JPS6058537B2 - magnetic recording and playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a rotating magnetic head in a magnetic recording/reproducing device or the like.

In general, in an oblique scanning type magnetic recording/reproducing device using a plurality of rotating magnetic heads, one field of the video signal or an integral multiple thereof is tracked diagonally with respect to the tape traveling direction by one scan of each rotating head. , and then play it back.

In such a system, a plurality of rotating heads are arranged at equal angular intervals on the circumference of one rotating body (for example, in a two-rotating head system, the rotating heads are arranged at 1800 degrees of rotation on the circumference of one rotating body). Video tracks equal to the number of heads are sequentially recorded during one rotation of the rotating body (to which the heads are attached).

At this time, the rotational phase of the head is controlled so as to be synchronized with the video signal, but for this purpose, the rotation detection pulse of the head and a pulse obtained by frequency-dividing the vertical synchronization signal in the video signal (for example, in a two-head system, Vertical sync signal 11
The rotation control output is obtained by comparing the phase with the pulse whose frequency is divided by 2). The present invention relates to rotational control of a rotary head in such a magnetic recording/reproducing apparatus, and in particular provides means for quickly achieving synchronization during recording.

An example of the configuration of a rotation control system of a conventional magnetic recording and reproducing apparatus of this type is shown in FIG.

FIG. 1 is a block diagram of the circuit of a conventional device plus an illustration of the actual state of the mechanism. In the figure, 1 is a magnetic tape;
2 and 3 are rotary heads, 4 is a rotary head motor, 5 is a magnet piece, 6 is a pickup coil, 7 and 8 are magnetic tapes 1
Video track on top, 9 is capstan motor, 10
is an input terminal, 11 is a synchronous separation circuit, 12 is a 112 frequency divider circuit, 13 and 14 are respective selector switches, 15 is an amplifier, 16 is a control head, 17 is a control signal, 18 is a phase comparator, and 19 is a low frequency Filter, (hereinafter referred to as L
20 is a voltage controlled oscillator (hereinafter referred to as VCO), 21 is an amplifier, 22 is a phase shifter, and 23 is a rotating body. Next, the connection will be explained with reference to FIG. The magnetic tape 1 is fed by a capstan motor 9 at a constant speed in the direction of the arrow in the figure. The output side of the synchronous separation circuit 11 connected to the input terminal 10 is connected to the 112 frequency divider circuit 12, and the output side is branched, and one side is connected to the changeover switch 13.
The other one is led to the changeover switch 14. Further, a contact C of the changeover switch 13 is connected to a phase comparator 18. Further, a contact C of the changeover switch 14 is connected to the control head 16. A contact P of the changeover switch 14 is connected to an amplifier 15, and its output side is connected to a contact P of the changeover switch 13. Next, the phase comparator 18 is connected to LPF19. Furthermore, the output side of this LPF19 is connected to VCO2O, the output side thereof is connected to an amplifier 21, and the output side of this amplifier 21 is connected to the rotary head motor 4. A rotary head 2 for recording video signals is attached to the peripheral edge of the rotary body fixed to the shaft of the rotary head motor 4.
3 and a rotation detection magnet piece 5 are provided. In order to obtain a signal from this magnet piece 5, a pickup coil 6 is placed at a predetermined position, and is connected so that the pickup output accompanying rotation of the rotary head is applied to a phase shifter 22. The output of the phase shifter 22 is connected to the phase comparator 18. Next, the operation of the conventional control system connected and configured as described above will be explained. Note that FIG. 2 shows the output signals of the main parts of FIG. 1 with respect to time. First, during recording, the changeover switches 13 and 14 are each turned toward the R side contact. Now, the video signal is applied to the input terminal 10, and a 60 Hz vertical synchronization signal is separated from the video signal by the synchronization separation circuit 11 as shown in FIG. 2a. This vertical synchronizing signal is then frequency-divided by a 1'2 frequency divider circuit 12 into a 30 Hz signal as shown in FIG. 2b.
This 30Hz signal. is applied to the phase comparator 18 via the changeover switch 13 and simultaneously applied to the control head 16 via the changeover switch 14, and is recorded as a control signal 17 on the end of the tape 1. Further, as the rotary heads 2 and 3 rotate, a video signal track 7 is formed by the rotary head 2 and a video signal track 8 is formed by the rotary head 3 on the tape 1, respectively. Further, a rotation detection pulse signal is induced in the pickup coil 6 by the rotation detection magnet piece 5 in synchronization with the rotation of the head, and this signal output is given a phase shift by the phase shifter 22, as shown in FIG. After becoming the rotation detection pulse φ2 as shown in FIG. 2, it is applied to the phase comparator 18.
This phase comparator 18 uses the rotation detection pulse φ2 from the pickup coil 6 that has undergone the phase shift and the rotation detection pulse φ2 as described above.
The phases of the vertical synchronizing signal φ1 divided by 2 are compared, and the output is generated according to the phase difference 0=φ2−φ1 between the phase φ1 of the vertical synchronizing signal divided by 112 and the phase φ2 of the rotation detection pulse. , this), the output E of this phase comparator 18 is expressed as, for example, the formula E=KsinO, where k is a constant, -180 example 0 x 18
Set it to 0. Output E is connected to VC via LPF19
Added to O2O. In this VCO2O, the above LPF
The oscillation frequency is changed according to the magnitude and polarity of the output of I9, and the output is applied to the motor 4 via the amplifier 21 to control its rotation. Now, if we assume that when the output E of the phase comparator 18 is zero, the rotary head is synchronized with the vertical synchronization signal divided by 112, then in the state of Fig. 2, the rotation detection pulse indicated by c will continue until θ=0. A rotation control action is performed,
A synchronized state is achieved when the pulse phase is as shown by the dotted line c.

It can be easily inferred from this explanation that the more the vertical synchronization signal divided by 112 and the rotation detection pulse are out of phase, the more θ=
It takes time for the control action to reach zero. For example, θ is 1
The longest time is required if the control operation starts at 80 or around -180. As described above, diagonal video tracks 7 and 8 are sequentially formed every half rotation of the rotary head, and by appropriately adjusting the phase shifter 22, a vertical synchronization signal is recorded at the start end of the video track.

The control signal is the vertical synchronization signal divided by 1'2, and as can be seen from the above explanation, this is recorded as one pulse exactly corresponding to one rotation of the rotating head.) Become.

Next, when playing back the video signal recorded in this way,
The changeover switches 13 and 14 are each switched to the P side contact.

The control signal recorded on one end of the magnetic tape 1 is reproduced by the control head 16, and the changeover switch 1
4, the signal is amplified by an amplifier 15, and further applied to the phase comparator 18 via a changeover switch 13.
The other input of the phase comparator 18 is applied after the rotation detection pulse passes through the phase shifter 22, as described above. The operations after the phase comparator 18 are the same as those during recording described above.
As described above, the rotary heads 2 and 3 rotate in synchronization with the control signal 17, and the rotary head 2 moves on the video track 7.
The rotary head 3 is controlled to run correctly on the video track 8. In the device that records and plays back as described above,
If the video track is not formed correctly, a normal playback signal cannot be obtained.

To this end, during recording, it is necessary for the rotary head to rotate in synchronization with the vertical synchronization signal as quickly as possible. In view of these points, it is an object of the present invention to provide a magnetic recording and reproducing apparatus that speeds up synchronization during recording.

The present invention will be explained below with reference to the drawings.

FIG. 3 is a block diagram of a circuit showing an embodiment of the magnetic recording/reproducing apparatus according to the present invention, together with an explanatory diagram of the actual state of the mechanism. The same reference numerals in FIG. 3 as in FIG. 1 indicate the same or corresponding parts. 26 is a gate circuit, which is inserted in place of the 112 frequency divider circuit 12 in FIG.

Further, 24 is a pulse delay circuit composed of, for example, a delay multiplier, and is inserted between the phase shifter 22 and the phase comparator 18. Furthermore, 25 is a gate pulse generation circuit composed of, for example, a multi-channel circuit, and the timing is adjusted so that the output pulse of the pulse delay circuit is generated at a time corresponding to approximately the center of the gate pulse.
This gate pulse generation circuit 25 is inserted between the phase shifter 22 and the gate circuit 26. Others 1st
Components with the same numbers as those in the drawings will not be described. Next, the operation of the magnetic recording and reproducing apparatus configured as described above will be explained.

Note that FIG. 4 shows the output signals of the main parts during the operation of FIG. 3 versus time. During recording, the changeover switches 13 and 14 are each turned to the R side contact.

Adding the video signal from the input terminal 10 to the synchronization separation circuit 11,
60Hz vertical synchronization signal is separated. On the other hand, as the rotary heads 2 and 3 rotate, the rotation detection magnet piece 5 induces a pulse in the pickup coil 6 every rotation, and this signal is given a phase shift by the phase shifter 22 to generate a rotation detection pulse. becomes. This rotation detection pulse is applied to both the delay circuit 24 and the gate pulse generation circuit 25. The output pulse width of the gate pulse generation circuit 25 is set to a width approximately equal to the repetition period (116') of the vertical synchronization signal, and the rotation detection pulse is delayed and generated by the delay circuit 24. The timing of the delayed pulse corresponds to approximately the center of the output pulse of the gate pulse generating circuit 25. To illustrate this diagrammatically, FIG. 4 a shows a gate pulse and b shows a delay pulse.
The gate pulse obtained from the gate pulse generation circuit 25 is applied to the gate circuit 26, through which the output of the synchronization separation circuit 11 passes during the gate pulse period.
That is, as shown in FIG. 4C, among the vertical synchronization signals output from the sync separation circuit 11, only the vertical synchronization signal that falls within the gate pulse period becomes the output of the gate circuit 26 and is obtained as shown in FIG. 4D. In the figure, vertical synchronization signals cm1, c-2, .
. . . Vertical synchronization signal cm within the gate pulse period
Only 1, c-3, c-5, . . . pass. These passing pulses are applied to the phase comparator 18 via the changeover switch 13, and at the same time are applied to the control head 16 via the changeover switch 14, and are recorded as a control signal 17 on the end of the tape 1. Further, as the rotary heads 2 and 3 rotate, a video signal track 7 is formed by the rotary head 2 and a video track 8 is formed by the rotary head 3 on the tape 1, respectively. Further, in the phase comparator 18, the phase of the delayed pulse, that is, the delayed pulse of the rotation detection pulse (FIG. 4b) and the vertical synchronization signal obtained from the gate circuit 26 are compared, and the output thereof is applied to the VCO2O via the LPF19. . In this VOC2O, the oscillation frequency is changed according to the magnitude and polarity of the output of the LPF19, and the output is passed through the amplifier 21 to the motor 4.
In addition to controlling its rotation. In this case as well, if we assume that the rotation is in a synchronous state at θ = 0 as in the example in Figure 1, when the recording mode is set, the initial state is -904 θ with respect to the delayed pulse in Figure 4C. Control is applied so that the rotary head is pulled into synchronization with the vertical synchronization signals cm1, c-3, .

Next, let us consider a case where the vertical synchronizing signals cm1, c-3, . . . are out of phase with respect to the delayed pulse by more than the above range. In this case, when you enter recording mode,
Vertical synchronizing signal cm1,c for the delayed pulse in Fig. 4c
-3, the initial state becomes, for example, as shown in FIG. 4e, which is outside the gate pulse period. However, since the other vertical synchronizing signal cm2, c-4 is within the gate pulse period, the vertical synchronizing signal cm2, c-4 is output from the gate circuit 26.
4,... are obtained. Therefore, the vertical synchronizing signals cm2, c-4, . As shown in FIG. 4, rotation control is performed so that .theta." and .theta."=0, and the rotary head is retracted in synchronization with the vertical synchronization signals cm2, c-4, . . . . At this time, of course, these vertical synchronizing signals cm2,
c-4, . . . are recorded at the end of the tape 1 as control signals. In conventional equipment, the vertical synchronization signal was first divided by 112 and then applied to the phase comparator, so this)
The initial phase difference .theta. between the signals to be compared is over a wide range of -1800 to 1180 signals, and if the initial phase difference between the two signals is large, it will take time for the rotary head to synchronize.

However, in this invention, as explained above, the vertical synchronizing signal that is closer in phase to the input pulse to the phase comparator obtained from the rotary head is selected and applied to the phase comparator, so the comparison is not made. The initial phase difference between the signals is −90〈0
+900, and the synchronization pull-in time becomes shorter. Therefore, regular video tracks 7 and 8 are recorded on the tape 1 within a short time, and disturbances in the reproduced video signal during reproduction are reduced. In the above explanation, for convenience, the phase comparator 1
Although the rotary head is assumed to synchronize with the vertical synchronization signal when the phase difference between the two input signals to 8 becomes zero, it is of course not limited to this, and in general, when θ=θo, the rotary head synchronizes with the vertical synchronization signal. If the setting is such that the time relationship between the delay pulse and the gate pulse is θ from the above.

It is only necessary to shift the setting by a time corresponding to . Furthermore, in the above explanation, the timing of the delayed pulse was set to be approximately at the center of the -gate pulse, but the output sensitivity curve for the input signal phase difference of the phase comparator may be asymmetrical with respect to the positive or negative phase difference. If the rotation control characteristics differ depending on whether the phase difference is positive or negative, the timing of the delay pulse may be set to be shifted from the above relationship, or the period of the gate pulse may be changed.

Furthermore, although the above description has been made regarding a two-rotary head type, it goes without saying that the present invention can be easily applied to magnetic recording and reproducing apparatuses generally equipped with a plurality of rotary heads.

As described above, the present invention has the effect of controlling the rotation of the rotary head to speed up synchronization with the vertical synchronization signal, thereby speeding up the recording of regular video tracks.

[Brief explanation of the drawing]

FIG. 1 is a block diagram and mechanism explanatory diagram showing an example of a conventional magnetic recording/playback device, FIG. 2 is a waveform diagram showing the main signals of FIG. 1, and FIG. 3 is an example of an embodiment of the present invention. FIG. 4 is a waveform diagram showing signals of the main parts of FIG. 3. In the drawing, 1 is a magnetic tape, 2 and 3 are rotating heads,
4 is a rotary head motor, 5 is a magnet piece, 6 is a pickup coil, 7 and 8 are video tracks, 9 is a capstan motor, 10 is an input terminal, 11 is a synchronous separation circuit, 12 is 1
2 frequency divider circuit, 13 and 14 are selector switches, 15 is an amplifier, 16 is a control head, 17 is a control signal, 18 is a phase comparator, 19 is a low-pass filter (LPF)
), 20 is a voltage controlled oscillator (■CO), 21 is an amplifier,
22 is a phase shifter, 23 is a rotating body, 24 is a delay circuit, 2
5 is a gate pulse generation circuit, and 26 is a gate circuit.

Claims (1)

[Claims] 1. In a rotary head type magnetic recording and reproducing apparatus equipped with a plurality of rotary heads, a means for separating a vertical synchronization signal in a video signal to be recorded and a rotation detection pulse for detecting the rotational phase of the rotary head are provided. means for generating a gate pulse having a constant phase relationship and a constant time width with respect to the rotation detection pulse; and a gate for extracting only a vertical synchronization signal within the gate pulse period in response to the gate pulse. and phase comparison means for comparing the phases of the rotation detection pulse and the extracted vertical synchronization signal, and controlling the rotation of the rotary head during recording based on the output of the phase comparison means. Features a magnetic recording and playback device.