Projection lens apparatus and projection type image display apparatus
US6560041B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 13, 2001 |
| Grant date | May 6, 2003 |
| Priority date | — |
| Expiry date | Jul 13, 2021 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B13/02
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
Compactness of a projection type image display apparatus is realized by achieving miniaturization and wide-angle of a projection lens apparatus while various kinds of aberration are satisfactorily compensated. A first lens group having a negative refracting power, a second lens group having a positive refracting power, and a third lens group having a positive refracting power are positioned in this order, from a screen side, toward an image display element side, in the projection lens apparatus. When f, f1, f3, f23, and fb represent, respectively, a focal length of the whole lens system, a focal length of the first lens group, a focal length of the third lens group, a combined focal length of the second and third lens groups, and a back focus of the whole lens system, the projection lens apparatus satisfies the following conditions:1.4<|f1|/f  (1) 2.8<f3/f  (2) 3.6<fb/f  (3) 0.1<|f1/f23|<0.3.  (4)
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.