JPH1125478A - Focusing controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focusing controller performing stable automatic offset adjustment even when the frequency characteristic of a focusing control system is dispersed in an optical disk device. SOLUTION: A focusing controller is provided with an error signal synthesizer 102 generating a focusing error signal by synthesizing the sensor signals of a sensor 101, an arithmetic unit 103 inputting the focusing error signal and outputting a driving signal, a driving circuit 108 outputting a driving current in proportion to the driving signal, a focus actuator 109 driving an objective lens 110 according to the driving current of the driving circuit 108 and an information reproducing circuit 112 reproducing the recorded information of the optical disk. The arithmetic unit 103 is provided with a phase compensating part, a wobbling part, a focus adjusting part and a control gain adjusting part and the operation of the focus adjusting part is performed after the completion of the operation of the control gain adjusting part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus control device for causing a focus position to follow a recording surface of an optical disk in an optical disk device or the like.

[0002]

2. Description of the Related Art As a method of detecting a focus error signal, there is an astigmatism method using astigmatism of an optical system. In the astigmatism method, the quadrant sensor is installed at a position where the cross section of the reflected light of the astigmatism optical system becomes circular when the recording surface of the optical disc is at the focal position of the objective lens. Then, a focus error signal FE is obtained by arithmetically synthesizing the four sensor signals A, B, C, and D obtained from the four-divided sensor by an arithmetic circuit. For example, a focus error signal is generated by the calculation of FE = (A + B)-(C + D). Hereinafter, the focus error signal of the astigmatism method will be briefly described.

First, when the recording surface of the optical disk is at the focal position of the objective lens, the beam cross section on the four-divided sensor becomes circular, and the focus error signal FE becomes zero ((A +
B) = (C + D)). When the optical disk approaches the objective lens from the focal point of the objective lens, the cross section of the reflected light on the quadrant sensor becomes a vertically long ellipse, and the focus error signal FE becomes a positive value ((A + B)> (C + D)). Conversely, when the optical disk moves away from the focal point of the objective lens, the cross section of the reflected light on the quadrant sensor becomes a horizontally long ellipse, and the focus error signal FE becomes a negative value ((A + B) <(C + D)).

In this way, a signal corresponding to a shift between the focal position of the objective lens and the recording surface of the optical disk (hereinafter, referred to as defocus) is obtained as a focus error signal FE. Detection of the focus error signal by the astigmatism method
This method is a focus error signal detection method that is frequently used because of its simple configuration and good detection sensitivity.

However, the recording surface of the optical disk has an objective lens due to misalignment between the four-split sensor and the incident beam, variation in sensitivity of the four-split sensor, and variation in the amplification factor of the amplifier for amplifying each sensor signal. , The value of the focus error signal FE does not become zero and an offset error may occur.

For this reason, in an optical disc device in which the offset adjustment of the focus error signal has not been correctly performed, recording and reproduction are performed in a state where the recording surface is not aligned with the focal position of the objective lens (defocused state). In this case, problems such as a decrease in the amount of reflected light and a deterioration in frequency characteristics due to defocusing occur, and the reliability of the optical disc device is reduced.

As described above, there is an optical disc apparatus disclosed in Japanese Patent Application Laid-Open No. H8-7300 as an optical disc apparatus that automatically performs offset adjustment indispensable for good recording and reproduction. This optical disk device is provided with the following focus control device in addition to the system control means for controlling the entire device and the focus servo control means of the optical disk device. That is, the focus control device includes a wobbling signal generating unit that generates a wobbling signal to be injected into a servo loop to detect an offset, and a wobbling signal that is generated by the wobbling signal generating unit to inject the wobbling signal into the focus servo loop. Signal adding means, specific signal extracting means for extracting only a specific signal from a focus sum signal or a pit reproduction signal when a wobbling signal is injected, and envelope detecting means for detecting an envelope of the specific signal extracted by the specific signal extracting means Sample and hold means for sampling and holding the envelope value of the specific signal detected by the envelope detection means, and the error of the specific signal sampled and held by the sample and hold means for each of the positive and negative sections of the wobbling signal. Integrating means for integrating the envelope value; comparing means for comparing the integration results of the specific signal envelopes in the positive and negative sections of the wobbling signal by the integrating means; and an offset voltage to be added to the focus error signal from the result of the comparing means. And an offset adding means for adding the offset voltage output by the offset calculating means to the focus error signal.

With the above-described configuration, the optimal focus offset adjustment is always performed automatically in consideration of changes in the ambient temperature and aging of component characteristics, taking into account the state of the optical disk for recording and reproduction and the difference in the recording and reproduction environment. Done in As a result, the reliability of information reproduction of the optical disk is improved. The simplification of the adjustment process also contributes to an improvement in the production efficiency of the optical disk device.

[0009]

However, such a conventional focus control device as described above sometimes has an adverse effect on the focus control system when a wobbling signal is injected. When a wobbling signal is injected into the focus control system, vibration of an amplitude corresponding to the amplitude of the wobbling signal occurs in the objective lens. The relationship between the amplitude of the wobbling signal and the vibration amplitude of the objective lens largely depends on the frequency characteristics of the focus control system. Further, the frequency characteristics of the focus control system change due to various factors such as the gain of the focus error signal generation unit, the gain of the calculation unit, and the gain variation between the drive unit and the focus actuator, which form the focus control system. As a result, the oscillation amplitude of the objective lens varies with respect to the amplitude of the wobbling signal. If the variation is large, a problem occurs that the focus control is lost.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a focus control apparatus capable of performing stable automatic offset adjustment (focus position adjustment) even when the frequency characteristics of a focus control system vary. I do.

[0011]

A first configuration of a focus control device according to the present invention comprises a sensor means for receiving reflected light from an optical disk and outputting a plurality of sensor signals, and a plurality of sensor means of the sensor means. An error signal synthesizing unit that synthesizes a signal to generate a focus error signal; an information reproducing unit that reproduces information recorded on the optical disk from reflected light from the optical disk; a focus error signal and a reproduction signal of the information reproducing unit; A calculating means for outputting a driving signal; a driving means for outputting a driving current proportional to the driving signal; and a focus actuator for driving the objective lens in accordance with the driving current of the driving means. A wobbling means for outputting a signal to which a predetermined wobbling signal is added; Phase compensating means for performing a phase compensating operation and an amplifying operation and outputting a drive signal; a focus adjusting means for adjusting a focus position according to a wobbling signal and a reproduction signal of an information reproducing means; Gain adjusting means for adjusting the gain of the amplification operation of the phase compensating means, wherein the operation of the focus adjusting means is performed after the operation of the gain adjusting means is completed.

The error signal synthesizing means generates a focus error signal by adding a predetermined offset signal after adding and synthesizing a plurality of sensor signals, and the focus adjusting means includes a wobbling signal and a reproduction signal of the information reproducing means. It is preferable to adjust the focal position by changing a predetermined offset signal of the error signal synthesizing means in accordance with the above.

Further, it is preferable that the frequency of the wobbling signal of the wobbling means when the focus adjusting means operates is a frequency within the focus control band after the operation of the gain adjusting means. Further, it is preferable that the focus adjusting means starts its operation after a predetermined time has elapsed after the wobbling means adds the wobbling signal to the focus error signal.

A second feature of the focus control device according to the present invention is that a sensor means for receiving reflected light from an optical disk and outputting a plurality of sensor signals, and a plurality of sensor signals of the sensor means for combining and focusing. Error signal synthesizing means for generating an error signal, information reproducing means for reproducing information recorded on the optical disk from reflected light from the optical disk, and arithmetic means for inputting a focus error signal and a reproduction signal of the information reproducing means and outputting a drive signal; A driving means for outputting a driving current proportional to the driving signal, and a focus actuator for driving the objective lens according to the driving current of the driving means, wherein the calculation means inputs a focus error signal, and performs at least phase compensation calculation and A phase compensator for performing an amplification operation and outputting a drive signal; and adding a predetermined wobbling signal to the focus error signal. Wobbling means, focus adjustment means for adjusting a focus position according to a wobbling signal and a reproduction signal from the information reproduction means, and gain adjustment means for adjusting the gain of the amplification operation of the phase compensation means according to the wobbling signal and the focus error signal. Operation control means for performing the operation of the focus adjustment means after the operation of the gain adjustment means is completed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a focus control device according to an embodiment of the present invention. In FIG. 1, an optical disk 113 is driven to rotate by a motor 114. The four-divided sensor 101 converts reflected light from the optical disk 113 into an electric signal, and outputs a sensor signal A, a sensor signal B, a sensor signal C, and a sensor signal D corresponding to each sensor. The error signal synthesizer 102 receives the sensor signals A, B, C, and D and an offset signal OF of a calculation device 103 described later, and outputs a focus error signal FE.

FIG. 2 is a specific circuit diagram of the error signal synthesizer 102. 2, a sensor signal A of the quadrant sensor 101 is input to one input terminal of an adder 201, and a sensor signal B of the quadrant sensor 101 is input to the other input.
Is entered. The sensor signal C of the four-divided sensor 101 is input to one input terminal of the adder 202,
The sensor signal D of the four-divided sensor 101 is input to the other input. The output signal of the adder 201 is input to the + input terminal of the subtractor 203, and the output signal of the adder 202 is input to the-input terminal of the subtractor 203. As a result, the output signal of the subtractor 203 becomes the sensor signals A, B,
Using C and D, the calculation result is (A + B)-(C + D).

The output signal of the subtractor 203 is input to one input terminal of the adder 204 in FIG. 2, and the offset signal OF is input to the other input. Then, the output signal of the adder 204 is output as the focus error signal FE. Hereinafter, the operation of the error signal synthesizer 102 of FIG. 2 will be described.

FIG. 9 shows the quadrant sensor 101 and the shape of the reflected light on the quadrant sensor 101 when the focal position is changed near the recording surface of the optical disk 113. FIG. 9 (b)
This shows a state where the focal position matches the recording surface of the optical disc 113. In this state, since the light receiving amounts of the sensor signals A, B, C, and D are equal, the output signal of the subtractor 203 in FIG. 2 becomes zero.

FIGS. 9A and 9C show a state where the focal position does not coincide with the recording surface of the optical disk 113. FIG. FIG. 9A shows that the objective lens 110 is the optical disk 11.
3 illustrates a case where defocusing is performed in a direction away from 3. In this case, since the signal amount (C + D) obtained by adding the sensor signal C and the sensor signal D is larger than the signal amount (A + B) obtained by adding the sensor signal A and the sensor signal B, the output signal of the subtractor 203 in FIG. Signal. FIG. 9C shows a case where the objective lens 110 is defocused in a direction approaching the optical disk 113. In this case, since the signal amount (A + B) obtained by adding the sensor signals A and B is larger than the signal amount (C + D) obtained by adding the sensor signals C and D, the output signal of the subtractor 203 in FIG. Signal.

As described above, the output signal of the subtractor 203 shown in FIG. 2 has an amount corresponding to the shift amount (defocus amount) of the focal position.
Becomes positive when defocusing in a direction approaching.

When the offset signal OF is zero, the focus error signal FE has an amount corresponding to the defocus amount. When the objective lens 110 defocuses in the direction approaching the optical disk 113, the focus error signal FE has a positive value. Becomes Further, when the offset signal OF changes by a predetermined amount, since the offset signal OF is added to the focus error signal FE by the adder 204, the focus error signal FE is also a signal offset by a predetermined amount.

In FIG. 1, the information recorded on the optical disk 113 is converted into an optical signal by a sensor 111 and input to an information reproducing circuit 112. The information reproducing circuit 112 extracts the amplitude information of a predetermined signal from the output signal of the sensor 111 and outputs it as an amplitude signal RF3T. FIG. 3 shows a specific block diagram of the information reproducing circuit 112. The output signal of the sensor 111 is a bandpass filter (BPF) 30
1 and a band-limited signal is output. BP
The output signal of F301 is input to an envelope detection circuit 302, and an envelope-detected signal is output.
The output signal of the envelope detection circuit 302 is an amplitude signal RF.
Output as 3T. As a result, among the recorded information on the optical disk 113 detected by the sensor 111, the BPF
Only the signal extracted at 301 passes, is detected by the envelope detection circuit 302, and is output as an amplitude signal RF3T.

In FIG. 1, an arithmetic unit 103 includes an arithmetic unit 105, a memory 106, two DA converters (digital-analog converters) 107a and 107b, and two A
D converter (analog-digital converter) 104a, 10
4b. When the focus error signal FE and the amplitude signal RF3T of the error signal combiner 102 are input, the arithmetic unit 103 executes a later-described calculation process based on a program stored in the memory 106 to thereby obtain the drive signal FOD and the offset signal OF. Is output. The drive signal FOD output from the arithmetic unit 103 is input to the drive circuit 108, which amplifies the power and supplies power to the focus actuator 109, and
Drive 0. When the driving signal FOD is a positive signal, the driving force acting on the objective lens 110 is
3 in the direction away from it.

Accordingly, the four-divided sensor 101 (sensor means), the error signal synthesizer 102 (error signal synthesis means), the arithmetic unit 103 (calculation means), the focus actuator 109, the information reproduction circuit 112 (information reproduction means), and the drive circuit 108 (driving means) constitutes a focus control device.

The memory 106 of the arithmetic unit 103 shown in FIG.
It is divided into a ROM (read only memory) area 106a in which predetermined programs and constants are stored, and a RAM (random access memory) area 106b in which necessary values are stored as needed. The arithmetic unit 105 performs a predetermined process according to a program in the ROM area 106a. An example of the processing by this program will be described in detail with reference to the flowchart shown in FIG.

First, in a process 401, initial setting of variable values necessary for a process to be described later is performed. Specifically, the focus adjustment unit 4
As the initial setting of the operation of 07, the contents of the variable FOSW are initialized to zero (FOSW ← 0), the contents of the variable SUM are initialized to zero (SUM ← 0), and the contents of the offset value FO are initialized to zero (FO ← 0). Further, the offset value FO is output to the DA converter 107a of the arithmetic unit 103 in FIG. 1 and is converted into the offset signal OF.

In the process 401, the contents of the variable LGSW are initialized to zero (LGSW ← 0), and the contents of the variable FEA are initialized to a predetermined value FE_MIN (FEA ← FE_MI
N), the content of the variable FEB is initialized to a predetermined value FE_MAX (FEA ← FE_MAX). Here, the predetermined value FE_
MIN is the minimum numerical value that the arithmetic unit 105 of the arithmetic unit 103 can handle, and the predetermined value FE_MAX is the maximum numerical value that the arithmetic unit 105 of the arithmetic unit 103 can handle. The variable FE is set as an initial setting of the operation of the phase compensating unit 409 described later.
_I is initialized to zero (FE_I ← 0), and the variable FAD
The contents of D are initialized to zero (FADD ← 0). afterwards,
The operation of the process 402 is performed.

In the process 402, a focus search operation for detecting a focus position is performed. Specifically, first, a current value of a predetermined pattern is supplied to the focus actuator 109 of FIG. 1 to move the objective lens 110 in a direction perpendicular to the optical disc 113. Next, the fact that the focus position has come near the recording surface of the optical disc 113 is detected by a change in the focus error signal FE, the focus position is detected, and preparation for focus control is performed. After that, the operation of the process 403 is performed.

In the process 403, the focus error value FED
Input operation. That is, the focus error signal FE signal of the error signal combiner 102 input to the AD converter 104a of the arithmetic unit 103 is AD-converted and converted into a focus error value FED. After that, the operation of the process 404 is performed.

In the process 404, the operation to be performed next is selected according to the content of the variable LGON. That is,
If the value of the variable LGSW is zero, the operation of step 405 is performed. If the value of the variable LGSW is not zero, the operation of step 406 is performed. Step 404 constitutes an operation control unit (operation control means).

In the process 405, the operation of the control gain adjustment unit described later is performed. By performing the operation of the control gain adjustment unit,
The frequency characteristic of the focus control system becomes a desired value. After that, the operation of the process 408 is performed. The processing 405 forms a control gain adjustment unit (gain adjustment means).

In the process 406, the next operation to be performed is selected according to the contents of the variable FOSW. That is,
If the value of the variable FOSW is zero, the operation of the process 407 is performed, and if the value of the variable FOSW is not zero, the operation of the process 408 is performed.

In the process 407, the operation of the focus adjustment unit described later is performed. By performing the operation of the focus adjustment unit, the focus position matches the recording surface of the optical disc 113. Then processing 4
08 is performed. The processing 407 constitutes a focus adjustment unit (focus adjustment means).

In step 408, the focus error value FED
Is added to the wobbling signal FADD to obtain an error signal FOE (FOE ← FED + FADD). afterwards,
The operation of processing 409 is performed. The processing 408 constitutes a wobbling unit (wobbling means).

In step 409, a phase compensation operation is performed on the error signal FOE. Specifically, first, the error signal FOE is
Is multiplied by k1 (where k1 is a positive integer) and the value obtained by adding the variable FE_I is set as a new variable FE_I value (FE_I ← FE_I + FOE × k1). Variable F
Multiply the value of E_I by k2 (where k2 is a positive real number)
From the value obtained by adding the value obtained by multiplying the error signal FOE by k3 (where k3 is a positive integer), a variable F
A value obtained by subtracting a value obtained by multiplying the value of E1 by k4 (where k4 is a positive integer smaller than k3) is multiplied by a value of a variable kg (described later), and the value is set as a value of a variable FD (FD ← (F
E_I × k2 + FOE × k3-FE1 × k4) × k
g). Further, the value of the error signal FED is set as a new value of the variable FE1 (FE1 ← FED). Thereafter, the operation of the process 410 is performed. By performing the above calculation, the error signal FOE is obtained.
Is performed, and the result becomes the value of the variable FD.
The value of the variable kg represents the amplification factor of the amplification operation, and the process 409 constitutes a phase compensation operation unit (phase compensation means).

In the process 410, the contents of the variable FD are output to the DA converter 107a of the arithmetic unit 103 and converted into a drive signal FOD proportional to the value of the variable FD. Then, processing 4
11 is performed.

In the process 411, a delay operation is performed. That is, the delay operation is performed such that the operations from the process 403 to the process 410 are performed at a predetermined cycle (for example, 23 μs).
Thereafter, the operation returns to the operation of the process 403.

By performing the above processing, the focus control by the focus control system is realized. Hereinafter, an example will be described in which the offset signal OF is zero and the operations of the control gain adjustment unit 405 and the focus adjustment unit 407 are stopped.

First, when the focus position is on the recording surface of the optical disk 113, the focus error signal FE becomes zero, so that the focus error value FE obtained in the process 403 of FIG.
D also becomes zero. In the process 408, since the initial value of the variable FADD is zero, the error signal FOE is also zero. Error signal FOE
Is zero, the value of the variable FD, which is the calculation result of the process 409, is also zero. When the value of the variable FD is zero, the drive signal FOD
Is also zero, and no driving force for the objective lens 110 is generated.
As a result, the objective lens 110 maintains the focal position on the recording surface of the optical disc 113.

Next, when the objective lens 110 is
When the focus is defocused in the direction approaching 13, the focus error signal FE has a positive value, so that the focus error value FED obtained in the process 403 in FIG. 4 also has a positive value. In the process 408, since the initial value of the variable FADD is zero, the error signal FOE also has a positive value. When the error signal FOE has a positive value, the value of the variable FD, which is the calculation result of the process 409, also has a positive value. When the value of the variable FD is a positive value, the driving signal FOD
Becomes a positive signal, and the driving force of the objective lens 110 acts in a direction away from the optical disc 113. Thereby, the defocus is corrected.

Next, when the objective lens 110 is
When defocusing is performed in a direction away from 13, the focus error signal FE has a negative value.
Is also a negative value. In the process 408, since the initial value of the variable FADD is zero, the error signal FOE also has a negative value. When the error signal FOE has a negative value, the value of the variable FD, which is the calculation result of the process 409, also has a negative value. When the value of the variable FD is a negative value, the driving signal FOD
Becomes a negative signal, and the driving force of the objective lens 110 acts in a direction approaching the optical disc 113. Thereby, the defocus is corrected.

Therefore, when the focus control system is configured as described above, the defocus is automatically corrected.
In this way, focus control (focus position control) is performed.

Next, consider the case where the offset signal OF is a positive value and the operations of the control gain adjustment unit 405 and the focus adjustment unit 407 are stopped. First, when the focus position is on the recording surface of the optical disk 113, the focus error signal FE has a positive value because the offset signal OF has a positive value. In this case, in the same manner as described above, the objective lens 110
The driving force acts in the direction away from the optical disk, and the output signal of the subtractor 203 in FIG. 2 becomes a negative value. This operation becomes steady at the operating point where the value of the focus error signal FE becomes zero. That is, due to the defocus, the output signal of the subtractor 203 in FIG. 2 becomes a negative value, and operates so as to be balanced with the offset signal OF.

This operation is the same when the offset signal OF has a negative value. Therefore, when a predetermined voltage is added as the offset signal OF, defocus occurs in an amount corresponding to the voltage value of the offset signal OF. The same phenomenon occurs when the value of the variable FADD is changed in the process 408. The adder 20 of FIG.
A similar phenomenon occurs when there is an electrical offset in 1, 202, 204 and the subtractor 203. Therefore,
Even if the focus control is operating normally, if there is an electrical offset or the like in the adders 201, 202, 204 and the subtractor 203 in FIG. 2, defocus occurs.

FIG. 5 shows an example of a flowchart of a program constituting the control gain adjusting section 405 of FIG. Processing 5
In 01, a value obtained by adding 5 to the value of the variable SC is set as a new value of the variable SC (SC ← SC + 5). By performing this operation, the content of the variable SC becomes 5 every time the process 501 is performed.
Increase by one. By adding 5, the content of the variable SC increases faster than by adding 1. Then, processing 5
02 is performed.

In the process 502, the variable S obtained in the process 501
Referring to the function table of the sine wave stored in the ROM area 106a of the memory 106 based on C, the value of the variable FADD of the process 408 in FIG. 4 is set. That is, calculation is performed using the following equation (Equation 1).

[0047]

FADD = Table (SC) Here, Table (n) represents a sine wave function table value of the address value n. By adding 5 to the variable SC in the process 501, the increase of the variable SC is accelerated, and in the process 502, the update of the address value is accelerated. Thereby, processing 5
A sine wave having a higher frequency than that obtained by adding 1 in 02 is obtained. After that, the processing of step 503 is performed.

In process 503, the focus error value FED
Is compared with the value of a variable FEA described later, and the next process is selected according to the comparison result. That is, when the focus error value FED is larger than the variable FEA, the operation of the process 504 is performed, and when the focus error value FED is not larger than the variable FEA, the operation of the process 505 is performed.

In step 504, the focus error value FED
Is the value of the new variable FEA (FEA ← FED). After that, the operation of the process 505 is performed. In the process 505, the focus error value FED is compared with the value of a variable FEB described later, and the next process is selected according to the comparison result. That is, when the focus error value FED is the variable FEB
If the focus error value FED is not smaller than the variable FEA, the operation of step 506 is performed.
07 is performed.

In step 506, the focus error value FED
Is the value of the new variable FEB (FEB ← FED). By performing the operations from the process 503 to the process 506, the maximum value of the focus error value FED is stored in the variable FEA.
EB holds the minimum value of the focus error value FED. Further, the value of the variable FEA
The value obtained by subtracting the value of EB corresponds to the signal amplitude of the focus error value FED. After that, the operation of the process 507 is performed.

In process 507, the variable SC and the reference value SC_
REF are compared, and the next process is selected according to the result. That is, the variable SC is equal to the reference value SC_REF.
If the value is larger than the reference value SC_REF, the operation proceeds to the next process, that is, the process 408 in FIG. Thereby, it is monitored that the operations of the processes 501 to 506 are performed a predetermined number of times.

In process 508, the variable FEA and the variable FE
The value of the variable kg in the process 409 in FIG. 4 is changed according to B and the reference value REF. Specifically, the value of the reference value REF is
The value obtained by subtracting the value of the variable FEB from the value of the variable FEA is divided, and the value obtained by multiplying the result by the variable kg is set as the value of the new variable kg. That is, in the process 508, the correction calculation of the variable kg is performed. Thereafter, the operation of the process 509 is performed.

In process 509, variables are initialized in preparation for the next correction calculation. That is, the value of the variable SC is set to zero (SC ← 0), and the value of the variable FEA is set to a predetermined value FE_M.
IN and the value of the variable FEB to a predetermined value FE_MAX. Thus, preparations for the next correction calculation are made. Thereafter, the operation of the process 510 is performed.

In the process 510, a value obtained by adding 1 to the value of the variable NLG is set as a new value of the variable NLG. By performing this operation, the variable NLG is changed from step 508 to step 510.
Since the contents increase each time the above operation is performed, the number of times the correction calculation in the process 508 is performed is held. afterwards,
The operation of the process 511 is performed.

In process 511, the variable NLG and the reference value NL
G_MAX is compared, and the process to be performed next is selected according to the result. That is, the variable NLG is equal to the reference value NLG.
If it is equal to _MAX, the operation of the process 512 is performed. If the variable NLG is not equal to the reference value NLG_MAX, the process proceeds to the next process, that is, the process 408 in FIG.

In the process 512, the value of the variable LGSW is set to 1. By performing this processing, the operation of the processing 405 will not be performed from the next time due to the branch determination of the processing 404 in FIG.

By performing the above processing, the frequency characteristic of the focus control system can be set to a desired value. This will be described below. First, since a sine wave value is set as the value of the variable FADD in the process 502, the variable FAADD is set in the state where the focus control is operating.
The objective lens 110 oscillates sinusoidally according to the value of DD, and the focus error signal FE also oscillates sinusoidally.

In the focus control system configured as shown in FIG. 4, the vibration amplitude of the objective lens 110 when a sine wave value is added as the variable FADD is represented by a curve L in FIG.
L. Here, the curve LL in FIG. 7 is the frequency characteristic of the focus control system.

In FIG. 7, the horizontal axis represents the frequency on a logarithmic scale, and the vertical axis represents the vibration amplitude of the objective lens 110 with respect to the amplitude value of the variable FADD in decibels. The curve LL in FIG. 7 has a right-down characteristic in a region where the frequency is higher than a predetermined value (a frequency slightly higher than fd). That is, in a high frequency region, the vibration amplitude of the objective lens 110 decreases as the frequency increases.

On the other hand, in a low frequency region, the curve LL has a flat characteristic. That is, in a low frequency region, the vibration amplitude of the objective lens 110 becomes substantially constant with respect to a change in frequency. This region is a region where the focus control system is exerting a control effect, and is called a control band (a region having a frequency lower than the frequency fd). In FIG. 7, a straight line L1 represents an asymptote of the curve LL in a high frequency region, and a straight line L2 represents an asymptote of the curve LL in a low frequency region. The frequency at the intersection of the straight line L1 and the straight line L2 is fd. The characteristics of the curve LL are called frequency characteristics of the focus control system. The frequency characteristic when the variable kg of the amplification calculation in the process 409 in FIG. 4 is a predetermined value is shown as a characteristic A in FIG. The frequency characteristics when the coefficient kg is smaller than the predetermined value are shown as characteristics B in FIG.

Also, in processing 501 of FIG.
By setting the addition amount of the variable SC used in 02 to 5, the sine wave function table in the process 502 is referred to while thinning out.

As a result, the frequency of the sinusoidal signal set to the variable FADD becomes a relatively high frequency. The frequency f2 in FIG. 8 indicates the frequency. At this relatively high frequency f2, the vibration amplitude of the objective lens 110 is
Greatly varies depending on the value of the coefficient kg of the amplification calculation in the processing 409 of the above.

By the processes 503 to 506 in FIG.
The minimum value and the maximum value of the focus error value FED corresponding to the vibration amplitude of the objective lens 110 are detected. Thereby, the vibration amplitude of the objective lens 110 is detected, and the magnitude of the coefficient kg of the amplification calculation in the process 409 in FIG. 4 is detected.
In process 508, the objective lens 11
If the zero vibration is small, the correction is made so that the value of the new coefficient kg becomes large.

That is, in the case of the characteristic B in FIG. 8, since the vibration amplitude of the objective lens 110 is small, the processing 503 in FIG.
After that, the amplitude of the focus error value FED detected in the process 506 also becomes smaller. In the process 508 of FIG. 5, when the amplitude of the focus error value FED is small (the value obtained by subtracting the value of the variable FEB from the value of the variable FEA is small), as a result of the correction calculation in the process 508, the variable kg increases. Will be corrected.

Further, as the reference value REF of the processing 508 of FIG. 5, the variable FE of the processing 508 of FIG.
When the value obtained by subtracting the variable FEB from A (FEA-FEB) is used, the result of the above correction becomes the characteristic A as a result of the control gain adjustment of the characteristic B in FIG. In the case of the characteristic A, the processing 5 in FIG.
Since the calculation result of REF / (FEA-FEB) of 08 becomes 1, the variable kg does not change after the correction but becomes a constant value. As described above, by appropriately setting the reference value REF in the process 508 in FIG. 5, the frequency characteristics of the focus control system after the control gain adjustment can be set to predetermined characteristics. As described above, the control gain of the focus control system is adjusted, and the frequency characteristics of the focus control become desired characteristics.

FIG. 6 shows an example of a flowchart of a program constituting the focus adjusting section 407 of FIG. Process 601
Then, the value obtained by adding 1 to the value of the variable SC is added to the new variable SC
(SC ← SC + 1). By performing this operation, the content of the variable SC increases by one each time the process 601 is performed. After that, the operation of the process 602 is performed.

In step 602, the variable S obtained in step 601
Referring to the function table of the sine wave stored in the ROM area 106a of the memory 106 based on C, the value of the variable FADD of the process 408 in FIG. 4 is set. That is, the calculation is performed using the above equation (Equation 1). After that, the process of the process 603 is performed.

In step 603, the value of the variable SC and the reference value S
C_TH is compared, and the next process is selected according to the comparison result. That is, if the value of the variable SC is larger than the reference value SC_TH, the operation of the process 604 is performed. If the value of the variable SC is not larger than the reference value SC_TH, the process proceeds to the next process, that is, the process 408 in FIG. By performing the operation of the process 603, the variable FADD
In the process 604 of monitoring that the value is set a predetermined number of times, the amplitude signal RF of the information reproducing circuit 112 in FIG.
3T is input and converted into a digital value to obtain an amplitude value M3T. After that, the operation of the process 605 is performed.

In the process 605, the value of the variable FADD is compared with zero, and the next process is selected according to the comparison result. That is, when the value of the variable FADD is larger than zero, the operation of the process 606 is performed, and when the value of the variable FADD is not larger than zero, the operation of the process 607 is performed.

In the process 606, the value obtained by adding the amplitude value M3T to the value of the variable SUM is set as a new value of the variable SUM (S
(UM ← SUM + M3T). Thereafter, the operation of the process 608 is performed.

In the process 607, a value obtained by subtracting the amplitude value M3T from the value of the variable SUM is set as a new value of the variable SUM (SUM ← SUM-M3T). When the amplitude value M3T is added to or subtracted from the value of the variable SUM, the addition or subtraction is performed in accordance with the value of the variable FADD. As a result, the value of the variable SUM becomes a value obtained by synchronously detecting the value of the amplitude value M3T with respect to the variable FADD. That is, when the amplitude value M3T and the value of the variable FADD vibrate in a sine wave shape, when the phases match, the content of the variable SUM becomes a positive numerical value, and the phase of both is about 1
When the angle differs by 80 degrees, the content of the variable SUM becomes a negative value. Thereafter, the operation of the process 608 is performed.

In step 608, the value of the variable SC and the reference value S
C_REF1 is compared, and the next process is selected according to the comparison result. That is, if the value of the variable SC matches the reference value REF1, the operation of the process 609 is performed. If the value of the variable SC does not match the reference value REF1, the process proceeds to the next process, that is, the process 408 of FIG. By performing this processing, the value is set to the variable FADD a predetermined number of times, and it is monitored that the synchronous detection operation is performed a predetermined number of times.

In the process 609, the value of the variable SUM is compared with zero, and the next process is selected according to the comparison result. That is, if the value of the variable SUM is greater than zero, the operation of the process 610 is performed, and if the value of the variable SUM is not greater than zero, the operation of the process 611 is performed.

In the process 610, a value obtained by adding the offset value FO and the correction value DFO is set as a new offset value FO (FO ← FO + DFO). The correction value DFD is a positive number of 1 or more, and is 1 in this case.

In the process 611, a value obtained by subtracting the correction value DFO from the offset value FO is set as a new offset value FO (FO ← FO−DFO). Thereafter, the operation of the process 612 is performed.

In the process 612, the offset value FO is set as shown in FIG.
Is output to the DA converter 107a of the arithmetic unit 103, and is converted into an offset signal OF. Steps 610 to 612
, A correction operation of the offset signal OF is performed. After that, the operation of the process 613 is performed.

In step 613, variables are initialized in preparation for the next correction operation. That is, the value of the variable SC is set to zero (SC ← 0), and the value of the variable SUM is set to zero (SU
M ← 0). Thus, preparation for the next correction operation is performed. Thereafter, the operation of the process 614 is performed.

In step 614, a value obtained by adding 1 to the value of the variable NFO is set as a new value of the variable NFO. By performing this operation, the variable NFO is changed from step 609 to step 613.
Since the content increases each time the above operation is performed, the number of times the correction operation is performed is held. Then, processing 61
5 is performed. In the process 615, the variable NFO is compared with the reference value NFO_MAX, and the next process is selected according to the result. That is, when the variable NFO is equal to the reference value N
When it is equal to FO_MAX, the operation of the process 616 is performed. When the variable NFO is not equal to the reference value NFO_MAX, the process proceeds to the next process, that is, the process 408 in FIG.

In step 616, the value of the variable FOSW is set to 1. By performing this process, the operation of the process 407 is not performed from the next time due to the branch determination of the process 406 in FIG.

With the above control, automatic focus adjustment is performed. The explanation is added below. First, the process 60 of FIG.
In 1, by adding 1 to the variable SC used in the process 602, the function table of the sine wave in the process 502 is referred to while thinning out. Thus, the variable FADD
Is set at a relatively low frequency. If this relatively low frequency is set within the control band of the focus control, the objective lens 110 vibrates according to the signal of the variable FADD.

When the focal position coincides with the recording surface of the optical disk 113, the value of the amplitude signal RF3T of the information reproducing circuit 112 of FIG. 1 becomes maximum, and the amplitude value M3T of the processing 604 of FIG. Become. Further, as the objective lens 110 defocuses from the focal position, the amplitude signal RF3T and the amplitude value M3T become smaller.

Here, when the objective lens 110 vibrates at a position defocused from the focal position, the phase of the variation of the variable FADD and the variation of the amplitude value M3T differ by about 180 degrees due to the difference in the defocus direction. That is, when the objective lens 110 is defocused in the direction away from the optical disk 113 and the variable FADD increases, the objective lens 110 moves further in the direction away from the optical disk 113, and the value of the amplitude value M3T decreases. Therefore, the variable FA
The phase of the increase / decrease relationship between the DD and the amplitude value M3T differs by about 180 degrees. On the other hand, when the objective lens 110 is defocused in the direction approaching the optical disc 113, if the variable FADD increases, the objective lens 110 moves in the direction away from the optical disc 113, so that defocus is improved and the value of the amplitude value M3T becomes To increase. Therefore, the phase of the increase / decrease relationship between the variable FADD and the amplitude value M3T matches.

Since the value of the variable FADD is changed in a sinusoidal manner by the process 602 in FIG. 6 and the amplitude M3T is detected in synchronization with the variable FADD by the processes 605 to 607, the direction of defocus is detected. it can.

In processing 609, processing 605 to processing 60
According to the direction of the defocus detected by the processing of step 7,
The offset value FO is corrected. Thereby, the defocus is corrected.

That is, when the objective lens 110 is defocused in a direction away from the optical disk 113,
The phase of the increase / decrease relationship between the variable FADD and the amplitude value M3T is 180.
Therefore, the synchronous detection result of the variable SUM is a negative value. When the value of the variable SUM is negative, the offset value FO is corrected in the negative direction in the processing 611. Thereby, the objective lens 110 moves in a direction approaching the optical disc 113, and the defocus is corrected.

On the other hand, when the objective lens 110 is
When defocusing in the direction approaching 3, the variable FA
Since the phase of the increase / decrease relationship between the DD and the amplitude value M3T matches,
The synchronous detection result of the variable SUM is a positive value. Variable SU
If the value of M is positive, the offset value F
Correct O in the positive direction. Thereby, the objective lens 110
Moves in a direction away from the optical disc 113 and the defocus is corrected. By performing the operation of the focus adjustment unit 407 as shown in FIG. 6 as described above, the focus adjustment of the focus control system is performed.

In this embodiment, the variable LGSW shown in FIG.
Are used to control the operations of the control gain adjustment unit 405 and the focus adjustment unit 407. That is, the operation control unit 404 of FIG.
Accordingly, when the variable LGSW is 0, the operation of the focus adjustment unit 407 is not performed. When the operation of the control gain adjustment unit 405 is completed, the variable LGSW is set to 1 by the process 512 in FIG. As a result, the operation of the focus adjustment unit 407 is performed by the operation of the operation control unit 404 in FIG.

By the processing as shown in FIG.
The operation of the control gain adjustment unit 405 is always performed before the operation of 07. This stabilizes the operation of the focus adjustment unit 407. Hereinafter, this will be described.

The frequency characteristic when the variable kg of the amplification calculation in the process 503 of FIG. 5 is a predetermined value, that is, the frequency characteristic after the control gain adjusting unit 405 operates is shown as a characteristic A in FIG.
8 shows the frequency characteristic when the variable kg is smaller than a predetermined value, that is, when the control gain adjustment unit 405 is not operating. FIG. 8 shows the vibration frequency f1 of the objective lens 110 during the focus adjustment.

In FIG. 8, the frequency f1 in the case of the characteristic A
The vibration amplitude of the objective lens 110 at the frequency f1 in the case of the characteristic B is R4. As shown in FIG. 8, in the frequency characteristic (characteristic B in FIG. 8) when the control gain adjustment is not performed in the focus control system, the vibration of the objective lens 110 is large. When the swing of the objective lens 110 is large, the focus control may not be possible because the control limit of the focus control system is exceeded.

However, as in the present embodiment, the focus adjustment unit 4
If the operation of the control gain adjustment unit 405 is performed before the operation of the operation 07, the frequency characteristic shown in the characteristic A of FIG. 8 is obtained. Therefore, the vibration amplitude of the objective lens 110 at the frequency f1 is changed to the initial frequency characteristic state. It does not depend and becomes constant. Thereby, the stability of the operation of the focus adjustment unit 407 is improved.

In this embodiment, the frequency f1 shown in FIG. 8 is set within the control band of the focus control. Thus, even when the value of the frequency f1 slightly changes, the vibration amplitude of the objective lens 110 is maintained at a predetermined amount. This further improves the stability of the operation of the focus adjustment unit 407.

Further, in the present embodiment, in process 603 of FIG. 6, the process waits for the value of the variable SC to reach a predetermined value SC_TH. This is for taking in the amplitude signal RF3T after a lapse of a predetermined time since the value is set to the variable FADD. With this configuration, since the correction calculation operation of the focus adjustment unit 407 starts after the vibration of the objective lens 110 is settled, the detection accuracy of the amplitude signal RF3T is improved, and the adjustment accuracy of the focus adjustment unit 407 is improved. Further improve.

As described above, by performing the operation of the control gain adjustment unit 405 before the operation of the focus adjustment unit 407,
The adjustment accuracy and stability of the focus adjustment unit 407 are improved. In this embodiment, the offset signal is added in the error signal combining unit to adjust the offset of the focus error signal. However, the focus error signal is generated by combining and adding a plurality of sensor signals at a predetermined combining ratio. However, the same effect can be obtained even if the combining ratio is changed by the offset signal.

In the operation of the focus adjustment unit, in the present embodiment, the focus position is adjusted by changing the offset signal of the error signal synthesis unit. However, a DC offset may be given to the variable FADD.

In this embodiment, the addition of the wobbling signal is realized by changing the set value to the variable FADD. However, the same effect can be obtained by changing the offset signal of the error signal synthesizing unit.

In this embodiment, the astigmatism method is used as a method for generating the focus error signal.
An edge method or another detection method may be used. Similar effects can be obtained regardless of the focus error detection method.

Further, the arithmetic unit may be constituted by hardware, and may perform the same operation as the operation according to the program of the present embodiment. In addition, various changes can be made to the above embodiment without departing from the gist of the present invention.

[0099]

As described above, according to the present invention, the stability of the operation of the focus adjustment unit is improved by performing the operation of the control gain adjustment unit before the operation of the focus adjustment unit. Therefore, stable focus adjustment can be performed regardless of the initial state of the focus control system, and the focus control device according to the present invention can be applied to various optical disk devices.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a focus control device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating an example of an error signal synthesizer included in the focus control device of FIG. 1;

FIG. 3 is a block diagram showing an example of an information reproducing circuit constituting the focus control device of FIG. 1;

FIG. 4 is a flowchart illustrating an example of a process performed by an arithmetic unit that forms the focus control device in FIG. 1;

FIG. 5 is a flowchart showing a control gain adjustment process in the flowchart of FIG. 4;

FIG. 6 is a flowchart showing focus adjustment processing in the flowchart of FIG. 4;

FIG. 7 is a graph showing a frequency characteristic of a vibration amplitude of an objective lens in the focus control device of FIG. 1;

8 is a graph showing a frequency characteristic of an oscillation amplitude of an objective lens in focus adjustment by the focus control device of FIG. 1;

FIG. 9 is a diagram showing a quadrant sensor and a spot shape of reflected light.

[Explanation of symbols]

 Reference Signs List 101 quadrant sensor 102 error signal synthesizer 103 arithmetic unit 108 drive circuit 109 focus actuator 112 information reproduction circuit 404 operation control unit 405 control gain adjustment unit 407 focus adjustment unit 408 wobbling unit 409 phase compensation unit

Claims (5)

[Claims] 1. A sensor means for receiving reflected light from an optical disc and outputting a plurality of sensor signals, and an error signal combining means for combining a plurality of sensor signals of the sensor means to generate a focus error signal. Information reproducing means for reproducing the recorded information of the optical disk from the reflected light from the optical disk, an arithmetic means for inputting the focus error signal and the reproduced signal of the information reproducing means and outputting a drive signal,
A driving unit that outputs a driving current proportional to the driving signal; and a focus actuator that drives an objective lens according to the driving current of the driving unit. The arithmetic unit outputs a predetermined wobbling signal to the focus error signal. A wobbling means for outputting the added signal, a phase compensation means for receiving an output signal of the wobbling means, performing at least a phase compensation operation and an amplification operation and outputting the drive signal, and reproducing the wobbling signal and the information reproducing means A focus adjusting means for adjusting a focus position according to a signal; and a gain adjusting means for adjusting a gain of an amplification operation of the phase compensating means according to the wobbling signal and the focus error signal. Focusing control after the operation of the gain adjusting means is completed. 2. An error signal synthesizing unit generates a focus error signal by adding a predetermined offset signal after adding and synthesizing a plurality of sensor signals, and a focus adjusting unit includes a wobbling signal and a reproduction signal of the information reproducing unit. 2. The focus control device according to claim 1, wherein a focus position is adjusted by changing a predetermined offset signal of said error signal synthesizing means in accordance with the following. 3. The focus control device according to claim 1, wherein the frequency of the wobbling signal of the wobbling means when the focus adjustment means operates is a frequency within a focus control band after the operation of the gain adjustment means. . 4. The focus control device according to claim 1, wherein the focus adjustment means starts operation after a predetermined time has elapsed after the wobbling means adds the wobbling signal to the focus error signal. 5. A sensor means for receiving reflected light from an optical disk and outputting a plurality of sensor signals, and an error signal combining means for combining a plurality of sensor signals of the sensor means to generate a focus error signal. Information reproducing means for reproducing the recorded information of the optical disk from the reflected light from the optical disk, an arithmetic means for inputting the focus error signal and the reproduced signal of the information reproducing means and outputting a drive signal,
A drive unit that outputs a drive current proportional to the drive signal; and a focus actuator that drives an objective lens in accordance with the drive current of the drive unit. Phase compensating means for performing compensation operation and amplification operation and outputting the drive signal, wobbling means for adding a predetermined wobbling signal to the focus error signal, and a focal position according to the wobbling signal and a reproduction signal of the information reproducing means. Focus adjusting means for adjusting the gain of the amplification operation of the phase compensating means in accordance with the wobbling signal and the focus error signal, and completing the operation of the focus adjusting means. A focus control device comprising: operation control means to be performed later.