Objective lens and optical system for optical pick-up

Details Objective lens and optical system for optical pick-up Objective lens and optical system for optical pick-up

2006-02-13

2010-11-23

Klimowicz, William J (Department: 2627)

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

C369S112080

Reexamination Certificate

active

07839751

ABSTRACT:
An optical system of an optical pick-up is provided. The optical system includes an optical element including at least a phase shift surface among the surfaces thereof, and located closer to a light source than the objective lens. In this configuration, t1≦t2is satisfied, where t1represents a thickness of a cover layer of a first optical disc for which a first laser beam is employed, and t2a thickness of a cover layer of a second optical disc for which a second laser beam, having a longer wavelength than the first laser beam, is employed. NA1≧NA2is satisfied, where NA1represents a numerical aperture for the first optical disc, and NA2the numerical aperture for the second optical disc. The phase shift surface includes a first region that converges the first laser beam on a recording surface of the first optical disc, and the second laser beam on a recording surface of the second optical disc. The first region includes at least an annular zone structure having an annular zone group including a step that gives an additional optical path length to the first laser beam generally by two wavelengths, with respect to an inner refracting surface at a boundary between adjacent refracting surfaces, and a return step portion located at an outer position of the annular zone group.

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English Language Abstract of JP 2001-093179, date: 2001.
English Language Abstract of JP 9-054973, date: 1997.

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