Method and apparatus for thickness measurement on transparent films

摘要

A method and an apparatus for thickness measurement on transparent films is described. An illumination beam (4) is directed through an objective (5) onto an object (1) having a transparent film (2). A structured focusing aid (9) is arranged in the illumination beam (4), and a camera (13) in an imaging beam (12), each in locations conjugated with the focal plane (8) of the objective (5). The focal plane (8) of the objective (5) is displaced stepwise through the object (9). At each position, a camera image is recorded and its focus score is determined, the image of the focusing aid (9) being used as the sharpness indicator. The positions with maximal focus scores are assigned to the locations of the interfaces. The thickness of the transparent film (2) is calculated from the difference between the positions of its interfaces. <IMAGE>