JPH0458082B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a helical scan magnetic recording/reproducing device, typified by a video tape recorder.

[Summary of the invention]

The present invention provides a helical scan magnetic recording and reproducing apparatus for recording and reproducing information on tracks inclined with respect to the running direction of a magnetic tape using a rotating head.
a drive means for driving the rotary head in its width direction;
When a drive signal generation circuit that generates a drive signal with a predetermined waveform is provided and the magnetic tape is running at a faster speed than the normal speed, position information is recorded during the period when the rotating head traces the magnetic tape once. The drive signal generation circuit generates a drive signal at least once during a part of the period, the drive signal generated by the drive signal generation circuit is supplied to the drive means, and during the part of the period, the drive signal is supplied to the drive means. By driving the rotary head in the width direction and not driving the rotary head in the width direction during the remaining period, the rotary head can accurately trace only a predetermined part of one track of a magnetic tape running at high speed. This is how it was done.

[Conventional technology]

In a 1/2 inch video tape recorder, etc., there are two rotating heads A, 180 degrees apart from each other.
A magnetic tape is wound 180 degrees around a rotating drum having a head B, and two rotating heads A and B are alternately switched by a switching pulse (SWP) to record video information and the like. In this case, tracks inclined with respect to the running direction are formed for each field on the magnetic tape. On the other hand, audio information is recorded on tracks parallel to the running direction of the magnetic tape, or is frequency modulated and frequency multiplexed with video information.
recorded on the slope track.

In contrast, in the so-called 8mm video tape recorder, which has recently been standardized, magnetic tape is wound around a rotating drum 221 degrees, and normal video information is recorded in a 180 degree area, and in a 36 degree area. Digital (PCM) audio information can be recorded (the remaining 5 degree area is a margin for video information).
As shown in FIG. 4, a video area and an audio (PCM) area are formed on the inclined track on the magnetic tape in such an 8 mm video tape recorder. In addition to the PCM audio signal, this PCM area contains information such as the program number, the start point of the magnetic tape or elapsed time from the start point of the program (hours, minutes, seconds), recording date and time, etc. information). Therefore, by reading this code, it is possible to search for a desired location (program) on the magnetic tape.

[Problem that the invention seeks to solve]

By the way, when searching for a desired position, the magnetic tape is run at high speed in order to shorten the search time. For example, as shown in FIG. 4, when rewinding at a speed n times the normal recording and reproducing speed, while one rotary head (A or B) traces the magnetic tape once from the bottom end to the top end, (n+1)(1
+36/180) tracks ((n+1)(1+36/180) tracks when fast forwarding). Of these, only every other track has the same azimuth, so the RF of the reproduced signal
The envelope of the signal becomes as shown in FIG.
That is, the level of the reproduced signal from tracks whose azimuths match becomes high, but from tracks whose azimuths do not match, it becomes low. As the level of the reproduced signal decreases, noise increases, making it difficult to read the code. Therefore, with conventional devices, it is not possible to increase the traveling speed during a search,
(At best, it takes several times as long as it takes to record and play back.) It has the disadvantage that searching takes a long time.

[Means for solving problems]

FIG. 1 is a block diagram of a video tape recorder according to the present invention. 1 and 2 are two (A, 2) mounted on a rotating drum (not shown) 180 degrees apart from each other.
B) is a rotating head which can be driven in the width direction of the track by drive means 3 and 4 such as piezoelectric elements. Reference numeral 5 denotes a drive signal generation circuit, into which are input switching pulses for switching the rotary heads A and B, as well as cue signals, review signals, etc. as command signals when fast forwarding or rewinding the magnetic tape at high speed to search for a desired position. has been done. When the drive signal generation circuit 5 receives the cue signal or the review signal, it outputs a drive signal with a predetermined waveform in synchronization with the edge timing of the switching pulse. Reference numerals 6 and 7 designate drivers that boost the drive signal and supply it as a high voltage signal to the respective drive means 3 and 4 that drive the rotary heads A and B.

[Effect]

The operation will be explained with reference to FIGS. 2 and 3. When a magnetic tape is run at a normal recording/playback speed (for example, during normal playback operation),
Tracking error signals for each of the rotating heads A and B are generated by means not shown in synchronization with the switching pulse (FIG. 2a). For example, in the case of a so-called four-frequency pilot signal tracking method, a tracking error signal is generated from the beat components of the pilot signal recorded in each tracking and the pilot signal from an external oscillator having the same frequency. This tracking error signal is input to the drivers 6 and 7, where it is boosted to become a high voltage signal and is supplied to the driving means. Therefore, the driving means moves the rotary heads 1, 2 (A, B) in the width direction in response to the tracking error signal, thereby performing tracking control.

On the other hand, a queue signal or a review signal is generated,
When the magnetic tape is run in the forward or reverse direction at a speed n times the normal recording/reproducing speed and a search operation is performed, the drive signal generation circuit 5 generates an input switching pulse (FIG. 2a). In synchronization, the PCM area (36
a sawtooth signal is generated at least once at a certain point (FIG. 2b). The same is true when the rotating head B traces the magnetic tape from the bottom edge to the top edge (FIG. 2c). The height (level) e(v) of this sawtooth wave signal is set to a value corresponding to the width of the number of tracks traversed by each rotary head A, B in the PCM area.

In other words, the number of tracks crossed in the PCM area is 36(n-1)/180 during queue operation.
During review operation, it is 36(n+1)/180, so if the displacement of the piezoelectric element is d (μm/v) and the width of one track is t (μm), the height of the sawtooth wave signal is e. During queue operation, e=-36t(n-1)/180d...(1) During review operation, e=36t(n+1)/180d...(2).

Such sawtooth wave signals are input to the driving means 3 and 4 via drivers 6 and 7. Therefore, the rotary heads A, B are driven by drive means 3, 4 and trace the magnetic tape as shown in FIG. In other words, when the rotary heads A and B are not driven by the sawtooth wave signal, they trace linearly from the bottom end to the top end as shown in Figure 4, but in the PCM region of one trace from the bottom end to the top end. Since a sawtooth signal is applied, one track is traced from the bottom edge to the end of the PCM region by the sawtooth signal, and the rest is the same as when not driven by the sawtooth signal. Therefore, although video information recorded in the video area is reproduced with noise, code information recorded in the PCM area can be reproduced without noise and can be read. The code information (position information) includes the program number, the start point of the magnetic tape or the elapsed time from the start point of the program (hours, minutes, seconds),
Information such as recording date and time may be considered, but is not limited to this. Furthermore, the recording format does not necessarily have to be digital.

Incidentally, if the maximum displacement of the piezoelectric element is, for example, 200 μm,
Assuming that the width t of one track is 20.5 μm and substituting this into the above equations (1) and (2), in equation (1), n =
49, n=47 in equation (2). This means that it is possible to search by running the magnetic tape at 49 or 47 times the speed of normal recording and playback.

In the above, the
Although the PCM area is played back, if the video area is divided into multiple (for example, five) PCM areas and code signals etc. are recorded there, as disclosed in Japanese Patent Application No. 59-148190, for example, By generating a drive signal by shifting the timing from the edge of the switching pulse, it is possible to reproduce a PCM area at an arbitrary position.

〔effect〕

As described above, the present invention provides a helical scan magnetic recording and reproducing apparatus that uses a rotary head to record and reproduce information on a track inclined with respect to the running direction of a magnetic tape. A drive signal generation circuit that generates a drive signal with a waveform of
The drive signal generation circuit generates a drive signal at least once during a part of the period in which position information is recorded during the period in which the rotating head traces the magnetic tape once, and the drive signal generated by the drive signal generation circuit is The rotary head is driven in the width direction during a part of the period in response to the drive signal, and the rotary head is not driven in the width direction during the remaining period. Only a predetermined part of one track can be accurately traced by the rotary head, and the codes etc. recorded therein can be accurately read. Further, since no drive signal is applied to the remaining portions, the speed of the magnetic tape during retrieval can be increased, and the retrieval time can therefore be shortened.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the video tape recorder of the present invention, FIG. 2 is a waveform diagram thereof, FIG. 3 is a schematic plan view showing the track on the magnetic tape and the trace locus of the rotary head, and FIG. FIG. 5 is a schematic plan view showing a track on a conventional magnetic tape and a trace locus of a rotary head, and a waveform diagram thereof. 1, 2...Rotating head, 3, 4...Driving means,
5... Drive signal generation circuit, 6, 7... Driver.

Claims (1)

[Scope of Claims] 1. A helical scan magnetic recording and reproducing device that uses a rotating head to record and reproduce information on a track that is inclined with respect to the running direction of a magnetic tape, comprising: a drive means that drives the rotating head in its width direction; a drive signal generation circuit that generates a drive signal with a waveform of The drive signal generation circuit generates the drive signal at least once during a part of the period during which the drive signal is recorded, and the drive signal generated by the drive signal generation circuit is supplied to the drive means, A helical scan magnetic recording/reproducing apparatus characterized in that during a period, the rotary head is driven in the width direction in accordance with the drive signal, and during the remaining period, the rotary head is not driven in the width direction.