JPS646617Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention enables R, G, B
(R: Red primary color signal, G: Green primary color signal,
The present invention relates to a playback device such as a video tape recorder that forms and outputs a blue primary color signal (B: blue primary color signal), and is intended to prevent a decrease in the fidelity of a playback image based on R, G, and B.

An example of a conventional playback device of this type, namely a video tape recorder, records a luminance signal in FM modulation on a video tape as a recording medium, and also modulates a color signal in a television signal at a frequency lower than that of the recording frequency of the luminance signal. Conversion recorded.

And in order to simplify the configuration during playback,
R is extracted from the reproduced color signal without performing frequency conversion of the reproduced color signal extracted from the reproduced signal of the tape.
-Y, B-Y reproduced color difference signals are formed and output.

That is, the reproduced luminance signal is extracted and demodulated from the reproduced signal, and the reproduced color signal is extracted from the reproduced signal.

Also, the oscillator is controlled to oscillate based on the horizontal synchronization signal separated and extracted from the reproduced luminance signal, and the oscillator outputs an oscillation signal at the low frequency conversion frequency of the color subcarrier when recording on the tape, for example, 688 KHz.

Then, the reproduced color signal is synchronously detected using the oscillation signal and a signal obtained by shifting the phase of the signal by 90 degrees, and the R-Y, B-Y
A reproduced color difference signal is formed, and further, R,
Form G and B.

By the way, in the above case, since the oscillator is AFC controlled by PLL control of the frequency of the horizontal synchronization signal,
Even if phase fluctuations occur in the 688KHz reproduced color signal,
688KHz is much higher than the horizontal synchronization signal frequency,
There is no change in the phase of the horizontal synchronization signal,
Therefore, the phase of the oscillation signal does not change following the phase fluctuation, and in this case, there is a drawback that the detection phase shifts during synchronous detection, resulting in a decrease in the fidelity of the reproduced image based on R, G, and B. .

This invention was made with the above-mentioned points in mind, and includes a recording medium in which a color signal is recorded in a lower frequency range than the recording frequency of a luminance signal by low-frequency conversion of a color subcarrier in a television signal; a luminance signal extraction processing section that outputs a reproduced luminance signal by extraction and demodulation of the reproduced signal of the medium; a synchronization separation section that separates and extracts a horizontal synchronization signal from the reproduced luminance signal; and a synchronization separation section that receives the horizontal synchronization signal and outputs a phase difference signal. an oscillator whose oscillation is controlled by the phase difference signal and which outputs an oscillation signal at a low frequency conversion frequency of the color subcarrier; and a frequency-divided oscillator that divides the oscillation signal and feeds it back to the phase comparison section. a color signal extraction section that extracts a reproduced color signal from the reproduced signal; and a reproduced color difference signal of RY (R: red primary color signal, Y: luminance signal) from the reproduced color signal based on the oscillation signal. and a first synchronous detection section forming a B-Y signal from the reproduced color signal based on a signal obtained by shifting the phase of the oscillation signal by 90 degrees.
(B: blue primary color signal); a second synchronous detection unit that forms a reproduced color difference signal of (B: blue primary color signal); and a primary color signal output unit that outputs red, green, and blue primary color signals based on the reproduced luminance signal and both reproduced color difference signals. A correction signal forming unit that extracts a burst detection component of the RY reproduced color difference signal and outputs a correction signal corresponding to a phase shift of the burst component of the RY reproduced color difference signal; The present invention provides a reproducing device including an addition section that adds the correction signal to the phase difference signal and inputs the result to the oscillator to correct the oscillation signal.

Therefore, according to the reproducing device of this invention, R
- Since the burst detection component of the reproduced color difference signal of -Y changes in phase following the phase fluctuation of the reproduced color difference signal, the correction signal changes in accordance with the phase fluctuation of the reproduced color signal, and the oscillation signal for the reproduced color signal changes. The phase shift is corrected based on the correction signal.

Since the phase of the oscillation signal is corrected and changed to follow the phase shift of the reproduced color signal, the detection phases of the first and second synchronous detection sections will not shift even when a phase fluctuation occurs in the reproduced color signal. , R, G, and B, and the reproduction quality can be improved.

Next, this invention will be explained in detail with reference to drawings showing embodiments thereof.

First, an embodiment applied to a video tape recorder for recording and reproducing NTSC television signals will be described with reference to FIGS. 1 and 2.

The brightness signal in the NTSC television signal is
At the same time, the color signal in the television signal is FM modulated and recorded on the video tape 1, and the color signal in the television signal is converted to the lower frequency side of the recording frequency of the luminance signal, for example, 688 KHz, by low frequency conversion of the color subcarrier, and then recorded on the tape 1. has been done.

During playback, the video head 2 plays back the tape 1, the playback signal of the tape 1 is output from the head 2 to the high-pass filter 3 and the low-pass filter 4, and the playback luminance signal located on the high frequency side of the playback signal is sent to the filter 3. At the same time, a reproduced color signal located on the low frequency side of the reproduced signal is extracted by the filter 4.

Further, the reproduced luminance signal of the filter 3 is demodulated by the FM demodulator 5, and the demodulated reproduced luminance signal Y is output from the demodulator 5 to the primary color signal output section, that is, the color output circuit 6.

Note that the filter 3 and the demodulator 5 form a luminance signal extraction processing section 7.

Furthermore, the reproduced color signal from the filter 4 forming the color signal extraction section is input to first and second synchronous detection sections 8 and 9, which are composed of multipliers and the like.

On the other hand, the reproduced luminance signal Y of the demodulator 5 is also input to the synchronization separator 10, and the horizontal synchronization signal of the reproduced luminance signal Y is separated and extracted by the synchronization separator 10.

The horizontal synchronization signal of the synchronization separation section 10 is inputted to one input terminal of the phase comparison section 11, and at this time, the other input terminal of the phase comparison section 11 is inputted to the frequency division section 12.
A frequency-divided signal is input, and a phase difference signal between the horizontal synchronization signal and the frequency-divided signal is outputted from the phase comparator 11 to one input terminal of the adder 13. Note that the horizontal synchronization signal is also output to the synchronization output terminal 14.

Further, the output signal of the adder 13 controls the oscillation of the voltage controlled oscillator 15, and the oscillator 15
An oscillation signal with a low conversion frequency, that is, 688KHz, is output from the converter.

The oscillation signal of the oscillator 15 is output to the first synchronous detection section 8 and also output to the 90° phase shifter 16, and a signal obtained by shifting the phase of the oscillation signal by 90° by the phase shifter 16 is sent to the second synchronous detection section. 9 is output.

In other words, since the phase of the oscillation signal is the phase of the RY axis, the phase shifter 16 shifts the phase of the oscillation signal to B.
- Set to Y-axis phase.

The oscillation signal of the oscillator 15 is also fed back and output to the frequency divider 12, and the frequency divider 12 divides the oscillation signal to the frequency of the horizontal synchronization signal to form a frequency-divided signal. 11.

The first synchronous detection section 8 forms and outputs a reproduced color difference signal of R-Y from the reproduced color signal as a carrier signal for detection of the oscillation signal, and the second synchronous detection section 9
uses the 90° phase-shifted signal of the oscillation signal as the carrier wave signal for detection, and forms and outputs a B-Y reproduced color difference signal from the reproduced color signal.

Furthermore, the reproduced color difference signals of R-Y, B-Y are inputted to the color output circuit 6, and the reproduced luminance signals Y and R-Y,
By processing with the B-Y reproduced color signal, the color output circuit 6 outputs the first to third primary color output terminals 16a, 16.
R, G, and B are output to b and 16c, respectively.

By the way, the PLL circuit of the phase comparator 11, the oscillator 15, and the frequency divider 12 forms a conventional AFC circuit, that is, a circuit that performs PLL control of the oscillator 15 at the frequency of the horizontal synchronizing signal.

In the case of only the AFC circuit, the frequency of the horizontal synchronization signal is much lower than the carrier frequency of the reproduced chrominance signal, 688 KHz, so even if a phase change occurs in the carrier of the reproduced chrominance signal, the horizontal synchronization signal does not follow the change, and the second
As shown in the figure, even if a phase change of Δθ occurs in the reproduced color signal and the reproduced color signal changes from A to A', the oscillation signal remains fixed on the R-Y axis, and the primary color signals of R, G, and B The reproduced image formed from the image will have a hue shift, which will reduce the fidelity of the reproduced image and make it unsightly.

On the other hand, as shown in Fig. 2, due to the phase fluctuation of Δθ of the reproduced color signal, the burst component of the reproduced color signal is also
It changes by Δθ from to B′.

Since the burst detection component in the RY reproduced color difference signal becomes the RY axis component of the burst component in Fig. 2, if the oscillation signal is auxiliary controlled by the burst detection component, the oscillation signal can be changed into the reproduced color signal. It can be changed to follow phase fluctuations.

Therefore, the reproduced color difference signal of R-Y is input to the burst gate circuit 17, and the burst gate circuit 17 is controlled by the burst gate pulse formed by delaying the horizontal synchronization signal of the synchronization separation section 10 by the delay circuit 18. A circuit 17 extracts a burst detection component from the RY reproduced color difference signal.

Furthermore, the voltage of the burst detection component is input to the non-inverting input terminal (+) of the differential amplifier 19, and the voltage of the reference power supply 20 is input to the inverting input terminal (-) of the amplifier 19. A correction signal is formed and output.

In other words, when the burst component shifts by Δθ,
A positive voltage correction signal proportional to the magnitude of Δθ is output from the amplifier 19, and conversely, when the burst component is -Δθ
When there is a deviation, the amplifier 19 outputs a negative voltage correction signal proportional to the magnitude of Δθ.

By the way, since the correction signal is output from the amplifier 19 only during the period when the burst detection component is extracted, the correction signal of the amplifier 19 is input to the hold circuit 21, and then the correction signal is inputted to the hold circuit 21 until the correction signal is output from the amplifier 19. Hold the correction signal.

Note that the burst gate circuit 17 and the delay circuit 1
8, a differential amplifier 19, a reference power source 20, and a hold circuit 21 form a correction signal forming section 22, and the hold circuit 21 forms a correction signal forming section 22.

The correction signal held by the hold circuit 21 is then input to the other input terminal of the adder 13, and the adder 13 adds the correction signal to the phase difference signal of the phase comparator 11.

Therefore, when there is no phase variation in the reproduced color signal, the output signal of the adder 13 is only a phase difference signal, and the oscillator 15 is voltage-controlled by the phase difference signal, and when there is a phase variation in the reproduced color signal, the adder 13 The output signal of 13 becomes a sum signal of the phase difference signal and the correction signal, and the oscillator 15 is voltage-controlled by the phase difference signal and the correction signal.

Then, when the phase fluctuation of the reproduced color signal is Δθ, that is, when the phase of the reproduced color signal changes to a delayed phase, the oscillation signal changes by −Δθ based on the correction signal and becomes a delayed phase by Δθ. When the phase variation of the color signal is -Δθ, that is, when the phase of the reproduced color signal advances and changes to the phase, the oscillation signal advances by Δθ based on the correction signal and becomes in phase.

Therefore, according to the embodiment, the conventional
Formed by the AFC circuit and the correction signal forming section 22
APC circuit is provided, and the adder 13 adds the correction signal of the hold circuit 21 to the phase difference signal of the phase comparator 11 to control the voltage of the oscillator 15.
When the phase of the reproduced color signal fluctuates, the oscillator 15
The phase of the oscillation signal changes in accordance with the phase fluctuation, and the detection phases of both detection sections 8 and 9 are corrected in accordance with the phase fluctuation, and R, G, and B are input to the primary color input terminals of the television receiver. There is no hue shift in the reproduced image when the CRT is directly driven by R, G, and B, and the fidelity of the reproduced image is improved and the reproduction quality is significantly improved.

Note that the reference power source 20 is formed by a variable power source so that hue adjustment can be performed;
0 is not provided, and the inverting input terminal (-) is connected to the amplifier 19.
may be grounded.

In addition, by inserting a comb filter after filter 4, crosstalk processing can be performed.
Playback quality is further improved.

Next, an embodiment applied to a video tape recorder for recording and reproducing PAL television signals will be described with reference to FIGS. 3 and 4.

In Fig. 3, the same symbols as in Fig. 1 indicate the same or equivalent parts, and in the case of the PAL system, as shown in Fig. 4, the burst component is plotted against the B-Y axis for each horizontal period. The PAL switch circuit 23 is provided between the oscillator 15 and the first synchronous detection section 23, and the PAL switch circuit 23 is switched and controlled by the output of the flip-flop 24.
The oscillation signal input to the first synchronous detection section 23 is inverted every horizontal period.

Note that the flip-flop 24 receives the horizontal synchronizing signal at its set terminal, and also receives the output signal of the amplifier 19 at its reset terminal, and when the phase of the oscillation signal is the inverted phase of the reproduced color signal,
Since the correction signal output from 9 becomes a negative large voltage signal, the flip-flop 24 is reset by the large voltage signal and the oscillation signal input to the first synchronous detection section 23 is inverted.

Furthermore, the negative large voltage signal is applied to the hold circuit 2.
1, the oscillation signal will be controlled to fluctuate rapidly. Therefore, a protection switch circuit 25 is provided between the amplifier 19 and the hold circuit 21, and the switch circuit 25 is turned off by the reset output of the flip-flop circuit 24. The input of the negative large voltage signal to the hold circuit 21 is cut off.

Therefore, also in the case of FIG. 3, the phase of the oscillation signal is corrected and changed following the phase fluctuation of the reproduced color signal, and the same effect as in the case of FIG. 1 can be obtained.

Note that in the case of the PAL system, since hue adjustment is not necessary, the reference power source 20 is formed by a fixed power source.

Furthermore, although both of the above embodiments have been applied to a video tape recorder, it is of course applicable to various playback devices such as a video desk.

[Brief explanation of the drawing]

The drawings show an embodiment of the playback device of this invention, FIG. 1 is a block diagram of one embodiment, FIG. 2 is a vector diagram for explaining the operation of FIG. 1, and FIG. 3 is a block diagram of another embodiment. , FIG. 4 is a vector diagram for explaining the operation of FIG. 3. 1...Video tape, 2...Video head, 4
...Low pass filter, 6...Color output circuit, 7...
... Luminance signal extraction processing section, 8, 9 ... First and second synchronous detection section, 10 ... Synchronization separation section, 11 ... Phase comparison section, 12 ... Frequency division section, 13 ... Addition section, 15 ...
...oscillator, 16...90° phase shifter, 22...correction signal forming section.

Claims (1)

[Scope of utility model registration request] A recording medium in which a color signal is recorded in a lower frequency range than the recording frequency of a luminance signal by low-frequency conversion of a color subcarrier in a television signal, and a luminance signal that outputs a reproduced luminance signal by extracting and demodulating a reproduced signal of the medium. an extraction processing section; a synchronization separation section that separates and extracts a horizontal synchronization signal from the reproduced luminance signal; a phase comparison section that receives the horizontal synchronization signal and outputs a phase difference signal; an oscillator that outputs an oscillation signal at a low frequency conversion frequency of a color subcarrier; a frequency divider that divides the frequency of the oscillation signal and returns it to the phase comparator; and a color signal extractor that extracts a reproduced color signal from the reproduced signal. a first synchronous detection section that forms a reproduced color difference signal of R-Y (R: red primary color signal, Y: luminance signal) from the reproduced color signal based on the oscillation signal; a second synchronous detection unit that forms a reproduced color difference signal of B-Y (B: blue primary color signal) from the reproduced color signal based on the matched signals; , and a primary color signal output section that outputs a blue primary color signal, extracting a burst detection component of the R-Y reproduced color difference signal and adjusting the phase shift of the burst component of the R-Y reproduced color difference signal. A reproducing device comprising: a correction signal forming section that outputs a corresponding correction signal; and an addition section that adds the correction signal to the phase difference signal and inputs the result to the oscillator to correct the oscillation signal.