Objective lens for optical pick-up

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

2006-01-03

2006-01-03

Epps, Georgia (Department: 2873)

Optical: systems and elements

Lens

Including a nonspherical surface

C359S742000, C369S044230, C369S112030

Reexamination Certificate

active

06982838

ABSTRACT:
There is provided an objective lens used for at least three types of optical discs when thicknesses are respectively represented by t1, t2and t3, t1as 0.6 mm, t2is 0.6 mm and t3is 1.2 mm. When numerical apertures for the first, second and third optical discs are respectively represented by NA1, NA2and NA3, a relationship NA1>NA2>NA3is satisfied. When the first and second optical discs are used, collimated light beams are incident on the objective lens. When the third optical disc is used, a diverging beam is incident on the objective lens. The following conditions are satisfied: −0.02<f1×M1<0.02 * * * (1), −0.02<f2×M2<0.02 * * * (2), and −0.29<f3×M3<−0.19 * * * (3). The objective lens includes a diffracting structure having the first region configured such that a diffraction order at which diffraction efficiency of a first light beam is maximized is a second order and the diffraction orders at which diffraction efficiency of second and third light beams are maximized are first orders.

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