G - Physics – 11 – B
Patent
G - Physics
11
B
352/32.21
G11B 7/13 (2006.01) G11B 7/09 (2006.01) G11B 7/135 (2006.01)
Patent
CA 2012401
An apparatus and method is described for detecting focus errors in an optical head by positioning a prism in the optical path of a return light beam reflected from an optical recording medium. The prism reduces the beam in one dimension by a factor of M and concurrently increases the divergence/convergence angle associated with a focus-error of the beam by a factor of M in said dimension, thereby desirably enhancing the focus error signal by a factor of M2. A focus error is detected by a segmented photodetector having inner and outer photosensitive regions. The photodetector generates an electrical signal indicative of the focus error from the difference in light intensities at the inner and outer regions. The photodetector preferably is segmented in such manner as to also provide a track error signal.
Dewey Anthony G.
Lenth Wilfried
Rugar Daniel
International Business Machines Corporation
Saunders Raymond H.
LandOfFree
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