JPH0419852A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To shorten a run-up section at the time of shifting a stop mode to a reproducing or a video recording mode by stopping once a capstan in prescribed timing after detecting a CTL pulse and immediately restarting the capstan in prescribed timing from a switching pulse showing phase information of a rotary head. CONSTITUTION:When the stop mode is shifted to the reproducing or the video recording mode, first of all, an AFC control is effected after a compulsory start-up which performs an intermittent feed under the working state of a speed detecting circuit (AFC) 8, and under these circumstances, the capstan 2 is once stopped by means of a capstan brake in the prescribed timing after detecting the CTL pulse. Afterward, a control for shifting the above state to a normal servo operation (APC + AFC control) is performed after compulsorily restarting the capstan 2 in the prescribed timing from a head switching pulse. By this method, irrespective of a tape phase under the stopping state, the tape phase immediately before the restart-up can be managed by the intermittent feed immediately after the start-up (start-up AFC control brake stop), and APC drawing in the run-up section is smoothly performed.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention relates to a magnetic recording/reproducing device such as a VTR, and in particular, to shortening the time from the magnetic tape stop state to the start of playback or recording. The present invention relates to a magnetic recording/reproducing device.

(Prior art) In a magnetic recording/reproducing device such as a VTR, a rotating head performs recording.
- The capstan servo loop is configured to accurately trace over the rack.

FIG. 5 is a capstan servo block diagram in a steady state in a conventional magnetic recording/reproducing device.

In this figure, a capstan motor 1 rotates a capstan 2 to drive a magnetic tape 3.

This capstan motor 1 is driven by a drive signal supplied from a motor driver 4. A frequency generator (hereinafter referred to as C, FG) 5 disposed around the capstan motor 1 outputs a detection signal based on the rotation of the capstan motor 1. After the detection signal is amplified by the C, PG amplifier 6, it is supplied to the Schmitt circuit 7, which shapes the waveform and outputs the C, FG.
Outputs pulses. A speed detection circuit (hereinafter referred to as a C, AFC circuit) 8 outputs a DC voltage (C, AFC signal) proportional to the frequency of the C, FG pulse, and supplies it to one (-) input terminal of a mix amplifier 9. The mix amplifier 9 includes an operational amplifier 10 and a filter 11 connected to its output terminal and (-) input terminal.

On the other hand, the CTL pulse reproduced from the magnetic tape 3 by the control head (hereinafter referred to as CTL head) 12 is CT
After being amplified by the L amplifier 13, the waveform is shaped by the Schmitt circuit 14 and input to the phase comparator circuit (hereinafter referred to as the C, APC circuit) 15, where the phase is compared with the capstan reference signal of the vertical period. Phase comparison output (hereinafter referred to as C
, APC output) are smoothed by a lag filter 16 and then applied to the other input terminal of the mix amplifier 9. In the mix amplifier 9, the C, AFC signals and the C
, APC outputs are mixed and given to the motor driver 4 as a capstan control signal for controlling the rotational frequency and phase of the capstan motor 1. The motor driver 4 drives the capstan motor 1 based on the control signal. This servo loop causes the capstan motor 1 to rotate at a constant speed.

By the way, if you pause the tape during recording and then start recording again, you need to change the recording pattern and CTL to avoid distortions in the picture or audio at the seams when you play back that part later. Signal 3! It is necessary to maintain continuity before and after.

Therefore, in continuous recording, - after recording on a fishing boat, -
The tape is first rewound, and then the tape is driven in the normal rotation direction less than the rewound direction, thereby stopping the tape, that is, entering a recording standby state. After a certain amount of time, recording starts again.

Here, the reason why the rewind amount is greater than the forward rotation amount is because the capstan servo is applied during the period from when the recording standby state is released and the capstan is started until when recording starts, and The reproduction CTL pulse and the recording CTL to be recorded from now on
This is to provide a so-called run-up section (referred to as an assembly section m1) for performing phase matching of pulses.

In assemble mode, the rotary cylinder phase control system (cylinder APC system) is based on the vertical synchronization signal as in the recording mode, but the capstan phase control system (C, APC system)
is controlled to put the CTL pulse in a reproduction state and to align the phase of the reproduction CTL pulse with the recording CTL signal generated based on the vertical synchronization signal.

Note that even in the case of transitioning from playback mode to stop and then to playback mode, a run-up section is provided, the capstan servo is applied, and after the servo is stabilized, the playback image is output. That is, in playback mode,
The assemble period is provided to match the phase of the reproduced CTL pulse with a signal created based on a vertical synchronization signal that serves as a reference for the rotating cylinder system.

When transitioning from recording to stop, - In boat fishing, C and FG pulses are counted for the purpose of controlling the amount of rewind and forward rotation, but the C and FG pulses are based on the tape phase, that is, the CT on the tape.
Since it is completely unrelated to the L pulse, CTL is
The position of the CTL pulse relative to the head becomes undefined.

Furthermore, when transitioning from playback to stop, the position of the CTL pulse is, of course, undefined because the playback is stopped by inertia.

Furthermore, even if the phase of the CTL pulse could be controlled during the stop state, since the pinch roller is separated from the capstan during the stop state, tape slack may occur, resulting in inaccurate control.

Therefore, when starting the capstan from this stopped state,
Depending on the phase of the regenerated CTL pulse, C, APC
may be out of the pull-in range.

Figure 6 shows the CTL pulse phase and C in the conventional example shown in Figure 5.
, APC output is an explanatory diagram showing the relationship between (a),
(b) shows different static states of the CTL pulse position relative to the CTL head. When starting from the tape stationary state shown in FIG. 6(a), the phase of the reproduced CTL pulse is earlier than the reference signal (C, trapezoidal wave for APC phase comparison), the C, APC output becomes low level, The charge on capacitor C of lag filter 16 will decrease. Further, when starting from the tape stationary state shown in FIG. 6(b), the phase of the reproduced CTL pulse is slower than the reference signal, the CAPC output becomes high level, and the charge of C of the lag filter 16 increases.

FIG. 7 shows the C and APC outputs in the run-up section, where the horizontal axis shows time t and the vertical axis shows the C and APC outputs after smoothing by the lag filter 16.

(a) and (b) are respectively (a) and (b) in Figure 6.
It corresponds to b). After starting the tape, the APC approaches the final target value (center value) from the low level in (a), and (
In b), the APC is approaching the final target value from a high level.

In the NTSC system, the C, APC loop has a low sampling frequency (CTL pulse reproduction frequency) of about 30 H7, so it is often interpolated in series with a lag filter to improve the stability of the loop.

Due to this sampling frequency and the time constant of the lag filter, the response time from the state where APC is off to the time when it returns to a steady state is quite long. Therefore, the approach period takes into account the response time of this C, APC loop. Currently, it is necessary to set the interval to be a little longer (approximately 1.5 seconds in time), assuming that the APC is greatly disturbed.

(Problem B to be solved by the invention) In this way, in the conventional magnetic recording/reproducing device, when transitioning from the stopped state to the regeneration or recording mode, the phase of the CTL pulse detected immediately after the capstan is activated is Therefore, it was necessary to set the time (run-up section) until the actual recording and playback state starts to be longer in consideration of the variation in APC pull-in time. Once the APC was severely disrupted, it took more than one second to recover.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording and reproducing device that can minimize the pull-in time of the capstan APC when transitioning from stop to regeneration or recording mode, and can shorten the run-up section as much as possible. .

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a method for controlling the drive of a capstan motor so that the rotary head can correctly trace the recording l/rack on the magnetic tape during recording and playback. In a magnetic recording and reproducing device that sometimes controls the running of a magnetic tape, when transitioning from stop mode to playback or recording mode, first perform intermittent forwarding with only AFC applied (i.e., only AFC control after forced startup), In that state, CTl-
After detecting the pulse, apply the capstan brake at a predetermined timing to temporarily stop the capstan, then forcefully start the capstan again at a predetermined timing from the head switching pulse, and then perform normal servo operation (APC + AFC control). ).

(Function) According to the above means, regardless of the tape phase in the stopped state, the tape phase immediately before restart can be managed by intermittent feeding immediately after startup (start → AFC control → brake → stop), and the APC in the run-up section can be controlled. Retraction is performed smoothly, l.
-In terms of total time, the time it takes to play back an image and start recording is shorter than before.

(Example) Examples will be described with reference to the drawings.

As mentioned above, the present invention is basically based on control of the stop position of the tape and timing control at the time of starting.
The intermittent still-throw system, which is a well-known technology, can be applied almost as is. Therefore, one embodiment of a servo system according to the present invention using an intermittent still-throw system will be described below with reference to the drawings.

FIG. 1 shows a servo block diagram based on the present invention. In this figure, the same parts as in FIG. 5 are given the same reference numerals. Capstan motor 1° Capstan 2. Magnetic tape 3. Motor driver 4, frequency generator 5. C,F
G amplifier 6, Schmitt circuit 7, 14. C. AFC circuit 8. Mix amplifier 9 (op amp 10 and filter 1
1).

CTL head 12. CTL amplifier 13. C. APC circuit 15. The lag filter 16 is the same as that shown in FIG. 5. In this embodiment, a switch circuit 17 is inserted after the mix amplifier 9 in the cab scan servo loop, and the output end of the mix amplifier 9 is connected to one input of the switch circuit B17. The terminal a is connected to the other input terminal of the switch circuit 17 so that a starting voltage or a brake voltage can be appropriately applied from the bias circuit 18, and the output of the switch circuit 17 is inputted to the motor driver 4. The system control circuit controls the input switching of the switch circuit 17 based on the reproduction CTL pulse, the reproduction COFG pulse, and the head switching pulse synchronized with the rotation of the cylinder.

FIGS. 2 and 3 show a schematic timing chart and head/race diagram of the present invention from stop to recording, which is based on intermittent still slow operation using a wide single 2 head dedicated to the standard mode (referred to as SP mode).

In Figures 2 and 3, (a) is the herad switching pulse, (b) is the tape speed (rotational frequency is converted into voltage), and (C) is the capstan control voltage (d).
is the CTL pulse. Further, (e) shows a head trace diagram, and (f) shows a tape running mode.

During intermittent slowing, only the positive pulse side indicating the tape phase is used for the CTL pulse, so it is necessary to waveform shape the reproduced CTL signal by threshold level shifting, forced inversion processing, or the like. The above CTL pulse (d) is a pulse after waveform shaping. Furthermore, in the head trace diagram in (e), the shaded portions indicate the tracks of the A and B azimuths that are reproduced in response to the head switching pulses A and H in (a).

First, as shown in FIG. 2, intermittent feeding (forced start->AFC control->brake->stop) is performed - times on the tape stopped at an arbitrary tape phase.

Note that the tape phase at the time of stopping is the mechanical position of the CTL pulse with respect to the CTL head.

In other words, after a certain period of time T1 has passed after forced activation (switch 17 is set to b side and bias voltage is set to Vl), switch 1
7 to the a side and the servo system is controlled only by AFC (APC is fixed). If a CTL pulse is detected in this section,
After detection, brake (switch 17) is applied at a predetermined timing TS.
b III and bias voltage V2) to stop the operation. Depending on the mechanical load, motor characteristics, etc., it may not necessarily be Vl-V2. Note that the stop in this case is a temporary stop state (PAUSE) in which the pinch roller is not separated from the capstan shaft.

Now, after stopping at -, as shown in Figure 3, the servo system is immediately set to playback mode (if the next mode is playback) or assemble mode (if the next mode is record), and then the predetermined head switching pulse is activated. After forcing the capstan to start again with timing TK, switch to normal servo mode (A
PC+AFC control). It is clear that there is no need to particularly consider the phase relationship with the head switching pulse regarding the timing of the first forced activation during intermittent feeding.

This will be explained in more detail below.

In Fig. 2, in order to ensure a variable range of the time TS from CTL pulse detection to brake timing (that is, slow tracking margin), the constant speed section is set at 2/3 the speed of normal SP mode playback. This shows the case where AFC is applied. CTL pulse detection timing after startup is C
Although it depends on the shift amount of the mechanical position of the TL head, the second
The figure and FIG. 3 show the case where the shift amount is zero.

Therefore, the timing at which the CTL pulse is detected is the intersection M1 of the straight line AA' connecting the head trace lower end line HH' and the lowest end of the A azimuth track to be reproduced.

In this way, intermittent feed is performed immediately after starting from a stopped state, but when the final mode is "record", the slow tracking amount Ts is fixed at the center value, and after braking, the servo is immediately turned on as shown in Figure 3. Change the system mode to assemble mode and restart.

In addition, when the final mode is "playback", it is necessary to link the slow tracking iTS with the tracking amount Tp during playback, so the microcomputer calculates both and adjusts the tracking amount during other recording and playback. Even if you have made changes, you should be able to deal with it. After braking in "Regeneration", immediately switch to Regeneration mode and restart.

In any case, if the capstan is forcibly started based on the timing Tk of the head switching pulse (a) in the same way as in the transition from intermittent slow → (still) → playback, the trace state will be almost normal at point M2 where the CTL pulse is detected. (Diary playback section). Therefore, disturbances and fluctuations when the capstan APC is retracted are minimized, and the phase is smoothly locked.

FIG. 4 shows an example of C and APC outputs in the run-up section in the above embodiment. C, APC output shows the output after smoothing by the lag filter 16.

In the run-up section, first the C, APC output is fixed at the center value and is driven intermittently, and then the APC is driven, so that the C, APC output converges to the final target value, the center value, with only a slight initial fluctuation. can do. Therefore, it is possible to shorten the period from the start of run-up to the start of playback image or recording.

[Effects of the Invention] As described above, according to the present invention, the pull-in response of the capstan APC is improved in the run-up section when transitioning from stop to regeneration or recording mode. This makes it possible to speed up the playback output timing and timely recording.

[Brief explanation of the drawing]

FIG. 1 is a servo block diagram of a magnetic recording/reproducing device according to an embodiment of the present invention, and FIG. 2 is an intermittent drive timing chart and head trace diagram from start to stop based on the present invention.
Fig. 3 is a timing chart and head trace diagram from restart to recording based on the present invention, Fig. 4 is an explanatory diagram showing an example of APC output in the run-up section based on the present invention, and Fig. 5 is a conventional magnetic recording/reproducing device. Fig. 6 is an explanatory diagram showing the relationship between CTL phase and APC output in a conventional magnetic recording/reproducing device, and Fig. 7 is a capstan servo block diagram in a steady state in a conventional magnetic recording/reproducing device.
FIG. 3 is an explanatory diagram showing an example of C output. 1...Gear bustan motor, 2...Capstan,
3...Magnetic tape, 4...Motor driver 5...
Frequency generator, 8... Speed detection circuit, 9... Mix amplifier, 12... CTL head, 15... Lag filter, 17... Switch circuit, 18... Bias circuit, 19... System control circuit.

Claims (1)

[Claims] A magnetic recording and reproducing device that controls the running of a magnetic tape during recording and reproducing so that a rotary head can correctly trace a recording track on the magnetic tape by driving and controlling a capstan motor, FG pulse generation means for generating FG pulses based on the rotation of the capstan motor; speed detection means for detecting the FG pulses and obtaining a voltage proportional to the rotational speed; and a CTL pulse with a vertical period recorded on the magnetic tape. CTL pulse reproducing means for reproducing, comparing the phase of this CTL pulse with a reference signal of vertical period,
a phase detection means for obtaining a voltage according to the phase difference; and a rotational frequency and phase of the capstan motor during constant speed running based on the speed detection signal from the speed detection means and the phase detection signal from the phase detection means. a capstan control signal generating means for generating a capstan control signal for controlling the capstan motor; and a switching device for switching between this capstan control signal and a control signal for starting and stopping and supplying the same to the driving means for the capstan motor. When transitioning from stop mode to playback or recording mode, start the capstan,
After a certain period of time has elapsed, only speed control is performed based on the speed detection signal (the phase detection signal is fixed at a predetermined value), and after detecting a CTL pulse by the CTL pulse reproducing means in this control period, capping is performed at a predetermined timing. The capstan is temporarily stopped, and then the capstan is immediately restarted at a predetermined timing from a switching pulse indicating phase information of the rotating head, and then the switching means is switched to perform normal control based on the speed detection signal and the phase detection signal. What is claimed is: 1. A magnetic recording and reproducing apparatus comprising: a control means for causing the transition to occur.