Photographic camera with exposure-control and focussing means

摘要

A focussing system emits an infrared light beam towards the subject, the reflected beam passing through an infrared filter and being projected by a spot optics as a small spot onto a pair of photosensitive elements. The spot optics shifts in a plane normal to the camera's optical axis in dependence upon rotation of the camera's focussing ring, to vary the distribution of the reflected beam onto the two elements, the distribution being equal between them when the state of focus is correct. A circuit derives, from the output signals of the two photosensitive elements, a state-of-focus signal used to automatically focus or else to indicate to the user the direction in which he should manually adjust focus. When focussing is finished, the photosensitive elements are disconnected from the focussing circuitry and connected to the camera's exposure-control circuitry, to thereby serve a dual function. The infrared filter moves out of the light path of the photosensitive elements. The spot optics is moved out of the light path of the photosensitive elements, so that for exposure control a larger light field can be established, or else an auxiliary optics moves into the light path to enlarge the light field in that manner.