JP2640046B2 - Contour correction device for television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour correcting device for a television receiver, and more particularly, to a picture tube provided with a scanning speed modulating deflection means separately from a main deflection means, and supplying a correction signal to this means. And a contour correction device for improving the sharpness of a television image by modulating the scanning speed of an electron beam on a screen.

[0002]

2. Description of the Related Art Various contour correction devices for modulating the scanning speed of an electron beam on a screen to improve the sharpness of a television image have been proposed in, for example, Japanese Patent Publication Nos. 43-8728 and 54-43843. I have.

FIG. 6 shows a basic configuration of this prior art, and FIG. 7 shows a basic signal waveform. The principle of operation will be briefly described.

When the video signal a is input to the differentiating circuit 1, the differentiated output signal has a waveform of b, and this signal is used as a correction signal via the amplifying circuit 2 and the driving circuit 3 for the scanning speed modulating deflection coil 4. , The horizontal scanning speed is modulated at the conversion points from the black level to the white level and from the white level to the black level of the video signal as shown in FIG. That is, in the conversion point from the white level to the black level, the scanning speed becomes once late in the period of time T _1, it becomes excessively fast in a period of time T _2. In such a case, the period of T ₁ which scanning speed is slow, the horizontal distance L ₁ on the screen is short, a thin, crisp white contour correction. On the other hand in the opposite this, in the period of the scanning speed is increased T _2, the horizontal scanning distance L ₂ on the screen becomes longer, resulting in a black wide contour correction.

The same phenomenon occurs at the conversion point from the black level to the white level, but redundant description is avoided.

[0006]

As described above, during the period in which the scanning speed is high, the horizontal distance on the screen becomes long, and as a result, black wide contour correction is solved. Then, it is improved so as to obtain a thin and sharp black outline correction.

[0007]

SUMMARY OF THE INVENTION The present invention provides a first differentiating circuit for differentiating a video signal, a second differentiating circuit for further differentiating a first differential signal of the first differentiating circuit, and a second differentiating circuit. Extracting means for extracting a positive differential signal from the second differential signals from the differentiating circuit, inverting means for inverting an output signal of the extracting means, and synchronizing with the first differential signal. Selecting means for selecting the output signal of the inverting means when the polarity of the first differential signal is positive, and selecting the output signal of the extracting means when the polarity of the first differential signal is negative; An adding circuit for adding the output signal of the selecting means and the first differential signal; an amplifying circuit for amplifying the output signal of the adding circuit; and an output signal from the amplifying circuit for modulating a scanning speed of the electron beam of the cathode ray tube by the output signal from the amplifying circuit. Circuit for outputting a driving signal for performing the driving, and a driving signal from the driving circuit. There is a contour correcting device of the television receiver comprising a scan velocity modulation coil being supplied.

[0008]

[Act as the correction signal output of the aforementioned adding circuit, by supplying to the scan velocity modulation deflection means, the period T ₂ in which the scanning speed becomes excessively fast becomes shorter than conventional, so that the horizontal scan on the screen distance L ₂ is shortened, the thinner crisp black contour correction.

[0009]

FIG. 1 is a block diagram showing an outline correction apparatus according to the present invention, and its configuration will be described.

A primary differentiating circuit 5 for differentiating a video signal, a secondary differentiating circuit 6 for further differentiating the primary differential signal, and an extracting means 7 for extracting a positive half cycle of the secondary differential signal.
And inverting means 8 for inverting the output signal of the means, and selecting the output signal of the inverting means 8 when the polarity of the primary differential signal is in the negative direction in synchronization with the primary differential signal. When the polarity of the primary differential signal is in the positive direction, there is provided a selecting means 9 for selecting an output signal of the extracting means 7, and an adding circuit 10 for adding the output signal of the selecting means and the primary differential signal, This is a contour correction device for a television receiver which supplies an output signal of the addition circuit to a scanning speed modulation deflecting means 13 via an amplifier circuit 11 and a drive circuit 12. A limiter amplifier circuit 14 shapes the waveform of the primary differential signal.

Next, FIG. 2 shows input / output waveforms of the respective blocks, and the operation will be described with reference to the waveform diagrams.

When the video signal a is input to the primary differentiating circuit 5, a primary differential signal b is generated at its output. This signal is 2
The waveform c is further differentiated by the next differentiating circuit 6. And
When the extraction means (rectifier circuit) 7 extracts a positive half cycle of the secondary differential signal c, an output waveform d is obtained. When the output waveform d is inverted by the inversion means 8, a waveform e is obtained. The selection means 9
Controlled by the output signal of the limiter amplifier circuit which shaped the primary differential signal b, when the polarity of the primary differential signal is in the positive direction, the waveform e is selected, and the polarity of the primary differential signal b is in the negative direction. At this time, the output waveform d is selected. Therefore, the output waveform of the selection means 9 is f.

When the output waveform f and the primary differential signal b are added by the adding circuit 10, an output waveform g is obtained. The output waveform g as a correction signal, the amplifier circuit 11, via the drive circuit 12, as in FIG. 3 is supplied to the scan velocity modulation deflection means 13, the period T ₂ in which the scanning speed becomes excessively fast becomes shorter than conventional as a result, shorter horizontal scanning distance L ₂ on the screen, a thin, crisp black contour correction.

FIG. 4 shows a circuit diagram of the secondary differentiating circuit 6, extracting means 7, inverting means 8, selecting means 9, and adding circuit 10.

A first-order differential signal is applied to a terminal T1 and is secondarily differentiated by a resistor R1 and a peaking coil L1. C
Reference numeral 1 denotes a DC cut capacitor. A resistor R2 is provided at the base of the transistor TR1 to which the secondary differential signal is applied.
The voltage divided by R3 is applied via a resistor R4.
The same voltage is applied to the diode D via the resistor R5.
Is also applied to the cathode side. The emitter of TR1
A voltage approximately 0.6 volts _DC higher than the base voltage is output. Therefore, the diode D is turned on at TR1
Is applied only when the secondary differential signal is applied in the positive direction, and when the secondary differential signal is applied in the negative direction, the diode D is turned off, and a signal having a waveform d in FIG. 2 is obtained. This signal is input to the inversion means 8 via the capacitor C2. The inverting means 8 includes a differential amplifier TR
2, the base of each transistor is biased by resistors R6, R7, R8, and R9. TR4
Is a constant current transistor. At the collector of the transistor TR2, a signal of waveform e in FIG. On the other hand, the collector of the transistor TR3 has
A signal of waveform d that is not inverted occurs. Each signal is input to the selection means 9 via the emitter follower transistors TR5 and TR6.

The lower transistors TR7, T of the selection means 9
The output signal of the limiter amplifier circuit 14 is applied to the base of R8 from the terminal T2. Note that the limiter amplifier circuit 14 will be described later.

When the polarity of the primary differential signal output from the primary differentiating circuit 5 is in the positive direction, control is performed so that TR7 is turned off and TR8 is turned on. Therefore, the upper transistor T
R9 is turned off, TR10 is turned on, and an inverted signal e is generated in the common collector resistor R10. Conversely, when the polarity of the primary differential signal is in the negative direction, the upper transistor TR9 is turned on and TR10 is turned off, and the common collector resistance R1 is turned off.
At 0, a signal of waveform d that is not inverted occurs. Therefore,
A correction signal having an output waveform f is generated at the output of the emitter follower transistor TR11. When the output waveform f and the primary differential signal b are added by the resistors R12 and R13 of the addition circuit 10, an output waveform g of FIG. 2 is generated at the output terminal T3.

Next, FIG. 5 shows an embodiment of the limiter amplifier circuit, and its operation will be described. A first derivative signal is applied to the terminal T1. The transistors TR12, TR13,
TR14 and TR15 constitute a double differential amplifier. T
R16 and TR17 are constant current transistors. The voltages divided by the resistors R13 and R14 are combined with the resistors R15, R16 and R15.
Each of the transistors TR12 to TR15 via 17, 18
, The collector potential of each transistor becomes the same potential.

The output of the double differential amplifier is taken out via the emitter follower transistors TR18 and TR19TR20. D1, D2, D3, D4 are amplitude limiting diodes. Therefore, the terminal T2 has a primary differential signal b
Is generated, and the selection means 9 is controlled by the control signal as described above.

[0020]

According to the present invention, the horizontal distance on the screen is increased during the period in which the scanning speed is high, and as a result,
The problem of black wide contour correction can be solved, and fine and sharp contour correction can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a contour correction device according to the present invention.

FIG. 2 is a signal waveform diagram of each section for explaining the contour correction device of the present invention.

FIG. 3 is a technical explanatory diagram for explaining the contour correction device of the present invention.

FIG. 4 is a circuit diagram showing one embodiment of the contour correction device of the present invention.

FIG. 5 is a circuit diagram showing one embodiment of a limiter amplifier in the contour correction device of the present invention.

FIG. 6 is a basic block diagram showing a conventional contour correction device.

FIG. 7 is a technical explanatory diagram for explaining a conventional contour correction device.

[Explanation of symbols]

 Reference Signs List 5 primary differentiator circuit 6 secondary differentiator circuit 7 extracting means 8 inverting means 9 selecting means 10 adding circuit 11 amplifying circuit 12 drive circuit 13 scanning speed modulation deflecting means 14 limiter amplifier circuit

Claims (1)

(57) [Claims] A first differentiating circuit for differentiating a video signal;
A second differentiating circuit for further differentiating the first differential signal of the first differentiating circuit, and extracting means for extracting a positive differential signal from the second differential signals from the second differential circuit. An inverting means for inverting an output signal of the extracting means; and selecting the output signal of the inverting means when the polarity of the first differential signal is positive in synchronization with the first differential signal. Selecting means for selecting the output signal of the extracting means when the polarity of the differential signal is in the negative direction; an adding circuit for adding the output signal of the selecting means and the first differential signal; and an output signal of the adding circuit Amplifying circuit, a driving circuit for outputting a driving signal for modulating a scanning speed of an electron beam of a cathode ray tube by an output signal from the amplifying circuit, and a scanning speed for supplying a driving signal from the driving circuit Contour correction device for television receiver consisting of modulation coil .