Patent ID: 7760591
Filing Date: 2010-07-20
Classification: G11B

Abstract:
1. Optical disc reproduction apparatus comprising: a photodetector divided into four light-receiving regions of a first quadrant light-receiving region, a second quadrant light-receiving region, a third quadrant light-receiving region, and a fourth quadrant light-receiving region by an X-axis and a Y-axis in X-Y coordinates when a radial direction of an optical disc is taken to be the X-axis and a track direction of the optical disc is taken to be the Y-axis; an optical pick-up for irradiating laser light from a DVD (Digital Versatile Disc) laser diode or a CD (Compact Disc) laser diode onto the optical disc via an objective lens, receiving light reflected from the optical disc at the photodetector, and outputting first, second, third, and fourth detection signals of the first, second, third, and fourth quadrant light-receiving regions, respectively; a tracking servo section for shifting the objective lens in the radial direction of the optical disc; a focus servo section for shifting the objective lens in a vertical direction with respect to a recording surface of the optical disc; and a moving section for moving the optical pick-up in the radial direction of the optical disc, wherein the optical disc reproduction apparatus further comprises a system controller, the system controller comprising: a DVD signal level acquiring and storing section for moving the objective lens upwards with the CD laser diode turned off and the DVD laser diode turned on, and acquiring levels of the first, second, third, and fourth detection signals from the photodetector for storage in a memory; a DVD ratio calculating section for calculating a ratio (A+D)/(B+C) in a direction of the X-axis when the levels of the first, second, third, and fourth detection signals stored in the memory are taken to be A, B, C, and D, respectively; a DVD lens shift correction amount calculating section for calculating a lens shift correction amount for the calculated ratio based on a correction table indicating a relationship of the ratio and the lens shift correction amount when the calculated ratio exceeds a predetermined value; and a DVD lens shift section for controlling the tracking servo section in accordance with the lens shift correction amount that is calculated so as to shift the objective lens in the direction of the X-axis when the calculated ratio exceeds the predetermined value, wherein the system controller executes processing provided by said sections included therein and reflects results in a succeeding series of processes required for achieving a focus-on state.