Distance measuring instrument

摘要

A distance measuring instrument comprising a source of coherent light and a receiver is disclosed which may be used to measure the one dimensional position of an object surface. Coherent light is directed at a predetermined angle onto the object surface and the angle at which diffusely reflected light from this surface enters the receiver is measured. This entrance angle is measured with a photosensor and a movable aperture formed by the intersection of a fixedly mounted diaphragm and a movably mounted diaphragm. By measuring the position of the movably mounted diaphragm when the movable aperture is placed so as to allow reflected light to pass from the illuminated surface to the photosensor, the entrance angle of the reflected light and hence the position of the object is determined.