System for contactless continuous measurement of substrate thickness - has laser generating diffused light from substrate sensed by CCD camera under positional control of eddy current sensor and piezo-actuator

摘要

An apparatus for the contactless and continuous measurement of the thickness of a thin substrate supported by the reference surface (5) of a conveyor roller (10) eg during paper/cardboard manufacture projects a focussed laser (1) beam normal to the paper surface (P) via the optical system (2). A proportion of the diffused light flux travels to an optical receiver (6) and is registered by eg a CCD line camera for evaluation by the unit (8). A fixed clearance of 0.2 to 0.3 mm between the projector optics (2) and reference surface (5) is rigidly maintained by the eddy current sensor coils (12, 13) whose signals control the piezo-electric or magnetostrictive actuator stem (3). USE/ADVANTAGE - Enables accurate and contactless measurements of thickness in order of 1 to 2 microns on high-speed production lines operating at 2000 metres/min.