JPH0536163A - Magnetic tape reproducing device - Google Patents

Abstract

PURPOSE:To rapidly perform the tracking even when the vicinity of a reverse track is traced by a reproducing head. CONSTITUTION:A signal regenerated from a head is converted into a digital level by a comparator 15, to which a 1st synchronizing signal detecting circuit 16 for detecting a 1st synchronizing signal for a 1st head 2a and a 2nd synchronizing signal detecting circuit 17 for detecting a 2nd synchronizing signal for a 2nd head 2b are provided. From these detecting results, whether the reverse track is traced by the head or not is decided by a trace deciding circuit 18. Then, when it is decided that the reverse track is traced, a tape driving speed is temporarily changed by an offset generating circuit 13, and the tracking is rapidly performed to make a regular track traced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape reproducing apparatus using a rotating cylinder such as a digital audio tape recorder (called DAT) or a video tape recorder (called VTR).

[0002]

2. Description of the Related Art In recent years, as the density of magnetic recording has increased, in devices such as VTRs and DATs that record and reproduce by forming oblique tracks on a magnetic tape, tracking is promptly performed in order to improve sound quality and image quality. Is important to do. Tracking is forcing the reproducing head to trace the above-described track in a desired locus.

Below, the conventional magnetic tape reproducing apparatus is DAT
Will be described. In DAT, an ATF signal (Automat) for accurate tracking is obtained at two distant points on a diagonal track formed on a magnetic tape.
ic TrackFinding) is recorded. The ATF signal is composed of a pilot signal for detecting tracking deviation from the amount of crosstalk from adjacent tracks and a synchronization signal for generating a timing pulse for detecting the amount of crosstalk. Generally, adjacent tracks are reproduced by reproducing heads having angles (azimuths) symmetrical with respect to the tape running direction. It is mounted in a diametrically symmetrical position on the rotating cylinder around which the magnetic tape is wrapped. These adjacent tracks are called reverse tracks.

[0004]

In the above-mentioned conventional configuration, if the reproducing head traces the vicinity of the reverse track, the probability of correctly detecting the sync signal is significantly reduced. Therefore, there is a problem that the time required for tracking becomes long.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a magnetic tape reproducing apparatus capable of performing quick tracking even when the reproducing head traces the vicinity of a reverse track.

[0006]

In order to achieve the above object, the present invention converts two or more types of heads, rotary cylinders to which these heads are attached, and signals reproduced from these heads into digital levels. A comparator, a first sync signal detecting means for detecting a first sync signal for the first head, a second sync signal detecting means for detecting a second sync signal for the second head, and the first
And a trace determination means for determining that the head is tracing a reverse track based on the detection result of the second synchronization signal detection means, and an offset generation for temporarily changing the tape drive speed according to the result of the trace determination means. Means are provided.

[0007]

With this configuration, when more sync signals from the reverse track are detected than sync signals from the original track, the trace determining means determines that the reproducing head has traced the vicinity of the reverse track, and The tape drive speed is forcibly changed so that the reproducing head traces the vicinity of the regular track. Therefore, tracking can be performed quickly.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a magnetic tape reproducing apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a magnetic tape, 2a and 2b are first and second heads having positive and negative azimuths, respectively, and 3 is a first and second head.
Rotary cylinders with attached heads 2a, 2b of
Reference numerals 6 and 7 are reels for winding the magnetic tape 1, and numerals 4 and 5 are posts for winding the magnetic tape 1 on the rotating cylinder (3) so that the magnetic tape 1 can take a desired traveling path. Reference numeral 141 is a low-pass filter for extracting a pilot signal from the signal output reproduced from the first and second heads 2a and 2b, and 142 is a full-wave rectifier for detecting a crosstalk component of a pilot signal from an adjacent track. A circuit, 143 is a first sampling and holding circuit for sampling and holding the level of the pilot signal detected by the full wave rectifying circuit 142, and 144 is the level of the pilot signal sampled and held by the first sampling and holding circuit and the input pilot. It is a subtractor that performs subtraction with the signal level. 145 is a second sampling and holding circuit for sampling and holding the result of the subtractor 144, 15 is a comparator for converting the signal output reproduced by the first and second heads 2a and 2b into a digital signal, and 146 is a comparator 15 Timing signal generating circuit 147 that detects only the synchronizing signal from the output of the first sampling and holding circuit 143 and generates the sampling and holding pulse of the first sampling and holding circuit 143. The timing signal generating circuit 146 outputs the sampling and holding pulse to the first sampling and holding circuit 143. The second sampling and holding circuit 145 two blocks after
It is a delay circuit that generates a sampling and holding pulse. Reference numeral 16 is a first sync signal detection circuit for detecting a sync signal written in the plus azimuth track, 17 is a second sync signal detection circuit for detecting a sync signal written in the minus azimuth track, and 18 is a first sync signal. A trace determination circuit for determining whether or not the head is tracing a reverse track based on the detection results of the signal detection circuit 16 and the second synchronization signal detection circuit 17, and 19 is a trace determination circuit 18 for the head to run on the reverse track. When it is determined that the tape is running, the offset generating circuit outputs an offset pulse for temporarily changing the running of the tape. 10 is a pinch roller, 8 is a capstan shaft, 9 is a capstan motor that shares a shaft with the capstan shaft 8, 12 is an F / V converter that converts the rotational speed of the capstan motor into voltage, and 13 is a second Output of the sampling and holding circuit 145 and the F / V converter 12, and the offset generation circuit 19
The adder 11 adds the offset pulse generated by the drive circuit 11 and the drive circuit 11 drives the capstan motor 9 by the output of the adder 13.

In the configuration of this embodiment described above, the low-pass filter 141, the full-wave rectifier circuit 142, the first sampling and holding circuit 143, the subtractor 144, the second sampling and holding circuit 145, and the timing signal generating circuit 1
46, the delay circuit 147 constitutes a tracking detection circuit 14 for outputting a signal for tracking by sampling and holding the pilot signal using a synchronizing signal.

The operation of the embodiment configured as described above will be described below. FIG. 2 is a concrete example of a recording pattern of the ATF signal recorded on the magnetic tape 1 in FIG. 1, which is recorded without a guard band by a head having two different azimuth angles and is repeated every four tracks. An example of a dynamic pattern is shown. In FIG. 2, 102 is a pilot signal for detecting the amount of tracking deviation due to crosstalk, and 103a and 103b are synchronization signals for detecting the positions of pilot signals of adjacent tracks, each head having a positive azimuth. , Recorded with a head with negative azimuth. In FIG. 2, B1, A2, B2, A3, B3
Indicates the distinction between tracks. These tracks are B
Playback is in the order of 1, A2, B2, A3, B3. or,
An arrow 40 indicates the moving direction of the first and second heads 2a and 2b, and 50 indicates the moving direction of the magnetic tape 1.

FIG. 3, FIG. 4 and FIG. 5 are operation waveform charts when reproduction is performed in the embodiment shown in FIG. FIG. 3 shows operation waveforms when performing general tracking.

FIG. 3 (a) shows a pattern of the ATF signal recorded on the magnetic tape 1 shown in FIG. 2, in which 102a, 102b and 102c are pilot signals and 101 is a plus signal. The head gap of the first head 2a having azimuth is shown.

In FIG. 1, the rotary cylinder 3 is rotating at a constant speed, although a control circuit is not shown, and the first and second heads 2 mounted on the rotary cylinder 3 are rotated.
The signals a and 2b reproduce the signals recorded on the magnetic tape 1. The reproduced signals from the first and second heads 2a and 2b are input to the low pass filter 141 and the comparator 15. This low pass filter 141 is a magnetic tape 1.
The pilot signal 102 recorded above is separated from the outputs of the first and second heads 2a, 2b. On the other hand, the output of the low-pass filter 141 is rectified by the rectifier circuit 142, and the amplitude information signal can be obtained. Therefore, when the head gap 101 shown in FIG. 3A travels in the direction of arrow 40, the output of the low-pass filter 141,
The outputs of the rectifier circuit 142 are as shown in FIGS. 4B and 4C, respectively. The case of FIG. 3 shows the case where the head gap 101 is slightly shifted to the right with respect to the traveling direction. Further, the comparator 15 converts the signals reproduced by the first and second heads 2a and 2b into digital levels. The timing signal generating circuit 146 reproduces the digital output signal from the comparator 15 from the first signal.
Also, the synchronizing signals 103a and 103b corresponding to the azimuth of the second heads 2a and 2b are detected and the sampling pulse is supplied to the first sampling and holding circuit 143. What is shown in FIG. 3D is a sample pulse output from the timing signal generation circuit 146.

On the other hand, the second sampling and holding circuit 1
Reference numeral 45 samples and holds the signal level obtained by subtracting the crosstalk signal from the pilot signal of the track adjacent to the left side held by the first sampling and holding circuit 143 by the subtractor 144 by the sample pulse output from the delay circuit 147.

The second sampling and holding circuit 14
The signal output from 5 corresponds to the deviation of the head center from the center of the traveling track. The F / V converter 12 converts the difference between the actual rotation speed and the desired rotation speed of the capstan motor 9 into a voltage and outputs it. F / V converter 1
The output voltage of 2 and the output voltage of the tracking detection circuit 14 are added by the adder 13 and input to the drive circuit 11.
The output of the drive circuit 11 drives the capstan motor 9. The rotation of the capstan motor 9 is equal to the rotation of the capstan shaft 8, and the magnetic tape 1 is run by pressure contact with the pinch roller 10. At this time, adder 1
The operating point of the addition ratio of 3 is set so that the output of the tracking detection circuit 14 becomes zero.

As described above, in the block diagram of FIG. 1, the method of controlling the running of the magnetic tape 1 has been described. Next, the tracking operation according to the present invention will be described with reference to the block diagram of FIG. The operation waveforms in FIG. 5 will be described.

FIG. 4 shows operation waveforms when the head traces a regular track. That is, the first head 2a having the positive azimuth traces the track recorded with the positive azimuth, and the second head 2b having the negative azimuth tracks the track recorded with the negative azimuth. Is the operation waveform when traced. FIG. 5 shows operation waveforms when the head traces a reverse track. That is, the first head 2a having the positive azimuth traces the track recorded with the negative azimuth, and the second head 2b having the negative azimuth tracks the track recorded with the positive azimuth. Is the operation waveform when traced.

FIGS. 4A and 4B show reproduction waveforms when the signals recorded on the magnetic tape 1 are reproduced by the first and second heads 2a and 2b. The distinction between Ach and Bch in FIGS. 4 and 5A means that the signals are reproduced by the first head 2a having a positive azimuth and the second head 2b having a negative azimuth, respectively. ing. 4 and 5 are waveforms output from the first sync signal detection circuit 16 that detects the sync signal 103a recorded by the positive azimuth head.
(C) is a waveform output from the second sync signal detection circuit 17 that detects the sync signal 103b recorded by the minus azimuth head.

When the head traces the reverse track, as shown in FIG. 5, when the second head 2b having a negative azimuth traces the track from the first sync signal detection circuit 16, the sync signal is detected. Is detected, and the second sync signal detection circuit 17 detects a sync signal when the first head 2a having a positive azimuth traces a track. The number of sync signals detected by the first sync signal detection circuit 16 when the first head 2a having a positive azimuth traces a track;
The sum of the detection numbers of the synchronization signals detected by the second synchronization signal detection circuit 17 when the second head 2b having a negative azimuth traces a track is the correct answer number.
In this case, a regular truck is traveling. In this case, the offset generation circuit 19 outputs nothing to the adder 13. As described above, the adder 13 has the second
The sampling and holding circuit 145 and the output of the F / V converter 12 are supplied and only normal tracking is performed.

Second, with a negative azimuth
The number of sync signals detected by the first sync signal detection circuit 16 when the head 2b of FIG.
The sum of the detection numbers of the synchronization signals detected by the second synchronization signal detection circuit 17 when the first head 2a having a positive azimuth traces a track is set as the misunderstanding number. In this case, the reverse track is being traced.

The trace determination circuit 18 counts the number of appearances of the correct answer number and the number of appearances of the incorrect answer number and compares them. It is determined that the vicinity of is traced. In this case, the offset generation circuit 19 controlled by the trace determination circuit 18 outputs nothing to the adder 13. As described above, the adder 13 is supplied with the second sampling and holding circuit 145 and the output of the F / V converter 12, and only normal tracking is performed. On the contrary, when the number of appearances of the wrong answer number is larger than the number of appearances of the correct answer number, it is determined that the head is tracing near the reverse track. In this case, the trace determination circuit 18 outputs an offset pulse to the adder 13 via the offset generation circuit 19. As described above, the adder 13 includes the second sampling and holding circuit 145 and the F / V converter 1.
Although the output of 2 is supplied and normal tracking is performed, the head traces the vicinity of the regular track rapidly by forcibly changing the tape drive speed by adding an offset pulse. Let them do it.

The trace determination circuit 18 is a circuit for distinguishing the signals reproduced by the counter, the subtractor, and the first and second heads 2a and 2b which are cleared once during one rotation of the rotary cylinder 3. It can be configured with a simple circuit such as.

[0024]

As is apparent from the above embodiment, the present invention has two or more types of heads, rotary cylinders to which these heads are attached, a comparator for converting a signal reproduced from these heads into a digital level. First
First sync signal detecting means for detecting a first sync signal for the head, second sync signal detecting means for detecting a second sync signal for the second head, and the first and second
Trace determining means for determining that the head is tracing a reverse track based on the detection result of the synchronization signal detecting means, and offset generating means for temporarily changing the tape drive speed according to the result of the trace determining means are provided. ing. With this configuration, when more sync signals from the reverse track than the sync signals from the original track are detected, it is determined by the trace determination means that the head has traced the vicinity of the reverse track, and the offset pulse is used. The tape drive speed is temporarily forced to change so that the head traces in the vicinity of the regular track. Therefore, it is possible to realize an excellent magnetic tape reproducing device that can perform tracking quickly.

[Brief description of drawings]

FIG. 1 is a block diagram of a magnetic tape reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a recording pattern diagram of a magnetic tape of the same device.

FIG. 3 is an operation waveform diagram of the device.

FIG. 4 is an operation waveform diagram of the device.

FIG. 5 is an operation waveform diagram of the device.

[Explanation of symbols]

 1 Magnetic Tape 2a First Head 2b Second Head 3 Rotating Cylinder 4 Post 5 Post 6 Reel 7 Reel 8 Capstan Shaft 9 Capstan Motor 10 Pinch Roller 11 Drive Circuit 12 F / V Converter 13 Second Sampling Hold Circuit 14 tracking detection circuit 15 comparator 16 first synchronization signal detection circuit 17 second synchronization signal detection circuit 18 trace determination circuit 19 offset generation circuit

Claims (1)

Claim: What is claimed is: 1. Two or more types of heads, a rotary cylinder to which these heads are attached, a comparator for converting a signal reproduced from these heads into a digital level, and a first head. A first sync signal detecting means for detecting a first sync signal for the second head, and a second sync signal for the second head.
Second sync signal detecting means for detecting the sync signal of the head, trace determining means for judging that the head is tracing a reverse track based on the detection results of the first and second sync signal detecting means, and the trace determining means. A magnetic tape reproducing apparatus comprising: an offset generating means for temporarily changing the drive speed of the tape according to the result of the judging means.