JPH11238231A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk device enlarging a system tolerance for a tilt of an optical disk in the radial direction. SOLUTION: This optical disk device is provided with actuators 13b, 13d drive adjusting an optical convergent means such as an objective lens etc., in the servo direction of the optical disk, control circuit 13a, 13c driving and controlling these actuators in the tracking direction and focus direction based on a tracking error signal TE and a focus error signal FE based on detection signals from respective divided light receiving parts of a photodetector, a measuring means 15 respectively detecting jitters values related to the sum signal of the detection signals of all light receiving parts and the sum signal of the detection signals of the light receiving parts of optional combination among the detection signals from respective light receiving parts of the photodetector and the means 16 comparing respective jitters values and selecting the sum signal of the combination imparting the minimum jitters value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus for irradiating a surface of a rotating optical disk such as a compact disk (CD) with light and detecting return light.

[0002]

2. Description of the Related Art Conventionally, for example, when reproducing an optical disk, a signal recording surface of an optical disk which is driven to rotate is
Light is emitted from the optical pickup, and the return light is detected by the optical pickup to reproduce a signal from the optical disk. In this case, tracking control is performed so that the light emitted from the optical pickup accurately traces the center of the track on the optical disk.

As such tracking control, a push-pull method, a three-spot method, a DPD method, a TPP method and the like are known. Among them, for example, in the push-pull method, the photodetector of the optical pickup is divided into two in the vertical and horizontal directions, that is, in the tracking direction (radial direction) and the track direction (tangential direction) of the optical disk, respectively, so that a total of four is obtained.
It has two divided light receiving sections. A push-pull signal is generated based on a detection signal from each light-receiving unit of the divided light-receiving unit, and tracking servo is performed using the push-pull signal as a tracking error signal.

[0004]

By the way, as a reproduction signal of such an optical pickup, a sum signal of all the divided light receiving portions of the photodetector is used as a reproduction signal. The system tolerance with respect to the inclination of, for example, ± 0.1.
Since the angle is about 6 to 0.7 degrees, there is a problem that an optical disk having a large warp cannot be reproduced.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide an optical disk apparatus which increases the system tolerance for the radial inclination of the optical disk.

[0006]

According to the present invention, a signal recording surface of an optical disk is irradiated with light from a light source of an optical pickup via a light focusing means, and the return light is detected by light detection. An optical disk drive for recording and / or reproducing a signal from / to an optical disk by detecting with a detector, an actuator for driving and adjusting the light focusing means with respect to a servo direction of the optical disk; A control circuit that generates a tracking error signal and a focus error signal based on the detection signal from the control circuit that drives and controls the actuator in the tracking direction and the focus direction, and among the detection signals from each light receiving unit of the photodetector, The sum signal of the detection signals of all the light receiving sections,
Measuring means for detecting a jitter value for each of the sum signals of the detection signals of the light-receiving units in any combination, and comparing each of the above-mentioned jitter values, selecting the sum signal of the combination giving the minimum jitter value, and selecting this sum This is achieved by an optical disk device comprising: a selection unit that selects a signal as a reproduction signal.

[0007] According to the above arrangement, the tracking control or the focus control is performed by driving and adjusting the light focusing means of the optical pickup in the servo direction, that is, the tracking direction or the focus direction by the actuator.
When performing signal reproduction on a desired track of the optical disc, the measuring unit detects a detection signal from the photodetector.
The jitter value is measured for the sum signal of all the light receiving units and the sum signal of the light receiving unit in an arbitrary combination, and the selecting unit selects the sum signal giving the minimum jitter value and outputs it as a reproduction signal. Thereby, even if the spot of the light beam deviates from the track center due to, for example, an offset in the tracking error signal, the influence of the offset is reduced by outputting the sum signal having the minimum jitter value as the reproduction signal. Will be.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. still,
Since the embodiments described below are preferred specific examples of the present invention, various technically preferred limitations are added.
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows the configuration of an embodiment of an optical disk apparatus according to the present invention. In FIG. 1, an optical disk device 10 includes an optical pickup 12 that records or reproduces signals on an optical disk 11 that is driven to rotate.
An optical disc control device 13 that performs tracking control and focus control of the optical pickup 12, a data reproducing unit 14 that generates a reproduction signal based on a detection signal from the optical pickup 12, and a jitter measuring circuit 15 as a measuring unit. Selection means 16 and the optical disk 11
A spindle drive unit 17 for rotating the drive at a predetermined rotation speed;
And a sled drive section 18 for moving the entire optical pickup 12 in the radial direction of the optical disk.

The optical pickup 12 has an objective lens (not shown) as a light focusing means,
Are movably supported in a biaxial direction, that is, in a tracking direction and a focusing direction, irradiate a signal recording surface of the optical disk 11 with light from a light source (not shown), and return the returned light to a photodetector (described later). To detect.

As shown in FIG. 2, the optical pickup 12 has a photodetector 12a having four light receiving portions A, 4a divided in a tracking direction (radial direction) and a track direction (tangential direction) of the optical disk. B, C, and D. Each of the light receiving units A, B, C, and D outputs a detection signal Sa, Sb, Sc, and Sd, respectively. As shown in FIG. 2, the detection signals Sa and Sb are added to each other by an adder 12b by, for example, an arithmetic circuit configured adjacent to the photodetector, and the detection signals Sc and Sd is added to each other by the adder 12c, and these added signals are added to each other by the adder 12d.
A sum signal S0 described later is generated. Further, based on the detection signal of each light receiving unit, a tracking error signal TE by the DPD method generated from (Sc + Sd)-(Sa + Sb).
Then, the focus error signal FE is generated based on (Sd + Sb)-(Sc + Sa).

The optical disk control device 13 includes a tracking servo circuit 13a for performing tracking control based on a tracking error signal TE generated by a push-pull method from a detection signal detected by the optical pickup 12, and a tracking servo circuit 13a. 13
a tracking actuator 13b for driving and adjusting the objective lens of the optical pickup 12 in the tracking direction based on the tracking control signal from the optical pickup 12; and a focus error signal FE similarly generated by the astigmatism method from the detection signal from the optical pickup. A focus servo circuit 13c that performs focus control based on the focus control signal, and a focus actuator 13 that drives and adjusts the objective lens of the optical pickup 12 in the focus direction based on the focus control signal from the focus servo circuit 13c.
d.

The data reproducing section 14 includes an equalizer 14a, a binarizing circuit 14b, a demodulation and error correction circuit 14c, and a PLL circuit 14d which are connected in sequence. The equalizer 14a includes the optical pickup 12
The sum signal S0 (= Sa + Sb +) of the detection signals Sa, Sb, Sc, and Sd from the photodetector
Sc + Sd) and, for example, the first signal S1 (= Sa + Ab) on one side in the tracking direction by the adder 12b.
And the second signal S2 (= S2) on the other side by the adder 12c.
c + Sd) is the switching circuit 15 of the selector 15 described later.
b, the signal is selectively input as a reproduction signal RF and an equalizing process is performed.

The binarizing circuit 14b includes an equalizer 14
The output signal from a is corrected (asymmetry correction), and a binarization process is further performed. And the binarization circuit 1
4b outputs the binarized data relating to the reproduction signal RF to the demodulation and error correction circuit 14c and the PLL circuit 14d, and outputs the binarized data to the jitter measurement circuit 15d.
Output to The demodulation and error correction circuit 14c
The LL circuit 14d performs a demodulation process and an error correction process on the binarized data based on a clock signal generated based on the binarized data. Further, the data reproducing unit 1
4 is provided with a clock generation circuit 14e provided for generating a reference clock.

The jitter measuring circuit 15 generates signals S0, S0 based on a reference clock from the clock generating circuit 14e and a clock signal from the PLL circuit 14d.
The jitter value of S1 or S2 is measured. Selection section 1
6 has a comparison circuit 16a and a switching circuit 16b. The jitter value of each signal S0, S1 or S2 is given from the jitter measurement circuit 15 to the comparison circuit 16a.
That is, the switching circuit 16b of the selection means 16 sequentially switches the signals S0, S1, or S2 and supplies the signals to the data reproducing unit 14. In the data reproducing section 14, the jitter measuring circuit 15 measures the jitter of each signal by the above-described processing and supplies the measured signal to the comparing circuit 16a. Comparison circuit 16a
Stores each jitter value sequentially in, for example, a built-in memory. Then, the comparison circuit 16a compares these jitter values, and
The signal S0, S1 or S giving the smallest jitter value
2 is specified, and the comparison result is provided to the switching circuit 16b.

The switching circuit 16b outputs signals S0, S
1 and S2, respectively, are provided with switching contacts. When the switching operation is performed by the comparison circuit 16a, the comparison circuit 16a reproduces the signal S2 selected from the signals S0, S1, or S2, for example, the signal S2 in the illustrated case. Signal RF
Is output to the data reproducing unit 14.

Further, the spindle driving section 17 includes a spindle motor 17a for driving the optical disc 11 to rotate.
, Rotation detecting means 17b, spindle servo circuit 17
and a spindle drive circuit 17d. The rotation detecting means 17b detects the rotation speed of the spindle motor 17a and outputs a detection signal. The spindle servo circuit 17c includes the rotation detecting unit 1
The spindle error signal SPE is output based on the detection signal from the optical pickup 7b and a thread position signal indicating the thread position of the optical pickup 12. The thread position signal is detected by a thread position detecting means 12a provided in the optical pickup 12. Spindle drive circuit 1
7d drives and controls the spindle motor 17a based on a spindle error signal from the spindle servo circuit 17c, and drives the spindle motor 17a to rotate at a predetermined rotation speed.

The sled drive section 18 includes a smoothing circuit 18a for smoothing a tracking control signal from a tracking servo circuit 13a of the optical disk control device 13.
, A thread servo circuit 18b, and a thread driving unit 1
8c. The smoothing circuit 18a detects the deviation of the thread position by smoothing the tracking control signal, and outputs this detection signal. The thread servo circuit 18b outputs a thread error signal based on the detection signal from the smoothing circuit 18a. The sled drive unit 18c drives the optical pickup in sled, that is, drives and controls the optical pickup 11 in the radial direction based on the sled error signal.

The optical disk device 10 according to the present embodiment comprises:
It is configured as described above and operates as follows.
First, the optical disk 11 is rotationally driven by a spindle driving unit 17, and the optical pickup 12 is moved by a thread driving unit 18 along a guide (not shown).
, The optical axis of the objective lens is moved to a desired track position on the optical disk 11 to perform access.

In this state, the light beam emitted from the optical pickup 12 is focused on the signal recording surface of the optical disk 11, and the return light from the optical disk 11 is incident on the photodetector 12a of the optical pickup 12. Then, detection signals Sa, Sb, Sc, and Sd are output from the respective light receiving portions A, B, C, and D of the photodetector 12a, and are added by the adders 12b, 12c, and 12d, respectively, to thereby add the signal S1. , S2 and the sum signal S0 are generated, and the tracking error signal TE and the focus error signal FE are generated.

Here, before the reproduction of the optical disk 11, the switching circuits 16b are sequentially switched to the respective switching contacts, whereby the signals S0, S1, S2 are input to the equalizer 14a of the data reproducing unit 14, respectively. After being equalized and corrected and binarized by the binarization circuit 14b, an operation signal is generated by the PLL circuit 14d and input to the jitter measurement circuit 15. The jitter measurement circuit 15 measures the jitter value of each signal S0, S1, S2 from the operation signal of the PLL circuit 14d and the clock generation circuit 14e. Here, each signal 0, 1, 2,
Varies with respect to the tilt of the optical disc, for example, as shown in FIG.

The jitter values relating to the signals S0, S1, S2 are input to the comparison circuit 16a of the selector 16, and are compared to select the signal S0, S1, or S2 that gives the smallest jitter value. And
The comparison circuit 16a switches the switching circuit 16b based on the selected signal S0, S1, or S2. As a result, the signal S0, S1, or S2 that gives the selected minimum jitter value is input to the data reproducing unit 14 as the reproduced signal RF.

Thus, the switching circuit 16b of the selector 16
Are input to the equalizer 14a of the data reproducing unit 14, are equalized, corrected and binarized by the binarization circuit 14b, and then demodulated. Error correction circuit 14c
And demodulated and error-corrected based on the clock signal from the PLL circuit 14d, and output to the outside as a reproduced signal. At this time, the tracking servo circuit 13a generates a tracking control signal based on the tracking error signal TE including the offset,
Since the drive control of the tracking actuator 13b is performed based on the tracking control signal, the light beam from the optical pickup 12 always traces the spot formed on the optical disk 11 at the center of a desired track. Here, for example, considering the reproduction of the optical disk 11 having a large warp, in the full addition signal S0, the aberration occurs in the objective lens due to the warp, and the frequency transmission characteristic and the phase transmission characteristic of the reproduction signal RF change. Signal quality decreases. Therefore, when a reproduction signal of only one side such as S1 and S2 is generated, the phase characteristic is particularly different, and the jitter of either one of S1 and S2 may be better than that of the signal S0. By using the signal S1 or S2 having the smallest jitter value (including S0) as a reproduction signal, even if the optical disk has a particularly large inclination, such as an optical disk having a large warp, the optical disk 11
Will be expanded, and the reproduction will be performed.

In the above-described embodiment, the first signal S1 and the second signal S2 are used together with the sum signal 0 as the signal for comparing the jitter value. However, the present invention is not limited to this. (Sa + Sb + Sc) as one signal
, And (Sb + Sc + Sd) as the second signal.
Obviously, any combination of C and D that is symmetrical with respect to the track direction is also employed.

[0025]

As described above, according to the present invention, it is possible to provide an optical disk apparatus in which the system tolerance with respect to the radial inclination of the optical disk is increased.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a configuration of an embodiment of an optical disk device according to the present invention.

FIG. 2 is a schematic plan view showing a photodetector of an optical pickup in the optical disk device of FIG. 1 and signal processing thereof.

FIG. 3 is a graph showing a jitter value of each signal by a jitter measuring circuit in the optical disc device of FIG. 1;

[Explanation of symbols]

10 optical disk device, 11 optical disk, 1
2 ... optical pickup, 13 ... optical disk control device, 13a ... tracking servo circuit, 13b
..Tracking actuator, 14 ... data reproducing unit, 14a ... equalizer, 14b ... binarization circuit, 14c ... demodulation and error correction circuit, 14d ...
・ PLL circuit, 15 ・ ・ ・ Jitter measurement circuit, 16 ・ ・
A selection unit, 16a: a comparison circuit, 16b: a switching circuit, 17: a spindle drive unit, 18: a thread drive unit.

Continued on the front page (72) Inventor Nobuyasu Kikuchi 6-35 Kita Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (2)

[Claims] 1. A signal recording surface of an optical disk is irradiated with light from a light source of an optical pickup via a light focusing means, and its return light is detected by a photodetector to record a signal on the optical disk and / or record the signal on the optical disk. An optical disk device for performing reproduction, comprising: an actuator for driving and adjusting the light focusing means with respect to a servo direction of the optical disk; a tracking error signal and a focus error signal based on detection signals from each of the divided light receiving units of the photodetector. A control circuit that drives and controls the actuator in the tracking direction and the focus direction; and a detection signal from each of the light receiving units of the photodetector. Measuring means for detecting a jitter value for each of the sum signals of the detection signals of the light-receiving units, And compare, and select the sum signal of the combination that gives the lowest jitter value, the optical disk apparatus characterized by comprising selecting means for selecting the sum signal as a reproduction signal. 2. The method according to claim 1, wherein the measuring means includes a sum signal of detection signals of all light receiving sections of the light receiving sections of the light detector of the optical pickup, and a first signal from the light receiving section on one side in the tracking direction. Based on the signal and the second signal from the light receiving unit on the other side, a jitter value is detected, and the comparison circuit compares the jitter values to select a signal that gives the minimum jitter value. 2. The optical disk device according to claim 1, wherein said selected signal is selected by said selecting means and used as a reproduction signal.