JPH0536162A - Drum phase correction device for video tape recorder - Google Patents

Abstract

(57) [Summary] [Object] To provide a drum phase correction device of a video tape recorder capable of correcting a reproduced video signal and a drum phase reference signal so as to have an original phase relationship. [Structure] When recording a video signal, an input video signal added with a drum phase detection signal by a drum phase detection signal adding circuit 6 is recorded on a magnetic tape 10 and reproduced by a drum phase detection signal extracting circuit 13 during reproduction. Drum phase detection signal extracted from video signal and reference signal generation circuit 11
The phase comparison circuit 14 compares the drum phase reference signal output from the drum phase reference signal and outputs the phase error signal to the drum phase control circuit 3 for phase correction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drum phase correction device for a video tape recorder for recording a video signal on a magnetic tape and reproducing the recorded video signal.

[0002]

2. Description of the Related Art An example of a drum servo system of a conventional video tape recorder is shown in FIG.

The head drum 1a has a PG for phase control.
A magnet (not shown) for extracting a signal is embedded, and the PG signal S1 extracted from this magnet is
It is guided to the drum phase control circuit 3. Further, a frequency generator (not shown) for extracting an FG signal for speed control is provided in the drum motor 1b, and the FG signal S2 output from this frequency generator is guided to the drum speed control circuit 2. It has been.

The output of the drum speed control circuit 2 and the output of the drum phase control circuit 3 are led to the mixing circuit 4, and the output of the mixing circuit 4 is sent to the drum motor 1b via the drive circuit 5. Have been guided.

On the other hand, the input video signal S3 recorded on the recording track of the magnetic tape 10 is guided to the recording video processing circuit 7 and the reference signal generating circuit 11, and the output of the reference signal generating circuit 11 is the drum phase. It is guided to the drum phase control circuit 3 as the reference signal S4.

The output of the recording video processing circuit 7 is connected to one fixed terminal a of the recording / reproducing switch 8,
The common terminal c of the recording / reproducing switch 8 is connected to a video head 9 that records and reproduces a video signal on the magnetic tape 10. The other fixed terminal b of the recording / reproducing changeover switch 8 is connected to the reproduced video processing circuit 12.

The video head 9 is mounted on the head drum 1a so as to rotate integrally with the head drum 1a.

Next, the operation of the video tape recorder having the above configuration will be described.

By comparing the PG signal S1 with the drum phase reference signal S4 output from the reference signal generating circuit 11, the error signal S8 output from the drum phase control circuit 3 and the drum speed based on the FG signal S2. Control circuit 2
After being mixed with the error signal S9 output from the mixing circuit 4 and amplified to a required level by the drive circuit 5,
It is supplied to the drum motor 1b as a drive control signal. The drum motor 1b is adapted to rotate at a constant speed and phase based on this drive control signal.

On the other hand, at the time of recording, the common terminal c of the recording / reproducing changeover switch 8 is connected to the fixed terminal a. As a result, the input video signal S3 is supplied to the video head 9 via the recording / reproducing switch 8 after being subjected to signal processing necessary for recording in the recording video processing circuit 7, and a predetermined recording track of the magnetic tape 10 is supplied. Will be recorded in sequence.

At this time, since the input video signal S3 is also given to the reference signal generation circuit 11, the drum phase reference signal S4 output from the reference signal generation circuit 11 to the drum phase control circuit 3 is the input video signal. It is synchronized with S3 and has a fixed phase relationship. Therefore, since the drum motor 1b controlled by the drum phase reference signal S4 also has a fixed phase relationship with the input video signal S3, the input video signal S3 is accurately recorded on a predetermined recording track of the magnetic tape 10. I will go.

On the other hand, during reproduction, the common terminal c of the recording / reproducing changeover switch 8 is connected to the fixed terminal b. As a result, the video signal recorded on the recording track of the magnetic tape 10 is
It is sequentially reproduced by the video head 9. This reproduced video signal is given to the reproduced video processing circuit 12 through the recording / reproducing switch 8, and after being subjected to necessary signal processing here,
The image is output to a CRT or the like (not shown).

At this time, since the drum motor 1b is controlled by the drum phase reference signal S4 generated from the reference signal generation circuit 11, the reproduced video signal has a constant phase relationship with the drum phase reference signal S4. become.

[0014]

As described above, in the conventional video tape recorder, the phase control of the drum is always performed based on the drum phase reference signal S4. That is, components such as drift and jitter generated during recording and reproduction of video signals, expansion and contraction of the magnetic tape and head drum due to environmental conditions, and variations in circuits and mechanical parts are not taken into consideration at all. Therefore, the phase of the reproduced video signal is
Under the influence of these various conditions, it is originally deviated from the drum phase reference signal S4.

Therefore, in order to improve such phase shift, time axis correction is performed in the process of processing the reproduced video signal. This time axis correction is mainly performed to absorb the jitter component, and the margin for the phase fluctuation of the reproduced video signal is set accordingly.

Therefore, it is necessary to suppress fluctuations in reproduced video signals due to drift components including changes in environmental conditions other than jitter components, variations in circuits and mechanical parts, etc.

When these variations cannot be suppressed, the margin for the phase variation of the reproduced video signal must be increased so that the time axis correction circuit can perform the time axis correction corresponding thereto.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a drum phase correction device for a video tape recorder capable of correcting a reproduced video signal and a drum phase reference signal so as to have an original phase relationship. To provide.

[0019]

In order to solve the above-mentioned problems, a drum phase correction device of the present invention is based on a PG signal detected by rotation of a drum and a drum phase reference signal generated by a reference signal generation circuit. In a video tape recorder equipped with a drum phase control circuit that controls the drum phase, the drum phase detection signal addition circuit that adds the drum phase detection signal to the input video signal when recording the input video signal, and the recording video signal At the time of reproduction, a drum phase detection signal extraction circuit for extracting the drum phase detection signal added to the reproduction video signal, a drum phase detection signal extracted by the drum phase detection signal extraction circuit, and the reference signal generation The drum phase reference signal generated by the circuit is compared and the phase error signal is output to the drum phase control circuit. And a phase comparator circuit for, performs a phase correction based on the phase error signal by the drum phase control circuit.

[0020]

When the input video signal is recorded, the drum phase detection signal adding circuit adds the drum phase detection signal to the input video signal, and the video signal to which the drum phase detection signal is added is passed through the recording video processing circuit. To record on the magnetic tape from the video head.

On the other hand, at the time of reproducing the recorded video signal, the video signal reproduced from the magnetic tape by the video head is given to the drum phase detection signal extracting circuit via the reproduction image processing circuit. The drum phase detection signal extraction circuit extracts the drum phase detection signal added to the reproduced video signal and supplies the extracted drum phase detection signal to the phase comparison circuit.

A drum phase reference signal generated by a reference signal generation circuit is given to the phase comparison circuit,
The phase comparison circuit compares the drum phase detection signal with the drum phase reference signal and outputs the phase error signal to the drum phase control circuit.

The drum phase control circuit performs the phase correction based on the phase error signal in addition to the drum phase control based on the PG signal detected by the rotation of the drum and the drum phase reference signal generated by the reference signal generation circuit. ..

As a result, components such as drift and jitter generated in the process of recording and reproducing the video signal, expansion and contraction of the magnetic tape and the head drum due to environmental conditions, and fluctuations in the phase of the video signal due to variations in circuits and mechanical parts. Even if
The reproduced video signal and the drum phase reference signal have an original phase relationship, which enables excellent reproduction of the video signal.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the electrical construction of a drum phase correction device of a video tape recorder according to the present invention.

In the figure, a magnet (not shown) for extracting a PG signal for phase control is embedded in the head drum 1a, and the PG extracted from this magnet is shown.
The signal S1 is guided to the drum phase control circuit 3. Further, a frequency generator (not shown) for extracting the FG signal for speed control is provided in the drum motor 1b, and the FG signal S2 output from this frequency generator is
It is led to the drum speed control circuit 2. Then, the output of the drum speed control circuit 2 and the output of the drum phase control circuit 3 are guided to the mixing circuit 4, and the output of the mixing circuit 4 is guided to the drum motor 1b via the drive circuit 5. There is.

On the other hand, the input video signal S3 recorded on the recording track of the magnetic tape 10 is led to the drum phase detection signal addition circuit 6 and the reference signal generation circuit 11, and the drum phase detection signal addition circuit 6 is supplied. Is output to the recording video processing circuit 7. The output of the reference signal generation circuit 11 is supplied to the drum phase control circuit 3 as the drum phase reference signal S4, and the drum phase detection signal addition circuit 6 is provided as the drum phase detection signal S5 having a certain time difference from the drum phase reference signal S4. And the phase comparison circuit 14 respectively.

The output of the recording video processing circuit 7 is connected to one fixed terminal a of the recording / reproducing changeover switch 8,
The common terminal c of the recording / reproducing switch 8 is connected to a video head 9 that records and reproduces a video signal on the magnetic tape 10. Further, the other fixed terminal b of the recording / reproducing switch 8 is connected to the reproduced video processing circuit 12, and the output of the reproduced video processing circuit 12 is led to the drum phase detection signal extracting circuit 13. The output of the drum phase detection signal extracting circuit 13 is guided to the phase comparison circuit 14, and the output of the phase comparison circuit 14 is guided to the drum phase control circuit 3 as the phase error signal S7. There is.

The video head 9 is the head drum 1a.
Is mounted on the head drum 1a and rotates integrally with the head drum 1a.

In the above structure, the PG signal S1 and the drum phase reference signal S4 are compared with each other, and the error signal S8 output from the drum phase control circuit 3 and the FG signal S2 are output from the drum speed control circuit 2. The mixed error signal S9 is mixed by the mixing circuit 4, and the drive circuit 5
Drive control signal S10 after being amplified to the required level at
Is supplied to the drum motor 1b. Drum motor 1
b is rotated at a constant speed and phase based on the drive control signal S10.

On the other hand, at the time of recording, the common terminal c of the recording / reproducing changeover switch 8 is connected to the fixed terminal a. In this state, the input video signal S3 is first input to the drum phase detection signal addition circuit 6 and the reference signal generation circuit 11. As a result, the input video signal S from the reference signal generation circuit 11
3, a drum phase detection signal S5 having a constant phase relationship with 3 is provided to the drum phase detection signal addition circuit 6.

The drum phase detection signal adding circuit 6 adds the drum phase detection signal S5 to the input video signal S3 and outputs it to the recording video processing circuit 7.
After the signal processing necessary for recording is performed in (1), the signal is supplied to the video head 9 via the recording / reproducing switch 8 and sequentially recorded on predetermined recording tracks of the magnetic tape 10.

At this time, the drum phase reference signal S4 output from the reference signal generation circuit 11 to the drum phase control circuit 3
Are synchronized with the input video signal S3 and have a constant phase relationship. Therefore, the drum motor 1b controlled by the drum phase reference signal S4 also receives the input video signal S
3 has a fixed phase relationship with the input video signal S3.
Will be accurately recorded on a predetermined recording track of the magnetic tape 10 together with the added drum phase detection signal S5.

On the other hand, during reproduction, the common terminal c of the recording / reproducing changeover switch 8 is connected to the fixed terminal b. In this state, the video signal S3 recorded on the recording track of the magnetic tape 10 is sequentially reproduced by the video head 9 together with the added drum phase detection signal S5. The reproduced video signal S3 is applied to the reproduced video processing circuit 12 via the recording / reproduction changeover switch 8, where necessary signal processing is performed and then applied to the drum phase detecting signal extracting circuit 13.

Then, the drum phase detection signal S6 extracted by the drum phase detection signal extraction circuit 13 is obtained.
Are supplied to the phase comparison circuit 14.

The phase comparison circuit 14 compares the drum phase detection signal S5 output from the reference signal generation circuit 11 with the drum phase detection signal S6 extracted by the drum phase detection signal extraction circuit 13, The phase error signal S7 is output to the drum phase control circuit 3.

In the drum phase control circuit 3, the PG signal S1 detected by the rotation of the head drum 1a and the drum phase reference signal S generated by the reference signal generation circuit 11.
In addition to the drum phase control based on 4 and 4, the phase correction based on the phase error signal S7 is also performed.

As a result, the phase of the video signal is changed due to components such as drift and jitter generated in the process of recording and reproducing the video signal, expansion and contraction of the magnetic tape and head drum due to environmental conditions, and variations in circuits and mechanical parts. Even if there is fluctuation, the reproduced video signal and the drum phase reference signal S4 have the original phase relationship.

Next, the above-mentioned phase correction operation will be specifically described with reference to the timing charts shown in FIGS.

As an initial condition, the drum phase reference signal S
4, the PG signal S1 and the drum phase detection signal S5 are set to have a phase relationship as shown in FIG. That is, P with respect to the drum phase reference signal S4
It is assumed that the G signal S1 is advanced by the period T1 and the drum phase detection signal S5 is delayed by the period T2.

Now, as shown in FIG. 3, it is assumed that the PG signal S1 'is ahead of the drum phase reference signal S4 by a period T1 + α due to a drift at the time of recording, a variation in a circuit, a mechanical portion and the like. At this time, the drum phase detection signal S5
Is delayed by the period T2 with respect to the drum phase reference signal S4, and this drum phase detection signal S5 is added to the input video signal S3. That is, the PG signal S1 '
In contrast, the drum phase detection signal S5 is in the period T1 + T2 +
It will be delayed by α.

On the other hand, when the drum phase control is performed in the state where there is no drift or variation in the circuit or mechanism portion during the reproduction, the PG signal S1 becomes the drum phase reference signal S4 as shown in FIG. However, the period T1 is advanced. On the other hand, the drum phase detection signal S5 'extracted from the reproduced video signal is delayed by the period T2 + α with respect to the drum phase reference signal S4.

In the phase comparison circuit 14, the drum phase detection signal S5 output from the reference signal generation circuit 11 is output.
And the drum phase detection signal S5 'extracted from the drum phase detection signal extraction circuit 13 are compared in phase, and the extracted drum phase detection signal S5' is delayed from the drum phase reference signal S4 by a period T2. The phase error signal S7 for correction is output to the drum phase control circuit 3.

As a result, the drum phase detection signal S5 "extracted from the reproduced video signal is corrected and controlled so as to be delayed from the drum phase reference signal S4 by the period T2, and at the same time, the PG signal S1" is also changed to the drum phase reference signal. The position is advanced from the signal S4 by the period T1 + α, and has the same phase relationship as the phase relationship at the time of recording (the phase relationship shown in FIG. 3).

In the above embodiment, the input video signal S1
The drum phase detection signal S5 is added to the input video signal S1. However, when a vertical synchronization signal or the like is added to the input video signal S1, this can be used as the drum phase detection signal. ..

[0047]

The drum phase correction apparatus for a video tape recorder according to the present invention records an input video signal to which a drum phase detection signal is added by a phase detection signal addition circuit on a magnetic tape when recording a video signal. During playback, the drum phase detection signal extracted by the phase detection signal extraction circuit is compared with the drum phase reference signal output from the reference signal generation circuit, and the phase error signal is compared to the drum phase control circuit. Since it is configured to perform phase correction by outputting to, the components such as drift and jitter generated in the process of recording and reproducing the video signal, the expansion and contraction of the magnetic tape and the head drum depending on the environmental conditions, the circuit and mechanism parts. The reproduced video signal and the drum phase reference signal can always be kept in a constant phase relationship regardless of variations and the like. Therefore, even when the time axis correction is performed in the reproduction video processing process, it is possible to reduce the margin of the time axis correction circuit with respect to the phase fluctuation of the reproduction video signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a drum phase correction device of a video tape recorder according to the present invention.

FIG. 2 is a timing chart for explaining the operation of the drum phase correction device of the present invention.

FIG. 3 is a timing chart for explaining the operation of the drum phase correction device of the present invention.

FIG. 4 is a timing chart for explaining the operation of the drum phase correction device of the present invention.

FIG. 5 is a block diagram showing an example of a drum servo system of a conventional video tape recorder.

[Explanation of symbols]

 1a Head Drum 1b Drum Motor 3 Drum Phase Control Circuit 6 Drum Phase Detection Signal Addition Circuit 11 Reference Signal Generation Circuit 13 Drum Phase Detection Signal Extraction Circuit 14 Phase Comparison Circuit

Claims (1)

[Claims] 1. A video tape recorder equipped with a drum phase control circuit for controlling a drum phase based on a PG signal detected by rotation of a drum and a drum phase reference signal generated by a reference signal generating circuit. A drum phase detection signal addition circuit that adds a drum phase detection signal to the input video signal during signal recording, and a drum that extracts the drum phase detection signal added to the playback video signal during playback of the recorded video signal The phase detection signal sampling circuit compares the drum phase detection signal sampled by the drum phase detection signal sampling circuit with the drum phase reference signal generated by the reference signal generation circuit, and outputs the phase error signal. A phase comparison circuit for outputting to the drum phase control circuit, Drum phase correcting apparatus of a video tape recorder and performing phase correction based on the difference signal.