Objective lens for endoscope
US6181481A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 29, 1999 |
| Grant date | Jan 30, 2001 |
| Priority date | — |
| Expiry date | Oct 29, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B23/243
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An endoscope objective lens comprises, successively from the object side, a first lens group G.sub.1 constituted by a first lens L.sub.1 made of a planoconcave lens having a concave surface directed onto the image side and a second lens L.sub.2 made of a convex meniscus lens having a convex surface directed onto the object side, a stop 1, and a second lens group G.sub.2 having a positive refracting power, wherein the image-side surface of the first lens L.sub.1 is formed as a diffraction optical surface. This endoscope objective lens further satisfies the following conditional expressions: EQU E>0 (1) EQU -2.0<f.sub.N /f<-0.3 (2) where E is the coefficient of the second-order term of the phase difference function of the diffraction optical surface; f.sub.N is the focal length of the lens having the diffraction optical surface and the strongest negative refracting power in the first lens group; and f is the focal length of the whole lens system. This endoscope objective lens favorably corrects chromatic aberration in magnification in particular, and reduces adverse effects of unnecessary diffracted light, flare light occurring due to errors in manufacture or the like, and so forth, …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.