Projection zoom lens and image projection apparatus
US9983392B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 6, 2017 |
| Grant date | May 29, 2018 |
| Priority date | — |
| Expiry date | Mar 6, 2037 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03B21/142
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A projection zoom lens includes, sequentially from an enlargement conjugate side: a first lens group having negative refractive power; a second lens group having positive or negative refractive power; a third lens group having positive refractive power; a fourth lens group having negative refractive power; a fifth lens group having positive refractive power; and a sixth lens group having positive refractive power, and configured to perform a magnification variation by changing the interval between the respective lens groups, wherein the fourth lens group includes at least one positive lens and at least one negative lens, at least one of the positive lenses included in the fourth lens group satisfies the following Conditional Expressions: 0.71≤θg_Fp+0.004×νdp≤0.73 and 15≤νdp≤25, and the back focus of the entire projection zoom lenses satisfies the following Conditional Expression 1.0≤BF/Fw≤2.7.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.