GB799348A - Improvements in or relating to optical rangefinders - Google Patents

Abstract

799,348. Optical rangefinders. ZEISS IKON AKT.-GES. Aug. 17, 1955 [Aug. 17, 1954; Feb. 17, 1955], No. 23715/55. Classes 97(1) and 98(1) An arrangement for estimating the range of an object comprises an optical system forming a virtual image or images of the object and adjustable to vary the distance of that image from the observer, and a verifier system for focusing two separate secondary images of the said virtual image or images and so arranged that the secondary images coincide when the virtual image is at a standard distance the range being deduced from the adjustment of the system necessary to bring the virtual image to that standard distance at whidh coincidence is effected. The system may be an astronomical or terrestrial telescape, a Gablean telescope in normal or inverted position or a simple or complex magnifying lens system and the standard distance may be infinity. As shown in Fig. 4 from the diverging or parallel rays of light from the eyepiece of a telescope a beam 14 is directed by a mirror 10 to the eye 15 via a mirror 11 and a beam 14 reaches the eye directly. The images formed by the beams will coincide if the virtual image from which they come is at a certain standard distance dependent on the inclination of the mirrors 10 and 11 and the objective (not shown) of the telescope is adjusted until such coincidence is effected. The mirrors may be replaced by a variety of prism systems for selecting the two beams. To allow the telescope to be used as such while, measuring range the ranging beams may be deflected by a prism placed at the real image formed by the objective. The invention may be applied to test the setting of an objective within a photographic camera by placing an illuminated object in the focal plane, using the camera lens to produce a virtual image thereof which is observed by a system such as that shown in Fig. 4 arranged to give coincidences for a virtual image at infinity, and adjusting the objective until such coincidence is achieved. Fig. 12 shows the system applied to the focusing of a reflex photographic camera in which the optical system giving virtual image is composed of the camera objective 41, 42 and an eyepiece 43 behind which is a prism 49 carrying the reflecting surfaces 10 and 11 of Fig. 4. A mirror 44, Fresnel lens 45, field lens 46 and prism 47 are also provided. The standard distance of the virtual image is arranged for infinity so that when the objective 41 is adjusted to give coincidence of the two images of an object seen in the prism 49 the object will be in focus on the photographic film. Alternatively a separate objective may be provided fixed to and movable with the camera objective.