JPH05145782A - Scanning speed modulating circuit for television set - Google Patents

Abstract

PURPOSE:To widen width of an outline correction added to both sides of a signal, and to make contrast sufficient. CONSTITUTION:By using a switching 11 circuit for setting a video signal which passes through a delay line 9 and a high-pass filter 10, as a switching signal, a scanning speed modulation signal period is shortened. In such a manner, outline correction width of both sides of the signal can be narrowed, and also, its contrast can be emphasized.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, color television receivers have been increased in size, and there is focus deterioration including the periphery of the screen due to reasons such as a larger screen and an increase in beam current due to an increase in brightness.

Therefore, in many television receivers,
A scanning speed modulation circuit is provided for the purpose of narrowing the beam lateral diameter by changing the scanning speed and adding contour correction.

FIG. 3 shows an example of a conventional circuit block and FIG. 4 shows its operation waveform. In the conventional circuit example, the waveforms a, b, c,
As can be seen from d, the differential waveform for scanning speed modulation is created by subtracting the video signal and the delayed video signal.

With this signal, a current is passed through a scanning speed modulation coil mounted on a CRT (cathode ray tube) gun to change the scanning speed.

At this time, if the scanning speed becomes faster, the signal width on the screen becomes wider and the brightness is lowered. Further, if the scanning speed becomes slow, the signal width on the screen becomes narrow and the brightness increases.

Next, the case where the video signal is a white peak video signal as shown in FIG. 4 will be described. At this time, if the polarities of the scanning speed modulation circuits are matched so that the speed becomes slow during the white peak video signal period, the width of the white peak video signal becomes narrow on the screen, as can be seen from the waveforms e, f, and g. And the brightness goes up. Further, black contour correction is added to both sides of the white peak video signal, so that image quality can be improved.

[0008]

However, the above-mentioned conventional circuit example has the following drawbacks. Generally, a differential waveform generated from a video signal has a drawback that its period is longer than that of the original video signal regardless of the delay line using circuit shown in the conventional example.

The contour correction applied to both sides of the signal therefore has the drawback that it is wide and its brightness does not have sufficient contrast with the original video signal.

In view of the above problems, the present invention provides a circuit for narrowing the contour correction width on both sides of a signal and obtaining a sufficient contrast.

[0011]

In order to solve the above-mentioned problems, the scanning speed modulation circuit of the present invention uses a switching circuit which uses a video signal passing through a delay line and a high-pass filter as a switching signal. is there.

[0012]

According to the present invention, the scanning speed modulation signal, which generally has a longer period than the video signal, can have the same period as the video signal.

As a result, the scanning speed modulation period for performing contour correction on both sides of the signal is shortened, the width of contour correction can be narrowed, and sufficient contrast can be secured.

[0014]

1 is a circuit block diagram of an embodiment of the present invention.

A portion surrounded by a dotted line in FIG. 1 is a configuration of an embodiment of the present invention added to the conventional circuit block diagram shown in FIG.

Reference numeral 9 is a delay line, 10 is a high-pass filter, and 11 is a switching circuit.

FIG. 2 shows operation waveforms of the embodiment of the present invention shown in FIG. The operation will be described below.

As shown by the waveform b in FIG. 2, the scanning speed modulation signal is switched by the switching 11 video signal generated by passing through the delay line 9 and the high-pass filter 10, and the scanning speed modulation period is changed to the video signal. Make them the same.

Due to this shortening of the period, the scanning speed modulation portion serving as the contour correction portion is reduced. It is shown in waveform c.

As a result, as shown by the waveform f, the contour correction width on both sides of the signal becomes narrow. In addition, by performing the contour correction with a shorter scan, the contour correction is extended to the black side, and a higher-contrast contour correction can be realized.

[0021]

As described above, according to the scanning speed modulation circuit of the television receiver of the present invention, the scanning is performed by using the switching circuit that uses the video signal that has passed through the delay line and the high-pass filter as a switching signal. The contour correction width on both sides of the signal due to velocity modulation can be narrowed, and the contrast thereof can be emphasized.

As a result, it is possible to provide a television receiver with improved image quality.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

2 is an operation waveform diagram of each part of the embodiment of FIG.

FIG. 3 is a block diagram of a conventional circuit example.

FIG. 4 is an operation waveform diagram of each part of a conventional circuit example.

[Explanation of symbols]

 1 4 9 Delay Line 2 Subtractor 3 Amplifier 5 Video Amplifier 6 CRT 7 Scanning Speed Modulation Coil 8 CRT Cathode 10 High Pass Filter 11 Switching

Claims (1)

[Claims] 1. A signal for scanning speed modulation, which comprises a signal for scanning speed modulation which is a differential waveform made from a television video signal, and a switching circuit which uses a video signal passing through a delay line and a high-pass filter as a switching signal. Speed modulation circuit of a television receiver with a drive signal