JPS59185482A - Auto-tracking device - Google Patents

Abstract

PURPOSE:To improve the accuracy of auto-tracking by comparing the magnitude of mean value of sampling and the previous mean value, in a sheet recorder, and deciding a feed direction of a reproducing head is accordance with its result. CONSTITUTION:When a track to be reproduced is designated, a head driving mechanism 11 is controlled by a controlling circuit 10, a head 3 is sent to a designated track, and a rough position is decided. Subsequently, reproducing is executed, feeding the head 3 by a fine adjusting step, and a magnitude relation of a mean value of sampling signals S1-S12 in that case and the previous mean value is checked. When the mean value becomes smaller than the previous time, a position of the previous head 3 is set to a position where the maximum level of a reproducing signal is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an auto-tracking device for a reproducing head used when reproducing a sheet-like recording medium on which circular tracks are formed.

BACKGROUND ART AND PROBLEMS In a sheet recorder that records and reproduces still images using a disc-shaped magnetic sheet (hereinafter simply referred to as a sheet), the sheet is rotated during recording, and each time the sheet rotates, By step-feeding the recording head, a large number of circular tracks are formed concentrically, and one
One field or one frame of a video signal is recorded for each track of a book. Therefore, during playback, it is necessary to accurately trace the playback head over the recorded trunk and track the head so that the level of the playback signal is maximized.

OBJECTS OF THE INVENTION The present invention provides an auto-tracking device for automatically tracking the above-mentioned head.

SUMMARY OF THE INVENTION The present invention provides a method for reproducing one or two circular tracks on which one field of video signals is recorded by a playback head.

If one still image is reproduced several times, each time the reproduction of one still image is completed, the reproduction head is moved on the circular track in the outer circumferential direction or the inner circumferential direction along the radius of the circular track. At this time, the playback level detected by the playback of one still image is determined by detecting the playback level at an even number of sampling points at four or more points set on the circular track. Find the average value of , compare the magnitude relationship between this average value and the average value obtained in the previous reproduction, and determine the feeding direction of the reproduction head in the outer circumferential direction or the inner circumferential direction according to the result of this comparison. This is an auto-tracking device designed to

Embodiment In this embodiment, auto-tracking of the head when playing back a sheet using the sheet recorder described above is performed in the following procedure.

(1) First, the head is sent to the designated track and roughly positioned. The head feeding mechanism used is capable of step feeding for each track and step feeding for fine adjustment of, for example, several microns to the same track.

(2) Next, rotate the sheet and perform the first reproduction.

At this time, the level of playback (No. 8) is sampled at four or more predetermined locations on the track and even number of locations, and the average value of these sampling values is determined and stored in the memory in correspondence with the position of the head.

(3) Advance the head one step in the fine adjustment step.

(4) A second reproduction is performed, and at this time sampling is performed in the same manner as in (2), and the average value is determined and stored in the memory.

(5) Examine the magnitude relationship between the average value obtained in the first reproduction and the average value obtained in the second reproduction.

(61. If the second average value is larger, fine-adjust the head one step in the same direction as in (3),
If the average value of the second time is smaller, the head is finely adjusted one step in the opposite direction to the above direction.

(7) Perform a third reproduction if necessary to obtain the above average value and store it in the memory.

(8) Check the magnitude relationship between the third average value and the second average value, and move the head one step in the same manner as in (6).

(9) As described above, playback is performed while finely adjusting the head one step at a time, and by checking the magnitude relationship between the average value of the sampling at that time and the previous average value, the average value is higher than the previous one. When it becomes smaller, the previous head position is used as the position where the maximum level of the playback signal can be obtained.
can be done.

Next, the sampling points on the track will be described.

When playing back a sheet using the sheet recorder described above, eccentricity of the sheet becomes an important problem. Eccentricity of the seat is caused by replacing and attaching/detaching the seat, eccentricity of the motor for rotating the seat, diameter tolerance of the motor spindle, and the like.

Consider the case where the center O' of the circular track (2) during reproduction, indicated by the dotted line, is eccentric by Δr with respect to the center O of the circular track (1) during recording, indicated by the solid line in FIG.

It is assumed that sampling is performed when the head (3) having W1 in the reciprocating track comes to the positions indicated by A and B on the track (2), which are approximately 180 degrees opposite to each other. When the head (3) is stepped in the direction indicated by the arrow a%b, the signal becomes W2 during actual reproduction, and the position where this W2 becomes maximum is the position where the maximum level is obtained. In this case, even if sampling is performed at a position indicated by C1D in the figure, which is approximately 180 degrees opposite to each other and 90 degrees apart from A and B, the level will hardly change. That is, it is impossible to perform auto-tracking by sampling only points C and D. Therefore, as shown in the figure, it is necessary to perform sampling at at least four locations and at approximately equal intervals. Note that the more evenly spaced the sample, the greater the effect when increasing the number of samples. In this case, a racking operation is performed based on the average value of all sampling values (at least 8 locations) of both tracks.

Figure 2 shows a booklet for performing operations (1) to (9) described above in the case where one still image is composed of two tracks, and six sampling points are set on each track, for a total of 12 sampling points. DESCRIPTION OF THE INVENTION An autotracking device according to the invention,
FIG. 6 shows the timing chart.

In FIG. 2, it is assumed that a spindle motor (5) rotates a twist sheet (not shown), and the head (3) reproduces this. Every rotation of this motor (5), PG (
1 in FIG. 6A from pulse generator) (7).

When the track to be reproduced has been specified, the head drive mechanism (1υ) is controlled by the system control circuit (hereinafter simply referred to as system controller), and the head (3) is sent to the specified track and roughly positioned. .

Incidentally, the system controller (10) includes a head feeding circuit, an arithmetic circuit, a memory, and the like. Next, the sheet is played back each time the head (3) is advanced in fine steps. The regenerated F signal is passed through the I(, F amplifier (121),
It is demodulated by a demodulator (13) and becomes a still image video signal,
This video signal passes through a video amplifier (14) and is reproduced in a subsequent circuit. At the same time, the RF signal (i) is envelope-detected by the envelope detection circuit (19), and the detection output is applied to the sample gate circuit (T71) through the DC amplifier (16).

On the other hand, the FG pulse passes through the FG amplifier (18) and is frequency-divided by the frequency dividing circuit (19) into the pulse Fx shown in FIG. 6C.

The timing circuit (20) based on the Fx pulse and the PG pulse obtained through the PG amplifier (21),
Twelve sampling pulses 01 to G12 are generated in one rotation as shown in Fig.
Add to 7). In addition, the timing circuit (20) has a system controller (1
0), the AD standard H8s UK double signal of Figure 6 is added.

After a predetermined time T1 from this signal, mechanical vibrations etc. disappear and the system becomes stable, the above-mentioned sampling pulses 01 to G12 are generated based on the pulse PG of (2).

The gate circuit αη converts the above detection output into pulses 01 to G12.
The signals S1 to S12 representing the sampled levels shown at N in FIG. 6 are obtained. These signals 81 to 12 are added to the sample and hold circuit (221) and averaged. The signal Sa shown in FIG.
A 7 D 8 TART i is converted into digital data SD, and written to the memory in the system controller (101) by the write instruction signal W from the system controller (tQl).The system controller (10) stores the data SD from the previous playback. and the current data SD, and control the head drive mechanism according to the result.

Next, when playing a sheet in which one still image consists of two tracks, an odd field track and an even field track, auto tracking is performed based on the average value of all sampling values of both tracks. Explain what you will do.

Considering sheet compatibility, etc., the odd and even track pitches will be different and the track width will have an error, so if you do not sample from both fields, the balance between the odd and even playback signal output will deteriorate. Therefore, the total force becomes smaller and the noise increases.

Now, as shown in FIG. 4, it is assumed that the track pitch, etc. during recording and reproduction can be set, and there are three specific examples of numerical values, ``■'', ``■,'' and ``■'' shown in the table of FIG.

If the odd field track is c)i-A and the even field track is CH-B, CH-A and C are shown in Figure 6.
The average output of both heads is shown when sampling HB. FIG. 7 shows the output difference of each head when CH-A%CH-B is sampled separately when the centers of 0H-A and CH-B are shifted. For example, in the case of ■, when both tracks are sampled, it can be seen from FIG. 6 that the center deviation due to sampling is ±2.5 μm. That is, from Fig. 7, the outputs of CH-A and CH-B are both 91% to 1.
00%.

Also, when sampling is performed only with CH-A, the center deviation due to the sampling number is 25 μm to 7.5 μm as shown in Figure 7.
tt m, and the output of CH-A is 100q6, but the output of CH-B is 81 to 91. It can be seen that in the video signal, it is better to have a small reciprocating output difference between CH-A and CH-B, and it is better to sample from both tracks.

Effects of the Invention Auto tracking can be performed with high precision. Particularly when reproducing a sheet in which one still image is recorded on two tracks, an odd field track and an even field track, it is possible to achieve a well-balanced reproduction output and to reduce noise.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the eccentricity of the recording track and the reproduction track, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a timing chart of Fig. 2, and Fig. 4 is a recording trunk. Figure 5 is a table showing examples of head width, track pitch, etc. during recording and reproduction, Figures 6 and 7 are sheets on which still images are recorded on two tracks. FIG. 3 is a characteristic diagram showing the relationship between track slippage and playback output when playing back. In addition, in the symbols used in the drawings, (1)・・・・・・・・・・・・ Recording track (
2)・・・・・・・・・・・・・・・Playback track (3
)・・・・・・・・・・・・・・・Play・＼rad(51
・・・－・・・・・・・・・・・・Spindle motor 00
)...................................................System control circuit 01)...................................Head drive circuit (17)...・・・・・・Sampling gate circuit (22・・・・・・・・・・・・
...This is a Zumblebold circuit. Agent Masaru Saturn〃 Yoshio Tsunekako〃 Shunkai Sugiura

Claims (1)

[Claims] The playback head plays back one or two circular tracks on which one field of video signals have been recorded multiple times to play back one still image, and each time the playback of one still image is completed, the above-mentioned The reproduction head is moved along the radius of the circular track by a predetermined distance in the outer circumferential direction or in the inner circumferential direction, and the reproduction level of an even number of sampling points is detected. The average value of the playback levels detected during playback is calculated, the magnitude relationship between this average value and the average value obtained during the previous playback is compared, and this ratio V! An auto-tracking device that determines a feeding direction of the reproducing head in the outer circumferential direction or the inner circumferential direction depending on the result.