GB1273799A - Electro-optical rangefinder - Google Patents

Abstract

1,273,799. Optical range finder. EASTMAN KODAK CO. 8 Aug., 1969 [8 Aug., 1968], No. 39785/69. Heading H4D. Specification describes a split image range finder, i.e. one in which the lower half of an observation frame Fig. 4 is occupied by a direct view of a scene and the upper half is occupied by a view of said scene, as seen from a laterally offset position A, Fig. la, and presented at said frame by a hinged mirror M2 and upper half frame mirror Ml, the range being given by the necessary orientation of mirror M2 to obtain alignment of the scenes, Fig. 3, provided with photo-electric means detecting said alignment, said means comprising a plurality of pairs of photodiodes 1, 2, 3-(n-1), n, arranged along the shear axis of the frame, the two diodes of each pair viewing respectively different halves of the frame and producing equal outputs for the infocus condition of Fig. 3, differential connections of said diodes, Fig. 5, enabling preamplifiers 30/36 to give voltages of -0À1 v. and +0À1 v. for infocus and out of focus conditions respectively and sense amplifiers 38/44 to give corresponding 0 and 1 outputs. Logic circuits 46 &c. detect when all of the diode pairs are equally illuminated i.e. all amplifiers 38/44 give 0 outputs and an infocus condition prevails, and causes activation of a focusing lens controlling motor M when a departure from the above condition is detected. NOR gate 46 gives a 1 output when all the amplifier (38/40) outputs are 0 which output is applied to input C and (via inverter 52) as a signal 0, to input 5 of JK flipflop 54. The logic circuitry comprising JK flipflops 54, 56, NOR gate 60, clock generator 62 and inverter amplifier 64 operate such that the out of focus (F= 0) condition energizes relay 68, closing contact 74 and energizing motor M. The in focus condition may be defined by some number, less than all of the diode pairs, giving balanced outputs. A circuit utilizing each a definition is shown in Fig. 6 (not shown).