JPS6012684B2 - magnetic recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In a helical scan type VTR (energy recording and reproducing apparatus), two rotating magnetic heads IA and IB are generally spaced at an angular interval of 180 degrees, as shown in FIGS. 1 and 2. is attached to the upper drum 3 in a state having a
The lower drum 4 is rotated integrally with the lower drum 4 at the frame frequency, and the lower drum 4 is fixed.

The magnetic tape 2 is wound diagonally around the circumferential surfaces of the drums 3 and 4 over an angular range of just over 180 degrees, and is run at a constant speed. In this way, the luminance signal is in the state of an FM signal, and one field of the luminance signal is a diagonal one.
It is recorded on the tape 2 to form the magnetic tracks of the book.

However, in such a VTR, the head IA,
If an attempt is made to increase the relative speed between the IB and the tape 2 to obtain a sufficient frequency band, the diameters of the drums 3 and 4 will increase, resulting in an increase in the size of the VTR.

Furthermore, as is clear from FIG. 2, at the contact start point and end point of the tape 2 with the drums 3 and 4, the tape 2 runs with a step approximately equal to the width thereof.
The height of the drums 3 and 4 increases, and this also makes the VTR larger. Furthermore, of the contact area between the tape 2 and the drums 3 and 4, the half area shown by diagonal lines is the contact area with the non-rotating drum 4, so there is a large amount of friction when the tape runs, and therefore the tension of the tape 2 is reduced. It gets bigger.

Moreover, the difference in the tension of the tape 2 between the contact start point and the end point of the tape 2 with respect to the drums 3 and 4 becomes large, and the contact pressure between the heads IA and IB and the tape 2 becomes uneven. The invention aims to provide a VTR that eliminates these problems.

Therefore, in the present invention, the rotary magnetic head device is constructed as shown, for example, in FIGS. 4 and 5, and the track pattern on the tape 2 is made, for example, as shown in FIG. 7.

That is, as shown in FIGS. 4 and 5, the three rotating magnetic heads IA to IC have an angular spacing of 1200 mm from each other and are 1' consular of the width of the magnetic tape 2 in the track width direction. These heads IA to IC are attached to the upper drum 3 with successive steps of
As shown in FIG. 3, it is rotated together with the drum 3 at a speed of two revolutions per field period. And this head I
The tape 2 is wrapped around the rotational surface of A to IC and the drum 3 over an angle range of over 2400 degrees, and in this corner range of 240 degrees, the tape 2 has a step in the width direction of a little over 1/box of the width. Furthermore, the lower drum 4 is fixed. During recording, the rotation of the heads IA to IC is synchronized with the brightness signal. It will be done.

That is, in FIG. 3, 30 indicates a servo circuit,
In the synchronization separation circuit 31, a vertical synchronization pulse Pv is extracted from the luminance signal as shown in FIG.
The signal is supplied to the phase comparator circuit 32 through.

Further, a pulse generating means 33A is provided on, for example, the rotating shaft 5 of the heads IA to IC, and from this, one of the heads IA to IC
One pulse is taken out per revolution, and this pulse is
The signal is supplied to the frequency divider 35 through the shaping amplifier 34A and divided into pulses of the field frequency, and this frequency-divided pulse is supplied to the comparator circuit 32. The comparison output of the comparison circuit 32 is then supplied to the motor 6 which drives the heads IA-IC through the amplifier 36, and the heads IA-IC are synchronized with the luminance layer signal at twice the field frequency. be rotated.

//Therefore, if we divide the configuration grade period into periods Ta to Tc of 1'3 each, we get the head IA
As shown by the solid line in the upper part of FIG. 6C, the tape 2 is scanned during the first period Ta and several horizontal periods before and after it,
Subsequently, the tape 2 is scanned as shown by the broken line.

The heads IB and IC also sequentially scan the tape 2 with a delay of 1'3 field periods relative to the scan of the head IA, as shown by solid lines and broken lines in the middle and lower rows of FIG. 6C. In addition, in this state, the pulse from the amplifier 34A is located at this point several horizontal periods before the period Ta and 1'2 field periods later (after one rotation), as shown in the upper part of FIG. 6D. Suppose that the phase of the pulse P is difficult.

Then, during the period shown by the solid line in FIG. 6C, the heads IA to IC
Recording is done by. That is, the luminance signal (black and white video signal) is supplied to the FM modulation circuit 16 through the line of input terminal 1 1 → AGC amplifier 1 2 → clamp circuit 1 3 → preamplification circuit 14 → dark and white clip circuit 15, and outputs the FM signal Sf. This signal Sf is supplied to switch circuits 17A to 17C.

Further, a pulse generating means 3 is connected to the rotating shaft 5 of the heads IA to IC.
3B and 33C are provided, and their output pulses are supplied to shaping amplifiers 34B and 34C, and as shown in the middle and lower rows of FIG. 6D, the pulse P whose phase is delayed by 1'6 field period with respect to the pulse P scale is The pulses Pga to Pg are supplied to the switching signal forming circuit 41, and the vertical synchronizing pulse Pv is supplied from the separation circuit 31.
The signal is supplied to the forming circuit 41 through the switch 62. In this way, the forming circuit 41 is triggered by the pulse located immediately before the period Ta-Tc among the pulses Pga-Pgc, and rises in the period Ta-Tc and several horizontal periods before and after it, as shown in FIG. 6E. Rectangular wave signals Sra to Src are formed. Then, the signals Sra to Src are supplied to the switch circuits 17A to 17C as control signals.
From A~17C, as shown in Figure 6, period hawk ma~
At Tc and every several horizontal periods before and after it, the FM signal Sf is sequentially extracted as output signals S to S in a time-division manner.

Then, these FM signals S~S are sent to the recording amplifier 18.
Through A to 18C, the recording/playback selector switch 5
Heads IA to IC through recording side contacts R of 1A to 51C.
is supplied to In this case, as explained in FIG. 5, the heads IA to IC and the tape 2 each have a step of 1/3 of the tape width, so as shown by the arrow 8A in FIG. Therefore, as shown in FIG. 7, the signal Sfa is applied to the area 2A of the tape 2 by the head IA as an oblique magnetic track 7A. recorded.

Similarly, the signals Sfb, Sfc are applied to the oblique magnetic tracks 7B, 7C by the heads IB, IC onto the approximately 1/3 central area 2B of the tape 2 and the remaining approximately 1'3 area 2C.
are recorded respectively. That is, the FM signal Sf for one field period is divided into three signals Sfa to S, and recorded in areas 2A to 2C of the tape 2 as tracks 7A to 7C. Note that at this time, the luminance signal from the amplifier 12 is supplied to the separation circuit 31, and the vertical synchronization pulse Pv is extracted as described above.

Further, this vertical synchronizing pulse Pv is supplied to the magnetic head 38 through the recording amplifier 37 and the recording side contact R of the recording/reproduction changeover switch 53, and is recorded as a magnetic track 7D on, for example, the green portion of one side of the tape 2. , audio signals, cue signals, etc. are recorded as tracks 7E to 7G on each boundary line of the areas 2A to 2C and in the green area on the other side.On the other hand, during playback, the vertical synchronization pulse Pv is output from the tape 2 by the head 38. is reproduced, and this pulse Pv is supplied to the comparator circuit 32 through the line from the reproduction side contact P of the switch 53 → the reproduction amplifier 39 → the reproduction side contact P of the switch 52. Tracking servo for heads IA-IC is performed, heads IA-IC scan tracks IA-IC in the same manner as during recording, and signals S-S are sequentially reproduced from tracks 7A-7C.
Then, these signals S~Sfc are connected to the switch 5 1A.
~ Through the playback side contact P of 51C, the playback amplifier 21
It is supplied to switch circuits 22A to 22C through A to 21C.

Further, the vertical synchronizing pulse Pv from the amplifier 39 is supplied to the forming circuit 41 through the switch 52, and signals Sra to Src are formed in the same manner as during recording.
ra to Src are the second switching signal forming circuit 42
At the same time, a horizontal synchronizing pulse is taken out in a synchronizing separation circuit 43, and this pulse is supplied to a forming circuit 42.

In this way, in the forming circuit 42, as shown in FIG.
Spc is formed, and these signals Spa to Spc are supplied to switch circuits 22A to 22C as control signals thereof. Therefore, signals Sfa to Sfc are sequentially taken out from the switch circuits 22A to 22C for each period Ta to Tc, with the horizontal blanking period as a delimiter.

Then, this signal S~S is supplied to the adder circuit 23, and as shown in FIG. 6, the continuous original FM signal Sf
This signal Sf is supplied to the FM demodulation circuit 25 through the limiter 24 to demodulate the luminance signal, and this signal is sent to the differential assist circuit 26 and the buffer amplifier 27.
2M output terminals are taken out through the output terminal.

Also, at this time, the luminance signal from the de-emphasis circuit 26 is supplied to the separation circuit 43, and the horizontal synchronization pulse is taken out and supplied to the formation circuit 42 as described above.

In this way, it is possible to record and reproduce luminance signals.
In this case, according to the present invention, the rotational speed of the heads IA to IC is four times that of the conventional VTR (the VTR shown in FIGS. 1 and 2), so that the heads IA to IC and the tape 2 are If the relative speed of the drums can be the same as that of a conventional VTR, the diameters of the drums 3 and 4 can be reduced to 1'4 as compared to the conventional VTR, allowing for a very large size and shortening the tape running path.

Further, since the step of the tape 2 is 1'3 of the tape width, the drums 3 and 4 can be lowered and the tape running path can be made smaller. Since the drums 3 and 4 and the tape running path can be made smaller in this way, the entire VTR can also be made smaller, making it possible to realize a small and lightweight portable VTR for, for example, broadcasting station coverage.

Furthermore, if there is no need to reduce the size so much, the relative speed between the heads IA to IC and the tape 2 can be increased, and the frequency band can be greatly expanded.

For example, in the so-called Umatic standard VTR,
While the drums 3 and 4 have a diameter of 110 ribs, according to the present invention, the diameter can be reduced to 61 ribs, and moreover, it is possible to record and reproduce FM signals up to about 11M. Furthermore, since the recording and reproducing band is extremely wide, it can be used as a so-called no-band type VTR, and when recording and reproducing color video signals, there is no need to perform low frequency conversion of the carrier color signal.

In addition, since the portion of the tape 2 that contacts the fixed drum 4 is 1'6 of the portion that contacts the drums 3 and 4, the friction is extremely small, so the tape tension can be reduced by 4. The tension difference between the contact start point and end point can be reduced by 4.
~The contact pressure between the IC and the tape 2 can be made uniform. moreover,
Since the tape tension can be made small, the tape 2 can be made thinner, and long-time recording and playback can be performed with a small tape cassette.

In addition, since it is a helical scan method, slow motion playback can be achieved by changing the running speed of tape 2 from that during recording.
Still playback and fast motion playback are possible.

By the way, in this VTR, one field of screen is divided into three parts and recorded, so if the tape 2 expands or contracts or there is an error in the angular spacing between heads IA to IC,
As shown in FIG. 8, on the playback screen 9, there are
Skew distortion may occur in the portion corresponding to the start point of c.

Therefore, in the present invention, this skew distortion is also corrected and removed. Therefore, in the present invention, the skew amount of the reproduced signal is detected, and based on the detected signal, the heads IA and IC are displaced in the length direction of the tracks 7A and 7C to perform time axis correction.

That is, as shown in FIGS. 9 and 10, an electromechanical transducer, such as a bimorph board 61, is prepared, and the head IA and IC are attached to one end of the element through a support piece 62, and the other end is attached to a substrate 63. At the same time, a damper material 64 is provided between the substrate 63 and the bimorph board 61.

In this case, when voltage is supplied to the bimorph plate 61, the bimorph plate 61 is moved so that the head lAP jC is displaced in the length direction of the tracks 7A and 7C as shown by the arrow 65 according to the polarity and level of the voltage. 61 is selected. Then, the substrate 63 is attached to the drum 3 so that the heads IA and IC have the above-mentioned positional relationship. Also, the time axis error detection circuit 70 is installed as shown in FIG. It is configured as follows.

That is, the horizontal synchronizing pulse from the separation circuit 43 is
L (AFC circuit) 71, and as shown on the right side of FIG. 8 and FIG. This signal Sk is then supplied to switch circuits 72A and 72C. Furthermore, the signals Srb and Src from the forming circuit 41 are supplied to the monostable multipipe layers 73A and 73C, and are triggered by the signals Sb and Src, forming pulses that rise near the start points of the periods Tb and Tc. and these pulses are sent to the switch circuit 7.
2A and 72C as their control signals. In this way, in the switch circuits 72A and 72C, as shown in FIG. are supplied to DC voltages Ea, Ec at a level corresponding to the level of the signals Ska, Skc, that is, DC voltages Ea, Ec at a level corresponding to the skew amount at the start of periods Th, Tc, and this voltage Ea , Ec through the playback side contacts P of the recording/playback selector switches 54A, 54C,
Furthermore, amplifier 75. Head IA, I through A, 75C
It is supplied to bimorph plates 61, 61 supporting C.

Therefore, the bimorph plate 61 supporting the head IC is deflected in response to the voltage Ec in accordance with the polarity and level of the voltage Ec, so the head IC is displaced in the length direction of the track 7C in response to the voltage Ec. The skew distortion at the start of period c is removed.

Furthermore, a similar operation should be performed by the voltage insect a, but in this case, the head IB is fixed to the drum 3, the head IA is supported by the bimorph plate 61, and the head IB is supported by the bimorph plate 61. A voltage Ea is supplied.

Therefore, using the time axis of the reproduced signal Sfb of the head IB as a reference, the head IA is displaced so that the time axis of the reproduced signal Sfa of the head IA coincides with the time axis of the reproduced signal Sfb of the head IB, and the skew distortion at the start of the period Th occurs. That is, using the time axis of the reproduced signal Sfb of the head IB as a reference, the time axes of the reproduced signals Sfc of the heads IA and IC coincide with this, and the skew at the start of periods Tb and Tc is eliminated. Distortion is removed.

In this case, there is originally a skew distortion at the start of the period Ta, and the skew distortion at the start of the period Ta is replaced by the skew distortion at the start of the period Ta. The starting point is in the vertical planking period, and the skew distortion does not appear on the effective screen of the playback screen 9.

Thus, according to the present invention, even if the tape 2 expands or contracts or there is an error in the angular spacing between the heads IA to IC, skew distortion will not occur on the playback screen 9.Moreover, this skew distortion can be removed. Therefore, since a TBC (time base error correction device) is not required, for example, when reporting on a VTR, the recording state can be reproduced and monitored without bringing a large TBC to the reporting location.

In addition, in the forming circuit 41, the pulses Pv, Pga to P
When forming signals Sra to Src from nails, for example, the first
It can be formed as shown in FIG.

That is, as shown in FIGS. 11A and 11C, the monostable multipipelator is triggered by the vertical synchronizing pulse Pv, and a rising signal Sa is formed during the period Ta, and the AND of this signal Sa and the pulse P scale is As an output, as shown in FIG.
is extracted, and this pulse Pc triggers the monostable multipipulator to generate the signal S as shown in FIG. 11E.
rb is formed.

Further, as an AND output of this signal Srb and pulse Pgb, a pulse Pb is extracted every time the pulse P of the period information b is output as shown in FIG. Then, a signal Src is formed as shown in FIG. 11G.

Furthermore, in the same manner, a pulse Pa is formed from the AND output of the signal Src and the pulse P, as shown in FIG. 11, and a signal Sra is formed from this pulse Pa. Also,
When using a TBC, the support of the head IA and IC by the bimorph plates 61 and 61 and the detection circuit 70 may not be provided.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams for explaining the conventional example, Figure 3 is a system diagram of an example of the present invention, and Figures 4, 5, 9, and 10 are examples of its essential parts. , FIGS. 6 to 8, and FIG. 11 are diagrams for explaining the operation. 16 is an FM modulation circuit, 25 is an FM demodulation circuit L, 30 is a servo circuit, and 70 is a time axis error detection circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11

Claims (1)

[Claims] 1. Three rotating magnetic heads are rotated at a predetermined speed with predetermined steps and angular intervals from each other, and the magnetic tape is diagonally fixed over a predetermined angular range with respect to the rotating peripheral surface of the rotary magnetic head. On the magnetic tape, one field or one frame of the video signal is divided into three magnetic tracks, and the magnetic tape is divided into three magnetic tracks.
A magnetic track of a book is formed diagonally in each of three areas divided in the width direction of the magnetic tape, and the video signal is transmitted from the magnetic track by the rotating magnetic head in synchronization with the rotation of the rotating magnetic head. The video signals are sequentially taken out in a time-division manner and reproduced, and the rotating magnetic heads corresponding to the regions on both sides of the three regions of the magnetic tape correspond to the amount of skew of the reproduced video signals. A magnetic recording/reproducing device in which skew distortion of the reproduced video signal is corrected by displacing the magnetic track in the length direction.