JP2738755B2 - Optical disk tracking method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a tracking method in a write-once or erasable optical disk memory device using both a pre-groove and a pre-wobbling mark.

[Prior art]

As described in Japanese Patent Application Laid-Open No. 59-38939, an optical disk tracking method using the composite track wobbling method combines a push-pull tracking system and a wobbling tracking system, and causes various factors (p. For example, it is an object to suppress track deviation due to disc tilt, deformation, eccentricity, optical / mechanical / electrical drift, and the like. It had a double feedback control system structure. As a solution to the problem that the sampling frequency of the wobbling tracking system of the prior art has a low value, a wobbling feedforward system is added to the double feedback control system as shown in Japanese Patent Application Laid-Open No. 62-145538. I was

[Problems to be solved by the invention]

In any of the above prior arts, a double feedback control system is fundamental, and a track shift suppression effect caused by a large gain change caused when a disk carrier whose reflectance or the like has significantly deteriorated is used. Of the disc, the tracking servo system becomes unstable, and the disc tilt angle differs between the inner and outer circumferences when using a disk carrier that has been irregularly deformed into a spherical shape. No consideration has been given to problems such as a difference in the amount, and there has been a problem that a track deviation more than expected occurs. SUMMARY OF THE INVENTION An object of the present invention is to provide a tracking method for an optical disk which can cope with a disk carrier whose reflectivity and the like has significantly deteriorated without impairing the frequency characteristics of a push-pull tracking system and has a small track offset. It is in. Another object of the present invention is to be able to cope with significant characteristic fluctuations in mechanical and optical systems, as well as disk carriers that have been irregularly deformed into a spherical shape without impairing the frequency characteristics of the push-pull tracking system, and Another object of the present invention is to provide an optical disk device having a small track offset.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides a method for detecting track deviation obtained from a wobbling mark for track deviation correction (the principle of detecting a track deviation accurately by using a wobbling mark is described in detail in JP-A-62-229534 and the like. When the laser beam passes through the center of the relative position between the wobbling pits 27-1 and 27-2 shown in FIG. Using the fact that the size becomes equal), the optimum track deviation correction value obtained in advance is stored, and a feedforward system using this stored correction value is added to the push-pull tracking system. It was done. In order to achieve the above and other objects, the present invention uses a track shift information obtained from a track shift correcting wobbling mark to calculate an optimum track shift correction value obtained in advance to determine a disk radial position and a disk rotation angle. This is stored as two-dimensional information as a parameter, and a feedforward system using this stored correction value is added to the push-pull tracking system. In addition, in order to cope with remarkable characteristic fluctuations in the mechanical system and the optical system, the optimal track shift correction is always performed by using the track shift information obtained from the track shift correcting wobbling mark using the idle time as the optical disc apparatus. The stored contents are updated by detecting the value, and a feed-forward system using the stored optimum correction value is added to the push-pull tracking system during operation.

[Action]

The feed-forward system using the stored correction value added to the push-pull tracking system is a control system completely independent of the push-pull system, and is affected by the largest fluctuation factor, the gain fluctuation of the push-pull system. Without compensating and automatically compensating for the characteristics of the tracking actuator and the reflectivity of the optical disc carrier,
It operates to correct the tracking offset. Thereby, only the push-pull tracking system or the tracking of the double feedback configuration to which the wobbling tracking system is added can cope with a large gain variation of the push-pull system and an occurrence of an extremely large offset factor which cannot be solved, and Since high-speed response can be maintained, the laser beam can always be guided to the center of the track.

【Example】

Before specifically describing some embodiments according to the present invention, the structure of an optical disk carrier used in the present invention and the overall system configuration will be described with reference to the drawings. FIG. 7 is a diagram showing a format structure of an optical disk. FIG. 7A is an overall view of the disk 6,
The figure shows a state in which the circumference of an inch disk is divided into several physical sectors. FIG. 2B shows the breakdown of the physical sector, and shows that the physical sector is divided into a preformatted ID information area and a user data area to be used later by the user. Fig.
(C) is a diagram specifically showing the head of the ID information area, and shows adjacent tracking guide grooves 7-1 and 7-.
The center of the land, that is, the center of the land, has a pair of wobbling pits 27-1 and 27-2 which are distributed up and down from the center of the track. Are formed. The tracking guide groove 7 is also formed continuously in the user data area. FIG. 8 is a conceptual diagram showing the overall configuration of the optical disk device according to the present invention. The entire optical system 73 is placed on the moving stage 70 and moved to the inner and outer circumferences of the optical disk 6 by a linear motor controlled by the linear motor controller 71, and the coordinates (radial position) thereof are detected by the scaler 72. The detected radial position is determined by the tracking servo circuit 74.
In addition, it is supplied to the optical disk control unit (ODU) 76. The optical disk 6 is a spindle motor controller
The rotation speed is controlled by the constant speed control 75, and the rotation angle information obtained by the spindle motor controller 75 is supplied to the tracking servo circuit 74. The optical disk control unit (ODU) 76 receives instructions from the host computer 77 via SCSI (small computer system bus), handles the progress of a specific sequence, and turns on and off various servo systems and reads. / Write control command, etc. Next, an embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, FIG. 3, and FIG. FIG. 1 is a functional block diagram of a tracking hobo circuit to which a prediction control system according to the present invention is added. The laser beam 2 output from the semiconductor laser 1 becomes parallel light by the lens 3, is deflected by the polarization beam splitter 8, passes through the half mirror 4, and is transmitted by the objective lens 5 to the optical disk 6.
Focus on the recording surface of. The laser beam reflected from the disk 6 passes through the objective lens 5 in reverse, and is
, A part of which is received by a photodetector 14 for detecting a push-pull tracking error, and most of the remaining light beam goes straight through a polarizing beam splitter 8, passes through a condenser lens 9 and a cylindrical lens 10, and passes through an analyzer. A photodetector 12 for detecting the polarization angle of the laser beam by the action of 11 and
Focus on 13 By calculating the difference CD between the output signals C and D of the photodetector 12 and the photodetector 13 by the subtraction circuit 19, a magneto-optical signal 30 can be obtained. Also a photo detector
The sum of the respective output signals of 12 and 13 is added to an adding circuit 20.
, An information signal indicating the intensity of the reflected laser beam from the disk 6 is obtained as a light / dark signal 31. The light / dark signal 31 is input to a mark detection pattern matching circuit 21, where the wobbling mark is recognized and, at the same time, the signal is digitized by the AD converter 22.
The original signal information of the wobbling track error is obtained by taking the differential between the crest value of the preceding pit portion and the crest value of the following pit portion of the wobbling mark portion included in Is stored in the input memory section of the memory 21. The stored data is subjected to operations such as noise removal and smoothing processing by the controller 25, and then stored in the output memory of the memory 23. The data in the output memory section is sequentially synchronized with the mark detection pulse 33 while synchronizing the data with the mark detection pulse 33. By outputting to the / A converter 24, an analogized prediction correction signal 32 is obtained. This prediction correction signal 32 is a push-pull tracking error signal 29 obtained by obtaining the difference between A and B of the photodetector 14 for detecting a push-pull tracking error by the subtractor 15.
Is used to offset-correct the signal, which has been phase-compensated by the phase compensation circuit 16, by the offset correction subtractor 17 .The output of the subtracter 17 drives the tracking actuator 26 via the power amplifier 18, and outputs the laser beam. Is performed. FIG. 2 shows a specific example of the microprocessor unit section 40 including the controller 25 shown in FIG. 1, and is configured using a single-chip microprocessor HD68P01V07 (manufactured by Hitachi). When a reset signal is input at the time of power-on or the like, the processor 25 is initialized to the single-chip mode state, and enters a state where it can operate using the 4 MHz crystal oscillator 37 as a clock. Under this condition, a data sample command is sent from the optical disk control unit (76 in FIG. 8) to the NMI of the processor.
(Non-Maskable Interrupt) When input to the terminal, it causes an unconditional interrupt. First, set the data so that the output of the D / A converter 24 for generating the prediction correction signal becomes 0V output, and set the mark detection pulse. It waits for 33 to enter the IRQ (interrupt request) terminal.
At this time, when a wobbling mark is detected by the mark detection pattern matching circuit 21, a mark detection pulse 33 is input, and the difference between the magnitudes of the reflected light amounts of the pair of wobbling pits temporarily stored, that is, the wobbling track error is detected. Calculate original signal information. The magnitude of each of the reflected light amounts of the pair of wobbling pits is
The signal is digitized by the A / D converter 22 at the timing of the AD timing pulse, reflected on the input ports P40 to P47 of the single-chip microprocessor 25, and temporarily stored in the working register of the processor. . In this manner, it is determined whether or not the original signal data of the wobbling track error for one round of the track, that is, the steady track offset information for one rotation of the disk has been collected. Upon completion, a noise removal operation, a data interpolation operation, a phase shift operation and the like are performed on the original signal data of the wobbling track error stored in the input memory area, and the result is output to the output memory area of the internal memory 23 of the processor. Store in Thereafter, the apparatus enters a state of waiting for the mark detection timing 33, and when a wobbling mark is detected and an IRQ interrupt occurs, the data in the output memory area is transferred to the output ports P30 to P3 for D / A converter input data.
7 and the interpolation data for smooth continuation within the sampling period of the wobbling track error is set to N.
Is output twice and waits for the detection pulse 32 of the next mark. Thereafter, by repeating this operation, the D / A converter 24 outputs the prediction correction signal 32 as continuous analog data, and operates to correct a steady offset component. FIG. 3 is a flow chart showing an initial setting operation when a disc is mounted in the present embodiment. First, the disk 6 is mounted on the apparatus, and the spindle motor is rotated by the spindle motor controller 75 at a predetermined rotation speed to focus the laser beam (FIG. 50). Next, the push-pull servo system is turned on and a temporary tracking state is set (-51 in FIG. 31). Next, as shown in FIG. 52, a data sample command (see FIG. 2) is issued, and a prediction correction sequence is executed. This prediction correction sequence is basically based on the operation described in the description of FIG. 1 and FIG. 2, but FIG. 4 shows the flow as a flowchart and will be described below. First, in the tracking state using only push-pull tracking, the tracking deviation amount for one round of the track is measured using the wobbling mark 27 and stored in the input memory unit (FIG. 53). Next, the track shift amount stored in the input memory (in this embodiment, 17 tracks per track rotation).
Since a disk having a pair of wobbling marks 27 was used, the track shift amount for 17 samples is stored. ), A noise removal operation, a data interpolation operation (smoothing), a phase shift operation, and the like are performed, and the results are stored in the output memory unit (FIG. 54). afterwards,
The contents of the output memory section are sequentially output to the DA converter 24 (in the present embodiment, the result of the smoothing processing is 136 data per track rotation), and a correction operation is performed for track deviation (see FIG. (Figure 55). While performing the prediction correction as described above, the track error component due to the detected wobbling mark is monitored, and it is determined whether the error value is equal to or less than a predetermined value or whether a loop described below has been executed a predetermined number of times. If so, the sequence escapes from this sequence (FIG. 56), and then the prediction correction operation is continued. When it is determined in the determination state (FIG. 56) that the track shift amount is larger than a predetermined value, the track shift amount for one round of the track stored simultaneously with the execution of the prediction correction operation (see FIG. 56). Using FIG. 57), the output memory data previously used for the correction operation is corrected, the result is re-stored in the output memory unit (FIG. 58), and the loop returns to the state of FIG. 55. Configure. According to the above embodiment, it is possible to easily correct the occurrence of track deviation due to inclination, deformation, eccentricity, and electrical / mechanical fluctuations at the time of mounting a disk, and to achieve frequency characteristics (response, Characteristic) can be realized. Another embodiment according to the present invention will be described with reference to FIG.
The circuit configuration is the same as that shown in the above embodiment (FIGS. 1 and 2), and FIG. 5 is a flowchart corresponding to FIG. 3 shown in the previous embodiment. The operation is the same up to the point where the disk 6 is set and the focus is set (FIG. 5-50), but the tracking is turned on after moving the optical head 73 to the innermost circumference of the disk 6 (FIG. 5-59). (Fig. 5-51), and then enters the prediction correction sequence (Fig. 5-5).
2). When the correction data for one track is completed, the optical head 73 is moved stepwise in the outer peripheral direction (FIG. 5-60), and the prediction correction sequence is executed again at the radial position to collect the correction data. Execute Thereafter, when it is determined that the optical head 73 has reached the outermost periphery (FIG. 5-61), the initial setting operation is terminated,
Subsequent prediction correction for the track deviation is performed according to the radial position where the optical head 73 is located and the rotation angle. According to the present embodiment, the occurrence of track deviation can be easily corrected even for the disk 6 which has been deformed in an arc shape and irregularly, and the frequency characteristics (response characteristics) at the time of a seek operation or the like can be improved. An excellent tracking method can be realized. Another embodiment according to the present invention will be described with reference to the flowchart of FIG. This embodiment is a development of the embodiment described with reference to FIG. 5, and the circuit configuration and control flow basically use the second embodiment. First, the disk / drive two-dimensional initialization operation described in FIG. 5 is executed (FIG. 6-62), and the two-dimensional correction data is stored in the output memory. Next, after completion of operations such as recording / reproducing and erasing (FIG. 6-63), 55 and later in the prediction correction sequence shown in FIG. 4 are executed again (FIG. 6-64),
The correction data at the current radial position of the optical head 73 is updated, and the next operation is waited for again. According to this embodiment, the occurrence of a track shift factor after the disc is mounted, for example, the occurrence of a track shift due to a large change in push-pull gain due to a change in groove shape due to recording or erasing and a change in ambient temperature, etc. Can be easily corrected, and a tracking method excellent in frequency characteristics (response characteristics) during a seek operation or the like can be realized. In the above-described embodiment, an addition (subtraction) method as shown in FIG. 1 is used as a means for performing prediction correction on push-pull tracking. However, the balance of the push-pull signal as shown in FIG. The same effect is obtained by adjusting. That is, the B-side output of the photodetector 14 for the push-pull signal and the DA converter for the correction value output (first
The output signal of FIG. 24) is multiplied by a multiplier 39, and the output of the multiplier 39 is multiplied by the A side output of the photodetector 14 to a subtractor 15.
By performing the difference calculation at, a push-pull tracking error signal 29 is obtained. Further, as a modification of the present invention, control is performed so that the track shift correction data is constantly updated even during the recording / reproducing and erasing operations (for example, in the flowchart of FIG. Program and
By unconditionally entering the 57 states), it is possible to configure a double closed loop tracking system to which a kind of software servo is added, and it is also possible to use these as needed. . Further, by using a disk having the structure shown in FIG. 7, that is, an optical disk having a composite track wobbling structure having a plurality of pairs of wobbling pits around one track, there is no prediction correction circuit (such as 40 in FIG. 1). Also in the optical disk device, the size of the pair of wobbling pits described above can be known by means such as waveform observation (for example, the location of the light / dark information 31 in FIG. 1), so that the current state of the track deviation can be known. Not only is it effective when adjusting the system and the like, but it can also be used as a material for determining whether or not operations such as recording, reproduction, and erasure can be reliably performed.

【The invention's effect】

According to the present invention, the track offset generated in the push-pull servo system can be reliably predicted and corrected using the track shift amount obtained from the wobbling mark stored in advance, so that the response characteristic and the track tracking accuracy are excellent. Tracking servo system can be realized.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an embodiment of the present invention.
FIG. 3 is a block diagram of the microprocessor section 40, FIG. 3 is a flowchart showing one embodiment of the present invention, FIG. 4 is a flowchart of a prediction correction sequence, and FIG. 5 shows another embodiment of the present invention. FIG. 6 is a flowchart showing an embodiment of the present invention, FIG. 7 is a structural diagram of an optical disk carrier used in the present invention, FIG. 8 is a conceptual diagram of the overall configuration of an optical disk device according to the present invention, and FIG. FIG. 9 is a circuit diagram showing another method of adding a prediction correction system. DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Laser beam, 6 ... Optical disk, 7 ... Groove, 12, 13, 14 ... Photodetector, 15 ... Subtractor for push-pull, 17 ... Subtractor for offset correction, 20 ... Bright / dark signal Adder for detection, 21 ... Wobble pit pattern detector, 22 ... AD converter, 23 ... Memory, 24 ... DA converter, 25 ... Single chip computer, 26 ... Tracking coil, 27 ... Wobbling pit, 28 ... Predata pit, 31: Light / dark signal, 32: Prediction correction signal, 40: Microprocessor.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-145538 (JP, A) JP-A-63-271734 (JP, A) JP-A-61-260432 (JP, A) JP-A-61-260432 57084 (JP, A) JP-A-59-38939 (JP, A) JP-A-61-177690 (JP, A) JP-A-62-229534 (JP, A)

Claims (2)

(57) [Claims] A laser beam is applied to a predetermined track position of an optical disk using an optical disk having a groove for tracking guide and a wobbling mark for correcting track deviation which is discretely arranged along the groove. Therefore, when tracking is performed using a push-pull tracking control system using diffracted light from the groove, a correction value is stored in advance using track deviation information obtained from the wobbling mark, and Performing a prediction correction of a track deviation with respect to the tracking control system based on the correction value, and generating a correction value for the optical disk even after performing recording, reproduction or erasing of the optical disk, and updating the recorded correction value. A tracking method for an optical disk, comprising: 2. The method according to claim 1, wherein the correction value is stored as two-dimensional information using the rotation angle and the radius dimension of the optical disc as parameters, and the two-dimensional information corresponding to the radial position and the rotation angle of the optical disc irradiated by the laser beam. 2. The tracking method for an optical disc according to claim 1, wherein the tracking control system performs a prediction correction of a track deviation using the stored correction value.