JPH08293109A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE: To provide a magnetic recording/reproducing device capable of surely acquiring the searching data even in high speed search by reducing scan position deviation of a head at a searching time and always making it a fixed value regardless of a search speed. CONSTITUTION: This device is provided with at least three heads of a first head 3a and a second head 3b having a first azimuth angle and a third head 3c having a second azimuth angle. Then, the first head 3a is confronted with the second head 3b by 180 deg. on a rotary drum 1, and the second head 3b and the third head 3c are arranged adjacently at a minute phase difference in the circumferential direction of the rotary drum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus such as a video tape recorder for recording / reproducing a signal on / from a magnetic tape by a helical scan system using a rotary head.

[0002]

2. Description of the Related Art Conventionally, a video tape recorder (VT)
In the magnetic recording / reproducing apparatus such as R), the helical scan method has been widely adopted which can increase the recording density of signals on the magnetic tape. Further, in recent years, a helical scan method has often been adopted in a magnetic recording / reproducing apparatus for recording / reproducing a digital signal such as a data recorder or a digital VTR in order to handle a large capacity digital signal. The data rate of a digital signal varies, and for example, a video signal is compressed from a fraction of the original data to a few tenths of the original data by high-efficiency encoding, and has various data rates. Therefore, the recording / reproducing apparatus also supports a plurality of data rates, and at a low data rate, the recording time is lengthened accordingly. The configuration and operation of an example of the magnetic recording / reproducing apparatus that handles a plurality of data rates will be described below.

FIG. 8 shows the structure of a conventional magnetic recording / reproducing apparatus. Further, FIG. 9 is an explanatory view showing a head mounting position of a conventional magnetic recording / reproducing apparatus. The conventional magnetic recording / reproducing apparatus includes a standard mode and a long-time mode in which the recording time is N times (N is a natural number) the standard mode.

In FIG. 8 and FIG. 9, 21 is a rotary drum,
22 is a magnetic tape, 24 is a capstan, 25 is a pinch roller, and 26 is a capstan controller. The rotating drum 21 rotates at a constant speed regardless of the mode. The magnetic tape 22 is obliquely wound on the rotary drum 21 over a little over 180 °, and is driven at a predetermined speed by the capstan 24 and the pinch roller 25. Capstan control unit 26
Is 1 / N of the standard mode in the case of N times the long time mode
The rotational speed of the capstan 24 is controlled so that the magnetic tape 22 runs at a constant speed. 23a is the first head,
23b is a second head and 23c is a third head.
The head 23a and the head 23b have a first azimuth angle (L).
And the head 23c has a second azimuth angle (R). The head 23a and the head 23c are the rotary drum 2
The head 23b and the head 23c are mounted close to each other with a phase difference θ in the circumferential direction of the rotary drum 21. Also, the head 23
The head a, the head 23b, and the head 23c are attached at the same height in the rotation axis direction of the rotary drum 21.

Reference numeral 27 is a head selecting means, 28 is a head amplifier, 29 is a signal processing section, and 30 is a digital signal input / output terminal. The head selecting means 27 selects a head for recording or reproducing at a timing according to the mode, and the head amplifier 28 adjusts gains of recording and reproducing signals.
The signal processing unit 29 compresses and encodes the signal in the long time mode,
Decompression / decoding, time axis compression / decompression are performed. That is, at the time of recording in the N times long time mode, the digital signal input to the digital signal input / output terminal 30 is compression-encoded and time-axis compressed to 1 / N by the signal processing unit 29 and output to the head amplifier 28. Further, during reproduction in the N times long time mode, the reproduction signal from the head amplifier 28 is supplied to the signal processing unit 29.
Then, the time axis extension and extension decoding are performed N times and output to the digital signal input / output terminal 30.

Next, head selection and recording timing in this conventional example will be described. In the standard mode, the head scan has one track pitch (hereinafter, the track pitch is abbreviated as Tp) while the rotary drum 21 rotates 1/2 turn.
The magnetic tape 22 runs at a deviating speed, and the rotating drum 21
The recording is alternately performed by the head 23a and the head 23c for every 1/2 rotation.

In the long time mode in which the recording time is twice as long as in the standard mode (double time long time mode), the magnetic tape 22 runs at a speed at which the head scan shifts by 1 Tp while the rotating drum 21 makes one revolution. The recording is alternately performed by the head 23b and the head 23c every one rotation of the rotary drum 21.

Now, the influence of the phase difference θ between the heads 23b and 23c will be described. Normally, two heads 23b and 23c cannot be mounted at the same position,
The head-to-head distance is at least about 1 to 2 mm. This is a phase difference corresponding to an angle of about 5 to 10 ° when the rotating drum diameter is 20 mm. Therefore, the head 23b precedes the head 23c by the phase angle θ with respect to the rotation direction of the rotary drum 21, and the head 23b
There is a time difference between the scanning start of c and the head 23b. Therefore, the scanning positions of the heads 23b and 23c are displaced in the track width direction by an amount obtained by converting the amount of travel of the magnetic tape 22 in the track width direction during this time difference. As a result, the track pitch of the recording tracks deviates. In the long time mode twice as long as the conventional example, the magnetic tape 22 is rotated while the rotating drum makes one rotation (= 360 °).
Runs 1 Tp in the track width direction, the scan position shift is Δx = Tp × θ / 360. In addition,
The digital signal recorded in the double long-time mode is a digital signal compression-coded at a data rate of about ½ of the data rate of the standard mode and time-compressed to ½. .

The operation in the standard mode and the double long time mode has been described above. Generally, in the case of the N long time mode (N is a natural number), the running speed of the magnetic tape 22 is 1 / th of the standard mode. N, every N / 2 rotations of the rotary drum 21,
When N is an odd number, the head 23a and the head 23c
When the number is even, recording is alternately performed by the heads 23b and 23c to form recording tracks having a track pitch of about Tp and adjacent tracks having opposite azimuths. Note that N
In the double long-time mode, a digital signal is compression-encoded at a data rate of about 1 / N with respect to the data rate of the standard mode, and a time-axis compressed digital signal is recorded at 1 / N.

The operation during recording has been described above.
Since the recording track can be traced at the time of reproduction by the same operation as that at the time of recording, detailed description will be omitted. The reproduced digital signal in the N-time long-time mode is time-axis expanded and expanded-decoded N times in the signal processing unit 29.

Next, the operation at the time of search will be described. FIG. 10 is an explanatory diagram showing the layout of the head scan locus and search data during a search. In FIG. 10, reference numeral 33 is search data. Now, it is assumed that a search (10 times speed search) in which the magnetic tape 22 is run at a speed 10 times that of the standard mode is performed, and the search data 33 is arranged on the track recorded at the first azimuth angle. Since the search data is arranged on the track having the first azimuth angle, the search data is acquired by using the head 23a and the head 23b having the first azimuth angle. 31 is 10
Scan trajectory of the head 23a during double speed search, 3
Reference numeral 2 is a scan locus of the head 23b. At the time of search, as shown in FIG. 10, the search data is arranged at a specific position on the track, and the capstan 24 is controlled so that the head scans the position to obtain the search data.

Here, the head 23b is the same as the head 23a.
The phase angle θ leads the direction of rotation of the rotary drum 1 from a position facing each other by 80 °, and the rotary drum 21 has an angle θ.
The head 23c starts scanning earlier by the time it rotates.
Due to this time difference, the position where the head 23b and the head 23c scan the magnetic tape 22 is displaced. The deviation amount of the scan position is an amount obtained by converting the amount of travel of the magnetic tape 22 in the time when the rotary drum 21 rotates by the phase angle θ in the track pitch direction. In the 10 × speed search, the magnetic tape 22 is running at a speed at which the head scan deviates by 10 · Tp while the rotary drum 1 makes 1/2 rotation (= 180 °). , Δx = 10 · Tp × θ / 180.

Although the 10 × speed search has been described above, in the case of a search in which the magnetic tape 22 is run at a speed K times faster than the standard mode (called a K speed search), the scan position shift amount of the head 23b is generally. Is Δx = K
× Tp × θ / 180.

[0014]

However, in the above configuration, in the search in which the magnetic tape is run at a speed K times faster than the standard mode, the scan position of the head 23b is 180 ° opposite to the head 23a. The position was deviated by Δx = K × Tp × θ / 180.
The amount of deviation of the scan position increases in proportion to the search speed, which causes a problem that it is difficult to acquire search data in high speed search. For example, Tp = 10μ
Assuming that a search of 10 times is performed with m and θ = 10 °, the scan position shift amount is Δx = 5.6 μm, and the search data is obtained by both the head 23a and the head 23b while the rotary drum 21 makes one rotation. It will be very difficult to obtain.

In view of the above-mentioned problems, the present invention can reduce the scan position deviation at the time of search and make it constant regardless of the search speed, and can reliably acquire data even at the time of high-speed search. The purpose is to provide.

[0016]

In order to solve the above problems, a magnetic recording / reproducing apparatus of the present invention comprises a first head, a first head for performing a recording or reproducing operation by scanning a magnetic tape on the circumference of a rotating drum. At least three heads of a second head and a third head, wherein the first head and the second head have a first azimuth angle, and the third head has a second head.
The first head and the second head face each other by 180 ° on the rotary drum, and the second head and the third head are minute in the circumferential direction of the rotary drum. The configuration is such that they are close to each other with a phase difference.

The first head and the third head are attached with a first minute step in the rotation axis direction of the rotary drum, and the second head and the third head are attached in the rotation axis direction of the rotary drum. It has a structure in which it is attached with two minute steps.

[0018]

With the above-described structure, the present invention can reduce the scan position deviation between the first head and the second head during the search, and can keep the scan position constant regardless of the search speed. It becomes possible to acquire search data.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of a magnetic recording / reproducing apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a rotary drum, and 2 is a magnetic tape. 3a is a first head, 3b is a second head, 3c is a third head, the heads 3a and 3b have a first azimuth angle (L), and the head 3c has a second azimuth angle (R). ing. 4 is a capstan, 5 is a pinch roller, and 6 is a capstan controller. Reference numeral 7 is a head selecting means, 8 is a head amplifier, 9 is a signal processing unit, and 10 is a digital signal input / output terminal.

FIG. 2 is an explanatory view showing the head mounting position of the magnetic recording / reproducing apparatus in the embodiment of the present invention. Figure 2
In FIG. 1, the same components as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 2, the head 3a and the head 3b are attached to the rotary drum 1 so as to face each other by 180 °. Further, the head 3b and the head 3c are mounted close to each other with a phase difference θ provided in the circumferential direction of the rotary drum 1. The head 3a and the head 3c are attached by providing a first minute step ΔH1 in the rotation axis direction of the rotary drum 1. Further, the head 3b and the head 3c are attached by providing a second minute step ΔH2 in the rotation axis direction of the rotary drum 1.

The operation of the magnetic recording / reproducing apparatus configured as described above will be described below with reference to FIGS. 1 and 2.

The magnetic recording / reproducing apparatus of this embodiment has a standard mode and a long-time mode in which the recording time is N times (N is a natural number) the standard mode. The rotary drum 1 rotates at a constant speed regardless of the mode. The magnetic tape 2 is wound around the rotary drum 1 obliquely over 180 °, and is driven at a predetermined speed by the capstan 4 and the pinch roller 5. In the long time mode of N times, the capstan control unit 6 controls the rotation speed of the capstan 4 so that the magnetic tape 2 runs at a constant speed of 1 / N of the standard mode. The head selecting means 7 selects a head for recording or reproducing at a timing according to the mode. The head amplifier 8 amplifies recording and reproducing signals. Signal processing unit 9
Performs signal compression coding, decompression decoding, and time axis compression / decompression in the long time mode. That is, at the time of recording in the N times long time mode, the digital signal input to the digital signal input / output terminal 10 is compression-encoded and time-axis compressed to 1 / N by the signal processing unit 9 and output to the head amplifier 8. Further, during reproduction in the N times long time mode, the reproduction signal from the head amplifier 8 is subjected to N times time axis expansion and expansion decoding by the signal processing unit 9 and output to the digital signal input / output terminal 10.

FIGS. 3 and 4 are explanatory diagrams showing head selection and recording timing at the time of signal recording of the magnetic recording / reproducing apparatus in the embodiment of the present invention. A is a recording track, B is a head used for recording, and C is a time axis indicating recording timing. Here, on the time axis, the time during which the rotary drum 1 makes one rotation is represented by T, and the recording section is shown by a rectangle.

FIG. 3 shows the head selection and recording timing in the standard mode. In the standard mode, the head scan is 1T while the rotary drum 1 rotates 1/2 turn.
The magnetic tape 2 runs at a speed that deviates. Further, in the standard mode, the recording is alternately performed by the head 3a and the head 3c every 1/2 rotation of the rotary drum 1. Here, the head 3c is
Since the head 3a is ahead of the head 3a by 180 ° with respect to the rotation direction of the rotary drum 1 by a phase angle θ, the head 3c starts scanning earlier by the time when the rotary drum 1 rotates by the angle θ. Therefore, in consideration of the amount of travel of the magnetic tape 2 during the time when the rotary drum 1 rotates by the angle θ, the head 3c is attached above the head 3a by a minute step ΔH1. By providing such a minute step ΔH1, a recording track having a track pitch Tp can be formed. The optimum small step ΔH1 in the standard mode is the rotary drum 1
Since the head scan is deviated by 1 Tp while ½ rotation (= 180 °), ΔH1 = Tp × θ / 180. Further, by alternately recording with the head 3a and the head 3c, adjacent tracks have mutually opposite azimuths,
High-density recording is possible without a guard band.

FIG. 4 shows that the recording time is 2 for the standard mode.
It shows the head selection and recording timing in the double long-time mode (double long-time mode). In the double long-time mode, the magnetic tape 2 runs at a speed at which the head scan shifts by 1 Tp while the rotating drum 1 makes one rotation. Also, in the double long time mode,
The recording is alternately performed by the head 3b and the head 3c for each rotation. Here, the head 3c leads the head 3b by the phase angle θ with respect to the rotation direction of the rotary drum 1, and the scanning start of the head 3c is advanced by the time when the rotary drum 1 rotates by the angle θ. Therefore, in consideration of the amount of travel of the magnetic tape 2 during the time when the rotating drum 1 rotates by the angle θ, the head 3c
Is attached above the head 3b by a minute step ΔH2. By providing such a minute step ΔH2, a recording track having a track pitch Tp can be formed. The optimum minute step ΔH2 in the long time mode of 2 times is ΔH2 = Tp × θ / 360 because the head scan is shifted by 1 Tp while the rotating drum 1 makes one rotation (= 360 °).
Becomes Further, by alternately recording with the head 3b and the head 3c, adjacent tracks have mutually opposite azimuths, so that high-density recording is possible without a guard band. Note that the digital signal recorded in the double long-time mode is a digital signal compressed and encoded at a data rate of about 1/2 of the data rate of the standard mode.
The time axis is compressed.

The operation in the standard mode and the double long time mode has been described above. Generally, in the case of the N long time mode (N is a natural number), the running speed of the magnetic tape 2 is 1 / th of the standard mode. N, and for every N / 2 rotations of the rotary drum 1, by alternately recording with the heads 3a and 3c when N is an odd number and with the heads 3b and 3c when N is an even number, the track pitch Is about Tp, it is possible to form recording tracks in which adjacent tracks have mutually opposite azimuths. Then, in the N-time long-time mode, a digital signal is compression-encoded at a data rate of about 1 / N with respect to the data rate of the standard mode, and a time-axis compressed digital signal is recorded at 1 / N.

The operation during recording has been described above.
Also during reproduction, the recording track can be traced by the same operation as during recording, and therefore description thereof will be omitted. The reproduced digital signal in the N-time long-time mode is time-axis expanded and expanded-decoded N times in the signal processing unit 9.

Next, the operation at the time of search will be described. FIG. 5 is an explanatory diagram showing the arrangement of the head scan locus and search data during a search. In FIG. 5, reference numeral 13 is search data. Now, a search for running the magnetic tape 2 at a speed 10 times faster than the standard mode (10 times speed search)
It is assumed that the search data 13 is arranged on the track having the first azimuth angle. Since the search data is arranged on the track having the first azimuth angle, the search data is acquired using the heads 3a and 3b having the first azimuth angle. 11 is a head 3 at the time of 10 times speed search
The scan locus of a and the scan locus 12 of the head 3b. At the time of search, as shown in FIG. 5, the search data 13 is arranged at a specific position on the track, and the capstan 4 is controlled so that the head scans that position to obtain the search data.

Here, in the present embodiment, a first minute step ΔH1 is provided between the head 3a and the head 3c, and the head 3
Since the second minute step ΔH2 is provided between the head 3b and the head 3c, the minute step ΔH3 also occurs between the head 3a and the head 3b. The amount is ΔH3 = ΔH1-ΔH2 = Tp × θ /
It becomes 360. Therefore, the scan positions of the head 3a and the head 3b are deviated during the search by the minute step difference ΔH3. In this embodiment, the head 3 used for the search
Since a and the head 3b are mounted on the rotary drum 1 so as to face each other by 180 °, the head 3a and the head 3b during the search are
The scan position shift amount is always constant regardless of the search speed.

FIG. 6 shows that Tp =
It shows the relationship between the search speed and the scan position deviation when 10 μm and θ = 10 °. In FIG.
The scan position deviation of the conventional example increases in proportion to the search speed and is 5.6 μm at 10 × speed, whereas the scan position deviation of the present embodiment is always constant regardless of the search speed, and its value is Δx. = 0.28 (μm). With such a scan position shift, the search data 13 can be sufficiently acquired even in consideration of error factors such as tape speed fluctuations. Therefore, in this embodiment, it is possible to obtain the search data by both the head 3a and the head 3b while the rotary drum 1 makes one revolution.

As described above, according to this embodiment, the head 3a and the head 3b having the first azimuth angle are attached to the rotary drum 1 one by one.
Since the heads 3c having the second azimuth angle are arranged close to each other with a phase difference θ by mounting the heads 80 facing each other by 80 °,
It is possible to reduce the scan position shift amount between the head 3a and the head 3b at the time of search and keep the value constant regardless of the search speed. As a result, the search data 13 can be surely acquired even during the high speed search.

The first minute step is defined as ΔH1 = Tp × θ
/ 180, and the second minute step is ΔH2 = Tp × θ / 3
By setting the number to 60, it is possible to eliminate the scan position shift in the standard mode and the double long-time mode. As a result, the track pitch for recording / reproducing can be set to the normal value Tp in the standard mode and the double long-time mode. .

In this embodiment, in the N times long time mode when N is an even number, the running speed of the magnetic tape 2 is set to 1 / N of the standard mode, and the head 3b is rotated every N / 2 rotations of the rotary drum 1. And the head 3c alternately perform recording and reproducing, but if the magnetic recording and reproducing apparatus has only the time mode when N is an even number, the head 3b and the head 3c simultaneously rotate every N rotations of the rotary drum 1. Recording and reproduction may be performed. In this case, the head 3b and the head 3c are attached with a step difference of about Tp provided in the rotational axis direction of the rotary drum 1, and the head 3a and the head 3b are attached at the same height in the rotational axis direction of the rotary drum 1. As a result, the head scan position does not shift during the search.

In the present embodiment, the first mode is adopted so that the scan position shift is eliminated in the standard mode and the long time mode twice as long.
The minute step difference of ΔH1 = Tp × θ / 180 and the second minute step difference of ΔH2 = Tp × θ / 360 are set. It suffices to make settings so that a scan position shift does not occur. For example, if the first minute step ΔH is set so that the scan position shift does not occur in the triple long time mode,
In the double long time mode, the rotating drum 1 rotates 3/2 times (= 5
Since the head scan is shifted by 1 Tp during 40 °), ΔH1 = Tp × θ / 540. Further, the first minute step ΔH1 and the second minute step ΔH2 may be set so that the scan position becomes the minimum in a plurality of modes. For example, in order to minimize the scan position deviation in both the standard mode and the triple long time mode, the minute step ΔH1 is set to the intermediate value ΔH1 = Tp × of both modes.
It may be set to θ / 270.

The second embodiment of the present invention will be described below. The configuration and operation of the magnetic recording / reproducing apparatus according to the second embodiment of the present invention are the same as those of the first embodiment, and the description thereof will be omitted. The head mounting position and scan position shift different from those in the first embodiment will be described here.

FIG. 7 is an explanatory view of the head mounting position of the magnetic recording / reproducing apparatus in the second embodiment of the present invention. In FIG. 7, the head 3a and the head 3b are mounted on the rotating drum 1 so as to face each other by 180 °.
c is mounted with a minute phase difference θ in the circumferential direction of the rotary drum 1. Further, the head 3a and the head 3b have the same height in the rotation axis direction of the rotary drum 1, and the head 3b and the head 3c are attached with a minute step ΔH provided in the rotation axis direction of the rotary drum 1. Therefore, even a small step between the head 3a and the head 3b in the direction of the rotation axis of the rotary drum 1 is Δ.
It becomes H.

Here, a method of setting the minute step difference ΔH will be described. In the second embodiment, the head scan deviation can be eliminated in a specific mode by setting the minute step ΔH to an appropriate size. The setting method of ΔH is the same as that of the first embodiment, and the minute step difference ΔH is set by converting the amount of travel of the magnetic tape 2 during the rotation of the rotary drum 1 by the angle θ in the track pitch direction. For example, in the standard mode, the head scan shifts by 1 Tp while the rotary drum 1 rotates 1/2 rotation (= 180 °). Therefore, by setting the minute step difference to ΔH = Tp × θ / 180, the head 3a in the standard mode is It is possible to eliminate the scan position shift of the head 3c. Similarly, the minute step is ΔH = Tp × θ
/ 360, the head 3b in the double long time mode
Therefore, the scan position deviation of the head 3c can be eliminated.

Therefore, in the N times long-time mode, by setting the minute step difference to be ΔH = Tp × θ / 180 · N, the scan position deviation of the head can be eliminated.

Generally, as the running speed of the magnetic tape 2 becomes slower, the running speed error of the magnetic tape 2 becomes larger.
In the long-time mode in which the tape speed is slower than in the standard mode, the recording / reproducing accuracy becomes poor. Therefore, when the scan position shift of the head occurs in the long time mode, there arises a problem that the recording / reproducing accuracy further deteriorates.
If the minute step ΔH is set so as to eliminate the scan position shift in the long time mode in which the traveling speed is slow, the deterioration of the recording / reproducing accuracy can be prevented.

Next, the scan position shift at the time of search will be described. In the second embodiment, the head 3a and the head 3b
Is mounted on the rotary drum 1 at 180 ° and at the same height in the rotation axis direction of the rotary drum 1, so that the scanning positions of the heads 3a and 3b do not shift during the search. Therefore, the accuracy of the search is further improved as compared with the first embodiment.

As described above, according to the second embodiment, the first
Head 3a and head 3b with azimuth angle of the rotary drum 1
Since they are mounted 180 ° opposite to each other and mounted at the same height in the direction of the rotation axis of the rotary drum 1, it is possible to eliminate the head scan position deviation at the time of search and further improve the search accuracy.

[0043]

As described above, the present invention comprises at least three heads, the first head and the second head having the first azimuth angle and the third head having the second azimuth angle. , The first head and the second head are opposed to each other by 180 ° on the rotary drum, and the second head and the third head are arranged close to each other with a minute phase difference in the circumferential direction of the rotary drum. Since the amount of head-to-head scan position deviation can be reduced and can be kept constant regardless of the search speed, the search data can be reliably obtained even during high-speed search. .

Further, by mounting the head with a minute step in the direction of the rotation axis of the rotary drum and setting the value of the minute step appropriately, the scan position deviation is eliminated in a specific mode, and recording / reproducing accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a magnetic recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a head mounting position in the first embodiment.

FIG. 3 is a timing chart for explaining an operation in the first embodiment.

FIG. 4 is a timing chart for explaining an operation in the first embodiment.

FIG. 5 is an explanatory diagram of a search operation in the first embodiment.

FIG. 6 is a diagram showing a relationship between a search speed and a scan position in the first embodiment and the conventional example.

FIG. 7 is an explanatory diagram of a head mounting position in the second embodiment.

FIG. 8 is a block diagram of a conventional magnetic recording / reproducing apparatus.

FIG. 9 is an explanatory diagram of a head mounting position in a conventional example.

FIG. 10 is an explanatory diagram of a search operation in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotating drum 2 magnetic tape 3a first head 3b second head 3c third head 4 capstan 5 pinch roller 6 capstan control section 7 head selecting means 8 head amplifier 9 signal processing section 10 digital signal input / output terminal

Front page continuation (72) Inventor Yoshifumi Yanagawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (8)

[Claims] 1. A magnetic recording / reproducing apparatus for recording / reproducing a signal by a helical scan method on a magnetic tape wound obliquely on a rotating drum, and recording or reproducing operation by scanning the magnetic tape on the circumference of the rotating drum. The first head to do
At least three heads, a second head and a third head, are provided, wherein the first head and the second head have a first azimuth angle, and the third head has a second azimuth angle. In addition, the first head and the second head oppose each other by 180 ° on the rotary drum, and the second head and the third head are close to each other with a minute phase difference in the circumferential direction of the rotary drum. A magnetic recording / reproducing apparatus characterized by being arranged. 2. A magnetic recording / reproducing apparatus for recording / reproducing a digital signal by a helical scan method on a magnetic tape wound obliquely on a rotary drum, where N is a natural number,
The tape speed is 1 / N times the standard tape speed,
A first head that has a plurality of recording / reproducing modes with a data rate approximately 1 / N times the reference data rate, and performs the recording or reproducing operation by scanning the magnetic tape on the circumference of the rotating drum. At least three heads of a second head and a third head, the first head and the second head having a first azimuth angle, and the third head having a second azimuth angle. And the first head and the second head are mounted on the rotary drum by 180
Facing each other, the second head and the third head are close to each other with a minute phase difference in the circumferential direction of the rotary drum,
Is odd, recording or reproducing is performed using the first head and the third head, and when N is even, recording or reproducing is performed using the second head and the third head. A magnetic recording / reproducing apparatus characterized by the above. 3. When N is an odd number, the first head and the third head are used to alternately record or reproduce one track for every N / 2 revolutions of the rotary drum, and when N is an even number, 3. The magnetic recording / reproducing apparatus according to claim 2, wherein one head is alternately recorded or reproduced for every N / 2 rotations of the rotary drum by using the second head and the third head. 4. The first head and the third head are attached with a first minute step in the rotation axis direction of the rotary drum, and the second head is attached.
4. The magnetic recording / reproducing apparatus according to claim 1, wherein the head and the third head are mounted with a second minute step in the rotation axis direction of the rotary drum. 5. The track pitch is Tp, the phase angle between the second head and the third head in the circumferential direction of the rotary drum is θ °, the first minute step is ΔH1, and the second minute step is ΔH2. At this time, ΔH1 = Tp · θ / 180
And when N is an even number, the second minute step is ΔH2 =
5. The magnetic recording / reproducing apparatus according to claim 4, wherein Tp · θ / (180 · N). 6. The first head and the second head are mounted at the same height in the rotational axis direction of the rotary drum, and the first head and the third head have a minute step in the rotational axis direction of the rotary drum. It attached, Claim 1 characterized by the above-mentioned.
2. The magnetic recording / reproducing apparatus according to any one of 2 and 3. 7. When the track pitch is Tp, the phase angle of the second head and the third head in the circumferential direction of the rotary drum is θ °, and the minute step is ΔH, the minute step is ΔH = Tp ·
7. The magnetic recording / reproducing apparatus according to claim 6, wherein θ / (180 · N). 8. When the track pitch is Tp, the phase angle of the second head and the third head in the circumferential direction of the rotary drum is θ °, and the minute step is ΔH, the minute step is ΔH = Tp.
7. The magnetic recording / reproducing apparatus according to claim 6, wherein θ / 180 is set.