JP2000011404A - Disk drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability of the device by arranging it so that a control process based on more accurate and stable middle point error signal is executed. SOLUTION: At first, an eccentricity amount (x) of a disk is detected to obtain an amplitude Vp-p of a middle point error signal appearing at one revolution cycle of the disk. And, sensitivity Ers of the middle point error signal is obtained by executing an operation processing of Ers=Vp-p/x [V/μm] on the eccentricity amount (x) and the amplitude Vp-p of the middle point error signal. And, based on the sensitivity Ers of this middle point error signal, the transition amount of an actual object lens corresponding to the level of the middle point error signal is obtained and this is used for a necessary control processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk drive, and more particularly to a required control process relating to a recording or reproducing operation using a midpoint error signal indicating a shift of a visual field position from a reference position in a tracking direction of an objective lens. The present invention relates to a disk drive device that can execute the above.

[0002]

2. Description of the Related Art In recent years, as recording media for various data and programs used in personal computers and the like, disc-shaped recording media such as CD-ROMs (hereinafter simply referred to as discs) have been known. I have. Also, while the CD-ROM is read-only and data cannot be recorded, the MO (Magnet
Data can be recorded on a disk such as a magneto-optical disk such as an optical disk.

[0003] Disk drive devices capable of reproducing or recording / reproducing the above-mentioned respective disk media are also widely known. In such a disk drive device, data is recorded / reproduced on / from the disk by irradiating a laser beam to a signal surface of the disk with an objective lens forming an optical system of an optical pickup as an output end.

[0004]

In the above-described disk drive device, the visual field position of the objective lens in the tracking direction is, for example, a neutral position of the objective lens (here, the objective lens is driven in the tracking direction). (Meaning a position in the tracking direction when the drive mechanism is supported by the drive mechanism in a non-moving state). Is configured to execute the control processing described above.

However, the sensitivity of the above-mentioned midpoint error signal, that is, the actual value of the objective lens, is affected by, for example, the degree of modulation due to the light reflectance of the disk being different for each disk, and the characteristics of the optical pickup being different for each device. It has been found that the amount of change of the midpoint error signal per unit movement amount is not unique. For this reason, the information actually obtained as the midpoint error signal can only indicate the position of the objective lens at a considerably low level of accuracy. Therefore, even if a required control process is executed based on such a midpoint error signal, the accuracy and stability may be insufficient depending on the type of the control process.

In view of such circumstances, it is possible to obtain more accurate information on the position information of the objective lens obtained based on the midpoint error signal, and to obtain a more accurate and stable midpoint error. It is preferable that the control process based on the signal is executed.

[0007]

In view of the above-mentioned problems, the present invention drives the objective lens along the tracking direction as the position of the objective lens for irradiating the disk-shaped recording medium with laser light. A midpoint error signal output unit that outputs a midpoint error signal indicating a shift of the visual field position with respect to the reference position in the tracking direction, with the visual field position in a neutral state in which the driving by the driving mechanism that supports it is not performed as a reference position, Signal sensitivity detecting means for detecting a change amount of the midpoint error signal per unit movement amount of the objective lens as a sensitivity of the midpoint error signal, and a recording / reproducing of the disk-shaped recording medium based on the midpoint error signal. Control processing means for executing the control processing of the intermediate point error signal based on the sensitivity of the intermediate point error signal. Obtaining a moving distance with respect to the reference position in the tracking direction of the objective lens to respond, it was decided to executable configure the required control processing based on the information of the movement distance.

According to the above configuration, it is possible to accurately grasp the visual field position in the tracking direction of the objective lens corresponding to the level of the midpoint error signal based on the sensitivity of the detected midpoint error signal. Then, as the control processing to be executed based on the midpoint error signal, it is possible to use the information on the accurate visual field position of the objective lens obtained as described above.

[0009]

Embodiments of the present invention will be described below. In the present embodiment, for example, a disk driver configured as a reproducing device capable of reproducing at least a CD-ROM will be described as an example. The following description will be made in the following order. 1. Disk driver 2. 2. Generation of midpoint error signal based on RF signal 3. Sensitivity detection of middle point error signal (first example) 4. Sensitivity detection of midpoint error signal (second example) Example of control processing using middle point error signal 5-1. Middle point servo 5-2. Thread servo 5-3. 5. Monitor the abnormality of the objective lens. Modified example (Generation of midpoint error signal by midpoint sensor)

[0010] 1. FIG. 1 is a block diagram showing a configuration of a main part of a reproduction circuit system and a servo system of a disk drive device according to the present embodiment. The disc D shown in this figure is placed on a turntable 7 and is driven by a spindle motor 6 at a constant linear velocity (CLV) or a constant angular velocity (CAV) during a reproducing operation.
Is driven to rotate. Then, the data recorded on the signal surface of the disk D is read by the optical pickup 1. In this case, the spindle motor 6 outputs a frequency signal synchronized with the rotation speed of the spindle motor 6 as an FG pulse to the spindle FG (Frequency G).
enerator) 6a. In this case, the FG pulse is input to the servo processor 14.

The optical pickup 1 is provided with a laser diode 4 as a light source of laser light, an optical system including a deflection beam splitter and an objective lens 2, a photodetector 5 for detecting laser light reflected on a disk, and the like. It is configured. Here, the objective lens 2 is movably supported by the biaxial mechanism 3 in the tracking direction and the focus direction.

The laser light reflected from the disk D by the reproducing operation of the disk drive device is detected by the photodetector 5 as a light receiving current. And
This light receiving current is output to the RF amplifier 9 as an information signal read from the disk. The RF amplifier 9 includes a current-voltage conversion circuit, an amplification circuit, a matrix operation circuit (RF
And a necessary signal based on a signal from the photodetector 5. For example, an RF signal as reproduction data, a push-pull signal PP for servo control, a focus error signal FE, a tracking error signal TE, a pull-in signal PI as a so-called sum signal
Generate etc.

The photodetector 5 is provided with a four-divided detector 5a including detectors A, B, C, and D in the direction shown in FIG. 2A. In this case, the focus error signal FE is supplied to the detectors A, For the outputs of B, C, and D,
It is generated by the calculation of (A + C)-(B + D). Further, the pull-in signal PI = (A + B + C + D). Also,
When the push-pull signal PP is generated by the quadrant detector 5a, as shown in FIG.
The outputs of the detection units A, B, C, and D of FIG.
It can be generated by performing the operation of (A + D)-(B + C) with b. In addition, the tracking error signal T
In consideration of the so-called three-beam system, E is equal to 4 shown in FIG.
Detectors E and F for side spots may be prepared separately from the divided detectors, and may be generated by EF calculation.

Various signals generated by the RF amplifier 9 are supplied to a binarization circuit 11 and a servo processor 14. In other words, the reproduced RF signal from the RF amplifier 9 is
To push-pull signal PP and focus error signal F
E, the tracking error signal TE, and the pull-in signal PI are supplied to the servo processor 14.

In particular, the RF amplifier 9 according to the present embodiment is configured to be able to generate the midpoint error signal Cen based on the tracking error signal TE obtained here. The system controller 10 is configured to be able to execute various required control processes based on the midpoint error signal. These items will be described later.

The reproduced RF signal output from the RF amplifier 9 is binarized by a binarization circuit 11 to obtain a so-called EFM.
Signal (8-14 modulated signal) or EFM + signal (8-
16 modulated signal) and supplied to the decoder 12.

In the decoder 12, EFM demodulation or EFM
+ Demodulation, CIRC decoding, etc., to reproduce information read from the disk D. The data decoded by the decoder 12 is supplied to a host computer (not shown) via the interface unit 13. In the decoder 12, the supplied EFM
By inputting the signal or the EFM + signal to the internal PLL circuit, a reproduction clock based on a frequency signal synchronized with the channel bit frequency of the EFM signal or the EFM + signal is extracted. This reproduction clock is used as a reference clock which is a reference of signal processing timing inside the decoder 12, for example, and disk rotation speed information is obtained from this clock. This disk rotation speed information indicates a relative speed between a laser spot output from the optical pickup 1 and a track on which recording pits are formed.

The servo processor 14 generates various servo drive signals for focus, tracking, sled, and spindle from the focus error signal FE, the tracking error signal TE, the push-pull signal PP, and the like from the RF amplifier 9, and executes the servo operation. . That is, a focus drive signal FDR and a tracking drive signal TDR are generated in accordance with the focus error signal FE and the tracking error signal TE, and are supplied to the biaxial driver 16.

The biaxial driver 16 includes, for example, a focus coil driver 16a and a tracking coil driver 16b. The focus coil driver 16a supplies the drive current generated based on the focus drive signal FDR to the focus coil of the biaxial mechanism 3 to drive the objective lens 2 in the direction of moving toward and away from the disk surface. The tracking coil driver 16b supplies the drive current generated based on the tracking drive signal TDR to the tracking coil of the biaxial mechanism 3 to drive the objective lens 2 to move in the disk radial direction. Thereby, the optical pickup 1, the RF amplifier 9, the servo processor 1
4. A tracking servo loop and a focus servo loop by the two-axis driver 16 are formed.

The servo processor 14 supplies a spindle drive signal generated from the spindle error signal SPE to a spindle motor driver 17 described later. The spindle motor driver 17 applies, for example, a three-phase drive signal to the spindle motor 6 in accordance with the spindle drive signal, and drives the spindle motor 6 to rotate at a required rotational speed. Servo processor 1
A spindle motor driver 17 generates a spindle drive signal in response to a spindle kick (acceleration) / brake (deceleration) signal from the system controller 10.
, Such as starting or stopping the spindle motor 6.

In the present embodiment, the rotational drive speed of the disk for reproducing the disk can be made variable. In this case, for example, a double speed of 1 × or lower is set to CLV, and a double speed of 2 × or higher is set to CAV.

For this purpose, the system controller 10 is configured so that the reference speed information can be variably set to the servo processor 14. For example, when the rotational drive speed is controlled by the CLV, the rotational speed information obtained from the above-described decoder 12 is compared with the set reference speed information, and a spindle error signal SPE corresponding to the error is generated. However, if the reference speed information to be set for the servo processor 14 is changed, the CLV speed can be varied.

When the rotational drive speed is controlled by the CAV, for example, the servo processor 14 detects the rotational speed of the spindle motor 2 by an FG pulse (frequency signal synchronized with the rotational speed) from the spindle motor 2 or the like. At the same time, the system controller 10 supplies reference speed information corresponding to a required CAV speed. Then, the reference speed information is compared with the rotation speed of the spindle motor 2, a spindle error signal SPE is obtained based on the error information, and the spindle motor 2 is accelerated / decelerated based on the spindle error signal SPE. The required CAV speed is obtained. Then, for example, in the system controller 10, the above C
The CAV speed can be changed by changing the reference speed information corresponding to the AV speed according to the required double speed.

Further, the servo processor 14 generates a thread drive signal based on, for example, a thread error signal obtained from a low-frequency component of the tracking error signal TE and an access execution control from the system controller 10. Supply. The thread driver 15 drives the thread mechanism 8 according to a thread drive signal. The thread mechanism 8 includes the optical pickup 1
This is a mechanism for moving the entirety in the disk radial direction. The sled driver 15 drives a sled motor inside the sled mechanism 8 according to a sled drive signal, so that the optical pickup 1 is appropriately slid.

Further, the servo processor 14 also performs light emission drive control of the laser diode 4 in the optical pickup 1. The laser diode 4 is a laser driver 18
The servo processor 14 generates a laser drive signal for performing laser emission at the time of reproduction or the like based on an instruction from the system controller 10, and supplies the laser drive signal to the laser driver 18. In response, the laser driver 18 drives the laser diode 4 to emit light.

Various operations such as servo and decoding as described above are controlled by a system controller 10 including a microcomputer including a RAM 10a. For example, operations such as reproduction start, end, track access, fast forward reproduction, and fast reverse reproduction are realized by the system controller 10 controlling the operation of the optical pickup 1 via the servo processor 14.

The traverse counter 1 shown in FIG.
Reference numeral 9 denotes, for example, a so-called traverse signal obtained when the laser light emitted from the objective lens 2 traverses the track of the disk D as the tracking error signal TE. Based on the traverse signal, the laser light This is a circuit part for detecting the number of traversed tracks.
The information on the number of traversing tracks detected by the traverse counter 19 is used for control at the time of track jump when moving the objective lens 2 (or the optical pickup 1 itself) in the radial direction of the disc at the time of random access or the like. In the present embodiment, as will be described later, the present embodiment is also used for detecting the sensitivity of the midpoint error signal as the first and second examples. The configuration for detecting the number of traversing tracks by the traverse counter 19 will be described later.

The midpoint sensor 20 is shown as a circuit block enclosed by a broken line in the optical pickup 1, which will be described later as a modified example.

2. Generation of Midpoint Error Signal Based on RF Signal As described above, the servo processor 1 of the present embodiment
In No. 4, it is possible to detect (generate) a midpoint error signal based on the tracking error signal TE. The midpoint error signal here is a field position in the tracking direction (disc radial direction) of the objective lens, for example, in a state where the objective lens is not driven in the tracking direction and is supported by the biaxial mechanism 3. The position is defined as a neutral position (reference position), and the amount of displacement of the objective lens with respect to this reference position (corresponding to the movement distance)
Is a signal indicating

Such a middle point error signal can be detected as follows. Here, it is assumed that a one spot push-pull system is adopted.

As shown in FIG. 3A, the beam spot S1 is located at the center of the photodetector 5 having a light receiving area E1 (corresponding to A + D in FIG. 2) and F1 (corresponding to B + C in FIG. 2). When the beam spot S1 crosses the track of the disk D, the photodetector 5
Since light and dark appear above, the zero cross point of the tracking error signal TE becomes the track center. Thus, tracking servo control can be performed using the tracking error signal TE. However, in the push-pull method, as shown in FIG. 3B, when the beam spot S1 moves away from the center of the photodetector 5, that is, when the objective lens 2 is driven in the radial direction, the beam spot S1 is moved. Is moved on the photodetector 5, the tracking error signal TE becomes a signal having an offset component OF which has a slow swell.

If the tracking error signal TE having such an offset component OF is used as it is,
Proper tracking servo control cannot be performed.
Therefore, for example, an offset signal which is an offset component OF of the tracking error signal TE shown in FIG. 3B is extracted, and the offset signal is used to apply a waveform to the tracking error signal TE shown in FIG. In this case, the tracking error signal TE having the waveform shown in FIG. As can be seen from the above description, the offset component OF is used as the visual field position of the objective lens 2 as
This corresponds to the amount of deviation from the neutral position. Therefore, in the present embodiment, an offset signal corresponding to the offset component OF is used as a midpoint error signal.

In the case of the configuration of the disk drive device shown in FIG. 1, for example, in a servo processor, FIG.
The tracking error signal TE obtained as shown in FIG.
The low-pass signal component corresponding to the envelope of the tracking error signal TE is extracted by holding the peak value from the low-pass signal or by applying a low-pass filter, and by removing the DC component from the low-pass signal component, the offset signal (FIG. b) a signal corresponding to the offset component OF). In the present embodiment, the generation process of the offset signal is performed in the RF amplifier 9 as described above, for example. In the present embodiment, a signal obtained by using this offset signal is output to the system controller 10 as a midpoint error signal Cen.

3. Sensitivity detection of middle point error signal (first example) The middle point error signal Cen can be obtained as described above based on the RF signal.
As described above, n has a different sensitivity even in the same disk driver due to a difference in the degree of modulation for each disk. Also, if they are between the same model,
The sensitivity of the midpoint error signal varies depending on the sensitivity of the biaxial mechanism, the variation in the characteristics of the optical pickup caused by the laser power, the characteristics of the optical system, and the like. For confirmation, the “sensitivity of the midpoint error signal” here refers to the amount of change in the midpoint error signal per actual unit movement amount of the objective lens. For this reason, when a change due to a certain level is obtained as the midpoint error signal, it is necessary to uniquely determine how much the level change corresponds to the actual position of the objective lens. It is difficult. In other words, if only the midpoint error signal is used, the position of the objective lens cannot be detected accurately. Therefore, when performing a specific control process using the midpoint error signal, the actual objective It is difficult to obtain an accurate effect according to the position of the lens.

Therefore, in the present embodiment, by detecting the sensitivity of the midpoint error signal, the amount of change of the midpoint error signal per actual unit movement amount of the objective lens is obtained. If information on the sensitivity of the midpoint error signal is obtained, it is possible to obtain as information the correspondence between the level of the midpoint error signal and the actual position of the objective lens in the tracking direction.

First, the sensitivity detection of the midpoint error signal as a first example will be described with reference to FIGS. In detecting the sensitivity of the midpoint error signal as the first example, first, the amount of eccentricity of the disk loaded in the disk driver is detected. The term “eccentricity” of the disk referred to here means a state called “eccentricity” or “eccentricity”. “Eccentric” means that the center of the center hole of the disc physically coincides with the center of gravity, but the center of the center hole does not coincide with the center of the track (radially or concentrically). The term “eccentricity” means that the center hole of the disk physically coincides with the center of the track, but the position of the center hole does not coincide with the position of the center of gravity of the disk.

Various methods for detecting the amount of eccentricity of the disk have been previously proposed by the present applicant. One example is to rotate the disk without performing tracking servo control by a closed loop. And a method of obtaining the tracking error signal TE (traverse signal) obtained under this condition. The detection of such an eccentric amount will be described with reference to FIGS.

FIG. 4 is a schematic diagram for explaining the relationship between the track pitch of the disk D and the traverse pulse.
4A shows a groove and a land in a state where a part of the disk D is enlarged to be a cross section in the radial direction, and FIG.
FIG. 4A is a schematic diagram of a tracking error signal obtained when the optical pickup is moved in the radial direction with respect to the disk, and FIG. 4C is generated by the traverse counter 19 based on the tracking error signal. 5 shows a traverse pulse (traverse signal).

As shown in FIG. 4A, when the disk D is viewed in cross section along the radial direction, the lands 30 and the grooves 31 are located alternately. For example, in this case, the groove 31 is a track on which data pits are recorded. Therefore, as shown in FIG.
The distance between the respective center positions 31 is the track pitch tp. Here, the objective lens 2 was irradiated with the laser beam while moving as shown in the movement locus 33 of FIG. 4A as a relative positional relationship with respect to the disk surface, that is, while moving across the disk radial direction. Then, it is known that a waveform shown in FIG. 4B is obtained as the tracking error signal TE. That is, a sinusoidal waveform is obtained in which zero level is obtained when the center of the land 30 and the groove 31 is irradiated with the laser beam.

The traverse counter 19 according to the present embodiment receives a tracking error signal TE and outputs, for example, a pulse signal which is compared with a level 0 as a reference, as a comparator pulse, and a pulse of this comparator pulse. And a counter capable of counting the number. For example, when the tracking error signal TE shown in FIG. 4B is compared by the comparator of the traverse counter 19, a traverse pulse having a pulse waveform shown in FIG. 4C is obtained. This figure 4
Comparing the waveform shown in (c) with the cross-sectional view of the disk shown in FIG. 4 (a), it can be seen that one cycle of the traverse pulse corresponds to a state of traversing one track. Therefore,
The number of H-level or L-level pulses of the traverse pulse corresponds to the number of track crossings. The traverse counter 19 counts, for example, the number of compare pulses, and outputs information on the count value to the system controller 10. System controller 10
Then, the amount of eccentricity of the disk D can be calculated based on the input count value of the compare pulse as described below.

First, in order to calculate the amount of eccentricity, after the disk D is driven to rotate, the focus servo loop is turned on and the tracking servo loop is turned off so that no tracking drive signal is applied. Thus, the movement of the objective lens 2 is fixed in the tracking direction. In this state, for example, each time the disk makes one revolution, the laser beam of the objective lens 2 crosses a certain number of tracks according to the degree of eccentricity. Therefore, at this time, the count value of the traverse pulse obtained by the traverse counter 19 for each rotation cycle corresponds to the disk eccentricity. Therefore, the system controller 10 can obtain the eccentricity of the disk by performing the following calculation.

FIG. 5 shows a change in the amount of eccentricity of the disk D detected corresponding to one rotation cycle of the disk D. The ordinate indicates the amount of eccentricity x, and the abscissa indicates the rotation angle of the disk D. Is shown. As the eccentric amount x to be calculated by the system controller 10, for example, if an absolute amount (range of PP (Peak to Peak) in FIG. 5) corresponding to one rotation of the disk D is obtained, the absolute value is obtained corresponding to one rotation of the disk D. Assuming that the count value of the obtained traverse pulse is N and the track pitch is Tp (see FIG. 4A), x = N × Tp / 2 (PP) (Equation 1). That is, the count value N is 1
Since the number of tracks to be traversed by the rotation is reciprocated, the actual number of traversed tracks according to the eccentricity x is calculated by the count value N / 2. Then, the count value N /
By multiplying 2 by the track pitch tp, eccentricity information can be physically obtained. If the amount of eccentricity x as the amount of deviation based on the 0 level is obtained, it can be obtained by the following equation: x = N × Tp / 4 (0−P) (2) When calculating the amount of eccentricity x, either (Equation 1) or (Equation 2) may be used.

Further, in order to detect the sensitivity of the midpoint error signal as the first example, together with the information of the eccentricity x,
For example, information on the amplitude level of the midpoint error signal described below is required. Here, a midpoint error signal for one rotation cycle of the disk is obtained under the condition that the focus servo control and the tracking servo control by the closed loop are performed on the loaded disk. At this time, the optical pickup 3 is fixed without being moved by the sled mechanism 8. FIG. 6 conceptually shows the midpoint error signal obtained as described above. In this case, information of the peak-to-peak (pp) level of the amplitude of the midpoint error signal obtained within one rotation cycle of the disk is obtained. That is, it is the level of the amplitude Vp-p shown in FIG.

The midpoint error signal shown in FIG. 6 is obtained by the objective lens 2 moving in the tracking direction in response to the objective lens 2 tracing a track on the disk. At this time, the objective lens 2 traces the track on the disk following the eccentricity of the disk. Therefore, the amplitude Vp-p indicating the maximum displacement of the objective lens 2 in one rotation cycle of the disk directly corresponds to the eccentricity of the disk.

In the present embodiment, the sensitivity Ers of the middle-point error signal is obtained by using the eccentricity x and the amplitude Vp-p of the middle-point error signal. Ers = Vp-p / x [V / Μm] (Equation 3). That is, as the sensitivity Ers of the middle point error signal, the unit movement amount (1 μm) of the objective lens is used.
m) to obtain the variation of the midpoint error signal level.

In the present embodiment, for example, the value as the sensitivity Ers of the midpoint error signal is stored in, for example, the RAM 10a in the system controller 10. Then, when various control processes are executed based on the midpoint error signal as described later, for example, the level of the actually obtained midpoint error signal is set to V, and Ers × V [μm]. By performing the calculation of Expression 4), it is possible to know the movement amount (movement distance) of the objective lens 2 from the actual neutral position (reference position), and to calculate the movement amount of the objective lens 2 obtained in this manner. The control processing is executed based on the control processing. As a result, for example, a more accurate and better control result can be obtained than when the control process is executed based on a midpoint error signal whose sensitivity is not detected.

Further, for example, as previously proposed by the present applicant, based on the detected eccentricity of the disk, the disk rotation driving speed is set to such an extent that inadvertent vibration does not occur. In such a case, the disk driver has a function of detecting eccentricity of the disk in advance. Therefore, when the function of detecting the sensitivity Ers of the midpoint error signal is applied to a disk driver having the above-described disk eccentricity detection function as in the first example, this eccentricity detection function is used. You only have to share.

FIGS. 7 and 8 are flowcharts showing processing operations for actually detecting the sensitivity of the midpoint error signal by the above-described method by the disk driver of the present embodiment. The processing shown in these figures is executed by the system controller 10.

In detecting the sensitivity of the middle point error signal, first, the amount of eccentricity x is detected by the processing of step S101 in FIG. The process for detecting the amount of eccentricity x in step S101 is as shown in FIG. That is, in step S201, the loaded disk D is driven to rotate at a predetermined speed, and in step S202, control processing for turning on the focus servo loop is executed. As a result, a state in which the objective lens 2 is focused on the signal surface of the disk D is obtained.

In the following step S203, a traverse pulse during which the M wave is detected as the FG pulse of the spindle FG 6a is counted to detect a count value N. In this case, the number M of FG pulses is set to, for example, 12 waves in one rotation and to, for example, four waves in 1/3 rotation.
When eccentricity is detected by three rotations, it is only necessary to count how many traverse pulses are detected while four FG pulses are detected.

In FIGS. 2 and 3 described above, an example of calculating the eccentric amount in one rotation has been described.
The count value N obtained when the disk D is rotated in an angle range smaller than ° can also be calculated by correcting the count value N obtained when the disk D is rotated once, for example. Therefore, the amount of eccentricity x can be calculated almost accurately by the count value N obtained during 1/3 rotation. Thereby, the time for detecting the amount of eccentricity x can be reduced. When the count value N in the M wave period is detected as described above, in step S204, the eccentricity x is calculated using the count value N by applying, for example, the above-described (Equation 1) and (Equation 2). calculate. Upon completion of the process in the step S204, the process shifts to a step S102 in FIG.

At the stage after step S101, the focus servo loop is turned on, but the tracking servo control is not executed.
Therefore, in step S102, the tracking servo loop is turned on to obtain an on-track state, and the process proceeds to step S103.

In step S103, the amplitude Vpp of the midpoint error signal described above with reference to FIG. 6 is obtained. This processing is performed, for example, by the system controller 1
0 takes in the midpoint error signal Cen in the disk rotation cycle from the servo processor 14 and performs peak hold or the like on each of the plus side and the minus side of the midpoint error signal. What is necessary is just to obtain the maximum value.

In the following step S104,
Based on the eccentricity x obtained by the above processing and the amplitude Vp-p of the midpoint error signal, the sensitivity Ers of the midpoint error signal is obtained by executing the arithmetic processing shown in (Equation 3) first.
Get. Then, in step S105, the information on the sensitivity Ers of the middle point error signal is written and held in a predetermined area of the RAM 10a, and thereafter, in step S106, a process for a required end is executed, and the process exits this routine.

As the end processing, for example, if a recording or reproducing operation is performed after the processing shown in this figure, a control processing for starting recording / reproducing is executed. If so, a control process or the like for stopping the disk drive is executed.

In the above processing operation, the detection of the amplitude of the middle-point error signal is performed following the detection of the eccentricity x. For example, the detection of the amplitude Vp-p of the middle-point error signal is performed. After that, the eccentricity x may be detected. Further, the detection of the amount of eccentricity x and the detection of the amplitude Vp-p of the midpoint error signal may not be performed continuously, but may be performed at different times.

4. Detection of Sensitivity of Mid-Point Error Signal (Second Example) Subsequently, detection of sensitivity of a mid-point error signal as a second example will be described. As a second example, the sensitivity Ers of the midpoint error signal is obtained by executing the processing operation as shown in the flowchart of FIG. 9 without using the information of the eccentric amount as in the first example. Note that the processing shown in this figure is also executed by the system controller 10.

In the process shown in FIG.
At 301, the loaded disk is driven to rotate,
In a succeeding step S302, the focus servo loop is turned on. At this stage, it is assumed that the state in which the objective lens 2 is instructed at the neutral position in the tracking direction has been obtained. Then, in the following step S303, the object lens 2 is kept in a state where the position of the optical pickup 1 is fixed without moving the sled.
Forcibly starts moving from the neutral position to either the outer circumferential direction or the inner circumferential direction of the disk. It is assumed that the movement of the objective lens 2 is executed for a certain predetermined time T. This control process is realized by causing the servo processor 14 to output a tracking drive signal TDR at a predetermined level for forcibly moving the objective lens 2 in a required tracking direction.

During the period in which the objective lens 2 is being moved by the processing of step S303, the traverse counter 19 counts the number of traverse pulses (ie, the number of traversing tracks) by the subsequent processing of steps S304 and S305. The level of the midpoint error signal obtained by the servo processor 14 is monitored.

In the following step S306, the process waits for the predetermined time T to elapse, and proceeds to step S307. In step S307, the control for forcibly moving the objective lens 2 is terminated.
By the processing of the subsequent step S308, the counting operation of the traverse pulse and the monitoring of the midpoint error signal level so far are terminated.

Then, in a succeeding step S309,
During the period in which the objective lens 2 is forcibly moved, the traverse pulse count value N counted by the traverse counter 19 is fetched. In the following step S310, similarly, a change amount ΔV of the level of the midpoint error signal during the period (predetermined time T) during which the objective lens 2 is forcibly moved is obtained.

In the next step S311, based on the traverse pulse count value N, an arithmetic process for obtaining the physical lens movement amount L during the period in which the objective lens 2 is forcibly moved is performed. Execute. This arithmetic processing is performed by setting the track pitch of the disk D to Tp [μ
m] is obtained by an operation represented by L = N × Tp [μm] (Equation 5).

Here, the lens movement amount L and the change amount ΔV of the midpoint error signal obtained earlier are values obtained during the period during which the objective lens 2 was forcibly moved. It is. Therefore, the change amount ΔV of the middle point error signal corresponds to the lens movement amount L. Then, in step S312 following step S311, the sensitivity of the midpoint error signal (per unit movement amount (1 μm) of the objective lens) is obtained by the calculation of Ers = ΔV / L [V / μm] (Equation 6) (A variation amount of the midpoint error signal level). In this case as well, the information of the sensitivity Ers of the midpoint error signal is written and held in a predetermined area of the RAM 10a in the following step S313, and thereafter, a necessary process is executed in step S314 to execute this routine. Exit.

5. Example of control processing using middle point error signal 5-1. Mid-point Servo As described above, after detecting the sensitivity of the mid-point error signal, and executing a predetermined control process based on the mid-point error signal, the above-described equation (4) is used. As described above, it is possible to obtain an accurate and good control result by using the above. Here, in the disk drive of the present embodiment, the detected midpoint error signal An example of a control process that is effective as a control process using sensitivity will be described with some examples.

One of the control processes based on the midpoint error signal is a so-called midpoint servo. The midpoint servo means, for example, when the optical pickup is slid by the sled mechanism 8 during a seek operation,
Is to perform control for defining its position so that it does not inadvertently oscillate in the tracking direction. The position of the objective lens 2 at the time of seeking is required to be at a neutral position in consideration of, for example, an appropriate data reading operation after seeking. Therefore, the position state of the objective lens 2 in the tracking direction during the seek is monitored by the middle point error signal Cen, and based on the middle point error signal Cen,
It controls the tracking driver so that the objective lens 20 is defined at the neutral position.

At this time, as in the present embodiment, the reliability of the middle point servo can be improved by utilizing the sensitivity of the detected middle point error signal, and in particular, the movement of the optical pickup 1 by the sled mechanism. When the speed becomes high and excessive acceleration is applied to the objective lens 2,
It turns out to be effective.

5-2. Thread Servo Another example is a thread servo. As tracking control, for example, as is well known, the objective lens 2 is moved in the disk radial direction by a biaxial mechanism to trace a track in a state where the optical pickup 1 is not moving. The tracking is performed continuously by moving the mechanism. This is a thread servo. Here, when making a determination for moving the sled mechanism, it may be detected that the amount of deviation of the objective lens 2 has become equal to or greater than a predetermined value based on the midpoint error signal. At this time, the thread servo can be performed more accurately by utilizing the sensitivity of the detected midpoint error signal.

5-3. Object Disk Abnormality Monitoring In the disk drive device, a servo error may occur because the objective lens 3 cannot return from a state where the objective lens 3 has been moved to the limit in the tracking direction due to some factor such as disturbance. It can happen.
Therefore, in the disk drive device, for example, by monitoring a midpoint error signal, for example, there may be a case where control is performed so as to prevent the abnormal state as described above, or to return from the abnormal state to a normal state. For example, if there is no information on the actual amount of movement of the objective lens 2 corresponding to the midpoint error signal level, the possibility of an error state is high even if the midpoint error signal is monitored. Become. Therefore, as in the present embodiment, the sensitivity of the midpoint error signal is detected, and the relationship between the midpoint error signal level and the actual amount of movement of the objective lens 2 is grasped. It is possible to accurately grasp the undesired movement and appropriately execute the control corresponding to this. It should be noted that if there is another necessary control process based on the midpoint error signal, the control process can naturally be a control process using sensitivity information of the midpoint error signal.

6. Modified Example (Generation of Mid-Point Error Signal by Mid-Point Sensor) In the above description, a case where the mid-point error signal is obtained based on the RF signal has been described as an example. The signal can also be obtained by providing a midpoint sensor 20 in the optical pickup 3, as shown by the dashed block in FIG.

Although a specific illustration showing the structure of the midpoint sensor 20 is omitted, a thin plate attached so as to interlock with the movement of the objective lens 2 in the tracking direction is provided.
A light-emitting diode element provided at a neutral position of the objective lens 2 for emitting light to the thin plate; and a photodetector for receiving light of the light-emitting diode element divided by the thin plate as a boundary , And a differential amplifier for detecting a difference in the amount of divided light detected by the photodetector. In this case, since the difference in the amount of light of the divided light detected by the photodetector indicates the amount of displacement with respect to the neutral position of the objective lens 2, the output signal of the differential amplifier is used as the middle point error signal Cen. Become. As such a midpoint sensor 20, a sensor provided in an optical pickup of a disk drive device corresponding to, for example, an MO (magneto-optical disk) is generally well known.

In general, the mid-point error signal obtained by the mid-point sensor has a smaller variation in the modulation factor depending on the reflectivity of the disc than the mid-point error signal obtained based on the RF signal. There is a corresponding variation in the sensitivity of the midpoint error signal. Therefore, even when the midpoint error signal is detected by the midpoint sensor, the sensitivity of the midpoint error signal is detected as in the present embodiment, and for example, the various control processes described above are executed based on this information. This is effective in seeking stability and certainty of the control operation.

In the case of employing a configuration in which a midpoint error signal is detected by a midpoint sensor, the detection of the sensitivity of the midpoint error signal is performed in the same manner as described in the first and second examples. That is all we need to do.

Further, the C described in the above embodiment as an example
In addition to the D-ROM disk drive, for example, M
The present invention can be applied to disk drive devices such as D, MO, and DVD. Furthermore, in the present embodiment, only the case of reproduction has been described as an example, but the disc drive of the present invention is applied to a recording device, and the sensitivity of the detected midpoint error signal is used to perform recording. It can be configured to execute a required control process based on a required midpoint error signal.

[0074]

As described above, according to the present invention, as the sensitivity of the middle point error signal, the change amount of the middle point error signal corresponding to the unit movement amount of the objective lens is detected. The sensitivity of the point error signal is used when executing a required control process based on the midpoint error signal. Thereby, for example, since it is possible to accurately grasp the actual position of the objective lens corresponding to the level of the midpoint error signal, for example, so-called midpoint servo control,
A more accurate and stable control state can be obtained than when the thread servo control and the control processing such as the position monitoring of the objective lens are performed based only on the level information of the midpoint error signal. This has the effect of improving the performance.

In detecting the sensitivity of the midpoint error signal, the amount of eccentricity of the disk and the amount of change in the amplitude of the midpoint error signal corresponding to this amount of eccentricity (pp level corresponding to one rotation cycle of the disk) are determined. ) To calculate the change amount of the midpoint error signal corresponding to the unit movement amount of the objective lens.
Alternatively, based on the amount of movement of the objective lens obtained by the number of track traversals obtained while forcibly moving the objective lens and the amount of change in the amplitude of the middle point error signal, the midpoint of the objective lens per unit movement amount By adopting the configuration of calculating the amount of change in the error signal, the configuration can be realized by a relatively simple configuration and control processing operation without adding a special function circuit unit or the like. As a result, an increase in the circuit scale and an increase in cost are suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a disk drive device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a detection operation by a photodetector of the optical pickup. It is a figure explaining a detection method.

FIG. 3 is a diagram illustrating a method of detecting a midpoint error signal based on a tracking error signal.

FIG. 4 is a schematic diagram illustrating a traverse pulse.

FIG. 5 is a schematic diagram illustrating the amount of eccentricity per one rotation (360 °) of the disk.

FIG. 6 is a waveform diagram showing a midpoint error signal obtained in one rotation cycle of the disk.

FIG. 7 is a flowchart illustrating a process of detecting a middle-point error signal sensitivity as a first example.

FIG. 8 is a flowchart showing a process of detecting the amount of eccentricity of a disk.

FIG. 9 is a flowchart illustrating a process of detecting a middle-point error signal sensitivity as a first example.

[Explanation of symbols]

1. Optical pickup, 2. Objective lens, 3. Biaxial mechanism, 4. Laser diode, 5. Photodetector, 5.
a detector, 5b differential amplifier, 6 spindle motor, 6a spindle FG, 9 RF amplifier, 7 turntable, 8 thread mechanism, 10 system controller, 10a RAM, 11 binarization circuit, 12 decoder, 13 interface section, 14 servo Processor, 15 thread driver, 16 two-axis driver, 16a focus coil driver, 16b tracking coil driver, 17 spindle motor driver, 18 laser driver, 19 traverse counter, 20 middle point sensor, D disk

Claims (6)

[Claims] 1. A field of view in a neutral state in which a driving mechanism for drivingably supporting an objective lens along a tracking direction is not performed as a position state of an objective lens for irradiating a disk-shaped recording medium with laser light. A midpoint error signal output means for outputting a midpoint error signal indicating a shift of the visual field position with respect to the reference position in the tracking direction with the position as a reference position; Signal sensitivity detection means for detecting the amount of change in the point error signal; and control processing means for executing a required control process relating to recording or reproduction of the disk-shaped recording medium based on the midpoint error signal. Is a reference in the tracking direction of the objective lens corresponding to the level of the midpoint error signal based on the sensitivity of the midpoint error signal. A disk drive device which is configured to obtain a moving distance with respect to a quasi-position and execute the required control processing based on the information on the moving distance. 2. The signal sensitivity detecting means according to claim 1, wherein said signal sensitivity detecting means detects an eccentric amount of a disk-shaped recording medium loaded in said disk drive device; A midpoint error signal obtained corresponding to one rotation cycle of the disk-shaped recording medium under a state where the tracking servo control for controlling the position state of the objective lens in the tracking direction so as to trace the object is performed. And an eccentricity detected by the eccentricity detection means, and an amplitude change of the midpoint error signal detected by the midpoint error signal amplitude detection means. The amount of change of the midpoint error signal per unit movement amount of the objective lens is detected based on the amount. The disk drive device according to claim 1. 3. The signal sensitivity detecting means includes: an objective lens movement control means for forcibly moving an objective lens along a tracking direction; and an objective lens moved along the tracking direction by the objective lens movement control means. A track number detecting means for detecting the number of tracks formed on the disk-shaped recording medium traversed by the laser light, and an objective lens moving control means for moving the objective lens along the tracking direction. A midpoint error signal amplitude detecting means for detecting an amplitude change amount of the point error signal, wherein the movement amount of the objective lens determined in accordance with the number of tracks detected by the traversing track number detecting means; Based on the amplitude change amount of the midpoint error signal detected by the signal amplitude detection means, the unit of the objective lens is Disk drive according to claim 1, characterized in that it is configured to detect the amount of change in the midpoint error signal per amount of movement. 4. The control processing means is capable of executing, as the required control processing, a control processing for maintaining a visual field position of the objective lens in a tracking direction in a neutral state at a required opportunity. 2. The disk drive device according to claim 1, wherein: 5. The control processing means controls a position state of an objective lens in a tracking direction so that the laser light is traced on a track formed on a disk-shaped recording medium, as the required control processing. The transfer control for transferring the optical head including the objective lens itself in the tracking direction under a state in which the tracking servo control is being executed, can be executed. 2. The disk drive device according to 1. 6. The control processing means according to claim 1, wherein said required control processing includes:
The visual field position of the objective lens in the tracking direction is monitored, and when the monitored visual field position of the objective lens is determined as an abnormal operation, a control for a required normalization can be executed. 2. The disk drive device according to claim 1, wherein: