JPH0352666B2 - - Google Patents

Description

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

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

Further, the recording medium expands and contracts depending on the environment such as temperature and humidity, and the position of the track also changes depending on the recording device. Therefore, the position of the playback head of the playback device and the position of the track will be 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. However, if the playback output level of the playback head is low, or if no signal is recorded on the track with the specified track number, the movement control may cause the playback head to move to an adjacent track. do. In this case, it becomes impossible to manage track numbers, and the displayed track number and the track number being played back will be different. Therefore, once this discrepancy occurs, unless the track number is written in the track, it becomes impossible to designate it as a playback track number from the outside.

<Objective> In view of the above problems, it is an object of the present invention to provide a reproducing apparatus that can accurately grasp track numbers by limiting the amount of movement by the movement control.

<Embodiment> Hereinafter, an example will be described in which a video signal is reproduced from a disk-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 the moving table, 7 and 8 are gears, 9 is a step motor, and 10 is a screw shaft 10' that rotates by the rotation of the step motor 9 and moves the moving table 5; This is a guide shaft that supports the stand 5.

In the configuration as described above, the magnetic sheet 1 is rotated by the rotation of the sheet motor 2, and the Hall element 4 is opposed to the magnet on the rotating body 3 once per rotation of the sheet 1, so that an output pulse is obtained. Further, head feeding is controlled by a step motor 9, and 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 controlling the feeding and tracking of the head 6 shown in FIG.

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 sending control circuit that forms a track sending signal from an external track movement signal IS; 14 is a preamplifier that amplifies the output of the magnetic head 6; and 15 is a signal that processes the output of the preamplifier 14 to form a television signal. Processing circuit, 16 is a monitor that displays from the television signal, 17 is an envelope detection circuit, 18 is a sample and hold circuit, 19 is a delay circuit that delays one rotation of the sheet, 20 is a comparator, and 21 is a comparator 2
A detection circuit that detects when the output i of 0 is inverted 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 times of inversion, 23 is an OR circuit, and 24 is a multiplexer. ,2
Reference numeral 5 designates up-down counters for detecting the absolute amount of movement from the absolute track of the head.

In FIGS. 2, 3, and 4, 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 b is a step motor drive pulse generated during tracking control, signal c is a step motor drive pulse generated when moving one track, and the number of pulses required for moving one track is 10 pulses in total. d is a signal indicating the direction of movement when moving one track. Reference character e is a tracking control start signal, which is a pulse signal that becomes "H" at the end of movement of one track, that is, after movement to the absolute track of the head. f is the output of the OR circuit 23 and represents a step motor drive pulse. g is sample hold circuit 1
8 sampling pulses are obtained by delaying pulse a. h indicates an envelope hold signal held by the sample hold circuit 18. i
is the output signal of the comparator 20, and when it is “H”, it is 1
The hold output h' before rotation is larger, and in the case of "L", the current hold output h is larger. Therefore, i also indicates the direction of movement of the head. j is a pulse signal generated when the inversion detection circuit 21 detects that the signal i is inverted from "L" to "H". k is a tracking enable signal that becomes "L" when the counter 22 detects the inverted pulse signal j three times in this embodiment and becomes "H" when the counter 20 is reset by the signal e, and l indicates " m is a signal indicating the moving direction of the head selected by the multiplexer 24, and n is a signal when the up-down counter 25 counts up, that is, the absolute amount of movement is one track feeding. This is a pulse signal that is generated when the number of pulses reaches 5, which is half of the number of pulses required.

First, normal operation will be explained.

A reproduced video signal from the magnetic head 6 is inputted to an envelope detection circuit 17 and a signal processing circuit 15 via a preamplifier 14. Signal processing circuit 15
converts the playback video signal to a television signal,
It is displayed on the monitor 16.

According to this embodiment, the magnetic head 6 realizes a reproduction means for reproducing an information signal from an information track on a recording medium as described in the claims of the present application, and the envelope detection circuit 17 realizes a reproduction means of the reproduction means. This realizes a detection means for detecting an output level.

When the track movement signal IS is input from the outside, the track feed control circuit 13 is activated and t ₀
Ten pulses c are applied to the step motor 9 via the OR circuit 23 at the timing . Further, a signal d indicating the direction of track movement is output to the multiplexer 23. At this time, multiplexer 2
4 selects the signal d based on the signal l. Therefore, the step motor 9 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. When 10 pulses c are output, a tracking control start pulse e is output at time _t1 , the counter 22 is reset, and the tracking enable signal k is set to "H". At the same time, the track feed enable signal l becomes "L", one track feed is prohibited, and the multiplexer 24
selects signal i.

According to this embodiment, as described above, the step motor drive pulse c and the direction signal d generated when moving one track are controlled by the track feed control circuit 13.
By driving the step motor 9 and moving the magnetic head 6 in units of tracks, the first moving means for moving the reproduction means in units of tracks in the claims of the present application is realized.

In this way, the tracking control operation is started at timing _t1 . The tracking control operation will be explained below.

The output of the envelope detection circuit 17 is sent to the sample hold circuit 18, which outputs the pulse g of the pulse shaping circuit 11.
The sample is held at the timing of . The hold output h is then input to the comparator 20 and the delay circuit 19. That is, comparator 20
compares the current hold signal output h and the hold signal output h' from one revolution before, and outputs a signal i. The signal i is "H" when the hold output from one revolution before is larger, and "L" when the hold output from one revolution before is smaller. In other words, when the level of hold signal h decreases, signal i goes high at the timing of signal g.
Thus, the rotation direction of the step motor 9 is reversed. When the level of the hold signal h increases, the step motor 9 is driven by the pulse b once per rotation of the seat. Then, at time _t3 , when the signal i rises from "L" to "H", the moving direction of the step motor 9 is reversed and at the same time a reversal detection pulse j is output. and t ₄ and 3
When the second inversion detection pulse j is output, the output k of the counter 22 becomes "L", the next step motor drive pulse b is output, and the tracking control ends. When the tracking control is completed, the signal 1 becomes "H" and one track feed is permitted.

That is, according to this embodiment, as described above, the step motor 9 is driven based on the step motor drive pulse b generated by the timing control circuit 12 during tracking control and the signal i representing the direction output from the comparator 20. By moving the magnetic head in microscopic units, the magnetic head, that is, the reproducing means, is moved in the direction in which the detection output of the detection means becomes higher, with the track position moved by the first moving means in the claims of the present application being the initial position. A second moving means for moving in minute units is realized.

Next, when moving the head from a non-recording track TA on which no video signal is recorded to a similar non-recording track TB, there is a discrepancy between the absolute track position of the head and the recording track, and the next track in the direction in which the head has shifted is An example in which a video signal is recorded on the TC will be explained with reference to the time chart in FIG.

Ten pulses C are output at time t ₀ ', and the head moves from track TA to track TB.

At this time, the level of hold signal h is almost 0.
level, but when the head is moved in the track TC direction, leakage from the track TC is detected.
The head begins moving towards the center of the track TC. Therefore, the up-down counter 25 counts the step motor drive pulses b from the start of the tracking control, and outputs the pulse signal n at the time t ₂ ' when the absolute number reaches 5. The signal n is input to a timing control circuit 12 and a track feed control circuit 13. The timing control circuit 12 sets the track feed enable signal l to "H", and the multiplexer 24 selects the direction signal d. Further, the one-track feed control circuit 13 sets the signal d to a level "H" which is the inversion of the output signal i of the comparator 20 at that time, and outputs five step motor drive pulses c.
Return the head to absolute track position.

Here, the up-down counter 25 counts the step motor drive pulses b output from the timing control circuit 12 during tracking control, thereby determining the amount of movement of the magnetic head 6 during tracking, that is, the amount of movement by the second moving means. This is for returning the amount to the initial position when the amount reaches a predetermined amount, and realizes the control means described in the claims of the present application.

With this configuration, it is possible to prevent the head from moving to an adjacent track and reproducing the video signal recorded on the adjacent track. Therefore, it is possible to reliably reproduce the track designated by the operator, and track numbers can be managed reliably. Furthermore, the head does not move significantly when the signal level is small.

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, it is applicable not only to disk-shaped media but also to playback from linear tracks of tape-shaped media, for example.

<Effects> As claimed in detail above, according to the present invention, it is possible to accurately manage track numbers, and it is also possible to prevent large movements of the head.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the playback device of this embodiment, Fig. 2 is a control circuit diagram of this embodiment, Fig. 3 is a diagram showing an example of a timing chart of each part in Fig. 2, and Fig. 4 is a timing chart. It is a figure which shows another example. In the figure, 1... disk-shaped magnetic sheet as a recording medium, 5... a moving table, 6... a magnetic head as a reproducing means, 9... a step motor as a moving means, 17... an envelope detection circuit, 18...
...Sample hold circuit, 20...Comparator, 21...Reversal detection circuit, 22...Counter,
25...indicates up/down counters, respectively.

Claims (1)

[Scope of Claims] 1. Reproducing means for reproducing an information signal from any one of a plurality of information tracks on a recording medium, a first reproducing means for moving the reproducing means in track units;
a moving means, a detecting means for detecting a playback output level of the playback means, and a track position moved by the first moving means as an initial position, and moving the playback means in a direction in which the detection output of the detection means becomes higher. A reproducing device comprising: a second moving means for moving the reproducing means in minute units; and a control means for returning the reproducing means to the initial position when the amount of movement of the reproducing means by the second moving means reaches a predetermined amount.