Optical instrument with a continuously adjustable zoom

摘要

PCT No. PCT/AU91/00387 Sec. 371 Date Apr. 21, 1993 Sec. 102(e) Date Apr. 21, 1993 PCT Filed Aug. 26, 1991 PCT Pub. No. WO92/03085 PCT Pub. Date Mar. 5, 1992.An optical instrument for indirectly observing an object includes a first lens system for producing a first image of the object, and an adjustable second lens system for producing a second image of the object. The second lens system is continuously adjustable between a first position wherein the second image has maximum magnification and/or a minimum area of view, and a second position wherein the second image is of a minimum magnification and/or a maximum area of view. In one aspect of the invention, the second lens system is a zoom lens system having two substantially fixed conjugate planes. In another aspect of the invention, the instrument defines a folded optical path through the lens systems which includes a generally U-shaped portion so as, in use, to reduce the separation of the observer and the observed object.