JPH0711879B2 - Auto tracking device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an auto-tracking device which is used in, for example, a VTR and automatically controls tracking of a magnetic head.

[Conventional technology]

For example, as shown in FIG. 6 (a), when the signal recorded on the magnetic recording medium 11 is reproduced, the relative position in the tracking direction between the recording track 12 and the magnetic head 13 formed on the magnetic recording medium 11. Is deviated, that is, when the tracking phase amount is greatly different from the center trace state, the level of the reproduction envelope signal becomes small as shown in FIG.

Therefore, in the conventional auto-tracking device, the recording track 12 increases in the direction in which the level of the reproduction envelope signal increases.
And the relative position of the magnetic head 13 in the tracking direction are changed. Then, the relative position shift amount gradually decreases, and as shown in FIG. 6B, the relative position change is stopped when the center trace state is reached.

That is, the recording track formed on the magnetic recording medium 11.
The relative position between the magnetic head 12 and the magnetic head 13 in the tracking direction is always in the center trace state, and the tracking control is performed so that the level of the reproduction envelope signal is maximized.

Also, an edge traced state has been proposed (Japanese Patent Laid-Open No. 59-11526). However, the proposed method does not consider variations in the head width of the magnetic head during the manufacturing process. One end of the reproducing head is either one end or the other end of the recording track (either end is acceptable)
Tracking control is performed so as to almost match with.

[Problems to be Solved by the Invention]

When azimuth recording is performed on the magnetic recording medium 11, adjacent recording tracks 12 are formed so as to have opposite azimuths. Therefore, even if the magnetic head 13 protrudes from the recording track 12 on which the recording signal is reproduced and overlaps with the adjacent track, the signal recorded on the adjacent track has a small crosstalk due to azimuth loss. It is like this.

By the way, the magnitude of the azimuth loss depends on the frequency of the recording signal, the azimuth angle, the amount of overlap with an adjacent track, and the like. In a normal operation state, the larger the overlap amount with the adjacent track, the larger the azimuth loss.

However, in the above-described conventional auto-tracking device, as described above, the tracking control is performed so that the relative position between the recording track 12 and the magnetic head 13 in the tracking direction is in the center trace state. The amount of overlap with the track is kept small.

Therefore, there is a problem in that the influence of crosstalk from both adjacent tracks is large and the quality of the reproduced signal tends to deteriorate.

Further, in the technique proposed in Japanese Patent Laid-Open No. 59-11526, tracking control is performed so that one end of a reproducing head substantially coincides with either one end or the other end of a recording track (either end may be used). Therefore, for example, as shown in FIG. 8, when L head width> R head width due to variations in the manufacturing process of the magnetic head and the like, one end of the wide head R has one end of the wide head R in the running direction of the magnetic recording medium in the recording track. In the edge trace state that coincides with one end on the opposite side, the wide head L does not enter the edge trace state and there is a problem that the reproduced image deteriorates.

The present invention has been made in view of such points,
By performing tracking control so that one end of the magnetic head is in an edge trace state that coincides with one end of the recording track formed on the magnetic recording medium on the running direction side of the magnetic recording medium, a plurality of magnetic fields having different head widths are obtained. (EN) Provided is an auto-tracking device capable of improving the quality of a reproduced signal by suppressing the influence of crosstalk from an adjacent track on the reproduced signal in all magnetic heads even if the head is provided. The purpose is to

[Means for Solving the Problems]

In order to solve the above problems, an auto-tracking device according to the present invention includes a magnetic head for converting a magnetic signal recorded on a magnetic recording medium into an electric signal, a recording track formed on the magnetic recording medium, and a magnetic head. Driving means for changing the relative position in the tracking direction with the head, reproducing signal detecting means for detecting an electric signal converted by the magnetic head and outputting a reproducing envelope signal, and a reproducing envelope outputted from the reproducing signal detecting means. Tracking phase control means for outputting a tracking phase control signal based on the signal so that the relative position in the tracking direction between the recording track formed on the magnetic recording medium and the magnetic head is in an edge trace state; and the tracking phase control Drive based on the tracking phase control signal output from the means In an auto-tracking device provided with a servo control means for performing a stepped tracking phase control, the tracking phase control means outputs when the relative position of the magnetic head in the tracking direction is changed by the driving means. While the level of the reproduction envelope signal is not lower than the previous output value, the driving means is changed so that the tracking phase amount continues to increase,
When the level of the reproduction envelope signal decreases, the driving means is changed so that the tracking phase amount decreases, and thereafter, when the level of the reproduction envelope signal starts to decrease, the tracking direction of the recording track and the magnetic head changes. Based on the relative position, one end of the magnetic head is configured to obtain an edge trace state in which one end of the magnetic track coincides with one end of the magnetic recording medium on the running direction side.

[Work]

With the above structure, the tracking phase control means, based on the reproduction envelope signal output from the reproduction signal detection means, has one end of the magnetic head on the recording track formed on the magnetic recording medium in the running direction of the magnetic recording medium. A tracking phase control signal is output so as to be in an edge trace state that coincides with one end of, and the servo control means performs servo control of the driving means based on the tracking phase control signal.

That is, the portion of the magnetic head that is protruding from the recording track that is reproducing the recording signal always overlaps only with the adjacent track on the opposite side of the running direction of the magnetic recording medium, and the overlap amount is the largest. Therefore, the azimuth loss of the signals recorded on the adjacent tracks becomes large.

Therefore, even if a plurality of magnetic heads having different head widths are provided, the influence of crosstalk from the adjacent tracks on the reproduced signal is always suppressed in all the magnetic heads, and the quality of the reproduced signal is improved. Can be made.

〔Example〕

As one embodiment of the present invention, a helical scan type VTR
An example of the auto-tracking device used for the (video tape recorder) will be described below with reference to FIGS. 1 to 5.

As shown in FIG. 1, the VTR is provided with a capstan motor 22 for running and driving a magnetic tape 21 which is a magnetic recording medium. This capstan motor 22 is a magnetic tape
By changing the running speed of the magnetic tape 21, the recording track 21a formed on the magnetic tape 21 and the magnetic head 2 described later
It acts as a drive means for changing the relative position in the tracking direction with respect to 4.

Further, the VTR is provided with a rotary magnetic head device 23 having a rotation shaft in a direction inclined with respect to the traveling direction of the magnetic tape 21. This rotary magnetic head device 23 has a magnetic head 24 that is set to different azimuth angles and converts a magnetic signal recorded on the magnetic tape 21 into an electric signal.
・ 24 is installed.

The magnetic heads 24, 24 are connected to a reproduction signal detection circuit 31, which is reproduction signal detection means for detecting the electric signal converted by the magnetic heads 24, 24 and outputting a reproduction envelope signal.

The reproduction signal detection circuit 31 is an AD converter 32 for converting a reproduction envelope signal which is an analog signal into a digital signal.
It is connected to the. The A-D converter 32 is an A-D converter 32.
It is connected to a microcomputer 33 that outputs a tracking phase control signal based on the digital signal output from the.

Based on the reproduction envelope signal output from the reproduction signal detection circuit 31 by the A / D converter 32 and the microcomputer 33, the recording track 21a formed on the magnetic tape 21 and the magnetic head 24 are relative to each other in the tracking direction. Tracking phase control means for outputting a tracking phase control signal is configured so that the position is in an edge trace state.

The tracking phase control signal output from the microcomputer 33 is connected to the capstan servo device 34. The capstan servo device 34 performs servo control of the capstan motor 22 based on a control signal detected by the control head 35 and a pulse signal output from a pulse generator (not shown) included in the rotary magnetic head device 23. I am supposed to do it. In addition, the capstan servo device 34 is a micro computer.
Based on the tracking phase control signal output from 33, it also functions as servo control means for controlling the tracking phase of the capstan motor 22.

The operation performed by the microcomputer 33 in the above configuration will be described below with reference to the flowchart shown in FIG.

First, based on the digital signal output from the A / D converter 32, the level of the reproduction envelope signal at that time is stored. Further, the rotational phase of the capstan motor 22 is reduced by a small amount, and the relative position of the recording track 21a of the magnetic tape 21 and the magnetic head 24 in the tracking direction is set so that the magnetic head 24 is closer to the running direction side of the magnetic tape 21. It is changed so as to move in a deviating direction, that is, the tracking phase amount of the magnetic head 24 increases (S1).

Next, the difference between the levels of the reproduction envelope signal before and after increasing the tracking phase amount of the magnetic head 24 is calculated, and based on the difference, the level of the reproduction envelope signal is changed by increasing the tracking phase amount. Determine whether (S2).

If it is determined in S2 that the level of the reproduction envelope signal has not changed, the process returns to S1 to further increase the tracking phase amount. If it is determined that the level of the reproduction envelope signal has changed, the process proceeds to S3, and it is determined whether the level of the reproduction envelope signal has increased.

When it is determined in S3 that the level of the reproduction envelope signal has increased, the process proceeds to S4, the level of the reproduction envelope signal is stored, and the level of the reproduction envelope signal decreases after further increasing the tracking phase amount. It is determined whether or not (S5), and the tracking phase amount is increased by repeating S4 and S5 until the level of the reproduction envelope signal decreases.

That is, when the level of the reproduction envelope signal is increased when the tracking phase amount is increased, the tracking phase amount is, for example, as shown by A in FIG. 3, and the magnetic head 24 and the recording track 21a. The relative position in the tracking direction of is, as shown in FIG.
The magnetic head 24 causes the magnetic tape 21 to move more than the recording track 21a.
It is in a state of being displaced in the direction opposite to the traveling direction of.

Therefore, by increasing the tracking phase amount,
The reproduction envelope amount is eventually saturated, and as shown in FIG. 4 (d), a center trace state in which the tracking phase amount is D is reached, and the tracking phase amount is further increased to E.
The magnetic head 24 and the recording track 21 are
As shown in FIG. 4 (e), when the relative position of the magnetic head 24 with respect to a is displaced toward the running direction side of the magnetic tape 21 from the recording track 21a, The level of the reproduction envelope signal starts to decrease, and the process proceeds to S6.

At S6, the level of the reproduction envelope signal is stored, and then the tracking phase amount is decreased, and then it is determined whether or not the level of the reproduction envelope signal has decreased (S
7) S until the level of the playback envelope signal decreases
Repeat 6 and S7 to decrease the tracking phase amount. Then, contrary to the above S4 and S5, when the tracking phase amount decreases to the size indicated by B, as shown in FIG. And the relative position of the recording track 21a in the tracking direction is slightly shifted in the magnetic head 24 to the side opposite to the running direction of the magnetic tape 21 than the recording track 21a, and the level of the reproduction envelope signal is lowered. And move to S8.

At S8, the tracking phase amount C is increased so that the tracking phase amount B is increased by a correction amount corresponding to the envelope detection characteristic of the reproduction signal detection circuit 31, the accuracy of tracking phase control, the response characteristic, and the like. The rotation phase of the stun motor 22 is reduced. Therefore, the relative position of the magnetic head 24 and the recording track 21a in the tracking direction is
As shown in FIG. 4 (c), the magnetic head is controlled so that one end of the magnetic head coincides with one end of the recording track formed on the magnetic recording medium in the running direction of the magnetic recording medium. It

Also, after it is determined in S2 that the level of the playback envelope signal has changed, if it is determined in S3 that the level of the playback envelope signal has not increased, the playback envelope signal is increased when the tracking phase amount is increased. This means that the level of has decreased. In this case, the tracking phase amount is, for example, as shown by F in FIG. 3, and the relative position in the tracking direction between the magnetic head 24 and the recording track 21a is as shown in FIG. 4 (f). In addition, the magnetic head 24 is in a state of being displaced toward the running direction side of the magnetic tape 21 from the recording track 21a.

Therefore, the process proceeds to S6 as it is, and in S6 to S8, control is performed so that the relative position of the magnetic head 24 and the recording track 21a in the tracking direction is in the edge trace state as described above.

In this way, the control is performed so that the relative position between the magnetic head 24 and the recording track 21a in the tracking direction is in the edge trace state, so that the level of the reproduction envelope signal is the maximum as shown in FIG. The length of the portion protruding from the recording track 21a where the magnetic head 24 reproduces the recording signal, that is, the overlap amount W with the adjacent recording track 21 of the reverse azimuth becomes maximum.

By the way, the azimuth loss La of the signal recorded on the reverse azimuth recording track 21b is the overlap amount W between the magnetic head 24 and the recording track 21b, and the azimuth angle of the magnetic head 24 and the azimuth angle of the recording track 21b. Tilt angle (=
When the azimuth angle is twice) and the wavelength of the magnetic signal recorded on the magnetic tape 21 is λ, And the larger the overlap amount W, the azimuth loss
La becomes larger.

Therefore, the crosstalk with respect to the reproduction signal is only based on the signal recorded on the recording track 21b on one side of the recording track 21a, and moreover, the azimuth loss when the signal recorded on the recording track 21b is reproduced. Is large, the influence of crosstalk is suppressed to be small, and the image quality of reproduced video is improved.

〔The invention's effect〕

Since the auto-tracking device according to the present invention is configured as described above, the portion of the magnetic head that is always protruding from the recording track reproducing the recording signal is the adjacent track on the side opposite to the running direction of the magnetic recording medium. However, the overlap amount becomes the largest and the amimus loss of the signals recorded in the adjacent tracks becomes large.

Therefore, even if a plurality of magnetic heads having different head widths are provided, the influence of crosstalk from the adjacent tracks on the reproduced signal is always suppressed in all the magnetic heads, and the quality of the reproduced signal is improved. Can be made.

[Brief description of drawings]

1 to 5 show an embodiment of the present invention, in which FIG. 1 is an explanatory view showing the structure of an auto-tracking device, and FIG. 2 is a flow chart showing the operation performed by a microcomputer. FIG. 3 is a graph showing the relationship between the tracking phase amount and the envelope signal level, FIGS. 4 (a) to 4 (f) are explanatory views showing the positional relationship between the recording track and the magnetic head, and FIG. 5 is an edge trace state. FIG. 6 is an explanatory view showing the positional relationship between the recording track and the magnetic head. 6 to 8 show a conventional example.
7A and 7B are explanatory views showing the positional relationship between the recording track and the magnetic head, FIG. 7 is a graph showing the relationship between the tracking phase amount and the envelope signal level, and FIG. 8 is the L head width> FIG. 9 is an explanatory diagram showing a case where one end of the wide head R has an R head width and an edge trace state where one end of the wide head R coincides with one end on the opposite side in the running direction of the magnetic recording medium in the recording track. 21 is a magnetic tape (magnetic recording medium), 21a and 21b are recording tracks, 22 is a capstan motor (driving means), 24 is a magnetic head, 31 is a reproduction signal detection circuit (reproduction signal detection means),
32 is an AD converter (tracking phase control means), 33 is a microcomputer (tracking phase control means),
34 is a capstan servo device (servo control means).

Claims (1)

[Claims] 1. A magnetic head for converting a magnetic signal recorded in azimuth on a magnetic recording medium into an electric signal, and a driving means for changing a relative position in a tracking direction between a recording track formed on the magnetic recording medium and the magnetic head. A reproduction signal detecting means for detecting an electric signal converted by the magnetic head and outputting a reproduction envelope signal; and a reproduction envelope signal output from the reproduction signal detecting means, which is formed on the magnetic recording medium. Based on the tracking phase control signal output from the tracking phase control means for outputting the tracking phase control signal so that the relative position in the tracking direction between the recording track and the magnetic head is in the edge trace state, A servo control means for controlling the tracking phase of the driving means. In the automatic tracking device, the tracking phase control means changes the relative position in the tracking direction with respect to the magnetic head by the driving means, and the level of the reproduced envelope signal output is relative to the previous output value. While not decreasing, the driving means is changed so that the tracking phase amount continues to increase, and when the level of the reproduction envelope signal decreases, the driving means is changed so that the tracking phase amount decreases.
After that, based on the relative position in the tracking direction between the recording track and the magnetic head when the level of the reproduction envelope signal turns to lower, one end of the magnetic head coincides with one end of the recording track on the running direction side of the magnetic recording medium. An auto-tracking device, which is configured to obtain an edge trace state.