JP2644594B2 - Tracking control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a tracking control method for a helical scanning type magnetic recording / reproducing apparatus, and more particularly to a method for controlling a narrow track such as a digital VTR or a high vision VTR which requires high density recording. It relates to a tracking control method.

(Summary of the Invention) The present invention relates to a VTR and a DAT (Digital Audio Taperecorder).
And related to a tracking control method of a helical scanning type magnetic recording / reproducing apparatus. When reproducing recorded information from a track on which azimuth recording is performed, two types of heads having the same azimuth angle as the recording track preceding the reproducing head are used. In preparation, the adjacent tracks are simultaneously scanned, and the differential output of both heads is detected as a tracking error signal to track the reproducing head.

Thus, stable and reliable tracking can be performed even when a signal recorded on a narrow track is reproduced.

(Prior art) Conventionally, the most frequently used method for this type of tracking is to provide a control track at the bottom or top of the tape separately from video and audio signals during recording, and to use a CTL (contro
1, a CTL pulse method in which a pulse is recorded in the longitudinal direction and tracking is performed based on this signal during reproduction.

Recently, pilot signals of four kinds of frequencies are
It is multiplexed with the main signal for each field and recorded. During reproduction, a four-frequency system that performs tracking by detecting the track shift amount and shift direction from the difference frequency of the pilot signal between adjacent tracks, or independent of a part of the main signal A pilot signal is recorded directly at the beginning and end of a track by detecting the main pilot signal and the crosstalk components from both sides, and the tracking is performed by detecting the track shift amount and the shift direction. Area division methods and the like have been put to practical use.

(Problems to be Solved by the Invention) Conventionally, the most widely used CTL pulse method has advantages such as a simple circuit system and resistance to noise.
However, there are disadvantages that a separate track is required, the track cannot be followed, and the mechanical position accuracy of the CTL head is required for compatibility.

In addition, although the four-frequency method can detect tracking errors over the entire track area, it can follow track bends, and has some parts that compensate for the drawbacks of the CTL pulse method, such as the fact that a CTL head and CTL track are unnecessary. It has disadvantages such as being affected by the level difference of the reproduced pilot signal, being affected by the level change of the head difference, and having poor overwrite characteristics.

Further, the area division method has the advantages that tracking error detection is performed at two locations on the track, so that it can follow a certain degree of track bending, and that overwriting characteristics are good because the pilot signal is directly recorded. However, there are disadvantages such as the use of a part of the main signal recording track and the complicated circuit system.

Therefore, the object of the present invention is to eliminate the above-mentioned disadvantages,
It is an object of the present invention to provide a tracking control method capable of realizing stable and reliable tracking control in response to narrowing of tracks accompanying high density.

(Means for Solving the Problems) To achieve this object, a tracking control method according to the present invention provides a helical scanning type magnetic recording / reproducing apparatus,
In reproducing the recorded information of the azimuth-recorded track by changing the azimuth angle between adjacent tracks on the recording medium using the reproducing head of the magnetic recording / reproducing apparatus, the rotating drum precedes the reproducing head. Two types of heads, each having the same azimuth angle as the recording track on which the recording information is recorded, and tracing the same trajectory before and after the rotation of the rotating upper drum are provided. The scanning is performed so as to straddle the two recording tracks, and the output difference between the two types of heads is used as a tracking error signal to track the reproducing head.

(Example) Hereinafter, the present invention will be described in detail by way of examples with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing a positional relationship between a reproducing head and a tracking detection head in a magnetic recording / reproducing apparatus according to an embodiment of the present invention. In the figure, the direction of the arrow indicates the relative movement direction of the recording medium (tape) with respect to the reproduction head.

In the figure, a tracking detection head (A) 3 having the same azimuth angle as the reproducing head (A) 1 preceding the reproducing head (A) 1 and an inverted azimuth reproducing head paired with the reproducing head (A) 1. (B) A tracking detection head (B) 4 having the same azimuth angle as 2 is mounted on the rotating upper drum 5 so as to scan over adjacent recording signal tracks. Therefore, the tracking detection head (A) 3 and the tracking head (B) 4 trace the same trajectory before and after the rotation of the drum 5 (see FIGS. 2 and 4 described below).
And FIG. 5).

FIG. 2 is a diagram for explaining the operation according to the method of the present invention, in which the direction of the arrow is the running direction of the recording medium.

When the reproducing head (A) 1 is on-track in a good state as shown in FIG. 2 (a), the differential outputs of the tracking detection head (A) 3 and the tracking detection head (B) 4 are set in advance. It has been adjusted to be zero. When tracking deviation occurs as shown in FIG. 2 (b),
When the output of the tracking detection head (A) 3 becomes larger than the output of the tracking detection head (B) 4 and a tracking shift occurs as shown in FIG.
Since the state is reversed, the direction and amount of tracking deviation can be obtained by differentially detecting this signal.

FIG. 3 shows a block diagram of an embodiment of the detection system according to the method of the present invention.

The outputs of the tracking detection heads (A) 3 and (B) 4 are amplified by head amplifiers 8 and 9 and peak detectors 10 and 11 perform peak detection. The calibrations 12 and 13 are adjusted so that the outputs of the two heads when the reproduction head is on-track in a good state are equal, and the output is amplified by the differential amplifier 14. This signal is fed back as a tracking error signal to a capstan or a dynamic tracking head to perform highly accurate tracking.

The method of the present invention can be applied to a standard having a guard band 15 as shown in FIG.

If it is anticipated that the placement of the tracking detection heads 3 and 4 in the vicinity of the reproduction head 1 will cause the reproduction head to hit the tape poorly, separate the head from the reproduction head 1 as shown in FIG. It is also possible to arrange on the previous track.

Although several embodiments according to the method of the present invention have been described above, the present invention is not limited to only these embodiments, and various modifications can be made without departing from the gist of the present invention.
Variations will be obvious to those skilled in the art.

(Effects of the Invention) The conventional CTL method and area division method require an area dedicated for tracking on the tape, but the method of the present invention
Since the main signal track is used for tracking detection as it is, there is no useless area, it is suitable for high-density recording, and the detection system can be easily configured. Compared with the four-frequency system, there is no need to superimpose a pilot signal on the main signal track, so there is no effect of crosstalk, tracking error can be detected over the entire track, and differential output is detected. This is advantageous in that it is less susceptible to the effects of the level difference of the reproduced pilot signal and the level change of the head difference.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a positional relationship between a reproducing head and a tracking detection head according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining an operation according to the present invention. FIG. 3 shows a block diagram of an embodiment of the detection system according to the method of the present invention, and FIGS. 4 and 5 show another embodiment and still another embodiment of the method of the present invention, respectively. 1,2 Reproduction head 3,4 Tracking head 5 Upper drum 6,7 Track 8,9 Head amplifier 10,11 Peak detector 12,13 Calibration 14: Differential amplifier, 15: Guard band 16: Tape, 17: Lower drum

Claims (2)

(57) [Claims] In a helical scanning type magnetic recording / reproducing apparatus, information recorded on a track which is azimuth-recorded by changing an azimuth angle between adjacent tracks on a recording medium is reproduced using a reproducing head of the magnetic recording / reproducing apparatus. In doing so
Two types of heads, each having the same azimuth angle as the recording track on which the recording information was recorded prior to the reproduction head on the rotating upper drum, and tracing the same trajectory successively with the rotation of the rotating upper drum, The two types of heads are scanned so as to straddle two recording tracks adjacent to each other, and the output difference between the two types of heads is used as a tracking error signal to track the reproduction head. And a tracking control method. 2. The control method according to claim 1, wherein the leading positions of the two types of heads preceding the reproducing head are:
A tracking control method, comprising a recording track currently being reproduced by the reproduction head and immediately before the reproduction head.