Patent · US Active

Optical attachment for reducing the focal length of an objective lens

US8879901B2 · kind B2 · utility

24Cited by

6References

17Claims

0Family size

Assignee

Caldwell Photographic, Inc. · US

Inventors

J. Brian Caldwell · Petersburg, US
Wilfried Bittner · Sha Tin, CN

Key dates

Filing date	Aug 20, 2012
Grant date	Nov 4, 2014
Priority date	—
Expiry date	Jan 20, 2033

Classification

Technology area (CPC G)Physics
CPC primaryG02B13/18
WIPO fieldOptics
WIPO sectorInstruments

Abstract

An optical attachment configured to be operably attached to the image side of an objective lens to reduce the focal length and focal ratio of the objective lens. The focal-reducing attachment includes four lens elements and has a magnification of between 0.5 and 1. The focal-reducing lens can work with objective lenses having relatively large working distances for a large format size as well as with cameras having a smaller format size and relatively small permissible working distance.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.