JPH06131757A - Control device for motor servo for vtr - Google Patents

Abstract

PURPOSE:To obtain a high quality reproduced picture without occurring of step out of vertical synchronism even if a reproduced video signal is projected to any television set at the time of quick traversing reproduction or rewinding reproduction. CONSTITUTION:A operation section 14 operates controlled variable of a rotary phase of a capstan motor 3 and a cylinder motor 2 so that a reproduced envelop is not compared with the one lower than the reference level by an envelop level comparing section 4 at a leading edge section of a switching pulse inputted from a switching pulse generation section 13, and outputs it to a servo control section 12. A servo control section 12 controls rotational speed and phase of the cylinder motor 2 and the capstan motor 3 by a frequency divided signal CTL inputted from a frequency divider 11, a FG signal inputted from the capstan motor 3, and controlled variable inputted from the operation section 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a VTR motor control device for controlling the rotation of a capstan motor and a cylinder motor used in a video tape recorder (VTR), and particularly to a fast forward reproduction and a rewind reproduction. Regarding servo control.

[0002]

2. Description of the Related Art Conventionally, a VTR which records and reproduces a video signal by helically scanning a magnetic tape with a two-head structure can usually perform fast-forward reproduction and rewind reproduction. However, the two-head configuration means a configuration in which two video heads having different azimuths are mounted on a rotary cylinder so as to face each other by 180 degrees. by the way,
When fast forward playback or rewind playback is performed on the above VTR, the video head (functions as a playback head)
Scans over the video track on the magnetic tape, which causes noise on the playback screen. That is, when the video head is reproducing at the same azimuth track on the magnetic tape, a reproduction envelope signal is output from the video head, and when reproducing at a different azimuth track, the envelope signal is not output. . Therefore, when the video head reproduces different azimuth tracks, this appears as noise on the screen, and this noise is called a noise bar.

The position of the noise bar generated on the reproduction screen during such fast-forward reproduction and rewind reproduction is a video head switching signal (hereinafter referred to as SW pulse) for switching the reproduction timing of video heads having two different azimuths.
And the control pulse (CTL pulse) reproduced from the magnetic tape at this time. For example, when the magnetic tape is fast-forwarded and reproduced at N times speed, the obtained reproduced CTL pulse is divided by N, and the phase difference between the obtained divided N pulse and the SW pulse is controlled to be constant, The position of the noise bar generated on the playback screen can be fixed, and by making the phase difference between the N frequency division pulse and the SW pulse constant in this way, even during fast forward playback and rewind playback, The screen can be reproduced by using the same control method as in the case of reproducing.

FIG. 3 is a block diagram showing a conventional example of a VTR motor servo control device for controlling the rotational speed and phase of a cylinder motor and a capstan motor used in a VTR. During reproduction (including special reproduction), the FG signal indicating the rotation speed of the capstan motor 3 and the CTL signal divided by the frequency divider 11 after being reproduced from the magnetic tape 6 by the control head are servo-controlled. Part 1
Entered in 2. The servo control unit 12 generates a cylinder motor control signal for controlling the rotation speed and phase of the cylinder motor 2 and a capstan error control signal for controlling the rotation speed and phase of the capstan motor 3 based on the input signal. Then, these control signals are output to the cylinder motor 2 and the capstan motor 3. This allows
The rotation speed and phase of the cylinder motor 2 and the capstan motor 3 are controlled in accordance with various modes such as standard reproduction, fast-forward reproduction and rewinding reproduction.

At the same time, the SW pulse generator 13 outputs a PG / F indicating the rotation phase and rotation speed of the cylinder motor 2.
A G signal is input and the reproduction timing of a pair of video heads (not shown) is switched from these signals (FIG. 4A).
A SW pulse as shown in (1) is created and output to a video circuit (not shown) or the like. The calculation unit 14 caps the SW pulse created by the SW pulse creation unit 13 and the divided CTL signal input from the frequency divider 11 as shown in FIG. Stun motor 3
Also, a control amount for controlling the rotation phase of the cylinder motor 2 is calculated, and this is given to the servo control unit 12. As a result, the servo control unit 12 controls the rotation phases of the cylinder motor 2 and the capstan motor 3 based on the control amount given from the arithmetic unit 14, and therefore the SW pulse created by the SW pulse creation unit 13 The phase difference of the divided CTL signal divided by the divider 11 can be kept constant as shown in FIG. Incidentally, FIG. 4B is a diagram showing a waveform example of the envelope signal reproduced from the magnetic tape 6 by the control head (not shown) at this time. Further, the frequency divider 11, the servo controller 12, the SW pulse generator 13, and the calculator 14 are configured as software in the microcomputer 1.

By the way, in order to simplify the control, the phase of the CTL pulse reproduced from the magnetic tape at the time of standard reproduction and each phase of the CTL pulse divided by N obtained at the time of fast-forward reproduction at N times speed as described above. The same method is generally used. However, in this method, as described with reference to FIG. 3, the phase difference between the SW pulse and the frequency-divided CTL signal is kept constant irrespective of the double speed number in the fast-forward reproduction or the rewind reproduction, so that the fast-forward reproduction or the rewind operation is performed. The noise bar generated during the return reproduction may be fixed around the front of the vertical synchronizing signal. When such a situation occurs, the noise bar causes a malfunction in the vertical synchronization system depending on the performance and characteristics of the television that projects the reproduced video signal by the fast-forward reproduction and the rewind reproduction, and so-called vertical play is generated. There was a flaw. To prevent this, set the phase difference between the SW pulse and the divided CTL pulse so that the noise bar is not fixed around the front of the vertical sync signal, depending on the multiple speed during fast forward playback and rewind playback. If
Although the problem as described above can be avoided, there is a drawback in the apparatus having a large number of double speeds N that the setting of the phase becomes complicated and the manufacturing cost of the apparatus increases. In addition, as described above, the C pulse frequency-divided by the SW pulse according to the double speed during special reproduction
Even if the phase of the TL pulse is optimally set, it is not possible to absorb the position variation of the noise bar due to the variation of the head width of the video head that differs depending on the device, and in some cases, the above vertical play occurs. There was a drawback that it would end up. Furthermore, when playing back a tape recorded by another device, the recording track width of the magnetic tape varies, and the position of the noise bar fluctuates due to this, but even in such a case the above method can be used However, there is a drawback that vertical play occurs.

[0007]

In the conventional VTR, when the position of the noise bar generated during fast forward reproduction or rewinding reproduction comes near the front of the vertical synchronizing signal, the television which projects the reproduced video signal. Depending on the type of John, there is a drawback that vertical play occurs on the playback screen.
In order to prevent this, the phase difference between the SW pulse and the divided CTL pulse should be set optimally in correspondence with each speed number during fast forward and rewind reproduction. There is a drawback that this setting is complicated and increases the manufacturing cost of the device, and even if this method is adopted, there are variations in the width of the video head, variations in the recording track width that occur when recording is performed with other devices, etc. However, there is a drawback in that it is not possible to absorb the variation in the position of the noise bar due to the above, and it is not possible to completely eliminate the above-described vertical play.

Therefore, the present invention eliminates the above-mentioned drawbacks and obtains a good quality reproduction screen which does not cause vertical play even when the reproduction video signal is projected by any television during fast forward reproduction or rewinding reproduction. It is an object of the present invention to provide a VTR motor servo control device.

[0009]

SUMMARY OF THE INVENTION The present invention is a VTR for controlling the rotational speed and phase of a capstan motor and a cylinder motor of a video tape recorder according to various reproduction modes.
In the motor servo device for use, a comparison means for comparing an envelope reproduced at the time of special reproduction from two video heads helically scanned of the video tape recorder with a reference level, and switching for switching reproduction timings of the two video heads. Section detecting means for detecting the preceding section of the edge of the pulse, and when the section detecting section detects the preceding section of the edge, the comparing section prevents the envelope from being compared with a reference level or lower. And a control means for controlling the rotation speed and phase of the capstan motor and the cylinder motor.

[0010]

In the VTR motor servo device of the present invention,
The comparing means compares the envelope reproduced at the time of special reproduction from the two video heads of the helical scanning of the video tape recorder with the reference level. The section detecting means detects the section before the edge of the switching pulse for switching the reproduction timing of the two video heads. The control means rotates the capstan motor and the cylinder motor so that the comparison means does not compare the envelope with a reference level or less when the section detection means detects the preceding section of the edge. Control speed and phase.

[0011]

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 an embodiment of a VTR motor servo control device of the present invention. Reference numeral 1 denotes a microcomputer which constitutes a motor servo system for controlling the rotation speed and rotation phase of the cylinder motor 2 and the capstan motor 3 and its peripheral circuit by software, and is a reproduction C
Frequency divider 11 for dividing the TL signal, divided reproduction CTL
A servo control unit 12 for generating a control signal for rotating the cylinder motor 2 and the capstan motor 3 at a predetermined speed and phase from a signal and a speed signal of the capstan motor 3, and a SW pulse for switching two video heads (not shown). It has a SW pulse creation unit 13 and a calculation unit 14 that calculates the amount by which the rotational phases of the cylinder motor 2 and the capstan motor 3 are deviated from the level of the reproduction envelope and the position of the SW pulse. 2 is a cylinder motor for mounting a video head and driving a rotating cylinder, 3
Is a capstan motor for rotating a capstan for running a magnetic tape (not shown), 4 is an envelope level comparing section for comparing a reproduction envelope signal with a reference level, and 5 is a reference level generating section for generating the reference level.

Next, the operation of this embodiment will be described. During reproduction (including special reproduction), the FG signal indicating the rotation speed of the capstan motor 3 and the CTL signal reproduced by the control head (not shown) from the magnetic tape 6 and divided by the frequency divider 11 are used as the servo control unit. 12 is input.
The servo control unit 12, based on the input signal,
A cylinder motor control signal for controlling the rotation speed and phase of the cylinder motor 2 and a capstan error control signal for controlling the rotation speed and phase of the capstan motor 3 are generated, and these control signals are sent to the cylinder motor 2 and the capstan motor. Output to 3. As a result, the rotation speed and phase of the cylinder motor 2 and the capstan motor 3 are controlled in accordance with the double speed number at the time of fast-forward reproduction and rewind reproduction.

At the same time, the SW pulse generator 13 outputs a PG / F indicating the rotation phase and rotation speed of the cylinder motor 2.
A G signal is input and the reproduction timing of a pair of video heads not shown is switched from these signals (FIG. 2A).
A SW pulse as shown in (1) is created and output to a video circuit (not shown) or the like. Magnetic tape 6 during special playback
An envelope signal as shown in FIG. 2B reproduced from a video head (not shown) for helically scanning is input to the envelope level comparison unit 4. Since the reference level generated from the reference level generating unit 5 as shown in FIG. 2B is also input to the envelope level comparing unit 4, the input envelope signal is supplied to the reference level by the envelope level comparing unit 4. Compared to the level,
The comparison result is output to the calculation unit 14. Computing unit 14
2 is input from the SW pulse generation unit 13 according to the comparison result input from the envelope level comparison unit 4.
A section T (T (T) before the edge of the SW pulse shown in (A))
Is a time), the divided CTL signal is provided so as to provide a difference between the phase of the SW pulse and the phase of the divided CTL signal so that the envelope is reproduced so as not to fall below the reference level. The phase shift amount is calculated and output to the servo control unit 12. As a result, the servo control unit 12 controls the rotation phases of the cylinder motor 2 and the capstan motor 3 based on the control amount given from the calculation unit 14, and the frequency divider is operated as shown in FIG. 2 (C). The phase of the divided CTL pulse output from 11 is controlled. Therefore, in this example, the SW of FIG.
In the T section before the edge of the pulse, the envelope signal is reproduced so that the level of the reproduced envelope signal becomes equal to or higher than the reference level. This is to prevent the phase difference between the SW pulse shown in FIG. 2A and the frequency-divided CTL pulse shown in FIG. 2C from being fixed at the position of the noise bar generated at this time around the front of the vertical synchronizing signal. Means to control.

According to this embodiment, during special reproduction, the phase difference between the SW pulse and the divided CTL pulse is adjusted so that the level of the envelope signal reproduced at this time is below the reference level in the section T before the edge of the SW pulse. Since it is controlled so as not to occur, the noise bar generated at this time can be prevented from being positioned before the vertical synchronizing signal. Therefore, no matter what type of television the VTR equipped with the motor servo control device of the present example is connected to and the special reproduction is performed, vertical play does not occur, and a good screen can be obtained. Moreover, since the method of this example can also absorb the variation in the width of the video head and the variation in the recording track width, the vertical play does not occur even in the state of the head of the VTR or the special reproduction of the tape recorded by another device. It is possible to provide various screens.

[0015]

As described above, according to the motor servo control device for a VTR of the present invention, vertical play does not occur even if the reproduced video signal is projected by any television during fast-forward reproduction or rewind reproduction. You can get a good playback screen.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a VTR motor servo control device of the present invention.

FIG. 2 is a time chart of each signal generated by the device shown in FIG.

FIG. 3 is a block diagram showing an example of a conventional VTR motor servo control device.

FIG. 4 is a time chart of each signal generated by the device shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Microcomputer 2 ... Cylinder motor 3 ... Capstan motor 4 ... Envelope level comparison unit 5 ... Reference level generation unit 6 ... Magnetic tape 11 ... Divider 12 ... Servo control unit 13 ... SW pulse creation unit 14 ... Calculation unit

Claims (1)

[Claims] 1. A VTR motor servo device for controlling the rotational speed and phase of a capstan motor and a cylinder motor of a video tape recorder according to various reproduction modes, and special reproduction from two video heads for helical scanning of the video tape recorder. Comparing means for comparing an envelope reproduced at some time with a reference level;
Section detecting means for detecting the preceding section of the edge of the switching pulse for switching the reproduction timing of each video head, and when the preceding section of the edge is detected by this section detecting means, the envelope is referenced by the comparing means. A VTR comprising a control means for controlling the rotational speed and phase of the capstan motor and the cylinder motor so that the VTR is not compared with a level or less.
Motor servo controller for car.