JP2692494B2 - Magnetic recording / reproducing method and magnetic recording / reproducing apparatus - Google Patents

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 having a reproducing function capable of surely searching index information recorded on a magnetic tape by a helical scan method at a high speed.

[0002]

2. Description of the Related Art Recently, a magnetic recording / reproducing apparatus has a high-speed search function for searching a specific program from a plurality of recorded programs. This function improves the usability of users and is used by many users.

A conventional magnetic recording / reproducing apparatus will be described below. In a digital audio tape recorder and an 8 mm video tape recorder, index information necessary for high speed search is recorded on a magnetic tape by a rotary head. Then, at the time of high-speed search, the rotary head reads data on the tape track to search for index information. The tape speed at that time is mainly determined in consideration of the tape damage and the accuracy of the mechanism.

[0004]

However, in the above-described conventional magnetic recording / reproducing apparatus, the tape speed at the time of high speed search does not consider the phase between the trace position and the track on the magnetic tape of the rotary head at that time. However, there is a problem that the index information may not be read.

The present invention solves the above-mentioned problems of the prior art. The tape speed at which the index information can be read is always used as the tape speed at the time of search regardless of the phase relationship between the trace position and the track on the magnetic tape of the rotary head. An object of the present invention is to provide a magnetic recording / reproducing apparatus which can surely search a specific position on a magnetic tape by setting.

[0006]

In order to achieve this object, a magnetic recording / reproducing apparatus of the present invention has at least one first rotary head having a first azimuth angle and at least a second azimuth angle. A second rotary head, a tape drive means for driving a magnetic tape, a trace position on the magnetic tape of the first rotary head, and a trace position on the magnetic tape of the second rotary head. Tape speed at which the interval is approximately an even multiple of the track interval, or
The tape speed at which the trace position interval on the magnetic tape of the first rotary head is approximately an odd multiple of the track interval is set as the search speed.

[0007]

As described above, according to the present invention, the tape speed is such that the intervals between the trace positions on the magnetic tape of the rotary heads having different azimuth angles are approximately even multiples of the track intervals, or the magnetic tapes of the rotary head having the same azimuth angle. The search speed is set to the tape speed at which the interval between the trace positions above is approximately an odd multiple of the track interval.

Further, according to the present invention, rotary heads having different azimuth angles are installed in the vicinity of each other to perform recording / reproducing with a magnetic tape. Then, at the time of high speed search, the tape speed is set by the same operation as the above operation.

[0009]

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

FIG. 1 is a block diagram showing the configuration of a magnetic recording / reproducing apparatus according to an embodiment of the present invention. In this figure,
The magnetic tape 1 is wound around a rotary drum 2 and driven by pressure contact with a pinch roller 11 to run.
The rotary drum 2 includes a rotary head pair 3 and a rotary head pair 4 each including two rotary heads having different azimuth angles.
Is attached. A frequency generator 6 is attached to the capstan motor 5. The frequency generator 6 generates a rotation frequency signal of the capstan motor 5 (hereinafter referred to as a capstan FG signal), and its output is given to the amplifier circuit 7. The amplifier circuit 7 amplifies the capstan FG signal of the frequency generator 6, and its output is given to the control means 8. The control means 8 controls the rotation of the capstan motor 5 using the capstan FG signal. The output from the control means 8 is the drive circuit 9
Is output to The drive circuit 9 inputs a signal from the control means 8 and outputs a drive signal to the capstan motor 5. The tape driving means 10 includes a capstan motor 5, a pinch roller 11, a frequency generator 6, an amplifier circuit 7,
It is composed of a control means 8 and a drive circuit 9.

Next, referring to FIGS. 2 and 3, the tape speed is n.
This leads to a condition that the index information on the magnetic tape can always be read at double speed (n is a real number).

FIG. 2 is a diagram showing the locus of the rotary head that scans on the magnetic tape. On the magnetic tape 1, an index area 21 (hereinafter, referred to as a search signal is written)
A track 20 including an index is recorded. The index 21 is recorded at one location on each track over a certain section of the magnetic tape 1. Locus a1,
A locus a2 shows a locus of the rotary head having the same azimuth angle, and a locus b1 shows a locus of the rotary head having a different azimuth angle from the loci a1 and a2. T in this figure
r is the track interval in the tape running direction, and X1
Is the distance between the track a1 and the track b1 in the tape running direction, and X2 is the track a1 and the track a2 in the tape running direction.
And shows the interval. Further, θ is the track angle, and V is the tape running speed (1 × speed) in the reproduction mode.

FIG. 3 is an enlarged view of the rotary drum 2 shown in FIG. r is the radius of the rotary drum 2, and α is the installation angle between the rotary heads 3 and 4 which have different azimuth angles. ω is the rotation speed of the rotating drum. Rotating head 3 on magnetic tape
Trace in the order of 0, 40, 31, 41. That is, in FIG. 2, when the locus a1 is the locus of the rotary head 30, the locus b1 is the locus of the rotary head 40, and the locus a2 is
Is the locus of the rotary head 31. Therefore, the rotary head 30 and the rotary head 31 have the same azimuth angle, and similarly, the rotary heads 40 and 41 have the same azimuth angle,
The rotary head 30 and the rotary head 40 have different azimuth angles. Therefore, the tracks recorded by the rotary heads 30 and 31 cannot be reproduced by the rotary heads 40 and 41. The same applies in the opposite case. Therefore, for example, at 1 × speed, each rotary head cannot reproduce every other track, that is, the index recorded in reverse azimuth cannot be read by the rotary head having the reverse azimuth angle. And it turns out that the probability that the index can be read at that time becomes 50%. Similarly, there are cases where the index cannot be read even at the n-fold speed. That is, the index may not be read depending on the phase relationship between the trace line on the magnetic tape of the rotary head and the recorded track. Therefore, by examining the relationship between the trace intervals X1 and X2 of each rotary head and the track interval Tr, the condition that the index information on the magnetic tape can always be read can be derived. Here, the rotation speed correction rate A of the rotary drum 2 is shown in the equation (1). A = a + b · n (1) where a and b are both constants.

Further, X1 and X2 in FIG. 2 can be expressed by equations (2) and (3). X1 = n · V (60 / A · ω) · (α / 360) (2) X2 = n · V (60 / A · ω) · (180/360) (3) Then, of the rotary heads 30 and 40 X which is the trace interval
If 1 is an even multiple of the track interval Tr, the formula (4) can be derived from the formula (2). n · V (60 / A · ω) · (α / 360) = 2m · Tr (4) However, m is an arbitrary integer.

The double speed number n in which the equation (2) satisfies the equation (4) is
If the rotary head 30 cannot read the index, the rotary head 40 can always read the index. Alternatively, if the rotary head 40 cannot read the index, the tape speed is such that the rotary head 30 can always read the index. That is, the equation (2) is the track interval Tr.
This is because either the rotary head 30 or the rotary head 40 will trace at the same azimuth angle as that of the track recorded on the magnetic tape when it becomes an even multiple of.

Therefore, if the double speed number n satisfying the expression (4) is obtained, it means that the index of the track recorded on the magnetic tape can be always read at the n times speed.

Next, if X2, which is the trace interval between the rotary heads 30 and 31, is an odd multiple of the track interval Tr, it is possible to derive Formula (5) from Formula (3). n · V (60 / A · ω) · (180/360) = (2m + 1) · Tr (5) However, m is an arbitrary integer.

The double speed number n in which expression (3) satisfies expression (5) is
If the rotary head 30 cannot read the index, the rotary head 31 can always read the index. Alternatively, if the rotary head 31 cannot read the index, the tape speed is such that the rotary head 30 can always read the index. That is, when the formula (3) becomes an odd multiple of the track interval Tr, either the rotary head 30 or the rotary head 31 traces the track recorded on the magnetic tape at the same azimuth angle. is there.

Therefore, if the double speed number n satisfying the equation (5) is obtained, it means that the index of the track recorded on the magnetic tape can be always read at the n times speed.

Therefore, the index can be read out without fail by finding the double speed number n satisfying the expression (4) or the expression (5) and setting the double speed number as the tape running speed in the high speed search.

Next, the probability that the rotary head can read the index on the magnetic tape will be described with reference to FIG. FIG. 4 is a graph created based on the data obtained by actually performing the simulation. FIG. 4A shows the detection probability in the case of the 2 to 4 head configuration as shown in FIG. On the other hand, FIG. 4B shows the detection probability in the case of the 1-to-2 head configuration.

First, the method of calculating the probability will be described. First, the phase at which the rotary head scans the magnetic tape is determined. For example, two adjacent tracks recorded by two rotary heads having different azimuth angles are recorded as 100
To divide. The locus of the rotary head passing through the 100 divided points has 100 different phases for the tracks on the magnetic tape. It is determined whether the index can be detected for each of the different phases. Probability is calculated based on the result. More specifically, since the index is recorded on the tape for a certain period of time, first the tape section where the index is recorded is set to 1 when the tape running speed is n times speed.
The number of times each rotary head can scan is calculated, and the number of times is set as the limit number of scans. Next, it is determined whether or not the index can be detected by the limit number of scans for one trajectory, that is, one phase. For example, if the index cannot be detected in the first scan, but the index can be detected in the second or third scan,
The locus is the detection of the index. In this way, all 100 loci are discriminated and the probability of how many of 100 loci have been detected is calculated.

The result of the above calculation is shown in FIG. The rotary head 30 and the rotary head 4 shown in FIG.
When the angle α with 0 is small, the result is as shown in FIG. 4 (a), and the speed multiple in the range indicated by n1, n2, n3, and n4 in the drawing is the tape speed at which the index can be detected with a probability of 100%. I understand. On the other hand, when the angle α shown in FIG. 3 is 180 degrees, the result shown in FIG.
There is a double speed number that can detect the index with 100% probability, but the probability is 100% if the double speed number changes even a little.
Will disappear. Therefore, if the angle α is reduced, the tape speed at the time of index search can be easily set, and even if there is some speed error, sufficient reliability for the search can be obtained.

As described above, according to this embodiment, the rotary head 30 having the first azimuth angle, the rotary head 40 having the second azimuth angle, and the tape drive means 10 for driving the magnetic tape 1 are provided. The tape speed at which the interval X1 between the trace position a1 on the magnetic tape of the rotary head 30 and the trace position b1 on the magnetic tape of the rotary head 40 is an even multiple of the track interval Tr, or the trace position on the magnetic tape of the rotary head 30. By setting the tape speed at which the interval X2 is an odd multiple of the track interval Tr as the search speed, the index can be read with a probability of 100% during the high speed search.

In this embodiment, the case where four or two rotary heads are used has been described, but if two or more rotary heads are used, the same effect can be obtained.

[0026]

As described above in detail, according to the present invention, when the index recorded on the magnetic tape is searched at high speed, the first rotary head having the first azimuth angle and the second azimuth angle. The index recorded at a specific position on the magnetic tape by the second rotary head having a track is the distance between the trace position on the magnetic tape of the first rotary head and the trace position on the magnetic tape of the second rotary head. By setting the tape speed that is an even multiple of the interval or the tape speed that the interval of the trace positions on the magnetic tape of the first rotary head is an odd multiple of the track interval as the search speed, a highly reliable high-speed search function can be achieved. The effect that it can be realized is obtained.

Further, according to the present invention, when the index recorded on the magnetic tape is searched at high speed, the first rotary head having the first azimuth angle and the second rotary head having the second azimuth angle are used. By installing the search speeds close to each other, it is possible to easily set a highly reliable search speed that is not affected by a slight speed change.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of a magnetic tape driving portion of a magnetic recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a trajectory of a rotary head on a magnetic tape in the example.

FIG. 3 is a configuration diagram showing a positional relationship of rotary heads in the embodiment.

FIG. 4 is a graph showing a probability that an index can be detected in the example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 magnetic tape 3,4 rotating head pair 5 capstan motor 6 frequency generator 7 amplification circuit 8 control means 9 drive circuit 10 tape drive means 20 tracks

Claims (8)

(57) [Claims] 1. Index information recorded at a specific position on a magnetic tape by at least one first rotary head having a first azimuth angle and at least one second rotary head having a second azimuth angle. , The search is performed at a tape speed such that the distance between the trace position on the magnetic tape of the first rotary head and the trace position on the magnetic tape of the second rotary head is approximately an even multiple of the track interval. And magnetic recording and reproducing method. 2. Index information recorded at a specific position on a magnetic tape by at least one first rotary head having a first azimuth angle and at least one second rotary head having a second azimuth angle. A magnetic recording / reproducing method characterized in that a search is performed at a tape speed such that a trace position interval on the magnetic tape of the first rotary head is approximately an odd multiple of a track interval. 3. At least one first rotary head having a first azimuth angle, at least one second rotary head having a second azimuth angle, and tape drive means for driving a magnetic tape. Then, the tape speed at which the interval between the trace position on the magnetic tape of the first rotary head and the trace position on the magnetic tape of the second rotary head is approximately an even multiple of the track interval is set as the search speed. A magnetic recording / reproducing apparatus characterized by: 4. At least one first rotary head having a first azimuth angle, at least one second rotary head having a second azimuth angle, and tape drive means for driving a magnetic tape. The magnetic recording / reproducing apparatus is characterized in that a tape speed at which a trace position interval of the first rotary head on the magnetic tape is approximately an odd multiple of a track interval is set as a search speed. 5. Identification on a magnetic tape by at least one head pair consisting of a first rotary head having a first azimuth angle and a second rotary head having a second azimuth angle, which are installed close to each other. In the index information recorded at the position, the distance between the trace position on the magnetic tape of the first rotary head and the trace position on the magnetic tape of the second rotary head is approximately an even multiple of the track interval. A magnetic recording / reproducing method characterized by searching at a tape speed. 6. Identification on a magnetic tape by at least one head pair consisting of a first rotary head having a first azimuth angle and a second rotary head having a second azimuth angle, which are installed close to each other. The magnetic recording / reproducing method is characterized in that the index information recorded at the position is searched at a tape speed at which the trace position interval on the magnetic tape of the first rotary head is approximately an odd multiple of the track interval. 7. A head pair comprising at least a first rotary head having a first azimuth angle and a second rotary head having a second azimuth angle installed near the first rotary head, Tape drive means for driving a magnetic tape, wherein a distance between a trace position on the magnetic tape of the first rotary head and a trace position on the magnetic tape of the second rotary head is approximately a track interval. A magnetic recording / reproducing apparatus characterized in that a tape speed that is an even multiple is set as a search speed. 8. A head pair comprising at least a first rotary head having a first azimuth angle and a second rotary head having a second azimuth angle, which is installed in the vicinity of the first rotary head. A tape drive means for driving a magnetic tape, wherein a tape speed at which a trace position interval of the first rotary head on the magnetic tape is approximately an odd multiple of a track interval is set as a search speed. Magnetic recording / reproducing device.