Digital photoelectric measurement of vehicle wheel geometry - has graticule image reflected from mirror attached to wheel, to photoelectric detector

摘要

The digital photoelectric measuring system for determining track and camber angles on vehicle wheel axles consists of a projector (13) whose beam is reflected by a mirror fixed to the wheel (10, 11). The light source shines through a semi-transparent, triangular graticule (14) of parallel lines. The image of the graticule is reflected by the wheel mirror onto the focal plane of a photoelectric detector (20). The output of the detector is amplified (22) and a Schmitt-trigger (23) produces a square-wave pulse to drive a digital display (24). The number of pulses counted is proportional to the angular displacement of the wheel from a datum position. The graticule lines are of different length and the plate is attached to an arm (15) which can be swung through the optical axis.