Pulse width modulation optical disk drive with pulsed laser preh

Details Pulse width modulation optical disk drive with pulsed laser preh Pulse width modulation optical disk drive with pulsed laser preh

1994-11-18

1996-10-01

Epps, Georgia Y.

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

369116, 3692751, 369 59, G11B 700

Patent

active

055616569

ABSTRACT:
A pulse width modulation (PWM) optical disk drive uses a modulator-controlled laser to emit the laser beam in a highly pulsed manner. The beam may be pulsed on any given write clock period and at any of several different power levels. The pulsed laser writes essentially circular submarks of substantially the same size on the disk when the power level is sufficiently high. The various PWM mark run-lengths are recorded on the disk either as a single isolated submark in the case of the shortest run-length or as a series of contiguous or overlapping submarks in the case of longer run-lengths. During the intervening PWM gap run-lengths the optical disk is preheated by a series of pulses at a power level below that which would write a submark on the disk. Both the number and duty cycle of these preheat pulses is varied depending on the length of the PWM gap run-length to ensure that the initial submark at the start of the subsequent PWM mark run-length is substantially the same size, regardless of the length of the preceding gap run-length. This ensures proper placement of the mark leading edges. When even finer control of the preheating is required, pattern-dependent gap preheat pulsing can be performed, wherein the number and duty cycle of the preheat pulses in the gap is varied depending not only on the length of the gap run-length but also the length of the preceding mark run-length.

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