JPS6226232B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recorded information reproducing device, which prevents errors on the time axis (hereinafter referred to as jitter) even when previously recorded information is not read for some reason when reproducing an information recording disk (hereinafter referred to as a disk). It is an object of the present invention to provide a recorded information reproducing device that can satisfactorily obtain a signal for correcting and/or a tracking control signal.

In general, when an information signal such as a video signal is recorded on a spiral or concentric information track on a disk, this recorded information signal is reproduced.
The disk and the reproduction scanner are moved relative to each other at a predetermined speed relationship, and the previously recorded information signal is picked up and reproduced by the reproduction scanner. Here, if there is a change (jitter) in the predetermined velocity relationship of the relative motion between the disk and the reproduction scanner, the information will not be reproduced correctly. Therefore, it is necessary to variably control the speed of the relative movement. In addition, even when the reproduction scanner is in a mistracking state in which it does not scan the track it should be scanning on the disk due to disk eccentricity, surface wobbling, or track meandering, or when there is a focus error, the recorded information is accurate. It is necessary to correct this because it is not played back. Also, when reproducing a flat disk without a needle guide groove, the reproducing scanner must be tracked.

However, conventionally, a signal for correcting the above-mentioned jitter (hereinafter referred to as jitter signal), a signal for correcting mistracking (hereinafter referred to as tracking signal), or a signal for correcting focus error was obtained from the disk playback signal. If part of the playback signal is dropped (hereinafter referred to as dropout) due to dust on the track or track damage during playback, it becomes impossible to obtain a jitter signal, tracking signal, or focus error correction signal, and the jitter or The drawback was that it became impossible to correct focus errors and perform normal tracking. Also, even if the dropout disappears and the playback signal starts playing again,
The drawback was that it was not possible to immediately return to the normal state due to the respective time constants.

The present invention eliminates the above-mentioned drawbacks, and embodiments thereof will be described below with reference to the drawings.

FIG. 1 shows a block system diagram of a first embodiment of the apparatus of the present invention. Tracking signal, focus error correction signal, or jitter signal (hereinafter abbreviated as tracking signal, etc.) obtained by a well-known method
is applied from input terminal 1 to terminal 2a of switch 2 and terminal 3a of switch 3, respectively. On the other hand, the disc playback signal input to the input terminal 4 is supplied to the dropout detection circuit 5, where its level is detected. The dropout detection circuit 5 closes the terminals 2a and 2c of the switch 2 and the terminals 3a and 3c of the switch 3 when the reproduced signal level is above a predetermined level, and closes the terminals 2b and 2c when the level is below the predetermined level. 2c, terminal 3
A switching signal is supplied to the switches 2 and 3, respectively, to close and connect the switches 2 and 3c.

Therefore, during normal playback, tracking signals etc. from the input terminal 1 are sent to the storage circuit 6 via the switch 2.
The signal is also supplied to the output terminal 8 via the switch 3 to perform jitter correction and tracking control. The storage circuit 6 is composed of, for example, a CCD (charge coupled device) or a BBD (bucket brigade device), and the signal accumulated charge is transferred by the output clock pulse of the clock pulse generator 7, and the disk is Tracking signals and the like during one rotation are stored. In this case, by generating the output clock pulse of the clock pulse generator 7 in synchronization with the rotation of the turntable, it is possible to more accurately store the tracking signal and the like during one rotation period of the disk in the storage circuit 6.

If a dropout occurs, the playback signal level will be zero or extremely low, so the output of the dropout detection circuit 5 that detects this will control the switching of switches 2 and 3, respectively.
The terminals b and 2c are connected, and the terminals 3b and 3c are connected. As a result, the tracking signal from the previous rotation stored in the memory circuit 6 is outputted from the memory circuit 6 via the switch 3 to the output terminal 8, and this output sets the relative speed of the disk and the reproduction scanner to a predetermined speed. , or control the reproduction scanner to track normally. Since the output signal of the memory circuit 6 is also fed back to its input side via the switch 2,
Normal tracking and other operations can be performed continuously even when there is no signal so that the track can be continuously tracked and reproduced.

Furthermore, tracking when there is no signal with a dropout uses the tracking signal from one revolution before, but the information to be reproduced is not changed, so still images of the same track with the same information content can be continuously reproduced. .

Note that the number of memory elements of the memory circuit 6 is the same as that of the disk 1.
When storing rotational tracking signals etc. in analog quantities, about 20 are sufficient. In addition,
Instead of the first embodiment shown in FIG. 1, it may be constructed as shown in FIG. 2, in which case the switch 3 can be omitted.

FIG. 3 is a block system diagram of a second embodiment of the device of the present invention, FIG. 4 is a front view of an example of the essential parts of a disc playback device to which the second embodiment can be applied, and FIG. 5 is a main part of FIG. FIG. In each figure, the same parts are given the same reference numerals. Tracking signals etc. obtained by a well-known method are sent to the hold circuit 1 from the input terminal 9.
0. On the other hand, the reproduced signal is input to the input terminal 11.
The signal is supplied to the dropout detection circuit 12 from the dropout detection circuit 12.
The hold circuit 10 only passes the input signal during normal playback, and is configured to hold the input voltage just before the dropout occurs using the output pulse of the dropout detection circuit 12 only when a dropout occurs, and output this hold voltage. ing.

Therefore, during normal playback, the tracking signal etc. passes through the hold circuit 10, passes through the normally closed terminal 13a and the common terminal 13c of the switch 13, and is output from the output terminal 14 to perform tracking etc. After the output tracking signal 10 is converted into a signal form suitable for magnetic recording by the write circuit 15, it is sent to the normally closed terminal 16 of the switch 16.
a, and are applied to the head 17 via the common terminal 16c, respectively. Tracking signals and the like are generated by this head 17 on magnetic records that have been previously erased by the erase head 20 to which an erase bias signal from an erase bias signal generation circuit 18 is applied through the normally closed terminal 19a and the common terminal 19c of the switch 19, respectively. Magnetic recording is performed on a medium (indicated by 24 in FIGS. 4 and 5).

For example, as shown at 24 in FIG. 4, the magnetic recording medium forms a concentric circle with the turntable 25 and is disposed below it, and its center position is fixed to a rotating shaft 26 together with the turntable 25, and a motor (not shown) It is formed on the circumferential edge of a disk that is rotated by obtaining power from the disk. A disk 27 is placed on the turntable 25, and recorded information is picked up and reproduced by a reproduction scanner 28. The head 17 and the erasing head 20 are located at the same height, and as shown in FIG. 5, the magnetic recording medium 24 rotates clockwise.
The portion erased by erase head 20 is transferred to head 1.
They are spaced apart so that they can be recorded at 7.

By the way, when a dropout occurs in the above embodiment, a dropout detection signal is sent from the dropout detection circuit 12 to the hold circuit 10,
The signals are output to the switch 19 and the delay circuit 22, respectively. As a result, the hold circuit 10 holds the voltage of the input tracking signal, etc. immediately before the dropout occurs, and outputs it. Also switch 1
9 is connected between its terminals 19b and 19c to immediately cut off the supply of the erase bias signal to the erase head 20.

Further, the delay time of the delay circuit 22 is selected so as to delay the input signal during the rotation of the magnetic recording medium 24 from the erase head 20 to the head 17. Therefore, the output signal of the delay circuit 22 is delayed from the switching of the switch 19.
3 and 16, respectively, to terminals 13b and 13.
c, a switching connection is made between terminals 16b and 16c. As a result, the already recorded tracking signal of the magnetic recording medium 24 is reproduced by the head 17 and supplied to the readout circuit 23 via the switch 16, where it is demodulated and then sent via the switch 13 to the output terminal 1.
4 is output as a tracking signal or the like.

In this way, when a dropout occurs, the erase head 20 is immediately inactivated, and the hold output of the hold circuit 10 is used as the hold output of the hold circuit 10 for the time period during which the magnetic recording medium 24 rotates from the erase head 20 to the magnetic head 17. After the elapse of time, the head 17 operates as a reproducing head and reproduced recorded tracking signals are outputted from the output terminal 14, so that even if a dropout occurs, tracking and other operations can be performed normally. It is preferable that the above-mentioned time be as short as possible, but there is no problem as long as it is less than the time (approximately 1/20 of one rotation of the disk) that allows sufficient tracking etc. even with the signal held by the hold circuit 10.

If the dropout disappears and the state returns to normal, the delay circuit 22 causes the erase head 20 to operate first and then the head 17 to operate, so there is no problem even if normal playback is resumed. Also, at this time, the hold circuit 10
Since the hold output is immediately provided as a tracking signal, etc., operations such as tracking can be performed immediately upon return to normality.

In the above embodiment, the reproducing scanner may be a non-contact element (for example, a lens) with respect to the disk 27, and the disk 27 may be cylindrical.

As described above, the recorded information reproducing apparatus according to the present invention supplies at least a signal for the reproduction scanner to track the information track among the signals read from the rotating recording medium in which the information signal is recorded on the information track. a storage circuit that stores a tracking signal for one rotation period;
A signal loss detection circuit is supplied with a reproduced signal and detects a signal loss period, and a signal from the input terminal and the output signal of the storage circuit is supplied, and normally detects an information track among the read signals. During the period when the reproduction scanner outputs a tracking signal and the output signal of the detection circuit is supplied,
Since it is composed of a signal switching circuit that switches and outputs the output signal of the storage circuit, the output signal of the storage circuit is a tracking signal from one revolution ago with a similar tendency in fluctuation components, so there is a dropout in the reproduced signal, which is normal. Tracking can be performed almost normally even when no signal is being read out, and tracking can be performed normally immediately after the normal state is restored.Furthermore, when there is a dropout and no signal, tracking can be performed using the tracking signal from one revolution before. Since the information to be used but reproduced is not changed, it has the advantage that still images of the same track with the same information content can be continuously reproduced.

[Brief explanation of the drawing]

1 and 2 are block system diagrams of a first embodiment and a modification thereof of the apparatus of the present invention, FIG. 3 is a block system diagram of a second embodiment of the apparatus of the present invention, and FIG. 4 is a block system diagram of the second embodiment of the apparatus of the present invention. FIG. 5 is a front view of an example of a main part of a disc playback device to which the embodiment can be applied, and FIG. 5 is a top view of the main part of FIG. 1, 9...Tracking signal etc. input terminal, 4, 1
DESCRIPTION OF SYMBOLS 1... Reproduction signal input terminal, 5, 12... Dropout detection circuit, 6... Memory circuit, 8, 14... Tracking signal etc. output terminal, 17... Recording or reproduction head, 18... Erasing bias signal generation circuit, 20... Erasing head, 22...Delay circuit, 24...Magnetic recording medium.

Claims (1)

[Claims] 1. An input terminal to which at least a signal is supplied for the reproduction scanner to track the information track among the signals read out from the rotating recording medium on which the information signal is recorded on the information track, and a tracking signal for one rotation period. a memory circuit that stores
A signal loss detection circuit is supplied with a reproduced signal and detects a signal loss period, and a signal from the input terminal and the output signal of the storage circuit is supplied, and normally detects an information track among the read signals. During the period when the reproduction scanner outputs a tracking signal and the output signal of the detection circuit is supplied,
It is characterized by comprising a signal switching circuit that switches and outputs the output signal of the storage circuit, and performs a tracking servo so that a track where a signal dropout occurs is continuously tracked and reproduced. Recorded information reproducing device.