JPH10177727A - Tracking error signal generation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tracking error signal generation circuit capable of generating a precise 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 revising frequency characteristics of waveform equalizing means 15A, 15B waveform equalizing an output signal of an optical pickup or its operation signal 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 isn't measured as at a searching time, the linear velocity is obtained by operation from a slider position and the number of revolution of a spindle motor 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.

[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]

When the phase difference detection method is applied to a high-density disk such as a DVD in an optical recording medium, the waveform of a short wavelength such as 3T becomes extremely small, so that it is binarized. The comparator does not function well, and thus noise occurs in the tracking error signal. In order to prevent such a problem, a method for preventing signal deterioration by inserting a waveform equalizer (high-frequency emphasis filter) in the preceding stage of the comparator and increasing the high-frequency gain is disclosed in Japanese Patent Application Laid-Open No. Hei 8-1.
No. 47724. 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. 4 optical pickups
It has a split sensor portion ABCD and its output signal is delayed by a corresponding delay circuit DL. The output signals on the diagonal lines of the four-divided sensor are added to each other by an adder, the waveforms of the delayed signals are equalized by two waveform equalizers, and then the output signals of the two waveform equalizers are compared by a comparator. Are respectively compared with predetermined reference values and 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.

In general, an optical disk such as a CD or a CD-ROM is read at a constant linear velocity (CLV). To read at a high speed, the optical disk may be rotated at a constant angular velocity (CAV). CLV does not occur during a so-called search operation in which multi-speed reproduction is performed and a light spot jumps to a position separated in the radial direction of the optical disk, instead of sequentially reading out signals from the optical disk in a fixed direction. When the linear velocity is not constant as described above, the frequency component of the reproduced signal changes, so that the frequency characteristics of the waveform equalizer cannot sufficiently cope with and an appropriate tracking error signal cannot be obtained.

Accordingly, an object of the present invention is to provide a tracking error signal generation circuit that can generate an accurate tracking error signal by the phase difference method even when the linear velocity changes.

[0007]

In order to achieve the above object, according to the present invention, a frequency characteristic of a waveform equalizing means for equalizing a waveform of an output signal of an optical pickup or an operation signal thereof is determined by an optical recording medium of an optical spot of the optical pickup. Is changed by the relative linear velocity. 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 that converges a light beam from an optical pickup onto a track of an optical recording medium to irradiate a light spot, detects reflected light or transmitted light thereof, and performs tracking servo control. A tracking error signal generating circuit for use in the above-mentioned operation, wherein two waveform equalizing means for equalizing the waveforms of a plurality of output signals of the optical pickup or their arithmetic signals, and the output signals of the two waveform equalizing means are respectively equalized by two. Two comparing means for quantifying,
A tracking error signal generation circuit comprising: a phase comparison unit that compares phases of output signals of the two comparison units; and a unit that generates a tracking error signal in response to the output signal of the phase comparison unit. Means for measuring and / or estimating the linear velocity of the light spot with respect to the optical recording medium, and frequency characteristics of the waveform equalizing means according to the linear velocity obtained by the means for measuring and / or estimating the linear velocity. And a frequency characteristic changing means for changing the frequency characteristic.

Further, 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, and a plurality of output signals of the optical pickup respectively delayed by the plurality of delay means or an arithmetic operation thereof Two waveform equalizing means for respectively equalizing the signals, two comparing means for respectively binarizing the output signals of the two waveform equalizing means,
A tracking error signal generation circuit comprising: a phase comparison unit that compares phases of output signals of the two comparison units; and a unit that generates a tracking error signal in response to the output signal of the phase comparison unit. Means for measuring and / or estimating the linear velocity of the light spot with respect to the optical recording medium, and frequency characteristics of the waveform equalizing means according to the linear velocity obtained by the means for measuring and / or estimating the linear velocity. And a frequency characteristic changing means for changing the frequency characteristic.

Further, according to the present invention, an optical disk apparatus that converges a light beam from an optical pickup onto a track of an optical recording medium to irradiate a light spot, detects reflected light or transmitted light, and performs tracking servo control. A tracking error signal generation circuit used for: a waveform equalizing means for waveform equalizing a plurality of output signals of the optical pickup, and a plurality of comparing means for binarizing output signals of the waveform equalizing means, respectively. Generating two signals from a plurality of delay means for respectively delaying the output signals of the plurality of comparison means, and a binary signal of the plurality of output signals of the optical pickup delayed by the plurality of delay means, respectively. Calculating means, phase comparing means for comparing phases of output signals of the two calculating means, and tracking in response to an output signal of the phase comparing means. A tracking error signal generating circuit having means for generating an error signal; means for measuring and / or estimating the linear velocity of the light spot by the optical pickup with respect to the optical recording medium; and measuring and / or estimating the linear velocity. A frequency characteristic changing means for changing a frequency characteristic of the waveform equalizing means in accordance with the linear velocity obtained by the 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 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-divided light sensor part among output signals of the divided light sensor part, and waveform equalization of output signals of the two adding means, respectively Two waveform equalizing means for performing binary conversion on output signals of the two waveform equalizing means.
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 a rotational speed of the spindle motor. , A slider position detecting means for detecting a radial position of the optical recording medium of the optical pickup movable by the slider, an output signal of the spindle motor rotating speed detecting means, A linear velocity calculating means for calculating a linear velocity at a light spot position by the optical pickup based on an output signal of a slider position detecting means; and a frequency characteristic of the waveform equalizing means being calculated by the linear velocity calculating means, or Frequency characteristic changing means for changing the linear velocity according to the linear velocity obtained by the method. Tsu King error signal generation circuit is provided.

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 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 four-wavelength equalizing means for waveform equalizing the output signal of the four-divided optical sensor, and binarizing the frequency characteristics of the four waveform equalizing means, respectively. The output signals of the four-division optical sensor portion binarized by the four comparing means and the four comparing means are respectively Four delay means that cast, the 4
Two adding means for adding the binary signals of the output signals of the two light sensor portions on the diagonal line of the four-division light sensor portion among the output signals of the two delay means; and the output signals of the two adding means. Phase comparison means for comparing the phases of the above, means for generating a tracking error signal in response to the output signal of the phase comparison means, spindle motor rotation number detection means for detecting the rotation number of the spindle motor, and the slider A slider position detecting means for detecting a position of the movable optical pickup in a radial direction of the optical recording medium; and an output signal from the spindle motor rotation speed detecting means and an output signal from the slider position detecting means. A linear velocity calculating means for calculating a linear velocity at the light spot position, and a frequency characteristic of the waveform equalizing means, Is calculated by degree calculation means, or other frequency characteristic changing means for changing in accordance with the linear velocity obtained by the method, the tracking error signal generating circuit having is provided.

[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
As for the output signal of D, the output signals on the diagonal lines of the four-divided sensor, that is, A + C and B + D are calculated by the adders 14A and 14B, respectively. , And the high-frequency gain is boosted. Waveform equalizer 15
The output signals of A and 15B are comparators (COMP) 16A and 1B.
6B is compared with a predetermined reference value ref,
It is binarized. The two binarized signals are supplied to a phase comparator 1
8, a phase difference between the two is detected, and the phase difference signal is
The tracking error signal TE is generated through the PF 20. Here, the delay circuits 12A, 12B, 12C, 12
D is supplied with a delay time adjustment signal (not shown), and the delay time is adjusted as necessary.

The output signal of the LPF 20 is used for tracking control known as a tracking error signal. 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 the slider that moves the optical pickup (not shown) in the radial direction of the optical disc,
A signal indicating the radial position is sent 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. Measures linear velocity and outputs linear velocity signal to control circuit 3
Send to 0.

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.
A control signal C1 to be applied to the waveform equalizers 15A and 15B is generated. The control signal C1 is common to the waveform equalizers 15A and 15B, and therefore, the same frequency characteristics are set to the waveform equalizers 15A and 15B.

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.

FIG. 2 is a wiring diagram showing a specific configuration of the waveform equalizers 15A and 15B. The waveform equalizers 15A and 15B select a plurality of capacitors 38 having different capacities from an input signal via a resistor 34. The switch 4 is supplied to the inverting input of the operational amplifier 36 via a switch circuit 40 which is selectively selected.
0 is controlled. FIG. 3 is a waveform equalizer 15A, 15A of FIG.
FIG. 9 is a frequency characteristic diagram schematically showing a change in the frequency characteristic of B. That is, by operating the switch 38 to move between the smallest capacity and the largest capacity, the frequency at which the high frequency starts to be boosted is paralleled along the frequency axis (horizontal axis) as shown by the solid line and the dotted line in FIG. Can be moved.

The frequency characteristics of the waveform equalizers 15A and 15B are changed in accordance with the measured or estimated linear velocities. As a method, the frequency characteristics corresponding to the linear velocities are shifted in advance (see FIG. 3). (Movement on the horizontal axis) is determined and stored in a memory in the control circuit 30. When the linear velocity is obtained, the corresponding frequency characteristic is uniquely selected, and the corresponding control signal C1 is generated. Is done.

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 equalized in waveform by the corresponding waveform equalizers 15A, 15B, 15C, and 15D. Comparators (COMP) 31A, 31B, 31 as digitizers
C and 31D are used for binarization and subsequent processing is performed. Output signals of the binarizers 31A, 31B, 31C, and 31D are output from delay circuits 32A, 32B, 32C, and 32D, respectively.
, And the output signals of the delay circuits 32A and 32C are added by the adder 34A, and the output signals of the delay circuits 32B and 32D are added by the adder 34B. Adders 34A and 34B
The output signal is provided to the phase comparator 36, and an output signal corresponding to the phase difference is output as the tracking error signal TE via the LPF 38. The configurations and operations of 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.

It is preferable that the delay time in the delay circuit is corrected according to the linear velocity in addition to the change of the frequency characteristic of the waveform equalizer. That is, a tracking error signal offset detecting means for detecting the offset of the tracking error signal is provided, the delay time of the delay circuit is initially set based on the offset of the tracking error signal, and set according to the measured and / or estimated linear velocity. The control circuit 30 can be configured to correct the set delay time.

[0022]

As described above, according to the present invention, even when the linear velocity is not constant, the frequency characteristic of the waveform equalizing 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 wiring diagram illustrating a configuration of a waveform equalizer in FIG.

FIG. 3 is a frequency characteristic diagram showing a manner of changing the frequency characteristic of the waveform equalizer in FIG. 2;

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) 15A, 15B Waveform equalizer (waveform equalization means) 16A, 16B Comparator (binarization means) 18, 36 Phase Comparator (phase comparing means) 20, 38 LPF (means for generating tracking error signal) 24 Spindle motor rotation speed detection circuit (spindle motor rotation speed detection means) 26 Slider position detection circuit (slider position detection means) (linear velocity measurement (A means for estimating the linear velocity is constituted together with the circuit and the control circuit.) 28 Linear velocity measuring circuit (linear velocity measuring means) 29 Operation panel 30 Control circuit (linear velocity calculating means, selecting means, frequency characteristic changing means) 31A, 31B, 31C, 31D binarizer

Claims (6)

[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 generator circuit, comprising: two waveform equalizing means for waveform equalizing a plurality of output signals of the optical pickup or their arithmetic signals; and two waveform equalizing means for respectively binarizing output signals of the two waveform equalizing means. A tracking error signal generation circuit comprising: a comparison unit; a phase comparison unit that compares phases of output signals of the two comparison units; and a unit that generates a tracking error signal in response to an output signal of the phase comparison unit. Means for measuring and / or estimating a linear velocity of a light spot by the optical pickup with respect to the optical recording medium; A frequency characteristic changing unit for changing a frequency characteristic of the waveform equalizing unit in accordance with the linear velocity obtained by the linear velocity measuring and / or estimating unit. 2. A tracking error signal used in an optical disc apparatus for irradiating a light spot from a light pickup onto a track of an optical recording medium by irradiating a light spot, detecting reflected light or transmitted light, and performing tracking servo control. A generation circuit, 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 waveforms of the arithmetic signals thereof, respectively. Two waveform equalizers, two comparators for respectively binarizing output signals of the two waveform equalizers, and a phase comparator for comparing phases of output signals of the two comparators. Means for generating a tracking error signal in response to an output signal of the phase comparing means. A means for measuring and / or estimating a linear velocity of a light spot with respect to the optical recording medium by the optical pickup; and the waveform equalizing means in accordance with the linear velocity obtained by the means for measuring and / or estimating the linear velocity And a frequency characteristic changing means for changing the frequency characteristics of the tracking error signal. 3. A tracking error signal used in an optical disc apparatus for irradiating a light spot from a light pickup onto a track of an optical recording medium by irradiating a light spot, detecting reflected light or transmitted light thereof, and performing tracking servo control. A generating circuit, wherein waveform equalizing means for waveform equalizing each of the plurality of output signals of the optical pickup; a plurality of comparing means each for binarizing an output signal of the waveform equalizing means; A plurality of delay means for respectively delaying output signals of the means, an arithmetic means for generating two signals from a binary signal of the plurality of output signals of the optical pickup respectively delayed by the plurality of delay means, Phase comparing means for comparing the phases of the output signals of the two arithmetic means; and generating a tracking error signal in response to the output signal of the phase comparing means. A tracking error signal generating circuit comprising: means for measuring and / or estimating a linear velocity of an optical spot by the optical pickup with respect to the optical recording medium; and means for measuring and / or estimating the linear velocity. A frequency characteristic changing unit for changing a frequency characteristic of the waveform equalizing unit in accordance with the obtained linear velocity. 4. A means for measuring and / or estimating the linear velocity, 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, the output signal of the linear velocity estimating means is selected. And means, any one of claims 1 to 3, characterized in that it has 1
A tracking error signal generation circuit according to any one of the first to third aspects. 5. 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; Two waveform equalizing means for waveform equalizing the output signal of the adding means, two comparing means for respectively binarizing the output signals of the two waveform equalizing means, and output signals of the two comparing means Phase comparison means for comparing the phases of the above; a means for generating a tracking error signal in response to an output signal of the phase comparison means; a spindle motor rotation number detection means for detecting the rotation number of the spindle motor; and the slider A slider position detecting means for detecting a radial position of the optical recording medium of the movable optical pickup; and an 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 linear velocity calculating means for calculating a linear velocity at the light spot position; and a frequency characteristic of the waveform equalizing means. A frequency characteristic changing unit that changes according to the linear velocity calculated by the linear speed calculating unit or obtained by another method. 6. 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 generating circuit, comprising: four waveform equalizing means for equalizing waveforms of the output signals of the four-divided optical sensor portions; and four comparing means for binarizing frequency characteristics of the four waveform equalizing means. Four delays for respectively delaying the output signals of the four-divided optical sensor portions binarized by the four comparison means. Extending means; and two adding means for adding, to the output signals of the four delay means, binarized signals of output signals of two light sensor portions on a diagonal line of the four-divided light sensor portion; Phase comparing means for comparing the phases of the output signals of the adding means, means for generating a tracking error signal in response to the output signal of the phase comparing means, and spindle motor speed detection for detecting the speed of the spindle motor Means, a slider position detection means for detecting a radial position of the optical recording medium of the optical pickup movable by the slider, an output signal of the spindle motor rotation number detection means and an output signal of the slider position detection means. A linear velocity calculating means for calculating a linear velocity at a light spot position by the optical pickup based on the optical pickup; and the waveform equalizing means. A frequency characteristic changing unit that calculates the frequency characteristic of the linear velocity according to the linear velocity calculated by the linear velocity calculating unit or changes the linear characteristic according to the linear velocity obtained by another method.