SPECKLE NOISE REDUCTION FOR A COHERENT ILLUMINATION IMAGING SYSTEM

摘要

Described are methods and apparatus for reducing speckle noise in images, such as images of objects illuminated by coherent light sources and images of objects illuminated by interferometric fringe patterns. According to one method, an object is illuminated with a structured illumination pattern of coherent radiation projected along a projection axis. An angular orientation of the projection axis is modulated over an angular range during an image acquisition interval. Advantageously, shape features of the structured illumination pattern projected onto the surface of the object remain unchanged during image acquisition and the acquired images exhibit reduced speckle noise. The structured illumination pattern can be a fringe pattern such as an interferometric fringe pattern generated by a 3D metrology system used to determine surface information for the illuminated object.