Optical: systems and elements – Lens – Including a nonspherical surface
Patent
1996-05-23
1997-10-21
Nelms, David C.
Optical: systems and elements
Lens
Including a nonspherical surface
359718, 359641, G02B 302, G02B 2730, G02B 1318
Patent
active
056802560
ABSTRACT:
The surface of a lens for reading out an optical recording medium facing a light source is formed as a convex aspheric surface which is rotationally asymmetrical with respect to the optical axis and defined by a predetermined aspheric surface equation, whereby, even when a light beam having an astigmatic aberration is emitted from the light source, a signal surface of the optical recording medium can be irradiated with a light beam whose astigmatic difference has been favorably corrected, while the lens can be easily manufactured. The surface of a single lens facing the light source is formed as a convex aspheric surface which is rotationally asymmetrical with respect to the optical axis and satisfies a predetermined aspheric surface equation, whereas its surface facing the optical disk is formed as a convex aspheric surface which is rotationally symmetrical with respect to the optical axis and satisfies a predetermined aspheric surface equation, and the radius of curvature of its surface facing the light source in xz cross section near the optical axis satisfies a predetermined expression. This single lens is used so as to eliminate the astigmatic difference of a laser beam (1) such that the beam spot can be efficiently narrowed on the signal surface (P).
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Fuji Photo Optical Co., Ltd.
Lester Evelyn A.
Nelms David C.
Snider Ronald R.
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