JPH09180227A - Tracking servo device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always attain a stable servo operation irrespective of change with the elapse of time, change in temperature, warpage of a disk, or variation in actuator position, etc. SOLUTION: This device detects deviation of an information detection point to the recording track center of a recording disk 6, and has tracking servo loops 9, 10, 11, 14, and 13 including a tracking error signal generation circuit 10 to generate a tracking error signal in accordance with the deviated value, and controls, in accordance with the tracking error signal, a relative position of the information detection point to a recording track of a recording disk in the radial direction of the disk. This device is further provided with a tracking error signal correction circuit 15 to correct the tracking error signal when the tracking servo loops are closed, based on the tracking error signal obtained when the tracking servo loops are open, after the focus servo is pulled in.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking servo device in a recording disk reproducing device.

[0002]

2. Description of the Related Art In a recording disk reproducing apparatus, in order to always accurately track a recording track of a disk at an information detection point of a pickup, a tracking error signal is generated according to the deviation amount of the information detection point from the center of the recording track. However, a tracking servo device that controls the position of the information detection point with respect to the recording track in the disk radial direction based on this tracking error signal is indispensable.

As a conventional device of this type, there is one shown in FIG. 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 one-beam method is used as a method for generating a tracking error signal, and the one-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-shaped curve characteristic of zero-crossing at the center of the recording track 7, and is normally positive / negative symmetrical with respect to the zero-crossing point. The waveform is adjusted by the preamplifier 9 or the tracking error signal generation circuit 10. This tracking error signal is supplied to the drive coil 12 that drives the tracking mirror 4 via the mirror drive circuit 11, and drives the mirror 4 to rotate.

A slider motor 13 drives a slider (not shown) having the pickup 1 mounted thereon, and the motor 13 is driven and controlled 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 13 picks up the pickup 1 so that the tilt angle is zero, that is, the tracking mirror 4 is in the neutral position.
Position control in the disk radial direction.

In the conventional device thus constructed, the adjustment is performed so that the signal waveform of the tracking error signal is symmetrical with respect to the zero cross point, but the adjustment is performed only in the manufacturing stage. . Therefore,
No correction is performed on 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 value, and tracking is performed using these. When the error signal drifts, there are drawbacks such that the tracking servo pull-in, search, and jump operations become unstable.

[0007]

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional ones, and is always stable regardless of changes with time, temperature changes, disk warpage, actuator position changes, and the like. It is an object of the present invention to provide a tracking servo device capable of performing the above servo operation.

[0008]

A tracking servo apparatus according to the present invention comprises a tracking error signal generating means for detecting a deviation of an information detection point with respect to a recording track center of a recording disk and generating a tracking error signal according to the deviation amount. A tracking servo device having a tracking servo loop including, for controlling the relative position of the recording track of the recording disk and the information detection point in the disk radial direction according to the tracking error signal, after the focus servo pull-in. The tracking error signal correction means for correcting the tracking error signal when the tracking servo loop is closed based on the tracking error signal obtained when the tracking servo loop is opened.

The tracking error signal correction means is
The tracking error signal generating means when the tracking servo loop is closed according to the difference between the average value of the positive side deviation values and the average value of the negative side deviation values of the tracking error signal obtained when the tracking servo loop is opened. The tracking error signal can be corrected by changing the offset voltage.

The tracking servo system according to the present invention comprises:
The drift of the tracking error signal is detected, the tracking error signal is corrected to eliminate this drift, and the relative position of the recording track of the disc and the information detection point in the disc radial direction is controlled according to the corrected tracking error signal. It is a eggplant composition.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 3 is a block diagram showing an embodiment of the present invention, in which the same parts as 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 the drift. The other configurations and operations are the same as those in FIG. 1, and 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. Positive average value detection circuit 16
The negative-side average value detection circuit 17 is composed of, for example, a diode detection circuit and an integration circuit, and detects each average value of the positive-side deviation value and the negative-side deviation value with respect to the target level (zero level) of the tracking error signal. . These average values are supplied to the differential amplifier 18,
By this, the difference between the two average values is derived. 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. A hold control signal is supplied from the system controller 20 to the peak hold circuit 19 when the tracking servo is pulled in or when the tracking servo loop is opened due to a search or a jump. Hold the peak value of 18 outputs,
A correction signal corresponding to this hold value is output. This correction signal is supplied to the tracking error signal generation circuit 10.

On the other hand, the tracking error signal generation circuit 1
When 0, the photodetection outputs above and below the dividing line on the same side with respect to the dividing line in the track direction and orthogonal to the dividing direction in the 4-division detector 8 are added by the adders 21 and 22, respectively, and the difference between the two addition outputs is calculated. The differential output is derived by the differential amplifier 23, and the difference output is output as a tracking error signal via the output amplifier 24. By the correction signal from the tracking error signal correction circuit 15, the offset voltage of the output amplifier 24 is controlled. The tracking error signal is corrected.

Next, the operation of this embodiment will be described with reference to the waveform chart of FIG. In the initial state, no hold control signal is generated from the system controller 20,
The output of the peak hold circuit 19 is set to zero. Now, at the time when the pull-in of the focus servo is completed, the waveform of the tracking error signal is asymmetric with respect to the zero cross point on the positive side and the negative side for some reason, as indicated by the solid line in FIG. 5 (A). To do. When the tracking servo is pulled in based on such a tracking error signal, the pulling may not be successful, or even if the pulling 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. 5B and 5C, respectively. Then, the differential signal (D) is obtained by differentially amplifying the respective average value outputs (B) and (C) by the differential amplifier 18. The difference signal (D) is peak-held by the peak hold circuit 19 and 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. Because this correction is done in 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 indicated by the broken line in FIG. 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.

Further, not only during the pull-in operation of the tracking servo, but also during the search or jump operation, when the tracking servo loop is opened, the hold control signal is generated from the system controller 20, and the same as during the pull-in operation. Since the correction is performed, the track count error and jump error are eliminated, and a better condition can be maintained.

In the above embodiment, the correction signal from the tracking error signal correction circuit 15 is fed back to the output stage of the tracking error signal generation circuit 10. However, if it is fed back to any portion before the output stage, the tracking error is returned. The signal can be corrected.

[0018]

As described above, according to the tracking servo device of the present invention, the servo operation and tracking servo pull-in operation are always stable regardless of changes over time, temperature changes, disk warpage or actuator position changes. , Search and jump operation can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a conventional example.

FIG. 2 is a diagram showing a relationship between a recording track and a tracking error signal.

FIG. 3 is a block diagram showing one embodiment of the present invention.

FIG. 4 is a block diagram showing a specific configuration of a tracking error signal generation circuit and a tracking error signal correction circuit in FIG.

5 is a waveform chart of each part for explaining the operation of the tracking error signal correction circuit in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 pickup 6 recording disk 8 4-division detector 10 tracking error signal generation circuit 15 tracking error signal correction circuit

Claims (1)

[Claims] 1. A tracking servo loop including a tracking error signal generating means for detecting a deviation of an information detection point with respect to the center of a recording track of a recording disk and generating a tracking error signal according to the deviation amount, the tracking error signal comprising: A tracking servo device for controlling the relative position in the disc radial direction between the recording track of the recording disc and the information detection point according to the above, wherein the tracking servo device is obtained when the tracking servo loop is opened after the focus servo is retracted. A tracking servo device comprising a tracking error signal correction means for correcting the tracking error signal when the tracking servo loop is closed based on the tracking error signal.