JPS63151289A - Color signal processor - Google Patents

Abstract

PURPOSE:To prevent fading of a color or hue variation in the upper part of a television screen by supplying a burst gate pulse to a second burst gate circuit also the periods of both vertical synchronizing signal and equalizing pulse to use a third burst gate pulse generated from a horizontal synchronizing signal. CONSTITUTION:A switch circuit 21 switches between second burst gate pulses and third burst gate pulses corresponding to V pulses. So, since color burst signals are not present during a V pulse period, no second burst gate pulses are generated, however, burst gate pulses can be made supplied to a burst gate circuit 22 even during a V pulse period by using third burst gate pulses during the V pulse period. Accordingly, error signals can hardly occur in a phase comparator during a V pulse period because there is no color burst signals, and the control voltage of a VCO26 can be made in about normal level. As a result, a color fading or hue variation in the upper part of the screen at the time of reproduction can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color signal processing device that can be applied to, for example, a video tape recorder that records and reproduces color video signals.

Conventional technology The video signal processing method conventionally used in consumer video tape recorders is to record the luminance signal by FM modulation, convert the color signal to a low frequency band, and record the luminance signal by FM modulation.
Demodulation is a method in which the color signal is frequency-converted again and restored to its original state.

FIG. 3 is a block diagram of a reproduction system for conventional VH8 color signal processing. In the figure, a reproduced signal inputted from an input terminal 1 is supplied to a low-pass filter (hereinafter referred to as LPF) 3 through an amplifier 2, and a low-pass converted carrier color signal is extracted. In addition, automatic gain control circuit (hereinafter referred to as AC
The amplitude is limited at 4 (denoted as C) and the frequency is converted at a balanced modulator 5.

Next, a band pass filter (hereinafter referred to as BPF) 6 removes unnecessary components generated during balanced modulation. Furthermore, in the 6 dB down circuit 7, the edB
The up color burst signal is reduced in edB to the original state, adjacent crosstalk components are removed in a comb-shaped filter 8, and a reproduced carrier color signal is outputted from an output terminal 9.

On the other hand, the reproduced signal output from the amplifier 2 is supplied to a bypass filter (hereinafter referred to as HPF) 11, and an FM-modulated luminance signal is extracted.

+) The amplitude is limited by the transmitter 12, and the FM demodulator 13
is demodulated into a luminance signal. Only the horizontal synchronizing signal is extracted from the demodulated luminance signal in the H separation circuit 14, and the first pulse generating circuit 15 generates a first burst gate pulse including a color burst signal period based on the extracted horizontal synchronizing signal. Create with. The first burst gate pulse is used in the burst 6 dB down circuit 7 to reduce the color burst signal by edB, and in the first burst gate circuit 10 to extract only the color burst signal from the output signal of the comb filter 8. The color burst signal from the first burst gate circuit 10 is
When the voltage level of the color burst signal is detected by the level detection circuit 19, the voltage level 51\-'7 outputs a detection signal during the period in which the color burst signal actually exists, and the second pulse generation circuit 20 generates a waveform. shaping to create a second burst gate pulse. The second burst gate circuit 22 further extracts a color burst signal and supplies it to the phase comparator 23 at the timing of the second burst gate pulse. A configuration for creating a burst gate pulse according to the level of a color burst signal as described above is described in, for example, Japanese Patent Laid-Open No. 13484/1984. Now, the phase comparator 23 compares the phases of the color burst signal and the signal from the reference oscillator 24 which oscillates at the subcarrier frequency.

The error signal from the phase comparator 23 is smoothed by the LPF 25, and the voltage controlled oscillator (hereinafter referred to as VCO) whose center frequency is approximately 320 times the horizontal scanning frequency (hereinafter referred to as fH)
) 26 is controlled. The output frequency of VCO28 is %
The frequency is divided by % in the frequency divider 27, and four-phase signals whose phases differ by 90 degrees are output. Next, one of them is selected by the selection circuit 28 and supplied to the balanced modulator 29.

Equilibrium change 6 ・＼−.

The output signal of the reference oscillator 24 is used as the carrier of the modulator 29, and the output signal has unnecessary components removed by the BPF 30 and becomes the carrier of the balanced modulator 5.

Problems to be Solved by the Invention However, in the above configuration, since no color burst signal exists in the vertical synchronization signal period or the equivalent pulse period, the second burst gate pulse is generated from the second pulse generating circuit 2o. will no longer be output. For this reason, VC
The control voltage that controls O26 gradually deviates between the vertical synchronizing signal period and the equivalent pulse period, and after the vertical synchronizing signal period and the equivalent pulse period end, it takes time to return the control voltage to the normal voltage, and the TV This has the disadvantage that color fading and hue fluctuation occur in the upper part of the screen, giving the user a sense of discomfort.

Means for Solving the Problems In order to solve the above problems, the color signal processing device of the present invention emits a first burst gate pulse including a color burst signal period based on a horizontal synchronizing signal. a first pulse generating circuit for extracting a color burst signal from a carrier color signal using a first burst gate pulse; and a first pulse generating circuit for extracting a color burst signal from a carrier color signal using a first burst gate pulse; a level detection circuit that detects the voltage value of the burst signal; a second pulse generation circuit that generates a second burst gate pulse by shaping the output signal of the level detection circuit; a third pulse generation circuit that generates a third burst gate pulse including a burst signal period; a pulse generation circuit that generates a pulse indicating a vertical synchronization signal period and an equivalent pulse period; a switch circuit that selects the second burst gate pulse during periods other than the above-mentioned pulse period; and a switch circuit that selects the second burst gate pulse during periods other than the above-mentioned pulse period, and corrects time axis fluctuations during reproduction using the burst gate pulse from the switch circuit. This configuration includes a second burst gate circuit for extracting a color burst signal that should not be processed.

According to the above-described configuration, the present invention generates the second burst gate pulse based on the horizontal synchronizing signal during the vertical synchronizing signal period and the equivalent pulse period without using the second burst gate pulse, which is generated based on the voltage level of the color burst signal. Since the third burst gate pulse is used, the burst gate pulse is also supplied to the second burst gate circuit during the vertical synchronization signal period and the equivalent pulse period. Since there is no color burst signal during the vertical synchronization signal period and the equivalent pulse period, the control voltage that controls VC○ is close to the normal voltage, which can prevent color fading and hue fluctuations at the top of the TV screen. .

Embodiments Hereinafter, color signal processing apparatuses according to embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a color signal processing device according to an embodiment of the present invention. What some people call the conventional example shown in FIG.
A pulse generation circuit 16, a V separation circuit 17 that separates the vertical 9th and -7 period signals and equivalent pulses from the FM demodulated luminance signal, and 1) The signals from the separation circuit 17 separate the vertical synchronization signal period and the equivalent pulse. V pulse generation circuit 1 that creates a V pulse indicating a period
8, and (1) a switch circuit 21 that selects the third burst gate pulse during the pulse period and selects the second burst gate pulse at other times; This means that we are supplying The other functions are the same as those of the conventional example shown in FIG. 3, and will therefore be omitted here. Now, the reason why the switch circuit 21 switches between the second burst gate pulse and the third burst gate pulse according to the pulse is as follows: - During the pulse period, there is no color burst signal, so the second burst gate pulse cannot be generated. However, by using the third burst gate pulse during the ■ pulse period, the burst gate pulse can be supplied to the second burst gate circuit 22 even during the ■ pulse period. As a result, the error signal of the phase comparator during the pulse period (1) is almost non-existent since there is no color burst signal, and the control voltage of the VCO 26 can be kept at a substantially normal level. Therefore, it is possible to prevent color fading and hue fluctuations at the top of the screen during playback. FIG. 2 shows the waveforms and timings of the color burst signal (a), the first burst gate pulse (b), the second burst gate pulse (c), and the third burst gate pulse.

As described above, according to the flood control side, the first pulse generation circuit 15 generates the first burst gate pulse including the color burst signal period based on the horizontal synchronization signal, and the first pulse generation circuit 15 generates the first burst gate pulse including the color burst signal period based on the horizontal synchronization signal, and a first burst gate circuit 10 that extracts a color burst signal using a gate pulse; a level detection circuit 19 that detects the voltage value of the color burst signal extracted by the first burst gate circuit;
By shaping the output signal of the level detection circuit, the second
a second pulse generating circuit 20 that generates a burst gate pulse of; a third pulse generating circuit 16 that generates a third burst gate pulse including a color burst signal period based on a horizontal synchronizing signal; 11/; -2 A V pulse generation circuit 18 that generates pulses indicating the vertical synchronization signal period and equivalent pulse period; Switch circuit 2 to select
1, and a second burst gate circuit 22 that uses the burst gate pulses from the switch circuit 2 to extract a color burst signal for correcting time axis fluctuations during reproduction.
By configuring it in this way, it is possible to prevent the burst gate pulse from disappearing even during the pulse period (1), and to make it resistant to fading of color in the upper part of the television screen and hue fluctuation during playback.

Effects of the Invention With the above-described configuration, the present invention prevents the burst gate pulse used for time axis fluctuation correction during reproduction from disappearing during the vertical synchronization signal period and the equivalent pulse period, and at this time, the VC
Since the control voltage of ○ can be brought to almost the normal level, it has the excellent effect of preventing color fading and hue fluctuations that occur at the top of the TV screen and eliminating user discomfort. can.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a color signal processing device according to an embodiment of the present invention, FIG. 2 is a timing diagram of FIG. 1, and FIG. 3 is a block diagram of a conventional color signal processing device. 1...Input terminal, 2...Amplifier, 3.
...LPF, 4...ACC, 5...
...Balanced modulator, 6...B P F. 7...Burst 6dB down circuit, 8...
・Comb filter, 9...Output terminal, 1o...
...First burst gate circuit, 11...HP
F, 12...Limiter, 13...FM
Demodulator, 14...H separation circuit, 15...
・First pulse generation circuit, 16...Third pulse generation circuit, 17...■ Separation circuit, 18...
... V pulse generation circuit, 19 ... Level detection circuit, 2゜ ... Second pulse generation circuit, 21 ...
... Switch circuit, 22 ... Second burst gelt circuit, 23 ... Phase comparator, 24 ...
...Reference oscillator, 25...LPF, 26...
...VCO127...% frequency divider, 28...
...Selection circuit, 2e...Balanced modulator, 30
...13 l\-・BPF.

Claims (3)

[Claims] (1) A color signal processing device in a recording and reproducing device that converts the frequency of a carrier color signal to a low frequency band, records it, and converts it back to a carrier color signal during playback, which converts a color burst signal period based on a horizontal synchronization signal. a first pulse generating circuit that generates a first burst gate pulse including a first burst gate pulse;
a first burst gate circuit that extracts a color burst signal using a burst gate pulse of the first burst gate circuit; a level detection circuit that detects a voltage value of the color burst signal extracted by the first burst gate circuit; a second pulse generation circuit that generates a second burst gate pulse by shaping the output signal of the circuit; and a third pulse generation circuit that generates a third burst gate pulse including a color burst signal period based on the horizontal synchronization signal. a V-pulse generating circuit that generates a V-pulse indicating a pulse period equivalent to the vertical synchronizing signal period; a V-pulse generating circuit that selects the third burst gate pulse during the V-pulse period; The apparatus includes a switch circuit that selects a second burst gate pulse, and a second burst circuit that uses the burst pulse from the switch circuit to extract a color burst signal for correcting time axis fluctuations during reproduction. A color signal processing device characterized by: (2) The color signal processing device according to claim 1, wherein the third burst gate pulse has a narrower pulse width than the first burst gate pulse. (3) The third burst gate circuit is shared with the first burst gate circuit, and the first burst gate pulse and the third burst gate pulse are the same pulse. The color signal processing device according to scope 1.