Patent Application
20080151709
1. Field of the Invention
The present invention generally relates to servo methods for optical disk drives, and more particularly to a seeking method for seeking a target track area of an optical disk and an optical disk drive adopting the seeking method.
2. Description of Related Art
Generally, an optical disk includes a plurality of concentric tracks or a continuous spiral track on a recording surface thereof. Data recorded on the optical disk are reproduced by first projecting light beams onto the tracks, and then detecting reflected light beams from the tracks to obtain an analog signal. An optical disk drive is such a device to reproduce data from the optical disk. The optical disk drive includes a pickup head emitting the light beams and converting the reflected light beams to an analog electronic signal, an analog signal processor (ASP) converting the analog electronic signal to a digital electronic signal, and a digital signal processor obtaining information including a position of the pickup head and a track address of a corresponding track on the disk by decoding the digital electronic signal.
In an optical disk drive, two kinds of servo operations, seek operation and track operation, are sequentially performed. The seek operation is a movement of a projecting light beam from a current track area to a target track area, and the track operation is a movement in the target track area to precisely reach a target track. In other words, the seek operation is a coarse adjustment reaching the target track area, and the tracking operation is a delicate adjustment after the seeking operation to precisely reach the target track so as to obtain desired information on the target track.
Referring to
Unlike direct current (DC) motors, the stepping motor (also called a step motor or a stepper motor) 440 does not produce a continuous motion from a continuous input voltage. One pulse into the stepping motor 440 causes a rotor (usually a worm) thereof to move one precise angle (technically called step angle). This movement is repeated with each input pulse. For a given application, the step angle of the stepping motor 440 and a thread pitch of the worm 442 are adjustable. For an optical disk drive, the step angle and the screw interval determine distance per step N of the optical disk drive, which indicates the number of the tracks that the pickup head jumps over in one seeking step.
Before a seek operation, the pickup head 450 is at an initial position 443 corresponding to an initial track area 533 of the optical disk 530. During the seek operation, the pickup head 450 is moved from the initial position 443 toward a target position 445 corresponding to a target track area 535 on the optical disk 530. In practice, the pickup head 450 directly reaches an actual track 534 other than the target track 535, because different optical disks or even different track areas on one optical disk are not exactly the same, and parameters of the optical disk drive are accordingly not exact for these different optical disks or different track areas. A further seek operation or a plurality of track seek operations need be done to reach the target track area 535. Whenever the pickup head 450 is moved to a new target track area, it cannot directly reach the new target track area expectedly and a further seek operation should be done.
As described above, before the pickup head 450 reaches the target track area 535, the seek operation may be performed many times. Thus, the seek operation is time-consuming.
Therefore, a track seeking method for an optical disk drive and an optical disk drive utilizing the track seeking method are needed in the industry to address the aforementioned deficiencies and inadequacies.
An optical disk drive is used for recording data to and/or reproducing data from an optical disk. The optical disk drive includes a pickup head, a stepping motor, an ASP, and a DSP. The stepping motor is used for moving a pickup head to seek a target track of the optical disk from an initial track. The ASP is used for converting an analog electronic signal from the pickup head to a digital electronic signal. The DSP is used for obtaining a current position of the pickup head by analyzing the digital electronic signal, and for calculating a current track count between the current track area and the target track area and modifying a current distance per step of the stepping motor with an actual distance per step calculated based on the current track count. A seeking method is also disclosed.
Other systems, methods, features, and advantages of the present optical disk drive and seeking method will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present device, and be protected by the accompanying claims.
Many aspects of the present optical disk drive and the present seeking method can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being positioned upon clearly illustrating the principles of the present device. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Reference will now be made to the drawings to describe preferred embodiments of a present optical disk drive and a preferred embodiment of the present seeking method.
Referring to
The interface 110 is used for receiving an external seeking command, including information of a target track area on the optical disk 610. The DSP 120 stores a distance per step N therein, and calculates a total step count N2 of steps that the stepping motor 140 needs to move the pickup head 450 to a target track area, and modifying a current distance per step N1 of the stepping motor 140. The controller 130 receives the current distance per step N1 from the DSP 120 and generates a control signal to be sent to the stepping motor 140. The stepping motor 140 is used for generating a driving force to move the pickup head 150 from an initial position to a target position. The pickup head 150 is used for emitting a light beam to the optical disk 610, receiving a reflected light beam from the optical disk 610, and converting the reflected light to an analog electronic signal. The ASP 160 receives the analog electronic signal from the pickup head 150 and processes the analog electronic signal to be sent to the DSP 120. The DSP 120 converts the analog electronic signal to a digital electronic signal, and analyzes the digital electronic signal to obtain information of a current track area and a current position of the pickup head 150 corresponding to the current track area.
Referring also to
Many calculating methods can be used by the modifying unit 128 to calculate the actual distance per step N3, and many corresponding modifying methods also can be used. For example, the actual distance per step N3 is obtained by dividing the current track count N5 by the total step count N2, which is indicated in the following equation (1).
N3=N5/N2 (1)
The actual distance per step N3 is added to the current distance per step N1, or subtracted from the current distance per step N1. For a second example, the actual distance per step N3 is also be obtained by dividing a sum of the initial track count N4 and the current track count N5 by the total step count N2, which is indicated in the following equation (2).
N3=(N4+N5)/N2 (2)
The actual distance per step N3 is used to replace the current distance per step N1. For a third example, the actual distance per step N3 is also obtained by dividing a difference between the initial track count N4 and the current track count N5 by the total step count N2, which is indicated in the following equation (3).
N3=N4−N5|/N2 (3)
In this embodiment, a distance per step is modified, which leads to a more accurate movement of the pickup head 150. Therefore, in practice, the optical disk drive 100 can adjust parameters by itself, resulting in a more rapid seek operation.
Referring to
The interface 110 receives a seeking command including information of a target track (step 902).
The calculating unit 124 calculates an initial track count N4 of tracks between an initial track and the target track (step 904).
The calculating unit 124 calculates a total step count N2 by dividing the initial track count N4 by a current distance per step N1 stored in the storing unit 126 (step 906).
The controller 130 receives information including the total step count N2 and the current distance per step N1, and generates a first control signal to be sent to the stepping motor 140 (step 908).
The stepping motor 140 generates a first driving force to move the pickup head 150 based on the first control signal (step 910).
The pickup head 150 receives the reflected light, and converts the reflected light to an analog electronic signal (step 912).
The converting unit 122 converts the analog electronic signal to a digital electronic signal (step 914).
The calculating unit 124 obtains information of the current operation of the pickup head 150 and the current track area by analyzing the digital electronic signal (step 916)
The calculating unit 124 calculates a current track count N5 of tracks between the current track area and the target track area (step 918).
The modifying unit 128 calculates an actual distance per step N3 based on the current track count N5 (step 920).
The modifying unit 128 modifies the current distance per step N1 using the actual distance per step N3 to use the modified current distance per step N1 in a next seek operation (step 922).
As mentioned above, the current distance per step N1 of the distance per step is modified with the actual distance per step N3. Therefore, a more accurate movement of the pickup head 150 can be accomplished.
It should be emphasized that the above-described preferred embodiments, are merely possible examples of implementation of the principles of the invention, and are merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiments of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and be protected by the following claims.
