Objective lens for optical disk
US4995710A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 25, 1990 |
| Grant date | Feb 26, 1991 |
| Priority date | — |
| Expiry date | May 25, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B13/24
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An objective lens for an optical disk has a first lens group constructed by joining a negative meniscus lens, a biconvex lens, and a negative meniscus lens sequentially arranged from the side of a light source; and a second lens group constructed by a positive meniscus lens. The first and second lens groups are sequentially arranged from the side of the light source toward the side of the optical disk. A combined focal distance f of the entire lens system, a focal distance f.sub.1 of the first lens group, a radius r.sub.i (i=1 to 6) of curvature of an i-th lens face from the side of the light source, and a refractive index n.sub.j and an Abbe number .nu..sub.j (j=1 to 4) of a j-th lens from the side of the light source satisfy the following conditions, PA1 (I) 0.7.gtoreq.f.sup.2 /.vertline.r.sub.2 .multidot.r.sub.3 .vertline.<2.0,r.sub.2 >0,r.sub.3 <0 PA1 (II) 2.0<[(n.sub.1 -1)+(n.sub.3 -1)]/(n.sub.2 -1)<3.0 PA1 (III) 15<[(.nu..sub.2 -.nu..sub.1)+(.nu..sub.2 -.nu..sub.3)]<90 and PA1 (IV) 2.0<(f.sub.1 /f)<6.0
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.