JPH09120551A - Optical disk drive device and servo loop gain setting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the dispersion of drive sensitivity together with the dispersion of signal sensitivity by deciding a loop gain based on an oscillation frequency of a focus error signal. SOLUTION: Outputs of photodetectors become their respective voltages V1-V4, which are then inputted to an FE signal generating circuit 7 in which an FE signal for showing focus displacement of a light spot is generated. This FE signal is inputted to a 1st variable gain amplifier 6 and is amplified. Then, the FE signal is subjected to a phase advancing compensation by a 1st phase compensation circuit 5. An objective lens 3a of an optical pickup 3 is moved via a focus actuator driving circuit 4 by the phase-compensated FE signal to perform a focus servo. The voltages V1-V4 are simultaneously inputted to a TE signal generating circuit 11 to generate a TE signal showing a track deviation. This TE signal is subjected to a phase lead compensation by a 2nd phase compensation circuit 9, and hence the objective lens 3a is moved to perform a track servo.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a CD-R and a CD.
-ROM, CD-DA, MO drive, and other optical disk drive devices, and more particularly, an optical disk drive device and a servo loop gain control device that enable accurate correction of loop gain in focus servo, track servo, and carriage servo of an optical disk drive. Regarding the setting method.

[0002]

2. Description of the Related Art Conventionally, by making a track jump, the level of a tracking error signal (TE signal) is detected, and the gain of a variable gain amplifier circuit can be set according to the level of the tracking error signal (TE signal). There is known an optical reproducing device in which variations in loop gain are reduced (for example, Japanese Patent Laid-Open No. 62-114126). However, with this method, variations in signal sensitivity can be corrected, but variations in drive sensitivity cannot be corrected (lines 5 to 8 in the lower left column of page 2 of the above publication).

[0003]

In the conventional optical disk drive, it is possible to correct the variation in the signal sensitivity of the loop gain of the track servo, but it is impossible to correct the variation in the driving sensitivity. The same applies to variations in focus drive sensitivity and variations in carriage drive sensitivity, which are unsolved problems that cannot be corrected.

In the present invention, it is an object of the present invention to reduce the variation in drive sensitivity in addition to the variation in the signal sensitivity of the loop gain of the focus servo (the inventions of claims 1 and 4). Similarly, with respect to the loop gain of the track servo, the variation in the driving sensitivity is also reduced together with the variation in the signal sensitivity (the inventions of claims 2 and 5). Further, with respect to the variation of the loop gain of the carriage servo, the variation of the driving sensitivity is reduced together with the variation of the signal sensitivity (the inventions of claims 3 and 6).

[0005]

According to another aspect of the present invention, there is provided an optical disk drive apparatus comprising: a variable gain amplifying means for controlling a loop gain of a focus servo; and a detecting means for detecting an oscillation frequency of a focus error signal. In the drive device, the loop gain is determined based on the oscillation frequency of the focus error signal.

According to another aspect of the present invention, there is provided an optical disc driving device including a variable gain amplifying means for controlling a loop gain of a track servo and a detecting means for detecting an oscillation frequency of a tracking error signal.
The loop gain is determined based on the oscillation frequency of the tracking error signal.

According to a third aspect of the present invention, there is provided an optical disc driving device including a variable gain amplifying means for controlling a loop gain of a carriage servo of an optical head and a detecting means for detecting an oscillation frequency of the carriage servo. The loop gain of the carriage servo is determined based on the oscillation frequency of the carriage servo.

According to a fourth aspect of the present invention, there is provided a focus servo loop gain setting method for an optical disk drive, comprising: a variable gain amplifying means for controlling the focus servo loop gain; and a detecting means for detecting the oscillation frequency of the focus error signal. In the optical disk drive, a desired loop gain G is obtained based on the focus error signal oscillation frequency fn, the focus servo loop gain G (N), and the focus servo loop gain characteristic [frequency fx, loop gain G]. Is determined by a calculation formula of G = G (N) × (fx / fn).

According to a fifth aspect of the present invention, there is provided a track servo loop gain setting method for an optical disk drive, comprising: a variable gain amplifying means for controlling a loop gain of the track servo; and a detecting means for detecting an oscillation frequency of a tracking error signal. In the optical disk drive, a desired loop gain G is obtained based on the oscillation frequency ft of the tracking error signal, the loop gain G (T) of the track servo, and the loop gain characteristic [frequency fy, loop gain G] of the track servo. Is determined by a calculation formula of G = G (T) × (ft / fy).

According to another aspect of the present invention, there is provided a method for setting a loop gain of a carriage servo of an optical disk drive, comprising: a variable gain amplifying means for controlling a loop gain of a carriage servo of an optical head; and a detecting means for detecting an oscillation frequency of the carriage servo. In an optical disc drive including: a carriage servo oscillation frequency fc, a carriage servo loop gain G (C), and a carriage servo loop gain characteristic [frequency fz, loop gain G],
The desired loop gain G is determined by a calculation formula of G = G (C) × (fc / fz).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an optical disk drive device and a servo loop gain setting method according to the present invention will be described in detail with reference to the drawings. First, the overall configuration of the optical disk drive device of the present invention will be described.

FIG. 1 is a functional block diagram showing an example of an embodiment of a main part configuration of an optical disk drive of the present invention. In the figure, 1 is an optical disk, 2 is a spindle motor, 3 is an optical pickup, 3a is an objective lens, 4 is a focus actuator drive circuit, and 5 is a first.
Phase compensation circuit, 6 is the first variable gain amplifier, and 7 is FE
(Focus error) signal generation circuit, 8 is a track actuator drive circuit, 9 is a second phase compensation circuit, 10 is a second variable gain amplifier, 11 is a TE (tracking error) signal generation circuit, and 12 is a linear motor drive circuit. , 13
Is a third phase compensation circuit, 14 is a third variable gain amplifier,
15 is a PES (position error) signal generation circuit, 16
Is a frequency counter, 17 is a control signal generation circuit,
Reference numeral 18 is a CPU bus, SW1 to SW3 are analog switches, and V1 to V4 and Va and Vb are voltages of detection output of the optical pickup 3.

FIG. 2 is a view showing a light receiving surface of a photodetector provided in the optical pickup 3 of FIG. 1, in which (1) is a focus,
A first photodetector for detecting the track position and (2) a second photodetector for detecting the position of the objective lens. In the figure, 31 is a first photodetector, 32 is a second photodetector, V
Reference numerals 1 to V4 indicate the respective detection outputs of the four-divided light receiving elements of the first photodetector 31, and Va and Vb indicate the respective detection outputs of the two-divided light receiving elements of the second photodetector 32.

The optical disk drive device shown in FIG.
The basic configuration is the same as that of the conventional apparatus, but is characterized in that a frequency counter 16 is added and that an optical disc drive control and a loop gain setting control are performed by a system controller (not shown). The function and operation of each part are as follows. Optical pickup 3
Has a function of detecting the focus and track position of the optical disc 1, and is provided with a first photodetector 31 composed of four-division light receiving elements as shown in FIG. 2 (1). Further, the optical pickup 3 has a function of detecting the position of the objective lens 3a, and as shown in FIG. 2 (2), is provided with a second photodetector 32 composed of a two-divided light receiving element. There is.

First, the focus servo system will be described. The first photodetector 31 includes a photodiode and I /
It is composed of a V (current-voltage conversion) amplifier, and each output has voltages V1 to V4 as shown in FIG. 2 (1). These outputs are input to the FE signal generation circuit 7 in FIG. 1 and subjected to matrix calculation to generate an FE signal indicating the focus shift of the light spot. This FE signal is input to the first variable gain amplifier 6 and amplified by an arbitrary gain.

The first variable gain amplifier 6 can be composed of, for example, a resistance attenuator and an OP amplifier. The gain of the first variable gain amplifier 6 can be set to an arbitrary level by a signal given from the system controller CPU via the CPU bus 18. This signal is input to the frequency counter 16 through the analog switch SW1 and transmitted to the system controller CPU through the CPU bus 18. Therefore, the system controller CPU can read the oscillation frequency of this signal.

Further, the FE signal is subjected to phase lead compensation by the first phase compensation circuit 5 in order to stably operate the focus servo. The FE signal thus phase-compensated moves the objective lens 3a of the optical pickup 3 via the focus actuator drive circuit 4, and the focus servo is performed.

Next, the track servo system will be described. Voltages V1 to V4 output from the first photodetector 31
Is simultaneously input to the TE signal generation circuit 11 to generate a TE signal indicating a track deviation. This TE signal is amplified to an arbitrary gain by the control of the system controller CPU via the second variable gain amplifier 10.

This TE signal is also an analog switch SW.
2. The frequency counter 16 allows the system controller CPU to read the oscillation frequency. Further, this TE signal is subjected to phase advance compensation by the second phase compensation circuit 9, and the TE signal whose phase has been compensated is
The objective lens 3a of the optical pickup 3 is moved via the track actuator drive circuit 8 to perform track servo. Although the track servo system is briefly described, it is basically the same as the focus servo system described above.

Finally, the carriage servo system will be described. The voltages Va and V output from the second photodetector 32
b is input to the PES signal generation circuit 15, and a PES signal indicating the positional deviation of the objective lens 3a of the optical pickup 3 is generated. This PES signal is also input to the frequency counter 16 via the analog switch SW3 via the third variable gain amplifier 14 and transmitted to the system controller CPU via the CPU bus 18. Therefore,
The system controller CPU can read the oscillation frequency of this PES signal.

The PES signal is also input to the third phase compensating circuit 13 for phase lead compensation. The phase-compensated PES signal is given to the linear motor drive circuit 12 to move the carriage on which the optical head is mounted to perform carriage servo. The above is the outline of the configurations and operations of the focus servo system, the track servo system, and the carriage servo system.

The present invention is characterized by the loop gain setting method for each of these servo systems (inventions 1 to 6).

FIG. 3 is a diagram showing the open loop characteristics of the focus servo loop. The horizontal axis of the figure shows the frequency f, the vertical axis shows the gain G, A to D are gain characteristics caused by variations in detection sensitivity and drive sensitivity,
fa to fd indicate respective gain intersection points.

The characteristics shown in FIG. 3 are so-called gain characteristics (gain curves), and the loop gains (A to D) and the gain intersections (fa to fd) also vary due to variations in detection sensitivity and drive sensitivity. Has occurred. The relationship between the gain characteristics A to D is A <B <D <C, and the corresponding gain intersection points fa to fd (frequency) are also fa <f.
The relationship is b <fd <fc. Then, each gain characteristic A
Each of ~ D changes at substantially equal intervals (the linear relationship is maintained).

Here, as an example, the gain intersection is fb.
A method of setting the loop gain so as to satisfy (characteristic of B) will be described. First, the system controller CP
With U, the gain of the variable gain amplifier is set low, and the focus servo is turned on.

Since the characteristic at this point is the case where the gain is the lowest, it is the characteristic line of A in FIG. 3, and the corresponding gain intersection is fa. From this state, the gain is adjusted and gradually increased. In this case, the loop gain is gradually increased, and C is gradually increased as A → B → D → C.
Will approach the characteristics of. However, as the gain becomes higher, the phase margin disappears, and the focus error signal FE oscillates from a certain frequency (D in FIG. 3).
Line).

Therefore, when the focus error signal FE oscillates, the contents of the frequency counter 16 are read by the system controller CPU. Since this oscillation frequency is the frequency at the gain intersection point, it corresponds to fd in FIG. The above is the operation for setting the loop gain so that the gain intersection is fb (characteristic of B). The set gain is the characteristic of D larger than the target value, and the gain intersection is fd (= Oscillation frequency).

Next, calculation is performed to set the loop gain. Here, the gain set by the system controller CPU is G (D), and the desired gain is G. As is clear from FIG. 3, the gain characteristics A to D
And the gain intersection point are in a substantially linear relationship.
Then, by the previous operation, the system controller CP
The gain set by U is G (D), and the gain intersection is fd.
Has been measured. The gain G you want to set is
This is the characteristic of B, and the gain intersection is fb, but the gain intersections fb and fd can be obtained from FIG. 3, and the gain G (D) is also a known value.

Therefore, the desired gain G can be obtained by calculating the gain G to be set according to the following equation: G = G (D) × (fb / fd). This calculation is performed by the system controller CPU. The gain G thus obtained is set in the variable gain amplifier.

In this state, the gain characteristic of FIG. 3 becomes the characteristic of B, and the gain intersection point becomes the target fb (the invention of claims 1 and 4). FIG. 3 shows the gain characteristic in the case of the focus servo, but the gain characteristic is almost the same in the track servo and the carriage servo. Therefore, also for the track servo and the carriage servo, if the loop gain is similarly increased, the gain G is calculated from the oscillation frequency and the set gain at that time, and the servo loop is determined so as to become the target gain intersection point. Good (inventions of claims 2 and 3, and claims 5 and 6).

[0031]

According to the optical disk driving apparatus of the first aspect, the set gain of the focus servo loop is determined by detecting the oscillation frequency of the focus error signal and performing calculation based on the value. Therefore, it is possible to cancel the variation in the detection sensitivity and the driving sensitivity, and it is possible to set the focus servo loop having the target gain intersection point.

According to another aspect of the present invention, the set gain of the track servo loop is determined by detecting the oscillation frequency of the tracking error signal and performing calculation based on the detected value. Therefore, it is possible to cancel the variation in the detection sensitivity and the driving sensitivity, and it is possible to set the track servo loop having the target gain intersection point.

In the optical disk drive apparatus according to the third aspect, the set gain of the carriage servo loop is determined by detecting the oscillation frequency of the carriage servo and performing calculation based on the value. Therefore, it is possible to cancel the variation in the detection sensitivity and the driving sensitivity, and it becomes possible to set the carriage servo loop having the target gain intersection point.

According to another aspect of the present invention, there is provided a focus servo loop gain setting method for an optical disk drive, wherein the focus error signal oscillation frequency fn, the focus servo loop gain G (N), and the focus servo loop gain characteristic [frequency fx, Loop gain G], the desired loop gain G is determined by the calculation formula G = G (N) × (fx / fn). Therefore, similarly to the optical disk drive device according to the first aspect, it is possible to cancel the variation in the detection sensitivity and the drive sensitivity, and it is possible to set the focus servo loop having the target gain intersection point.

In the track servo loop gain setting method for an optical disk drive according to a fifth aspect of the present invention, the tracking error signal oscillation frequency ft, the track servo loop gain G (T), and the track servo loop gain characteristic [frequency fy, Loop gain G], the desired loop gain G is determined by the calculation formula G = G (T) × (ft / fy). Therefore, similarly to the optical disk drive device according to the second aspect, it is possible to cancel the variation in the detection sensitivity and the drive sensitivity, and to set the track servo loop having the target gain intersection point.

In the loop gain setting method for the carriage servo of the optical disk drive according to the sixth aspect, the oscillation frequency fc of the carriage servo, the loop gain G (C) of the carriage servo, and the loop gain characteristic of the carriage servo [frequency fz, loop Gain G], a desired loop gain G is determined by a calculation formula of G = G (C) × (fc / fz). Therefore, similarly to the optical disk drive device according to the third aspect, it is possible to cancel the variation in the detection sensitivity and the drive sensitivity, and it becomes possible to set the carriage servo loop having the target gain intersection point.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an example of an embodiment of a main part configuration of an optical disk drive of the present invention.

FIG. 2 is a diagram showing a light receiving surface of a photodetector provided in the optical pickup 3 of FIG.

FIG. 3 is a diagram showing a loop open loop characteristic of a focus servo loop.

[Explanation of symbols]

 1 Optical Disc 2 Spindle Motor 3 Optical Pickup 3a Objective Lens 4 Focus Actuator Drive Circuit 5 First Phase Compensation Circuit 6 First Variable Gain Amplifier 7 FE (Focus Error) Signal Generation Circuit 8 Track Actuator Drive Circuit 9 Second Phase Compensation Circuit 10 Second variable gain amplifier 11 TE (tracking error) signal generation circuit 12 Linear motor drive circuit 13 Third phase compensation circuit 14 Third variable gain amplifier 15 PES (position error) signal generation circuit 16 Frequency counter 17 Control Signal generation circuit 18 CPU bus

Claims (6)

[Claims] 1. An optical disc driving apparatus comprising: a variable gain amplifying means for controlling a loop gain of a focus servo; and a detecting means for detecting an oscillation frequency of a focus error signal. An optical disk drive device, wherein the loop gain is determined. 2. An optical disk drive comprising a variable gain amplifying means for controlling a loop gain of a track servo and a detecting means for detecting an oscillating frequency of a tracking error signal, which is based on the oscillating frequency of the tracking error signal. An optical disk drive device, wherein the loop gain is determined. 3. An optical disk drive comprising a variable gain amplifying means for controlling a loop gain of a carriage servo of an optical head and a detecting means for detecting an oscillation frequency of the carriage servo, wherein the oscillation frequency of the carriage servo is An optical disk drive device, wherein the loop gain of the carriage servo is determined based on the above. 4. An optical disc driving apparatus comprising: a variable gain amplifying unit for controlling a loop gain of a focus servo; and a detecting unit for detecting an oscillation frequency of a focus error signal. , Based on the focus servo loop gain G (N) and the focus servo loop gain characteristic [frequency fx, loop gain G], the desired loop gain G is G = G (N) × (fx / fn) A loop servo gain setting method for a focus servo of an optical disk drive, characterized by being determined by the following formula. 5. An optical disc driving device comprising a variable gain amplifying means for controlling a loop gain of a track servo and a detecting means for detecting an oscillation frequency of a tracking error signal, wherein an oscillation frequency ft of the tracking error signal is set. , Based on the track servo loop gain G (T) and the track servo loop gain characteristic [frequency fy, loop gain G], the desired loop gain G is G = G (T) × (ft / fy) A method for setting a loop gain of a track servo of an optical disk drive, characterized by being determined by the following formula. 6. An optical disk drive comprising a variable gain amplifying means for controlling a loop gain of a carriage servo of an optical head and a detecting means for detecting an oscillation frequency of the carriage servo, wherein the oscillation frequency fc of the carriage servo. And a loop gain G (C) of the carriage servo and a loop gain characteristic [frequency fz, loop gain G] of the carriage servo, a desired loop gain G is expressed as G = G (C) × (fc / fz ) A loop gain setting method for a carriage servo of an optical disk drive, characterized in that the loop gain for the carriage servo is determined based on the equation (4).