JPS61258359A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent the omission of reproduction signals due to the changeover of heads and to obtain the reproduction signal having high picture quality, by switching heads with an overlap period set in a record mode and then with no overlap period set in a reproduction mode respectively. CONSTITUTION:A pulse signal SW is supplied to an input terminal 11, and head switch signals (c-f) which are used in a record mode are supplied to input terminals 12-15 respectively. The signal SW has a 1/2 cycle compared with those of signals (c-f) and a 50% duty ratio. Then the leading and trailing edges of the signal SW are set within the overlap period of signals (c-f) and furthermore within a period when two heads have a simultaneous touch to a magnetic tape. In a reproduction mode the pulse signal (g') serves as the head switch signal for a head 5 together with pulse signals (h', i' and j') serving as the head switch signals for head 6, 7 and 8 respectively.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] [The present invention relates to a helical scan type magnetic recording/reproducing device using four heads for recording and reproducing. This relates to the switching timing of these four heads in FIG.

[Background of the invention]

Traditionally, helical scan type magnetic recording and reproducing devices generally used two heads for recording and reproducing, but in recent years, helical scan type magnetic recording and reproducing devices have been modified to use four heads. magnetic recording and reproducing devices have been proposed (for example, Japanese Unexamined Patent Publication No. 56-85811,
JP-A-56-83813, JP-A-56-8581
Publication No. 4, etc.).

Here, a helical scan type magnetic recording/reproducing apparatus (hereinafter referred to as
A two-head type magnetic recording/reproducing apparatus) and a helical scan type magnetic recording/reproducing apparatus using four heads (hereinafter referred to as a four-head type magnetic recording/reproducing apparatus) will be schematically explained by comparing them with the drawings.

FIG. 3(4) is a plan view showing the rotating cylinder portion of the two-head magnetic recording/reproducing device, in which 1 is the rotating cylinder;
2.3 is the head.

In the same figure, two heads 2.3 having different azimuth angles are mounted on the rotating cylinder 1 at an angular interval of 180°, and the heads 2.3 are attached to the rotating cylinder 1 over an angle slightly larger than 180°, as shown in the figure. The magnetic tape is wound in a spiral. When the rotary cylinder 1 rotates in the direction of the arrow and the magnetic tape runs in its longitudinal direction, the head 2.5 alternately scans this magnetic tape.

Note that in order to indicate that the heads 2.3 have different azimuth angles, the reference numeral O20 is given on the drawing.

FIG. 3(8) shows a track pattern on a magnetic tape by such a two-head type magnetic recording/reproducing apparatus, where 4 is the magnetic tape e T2 *Ts is a track.

In FIG. 5(B), tracks Tz*T are formed on the magnetic tape 4 at a predetermined inclination angle with respect to its longitudinal direction.
31 T21 T3*... are formed in sequence. Here, every other track T2 is head 2 (Fig. 3 (4))
It is assumed that every other track T3 is formed by the head 5 (FIG. 6(A)), and these tracks T2. The magnetization direction differs between T3. Also, these tracks T2. A video signal is recorded for each field of T3ζ.

During reproduction, the rotational phase of the rotary cylinder 1 is controlled so that the head 2 scans the track T2 and the head 3 reproduces the track T3, and the reproduction signal from the head 2.5 is switched (that is, the head switching is performed). ) so that a continuous reproduction signal can be obtained. In this case, in order to obtain a continuous reproduction signal, the head 2.
A section (that is, an overlap section) in which heads 2 and 3 simultaneously record and play back is provided, and during playback, head switching is performed during this overlap section in which playback signals are obtained at the same time at heads 2 and 3, and there are no gaps in the playback signal after head switching. This prevents the occurrence of any problems.

FIG. 4 (4) is a plan view showing a rotating cylinder portion of a four-head magnetic recording/reproducing device, in which 1 is a rotating cylinder;
Reference numerals 5, 6, and 7.8 are heads; 0. Also, FIG. 4 CB) shows track patterns formed on the magnetic tape 4 in this case, and Ts to T8 are tracks.

In the figure, a rotary cylinder 1 is provided with four heads 5, 6, 7, 8 at angular intervals of 90°, and a magnetic tape 4 is spirally attached to the rotary cylinder 1 over an angle of 270°. It is wrapped. The azimuth angles of the heads 5 and 7, which are provided opposite to each other, are equal, and this is represented by the symbol O. Also, the azimuth angles of the other heads 6 and 8, which are provided opposite to each other, are the same, but they are different from the azimuth angle of the heads 5°7, and for this reason, the azimuth angle of the heads 6.8 is represented by the symbol ■. .

When the rotary cylinder 1 rotates in the direction of the arrow and the magnetic tape 4 runs in its longitudinal direction, each head 5, 6, 7 .
8 is sequentially delayed by 1/4 of the rotation period of the rotating cylinder and 2
The magnetic tape 4 is scanned for a period of 700 rotations. Therefore, as will be described in detail later, by repeatedly supplying video signals to each field in the order of 5, 6, and 7.8, a video signal is recorded on the magnetic tape 4 as shown in FIG. 4(B).
Tracks Ts, Ts are inclined at a predetermined angle with respect to the longitudinal direction, and have video signals recorded field by field.
, T7. Ts are formed sequentially. In addition, track T
5 by head 5, track T6 by head 6,
The track T7 is formed by the head 7, and the track T8 is formed by the head 8, and every other track Ts.

T7 has the same magnetization direction, and the other every other tracks T6 and Ts also have the same magnetization direction, but the magnetization directions are different between adjacent tracks.

During reproduction, the azimuth angle of the head is controlled in the same way as above so that the magnetization direction of the track matches the azimuth angle of the head, and the head 5, 6, 7.8
The heads are switched sequentially to obtain a continuous reproduction signal.

Here, if the two-head type magnetic recording/reproducing main device shown in FIG. 5 and the four-head type magnetic recording/reproducing device shown in FIG. 4 are made compatible, it is also explained in the previous patent publication. The diameter of the rotating cylinder 1 in FIG.
It can be made as small as 2/3 times the diameter of the rotating cylinder in the figure, and the four-head type magnetic recording/reproducing apparatus can be made smaller than the two-head type magnetic recording/reproducing apparatus.

By the way, the diameter of the rotating cylinder in a 2-head magnetic recording/reproducing device is approximately 60 mm, whereas the diameter of the rotating cylinder in a 4-head magnetic recording/reproducing device is approximately 4 mm.
It becomes 0111.

The switching order of heads 2.3 and 4th head in FIG. 3 in response to a 50Hz (frame frequency) head switching signal
The switching order of the heads 5, 6, 7, and 8 shown in the figure is as shown in FIG. However, in Fig. 5, (4) is the head switching signal, and (g) is the switching order of heads 2.3 in Fig. 3.
(Yutoshi shows the switching order of heads 5.6 and 7.8 in FIG. 4, respectively.

Next, FIG. 6 shows a specific configuration of a rotating cylinder portion of a four-head type magnetic recording/reproducing apparatus.

The operation will be explained in more detail. In addition, in the same figure, 9
．． 10 is a guide roller, and parts corresponding to those in FIG. 4 are given the same reference numerals.

As explained earlier, the rotary cylinder 1 has a head 5.
, 6, 7.8 are installed at angular intervals of 90°,
The magnetic tape 4 is helically wound around the rotary cylinder 1 over an angle slightly larger than 270° by guide rollers 9 and 10 and runs. Rotating cylinder 1
is rotating in the direction of the arrow, heads 5, 6, 7
8 is sequentially delayed by 1/4 of the rotation period of the rotary cylinder 10, and the magnetic tape 4 is scanned every rotation period of 270 degrees.

Although not shown in the figure, this rotating cylinder part has eight tack signal generators for every 101 rotations of the rotating cylinder, similar to a tack signal generator that detects 10 rotations of the rotating cylinder and generates a tack signal consisting of one pulse per rotation of the rotating cylinder 1. An F'G (FG signal generator that generates a frequency sporadic signal) consisting of pulses is provided.Here, as explained earlier,
One field (
If a video signal (1760 seconds) is to be recorded or played back, the number of revolutions of the rotating cylinder 1 is 45 revolutions/second, and the frequency of the tack signal is 45 flz,
The FG double signal frequency is 560Hz.

The timing at which the tack signal is generated is that a specific head (head 5 here) is slightly ahead of the scanning start point of the magnetic tape 4, and these tack signals and the FG
A head switching signal during recording and reproduction is formed from the double signal.

Here, a method of forming a head switching signal during recording will be explained with reference to FIGS. 7 and 8. In addition, the seventh
The figure shows changes in the positions of the heads 5, 6, and 7.8 over time, and the positions of the heads are A, B, and C each time the rotary cylinder 1 makes a 3/4 rotation (rotation of 270 degrees). ,D,E
The winding range of the magnetic tape 4 around the rotary cylinder 1 in B-H is the same as in A, although it is omitted. FIG. 8 is a timing chart of the tack signal, the FG double signal, and the head switching signal, where a is the tack signal, b is the FG signal +Ce (1+e@f is the head switching for the head 5.6° and 7.8°, respectively). To simplify the explanation, let us assume that the magnetic tape 4 is wound around the rotating cylinder 1 such that the heads 5, 6, 7° 8 are in contact with the magnetic tape 4 for a period of 270° rotation. do.

7 and 8, the head switching signal (!, a
l e, f are formed by dividing the frequency of the FG multiplied signal, and the reference timing of this frequency division operation is when the tack signal a is
It is set by a divided pulse of 15 tlz. As a result, if the head 5 starts contacting the magnetic tape 4 in state A in FIG. 7, the head switching signal C rises slightly before the time tl, and the head 5 completes contact with the magnetic tape 4. The fall occurs later than the time t2 in state B in FIG. 7, during which time the head switching signal C becomes 'H' (high level) and a video signal is supplied to the head 5, and from state A to state B. One field of video signal is recorded on the magnetic tape 4 at .Furthermore, in state B, the hand drive starts to come into contact with the magnetic tape 4, but a little before this time t2, head switching 1, No. d, becomes ``H''. Then, the video signal begins to be supplied to the head 6. This head switching signal d is output to 'L' a little later than the time t3 when the state C in FIG. 7 is reached.
" (low level), and the head 6 sends one field of video signal to the magnetic tape 4 from state B to state C.
4 records are recorded. Thereafter, in the same manner, the head switching signal e becomes %H" from a little before time t3 until a little later than time t4 when the state becomes D, and during this time the video signal is supplied to the head 7 for one field period. recorded and also
The head switching signal f becomes 1H from a little before time t4 until a time later than the time ts when the state E is reached, and during this time the video signal is supplied to the head 8i and recorded for one field period. Then, a video signal is repeatedly recorded one field at a time on the magnetic tape 4 in the order of heads 5, 6, 7.8.When the magnetic tape 4 is wound around the rotating cylinder 1 at an angle slightly larger than 270°. (This is the same,
The point in time when each head starts contacting the magnetic tape 4 is a little earlier than in the above case, and each head starts contacting the magnetic tape 4.
The respective head switching signals c, d are only slightly later in contact completion time than in the above case.

The times when e and f rise and fall are a little before the time when the heads 5, 6, 7.8 start contacting the magnetic tape 4, or from the time when they leave the magnetic tape 4, respectively, as in the above case. is also a little later.

Therefore, as shown in FIG. 9, the switching signal C9d, (1,
There is a temporally overlapping time Tov between f. This period Tov will hereinafter be referred to as an overlamp period. During this overlap period 'l'ov, two heads are simultaneously turned on and a video signal is supplied. That is, during the overlap period Tov of the head switching signals c and d, the video signal is simultaneously supplied to heads 5.6 (FIG. 6), and similarly, the head switching signals d and e
In the overlap period Tov, head 6.7 (Figure 6)
, the head switching signal e.

In the overlap period Tov of f, head 7.8 (sixth
Figure) shows an overlap period T of the head switching signals f and c.
ov, video signals are simultaneously supplied to each head 8.5. In this case, during these overlap periods Tov, of the two heads to which video signals are simultaneously supplied,
There is a period when either one is away from the magnetic tape 4.

By the way, during reproduction, the head switching signal C9d + e + used during recording is used as a switching signal for each head.
In this case, as explained earlier, head switching signals c, d, e are formed by inverting f.

The overlap period Tov is provided between 1 and 2.
As is well known in head-based magnetic recording and reproducing devices, this is intended to prevent playback signal loss from occurring at seams due to head switching during playback. If the signal is formed by inverting the head switching signal (!+d+e+f) at the time of recording, an overlap period Tov is provided between them, and a missing portion will occur in the reproduced signal at the seam due to head switching during reproduction.

That is, in FIG. 9, g is the head switching signal of head 5 (FIG. 6) during reproduction, and i and j are the head switching signals of heads 6, 7, and 8 (FIG. 6) during reproduction, respectively. signal, the head switching signal g is the head switching signal C during recording.
Hereinafter, the head switching signal is the inverted version of i.

” is the head switching signal do at the time of recording.6. This is the inversion of f. Also, during playback, when the head switching signal g is 'L'', the head 5 is turned on (this on means:
(meaning that the head is connected to a playback signal processing circuit (not shown)); hereinafter, the head switching signal is 'L' of i and j.
” period, heads 6, 7, and 8 are turned on, respectively.

By the way, head switching signals c and d during recording.

By providing an overlap period Tov in e and f, an overlap period To'v also occurs in the head switching signal g*b+1+j during reproduction. That is, the head switching signal g.

5, head switching signal he i, head switching signal t+
An overlap period To'v occurs between the head switching signals J and g, respectively.

If two heads are turned on at the same time during these overlap periods, the playback signals from these heads will be combined to produce a beat, which will be supplied to the playback signal processing circuit. Only one head is controlled to be turned on. For example, if priority is given to the head switching signal of the head to be scanned next for reproduction, the head switching signal g is 'L'' and the head 5
When is on, the head switching signal g appears as 'L', and the head 5 is turned off and the head 6 is turned on, and the head switching signal g.

During the overlap period To'v of h, only the head 6 is turned on. Similarly, in the overlap period To'v of the head switching signal i, only the head 7, in the overlap period To'v of the head switching signal x+j, only the head 8, and in the overlap period To'v of the head switching signal j1g. Only the heads 5 are each turned on, and only one head is always turned on without interruption, so that no beat occurs in the reproduced signal after head switching.

However, as is clear from the previous description of the operation during recording, there is a period during which either one of the heads does not come into contact with the magnetic chip 4 even during the overlap period To'v. For example, looking at the overlap period To'v between the head switching signals g and h, the head 6 is not in contact with the magnetic tape 4 for a certain period after the head switching signal becomes 1L. When the signal is inverted from 1H" to "L" and the head 5 is switched on from the head 6, a missing portion occurs in which no reproduced signal is obtained from any of the heads 5 and 6 for a certain period of time. During this time, as is clear from FIG.
Reference numeral 8 scans the magnetic tape 4, and each reproduced signal leaks into the transmission path of the head 6 via a rotary transformer or the like, and is sent to the reproduced signal processing circuit as crosstalk.

Such crosstalk occurs during the overlap period To in FIG.
'v, and this will affect the playback image quality.

[Purpose of the invention]

An object of the present invention is to provide a four-head type magnetic recording/reproducing device which eliminates the drawbacks of the prior art described above, suppresses the loss of reproduction signals due to head switching, and makes it possible to obtain reproduction signals of good image quality. It is on offer.

[Summary of the invention]

In order to achieve this object, the present invention performs logical operation processing on a head switching signal having an overlap period used during recording and a pulse signal having a half period of the head switching signal. The feature is that a head switching signal is formed.

[Embodiments of the invention]

Below, one example of 4ti of the present invention will be explained with reference to the drawings. Figure 1 shows a main circuit of an embodiment of a magnetic recording/reproducing device according to the present invention, in which 11 to 15 are input terminals, 16 is an N
OT gates, 17-20 are NAND gates, 21-24
is the output terminal. 1+, FIG. 2 is a timing chart of signals of each part in FIG. 1, and signals corresponding to those in FIG. 1 are given the same symbols.

1 and 2, the input terminal 11 is supplied with a pulse signal SW, and the input terminals 12, 15, 14
．． 15 are head switching signals c and 15 used during recording, respectively.
d, e, f are supplied. Here, the head switching signal c,
d, e, and f are the head switching signals ew ds shown in FIG.
This is similar to 6*f. In addition, the pulse signal SW
is a pulse signal having a period of 172 times the period of these head switching signals e* do eg f and a duty ratio of 50%, and its rising and falling edges are within the overlap period of the head switching signal et(1+ewf, Moreover,
There is a period during which two heads contact the magnetic tape at the same time. Such a pulse signal SW can be obtained, for example, by delaying the tack signal described above for a predetermined period of time, and then dividing and multiplying the signal. As explained in Figure 6, when recording and reproducing one field of video signals while the head rotates 270 degrees, the 45) iz tack signal is simultaneously magnetically transmitted by two heads in the overlap period. Delayed within the period of contact with tape 4, and then
By dividing the frequency by 3 and multiplying by 2, a desired pulse signal SW of 50H2 can be obtained.

The head switching signal C from the input terminal 12 is supplied to the NAND gate 17, hereinafter referred to as the head switching signal d.

e and f are NAND gates 18.1? , 20tC is supplied. Moreover, the pulse signal SW is the NAND gate 17
191 is directly supplied, and the pulse signal SW is inverted by the NOT gate 16 and supplied to the NAND gates 18 and 2o, respectively.

Therefore, the head switching signal C is output from the NAND gate 17.
'L' only during the 1H period of the pulse signal SW during the 'H' period of
The NAND gate 18 obtains a pulse signal h' which is 'L' only during the 'H' period of the head switching signal d and the 'L' period of the pulse signal SW. From 19 onwards, the head switching signal e
'L' only during the 'H' period of the pulse signal SW during the 1H' period of
A pulse signal i' is obtained, and from the NAND gate 20, a pulse signal SW of the 'H' period of the head switching signal f is obtained.
A pulse signal j' that is 'L' only during the 1L period is obtained. Therefore, the rising edge of pulse signal g' and the falling edge of pulse signal h' match, and hereinafter, the rising edge of pulse signal h', the falling edge of pulse signal i', and the rising edge of pulse signal i' Since the falling edge of pulse signal j', the rising edge of pulse signal j' and the falling edge of pulse signal g' coincide, there is no overlap period between these pulse signals g's h's IZj'. Moreover, at each rising edge and falling edge, two heads are in contact with the magnetic tape at the same time.

During reproduction, the pulse signal g' becomes a head switching signal for head 5 in FIG. 6, the pulse signal h' becomes a head switching signal for head 6, and the pulse signal i' becomes a head switching signal for head 7. Similarly, j' is a head switching signal for the head 8. For this reason, during playback, missing parts of the playback signal when switching heads can be greatly suppressed, crosstalk between head channels is greatly reduced, and no beats occur, allowing playback images of good quality. Obtainable.

〔Effect of the invention〕

As explained above, according to the present invention, during recording, the head is switched with an overlap period provided, and during playback, the head is switched without the overlap period. By suppressing missing parts of the playback signal during switching, crosstalk between head channels can be significantly reduced, and playback images of good quality with less jitter and color unevenness can be obtained.
It is possible to provide a magnetic recording/reproducing device with superior functionality not found in the above-mentioned prior art.

[Brief explanation of the drawing]

Fig. 1 is a main circuit diagram showing an embodiment of a magnetic recording/reproducing device according to the present invention, Fig. 2 is a timing chart of signals of each part in Fig. 1, and Fig. 3 is a two-head type magnetic recording/reproducing device. Figure 4 (B) is a plan view showing the rotating cylinder part of a 4-head type magnetic recording/reproducing device. A track pattern diagram on a magnetic tape. Figure 5 is a schematic diagram showing the switching order of each head in a two-head magnetic recording/reproducing device and a four-head magnetic recording/reproducing device. Figure 6 is a four-head magnetic recording/reproducing device. FIG. 7 is a plan view showing the rotating cylinder part of the device in more detail. FIG. 7 is a schematic diagram showing temporal positional changes of each head in a four-head magnetic recording/reproducing device. FIG. FIG. 9 is a timing chart showing the generation timing of head switching pulses with respect to the state. FIG. 9 is a timing chart showing head switching signals during recording and playback in a conventional four-head magnetic recording/reproducing device. ...Magnetic tape 5~B・
...Head 11-15...Input terminal 16...
NOT gates 17-20...NAND gates 21-24...Output terminals

Claims (1)

[Claims] A rotating cylinder is provided with four recording/reproducing heads at equal angular intervals, and during recording, tracks are created on the magnetic tape by sequentially switching the heads using recording head switching signals that partially overlap each other. In a magnetic recording and reproducing apparatus configured to sequentially form a reproducing head switching signal, a means is provided for forming a reproducing head switching signal that does not overlap with each other from the recording head switching signal, and during reproduction, the reproducing head switching signal causes the head to be switched. A magnetic recording/reproducing device characterized in that it is configured to sequentially switch.