Patent ID: 7369253
Filing Date: 2008-05-06
Classification: G01B,G06T

Abstract:
1. A method for measuring surface flatness of a continuously moving sample comprising the steps of: conveying the sample on a conveyor surface that extends beneath a grating disposed at a non-zero angle with respect to the plane of conveyance; capturing a time sequence of images of the sample at different locations beneath the grating using a camera, each image comprising a shadow moiré fringe pattern that is indicative of the surface flatness of the sample; calculating a lateral offset of the sample, in pixels, between each image acquisition; in a first of the images, selecting a set of pixel locations in the sample and determining the intensity value at each of the pixel locations; in each of the other images, selecting the set of pixel locations based on the lateral offset and determining the intensity value at each of the pixel locations; calculating a phase value for each selected pixel location based on the intensity values; and calculating a relative height of the sample surface at each pixel location based on the phase values.