JPS6110392Y2 - - Google Patents

Description

[Detailed description of the invention] One field or one frame of a video signal is recorded in a circular track on a disc-shaped magnetic sheet, and a still image signal is obtained by repeatedly reproducing this circular recording track. A recording/playback device that does this is known.

In this case, when recording one frame on a circular track, if the video signal is moving and the content is different between the even field and the even field, there is an inconvenience that the reproduced still image recording will be blurred. For this reason, one field is generally recorded on a circular track.

By the way, as shown in Figure 1, when recording one field along a circular track,
Since one field consists of 262.5 horizontal periods, in the reproduced still image signal, the interval between horizontal synchronization signals is 1/2 of the horizontal period for each field, and this reproduced still image signal is supplied to the monitor receiver. When this happens, the problem arises that horizontal synchronization is disturbed.

For this reason, as shown in FIG. 2, it is conceivable to record a predetermined integer horizontal period, for example, 262 horizontal periods, which is slightly shorter than one field or slightly longer than one field, on a circular track. In this case, since the interval between the horizontal synchronization signals in the reproduced still image signal is always constant, the horizontal synchronization will not be disturbed when the reproduced still image signal is supplied to the monitor receiver.

However, in this way, one
In order to record 262 horizontal periods, which are slightly shorter than one field, the magnetic sheet must be rotated once in 262 horizontal periods, which are slightly shorter than one field. On the other hand, when obtaining a still image signal by repeatedly reproducing this annular recording track, the magnetic sheet is
It is necessary to rotate at the speed of one rotation in the field. Of course, one horizontal period of the reproduced still image signal is slightly longer than the original 63.5 μsec.

The following methods can be considered to easily achieve this. This is done by synchronizing the magnetic sheet with the vertical synchronization signal in the input video signal and rotating it at a speed of one rotation per field, and then applying a disturbance to the speed control loop to rotate the magnetic sheet. This changes the speed temporarily, and in this way, the sheet will make one revolution in 262 horizontal periods during the change, and therefore, in this section, it will make a circular track for 262 horizontal periods. can be formed and recorded.

In this case, a still image signal can be obtained by repeatedly reproducing the annular recording track immediately after recording. However, the effect of the disturbance, that is, the change in the rotational speed of the sheet, does not disappear immediately after recording for 262 horizontal periods as described above, and continues for some time thereafter. Therefore, when a still image signal is extracted immediately after recording, the period of the vertical synchronization signal in the still image signal changes at first, disrupting the vertical synchronization and making the screen of the monitor receiver unsightly.

In consideration of these points, this invention is based on the above-mentioned recording section and the section where the influence of the subsequent disturbance is still continuing, that is, the rotation speed of the sheet that includes the recording section is one rotation per field. In a predetermined section where the speed is not high, the reproduced still image signal is not taken out from the annular track.

FIG. 3 is an example of this, where the input video signal from the input terminal 1 is supplied to the vertical synchronization signal separation circuit 11, and the vertical synchronization signal S _V (A in FIG. 5) from the input video signal is taken out. 12 to obtain a signal synchronized with the vertical synchronization signal S _V , which is phase-compared with the pulse obtained by the detector 23 when the magnetic sheet 21 reaches a predetermined rotation angle position in the phase comparator 13. The comparison output voltage is passed through the adder 14, and is then passed through the amplifier 15 to the sheet 21.
As a result, the sheet 21 rotates at a speed of one rotation per field in synchronization with the vertical synchronization signal S _V in the input video signal. The input video signal is supplied to terminal A of the switch circuit 31, and is subjected to FM modulation, for example, by a modulator 33, and then supplied to the switch circuit 34.

In this state, by momentarily turning on the switch 41 (FIG. 5B), the flip-flop circuit 43 is brought into the set state. When the flip-flop circuit 43 enters the set state at time _t1 , its output S _C (FIG. 5C) becomes "1", the switch circuits 31 and 32 are respectively switched to the terminal A side, and the input video signal is output to the monitor receiver. 51 and is displayed on the screen, and the sheet 21
It is now possible to record signals. When the output S _C of the flip-flop circuit 43 becomes "1",
Since the lamp 44 lights up, it can be confirmed that the recording is possible.

In this state, that is, with the output _SC of the flip-flop circuit 43 at "1", the switch 42 is momentarily turned on while watching the screen displayed on the monitor receiver 51, for example (FIG. 5D).
When the switch 42 is turned on while the output S _C of the flip-flop circuit 43 is in the "1" state, the set-priority type flip-flop circuit 45 is in the set state, and its output S _E (FIG. 5E) becomes "1". Then, the flip-flop circuit 45 is reset by the vertical sync signal S _V immediately thereafter, and the output S _E is inverted to "0". When the output S _E of the flip-flop circuit 45 falls, the set-priority type flip-flop circuit 46 is in the set state, and its output S _F (FIG. 5F) becomes "1", and the flip-flop circuit 46 is reset by the vertical sync signal S _V one field later,
The output _SF is inverted to "0".

Then, the output S _F of the flip-flop circuit 46 is added as an external pulse voltage to the comparison output voltage from the phase comparator 13 in the adder 14, and is supplied to the motor 22 through the amplifier 15, and the rotation speed of the seat 21 is adjusted. change temporarily.
That is, as shown in _FIG .
At t ₂ , the speed changes, for example, first increasing, and then conversely decreasing. Then, by appropriately selecting the magnitude of the external pulse voltage, etc., the sheet 21 instantaneously rotates once in a horizontal period of 262 from time t ₃ , one field after time t ₂ , as shown in the figure. I come to do it.

At this point _t3 , the flip-flop circuit 4
When the output S _F of 6 falls, the flip-flop circuit 47 of the set priority type enters the set state, its output S _G (G in Fig. 5) becomes "1", and the flip-flop circuit 47 is activated by the vertical synchronizing signal S _V after one field. is in a reset state, and the output S _G is inverted to "0". Then, during the period when the output S _G of the flip-flop circuit 47 is "1", the switch circuit 34 is turned on, and the modulated video signal for one field is taken out, and is supplied to the head 24 through the amplifier 35 and the switch circuit 32. and recorded on the sheet 21.

Therefore, as shown in FIG. 2, 262 horizontal periods are recorded on the sheet 21 forming a 360° track.

The point at which recording ends, one field after time t ₃
Even when t ₄ is reached, playback output is not immediately extracted. In other words, it is predicted how long it will take from time _t2 for the sheet 21 to return to the state of rotating at a speed of one rotation in one field after the influence of the disturbance disappears. t ₄
When the output S _G of the flip-flop circuit 47 falls, the monostable multivibrator 48 is triggered, and its output S _I (FIG. 5 I) changes from the time t ₄ to the above predicted time or somewhat later. It remains "1" for a period up to time _t5 , and when the output S _I falls at time _t5 , the flip-flop circuit 43 enters the reset state and the output S _C (FIG. 5C) becomes "0", and the switch circuit 31 and 32
Both are switched to the terminal B side.

Therefore, even if the annular track is repeatedly reproduced in the head 24 from time t ₄ and a reproduced still image signal is obtained, this signal is not extracted from time t ₄ to time t ₅ , and after time t ₅ . The signal is taken out from the switch circuit 32, supplied to the demodulator 37 through the reproducing amplifier 36 for demodulation, and supplied to the monitor receiver 51 through the switch circuit 31, where it is displayed on its screen.

FIG. 4 shows another example of a recording fixed magnetic head 25.
There are a fixed magnetic head 26 for reproduction, and two monitor receivers 52 and 53.

The input video signal is constantly supplied to the monitor receiver 52 and displayed on its screen, and the switch 41 and flip-flop circuit 43 of the example shown in FIG. Similar records will be made. The reproduced still image signal obtained by repeatedly reproducing the annular recording track in the head 26 is directly transferred to the reproduction amplifier 2.
6 to a demodulator 37 for demodulation, and then to a monitor receiver 53 via a muting circuit 38.
is supplied to

In this example, when the output S _E of the flip-flop circuit 45 falls at time t ₂ , the monostable multivibrator 68 is triggered, and its output S _J (FIG. 5 J) changes from time t ₂ to the above-mentioned time t. During _this period, the reproduced still image signal is muted by the muting circuit 38 so that it is not supplied to the monitor receiver 53.

As shown in FIG. 5H, the sheet 21 may make one rotation in 263 horizontal periods after time _t4 , so 263 horizontal periods form an annular track and are recorded during this period. It may be done as it is done.

According to this invention, by applying a disturbance to the speed control loop of the sheet, the sheet is instantaneously made to make one rotation in an integer horizontal period, and during this period, an integer horizontal period of the video signal is used to form an annular track. In a recording device, the reproduction output is not taken out in the section where the rotation speed of the sheet does not reach the speed of one revolution in one field, and the reproduction output is taken out after the sheet rotation speed returns to the speed of one revolution in one field. There is no possibility that the vertical synchronization will be disrupted at the beginning of the playback output, resulting in an unsightly screen.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining the case where an annular track is formed on a magnetic sheet to record a video signal, FIGS. 3 and 4 are a system diagram of an example of this invention, and FIG. The figure is a waveform diagram for explaining the same. 1 is a video signal input terminal, 11 is a vertical synchronizing signal separation circuit, 12 is a synchronous oscillator, 13 is a phase comparator,
21 is a magnetic sheet, 22 is a driving motor thereof, 3
3 is a modulator, 37 is a demodulator, 38 is a muting circuit, 43, 45, 46 and 47 are flip-flop circuits, 48 and 68 are monostable multivibrators, and 51 to 53 are monitor receivers.

Claims (1)

[Scope of utility model registration request] While the magnetic sheet is rotating at a speed of one rotation in one field in synchronization with the vertical synchronization signal in the input video signal, by applying a disturbance to the speed control loop, the magnetic sheet instantaneously rotates in one field. One rotation is made in a predetermined integer horizontal period that is slightly shorter than or slightly longer than one field, and during one rotation in this predetermined integer horizontal period, the input video signal for the predetermined integer horizontal period is In a device in which a signal is recorded by forming an annular track on the magnetic sheet, in a predetermined section where the rotational speed of the magnetic sheet, including the recording section, does not reach the speed of one rotation in one field, the signal is recorded from the annular track. A recording/reproducing machine using a rotating magnetic sheet, which prevents the reproduction output from being taken out, and allows the reproduction output to be taken out in a section where the rotational speed of the magnetic sheet thereafter becomes one rotation per field.