Focus capture method for magneto-optic disk drives.

摘要

A method for operating a digital signal processor (34) in a focus servo system of an optical disk drive (10) to obtain focus capture. During a calibration subroutine (90), the servo system is operated in an open-loop mode and the processor (34) generates focus drive signals causing an objective lens (20) to be driven about a focus axis (54) at a calibration velocity. Focus error signals produced while the objective lens (20) is driven at the calibration velocity are peak detected to determine a peak focus error signal. A calibration threshold value generated as a function of the peak focus error signal is stored in memory. After the calibration routine, the processor (34) executes a focus capture subroutine (94) to bring the objective lens (20) within focus capture distance of the optical disk (12). The processor (34) generates focus drive signals causing the objective lens (20) to be driven about the focus axis (54) at a focus capture velocity which is less than the calibration velocity. Focus error signals produced while the lens (20) is being driven at the focus capture velocity are compared to the calibration threshold value. When the focus error signals reach the calibration threshold value, the digital signal processor (34) generates focus drive signals causing the objective lens (20) to accelerate for a predetermined time period. The servo loop is then closed and the focus servo system operated in the closed-loop mode.