JP2839270B2 - Target position adjustment method for tracking control - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control for driving a moving means in accordance with a signal from a track deviation detecting means and controlling a reproducing position to always be located on a track. In particular, the present invention relates to a target position adjustment method for tracking control and a record carrier used therefor.

2. Description of the Related Art Conventionally, a light beam generated from a light source is converged and irradiated on a rewritable record carrier such as a phase change optical disk or a magneto-optical disk, and tracking is performed so that the light beam on the record carrier is positioned on a track. 2. Description of the Related Art There is known an optical disk device which performs recording or reproduction of a signal while controlling (for example, Japanese Patent Application No. 55-125283).

An uneven guide groove (track) for recording a signal is provided on the record carrier in advance, and reflected light or transmitted light from the record carrier is received by a photodetector having a two-segment structure. The positional deviation (track deviation) between the light beam and the track on the record carrier is detected from the light amount difference.

More specifically, the photocurrents of both photodetectors are subjected to current-voltage conversion, and the difference between the voltages is obtained by a differential amplifier to obtain a trunk shift signal.

After this track shift signal is processed by the tracking control circuit, the light beam on the record carrier is applied to a tracking actuator that moves in a direction substantially perpendicular to the longitudinal direction of the track, and the light beam on the record carrier is positioned on the track. Tracking control.

The control target of the tracking control is a position on the track where the output of the differential amplifier for obtaining the track deviation signal is a predetermined value, that is, the light amount received by both photodetectors is equal, and the light beam on the record carrier is the target position. Is controlled to always be located at

Problems to be Solved by the Invention In the above-described apparatus, it is very important to maintain compatibility because the record carriers are exchangeable. That is, when a signal recorded by another device is reproduced with high reliability, or when a signal recorded by another device is erased and a new signal is recorded, a signal recorded by another device is not erased and there is no remaining. It is necessary to erase accurately.

For compatibility, all devices require tracking control so that the light beam on the record carrier is accurately located at the reference position of the track, for example, at the center of the track.

For this purpose, the target position of tracking control must be the same in all devices.

As described above, the tracking control is performed so that the output of the differential amplifier for obtaining the track deviation signal has a predetermined value, but the target position of the tracking control differs depending on the device.

Causes of this occurrence include, for example, a sensitivity difference between the two-split photodetectors, a difference between the conversion rates of the two I / V converters that convert the photocurrent into a voltage, and a gain difference between the differential amplifiers that obtain the track shift signal. .

Also, the aberration of the light beam on the record carrier, and the manner in which the reflected light reflected by the record carrier or the transmitted light transmitted by the optical system that guides the light to the two-segment photodetector slightly differs depending on the device. The state of the light beam on the two-segment photodetector varies. If the state of the light beam on the two-segment photodetector varies, the target position of the tracking control also varies, and the compatibility deteriorates.

As described above, in the conventional apparatus, the target position after tracking control is not adjusted for each apparatus, and therefore, varies from one apparatus to another, and therefore, compatibility between the apparatuses is poor.

SUMMARY OF THE INVENTION An object of the present invention is to provide an adjustment method capable of eliminating the above-mentioned drawbacks and allowing a target position of tracking control to accurately match a desired target position, and a record carrier used therefor.

Means for Solving the Problems In the tracking control target position adjusting method of the present invention, first and second adjustment signals arranged to be deviated left and right with respect to the center of a concave or convex guide groove are provided. Irradiating a light beam onto a recording carrier having the same, detecting at least two photodetectors with reflected light from the recording carrier, and displacing the light beam and the guide groove based on an output difference between the two photodetectors. A tracking control device that records a signal on the guide groove or reproduces a signal recorded on the guide groove while performing tracking control so that the light beam is positioned on the guide groove based on the position shift signal. A target position for tracking control is detected by detecting an amplitude difference between the first and second adjustment signals from the sum of outputs from the two photodetectors, and adjusting the displacement signal based on the signal of the amplitude difference. Is to adjust.

Operation According to the above configuration, the present invention provides an adjustment signal, so that a deviation of the target position of the tracking control can be easily detected, and the adjustment is performed by using the signal. The position can be accurately adjusted, and the compatibility between the devices can be made extremely good with a simple configuration.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same numbers are used for the same numbers.

FIG. 1 shows an optical recording and reproducing apparatus 1 according to the present invention.
This is an example.

A light beam 2 generated from a light source 1 such as a semiconductor laser is
After being converted into substantially parallel light by the coupling lens 3, the light is reflected by the polarization beam splitter 4, passes through a 収束 wavelength plate, and is converged by the converging lens 6 onto the information carrier surface of the disc-shaped record carrier 7 for irradiation. .

The record carrier 7 provided with the uneven groove track is
The motor 8 is attached to a rotation shaft and is rotated at a predetermined rotation speed.

Reflected light 9 of light beam 2 reflected by record carrier 7
Is passed through a converging lens 6, a quarter-wave plate 5, and a polarizing beam splitter 4, and is irradiated onto a photodetector 10 having a two-segment structure.

The converging lens 6 is attached to a tracking actuator 11, and the tracking actuator 11 is configured to move the converging lens 6 in a radial direction of the record carrier 7, that is, in a width direction of a track on the record carrier 7.

A light source 1, a coupling lens 3, a polarizing beam splitter 4, a quarter-wave plate 5, a photodetector 10, and a tracking actuator 11 are fixed to a transfer table 12, and are integrated integrally by a linear motor 13 in the radial direction of the record carrier. It is configured to move.

Each photocurrent is supplied to the photodetector 10 by the I / V converters 14 and 1.
After the current is converted into a voltage by 5, the current is input to the differential amplifier 16 and the adder circuit 17, respectively. The differential amplifier 16 outputs a signal corresponding to the difference between the two input signals, and the adder circuit 17 outputs a signal corresponding to the sum of the two input signals.

The direction of the division line of the photodetector 10 is the track direction on the irradiation surface of the reflected light 9, and the operational amplifier 16 outputs a signal corresponding to the position shift between the light beam 2 on the record carrier 7 and the track, ie, a track shift signal. Is output.

The signal of the differential amplifier 16 and the signal of the adding circuit 17 are input to the dividing circuit 18 via the line 19, and the dividing circuit 18 outputs a signal corresponding to a value obtained by dividing the signal of the differential amplifier 16 by the signal of the adding circuit 17. Is output.

The signal of the adding circuit 17 output through the line 19 is I /
The signals of the V converters 14 and 15 are added, and a high-frequency component of the added signal, for example, a component of 50 KHz or more is removed by a low-pass filter. By removing the high frequency components in this manner, it is possible to remove disturbances due to noise on the record carrier, scratches or address signals of the tracks recorded in the form of irregularities on the tracks, and more stably perform the tracking control. can do.

The signals of the division circuit 18 are added to an addition circuit 20, a phase compensation circuit 21 for compensating the phase of the tracking control system, a switch 22 for disabling the tracking control, and an addition circuit 23.
And a tracking circuit 11 via a drive circuit 24 for power amplification. Also switch
22 is applied to the linear motor 13 via a drive circuit 25 for amplifying the output signal power.

Therefore, when the switch 22 is in a short-circuit state, the tracking actuator 11 and the linear motor 13 are driven according to the signal of the differential amplifier 16 so that the light beam 2 is positioned on the track on the record carrier 7.

 The effect of the division circuit 18 will be described.

Signal output of the differential amplifier 16 for unit track deviation,
That is, the track shift detection sensitivity changes according to the light amount of the light beam 2 generated from the light source 1, the reflectance of the record carrier 7, the sensitivity of the photodetector 10, the light transmission rate of the optical system, and the like. If the track shift detection sensitivity changes, the gain of the tracking control system changes when there is no division circuit 18, so that the tracking control becomes unstable, or in some cases, oscillates and the tracking control is not applied. I will. According to the configuration of the present invention, even if the track shift detection sensitivity changes N times for the above reason, the signal of the adder circuit 17 output through the line 19 also becomes N times, so that the division circuit 18 for unit track shift Becomes constant and the gain does not change, so that the tracking control can be made extremely stable.

Briefly describing the search for the desired track,
An address signal is recorded in advance on a track on the record carrier 7 in the form of irregularities, and the search is performed based on the address signal. The address is read by the address reading circuit from the signal of the adding circuit 17 (omitted).

The microcomputer (MPU) 26 detects the address of the track on which the light beam 2 is located on the record carrier 7 from the signal of the address reading circuit, and finds the difference from the address of the desired track. If the value is greater than or equal to the value, a rough search is performed. That is, a signal corresponding to the address difference is sent to the drive circuit 25 via the line 27, and the switch 22 is sent via the line 28.
A signal to release the signal to make the tracking control inoperative. When the transfer table 12 is moved in the radial direction of the record carrier 7 by the linear motor 13 and the light beam 2 comes close to the desired track, the MPU 26 stops the signal transmitted through the line 27 and switches the switch 22. As a result, the tracking control is operated to read the address of the track on the record carrier 7 where the light beam 2 is located. When the track is different from the desired track, an address difference from the desired track is obtained, and when this value is smaller than a predetermined value, a fine search in which one jumping is repeated a number of times corresponding to the difference is performed to perform the desired search. Search for a track. When performing one jumping, MPU2
The switch 6 opens the switch 22 and sends a signal via the line 29 to drive the tracking actuator 11 to move the light beam 2 on the record carrier 7 to the next track and short-circuit the switch 22 again.

Hereinafter, adjustment of the target position of the tracking control will be described.

The adding circuit 17 adds the signals of the I / V conversion records 14 and 15 and separates, via a line 30, a signal obtained by removing a low-frequency component of the added signal, for example, a component of 10 KHz or less by a high-pass filter. The signal is transmitted to the circuit 31.

A target position adjustment area is provided on the record carrier 7 at an outer peripheral portion or an inner peripheral portion which is not normally used. The target position adjustment region includes one adjustment circumferential track for positioning a light beam during adjustment, The first adjacent to the adjustment circumferential track
And three circumferential tracks of a second circumferential track. F1 and f2 for the first and second circumferential tracks
For example, a signal of a single frequency, for example, a signal of 1.0 MHz on the first circumferential track, and a signal of 1.5 MHz on the second circumferential track are recorded in advance in the form of irregularities.

One circumferential track means one concentric track when the track on the record carrier is concentric, and starts from a point A on the track when the track on the record carrier is spiral, and goes around the record carrier once. It means a track up to a point B which intersects a straight line connecting the point A and the center of the carrier.

When adjusting the target position, the MPU 26 first searches for the adjustment circumferential track, and performs tracking control so that the light beam 2 on the record carrier 7 is located on the adjustment circumference track. When the track on the record carrier 7 is spiral, one back is made every time the record carrier 7 makes one rotation, and still control is performed so that the record carrier 7 is located on the same circumference.

The adjustment of the target position is performed by detecting signals of the frequencies f1 and f2 mixed by crosstalk in a state where the light beam 2 on the record carrier 7 is controlled to be positioned on the circumferential track for adjustment.

The separating circuit 31 separates the signals of the frequencies f1 and f2 from the signal of the adding circuit 17 inputted via the line 30, performs envelope detection of each signal, and sends the detected signal to the differential amplifier 32.

The differential amplifier 32 outputs a signal corresponding to the difference between the two input signals, and converts this signal from an analog signal to a digital signal.
Send to A / D converter 33. The A / D converter 33 converts the signal of the differential amplifier 32 into a digital signal, and converts this digital signal to an MPU2 signal.
Send to 6. The MPU 26 detects a direction in which the target position of the tracking control is deviated from the value of the A / D converter 33, and sends a signal to the D / A converter 34 to shift the target position in the detected direction. The signal for short-circuiting the switch 36 is sent via 35. The signal of the D / A converter 34 is transmitted to the addition circuit 20 via the switch 36. The addition circuit 20 adds the signal of the division circuit 18 and the signal of the switch 36 and sends this signal to the phase compensation circuit 21, so that the target position for tracking control changes according to the signal of the D / A converter 34. The MPU 26 inputs a gradually increasing signal to the D / A converter 34 while checking the output of the A / D converter 33 so that the target position gradually approaches the desired position, and outputs the value of the A / D converter 33. Within a predetermined range.

FIG. 2 shows the output of the differential amplifier 32 with respect to the track shift. The horizontal axis indicates the track shift and the vertical axis indicates the output of the differential amplifier 32. As can be seen from the figure, the output of the differential amplifier 32 increases in the positive direction when it deviates in one direction from the true target position, and the output of the differential amplifier 32 deviates in the opposite direction.
Output increases in the negative direction. Assuming that the track deviation is X and the output of the differential amplifier 32 is, the relationship of Y = K1 * SIN (2πX / P) is almost satisfied. Here, K1 is a constant, π is a circle ratio, and P is a track pitch.

In the configuration of the present invention, as described above, the signal output of the division circuit 18 for the unit track deviation is substantially constant, so that the relationship between the value of the A / D converter 33 and the deviation amount of the target position is also substantially constant. Therefore, the deviation amount of the target position can be easily measured from the value of the A / D converter 33. For example, if MPU26 is A
The value to be sent to the D / A converter 34 with respect to the value of the / D converter 33 may be stored in a table in advance. The value D0 corresponding to the value of the A / D converter 33 is sent to the D / A converter 34, and after the target position of the tracking control is shifted, the MPU 26 re-starts the A / D converter 33.
Is measured, and if this value is not within the predetermined range, a value D1 to be sent to the D / A converter 34 corresponding to the value of the A / D converter 33 is obtained, and D0 and D1 are calculated. D / A is the sum (D0 + D1)
Send to converter. The MPU 26 repeats the above until the value of the A / D converter 33 falls within a predetermined range. In this way, the number of repetitions is reduced, and the target position can be set at high speed. When the value of the A / D converter 33 does not fall within the predetermined range even after the predetermined number of repetitions, the MPU 26 generates an abnormal signal assuming that the value is abnormal, and stops at least the recording operation. In this way, not only can the abnormality of the device be known from the outside, but also since erroneous recording is not performed, the reliability of the device can be improved.

Also, the relationship between the value of the A / D converter 33 and the value to be sent to the D / A converter 34 is converted into a function, and the D / A is calculated from the value of the A / D converter 33.
A value to be sent to the converter 34 may be obtained, and this value may be sent to the D / A converter 34. That is, the value of the A / D converter 33 is X1, D
If the value to be sent to the / A converter 34 is Y1, then Y1-K2 * SI
N (K3 * X1) may be used. Here, K2 and K3 are constants. In this way, the memory required for the table can be omitted, and the cost can be reduced.

Further, since the track deviation is not large at about 0.1 μm, it can be approximately Y1-K2 * K3 * X1. With this approximation, you can calculate faster than sine wave calculation,
It can be adjusted in a short time.

Needless to say, even in a configuration in which the division circuit 18 is not provided, the adjustment can be performed at a high speed by forming a table or a function.

The separating circuit 31 will be described with reference to FIG. 3. The separating circuit 31 includes an equalizer 101, band filters 102 and 103 for extracting the signals of f1 and f2, and a band filter.
Detection circuit for envelope detection of 102 and 103 signals
It is composed of 104 and 105.

When reproducing the signal on the record carrier 7, the amplitude of the reproduced signal differs depending on the frequency of the recorded signal. Although it depends on the frequency characteristics of the photodetector 10, the I / V converters 14 and 15, or the adder circuit 17, it largely depends on the spatial frequency of the signal recorded on the record carrier 7. That is, the record carrier 7
The frequency characteristics of the reproduced signal amplitude are substantially determined by the beam diameter of the light beam 2 and the pit length of the signal. Equalizer 10
Numeral 1 is provided to correct the frequency characteristics of the reproduced signal amplitude. Therefore, since the frequency characteristic is corrected by the equalizer 101, when the target position of the tracking control is at a correct position, the outputs of the detection circuits 104 and 105 become equal, and the adjustment is simplified.

The target position adjustment area provided in advance on the record carrier 7 will be described with reference to FIG.

FIG. 4 is an enlarged and exaggerated drawing of a part of the plane of the record carrier 7, wherein 111 is a first circumferential track on which a single frequency f1 is recorded, and 112 is a single circumferential track on which a single frequency f2 is recorded. The reference numeral 113 denotes a circumferential track for adjustment between the tracks 111 and 112, and the reference numeral 114 denotes a normal track for recording a signal. Track 11
1 is composed of the bit sequence indicated by 116, and the track 112 is composed of the bit sequence indicated by 117. W1 for trucks 113 and 114
And 115, and W2 indicates the width of the tracks 111 and 112. If W1 <W2, the light beam 2
When the target position of the tracking control is adjusted so as to be located above, the amount of crosstalk from the tracks 111 and 112 increases, so that the S / N ratio of the outputs of the bandpass filters 102 and 103 in FIG. 3 is improved. And more accurate adjustment can be performed.

The skew (inclination) due to the surface deflection of the record carrier 7 differs depending on the location. Generally, it is small at the inner periphery and larger at the outer periphery. Therefore, the target position adjustment area is provided in two places of the inner circumference and the outer circumference where no signal is recorded, and the value to be set in the D / A converter 34 when adjusted in the inner circumference and the adjustment in the outer circumference are adjusted. If the average value of the values to be set in the D / A converter 34 at that time is set in the D / A converter 34 and recording or reproduction is performed, the reliability of the device can be further improved.

Further, target position adjustment areas are provided at a plurality of locations, for example, at predetermined intervals, adjustment is performed in all target position adjustment areas, respective adjustment values are stored, and a D / A converter is used depending on a track to be recorded or reproduced. By changing the value set to 34, the reliability of the device can be further improved. In this case, an area to be recorded / reproduced with respect to one target position adjustment area is determined using the address of the track, and is set in the D / A converter 34 when a desired track is searched. However, the time required for setting can be reduced, and there is no problem in terms of the system.

By pre-recording information that can be identified as the target position adjustment track on the adjustment circumferential track, it is possible to identify when the address signal cannot be read due to dropout or the like, or when the address signal is read erroneously. The processing of the apparatus can be simplified and the reliability can be improved.

When a target position adjustment area as shown in FIG. 4 is provided, when a signal is recorded on the tracks 114 and 115 adjacent to the track 111 and the track 112, or when the recorded signal is reproduced, the signal is recorded on the track 111 or the track 112. Signal may be affected. Therefore, track 114
And 115, it is desirable to manage the system so that no signal is recorded.

In order to eliminate the above-mentioned disadvantage, the target position adjustment area may be set as shown in FIG.

FIG. 5 is an enlarged and exaggerated drawing of a part of the plane of the record carrier 7 as in FIG.
Is recorded on the center of the first circumferential track, 122
Indicates the center of the second circumferential track on which the single frequency f2 is recorded, 123 indicates the center of the circumferential track for adjustment, and 124 and 125 indicate the centers of tracks adjacent to the target position adjustment area. P1 indicates the distance between the centers 121 and 123 and the centers 122 and 123, that is, the track pitch, and P2
Indicates the distance between the centers 121 and 124 and the centers 122 and 125, respectively. If the normal track pitch is P0,
When P1 <P0 <P2, and the light beam is located on the center 124 or 125, the influence of the crosstalk of the signals recorded on the first and second circumferential tracks is small, When it is located on a circumferential track, the influence of crosstalk is large. Therefore, the information signal can be recorded also on the track adjacent to the target position adjustment area,
A decrease in the recording capacity can be prevented.

If the adjustment of the target position is automatically performed immediately after the power of the apparatus is turned on or immediately after the exchange of the record carrier, the reliability of the apparatus is improved.

Further, if the temperature rise of the device is detected and the adjustment is performed according to the predetermined temperature rise, the reliability of the device can be further improved.

Further, if the adjustment is made using the idle time of the apparatus at every predetermined time, a temperature sensor or the like becomes unnecessary, and the reliability of the apparatus can be improved.

Further, the light beam may be automatically positioned on the adjustment circumferential track when the apparatus is not used, and may be adjusted again when the target position is shifted due to temperature or the like.

Although the present invention has been described in detail, the present invention should not be limited by the examples.

For example, the form of the signal recorded on the tracks 111 and 112 may be the same as the form of the signal recorded on the record carrier 7, for example, a light and shade recording. In this case, recording may be performed by a reference device determined after the completion of the record carrier, and the same signal may be recorded on all record carriers.

In addition, at least one target position adjustment region for tracking control may be provided. In this case, it is desirable to provide the outer peripheral portion or the inner peripheral portion that is not normally used.

Further, in the embodiment, the reflection optical system is used.
It may be a transmission optical system. In this case, the transmitted light transmitted through the record carrier may be received by the photodetector, and the received signal may be used in the same manner as in the embodiment shown in FIG. That is, although various optical systems have been devised, the present invention is not based on the optical system.

Further, even if the present invention is applied to an optical reproducing apparatus, the target position of tracking control is adjusted to a predetermined position,
The quality of the reproduced signal is improved, and the device can be made more reliable.

Needless to say, the present invention can be applied to a magneto-optical recording / reproducing device, a magnetic recording / reproducing device (VTR, hard disk device, floppy disk device, etc.), a capacitive reproducing device, and the like.

According to the present invention, since the target position of the tracking control is adjusted to a predetermined position, the compatibility between the devices is improved, the reliability of recording and reproduction is significantly improved, and the effect is extremely large. .

In particular, if the automatic adjustment is performed based on the signal provided in the target position adjustment area of the tracking control on the record carrier, all the devices are adjusted based on the record carrier to be used. , You can maintain even more compatibility.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the apparatus of the present invention, FIG. 2 is a diagram showing the relationship between track deviation and the output of a differential amplifier, FIG. 3 is a block diagram of a separation circuit, and FIG. FIG. 5 is an enlarged view of the target position adjustment area in the first embodiment of the carrier, and FIG. 5 is an enlarged view of the target position adjustment area in the second embodiment of the record carrier of the present invention. DESCRIPTION OF SYMBOLS 1 ... Light source, 3 ... Coupling lens, 4 ... Polarization beam splitter, 5 ... 1/4 wavelength plate, 6 ... Convergent lens, 7 ... Record carrier, 10 ... Photodetector, 12 ... Transfer table,
13 …… Linear motor, 14,15 …… I / V converter, 16,32 ……
Differential amplifier, 17, 20, 23 …… Addition circuit, 18… Division circuit,
21 ... Phase compensation circuit, 22,34 ... Switch, 24,25 ... Drive circuit, 26 ... Microcomputer, 31 ... Separation circuit, 33 ... A / D converter, 34 ... D / A conversion vessel.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hiroyuki Yamaguchi 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Shinichi Yamada 1006 Kadoma Kadoma, Kadoma City Osaka Pref. (72) Inventor Katsuya Watanabe 1006 Kadoma, Kazuma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (56) References JP-A-63-231733 (JP, A) JP-A-63-222335 (JP, A) JP-A-63-255846 (JP, A) JP-A-63-247928 (JP, A) JP-A-63-50933 (JP, A) JP-A-62-239332 (JP, A) JP-A-61-192047 (JP, A) JP-A-63-86125 (JP, A) JP-A-61-292226 (JP, A)

Claims (2)

(57) [Claims] 1. A light beam is irradiated onto a record carrier having first and second adjustment signals, which is arranged to be deviated left and right with respect to the center of a concave or convex guide groove, and Detecting the reflected light from at least two photodetectors,
A position shift between the light beam and the guide groove is detected from an output difference between the two photodetectors, and a signal is output on the guide groove while performing tracking control based on the position shift signal so that the light beam is positioned on the guide groove. In a tracking control device for recording or reproducing a recorded signal, an amplitude difference between the first and second adjustment signals is detected from a sum of outputs from the two photodetectors, and based on the signal of the amplitude difference, ,
A target position adjustment method for tracking control, wherein a target position for tracking control is adjusted by adjusting the position shift signal. 2. A light beam is irradiated onto a record carrier having first and second adjustment signals which are arranged to be deviated left and right with respect to the center of a concave or convex guide groove, and said record carrier is irradiated with a light beam. Detecting the reflected light from at least two photodetectors,
A position shift between the light beam and the guide groove is detected from an output difference between the two photodetectors, and a signal is output on the guide groove while performing tracking control based on the position shift signal so that the light beam is positioned on the guide groove. In a tracking control device for recording or reproducing a recorded signal, at an outer peripheral portion and an inner peripheral portion of the record carrier, amplitudes of the first and second adjustment signals are obtained from a sum of outputs of the two photodetectors. The target position of the tracking control is adjusted by detecting the difference, measuring the deviation of the target position of the position deviation signal based on the signal of the amplitude difference, and adjusting the position deviation signal based on both the measured values. A target position adjustment method for tracking control.