Alan August Fennema

Rewritable optical disk drive technology

Optical disk drives provide an effective solution to the growing need for removable high-capacity storage. In this paper, we review the technology behind the optical disk drives used in IBMs optical storage systems. The basic physics of data recording and readout and the engineering of the primary building blocks of an optical drive (the optical head, the servo system, and the data channel) are discussed. We also outline the technological directions of future optical drives as they must continue to improve in performance and capacity.

Interactions between Servo Loops of an Optical Disk Drive

In optical disk drives, interactions between the electromechanical actuators and the servo error generation systems can cause instabilities in the operation of individual servo loops. We examine the effects of these interactions on the servo loops of an optical disk drive in which a galvano fine-tracking actuator, a push-pull tracking error detection scheme, and an astigmatic focus error detection method are used. Also, we describe a digital servo controller that effectively cancels the effects of the deleterious interactions, resulting in stable operation.

State-Space Intercept Method for Seek Control of Optical Disk Drives

This paper proposes a novel digital seek control method which guarantees a disk drive head moves to the desired trajectory at the next sample. Comparison of the performance with that of a conventional optimal control method by computer simulation showed that this method is more robust to disturbances and unmodeled dynamics, and that the seek time is shorter. This digital control method was implemented on a 5.25-inch MO disk drive of a half-high form factor by using a conventional microprocessor, and it was confirmed that the tracking performance is good and that the average seek time is less than 29 ms.