JPH0591363A - Velocity modulator - Google Patents

Abstract

PURPOSE:To realize a velocity modulator capable of reducing the phase distortion occurring at a differentiating circuit and keeping in good the contour correction effect, in the velocity modulator used for a television receiver, etc. CONSTITUTION:This modulator is provided with a distributor 2 to distribute a signal, a delaying device 3 to delay a signal, a subtracter 4 to subtract the output signal of the distributor 2 and the delaying device 3, an amplifier 5 to amplify the output signal of the subtracter 4 and a velocity modulating coil 6 to perform the velocity modulation based on the output of the amplifier 5. And the differential component of the luminance signal of the video signal is generated by the distributor 2, the delaying device 3 and the subtracter 4.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, television receivers have become larger in screen size. Even on a large screen, the image contour is emphasized in order to improve the sharpness of the screen. For this contour enhancement, a secondary differential signal is created from the luminance signal of the video signal,
A luminance modulation method that emphasizes the luminance signal of the video signal and the overlapping edge portion, and a velocity modulation method that changes the horizontal scanning speed without changing the amount of the electron beam of the cathode ray tube at the portion where the luminance signal of the video signal changes. There is. When the luminance signal has high luminance, blooming may occur in the luminance modulation method, and the velocity modulation method that does not change the amount of the electron beam of the cathode ray tube is more effective.

A conventional velocity modulator will be described below. FIG. 4 shows a block diagram of a conventional velocity modulator. In FIG. 4, reference numeral 1 is an input terminal to which a luminance signal component of a video signal is input. Reference numeral 5 is an amplifier, and 6 is a velocity modulation coil. Reference numeral 7 is a differentiating circuit, which is composed of a capacitor, a resistor, and an inductor.

The operation of the velocity modulator constructed as described above will be described below with reference to FIG. The luminance signal of the video signal as shown in FIG. 6 (a) inputted from the input terminal 1 is inputted to the differentiating circuit 7 (FIG. 6 (b)).
A change amount of the luminance signal as shown in is extracted. The extracted change in the luminance signal is amplified by the amplifier 5, and its output is added to the velocity modulation coil 6. Since the deflection magnetic field in the horizontal direction is modulated by the velocity modulation coil 6, (see FIG.
As shown in (c), the horizontal deflection speed of the electron beam of the cathode ray tube is also modulated. Due to this modulation action, the horizontal deflection speed is decelerated in the falling period of the luminance signal of the video signal and accelerated in the rising period. The deceleration portion becomes bright because the light emission period is long, and the acceleration portion becomes dark because the light emission time is short, and the image contour on the tube surface of the cathode ray tube is emphasized as shown in FIG. 6 (d).

(Reference: NHK Television Technical Textbook [1] Japan Broadcasting Corporation)

[0006]

However, in the above-mentioned conventional configuration, since the differentiating circuit for extracting the change in the luminance signal of the video signal is composed of the capacitor, the inductor and the resistor, phase distortion occurs and the differentiating circuit Ringing occurs at the output. The state is shown in FIG.

Therefore, since this ringing is output to the velocity modulation coil, there is a problem that the velocity modulation is applied to a portion other than the portion where the original luminance signal is changed, and the image quality is deteriorated.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a velocity modulation device with less image quality deterioration.

[0009]

In order to solve the above-mentioned problems, a velocity modulation device of the present invention comprises a distributor for distributing signals,
It is characterized by including a delay device for delaying a signal, a subtractor for subtracting two signals, an amplifier for amplifying the signal, and a velocity modulation coil for velocity modulation.

[0010]

According to the present invention, the input signal is distributed by the distributor, and one output of the distributor is delayed by the delay device. The other output of the distributor is input to the subtractor together with the signal delayed by the delay device. The subtractor subtracts the signal delayed by the delay device and the signal from the distributor to output a differential component of the luminance signal of the video signal. The amplifier amplifies the output of the subtractor and drives the velocity modulation coil. Since the signal input to the velocity modulation coil is a signal produced by subtracting the original signal and the delayed signal by the distributor, the delay device, and the subtractor, there is no ringing due to phase distortion. .. Therefore, the waveform that drives the velocity modulation coil is only the differential component of the luminance signal of the video signal, and the effect of contour correction by velocity modulation can be further improved.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 is an input terminal. The luminance signal component of the video signal is input to the terminal 1.
2 is a distributor, 3 is a delay device, 4 is a subtractor, 5 is an amplifier, 6
Is a velocity modulation coil.

The operation of the velocity modulator constructed as above will be described below with reference to FIG. The luminance signal of the video signal as shown in FIG. 2A input from the input terminal 1 is input to the distributor 2 and is split into two. The first output of the distributor 2 is input to the delay device 3 and becomes a signal delayed by the delay time of the delay device 3 by the delay device 3 as shown in FIG. 2B. The output of the delay device 3 and the second output of the distributor 2 are input to the subtractor 4 where they are subtracted and extracted as a differential component of the luminance signal of the video signal as shown in FIG. 2 (c). The differential component of the extracted luminance signal is amplified by the amplifier 5, and its output is added to the velocity modulation coil 6. Then, similarly to the conventional example, the velocity modulation coil 6 controls the horizontal deflection velocity of the electron beam of the cathode ray tube, and the image contour on the tube surface of the cathode ray tube is emphasized.

The delay device 3 can be constructed by using a delay element. Further, the subtractor 4 can be realized by using a transistor differential amplifier circuit as shown in FIG. Here, RL is a load resistance of the transistor Q2, R1 and R2 are emitter resistances of the transistors Q1 and Q2, and I is a current source. If the + input amplitude of this differential amplifier circuit is Va and the-input amplitude is Vb, the output amplitude is RL if R1 = R2 = Re.
It becomes × (Va-Vb) / 2Re, and two signals can be subtracted.

According to this structure, since the signal input to the amplifier 5 is a differential component of the luminance signal without ringing, the velocity modulation is not applied to a portion other than the changed portion of the luminance signal, and the contour enhancement is performed well. be able to. In addition,
If the subtracter 3 has a function of subtracting two signals, the third
A circuit other than the one shown may be used. Further, the delay element may be shared with the one used for the delay line aperture controller.

[0016]

As described above, according to the present invention, a distributor for distributing an input signal, a delay device for delaying a signal using the first output of the distributor as an input, and a second output for the distributor. Drives the velocity modulation coil by including a subtracter that subtracts the output of the delay device, an amplifier that amplifies the signal using the output of the subtractor as input, and a velocity modulation coil that inputs the output of the amplifier and performs velocity modulation It is possible to realize an excellent velocity modulation device that can eliminate the phase distortion of the waveform to be generated and can favorably perform contour enhancement by velocity modulation.

[Brief description of drawings]

FIG. 1 is a block diagram of a speed modulator according to an embodiment of the present invention.

FIG. 2 is a diagram showing the principle of generation of a differential waveform according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of a subtractor

FIG. 4 is a block diagram of a conventional velocity modulator.

FIG. 5 is a diagram showing a conventional differential waveform example.

FIG. 6 Principle diagram of velocity modulation

[Explanation of symbols]

 1 Input terminal for luminance signal of video signal 2 Distributor 3 Delay device 4 Subtractor 5 Amplifier 6 Speed modulation coil 7 Differentiation circuit

Claims (1)

[Claims] 1. A distributor for distributing an input signal, a delay device for delaying a signal with the first output signal of the former distributor as an input, a second output signal of the distributor and an output signal of the delay device. A velocity modulation device comprising: a subtractor for subtracting the output of the subtractor, an amplifier for amplifying an output signal of the subtractor, and a velocity modulation coil for inputting the output signal of the amplifier to perform velocity modulation.