AMPLITUDE MODULATED COARSE POSITION ERROR SIGNAL GENERATION IN AN OPTICAL DISK STORAGE SYSTEM EMPLOYING COARSE SERVO TRACKS

摘要

ABSTRACT OF THE DISCLOSUREA linear detector (31) for use in a coarse positioning servosystem of an optical disk storage system. The linear detectorproduces an error signal (67) having an amplitude linearlyproportional to the distance that a center of mass of incidentradiant energy (63) falls on a collection surface (62) of thedetector as measured relative to a fixed reference point on saidcollection surface. Two reference signals (65, 66) are derived fromcircuitry associated with the collection surface. A first referencesignal (65) has an amplitude proportional to the intensity of thefocused light energy and the location that said light energy fallson the collection surface relative to a first reference point. Asecond reference signal (66) has an amplitude proportional to theintensity of the focused light energy and the location that saidlight energy falls on the collection surface relative to a secondreference point. The sum and difference of the amplitudes of thefirst and second reference signals are derived to produce sum anddifference signals (Y, X), respectively. The difference signal isdivided by the sum signal (X/Y) to produce the desired error signal,which error signal has an amplitude that is substantiallyindependent of the intensity of the focused light energy. Signalprocessing circuitry (84, 86, 88; and 85, 87, 89) may be used todemodulate the reference signals so that the desired error signal isderived only from that portion of the incident radiant energyreflected from a coarse servo track of the optical disk, and notfrom radiant energy reflected from other areas of the disk.