JPH079210Y2 - Tracking servo device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tracking servo device in a recording disk reproducing device.

BACKGROUND ART In a recording disk reproducing apparatus, in order for an information detection point of a pickup to always accurately track a recording track of a disk, a tracking error signal is generated according to the deviation amount of the information detection point with respect to the center of the recording track. A tracking servo device that controls the position of the information detection point with respect to the recording track in the radial direction of the disk based on the tracking error signal is indispensable.

Conventionally, there is a device shown in FIG. 1 as this type of device. In the figure, a laser beam emitted from, for example, a laser diode 2 in a pickup 1 passes through a prism 3, a tracking mirror 4, an objective lens 5, and the like to become spot light (information detection point), which is a recording track (pit) of a disc 6. (Row) 7 is illuminated. The reflected light of the spot light passes through the objective lens 5, the tracking mirror 4, and the prism 3 and is incident on a so-called four-divided detector 8 including a photodiode or the like built in the pickup 1. The output of the detector 8 is amplified by the preamplifier 9 and supplied to the tracking error signal generation circuit 10.

A so-called 1-beam method is used as a method of generating the tracking error signal, and the 1-beam method includes a so-called push-pull method and a heterodyne method. Note that the so-called three-beam method can be used instead of the one-beam method. As shown in FIG. 2, the tracking error signal generated by the tracking error signal generation circuit 10 has a so-called S-curve characteristic of zero-crossing at the center of the recording track 7, and is usually positive or negative with respect to the zero-crossing point. It is adjusted by the preamplifier 9 or the tracking error signal generation circuit 10 so as to have a symmetrical waveform. This tracking error signal is supplied to the drive coil 12 that drives the tracking mirror 4 via the mirror drive circuit 11.
The mirror 4 is driven to rotate.

13 is a slider equipped with the pickup 1 (not shown)
The motor 13 is driven by a motor drive circuit 14. The motor drive circuit 14 detects the tilt angle of the tracking mirror 4 based on the output of the mirror drive circuit 11, and the slider motor is adjusted so that the tilt angle is zero, that is, the tracking mirror 4 is in the neutral position.
The position control of the pickup 1 in the radial direction of the disk is performed by 13.

In the conventional device thus configured, the adjustment is performed so that the signal waveform of the tracking error signal becomes positive / negative symmetrical with respect to the zero cross point, but the adjustment is only performed in the manufacturing stage. Therefore, the drift of the tracking error signal due to changes over time, changes in temperature, warpage of the disk, changes in the position of the actuator (tracking mirror 4 in this example), that is, errors with respect to the original values are not corrected. If a tracking error signal drifts due to the above, there are drawbacks such that the tracking servo pull-in, search, and jump operations become unstable.

SUMMARY OF THE INVENTION The present invention has been made to eliminate the above-mentioned drawbacks of the conventional ones, and enables stable servo operation regardless of changes with time, temperature changes, disk warpage, actuator position changes, etc. It is an object of the present invention to provide a flexible tracking servo device.

The tracking servo device according to the present invention detects the drift of the tracking error signal and corrects the tracking error signal to eliminate this drift, and according to the corrected tracking error signal, the disc radius between the recording track of the disc and the information detection point. It is configured to control the relative position in the direction.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 3 is a block diagram showing an embodiment of the present invention,
In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals.
In the figure, a tracking error signal correction circuit 15 is provided which detects a drift of the error signal based on the tracking error signal output from the tracking error signal generation circuit 10 and corrects the tracking error signal to eliminate this drift, The other configurations and operations are the same as those in FIG. 1, and the description thereof will be omitted.

FIG. 4 shows an example of a specific configuration of the tracking error signal correction circuit 15. In the figure, the tracking error signal output from the tracking error signal generation circuit 10 is supplied to the positive side average value detection circuit 16 and the negative side average value detection circuit 17. The positive-side average value detection circuit 16 and the negative-side average value detection circuit 17 are configured by, for example, a diode detection circuit and an integration circuit, and the positive-side deviation value and the negative-side deviation value with respect to the target level (zero level) of the tracking error signal. Each average value is detected. These average values are supplied to the differential amplifier 18, and the difference between the two average values is derived by the differential amplifier 18. This difference signal becomes a signal corresponding to the drift of the tracking error signal and is supplied to the peak hold circuit 19 in the next stage. The peak hold circuit 19 is supplied with a hold control signal from the system controller 20 when the tracking servo loop is opened due to tracking servo pull-in, search, jump, etc., and the peak hold circuit 19 responds to this by a differential amplifier. Holds the peak value of the output of 18, and outputs a correction signal according to this hold value. This correction signal is a tracking error signal generation circuit
Supplied to 10.

On the other hand, in the tracking error signal generation circuit 10, the photodetection outputs above and below the dividing line on the same side of the dividing line in the track direction in the 4-division detector 8 and orthogonal to the dividing line are added by adders 21 and 22, respectively. , The difference between the two addition outputs is derived by the differential amplifier 23, and the difference output is output as a tracking error signal via the output amplifier 24. The offset of the output amplifier 24 is output by the correction signal from the tracking error signal correction circuit 15. The tracking error signal is corrected by controlling the voltage.

Next, the operation of the device of the present invention will be described with reference to the waveform diagram of FIG.

In the initial state, the hold control signal is not generated from the system controller 20, and the output of the peak hold circuit 19 is set to zero. Now, when the pull-in of the focus servo is finished, the tracking error signal has a waveform asymmetrical with respect to the zero cross point on the positive side and the negative side for some reason, as shown by the solid line in FIG. 5 (A). And When the tracking servo signal is pulled in based on such a tracking error signal, the pulling-in may not be successful, or even if the pulling-in is performed, even a slight scratch on the disk may easily cause a track jump. .

Therefore, the tracking error signal correction circuit 15 is activated by the hold control signal generated from the system controller 20 when the tracking servo is pulled in. In this state, first, the average values of the positive side deviation value and the negative side deviation value with respect to the zero level of the tracking error signal are detected by the positive side and negative side average value detection circuits 16 and 17. These average value outputs are shown in FIGS. 5 (B) and 5 (C), respectively. Then, the difference signal (D) is obtained by differentially amplifying the respective average value outputs (B) and (C) by the differential amplifier 18. This difference signal (D) is peak-held by the peak-hold circuit 19,
It is supplied to the tracking error signal generation circuit 10 as a correction signal (E) having a polarity opposite to that of the difference signal. This correction signal (E) cancels the drift of the tracking error signal by changing the offset voltage of the output amplifier 24 of the tracking error signal generation circuit 10 and corrects the tracking error signal. Since this correction is performed in the closed loop, the tracking error signal always has a waveform symmetrical with respect to the zero cross point on the positive side and the negative side as shown by the broken line in FIG. 5 (A). In this state, if the output of the hold control signal from the system controller 20 is stopped and the tracking servo pull-in is started, a reliable pull-in operation is performed.

Also, not only during the tracking servo retract operation,
When the tracking servo loop is opened even during search or jump operation, the system controller
Since the hold control signal is generated from 20, and the same correction is performed at the time of the pull-in operation, the track count error and the jump error are eliminated, and the better condition can be maintained.

In the above embodiment, the correction signal from the tracking error signal correction circuit 15 is used as the tracking error signal generation circuit.
Although the feedback was made to the 10 output stages, the tracking error signal can be corrected by returning to any part before the output stage.

Effect of the Invention As described above, the tracking servo device according to the present invention is configured to detect the drift of the tracking error signal and correct the tracking error signal to eliminate this drift. It is possible to always perform stable servo operation, tracking servo pull-in operation, search, jump operation, etc., regardless of changes, warpage of the disk, or actuator position change.

[Brief description of drawings]

FIG. 1 is a block diagram showing a conventional example, FIG. 2 is a diagram showing the relationship between recording tracks and tracking error signals, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. 4 is FIG. FIG. 5 is a block diagram showing a specific configuration of the tracking error signal generation circuit and the tracking error signal correction circuit in FIG. 5, and FIG. 5 is a waveform diagram of each part for explaining the operation of the tracking error signal correction circuit in FIG. Description of main part code 1 …… Pickup 6 …… Recording disk 8 …… Quadrature detector 10 …… Tracking error signal generation circuit 15 …… Tracking error signal correction circuit

Claims (1)

[Scope of utility model registration request] 1. A tracking error signal generating means for detecting a deviation of an information detection point with respect to a center of a recording track of a recording disk and generating a tracking error signal according to the deviation amount, the recording disk according to the tracking error signal. A tracking servo device for controlling the relative position of the recording track and the information detection point in the radial direction of the disc, the predetermined value on the positive side and the predetermined value on the negative side with respect to the target level of the tracking error signal. The tracking servo device is provided with a tracking error signal correcting means for detecting the difference between the two and correcting the tracking error signal to eliminate this difference.