Optical projection system
US4948238A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 10, 1989 |
| Grant date | Aug 14, 1990 |
| Priority date | — |
| Expiry date | Mar 10, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B13/24
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A first lens, a second lens, means and a third lens means are arranged successively in a direction of travel of a ray. The first lens means each comprising a single lens element power. The second lens means has a predetermined negative refracting power. The third lens means has a predetermined positive refracting power. A fourth lens means consisting of a plurality of lens elements follows the third lens means in the direction of travel of the ray and has a predetermined positive refracting power. At least one surface of the first, second, third, and fourth lens elements is aspherical. The follwoing conditions (1), (2), and (3) are satisfied: EQU 4f<f3<20f (1) EQU 0.65<(f4/d34)<1.40 (2) EQU 10f<R5 (3) where the character "f" denotes a focal length of the optical projection system, the character "f3"denotes a focal length of the third lens means, the character "f4" denotes a focal length of the lens group, the character "d34" denotes a distance between a rear principal point of the third lens means and a front principal point of the fourth lens, and the character "R5" denotes a radius of curvature of a front surface of the third lens means.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.