Speed variation measurement appts. for patterned moving body, e.g. rotating disc - evaluates frequency difference derived from transversely pivotable lens movements as pattern is scanned by focused beam

摘要

The body (3) carries a pattern (4) of marks which are scanned by an overhead focusing lens (6) under a scanning head (1) with provision for small displacements of the order of 1 mm in both directions parallel to the movement of the body (3). A processing circuit (7,27) evaluates the frequency difference in the scan signal introduced by movements of the scanning beam (5) in and against the direction of body movement, and interprets the difference in terms of speed variation of the body. ADVANTAGE - Variations in the rate of translatory motion within very short periods are detectable.