Optical appts. e.g. single lens reflex camera - has laser beam superimposed on optical path via mirror to produce visible spot on object to be photographed

摘要

The optical appts. has a focussing device which detects a linear extension of the optical axis. The focussing device includes a laser source (4) which produces a beam parallel to the optical axis of the appts., for focussing the camera. The laser beam is passed through a camera lens (9) to produce a light spot on an object. The beam is pref. superimposed in the viewfinder of the camera via a mirror arrangement (6). The laser source may be a battery operated laser diode. USE/ADVANTAGE - For night photography etc., when distance setting via viewfinder is unreliable. Allows focussing without looking through viewfinder.