Method for track seeking of a reading head in an optic disk drive

The present invention relates to a method for track seeking of a reading head in an optic disk drive, and especially to a learning track seeking method by which variations of an optic disk drive due to mechanical friction or torque variation of motor can be overcome so as to achieve the same accuracy as that of rough seek with a speed sensor.

In the track seeking of an optic disk drive, a laser beam passes through an objective lens to find the track in an optic disk and an optic head serves to track the objective lens.

When any track in the optic disk drive is desired to be tracked, in general, two actions can be performed. (1) An optic head is moved at first to be proximate to the objective track. (2) The objective lens is fine adjusted so that the laser beam attains the objective track. The first action (1) is call as “rough seek”, and the second action (2) is called as “fine seek”.

In order to achieve the accuracy in the rough seek, a speed sensor is added and a feedback control is used. Since the speed sensor is expensive, it is not suitable in practical.

Further, referring to FIG. 1, a prior art optic disk drive 1 is illustrated. A motor 12 serves to drive a reading head 14 through a gear set of a guide screw rod 13 . In seeking, a microprocessor (not shown) sends a control voltage waveform (as shown in FIG. 2) to drive the optic reading head 14 to accelerate to an fixing speed section from a still condition and then decelerate to a still condition.

The designer may determine the number of tracks (acceleration track) for switching to a max speed and then the head move in a fixed speed. In general, the acceleration track makes no problem (for example, increasing seeking time). However, it is difficult to find the number of deceleration track for the head to decelerate and to move along the track as a control voltage is over.

Means with a small friction or a motor with a larger torque will introduce an over rough seek, while means with a large friction or a motor with a small torque will introduce an insufficient rough seek.

Therefore, there is an eager demand for a method for track seeking of a reading head in an optic disk drive, by which the variation of an optic disk drive due to mechanical friction or torque. variation of motor can be overcome so as to achieve the same accuracy.

Accordingly, the primary object of the present invention is to provide a method for track seeking of a reading head in an optic disk drive, wherein in seeking a track in a disk, the track number and the direction in the fine seek are used for adjusting a voltage waveform in the rough seek. If the direction of fine seek is identical to that in the rough seek, and the number of tracks in fine seek is over a fine seek tolerance, then the number of deceleration tracks is subtracted by a learning gap, i.e., an adaptive number of tracks. If the direction of fine seek is reverse to that of the rough seek, and the number of tracks in fine seek is over a fine seek tolerance, then the number of deceleration tracks is added with a learning gap.

Another object of the present invention is to provide a method for track seeking of a reading head in an optic disk drive, wherein the acceleration track and max speed can be set as learning parameters to optimize.

A further object of the present invention is to provide a method for track seeking of a reading head in an optic disk drive, wherein since no speed sensor is required to be installed on the track seeking means, the cost in manufacturing is reduced greatly.

The various objects and advantages of the present invention will be more readily understood from the following detailed description when reading in conjunction with the appended drawing.

FIG. 1 shows the structure of a prior art optic disk drive.

FIG. 2 shows the waveform for the control voltage of the rough seek.

FIG. 3 shows the flow diagram that the track number and the direction in the fine seek.

The present invention relates to a method for track seeking of a reading head in an optic disk drive, wherein when seeking a track in a disk, the track number and direction in the fine seek are determined for adjusting the voltage waveform in the rough seek, as shown in FIG. 3 .

Referring to FIG. 3, the method for track seeking of a reading head in an optic disk drive comprises the steps of firstly moving the optic head approximately to a target track (step 31 ); then count the track number in the fine seek (Step 32 ), determining whether the number of tracks traversed in the fine seek is over the fine seek tolerance (Step 33 ).

If the direction in fine seek is identical to that in the rough seek, then the number of deceleration tracks will be subtracted by a learning gap (step 35 ). The learning gap is a variable number of disk tracks used to adjust the number of tracks over which the deceleration of the rough seek occurs. It is adjusted continually over a number of seeks until the number of tracks traversed by the read head during the fine seek is within a fine seek tolerance.

If the direction in fine seek is reversed to that in the rough seek, then the number of deceleration tracks will be added by a learning gap (step 36 ).

Therefore, as the read head seeks the track in a disk, the system learns repeatedly until the number of fine seek is within the fine seek tolerance. If temperature is changed so that the number of fine seek is over the fine seek tolerance, the learning action is repeated in the seeking.

In fact, the acceleration track and max speed can be set as learning parameters for optimization.

In summary, the method for track seeking of a reading head in an optic disk drive of the-present invention has the following advantages.

(1) The variation of an optic disk drive due to friction or twisting of motor can be overcome so as to achieve the same accuracy as being installed with a speed sensor.

(2) Since no speed sensor is required to be installed on the track seeking means, the cost in manufacturing is reduced greatly.

Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.