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12 February 1980 Focus Error Detection In Optical Data Storage Systems
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One of the most distinctive features of the optical disk mass storage technology which has been under development at Xerox Electro-Optical Systems is the extremely high numerical aperture (NA) of the objective lenses used for writing and playback. A disk system with a 0.90 NA lens has over five times the data capacity of a comparable disk system with a 0.40 NA lens. This increased data capacity comes at the price of a reduced depth of focus and significantly increased sensitivity to aberrations. The subject of this paper is the performance of the "skew beam" and the "Foucault knife-edge" techniques for sensing focus errors. Specific topics include: (1) An analysis for optimizing the sensitivity of the skew beam configuration, (2) An observation of the close similarity between the skew beam and the Foucault knife-edge techniques, and (3) A partial list of sources of aberrations unique to high numerical aperture optics, and their impact upon the performance of the focus error sensing detector.
© (1980) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Richard V. Johnson "Focus Error Detection In Optical Data Storage Systems", Proc. SPIE 0200, Laser Recording and Information Handling, (12 February 1980);


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