JP3107189B2 - Offset correction method for tracking error signal in optical disk device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting an offset of a tracking error signal (hereinafter referred to as a "TE signal") in an optical disk apparatus.
The present invention relates to a correction method for removing an offset component generated in a TE signal in an optical disc device that performs tracking by detecting a signal and moving an objective lens.

[0002]

2. Description of the Related Art In an optical disk drive, it is necessary for a laser beam to accurately trace a track in order to read pit information on the disk. Conventionally, there are push-pull methods and track wobbling methods as tracking methods. The push-pull method is widely used because it can be constituted by a relatively simple optical system using a single beam.

In this push-pull method, reflected diffracted light obtained from a groove on a disk is received by a two-divided photodetector disposed at an optically symmetric position with respect to the center of a track, and the output difference of each light receiving unit is detected. Is detected as a TE signal. That is, in the region where the 0th-order and 1st-order diffracted light overlap, the intensity distribution of the beam spot changes due to the interference effect due to the deviation from the track, and the TE signal is detected by providing the photodetector in that region. You.

However, in the push-pull method, a DC offset component occurs in the TE signal from various causes, and
Even if the E signal indicates 0, the beam spot may be shifted from the center of the track. The main causes are deviation of the optical axis of the objective lens, inclination of the disk in the radial direction, imbalance of the groove shape of the disk, and the like.In particular, the objective lens is moved in a direction orthogonal to the optical axis. In the tracking method, the beam spot moves on the photodetector due to the movement of the objective lens, and it is inevitable that an offset occurs in the TE signal.

Therefore, conventionally, in an optical disk device employing the push-pull method, the offset of the TE signal is removed by a system configuration as shown in FIG. In the figure, 1 is an optical disk, 2 is a spindle motor for rotating the optical disk 1, and 3 is an optical pickup (P) equipped with an optical system including an objective lens and a photodetector.
U), 4 is an objective lens, 5 is a lens actuator for moving the objective lens 4, 6 is a lens position sensor for directly detecting the lens position, and 7 is light for differentially amplifying and outputting each output of the two-part light receiving unit. Detector, 8 is a linear motor that drives the entire PU3, 9 is a head amplifier that amplifies the output of the photodetector, 1
0 is a gain control (GC) amplifier capable of amplifying the output of the head amplifier 9 by changing the gain, and 11 is a TE amplifier.
A D / A converter for correcting the signal offset; 12 a microcomputer circuit for controlling the gain of the GC amplifier 10 and the output level of the D / A converter 11;
Is an adder that adds the output of the GC amplifier 10 and the output of the D / A converter 11, 14 is a sensor amplifier that amplifies the output of the lens position sensor 6, and 15 is the difference between the output of the adder 13 and the output of the sensor amplifier 14. A differential amplifier for amplifying the signal, 16 is a peak and bottom (P & B) hold circuit for holding the peak value and the bottom value of the output of the differential amplifier 15, and 17 is a tracking control signal based on the output signal of the differential amplifier 15. A servo circuit 18 to be created is a tracking drive circuit for driving the lens actuator 5 and the linear motor 8 based on a tracking control signal of the servo circuit 17. The microcomputer circuit
Numeral 12 converts an analog signal input into a digital signal by a built-in A / D converter and takes in the digital signal.

This optical disc apparatus employs a system in which an offset component included in a TE signal obtained from the photodetector 7 is canceled by an output from the lens position sensor 6, and the following is performed in the offset correction mode in advance. A simple automatic correction procedure is executed. First, when the correction mode is set, the servo circuit 17 is turned off, and the microcomputer circuit 12 puts the GC amplifier 10 in a constant gain state,
The output of the A converter 11 is set to 0. Here, the output of the GC amplifier 10 (the amplified output of the TE signal) is output by the differential amplifier 15.
And a difference signal between the output of the sensor amplifier 14 and the output of the sensor amplifier 14 (amplified output of the lens position sensor 6). The difference signal is held by the P & B hold circuit 16 and taken into the microcomputer circuit 12. Then, the microcomputer circuit 12 obtains the level of the received difference signal and its offset, and sets the G signal so that the offset of the TE signal (TE signal used by the servo circuit 17 for tracking control) obtained as the output of the differential amplifier 15 becomes zero.
The gain of the C amplifier 10 and the output signal level of the D / A converter 11 are adjusted.

[0007]

However, in the correction procedure using the above-described circuit, the offset is simply removed by electrical adjustment, and the optical relative position between the objective lens 4 and the photodetector 7 is determined. Since the adjustment is not performed, the positional relationship is actually shifted. Specifically, in FIG. 5, a solid line indicates a state in which the optical axis of the objective lens 4 is at an optically appropriate position with respect to the photodetector 7, and a dotted line indicates a state in which the optical axis of the objective lens 4 is greatly shifted. However, there are many cases where the latter state is caused by an error in assembling the objective lens or the like. In such a state, since the region where the 0th-order and 1st-order diffracted light overlap enters from one of the divided light receiving surfaces A of the photodetector 7 to the other light receiving surface B, the difference is obtained by electrical adjustment. Even if the offset of the TE signal output from the dynamic amplifier 15 is 0, a crosstalk component appears in the TE signal during an actual tracking operation, and accurate tracking control becomes impossible. In particular, when a guide groove (pre-groove) in which wobbling is formed is formed in advance on a disc and a TE signal and a modulated address signal (wobbling signal) are superimposed on each other, the above-described crossing is performed. The talk deteriorates the C / N ratio of the signal and makes it impossible to obtain an accurate address signal.

Therefore, the present invention corrects the deviation of the optical relative positional relationship between the objective lens and the photodetector 7 as shown in FIG. Offset can always be accurately canceled with the output of the lens position sensor,
It was created to provide an offset correction method for achieving error-free tracking control.

[0009]

According to a first aspect of the present invention, a tracking error signal is detected by a push-pull method, and an objective lens is moved by an actuator in a direction orthogonal to an optical axis by an actuator to perform tracking. Provided in the servo loop, a signal adding means for moving the objective lens with a signal obtained by adding an offset adjustment signal to a tracking control signal is provided at a stage preceding the tracking drive circuit that drives the actuator, and at the time of offset correction, The tracking servo loop is turned off in advance , and a signal of a constant level is output to the signal adding means, and a tracking error signal obtained from the photodetector is turned off between the objective lens and the photodetector.
Measured as an offset and set the measured offset to 0
Set and adjust the level of the offset adjustment signal to
And adjusts the set / adjusted offset adjustment signal to the
The signal is added to the signal adding means to move the objective lens and
Adjust the offset between the objective lens and the photodetector,
The present invention relates to a method of correcting an offset of a tracking error signal in an optical disk device, wherein during the operation of the optical disk device thereafter, the signal level adjusted and set is always output to the signal addition means to execute tracking control.

A second aspect of the present invention is an optical disc apparatus for detecting a tracking error signal by a push-pull method, and performing tracking by moving an objective lens by an actuator in a direction perpendicular to the optical axis. Amplifying the tracking error signal obtained from the photodetector, in a case where a method of canceling the offset included in the tracking error signal with the output of the lens position sensor that detects the amount of movement of the objective lens is adopted, A first amplifying means capable of variably setting the gain, and an offset adjustment signal provided to the tracking servo loop for adding the offset adjustment signal to the tracking control signal.
Activator to move the objective lens with the
Before the tracking drive circuit that drives the
A first adder provided, a second adder for adding an adjustment signal to an output signal of the lens position sensor, a first detector for detecting a signal added by the second adder, A second amplifying means capable of amplifying the signal after addition by the two adding means and variably setting its gain, and a difference obtained by subtracting an output signal of the second amplifying means from an output signal of the first amplifying means. And a second detecting means for detecting a signal. In the offset correction, the tracking servo loop is turned off, and a tracking error signal of a specified level is obtained with the gain of the second amplifying means set to 0. A first procedure for adjusting and setting the gain of the first amplifying means, and outputting a signal of a constant level to the first adding means in a state where the gain of the second amplifying means is set to 0, thereby controlling the objective lens. A second procedure for moving the objective lens, a third procedure for measuring the offset of the tracking error signal based on a signal obtained from the second detecting means by the movement of the objective lens in the second procedure, and a third procedure for measuring the offset. In order to set the offset to 0,
A fourth step of adjusting and setting the level of the offset adjustment signal
A fifth procedure for adjusting and setting the level of the addition signal to the second addition means so as to make the signal level detected by the first detection means zero, and setting the gain of the second amplification means to zero. In this state, a sixth procedure for outputting a signal at a level different from the fixed level to the first adding means to move the objective lens to another position, and the second detecting means has detected. a signal level consists of a seventh procedure for adjusting and setting the gain of said second amplifying means so as to zero, since optical de
The present invention relates to a method of correcting an offset of a tracking error signal in an optical disk device, wherein the tracking control is executed in a state after the adjustment and setting when the disk device is operated .

[0011]

[Action]

Regarding the first invention; in this invention, the tracking servo loop is set to the off state at the time of offset correction. In this state, the objective lens can be moved intentionally by outputting a signal of a certain level to the signal adding means, and the offset generated in the signal is measured based on the TE signal obtained from the photodetector. can do. This offset is caused by the fact that the objective lens does not converge the beam spot at the center of the photodetector as shown in FIG. 5 described above. An addition signal level can be obtained. That is, the measured offset of the TE signal is set to 0.
The objective lens 4 can be moved to an appropriate position by calculating an addition signal level to be output to the signal addition means. If the added signal level is always added to the signal detecting means even during the operation of the optical disk device, the objective lens can be moved with reference to the appropriate position, and accurate tracking control can always be performed. realizable. The present invention does not matter whether or not the pickup of the optical disk device has a lens position sensor.

Regarding the second invention, in this invention as well, at the time of offset correction, the tracking servo loop is set to the off state and the correction procedure is executed. However, the optical disk device of the present invention uses the output of the lens position sensor to output the offset of the TE signal. To cancel, the gain of the second amplifying means is set to 0. Then, after the TE signal is set to the specified level in advance in the first procedure, the same correction relating to the offset as in the first invention is executed in the second to fourth procedures, and as a result, the objective lens is connected to the photodetector. It is adjusted to an appropriate position.

However, in the second to fourth procedures, only the reference position of the objective lens is determined. In this optical disk device, the operation of canceling the offset by the output of the lens position sensor is performed as described above. If it moves to a position other than the position, an offset occurs in the TE signal. Further, the fourth procedure is executed irrespective of the output of the lens position sensor. In the fifth procedure, the addition signal level of the second addition means is adjusted so that the signal level detected by the first detection means becomes zero, and the output from the lens position sensor side becomes zero at the position of the objective lens. Set so that According to the fifth procedure, when the objective lens moves to a position other than the reference position, an output proportional to the amount of movement centering around 0 is obtained from the lens position sensor.

The fourth and fifth procedures are correction procedures in independent loops.
If there is a difference between the gains of the amplifying means, the offset included in the TE signal cannot be canceled by the output of the lens position sensor. Therefore, the offset is intentionally generated by changing the level of the addition signal of the first adding means again in the sixth procedure and moving the position of the objective lens to another position. Then, in the seventh procedure, the gain of the second amplifying means is adjusted and set so that the output signal of the second detecting means becomes zero. As a result, no offset occurs in the TE signal obtained as the output of the second detection means regardless of the position of the objective lens, and thereafter, accurate tracking control is performed using the output signal of the second detection means. Will be possible.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a description will be given of the "T
FIGS. 1 to 3 show an embodiment of the "method of correcting offset of E signal".
This will be described in detail with reference to FIG. First, FIG. 1 is a system configuration diagram of an optical disk device that executes the offset correction method of the present invention, and the components denoted by the same reference numerals as those of the optical disk device shown in FIG. Equivalent to.

The features of this optical disk device are as follows: (1) An adder 20 is provided between the servo circuit 17 and the tracking drive circuit 18, and the microcomputer circuit 12
Can input an adjustment signal via the D / A converter 21. (2) As shown in FIG.
(3) The lens for the differential amplifier 15 is that the output of the GC amplifier 10 is directly input to the differential amplifier 15 without using the method of adding the adjustment signal by providing the adder 13 on the input side of the TE signal. Adder 22 and GC in signal input circuit on position sensor 6 side
An amplifier 23 is provided, and the microcomputer circuit 12
Can input an adjustment signal via the D / A converter 24, the microcomputer circuit 12 can detect the output of the adder 22, and the microcomputer circuit 12 can adjust the gain of the GC amplifier 23. And (4) the microcomputer circuit 12 stores a program for automatically executing a procedure described later in the offset correction mode.

Next, the operation procedure of the optical disk device in the offset correction mode will be described with reference to the flowchart of FIG. In this correction procedure, the servo circuit 17 is always set to the off state. First, the gain of the GC amplifier 23 provided in the signal input circuit of the lens position sensor 6 is set to 0, and in this state, the microcomputer circuit 12 measures the level of the output signal of the differential amplifier 15 (S1). in this case,
Since the P & B hold circuit 16 holds the output of the GC amplifier 10 as it is, the microcomputer circuit 12 measures the amplified signal level of the TE signal output from the photodetector 7. Here, the microcomputer circuit 12 checks whether or not the signal level measured as described above is a specified value, and if the measured signal level is out of the specified value, obtains a correction amount thereof so that the measured signal level matches the specified value. Adjust and set the gain of GC amplifier 10
(S2-S4 → S1, S2).

When the above-mentioned adjustment and setting are completed, the microcomputer circuit 12 temporarily sets V0 shown in FIG. 3 to 0 as the output of the D / A converter 21 and keeps the servo circuit 17 in the off state. The objective lens 4 is moved via the A / A converter 21, and in this state, the TE signal held by the P & B hold circuit 16 from the photodetector 7 via the head amplifier 9, the GC amplifier 10, and the differential amplifier 15 is measured. Then, the offset value is saved in the internal RAM (S5, S6). Also, microcomputer circuit 1
2 sets the output of the D / A converter 21 to V1, measures the TE signal in the same manner as described above, and saves its offset value (S7, S8). Then, a correlation coefficient between the offset of the TE signal and the amount of movement of the objective lens 4 (output level with respect to the D / A converter 21) is calculated based on the two offset amounts obtained above, and the offset of the TE signal becomes 0. Is set in the D / A converter 21 as V2 shown in FIG.
~ S12). That is, the tracking drive circuit 18 is
The objective lens 4 is moved to the position corresponding to each signal level by operating the lens actuator 5 corresponding to each signal level obtained from the optical sensor, but the offset is focused on the photodetector 7 by the objective lens 4. Since the beam spot to be detected appears in proportion to the shift amount when the beam spot is shifted from the center of the photodetector 7, the above-described correlation coefficient is obtained, and the offset for the TE signal is set to 0 using the correlation coefficient. An output level for the D / A converter 21 can be obtained. As a result, the optical positional relationship between the objective lens 4 and the photodetector 7 is in an appropriate state as shown by the solid line in FIG.

Next, when the objective lens 4 is adjusted to an appropriate position by the above procedure, the microcomputer circuit 12 measures the output level of the adder 22 and outputs a correction value for setting the level to 0 to the D / A converter. Set to 24 (S13-S15). That is, the signal obtained from the lens position sensor 6 is adjusted to be 0 in a state where the objective lens 4 is at the proper position, and the objective lens 4 is adjusted.
Is shifted from that position, the signal input from the lens position sensor 6 to the GC amplifier 23 changes to a level centered on the 0 level and proportional to the amount of shift of the objective lens 4.

By the way, in the above adjustment procedure, the offset of the TE signal is set to 0 in a state where the objective lens 4 is at an appropriate position (a state where V2 is set in the D / A converter 21).
In this state, the output of the adder 22 provided in the signal circuit of the lens position sensor 6 is adjusted to be 0. In this optical disk device, however, the output is obtained from the photodetector 7 by the differential amplifier 15. A method is adopted in which the offset included in the TE signal is canceled by a signal obtained from the lens position sensor 6 side, and the servo circuit 17 uses the output signal of the differential amplifier 15 in actual tracking servo control. Therefore, even when the objective lens 4 is moved from the appropriate position to another position, it is necessary that the TE signal obtained as the output of the differential amplifier 15 does not include an offset.

Therefore, the microcomputer circuit 12 changes the output of the D / A converter 21 to V3 while keeping the gain of the GC amplifier 23 at 0.
(≠ V2), and the objective lens 4 is moved from the appropriate position to another position (S16). Due to the movement of the objective lens 4, an offset occurs in the TE signal obtained as the output of the differential amplifier 15.
Measures the offset (S17). Then, a gain correction amount is obtained by using a known correction coefficient related to the gain control of the GC amplifier 23, and the gain of the GC amplifier 23 is adjusted and set so that the TE signal offset becomes zero (S18 to S20). . As a result, the offset of the TE signal obtained from the photodetector 7 via the head amplifier 9 and the GC amplifier 10 is canceled by the output of the GC amplifier 23 (the amplified signal on the lens position sensor 6 side) by the differential amplifier 15. Is done.

Incidentally, the offset of the TE signal and the output of the lens position sensor 6 increase and decrease in proportion to the amount of deviation of the objective lens 4 from the proper position. Therefore,
Since the gain of the GC amplifier 23 is adjusted as described above, the differential amplifier 1 can be used regardless of the position of the objective lens 4.
The condition that the offset component is canceled from the TE signal obtained as the output of 5 is satisfied, and the TE signal used by the servo circuit 17 does not include the offset.

After completing the above procedure, the microcomputer exits the offset correction mode. Thereafter, in this optical disk device, the microcomputer circuit 12 adjusts the set values of the D / A converters 21 and 24 and the gains of the GC amplifiers 10 and 23. The tracking servo control at the time of the actual operation is performed while maintaining the above adjustment value.

[0024]

According to the present invention, "TE in optical disc apparatus"
The “signal offset correction method” has the following configuration, and thus has the following effects. According to the first aspect of the present invention, there is provided an optical disc apparatus that detects a TE signal by a push-pull method and performs tracking by moving an objective lens. In the related art, the optical axis of the objective lens is merely corrected by electrical adjustment. Although the optical position relationship between the optical detector and the photodetector could not be optimized, an appropriate optical position relationship was secured by the correction procedure of the present invention, and the TE signal was always detected based on the position relationship to obtain an accurate signal. T
It becomes possible to obtain the E signal and the address signal. That is,
When tracking control is performed on the basis of the optical positional relationship as indicated by the dotted line in FIG. 5, a crosstalk component occurs in the TE signal. Such a problem can be prevented by the present invention. Even when a TE signal and a modulated address signal superimposed on the TE signal are detected from the pregroove, an accurate TE signal and address signal can always be obtained, and tracking control without error can be realized. According to a second aspect of the present invention, a TE obtained from a photodetector is provided.
Applied when the method of canceling the offset included in the signal by the output of the lens position sensor that detects the moving amount of the objective lens is used, and the offset of the TE signal generated with the movement of the objective lens is used as the lens position sensor. , It is possible to accurately cancel the output, and the same effect as the invention of claim 1 is realized.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an optical disk device that executes a “method for correcting an offset of a TE signal in an optical disk device” of the present invention.

FIG. 2 is a flowchart illustrating an automatic correction procedure in an offset correction mode.

FIG. 3 is a diagram showing a relationship between an output of a D / A converter provided in a tracking servo loop shown in FIG. 1 and an offset of a TE signal.

FIG. 4 is a system configuration diagram of an optical disk device that executes a conventional offset correction procedure.

FIG. 5 is a diagram showing an optical positional relationship between an objective lens and a photodetector. However, the solid line indicates a state where the objective lens is at an appropriate position, and the dotted line indicates a state where the objective lens is at a shifted position.

[Explanation of symbols]

1 ... optical disk, 2 ... spindle motor, 3 ... optical pickup, 4 ... objective lens, 5 ... lens actuator, 6 ...
Lens position sensor, 7: photodetector (including differential amplifier circuit), 8: linear motor, 9: head amplifier, 10, 23: GC
Amplifiers (10: first amplifying means, 23: second amplifying means), 11, 21, 24
... D / A converters (21: first adding means, 24: second adding means), 12
... microcomputer circuits (first detecting means, second detecting means, first adding means, second adding means, first amplifying means, second amplifying means), 13, 2
0,22 ... adder (20: first adding means, 22: second adding means), 14
... Sensor amplifier, 15 ... Differential amplifier (second detection means), 16 ...
P & B hold circuit (second detection means), 17 ... servo circuit,
18… Tracking drive circuit.

Continued on the front page Judge Eiji Mitomo Judge Hiroaki Takase Judge Hiroshi Inukai (56) References JP-A-3-66031 (JP, A) JP-A-2-185723 (JP, A) JP-A-4- 61631 (JP, A)

Claims (2)

(57) [Claims] 1. An optical disk device that detects a tracking error signal by a push-pull method and performs tracking by moving an objective lens by an actuator in a direction perpendicular to an optical axis, and is provided in a tracking servo loop and includes a tracking control signal. On the other hand, a signal adding means for moving the objective lens with a signal obtained by adding the offset adjustment signal is provided at a stage preceding the tracking drive circuit for driving the actuator, and at the time of offset correction, the tracking servo loop is turned off in advance , and wherein the tracking error signal obtained from the photodetector to output a constant level of the signal to the signal summing means objective
Measured as the offset between the lens and the photodetector,
The offset to make the measured offset of 0
Set and adjust the level of the adjustment signal, and
Added to the signal adding means,
Moving the objective lens to detect the objective lens and the light;
A tracking error in the optical disc device, wherein the tracking control is executed by always adjusting the offset with respect to the optical disc device and outputting the adjusted / set signal level to the signal addition means during the subsequent operation of the optical disc device. Signal offset correction method. 2. An optical disc device for detecting a tracking error signal by a push-pull method and performing tracking by moving an objective lens by an actuator in a direction perpendicular to an optical axis, wherein the tracking error signal obtained from a photodetector is provided. In the case where a method of canceling the offset included in the above with the output of the lens position sensor that detects the moving amount of the objective lens is adopted, the tracking error signal obtained from the photodetector is amplified and the gain is variable. A first amplifying means that can be set, and a tracking drive circuit that is provided in a tracking servo loop and drives the actuator to move the objective lens with a signal obtained by adding an offset adjustment signal to a tracking control signal. A first adding means provided in the preceding stage; Second adding means for adding the adjustment signal to the output signal of the shift position sensor, first detecting means for detecting the signal added by the second adding means,
A second amplifying means capable of amplifying the signal after addition by the adding means and variably setting its gain, and a difference signal obtained by subtracting an output signal of the second amplifying means from an output signal of the first amplifying means. And a second detecting means for detecting the tracking error. When the offset is corrected, the tracking servo loop is turned off, and the tracking error signal of a specified level is obtained with the gain of the second amplifying means set to 0. (1) a first procedure for adjusting and setting the gain of the amplifying means, and a second procedure for outputting a signal of a constant level to the first adding means and moving the objective lens with the gain of the second amplifying means set to zero. A third procedure of measuring an offset of a tracking error signal based on a signal obtained from the second detection means by moving the objective lens in the second procedure; A fourth step of adjusting and setting the level of the offset adjustment signal for the first adding means so as to set the offset measured in the third step to zero, and setting the signal level detected by the first detecting means to zero. A fifth procedure for adjusting and setting the level of the addition signal to the second addition means, and providing a signal having a level different from the fixed level to the first addition means with the gain of the second amplification means being 0. And moving the objective lens to another position, and adjusting the gain of the second amplifying means to reduce the signal level detected by the second detecting means to zero.
A method for correcting an offset of a tracking error signal in an optical disk device, comprising a seventh procedure for setting, and performing a tracking control in a state after the adjustment and setting in the subsequent operation of the optical disk device.