JPH0770061B2 - Optical disc playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention relates to an optical disc reproducing apparatus in which an optical pickup is moved to read information on a disc. When it reaches the mirror surface part of, it is detected and automatically returned to the information recording part.

[Industrial application field]

The present invention relates to an optical disc reproducing device for optically reading disc information.

[Conventional technology]

In an optical disc reproducing apparatus such as a CD (Compact Disc) player, if the optical pickup is sent to the mirror surface of the inner or outer circumference of the disc for some reason, the disc rotates at high speed or the pickup feed gear bites,
Alternatively, problems such as deviation from the disk surface occur. For example, if there is a scratch or the like on a track in the middle of a track jump operation for the first time, accurate time information cannot be obtained, and thus the track surface may gradually move to the mirror surface portion. Since no information is recorded on the mirror surface portion, it is impossible to recover by the usual method. Therefore, conventionally, (1) whether the boundary position between the information part and the mirror surface part is detected by a micro switch (position detection method) or not (2)
The contents of the disc are read to detect whether the data is normal or not (disc content judgment method).

[Problems to be solved by the invention]

However, the position detection method of (1) has the disadvantages that it requires cost and space for installing the switch, and that a dedicated port is required for the microcomputer to make the determination. Further, the method (2) for disc content determination has a drawback of making an erroneous determination when synchronization cannot be achieved due to an abnormality in the disc rotation system.

The present invention focuses on the fact that the mirror surface portion is flat (there is no unevenness like the information portion), and attempts to return the pickup to the information recording portion by a method without the above-mentioned drawbacks.

[Means for solving problems]

The present invention relates to an optical disc reproducing apparatus in which information on a disc surface is optically read along a track by a pickup (1), by detecting reflected light of information reading light from the disc surface, the pickup (1) A mirror detection circuit (8) that generates a mirror signal () that takes one of H and L levels while the track is on the track and takes the other level between tracks and on the mirror surface of the disk.
And a controller (7) for sending a return command to the servo control unit (6) to move the pickup (1) in the opposite direction when the mirror signal () takes the other level for a certain period of time or longer. And is provided.

[Action]

Regarding the mirror signal obtained by the mirror detection circuit 8, the reading position of the pickup 1 has opposite levels at the information recording portion (track) and the mirror surface portion of the disc. However, at the time of track jump, the same level as that of the mirror surface portion appears temporarily, so the controller 7 manages time in order to distinguish it from this. When it is determined that the pickup 1 has reached the mirror surface portion on the inner or outer circumference of the disc, the controller 7 issues a return command to the servo control portion 6 to promptly move the pickup 1 in the reverse direction (to the information recording portion side). ) Move it.

By doing so, it is possible to prevent high-speed rotation of the disc and damage to the pickup feed mechanism.

〔Example〕

1 to 3 are explanatory views showing an embodiment of the present invention, and FIG. 1 is a schematic block diagram of the entire optical disk reproducing apparatus. In the figure, 1 is an optical pickup whose relative position and focus are adjusted by an actuator by a actuator, 2 is a waveform shaping section for shaping the output of the optical pickup and converting it into individual pulses, and 3 is a signal for error correction of the pulse train. The processing unit 4 is a D / A conversion unit that converts a digital signal into an analog signal (audio output). Reference numeral 5 is an error detection circuit that detects a focus or tracking error from the output of the pickup 1 and outputs a signal that corrects it. 6 is a servo control unit that controls a track jump or a pickup feed mechanism. 9 is the servo control unit. The driver for driving the actuator of the pickup 1 in response to the output of the above, while monitoring the time information (included in the subcode) indicating which track position the pickup 1 is in the information from the signal processing unit 3, This is a controller (microcomputer) that gives a command such as a track jump to the servo control unit 6 at the time of cueing.

When the servo control unit 6 receives a track jump command, it interrupts the input signal from the error detection circuit 5 and outputs a movement signal to the driver 9. During this period, whether or not the track jump is normally performed can be determined by monitoring the output (mirror signal) of the mirror detection circuit 8 by the servo control unit 6 and the controller 7. The servo control unit 6 detects the mirror signal and drives the driver 9
Control so that the output to the output does not greatly disturb. (For example, hold error signal). In the present invention, the mirror signal is monitored by the controller 7 to detect the deviation of the pickup 1 from the disk mirror surface portion, and a command is given to the servo control portion 6 to return it to the information recording portion.

The mirror detection circuit 8 is configured, for example, as shown in FIG.
In the figure, 11 is a photoelectric conversion element in the pickup 1. The current flowing in this element is converted into a voltage by the current-voltage conversion amplifier 12, and the amplified output (RF signal) becomes the input of the mirror detection circuit 8. C is a coupling capacitor, and 81 is an inverting amplifier (mirror amplifier). The positive part of the output of the amplifier 81 is input to the peak hold circuit 82 through the diode D ₁ , and the negative part is input to the bottom hold circuit 83 through the diode D ₂ . The time constants of these hold circuits are set to values that can follow the traverse signal and the envelope fluctuation of the rotation cycle. When the difference signal between the peak hold output and the bottom hold output (this is the envelope signal reproduced by direct current) is obtained by the differential amplifier 84, this difference signal is compared with the reference voltage by a comparator 85 called a mirror comparator. A mirror signal is obtained. The reference voltage is the difference signal peak-held by a hold circuit 86 (called a mirror hold amplifier) having a large time constant.

FIG. 3 is a signal waveform diagram of each part, and shows a case where a track jump for cueing is performed during play and deviation to the mirror surface part occurs in the middle of the track jump. The mirror signal is always at the L (low) level when the pickup 1 is reading the information along the track having the information (during play). However, when the pickup 1 moves across the track, the mirror signal temporarily becomes H (high) level at the track jump portion. The controller 7 counts the number of track jumps from the change of the mirror signal during the track jump. In addition to this, in the present invention, the H level time length of the mirror signal is detected, and when it exceeds a certain value, it is determined that the mirror surface portion is deviated. At this time, the controller 7 issues a return command for moving the pickup 1 in the reverse direction to the error detection control section 5 instead of the track jump command. The fact that the pickup 1 has actually returned to the information recording section can be determined by the change in H and L of the mirror signal. Alternatively, it can be determined from the subcode. After this, a track jump command can be issued again or another operation (performance, etc.) can be performed.

The appearance of H and L level changes in the mirror signal is explained as follows. The RF signal or high-frequency component of the signal corresponds to the presence or absence of information (pits on a CD) on the disk surface, and therefore disappears on the mirror surface. Also, since the envelope of the RF signal changes according to the difference in the amount of reflected light between the track and the part that does not, it is constant during play, but changes greatly during track jumps. Therefore, if the reference voltage is set appropriately, a mirror signal which is always L during the play and changes to H and L during the track jump is obtained. Since this mirror signal has no high-frequency component on the mirror surface portion, it is always H. By using such a property, the deviation to the mirror surface portion can be easily detected (only by managing the time).

〔The invention's effect〕

As described above, according to the present invention, since the deviation of the pickup is detected by paying attention to the optical feature of the mirror surface portion, it is not necessary to add a hardware configuration such as the conventional position detection method, and the disc content determination method. There is no need to worry about wrong decisions such as.
In addition, since the mirror detection circuit is provided in the ordinary optical disc reproducing apparatus, it is possible to detect the deviation to the mirror surface portion only by controlling the time with the controller. This requires only minor changes to the controller program.

[Brief description of drawings]

 FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a detailed diagram of a mirror detection circuit, and FIG. 3 is a signal waveform diagram of each part of FIG.

Claims (1)

[Claims] 1. An optical disc reproducing apparatus in which a pickup (1) optically reads information on a disc surface along a track, by detecting reflected light of the information reading light from the disc surface (1). ) Takes a level of H or L while the track is on the track and takes the other level between tracks and on the mirror surface of the disk. A mirror detection circuit (8) for generating a mirror signal ().
And a controller (7) for sending a return command to the servo control unit (6) to move the pickup (1) in the opposite direction when the mirror signal () takes the other level for a certain period of time or longer. An optical disc reproducing apparatus comprising: