JPS6135614B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking control system, and an object of the present invention is to automatically, quickly, and accurately perform tracking control of a rotary head type video tape recorder or the like.

In a rotary head type video tape recorder, the tape is wound diagonally around a playback drum and run, while a head attached to the side of the rotary drum scans the tape diagonally as shown in Figure 1 to perform recording and playback. conduct. In FIG. 1, 1 is a tape, 2 is one of the recording tracks, and 3 is a control signal track.

By the way, during playback, it is necessary to faithfully trace and scan the recorded track, and if it deviates, the detection level may drop or signals from adjacent tracks may leak. This causes inconvenience.

Therefore, the method currently used to accurately perform this tracking will be explained.

First, in addition to a rotary head for recording and reproducing signals, a fixed head for recording and reproducing control signals is provided, and during recording, a control signal synchronized with the rotation of the rotary head is transmitted as shown in Fig. 1. Record the location. During playback, tracking control is performed by controlling the tape running speed so that the control signal detected by the fixed head and the rotation of the rotary head are synchronized.

With the tracking control method described above, if recording and playback are performed using the same video tape recorder, there are relatively few problems as long as the positional relationship between the rotary head and the fixed head does not change. If a different video tape recorder is used for playback, the positional relationship between the rotary head and the fixed head does not necessarily match exactly, which may cause tracking errors. Furthermore, even when recording and playback are performed using the same video tape recorder, if the positional relationship between the rotary head and the fixed head changes for some reason, tracking errors will still occur if a tape recorded before the change is played back after the change.

In addition to the above, there is a method called wobbling as a conventional tracking control method.

This method detects the direction and magnitude of tracking deviation by slightly varying the running speed of the tape at a constant frequency during playback, and comparing the phase of the resulting change in the playback signal with the signal at the above frequency. ,
This is a method of making corrections. However, when the traveling speed is varied, the frequency at which the traveling speed is varied cannot be made very high due to limitations imposed by the response speed of the traveling system, which has the disadvantage that the tracking deviation detection speed becomes slow.

Furthermore, there is a problem in that detection accuracy is degraded because disturbance factors such as tape shake, expansion and contraction, and shaft play occur between the tape running means and the rotating head.

The present invention provides a tracking control method that solves the above problems.

In a normal rotating head with two heads,
The two heads are set in exactly symmetrical positions with respect to the cylinder axis of the rotary head.
Therefore, the scanning tracks recorded on the tape are arranged at equal intervals as shown in FIG.

However, in the present invention, the positions of these two heads are slightly shifted, and the scanning track is set to repeat the sparse and dense patterns as shown in FIG. In FIG. 2, 4 and 5 indicate odd-numbered and even-numbered recording tracks, and 6 and 7 indicate odd-numbered and even-numbered reproduction tracks, respectively.

In the case of FIG. 2, the recording track and reproduction track are set to have a phase shift of 180 degrees. Therefore, when playing back odd-numbered recorded tracks,
The relationship is such that even-numbered recording tracks are traced, and even-numbered recording tracks are traced to odd-numbered tracks. As shown in FIG. 2, the respective recording tracks and reproduction tracks are slightly shifted in position.

Therefore, for example, if the phase of reproduction tracks 6 and 7 is shifted to the left with respect to recording tracks 4 and 5, resulting in a relationship as shown in FIG. For playback track 6, even-numbered playback track 7
becomes larger, and as a result, the even-numbered reproduction signal level becomes higher than the odd-numbered reproduction signal level.

Conversely, when the phase of the reproduction tracks 6 and 7 shifts to the right with respect to the recording tracks 4 and 5, the fourth
With the relationship shown in the figure, the even-numbered reproduction signal level is lower than the odd-numbered reproduction signal level.

As described above, it is possible to determine in which direction the playback tracks 6 and 7 are shifted relative to the recording tracks 4 and 5, and thereby the shift can be corrected to perform optimal tracking. can be controlled.

In the tracking control system of the present invention, the direction and degree of tracking deviation can be determined by reproducing at least two tracks using the signals picked up by the rotary head itself, so tracking can be performed with extremely fast response.

In the explanation using Figures 2 to 4, the head positions are shifted during both recording and playback, but it is possible to shift the head position only during recording and playback to create a coarse/fine track. Tracking deviation can be detected in exactly the same way even when
This means that the tracking control of the present method is effective even when a tape recorded with a video tape recorder in which the head position is not shifted is played back with a video tape recorder equipped with the tracking control device of the present invention. ing.

In the present invention, in order to record/reproduce with the relationship shown in FIG. 2 by shifting the positions of two heads, the even-numbered track is traced by the head that records the odd-numbered track, and the even-numbered track is The head for recording the odd-numbered track may be used to trace the odd-numbered track, for example, by switching the head during recording and playback.Also, as another method, the phase of the scanning track relative to the signal of the control track may be changed. This can also be achieved by shifting the angle by 180 degrees during recording or playback.

It goes without saying that the rotary head type video tape recorder of the present invention includes a PCM audio tape recorder.

As described above, according to the present invention, (1) Tracking deviation does not occur even between different video tape recorders.

(2) Even when the tape expands and contracts, tracking does not occur.

(3) Tracking does not shift even if the position between the rotating head and the control head shifts.

(4) No additional circuit for wobbling is required.

(5) Faster response than the wobbling method.

This excellent effect can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a recording track by a conventional rotary head type video tape recorder, and Figs.
The figure shows a recording and reproducing track according to the invention. 4, 5... Recording track, 6, 7... Playback track.

Claims (1)

[Claims] 1. In a recording and reproducing system that performs recording and reproducing by scanning perpendicularly or obliquely to the running direction of a recording medium, in at least one scan during recording or reproducing, an odd number Even-numbered scans are slightly delayed or advanced relative to scans of A tracking control method that controls the traveling speed or scanning speed depending on the size relationship. 2. In claim 1, the recording/playback system is comprised of a rotating head type video tape recorder having a plurality of heads, and by slightly shifting the positional relationship of the plurality of heads, A tracking control method characterized in that even-numbered scans are delayed or advanced relative to odd-numbered scans. 3 In claim 1, even-numbered scans are delayed or advanced with respect to odd-numbered scans during both recording and playback, and the odd-numbered tracks scanned during recording are set to the even-numbered tracks during playback. A tracking control method characterized in that the even-numbered track scanned during recording is scanned as the odd-numbered track during playback.