JPH081215U - Tracking servo device - Google Patents

Abstract

(57) Abstract: It is possible to always perform a stable servo operation regardless of changes over time, changes in temperature, warpage of a disk, changes in the position of an actuator, and the like. This tracking servo device includes a tracking servo loop including a tracking error signal generation circuit (10) for detecting a deviation of an information detection point with respect to a recording track center of a recording disk (6) and generating a tracking error signal according to the deviation amount. 1, 9, 10, 11, 14,
13), the relative position of the recording track of the recording disc and the information detection point in the disc radial direction is controlled according to the tracking error signal. The apparatus is further provided with a tracking error signal correction circuit 15 that corrects the tracking error signal when the tracking servo loop is closed based on the positive and negative values of the tracking error signal obtained when the tracking servo loop is opened. To be

Description

[Detailed description of the device]

[0001]

[Technical field to which the device belongs]

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

[0002]

[Prior art]

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

Conventionally, there is an apparatus of this type 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, and becomes spot light (information detection point), which is a recording track of a disc 6 ( It is irradiated on the (pit row) 7. The light reflected by 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.

As a method of generating the tracking error signal, a so-called 1-beam method is used, and the 1-beam method includes a so-called push-pull method, a heterodyne method, and the like. Note that not only the one-beam method but also a so-called three-beam method can be used. 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 to drive the mirror 4 to rotate.

A slider motor 13 drives a slider (not shown) mounted with the pickup 1, 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 causes the disk radius of the pickup 1 to move so that the tilt angle is zero, that is, the tracking mirror 4 is in the neutral position. Position control in the direction.

In the conventional device thus configured, 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 only performed in the manufacturing stage. It was Therefore, no correction is made for 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. However, if a drift occurs in the tracking error signal due to these, there are drawbacks such that the tracking servo pull-in, search, and jump operations become unstable.

[0007]

[Problems to be solved by the device]

 The present invention has been made to eliminate the above-mentioned drawbacks of the conventional ones, and a tracking servo that can always perform stable servo operation regardless of changes with time, temperature changes, disk warpage, actuator position changes, etc. The purpose is to provide a device.

[0008]

[Means for Solving the Problems]

 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 radius of the disk between the recording track of the disk and the information detection point. It is configured to control the relative position in the direction.

[0009]

[Embodiment of device]

 Hereinafter, embodiments 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 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 for detecting a drift of the error signal based on the tracking error signal output from the tracking error signal generation circuit 10 and correcting the tracking error signal to eliminate this drift is provided. 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 detect 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 during tracking servo pull-in, search, jump, etc., and the peak hold circuit 19 responds to this by a differential amplifier. The peak value of the output of 18 is held, and the correction signal according to this hold value is output. This correction signal is supplied to the tracking error signal generation circuit 10.

On the other hand, in the tracking error signal generation circuit 10, in the four-divided detector 8, 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 line are added by the adders 21, 22. Respectively, the difference between the two added outputs 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 tracking error signal is corrected by controlling the offset voltage of the output amplifier 24.

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. At the time when the pull-in of the focus servo is completed, the tracking error signal is 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). To do. When the tracking servo is pulled in based on such a tracking error signal, the pull-in may not be successful, or even if the pull-in is performed, even a slight scratch on the disk may easily cause a track jump. is there.

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 difference 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. 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. 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, a hold control signal is generated from the system controller 20, and the hold control signal is generated. Since the same correction is performed, track miscounts and jump misses can be 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. The error signal can be corrected.

[0016]

[Effect of device]

 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 in order to eliminate this drift. It is possible to always perform stable servo operation, tracking servo pull-in operation, search and jump operation, etc. regardless of the warp of the disk or the change of the actuator position.

[Brief description of 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 an 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 for main parts]

 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 (2)

[Scope of utility model registration request] 1. A tracking servo loop including 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 tracking error signal comprising: A tracking servo device 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 above, wherein the tracking error signal obtained when the tracking servo loop is opened is positive. 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 values on the negative side and the negative side. 2. The tracking error signal correction means is responsive to a difference between an average value of positive side deviation values and an average value of negative side deviation values of the tracking error signal obtained when the tracking servo loop is opened. 2. The tracking servo device according to claim 1, wherein the tracking error signal is corrected by changing an offset voltage of the tracking error signal generating means when the tracking servo loop is closed.