JP2748561B2 - Seek stroke correction method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting a seek stroke in an access to an optical disc by moving a light beam for recording and reproducing information on the optical disc to an arbitrary information track on the optical disc. About.

[Conventional technology]

In an optical disk device, when a light beam is moved to an arbitrary information track on which information is recorded and reproduced, generally, a coarse seek operation for moving the light beam to a position near a target track is performed, and then an address is read from the disk to read light. The access is completed by three operations of performing a precision seek operation for accurately positioning the beam on the target track, and finally performing a disk rotation waiting operation to a recording / reproducing position on the information track.

As a technique for realizing high-speed access to optical discs,
Reading the track address where the light beam is located from the optical disc, calculating the relative number of tracks to the target track, setting the seek stroke, detecting the crossing of the light beam during the access operation, and counting the number of track crossings. Japanese Patent Application Laid-Open No. Sho 61-177640 discloses a method of calculating the amount of movement of a light beam during a seek operation, simultaneously detecting the relative speed between the light beam and the optical disk, and directly moving the light beam to a target track by speed control. Track address device ".

In the above-mentioned access method, a track crossing pulse corresponding to the track traversal of the light beam is utilized by utilizing the fact that the tracking position error signal optically detected when the light beam traverses the track on the optical disk changes periodically. Is generated, and the amount of relative movement between the light beam and the track of the optical disk is detected by counting the track crossing pulse. As the seek stroke in the access operation, the target seek stroke obtained as the difference between the track addresses of the current track and the target track where the light beam is located immediately before the seek operation is used as it is. As described above, the use of the access device disclosed in the above publication enables a high-speed access operation in which the light beam is directly moved to an arbitrary target track for recording and reproduction.

Further, as another conventional technique for performing a coarse seek while detecting the movement amount of a light beam using a tracking position error signal detected from a disk, a device employing a separate type optical head is disclosed in Nikkei Electronics 1988.4.18 No. .445 P.2
11-P.224 It is disclosed in the article of "5.25-inch magneto-optical disk drive, average access time less than 50 ms". Since the configuration of the optical system is a separate type optical head, the configuration of the access means and the control method of the optical head are different.However, the point that the moving amount of the light beam is detected by detecting the crossing of the track is described above. It is equivalent to the prior art.

[Problems to be solved by the invention]

If the light beam for recording and reproducing information passes through a preformat area for adding scratches on the disk, defects on the recording medium, address information, etc. to the information track during the coarse seek operation, the reflected light of the light beam will be disturbed. Is done.
This causes the optically detected tracking position error signal to be disturbed, causing an error in the detection of the track crossing from the tracking position error signal, and the number of track crossing pulses generated for the actual track crossing is excessively or too small. Becomes

In the prior art, since the movement amount of the light beam is detected by counting the number of track crossing pulses, if the number of track crossing pulses does not match the number of track crossings of the light beam, the light beam moves away from the target track at the end of the seek operation. Is positioned on the track.

As described above, in the related art, if a track count error occurs during a seek operation due to disturbance of the tracking position error signal, a track seek error occurs at the end of the seek operation. In addition, there is a problem to be solved in that an accurate seek operation is required, and the time required for the access operation of the optical disk is lengthened.

An object of the present invention is to provide a seek stroke correction method that solves such a problem.

[Means for solving the problem]

According to the present invention, when performing a seek operation for moving a light beam to an arbitrary target track on an optical disc, a target seek stroke is calculated based on a difference between a start track address read from the optical disc before the start of a seek and an arbitrary target track address. A seek stroke correction method for correcting the target seek stroke and setting a corrected seek stroke in the access control means, wherein a light beam is obtained from a start track address and an end track address detected from an optical disk before and after a seek operation. Calculates the movement seek stroke actually moved, calculates the track seek error from the corrected seek stroke and the movement stroke set in the access control means, and calculates the average value of the track seek error with respect to the target seek stroke to calculate the average seek error. Then, the average seek error is stored in a seek error table, and at the start of a seek operation, an average seek error corresponding to a target seek stroke is taken out of the seek error table, and a value obtained by subtracting the average seek error from the target seek stroke is corrected. It is characterized by a seek stroke.

[Action]

According to the present invention, in the coarse seek operation of the track access, a track seek error is calculated in an operation state of the apparatus by obtaining a difference between a seek stroke set in the access unit and a movement stroke of the light beam actually moved at the end of the seek operation. . At this time, the target seek stroke from the track where the light beam is located to the target track immediately before the seek is collectively treated as one block in units of 1024 tracks, for example, and the average track seek error for each block is calculated and stored in the seek error table. Let it. As a result, the average track seek error of the optical disk in use for each block of the target seek stroke is stored in the seek error table.

At the time of executing the coarse seek operation, the average seek error of the block corresponding to the target seek stroke is read from the seek error table, and a value obtained by subtracting the average seek error from the target seek stroke is set as a correction seek stroke in the access means. Let it be a seek stroke.

By the above operation in the present invention, the information track where the light beam is located at the end of the coarse seek can be substantially on the target track, and the track seek error at this time is approximately 1 / (variation of the track seek error).
2 can be reduced.

The track seek error has a large effect on the optical characteristics of each disk.However, the average value of the seek error is calculated in the operating state of the disk drive. The optimum value is always stored in the seek error table even when the optical disk is changed.

As described above, it is possible to reduce the track seek error requiring the precise seek by using the seek stroke correction method of the present invention, and to shorten the access time.

〔Example〕

FIG. 1 is a block diagram of an optical disk apparatus for implementing a seek stroke correction method according to the present invention.

According to an embodiment of the present invention, as an initial state, the seek error table 5 is set to 0 or a typical average track seek error value by an initialization signal 36 output from the controller 30.

When the optical disk device is in operation, the reproduction signal 20 detected by the optical head 43 is input to the address recognizing means 1, and the track address 21 of the information track on which the light beam 41 is located on the optical disk 40 is output. At the start of the coarse seek operation, the controller 30 generates a latch signal 31 for the start address register 2, and the start address 22 is output from the start address register 2. The stroke calculation means 3 outputs the absolute value of the difference between the target address 23 and the target address 22 output from the controller as a target seek stroke 24, and simultaneously determines the magnitude relationship between the start address 22 and the target address 23 to determine the seek direction. Outputs 37.

The target seek stroke 24 is input to the table control means 4, reads out the average seek error value corresponding to the target seek stroke 24 from the seek error table 5, and outputs it as a correction value 25. The subtraction means 6 outputs the difference between the target seek stroke 24 and the correction value 25, the output of the subtraction means 6 is latched by the stroke register 7 by the latch signal 32 from the controller 30, and the access control means is used as the correction seek stroke 26. Set to 45.

The average seek error stored in the seek table 5 is stored together with the target seek stroke 24 in units of, for example, 1024 tracks. That is, in this example, the first element of the seek error table 5 stores the average value of the track seek error for the target seek stroke 24 having a stroke of 0 to 1023 tracks, and the second element stores the average of the track seek errors of 1024 to 2047 tracks. Goal seek stroke of 24
Are stored in the seek error table 5 in the same manner up to the element corresponding to the maximum value of the target track stroke 24. Here, when the average value of the track seek error is stored in the seek error table 5 in units of 2 ⁿ of the target seek stroke, the element number corresponding to the target track stroke 24 in the seek error table 5 is set to n. Since it is obtained by bit shifting, the table control means 4 can be simply realized.

The access control means 45 controls the tracking servo system 44 based on the control signal 33 from the controller 30 to move the light beam 41 in the inner and outer circumferences of the optical disc 40 by the correction seek stroke 26 in the seek direction 37. Here, as described in the section of the prior art, the access method and the control method of the optical head depend on the configuration of the optical head and the like, and these are not the subjects of the seek stroke correction method according to the present invention. As the control means 45 uses a control method equivalent to that of the conventional technique, refer to the above-mentioned reference.

The end of the coarse seek operation is notified to the controller 30 by an end signal 38 output from the access control means 45.
The end address 27 is output after the track address 21 recognized by the address recognition means 1 is latched by the end address register 8 by the latch signal 34 output from the controller 30 similarly to the start address 22.

The stroke calculation means 9 calculates the absolute value of the difference between the start address 22 and the end address 27 before and after the coarse seek, and outputs a movement stroke 28 in which the light beam 41 has actually moved with respect to the optical disc 40.

The subtraction means 10 calculates the difference between the correction stroke 26 and the movement stroke 28 actually set in the access control means 45,
Outputs track seek error 29.

The average value calculating means 11 newly calculates the average track seek error 12 from the correction value 25 which is the average value of the track seek errors up to the present and the calculated track seek error 29. The average track seek error 12 is input to the table control means 4 and a storage control signal 35
Thus, the element of the seek error table 5 corresponding to the target seek stroke 24 is rewritten to the newly calculated average track seek error 12.

The calculation method of the average track seek error 12 is A,
Assuming that B is a constant coefficient, Y = (average seek error 12) X = (correction value 25) U = (track seek error 29) By appropriately determining the values of A and B, Y = A × X + B × U .. (1) can be calculated. Coefficients A and B in equation (1)
Can be determined by a method equivalent to the design of a low-pass filter in a discrete value system.

By repeating the above-described operation every time coarse seek is performed, the values of the respective elements of the seek error table 5 converge to the average value of the track seek error for the target seek stroke 24 on the optical disc 40 in use, and this value is corrected. As the value 25, the correction of the target seek stroke 24 can be realized.

Next, the effectiveness of the seek stroke correction method according to the present invention will be described. The tracking position error signal when the light beam 41 passes over the information track during the seek operation is set to the second position.
Shown in the figure. As a method for optically detecting the track position error signal 46 of the light beam 41, a push-pull method or the like is generally well known. As shown in FIG. 2A, the light beam 41 is detected as a periodically changing signal as shown in FIG. Means for generating a track crossing pulse of the light beam 41 from the tracking position error signal 46 includes, for example, a third
Track crossing pulse 47 using a comparator 48 as shown
Can be considered, and a track crossing pulse 47 as shown in FIG. 2C can be generated.

Here, a case where the light beam 41 during the seek operation passes through the preformat area of the optical disc 40 is considered. In a normal optical disk 40, address information and the like are recorded in a preformat area 49 on the information track 42 in the form of projections and depressions at the stage of manufacturing the optical disk 40 as shown in FIG. As shown in FIG. 5, when the light beam 41 passes through the preformat area 49, the tracking position error signal 46 is disturbed as shown in FIG. For this,
As shown in FIG. 5C, an erroneous detection occurs in the track crossing pulse 47.

In such a case, in the conventional seek stroke generation method shown in FIG. 6 (the same elements as those in FIG. 1 are denoted by the same reference numerals), the start address 22 at which the current light beam 41 is located is simply referred to as the start address 22. Since the target seek stroke 24 obtained as the absolute value of the difference between the target track addresses 23 is set in the access control means 45, an error in the generation of the track crossing pulse 47 as shown in FIG. As shown in a), the average track seek error for the target seek stroke 24 is shown by a curve 50, and the upper and lower limits of the variation of the track seek error produce track seek errors as shown by broken lines 51 and 52, respectively. .

On the other hand, according to the track seek correction method of the present invention, the coarse seek operation is performed by the correction seek stroke 26 obtained by correcting the target seek stroke 24 shown in FIG. 7A by the correction value 25 corresponding to the average value of the track seek error. Is performed, the track seek error 29 with respect to the target seek stroke 24 after execution of the coarse seek is reduced to about 1/2 of the variation of the track seek error indicated by broken lines 53 and 54, as shown in FIG. 7B. This makes it possible to shorten the precision access time executed by a track jump or the like after executing the coarse seek, thereby realizing high-speed access.

〔The invention's effect〕

As described above, by using the seek stroke correction method according to the present invention, the average value of the track seek error at the end of the coarse seek due to the influence of the scratches on the disk, the preformat area, and the like is set to 0, and precise access is required. The value of the track seek error is roughly 1 /
Can be reduced to about 2.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an optical disk apparatus for implementing a seek stroke correction method of the present invention, FIG. 2 is a diagram showing a relationship between a track position error signal of a light beam and a track crossing pulse, and FIG. FIG. 4 is a view showing an example of a pulse detection method, FIG. 4 is a view for explaining the state of a preformat area on an optical disk, and FIG. FIG. 6 is a diagram for explaining the effect, FIG. 6 is a diagram for explaining the prior art, and FIG. 7 is a diagram for explaining a track seek error when a coarse seek is executed. 2 ... Start address register 3,9 ... Stroke calculation means 5 ... Seek error table 8 ... End address register 11 ... Average value calculation means 12 ... Average track seek error 22 ... Start track address 23 ... Target Track address 24 …… Target seek stroke 25 …… Correction value 26 …… Corrected seek stroke 28 …… Movement stroke 29 …… Track seek error

Claims (1)

(57) [Claims] When performing a seek operation for moving a light beam to an arbitrary target track on an optical disk, a target seek is performed based on a difference between a start track address read from the optical disk before the start of a seek and an arbitrary target track address. A seek stroke correction method that calculates a stroke, corrects the target seek stroke, and sets a corrected seek stroke in the access control means. The seek stroke correction method comprises the steps of: detecting a start track address and an end track address detected from an optical disk before and after a seek operation; Calculate a movement stroke of the beam actually moved, calculate a track seek error from the corrected seek stroke and the movement stroke set in the access control means, and calculate an average value of the track seek error with respect to the target seek stroke to obtain an average seek error. The average seek error is stored in a seek error table, the average seek error corresponding to the target seek stroke is taken out of the seek error table at the start of the seek operation, and the average seek error is subtracted from the target seek stroke. Is a correction seek stroke.