Kenny Y Wong

US Patent:

54882400, Jan 30, 1996

Filed:

Dec 27, 1993

Appl. No.:

8/172899

Inventors:

Louis Hlousek - Fremont CA
K. C. Odencrantz - Fremont CA
Richard K. Oswald - Fremont CA
Donald W. Dahlin - Fremont CA
Saied Motaei - Fremont CA
Paul W. Siggins - Fremont CA
Kenny Wong - Fremont CA
Ronald A. Smith - Fremont CA
Philip M. Scheinert - Fremont CA

International Classification:

H01J 3150

US Classification:

25023116

Abstract:

An apparatus and method for rotating an optical element, such as a diffraction grating or mirror, utilizes a moving coil actuator and an optical encoder to provide precise element position control. The moving coil actuator, which is coupled to the optical element, is comprised of a coil immersed in a magnetic field created by a pair of magnets. Current flowing in the coil windings causes the coil, and ultimately the optical element, to rotate. An optical encoder monitors the rotation of the element and provides rotation signals representative of the instantaneous element position to an actuator control circuit. The actuator control circuit phase shifts the rotation signals and compares the phase shifted rotation signals to a desired reference signal to generate position and velocity error signals. In a track follow mode, the position error signal is applied to the moving coil actuator via a loop compensator. When the apparatus is operating in an optimal seek mode, a trajectory generator receives the velocity error signals and generates an optimum velocity signal based on a preprogrammed velocity curve.