Abstract: An optical disk storage unit has an improved access and tracking system in which a low speed velocity signal is derived from a differentiated position error signal. The output of the differentiator is applied to a blanking circuit which disconnects the steep slope portion of the position error signal from a sample and hold circuit. A medium speed velocity signal is derived from the integral of motor current and a high speed velocity signal is derived by digitally counting the band crossings in the position error signal.

Abstract: A beam alignment system and method for aligning a first radiation beam with respect to a second radiation beam as these beams share a desired optical path. Beam steering means, such as a galvonometer controlled mirror, steer the alignment of the first beam as it enters the shared optical path. Detection means are employed to sense the relative alignment between the first and second beams as they travel through the shared path. This sensed alignment is compared to a desired alignment, and a position error signal is generated to indicate the error therebetween. The position error signal, in turn, is used to steer the galvonometer controlled mirror in order to force the beam alignment error between the two beams to zero.