Zoom lens
US5638216A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 10, 1994 |
| Grant date | Jun 10, 1997 |
| Priority date | — |
| Expiry date | Mar 10, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/144113
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A zoom lens includes, from front to rear, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power, zooming being performed by moving the second and fourth lens units, and focusing being performed by moving the fourth lens unit, wherein the second lens unit is constructed from three single lenses, i.e., from front to rear, a negative first lens having a strong concave surface facing the image side, a negative second lens of bi-concave form and a positive third lens having a strong convex surface facing the object side.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.