GB1470454A - Range-finders - Google Patents

Abstract

1470454 Optical range finding SOC DE FABRICATION D'INSTRUMENTS DE MESURE 12 June 1974 [29 June 1973] 25984/74 Heading H4D To determine the range D=MO<SP>1</SP> of a punctiform object M visibly contrasting with its background, two images I 1 , I 2 of the object are formed on the target 3 of a detector by means of an optical system arranged symmetrically around the perpendicular bisector 3<SP>1</SP>0<SP>1</SP>3 of the base line 0 1 0 2 and comprising a first pair of mirrors M1 and M2, inwardly directing the rays from the object towards the bisector 31013 and a second pair of mirrors M3, M4 receiving the directed rays and reflecting them through a focusing means 2. The distance D is related to the distance d between images by the formula where: f = focal length of means 2; D 1 = range for which d=0; L=length of base line. The distance d is determined by scanning the target of the detector (which may be a television camera) in a series of lines at right angles to the line X, X<SP>1</SP> joining the images, to produce a video signal having pulses when the images are encountered, the first pulse starting a counter and the second pulse stopping the counter, such that the count represents d. The Formula (1) is non-linear, but may be rendered linear by the intervention of optical deflecting means-e.g. prisms P 1 , P 2 -or by computer processing of the count.