JPH01245455A - Digital servo device - Google Patents

Abstract

PURPOSE:To prevent the rolling of a reproduced picture at the time of slow action and to prevent the occurrence of color dislocation in the reproduced picture by making the phase difference in a phase error output into '0' in a next cycle when the speed control output of a cylinder motor at the time of operating slowly is corrected. CONSTITUTION:The title device is equipped with a speed control means 8 to control the rotating speed of a cylinder motor 3 so that the rotating speed can be constant, a phase setting means to set the phase of the reference phase signal of a reference phase signal generating means 9 to the phase of the rotational phase signal of the cylinder motor 3, etc. When the speed control output of the cylinder motor 3 at the time of the slow action is corrected, it is made difficult to receive the influence of phase control by making the output of a phase control means 10 into the one in which the phase error is 0 and changing the phase of the reference phase signal so that the phase difference between the rotational phase of the cylinder motor 3 and its reference phase can be a previously set phase difference. Thus, the rolling of the reproduced picture at the time of operating slowly can be corrected without the occurrence of the color dislocation in the reproduced picture.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a so-called helical scan type magnetic recording and reproducing apparatus that records or reproduces video signals and the like obliquely on a magnetic tape using a rotating magnetic head. This invention relates to a digital servo device.

Conventional technology Video signal magnetic recording and reproducing device (hereinafter abbreviated as VTR)
2. Description of the Related Art Various devices are known that perform slow motion playback (hereinafter referred to as slow playback) by intermittently feeding a magnetic tape (hereinafter referred to as tape). However, even if the rotational speed of the cylinder motor equipped with the rotating head that reproduces the video signal is constant, if the moving speed of the tape changes rapidly, the rotating head will trace the recording track of the tape while feeding the magnetic tape. The drawback is that the speed changes and the horizontal synchronization signal frequency in the video signal changes. This causes the inconvenience that the playback screen is tilted sideways when the tape is running. As a method to solve this problem, Japanese Patent Application Laid-Open No. 57-8945 proposes a method in which the relative speed between the tape and the magnetic head attached to the cylinder motor is made constant by correcting the speed control system of the cylinder motor. , to prevent the playback screen from shaking horizontally. Further, during speed correction, phase control is not performed so as not to be influenced by 19 phase control.

Problems to be Solved by the Invention However, in the above configuration, the cylinder motor is controlled only by speed control without phase control, so the speed error output circuit and cylinder motor drive error signal input circuit are If there is an offset between the two, the rotational speed of the cylinder motor will deviate from the reference speed, causing phenomena such as color shift on the playback screen during the stop operation. Furthermore, since phase control is not performed, when the mode is changed from slow mode to normal mode, the transition cannot be made smoothly and the playback screen becomes distorted.

Means for Solving the Problems In order to solve the above problems, the digital servo device of the present invention includes a capstan motor that drives a magnetic tape to travel, and a rotary head that rotates and drives a rotary head to reproduce signals recorded on the magnetic tape. a cylinder motor, a speed control means for controlling the rotational speed of the cylinder motor to be constant, a reference phase signal generation means for generating a reference phase signal serving as a reference for the rotational phase of the cylinder motor; a phase control means for controlling the difference between the rotational phase signal and the reference phase signal outputted by the reference phase signal generation means to be constant; a digital filter for low-frequency compensation for the output of the phase control means; intermittent drive means for intermittently driving the magnetic tape; and the speed control means causes the cylinder motor to correct a speed according to the moving speed of the magnetic tape in synchronization with the timing at which the intermittent drive means intermittently drives the magnetic tape. speed correction means for providing a rotational phase signal of the cylinder motor; The present invention is characterized by comprising a phase matching means for matching the phases of the two.

Effect of the Invention With the above-described configuration, when correcting the speed control output of the cylinder motor during slow operation, the present invention sets the output of the phase control means to an output with a phase error of "0°" and further adjusts the rotational phase of the cylinder motor. By changing the phase of the reference phase signal so that the phase difference between the reference phase and the reference phase becomes a preset phase difference, it is made less susceptible to the effects of phase control, so color shift occurs on the playback screen during slow motion. It is possible to compensate for horizontal shaking, and it is also possible to smoothly transition from slow mode to normal mode without disturbing the playback screen.

Embodiment Hereinafter, a digital servo device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram showing an embodiment of the present invention, in which 1 is a tape, 2 is a capstan motor that drives the tape 1, and 3 is a rotating magnetic head 3a that records or reproduces video signals. .

3b is a cylinder motor for rotating at a constant speed; 4 is a head (hereinafter referred to as a control head) for recording or reproducing a control signal for the purpose of controlling tape feeding near the edge of the tape l; 5 is a capstan motor tape feed control means 6 which manually inputs the speed control signal (FC signal) of No. 2, the playback signal from the control controller 4 and the phase signal of the cylinder motor 3, and controls the feed of the tape 1 based on these signals; 7 is a drive circuit for driving the capstan motor 2 based on the output signal of the tape feed control means 5; 7 is a speed correction means for correcting the rotational speed of the cylinder motor 3 according to the amount of tape l fed by the capstan motor 2; 8
9 is a speed control means that controls the speed of the cylinder motor 3 so that the period of the FG multiplication signal becomes a preset period, and the output signal of the speed correction means 7 is also input. Reference phase signal generation means outputs a reference phase signal of the cylinder motor 3, and reference numeral 10 keeps the phase difference between the phase signal of the cylinder motor 3 (hereinafter referred to as H3W signal) and the output signal of the reference phase signal generation means 9 constant. ll is the trailing edge (
The period phase control means I adjusts the reference phase of the reference phase signal generating means 9 based on the trailing edge) so that the phase error with the reference phase signal becomes 0°, and performs phase matching.
12 is a digital filter that filters the output signal of the phase control means 10 and performs low frequency compensation. This is a drive circuit that drives the cylinder motor 3 based on a signal obtained by adding the output signal of the digital filter 12, which is the output of the phase control system, and the output signal of the speed control means 8, which is the output of the speed system.
14 is a pinch roller.

FIG. 2 is an operational waveform diagram of each part for explaining the operation during slow playback.

The slow operation is a repetition of intermittent feeding and stopping of the tape (still operation), and FIG. 2 explains the operation during intermittent feeding. In FIG. 2, a is the reference phase signal output from the reference phase signal generating means 9, and b is the reference phase when the phase of the reference phase generating means is matched with the phase of the cylinder motor 3 by the phase matching means 11. It's a signal. C is the H5W signal waveform of the cylinder motor 3 and also serves as a switching signal for the magnetic heads 3a and 3b.

d is a drive current waveform for driving the capstan motor 2, and e is a tape speed of the tape l run by the capstan motor 2. f is a speed correction signal of the cylinder motor 3 outputted from the speed correction means 7. g indicates the relative speed between the tape l and the magnetic heads 3a, 3b, and h is the signal waveform of the error output of the phase control means lO of the cylinder motor 3.

First, the period up to time (2 is the still operation state, and d
Since the driving current waveform of is '0'', the capstan motor 2 is stopped and the tape 1 is also stopped. Also, the H3W signal of the cylinder motor 3 changes to the phase control means 10 at time [l].
The phase control means 10 is controlled manually by the digital filter 1.
However, since the cylinder motor 3 rotates at a sufficiently stable constant speed until time L1, the output of the phase control means 10 becomes 0°, and the digital filter 12
outputs the same output signal as when the previous H3W signal was input.

Since the rotation speed of the cylinder motor 3 is constant and the tape 1 is also stopped, the magnetic head 3a attached to the tape l and the cylinder motor 3.

The relative velocity of 3b is constant as shown in g. Since the relative speed is constant, there is no need to perform speed correction.
The output signal of the speed correction means 7 is "0" as shown at f.

Next, when the intermittent feeding operation of slow playback starts at time L2, a drive current flows through the capstan motor 2, and the capstan motor 2 starts rotating. When the capstan motor 2 rotates, the tape l runs, and if the rotational speed of the cylinder motor 3 is the same as when the tape 1 is stopped, the relative speed is not constant but slows down, as shown by the wavy line at g. go. In this way, when the relative speed is no longer constant, it appears on the playback screen as horizontal shaking of the screen. Therefore, the speed correction means 7 sends a correction amount according to the feed speed of the tape 1 to the speed control means 8, and rotates the cylinder motor 3 so that the rotation speed of the cylinder motor 3 and the relative speed of the tape l are always constant. Correct speed.

Since the tape feed control means 5 accelerates the capstan motor 2 until time t3, the moving speed of the tape 1 also increases, and the correction amount of the speed correction means 7 of the cylinder motor 3 similarly increases.

Since the capstan motor 2 rotates at a constant rotation speed from time t3 to time t5, the moving speed of the tape 1 is also constant, and the speed correction amount of the cylinder motor 3 is also constant.

At time t4, when the H3W signal of the cylinder motor 3 is input to the phase control means 1O, the phase control means 1O calculates a phase error. At this time, due to the speed correction input to the speed control means 8, the phase of the cylinder motor 3 is ahead of the reference phase signal output from the reference phase signal generation means 9, as shown in a.

Therefore, the phase control means lO outputs an error signal that delays the phase, that is, an error signal like the broken line h, but since the phase is adjusted by intermittent feeding, it outputs an error output with a phase error of O''. , this error output is input to the digital filter 12 for low frequency compensation,
Since the input value is "0", the output of the digital filter 12 does not change.

Next, the magnetic nod 3 attached to the cylinder motor 3
In order to stop the capstan motors a and 3b on the video track, the drive circuit 6 outputs a drive current to the capstan motor 2 at time t6 based on the output signal from the node to the control so that the capstan motor 2 rotates in the opposite direction. (At the time of field throw, there is no control signal in the field, and in the field where there is no control signal, the FG of capstan motor 2 after the control signal is input manually)
The magnetic heads 3a, 3b are multiplied by counting signals.
(can be positioned so that it is on-trunk to the video trunk). Therefore, the rotational speed of the capstan motor 2 is reduced, and the moving speed of the tape 1 is also reduced accordingly, so that the rotational speed of the cylinder motor 3 is reduced at time t3.
If the rotational speed is corrected by the speed correction means 7 at , the relative speed between the tape 1 and the heads 3a and 3b will become faster as shown by the broken line g. Therefore, from time L6, the rotational speed of the capstan motor 2 will change. In response to the deceleration, the speed correction means 7 changes the correction output so that the rotational speed of the cylinder motor 3 is decelerated.

The tape feed control means 5 operates immediately before the capstan motor 2 starts to reverse rotation, or at the time when the capstan motor 2 starts to reverse rotation, that is, at time t.
At 7, an output for stopping the capstan motor 2 is output to the drive circuit 6. Therefore, after time t7, the capstan motor 2 stops, and the tape l also stops. The speed correction means 7 also stops correcting the rotational speed of the cylinder motor 3 since the tape l stops.

After time t7, the tape 1 stops, so it becomes a still operation, and the state is the same as up to time 2. Therefore, if the rotational speed of the cylinder motor 3 is the same as the rotational speed at time t2, the tape 1 and the magnetic head 3a.

The relative velocity of 3b remains constant.

However, at time t4, the phase error means IO outputs "0°" as a phase error, eliminating the influence of the phase system on speed correction. It came off and the next H
A phase error occurs when the SW signal is input, resulting in a phenomenon called swing back.

In order to prevent horizontal shaking from appearing on the playback screen during still shooting, when the tape l comes to a halt, the output of the phase error means 10 is "0°, that is, the phase is locked, and the output of the digital filter 12 is Since the output when the tape l is stopped is sufficient, the H3W signal of the cylinder motor 3 is used to adjust the phase of the reference phase signal generating means 9 so that the phase error becomes 0°, and the tape l
Even if a phase error occurs during intermittent feeding, by setting it to 0°, the phase control means 1 when transitioning to still operation
The error output of 0 is 0°, and the output of the digital filter 12, which is the input signal of the drive circuit 13, is also the same as the output during the previous still.

Hereinafter, a method of phase matching will be explained. At time [4], when the HS W signal is input manually, the phase control means l
O calculates a phase error, but outputs a phase error of "0°" to the digital filter 12.

At this time, the phase matching means 11 shifts the phase of the reference phase signal generating means 9 so that the calculated phase error becomes 0. That is, as shown in b, using the time difference between the time t5 when the phase error originally becomes °O' and the time t4 when the H3W signal is input, the phase matching means 11 adjusts the leading edge of the next reference phase. Edge) is corrected from time [9 to time L8.

Accordingly, the phase error will be “0” in the next period.
The time at which this happens is from t12 to 111.

When the trailing edge of the H5W signal is input to the phase control means lO at time 110, the phase error is not the difference between time t12 and time [10], but the difference between time tit and time tlo. Therefore, the phase error is reduced by phase matching.

The reason why the phase error is not 0° even though the phase is adjusted here is because speed correction is performed from time t4 to t7, which causes the phase to be lower than the value set at time [4]. 0 time [10
Also, the phase error output to the digital filter 12 is 0° because phase matching is performed.

When the phase matching means 11 performs phase matching at time 110 as it did at time t4, the time of the leading edge of the next reference phase will be t13 due to the time difference between time tll and time tlo, and the reference phase signal will not perform phase matching. The phase advances by the time difference between time t13 and time t14 compared to when it was not present.Here, the phase adjustment means 11 performs this operation only during slow operation and does not operate during normal playback, but performs phase adjustment for the purpose of speeding up phase pull-in. Sometimes.

When the H3W signal is input at time t15, phase adjustment is performed at time t13, so the phase error is 0°.
becomes. Since phase matching is not performed at time t15, the phase control means 10 outputs the obtained phase error to the digital filter 12, but here, since the phase error is 0° due to the phase matching at time 110, the digital The output of filter 12 remains unchanged. the result,
The influence of the phase system does not appear.

Next, Figure 3 shows the digital filter 1 that performs low frequency compensation.
2, its frequency characteristics are shown in FIG. 3 tal, and its block diagram is shown in FIG. 3 tbl.
sl represents the integral characteristic, (pl represents the proportional characteristic.The characteristics of the digital filter 12 are a combination of the integral characteristic and the proportional characteristic. , Gl is the gain of the filter, and G2 is the bending point f1 of the filter.
is a constant that determines

Note that Z -1 in FIG. 3 (bl) represents a l sample delay.

As described above, according to this embodiment, when correcting the speed control output of the solider motor 3 during slow operation, the phase error output generated by speed correction is adjusted so that the phase error becomes °O° in the next cycle. At the same time, the phase control means 10 outputs an output with a phase error of 0 to the digital filter 12, so the rotation speed is not affected by the phase control, so the playback screen during slow motion is It is possible to prevent horizontal shaking. In addition, since the phase system is not cut, there is no color shift, and furthermore, the transition from slow mode to normal mode can be smoothly performed without disturbing the playback screen.

Note that in this embodiment, the speed control is one-phase control.

Although we did not provide a detailed explanation of the operation of the tape feed control means, for example, [Hashimoto et al.
5 method 2-6 field throw VTRjp29-p38
[National Technical Report
Technical Report) Vol 128
This can be achieved by using the method described in NlX3 June 1982) J.

Moreover, the above means can also be realized by software using a microprocessor.

Effects of the Invention As described above, the present invention includes a capstan motor that drives a magnetic tape to run, a cylinder motor that rotationally drives a rotary head to reproduce signals recorded on the magnetic tape, and a rotational speed of the cylinder motor. a speed control means for controlling the rotational phase of the cylinder motor to be constant, a reference phase signal generation means for generating a reference phase signal serving as a reference for the rotational phase of the cylinder motor, and a rotational phase signal of the cylinder motor and the reference phase signal generation means a phase control means for controlling the difference from a reference phase signal to be outputted to be constant; a digital filter for low-frequency compensation of the output of the phase control means; an intermittent drive means for intermittently driving the capstan motor; a speed correction means for providing the speed control means with a speed correction of the cylinder motor according to the moving speed of the magnetic tape in synchronization with the timing at which the intermittent drive means intermittently drives the magnetic tape; and the intermittent drive operation mode. and a phase adjusting means for adjusting the output of the phase control means to an output with a phase error of O'' during the period of , and adjusting the phase of the reference phase signal of the reference phase signal generation means to the rotational phase signal of the cylinder motor. When correcting the speed control output of the cylinder motor during slow operation, the phase error output generated by speed correction is adjusted so that the phase error becomes 0° in the next cycle. At the same time, the phase control means 10 outputs an output with a phase error of "O'" to the digital filter 12, so the rotation speed is not affected by the phase control, so the playback screen does not cause horizontal shaking during slow motion. You can do it like this. Furthermore, since the phase system is not cut, color shift does not occur. Furthermore, it is possible to smoothly transition from the slow mode to the normal mode without disturbing the playback screen, which is a very significant effect.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the characteristics and configuration of a digital filter in an embodiment of the present invention. 2... Capstan motor, 3... Cylinder motor, 4... Control head, 5
...8 means of tape feed control, 6.13...
...Drive circuit, 7... Speed correction means, 8...
... Speed control means 8, 9 ... Reference phase signal generation means, lO ... Phase control means, 12 ...
...Digital filter. Name of agent: Patent attorney Toshio Nakao Haka1 Q+
-L

Claims (3)

[Claims] (1) A capstan motor that drives the magnetic tape to run, a cylinder motor that rotationally drives a rotary head to reproduce signals recorded on the magnetic tape, and a speed that controls the rotational speed of the cylinder motor to be constant. a control means, a reference phase signal generation means for generating a reference phase signal serving as a reference for the rotational phase of the cylinder motor, and a difference between the rotational phase signal of the cylinder motor and the reference phase signal output by the reference phase signal generation means; a digital filter for low-frequency compensation of the output of the phase control means; an intermittent drive means for intermittently driving the capstan motor; a speed correction means for giving the speed control means a speed correction of the cylinder motor in accordance with the moving speed of the magnetic tape in synchronization with the timing of the intermittent drive; A digital servo characterized by comprising: a phase matching means for outputting an output with a phase error of '0' and matching the phase of the reference phase signal of the reference phase signal generation means to the rotational phase signal of the cylinder motor. Device. (2) The digital servo device according to claim (1), wherein the low-pass compensation digital filter is constructed by combining an integral term and a proportional term. (3) Using the rotational phase signal of the cylinder motor, the reference phase signal is sent to the reference phase generation means so that the phase difference between the reference phase signal of the reference phase signal generation means and the rotational phase signal becomes a preset phase difference. 2. The digital servo device according to claim 1, further comprising phase matching means for changing the phase.