JPH0424782B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [A Field of Application] The present invention relates to a special playback device that can be applied to recently proposed optical disc players. In particular, the present invention relates to a special playback device that can be applied to optical disc players that have been proposed recently. The present invention relates to a special playback device that enables playback while playing.

[B. Prior Art] Recently proposed disk players employ an optical pickup. It also has a tracking function so that it can reliably follow the recording track. That is, since the center of the track recorded on the disk generally does not coincide with the center of rotation of the disk and is eccentric, tracking control is performed to move the objective lens constituting the pickup. Tracking control is performed, for example, as follows. A permanent magnet is attached to the support frame that supports the objective lens, and a tracking coil is provided on the base opposite to the permanent magnet, and a control current is passed through this coil.
Then, the objective lens is moved by the force acting on it based on Fleming's left-hand rule, and tracking control is performed (the force acts on the coil, but since the coil is fixed on the base side, the result is (The magnet side, that is, the objective lens moves).

Assume now that the eccentric state of the disk is as shown in FIG. That is, assume that the center of the disk with respect to the recording track is point X, while the center of rotation of the disk is point Y. Then, when playing point A on the disk, it is necessary to move the pick-up toward the outside of the disk, and when playing back point B on the disk, it is necessary to move the pick-up toward the inside of the disk.

In the eccentric state described above, consider shifting the pick-up readout point outward one track at a time (track jump). In this case, a track jump pulse (forward pop pulse) is applied to the tracking coil to shift the pick-up readout point outward by one track, but it just so happens that the timing at which this track jump pulse is applied is Even in a normal tracking control system, if the timing coincides with the application of a drive voltage to the tracking coil in a direction that shifts the pick-up readout point outward, the tracking coil will be driven by the sum of the two. Voltage will be applied. Therefore, the driving voltage changes greatly, causing a phenomenon in which the objective lens moves significantly and tracking becomes erroneous.

[Objective of the present invention] Even when track jump is performed to repeatedly play the same track or to jump the pick-up readout point outward one track at a time, it is desirable to prevent the tracking from shifting significantly. It is something to do.

[Configuration of the present invention] The present invention has a configuration in which the tracking state of the tracking means is detected, and a track jump pulse is generated at a timing that does not adversely affect subsequent tracking, thereby performing a track jump. be.

[E Example] In Fig. 2, D is a disk, 1 is a disk drive motor, 2 is an optical pickup, and an objective lens 2a is used for tracking to drive this objective lens in a direction perpendicular to the tracking direction. It includes a coil (tracking means) 2b. Reference numeral 3 denotes an amplifier, which amplifies the signal read out by the pickup 2. The pickup includes, for example, a plurality of optical sensors, and by appropriately processing the output signals of the optical sensors in the amplifier 3, a tracking error signal can be derived from the output side of the amplifier 3. These configurations are already well known.

The output signal of the amplifier 3 is applied to a tracking system servo amplifier 5 via a phase compensation circuit 4.
The output of this amplifier 5 is applied to a driver circuit 7 via an analog switch 6, and the output of this driver circuit 7 is applied to a tracking coil 2a, thereby performing tracking control.

If the disc is currently in a normal playback state, an AC voltage as shown in FIG. 3a is applied to the tracking coil 2b to perform tracking control in order to compensate for tracking deviation due to disk eccentricity. One period of the waveform in FIG. 3a corresponds to one rotation of the disk. A positive half cycle is a cycle in which tracking is performed by moving the pick-up readout point, which is normally located outside the track, inward, and a negative half cycle is the opposite.

Now, let's consider making the pickup readout point jump outward one track at a time. In the present invention, this tracking jump is not performed at an arbitrary timing, but when the pickup is in the tracking state at the time of switching from a state in which the pick-up readout point is shifted toward the outside of the disk to a state in which it is shifted toward the inside. It is something that is done.

When the output of the driver circuit 7 is applied to the input side of the comparator 8 via the capacitor C1, a waveform as shown in FIG. 3b is obtained from the output side. The rise of this waveform b indicates the point in time when the tracking state changes from a state in which the pickup readout point is shifted toward the outside of the disk to a state in which it is shifted toward the inside of the disk. That is, the comparator 8 serves as a tracking state detection circuit.

Therefore, at this point of switching, Fig. 3 e
A pulse e shown in is applied to the switch 9 to open the switch 9, and the analog switch 6 is opened. Then, the normal tracking control system is opened. At the same time, the switch 10 is closed by the pulse f shown in FIG. 3f, and a forward hop pulse corresponding to the pulse f is applied to the tracking coil 2b.

The tracking state in such a state can be known by the comparator 11. As mentioned above, the output of the amplifier 3 includes a tracking error signal (see Figure 2 C), and this tracking error signal becomes O level at the point where the pick-up readout point crosses the track (signal pit). . Therefore, if a tracking error signal is applied to the comparator 11 via the capacitor C2 in order to remove the offset voltage of the amplifier 3, a signal indicating that the pick-up readout point crosses the track is output from the output side of the comparator 11. (Fig. 3d) can be obtained. That is, the third
The falling edge of the pulse shown in FIG. d indicates that the read point has finished moving one track outside.
Therefore, in response to the fall of this pulse, the pulse shown in FIG. 3f, that is, the forward flip pulse, is caused to fall.

To quickly suppress tracking disturbances caused by tracking jumps, use a narrow pulse g (approximately
It is preferable to close the switch 12 at 200 μsec) and then apply a positive backhop pulse corresponding to the pulse g to the tracking coil 2b. Then, in response to the fall of this backhop pulse, pulse e falls, and switch 6
is closed again, and the normal tracking control system is resumed. In this state, the tracking error signal C is almost at O level and contains only a slight error component.

FIG. 4 shows a time chart when the same track is played repeatedly. In a digital audio disk, the signal is directed from the inside of the disk to the outside, so under normal tracking conditions the pick-up readout point moves toward the outside of the disk. Therefore, by detecting one rotation of the disk and performing an inward track jump, the same track can be repeatedly played. That is, the falling edge of the pulse shown in FIG. 4b indicates the point in time when the tracking state changes from a state in which the pick-up readout point is shifted toward the inside of the disk to a state in which it is shifted toward the outside of the disk. At this time, a positive backhop pulse corresponding to the pulse shown in FIG. 4g is applied to the tracking coil 2b. Then the fourth
A narrow negative forward hop pulse corresponding to the pulse in FIG. f is applied to the tracking coil 2b to complete the inward tracking jump.

Note that the pulses d, e, f, and g are preferably created using a microcomputer, for example.

[Effects] According to the present invention, since the track jump is performed in consideration of the tracking state, the tracking will not be greatly disturbed even after the track jump.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the eccentric state of a disc, Fig. 2 is a diagram showing a special playback device for an optical disc player according to the present invention, and Figs. 3 and 4 are time charts when performing a track jump. be. 2 is a pickup having an objective lens 2a and a tracking coil 2b; 8 is a comparator (tracking state detection circuit); and 10 and 12 are switches for generating tracking jump pulses.

Claims (1)

[Scope of Claims] 1. Tracking means for following a read point of a pick-up for reading information from a disk, and a tracking state detection circuit for detecting a tracking state in which a tracking control signal from the tracking means is near zero level. ,
A special playback device comprising a track jump pulse generation circuit for generating a track jump pulse for the tracking means in response to the output of the detection circuit. 2. When the tracking state detection circuit detects that the tracking state is at a switching point from a state in which the pick-up readout point is shifted toward the outside of the disk to a state in which it is shifted toward the inside of the disk,
2. The special playback device according to claim 1, wherein the track jump pulse generating circuit generates a track jump pulse in an outward direction in response to this detection output. 3. When the tracking state detection circuit detects that the tracking state is at a switching point from a state in which the pick-up readout point is shifted toward the inside of the disk to a state in which it is shifted toward the outside of the disk,
2. The special playback device according to claim 1, wherein the track jump pulse generating circuit generates a track jump pulse in an inward direction in response to this detection output.