An optical pickup has been developed for both digital versatile discs (DVD) and compact discs (CD) using an annular mask on an objective lens. A conventional lens without the annular mask has been optimized only for DVD disc with 0.6 mm-thickness. The intensity of the secondary peaks of the spot focused by the objective lens with an annular mask to a CD is reduced and the pickup is found to have large tolerance for disc tilt variation compared with a conventional objective lens without an annular mask.
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Lee et al. (1997) studied this question.
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