JPH0369233B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording and reproducing device, and in particular, it sequentially switches four magnetic heads attached to a rotating body at equal angular intervals of 90° to record signals on a magnetic tape. record,
The present invention relates to a magnetic recording/reproducing apparatus which suitably switches the recording currents to the four magnetic heads and the reproduction signals from the four magnetic heads during reproduction.

Prior Art The present applicant has previously proposed, for example, in Utility Model Application No. 122921/1987, a magnetic recording/reproducing apparatus having a head arrangement as shown in FIG. In the figure, the diameter L of a rotary body 1 such as a rotary drum or a rotary plate is determined by the diameter L of a rotating body 1 such as a rotary drum or a rotary plate.A magnetic tape is spliced and wound over a little over 180 degrees, and two pieces of magnetic tape are attached at equal angular intervals of 180 degrees on the rotary body. The diameter M of the rotating body of the current 2-head helical scanning type VTR, which records and plays back with a video head, is selected to be 2/3 times larger, and the video is recorded and played back by a motor (not shown). It is rotated counterclockwise at a rotation speed related to the signal field frequency (for example, 45 rps). This rotating body 1 includes a recording/reproducing magnetic head (video head) A,
B, C and D are mounted and fixed at equal angular intervals of 90 degrees. Video heads A and C each have the same azimuth angle gap, and video heads B and D each have the same azimuth angle gap and a different azimuth angle than that of video heads A and C. It has an angular gap.

Furthermore, a magnetic tape 2 is placed on the outer peripheral side of the rotating body 1.
is guided by guide poles 3a and 3b and is spliced and wound over an angle of just over 270°, which is 270° plus the angle for recording the overlap. This tape winding angle is an angle that does not put too much strain on the tape running, and automatic loading is also possible.The diameter L of the rotating body 1 is also 2/3 times that of the current 2-head helical scanning VTR. Therefore, the diameter reduction rate of the rotating body can also be increased. The magnetic tape 2 is held and driven by a capstan and a pinch roller (none of which are shown) and is made to run in the direction of arrow X.
The value is selected so that when one video head of ~D rotates at 45 rps over an angular range of over 270 degrees, it travels one track pitch.

As a result, the circumferential distance of the magnetic tape 2 at the tape winding angle is equal to that of the current two-head VTR, so the video track locus on the magnetic tape 2 is equal to that of the current one, and the relative linear velocity between the tape and the head is the same as that of the current two-head VTR. Equivalent to that of the current VTRR, a video signal with a field frequency of 60 Hz (or 59.94 Hz) is sequentially recorded by video heads A, B, C, and D at a rate of one field per track, as detailed below. A completely tape-compatible tape pattern is formed.

It is clear that when a video signal with a field frequency of 50 Hz is recorded and reproduced at a rate of one field per track, the rotating body 1 is rotated at 37.5 rps.

The scanning trajectory by the four video heads A to D in the above-mentioned 4-head VTR is as shown in FIG. 2, which is different from that of the current 2-head VTR. That is, video head A is now on guide pole 3a.
Assuming that the magnetic tape 2 is positioned at the side and begins scanning, a scanning locus shown by a solid line 4A in FIG. When the video head D, which is placed at a position 90 degrees behind the rotational direction, begins to come into contact with the magnetic tape 2, and when the video head A comes to record about 2/3 of the trajectory 4A, The video head C starts to come into contact with the magnetic tape 2, and the video head B starts to come into contact with the magnetic tape 2 at the point when the trajectory 4A is finished being formed. Therefore, when the head trajectory shown by the solid line 4A in FIG. 2 is drawn by the video head A, the head trajectory by the video head D shown by the two-dot chain line 4D in the same figure and by the video head C shown by the one-dot chain line 4C in the same figure are drawn. The head trajectories are drawn sequentially with a certain time delay, and when the head trajectories 4A have been drawn, the video head B shown by the broken line 5B in the figure is drawn.
The trajectory of the head begins to be drawn.

Hereinafter, in the same manner as above, 5A, 5
D, 6C, 6B, 6A, 7D, 7C, 7B, 8
Track trajectories are sequentially drawn by heads A, D, C, B in the order A,... ). Also, in FIG. 2, a track 9 along the longitudinal direction of the tape is a control track, on which control pulses are recorded, for example, at a two-field period.

Here, in order to record and form the tape pattern as shown in FIG. 3, which is the same as that of the current two-head VTR, it is necessary to
By supplying video signals only to the video heads depicting 6C, 7D38A,...
The video track indicated by _t1 is a track recorded by video head A. Similarly, the video track can be created by switching the recording head approximately every one field period in the order of video head B→C→D→A→... are formed sequentially in the order t ₂ → t ₃ → t ₄ → t ₅ →...

Therefore, during recording, four video heads A to D are used.
It is necessary to sequentially switch and supply video signals to
Similarly, during reproduction, it is necessary to sequentially switch the reproduction signals of video heads A to D. As a method of generating this head switching signal, the current two-head
A VTR extracts one pulse per rotation of a rotating body to which two video heads are attached, and uses it as a reference to generate a rectangular wave with a repetition rate of 30 Hz and a duty cycle of 50%. The low level period of is the scanning period of the first video head,
Assuming that the high level period is the scanning period of the second video head, each rotational phase of the head and the rotating body is uniquely determined. Moreover, in a two-head VTR, even if video signals are constantly supplied to both heads during recording, while one video head is scanning, the other video head is not in contact with the magnetic tape, except during overlap recording periods. There is no problem in that.

Problems to be Solved by the Invention On the other hand, in the case of a 4-head VTR, as mentioned above, the video signal is switched not only during playback but also during recording, and is sent to one of the four video heads A to D. Moreover, the rotating body 1 rotates at, for example, 45 rps, whereas the period during which each video head scans the magnetic tape 2 is approximately 270° rotation period (approximately 3/4 rotation period) of the rotating body 1. Since there is no contact with the magnetic tape 2 during the approximately 90° rotation period (approximately 1/4 rotation period), the phase of the head and the rotating body 1
Therefore, the two heads do not match the rotational phase of
There was a problem in that the VTR head switching signal generation method could not be directly adopted.

Therefore, the present invention extracts a rotation detection pulse that is synchronized with the rotational phase of the rotating body to which the magnetic head is attached, and generates a signal with a period 3/2 times the period of one rotation of the rotating body from the rotation detection pulse, It is an object of the present invention to provide a magnetic recording and reproducing apparatus which solves the above-mentioned problems by determining head switching timing during recording and reproducing based on this signal.

Measures to solve the problem Add the angle for the overlap period to 270°
A rotating body, on which a magnetic tape is wound over an angular range of more than 270 degrees, and the first to fourth heads are attached at equal angular intervals of 90 degrees, is used to record and reproduce video signals. means for rotating at a rotational speed of 270° per field period, and means for extracting a rotation detection pulse synchronized with the rotational phase of the rotating body;
The rotation detection pulse is frequency-divided to output a first frequency-divided signal having a period approximately equal to 3/2 times the period of one rotation of the rotating body, and a reset signal that is generated every three rotations of the rotating body. a first frequency dividing means for outputting a signal;
a delay means for outputting a delayed signal obtained by delaying the symmetrical rectangular wave signal generated from the first frequency-divided signal by a predetermined time; and a delay means that is reset by the reset signal,
A second frequency-divided signal obtained by dividing the frequency of the inverted delayed signal by 1/2 and a third frequency-divided signal obtained by inverting the second frequency-divided signal are respectively outputted. A fourth frequency-divided signal obtained by dividing the delayed signal by 1/2 and a fifth frequency-divided signal obtained by inverting the fourth frequency-divided signal are reset in accordance with the second frequency-divided signal. a second frequency dividing means that outputs a frequency-divided signal, a first output signal that is at an L level for a certain period of time from the falling point of the delayed signal, and a first output signal that is at an L level for a certain period of time from the rising point of the delayed signal; a first AND signal of the third frequency-divided signal and the first output signal; a first AND signal of the second frequency-divided signal and the first output signal; 2, a third AND signal of the fifth frequency-divided signal and the second output signal, and a fourth AND signal of the fourth frequency-divided signal and the second output signal, respectively. and the first to fourth AND signals have a pulse width equal to each tape scanning period of the first to fourth heads including the overlap period,
In addition, the sections of the first to fourth AND signals that are a certain period before each falling point and the sections that are a certain period of time after each rising point are sequentially overlapped with each other. 1 to the switch means of the fourth head, and
outputs the AND signal to the switch means of the second head, outputs the third AND signal to the switch means of the first head, and outputs the fourth AND signal to the switch means of the third head. In the reproduction mode, a signal obtained by inverting the first AND signal is output to the switch means of the fourth head,
A signal obtained by inverting the AND signal of the third head is output to the switch means of the second head, and a signal obtained by inverting the third AND signal is output to the switch means of the first head. , a switching means for outputting a signal obtained by inverting the fourth AND signal to the switching means of the third head, and also has a switching means for outputting a signal obtained by inverting the fourth AND signal to the switching means of the third head, and also inverts the reset signal and the tape during insert recording or splice recording. A control signal for temporarily stopping tape running or restarting running is supplied, and a means for temporarily stopping tape running or restarting running is provided in phase synchronization with the reset signal. explain.

Embodiment FIG. 4 shows a circuit diagram of an embodiment of the main part of the device of the present invention. In the figure, a rotation detection pulse synchronized with the rotational phase of the rotating body 1 shown in FIG. 1 is input to the input terminal 11. As a method for obtaining this rotation detection pulse, for example, a light reflecting section is provided in a half-rotation section of a rotating section that rotates integrally with the rotating body 1, and a light non-reflecting section is provided in the remaining half-rotation section. By arranging the photo sensors facing each other, one pulse per rotation of the rotating body 1 is extracted as a rotation detection pulse.

The rotation detection pulse mentioned above is a rectangular wave with a duty cycle of about 50%, as shown by a in FIG. 5A,
Assuming that the rotating body 1 rotates at 45 rps, its repetition frequency will be 45 Hz. That is, the 3/4 period of the pulse a is a 270° rotation period, which is equal to one field period of the video signal to be recorded and reproduced. This pulse a is applied to the counter 12 and counted there. The counter 12 outputs the pulse b shown in FIG. 5B from its first bit output terminal _O1 ,
Pulse c shown in figure C is output from the second bit output terminal _O2 , and these pulses b and c are
It is reset by the pulse d shown in FIG. 5D obtained through the AND circuit 13. As is clear from Figure 5 A and D, the repetition frequency of this pulse d is 15
Hz, and one reset pulse is output every 33 rotations of the rotating body 1 as will be described later. This also means that a pulse d is output every four fill periods.

On the other hand, rotation detection pulse a and pulse c
The signal is supplied to the AND circuit 14, where it is converted into a pulse f with a repetition frequency of 15 Hz as shown in FIG. Pulse e with a repetition frequency of 15 Hz shown in E
is converted to These pulses e and f are respectively
It is supplied to the OR circuit 17, from which it is converted into a pulse g with a repetition frequency of 30Hz as shown in Fig. 5G, and then supplied to a monostable multivibrator (hereinafter referred to as "monomulti") 18, which is triggered at the rising edge of the pulse g. And at the same time, mono multi 19
is supplied to trigger this on its falling edge.
As a result, the waveforms of the charging and discharging capacitors in the monomultis 18 and 19 become as shown in FIG. , is applied as a set pulse. As a result, the output signal waveform of the flip-flop 20 changes to the fifth
This results in a rectangular wave i shown in Figure I. Here, each time constant of the monomultipliers 18 and 19 is the flip-flop 2
The output signal i of 0 is adjusted to be a symmetrical rectangular wave with a duty cycle of 50%.

In this way, blocks 12 to 20 in FIG.
A repetition frequency of 30 Hz generated by a frequency dividing means consisting of 2/3 of one rotation period of the rotating body 1
A symmetrical rectangular wave i whose period is twice the period is output terminal 2.
1 as a switching signal to switch circuits 58 and 5 via an input terminal 60 shown in FIG. 7, which will be described later.
9, respectively, and a 1/2 frequency divider 22 and a delay circuit 24, respectively. The 1/2 frequency divider 22 is reset by the pulse d, and divides the symmetrical rectangular wave i by 1/2 to output a symmetrical rectangular wave j with a repetition frequency of 15 Hz to the output terminal 2, as shown in FIG. 5J.
3. Output as a switching signal to a switch circuit 62 via input terminals 61 shown in FIG. 7, which will be described later.

The above-mentioned pulses i and j are used for switching the reproduction signal, whereas the switching signal for switching the recording current (recording video signal) supplied to the video heads A to D during recording is It is generated as follows. If only the video signal of one field period is recorded on one track on the magnetic tape 2, the reproduced video signal may be dropped or partially overlapped near the field boundary during compatible playback. Therefore, in order to prevent this, the magnetic tape 2 is placed on the rotating body 1 in order to record with a slight overlap over one field period.
Overlap recording at 270° (for example, about 20°)
A large number of windings are made, and a recording current is caused to flow through each video head for a period slightly longer than one field period. For this purpose, it is necessary to overlap the switching signals for switching the recording current.

Therefore, the delay circuit 24 first generates the symmetrical rectangular wave i.
by delaying the repetition frequency as shown in Figure 5 K.
Obtain a 30Hz symmetrical rectangular wave k. In FIG. 5K, Td is the delay time caused by the delay circuit 24, for example, 1.2ms.
selected according to the degree. For example, the delay circuit 24 has a configuration as shown in FIG.
After being delayed by a circuit section consisting of a capacitor 52 and a capacitor 52, a Schmitt circuit 53 shapes the waveform and outputs a symmetrical rectangular wave k to an output terminal 54.

This symmetrical rectangular wave k is inverted by an inverting circuit 25 into a signal l shown in FIG. 5L, and then supplied to a 1/2 frequency divider . The 1/2 frequency divider 26 is reset by the pulse d, and divides the input signal 1 by 2 to output a symmetrical rectangular wave m having a repetition frequency of 15 Hz as shown in FIG. 5M. With the above reset, for one timing (edge of pulse d),
The order of each head is determined. This symmetrical rectangular wave m is converted into a symmetrical rectangular wave n with an opposite phase as shown in FIG.
Furthermore, the rising edge is detected by the differentiating circuit 28 and applied to the 1/2 frequency divider 29 as a reset pulse. Note that it may also be set by pulse d.

The symmetrical rectangular wave q with a repetition frequency of 15 Hz, shown in FIG. It is considered as wave r
It is applied to the AND circuit 35. On the other hand, as shown in FIG. 5 O, a pulse o that is triggered by the fall of the delayed symmetrical rectangular wave k is taken out from the monomulti 30 and remains at a low level for a certain period T from the fall of the rectangular wave k. The monomulti 31, which is applied to the circuits 33 and 34 and triggered by the rising edge of the delayed symmetrical rectangular wave k, outputs a pulse that remains at a low level for a certain period of time T from the rising edge of the rectangular wave k, as shown in FIG. p is taken out and AND
applied to circuits 35 and 36, respectively.

The exclusive OR circuits 38, 39, 40 and 41 each have a recording/reproducing mode signal from the input terminal 37 applied to one input terminal, and a signal to the other input terminal.
Each output signal of AND circuits 35, 34, 36 and 33 is applied. Here, since the above-mentioned recording/reproduction mode signal is set to a low level in the recording mode and set to a high level in the playback mode, the exclusive OR circuits 38, 39, 40, and 41 are set in the recording mode.
The signal waveforms outputted to the output terminals 42, 43, 44, and 45, respectively, have a repetition frequency of 15 Hz, as shown in FIG. 5, S, T, U, and V. Pulses s, t, u with a pulse width equal to the scanning period
and v. In addition, both the section that is a certain period before the falling points of the pulses s, t, u, and v and the section that is a certain period after the rising points of the pulses t, u, v, and s are at high level. ing.

On the other hand, in the playback mode, the signal from the input terminal 37 is at a high level, so the output terminals 42, 4
3, 44 and 45 are shown in Figure 5 W, X, Y and Z.
As shown in FIG. 2, pulses w, x, y, and z having the opposite phase to the pulses s, t, u, and v are extracted.

In this way, blocks 24 to 41 in FIG.
Pulses s to v corresponding to the first switching signal are generated in the recording mode, and pulses w corresponding to the second switching signal are generated in the reproduction mode by the switching signal generating means consisting of
~z is generated.

Next, the head switching operation will be explained with reference to FIG. FIG. 7 shows a block system diagram of an embodiment of another essential part of the apparatus of the present invention. First, to explain the operation in recording mode, the opening/closing switch _SPA ,
While S _PB , S _PC and S _PD are each opened (off),
The on/off switches S _A , S _B , S _C and S _D are closed (on), respectively, and the preamplifiers 57A, 57B, 57
Short-circuit the input side of C and 57D to ground. on the other hand,
A recording video signal is input to the input terminal 55. This recording video signal, for example, separates a standard color video signal into a luminance signal and a carrier color signal, the luminance signal is frequency modulated, and the carrier color signal is a color signal proposed by the present applicant in, for example, Japanese Patent Publication No. 56-9073. This is a signal obtained by frequency-division multiplexing these two signals after converting them into a low-pass conversion carrier color signal that has been subjected to phase shift processing that takes into account crosstalk countermeasures.

The above recording video signal is applied to the input terminals of the switches S _RA , S _RB , S _RC and S _RD through the recording amplifier 56 . The switches S _RA , S _RB , S _RC and S _RD are composed of switch circuits whose opening and closing are controlled by switching signals, and their output terminals are connected to the video head via rotary transformers RT _A , RT _B , RT _C and RT _D. A, B, C and D are connected to each other. The switches S _RA to S _RD output the pulses s,
Switching is controlled separately by t, u, and v, and pulses s to v are turned on during high level periods and turned off during low level periods.

Here, the timing at which the pulse d is outputted is within the period in which the video head C records or reproduces a signal on the magnetic tape 2.
If the rotation pulse detection _mechanism , etc. _of
The pulse u is applied as a switching signal to the switch _SRC ,
The pulse v is applied to the switch _SRD as a switching signal. Therefore, if video head A now begins to draw the scanning locus shown at _4A in FIG. is supplied to video head A, and from these 1
A little over a field is recorded.

When video head A has recorded about one field, pulse t also becomes high level, so switch S _RB is turned on, and switches S _RB ,
Recording video signals are supplied through rotary transformers RT _B , and video heads A and B send the recording video signals of the same section to their respective tracks.
Recorded at t ₁ and t ₂ (overlap recording). Next, the pulse s becomes low level and the switch is turned off.
Although S _RA is turned off, pulse t remains at a high level and video head B continues to draw the scanning trajectory 5B on the magnetic tape 2, so video head B alone can record the next field. video signals are recorded. Thereafter, by the same operation as above, the pulses u and v become high level one after another, and the switches S _RC and S _RD are turned on one after another.
Recording video signals are sequentially recorded by video heads C and D. From a certain period of time before video head D finishes recording, video head A
scans the magnetic tape 2, and the pulse s becomes high level and the switch _SRA is turned on.
From this point until the point when the pulse v becomes low level, video heads D and A control the adjacent tracks.
The same recording video signal is recorded at t ₄ and t ₅ , and when the video head D finishes recording track t ₄ (when the pulse v becomes low level or the video head D leaves the magnetic tape 2). ) From then on, the video signal for recording is recorded only by video head A. Thereafter, the same operation as above is repeated.

Next, the operation in playback mode will be explained. In the reproduction mode, the switches S _PA -S _PD are kept on at all times to cut off the transmission path between the output end of the recording amplifier 56 and the rotary transformers RT _A - RT _D. In addition, the switches S _RA to S _RD are made of semiconductor switching elements and have an on-resistance when they are turned on. Therefore, if the output from the recording amplifier 56 is common, it will cause crosstalk. Therefore, during playback, the switches S _RA to S _RD is respectively turned off. Further, switches S _A , S _B , S _C and S _D are configured to output the pulses w, x, y
Switching is controlled by and z, RT _A ~ RT _D
One end of each of the rotary transformers of the three reproduced signal transmission lines that are not required during reproduction is short-circuited to ground.

That is, at the same time as the video head A starts scanning the video track _t1 in FIG. 3, the pulse w becomes low level and the switch S _A is turned off. At this time, pulses x and y are at high level, switches S _B and S _C are turned on, and pulse z is at low level, and switch S _D is turned off. The reproduced signal from track _t1 reproduced by video head A is output to output terminal 63 through rotary transformer RT _A , preamplifier 57A, and switch circuits 58 and 62, respectively. Here, the switch circuits 58 and 59 are switching-controlled by the pulse i inputted from the terminal 60, and during the period when the pulse i is at a low level, the output signals of the preamplifiers 57A and 57C inputted to the terminals 58L and 59L are selected. output, and during the period when pulse i is at high level, terminal 58H,
59H and preamplifiers 57B, 57
The output signal of D is selectively output. On the other hand, the switch circuit 62 is switching-controlled by the pulse j that enters the terminal 61, and selects and outputs the output signal of the switch circuit 59 that enters the terminal 62L during the period when the pulse j is at the low level, and when the pulse j is at the high level. The period is switched and connected to the terminal 62H and the switch circuit 5
It is configured to selectively output eight output signals.

Therefore, during the reproduction period of video head A when pulses i and w are at low level and pulse j is at high level, the signal reproduced by video head A is outputted to output terminal 63. Slightly before video head A finishes playing track _t1 , video head B starts playing track _t2 , and pulse x becomes low level, causing video head A to play track _t1 . Near the end point, pulses i and j each become high level. This allows video head A to track
Following the end of playback of track _t1 , the playback signal from track _t2 played back by video head B is output to output terminal 63 via rotary transformer RT _B , preamplifier 57B, switch circuits 58 and 62, respectively. .

Thereafter, in the same manner as above, after video head B finishes playing track _t2 , video head C
scans the track _t3 , and the pulses i and j become low level, respectively, and the switch circuits 58 and 59
Since the terminals 58L and 59L and the switch circuit 62 are respectively switched to the terminal 62L side, and the pulse y becomes low level to turn off the switch _SC , the track _t3 is reproduced by the video head C. The reproduced signal is output to the output terminal 63. Then, just before the end of the playback of track t ₃ , pulse z
goes low level and turns off the switch S _D , the video head D starts recording the tracks on the magnetic tape 2.
At the same time as scanning _t4 starts, the pulse j is switched to high level and pulse j is switched to low level, so that the reproduced signal of track _t4 reproduced by video head D is transmitted to rotary transformer RT _D and preamplifier 57.
D and are output to the output terminal 63 through the switch circuits 59 and 62, respectively. Thereafter, the same operation as above is repeated.

Next, other embodiments of the present invention will be described.
This embodiment is characterized in that tape running is stopped or restarted during splice recording or insert recording in phase synchronization with a signal having a period three times as long as one rotation period of the rotating body 1. The figure shows a block diagram of this embodiment. During continuous recording or insert recording, recording is temporarily stopped and then restarted, resulting in a temporally discontinuous recording operation.

A pause (temporary stop) command signal shown in FIG. 9A is now input to the input terminal 65, and the timing circuit 66
, the timing circuit 66
When this pause command signal is received, a high-level pause signal as shown in FIG. 9C is generated at the rising edge of the head switching pulse shown in FIG. 9B. The above head switching pulse is determined by the rotation speed of the rotating body 1.
In the case of 45 rps, a symmetrical rectangular wave i with a repetition frequency of 30 Hz, for example, generated from the reset pulse d shown in FIG. 5D is used. The above pulse d is phase synchronized with a signal obtained by dividing the vertical synchronization signal in the video signal to be recorded by 1/4, and the symmetrical rectangular wave i is also created by this pulse d, and after all, it has a repetition frequency of 115Hz. Pulse d determines the timing of continuous recording and insert recording.

FIG. 9C extracted from the timing circuit 66
The signal shown _in
Solenoid driver circuit 6 after being delayed by
8. The voltage is applied to the plunger solenoid 78 shown in FIG. 10 through the output terminal 69 to de-energize the plunger solenoid 78 shown in FIG.
The plunger 78a of No. 8 is made to protrude. As a result, the plunger 78
The lever 75 is rotated clockwise in the figure about the fulcrum 76 via the arm 77 connected to the arm 77, and the pinch roller 74 provided at one end of the lever 75 is separated from the capstan 73.
As a result, the running of the magnetic tape 2 is stopped with a delay of a certain period _TD1 from the rising edge of the head switching pulse.

On the other hand, when the pause release operation is performed, a low level signal is applied to the input terminal 65 shown in FIG. 8, and a low level signal is taken out from the timing circuit 66 in phase synchronization with the rising edge of the head switching pulse. . This low level signal is delayed by a predetermined time TD ₂ by the delay circuit 67, power amplified by the solenoid driver 68, and further applied to the plunger solenoid 78 via the output terminal 69 to energize it. As a result, the plunger 7
8a is attracted, the lever 75 is rotated counterclockwise in the figure about the fulcrum 76, and the lever 75 is rotated counterclockwise in the figure.
As shown by solid lines in the figure, a pinch roller 74 is pressed against the rotating capstan 73 via the magnetic tape 2.

Therefore, the magnetic tape 2 is wound around the rotating body 1 over an angular range of more than 270 degrees, and is sandwiched between the capstan 73 and the pinch roller 74 through the audio erasing head 71 and the audio control head 72, respectively. , tape running is resumed after a certain time _TD2 delay from the rising edge of the head switching pulse after the pause is released.

The above delay times TD ₁ and TD ₂ are provided for correcting the amount of delay in the operation of the mechanical system, and for setting which part of the input signal should be connected.
In this way, even when recording is performed discontinuously in time (that is, during continuous recording or insert recording), discontinuous control pulses can be recorded with a constant phase.

In addition, in the above explanation, the field frequency is 60Hz.
(or 59.94Hz) video signal recording and playback operations. However, when recording and playing back a video signal with a field frequency of 50Hz at a rate of 1 field per track, the rotational speed of the rotating body 1 is 37.5rps.
Therefore, the repetition frequency of the pulse d is
It becomes 12.5Hz.

Effects As described above, according to the present invention, the angle corresponding to the overlap period (for example, about 20°) is added to 270°.
A magnetic tape is wound over an angular range of over 270 degrees, and in the recording mode, the first to fourth heads are supplied with video signals to be recorded for a period slightly longer than one field period. Video signals to be recorded in the same section are sequentially overlap-recorded on the respective tracks by two adjacent heads among the first to fourth heads, and in the playback mode, the first to fourth heads record video signals from one field period. A video signal to be reproduced for a slightly longer period is supplied, and video signals to be reproduced in the same section are reproduced from respective tracks by two adjacent heads among the first to fourth heads. Therefore, when recording only the video signal of one field period on one track on a magnetic tape and reproducing it, the disadvantage of the conventional device is that the reproduced video signal is lost near the boundary between fields (i.e., the above-mentioned reproduced video signal is lost). An image played back from a video signal that was recorded with only the vertical synchronization signal of the signal missing has the disadvantage that the synchronization is always disrupted, and that only the signal portion other than the vertical synchronization signal of the reproduced video signal mentioned above is lost and recorded. The image obtained by playing back the video signal can completely eliminate the disadvantage that the missing part becomes a noise bar in the image, and the playback video signal can avoid the negative effects of the dropout near the field boundary, so the playback image It is possible to continuously obtain high-quality playback images without synchronization disturbances or noise bars, and in addition to this,
Even when performing discontinuous recording operations such as temporarily stopping recording and restarting recording during insert recording or continuous recording, the seam between the images before and after stopping and restarting recording is undisturbed, resulting in always high-quality images. The control pulse can be recorded at a constant phase during splice recording or insert recording, making it possible to reliably perform splice recording or insert recording. Conventional 2-head
It has many advantages, such as being smaller than a VTR, making it possible to downsize the entire device, and being particularly suitable for portable VTRs.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the head arrangement relationship previously proposed by the applicant that can be applied to the present invention, FIG. 2 is a diagram showing the scanning locus of each head in FIG. 1, and FIG. 4 is a circuit system diagram showing an embodiment of the main part of the apparatus of the present invention; FIG. 5 is a time chart for explaining the operation of the circuit system shown in FIG. 4; Figure 6 is the 4th
FIG. 7 is a block system diagram showing an embodiment of another main part of the device of the present invention, and FIG. 9A to 9D are time charts for explaining the operation of the block system shown in FIG. 8, and FIG. 10 is a schematic diagram showing an example of the tape running system of the apparatus of the present invention. 1...Rotating body, 2...Magnetic tape, 3a, 3b
... Guide pole, 11 ... Rotation detection pulse input terminal, 12 ... Counter, 22, 26, 29 ...
1/2 frequency divider, 24...delay circuit, 55...recording video signal input terminal, 58, 59, 62...switch circuit, 60, 61...switching signal input terminal, 63...playback signal output terminal , 66...timing circuit, 73...capstan, 74...pinch roller, 78...plunger solenoid, A,
B, C, D...video head, S _PA , S _PB , S _PC ,
S _PD , S _A ~ S _D , S _RA ~ S _RD ... switch.

Claims (1)

[Claims] 1 270° plus the angle for the overlap period
A rotating body, on which a magnetic tape is wound over an angular range of more than 270 degrees, and the first to fourth heads are attached at equal angular intervals of 90 degrees, is used to record and reproduce video signals. means for rotating at a rotation speed of 270 degrees per field period; means for extracting a rotation detection pulse synchronized with the rotational phase of the rotating body; a first frequency dividing means for outputting a first frequency-divided signal having a period approximately equal to /2 times the period and a reset signal generated every three rotations of the rotary body; a delay means for outputting a delayed signal obtained by delaying a symmetrical rectangular wave signal generated from the signal by a predetermined period of time; and a third frequency-divided signal obtained by inverting the second frequency-divided signal, and are reset in accordance with the second frequency-divided signal,
a fourth frequency-divided signal obtained by dividing the delayed signal by 1/2;
a second frequency dividing means that respectively outputs a fifth frequency divided signal obtained by inverting the fourth frequency divided signal; and a first output that is at an L level for a certain period of time from the falling point of the delayed signal. signal generating means for outputting a signal and a second output signal that is at an L level for a certain period from the rising edge of the delayed signal; and a first AND signal of the third frequency-divided signal and the first output signal. , a second AND signal of the second frequency-divided signal and the first output signal, a third AND signal of the fifth frequency-divided signal and the second output signal, and a fourth frequency-divided signal. and a fourth AND signal of the second output signal, and the first to fourth AND signals are applied to each tape scanning period of the first to fourth heads including the overlap period. The sections having the same pulse width and occurring a certain period before each falling point of the first to fourth AND signals and the sections after a certain period of rising point of each of the first to fourth AND signals sequentially overlap with each other. , in the recording mode, outputs the first AND signal to the switch means of the fourth head, outputs the second AND signal to the switch means of the second head, and outputs the second AND signal to the switch means of the second head. The product signal is the first
The fourth AND signal is output to the switch means of the third head, and in the reproduction mode, the signal obtained by inverting the first AND signal is output to the switch means of the third head. A signal obtained by inverting the second AND signal is output to the switch means of the second head, and a signal obtained by inverting the second AND signal is output to the switch means of the third head.
outputting a signal obtained by inverting the AND signal of the first head to the switch means of the first head, and outputting a signal obtained by inverting the fourth AND signal to the switch means of the third head. switching means, in the recording mode, the first to fourth heads are supplied with a video signal to be recorded for a period slightly longer than one field period, and the first to fourth heads are adjacent to each other; Video signals to be recorded in the same section are sequentially recorded overlappingly on the respective tracks by the two heads, and in the playback mode, the first to fourth heads are supplied with the video signals to be played back for a period slightly longer than one field period. A magnetic recording/reproducing apparatus characterized in that video signals to be reproduced in the same section are reproduced from respective tracks by two adjacent heads among the first to fourth heads. 2 Added the angle for the overlap period to 270°
A rotating body, on which a magnetic tape is wound over an angular range of more than 270 degrees, and the first to fourth heads are attached at equal angular intervals of 90 degrees, is used to record and reproduce video signals. means for rotating at a rotation speed of 270 degrees per field period; means for extracting a rotation detection pulse synchronized with the rotational phase of the rotating body; a first frequency dividing means for outputting a first frequency-divided signal having a period approximately equal to /2 times the period and a reset signal generated every three rotations of the rotary body; a delay means for outputting a delayed signal obtained by delaying a symmetrical rectangular wave signal generated from the signal by a predetermined period of time; A second frequency-divided signal and a third frequency-divided signal obtained by inverting the second frequency-divided signal are respectively output, and the delay signal is reset in accordance with the second frequency-divided signal. a second frequency dividing means that outputs a fourth frequency-divided signal obtained by dividing the frequency by 1/2 and a fifth frequency-divided signal obtained by inverting the fourth frequency-divided signal, respectively; signal generating means for outputting a first output signal that is at L level for a certain period of time from the falling point of the delayed signal; and a second output signal that is at L level for a certain period of time from the rising point of the delayed signal; a first AND signal of the frequency-divided signal and the first output signal, a second AND signal of the second frequency-divided signal and the first output signal, a second AND signal of the fifth frequency-divided signal and the second output signal; A third AND signal of the output signal, the fourth divided signal, and a fourth AND signal of the second output signal are respectively generated, and the first to fourth AND signals are generated during the overlap period. and a period having a pulse width equal to each tape scanning period of the first to fourth heads, including a certain period of time before each falling point of the first to fourth AND signals; The periods after a certain period of time after the rising time are sequentially overlapped with each other, and in the recording mode, the first AND signal is output to the switch means of the fourth head, and the second AND signal is output to the switch means of the fourth head. outputting the third AND signal to the switching means of the second head;
The fourth AND signal is output to the switch means of the third head, and in the reproduction mode, the signal obtained by inverting the first AND signal is output to the switch means of the third head. A signal obtained by inverting the second AND signal is output to the switch means of the second head, and a signal obtained by inverting the second AND signal is output to the switch means of the third head.
outputting a signal obtained by inverting the AND signal of the first head to the switch means of the first head, and outputting a signal obtained by inverting the fourth AND signal to the switch means of the third head. The switching means is supplied with the reset signal and a control signal for temporarily stopping or resuming tape running during insert recording or splice recording, and is configured to pause or restart tape running in phase synchronization with the reset signal. in the recording mode, the first to fourth heads are supplied with a video signal to be recorded for a period slightly longer than one field period, and the first to fourth heads are supplied with a video signal to be recorded for a period slightly longer than one field period, so that among the first to fourth heads adjacent to each other, The video signals to be recorded in the same section are sequentially overlap-recorded on the respective tracks by the two heads, and in the playback mode, the first to fourth heads record the video signals to be played back for a period slightly longer than one field period. A magnetic recording and reproducing apparatus characterized in that a video signal that is supplied and to be reproduced in the same section by two adjacent heads among the first to fourth heads is reproduced from each track.