Zoom element focusable zoom lens
US4364642A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 11, 1980 |
| Grant date | Dec 21, 1982 |
| Priority date | — |
| Expiry date | Aug 11, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B7/10
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A zoom objective includes four lens groups of which the first and fourth groups are stationary, while the second and third groups are movable independently of each other. Focus adjustment of one of the second and third groups is followed by zooming relative movement of the latter two. To maintain a constant zoom ratio throughout the entire focusing range, the relative movement of the second and third groups is controlled to effect monotonic variation of the magnifying powers of the second and third groups by means of the following formulae as embodied in a microcomputer. EQU Zoom Ratio=Z[S.sub.1, X.sub.1, X.sub.2 (S.sub.1, X.sub.1)] EQU dZ/dS.sub.1 =O wherein S.sub.1 is the object distance; and X.sub.1 and X.sub.2 are the amounts of movement of the second and third groups with zooming respectively.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.