Objective lens system for endoscope
US5587839A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 17, 1995 |
| Grant date | Dec 24, 1996 |
| Priority date | — |
| Expiry date | Oct 17, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B23/243
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An objective lens system for an endoscope includes first to fifth lens elements L.sub.1 to L.sub.5 arranged in this order from the front to the rear. An aperture stop is disposed between the second and third lens elements L.sub.2 and L.sub.3. The first lens element L.sub.1 is a negative lens concave to the rear, the second lens element L.sub.2 is a positive lens having a flat surface facing rearward, the third lens element L.sub.3 is a positive lens having a flat surface facing forward, the fourth lens element L.sub.4 is a positive lens having a flat surface facing forward and the fifth lens element L.sub.5 is a negative meniscus lens. The fourth and fifth lens elements L.sub.4 and L.sub.5 are cemented together to form a cemented lens having a positive refracting power. The following formulae (1) to (3) are satisfied, EQU 0.75<.vertline.f.sub.1 .times.Bf/f.sup.2 .vertline.<1.45 (1) EQU D.sub.i <.vertline.R.sub.i .vertline. (2) EQU .upsilon..sub.2 <45 (3) wherein f.sub.1 represents the focal length of the first lens element L.sub.1, Bf represents the back focal length of the overall objective lens system, f represents the combined focal length of the overall objective lens system, D…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.