JP3404072B2 - Tracking servo device for optical disk drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking servo device for an optical disk drive. 2. Description of the Related Art In an optical disk drive apparatus for recording and / or reproducing information by irradiating a laser beam from an optical pickup onto an optical disk as an optical spot, the optical spot is maintained at the center of a track on the optical disk. Tracking servo device is used. This tracking servo device keeps the light spot at the center of the track on the optical disk by closing the tracking servo loop. However, before the tracking servo loop is closed, the light spot moves the track on the optical disk due to the eccentricity of the track. Cross many. From such a situation, various improvements have been made in order to effectively pull in the tracking servo.For example, when the pickup is moving from the center of the track to the center between the tracks, the tracking error in the tracking servo loop is reduced. A tracking servo pull-in method in which the signal is a positive-phase signal and the tracking error signal in the tracking servo loop is a negative-phase signal during a period in which the pickup is moving from the center between the tracks to the center of the track is disclosed in Japanese Unexamined Patent Publication No. Hei. No. 21,552. Further, in a state where the tracking servo loop is closed, various improvements have been made to reduce a tracking servo error which repeatedly occurs in accordance with the rotation of the optical disk due to the eccentricity of the track and the like. The repetition component is extracted to obtain a correction signal, and the tracking servo error repeatedly generated in accordance with the rotation of the optical disk due to the eccentricity of the track or the like is corrected by the correction signal. [0005] For example, Japanese Patent Publication No. Hei 4-10145 discloses a disk file servo control system for rapidly reducing a repetitive tracking servo error generated according to disk rotation. In this disk file servo control system, in detail, a head reads servo information from a disk, generates a head position error from the servo information, generates a control signal from the head position error, and responds to the control signal by generating a head signal. In the disk file that locates at the center of the track, a group of tap weights is calculated from the sample of the head position error, the trigonometric function value, and the learning speed coefficient, and the tap weights in the group are summed to generate a repetitive error correction signal. Occurs, adding this repetitive error correction signal to the control signal. In recent years, there has been a demand for an optical disk drive device to improve the information recording / reproducing speed per unit time, and therefore, the rotational speed of the optical disk has been increased. Need to be done. Before closing the tracking servo loop, the light spot crosses several tracks due to track eccentricity, etc., but the relative speed of the light spot and the track in the radial direction of the optical disk is
Even if the eccentricity of the track is the same, it increases in proportion to the rotation speed of the optical disk. For this reason, in the conventional optical disk drive, when the number of rotations of the optical disk is increased, the pull-in of the tracking servo is apt to fail, and the frequency of retry is increased. As a result, the operation speed of the apparatus is reduced. There is a problem of doing it. When the tracking servo error having a repeatability caused by the rotation of the optical disk due to the eccentricity of the track or the like is reduced by the correction device after the tracking servo is pulled in, the correction device repeats the tracking servo error. Until a component is extracted and a correction signal is obtained, it is necessary to maintain a tracking state at least without a correction signal for reducing a tracking servo error. However, in the conventional optical disk drive device, when the rotational speed of the optical disk is increased, the tracking error increases until the correction device obtains the correction signal, and the tracking state cannot be maintained, so that the tracking error occurs. In some cases, there is a problem that the frequency of performing retries before the correction device operates properly increases, and as a result, the operation speed of the device decreases. The present invention solves the above-mentioned drawbacks, and enables the tracking servo to be quickly performed even when the rotation speed of the optical disk at the time of recording and / or reproducing information is increased. It is an object of the present invention to provide a tracking servo device of an optical disk drive device capable of quickly reducing a tracking servo error having repeatability generated according to the following. In order to achieve the above object, the invention according to claim 1 comprises a spindle motor for driving an optical disk to rotate and a pickup for irradiating a track on the optical disk with a light spot. In the tracking servo device of the optical disk drive device, the optical spot is maintained on a track of the optical disk .
A tracking servo loop for switching the rotation speed of the spindle motor between a first rotation speed and a second rotation speed higher than the first rotation speed; and a rotation speed switching device for controlling the rotation speed of the spindle motor to the first rotation speed. A control signal in the tracking servo loop is detected in a state where the number of revolutions is switched to 1, and then the control signal is detected by switching the number of revolutions of the spindle motor to a second number of revolutions by the number of revolutions switching means. Correction means for adding a correction signal generated based on the following to the tracking servo loop, wherein the correction means converts a control signal in the tracking servo loop when the rotation speed of the spindle motor is the first rotation speed. Upon detection, based on this control signal, a correction signal is generated when the rotation speed of the spindle motor is the second rotation speed. No. is characterized in that the coefficients based on the ratio between the second speed and the first speed is multiplied. According to the first aspect of the present invention, the optical disk has a spin
The pickup is rotated by a dollar motor and the pickup
The track on the disc is irradiated with a light spot. Truckin
G-servo loop places light spots on optical disc tracks
And the rotation speed switching means sets the rotation speed of the spindle motor.
To the first speed and a higher second speed
You. The correction means is used to switch the rotation speed of the spindle motor.
Tracking with the number of revolutions switched to the first number of revolutions
Detects the control signal in the servo loop and then turns off the speed.
Switching the rotation speed of the spindle motor to the second rotation speed
The correction signal generated based on the control signal
Signal during the tracking servo loop. further,
The compensating means determines that the rotation speed of the spindle motor is the first rotation speed.
Detect control signal in tracking servo loop at certain time
Then, based on this control signal, the rotation speed of the spindle motor
Generates a correction signal when is the second number of revolutions.
The signal is a coefficient based on the ratio of the first speed to the second speed.
Is multiplied. Therefore, the correction means
When detecting a control signal in the servo loop, the track
Tracking servo error becomes excessive and
Stable tracking servo pull-in
Therefore, the operation speed does not decrease due to the retry. FIG. 1 shows an embodiment of the present invention. The optical disc 1 is driven to rotate by a spindle motor 2, and the rotation speed of the spindle motor 2 is controlled by a spindle motor control circuit (S
PC) 3. The spindle motor control circuit 3 controls the rotation speed of the spindle motor 2 in two stages, a first rotation speed and a second rotation speed, according to a rotation speed switching signal from a microcontroller (MCU) 4. The first rotation speed is smaller than the second rotation speed. When the spindle motor is rotating at the first rotation speed, a tracking servo error having tracking servo pull-in and repeatability will be described later. The detection of the tracking actuator drive signal is performed in order to obtain a correction signal for reducing the tracking error. When the spindle motor is rotating at the second rotation speed, the tracking servo loop operates with the correction signal given as described later to record and reproduce information on and from the tracks on the optical disc 1. . The pickup 5 irradiates a focused laser beam from the objective lens 6 to the optical disc 1 to form a light spot on the optical disc 1. The laser beam reflected by the optical disk 1 returns to the pickup 5 via the objective lens 6 again, is received by the photo detector 7, and its light amount is detected. Detection amplifier (DETAMP) 8
Amplifies the output signal of the photodetector 7 and detects a tracking error signal TE indicating the deviation of the light spot from the track center and a reproduction data signal RD corresponding to the data recorded on the track of the optical disc 1. The tracking servo loop includes a photodetector 7, a detection amplifier 8, a switch (SW) 9, a phase compensation circuit (CMP) 10, an adder 11, and a power amplifier (P
A) 12, formed by the tracking actuator 13, and the MCU 4 opens and closes the tracking servo loop by opening and closing the SW9. When the microcontroller 4 performs the pull-in of the tracking servo, FIG.
In step 201, the spindle motor control circuit 3 switches the rotation speed of the spindle motor 2 to the first frequency (LOW). With the rotation speed of the spindle motor 2 maintained at the first frequency, the microcontroller 4 closes the switch 9 in step 202 shown in FIG. 3 to close and turn on the tracking servo loop. After the tracking error signal TE from the detection amplifier 8 is phase-compensated by the phase compensation circuit 10, the power is amplified by the power amplifier 12 via the adder 11 and supplied to the tracking actuator 13 so that the tracking actuator 13 The objective lens 6 is moved substantially in the radial direction of the optical disc 1. As a result, the tracking servo is pulled in and the light spot rides on the track of the optical disc 1. As described above, in this embodiment, the spindle motor 2 rotates at the first rotation speed set lower than the second rotation speed which is the rotation speed of the spindle motor 2 when recording and reproducing information. Since the pull-in of the tracking servo is performed when the tracking servo is in operation, the pull-in of the tracking servo is performed very stably. After the pull-in of the tracking servo is completed, the microcontroller 4
While the spindle motor control circuit 3 keeps the spindle motor 2 at the first rotation speed for one rotation of the optical disk 1, the output signal of the analog / digital converter (AD) 14 Sampling is performed in accordance with the rotation angle and stored in the memory (MEM) 15. Here, the analog / digital converter 14 is connected to the phase compensation circuit 10.
Is converted into a digital signal, and this digital signal corresponds to a drive signal of the tracking actuator 13. A track on the optical disc 1 is divided into a fixed number of sectors per round, and a sector address is recorded in advance in each sector in an ID portion thereof. The address detection circuit (ADRDET) 16 detects a sector address from the reproduction data signal RD from the detection amplifier 8 and outputs the sector address to the microcontroller 4. Microcontroller 4
In step 203 shown in FIG. 3, an output signal of the analog / digital converter 14 is sampled in accordance with an output signal of the address detection circuit 16 in accordance with each sector address, so that a tracking actuator corresponding to each predetermined rotation angle of the optical disc 1 is sampled. Thirteen drive signals are sampled. In this case, the microcontroller 4 samples the analog / digital conversion value of the analog / digital converter 14 by the sector address detection of the address detection circuit 16 and stores it in the memory 15 as shown in FIG. FIG. 2A is a schematic diagram showing the time relationship between the output signal of the phase compensation circuit 10, the sector address detected by the address detection circuit 16, and the sampling points. During such initial sampling (for example, during the time when the optical disc 1 makes one rotation after the tracking servo is pulled in), the tracking servo loop does not receive a special correction signal, and the repeatability caused by the track eccentricity or the like is lost. The correction of the tracking error is not performed. In this embodiment, however, the spindle motor 2 rotates at a first rotation speed set lower than the second rotation speed which is the rotation speed of the spindle motor 2 when recording and reproducing information. When the microcontroller 4 is sampling the output signal of the analog-to-digital converter (AD) 14, the tracking error becomes excessive during the sampling of the tracking servo, and the light spot goes off the track. This eliminates the problem of having The microcontroller 4 calculates a correction signal to be given to the tracking servo loop based on the sampling value stored in the memory 15 in accordance with a predetermined rotation angle of the optical disk 1. It is assumed that the tracking error having repeatability to be corrected is, for example, only the fundamental frequency component of the rotation speed of the optical disc 1. The microcontroller 4 is shown in FIG.
In step 204, the sampling value stored in the memory 15 is subjected to Fourier analysis to analyze the amplitude and phase of the fundamental frequency component of the rotation speed of the optical disc 1, and the sinusoidal waveform to be given to the tracking servo loop based on the amplitude and phase. Is calculated in accordance with the rotation angle of the optical disk 1 and the memory 1
Store in 5. In this case, the microcontroller 4 corresponds to FIG.
CS and SN are cleared to 0 and CS ← CS +
cos (2πA / N) × C (A), SN ← SN + sin (2πA /
After performing an operation of N) × C (A) for A = 0 to N−1, an operation of CS ← CS / N × 2, an operation of SN ← CS / N × 2 is performed, and D (A) ← CS × cos (2πA / N) + sin
By performing an operation of (2πA / N) for A = 0 to N−1, a fundamental frequency component is extracted by Fourier analysis. Further, the microcontroller 4 adds the first rotation speed n1 and the second rotation speed to the amplitude D (A) of the correction value.
The coefficient (n2 / n1) ² is multiplied based on the ratio with n2. This is because the track shake acceleration due to the track eccentricity or the like increases in proportion to the square of the rotation speed of the optical disc 1. That is, the microcontroller 4 multiplies the amplitude of the correction value by a coefficient to obtain the sampling value of the output signal of the analog / digital converter (AD) 14 when the spindle motor 2 is rotating at the first rotation speed. Then, a correction value to be given to the tracking servo loop when the spindle motor 2 is rotating at the second rotation speed is calculated. When the calculation of the correction value is completed, the microcontroller 4 causes the spindle motor control circuit 3 to switch the rotation speed of the spindle motor 2 to the second rotation speed (HIGH) in step 205 shown in FIG. At the same time, in step 206 shown in FIG. 3, the microcontroller 4 reads the correction value from the memory 15 corresponding to the sector address detected by the address detection circuit 16 as shown in FIG. ) Set to 17. Digital/
The analog converter 17 outputs a correction signal proportional to the correction value set by the microcontroller 4 to the adder 11. The correction signal is added to the output signal of the phase compensation circuit 10 by the adder 11, and
Drive signal. FIG. 2C shows the address detection circuit 16 when the spindle motor 2 is rotating at the second rotation speed.
FIG. 4 is a schematic diagram showing a time relationship between a sector address detected by the above and a correction signal given to a tracking servo loop corresponding to the sector address. FIG. 2 (b)
FIG. 3 is a reference diagram showing a state of a correction signal to be given to the tracking servo loop when the spindle motor 2 is rotating at the first rotation speed. As can be seen from the comparison of FIGS. 2B and 2C, in this embodiment, the tracking actuator sampled in accordance with the rotation angle of the optical disk 1 when the spindle motor 2 is rotating at the first rotation speed. Based on the drive signal, when the spindle motor 2 is rotating at the first rotation speed, a correction signal is generated based on the ratio between the first rotation speed and the second rotation speed in accordance with the rotation angle of the optical disc 1. To the tracking servo loop. The tracking servo error having repeatability caused by track eccentricity and the like is greatly reduced by the correction signal, and the tracking servo is stably performed.
In this state, a focused laser beam is irradiated from the pickup 5 toward the optical disk 1 via the objective lens 6 to record and reproduce information on tracks on the optical disk. In the above embodiment, the microcontroller 4 performs Fourier analysis on the sampling values stored in the memory 15 to analyze the amplitude and phase of the fundamental frequency component of the rotation speed of the optical disk 1, and based on the amplitude and phase. The sine wave correction value to be given to the tracking servo loop is calculated in accordance with the rotation angle of the optical disc 1 and stored in the memory 15, but the sampling value stored in the memory 15 is subjected to Fourier analysis to determine the rotation speed of the optical disc 1. The amplitude and phase of a frequency component that is an integral multiple of the number of revolutions of the optical disc 1 including the fundamental frequency component is analyzed, and a sine wave-like correction value to be given to the tracking servo loop is calculated based on the amplitude and phase. A corresponding operation may be performed and stored in the memory 15. In this way, even when the rotation speed of the optical disk for recording and / or reproducing information is increased, the tracking servo error having repeatability generated according to the rotation speed of the optical disk can be rapidly reduced, and the stability can be improved. As a result, an accurate tracking servo state is obtained, and information recording and reproducing speed is improved. As described above, according to the first aspect of the present invention, there is provided an optical disk drive apparatus having a spindle motor for driving an optical disk to rotate and a pickup for irradiating a track on the optical disk with a light spot. In a tracking servo device, a tracking servo loop for maintaining the light spot on a track of the optical disk, and a rotation speed switching for switching a rotation speed of the spindle motor between a first rotation speed and a second rotation speed higher than the first rotation speed Means for detecting a control signal in the tracking servo loop in a state where the rotation speed switching means switches the rotation speed of the spindle motor to the first rotation speed. 2nd rotation speed
Correction means for adding a correction signal generated based on the control signal detected by switching to the rotation speed of the spindle motor during the tracking servo loop, wherein the correction means is configured such that the rotation speed of the spindle motor is equal to the first rotation speed. At a certain time, a control signal in the tracking servo loop is detected, and the rotation speed of the spindle motor is adjusted to the second speed based on the control signal.
A correction signal is generated when the number of rotations is equal to the number of rotations. Since the correction signal is multiplied by a coefficient based on the ratio of the first rotation number and the second rotation number, the correction means is used during the tracking servo loop. When the control signal is detected, the tracking servo error does not become excessive and the track is not deviated, so that the tracking servo can be pulled in stably and the operation speed does not decrease due to the retry. For this reason, even when the rotation speed of the optical disk when recording and / or reproducing information is increased, the tracking servo can be quickly pulled in, and further, the tracking servo having repetitiveness generated according to the rotation speed of the optical disk. Errors can be reduced quickly. [0038]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the present invention. FIG. 3 is a flowchart showing a processing flow of a microcontroller in the embodiment. FIG. 4 is a flowchart showing a part of a processing flow of the microcontroller in detail. FIG. 5 is a flowchart showing another part of the processing flow of the microcontroller in detail. FIG. 6 is a flowchart showing another part of the processing flow of the microcontroller in detail. [Description of Signs] 1 Optical disk 2 Spindle motor 3 Spindle motor control circuit 4 Microcontroller 5 Pickup 7 Photodetector 8 Detection amplifier 9 Switch 11 Adder 13 Tracking actuator 16 Address detection circuit

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Claims (1)

(1) A tracking servo device for an optical disk drive, comprising: a spindle motor for rotatingly driving an optical disk; and a pickup for irradiating a track on the optical disk with a light spot. A servo loop for maintaining the rotation speed on the track of the optical disk, a rotation speed switching means for switching the rotation speed of the spindle motor between a first rotation speed and a second rotation speed higher than the first rotation speed, A control signal in the tracking servo loop is detected in a state where the rotation speed of the spindle motor is switched to the first rotation speed by the number switching means, and thereafter, the rotation speed of the spindle motor is changed to the first rotation speed by the rotation speed switching means. The correction signal generated based on the control signal detected by switching to the rotation speed of Correction means for adding a signal during a servo loop, the correction means detecting a control signal in the tracking servo loop when the rotation speed of the spindle motor is the first rotation speed, and detecting the spindle signal based on the control signal. Generating a correction signal when the rotation speed of the motor is the second rotation speed, wherein the correction signal is multiplied by a coefficient based on a ratio between the first rotation speed and the second rotation speed; A tracking servo device for an optical disk drive device, comprising: