GB1220340A - Measuring displacement utilizing energy beams - Google Patents

Abstract

1,220,340. Photo-electric distance measuring. BOEING CO. 29 Dec., 1967 [29 Dec., 1966; 19 Dec., 1967], No. 59191/67. Heading H4D. [Also in Division G1] A displacement characteristic of a movable object is determined by transmitting two defined beams of energy, at an angle to one another, through the path of the object, and producing a response when the object interrupts the two energy beams; the interval between the successive interruptions is a function of the displacement characteristic. In one embodiment a helium-neon laser 20 produces a narrow beam reflected by a mirror 30 on to a photo-diode 22; obturation by a helicopter blade tip in planes 24, 54 and 56 give corresponding output trains, Fig. 4, the interval e.g. 68 as compared with interval 58 being a measure of the distance of the corresponding plane from reference plane 24. In another embodiment the deflexion angle of the beam is 45 degrees. The measurement may utilize counting of clock pulses, a means on the aircraft being added to for associating a measurement with a particular helicopter blade, Figs. 8, 9, 10 (none shown). Two light sources each with a corresponding detector may be used, Figs. 12, 13, 14 (none shown). In one measuring arrangement, a cathode-ray tube display and a graticule are utilized, Fig. 11 (not shown). The radiant energy may be sound. The invention may be employed to measure the speed of rotating or linearly moving objects, or to track turbine blades.