Projection lens unit
US5642229A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 15, 1994 |
| Grant date | Jun 24, 1997 |
| Priority date | — |
| Expiry date | Jun 15, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B13/16
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A projection lens unit includes, in accordance with the order of disposition from a screen side, a first lens group including a positive meniscus lens, a second lens group including a double convex lens, and a third lens group which corrects curvature of field, wherein the third lens group has two concave lenses. A projection lens unit includes, in accordance with the order of disposition from a screen side, a first lens having a positive meniscus form, a second lens having a negative meniscus form, a third lens which is double-convex lens having a light gathering function, a fourth lens which is disposed near the third lens and is a double-convex lens having a positive power, a fifth lens provided at its central portion with a convex surface directed to a screen and provided at its peripheral portion with a concave portion directed to the screen, and a sixth lens having a concave surface directed to the screen, wherein each of the second, fourth and fifth lenses has at least one aspherical surface.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.