JPS6132277A - Reproducing device - Google Patents

Abstract

PURPOSE:To simplify constitution by providing a control means which shifts a reproducing means for reproducing an information signal in position and detects variation in output level due to the movement, and then moves the reproducing means in the opposite direction several times repeatedly when the output level drops and stops it. CONSTITUTION:When the level of a hold signal (h) falls, a signal (i) goes up to ''H'' at the timing of a signal (g) to invert the rotating direction of a stepping motor 9. When the hold signal (h) rises in level, on the other hand, the stepping motor 9 is driven once for every turn of a sheet as it is with a pulse (b); when the signal (i) rises from ''L'' to ''H'' at time t3, an inversion detection pulse (j) is outputted simultaneously with the inversion of the moving direction of the stepping motor 9. When the 3rd inversion detection pulse (j) is outputted at t4, the output (k) of a counter 22 goes down to ''L'' and a next stepping motor drive pulse (b) is outputted to complete the tracking control. Thus, the tracking control is carried out with the simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a reproducing device that reproduces an information signal from an information track on a recording medium, and more particularly to a reproducing device that can accurately trace an information track.

<Prior art> For example, when reproducing a video signal from a recording medium in which a number of concentric information tracks are formed, the closer the adjacent information tracks are and the higher the recording density and the higher the discrepancy, the more precise the tracking control of the reproducing head must be. is required.

Also, recording media expands and contracts depending on the environment such as temperature and humidity.
Furthermore, the track position changes depending on the recording device. Therefore, the playback head position of the playback device and the track position are misaligned.

In order to prevent this, it has been proposed in the past to control the movement of the playback head using the playback output of the playback head.

An example of this is a method in which the reproducing head is slightly vibrated and a match between the vibration frequency and the fluctuation frequency of the reproduced output is detected, but this method requires an extremely complicated configuration.

<Objective> In view of the above-mentioned drawbacks of the prior art, it is an object of the present invention to provide a reproducing apparatus that is capable of reliably tracing information tracks with an extremely simple configuration.

<Embodiment> Hereinafter, an example will be described in which a video signal is reproduced from a disc-shaped magnetic sheet in which one frame or one field of still image video signals is recorded on each concentric video track.

FIG. 1 is a sectional view of the reproducing apparatus of this embodiment. In the figure, 1 is a disc-shaped magnetic sheet as a recording medium, 2 is a sheet motor that rotates the magnetic sheet 1, and 3 is a rotating body attached to the shaft of the sheet motor 2, with a permanent magnet attached to a part of its outer periphery. . 4 is a Hall element that detects the rotation of the seat motor 2 and outputs an output once per rotation. 5 is a moving table;
6 is a magnetic head attached to a moving table, 7.8 is a gear,
9 is a step motor; 10 is a screw shaft that rotates multiple times according to the rotation of the step motor 9 to move the moving table 5;
' is a guide shaft that supports the movable table 5.

In the above configuration, due to the rotation of the seat motor 2,
The magnetic sheet 1 rotates, and during one rotation of the sheet 1, some of the Hall elements 4 face the magnets on the rotating body 3, and output pulses are obtained. Further, the head movement is controlled by a step motor 9. In this embodiment, by applying ten pulses to the step motor 9, the magnetic head 6 is moved by one track.

FIG. 2 is an example of a control circuit diagram for performing feeding control and dragging control of the head 6 shown in FIG. 1.

In the figure, 11 is a pulse shaping circuit that shapes the output of the Hall element 4, 12 is a timing control circuit, 13 is a track feed control circuit that forms a track feed signal from an external track movement signal S, and 14 is a magnetic head 6. 15 is a signal processing circuit that processes the output of the preamplifier 14 to form a television signal;
16 is a monitor that displays from a television signal;
17 is an envelope detection circuit, 18 is a sample hold circuit, 19 is a tiller circuit that delays by one rotation of the sheet, 2
0 is a comparator, 21 is a comparator 20 whose output 1 is from a low level (hereinafter referred to as "L") to a high level (hereinafter referred to as "H").
), 22 is a counter that counts the number of inversions, 23 is an OR circuit, and 24 is a multiplexer.

In FIG. 2.3, the signal a is a pulse signal obtained by pulse shaping the output of the Hall element 4 and is input to the timing control circuit 12. Signal S is a step motor drive pulse generated during tracking control, C is a step motor drive pulse generated when moving one track, and the number of pulses required to move one track is 10 pulses. d is a signal indicating the direction of movement when moving one track. When the movement of one track is completed by the θ tracking control start signal, that is, after the head has moved to the absolute track, “H” is generated.
” is the pulse signal. f is the output of the OR circuit 23 and indicates a step motor drive pulse. f is a sampling pulse of the sample and hold circuit 18, which is obtained by delaying the pulse atl. h indicates an envelope hold signal held by the sample hold circuit 18. 1 is the output signal of the comparator 20, and in the case of rHJO, the hold output h' from one revolution before is larger; in the case of rLJ, the inversion detection circuit 21 detects the current hold inversion, and it is a pulse signal generated at 9 o'clock. . k becomes rLJ when the counter 22 detects the inverted pulse signal j three times in this embodiment, and the signal θ
The tracking enable signal becomes "H" when the counter 20 is reset, and l becomes "H" when the tracking control is completed.
m is a signal indicating the moving direction of the head selected by the multiplexer 24.

The operation will be explained below.

The reproduced video signal from the magnetic head 6 is passed through a preamplifier 14 to an envelope detection circuit 17 and a signal processing circuit 15.
is input. The signal processing circuit 15 converts the reproduced video signal into a television signal and displays it on the monitor 16.

Here, when the track movement signal S from the outside is input, the track feed control circuit 15 is activated, and the pulse C is sent to the step motor 9 via the OR circuit 23 at the timing to.
is applied for 10 pulses.

Further, a signal d instructing the direction of track movement is output to the multiplayer 2B. At this time, the multiplexer 24 selects the signal d over the signal l. Therefore, the step motor is driven by 10 pulses in the direction indicated by the signal d, and the head moves by one track and is positioned on the absolute track.

Then, when 10 pulses C are output, a tracking control start pulse e is output at time t1, and the counter 2
2 and set the tracking enable signal k to rHJ. At the same time, the track transfer enable signal l becomes rLJ, one track transfer is prohibited, and the multiplexer 24 selects signal 1. Thus, the tracking control operation is started at the timing of tl. The tracking control operation will be explained below.

The output of the envelope detection circuit 17 is sampled and held in a sample and hold circuit 18 at the timing of the pulse t of the pulse shaping circuit 11.

The hold output is then input to the comparator 20 and the delay circuit 19. That is, the comparator 20 separates the current hold signal and the hold signal output h' from one rotation ago.
and outputs signal i. When the hold output one revolution before the signal is thicker, it is rHj, and when the hold output one revolution before the signal is smaller, it is rLJ. As a result, when the level of the hold signal decreases, the signal i changes to 1H at the timing of the signal V, and the direction of rotation of the step motor 9 is reversed. Then, when the level of the hold signal rises, the step motor 9 is directly activated by pulse b.
is driven once every 1-1 revolutions of the sea. and time t5
When the signal 1 rises from rLJ to "H", the moving direction of the step motor 9 is reversed and at the same time a reversal detection pulse j is output. Then, when the third inversion detection pulse j is output at t4, the output k of the counter 22 becomes rLJ.
The next step motor drive pulse b is output and tracking control ends. When the tracking control is completed, the signal 1 becomes rHJ and one track transmission is permitted.

Here, the comparator 20 is configured to invert the signal if it is not possible to determine the magnitude. Therefore, 3
During the reversal operation, the head always stops at the absolute track position.

Also, since tracking control is configured to end after multiple times, if the envelope output of the first position, that is, the absolute track, is at the highest level, it is configured so that playback will always return to the absolute track position and continue playback. has been done.

Therefore, if the number of inversions is two or more, the head normally stops at the maximum position of the envelope. In addition, if the number of inversions is set to an odd number of 3 or more times, even if there is no #1 difference in the envelope or there is no envelope level, the absolute track position, that is, the position moved by the track feed The head will stop at this point. Therefore, even in such cases, the head does not deviate significantly from the track position, and stable reproduction operation is possible.

In this embodiment, reproduction from a disk-shaped magnetic sheet has been explained as an example, but the present invention is applicable not only to magnetic sheets but also to optical disks and the like. Furthermore, the present invention is applicable not only to disk-shaped media but also to playback from linear tracks of tape-shaped media, for example.

As shown above, in order to find the maximum value of the envelope signal, send it to the absolute track and check it, then send one step. In order to detect the level difference of the envelope, send one step. When the envelope level is low compared to the absolute track, as shown in h, it is necessary to invert it and then invert it at least twice to find the peak of the envelope. That is, tracking can be performed reliably if there are at least two or more inversions.

Furthermore, when the envelope is minute or the t-round level does not change, the direction detection circuit output is
If you send a pulse, it will definitely come back on track every odd number of times. Therefore, by setting the count value j of the counter 22 to an odd number of 3 or more times, the envelope becomes minute (
You can reliably track everything from when there is no data to when the data is large.

<Effects> As explained in detail above, according to the present invention, reliable tracking control is possible with an extremely simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the reproducing apparatus of this embodiment, FIG. 2 is a control circuit diagram of this embodiment, and FIG. 3 is a timing diagram of each part of FIG. 2. In the figure, 1...disk-shaped magnetic sheet 5 as a recording medium...a moving table 6, a skewer, a magnetic head 9 as a reproducing means, a step motor 17 as a moving means, a fist envelope detection circuit 18, ...Sample hold circuit 2o0.・Comparator 21 . . . Inversion detection circuit 22 . . . Counters are shown respectively.

Claims (1)

[Claims] Reproducing means for reproducing an information signal from an information track on a recording medium, moving means for moving the position of the reproducing means, detecting means for detecting a change in the output level of the reproducing means as the reproducing means moves, and the reproducing means. If the output level decreases due to the movement of the playback device, the playback device may be moved to the opposite side, and control means may be configured to stop the movement of the moving device after repeating the movement to the opposite side a plurality of times. A playback device.