JPH10177726A - Tracking error signal generating circuit and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tracking error signal generating circuit and method capable of generating a accurate tracking error signal by a phase difference method even when a linear velocity is changed. SOLUTION: This circuit is provided with a control circuit 30 changing delay times of delay means 12A, 12B, 12C, 12D delaying an output signal of an optical pickup by the relative linear velocity of the light spot of the optical pickup with an optical recording medium. Further, when the linear velocity is measured from the output signal of the optical pickup, though a measured value is used, when the linear velocity is not measured as at a searching time, the linear velocity is obtained from a slider position and the number of revolution of a spindle motor by operation to be estimated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to tracking servo control of an optical pickup for an optical recording medium, and more particularly to a tracking error signal generation circuit and a tracking error signal generation method.

[0002]

2. Description of the Related Art When reproducing a signal from an optical disk with an optical pickup or writing a signal to the optical disk, a spot of a light beam from the optical pickup is accurately irradiated onto a predetermined track, and the eccentricity of the optical disk is reduced. So-called tracking servo control is performed so that the light spot follows the track and relatively moves even if there is external vibration or the like. To perform tracking servo control, a tracking actuator that generates a tracking error signal from the signal detected by the optical pickup and moves the objective lens of the optical pickup minutely in the radial direction of the optical recording medium using this error signal. Feedback control is also performed on a slider (also referred to as a traverse motor) that moves the optical pickup itself largely in the radial direction of the optical recording medium as necessary.

There are several types of methods for generating a tracking error signal. A phase difference detection (DPD) method detects a phase difference between output signals of an optical pickup having a plurality of optical sensor portions to generate a tracking error signal. According to the method, the number of beams of the optical pickup may be one, and
The structure of the optical system is simpler than the beam method. Also,
In the push-pull method, the offset and gain of the tracking error signal fluctuate due to the movement of the lens. However, the phase difference detection method is convenient in that once the adjustment is completed, there is no such fluctuation. Further, in the phase difference detection method, since it is not necessary to correct the offset and the gain of the tracking error signal, a complicated configuration such as adding a lens position sensor, which has been conventionally performed, is unnecessary. Further, in the phase difference detection method, since only the phase difference of the signal is used, the method is less susceptible to fluctuations in the reflectivity of the disk, and is advantageous in that stable servo control can be expected.

[0004]

FIG. 5 is a block diagram showing a configuration of a tracking error signal generation circuit based on such a conventional phase difference detection method. The optical pickup has a four-divided sensor part ABCD, and its output signal is delayed by a corresponding delay circuit DL. The delayed signal is 4
The output signals on the diagonal lines of the divided sensors are added by an adder, and the output signals of the two adders are compared with predetermined reference values by a comparator to be binarized.
A phase comparator detects a phase difference between the two binarized signals, and generates a tracking error signal through the LPF using the phase difference signal.

Here, each delay circuit is supplied with a delay time adjustment signal, and the delay time is adjusted as required. In the conventional delay time adjustment, first, the objective lens of the optical pickup is moved from the middle point by adding an offset for shifting the objective lens in the radial direction of the optical disk by a fixed amount. At this time, the offset of the tracking error signal is detected by the tracking error signal offset detector, and the delay time is adjusted so that the offset becomes zero. Generally, an optical disk such as a CD or a CD-ROM is read at a CLV (constant linear velocity). To read at high speed, the optical disk may be rotated at a CAV (constant angular velocity). Instead of sequentially reading out signals in a certain direction, the light spot is not CLV during a so-called search operation in which a light spot jumps to a place separated in a radial direction of the optical disk.

As described above, when the linear velocity is not constant, an offset occurs in the tracking error signal due to lens shift unless the delay time of the delay circuit is readjusted.
In order to make this offset 0, it is necessary to readjust the delay time of the delay circuit, but when searching, when tracking servo control is turned on, or when the linear velocity changes continuously like CAV It is extremely difficult to readjust the delay time every moment, and no effective countermeasures have been taken in the past.

Accordingly, the present invention provides a tracking error signal generating circuit and a tracking error signal generating method capable of generating an accurate tracking error signal by the phase difference method even when the linear velocity changes. Aim.

[0008]

In order to achieve the above object, according to the present invention, a delay time of a delay means for delaying an output signal of an optical pickup is changed by a relative linear velocity of an optical spot of the optical pickup with respect to an optical recording medium. Like that. When the linear velocity can be measured from the output signal of the optical pickup, the measured value can be used.However, when the linear velocity cannot be measured as in a search, the linear velocity is calculated from the slider position and the number of rotations of the spindle motor. It is a preferable mode to estimate by calculation.

That is, according to the present invention, an optical disk apparatus for converging a light beam from an optical pickup onto a track of an optical recording medium to irradiate a light spot, detecting reflected light or transmitted light, and performing tracking servo control. A plurality of delay means for delaying a plurality of output signals of the optical pickup,
Two comparing means for binarizing each of the plurality of output signals of the optical pickup or their operation signals delayed by the plurality of delay means, and a phase for comparing the phases of the output signals of the two comparing means. Comparing means for generating a tracking error signal in response to an output signal of the phase comparing means; tracking error signal offset detecting means for detecting an offset of the tracking error signal; and A tracking error signal generating circuit having delay time setting means for setting a delay time of the delay means; means for measuring and / or estimating a linear velocity of a light spot of the optical pickup with respect to the optical recording medium; According to the linear velocity obtained by the means for measuring or estimating A delay time correction means for correcting the delay time set by the length of time setting means, the tracking error signal generating circuit, characterized in that it comprises is provided.

According to the present invention, there is provided a spindle motor for rotating an optical recording medium, slider means for moving an optical pickup in a radial direction of the optical recording medium, and light from the optical pickup on a track of the optical recording medium. An optical disc device in which the optical pickup has a four-division optical sensor portion that irradiates a light spot by condensing a beam and detects reflected light or transmitted light, and performs tracking servo control based on an output signal from the four-division sensor. A tracking error signal generating circuit used in the above, wherein four delay means for respectively delaying the output signal of the four-division optical sensor portion, and the four delay means respectively delayed by the four delay means.
Two adding means for adding output signals of two light sensor parts on a diagonal line of the four-division light sensor part among output signals of the divided light sensor parts, and binarizing output signals of the two adding means, respectively Two comparing means, a phase comparing means for comparing phases of output signals of the two comparing means, a means for generating a tracking error signal in response to an output signal of the phase comparing means, and the tracking error signal A tracking error signal offset detecting means for detecting an offset of the optical disc; a spindle motor rotational speed detecting means for detecting the rotational speed of the spindle motor; and a radial position of the optical pickup medium movable by the slider. Slider position detecting means for detecting the position of the slider and the output signal of the tracking error signal offset detector. An initial delay time setting means for setting an initial delay time, and a line for calculating a linear velocity at a light spot position by the optical pickup based on an output signal of the spindle motor rotational speed detecting means and an output signal of the slider position detecting means. A tracking error signal generation circuit is provided, comprising: a speed calculating means; and an initial delay time correcting means for changing the initial delay time according to the linear velocity obtained by the calculation by the linear speed calculating means.

According to the present invention, a spindle motor for rotating an optical recording medium, slider means for moving an optical pickup in a radial direction of the optical recording medium, and light from the optical pickup on a track of the optical recording medium A tracking error signal generation method used in an optical disc apparatus for focusing and irradiating a light spot, detecting reflected light or transmitted light thereof, and performing tracking servo control, wherein a plurality of output signals of the optical pickup are delayed. A plurality of delay means for causing the plurality of output signals of the optical pickup respectively delayed by the plurality of delay means or an arithmetic signal thereof to be binarized; and an output signal of the two comparison means. A phase comparing means for comparing phases of the two, and a tracking error signal in response to an output signal of the phase comparing means. A tracking error signal including: a generating unit; a tracking error signal offset detecting unit that detects an offset of the tracking error signal; and a delay time setting unit that sets a delay time of the delay unit based on the offset of the tracking error signal. A step of reading a target address when executing a search by moving a light spot by the optical pickup in a radial direction of the optical recording medium by a jump in the tracking error signal generating method in the generating circuit; Calculating the slider position and the rotation speed of the spindle motor at the destination address; calculating the linear velocity at the destination address from the slider position and the rotation speed of the spindle motor; and And setting to modify the delay time using the ratio of the linear velocity at a linear velocity with the target address when was boss, a tracking error signal generation method with is provided.

Further, according to the present invention, an optical disc for converging a light beam from the optical pickup onto a track of an optical recording medium to irradiate a light spot, detecting reflected light or transmitted light thereof, and performing tracking servo control. A method for generating a tracking error signal for use in a device, wherein a plurality of delay units for delaying a plurality of output signals of the optical pickup,
Two comparing means for binarizing each of the plurality of output signals of the optical pickup or their operation signals delayed by the plurality of delay means, and a phase for comparing the phases of the output signals of the two comparing means. Comparing means for generating a tracking error signal in response to an output signal of the phase comparing means; tracking error signal offset detecting means for detecting an offset of the tracking error signal; and In a tracking error signal generation method in a tracking error signal generation circuit having a delay time setting means for setting a delay time of the delay means, a linear velocity of the light spot with respect to the optical recording medium is determined from a reproduction signal from the optical pickup. Calculating, and setting the delay time And setting by modifying the delay time, the tracking error signal generation method with is provided with a linear velocity and the ratio of the current linear velocity.

[0013]

Embodiments of the present invention will be described below with reference to the drawings, together with preferred embodiments. FIG. 1 is a block diagram of a main part of a preferred embodiment of a tracking error signal generation circuit according to the present invention. The present invention provides a spindle motor (SP) for rotating an optical disk as an optical recording medium, an optical pickup for irradiating a light spot on the optical disk and detecting reflected light or transmitted light, and moving the optical pickup in a radial direction of the optical disk. It is embodied as a part of an optical disk device having a slider and the like, and these parts of the optical disk device are not shown.

In FIG. 1, the optical pickup has a four-divided sensor portion 10, and each sensor portion and its output signal are indicated by ABCD. The output signal of each sensor part ABCD of the four-divided sensor is output to a corresponding delay circuit (D
L) Delay is possible by 12A, 12B, 12C and 12D, respectively. Delay circuits 12A, 12B, 12C, 12
The output signal of D is obtained by calculating the output signals on the diagonal lines of the four-divided sensor, that is, A + C and B + D by the adders 14A and 14B, respectively, and the output signals of the two adders 14A and 14B are compared with the comparator (COMP) 16A. 16B, each is compared with a predetermined reference value ref and binarized. The phase difference between the two binarized signals is detected by the phase comparator 18, and the tracking error signal TE is generated from the phase difference signal through the LPF 20. Here, the delay circuits 12A, 12B, 12C, and 12D are supplied with a delay time adjustment signal C1 or C2 described later, and the delay time is adjusted as necessary.

The output signal of the LPF 20 is supplied to a tracking error signal offset detector 22 where a DC offset is detected and supplied to a control circuit 30. The spindle motor rotation speed detection circuit 24 detects the rotation speed of a spindle motor (not shown) using an optical sensor or a Hall element, and sends a signal indicating the rotation speed to the control circuit 30. The slider position detection circuit 26 detects the position of the optical pickup moved by a slider that moves the optical pickup (not shown) in the radial direction of the optical disk, and sends a signal indicating the radial position to the control circuit 30. The linear velocity measuring circuit 28 responds to a synchronization signal (sync) separated from a reproduced signal obtained by processing a signal from the optical pickup by a signal processing circuit (not shown), and counts this with a counter. The linear velocity is measured, and the linear velocity signal is supplied to the control circuit 30.
Send to

The operation panel 29 is used for inputting a desired operation command to the optical disk device with, for example, a keyboard. As a desired operation, a search operation for inputting a desired address and jumping there, a CLV
There is a mode for switching data from CAV to CAV and performing high-speed data search. The control circuit 30 has a CPU (Central Processing Unit) not shown, an interface, a memory, and the like.
The delay circuits 12A, 12B, 12C, and 12D generate delay time adjustment signals C1 and C2. The delay time adjustment signal includes a first delay time adjustment signal C1 supplied to the delay circuits 12A and 12B, and a second delay time adjustment signal C2 supplied to the delay circuits 12C and 12D.
The delay times set for 2A and 12B are the same, and the delay times set for delay circuits 12C and 12D are also the same.
The difference between these two delay times will be set appropriately.

At the time of normal reproduction, a synchronizing signal is obtained from the reproduced signal. Therefore, the linear velocity measuring circuit 28 operates normally to measure the linear velocity, and the linear velocity signal is sent to the control circuit 30.
However, at the time of a high-speed search or the like, since the tracking servo control is not turned on and normal reproduction cannot be performed, the linear velocity measuring circuit 28 does not operate normally, and thus the linear velocity cannot be measured. In this case, the control circuit 30 estimates the linear velocity by calculation using the rotation speed of the spindle motor obtained by the spindle motor rotation speed detection circuit 24 and the position of the optical pickup obtained by the slider position detection circuit 26. Further, the linear velocity at the target address can be similarly estimated using the target address at the time of the search.

Next, generation of a tracking error signal at the time of search will be described with reference to the flowchart of FIG. When a search request for jumping to the destination address is detected in step S1, the destination address input from the operation panel 29 is read in step S2. The slider position and the spindle motor speed corresponding to the target address are calculated in step S3. When the target address is not directly input from the operation panel 29, address data (for example, TOC information read from a disc in a music CD) stored in a predetermined memory is read in accordance with a jump destination instruction from the operation panel 29. . Next, from the operation result obtained in step S3, step S4
Calculates the linear velocity V1 at the target address. The calculation of the linear velocity differs between the case of CLV and the case of CAV.
Next, in step S5, the delay amount at the target address, that is, the delay time d1 is calculated. This calculation is based on the following equation.

[0019]

D1 = k * v0 / v1 * d0 where, v0: linear velocity when initial value of delay amount is set v1: linear velocity at target address d0: initial value of delay amount (tracking error signal is zero) K: Correction coefficient

As can be seen from the above equation, the delay time is corrected by multiplying the ratio between the linear velocity v0 when the initial value of the delay amount is set to the initial value d0 of the delay amount and the linear velocity v1 at the target address. Is basically multiplied by a correction coefficient k. The correction coefficient k is for finely adjusting the delay amount according to the time of acceleration and deceleration of the spindle motor, and is set to a value larger than 1 at the time of acceleration and smaller than 1 at the time of deceleration. When the calculation of the delay amount is completed in step S5, the delay amount is set in the delay circuits 12A, 12B, 12C, and 12D from the control circuit 30 in step S6. Thereafter, the search operation is started in step S7. In addition,
In FIG. 4, the delay amount is corrected and set before the search, but the delay amount can be corrected and set in the same procedure after the search. At the time of operation with CLV, the linear velocity gradually returns to the initial linear velocity after the search, but by repeating the operation of correcting and setting the delay amount in the same procedure, the optimal delay time is set every moment. .

FIG. 3 is a flowchart showing a processing procedure when a signal is reproduced from an optical disk by CAV. In step S10, the linear velocity is calculated using the bit clock of the reproduction signal or the cycle of the synchronization signal. Next, step S1
At step 1, the delay amount d1 is calculated. This calculation is the same as step S5 in FIG. Next, the delay amount d1 obtained by the calculation in step S12 is set, and again in step S1
It returns to 0 and repeats the same operation. In the process shown in FIG. 3, when a signal is continuously read by CAV, a reproduced signal can be read.
If there is a search request while reading data with V,
After the processing in FIG. 2 is performed, and the processing returns to CAV, the processing in FIG. 3 is executed again.

FIG. 4 is a block diagram of a modification of the circuit of FIG. 1, that is, another preferred embodiment of the present invention. In this embodiment, each of the signals A, B, C, and D from the four-divided sensor 10 is (COMP) 31A, 31 as a corresponding binarizer.
B, 31C, and 31D are used to perform binarization and subsequent processing. Binarizers 31A, 31B, 31C, 31D
Are output from delay circuits 32A, 32B, 32
C, 32D, the output signals of the delay circuits 32A, 32C are added by an adder 34A, and the delay circuits 32B, 32D
The output signal of D is added by the adder 34B. Adder 34
A and 34B output signals are supplied to a phase comparator 36, and an output signal corresponding to the phase difference is output as a tracking error signal TE via an LPF 38. The configurations and operations of the tracking error signal offset detector 22, the spindle motor rotation speed detection circuit 24, the slider position detection circuit 26, the linear velocity measurement circuit 28, the operation panel 29, and the control circuit 30 are the same as those in FIG.

[0023]

As described above, according to the present invention, even when the linear velocity is not constant, the delay time of the delay means can be automatically corrected to a value suitable for the linear velocity.
An accurate tracking error signal can be obtained, and thus accurate tracking servo control is possible. In particular, tracking servo control can be stably performed even in a state different from normal CLV control, such as during search or CAV control.

[Brief description of the drawings]

FIG. 1 is a block diagram of a preferred embodiment of a tracking error signal generation circuit according to the present invention.

FIG. 2 is a flowchart showing a processing procedure at the time of search in the tracking error signal generation method of the present invention.

FIG. 3 is a flowchart showing a processing procedure at the time of CAV control in the tracking error signal generation method of the present invention.

FIG. 4 is a block diagram of another preferred embodiment of the tracking error signal generation circuit according to the present invention.

FIG. 5 is a block diagram illustrating an example of a conventional tracking error signal generation circuit.

[Explanation of symbols]

10 Four-division sensor part of optical pickup 12A, 12B, 12C, 12D, 32A, 32B, 3
2C, 32D Delay circuit (delay means) 14A, 14B, 34A, 34B Adder (addition means) 16A, 16B Comparator (binarization means) 18, 36 Phase comparator (phase comparison means) 20, 38 LPF (tracking) Means for generating an error signal) 22 Tracking error signal offset detector (Tracking error signal offset detecting means) 24 Spindle motor speed detecting circuit (Spindle motor speed detecting means) 26 Slider position detecting circuit (Slider position detecting means) (Line (A means for estimating the linear velocity is configured together with the velocity measuring circuit and the control circuit.) 28 Linear velocity measuring circuit (linear velocity measuring means) 29 Operation panel 30 Control circuit (delay time setting means, linear velocity calculating means,
Selection means, initial delay time setting means, initial delay time correction means) 31A, 31B, 31C, 31D Binarizer

Claims (5)

[Claims] 1. A tracking error signal used in an optical disc apparatus for irradiating a light spot from an optical pickup onto a track of an optical recording medium to irradiate a light spot, detecting reflected light or transmitted light thereof, and performing tracking servo control. A plurality of delay means for delaying a plurality of output signals of the optical pickup; and a plurality of output signals of the optical pickup delayed by the plurality of delay means or arithmetic signals of the plurality of output signals, respectively. Two comparing means for converting, a phase comparing means for comparing phases of output signals of the two comparing means, a means for generating a tracking error signal in response to an output signal of the phase comparing means, Tracking error signal offset detecting means for detecting a signal offset; and the tracking error signal And a delay time setting means for setting a delay time of the delay means based on the offset of the optical pickup. A means for measuring and / or estimating a linear velocity of a light spot by the optical pickup with respect to the optical recording medium. And a delay time correcting means for correcting the delay time set by the delay time setting means in accordance with the linear velocity obtained by the linear velocity measuring or estimating means. Signal generation circuit. 2. The means for measuring and / or estimating the linear velocity comprises: means for measuring a linear velocity based on a reproduction signal from the optical pickup; and detecting a rotation speed of a spindle motor for rotating the optical recording medium. Spindle motor rotation speed detection means, slider position detection means for detecting the radial position of the optical recording medium of the pickup moved by a slider, output signal of the spindle motor rotation speed detection means, and the slider position detection means A linear velocity estimating means having a linear velocity calculating means for calculating a linear velocity at a light spot position by the optical pickup based on the output signal of the optical pickup, and when there is a linear velocity signal from the linear velocity measuring means, A linear velocity signal is output, and when there is no linear velocity signal, a selection is made to output an output signal of the linear velocity estimating means. Tracking error signal generating circuit according to claim 1, characterized in that the means comprises. 3. A spindle motor for rotating an optical recording medium, slider means for moving an optical pickup in a radial direction of the optical recording medium, and condensing a light beam from the optical pickup on a track of the optical recording medium. A tracking error signal used in an optical disc device in which the optical pickup has a four-division optical sensor part for irradiating a light spot and detecting reflected light or transmitted light thereof, and performing tracking servo control based on an output signal from the four-division sensor. A delay circuit for delaying an output signal of the four-divided optical sensor portion, and a four-divided portion of the output signal of the four-divided optical sensor portion delayed by the four delay devices, respectively. Two adding means for adding output signals of two light sensor portions on a diagonal line of the light sensor portion; Binarize the output signals of the adder means 2
Two comparing means, a phase comparing means for comparing phases of output signals of the two comparing means, a means for generating a tracking error signal in response to an output signal of the phase comparing means, and an offset of the tracking error signal A tracking error signal offset detecting means for detecting the rotation speed of the spindle motor; a slider for detecting the rotational speed of the spindle motor; and a slider for detecting a radial position of the optical recording medium of the optical pickup movable by the slider. Position detecting means, initial delay time setting means for setting an initial delay time based on the output signal of the tracking error signal offset detector, output signal of the spindle motor rotation speed detecting means, and output signal of the slider position detecting means Based on the optical pickup by the optical pickup. A tracking error comprising: a linear velocity calculating means for calculating a linear velocity at the pot position; and an initial delay time correcting means for changing the initial delay time according to the linear velocity obtained by the linear velocity calculating means. Signal generation circuit. 4. A spindle motor for rotating an optical recording medium, slider means for moving an optical pickup in a radial direction of the optical recording medium, and condensing a light beam from the optical pickup on a track of the optical recording medium. A tracking error signal generating method for use in an optical disc apparatus for performing tracking servo control by irradiating a light spot with the light spot and detecting reflected light or transmitted light thereof, comprising: a plurality of delay means for delaying a plurality of output signals of the optical pickup. And two comparing means for binarizing the plurality of output signals of the optical pickup or their operation signals respectively delayed by the plurality of delay means, and comparing the phases of the output signals of the two comparing means. Means for generating a tracking error signal in response to an output signal of the phase comparing means. Tracking in a tracking error signal generation circuit having tracking error signal offset detection means for detecting an offset of the tracking error signal, and delay time setting means for setting a delay time of the delay means based on the offset of the tracking error signal In the error signal generating method, a step of reading a target address when performing a search by moving a light spot by the optical pickup in a radial direction of the optical recording medium by jumping, a slider position corresponding to the target address, Calculating the rotation speed of the spindle motor at the destination address; calculating the linear velocity at the destination address from the slider position and the rotation speed of the spindle motor; and setting the delay time. Correcting and setting the delay time using a ratio between a linear velocity and a linear velocity at the target address. 5. A tracking error used in an optical disc apparatus for converging a light beam from the optical pickup onto a track of an optical recording medium to irradiate a light spot, detecting reflected light or transmitted light thereof, and performing tracking servo control. A signal generation method, comprising: a plurality of delay means for delaying a plurality of output signals of the optical pickup; and a plurality of output signals of the optical pickup delayed by the plurality of delay means or their operation signals, respectively. Two comparing means for converting values, a phase comparing means for comparing phases of output signals of the two comparing means, a means for generating a tracking error signal in response to an output signal of the phase comparing means, Tracking error signal offset detection means for detecting an offset of an error signal; A tracking error signal generating circuit having a delay time setting means for setting a delay time of the delay means based on an offset of a signal, wherein the tracking error signal is generated from a reproduction signal from the optical pickup to the optical recording medium. Calculating a linear velocity of the light spot; and correcting and setting the delay time using a ratio of the linear velocity at the time of setting the delay time to a current linear velocity. .