JPH02139775A - Tracking device for rotational recording body - Google Patents

Abstract

PURPOSE:To shorten a time required up to the execution of tracking control by detecting the positions of a maximum value and a minimum value in the size of a reproduced envelope. CONSTITUTION:A video signal recorded on a magnetic disk 1 is detected by a reproducing head 7, its envelope is detected by an envelope detecting circuit 9 and a half output after detection is converted into digital data by an A/D converter 10 and read in a system controller 6. Since the output of an oscillator 5 and a PG pulse are also inputted to a system controller 6, the position of the digital data outputted from the A/D converter 10 on the circumference of the magnetic disk 1 can be decided. Then, the reproducing head 7 is fixed on a position for reproducing a specific track to reproduce data, a position on the circumference of the disk 1 on which the envelope becomes a maximum or minimum value is detected by the 2nd position detecting means and a head moving means 13 is controlled in accordance with the detected result so that the change of the envelope is minimized. Consequently, time up to the start of tracking control can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a rotating recording medium reproducing apparatus, and particularly to a rotating recording medium that reproduces information signals such as video signals recorded on a rotating magnetic recording medium such as a magnetic disk. The present invention relates to a tracking device for a playback device.

(b) Conventional technology Recently, subjects have been photographed in still form purely electronically by combining imaging devices such as solid-state image sensors and image pickup tubes with recording devices that use magnetic disks, which are inexpensive and have a relatively large storage capacity, as recording media. An electronic still camera system has been developed in which images are recorded on a rotating disk and reproduced using a separate television system or printer.

An example of a rotating magnetic recording medium used in an electronic still camera system is described in Nikkei Electronics, July 2, 1984 issue, pages 80 to 85. According to this, the track pitch is 100 μm on a small disk with a diameter of 47 mff1, that is, the track width is 50 to 6 mm.
5 when the guard band width is about 50 to 40 μm.
0 tracks are recorded. In a recording or reproducing recording device, this magnetic disk rotates at a constant speed of 3,600 revolutions per minute, and video signals are recorded or reproduced in units of fields or frames.

Such magnetic disks are prone to tracking failures due to various causes, especially eccentricity, and as a result, the playback envelope changes periodically, causing deterioration of the SN of the playback video and deterioration of the magnetic playback direction. There is a problem in that the target track may be affected by other tracks adjacent to the intended track, resulting in crosstalk.

As a technology to solve this problem, Japanese Patent Application Laid-Open No. 62-1348
There is No. 72 (G11B21/10).

The outline is shown below. moving a reproducing head in a radial direction of the rotating recording body at a plurality of predetermined phase angles of rotation of the rotating recording body;
Detect the position where the playback envelope shows a peak. Next, the average position of the detected positions is calculated, and the reproducing head is moved to that position to perform tracking.

That is, if the above technique is used, there is no need to separately record a tracking signal on the rotating recording medium. Moreover, compared to devices that use piezoelectric elements such as bimorphs to control the position of the playback head while responding sequentially so that the playback envelope always reaches its maximum value, there is less time delay in the trunking servo, and the load on the playback device is less eccentric. Even if the center of rotation of the rotary recording body in this state is shifted from the center of the recorded track, the amplitude for vibrating the head is minimized, and the recorded signal can be properly reproduced.

(c) Problems to be Solved by the Invention However, in the tracking device using the above technique, the position to which the reproducing head should be moved, that is, the average position, must be calculated before tracking control is performed. In order to do this, it is necessary to move the playback head in the radial direction of the rotating recording medium and detecting the position where the playback envelope shows a peak each time at a plurality of predetermined phase angles of the rotation of the rotating recording medium. This will require a considerable amount of time. Therefore, there is a drawback that it takes time to enter tracking control, during which time tracking control cannot be performed and the reproduced signal is disturbed.

(d) Means for Solving the Problems In order to solve the above problems, the present invention provides a head moving means for moving a playback head in the radial direction of a rotating recording medium, and detecting an envelope of a signal read by the playback head. a first position detecting means for detecting the circumferential position of the reproducing head on the rotating recording body; and a first position detecting means for detecting the position of the reproducing head on the circumference of the rotary recording medium; and/or a second position detection means for detecting a position on the circumference where the minimum value is taken.

(e) Operation First, the playback head is fixed at the position where a specific track is to be played back and playback is performed. Next, the second position detection stage detects the position on the circumference where the envelope takes the maximum value and/or the minimum value, and according to the result, the head moving means is controlled so that the change in the envelope becomes small.

(F) Embodiments Next, embodiments of the rotating recording medium tracking device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a system block diagram in which the present invention is applied to a playback device for an electronic still camera. In the figure, (1) is a magnetic disk, which is steadily rotated at 3600 revolutions per minute by a spindle motor (not shown). In addition, a plurality of tracks are formed on the magnetic disk with a locus in which the start and end of recording coincide, and each track has l.
Video signals for fields are recorded. (2) is a reference position detection pulse generator (hereinafter referred to as rPG yoke) provided in the disk clamp means (not shown) that fixes the magnetic disk (1) to the shaft of the spindle motor, and the PG coil ( 3), and generates one pulse (hereinafter referred to as rPG pulse) per rotation of the magnetic disk. (4) is a PG amplifier, and P
Amplify the G pulse and shape the waveform, and the output is an oscillator (5)
is input to the system controller (6).

(7) is a reproducing head which detects the video signal recorded on the magnetic disk (1), converts it into an electrical signal, and outputs it to the reproducing amplifier (8). The playback video signal is sent to the playback amplifier (8)
amplified by. The envelope detection circuit (9) detects the wave, and the half-wave output after detection is converted into digital data by the A/D converter (10) and read into the system controller (6). Further, the output of the reproduction amplifier (8) is supplied from an output terminal (11) to a video signal processing circuit and a television system (not shown), and the image is reproduced.

(12) is a motor driver that drives a head access motor (13) that moves the reproducing head (7) in the radial direction of the magnetic disk (1), and the system controller (
6).

FIG. 2 is a timing chart explaining the operation of the oscillator (5) and A/D converter (10). Oscillator (5)
is reset by the PG pulse, its output is synchronized with the PG pulse, and the period is 1/16 of the PG pulse. The A/D converter (10) converts the reproduced envelope output into digital data at the timing of the output pulse of the oscillator (5), and inputs it to the system controller (6). Note that the system controller (6) includes an oscillator (5).
) output and PG pulse are also input, so the digital data from the A/D converter (10) is transferred to the magnetic disk (
It is possible to determine at which position around the circle 1) the value is.
In the figure, the numbers are numbered from 0 to 0 with the PG pulse as a reference. Hereinafter, this number will be referred to as the position number.

Next, the outline of the tracking control operation in this embodiment will be explained using FIGS. 3 to 8.

First, before performing tracking control, first insert the magnetic disk (1)
Check the eccentricity situation. Therefore, the playback head (7) is moved by the head access motor (13) to the position where a specific track is to be played, that is, the position where the track would be accurately traced if there was no eccentricity, and fixed at that position and played back. Do the following. The state is shown in FIG. In the figure (
T I ) is the trajectory of the reproducing magnetic head, and (T2) is the recording track 1.5 formed on the magnetic disk (1). (2) is a PG yoke. The magnetic disk (1) is rotating clockwise around point P. Trajectory of reproducing magnetic head (T1)
The numbers marked with squares (■) attached to 1] are position numbers corresponding to the numbers in FIG. 2, and the A/I] converter (10) operates at the numbered positions.

Envelope detection circuit (9) in the state shown in Figure 3
The output is shown in Figure 4. The positions where the r-wave output of the reproduction envelope takes the maximum value are ■ and ■, and the positions where the r-wave output takes the minimum f position are ■ and @.

Therefore, the system controller (6) in FIG.
It is determined that the center line is eccentric in the ■-@ direction with ■-〇 as the center line. However, it is unclear whether the eccentricity is in the ■ direction or the @ direction. First, move the magnetic disk (1) in the ■ direction.
Assuming that the head is eccentric, the head access motor (13) is controlled through the motor driver (12) as shown in Figure 5, and the playback head (7) is moved outward at the position ■ and inward at the position ■. , move it inward at the ■ position and outward at the ■ position. Then, the output of the envelope detection circuit (9) is as shown in Figure 6, when the playback head (7) is not moved, that is, the width of the envelope change (△E) compared to the waveform in Figure 4.
becomes larger. Therefore, the system controller (6)
Judging that the eccentricity is in the @ direction rather than the ■ direction, contrary to the above, as shown in Figure 7, move the playback head (7) inward at the ■ position, outward at the ■ position, and at the 0 position. Move it outwards with the button , and move it inward with the ■ position. Then, the envelope detection circuit (9
) is shown in FIG. 8, and contrary to FIG. 6, the width of the envelope change (ΔE) is small, indicating that tracking is performed well.

Note 1. Position to move the playback head (7)■,■,■
, ■ are the positions between ■, ■, ■, and @, respectively, where the half-wave output of the reproduction envelope takes a local maximum value or a local minimum value. Further, the amount of movement is controlled by the system controller (6) after determining the eccentric direction so that the width of the change in the envelope becomes smaller.

Next, details of the operation of this embodiment will be explained with reference to the flowcharts shown in FIGS. 9 to 11, focusing on the system controller (6). In the description, N], N2, . . . indicate processing procedure (step) numbers.

First, move the playback head (7) to the position where a specific track is to be played using the access mode (13), then fix the playback head (7), rotate the magnetic disk (1), and play the state (N1). Next is the oscillator (5)
The A/D converter (10) is operated at the output timing of N2, and the half-wave output of the envelope detection circuit (9) is input to the system controller (6) as 16 digital data as shown in Figure 2 (N2 ). Next, on the track circumference, the position number a of the position where the digital data has the maximum value
1, a, is detected, and the maximum value of the digital data is set as E max (N3). Specifically, among the 16 pieces of data, the maximum value is first detected, the position number of the position where the maximum value is taken is set to al, and the position number of the position where the next largest value is taken is set as a. Next, in the same way as N3, detect the position numbers S, , b, which take the minimum value, and set the minimum value as Emin (N
4). Specifically, the minimum value is first detected, the position number that takes the minimum value is designated as bl, and the position number that takes the next smallest value is designated as bl.

shall be. Next, Emax-Emin is calculated, and if it is less than the predetermined value -■-, the process proceeds to the next routine in Figure 10 ('i' E S at N5), and if it is less than or equal to the specified value, the width of the change in the playback envelope is Since the playback head (7) does not need to be moved because it is small, tracking is unnecessary and playback is performed with the playback head (7) fixed (NO at N5).

Then at < a! 2. Replace the data as necessary so that the relationship is l b 1 < b 2 (N6.N
7. N8, N9). This is to detect whether the magnetic disk (1) is eccentric or not, and to facilitate calculation of the position number to which the reproducing head (7) is to be moved.

Next, the position where the maximum value is taken and the position where the minimum value is taken are 90 points on the circumference.
Please check if the positions are shifted by degrees.
Nl 1), otherwise (No or Nil in NIO
(NO) It is assumed that the disturbance in the playback envelope is not caused by eccentricity, and a separate process is used to deal with it. The separate processing uses, for example, a conventional tracking method, and a detailed explanation will be omitted. If both N10゜Nil are YES, it is determined that eccentricity is the cause, and the position number ClICl to which the playback head (7) is moved is determined.
Calculate IC,,C,(N12.N13.N14゜N
15). This is because, as shown in FIGS. 5 and 7, the position to which the reproducing head (7) is moved is between the position where the maximum value is obtained and the position where the minimum value is obtained.

Next, a 1 < b + < a 1 < b * or b
1 < a, < b * < a, N16
), if a + < b, then the direction in which the playback head (7) is moved is set to the inside at C1, the outside at C2, the outside at C8,
C1 is tentatively determined as inside, N16 is YES, N17), b
If +<at, it is tentatively determined that C2 is outside, C3 is outside, C8 is inside, and C4 is inside (N01N18 at N16).

This is due to the following reason. The magnetic disk (1) is eccentric in the direction connecting two positions s, , b, which have minimum values. Therefore, the movement of the reproducing head (7) must correspond to this. However, C1 to C4 are simply a1+ a
! Since the calculation is only performed using the value of + b + w b, there are 82 cases of the positional relationship of C3 to C4 with respect to b, , b, as shown in FIG. 12. Therefore, it is determined whether a + < b + or b < a +, and the moving direction at each position of C3 to C4 is tentatively determined.

Next, move the head a predetermined amount X in the direction tentatively determined in N17 or N18 at positions C5 to C4 (N19), and input digital data to the system controller (6) in the same way as N2 (N20). Detect the maximum value Emax' and minimum value Emin' of the digital data (N21
). Next, we proceed to the flowchart shown in Figure 11, and compare the width of the change in the playback envelope that occurred when the playback head (7) was fixed, and the width of the change in the playback envelope when it moved in the direction tentatively determined at N17 or N18. Comparatively, N22), if it is larger, the direction of movement is reversed at each position of C1 to C4 (YES at N22, N25).

Next, the amount of movement is determined. First, increase the movement amount by a predetermined value △X (N24), input digital data in the same way as N2 (N25), and detect the maximum value Emax'' and minimum value Emin of the input digital data (N26).
. Next, compare the width of the change in the playback envelope before and after increasing the amount of movement (N27), and if it is large, decrease the amount of movement by △X, determine the amount of movement, and continue tracking control (N27). YES, N28). If it is smaller, change Emax” to Emax”-Emin” to Emin.
' and return to the previous stage of N24 (No at N27, N
29), N24 to N27 are repeated. So-called hill-climbing control is performed. In addition, the movement amount X at N19 is
N22 and N23 are the predetermined amounts necessary to determine the direction of movement, and N24 to N27 perform hill-climbing control in the direction of increasing the movement amount, so it is preferable that the value is as small as possible.

Although the embodiments have been described in detail above, the present invention is not limited to the embodiments and can be modified in various ways. For example, in the embodiment, both the position where the size of the reproduction envelope takes the maximum value and the position where the size takes the minimum value are detected, but if one of them is known, the eccentric direction can be detected. That is, Fig. 3,
As shown in FIG. 4, the eccentric direction is a direction perpendicular to the direction connecting the two positions where the maximum value is taken, and also the same direction as the direction connecting the two positions where the minimum value is taken.

Therefore, there is no need to detect them together.

(G) Effects of the Invention As described above, according to the present invention, the position on the circumference, the direction of movement, and the amount of movement of the reproducing head can be determined in a shorter time than in the prior art. The time required to perform tracking control is shortened, that is, the time during which the reproduced signal is disturbed is shortened, and the effect is great.

[Brief explanation of the drawing]

FIG. 1 is a system block diagram showing an embodiment of the present invention;
FIG. 2 is a timing chart explaining the operation of the embodiment;
Figures 3, 4, 5, 6, 7, and 8 are diagrams for explaining the outline of the operation of the embodiment, and Figures 9, 10, and 11 are diagrams for explaining the operation of the embodiment. FIG. 12, a flowchart showing details of the operation, is a diagram for explaining the necessity of the processing in the flowchart of FIG. 10. (+)...Magnetic disk, (3)...PG coil,
(5)...Oscillator, (6)...System controller, (7)...Playback head, (9)...Envelope detection circuit, (13)...Head access morph

Claims (1)

[Scope of Claims] 1. A reproducing head that reads signals from a plurality of tracks formed on a rotating recording body that rotates steadily at a predetermined rotational speed with a locus in which the starting and ending ends of recording coincide; head moving means for moving the rotary recording body in the radial direction; envelope detection means for detecting an envelope of a signal read by the reproducing head; and a head moving means for detecting the circumferential position of the reproducing head on the rotary recording body. The position detecting means shown in FIG. 1, and the second position detecting means which uses the envelope detecting means and the first position detecting means to detect a position on the circumference where the envelope takes a maximum value and/or a minimum value. and the head moving means is synchronized with the rotation of the rotary recording body so that a change in the output from the envelope detection means becomes smaller depending on a position on a circumference where the envelope takes a maximum value and/or a minimum value. A rotating recording body tracking device characterized in that it is controlled by: