JPH0440776A - Picture signal recording and regenerating system - Google Patents

Abstract

PURPOSE:To regenerate a picture signal with an acculate time base by providing a dropout detecting means and controlling the phase of a sampling clock signal by using a phase erroneous signal. CONSTITUTION:A dropout detecting means 6 to detect whether a dropout is generated in a signal regenerated by a recording medium or not is provided and the phase of a sampling clock signal generated by a sampling clock generating means 16 is controlled by using a phase erroneous signal already outputted by a phase comparing means 11 during a period when it is detected that the dropout of the signal reproduced by the recording medium is generated in the dropout detecting means 6. Thus, the time base fluctuation of a picture signal generated at reproducing can be removed surely and stably without being affected by the dropout, etc., and the picture signal with a precise time base can be reproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image signal recording and reproducing system that records an image signal on a recording medium and reproduces the image signal recorded on the recording medium.

[Conventional technology]

2. Description of the Related Art Video tape recorders and electronic still video systems are conventional image signal recording and reproducing systems that record image signals on a recording medium and reproduce the image signals recorded on the recording medium.

In the above-mentioned system, in order to correct the time axis fluctuation that occurs when reproducing an image signal from a recording medium, a clock signal having the same time axis fluctuation as the image signal reproduced from the recording medium is formed, and the clock signal is After the reproduced image signal is digitized in synchronization, it is temporarily stored in a memory or the like, and when the image data is read from the memory, the image data is read out in synchronization with an accurate lock signal that does not cause time axis fluctuations. The so-called TBC (Time Base Control) corrects the time axis fluctuations that occur in the reproduced image signal during reproduction.
Ba5eCorrection) technology is used.

In addition, in the above-mentioned TBC technology, when forming a tarokk signal having the same time axis fluctuation as the reproduced image signal, in the case of a video tape recorder, a color burst signal added to the image signal in advance is used to generate the color signal. A clock signal that is phase-synchronized with the burst signal is
However, in the case of an electronic still video system, there is no signal with time axis information such as a color burst signal, so the rising or falling edge of the horizontal synchronizing signal added to the image signal A phase-synchronized tarok signal was formed using a PLL circuit, a gated onlator, or the like.

However, with the method using the horizontal synchronization signal described above, if the S/N ratio of the reproduced image signal is poor, it is not possible to accurately detect the rising or falling edge of the horizontal synchronization signal, and accurate correction of time axis fluctuations is not possible. The drawback was that it could not be done.

Therefore, in an electronic still video system, the applicant has proposed that when recording an image signal on a magnetic disk, which is a recording medium, a frequency between the color signal frequency band and the luminance signal frequency band (for example, 2.5 to 3.5 MHz) is used. ) is used as a reference signal for TBC, and is frequency-multiplexed near the horizontal blanking period (HBLK) and vertical blanking period (BLK) of the image signal, and then recorded. During playback, the pilot signal is frequency-multiplexed with the image signal. We devised a method of forming a clock signal having the same time axis fluctuation as the reproduced image signal using a PLL circuit or the like using a recorded pilot signal as a reference.

FIG. 3 is a diagram showing a schematic configuration of a reproducing device in a conventional image signal recording and reproducing system.

In order to simplify the explanation, the image signal is assumed to be a black-and-white image signal, and FIG. 5 shows a schematic configuration of a reproduction apparatus for a black-and-white image signal.

In FIG. 3, a reproduction signal reproduced by a magnetic head 3 from a magnetic disk 1 rotated by a motor 2 is amplified by a reproduction amplifier 4, and then sent to a demodulation circuit 5, a dropout detection circuit 6, and a pilot signal separation circuit 10. Supplied.

Then, the demodulation circuit 5 demodulates the supplied reproduced signal into a baseband signal and supplies it to the b terminal in the figure of the switch S1.

The switch S1 is normally connected to the b terminal side in the figure, and the baseband signal via the switch S is supplied to the IH (H is one horizontal scanning period) delay line 7, synchronous separation circuit 8, and TBC circuit 9. and delayed by the IH delay line 7
The baseband signal before H is supplied to the a terminal of switch S1.

On the other hand, the dropout detection circuit 6 detects whether or not a dropout has occurred in the reproduction signal supplied from the reproduction amplifier 4, and during the period when the dropout is occurring, the switch S1 is set to the a side in the figure. connected to switch S1
The baseband signal in which dropout has occurred is replaced by the baseband signal in which dropout has not occurred, which is delayed by the IH delay line 7, and is output.

Further, from the reproduced signal amplified by the reproduction amplifier 4, the pilot signal which is frequency multiplexed with the image signal during recording is separated by the pilot signal separation circuit 10, and the pilot signal f which is further amplified to an appropriate amplitude level, is supplied to the phase comparator 11.

By the way, the other input terminal of the phase comparator 11 has a VCO
(Voltage controlled oscillator) Clock signal f output from 12
SC is divided and supplied by a frequency divider 13 into a signal f,' having approximately the same frequency as the pilot signal f, and the phase comparator 11 generates an error voltage according to the phase difference between the signals f and fP'. V.

is supplied to switch S2.

The switch S2 supplies the error voltage V output from the phase comparator 11 to the loop filter 15 via the sample and hold (S/H) circuit 14 (when the switch S2 is connected to the a terminal in the figure), Loop filter 1 as is
5 (when switch S2 is connected to terminal b in the figure).The switching operation is controlled by the blanking pulse signal BLK-P output from the blanking pulse generator 17. Ru.

The operation of forming the blanking pulse signal BLK-P will be explained below using the timing chart shown in FIG. 4.

The blanking pulse generator 17 in FIG.
The PG pulse generated by the C coil every time the magnetic disk 1 rotates once (see FIG. 4(a)) and the synchronous separation circuit 8
Composite synchronization signal C-3Y separated from the reproduced image signal at
NC (see FIG. 4(b)) is supplied, and the blanking pulse generator 17 outputs P as shown in FIG. 4(f).
A blanking pulse signal BLK-P, which is at a high level during the period from the falling edge of the G pulse (SP in the figure) to the end of the vertical synchronizing signal V-BLK, is output to the switch S2, and the switch S receives the blanking pulse signal. When BLK-P is at a high level, it is connected to the b terminal side in the figure, and when it is at a low level, it is connected to the a terminal side in the figure.

Also, the composite synchronization signal C separated by the synchronization separation circuit 8
-3YNC is also supplied to the sample-and-hold pulse generator 16, and is synchronized with the composite synchronization signal C3YNC supplied from the sample-and-hold pulse generator 16.
) is supplied to the S/H circuit 14, and the S/H circuit 14 samples and holds the error voltage V supplied via the switch S according to the supplied sample and hold pulse SHP. do.

As described above, the pilot signal f separated by the pilot signal separation circuit 10 in FIG. The error voltage V, (see FIG. 4(d)) corresponding to the phase difference between the signals f and f % is supplied to the switch S2, and the switches S, , S as described above are supplied to the switch S2.
By controlling the /H circuit 14, the loop filter 15 receives a blanking pulse signal BL as shown in FIG. 4(g).
A continuous error voltage V is supplied during a period when KP is at a high level, and an error voltage V sampled and held every IH is supplied during other periods.

The error voltage ■, after being band-limited by the loop filter 15, controls the frequency of the clock signal fsc output from the VCO 12, and the time axis of the baseband image signal output from the demodulation circuit 5 is output from the VCO 12. The clock signal f sc has the same time axis variation as the variation
is generated and supplied to the TBC circuit 9.

The TBC circuit 9 converts the supplied baseband image signal into a clock signal fsc supplied from the VCO 12.
After being digitized in synchronization with , and stored in a memory etc., it is read out from the memory in synchronization with an accurate lock signal, and converted back into an analog baseband image signal. A baseband image signal from which is removed is output.

[Problem that the invention is trying to solve]

However, in the conventional example described above, if the pilot signal is lost during the period when the blanking pulse signal BLK-P is at a high level due to dropout or the like that occurs during reproduction, the phase comparator 11, VCO 12, frequency divider 13 in FIG. S/
Phase synchronization by the PLL circuit composed of the H circuit 14, the loop filter 15, and the switch S is not completed before the start of reproduction of the image period, and fluctuations due to jitter occur at the top of the reproduced image screen. There is a possibility that a malfunction may occur in which the PLL circuit performs phase clocking at a frequency that is an integral multiple of the horizontal synchronizing signal frequency (15,734 KHz) with the frequency of the pilot signal f as the center.

The present invention was made to solve such problems,
Provides an image signal recording and reproducing system that can reliably and stably remove time axis fluctuations in image signals that occur during playback without being affected by dropouts, etc., and that can reproduce image signals with accurate time axis. The purpose is to do.

[Means to solve the problem]

The image signal recording and reproducing system of the present invention is a system that records a single-frequency pilot signal together with an image signal on a recording medium, and reproduces the image signal recorded on the recording medium, wherein at least horizontal, A recording means for adding a single frequency pilot signal to a recording medium during a vertical blanking period, and a sampling clock signal for sampling an image signal separated from a signal reproduced from the recording medium. A sampling clock generating means that generates a pilot signal, separates a pilot signal from a reproduction signal reproduced from the recording medium, and separates a pilot signal from the separated pilot signal and a sampling clock generated by the sampling clock generating means. a phase comparison means for comparing the phase with a clock signal and outputting a phase error signal according to the result of the phase comparison; and a droplet for detecting whether or not a dropout has occurred in the signal reproduced from the recording medium. and a phase error signal already output from the phase comparison means during a period in which the dropout detection means detects that a dropout has occurred in the signal reproduced from the recording medium. Using,
and control means for controlling the phase of the sampling clock signal generated by the sampling clock generation means.

[Effect]

According to the above-mentioned configuration, it is possible to reliably and stably remove the time axis fluctuation of the image signal that occurs during reproduction without being affected by dropouts, etc., and it is possible to reproduce the image signal with accurate time axis. It will look like this.

〔Example〕

Hereinafter, the present invention will be explained using examples of the present invention.

FIG. 1 is a diagram showing a schematic configuration of a reproducing device in an image signal recording and reproducing system to which the present invention is applied, as an embodiment of the present invention.

In order to simplify the explanation, the image signal is assumed to be a monochrome image signal as in the conventional example reproducing apparatus shown in FIG. 3, and FIG. Indicated.

Further, in the reproducing apparatus shown in FIG. 1, the same components as those of the reproducing apparatus shown in FIG. 5 are given the same reference numerals, and detailed explanations will be omitted.

The operation of the embodiment shown in FIG. 1 will be explained below.

Incidentally, FIG. 2 is a timing chart showing signal waveforms at each part of FIG. 1.

In FIG. 1, a reproduction signal reproduced by a magnetic head 3 from a magnetic disk 1 rotated by a motor 2 is amplified by a reproduction amplifier 4, and then sent to a demodulation circuit 5, a dropout detection circuit 6, and a pilot signal separation circuit 10. Supplied.

Note that the reproducing apparatus of this embodiment differs from the conventional reproducing apparatus shown in FIG.
Since the configurations and operations of the L circuits are different, the differences will be explained below.

In the pilot signal separation circuit 10 to which the reproduced signal is supplied as described above, the pilot signal f, which is frequency-multiplexed with the image signal during recording (see FIG. 2(a)), is separated and further amplified to an appropriate level. After that, the signal is supplied to the phase comparator 11 and the switch S.

By the way, the other input terminal of the phase comparator 11 has a VCO
(Voltage controlled oscillator) Clock signal f output from 12
SC is divided and supplied by a separator 13 into signals f,' having approximately the same frequency as the pilot signal fp, and the phase comparator 11 generates an error voltage V according to the phase difference between the signals f and fP'.

is generated, and the a terminal of the switch S and the S/H circuit 14
supplied to

Further, the switch S to which the pilot signal f separated by the pilot signal separation circuit 10 is supplied is in an ON state while the blanking pulse signal BLK-P output from the blanking pulse generator 17 is at a high level. Then, the supplied pilot signal f is supplied to the RF detection circuit 18, and during other periods, it is in the FF state and the pilot signal f is not supplied to the RF detection circuit 18.

Then, the RF detection circuit 18 detects the supplied pilot signal f, and the comparator 19 compares the level of the detected output with a preset threshold, so that the pilot signal f, which is separated from the reproduced signal, is Detect whether or not dropout occurs.

As shown in FIG. 2(a), if a dropout is currently occurring at the position indicated by D in the figure, the comparator 19 outputs a dropout detection pulse VD (second
(see figure (C)) is output and supplied to the subsequent mono-multi vibrator (M-M) 20.

When the dropout detection pulse V is supplied to M-M2O, a positive pulse vM with a pulse width W as shown in FIG. Supplied. Incidentally, the pulse width W of the positive pulse (2) is set approximately to a period during which phase synchronization of the PLL circuit is completed.

Further, a blanking pulse signal BLK-P output from a blanking pulse generator 17 is supplied to the other input terminal of the AND gate 21, and the blanking pulse signal BLK-P is output from the NAND gate 21 as shown in FIG. 2(e). pulse signal v2'
is output and supplied to one input terminal of the AND gate 22. As described above, if dropout does not occur in the pilot signal f, the dropout detection pulse VD is not output from the comparator 19, so the NAN
Pulse signal ■ output from D gate 21. ' is always at a high level, and when a dropout occurs in the pilot signal f, the pulse signal VM output from the NAND gate 21 is output for a period of maximum W from the position of the dropout, or after the dropout. The frontage level is from the generation position to the position where the blanking pulse signal BLK-P falls.

By the way, the sample and hold pulse SHP is supplied from the sample and hold pulse generator 16 to the other input terminal of the AND gate 19, and the AND gate 19 generates a pulse signal VE as shown in FIG. 2(f). and S
/H circuit 14, and from the S/H circuit 14, the second
Sampled and held error voltage V as shown in figure (g).

is output and supplied to the b terminal side of the switch S.

As described above, during the period when a dropout occurs in the pilot signal f, the error voltage ■ output from the S/H circuit 14 continues to be held and output as the error voltage sampled and held before IH. It's going to happen.

Further, the pulse signal v&I output from M-M2O has its polarity inverted by the inverter 2-4, and then is connected to the AND gate to which the blanking pulse signal BLK-P generated from the blanking pulse generator 17 is supplied. - and 23
A pulse signal VC as shown in FIG. 2(h) is generated from the AND gate 23 and is supplied to the switch S.

The switch S receives the pulse signal V output from the AND gate 23 as described above. The switching operation is controlled by
The switch S is connected to the a terminal side in the figure, and during the period when the pulse signal V6 is at a low level, the switch S is connected to the b terminal side in the figure.

Then, by controlling the switching operation of the switch S by the pulse signal V6 output from the AND gate 23 as described above, the error voltage ■ is supplied to the loop filter 15. As shown in FIG. 2 (1), the error voltage at the part where dropout occurs is held and replaced by the error voltage before IH, and the error voltage band-limited by the loop filter 15 is used as the clock output from the VCO 12. The frequency of the signal fSC is controlled, and the clock signal fSC output from the VCO 12 is generated when, for example, the pilot signal f is dropped due to the occurrence of dropout during the period when the blanking pulse signal BLKP is at a high level. Also, the PLL circuit generates the sideband wave Ctp±n of the pilot signal f.
fH) and has the same time axis fluctuation as that of the baseband image signal output from the demodulation circuit 5 before the start of reproduction of the image period.
c is reliably formed and supplied to the TBC circuit 9.

Then, the TBC circuit 9 digitizes the supplied baseband image signal in synchronization with the clock signal fsc supplied from the VCO 12, and after storing it in a memory or the like,
Read from the memory in synchronization with an accurate lock signal,
By converting it again into an analog baseband image signal, the TBC circuit 9 outputs a baseband image signal from which time axis fluctuations have been removed.

Note that in this embodiment, the blanking pulse signal BL
The pilot signal f separated from the reproduced signal determines whether dropout has occurred in the pilot signal f while KP is at a high level.

However, without using the RF detection circuit 18 and comparator 19, the dropout detector 6 detects the detected pulse. Blanking pulse signal B L output from blanking pulse generator 17
An AND gate is provided to input K - P, and the AND gate is provided.
The output of the gate may be supplied to M-M 20.

Furthermore, in this embodiment, the image signal is a monochrome image signal, but
The present invention can also be applied to devices that use color image signals, and similar effects can be obtained.

Further, in this embodiment, the case where the present invention is applied to a playback device of an electronic still video system has been described, but the present invention is not limited to this, but can also be applied to systems such as video tape recorders.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to reliably and stably remove the time axis fluctuations of the image signal that occur during playback without being affected by dropouts, etc., and to accurately correct the time axis. It is possible to provide an image recording and reproducing system that can reproduce image signals.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic configuration of a reproducing device in an image signal recording and reproducing system to which the present invention is applied, as an embodiment of the present invention. FIG. 2 is a timing chart showing signal waveforms at various parts in FIG. 1 for explaining the operation of the apparatus shown in FIG. 1. FIG. 3 is a diagram showing a schematic configuration of a reproducing device in an image signal recording and reproducing system as another embodiment of the present invention. FIG. 4 is a timing chart showing signal waveforms at various parts in FIG. 3 for explaining the operation of the apparatus shown in FIG. 10... Pilot signal separation circuit 11... Phase comparator 12... C0 13... Frequency divider 14... Sample hold circuit 15... Loop filter 16... Sample hold pulse generator 17... Blanking pulse generator 18... RF detection circuit 19... Comparator 20... Mono multivibrator 21... NAND gate 22.23... AND gate 24... Inverter 2nd M ( [N H

Claims (1)

[Claims] A system for recording a single-frequency pilot signal together with an image signal on a recording medium and reproducing the image signal recorded on the recording medium, comprising: at least horizontal and vertical blanking periods of the image signal; recording means for adding a single frequency pilot signal to a recording medium and recording it on a recording medium; and generating a sampling clock signal for sampling an image signal separated from a signal reproduced from the recording medium. a sampling clock generating means for separating a pilot signal from a reproduced signal reproduced from the recording medium, and adjusting the phase of the separated pilot signal and the sampling clock signal generated by the sampling clock generating means. phase comparison means for comparing and outputting a phase error signal according to the phase comparison result; dropout detection means for detecting whether or not a dropout has occurred in a signal reproduced from the recording medium; During a period in which the dropout detection means detects that a dropout has occurred in the signal reproduced from the recording medium, the sampling clock is detected using the phase error signal already output by the phase comparison means. 1. An image signal recording and reproducing system comprising: control means for controlling the phase of a sampling clock signal generated by the clock generation means.