JPH11353668A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and speedingly conduct a focus balance adjustment when recording or reproducing information on a disk by a signal converting means. SOLUTION: A comparison is made between the previous adjustment result of a memory 22, in which the output signals of a balance deviation amount detector 19 are recored, and the present adjustment result. Based on the comparison, the converging gain value which is multiplied by a focus balance deviation compensation command of the detector 19 by a converging gain multiplier 20, is compensated by a converging gain compensator 23. Thus, a focus balance compensation is always conducted with an optimum value even though the characteristic of a balance control amplifier 12 is varied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus for recording or reproducing information on a recording medium such as a disk-shaped recording medium having a track on which information is recorded or a track for recording by a signal converting means. The present invention relates to an optical disk device.

[0002]

2. Description of the Related Art A CD-ROM device is a preferred recording / reproducing device to which the present invention is applicable. The CD-ROM device is obtained by converting an audio CD device to an external data storage device such as a personal computer. The adjustment of the balance of the optical servo system in the conventional CD-ROM device will be described with reference to FIG.

FIG. 4 is a configuration diagram of a CD-ROM device.
In FIG. 4, 1 is a disc, 2 is a condenser lens, 3 is a laser, 4 is a focus actuator, 5 is a beam splitter, 6 is a polarizing lens, 7 is a 4-split photodetector,
8 is an AC adder, 9 is a BD adder, 10 is the first IV
Converter, 11 is a second IV converter, 12 is a balance control amplifier, 13 is a subtractor, 14 is a focus loop filter, 15 is a disturbance generator, 16 is a driver,
7 is an adder, 18 is a detector, 19 is a balance deviation amount detector, 20 is a convergence gain multiplier, and 21 is a switch.

Tracks on which information is recorded are spirally arranged on the disk 1. The signal on the track is read by the laser light emitted from the laser 3. The laser light is reflected by the beam splitter 5 and is input to the condenser lens 2. The condenser lens 2 collects the laser light and collects the light on a track. The light on the track is reflected and input to the polarizing lens 6 through the condenser lens 2 and the beam splitter 5. The polarizing lens 6 changes the cross-sectional shape of the laser light according to the focus state of the laser light. It is a perfect circle when it is in focus, and an ellipse when it is out of focus. The laser light is input to the four-segment photodetector 7. The output current of the areas A and C on the four-segment photodetector 7 is AC
The addition is performed by the adder 8. Output currents from B and D are added by a BD adder 9. The addition result of AC is subjected to IV (current-voltage) conversion by the first IV converter 10 and the addition result of BD by the second IV converter 11, respectively.

The outputs of the IV converters 10 and 11 are both input to a balance control amplifier 12, and the balance is adjusted as described later. The output of the balance control amplifier 12 is input to a subtractor 13, and the output of the subtractor 13 becomes a focus error signal FE indicating the amount of focus defocus. Since the cross section of the laser beam when the focus is on the track is a perfect circle, the outputs of A + C and B + D become the same, and the focus error signal FE, which is the subtraction result, becomes 0. When the laser beam is out of focus, the cross section of the laser beam becomes elliptical, and the focus error signal FE outputs the amount of defocus. The focus error signal FE is input to the focus loop filter 14, and after being subjected to filter operations such as phase compensation and low-frequency compensation, is input to the driver 16. The output of the driver 16 is connected to the focus actuator 4 and moves the condenser lens 2 to a position in the optical axis direction. The condenser lens 2 is controlled so that the focus error signal FE becomes 0, that is, the laser beam is focused on the track.

At this time, the four-divided photodetector 7, the first
If the characteristics of the IV converter 10, the second IV converter 11, and the balance control amplifier 12 vary, an error occurs between the position where the focus error signal FE becomes 0 and the in-focus position. Focus balance adjustment is performed to remove this error. Next, a method of adjusting the focus balance will be described. Outputs of the first IV converter 10 and the second IV converter 11 are input to an adder 17. The output of the adder 17 becomes the data reproduction signal RF. The data reproduction signal RF is input to the detector 18 to generate an envelope signal indicating the amplitude of the data reproduction signal RF. At the time of focus balance adjustment, the switch 21 is closed, and a disturbance having a predetermined frequency is applied from the disturbance generator 15 to the focus servo loop.
By observing how the envelope of the data reproduction signal RF changes due to the disturbance, it is possible to detect the amount of focus balance deviation.

In a balanced state, as shown in FIG. 5, the envelope of the data reproduction signal RF is minimum, that is, the amplitude of the data reproduction signal RF is maximum. Here, FIG. 5 shows an envelope signal indicative of the amplitude of the data reproduction signal RF, (a) is a case where there is no balance deviation, the envelope signal P ₁ is the defocus amount is in the just-focus position of the 0. (B) if the envelope signal P ₂ is shifted to the right, (c) shows the case where the envelope signal P ₃ shifted to the left. When a disturbance is introduced in this state, the envelope value increases both when the disturbance is shaken in the positive direction and when the disturbance is shaken in the negative direction. When the balance is shifted, the direction in which the envelope is increased or decreased is reversed when the disturbance is shaken in the positive direction and when the disturbance is shaken in the negative direction. When the amount of deviation is small, the envelope initially decreases when disturbance is introduced, and reversely increases after passing the maximum amplitude position. The focus balance shift amount can be detected from the inversion position. A shift correction signal is output according to the shift amount detected by the balance shift amount detector 19.

Incidentally, the optimum value of the amount of the shift correction signal changes depending on the characteristics of the balance control amplifier 12. Here, in order to optimize the shift correction amount, it is necessary to previously obtain a convergence gain by which the shift correction amount is multiplied.
The obtained convergence gain is multiplied by the deviation correction signal by the convergence gain multiplier 20. The output of the convergence gain multiplier 20 enters the balance control amplifier 12, and the focus balance deviation is corrected. After the correction, the disturbance is further introduced to detect the focus balance deviation amount. When the focus balance deviation amount falls within the predetermined range, the focus balance adjustment ends. If not, the operation of disturbance input, focus balance deviation amount detection, and correction operations are repeated until they do.

[0009]

However, in the above configuration, the convergence gain is determined according to the characteristics of the balance control amplifier 12. However, in a plurality of devices, the balance control amplifier 12, the IV converters 10, 1 and 2 are used.
The optimal convergence gain value shifts due to a variation of 1, for example. Further, even with one device, the optimum convergence gain value is shifted due to a temperature change, an aging change, and the like.

FIG. 6 shows the amount of balance shift by a white circle. If the convergence gain shifts in a very high direction as shown in FIG. 6C, the correction result exceeds the target, and the next correction is performed. The operation of passing the target again is repeated, and a phenomenon occurs in which the focus balance adjustment does not end.
In order to prevent such a state, it is necessary to set the convergence gain to a relatively small value. However, if the convergence gain is reduced as shown in FIG. There was a problem that it took time.

As described above, in this optical disk device, it is required to perform the focus balance adjustment stably and at high speed while solving the above-mentioned problems. Therefore,
According to the present invention, the convergence gain is changed in accordance with the convergence state of the focus balance adjustment, so that the convergence gain is maintained at an optimum value even if there are variations in the balance control amplifier and the IV converter, temperature changes, and aging. It is an object of the present invention to provide an optical disk device which can always perform focus balance adjustment stably and at high speed.

[0012]

According to the present invention, there is provided an optical disk apparatus, comprising: a laser for irradiating a recording medium having a track on which information is recorded; and a first lens for focusing this laser on a track on the recording medium. A focus actuator that moves the first lens in the optical axis direction, a second lens that changes the shape of the return light from the recording medium according to the focus state, and a light amount of light that has passed through the second lens Photodetector comprising a plurality of areas for detecting the position, a balance adjusting means for adjusting the balance of the output signal of the photodetector, and a shift for generating a signal indicating the amount of shift from the focal point from the output of the balance adjuster Amount detection means, filter means for performing a filtering process on the output from the displacement amount detection means, and amplifying the output from the filter means to drive the focus actuator. A driver, reproduction signal generation means for generating a signal corresponding to data recorded on a recording medium from an output of the photodetector, detection means for detecting an envelope of the signal generated by the reproduction signal generation means, and a focus. A disturbance generating means for adding a disturbance to the output from the filter means at the time of balance adjustment; and a balance deviation amount of the output signal of the photodetector from the level of the disturbance generated from the disturbance generating means and the level of the envelope output from the detecting means. Balance deviation detecting means for detecting, a multiplying means for multiplying an output signal from the balance deviation detecting means by a predetermined coefficient, a memory for recording a signal output from the balance deviation detecting means, and recording in the memory Polarity comparing means for comparing the polarity of the value before memory with the value of the memory, and the amount of balance deviation according to the comparison result of the polarity comparing means. It is obtained by a coefficient changing means for changing the value of the predetermined coefficient to be multiplied by the multiplying means to fall within a predetermined range.

According to the optical disk device of the first aspect,
By changing a predetermined coefficient to be multiplied by the multiplying means for adjusting the focus balance, for example, a convergence gain according to the convergence state of the adjustment, the balance control amplifier, I
The convergence gain can always be kept at an optimum value even if there is variation of the -V converter, temperature change or aging, so that focus balance adjustment can be performed stably and at high speed in any case.

According to a second aspect of the present invention, in the optical disk apparatus according to the first aspect, the coefficient changing means multiplies by the multiplying means in accordance with the value before recording in the memory, the polarity of the value of the memory and the amount of difference. This is to change the value of the coefficient. According to the optical disk device of the second aspect, the same effect as that of the first aspect is obtained. An optical disk device according to claim 3, wherein a laser that irradiates a recording medium having a track on which information is recorded, a first lens that focuses the laser on a track on the recording medium, and a first lens that illuminates the first lens. A focus actuator that moves in the axial direction; a second lens that changes the shape of the return light from the recording medium in accordance with the focus state;
A photodetector comprising a plurality of regions for detecting the amount of light passing through the lens, balance adjusting means for adjusting the balance of the output signal of the photodetector, and deviation from the focal point from the output of the balance adjusting means A shift amount detecting means for generating a signal indicating the amount, a filter means for performing a filtering process on an output from the shift amount detecting means, a driver for amplifying an output from the filter means to drive a focus actuator, Signal generating means for generating a signal corresponding to the data recorded on the recording medium from the output of the recorder, detecting means for detecting the envelope of the signal generated by the reproducing signal generating means, and filtering means for adjusting the focus balance A disturbance generating means for adding a disturbance to the output from the
A balance shift amount detector for detecting a balance shift amount of an output signal of the photodetector based on a level of disturbance generated from the disturbance generator and an envelope level output from the detector, and an output from the balance shift amount detector. Multiplying means for multiplying the signal by a predetermined coefficient to correct the balance deviation of the balance adjusting means; a memory for recording a signal output from the balance deviation amount detecting means; a value before recording in the memory and a value of the memory And a coefficient calculating means for calculating a value of a predetermined coefficient to be multiplied by the multiplying means so that the amount of balance deviation falls within a predetermined range.

According to the optical disk device of the third aspect,
This has the same effect as the first aspect.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a first embodiment of the present invention. In FIG. 1, 1 is a disk, 2 is a condenser lens, 3 is a laser, 4 is a focus actuator, 5 is a beam splitter, 6 is a polarizing lens, and 7 is 4 8 is an AC adder, 9 is a BD adder, 10 is a first I
-V converter, 11 is a second IV converter, 12 is a balance control amplifier, 13 is a subtractor, 14 is a focus loop filter, 15 is a disturbance generator, 16 is a driver, 17 is an adder, 18 is A detector, 19 is a balance deviation amount detector, 20 is a convergence gain multiplier, 21 is a switch,
22 is a memory and 23 is a convergence gain corrector.

As in the conventional example, the laser light emitted from the laser 3 is reflected by the beam splitter 5 and input to the condenser lens 2 as the first lens. The condensing lens 2 condenses the laser light and collects the light on a track on the disk 1 as a recording medium. The light on the track is reflected and input to the polarizing lens 6 as the second lens through the condenser lens 2 and the beam splitter 5. Disk 1 for polarizing lens 6
It changes the shape of the return light from the lens according to the focus state.
For example, the sectional shape of the laser light is changed according to the focus state of the laser light. The laser light is input to a four-segment photodetector 7 which is a photodetector. The output currents of the areas A and C on the quadrant photodetector 7 are added by an AC adder 8. Output currents from the regions B and D are added by a BD adder 9.
The addition result of the areas A and C is subjected to IV conversion by the first IV converter 10 and the addition result of the areas B and D is subjected to IV conversion by the second IV converter 11, respectively. The outputs of the IV converters 10 and 11 are both input to a balance control amplifier 12 which is a balance adjusting means for adjusting the balance of the output signal. The output of the balance control amplifier 12 is input to a subtractor 13 which is a shift amount detecting means for generating a signal indicating the shift amount from the focal point, and a focus error signal FE is generated. The focus error signal FE is inputted to a focus loop filter 14 which is a filter means for performing a filtering process, and after being subjected to a filter operation such as phase compensation and low-frequency compensation, is amplified and inputted to a driver 16 for driving the focus actuator 4. You. The driver 16 supplies a current to the focus actuator 4 to move the condenser lens 2 to a position in the optical axis direction.

At the time of focus balance adjustment, the switch 21 is closed, and a disturbance of a predetermined frequency is applied to the focus servo loop by a disturbance generator 15 which is a disturbance generating means for adding a disturbance to the output from the filter means. At this time, the output of the first IV converter 10 and the output of the second IV converter 11 are output from an adder 17 which is a reproduction signal generating means for generating a signal corresponding to data recorded on a recording medium. , And the output is input to a detector 18 which is a detecting means for detecting an envelope, and an envelope signal indicating the amplitude of the data reproduction signal RF is generated. As described in the conventional example, the balance deviation detector 19 detects the focus balance deviation from the direction and level of disturbance increase and decrease, and the envelope level at that time. The detected shift amount is stored in the memory 22. The balance deviation detector 19 outputs a deviation correction signal according to the detected deviation amount. The shift correction signal is multiplied by a convergence gain which is a predetermined coefficient by a convergence gain multiplier 20 which is a multiplication means. The output of the convergence gain multiplier 20 enters the balance control amplifier 12, and the focus balance deviation is corrected. After the correction, the disturbance is further introduced to detect the focus balance deviation amount.
The balance deviation detector 19 determines whether or not the focus balance deviation falls within a predetermined range. If the focus balance deviation falls within the predetermined range, the focus balance adjustment ends. If not, the convergence gain corrector 23 stores the focus balance deviation amount at this time in the memory 22.
, That is, the previous focus balance deviation amount. That is, the convergence gain corrector 23 compares the value before recording in the memory 22 with the value in the memory 22, and converges so that the amount of balance shift falls within a predetermined range according to the comparison result of the comparing means. Coefficient changing means for changing the convergence gain multiplied by the gain multiplier 20. In the embodiment, the coefficient changing means determines the multiplier 2 according to the value before recording in the memory 22, the polarity of the value in the memory 22, and the amount of difference.
The value of a predetermined coefficient to be multiplied by 0 is changed.

First, a rough convergence state is determined by comparing codes (polarities). If the sign is not inverted, the convergence state is normal, for example, as shown in FIG.
Or judge that it is moderate. If the sign is inverted, it is determined that the convergence state is a hunting state, for example, as shown in FIG. Next, the amount of change is examined. If the sign is not inverted, the preset change amount setting value is compared with the actual change amount. If the actual change amount is smaller, it is determined that the convergence gain is small, and the convergence gain is increased. If the actual change amount is larger, the convergence gain is determined to be normal, and the convergence gain is not changed. If the sign is reversed,
Investigate the ratio of the positive and negative sides of the change. If the ratio is one to one, a perfect hunting state occurs and the target does not converge. The preset ratio is compared with the actual ratio. If the actual ratio is larger, it is determined that the convergence gain is larger, and the convergence gain is reduced. If the actual ratio is smaller, the convergence gain is determined to be normal and the convergence gain is not changed. Until the focus balance deviation amount falls within a predetermined range, disturbance input, focus balance deviation amount detection, convergence gain adjustment,
The operation of the focus balance correction is repeated.

According to this embodiment, the convergence gain by which the multiplier 20 is multiplied to adjust the focus balance is changed according to the convergence state of the adjustment, so that the variation of the balance control amplifier and the IV converter, the temperature, Since the convergence gain can always be maintained at an optimum value even if there is a change or aging, focus balance adjustment can be performed stably and at high speed in any case.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIGS.
FIG. 2 shows a second embodiment of the present invention. In FIG. 2, 1 is a disk, 2 is a condenser lens, 3 is a laser, 4 is a focus actuator, 5 is a beam splitter, 6 is a polarizing lens, and 7 is 4 8 is an AC adder; 9 is a BD adder; 10 is a first IV converter;
1 is a second IV converter, 12 is a balance control amplifier, 13 is a subtractor, 14 is a focus loop filter, 15 is a disturbance generator, 16 is a driver, 17 is an adder, 18 is a detector, and 19 is a detector. Balance deviation detector, 20
Is a convergence gain multiplier, 21 is a switch, 22 is a memory,
24 is a convergence gain calculator.

The difference from the first embodiment is that a convergence gain calculator 24 is provided in place of the convergence gain corrector 23, and the other points are the same as those of the first embodiment. As in the conventional example, the laser light emitted from the laser 3 is reflected by the beam splitter 5 and input to the condenser lens 2. The condenser lens 2 collects the laser light and collects the light on a track on the disk 1. The light on the track is reflected and passes through the condenser lens 2 and the beam splitter 5, and the polarizing lens 6
Is input to The polarizing lens 6 changes the cross-sectional shape of the laser light according to the focus state of the laser light. The laser light is input to the four-segment photodetector 7. The output currents of the areas A and C on the quadrant photodetector 7 are added by an AC adder 8. Output currents from the regions B and D are added by a BD adder 9. The addition result of the area AC is the first IV converter 1
0 and the addition result of the area BD are subjected to IV conversion by the second IV converter 11 respectively. Outputs of the IV converters 10 and 11 are both input to the balance control amplifier 12. The output of balance control amplifier 12 is subtracter 1
3 and a focus error signal FE is generated.
The focus error signal FE is input to the focus loop filter 14, and after being subjected to filter operations such as phase compensation and low-frequency compensation, is input to the driver 16. Driver 16
Supplies a current to the focus actuator 4 to move the condenser lens 2 to a position in the optical axis direction.

At the time of focus balance adjustment, the switch 21 is closed, and a disturbance of a predetermined frequency is applied from the disturbance generator 15 to the focus servo loop. At this time, the first I-
Outputs of the V converter 10 and the second IV converter 11 are input to an adder 17 and a detector 18 to generate an envelope signal indicating the amplitude of the data reproduction signal RF. As described in the conventional example, the balance deviation detector 19 detects the focus balance deviation from the direction and level of disturbance increase and decrease, and the envelope level at that time. The detected shift amount is stored in the memory 22. The balance deviation detector 19 outputs a deviation correction signal according to the detected deviation amount. The deviation correction signal is multiplied by a convergence gain in a convergence gain multiplier 20. The output of the convergence gain multiplier 20 enters the balance control amplifier 12, and the focus balance deviation is corrected. After the correction, the disturbance is further introduced to detect the focus balance deviation amount. When the focus balance deviation amount falls within the predetermined range, the focus balance adjustment ends. If not, the convergence gain calculator 24, which is a coefficient calculator, stores the focus balance deviation amount at this time and the memory 22.
, The correct convergence gain is determined from the relationship with the previous focus balance deviation amount.

That is, the coefficient calculating means calculates a predetermined coefficient, such as a convergence gain value, to be multiplied by the multiplier 20 from the value before recording in the memory 22 and the value in the memory 22 so that the amount of balance shift falls within a predetermined range. Ask. A method for obtaining the convergence gain will be described with reference to FIG. A is the first focus balance deviation amount detection result. Assuming that the initial convergence gain is X1, the correction amount is A · X1. Assuming that the corrected focus balance shift amount is B and the correct convergence gain is X, the first correction amount A.X1 is AX-BX. Therefore, the correct convergence gain X is (A · X1) / (A−
It is obtained by the equation of B). If the target value has not been reached in the first correction, the focus balance is continuously adjusted using the convergence gain calculated by the above equation. Until the focus balance shift amount falls within a predetermined range, the operations of disturbance input, focus balance shift amount detection, and focus balance correction are repeated.

Therefore, the same effects as in the first embodiment can be obtained.

[0026]

According to the optical disk device of the present invention, a predetermined coefficient multiplied by the multiplying means for adjusting the focus balance, for example, a convergence gain is changed in accordance with the convergence state of the adjustment, so that the balance control amplifier, The convergence gain can always be kept at an optimum value even if there are variations in the IV converter, temperature changes or aging, so that focus balance adjustment can be performed stably and at high speed in any case.

According to the optical disk device of the second aspect,
This has the same effect as the first aspect. According to the optical disk device of the third aspect, the same effect as that of the first aspect is obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an optical disc device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating an optical disc device according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a calculation method of a convergence gain according to a second embodiment.

FIG. 4 is a configuration diagram of a conventional optical disk device.

FIG. 5 is a schematic diagram showing a deviation of a focus balance amount and an RF envelope.

FIG. 6 is a schematic diagram showing a focus balance amount and a convergence gain.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disc 2 Condensing lens 3 Laser 4 Focus actuator 5 Beam splitter 6 Polarizing lens 7 Quadrant photodetector 8 AC adder 9 BD adder 10 1st IV converter 11 2nd IV converter 12 Balance control Amplifier 13 Subtractor 14 Focus loop filter 15 Disturbance generator 16 Driver 17 Adder 18 Detector 19 Balance deviation detector 20 Convergence gain multiplier 21 Switch 22 Memory 23 Convergence gain corrector 24 Convergence gain calculator

Claims (3)

[Claims] 1. A laser for irradiating a recording medium having a track on which information is recorded with light, a first lens for focusing the laser on a track on the recording medium, and a first lens for moving the first lens in an optical axis direction. A focus actuator to be moved, a second lens that changes the shape of the return light from the recording medium in accordance with the focus state, and a photodetector including a plurality of areas for detecting the amount of light passing through the second lens Balance adjustment means for adjusting the balance of the output signal of the photodetector, shift amount detection means for generating a signal indicating the shift amount from the focal point from the output of the balance adjustment means, and shift amount detection means. Filter means for performing a filtering process on the output of the filter; a driver for amplifying the output from the filter means to drive the focus actuator; Reproduction signal generation means for generating a signal corresponding to data recorded on the recording medium; detection means for detecting an envelope of a signal generated by the reproduction signal generation means; and A disturbance generating means for adding a disturbance to the output,
A balance shift amount detector that detects a balance shift amount of an output signal of the photodetector from a level of disturbance generated from the disturbance generator and an envelope level output from the detector; and a balance shift amount detector. Multiplying means for multiplying the output signal by a predetermined coefficient to correct the balance shift of the balance adjusting means, a memory for recording a signal output from the balance shift amount detecting means, and a value before recording in the memory. And a polarity comparing means for comparing the polarity of the value of the memory with the value of the predetermined coefficient to be multiplied by the multiplying means so that the amount of balance shift falls within a predetermined range according to the result of comparison by the polarity comparing means. An optical disk device comprising: a coefficient changing unit that changes the coefficient. 2. The coefficient changing unit according to claim 1, wherein the coefficient changing unit changes a value of a predetermined coefficient to be multiplied by the multiplying unit in accordance with a value before recording in the memory, a polarity of the value in the memory, and an amount of difference. Optical disk device. 3. A laser for applying light to a recording medium having a track on which information is recorded, a first lens for focusing the laser on a track on the recording medium, and a first lens for moving the first lens in an optical axis direction. A focus actuator to be moved, a second lens that changes the shape of the return light from the recording medium in accordance with the focus state, and a photodetector including a plurality of areas for detecting the amount of light passing through the second lens Balance adjustment means for adjusting the balance of the output signal of the photodetector, shift amount detection means for generating a signal indicating the shift amount from the focal point from the output of the balance adjustment means, and shift amount detection means. Filter means for performing a filtering process on the output of the filter; a driver for amplifying the output from the filter means to drive the focus actuator; Reproduction signal generation means for generating a signal corresponding to data recorded on the recording medium; detection means for detecting an envelope of a signal generated by the reproduction signal generation means; and A disturbance generating means for adding a disturbance to the output,
A balance shift amount detector that detects a balance shift amount of an output signal of the photodetector from a level of disturbance generated from the disturbance generator and an envelope level output from the detector; and a balance shift amount detector. Multiplying means for multiplying the output signal by a predetermined coefficient to correct the balance shift of the balance adjusting means, a memory for recording a signal output from the balance shift amount detecting means, and a value before recording in the memory. An optical disc device comprising: a coefficient calculating means for obtaining a value of a predetermined coefficient to be multiplied by the multiplying means so that the amount of balance deviation falls within a predetermined range from the value in the memory.