GB1389847A - Photo-electric range finder - Google Patents

Abstract

1389847 Photo-electric range finding K VOCKENHUBER and R HAUSER 23 June 1972 [23 June 1971 14 Jan 1972] 29497/72 Heading H4D A range finder has an optical system providing two separate images of a scene to be ranged which are always identical or mirror images of each other when the range setting of the optical system corresponds to the range of the scene, said condition being detected photo-electrically. In Fig. 2 a scene is split into two mirror images and photo-cell pairs n-1, n-1<SP>1</SP> to n-19, n-19<SP>1</SP> are sequentially interrogated to give electrical signals for each pair, the signals being compared in an electrical circuit. At correct range setting the composed signals are identical. In the prior art method in which the scene is split into two partial images which are not mirror images or identical (Figs. 1a, 1b, not shown), it is stated that the range finger may give a correct range setting indication when the two partial images are incorrectly matched (Fig. 1b, not shown). Fig. 5 illustrates the electrical circuit. Photocell lines n, n<SP>1</SP> are interrogated by pulses from generator 15, the interrogation being initiated by pulses C, D and an interrogation cycle being determined by device 16. A delay 18 is alternately enabled so that pulse D is alternately delayed with respect to pulse C, thus synthesizing a lateral shift in the mirror or identical images. The resulting signals are passed to amplifiers 20, 20<SP>1</SP>, enabled by device 24, only when signals are expected, to high pass filters 21, 21<SP>1</SP>, to suppress the effects of ambient light, amplifiers 22, 221 and Schmitt triggers 23, 23<SP>1</SP> to digitize the signals. The digitized signals are passed to an Exclusive - OR gate 25, integrator 26 and amplifier 27 feeding high pass filter 37. Two bi-stables 32, 33 receive the filter 31 output and the delay energizing signal E. The bi-stables form a phase detector and determine the lighting of the lamps 29, 30 which give no signal at correct range setting, and either one flashes according to the direction of the incorrect setting. The signals L, M may be used for auto-focusing. Fig. 8 illustrates a camera having an objective 41 and film plane 44. A beam splitter 42 directs light from the scene to a lens L3 and to two lenses L1, L2 via beam splitter 46, lens L1 being of short focal length and lens L2 being of long focal length. The lenses direct light on to photo-cells 47, 48. At correct range setting the images on the photo-cells are the same but at incorrect setting the images will be of different size and focus (see Fig. 9, not shown). The photo-cells may be replaced by a system similar to that of Figs. 2 and 5 or by a photo-cell consisting of concentric sensitive elements (Fig. 10, not shown). Optical apparatus for giving the images of Fig. 2 is detailed (Figs. 3, 4, not shown).