| 摘要 |
The present invention uses a stationary medium and a stationary optical pickup unit. The stationary optical pickup unit has a laser, which sends a beam of light through an objective lens, which focuses the beam on a point on the track of the stationary medium. The beam is then reflected toward a re-directing surface (e.g., prism) which diverts it to a photodiode array. Instead of the entire optical pickup moving to follow the track as in conventional systems, only the objective lens inside of the optical pickup moves. The position of the objective lens determines where on the information track the laser will reach. Depending upon where the laser beam reaches, the reflected light beam received by the photodetector array changes. This, in turn, affects the amount of light sensed by each photodetector in the array, thereby causing the output of each of the four photodetectors to change each time the objective lens moves. To implement the invention, the output of the photodetector array is manipulated wherein the manipulated signal corresponds to the signal that would be received if the photodetector were actually following the track directly above the laser as in prior art systems. In this manner, a signal can be used in a tracking servo that corresponds to movement within a conventional media player when actually the pickup and the medium are stationary.
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