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

摘要

linear detector (31) for use in a coarse positioning servo system of an optical disk storage system. The linear detector produces an error signal (67) having a linearly amplitude proportional to the distance that the center of gravity of incident radiant energy (63) falls onto a receiving surface (62) of the detector, measured distance to a fixed reference point on said receiving surface. Two reference signals (65, 66) are derived from circuits associated with the receiving surface. A first reference signal (65) has an amplitude proportional to the intensity of the focused light energy and to the location on which falls the light energy on the receiving surface relative to a first reference point. A second reference signal (66) has an amplitude proportional to the intensity of the focused light energy and to the location on which falls the light energy on the receiving surface relative to a second reference point. The sum and the difference of the amplitudes of the first and second reference signals are derived for generating sum and difference signals (Y, X), respectively. The difference signal is divided by the sum signal (X / Y) to produce the desired error signal, said error signal having a magnitude that is substantially independent of the intensity of the focused light energy. signal processing circuitry (84, 86, 88) and (85, 87, 89) can be used for demodulating such reference signals that the error signal derivative is desired that the portion of radiant energy incident reflected from a rough servo track on the optical disc, not radiant energy reflected from other areas of the disc.