Patent ID: 7595891
Filing Date: 2009-09-29
Classification: G01B

Abstract:
1. A method for producing a height map for a top surface of an object having a transparent thin film that forms at least a portion of the top surface, the method comprising the steps of: acquiring data frames of intensities of reflected light at pixel locations from the object and a separate reference surface at a series of optical path differences between the object and the separate reference surface, for each pixel location across the data frames, tabulating a dataset of the intensity at each optical path difference, calculating from the dataset for each pixel a modulation fringe envelope R(n), extracting a phase Φ for each pixel location at each optical path difference from the modulation fringe envelope, determining an offset point n calculating a height for each pixel based at least in part on the offset point, and producing the height map of the top surface of the object based at least in part on the calculated height for each pixel.