GB908030A - Improvements in or relating to range-finders - Google Patents

Abstract

908,030. Photo-electric range-finders. MAGYAR OPTIKAI MUVEK. May 5, 1959 [May 5, 1958], No. 15452/59. Class 40 (7). In an optical pulse-echo range-finder the echo light pulse is applied to a photo-cell 9 to give a corresponding electrical pulse and a reference electrical pulse is derived from and variably delayed relative to the transmitted light pulse to bring the reference pulse into coincidence with the electrical echo pulse, the magnitude of said delay being indicative of the range of the reflecting object. As shown, recurrent light pulses produced by a light source 1 and rotating mirror 2 are projected on to a beam-splitting mirror 3 and one of the resultant beams is projected by means of a mirror 4 and optical system 6 on to the reflecting object 7, the resultant echo pulses being focused on to the photo-cell 9 by an optical system 8. The other beam from the beam splitter 3 is focused on to a photo-cell 11 and the resultant electrical pulses are applied through a calibrated variable electrical delay means 12 to a coincidence detector 10 together with the electrical echo pulses from the photocell 9. The output from the coincidence detector 10 is applied to a coincidence indicator 13, e.g. a galvanometer or cathode-ray tube, and the indicator display and setting of the delay means 12 may be recorded automatically by a camera, Fig. 2 (not shown). Alternatively the recurrent light pulses may be produced (1) by replacing the rotating mirror 2 by an oscillating mirror, Fig. 2 (not shown), or (2) by a cathoderay tube whose fluorescent screen is covered with a mask having a narrow aperture, the luminous spot on the screen being oscillated across the aperture. The electrical delay means 12 may be replaced by an optical delay means interposed between the mirror 5 and photo-cell 11, said optical delay means comprising two spaced plane mirrors mutually inclined at a small angle so that the beam travels in a zig-zag path between the two mirrors. The delay means may also comprise a plurelity of coarse and fine electrical and/or optical delay means, the fine delay being continuously variable and the coarse delay being variable in discrete steps. The directional optical transmitting and receiving systems 6 and 8 may be duplicated to allow the simultaneous measurement of the ranges of two spaced objects, the distance between the objects being determined by said ranges and the angle between the objects.