be described with reference to FIG.

When the RF input electric field is lowered to about 55 dB, noise components are mixed in the video signal, and noise is noticeable on the screen of the television.

When the speed modulation circuit operates, noise on the screen becomes more noticeable. In such a case, the signal input to the RF input detection signal terminal 29 (eg, AGC voltage or the like) activates the RF input detection circuit 28, stops the operation of the variable amplification circuit 23, and stops the speed modulation circuit.

As described above, when the RF input electric field is lowered, the speed modulation circuit is stopped, noise generated on the screen is reduced, and a natural image quality can be provided.

(Embodiment 3) FIG. 3 shows a third embodiment of the present invention.
2 is a block diagram of a speed modulation circuit of the television receiver in FIG. In FIG. 3, 31 is a video input terminal and 3
2 is a differentiation circuit, 33 is a variable amplification circuit, 34 is an amplification circuit,
Reference numeral 35 is an output circuit, 36 is a velocity modulation coil, 37 is an input level detection circuit, and 38 is a video signal noise level detection circuit.

When the RF input electric field is lowered to about 55 dB, noise components are mixed in the image signal, and noise is conspicuous on the screen of the television. When the speed modulation circuit operates, noise on the screen becomes more noticeable. In such a case, the video signal noise level detection circuit 38 operates, the speed modulation circuit is stopped, noise generated on the screen is reduced, and a natural image quality can be provided.

(Fourth Embodiment) In this case, the second embodiment and the RF input detection circuit described in the third embodiment,
The image signal noise level detection circuit is combined and operated.

By combining the RF input detection circuit and the video signal noise level detection circuit, stable image quality without malfunction can be provided.

[0029]

As described above, according to the present invention, the effect of speed modulation is changed according to the amplitude level of the video input to provide a more natural image quality, and further, the RF input is lowered and the noise is conspicuous. In that case, the speed modulation operation is stopped, noise generated on the screen is reduced, natural image quality is reproduced, and a satisfactory image is provided to the user.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a speed modulation circuit of a television receiver according to an embodiment of claim 1 of the present invention.

FIG. 2 is a block configuration diagram of a speed modulation circuit of a television receiver according to an embodiment of claim 2 of the present invention.

FIG. 3 is a block configuration diagram of a speed modulation circuit of a television receiver according to an embodiment of claim 3 of the present invention.

FIG. 4 is a block configuration diagram of a speed modulation circuit of a conventional television receiver.

[Explanation of symbols]

 1, 21, 31 Video input terminal 2, 22, 32 Differentiation circuit 3, 23, 33 Variable amplification circuit 4, 24, 34 Amplification circuit 5, 25, 35 Output circuit 6, 26, 36 Speed modulation coil 7, 27, 37 Input level detection circuit 28 RF input electric field detection circuit 29 RF input detection signal terminal 38 Video signal noise level detection circuit

Claims (4)

[Claims] 1. A speed modulation circuit for causing a differential current synthesized from a video signal to flow in a speed modulation coil of a cathode ray tube to modulate a scanning speed to sharpen an outline of a video, and a video signal level input to the speed modulation circuit is changed. A speed modulation circuit that has a variable amplification circuit and a video input level detection circuit that detects and reduces the gain of the speed modulation circuit when the input level is high, and increases the gain of the speed modulation circuit when the input level is low. 2. A circuit for detecting an input electric field from RF is used in a velocity modulation circuit for flowing a differential current synthesized from an image signal to a velocity modulation coil of a cathode ray tube to modulate a scanning velocity to sharpen an outline of an image. , A velocity modulation circuit having a circuit for stopping the velocity modulation circuit when the electric field input from RF becomes a certain electric field or less. 3. A noise component of a video signal is detected and detected in a velocity modulation circuit for flowing a differential current synthesized from a video signal to a velocity modulation coil of a cathode ray tube to modulate the scanning velocity to sharpen the contour of the image. A speed modulation circuit having a circuit for stopping the speed modulation circuit when the ratio exceeds a certain level. 4. A noise component of a video signal is detected and detected in a velocity modulation circuit for flowing a differential current synthesized from a video signal to a velocity modulation coil of a cathode ray tube to modulate the scanning velocity to sharpen the contour of the image. There is a circuit for synthesizing each detection signal and stopping the speed modulation circuit when either the ratio exceeds a certain ratio or the electric field input from RF falls below a certain value. Speed modulation circuit.