JPH011392A - Color signal processing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color signal processing device useful for use in a video tape recorder.

Conventional technology The video signal processing method conventionally used in consumer video tape recorders is that during recording, the luminance 1y signal is FM modulated and the chrominance signal is frequency-converted to a low frequency band, and during playback, the luminance signal is FM demodulated and the chrominance signal is subjected to frequency conversion. is again frequency 9. It is common to convert it and restore it.

FIG. 4 is a block diagram of a reproduction system of a conventional color signal processing device using the S method. In the figure, the paleosignal input from input terminal 1 is passed through amplifier 2 to a low-pass filter (
(hereinafter referred to as LPF) 3, and a low-frequency converted color signal is extracted. Next, the amplitude is limited in an automatic gain control circuit (hereinafter referred to as ACC) 4, and the frequency is converted in a balanced modulator 5.

Furthermore, unnecessary components are removed by a band pass filter (hereinafter referred to as BPF) 6. Next, in the burst 6 dB down circuit, the color burst signal that has increased by 6 dB during recording is brought down by 6 dB and returned to its original state, and the comb-shaped filter 8
The crosstalk of the first contact is cooled down at the output terminal 9.
It is output from

On the other hand, the reproduced signal output from the amplifier 2 is supplied to a bypass filter (hereinafter referred to as HPF) 10, and the reproduced signal is outputted from the 2FM filter. The J'C5 degree signal is extracted, its amplitude is limited by a limiter 11, and demodulated into a luminance signal by an FM demodulator 12. Only the horizontal synchronizing signal is extracted from the demodulated luminance signal in the H intervention circuit 13.

]A first burst gate pulse including a color burst signal period is generated in the first pulse generation circuit 14 based on the horizontal synchronization signal outputted from the output horizontal synchronization signal.

Further, the second pulse generating circuit outputs a second burst gate pulse having a more comfortable pulse width both before and after the first burst gate pulse.

The first burst gate pulse is used for the timing to lower the color burst signal by 6 dB in the 6 dB down circuit 7 and the timing for extracting the color burst signal in the burst gate circuit 16. The color burst signal extracted from the burst gate circuit 16 is phase-compared with the output signal of the reference oscillator 21 in a phase comparator 20. The phase comparator 20 operates only during the second burst gate pulse period. Phase ratio [1]; The error signal from F320 passes through LPF 22 and adder 23, and is output to a 4-voltage controlled oscillator (hereinafter referred to as VCO) 2 with a center frequency of 82OfH (fH is the horizontal scanning frequency of 1 loss).
Control 4. The output signal of VCO24 is 1/8 frequency divider 2
7 is output. The 178 frequency divider 27 outputs four output signals having different phases by 90 degrees, and the selection circuit 28 selects one of them. The selected signal is provided to a balanced modulator 29. The output signal of the l&skew oscillator 21 is used as the carrier of the balanced modulator 29, and the output signal of the balanced modulator 29 passes through the BPF 30 and is then output to the balanced modulator 5.
career.

In this way, time axis fluctuations in the carrier color signal during reproduction are corrected. In addition, the frequency detector 25
In order for the VCO 24 not to enter the locked state at a value other than 32Of+, the oscillation frequency of the VCO 24 is detected and the VCO 24 is controlled through the LPF 2-generation adder 28. The above-mentioned groove formation has been described, for example, in Japanese Patent Publication No. 11484/1984.

Problems that L'] attempts to solve: Basics of color signal reproduction in video tape recorders +-i
One of the u points is the color at the top of the TV screen (old instability).In the conventional 4-channel system shown above, the output burst signal j Yo, Moto■
Since it is not phase-synchronized with the signal from the oscillator 21, the hue at the top of the television screen is not stable, which has the drawback of causing discomfort to the user.

Means for deciding the same point J: To help you decide the problem, the color signal processing plate of the present invention is horizontally open! Based on the 71 signal (color burst).

a π1 pulse generation circuit that generates and mains a first burst gate pulse including '3'' II ', 11, and a second burst gate pulse that generates a second burst gate pulse whose pulse width is smaller than that of the first burst date pulse. a second pulse generation circuit, a monomulti circuit that generates a pulse for a predetermined period from a head switch pulse for switching a signal from the head or a vertical synchronization signal, and a monomulticircuit that generates a pulse for a predetermined period from the monomulticircuit. A switch circuit that selects a burst gate pulse, selects the second burst gate pulse during periods other than the pulse period from the monomulti circuit, and outputs a burst gate pulse for correcting time axis fluctuations during reproduction. It is a thing that has been prepared.

Function The present invention uses the above-mentioned groove formation to control the burst pulse for correcting the time axis fluctuation of the carrier color signal during reproduction by changing the pulse width for a predetermined period from the vertical synchronizing signal or by turning off the head switch pulse. By adopting a first burst gate pulse with a wide width and a second burst gate pulse with a narrow pulse width in other periods,
When the first pulse is adopted, the gate period becomes longer, so the return gain becomes higher, and the quick stability of the color image can be checked.

Embodiment Below, drawings ff! about the color signal processing bag h1 according to the embodiment of the present invention will be described. I will explain while referring to it. Figure 1 shows one example of the present invention. FIG. 3 is a block diagram of a fake example. What is different from the conventional device 1 shown in FIG. 4 is that a head switch pulse circulator 17, a monomulti circuit 18, and a switch circuit 19 are newly added. Since the other parts are the same as those in FIG. 1, their explanation will be omitted here.

A circuit including the newly added head switch pulse input terminal 17, monomulti circuit 18, and switch circuit 19 is a circuit for a burst gate pulse indicating the period during which the phase comparator 208id is operated. A head switch pulse is input to input terminal 17, and 16
The mono multi-circuit 18 generates a pulse with a period of H (H indicates a horizontal scanning period).The switch circuit 19
During the H period, a wide first burst gate pulse 9!
and selects a narrower second burst gate pulse for other periods. The phase comparator 20 operates during the burst gate pulse period from the switch circuit 19.

FIG. 2 shows the waveforms and timing of the output signal p) of the burst gate circuit 16, the first burst gate pulse eS), and the second burst gate pulse eS, respectively. FIG. 3 shows the waveforms and timing of the output signal of the amplifier 2), the head switch pulse (e), and the output pulse of the monomulti circuit 18 (e).

As described above, the first pulse generating circuit 14 that generates the first burst gate pulse including the color burst signal period based on the horizontal synchronizing signal and the first burst gate pulse having the pulse width A second pulse generation circuit 16 that generates a narrow second burst gate pulse e→ and a head switch pulse (e) that switches the signal from the head.
Select the mono multi-circuit 18 that generates the pulse (to) for the 16H period from the switching of the mono multi-circuit 18, and the first burst gate pulse during the pulse period from the mono multi-circuit 18,
Otherwise, by having a configuration including a switch circuit 19 that selects the second burst gate pulse (c), the phase comparator 20 is used during the 16H period from the head switch.
The operation time is longer, so the feedback gain is higher and the hue stabilizes more quickly.

In the above description, a case has been described in which a head switch pulse (E) for switching the signal from the head is supplied to the input terminal 17 of the mono multi circuit 18, but the same effect can be obtained even if a weight synchronization signal is supplied to the input terminal 17. works.

Effects of the Invention The present invention uses the R4 configuration described above to quickly stabilize the hue by increasing the feedback gain during the period corresponding to the upper part of the TV screen. It is possible to obtain the excellent effect of being able to relieve the discomfort of

[Brief explanation of drawings]

FIG. 1 is a block diagram of a color signal processing device according to an embodiment of the present invention, FIGS. 2 and 3 are waveform and timing diagrams in FIG. 1, and FIG. 4 is a block diagram of a conventional color signal processing device. It is. 14... First pulse generation circuit, 15... Second pulse generation circuit, 16... Burst gate circuit, 17.
- Input terminal, 18... Mono multi circuit, 19...
Switch circuit, 20...phase comparator.

Claims (1)

[Claims] 1. A color signal processing device used in video tape recorders that converts the frequency of a carrier color signal to a lower frequency band, records it, and converts it back to a carrier color signal during playback. It generates a color burst signal based on a horizontal synchronization signal. a first pulse generating circuit that generates a first burst gate pulse that has a pulse width including a period; a second pulse generating circuit that generates a second burst gate pulse that has a narrower pulse width than the first burst gate pulse; and a head. a mono multi-circuit that generates a pulse of a predetermined period from a head switch pulse that switches a signal from a vertical synchronization signal, and selects the first burst gate pulse during a pulse period from the mono multi-circuit;
and a switch circuit that selects the second burst gate pulse during periods other than the pulse period from the monomulti circuit and outputs a burst gate pulse for correcting time axis fluctuations of the carrier color signal during reproduction. color signal processing device.