Optical pickup objective lens, optical pickup apparatus and optical disc apparatus
AssigneeHitachi Maxell, Ltd.
InventorsNaofumi Ueda, Yasuyuki Sugi, Yutaka Makino
Life of this patent
Estimating the term…
Abstract
A pickup lens has a plurality of ring zones on at least one surface, and steps are formed respectively between the plurality of ring zones. The plurality of steps have step differences causing laser light to have a phase difference to reduce aberration occurring in the pickup lens due to a change in ambient temperature. Further, when a numerical aperture of the pickup lens is NA, a focal length is f (mm) and a working distance is WD (mm), the pickup lens is fabricated to satisfy NA=0.85, 1.1=f=1.8 and WD=0.3.
Claims25
An optical pickup objective lens made of plastic for focusing light beam emitted from a laser light source on a Blu-ray disc (BD), wherein
- the optical pickup objective lens includes a plurality of ring zones on at least one surface,
- a plurality of steps are formed respectively between the plurality of ring zones,
- the plurality of steps have step differences causing incident light to have a phase difference to reduce aberration occurring in the optical pickup objective lens due to a change in ambient temperature, and
- if a numerical aperture of the optical pickup objective lens is NA, a focal length is f (mm), a working distance is WD (mm) and fifth-order spherical aberration is SA5 (λrms), when focusing light beam emitted from the laser light source on a multilayer optical disc by the optical pickup objective lens, following expressions (1) to (3) are satisfied upon correcting third-order spherical aberration occurring based on a difference in substrate thickness between recording layers of the multilayer optical disc:
- NA≧0.85 (1)
- 1.1≦f≦1.8 (2), and
- WD≧0.3 (3).
Dependencies are inferred from the claim text.