Optical pick-up and objective lens for use with different...

Details Optical pick-up and objective lens for use with different... Optical pick-up and objective lens for use with different...

2008-09-30

2008-09-30

Feild, Joseph (Department: 2627)

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

C369S112230

Reexamination Certificate

active

11036989

ABSTRACT:
There is provided an optical pick-up used for recording data to and/or reproducing data from at least three types of optical discs having at least two different thicknesses of cover layers. The optical pick-up includes light sources and an objective lens. A thickness t1of a first optical disc, a thickness t2of a second optical disc, and a thickness t3of a third optical disc satisfy a relationship t1≦t2<t3.A numerical aperture NA1for the first optical disc, a numerical aperture NA2for the second optical disc and a numerical aperture NA3for the third optical disc satisfy a relationship NA1≧NA2>NA3. Further, a first light beam for the first optical disc is incident on the objective lens as a converging light beam, and the second and third light beams for the second and third optical discs are incident on the objective lens as diverging light beams, respectively. Given that magnification of the objective lens is m1when the first optical disc is used, magnification of the objective lens is m2when the second optical disc is used, and magnification of the objective lens is m3when the first optical disc is used, following conditions are satisfied: m1>0, m3<m2<0.

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