Projection illumination system
US5742438A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 16, 1994 |
| Grant date | Apr 21, 1998 |
| Priority date | — |
| Expiry date | Sep 16, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B13/02
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A projection system includes a collection lens that minimizes apparent magnification of the light source, so that the resulting system more nearly conforms to a point source idealization. Attendant benefits include improved collimation, a smaller projection lens, and a greater depth of focus. The collection lens is desirably of a "wrap around" configuration to maximize light collection while contributing to reduced source magnification. The opposite side of the collection lens can be provided with a convex lens of Fresnel form. Use of the Fresnel optic moves the principal plane of the collection lens closer to the light source, further minimizing the source's apparent magnification. The projection system additionally includes condensing optics formed with a deliberate asymmetry so as to provide more uniform illumination of a rectangular image plane. The Fresnel surface of the collection lens can be designed to provide this asymmetry.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.