JPH084350B2 - PAL system color video signal reproducing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A. Industrial field of use B. Outline of the invention C. Background art [Figs. 3 to 8] D. Problems to be solved by the invention E. Means for solving the problems F. Action G. Embodiment [Figs. 1 and 2] a. Circuit configuration [Fig. 1] b. Circuit operation [Fig. 2] H. Effects of the invention (A. Industrial field of application) The present invention is a PAL color image. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal reproducing apparatus, and more particularly to a PAL system color image signal reproducing apparatus that corrects color alignment that is distorted by a track jump during variable speed reproduction.

(B. SUMMARY OF THE INVENTION) The present invention is directed to a carrier color signal which has been low-pass converted, recorded and reproduced, and frequency-converted into an original signal, and a carrier for frequency conversion whose carrier path signal has a frequency twice the frequency thereof. In a PAL system color video signal reproducing apparatus in which a phase-inverted carrier color signal whose phase is inverted on the V-axis is switched and output at the time of a track jump by using the A carrier color signal (a carrier color signal that has not been subjected to the above phase inversion; hereinafter referred to as a “through carrier color signal”) and V.
In order to prevent flicker from occurring due to a phase shift between the axis inversion (hereinafter referred to as “V inversion”) carrier color signal, the through carrier color signal and the V inversion carrier color signal are phase-compared, and By adjusting the phase of the frequency conversion carrier based on the phase comparison result, the carrier color signal and V
This is to eliminate the deviation of the phase relationship with the inverted carrier color signal.

(C. Background Art) [FIGS. 3 to 8] In the case of a popular VTR for home use or a so-called 8 mm video VTR integrated with a camera, the luminance signal is FM-modulated when recording a color image signal. The carrier color signal is frequency-converted to the low frequency side and recorded in a relatively high band.

By the way, when recording and reproducing a PAL system video signal by this VTR, it should be noted that one modulation color signal of the PAL system carrier color signal is inverted every horizontal section. That is, as shown in FIG. 3, the carrier color signal of the PAL type color video signal is represented by F ₊ = (E _B −E _Y ) + j (E _R −E _Y ), in every other horizontal section. , In the remaining every other horizontal section, F ₋ = (E _B −E _Y ) −j (E _R −E _Y ), and the phase of the modulation signal of the red color difference signal becomes one horizontal section. It is inverted every time, and the signal corresponding to this
F ₊ For are inserted ₊ B-Y phase burst signal advanced 135 ° relative to axis B, the signal F _- phase burst signal delayed 135 ° relative to B-Y axis with respect to B _- is inserted. The BY axis is referred to as the U axis, the RY axis is referred to as the V axis, and the carrier color signals in every other horizontal section are described with respect to the carrier color signals in every other horizontal section. The phase inversion is called V inversion.

When performing color demodulation of the PAL system color video signal, when the color video signal reproduced from the VTR is supplied to the television receiver, as described above, one of the modulated color signals, that is, one of the correct color signal It is necessary that the modulation phase of the red color difference signal be inverted every horizontal section.
During normal VTR playback, the continuity of the inversion of this modulated color signal is considered without any problem, but when the rotary head scans over multiple tracks, such as high-speed playback or slow-motion playback. However, the continuity of the inversion for each horizontal section may be impaired. This point will be specifically described.

FIG. 4 shows an example of a VTR track pattern of β format corresponding to a PAL system color video signal.
Every other track TA ₁ , TA ₂ ... Is the track recorded by one of the two rotary heads HA, and TB ₁ , TB ₂ ... is the head HA whose azimuth angle is the other. Shows the tracks recorded by different rotary heads HB, and the arrows in the figure show the phase for each horizontal section (1H) of the burst signal in the recorded carrier color signal. Since the signal actually recorded is for crosstalk removal of the carrier color signal between adjacent tracks, the carrier color signal has, for example, tracks TA ₁ , TA ₂ , ... The sub-carriers are recorded by being inverted and recorded on every other track TB ₁ , TB _2, ... Since the sub-carrier is recorded as it is, it does not indicate the phase of the burst signal on the actual recording pattern. is shown as a case of the those phase recovery to the reproduction time, the track TA ₁ ,, TA ₂ ···.

By the way, in this tape pattern, since the horizontal alignment is 1H, the PAL color video signal is not color-aligned. Therefore, when the rotary head HA draws and scans the locus shown by the broken line in FIG. 4 in the high-speed reproduction mode, the reproduction signal is extracted, for example, from the track TA ₁ to the track TA _{2 at} point a in FIG.
Jump to F. Looking at the phase of the burst signal in the reproduced signal obtained by this high-speed reproduction, as shown in FIG. 5A, at the time point a of this track jump, the continuity of the inversion of the burst signal for each horizontal section (hereinafter, The burst signal sequence) is reversed. Therefore, when the PAL color image signal thus formed is supplied to the monitor receiver to reproduce the image, correct color reproduction cannot be performed on the screen.

The above is the case of recording and reproducing PAL video signals by the beta type VTR, but also in the so-called 8 mm video standard, since the horizontal alignment is 1H or 2H, color alignment is not taken and the same. Problem arises.

Therefore, the carrier color signal that has been low-pass converted is frequency-converted to the original frequency (4.43MHz) with phase restoration, and the crosstalk between adjacent tracks is removed by a comb filter etc. 1H-λ / 4 (λ; wavelength of subcarrier) is provided with a delay means, and when the sequence is correct, a carrier color signal that does not pass through the delay means is output, and when the sequence is reversed, the delay means An attempt was made to output a delayed carrier color signal through the. In this case, a sequence detection circuit that detects whether the sequence is correct or reversed is required.This sequence detection circuit is a carrier color that has been converted to the original frequency by frequency conversion from the above low frequency conversion. The burst signal is extracted from the signal by the burst gate circuit, the output of the reference oscillator that generates the subcarrier is phase-inverted, and a carrier that does not invert V is output or V-inverted each time the horizontal synchronization signal arrives. The carrier shown in FIG. 5B, which serves as a reference for sequence detection, is generated by performing switching to output the carrier wave.
The signal extracted by the burst gate circuit (shown in FIG. 5A) is phase-compared to determine whether the sequence is normal or reverse. As shown in FIG. 5C, when the sequence is correct, the positive polarity is obtained. When the sequence is reversed, the negative determination signal is obtained. This is passed through a low-pass filter to be used as a switching control signal, and the switching control signal controls switching between the carrier color signal delayed by the delay means and the non-delayed through carrier color signal.

By the way, such a technical attempt requires a delay means for delaying the carrier color signal by 1H, and such a delay means is usually very expensive and must be composed of a large glass delay line, so that the VTR is low. It has the drawback of preventing price and size reduction. Therefore, a technical proposal for solving the drawback has been made by the applicant company of the present application, which is disclosed in Japanese Patent Laid-Open No. 60-132494.

FIG. 6 shows the outline of a sequence correction circuit according to the publication that does not use a delay line. In FIG. 6, reference numeral 51 denotes an input terminal for a converted color signal separated from a reproduced signal. The converted color signal is supplied to the frequency converter 52,
It is taken out to the output terminal 54 of the frequency converter 52. The bandpass filter 53 has a PAL carrier frequency fsc (≈4.43).
(MHz) as the center. The burst signal separated by the burst gate circuit 55 from the output signal of the bandpass filter 53 is supplied to the phase comparison circuit 56. A reference signal of frequency fsc is supplied to the phase comparison circuit 56 from, for example, a reference oscillator 57 having a crystal oscillator configuration.

The comparison output of the phase comparison circuit 56 is supplied as a control voltage to a VCO (voltage control type oscillation circuit) 58 via a low pass filter (not shown). The output signal of the VCO 58 is supplied to the frequency converter 59 under the control of phase shift (not shown), and the output of the reference oscillator 57 is supplied to the frequency converter 59. The frequency converter 59 forms a carrier wave for frequency conversion. The center frequency of the VCO 58 is set to be equal to the carrier frequency f _L (for example, 732 KHz) of the converted color signal. Therefore, from the frequency converter 59, (fsc + f
_L) (5.17MHz) and (fsc-f _L) (component of the frequency of each of 3.7 MHz) is generated. Component of one frequency (fsc + f _L) is selected by the bandpass filter 60 is supplied to one input terminal of the switch circuit 62, other frequency (fsc
The component of −f _L ) is selected by the bandpass filter 61 and supplied to the other input terminal of the switch circuit 62.

The output signal of the switch circuit 66 is supplied to the frequency converter 52. When the track jump is detected, the switch circuit 62 is switched from a state in which the output terminal is connected to one input terminal to a state in which the output terminal is connected to the other input terminal.

The angular frequency of the carrier of the converted color signal is ω ₁ , the angular frequency of the carrier of the PAL system is ω _2, and the phase of the converted color signal is θ.
Then, (ω ₂ + ω ₁ ) from the bandpass filter 60
When frequency conversion is performed using the angular frequency conversion carrier of
The converted output signal is represented by the following equation.

_{ω 2 + ω 1 - (ω} 1 + θ) ω 2 -θ other hand, the case of performing frequency conversion by converting the carrier wave angular frequency of _{(ω 2 -ω 1), ω} 2 -ω 1 + (ω 1 + θ) = Ω ₂ + θ. Considering (θ = 0 °) as the BY axis, the RY axis becomes + 90 ° and -90 ° with respect to the BY axis by switching the conversion carrier wave, and the RY axis is inverted. . Therefore, when a track jump is detected, the switch circuit
By switching 62, the RY axis can be inverted and the RY signal sequence can be corrected to the correct one.

However, this sequence correction circuit has a drawback that a phase jump occurs at the time of switching.

This is because when the bandpass filter 53 has a phase shift of −θ _B , the (ω ₂ +
If the output of ω ₁ ) is selected by the switch circuit 62, the APC function works so that the output of the bandpass filter 53 becomes ω ₂ . That is, the frequency converter 52
Output becomes ω ₂ + θ _B = (ω ₂ + ω ₁ + θ _B ) −ω ₁ , and the output of the bandpass filter 60 becomes ω ₂ + ω ₁ + θ _B = ω ₂ + (ω ₁ −θ _B ). Controlled. Therefore, the output of VCO858 is (ω
APC is stable in the state of ₁ + θ _B ).

In this state, if a track jump occurs,
The output of the bandpass filter 60 is converted to the bandpass filter 61.
The output of the band pass filter 61 and the output of the frequency converter 52 are as follows immediately after the switching.

ω ₂ − (ω ₁ + θ _B ) = ω ₂ −ω ₁ −θ _B (ω ₂ −ω ₁ −θ _B ) + ω ₁ = ω ₂ −θ _B Therefore, the output of the bandpass filter 53 is (ω ₂ −2θ
_B ), and the (-2θ _B ) phase jumps by switching. A phase jump also occurs due to the phase of the bandpass filter 60 or the bandpass filter 61 for the same reason. This phase jump is
It causes disturbance of hue.

Providing a phase circuit to correct the above-mentioned phase jump makes it difficult to perform good correction because the amount of phase shift of the bandpass filter varies, and also complicates the circuit configuration.

Therefore, a 1H-λ / 4 delay circuit or a 1H delay circuit is not required, and a correction circuit for the phase inversion sequence of the RY signal is provided independently of the loop of the APC circuit, and reproduction is performed by switching when a track jump occurs. It was proposed by the applicant company in Japanese Patent Application No. 60-180274 to prevent the image from being disturbed.

FIG. 7 and FIG. 8 show a PAL system color video signal reproducing apparatus according to the proposal, and FIG. 7 shows a color video signal reproducing apparatus as a whole. In the figure, reference numeral 1 denotes an input terminal to which a reproduction signal reproduced alternately by a pair of rotary heads is supplied. This reproduction signal is supplied to the high-pass filter 3 and the low-pass filter 4 via the reproduction amplifier 2. The luminance signal FM-modulated by the high-pass filter 3 is supplied to a luminance signal reproduction circuit including an FM demodulation circuit and the like (not shown).

The converted color signal is a signal having a carrier frequency f _L (for example, 732 KHz), and is frequency-converted into a signal having an original carrier frequency fsc (4.43 MHz) by the frequency converter 5 having a multiplier configuration. The unwanted signal in the output signal of the frequency converter 5 is removed by the bandpass filter 6. Then, the output signal of the bandpass filter 6 is supplied to a comb filter 9 composed of a 2H delay circuit 7 and a subtraction circuit 8.

The converted color signal is recorded as it is on one of the adjacent tracks, and is recorded on the other track with the phase of the carrier signal being shifted by 90 ° for each 1H. By the phase shift method, the comb filter 9 removes crosstalk regarding the color signal between the adjacent tracks. The output signal of the comb filter 9 has a carrier frequency of fsc.

The output signal of the comb filter 9 is supplied to the bust gate circuit 10, and the burst signal separated by the burst gate circuit 10 is supplied to the phase comparison circuit 11. Phase comparison circuit
A signal of frequency fsc is supplied to the reference oscillator 12 from the reference oscillator 12. The phase fluctuation of the reproduced carrier color signal with reference to the phase of this output signal of the reference oscillator 12 is detected, and the phase fluctuation is removed by frequency conversion. The comparison output of the phase comparison circuit 11 is supplied to the VCO 14 as a control voltage via the low pass filter 13.

The VCO 14 has a center frequency of f ₁ , and the output signal of the VCO 14 is supplied to the frequency converter 17 via the phase control circuit 15. The frequency converter 17 is supplied with the reference signal of the frequency fsc from the reference oscillator 12. The output signal of the frequency converter 17 is supplied to the bandpass filter 18.
At the output of the band filter 18, a carrier wave for frequency conversion (frequency is fsc-f ₁ ) is obtained. Then, the carrier wave for frequency conversion is supplied to the frequency converter 5.

The phase control circuit 15 uses the control signal from the terminal 16 to
It is for shifting the carrier signal for frequency conversion by 90 ° every 1H. In this case, the control signal from the terminal 16 controls the same phase during recording and during reproduction.

The output signal of the comb filter 9 is supplied to the sequence correction circuit 20. FIG. 8 shows an example of the sequence correction circuit 20, in which reference numeral 21 shows an input terminal to which the carrier color signal from the comb filter 9 is supplied.

The carrier color signal from the comb filter 9 is a switch circuit 24.
It is supplied to one input terminal 25 and the frequency converter 28. The output signal of this frequency converter 28 is a switch circuit.
It is supplied to the other input terminal 26 of 24. The frequency conversion output from the output terminal 27 of the switch circuit 24 is a bypass filter.
It is taken out to the output terminal 22 via 31. The bandpass filter 31 has a passband having a center frequency of fsc.

The switch circuit 24 is controlled by the detection signal of the track jump detection circuit 23 (see FIG. 7) from the terminal 23A. That is, when the track jump is detected, the output terminal 27 of the switch circuit 24 changes from the state in which it is connected to one of the input terminals 25 and 26 to the state in which it is connected to the other. The track jump detection circuit 23 detects a track jump from the phase change of the burst signal in the reproduction carrier color signal output from the sequence correction circuit 20, with the phase of the reference signal from the reference generator 12 as a reference.

In order to automatically perform tracking correction, when pilot signals of different frequencies are recorded in units of four video tracks (8 mm video), track jumps are detected from changes in the sequence of pyroto signals. It is possible to Furthermore, during high speed reproduction, the reproduction signal from the adjacent track cannot be extracted, and the reproduction signal from the adjacent track is used. During this high-speed playback,
Track jumps can be detected from changes in the RF signal envelope.

A carrier signal is supplied from the frequency multiplication circuit 29 to the frequency converter 28. This frequency multiplication circuit 29 generates a carrier wave of 2fsc which is obtained by doubling the frequency of the output signal of the reference oscillator 12 from the terminal 30. As the frequency multiplication circuit 29, it is possible to use, for example, one having a multiplier configuration that multiplies the output signals of the reference oscillator 12 with each other.

When the angular frequency of the reproduced carrier color signal from the input terminal 21 is represented by ω ₁ and its phase is θ, the output signal of the frequency converter 28 is 2ω ₁ − (ω ₁ + θ) = ω ₁ −θ 2ω ₁ + ( ω ₁ + θ) = 3ω ₁ + θ. Only the signal of (ω ₁ −θ) is selected by the bandpass filter 31. Assuming that (θ = 0 °) is the BY axis, the signal of (ω ₁ −θ) is an inverted signal with respect to the BY axis.

Therefore, when the track jap detection circuit 23 detects that the track being reproduced is moved to another track, the switch circuit 24 is switched, and the carrier color signal taken out to the output terminal 22 is related to the RY signal. The sequence is corrected to the correct one.

(D. Problems to be Solved by the Invention) The sequence correction circuit shown in FIG. 8 basically includes a carrier color signal which is low-pass converted, frequency-converted to the original signal after reproduction, and The carrier color signal is frequency-converted using a frequency conversion carrier having a frequency twice that of the carrier color signal, and the V-reversed carrier color signal, which is V-inverted, is switched and output at the time of track jump. As described above, the sequence for the RY signal can be corrected to the correct sequence, which is excellent in that respect. However, in this sequence correction circuit, between the through carrier color signal which is not V inverted and which is switched by the switch circuit 24 and the V inverted carrier color signal, the limit of the phase accuracy of the frequency multiplication circuit 29 and the frequency converter 28 are provided. The phase error is caused by the phase error of the switch circuit, and as a result, the switch circuit responds to the track jump.
The carrier color signal output by 24 is used as the through carrier color signal and V
There is a problem that flicker occurs in color by switching between the inverted carrier color signal.

The present invention has been made to solve such a problem, and a through carrier color signal which is low-frequency converted and recorded, and frequency-converted into an original signal after reproduction, and the carrier color signal of the frequency In a PAL system color video signal reproducing apparatus which outputs by switching the V-reversed V-reversed carrier color signal and the V-reversed carrier color signal by performing frequency conversion using a frequency conversion carrier having a double frequency, through carrier It is an object of the present invention to prevent a phase shift between the color signal and the V inversion carrier color signal, resulting in flicker.

(E. Means for Solving Problems) In order to solve the above-mentioned problems, the PAL system color video signal reproducing apparatus of the present invention is low-frequency-converted, recorded, and frequency-converted into an original signal after reproduction. Color signal is the frequency of 2
A frequency conversion circuit that outputs a phase-inverted carrier color signal that is phase-inverted by performing frequency conversion using a frequency-converting carrier wave having a double frequency, and switches between the carrier color signal and the phase-inverted color signal at the time of a track jump. A switching circuit for outputting the carrier color signal, a phase comparison circuit for comparing the phase of the carrier color signal and the phase inversion carrier color signal, and controlling the phase of the carrier wave for frequency conversion based on the output signal of the phase comparison circuit, A phase shift circuit that adjusts the phase relationship between the carrier color signal and the phase-reversed carrier color signal, and corrects the color alignment at the time of the track jump.

(F. Action) According to the PAL system color video signal reproducing apparatus of the present invention,
Since the loop for controlling the phase of the V inversion carrier color signal through the phase control of the frequency conversion carrier wave so that the relationship between the phase of the V reverse carrier color signal and the phase of the through carrier color signal becomes a predetermined one, the color alignment is simply corrected. Not only is there no deviation in the phase relationship between the through carrier color signal and the V-reversed carrier color signal. Therefore, there is no possibility that a phase shift will occur when the output is switched between the through carrier color signal and the V inverted carrier color signal by the track jump.
Therefore, flicker due to phase shift can be prevented.

(G. Embodiment) [FIGS. 1 and 2] A PAL system color video signal reproducing apparatus of the present invention will be described in detail below with reference to illustrated embodiments.

1 and 2 are for explaining one embodiment of a PAL system color video signal reproducing apparatus of the present invention, and FIG. 1 is a circuit diagram showing a main part.

(A. Circuit Configuration) [FIG. 1] This embodiment is largely different from the second background art shown in FIGS. 7 and 8 in the sequence correction circuit 20, but is different in other points. Therefore, the outline of the reproducing apparatus according to the present embodiment is exactly the same as that shown in FIG. 7. Therefore, the outline of the reproducing apparatus is not shown again and only the characteristic sequence correction circuit is shown in FIG. It is shown as an essential part of this embodiment, and FIG. 7 is used as necessary in the description of this embodiment.

In FIG. 1, 21 is a comb filter 9 shown in FIG.
The input terminal for receiving the carrier color signal from the
The carrier color signal input to is supplied to one input terminal 25 of the switch circuit 24 and the frequency converter 28. The output signal of the frequency converter 28 is supplied to the other input terminal 26 of the switch circuit 24. Then, the output terminal 27 of the switch circuit 24
The signal output from is output to the output terminal 22 via the bandpass filter 31. And the switch circuit 24 is the seventh
Switching control is performed by the track jump detection signal output from the output terminal 23A of the track jump detection circuit 23 in the figure.

29 is an input terminal 30 for the carrier wave from the reference oscillator 12 in FIG.
The frequency converter 28 receives the signal from the frequency fraction multiplier 29 as a frequency conversion carrier.

From the above points, the sequence correction circuit shown in FIG. 1 is common to the sequence correction circuit shown in FIG. However, the frequency converter 28 does not directly receive the frequency converting carrier from the frequency multiplying circuit 29, but rather the phase shifting circuit 32.
It is totally different from the sequence correction circuit shown in FIG. The phase shift circuit 32 detects the phase relationship between the carrier color signal V-inverted by the frequency converter 28 and the through carrier color signal, and then uses the carrier wave for frequency conversion so that the carrier wave signal can be exactly as specified. Phase shift control is performed, and 33 is a phase comparison circuit for detecting the phase relationship between the V inversion carrier color signal and the through carrier color signal. The phase comparison circuit 33 has a multiplier (balanced modulator) configuration and performs phase comparison 2
The phase error signal becomes 0 when the phase difference between the two signals is 90 ° instead of 0. The phase detection output of the phase comparison circuit 33 is input to the phase circuit 32 as a phase shift control signal via the low pass filter 44.

Reference numeral 34 is a switch circuit for inverting the through carrier color signal every other horizontal interval H and supplying the inverted signal to the phase comparison circuit 33. That is, the carrier color signal output through the output terminal 35 of the switch circuit 34 is supplied to the phase comparison circuit 33, the through carrier color signal is directly received by one input terminal 36 of the switch circuit 34, and the other input terminal 37. Receives a signal obtained by inverting the through carrier color signal by the inverting circuit 38, and controls the switching signal (f _{H / 2} ) having a duty ratio of 50% with the two horizontal periods 2H from the switch circuit 39 as one cycle. It is like this. As described above, a loop formed by using the phase comparison circuit 33 having a multiplier configuration unless the through carrier color signal inverted every horizontal period H is given to the phase comparison circuit 33 and the phase comparison is performed between this signal and the V inverted carrier color signal. The phase control by cannot be performed. This point will be described later.

The switch circuit 39 has one input terminal 40 with the above-mentioned 2H
A signal (f _H / 2) with a duty ratio of 50%, which is one cycle, and the signal (f _H / 2) is inverted to the other input terminal 41.
The switch circuit 39 receives the signal inverted by the switch 42 and supplies the signal output from the output terminal 43 to the switch circuit 34 as a switching signal. The switch circuit 39 controls the track jump detection circuit 23 shown in FIG. Output terminal 23
Every time the track jump is performed in response to the signal from A, the phase of the signal (f _H / 2) given to the switch circuit 34 is inverted or not inverted.

The relationship between the phase of f _H / 2 and the phase of the burst signal is related to the output of the switch circuit 39.
At any one of the horizontal section H of the fourth, ..., and the horizontal section H of the n + 1, n + 3, n + 5, ..., The through carrier color signal is inverted and given to the phase comparison circuit 33. Is set.

(B. Circuit operation) [FIG. 2] FIG. 2 is a time chart showing one example of the change of the phase of the burst signal of each signal, and the operation of the sequence correction circuit shown in FIG. 1 will be described according to this figure. To do.

A is a carrier color signal which is not input to the input terminal 21 of the sequence correction circuit and which is not V inverted, that is, a through carrier color signal. In the example shown in FIG.
In the n + 2nd, n + 4th, and n + 6th horizontal sections H, the phase advances by 135 ° with respect to the BY axis (U axis).
In the +1, n + 3, n + 5, and n + 7 horizontal sections, the phase is delayed by 135 ° with respect to the BY axis. That is, the sequence is such that the burst signal is V-inverted for each horizontal section.

However, the sequence is distorted from the n + 8th horizontal section H by, for example, a track jump, and in the n + 8th, n + 10th, and n + 12th horizontal sections H, it is delayed by 135 ° with respect to the BY axis, and the n + 9, n + 11th horizontal sections. H
Then, it is advanced by 135 ° with respect to the BY axis.

B is a track jump detection signal, which was at the low level from the nth to the n + 7th horizontal section H, but changes to the high level from the n + 8th horizontal section H due to the sequence error.

C is a snatching signal that is input from the switch circuit 39 to the switch circuit 34, and the signal (f _H / 2) with a duty ratio of 50% with one cycle being 2H until the track jump.
That is, in the n, n + 2, n + 4, and n + 6th horizontal sections H, the switch circuit 34 outputs the through carrier color signal A as it is, and then n + 1, n + 3, n + 5, n +.
In the seventh horizontal section H, the switch circuit 34 is caused to output the output signal of the inverting circuit 38 for inverting the phase of the through carrier color signal A. When the track jump occurs, the switching signal C becomes a signal obtained by inverting the signal (f _H / 2) by the inverting circuit 42, and the n + 8th, n + 10th, and n + 12th horizontal sections H.
To the switch circuit 34, a signal obtained by inverting the phase of the through carrier color signal A by the inversion circuit 38 is output, and the through carrier color signal A is output to the switch circuit 34 as it is in the n + 9th and n + 11th horizontal sections H.

D is the signal output from the switch circuit 34, and the phase of the burst signal of this signal is n, n + 2, n + 4, n.
The phase of the burst signal of the through carrier color signal A is +6, n + 9 (track jump has already occurred), and the phase of the n + 11th horizontal section H. However, n +
In the 1st, n + 3, n + 5, n + 7, n + 8, (track jump occurred), n + 10, and n + 12 horizontal sections H, the burst signal of this signal D has a phase advanced by 45 ° from the BY axis.

E is a V inversion carrier color signal obtained by V inverting the through carrier color signal A by the frequency converter 28. This V inversion carrier color signal is represented by the following equation, where E is its angular frequency and ω is its angular frequency. (However, in the formula, t represents time).

E = sinωt + sin3ωt Although the V-reversed carrier color signal E contains a frequency component three times the frequency of the carrier, the influence can be eliminated by linearly operating the phase comparison circuit 33.

The phase comparison circuit 33 compares the phase of the V inverted carrier color signal E with the signal D. Looking at the phase relationship between the V inversion carrier color signal E and the burst signal of the signal D, the burst signal of the signal D is 90 ° to the right of the burst signal of the V inversion carrier color signal E in any horizontal section H. It is around. Therefore, it becomes possible to perform the phase control by the phase control loop using the phase comparison circuit 33 in which the phase error signal becomes 0 when there is a phase difference of 90 °. In this loop, the burst signal of the V inversion carrier color signal E is switched. circuit
The lock is applied 90 ° ahead of the burst signal of the output signal D of 34.

If the through carrier color signal A is directly input to the phase comparison circuit 33 and the phase comparison between the through carrier color signal A and the V inverted carrier color signal E is made, n, n + 2, n + 4, n
In the + 6th, n + 9th, and n + 11th horizontal sections H, the through carrier color signal A is shifted by 90 ° clockwise from the V inverted carrier color signal E, but the other horizontal sections H are shifted by 90 ° counterclockwise. Therefore, phase control is impossible. A switch circuit 34, an inverting circuit 38, etc. are provided to invert the phase of the through carrier color signal A every other horizontal interval H so that one of the two signals compared by the phase comparison circuit 33 is 90 ° out of phase with the other. This is to ensure that is advanced.

By the way, the phase detection output of the phase comparison circuit 33 is expressed by the following equation (wherein θ is the phase difference).

Phase detection output = (sinωt + Sin3ωt) × sinωt−θ) = − (1/2) {cos (2ωt + θ) −cos (−θ)} − (1/2) {cos (4ωt + θ) −cos (2ωt−θ)} Then, cos (−θ) in the above equation remains as a DC component, and this is input to the phase shift circuit 32 as a phase error signal, and the frequency conversion carrier wave from the frequency multiplication circuit 29 shifts according to the phase error signal. Will be shared. The DC component corresponding to this phase difference is only for sin ωt. If the signal D includes the 3ωt component, si
A DC component also appears for n3ωt.

Then, the V-reversed carrier color signal E is phase-controlled so that the phase relationship between the burst signal and the burst signal of the through carrier color signal A has a predetermined relationship, that is, a relationship in which the V-reversed carrier color signal E is clearly V-reversed.

F is the output of the switch circuit 24. The switch circuit 24 outputs the through carrier color signal A as it is until the track jump in FIG. 2, and outputs the V inversion carrier color signal E when there is the track jump. Therefore, the output F of the switch circuit 24 is the track F. It becomes a signal obtained by correcting a sequence erroneous due to a jump, that is, a sequence signal that is properly received by a PAL system color television receiver. The through carrier color signal A and the V inversion carrier color signal E which are switched by the switch circuit 24 have the phase relationship of their burst signals properly adjusted to a predetermined relationship, so that switching by the switch circuit 24 may cause flicker. Absent.

Further, since the V inverted carrier color signal E can be compared in phase with the through carrier color signal A while being included in the 3fsc component therein, a filter for removing the 3fsc component for phase comparison is specially provided. Is not necessary.

(H. Effect of the Invention) As described above, the reproducing apparatus of the PAL system color video signal of the present invention converts the carrier color signal whose frequency is converted into the original signal after low-frequency conversion, recording, and reproduction to that frequency. A frequency conversion circuit that outputs a phase-inverted carrier color signal that is phase-inverted by performing frequency conversion using a frequency-converting carrier wave having a double frequency; A switching circuit for switching and outputting, a phase comparison circuit for comparing the phases of the carrier color signal and the phase inversion carrier color signal, and controlling the phase of the frequency conversion carrier wave based on the output signal of the phase comparison circuit. A phase shift circuit for adjusting the phase relationship between the carrier color signal and the phase-reversed carrier color signal, and correcting the color alignment at the time of the track jump. And butterflies.

Therefore, according to the PAL system color video signal reproducing apparatus of the present invention, the feedback loop is configured so that the phase of the V inversion carrier color signal is properly set to the predetermined relationship with the phase of the through carrier color signal. Not only is the color alignment corrected, but the phase relationship between the through carrier color signal and the V-reversed carrier color signal is eliminated. Therefore, it is possible to prevent the occurrence of flicker due to a phase shift when the output is switched between the through carrier color signal and the V inverted carrier color signal by the track jump.

[Brief description of drawings]

FIGS. 1 and 2 are for explaining one embodiment of a PAL system color video signal reproducing apparatus of the present invention. FIG. 1 is a circuit diagram showing a main portion (sequence correction circuit), and FIG. Is a time chart showing the change of the burst phase of each signal, FIG. 3 is an explanatory diagram of the phase of the signal related to the PAL system color, and FIG. 4 is a diagram showing the phase relationship of the burst signal between the horizontal sections of each track. , FIG. 5 is a time chart for explaining the sequence inversion, FIG. 6 is a sequence correction circuit diagram of the first background art, FIGS. 7 and 8 are the second background art, and FIG. FIG. 8 is a circuit diagram showing the overall structure of a PAL system color video signal reproducing apparatus, and FIG. 8 is a sequence correction circuit diagram. Explanation of symbols 24 …… Switch circuit, 28 …… Phase inversion (V inversion) circuit, 29 …… Frequency multiplication circuit, 32 …… Phase shift circuit, 33 …… Phase comparison circuit.

Claims (1)

[Claims] 1. A phase that is phase-inverted by frequency-converting a carrier color signal that has been low-pass converted, recorded, and frequency-converted to an original signal after reproduction using a frequency-converting carrier having a frequency twice that frequency. A frequency conversion circuit for outputting an inverted carrier color signal, a switching circuit for switching and outputting the carrier color signal and the phase inversion color signal at the time of a track jump, and the carrier color signal and the phase inversion carrier color signal A phase comparison circuit for comparing the phases, and a phase shift circuit for controlling the phase of the frequency conversion carrier based on the output signal of the phase comparison circuit and adjusting the phase relationship between the carrier color signal and the phase inversion carrier color signal. And a PAL system color video signal reproducing apparatus, characterized in that the color alignment at the time of the track jump is corrected.