JP2000251289A - Optical information recording/reproducing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve stability of tracking control by compensating for offset of tracking error signal resulting from displacement of position from the center of optical pickup of an objective lens and variation of amplitude thereof. SOLUTION: The offset amount and amplitude value of the tracking error signal 101 for displacement from the center of optical pickup of an objective lens 8 are searched previously, and displacement of objective lens 8 is estimated with an objective lens deviation observer 19 based on a tracking calibration signal 104. Offset amount and amplitude value of tracking error signal 101 are detected respectively with an offset detecting means 17 and an amplitude detecting means 18, and the tracking error signal is compensated with an offset compensating circuit 22 and an amplitude compensating circuit 23 to set the offset amount and amplitude value of the tracking error signal 101 to the value equal to that when the displacement of objective lens 8 is zero, based on the offset amount and amplitude value searched previously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus for recording or reproducing a signal on an optical disk by using a converged light spot.

[0002]

2. Description of the Related Art In an optical information recording / reproducing apparatus typified by a DVD-R apparatus or a DVD-RAM apparatus, a light spot having a diameter of about 0.5 .mu.m is applied to an information track of about 0.74 .mu.m pitch provided on a disk. To record and reproduce information. When irradiating the disk surface with the light spot, focus control is performed so that the light spot follows the disk surface with an accuracy of about ± 0.5 μm or less in the vertical direction. The tracking control is performed so that the tracking deviation between the information track and the light spot is about ± 0.1 μm or less.

One of the conventional methods for causing a light spot to follow a track is a one-beam push-pull method. Hereinafter, a conventional optical information recording / reproducing apparatus using the one-beam push-pull method will be described with reference to FIG. FIG. 17 is a block diagram showing the configuration of the conventional optical information recording / reproducing apparatus. In FIG. 17, a disk 2 having a spiral or concentric information track 1 shown in an enlarged manner is configured to be rotated by a spindle motor 3. Recording and reproduction on the information tracks 1 of the disk 2 are performed by the optical pickup 4. The optical pickup 4 is provided with a semiconductor laser 5, a collimator lens 6, a beam splitter 7, an objective lens 8, a two-part PD (photodetector) 9, and a tracking actuator 10 as lens moving means. The tracking actuator 10 includes a coil 11 fixed to the objective lens 8 and a magnet 13 fixed to a housing of the optical pickup 4, and the coil 11 is connected to the magnet 13 via a spring 12. Coil 1
When an electric current is passed through 1, an electromagnetic force is generated between the coil 11 and the magnet 13, and the objective lens 8 moves in the tracking direction. When the optical pickup 4 is not operated, that is, when there is no input signal to the tracking actuator 10, the objective lens 8 is designed to stop at the neutral position of the optical pickup 4.

The tracking error detection circuit 14 generates a tracking error signal 101 which is the amount of displacement of the objective lens 8 from the center of the information track 1 based on the difference between the outputs of the two divided PDs, and generates a tracking control circuit. Fifteen
Output to The tracking control circuit 15 outputs a tracking drive signal 103 to the tracking drive circuit 16 based on the tracking error signal. The tracking drive circuit 16 supplies a current corresponding to the tracking drive signal 103 to the coil 11 of the tracking actuator 10. One loop for this tracking control is called a tracking control loop 201.

Next, a specific operation will be described. The light beam emitted from the semiconductor laser 5 is converted into a parallel light by the collimator lens 6, and is condensed on the information track 1 of the disk 2 via the beam splitter 7 and the objective lens 8. Focus control is performed by using a part of the reflected light from the disk 2 to move the objective lens 8 in the vertical direction so that the focal position of the light beam focused by the objective lens 8 always matches the surface of the disk 2. I have. However, since the focus control is not directly related to the present invention, a detailed description is omitted.

A part of the light reflected from the disk 2 is incident on the two-part PD 9 via the objective lens 8 and the beam splitter 7. The two-divided PD 9 outputs a voltage indicating the amount of light detected by each PD. The tracking error detection circuit 14 calculates the difference between the outputs of the two-divided PD 9 and outputs to the tracking control circuit 15 a tracking error signal 101 indicating the amount of displacement between the focus of the light beam and the information track 1. By the operation of the tracking control loop 201, the tracking control circuit 15 sends the tracking drive signal 103 to the tracking drive circuit 16 so that the amplitude of the tracking error signal 101 becomes zero, that is, the light beam is positioned at the center of the information track 1. Is output. The tracking drive circuit 16 applies a current to the coil 11 to generate an electromagnetic force and move the objective lens 8. With this configuration, even if the disk 2 is eccentric, the optical disk 2
During the rotation, the objective lens 8 can be controlled so that the light spot follows the center position of the information track 1.

FIG. 18 shows a tracking control loop 201.
FIG. 7 is a diagram illustrating a change with time of the tracking error signal 101 when the signal is switched from an OFF state (a state in which the tracking control loop 201 does not operate) to an ON state (a state in which the tracking control loop 201 operates). When the tracking control loop 201 is OFF, the tracking actuator 1 shown in FIG.
Since no driving force acts on the optical pickup 4, the objective lens 8 is stopped at the neutral position of the optical pickup 4. If the eccentricity caused by the spindle motor 3 on which the disk 2 is mounted or the eccentricity of the disk 2 itself is slight, the information track 1 is also eccentric with respect to the rotation center. Therefore, the information track 1 crosses the focal position of the objective lens 8, and a tracking error signal 101 having a sine wave shape is output in synchronization with the rotation of the disk 2. When the tracking control loop 201 is turned on, as described above, the tracking control loop 201
The objective lens 8 is controlled so that the light spot follows the center position of the information track 1 by the function of the above, so that the amplitude of the tracking error signal 101 becomes almost zero.

[0008]

However, in the above configuration, if the center of the objective lens 8 is deviated from the neutral position of the optical pickup 4 for some reason, the center of the light beam emitted from the semiconductor laser 5 is shifted with respect to the center. The offset of the center of the lens 8 occurs. As a result, the distribution of the incident light from the disk 2 to the two-divided PD 9 fluctuates, the waveform of the tracking error signal 101 changes, and the control for following the information track becomes unstable.

A first problem that occurs when the center of the objective lens 8 is shifted is the offset of the tracking error signal 101. FIG. 19A shows the light beam of the reflected light and the light beam 2 when the optical axis of the objective lens 8 is shifted from the center position of the light beam.
It is a side view which shows the relationship of the position of division | segmentation PD9. When the objective lens 8 shifts from the position indicated by the solid line to the position indicated by the two-dot chain line and the center position A of the light beam shifts to the position B, the center of the light beam reflected from the optical disk 2 and entering the two-divided PD 9 becomes the distance x. Just shift. Accordingly, the quantity of incident light that enters the detection areas a and b of the two-divided PD 9 is smaller in the detection area a than in the detection area b, and an imbalance occurs between the two. The tracking error detection circuit 14 calculates the light amount difference between the detection areas a and b to obtain the tracking error signal 1.
01 is detected. Therefore, the detection area a of the two-divided PD 9
When an imbalance in light amount occurs between b and b, an offset occurs in the tracking error signal 101.

The second problem is that the tracking error signal 1
01 decrease in amplitude. In FIG. 19A, since the position of the objective lens 8 shifts, the light beam of the reflected light protrudes from the detection area of the two-divided PD 9 by a distance y, so that the total amount of incident light decreases. FIG. 19B shows the relationship between the displacement x of the objective lens 8 and the tracking error signal 101 output from the tracking error detection circuit 14 when the objective lens 8 crosses the information track 1. As the displacement distance x of the objective lens 8 increases, the offset of the center of amplitude increases, and the amplitude of the tracking error signal decreases.

FIG. 19 (c) shows the tracking control loop 201 when the objective lens 8 is displaced.
FIG. 7 is a diagram illustrating a change with time of a tracking error signal 101 when switching from an FF state to an ON state. A solid line indicates a case where the objective lens 8 is misaligned.
The case where no displacement occurs in the objective lens 8 is indicated by a two-dot chain line. The case where no displacement occurs in the objective lens 8 is the same as that in FIG.
When the tracking control loop 201 shown in FIG. 17 is OFF, the tracking error signal 101 is output in a sine wave form as shown by a two-dot chain line in FIG. However, as described above, if there is a positional shift of the objective lens 8, as shown by a solid line in FIG. As it occurs, the amplitude also decreases.

When the tracking control loop 201 is turned on, the amplitude of the tracking error signal 101 becomes substantially zero due to the operation of the control loop. However, since the center of the information track 1 corresponds to the position indicated by the one-dot chain line, if the amplitude of the tracking error signal 101 is controlled to be zero, the objective lens 8 is located at a position shifted from the center of the information track 1. Therefore, off-track (a shift between the objective lens 8 and the center of the track) occurs. Further, according to the amount of displacement of the position of the objective lens 8,
Since the amplitude of the tracking error signal 101 decreases,
Detection gain of tracking error detection circuit 14 (ratio of off-track amount to amplitude of tracking error signal 101)
Is reduced, the gain of one round of the tracking control loop 201 is also reduced, and the control performance is reduced. in this way,
When the position shift of the objective lens 8 occurs, both the offset correction and the amplitude correction of the tracking error signal are required.

The third problem is not only when the position of the objective lens 8 is displaced, but also because the optical axis of the objective lens 8 is not maintained perpendicular to the disk surface and tilts in the tangential direction of the track (tilt). However, there is a problem that the offset and the amplitude fluctuation occur in the tracking error signal 101 even when the error occurs. FIG. 20A is a side view showing the relationship between the light beam of the reflected light and the position of the two-part PD 9 when the optical disk 2 is inclined with respect to the optical axis of the optical pickup 4. As shown by the solid line, when the tilt angle is shifted from the state C where the optical axis is perpendicularly incident on the optical disk 2 to the state D indicated by the two-dot chain line, the light is reflected from the optical disk 2 and divided into two PDs 9.
Is shifted to the position shown by the two-dot chain line.
Therefore, the light amount of the detection areas a and b of the two-divided PD 9 is smaller in the detection area a than in the part b, and an imbalance occurs. Therefore, as shown in FIG. 20B, an offset occurs in the tracking error signal 101 output from the tracking error detection circuit 14, as in the case where the position of the objective lens 8 is displaced.
The amplitude decreases, off-track occurs, and control performance deteriorates. Therefore, it is necessary to correct the tracking error signal 101 using not only the information on the displacement of the objective lens 8 but also the information on the inclination angle with respect to the disk 2.

An object of the present invention is to solve the above first to third problems and greatly improve the stability of tracking control.

[0015]

An optical information recording / reproducing apparatus according to the present invention has a disk on which information is recorded along a track, an objective lens, and a light for irradiating a light spot on a recording surface of the disk. A pickup, a tracking error detecting means for detecting a displacement amount between the light spot and the information track recorded on the optical disc, and outputting a tracking error signal corresponding to the displacement amount, the optical pickup in a direction crossing the information track; Lens moving means for moving the objective lens, tracking control means including compensation calculating means for controlling the lens moving means in accordance with the tracking error signal, and light of the optical pickup based on the output of the compensation calculating means. Objective lens displacement to estimate the displacement of the optical axis of the objective lens from the center of the beam Determining means, offset detecting means for detecting an offset of the tracking error signal, storage means for storing the output of the offset detecting means and the output of the objective lens displacement estimating means in pairs, and the output of the objective lens displacement estimating means. And an offset correction unit for outputting an output of the offset detection unit corresponding to the above from the storage unit and correcting an offset of the tracking error signal.

From the output of the offset detecting means and the output of the objective lens displacement estimating means stored in pairs in the storing means,
The output of the offset detecting means corresponding to the output of the objective lens displacement estimating means is obtained. A tracking signal is obtained from the obtained output, and the offset of the tracking error signal is corrected. Thereby, the displacement of the objective lens of the optical pickup is corrected, and the light spot can be correctly positioned on the track of the disk.

According to another aspect of the present invention, there is provided an optical information recording / reproducing apparatus including: a disk on which information is recorded along a track; an optical pickup for irradiating a light spot on a recording surface of the disk; A tracking error detecting means for detecting a displacement amount between the light spot and the information track recorded on the optical disc and outputting a tracking error signal corresponding to the displacement amount, and an objective of the optical pickup in a direction crossing the information track. Lens moving means for moving a lens, tracking control means including compensation calculating means for controlling the lens moving means in accordance with the tracking error signal, and a light beam of the optical pickup based on an output of the compensation calculating means. Objective lens displacement estimating means for estimating the displacement of the optical axis of the objective lens from the center position, Amplitude detecting means for detecting the amplitude of the tracking error signal, storage means for storing the output of the amplitude detecting means and the output of the objective lens displacement estimating means in association with each other, and corresponding to the output of the objective lens displacement estimating means. An amplitude correction means for outputting an output of the amplitude detection means from the storage means and correcting an amplitude value of the tracking error signal.

The amplitude value of the tracking error signal corresponding to the output of the objective lens displacement estimating means is obtained from the output of the amplitude detecting means and the output of the objective lens displacement estimating means stored in correspondence with the storage means. The tracking error signal is corrected using the obtained amplitude value. Thereby, the displacement of the objective lens of the optical pickup is corrected, and the light spot can be correctly positioned on the track of the disk.

According to another aspect of the present invention, there is provided an optical information recording / reproducing apparatus comprising: a disk on which information is recorded along tracks, an objective lens, and an optical pickup for irradiating a light spot on a recording surface of the disk; A tracking error detecting means for detecting a displacement amount between the light spot and the information track recorded on the optical disc and outputting a tracking error signal corresponding to the displacement amount; an object of the optical pickup in a direction crossing the information track; Lens moving means for moving a lens, a tracking control loop for controlling the lens moving means in accordance with the tracking error signal, an object for estimating a deviation of an optical axis of the objective lens from a center position of a light beam of the optical pickup; Lens displacement estimating means, and the objective estimated by the objective lens displacement estimating means Characterized by comprising a tracking calibration control loop for controlling the lens moving means in response to the deviation amount of the optical axis of the lens.

In the tracking control loop, the lens moving means is controlled in accordance with the tracking error signal, and in the tracking calibration control loop, the lens moving means is controlled in accordance with the displacement of the optical axis of the objective lens. As a result, the tracking error is corrected, and the optical axis shift of the objective lens is corrected.

According to another aspect of the present invention, there is provided an optical information recording / reproducing apparatus comprising: a disk on which information is recorded along a track; an objective lens; A tracking error detecting means for detecting a displacement amount between the light spot and the information track recorded on the optical disc and outputting a tracking error signal corresponding to the displacement amount, and an objective of the optical pickup in a direction crossing the information track. Lens moving means for moving a lens, tracking control means for controlling the lens moving means in accordance with the tracking error signal, and objective lens displacement for detecting a deviation of an optical axis of the objective lens from a center position of a light beam of the optical pickup. Detecting means for detecting an offset of the tracking error signal Output means, tilt detection means for detecting the amount of tilt between the light beam of the optical pickup and the disk surface in the direction perpendicular to the information track, output of the offset detection means, output of the objective lens displacement detection means, and the tilt A storage unit for storing the output of the detection unit in association with the output of the objective lens shift detection unit and the output of the offset detection unit corresponding to the output of the inclination detection unit from the storage unit; It is characterized by comprising an offset correcting means for correcting an offset of a signal.

Based on the output of the offset detecting means, the output of the objective lens displacement detecting means and the output of the tilt detecting means, stored in the storage means, the output of the objective lens displacement detecting means and the output of the tilt detecting means are corresponded. The output of the offset detection means obtained is obtained. The obtained output tracking signal is obtained, and the offset of the tracking error signal is corrected.

An optical information recording / reproducing apparatus according to another aspect of the present invention has a disk on which information is recorded, an objective lens, an optical pickup for irradiating a light spot on a recording surface of the disk, and an optical pickup; Tracking error detecting means for detecting a positional deviation amount from an information track recorded on the optical disk and outputting a tracking error signal corresponding to the positional deviation amount, moving an objective lens of the optical pickup in a direction crossing the information track Lens moving means, tracking control means for controlling the lens moving means in accordance with the tracking error signal, objective lens displacement detecting means for detecting displacement of the optical axis of the objective lens from the center position of the light beam of the optical pickup, In the direction perpendicular to the information track between the light beam of the optical pickup and the disk surface Tilt detecting means for detecting the displacement, amplitude detecting means for detecting the amplitude of the tracking error signal, and storing the output of the amplitude detecting means, the output of the objective lens displacement detecting means, and the output of the inclination detecting means in association with each other. An output of the amplitude detecting means corresponding to an output of the objective lens displacement detecting means and an output of the inclination detecting means from the storing means; and an amplitude value of a tracking error signal of the tracking error detecting means. Is provided with amplitude correction means for correcting

The amplitude value of the tracking error signal corresponding to the output of the amplitude detecting means, the output of the lens displacement detecting means and the output of the inclination detecting means stored in the storage means is corrected.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described with reference to FIGS. << Embodiment 1 >> Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. Note that the same reference numerals are given to elements having the same configuration and function as those of the above-described conventional example, and description thereof will be omitted.

FIG. 1 is a block diagram showing the configuration of an optical information recording / reproducing apparatus according to this embodiment. In FIG.
An optical pickup 4, a tracking error detection circuit 14,
System control block 25 which will be described in detail later
A tracking control loop 201 includes a single loop control loop having the tracking drive circuit 16. The output terminal of the tracking error detection circuit 14 is connected to the input terminals of the system control block 25, the offset detection circuit 17 and the amplitude detection circuit 18, and is generated based on the difference between the outputs of the two PDs of the two-divided PD (photodetector) 9. Apply a tracking error signal. The offset detection circuit 17 detects a center value of the amplitude of the tracking error signal 101, and detects a difference between the center value and a predetermined reference value as an offset amount. The amplitude detection circuit 18 detects the amplitude value of the tracking error signal 101 when the objective lens 8 crosses the information track 1 of the disk 2.

The system control block 25 includes the tracking control circuit 15, the objective lens shift observer 1
9, a first storage circuit 20, a second storage circuit 21, an offset correction circuit 22, an amplitude correction circuit 23, a system controller 24, a switch 26, and a switch 27. In the system control block 25, the output terminal of the tracking error detection circuit 14 is connected to the input terminal of the offset correction circuit 22, and the output terminal of the offset correction circuit 22 is connected to the input terminal of the amplitude correction circuit 23. The output terminal of the amplitude correction circuit 23 is connected to the input terminal of the tracking control circuit 15. An output terminal of the tracking control circuit 15 is connected to an input terminal of the tracking drive circuit 16. The output terminal of the offset detection circuit 17 is connected to the input terminal of the first storage circuit 20, and the output terminal of the amplitude detection circuit 18 is connected to the input terminal of the second storage circuit 21. An output terminal of the offset detection circuit 17 and an output terminal of the first storage circuit 20 are connected to another input terminal of the offset correction circuit 22 via a switch 26 of a switching type.
The output terminal of the amplitude detection circuit 18 and the output terminal of the second storage circuit 21 are connected to the amplitude correction circuit 23 via the switch 27.
Is connected to the other input terminal.

The other pair of input / output terminals of the tracking control circuit 15 are connected to input / output terminals of the objective lens shift observer 19, respectively, to form a tracking calibration control loop 202 which will be described in detail later. The output end of the objective lens shift observer 19 is also connected to other input ends of the first and second storage circuits 20 and 21. Each circuit in the system control block 25 is connected to the system controller 24 and the system controller 2
4, a control signal is input, but connection lines are not shown for simplification of the drawing.

The main points of the first embodiment of the present invention are as follows. (1) As described in detail later, in the calibration mode, instead of the normal tracking control loop 201,
The tracking calibration control loop 202 is operated. (2) In the tracking calibration control loop 202, the operation of the optical pickup 4 is simulated by the objective lens shift observer 19, and the position shift amount of the objective lens 8 is estimated. (3) At the same time, the offset amount and the amplitude value of the tracking error signal 101 are learned by the offset detection circuit 17 and the amplitude detection circuit 18. (4) Based on the learned detection result, the tracking error signal is corrected with the offset amount and the amplitude value corresponding to the estimated displacement of the objective lens 8 in the normal mode described later.

The objective lens shift observer 19 estimates the amount of shift of the center of the objective lens 8 from the center of the light beam based on the tracking calibration signal 104 output from the tracking control circuit 15. First storage circuit 20
Is a memory circuit for storing the objective lens shift amount 105 estimated by the objective lens shift observer 19 and the offset amount of the tracking error signal 101 detected by the offset detection circuit 17 in pairs. Second
The storage circuit 21 stores the objective lens displacement amount 105 estimated by the objective lens displacement observer 19 and the amplitude detection circuit 1.
8 is a memory circuit for storing the amplitude value of the tracking error signal 101 detected by the counter 8 in pairs. Each of the storage circuits 20 and 21 is constituted by a digital circuit (not shown) or a memory in the system controller 24. When storing, the analog value is converted into a digital value by the digital circuit or an A / D converter built in the system controller 24.

The switch 26 is connected to the system controller 2
4 is a switch means for switching the input of the offset correction circuit 22 to the offset amount detected by the offset detection circuit 17 or the offset amount output from the first storage circuit 20 in response to a command from the control unit 4. The switch 27 converts the input signal of the amplitude correction circuit 23 into an amplitude detection circuit 18 in response to a command from the system controller 24.
Switch means for switching to the amplitude amount detected by the above or the amplitude amount output from the second storage circuit 21. Each of the switches 26 and 27 is a digital circuit having a hold function for storing the immediately preceding output value and continuously outputting the same value, and is controlled by software in the system controller 24.

The offset correction circuit 22 is provided with a switch 26 from the first storage circuit 20 or the offset detection circuit 17.
Is added to or subtracted from the tracking error signal 101 to correct the offset amount. The amplitude correction circuit 23 corrects the amplitude of the offset-corrected tracking error signal output from the offset correction circuit 22 using the amplitude value read from the second storage circuit 21 or the amplitude detection circuit 18 via the switch 27. And outputs a corrected tracking error signal 102. The tracking control circuit 15 outputs the corrected tracking error signal 10
2 or outputs a tracking drive signal 103 to the tracking drive circuit 16 based on the objective lens displacement amount 105 estimated by the objective lens displacement observer 19. The system controller 24 is an arithmetic circuit, and a system control block 25 according to the operation mode of the optical information recording / reproducing apparatus of the present embodiment which is input from the outside.
And a CPU for controlling the operation state of each circuit and performing arithmetic processing.

Embodiment 1 of the present invention configured as described above
The operation of the optical information recording / reproducing apparatus described above will be described for each of the calibration mode, the normal mode, and the initialization mode in the operation of tracking error signal correction. The calibration mode is a mode in which the offset correction amount and the amplitude correction amount are learned in advance. The normal mode is a mode in which the tracking control loop 201 is corrected based on a result learned in the calibration mode. What is initialization mode?
Before shifting to the normal mode, the tracking control loop 20
This is a mode for initializing the control signal in 1.

First, the calibration mode will be described. FIG.
(A) is a flowchart showing the operation in the calibration mode in the present embodiment. Normally, the calibration mode is executed when the apparatus is first started up and when the disk is changed. When shifting to the calibration mode, the tracking control loop 201 is turned off (stopping the operation of the tracking control loop 201), and the tracking calibration control loop 202 is turned on (the tracking calibration control loop 202).
Is operated) (step S1). And
The memory addresses of the first storage circuit 20 and the second storage circuit 21 are initialized. In this initialization, for example, the memory address is set to N
(N is an integer of 0 or more) (step S2). Next, the initial position of the objective lens 8 is set. This initial position is, for example, one end of the movable range of the objective lens 8. A tracking drive signal 103 is output from the tracking control circuit 15 to the tracking drive circuit 16,
The tracking actuator 10 is driven to move the objective lens 8 to the initial position (Step S3). At this time, the objective lens displacement amount 105 estimated by the objective lens displacement observer 19 and the offset amount detected by the offset detection circuit 17 are stored in the first storage circuit 20. The objective lens displacement amount 105 estimated by the objective lens displacement observer 19 and the amplitude detection circuit 18
Is stored in the second storage circuit 21 (step S4). First and second storage circuits 20,
+2 is added to each of the memory addresses 21 (step S5). Then, it is determined whether or not the displacement of the objective lens 8 has reached from one end to the other end (step S6). If the position of the objective lens 8 has not reached from one end to the other end, the position of the objective lens 8 is moved by ΔL (step S
7) Return to step S4 and repeat the same processing.
If the position of the objective lens 8 has reached from one end to the other end, the calibration mode ends. By performing the processing as described above, the tracking error signal 101 for a certain objective lens shift amount is stored in the first storage circuit 20 and the second storage circuit 21 as shown in FIGS. 2B and 2C. Can be recorded respectively.

Next, the normal mode will be described. FIG.
(A) is a flowchart showing the operation in the normal mode in the present embodiment. The normal mode is performed after execution of a standby mode described later, and the tracking control loop 20 is executed.
1 is ON. In the normal mode, first, the objective lens shift amount 105 is set by the objective lens shift observer 19.
Is estimated and stored in the first and second storage circuits 20 and 21 (step S11). Next, the memory addresses of the first storage circuit 20 and the second storage circuit 21 that record the estimated objective lens shift amount 105 are calculated (step S1).
2). The hold of the switches 26 and 27 is released, and the switches are switched to the storage circuit side, that is, to the Q1 and Q2 sides (step S13). First and second storage circuits 2
The offset amount and the amplitude value are read from 0 and 21, respectively (step S14). Then, the value of the corrected tracking error signal 102 is made equal to the tracking error signal 101 when the displacement amount of the objective lens 8 is zero,
The offset addition amount and the amplitude gain are calculated by the system controller 24 (step S15). The offset addition amount thus obtained is added by the offset correction circuit 22, and the amplitude gain is multiplied by the amplitude correction circuit 23, thereby correcting the tracking error signal (Step S).
16). The tracking control loop 201 sends a signal from the tracking control circuit 15 to the tracking drive circuit 16 so that the corrected tracking error signal 102 becomes zero.
To output a drive command. The tracking drive circuit 16 supplies a current to the coil 11 to generate an electromagnetic force to move the objective lens 8.

FIG. 3B shows the relationship between the tracking error signal 101 and the corrected tracking error signal 102 when the tracking control loop 201 is switched from OFF to ON when the objective lens is displaced in this embodiment. FIG. 6 is a waveform diagram showing a change with time. As shown in FIG. 3B, the tracking control loop 20
When 1 is OFF, the tracking error signal 101 is output as a sine wave. Since the operation of the tracking control circuit 15 is stopped, the values of the tracking drive signal 103 and the tracking calibration signal 104 are undefined. The objective lens displacement amount 105 estimated by the objective lens displacement observer 19 is also undefined. Therefore, the offset correction circuit 22 and the amplitude correction circuit 2
3, the correction tracking error signal 102 becomes equal to the tracking error signal 101. As indicated by the two-dot chain line, the center value of the amplitude of the signal increases from the zero level, causing an offset with respect to the center position of the information track. ON of the tracking control loop 201
At the same time, when the mode shifts to the normal mode, the control loop becomes transiently unstable due to the offset of the correction tracking error signal 201, and a problem occurs that recording and reproduction cannot be performed until the control loop becomes stable. In order to solve this, when switching the tracking control loop 201 from ON to OFF, processing in the initialization mode is executed. Hereinafter, the initialization mode will be described.

FIG. 4A is a flowchart showing the operation in the initialization mode in this embodiment. In the initialization mode, the switch 26 is switched to the output side (P1) of the offset detection circuit 17, and the switch 27
Is switched to the output side (P2) of the amplitude detection circuit 18 (step S21). The offset correction circuit 22 outputs the tracking error signal 1 output from the offset detection circuit 17.
01 is detected. The amplitude correction circuit 23
The amplitude value of the output of the amplitude detection circuit 18 is detected (Step S22). Then, the system controller 24 calculates the offset addition amount and the amplitude gain so that the value of the corrected tracking error signal 102 becomes equal to the tracking error signal 101 when the objective lens displacement amount is zero (step S23). The offset addition amount thus obtained is added by the offset correction circuit 22 and the amplitude gain is multiplied by the amplitude correction circuit 23 to correct the tracking error signal (step S24).

Next, the tracking control loop 201 is
N, the tracking control is started so that the corrected tracking error signal 102 becomes zero (step S).
25). However, when the tracking control loop 201 is ON, the tracking error signal 101 is controlled to be zero, and it is difficult to detect the offset amount and the amplitude value. Therefore, the tracking control loop is turned ON.
At the same time, the switches 26 and 27 are held (step S26) to prevent the tracking control loop 201 from malfunctioning due to erroneous detection of the offset amount and the amplitude value. After a predetermined time has elapsed (step S27), the system controller 24 switches the operation mode to the normal mode (step S28). That is, switch 2
6. Release the hold of the switch 27, switch to the respective storage circuits 20 and 21, and correct the offset based on the objective lens shift amount 105 detected by the objective lens shift observer 19.

FIG. 4B shows a tracking error signal 101 and a corrected tracking error signal 102 when the tracking control loop 201 is switched from OFF to ON in a state where the position of the objective lens 8 is displaced.
FIG. 7 is a diagram showing a temporal change of the sigma. The waveform indicated by the two-dot chain line is an output signal from the offset correction circuit 22. As shown in FIG. 4B, in the standby mode and in a state where the tracking control loop 201 is OFF, the tracking error signal 101 is output in a sinusoidal waveform. Offset detection circuit 17 and amplitude detection circuit 18
Detects the center value and amplitude of the sinusoidal tracking error signal as an offset amount and an amplitude value, respectively. The tracking error signal 101 is corrected according to the offset amount and the amplitude value thus detected. The tracking error signal 102 corrected by the offset correction circuit 22 can make the center value of the signal, that is, the center position of the information track coincide with the zero level, as shown by the two-dot chain line in FIG. Further, the amplitude of the correction tracking error signal 102 output from the amplitude correction circuit 23 can be made equal to that in the case where no displacement of the objective lens 8 occurs. That is, by controlling the correction tracking error signal 102 to be zero, the objective lens 8 can follow the center of the information track 1.

In the normal mode, the offset amount and the change in the amplitude value of the tracking error signal 101 are corrected in accordance with the positional shift of the objective lens 8 so as to obtain the signal shown in FIG.
As shown by the solid line (b), the zero level of the corrected tracking error signal 102 can be matched with the center position of the information track. Further, the detection gain of the tracking error signal for determining the amplitude value can be made equal to the case where no objective lens shift occurs. That is, even if the positional shift of the objective lens 8 occurs, the tracking control performance equivalent to the state where the positional shift is zero can be obtained.

Next, detailed operations of the tracking control circuit 15 and the objective lens shift observer 19 will be described. FIG. 5 shows a tracking control circuit 15 according to this embodiment.
FIG. 3 is a block diagram showing a specific configuration of the objective lens shift observer 19; As shown in FIG. 5, the tracking control circuit 15 includes an A / D converter 501 and a switch 50.
2. It is composed of an integral operation circuit 503, a proportional operation circuit 504, a differential operation circuit 505, a D / A converter 506, and a lens displacement setting circuit 513.

The correction tracking error signal is input to one switching contact P3 of the switch 502, and the output of the adder 525 is input to the other switching contact Q3. Switch 50
The two common contacts are connected to the input terminal of the A / D converter 501. The output terminal of the A / D converter 501 is connected to each input terminal of the integral operation circuit 503, the proportional operation circuit 504, and the differential operation circuit 505. Output terminals of the integration operation circuit 503 and the proportional operation circuit 504 are connected to two input terminals of an adder 526, and output terminals of the adder 526 are connected to input terminals of the adder 527 and the objective lens shift observer 19, respectively. I have. An output terminal of the differential operation circuit 505 is connected to another input terminal of the adder 527, and an output terminal of the adder 527 is connected to an input terminal of the D / A converter 506. D / A converter 5
The tracking drive signal 103 is output from the output terminal 06. An output terminal of the objective lens shift observer 19 and an output terminal of the lens displacement setting circuit 513 are connected to two input terminals of the adder 525, respectively.

The integration operation circuit 503 includes a multiplier 507 for gain GA, a multiplier 508 for gain GB, and a delay circuit 50.
9. The proportional operation circuit 504 has a multiplier 510 for gain GC. The differential operation circuit 505 has a multiplier 511 for gain GD and a delay circuit 512. The objective lens shift observer 19 includes an equivalent filter 514 having a gain GE multiplier 516, a gain GF multiplier 517, a gain GG multiplier 518, and delay circuits 519 and 520.

Next, a detailed operation of the tracking control circuit 15 will be described with reference to FIG. 5 for each of the above-described tracking error signal correction operation modes, such as the initialization mode, the normal mode, the calibration mode, and the standby mode. First, operations in the initialization mode and the normal mode will be described.
In the initialization mode, the tracking control loop 201
Is OFF, the tracking control circuit 15 is in an operation stop state. In the standby mode, when the tracking control loop 201 is ON, and in the normal mode, the switch 502 is switched to the switching contact P3, the correction tracking error signal 102 is input to the A / D converter 501, and the analog signal is converted to the digital signal. Convert to
The digital correction tracking error signal 102 is input to the integration operation circuit 503, the proportional operation circuit 504, and the differentiation operation circuit 505.

Integral operation circuit 503, proportional operation circuit 504
And each multiplier 50 provided in the differential operation circuit 505
7, 508, 510, and 511 gains GA,
The values of GB, GC and GD are the values of the system controller 2 shown in FIG.
4 is set. Multipliers 507, 508, 510,
511 and the adders / subtracters 528, 529, and 530 operate at a predetermined sampling period T. Delay circuits 509, 51
2 delays the input digital signal by a period T and outputs it. The gains GA, GB, GC, and GD are set to predetermined values, and the integral operation circuit 503 and the proportional operation circuit 5 are set.
By adding the output of the differential operation circuit 505 and the output of the differential operation circuit 505, a function as a compensation filter for securing a low-frequency gain and a phase margin of the control system can be realized.

FIG. 6 shows the frequency transfer characteristic of this compensation filter.
Shown in 6A shows the gain characteristics of the phase compensation filter, and FIG. 6B shows the phase characteristics of the phase compensation filter.
In both (a) and (b) of FIG. 6, the abscissa indicates the frequency in logarithm, the gain indicates the dB value, and the phase indicates the degree. The gain crossing point (frequency at which the gain becomes zero) of the tracking control system is generally about 1 kHz, and has a characteristic that the phase advances near 1 kHz. The output of the compensation filter is input to the D / A converter 506, converted into an analog signal, and output as the tracking drive signal 103.

Next, the operation in the calibration mode will be described with reference to FIG. In calibration mode, switch 50
2 switches to the switching contact Q3, differently from the initialization mode and the normal mode. As a result, a difference signal between the signal indicating the amount of displacement of the objective lens estimated by the objective lens displacement observer 19 and the signal of the lens displacement setting circuit is input to the A / D converter 501 via the switch 503. The output of the A / D converter 501 is input to an integral operation circuit 503, a proportional operation circuit 504, and a differentiation operation circuit 505 that constitute a compensation filter. With this configuration, FIG.
A signal indicating the amount of displacement of the position of the objective lens 8 set in steps S3 and S7 of the flowchart of FIG. Become.

Next, the detailed operation of the objective lens shift observer 19 will be described with reference to FIG. 5 for each of the above-described tracking error signal correction operation modes. First, operations in the initialization mode and the normal mode will be described.
In the initialization mode, the tracking control loop 201
Is OFF, the operation of the objective lens shift observer 19 is stopped. Otherwise, the equivalent filter 5
The values of the gains GE, GF, and GG of the multipliers 516, 517, and 518 provided in 14 are set by the system controller 24 in FIG. Multipliers 516, 51
7, 518 and the adder / subtracters 531 and 532 in the figure operate at the sampling period T, and the delay circuits 519 and 520 delay the input digital signal by the period T and output it.

In the optical pickup 4 shown in FIG. 1, the coil 11 to which the objective lens 8 is attached is bonded to one end of a spring 12, and the other end of the spring 12 is bonded to a magnet 13. Since the bonding portion of both roots of the spring 12 has viscosity, the frequency transmission characteristic G (s) of the displacement of the objective lens 8 with respect to the tracking drive signal 103 becomes a secondary system as shown in Expression (1).

G (s) = GH × Kt / (m × s ² + D × s + Ke) (1)

In the equation (1), GH is the gain of the tracking drive circuit 16 in FIG. 1, Kt is the propulsion force constant, m is the weight of the movable part including the objective lens 8 and the coil 11, D is the viscosity coefficient, and Ke is the spring. Indicates a constant. Hereinafter, the frequency transfer characteristic G (s) of the displacement of the objective lens 8 with respect to the drive command to the tracking actuator 10 is referred to as the transfer characteristic of the optical pickup.

A multiplier 516 inside the equivalent filter 514,
By setting the gains GE, GF, and GG of 517 and 518 to predetermined values, it is possible to make the frequency transfer characteristic of the equivalent filter 514 equal to the frequency transfer characteristic represented by the equation (1). For example, the transfer characteristics can be approximated by calculating the values of the gains GE, GF, and GG using the three relational expressions shown in Expression (2).

[0053]

(Equation 1)

In equation (2), each coefficient GH, Kt,
m, D, and Ke are the same as in Expression (1), and substitute the same coefficient values as in Expression (1). T indicates a sampling cycle. The three relational expressions of Expression (2) are one of conversion formulas for obtaining a digital filter having substantially equal frequency transfer characteristics from the transfer characteristic expression expressed in an analog form. Obtained by linear transformation. (Reference: "Digital Signal Processing and Control" by Hideki Kimura, Shokodo Shuppan)

S = (1−z ⁻¹ ) / T (3)

By substituting equation (3) into equation (1), equation (4) is obtained.

Gt (z) = GH × Kt / ｛(m / T ² ) × z ⁻² + (2 × m / T ² + D / T) × z ⁻¹ + m / T ² + D / T + Ke｝ ・ ・ ・ (4)

In equation (4), each coefficient GH, Kt,
The same coefficient values as in equation (1) are substituted for m, D, and Ke. From this equation (4), the equivalent filter 514 shown in FIG.
Are represented.

FIGS. 7A and 7B are diagrams showing the transfer characteristics of the equivalent filter 514 and the transfer characteristics of the optical pickup. FIG. 7A shows a gain characteristic,
(B) shows phase characteristics. The horizontal axis shows the frequency in logarithm. The gain is shown in dB value. 7A and 7B, the solid line indicates the transfer characteristic of the optical pickup, and the dotted line indicates the transfer characteristic of the equivalent filter 514. As shown in FIGS. 7A and 7B, at low frequencies, the transfer characteristics of the optical pickup 4 and the equivalent filter 514 are obtained.
Is almost equal in both gain and phase. However, since the equivalent filter 517 is a digital filter that operates at a constant sampling time T, aliasing occurs near the sampling frequency (1 / T), causing a difference in transfer characteristics. Therefore, an addition signal of the outputs of the proportional operation circuit 504 and the integration operation circuit 503 of the tracking control circuit 15 is input to the equivalent filter 517. Then, the transfer characteristics of the optical pickup 4 (that is, the ratio between the command value input to the optical pickup 4 and the displacement amount of the optical pickup (objective lens)) and the transfer characteristics of the objective lens shift observer 19 (that is, the transfer characteristic to the objective lens shift observer 19). The objective lens shift observer 19 is set so that the ratio between the input signal and the output signal) becomes substantially equal. When a signal substantially the same as the input signal to the optical pickup 4 is input to the objective lens shift observer 19, the output of the objective lens shift observer 19 becomes
It becomes almost equal to the displacement of the optical pickup (objective lens). As a result, the objective lens shift amount is estimated using only the signal components from which the high frequency components included in the tracking drive signal 103 have been removed. Generally, the sampling frequency (1
/ T) is sufficiently higher than the rotation frequency of the disk 2,
According to the configuration of the present embodiment, it is possible to almost completely estimate the displacement of the objective lens due to the eccentricity of the disk 2.

In this embodiment, the transfer characteristic of the optical pickup 4 is represented by a second-order transfer function equation, and the characteristic of the equivalent filter 514 is obtained by bilinear transformation. However, the order of the transfer characteristics of the optical pickup 4 and the method of converting it into a digital filter are not limited to those of the present embodiment.
By setting the order to the third order or higher and using a conversion method with higher approximation accuracy, the estimation accuracy of the objective lens shift can be further improved. Further, in the present embodiment, the displacement of the objective lens is estimated using the equivalent filter 514, but the same effect can be obtained by using a position sensor that optically detects the position of the objective lens 8. Further, the tracking drive signal 10 of the input signal to the objective lens shift observer 19
3 is a proportional operation circuit 50 in the tracking control circuit 15
4 and the sum signal of the integration operation circuit 503 are used. Since the output of the integration operation circuit 503 includes the objective lens deviation amount, the objective lens deviation amount can be estimated only by the output of the integration operation circuit 503, and the same effect can be obtained.

In the first embodiment, the equivalent filter 514
Is used to estimate the amount of displacement of the objective lens based on the tracking calibration signal 104 which is an internal signal of the tracking control circuit 15. FIGS. 8A and 8B are diagrams showing transmission characteristics of the optical pickup 4 when the temperature near the tracking actuator 10 changes. FIG. 8A shows a gain characteristic by a dB value, and FIG. 8B shows a phase characteristic. In each of FIGS. 8A and 8B, the horizontal axis represents the frequency in logarithm. As shown in FIGS. 8A and 8B, when the temperature near the tracking actuator 10 changes, the DC gain at the primary resonance frequency changes. The primary resonance frequency is a frequency at a resonance point determined by the weight m of the movable portion including the objective lens 8 and the coil 11, the viscosity coefficient D, and the spring constant Ke, and the center frequency is calculated by Expression (5). The gain at the primary resonance frequency is calculated by equation (6). The gain (DC gain) when the drive signal has only a DC component is calculated by Expression (7).

[0062]

(Equation 2)

[0063]

(Equation 3)

GH × Kt / Ke (7)

In equations (5) to (7), GH indicates the gain of the tracking drive circuit 16, and Kt indicates the propulsion constant. m indicates the weight of the movable portion including the objective lens 8 and the coil 11, D indicates the viscosity coefficient, and Ke indicates the spring constant. When the temperature around the tracking actuator 10 changes, mainly the characteristics of the spring 12 constituting the tracking actuator 10 and the bonding portion between both ends of the spring change. That is, the spring constant Ke and the viscosity coefficient D in Equations (5) to (7) change, and the frequency transfer characteristics of the optical pickup change. If this fluctuation causes a difference between the frequency transfer function of the equivalent filter 514 calculated according to the equation (2) and an error occurs in estimating the amount of displacement of the objective lens, the control system becomes unstable.

Embodiment 2 An optical information recording / reproducing apparatus according to Embodiment 2 of the present invention will be described with reference to FIGS.
Elements having the same configuration and function as those of the first embodiment are denoted by the same reference numerals, and redundant description is omitted. The main points of the second embodiment are as follows. (1) In the learning mode described later, the tracking learning control loop 203 is operated instead of the normal tracking control loop 201. (2) In the tracking learning control loop 203, the frequency transfer characteristic of the optical pickup is learned by the optical pickup transfer characteristic detecting circuit 31, and the gain of each multiplier inside the equivalent filter 514 is calculated. (3) Based on the learning result, the frequency transfer characteristic of the equivalent filter 514 is corrected in a correction mode described later.

FIG. 9 is a block diagram showing the configuration of the optical information reproducing apparatus according to the second embodiment. In FIG. 9, a tracking learning control loop 203 is constituted by a single loop of the optical pickup 4, the tracking error detection circuit 14, the optical pickup transfer characteristic detection circuit 31, the switch 30, and the tracking drive circuit 16. A temperature detection sensor 28 serving as a temperature detection unit detects a temperature in the vicinity of the tracking actuator 10 of the optical pickup 4 and outputs actuator temperature data 107.

The switch 30 is connected to the system controller 2
4 is a switch means for switching the drive signal to the tracking drive circuit 16 to the tracking drive signal 103 or the tracking learning signal 106 output from the optical pickup transfer characteristic detection circuit 31 in response to the command from the control unit 4. The system control block 29 includes the tracking control circuit 15, the objective lens shift observer 19, the first
Storage circuit 20, second storage circuit 21, offset correction circuit 22, amplitude correction circuit 23, system controller 2
4. An optical pickup transfer characteristic detection circuit 31, a third storage circuit 32, and a transfer characteristic correction circuit 33. Each circuit in the system control block 29 is connected to the system controller 24, and a control signal is input from the system controller 24, but connection lines are not shown for simplification of the drawing.

The optical pickup transfer characteristic detecting circuit 31
A tracking learning signal 106 is output to the tracking drive circuit 16 via the switch 30. Based on the tracking error signal 101 at that time, the optical pickup transfer characteristic detecting circuit 31 detects the optical pickup transfer characteristic,
This is an arithmetic circuit that calculates the values of the gains GE, GF, and GG of the multipliers 517 and 518 of the equivalent filter 514 inside the objective lens shift observer 19 shown in FIG.
The third storage circuit 32 pairs the temperature near the tracking actuator 10 detected by the temperature detection sensor 28 with the values of the gains GE, GF, and GG of the multipliers calculated by the optical pickup transfer characteristic detection circuit 31. It is composed of a memory circuit for storing. The third storage circuit 32 is a digital circuit or the system controller 24.
The analog amount is converted into a digital value by an A / D converter built in the system controller 24 when the analog value is stored. The transfer characteristic correction circuit 33 is configured to read the values of the gains GE, GF, and GG of the multiplier from the third storage circuit 32 and set the read gain to the multiplier inside the equivalent filter 514.

FIG. 10 shows an optical pickup transfer characteristic detecting circuit 31 and an objective lens shift observer 1 according to the second embodiment.
9 is a block diagram illustrating an example of a specific circuit configuration of FIG. As shown in FIG. 10, the objective lens shift observer 1
9 has an equivalent filter 514. The equivalent filter 514 has a gain GE multiplier 516, a gain GF multiplier 517, a gain GG multiplier 518, and delay circuits 519 and 520. Note that the values of the gains GE, GF, and GG of each multiplier can be changed by the transfer characteristic correction circuit 33. Multiplier 518 and adder / subtractor 53
1 and 532 operate at a predetermined sampling period T, and the delay circuits 519 and 520 delay the input digital signal by the period T and output it.

The optical pickup transfer characteristic detecting circuit 31
A disturbance frequency setting circuit 34, a disturbance amplitude setting circuit 35, a learning disturbance signal generator 36, an objective lens displacement detection circuit 37, a gain calculation circuit 38, a fourth storage circuit 39, and a transfer characteristic calculation circuit 40 are provided. Learning disturbance signal generator 36
Is a signal generator that outputs a sine-wave tracking learning signal 106, the frequency of which is set to the disturbance frequency setting circuit 3.
4 and the amplitude is set by the disturbance amplitude setting circuit 35. The objective lens displacement detection circuit 37 is configured by a digital circuit or the like for counting the number of tracks traversed by the objective lens 8 based on the tracking error signal 101.

The gain calculating circuit 38 is constituted by an arithmetic circuit for calculating the transmission gain of the optical pickup 4 based on the moving distance of the objective lens 8 detected by the objective lens displacement detecting circuit 36 and the value of the tracking learning signal 106. I have. The fourth storage circuit 39 is configured by a memory circuit or the like that stores the transmission gain of the optical pickup calculated by the gain calculation circuit 38 and the frequency of the tracking learning signal 106 as a pair. Note that the fourth storage circuit 3
Reference numeral 9 denotes a digital circuit or a memory in the system controller 24. When storing, the analog amount is converted into a digital value by an A / D converter built in the system controller 24. The transfer characteristic calculation circuit 40 determines the respective ones of the multipliers 516, 517, 518 of the equivalent filter 514 inside the objective lens shift observer 19 based on the relationship between the gain and the frequency of the optical pickup 4 stored in the fourth storage circuit 39. An arithmetic circuit such as a CPU for calculating the values of the gains GE, GF, and GG is provided.

Embodiment 2 of the present invention configured as described above
The operation of the optical information recording / reproducing apparatus described above will be described for each operation mode of the frequency transfer characteristic correction of the objective lens shift observer 19, that is, each of the learning mode and the correction mode. Hereinafter, the operation of each circuit in the system control block 29 of the present embodiment shown in FIG. 9 will be described for each operation mode with reference to FIG.

First, the learning mode will be described. FIG.
1 is a flowchart showing the operation of each circuit included in the system control block 29 and the switch 30 in the learning mode in the present embodiment. When shifting to the learning mode, the tracking control loop 201 is turned off,
The tracking learning control loop 203 is turned ON, that is, the switch 30 is switched to the P4 side, and the tracking drive circuit 16 is connected to the output terminal of the optical pickup transfer characteristic detection circuit 31 (step S41). Next, the memory address of the third storage circuit 39 is initialized. This initialization is performed, for example, by setting the memory address to N (N is an integer of 0 or more) (step S42). Disturbance frequency setting circuit 34
Is set to an initial value, and a predetermined amplitude value is set in the disturbance amplitude setting circuit 35. The tracking signal 106 having a sinusoidal waveform is output from the disturbance signal generator 36 (step S4).
3). The initial value of the frequency of the tracking learning signal 106 is, for example, 1/10 of the primary resonance frequency of the transfer characteristic of the optical pickup when the temperature near the tracking actuator 10 is 40 ° C. The amplitude is a value that displaces the objective lens 8 by の of its movable range.

The tracking learning signal 106 drives the tracking actuator 10 via the switch 30 and the tracking drive circuit 16 to displace the objective lens 8 at the same frequency as the tracking learning signal 106. The objective lens displacement detection circuit 37 counts the amount of displacement of the objective lens 8 as the number of zero-cross points of the tracking error signal 101, that is, the number of tracks that the objective lens 8 has traversed. (Step S44).

Next, the gain calculation circuit 38 divides the movement amount detected by the objective lens displacement detection circuit 37 by the amplitude of the tracking learning signal 106, that is, the amplitude set by the disturbance amplitude setting circuit 35, thereby obtaining the gain of the optical pickup 8. Is obtained (step S45). The gain value and the frequency of the tracking learning signal 106, that is, the set frequency of the disturbance frequency setting circuit 34 are stored in the fourth storage circuit 39 in pairs (step S46). Then, it is determined whether or not the set value of the frequency indicated by the disturbance frequency setting circuit 34 has reached a predetermined frequency. This frequency is, for example, ten times the primary resonance frequency of the transfer characteristic of the optical pickup 4 when the temperature near the tracking actuator 10 is 40 ° C. (Step S47). If not, the frequency of the disturbance frequency setting circuit 34 is set higher by Δf (step S48), and the memory address is set to N + 2 (step S4).
9) Return to step S44 and repeat the same processing. If it has reached, as shown in FIG. 11B, the value of the gain of the optical pickup 4 with respect to the frequency is recorded in the fourth storage circuit 39 as a pair. Then, the maximum value of the gain and the frequency at that time are obtained as the primary resonance gain by the transfer characteristic calculation circuit 40, and the spring constant Ke and the viscosity coefficient D are obtained according to the relationship between the expressions (5) and (6) (step S49). However, since the values of variables other than the spring constant Ke and the viscosity coefficient D in the equations (5) and (6) do not change with temperature, the same coefficient values as in the equation (1) are used.

The thus obtained spring constant Ke and viscosity coefficient D
, The multipliers 516, 5 5 inside the equivalent filter 514.
The respective gains GE, GF, and GG of 17, 518 are calculated according to equation (2) (step S50). However,
The same coefficient values as in equation (1) are substituted for the coefficients GH, Kt, and m other than Ke and D. Then, the values of the gains GE, GF, and GG and the actuator temperature data 107 detected by the temperature detection sensor 28 are stored in the third storage circuit 32 (step S51).

A series of processing from step S41 to step S51 is repeated while changing the temperature around the tracking actuator 10 from, for example, 20 ° C. to 60 ° C. in steps of 1 ° C. The obtained data is stored in the third storage circuit 32
1 is sequentially added from the memory address N of FIG.
As shown in FIG. 1C, the values of the gains GE, GF, and GG of the multipliers inside the equivalent filter 514 at a certain temperature can be recorded in the third storage circuit 32 as a pair. In the learning mode, the operations of the equivalent filter correction circuit 33 and the objective lens shift observer 19 are stopped.

Next, the correction mode will be described. FIG.
2 is a flowchart showing the operation of each circuit included in the system control block 29 in the correction mode in this embodiment. When the mode shifts to the correction mode, the tracking control loop 201 is turned on and the tracking learning control loop 203 is turned off in FIG. That is, the switch 30 is switched to Q4, and the output terminal of the tracking drive circuit 15 is connected to the input terminal of the tracking control circuit 15. And an optical pickup transfer characteristic detecting circuit 3
1 is stopped (step S61). Next, the tracking actuator 10 is detected by the temperature detection sensor 28.
The third storage circuit 32 that detects the temperature in the vicinity (step S62) and stores the actuator temperature data 107
Is obtained (step S63). The values of the gains GE, GF, and GG stored in pairs with the actuator temperature data 107 are read from the third storage circuit 32 (step S64). Equivalent filter characteristic correction circuit 33
, The multipliers 516 and 51 in the equivalent filter 514
The values of the gains GE, GF, and GG of 7, 518 are updated (step S65). Then, the operation of the objective lens shift observer 19 is started.

In this way, the frequency transfer characteristics of the optical pickup 4 with respect to the temperature in the vicinity of the tracking actuator 10 are learned in advance, and the multipliers 516, 517, and 5 inside the equivalent filter 514 corresponding to the temperature change.
18 is optimally switched. Thus, even if the transfer characteristics of the optical pickup 4 fluctuate with temperature, the frequency transfer characteristics of the equivalent filter 514 can be made equal to the transfer characteristics of the optical pickup 4. As a result, it is possible to suppress the deterioration of the estimation accuracy of the objective lens shift observer 19 and to stably correct the tracking error signal. further,
By executing the learning mode at the time of start-up or every time the disk is replaced, the frequency transfer characteristic of the equivalent filter 514 can be changed not only due to temperature fluctuations but also with time-dependent changes and individual differences in the transfer characteristics of the optical pickup 4. Pickup 4
Transfer characteristics can be matched. As a result, it is possible to suppress deterioration in estimation accuracy and achieve stable tracking control performance.

Third Embodiment A third embodiment of the present invention will be described below with reference to FIGS. In addition,
Elements having the same configurations and functions as those in the first embodiment of the present invention are given the same reference numerals, and descriptions thereof will be omitted. FIG. 13 is a block diagram showing the configuration of the optical information recording / reproducing apparatus in the present embodiment. In FIG. 13, the tilt sensor 44 is
The sensor detects the tilt of the disk 2, and detects a tilt angle 108 indicating the tilt between the light beam and the surface of the disk 2 in a direction perpendicular to the information tracks. The tilt sensor 44 irradiates, for example, the light of a semiconductor laser onto the surface of the disk 2 at a predetermined angle, and detects the reflected light with a two-part PD. When the surface of the disk 2 is tilted, the input of the two-divided PD changes, so that the tilt can be detected. The angle of the optical pickup 4 with respect to the disk surface can be set to an arbitrary value by a tilt actuator (not shown), which is a device for tilting the optical pickup 4. The system control block 41 includes a tracking control circuit 15, an objective lens shift observer 19, a fifth storage circuit 42, a fourth storage circuit 41, an offset correction circuit 22, an amplitude correction circuit 23, and a system controller 24. Each circuit in the system control block 41 is connected to the system controller 25, and a control signal is input from the system controller 25, but connection lines are not shown for simplification of the drawing.

The fifth storage circuit 42 stores the objective lens displacement amount 105 estimated by the objective lens displacement observer 19.
And the tilt angle 108 detected by the tilt sensor 44
This is a memory for storing a set of a tracking error offset value detected by the offset detection circuit 17 as a set. The sixth storage circuit 43 stores the objective lens displacement amount 10 estimated by the objective lens displacement observer 19.
5 and the tilt angle 108 detected by the tilt sensor 44
And a memory for storing the amplitude value of the tracking error detected by the amplitude detection circuit 18 as a set. Each of the storage circuits 42 and 43 is constituted by a digital circuit or a memory in the system controller 24.
When storing, the analog amount is converted into a digital value by an A / D converter built in the system controller 24. The system controller 24 is a CPU or the like for controlling the operation state of each circuit in the system control block 41 and performing arithmetic processing according to the operation mode of the optical information recording / reproducing apparatus of the present embodiment input from the outside. It is an arithmetic circuit configured.

Embodiment 3 of the present invention configured as described above
The operation of the optical information recording / reproducing apparatus will be described in each of a calibration mode and a normal mode, which are operation modes of tracking error signal correction. The calibration mode is a mode in which the offset correction amount and the amplitude correction amount are learned in advance. The normal mode is a mode in which the tracking control loop 201 is corrected based on a result learned in the calibration mode.

First, the calibration mode will be described. FIG.
4 is a flowchart showing the operation of each circuit included in the system control block 41 in the calibration mode in this embodiment. Normally, the calibration mode is executed when the apparatus is first started up and when the disk is changed. In the calibration mode, the tracking control loop 201 is turned off, and the tracking calibration control loop 202 is turned off.
N (step S71). Subsequently, the tilt angle 108
Set the initial angle of. This initial angle is, for example, one end within a movable range of a tilt actuator (not shown). The tilt actuator is driven to this angle to control the tilt of the optical pickup 4 or the disk 2 (step S72).

Next, the memory addresses of the fifth storage circuit 42 and the sixth storage circuit 43 are initialized. In this initialization, for example, the memory address is set to N (N is a positive number greater than 0). (Step S73). Next, the initial position of the objective lens 8 is set. This initial position is, for example, one end within the movable range of the objective lens 8, and the tracking control circuit 15 outputs the tracking drive signal 103 to the tracking drive circuit 16 up to that position. This drives the tracking actuator 10 to move the objective lens 8 (step S74). At this time, the objective lens displacement amount 105 estimated by the objective lens displacement observer 19
And the tilt angle 108 detected by the tilt sensor 44
And a tracking error offset amount detected by the offset detection circuit 17 as a pair.
Stored in 2. The sixth storage circuit 43 stores a pair of the objective lens displacement amount 105 estimated by the objective lens displacement observer 19, the tilt angle 108 detected by the tilt sensor 44, and the tracking error amplitude detected by the amplitude detection circuit 18. It is stored (step S75). A memory address is set by adding +3 to each memory address (step S76). Then, it is determined whether or not the displacement of the objective lens 8 has reached from one end of the movable range of the objective lens to the other end (step S77). If the objective lens 8 has not reached from one end to the other end, the position of the objective lens 4 is moved by a minute distance ΔL (step S68), and step S68 is performed.
Returning to step 74, the processing from step 75 to step 77 is repeated. If the objective lens 8 has reached from one end to multiple ends, it is determined whether or not the tilt angle has reached from one end to the other end of the variable range (step S79). If the tilt angle has not reached from one end to the other end of the variable range, the tilt angle is increased by the minute angle ΔT (step S
80), returning to step S75 to repeat the same processing. If the tilt angle has reached the other end of the variable range, the calibration mode ends. By performing the above processing, as shown in FIGS. 15A and 15B,
The fifth storage circuit 42 stores the offset amount of the tracking error signal with respect to the objective lens shift amount and the tilt angle by one.
Can be recorded in pairs. The sixth storage circuit 4
In No. 3, a set of the amount of shift of the objective lens and the amplitude value with respect to the tilt angle can be recorded.

Next, the normal mode will be described. FIG.
6 is a flowchart showing the operation in the normal mode in the present embodiment. The normal mode is executed after turning on the tracking control loop 201 in FIG.
In the normal mode, first, the objective lens displacement amount 105 is estimated by the objective lens displacement observer 19, and the tilt sensor 4
4 to detect a tilt angle (step S81). Then, the memory addresses of the fifth storage circuit 42 and the sixth storage circuit 43 which record the estimated objective lens shift amount, the offset amount at the tilt angle, and the amplitude value are specified (step S8).
2) The offset amount and the amplitude value are read from the respective storage circuits 42 and 43 (step S83). The value of the correction tracking error signal 102 is the tracking error signal 1 when the objective lens shift amount is zero and the tilt angle is zero.
The system controller 24 calculates the offset addition amount and the amplitude gain so as to be equal to 01 (step S84).

The offset addition amount thus obtained is added by the offset correction circuit 22 and the amplitude gain is multiplied by the amplitude correction circuit 23 to correct the tracking error signal (step S85). The tracking control circuit 15 outputs a drive command to the tracking drive circuit 16 so that the corrected tracking error signal 102 becomes zero. A current flows through the coil 11 according to the drive command,
The objective lens 8 is moved by generating an electromagnetic force. In this manner, the tracking error signal is corrected based on the amount of shift of the objective lens and the tilt angle. As a result, even when the objective lens shift and the tilt occur, the tracking control performance equivalent to the state where the objective lens shift and the tilt are zero can be realized.

By adding the initialization mode shown in the first embodiment to the third embodiment, the tracking control loop is turned off.
From ON to ON can be improved. Further, in the third embodiment, if the equivalent filter characteristics shown in the second embodiment are learned and the temperature is corrected, the stability with respect to a temperature change can be improved. In addition, if the minute distance ΔL and the minute angle ΔT, which are the data sample intervals in the calibration mode, are reduced, the correction accuracy can be increased. Become. Therefore, stable tracking control performance can be realized similarly to the present embodiment by reducing the number of samples and obtaining an amplitude amount and an offset amount to be corrected between data samples by, for example, taking a weighted average.

[0089]

As described in detail in each of the above embodiments, the optical information recording / reproducing apparatus according to the present invention is not limited by the effects of changes in the temperature environment and aging of the components constituting the optical pickup. Even when the characteristics fluctuate, the amount of deviation of the objective lens from the optical pickup center can be detected with high accuracy by the drive command of the tracking actuator by optimally changing the characteristics of the equivalent filter. That is, the relationship between the amount of displacement of the objective lens and the offset and amplitude of the tracking error signal is determined in advance, and the offset and amplitude of the tracking error signal are corrected so that the displacement of the objective lens becomes equal to zero. Thus, a stable tracking control operation can be performed even when the objective lens is displaced. Further, the relationship between the objective lens shift amount, the tilt amount, and the offset and amplitude of the tracking error signal is obtained in advance, and the offset and the tracking error signal are set so that the objective lens shift amount is equal to zero and the tilt angle is equal to zero. Correct the amplitude. This allows
Even when a tilt of the disk occurs in addition to the displacement of the objective lens, a stable tracking control operation can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical information recording / reproducing device according to a first embodiment of the present invention.

2A is a flowchart showing an operation of the optical information recording / reproducing apparatus in a calibration mode according to the first embodiment of the present invention. FIGS. 2B and 2C are optical information recording according to the first embodiment of the present invention. Diagram showing the contents of the storage circuit of the playback device

FIG. 3A is a flowchart illustrating an operation of the optical information recording / reproducing apparatus in the normal mode according to the first embodiment of the present invention. FIG. Showing the change in the level of the tracking error signal when switching to

FIG. 4A is a flowchart illustrating an operation of the optical information recording / reproducing apparatus in the initialization mode according to the first embodiment of the present invention. FIG. The figure which shows the change of the level of the tracking error signal at the time of switching to ON.

FIG. 5 is a block diagram illustrating a configuration of a tracking control circuit and an objective lens shift observer according to the first embodiment of the present invention.

FIGS. 6A and 6B are transfer characteristic diagrams of the phase compensation filter according to the first embodiment of the present invention.

FIGS. 7A and 7B are transfer characteristic diagrams of an equivalent filter according to the first embodiment of the present invention.

FIGS. 8A and 8B are transfer characteristic diagrams of the optical pickup according to the first embodiment of the present invention.

FIG. 9 is a block diagram illustrating a configuration of an optical information recording / reproducing apparatus according to a second embodiment of the present invention.

FIG. 10 is a block diagram illustrating a configuration of an optical pickup transfer characteristic detection circuit and an objective lens shift observer according to a second embodiment of the present invention.

11A is a flowchart illustrating an operation of the optical information recording / reproducing apparatus in the learning mode according to the second embodiment of the present invention. FIGS. 11B and 11C are optical information recording according to the second embodiment of the present invention. Diagram showing the contents of the storage circuit of the playback device

FIG. 12 is a flowchart showing an operation of the optical information recording / reproducing apparatus in the correction mode according to the second embodiment of the present invention.

FIG. 13 is a block diagram illustrating a configuration of an optical information recording / reproducing apparatus according to a third embodiment of the present invention.

FIG. 14 is a flowchart showing an operation of the optical information recording / reproducing apparatus in the normal mode according to the third embodiment of the present invention.

FIGS. 15A and 15B are tables showing the contents of a storage circuit of an optical information recording / reproducing apparatus according to Embodiment 3 of the present invention.

FIG. 16 is a flowchart showing an operation of the optical information recording / reproducing apparatus in the calibration mode according to the third embodiment of the present invention.

FIG. 17 is a block diagram showing a configuration of a conventional optical information recording / reproducing device.

FIG. 18 is a diagram showing a change in the level of a tracking error signal when the tracking control loop is switched from OFF to ON in a state where no objective lens shift occurs in the conventional optical information recording / reproducing apparatus.

FIG. 19A is a side view showing the positions of the optical axis and the two-divided PD when the position of the objective lens is shifted. FIG. FIG. 1C shows a tracking error signal when the tracking control loop is switched from OFF to ON in a state where an objective lens shift occurs in the conventional optical information recording / reproducing apparatus.

20A is a side view showing the position of the optical axis and the two-divided PD when the disk is tilted, and FIG. 20B is a diagram showing a tracking error signal with respect to a position shift of the objective lens due to the disk tilt.

[Explanation of symbols]

 1. Information track 2. Disk 3. Spindle motor 4. Optical pickup 5. Semiconductor laser 6. Collimator lens 7. 7. Beam splitter 9. Objective lens 9.2 divided PD Tracking actuator 11. Coil 12. Spring 13. Magnet 14. 14. Tracking error detection circuit Tracking control circuit 16. Tracking drive circuit 17. Offset detection circuit 18. Amplitude detection circuit 19. Objective lens shift observer 20. First memory circuit 21. Second memory circuit 22. Offset correction circuit 23. Amplitude correction circuit 24. System controller 25. System control block 26, 27. Switch 28. Temperature detection sensor 29. System control block 30. Switch 31. Optical pickup transfer characteristic detection circuit 32. Third storage circuit 33. Transfer characteristic correction circuit 34. Disturbance frequency setting circuit 35. Disturbance amplitude setting circuit 36. Learning disturbance signal generator 37. Objective lens displacement detection circuit 38. Gain calculation circuit 39. Fourth storage circuit 40. Transfer characteristic calculation circuit 41. System control block 42. Fifth storage circuit 43. Sixth storage circuit 44. Tilt sensor 101. Tracking error signal 102. Corrected tracking error signal 103. Tracking drive signal 104. Tracking calibration signal 105. Objective lens shift amount 106. Tracking learning signal 107. Actuator temperature 108. Tilt amount 201. Tracking control loop 202. Tracking calibration control loop 203. Tracking learning control loop 501. A / D converter 502. Switch 503. Integral operation circuit 504. Proportional operation circuit 505. Differential operation circuit 506. D / A converters 507, 508, 510, 511. Multipliers 509, 512. Delay circuit 513. Lens displacement setting circuit 514. Equivalent filters 516, 517, 518. Multipliers 519, 520. Delay circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor ▲ Yoshi ▼ Shuichi 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. 5D117 CC07 EE01 EE29 FF17 FF19 FF21 FX05 FX06 GG03 5D118 AA21 BA01 BF02 BF03 CB01 CD03 CD11 CD18

Claims (9)

[Claims] 1. A disc on which information is recorded along a track, an optical pickup having an objective lens, and means for irradiating a light spot on a recording surface of the disc, and an optical pickup recorded on the optical spot and the optical disc Tracking error detecting means for detecting a displacement amount with respect to an information track and outputting a tracking error signal corresponding to the displacement amount; lens moving means for moving an objective lens of the optical pickup in a direction crossing the information track; Tracking control means including compensation calculation means for controlling the lens movement means in accordance with an error signal; based on an output of the compensation calculation means, an optical axis of the objective lens from a center position of a light beam of the optical pickup; Objective lens displacement estimating means for estimating the displacement; Offset detecting means for detecting the offset, storage means for storing the output of the offset detecting means and the output of the objective lens displacement estimating means as a pair, and the offset detecting means corresponding to the output of the objective lens displacement estimating means. An optical information recording / reproducing apparatus, comprising: an offset correction unit that outputs an output from the storage unit and corrects an offset of the tracking error signal. 2. A disc on which information is recorded along a track, an optical pickup having an objective lens, and a means for irradiating a light spot on a recording surface of the disc, and an optical pickup recorded on the optical spot and the optical disc Tracking error detecting means for detecting a displacement amount with respect to the information track and outputting a tracking error signal corresponding to the displacement amount; lens moving means for moving an objective lens of the optical pickup in a direction crossing the information track; Tracking control means including compensation calculation means for controlling the lens movement means in accordance with an error signal; based on an output of the compensation calculation means, an optical axis of the objective lens from a center position of a light beam of the optical pickup; An objective lens displacement estimating means for estimating a displacement; An amplitude detecting means for detecting a width; a storage means for storing an output of the amplitude detecting means and an output of the objective lens displacement estimating means in association with each other; An optical information recording / reproducing apparatus, comprising: an amplitude correction unit that outputs an output from the storage unit and corrects an amplitude value of the tracking error signal. 3. A disc on which information is recorded along a track, an optical pickup having an objective lens, and means for irradiating a light spot on a recording surface of the disc, and an optical pickup recorded on the optical spot and the optical disc. Tracking error detecting means for detecting a displacement amount with respect to the information track and outputting a tracking error signal corresponding to the displacement amount; lens moving means for moving an objective lens of the optical pickup in a direction crossing the information track; A tracking control loop for controlling the lens moving means according to an error signal; an objective lens shift estimating means for estimating a shift of an optical axis of the objective lens from a center position of a light beam of the optical pickup;
An optical information recording / reproducing apparatus comprising: a tracking calibration control loop for controlling the lens moving means in accordance with the displacement of the optical axis of the objective lens estimated by the objective lens displacement estimating means. 4. The tracking control means includes at least an integral calculating means and a proportional calculating means, and the objective lens displacement estimating means includes observer means having a transfer characteristic substantially equal to a transfer characteristic of the lens moving means. The optical information recording / reproducing apparatus according to claim 1, 2 or 3, wherein: 5. An optical information recording / reproducing apparatus according to claim 4, wherein an output of said integration operation means or a signal obtained by adding an output of said integration means and said output of said proportional operation means is inputted to said observer means. . 6. When the tracking control means starts operation from an operation stop state, an offset amount detected by the offset detection means is input to the offset correction means, and an amplitude value detected by the amplitude detection means is inputted. Input to the amplitude correction means, and after a lapse of a predetermined time from the start of operation of the tracking control means, input of the output of the first storage means to the offset correction means, and output of the second storage means 5. The optical information recording / reproducing apparatus according to claim 4, wherein the signal is inputted to said amplitude correcting means. 7. The apparatus according to claim 1, further comprising a temperature detecting means for detecting a temperature in the vicinity of said tracking moving means, wherein a transfer characteristic of said observer means is changed based on an output of said temperature detecting means. The optical information recording / reproducing apparatus according to claim 1. 8. A disk on which information is recorded along a track, an optical pickup having an objective lens, and having means for irradiating a light spot on a recording surface of the disk, and an optical pickup recorded on the optical spot and the optical disk. Tracking error detecting means for detecting a displacement amount with respect to the information track and outputting a tracking error signal corresponding to the displacement amount; lens moving means for moving an objective lens of the optical pickup in a direction crossing the information track; Tracking control means for controlling the lens moving means in accordance with an error signal; objective lens displacement detection means for detecting a deviation of the optical axis of the objective lens from a center position of the light beam of the optical pickup; and offsetting the tracking error signal. Offset detecting means for detecting, the optical pickup Between the light beam and the disc surface,
Tilt detecting means for detecting an amount of tilt in a direction perpendicular to the information track; storage means for storing the output of the offset detecting means, the output of the objective lens shift detecting means, and the output of the tilt detecting means in association with each other; An output of the offset detecting means corresponding to an output of the objective lens shift detecting means and an output of the inclination detecting means is output from the storage means, and an offset correcting means for correcting an offset of the tracking error signal is provided. Optical information recording and reproducing device. 9. A disc on which information is recorded, an optical pickup having an objective lens, and a means for irradiating a light spot on a recording surface of the disc, wherein an optical track is provided between the light spot and an information track recorded on the optical disc. A tracking error detecting unit that detects a position shift amount and outputs a tracking error signal corresponding to the position shift amount; a lens moving unit that moves an objective lens of the optical pickup in a direction crossing the information track; Tracking control means for controlling the lens moving means, objective lens displacement detecting means for detecting a deviation of the optical axis of the objective lens from the center position of the light beam of the optical pickup, and a light beam of the optical pickup and the disk surface. Detection means for detecting the amount of tilt in the direction perpendicular to the information track Amplitude detecting means for detecting the amplitude of the tracking error signal; storage means for storing the output of the amplitude detecting means, the output of the objective lens displacement detecting means, and the output of the inclination detecting means in association with each other; and the objective lens An output of the amplitude detecting means corresponding to an output of the deviation detecting means and an output of the inclination detecting means is output from the storage means, and an amplitude correcting means for correcting an amplitude value of the tracking error detecting means is provided. Optical information recording and reproducing apparatus.