Zoom apparatus for a camera having count generating means and count modifying means for enhancing accuracy at selected focal lengths
US5634148A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 20, 1994 |
| Grant date | May 27, 1997 |
| Priority date | — |
| Expiry date | Oct 20, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B7/102
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
The present invention is directed to a zoom encoder for detecting an amount of angular movement and a direction of angular movement of a cam ring which is angularly moved about an optical axis of a photographing optical system to change a focal length of the photographing optical system. The zoom encoder is characterized by comprising a pulse generator of non-contact type for generating pulse signals in accordance with the angular movement of the cam ring that serves as a drive for changing the focal length of the photographing optical system, a counter for selectively adding or subtracting the pulse signals in accordance with the direction of angular movement of the cam ring, a position detector for detecting a predetermined position signal at least in the vicinity of a wide angle end and in the vicinity of a telephoto end of the focal length, a count-value modifier for modifying the count value of the counter to a predetermined value in accordance with a change in an output from the position detector, and a zoom-information detector for producing zoom information on the basis of the output from the counter.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.