Automatic object cross-sectional dimension measurement - using reflected optical interference patterns scanned by readout unit

The equipment is for measuring the external cross sectional dimensions of a sutable object, typically a pipe, wire or strip of material, by means of scanning an optical interference pattern reflected from the object. It consists of a laser source (1) which sends a light beam into interferometer (4) through a beam, expansion telescope (2), and a set of prisms and mirros (5, 6) which direct the resulting interference pattern on to both sides of the object (8). The pattern reflected from this is scanned by a revolving mirror (9), lens (10) and photodetector (12), or alternatively by a television camera, resulting in a time signal which is periodic for a length of time dependent on the cross sectional dimension of the object (8) being examined. An accurate measurement of that dimension can be made by axamination of this signal.