JPH02177152A - Tracking shift device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a tracking shift device in a capstan servo of a VTR, and relates to a high-speed tracking shift system such as auto-tracking.

Conventional technology In the capstan servo of a VTR, a signal corresponding to the rotational phase of the head cylinder is recorded as a control signal on a control track during recording, and during playback, the control signal is detected and used as the rotational phase signal of the head cylinder. The phase synchronization is maintained. In self-recording and playback, if the control system is set so that the phase of the cylinder rotation phase signal and recording control signal during recording is the same as the phase of the cylinder rotation phase signal and playback control signal during playback, it is possible to The recording head trajectory and the reproducing head trajectory become the same, resulting in the best reproduced image. However, when playing back a tape recorded on another VTR, there is a possibility that the recorded track and playback head trajectory may be misaligned.
In order to correct this, tracking servo is performed to shift the cylinder rotational phase signal and the lock phase of the reproduction control signal.

A detailed explanation will be given below with reference to the drawings. FIG. 2 is a block diagram showing an example of a conventional tracking servo. 1 is a head motor that rotationally drives the head cylinder 2, and 3 is a capstan motor. The head motor 1 is rotated at a predetermined speed by a speed control circuit (not shown), and at the same time, the output of the reference oscillator 4 is divided through a frequency divider 6 to obtain a phase reference signal a with a period T1 and a head motor 1. The phases of the PG multiplied signal, which is the phase signal of the cylinder 2, are compared by a phase comparator 6, and the head motor 1 is subjected to phase control so that the phases of both signals are locked. The capstan motor 3 compares the speed with a speed reference signal 8 indicating a predetermined reference speed V using the FG double signal speed discriminator 7, which is a speed detection signal, and feeds back the error signal to the capstan motor. By doing this, it is rotated at a predetermined speed V. Further, a phase comparator 11 compares the phase of the cylinder phase reference signal a with a signal delayed by a delay circuit 9 consisting of a mono-staple multivibrator (hereinafter abbreviated as tracking MM) and a reproduction control signal from the control head 1o. Phase control is applied to the capstan motor 3 so that the phase difference becomes a predetermined phase φ. At this time, by varying the time constant of the tracking MM9 using a tracking shift circuit 12 made up of a variable resistor, the phase between the phase reference signal and the reproduction control signal, and ultimately the phase lock position between the cylinder PG signal and the reproduction control signal, can be varied. can.

Beyond the problems that the invention aims to solve is the basic concept of tracking servo.
Considering the case where the phase lock position between the cylinder PG signal and the reproduction control signal is shifted by T2 from the current position, first, in the tracking shift circuit 12, the delay time of the tracking MM9 is shifted by τ2, and when the next reproduction control signal arrives, the tracking MM9 As a result of comparing the phase with the output of , it is naturally determined that there is a difference of T2, and a command to accelerate or decelerate is issued to the capstan motor to start a phase shift. When the next playback control signal comes, the phase is corrected, and the correction continues with the next playback control signal, and locking is achieved at a position shifted by T2 after several playback control signals. During this time, since acceleration and deceleration are performed by phase control, the speed deviates slightly from the reference speed of the speed system, which becomes a disturbance element in the speed system and causes a delay in phase locking. When adjusting tracking manually, it is done while monitoring the image quality, so there is no problem with such a delay. However, when performing tracking shift while monitoring the playback envelope using auto-tracking, the servo pull-in time for tracking shift is restricted, making it impossible to shift at high speed and requiring time for auto-tracking. The present invention solves these conventional problems, and it is possible to shift the tracking by a certain amount, that is, to shift the phase of the cylinder PG signal and the playback control signal by a certain amount, in just one frame period. This is the result.

Means for Solving the Problems The tracking shift device of the present invention changes the speed of the capster by a certain amount in order to shift the next playback control signal by a certain amount when the playback control signal arrives, thereby changing the speed in the speed system. At the same time, tracking MM
By shifting by a predetermined amount, tracking is basically shifted in the velocity system, and fine adjustments can be made in the phase system. The amount by which the speed of the speed system is changed is the stun reference speed V.

Effect According to the above configuration, the velocity system and the phase system cooperate to perform tracking shift at a constant speed, and high-speed tracking shift without any distortion can be performed. It becomes possible to perform operations at high speed.

EXAMPLE An example of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram of a tracking shift device in one embodiment of the present invention. Component blocks that are the same as those of the conventional example shown in FIG. 2 are designated by the same reference numerals. The difference from the conventional example is that it detects the point where the envelope of the playback output of the rotary head is at its maximum, detects whether or not it is in the optimal tracking state, and also indicates the direction of phase shift to achieve the optimal tracking state. A tracking state detecting means 14 is provided to output an output, and during a period when the tracking state detecting means 14 determines that the tracking state is not in the optimum tracking state, the tracking MM9 is activated in synchronization with the arrival of the reproduction control signal according to the detected output. A tracking shift circuit 16 is provided to sequentially change the delay time by a predetermined time T2, and a conversion device 16 is provided to increase or decrease the delay time by a period determined by the tracking state detection means 14 to be not in the optimum tracking state. It is at the point.

Next, this operation will be explained. In auto-tracking, the tracking is shifted several times by a certain amount T2 from the current tracking position, and the tracking state detection means 14 sequentially compares the envelope of the playback output of the rotary head during that period to detect the optimal tracking state. think of. In FIG. 1, if the shift operation is started by a certain amount T2 upon arrival of the control signal, it is sufficient to require time (T1 to T2) until the next control signal arrives. Therefore, when the control signal arrives, the speed reference of the speed discriminator 9 is shifted to the king of the normal reference speed V. If the tracking MM9 is shifted by T2, the phase error becomes zero at a position where the tracking signal is shifted by T2. If you want to continue shifting after that, you can shift the next tracking MM9 by T2 using the control signal. If this operation continues, the speed control and phase control will cooperate and the tracking will shift sequentially at a constant speed. The stability of the servo during this period is determined by the tracking M
It is stable and no different from the case where M is fixed and the servo is applied at a constant speed. When you finally stop at that position,
When the control signal arrives, the speed reference of the speed discriminator may be returned to the reference speed V, and the tracking MM9 may be fixed at that value.

Effects of the Invention As described above, according to the present invention, the speed of the capstan motor is set to a reference value when a control signal arrives. FIG. 2 is a block diagram showing an example of a conventional tracking servo.

1...Head motor, 2...Head cylinder, 3...Capstan motor, 4...
... Oscillator, 6 ... Frequency divider, 6 ... Phase comparator, 7 ... Speed discriminator, 8 ... Speed reference, 9 ... Tracking MM, 1°...control head, 11...phase comparator, 12.
15... Tracking shift circuit, 16...
. . . Speed reference conversion device, 14 . . . Tracking state detection means.

Name of agent: Patent attorney Shigetaka Awano By shifting one other person, the speed control and phase control cooperate to shift the tracking at a constant speed, making it possible to capture the envelope at high speed during auto-tracking. It is.

[Brief explanation of the drawing]

Claims (1)

[Claims] A speed control means for controlling a capstan motor to a speed according to a speed reference signal; and a first phase control means for driving a head cylinder motor for driving a rotary head to rotate in phase synchronization with a phase reference signal having a period T_1. , a variable delay means for delaying the phase reference signal; and a second phase control for controlling the rotational phase of the capstan motor according to a phase difference between the phase reference signal delayed by the variable delay means and a reproduction control signal. tracking state detection means for detecting a tracking state from the playback output of the rotary head and detecting an optimal tracking state; It is characterized by comprising means for changing the delay time of the variable delay means, and means for changing the speed reference signal to (T_1 to T_2)/T_1 times the standard speed V only during times when the optimum tracking state is not achieved. Tracking shift device.