JPH0325311Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention relates to a magnetic reproducing device, especially for rotating bodies.
The present invention relates to a magnetic reproducing device which obtains temporally continuous reproduction signals by switching the reproduction signals from four magnetic heads mounted at equal angular intervals of 90°.

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 each 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 travel 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. As described in detail below, video signals with a field frequency of 60 Hz (or 59.94 Hz) are sequentially recorded by video heads A, B, C, and D at a rate of one field per track. 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 a rate of 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
A track locus is drawn sequentially by heads A, D, C, B in the order of
In the figure, for convenience of illustration, the track width of each track locus is shown as being equal to the track pitch. ). Further, 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 period of two fields.

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, 7D, 8A, . . . , the video track indicated by _t1 in FIG. By switching the recording head approximately every one field period in the order of B→C→D→A→..., the video track changes from t ₂ → t ₃ → t ₄ → t ₅ →...
They are formed sequentially in this order.

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. Therefore, during playback of the above-mentioned 2-head helical scanning VTR, 2
The reproduction signals of the video heads can be alternately switched for each field.

Problems to be solved by the invention On the other hand, in the case of the 4-head VTR mentioned above,
For example, rotating body 1 rotates at 45 rps, whereas
The period during which the video heads A to D scan the magnetic tape 2 is approximately 270° rotation period (approximately 3/4 rotation period) of the rotating body 1, and approximately 90° rotation period (approximately 1/4 rotation period). Since it is not in contact with the magnetic tape 2,
The problem is that the phase of the head and the rotational phase of the rotating body 1 do not match, and therefore the rotational phase detection pulse of the rotating body 1 cannot be used as is to sequentially switch the reproduction signals of the four video heads. It was hot.

Therefore, the present invention uses a rotation detecting pulse synchronized with the rotational phase of a rotating body to which four magnetic heads are attached to a first pulse having a period three times as long as one rotation period of the rotating body.
A magnetic recording/reproducing device which generates a signal and a second signal having a period 1/2 times that of the first signal, and can suitably switch each reproduction signal of four magnetic heads based on these signals. The purpose is to provide

Means for Solving the Problems The present invention consists of a magnetic tape wound over an angular range of over 270 degrees, and each of the four heads
A magnetic device that reproduces recorded video signals by rotating rotating bodies installed at equal angular intervals of 90° at a rotation speed of 270° per period that is a natural number times one field period of the video signal to be reproduced. The reproducing device includes a means for extracting a rotation detection pulse that is synchronized with the rotation phase of the rotor and has the same period as the rotation period, and a means for dividing the rotation detection pulse to obtain a rotation period of one rotation of the rotor. frequency dividing means for respectively outputting a first signal having a period approximately equal to twice the period and a second signal having a period approximately equal to 3/2 times the one rotation period; signals or periods generated from these signals are the same as the first signal and mutually different;
Duty cycle with a 90° phase difference of approximately 25% 4
The apparatus is comprised of a switching means for sequentially switching and selectively outputting each reproduced signal from the four heads based on a seed pulse, and each embodiment thereof will be described below with reference to the drawings.

Embodiment FIG. 4 shows a rotation system diagram of an embodiment of the main part of the device of the present invention. In the figure, a rotation detection pulse is input to the input terminal 11 in synchronization with the rotational phase of the rotating body 1 shown in FIG. 1 and having the same period as the rotation period. 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 cycle of the pulse a is a 270° rotation period, which is equal to one field period of a 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 three rotations of the rotating body 1 as described later. This also means that a pulse d is output every four field 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. be done. As a result, the output signal waveform of the flip-flop 20 becomes a rectangular wave j shown in FIG. 5J. Here, the time constants of the monomultis 18 and 19 are adjusted so that the output signal j of the flip-flop 20 becomes a symmetrical rectangular wave with a duty cycle of 50%.

Repetition frequency 30Hz generated in this way
The symmetrical rectangular wave j is output from the output terminal 21 as a switching signal, and is also supplied to the 1/2 frequency divider 22. The 1/2 frequency divider 22 is reset by the pulse d, and divides the symmetrical rectangular wave j by 1/2 to output a symmetrical rectangular wave k with a repetition frequency of 15 Hz to the output terminal 23, as shown in FIG. 5K. Output as a switching signal.

Next, a first embodiment of the device of the present invention will be described with reference to FIG. In FIG. 6, the same components as in FIG. 1 are given the same reference numerals. A magnetic tape 2 having a tape pattern as shown in FIG. 3 is wound around a rotating body 1 to which video heads A to D are attached as shown in FIG. 1 over an angular range of over 270 degrees. , video heads A to D reproduce recorded video signals on the magnetic tape 2. The signal reproduced by video head A and the signal reproduced by video head B are supplied to terminals 26L and 26H of the switch circuit 26 through preamplifiers 25A and 25B, respectively, and are sequentially reproduced by video heads C and D. The generated signals are supplied to terminals 27L and 27H of the switch circuit 27 through preamplifiers 25C and 25D.

The switch circuits 26 and 27 selectively output the input signals of the terminals 26H and 27H during one field period when the pulse j from the input terminal 28 is at a high level.
During one field period when the pulse j is at a low level, switching control is performed by the pulse j so that the input signals of the terminals 26L and 27L are selectively output.
The reproduction signals taken out from the switch circuits 26 and 29, respectively, are transmitted to the terminals 29H and 2 of the switch circuit 29.
Applied to 9L. The switch circuit 29 is switching controlled by the pulse k from the input terminal 30, and during the two-field period when the pulse k is at high level, it is connected to the terminal 29H to selectively output the output reproduction signal of the switch circuit 26, and the pulse k is at the low level. During the 2 field period, the output reproduction signal of the switch circuit 27 is selectively output by being connected to the terminal 29L.

Therefore, as is clear from FIGS. 5J and 5K, the signal taken out from the switch circuit 29 to the output terminal 31 is transmitted to the rotating body 1 in the rotational direction as follows: A→B→C→D→A... Those reproduced signals are extracted one field at a time in the order of those attached before the field.

Next, a second embodiment of the device of the present invention will be described with reference to FIG. In the figure, the same components as those in FIG. 6 are denoted by the same reference numerals, and the explanation thereof will be omitted. The switch circuits 32 and 33 are interlocked and controlled by the pulse k input from the input terminal 34, and during the two-field period when the pulse k is at a high level, the video heads A and B input to the terminals 32H and 33H are switched. During the 2-field period in which the reproduction signal is output and the pulse k is at a low level, the terminals 32L, 3
The playback signals of video heads C and D input to 3L are selectively output. These switch circuits 32, 33
The output signal is output from terminals 35L and 3 of the switch circuit 35.
Applied to 5H. The switch circuit 35 selectively processes the reproduction signal of video head B or D in response to the pulse j input to the input terminal 36 during one field period when the pulse j is at a high level, and processes the reproduction signal of the video head B or D during one field period when the pulse j is at a low level. selectively outputs the reproduction signal of video head A or C. Therefore,
In the case of this embodiment as well, since the pulses j and k have the phase relationship as shown in FIG. 5 J and K, respectively, the video heads A→B→C→D→A→...
These reproduction signals are outputted to the output terminal 37 one field at a time in this order.

Next, a third embodiment of the device of the present invention will be described. FIG. 8 is a block system diagram of a third embodiment of the device of the present invention, in which the same components as in FIG. 6 are designated by the same reference numerals and their explanations will be omitted. switch circuit 38,
39, 40 and 41 are video heads A, B, respectively.
The reproduction signals C and D are supplied separately to the 10th input terminal 42, 43, 44 and 45, respectively.
The structure is such that the input signal is passed during the high level periods of the pulses shown in FIGS. A, B, C, and D.

Here, the four types of switching pulses shown in FIGS. 10A to 10D are generated as follows. The input terminal 49 shown in FIG. 9 synchronizes with the rotational phase of the rotating body 1 as shown in FIG.
A pulse j with a period equal to
1, and on the other hand, it is applied to the multiplexer 51 from the input terminal 50 in synchronization with the rotational phase of the rotating body 1 as shown in FIG. A pulse k with a period equal to 15 seconds) is supplied.

The multiplexer 51 is made up of a logic circuit, and has a duty cycle of 25% from these pulses j and k, which has the same period as pulse k (here, as an example, 4 field periods) and whose phases are different from each other by 90 degrees. Four types of pulses are generated as shown in FIGS. 10A to 10D, respectively, and are sent to output terminals 52 to 5.
Output to 5 in parallel. The first pulse shown in FIG. 10A is transmitted from the output terminal 52 to the input terminal 42, the second pulse shown in FIG. 10B is transmitted from the output terminal 53 to the input terminal 43, and the third pulse shown in FIG. The fourth pulse shown in D is transmitted from the output terminal 54 to the input terminal 44, and the fourth pulse shown in FIG.
5 to the input terminal 45.

As a result, when the video head A is scanning the video track, the switch circuit 38 is controlled to pass the input signal, and thereafter the switch circuits 39, 40, 41,
38, . Therefore, in the case of this embodiment, similarly to the first and second embodiments, the reproduced signals of the video heads are chronologically reproduced for each field in the order of A→B→C→D→A→... The output signal is synthesized into the output terminal 47 and taken out from the output terminal 47.

Although not shown in FIGS. 6, 7, and 8, video heads A to D each transmit and receive signals via their corresponding rotary transformers.
FIG. 11 is a partially cutaway perspective view showing the rotary transformer in the device of the present invention, in which the same components as in FIG. 1 are given the same reference numerals. A disk-shaped rotating core 60 is fixed to the lower surface of the rotating body 1, and a disk-shaped fixed core 61 is disposed opposite to and spaced apart from this rotating core 60 by a small distance.

Annular coils 62, 63,
64 and 65 are buried. Concentric annular coils 66, 67, 68, and 69 are embedded in the upper surface of the fixed core 61 at positions facing the annular coils 62, 63, 64, and 65, respectively. During recording and reproduction, the rotating core 60 rotates integrally with the rotating body 1, while the fixed core 61 is always stationary, and the above-mentioned annular coils 62, 66, 6
Signals are sent and received between 3 and 67, 64 and 68, and 65 and 69, respectively.

Here, in the case of the first embodiment, for example, the toroidal coil 62 is connected to the video head A, the toroidal coil 63 is connected to the video head C, the toroidal coil 64 is connected to the video head B, and the toroidal coil 65 is connected to the video head C. is connected to video head D. As a result, the annular coils 62 and 64 connected to video heads A and B and the annular coils 63 and 65 connected to video heads C and D are provided at separate positions, respectively. Crosstalk between video heads A and B and video heads C and D at each output of switch circuits 26 and 27 shown in the figure.
It is possible to prevent crosstalk between

Further, in the case of the second embodiment shown in FIG. 7, the annular coils 62, 63, 64 and 65 are connected to, for example, video heads A, B, C and D, respectively, so that a switch circuit can be established in the same manner as above. 32, 33
Crosstalk between video heads A and C and between video heads B and D at each output can be prevented.

Effects As described above, according to the present invention, in a four-head VTR in which the rotational phase of the rotating body and the rotational phase of the reproduction magnetic head do not match, each reproduction signal of the four magnetic heads is sequentially and cyclically transmitted at regular intervals. It has the advantage of being able to take out reproduced video signals temporally continuously from the inclined track formed on the magnetic tape without crosstalk.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the head arrangement of the device of the present invention, FIG. 2 is a diagram showing the scanning locus of the head shown in FIG. 1, and FIG. 4 is a circuit system diagram showing an embodiment of the main part of the device of the present invention, FIGS. 5A to 5K are time charts for explaining the operation of the circuit system shown in FIG. 4, and FIGS. 8 and 8 are block system diagrams respectively showing the first, second and third embodiments of the device of the present invention, and FIG. 9 shows an example of a switching pulse generation circuit used in the block system shown in FIG. 8. 10A to 10D are respectively a time chart for explaining the operation of FIG. 9, and FIG. 11 is a partially cutaway perspective view showing an embodiment of the rotary transformer structure in the device of the present invention. 1...Rotating body, 2...Magnetic tape, 3a, 3b
... Guide pole, 11 ... Rotation detection pulse input terminal, 12 ... Counter, 22 ... 1/2 frequency divider,
25A to 25D...Preamplifier, 26, 27, 2
9, 32, 33, 35, 38-41...Switch circuit, 31, 37, 47...Reproduction signal output terminal,
51... Multiplexer, 60... Rotating core, 6
1... Fixed core, A, B, C, D... Magnetic head (video head).

Claims (1)

[Claims for Utility Model Registration] (1) A rotating body on which a magnetic tape is wound over an angular range of more than 270°, and four heads are attached at equal angular intervals of 90°, A magnetic reproducing device that reproduces recorded video signals by rotating at a rotation speed of 270 degrees per period that is one natural number of one field period of the video signal to be reproduced, wherein the rotational phase of the rotating body means for extracting rotation detection pulses that are synchronized and have the same period as the rotation period; and a first signal that divides the rotation detection pulse and has a period approximately equal to three times the period of one rotation of the rotating body. a frequency dividing means for outputting a second signal having a period approximately equal to 3/2 times the period of one rotation; is the same as the signal, and
Duty circles that are 90° out of phase with each other
A magnetic reproducing device comprising switching means for sequentially switching and selectively outputting respective reproduction signals from the four heads based on four types of pulses of 25%. (2) The switching means switches the four heads attached to the rotating body into first, second, and third heads in the order of the heads attached in advance in the rotating direction of the rotating body.
and a fourth head, a first switch circuit that alternately switches each reproduction signal of the first head and the second head by the second signal, and a first switch circuit that alternately switches the reproduction signals of the first head and the second head, and a second switch circuit that alternately switches each reproduction signal of the head according to the second signal; and a third switch circuit that alternately switches each output signal of the first and second switch circuits according to the first signal. Utility model registration claim 1, comprising a circuit, configured to sequentially and cyclically extract reproduction signals of the first, second, third, and fourth heads from the third switch circuit in the order of the first, second, third, and fourth heads. The magnetic reproducing device described in Section 1. (3) The switching means switches the four heads attached to the rotary body into first, second, and third heads in the order of the head attached in advance in the rotational direction of the rotary body.
and a fourth head, a first switch circuit that alternately switches each reproduction signal of the first head and the third head by the first signal, and a first switch circuit that alternately switches the reproduction signals of the first head and the third head, and a second switch circuit that alternately switches each reproduction signal of the head in accordance with the first signal; and a third switch circuit that alternately switches each output signal of the first and second switch circuits in accordance with the second signal. Utility model registration claim 1, comprising a circuit, configured to sequentially and cyclically extract reproduction signals of the first, second, third, and fourth heads from the third switch circuit in the order of the first, second, third, and fourth heads. The magnetic reproducing device described in Section 1. (4) The switching means switches the four heads attached to the rotary body into first, second, and third heads in the order of the heads attached in advance in the rotational direction of the rotary body.
and a fourth head, the first and second heads
The reproduced signals of the first to fourth heads are generated by four types of pulses having the same period as the first signal and having a duty cycle of about 25% and having a phase difference of 90 degrees from each other. It consists of first to fourth switch circuits that select and output each separately, and from the first to fourth switch circuits, the first,
2. A magnetic reproducing apparatus according to claim 1, which is configured to sequentially and cyclically extract reproduction signals from the second, third and fourth heads in order.