JPS5823660B2 - magnetic recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing device for image signals using a rotating cylinder, and is aimed at preventing image disturbance during reproduction when recording is spliced during reproduction. This is the purpose.

During recording, the cylinder and capstan are phase-synchronized with the recording video signal, and a control signal corresponding to the vertical synchronization signal in the video signal or the rotational phase signal of the cylinder is recorded on the tape, and during playback, the cylinder is phase-synchronized with the reference signal. In the so-called capstan servo method, which controls the capstan so that the reference signal or the cylinder rotational phase signal and the reproduction control signal are synchronized in phase, when splicing to recording during reproduction,
The next time you play it back, the image will be distorted.

The present invention provides a frequency generator on a capstan shaft or a capstan motor, divides the output of this frequency generator by a frequency dividing circuit during recording, and adds the divided output to a phase comparator as a rotational phase signal. In addition to forming a capstan servo system during recording, the signal at the moment when all stages of the frequency dividing circuit return to the reset state is recorded on the magnetic tape as a recording control signal, and during playback, the output of the frequency generator is connected to the frequency dividing circuit. At the same time, a playback control signal is added to the frequency dividing circuit as a reset signal so that the playback control signal and the rotational phase signal obtained from the frequency dividing circuit approximately match, and when the state changes from playback to recording. In order to eliminate discontinuities in the signal applied to the phase comparator,
This prevents disturbances in the servo system.

This will be explained below with reference to the drawings.

FIG. 1 shows an example of a frequency dividing circuit used in the present invention to prevent discontinuity in the signal applied to the phase comparator during recording and reproduction.

In the figure, the output from the frequency generator is applied to the first stage clock terminal of a binary counter consisting of a JK flip-flop.

In the case of recording, since no playback control signal is applied, the moment when the Q terminal of the JK flip-flop in the final stage falls from the H level to the L level is when the capacitor C1 and resistor R1
The signal is differentiated by a differentiating circuit consisting of the following, and an H-level pulse is obtained at the collector of the transistor Trl, which is applied as a sample pulse to the phase comparator circuit.

During reproduction, since the reproduction control signal is applied as a forced reset pulse to each stage of the binary counter, a signal that substantially coincides with the reproduction control pulse is obtained as an H pulse at the collector of the transistor Tr1.

If the difference between the period of the playback control signal and the output frequency of the binary counter, that is, the frequency divider circuit when no reset pulse is applied, is sufficiently small, the phase of the sample pulse applied to the phase comparator circuit and the playback control signal during recording can be adjusted sufficiently. It can be matched.

Note that in addition to the binary counter, a frequency divider circuit having a built-in reset circuit and having an arbitrary division ratio can be used.

By using such a circuit, even if an unrecorded portion appears temporarily during playback, the capstan rotation phase signal will be automatically obtained, and the servo system will not be out of phase (the next When a recorded part appears, the retrieval is done very quickly.

FIG. 2 shows -fIl of a conventional magnetic recording/reproducing apparatus using such a frequency dividing circuit.

In the figure, a tape 1 is fed by a capstan 4 through a rotary cylinder 2 and a control head 3.

The cylinder 2 is rotated by a cylinder motor 5, and the capstan 4 is rotated by a capstan motor 8.

A pulse generator 6 and a frequency generator 7 are attached to the cylinder 2.

A frequency generator 9 is attached to the capstan motor 8.

From the input video signal 10, a vertical synchronization signal is extracted by a vertical synchronization signal separation circuit 11, and the vertical synchronization signal is extracted by a 1/2 frequency divider circuit 12.
This becomes a Hz pulse, which is applied as a reference signal to the phase comparators 15 and 19, and is recorded on the magnetic tape 1 by the control head 3 through the changeover switch 13.

The output of the pulse generator 6 is applied to a phase comparator 15, and the phase comparison output with a reference signal is applied to a drive circuit 16.

Further, the output of the frequency generator 7 is applied to the rotation speed detection circuit 14, this output is also applied to the drive circuit 16, and the output of the drive circuit 16 drives the cylinder motor 5.

The output of the Capstar 740 frequency generator 9 is applied to the rotation speed detection circuit 17 and the frequency division circuit 18.

The frequency dividing circuit 18 has a configuration as shown in FIG.
added to.

The output of the rotation speed detection circuit 17 and the output of the phase comparator 19 are applied to a drive circuit 20 to drive the capstan motor 8.

During reproduction, the reproduction control signal is applied as a tri-pulse to the frequency dividing circuit 18 through the changeover switch 13.

As described above, when switching from reproduction to recording, the output of the frequency dividing circuit 18 is connected continuously, and disturbances during reproduction can be prevented.

It is also possible to prevent the servo from coming off in the unrecorded portion during playback.

FIG. 3 shows a modification of FIG. 2, which is mostly the same as FIG.
8 is forcibly synchronized with the reproduction control signal, but the difference is that the reproduction control signal itself is added to the tracking shifter 21.

In this circuit, the output frequency of the frequency generator 9 is low, and the deviation at the transition between playback and recording can be tolerated. It can be used when there is a problem.

In this case, it is not possible to prevent the phase shift of the servo system in the unrecorded portion during reproduction.

If the width of the regeneration control pulse is wide and is equal to or more than one cycle of the output of the frequency generator 9, more preferable continuity can be obtained by shaping the width to be smaller.

The tracking shifter 21 is not placed on the output side of the frequency dividing circuit 18 (it can also be placed before the other input of the phase comparator 15).

FIG. 4 shows another example in which the circuit shown in FIG. 3 is partially modified.

In FIG. 4, the capstan rotational phase signal is directly applied to the phase comparator 19 during recording, and the reproduction control signal is applied to the phase comparator 19 through the tracking shifter 21 during reproduction.

Therefore, if the playback control signal is applied to the frequency dividing circuit 18 for generating the rotational phase signal as shown in FIGS. 2 and 3, discontinuity will occur at the transition from playback to recording. Instead, the phase comparison input signal passed through the tracking shifter 21 is applied to the frequency dividing circuit 18.

22 is a recording/reproduction changeover switch. If you are splicing tapes that you have recorded yourself or tapes that have been recorded on a fully compatible machine, the circuitry described above with respect to Figures 2, 3, and 4 will complete the process. It is possible to make various connections.

However, if splicing is performed on a tape in which the relative positions of the video track and control track are shifted on the tape pattern, there will be no servo disturbance at the joint between playback and recording, but the control The continuity of the signal is not maintained, and when this tape is played again, servo disturbances will be reproduced at the joints.

To prevent this, it is necessary to obtain the recording control signal not from the video signal but from a source that matches the playback control signal in phase.

5 and 6 show embodiments of the present invention, in which a monomulti 23 which is triggered at the falling edge of the output of the frequency divider circuit 18 is provided in the circuits of FIGS. 2 and 3 respectively, and this pulse as a control pulse with the selector switch 13
The control head 3 records on the tape 1 through the recording medium.

In this way, even when splicing onto a compatible tape, continuity of control pulses can be obtained and complete splicing can be achieved.

As long as the falling edge of the frequency dividing circuit 18 is recorded as a control pulse, the monomulti 23 may be of another type or may be omitted.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of -ψ1] of the frequency dividing circuit used in the present invention, Figure 2 is a block diagram of -flJ of a conventional magnetic recording/reproducing device, and Figures 3 and 4 are modified examples thereof. , FIG. 5 is a block diagram of one embodiment of the present invention, and FIG. 6 is a block diagram of another embodiment of the present invention. 1...Tape, 2...Cylinder, 3.
... Control head, 4 ... Capstan, 9 ... Frequency generator, 18 ...
- Frequency divider circuit, 19...phase comparison circuit.

Claims (1)

[Claims] 1 During recording, the cylinder and the capstan are phase-synchronized with the recording video signal, and during playback, the cylinder is phase-synchronized with the reference signal, and the capstan is synchronized so that the reference signal or the rotational phase signal of the cylinder and the playback control signal are phase-synchronized. In a capstan servo type magnetic recording and reproducing device that controls a stun, a frequency generator is provided on the capstan shaft or the capstan motor, and the output of the frequency generator is divided by a frequency dividing circuit, and the frequency of the frequency generator is divided by the frequency dividing circuit during recording. The signal at the moment when the circuit returns to the state in which all stages are reset is extracted, and this signal is added to the phase comparator either directly or through a phase shifter to control the capstan as a capstan rotational phase signal. The signal at the moment when the signal returns to the reset state is recorded on the magnetic tape as a recording control signal, and at the time of playback, the playback control signal is added to the frequency divider circuit as a reset signal, and the playback control signal and phase are output from the frequency divider circuit. 1. A magnetic recording and reproducing apparatus characterized in that the output of the frequency dividing circuit or a reproduction control signal is applied to a phase comparator directly or through a phase shifter to perform capstan control during reproduction.