Optical contact free measurement of surface displacement

摘要

A process for non-contact and mark-free optical measurement of surface displacement is based on the speckle effect. A point on the surface of the test object (1) is illuminated by a laser (2) passing through an optic (3) and its image transmitted through an imaging optic (4) to sensor elements (5) arranged in a CCD matrix. The imaging optic is so positioned that it or the sensor elements detect only one or a very few speckles (6). If the surface is displaced the position of the speckles and consequently the absolute brightness or relative brightness at each sensor element changes. The amount the point sensor (7) must move accordingly is the measure for the displacement of the object point. This shift in the point sensor is determined by an analogue or digital processor (8) and process device (9). The technique is quick and accurate.