JP2003228846A - Optical disk drive and optical disk reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk drive capable of preventing the out of servo due to the generation of distortion of an actuator control signal caused by the high speed rotation of an optical disk thereby stably controlling an actuator. <P>SOLUTION: In an optical disk reproducing device, a signal recording surface of the optical disk is irradiated with a light beam through an objective lens, and the light reflected on the optical disk is converted to an electrical signal by a detector, then the actuator control signal for driving the objective lens is generated. The actuator control signal is monitored to control the rotational speed of a spindle motor or characteristics of an actuator servo loop. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc reproducing technique for reproducing information on an optical disc by using an optical pickup.

[0002]

2. Description of the Related Art As a peripheral device for a personal computer, a CD-RO
M, CD-R / RW drive, DVD-ROM, DVD
-Optical disk devices such as RAM drives are widely used. The optical disc device rotates an optical disc on which an information signal is recorded by a spindle motor, irradiates a signal recording surface with a light beam, converts the reflected light from the signal recording surface into an electric signal by a detector, and uses a signal processing circuit. Obtain an optical disc recording information signal. At this time, the actuator that drives the objective lens is driven in the direction perpendicular to the optical disc (focusing direction) or in the radial direction (tracking direction) with respect to the disc.

In the optical disk device, in order to read the data recorded on the disk, it is necessary to control the actuator in the focus direction and the tracking direction with high accuracy with respect to the disk recording surface. Therefore, from the output signal of the optical pickup, the signal processing circuit generates the focus error signal and the tracking error signal,
A servo circuit having a phase compensation filter for stabilizing the servo operation outputs an actuator control signal, and a power amplifier generates an actuator drive signal to form a servo loop.

In the servo loop, a servo gain adjusting circuit provided in the servo circuit absorbs optical variations in the optical pickup, variations in the output signal of the optical pickup due to various disks, and variations in the sensitivity of the actuator to make a stable servo loop. Adjust the gain of the servo loop to. The required gain of this servo loop is calculated based on the disk standard, mechanical deviation such as spindle motor axis deviation, turntable shake, and disk rotation frequency. In consideration of the maximum standard amount of warp and the maximum shake amount of the turntable, the servo loop gain is set at the disc rotation frequency so as to suppress these variations in the focus direction within a defocus point where data can be read. Also in the tracking servo loop, a servo loop is configured by considering the maximum eccentricity of the disk and the maximum eccentricity of the turntable and setting the servo gain to be suppressed within the required deviation at the disk rotation frequency.

[0005]

By the way, when the optical disc is rotated at a high speed, the actuator control signal waveform may become a normal error signal superposed with a high frequency signal (hereinafter, this high frequency signal will be referred to as "high frequency signal"). Actuator signal distortion). This actuator control signal distortion is schematically shown in FIG. FIG. 5 is a characteristic diagram showing actuator signal distortion, FIG. 5 (a) is a characteristic diagram showing a state in which actuator control signal distortion is superimposed on an error signal, and FIGS. 5 (b) to 5 (f) are spindle motors. FIG. 6 is a characteristic diagram showing actuator signal distortion superimposed on an error signal for each rotation speed of.

In FIG. 5A, 501 is an error signal, and 502 is the actuator control signal distortion superimposed on the error signal. Reference numeral 503 represents an error signal maximum value, and 504 represents an error signal minimum value. FIG. 5B shows the case where the rotation speed of the spindle motor is 1500 r / m, and the actuator control signal distortion is not superimposed on the error signal 501a. FIG. 5C shows the case where the rotation speed of the spindle motor is 2500 r / m, and the actuator control signal distortion is not superimposed on the error signal 501b.
In Fig. 5 (d), the rotation speed of the spindle motor is 5000r /
In the case of m, the actuator control signal distortion 502c of small amplitude is superimposed on the error signal 501c.
In Fig. 5 (e), the rotation speed of the spindle motor is 7500r /
In this case, the actuator control signal distortion 502d having a large amplitude is superimposed on the error signal 501d. Further, FIG. 5F shows the case where the rotation speed of the spindle motor is 10000 r / m, and the error signal 5
01e has a large amplitude actuator control signal distortion 502
e is superimposed. Note that 503a to 503e indicate the maximum value of the error signal, and 504a to 504e indicate the minimum value of the error signal.

As shown in FIG. 5, with respect to the actuator control signal distortion 502, the frequency of superimposition and the signal level increase as the rotation speed of the optical disk increases. The actuator control signal distortion 502 is generated in a high frequency band that cannot be suppressed by the servo loop set as described above, destabilizes the actuator operation, deteriorates the error rate of the optical disk read data, and causes servo misalignment. There is a problem and the data reading speed deteriorates.

Therefore, in order to suppress the actuator control signal distortion in the servo loop, it is necessary to excessively set the servo loop gain and set the servo loop gain up to a high frequency. However, depending on the sensitivity of the actuator and the dynamic range of the servo processing circuit, there is a limit in setting stable servo loop settings up to a high frequency band. In addition, setting the servo loop gain excessively leads to an increase in power consumption of the actuator control system and raises the temperature of the entire optical disk device.

The actuator control signal distortion generated by rotating the optical disk at a high speed may cause servo misalignment, and as a result, refocus processing, retracking processing, and read retry processing are performed to improve the data reading speed. There is a problem that it is significantly reduced.

An object of the present invention is to provide an optical disk reproducing technique capable of stably reading optical disk information by monitoring the actuator servo control signal distortion and performing processing so as to reduce the actuator servo control signal distortion. To do.

[0011]

In order to achieve the above object, according to the present invention, a high frequency signal (actuator control signal distortion) superimposed on an actuator control signal is monitored, and based on the result, the rotation speed of an optical disk, or Controls servo loop characteristics.

Monitoring of the actuator signal distortion can be performed by detecting the amplitude of the actuator control signal and comparing it with a value larger or smaller than a predetermined amplitude value. Alternatively, it can be carried out by counting the number of signal components larger than a predetermined amplitude value.

Further, according to the present invention, the reproducing method of the optical disk comprises the steps of detecting the focus error signal and the tracking error signal, and the rotation speed of the spindle motor when the focus error signal or the tracking error signal exceeds a predetermined value. And reducing.

Alternatively, the reproducing method of the optical disc includes a step of detecting the focus error signal and the tracking error signal, and a rotation speed of the spindle motor when the focus error signal or the tracking error signal exceeds a first detection value. And a step of increasing the rotation of the spindle motor when the focus error signal or the tracking error signal is lower than a second detection value lower than the first detection value.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings using examples. FIG. 1 is a block diagram showing an embodiment of an optical disk device according to the present invention.
In the figure, 101 is an optical disc in which an information signal is recorded at a constant linear velocity. A spindle motor 102 generates a driving force for rotating the optical disc 101. A rotation detector 103 outputs a pulse signal according to the rotation speed of the spindle motor 102 using a Hall element. 104 is a rotation control circuit,
The spindle motor is controlled to rotate at a desired rotation speed based on the output signal pulse from the rotation detector and information read from the optical disk. In addition, the focus error signal level detector 11
3. The rotation speed of the spindle motor 102 is controlled by the signal from the tracking error signal level detector 114. Reference numeral 105 denotes an objective lens that focuses a light beam from a semiconductor laser on the signal recording surface of the disc 101. An actuator 106 drives the objective lens 105 in a direction perpendicular to the disc (focusing direction) or in a radial direction to the disc (tracking direction). An optical pickup 107 includes various prisms including a semiconductor laser,
It is composed of a detector for signal detection and the like. 1
A slider 08 moves the actuator 106 and the optical pickup 107 to an arbitrary radial position on the optical disc 101. A signal processing circuit 109 generates a focus error signal and a tracking error signal, which are control error signals of the actuator 106, according to an output signal from the optical pickup 107, and outputs a focus error signal level detector 113 and a tracking error signal level. Output to the detector 114 and the servo circuit 110. The servo circuit 110 includes a servo loop gain amplifier and a phase compensation filter, performs phase compensation based on the focus error signal and the tracking error signal from the signal processing circuit 109, and outputs the focus drive signal and the tracking drive signal to the power amplifier 111. To do. The power amplifier 111 drives the actuator 106 based on the output signal of the servo circuit 110. A control unit 112 controls the entire apparatus. A focus error signal level detector 113 determines whether the focus error signal level during focus servo control is equal to or higher than a predetermined detection level, and outputs the determination result to the rotation control circuit 104.

In the optical pickup 107, the detection distance range between the objective lens focused light in the focus direction and the signal recording surface of the optical disc is fixed (in a normal CD, 6 μm across the focal point), and the servo is performed only within the detection range. It becomes possible to control. FIG. 2 is a characteristic diagram for explaining the relationship between the focus error signal and the detection level. In the figure, the horizontal axis represents the distance d1 between the objective lens and the signal recording surface of the optical disc,
The vertical axis represents the focus error signal FE. In the figure,
A curve 201 is a focus error signal and draws an S-shaped curve having an extreme value with the in-focus position as a reference. 202 is the maximum value of the focus error signal, and 203 is the minimum value of the focus error signal. Here, the predetermined first detection level of the focus error signal is a threshold value determined at the time of design, and is set within the maximum value 202 and the minimum value 203 of the focus error signal curve 201, and servo control is possible. The value should not exceed the range (detection distance range). Further, two values in the plus direction and the minus direction around the focus error signal average operating point are set as the second detection level. Alternatively, either one may be set. As a means for setting, a fixed value may be set in advance, a value designated by the control unit, or some percentage of the amplitude of the focus signal 201 may be used. Also, it may be an electric circuit using a comparator circuit or a digital circuit that makes a determination based on a digital value after A / D conversion.

When the focus error signal level is changing to a small level, the following effects can be obtained by reducing the threshold level like the second detection level. (1) The rotation speed of the disc can be increased. (2) Power consumption can be reduced. (3) The servo stability can be increased. (4) Further, the servo gain can be further reduced.

In FIG. 1, the tracking error signal level detector 114 determines whether the tracking error signal level during tracking servo control is equal to or higher than a predetermined detection level, and outputs the determination result to the rotation control circuit 104.
FIG. 3 is a characteristic diagram for explaining the relationship between the tracking error signal and the detection level. In the figure, the horizontal axis represents the distance d2 between the light spot by the objective lens and the track of the optical disc, and the vertical axis represents the tracking error TE. In the figure, the curve 301 is the focus error signal. Thirty
2 is the maximum value of the focus error signal, and 303 is the minimum value of the focus error signal. As shown in FIG. 3, the tracking error signal changes its signal level depending on whether the focus position is a track portion formed by pits on the optical disk or a mirror portion between the tracks, and the tracking error signal has an extreme value. The curve 301 has. In order to read the data on the optical disc, it is necessary to perform servo control on the track portion, and the track portion becomes the servo control range.

Here, the predetermined first detection level of the tracking error signal is set within the maximum value 302 and the minimum value 303 of the tracking error signal and does not exceed the servo control range (track portion). Further, the second detection level is set between two values in the plus direction and the minus direction with the tracking error signal average operating point as the center. Alternatively, either one is set as the second detection level. As a means for setting, a fixed value may be set in advance, a value specified by the control unit, or any percentage of the maximum amplitude of the tracking signal may be used. It may be an electric circuit using a circuit or a digital circuit that makes a determination based on a digital value after A / D conversion. When the tracking error signal level is changing to a low level, if the threshold level is decreased like the detection level 2, the same effect as in the focus error control can be obtained.

By setting the detection level as described above, in the optical disc apparatus of the present embodiment, the error signal during actuator servo is detected by the signal level detector as in the control flow shown in FIG. Monitor
By detecting the actuator control signal distortion generated when the optical disc rotates at a high speed, the rotation speed of the spindle motor can be lowered before the servo deviation occurs, and a stable optical disc reading speed can be realized.

FIG. 4 is a flow chart showing an embodiment of the processing operation of the optical disk device according to the present invention. In the present embodiment, a predetermined detection level is set, and the magnitude of the focus error signal level value is determined, and the rotation of the spindle motor 102 is controlled based on the result. In the figure, in step 401, if the focus error signal level value is a predetermined value or more, in step 402, if the tracking error signal level value is a predetermined value or more, the rotation speed of the spindle motor 102 is decelerated in step 403. When the focus error signal level value or the tracking error signal level value is controlled to be lower than a predetermined value in both step 401 and step 402, the process directly returns to step 401.

Next, a second embodiment of the present invention will be described. FIG. 6 is a flowchart showing another embodiment of the processing operation of the optical disk device according to the present invention. The error signal level detectors 113 and 114 can detect the peak value of the error signal level within a certain fixed time. In addition, by setting the first detection level and the second detection level, which have two detection values in the plus direction and the minus direction, or one of them as the detection level, with the error signal average operating point as the center, for example, When the first detection level is detected as in the first embodiment, it is detected that there is actuator control signal distortion that occurs when the optical disc rotates at a high speed, and the rotation speed of the spindle motor before servo misalignment occurs. Can be lowered, and when it is below the second detection level which is set closer to the in-focus level than the first detection level, it is detected that there is no actuator control signal distortion that occurs when the optical disc rotates at high speed, It is possible to operate with maximum performance depending on the reading position of the optical disk, such as increasing the rotation speed of the motor.

In the figure, in step 601, it is determined whether or not the focus error signal level value is equal to or higher than the first detection level. If it is equal to or higher than the first detection level (in the case of Yes), step 602 spindle motor 102 of FIG.
Then, the rotational speed of the spindle motor 102 is controlled to be reduced. If it is lower than the first detection level (No in step 601), the process proceeds to step 603, and it is determined whether or not the tracking error signal level is equal to or higher than the first detection level. If it is equal to or higher than the first detection level (in the case of Yes), the rotation of the spindle motor 102 is controlled to be decelerated in step 602. In step 603, the tracking error signal level value is first
If it is determined to be lower than the detection level of (No)
Step 604 is also moved to. In step 604,
It is determined whether the focus error signal level value is less than or equal to the second detection level. If not, return to step 601 without doing anything. If the focus error signal is below the second detection level in step 604 (in the case of Yes)
In step 605, it is determined whether the tracking error signal level value is equal to or lower than the second detection level. If it is higher than the second detection level (No), the process directly returns to step 601. Step 605
Then, when the tracking error signal level value is equal to or lower than the second detection level, the process proceeds to step 606, and control is performed so as to accelerate the rotation speed of the spindle motor.

Next, a third embodiment will be described with reference to FIG. 7 is a block diagram showing a second embodiment of the optical disc apparatus according to the present invention, and FIG. 8 is a flowchart showing a third embodiment of the processing operation of the optical disc apparatus shown in FIG. In FIG. 7, the output of the focus error signal level detector 113 and the output of the tracking error signal level detector 114 are supplied to the servo circuit 110 to change the servo loop characteristic of the servo circuit, that is, the gain. Different from the device.

As in the second embodiment, the focus and tracking error signal level detectors 113 and 114 are set to the first detection level and the second detection level. When the error signal level detects the first detection level, it is detected that there is distortion of the actuator control signal generated when the optical disc rotates at high speed, and the servo loop gain setting of the servo circuit is increased by a certain value. The actuator control signal distortion is reduced by the servo loop characteristic. When the second detection level or less,
It detects that there is no actuator control signal distortion that occurs when the optical disc rotates at high speed, and controls the servo loop gain setting of the servo circuit to lower it by a certain value to prevent excessive servo loop characteristics and reduce power consumption. Try.

However, when changing the servo loop gain, there is a limit to maintaining stable servo loop characteristics. Therefore, the maximum amount and the minimum amount of the servo loop gain are set, and the actuator servo control is performed even with the maximum servo loop gain amount. When signal distortion is detected, control is performed to reduce the rotation speed of the spindle motor before servo deviation occurs.

A more specific description will be given with reference to FIG. In the figure, in step 801, it is determined whether or not the focus error signal level is equal to or higher than the first detection level. If it is equal to or higher than the first detection level, the process proceeds to step 802, and it is determined whether or not the focus loop gain is maximum. If the gain is the maximum, in step 803 the spindle motor 1
This is controlled so that the rotation speed of 02 is reduced. If the focus loop gain is maximum in step 802, the focus loop gain is increased in step 804. If the focus error signal level is lower than the first detection level (No in step 801), it is further determined in step 805 whether the focus error signal level is equal to or lower than the second detection level. If it is less than or equal to the second detection level (Yes), step 8
In 06, it is determined whether the focus loop gain is the minimum,
If it is the minimum (Yes), go to the next step 8
Go to 08. If the focus loop gain is not the minimum in step 806, the focus soup gain is decreased in step 807 and the process proceeds to step 808. When the focus error signal level is higher than the second detection level in step 805, the process proceeds to step 808.

In step 808, it is determined whether the tracking error signal level is equal to or higher than the first detection level. First
If the detection level is above (Yes), step 8
Then, in step 809, it is determined whether or not the tracking loop gain is maximum. When the loop gain is maximum, the rotation of the spindle motor 102 is decelerated in step 803, which is controlled. If the loop gain is not the maximum in step 809 (No), step 81
At 0, the tracking loop gain is controlled to be increased. If the level is lower than the first detection level in step 808, it is determined in step 811 whether the tracking error signal level is equal to or lower than the second detection level. If it is equal to or lower than the second detection level (Yes), it is judged in step 812 whether or not the tracking loop gain is maximum, and if it is maximum (Yes), the process returns to step 801. If the tracking loop gain is not the minimum (No), the tracking loop gain is decreased in step 813,
Return to step 801.

As described above, in the present embodiment, the unstable servo operation generated by the distortion of the actuator servo control signal is reduced by the servo loop characteristic, the optimum servo loop characteristic can be set, and the stable optical disk reading speed can be obtained. realizable.

Next, a fourth embodiment will be described. The error signal level detectors 113 and 114 perform the servo loop gain setting of the servo circuit by detecting the error signal level peak value within a certain fixed time and calculating the difference from the predetermined error signal level to be set. Thus, stable servo loop characteristics can be obtained instantaneously. Further, when the maximum amount and the minimum amount of the servo gain are set as in the third embodiment and the actuator servo control signal distortion is detected even with the maximum servo loop gain amount, the spindle motor of the spindle motor is generated before the servo deviation occurs. Controls to reduce the rotation speed. As described above, by controlling the servo loop characteristic according to the actuator servo control signal distortion level, the servo unstable operation generated by the actuator servo control signal distortion is reduced, and the stable optical disk with the optimum servo loop characteristic is obtained. Read speed can be realized.

[0031]

As described above, according to the present invention, it is possible to prevent servo deviation due to distortion of the actuator control signal generated when the optical disk operates at high speed and to perform stable actuator control.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram for explaining a relationship between a focus error signal and a detection level.

FIG. 3 is a characteristic diagram for explaining a relationship between a tracking error signal and a detection level.

FIG. 4 is a flow chart showing an embodiment of the processing operation of the optical disk device according to the present invention.

FIG. 5 is a characteristic diagram showing actuator signal distortion.

FIG. 6 is a flowchart showing another embodiment of the processing operation of the optical disk device according to the present invention.

FIG. 7 is a block diagram showing a second embodiment of the optical disk device according to the present invention.

8 is a flowchart showing a third embodiment of the processing operation of the optical disk device shown in FIG.

[Explanation of symbols]

101 ... Optical disc, 102 ... Spindle motor, 10
3 ... Rotation detector, 104 ... Rotation control circuit, 105 ... Objective lens, 106 ... Actuator, 107 ... Optical pickup, 108 ... Slider, 109 ... Signal processing circuit, 11
0 ... Servo circuit, 111 ... Power amplifier, 112 ... Control section, 113 ... Focus error signal level detector, 11
4 ... Tracking error signal level detector.

Continued front page    F-term (reference) 5D090 AA01 CC04 DD03 EE12 FF01                       FF21 HH03                 5D118 AA13 BA01 BB01 BF02 CA02                       CD01 CD17

Claims (7)

[Claims] 1. An information reading section for irradiating a signal recording surface of an optical disk with a light beam through an objective lens to read an information signal on the signal recording surface, a spindle motor for rotationally driving the optical disk, and the optical disk. A rotation speed detecting means for detecting the rotation speed of the optical disk, a rotation control circuit for controlling the rotation of the spindle motor, and an actuator control signal which is a signal corresponding to the signal recording surface of the optical disc and the focal point position of the light beam. A signal processing circuit for outputting, a servo circuit for controlling the focal point position of the light beam according to the actuator control signal, and monitoring the actuator control signal to determine whether the level of the actuator control signal exceeds a predetermined value. Signal level detection means for determining whether or not the predetermined value detected by the signal level detection means Optical disc apparatus characterized by controlling the rotation speed of the spindle motor according to the level value. 2. An information reading section for irradiating a signal recording surface of an optical disk with a light beam through an objective lens to read an information signal on the signal recording surface, a spindle motor for rotating the optical disk, and the optical disk. A rotation speed detecting means for detecting the rotation speed of the optical disk, a rotation control circuit for controlling the rotation of the spindle motor, and an actuator control signal which is a signal corresponding to the signal recording surface of the optical disc and the focal point position of the light beam. A signal processing circuit for outputting, a servo circuit for controlling the position of the condensing point of the light beam according to the actuator control signal, and a peak value of the actuator control signal level exceeding a predetermined value by monitoring the actuator control signal. A signal level detecting means for detecting whether or not the signal level is detected by the signal level detecting means. Optical disc apparatus characterized by controlling the rotation speed of the spindle motor in accordance with the peak value for the value. 3. An information reading section for irradiating a signal recording surface of an optical disk with a light beam through an objective lens to read an information signal on the signal recording surface, a spindle motor for rotationally driving the optical disk, and the optical disk. Rotation speed detection means for detecting the rotation speed of the optical disk, a rotation control circuit for controlling the rotation of the spindle motor, and an actuator control signal which is a signal corresponding to the signal recording surface of the optical disk and the focal point position of the light beam. A signal processing circuit for outputting, a servo circuit for controlling the position of the condensing point of the light beam according to the actuator control signal, a servo loop setting means for setting a loop gain of the servo circuit in actuator control, and the actuator control signal To determine whether the actuator control signal level exceeds a predetermined value. A signal level detecting means, depending on the level value for said predetermined value detected by said signal level detecting means, the optical disk apparatus characterized by controlling the servo loop setting of the servo circuit. 4. An information reading section for irradiating a signal recording surface of an optical disk with a light beam through an objective lens to read an information signal on the signal recording surface, a spindle motor for rotationally driving the optical disk, and the optical disk. Rotation speed detection means for detecting the rotation speed of the optical disk, a rotation control circuit for controlling the rotation of the spindle motor, and an actuator control signal which is a signal corresponding to the signal recording surface of the optical disk and the focal point position of the light beam. A signal processing circuit for outputting, a servo circuit for controlling the position of the condensing point of the light beam according to the actuator control signal, a servo loop setting means for setting a loop gain of the servo circuit in actuator control, and the actuator control signal Signal level for monitoring the actuator and detecting the peak value of the actuator control signal level And means output, and the detection result of said signal level detection means, by calculating the predetermined level difference, an optical disk apparatus characterized by performing the servo loop setting of the servo circuit. 5. A method comprising: detecting a focus error signal and a tracking error signal; and reducing a rotation speed of a spindle motor when the focus error signal or the tracking error signal exceeds a predetermined value. Optical disk reproduction method. 6. A step of detecting a focus error signal and a tracking error signal, and a step of reducing a rotation speed of a spindle motor when the focus error signal or the tracking error signal exceeds a first detection value. And a step of increasing the rotation of the spindle motor when the focus error signal or the tracking error signal is lower than a second detection value lower than a first detection value. 7. The optical disc reproducing method according to claim 6, further comprising the case where the focus error signal or the tracking error signal exceeds a first detection value, the focus error signal or the tracking error signal When the loop gain has not reached the maximum value, the loop gain is increased, and the focus error signal or the tracking error signal is lower than a second detection value. And a step of reducing the loop gain of the tracking error signal when the loop gain has not reached the minimum value.