JPH0620346A - Device for correcting drum phase of video tape recorder - Google Patents

Abstract

PURPOSE:To correct the phase deviation of a drum due to a drift, etc., occurring in the cource of recording and reproducing. CONSTITUTION:A first phase detection signal (c) from a reference signal generation circuit 1 is added to a recording signal (n) previously, and a drum PG signal (m) delayed with a certain fixed amt. at a recording time and a third phase detection signal (k) drawn out from a reproduced signal at a reproducing time is selected, and is phase-compared with a second phase detection signal (f) from the reference signal generation circuit 1. By varying the delay amt. of the drum PG signal (h) sent to a drum servo circuit 11 based on an information signal (g) showing the direction and the amt. of the phase deviation, and eliminating the phase deviation, the position of the signal recorded on a magnetic tape 6 is made the prescribed position always, and phase relations among the reproduced signal (d) from the magnetic tape 6 and a drum servo reference signal (b) to the drum servo circuit 11 and the system reference signal (a) of a VTR are controlled to be made constant always.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drum phase correcting device for a video tape recorder, and more particularly, to grasp a phase condition even if a drum phase shift occurs due to a drift or the like generated in the recording and reproducing processes. The present invention relates to a drum phase correction device for a video tape recorder, which is adapted to perform the correction.

[0002]

2. Description of the Related Art Generally, a video tape recorder (VT)
In R; Video Tape Recorder), the timing signal required for signal processing at the time of reproduction is generated based on the reproduction signal read from the magnetic tape, so that phase shift does not occur. When performing complicated digital processing, it is necessary to generate many clocks and timing signals, and it is not possible for a VTR system to generate the reference from the reproduced signal itself because it is possible that a signal is missing. It will be stable. Therefore, there is a reference signal generating circuit which is the system reference of the VTR, from which clocks and timing signals are output in synchronization with the reference signal system, and the drum servo circuit and the like are controlled so as to follow the reference signal system. For example, there is no phase shift between the reproduction signal and the signal processing timing signal.

FIG. 6 is a block diagram of a conventional drum phase correction apparatus. In the figure, 21 is a reference signal generation circuit, 22 is a reproduction processing circuit, 23 is a recording processing circuit, 24 is a recording / reproduction changeover switch, and 25 is A magnetic head, 26 is a magnetic tape, 27 is a drum servo circuit, and 28 is a drum motor.

At the time of recording, the recording signal n is input to the reference signal generating circuit 21, and from the reference signal generating circuit 21, the system reference signal a having a constant phase relationship in synchronization with the recording signal n and the drum servo. The reference signal b is output. The recording signal n is input to the recording processing circuit 23, and the output signal from the recording processing circuit 23 is supplied to the magnetic tape 2 by the magnetic head 25 via the recording / reproducing changeover switch 24.
Recorded in 6. During reproduction, a reproduction signal d read from the magnetic tape 26 by the magnetic head 25 is output via the recording / reproduction changeover switch 24 and the reproduction processing circuit 22. On the other hand, the drum servo circuit 27 controls so that the drum FG signal j and the drum PG signal h from the drum motor 28 maintain a constant phase relationship with the drum servo reference signal b.

FIGS. 7A to 7F are signal timing charts at the time of area division recording of the drum phase correction device in FIG. Figure (a) is a system reference signal a, Figure (b) is a drum servo reference signal b, Figure (c) is a reproduction signal d, and Figure (d).
Is a region-divided signal A of the system reference signal a, and FIG. 6 (e) is a region-divided signal B of the system reference signal a.
FIG. 6F shows a signal C obtained by dividing the system reference signal a into regions.
Is. Three different signals are divided into areas and recorded in one track area recorded / reproduced by one trace of the magnetic head 25, and a signal a- for dividing these areas is recorded.
Considering the case where A, aB, and aC are output from the reference signal generating circuit 21, the drum servo circuit 27 reproduces the switching points of the area division signals aA, aB, and aC. It must be controlled to fall within the guard portion x, y, z between the regions of signal d.

[0006]

As described above, in the conventional drum phase correcting apparatus, the phase control of the drum servo is performed only on the basis of the reference signal of the reference signal generating circuit. Due to components such as drift and jitter that occur during the playback process, tape and drum expansion and contraction due to environmental conditions, circuit and mechanical variations, etc., the phase of the playback signal is based on the phase relationship that should originally have with the drum servo reference signal. It shifts. In addition, the guard portion between the above areas is usually made as narrow as possible, and there is a problem that it is more difficult to control the drum phase to obtain the required phase of the reproduction signal.

The present invention has been made in view of such actual information, and at the time of recording, the delayed drum PG signal output from the second drum PG signal delay circuit and the first output signal from the reference signal generation circuit. It is generated in the process of recording and reproduction by comparing the phase of the second phase detection signal and the phase comparison of the third phase detection signal extracted from the reproduction signal and the second phase detection signal during reproduction. It absorbs expansion and contraction of tape and drum due to components such as drift and jitter and environmental conditions, and circuit and mechanical variations, and the reproduction signal has an original phase relationship with the drum servo reference signal and VTR system reference signal. SUMMARY OF THE INVENTION It is an object of the present invention to provide a drum phase correction device that does so.

[0008]

In order to achieve the above object, the present invention provides (1) a video tape recorder for recording and reproducing a video signal or the like on a magnetic tape 6, wherein a system reference signal a of the video tape recorder is used. And a drum servo reference signal b to the drum servo circuit 11 having a constant phase relationship, and a first phase detection signal c and a second phase detection signal f having a predetermined phase relationship with the reference signal b. A reference signal generating circuit 1 for generating, an additional circuit 2 for adding the first phase detection signal c to the recording signal n recorded by the magnetic head 5 on the rotating drum, and the third phase detection from the reproduction signal d. The extraction circuit 8 for extracting the signal k, and the second drum PG signal delay circuit 13 set to a certain delay amount
A switch circuit 14 for selecting and outputting the delayed drum PG signal m output from the PG signal delay circuit 13 and the third phase detection signal k extracted from the reproduction signal d, and output from the switch circuit 14. Signal e.g. and the second phase detection signal 5 output from the reference signal generation circuit 1 and a phase comparison circuit 9 for phase comparison, and a phase shift direction and amount output from the phase comparison circuit 9. Based on the information signal g shown, the first drum PG signal delay circuit 10 capable of changing the delay amount to eliminate the phase shift, and the third phase detection signal k extracted from the reproduction signal d during reproduction. ,
By performing a phase comparison with the second phase detection signal 5 output from the reference signal generation circuit 1, the reproduction signal d and the drum servo reference signal b to the drum servo circuit 11 and the system reference signal a of the video tape recorder are compared. And a control means for controlling so that the phase relation of is always constant, and further,
(2) During recording, a phase comparison is performed between the delayed drum PG signal m output from the second drum PG signal delay circuit 13 and the second phase detection signal f output from the reference signal generation circuit 1. Thus, the phase relationship between the rotating drum and the drum servo reference signal b to the drum servo circuit 11 and the system reference signal a of the video tape recorder is always kept constant, and the recording signal n recorded by the magnetic head 5 on the rotating drum is maintained. The control means for controlling the recording position on the magnetic tape 6 to be constant at a prescribed position is provided.

[0009]

By extracting the phase detection signal added to the recording signal from the reproduction signal and comparing the phases of the phase detection signal,
It is possible to know the exact phase status of the actual reproduction signal, and by varying the delay amount of the delayed drum PG signal sent to the drum servo circuit so as to eliminate the phase shift, the reproduction signal, the drum servo reference signal, and the VTR. The phase relationship with the system reference signal can be always kept constant. Similarly, at the time of recording, the drum P for which the delay amount is set in advance is similarly set.
By performing the phase comparison of the G signal, the recording position of the signal on the magnetic tape is always constant at the specified position, so that the phase of the reproduction signal can be made more stable.

[0010]

Embodiments will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining an embodiment of a drum phase correction device according to the present invention, in which 1 is a reference signal generation circuit, 2 is a phase detection signal addition circuit, 3 is a recording processing circuit, and 4 is a recording processing circuit. Is a first recording / playback selector switch, 5 is a magnetic head, 6 is a magnetic tape, 7 is a playback processing circuit, 8 is an extraction circuit for extracting a phase detection signal, 9 is a phase comparison circuit, and 10 is a first drum PG signal. A delay circuit, 11 is a drum servo circuit, 12 is a drum motor, 13 is a second drum PG signal delay circuit, and 14 is a second recording / reproducing changeover switch.

At the time of recording, the recording signal n is the reference signal generating circuit 1
And the phase detection signal are added to the additional circuit 2 and the reference signal generation circuit 1 synchronizes with the recording signal n to have a system phase signal a, a drum servo reference signal b, and a first phase detection signal c. , The second phase detection signal f and the like are output, and the phase detection signal addition circuit 2 adds the first phase detection signal c to the recording signal n. The output signal of the phase detection signal addition circuit 2 is supplied to the recording processing circuit 3 and the first recording / recording circuit 3.
Data is recorded on the magnetic tape 6 by the magnetic head 5 through the reproduction changeover switch 4. At the time of reproduction, the reproduction signal d read from the magnetic tape 6 by the magnetic head 5 is input to the extraction circuit 8 for extracting the phase detection signal through the first recording / reproduction changeover switch 4 and the reproduction processing circuit 7. It The extraction circuit 8 extracts the third phase detection signal k from the reproduction signal and outputs it, and outputs the extracted third phase detection signal k to the second recording / reproduction changeover switch 14.

To the second recording / reproducing changeover switch 14,
The second drum PG signal delay circuit 13 also inputs the delayed drum PG signal m delayed by a certain amount. The delay drum PG signal m has the same phase as the third phase detection signal k extracted from the reproduction signal in the control state during reproduction.
The phases are set as shown in FIGS. The second recording / reproducing changeover switch 14 selects the delay drum PG signal m at the time of recording and the third phase detection signal k extracted from the reproducing signal d at the time of reproducing to select the phase comparison circuit. Output to 9. The phase comparison circuit 9 compares the phase of the output signal e of the second recording / reproduction changeover switch 14 with the second phase detection signal f from the reference signal generation circuit 1, and the phase of the output signal e of the switch 14 advances. When the output signal e of the switch 14 is delayed in phase, the phase error information signal g for increasing the delay amount is sent to the first drum PG signal delay circuit. Send to 10. If the UP / DOWN counter is used to change the delay amount in the first drum PG signal delay circuit 10, the phase error information signal g is the phase shift signal according to UP / DOWN which indicates the counting direction. The amount of deviation is counted as the number of clocks.

In the first drum PG signal delay circuit 10,
The amount of delay of the drum PG signal h output from the drum motor 12 is varied based on the phase error information signal g, and the delayed drum PG signal i is output to the drum servo circuit 11. The drum servo circuit 11 receives the drum FG signal j from the drum motor 12 and the previously delayed drum PG signal i.
Is the drum servo reference signal b from the reference signal generating circuit 1.
Is controlled so as to maintain a constant phase relationship with.

Next, the actual correction operation will be described with reference to a timing chart. 2A to 2G are diagrams showing the timing relationship of the signals of the respective parts in FIG. 1, and are for the case where the normal drum phase control is performed. First, as a reference signal system,
The system reference signal a, the drum servo reference signal b, the first phase detection signal c and the second phase detection signal f added to the recording signal n are always output from the reference signal generating circuit 1 in a constant phase relationship. As shown in FIG. The delayed drum PG signal i has a fixed phase relationship with the drum servo reference signal b in the drum servo circuit 11.
That is, it is controlled so as to have a constant phase relationship with the system reference signal system. The delay amount of the drum PG signal h is the same as that of the delayed drum PG signal m delayed by a certain amount and the third phase detection signal k extracted from the reproduction signal d. D is the delay drum P
The output signal e of the switch 14, which is output by selecting the third phase detection signal k extracted from the G signal m and the reproduction signal d during recording and reproduction, has the same phase as the second phase detection signal f. It is set while changing as an amount.

FIGS. 3A to 3K are timing charts before and after the correction when the drum phase is advanced before the drum phase correction. Before the correction, the output signal e of the switch 14 should originally come to the position of T ₀ from the rising point of the drum servo reference signal b as shown in FIG. 2, but the phase error is caused by the phase error generated in the recording / reproducing process. And the phase reaches T ₀ -x, the delay amount D of the drum PG signal h is changed to D-
By correcting to x, the output signal e of the switch 14 comes to the position T ₀ from the rising point of the drum servo reference signal b, and has the same phase as the second phase detection signal f.

FIGS. 4A to 4K are timing charts before and after correction when the drum phase is delayed before the drum phase is corrected. Before the correction, the output signal e of the switch 14 should originally come to the position of T ₀ as shown in FIG. 2 from the rising point of the drum servo reference signal b, but due to the phase error generated in the recording / reproducing process. Phase lag, T ₀ + x
Then, by correcting the delay amount D of the drum PG signal to D + x, the output signal e of the switch 14 comes to the position T ₀ from the rising point of the drum servo reference signal b, and the second phase It has the same phase as the detection signal f.

As described above, according to the present invention, the recording signal n
The first phase detection signal c is added for phase comparison with the first phase detection signal. However, if the original recording signal n includes a signal that can be used for phase detection, the first phase detection signal c is added to the first phase detection signal c. It is also possible to substitute as.

[0018]

Since the present invention is constructed as described above, it has the following effects. That is, even if there are factors that cause the drum phase to deviate from its original state due to variations in circuits and mechanisms, including drift, jitter, and changes in environmental conditions that occur during the recording and playback processes,
It is possible to recognize the phase status by the preset delayed drum PG signal at the time of recording and the drum phase detection signal extracted from the reproduction signal at the time of reproduction, and thereby correct the drum phase to the original phase state. Therefore, the phase of the reproduction signal can always be kept stable and constant with the system reference signal system of the VTR.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of a drum phase correction device for a VTR according to the present invention.

FIG. 2 is a signal timing chart when the phase control of the drum phase correction device of the present invention is performed.

FIG. 3 is a signal timing diagram when the drum phase of the drum phase correction device of the present invention is advanced.

FIG. 4 is a signal timing chart when the drum phase of the drum phase correction device of the present invention is delayed.

5 is a signal timing chart of each part of the drum phase correction device in FIG.

FIG. 6 is a configuration diagram of a conventional drum phase correction device.

FIG. 7 is a signal timing diagram of the drum phase correction device in FIG.

[Explanation of symbols]

1 ... Reference signal generation circuit, 2 ... Phase detection signal addition circuit,
3 ... Recording processing circuit, 4 ... First recording / reproduction changeover switch, 5 ... Magnetic head, 6 ... Magnetic tape, 7 ... Reproduction processing circuit, 8 ... Extraction circuit for extracting phase detection signal, 9 ... Phase comparison circuit, 10 ... first drum PG signal delay circuit, 11 ...
Drum servo circuit, 12 ... Drum motor, 13 ... Second drum PG signal delay circuit, 14 ... Second recording / reproducing changeover switch.

Claims (2)

[Claims] 1. A video tape recorder for recording / reproducing a video signal or the like on a magnetic tape, the drum servo reference signal to a drum servo circuit having a constant phase relationship with the system reference signal of the video tape recorder, and the reference signal. A reference signal generating circuit for generating a first phase detection signal and a second phase detection signal having a certain defined phase relationship,
An addition circuit for adding the first phase detection signal to a recording signal recorded by a magnetic head on a rotating drum, and an extraction circuit for extracting the third phase detection signal from a reproduction signal,
A second drum PG signal delay circuit set to a certain delay amount, a delayed drum PG signal output from the PG signal delay circuit, and a third phase detection signal extracted from the reproduction signal are selected and output. Switch circuit, a phase comparison circuit for performing phase comparison between a signal output from the switch circuit and a second phase detection signal output from the reference signal generation circuit, and a phase output from the phase comparison circuit A first drum PG signal delay circuit that can change the delay amount to eliminate the phase shift based on an information signal indicating the direction and amount of the shift, and the third phase detection extracted from the playback signal during playback. By comparing the phase of the signal and the second phase detection signal output from the reference signal generation circuit, the reproduction signal and the drum servo reference signal to the drum servo circuit and the video tape recorder Always drum phase correcting apparatus of a video tape recorder which is characterized in that it consists of a control means for controlling so as to a constant phase relationship between the stem reference signal. 2. At the time of recording, a phase comparison is performed between the delayed drum PG signal output from the second drum PG signal delay circuit and the second phase detection signal output from the reference signal generation circuit. Recording the recording signal on the magnetic tape of the recording signal recorded by the magnetic head on the rotating drum, keeping the phase relationship between the rotating drum and the drum servo reference signal to the drum servo circuit and the system reference signal of the video tape recorder always constant. 2. The drum phase correction device for a video tape recorder according to claim 1, further comprising control means for controlling the position to be constant at a prescribed position.