Diffraction Pattern Analysis for Accurate 2D Non-Contact Dimensional Measurements

Z. Nagy and M. Kohoutek (Czech Republic)


diffraction of light, subpixel analysis, dimensional measurement


Orthographic projection of objects achieved by their highly telecentric illumination can be advantageously used in dimensional gauging applications, where highly accurate measurements are required. However, this type of illumination significantly emphasizes the wave nature of light used in the imaging process. The diffraction altered image of the measured object has to be adequately analyzed to determine its exact geometrical dimensions and location in the scene. the diffraction pattern present in the image of the measured object is partially caused by the imaging optics, firstly a highly telecentric illumination setup is described in the paper. Then a geometrical and a wave approach to image formation are discussed. The next paragraph deals with the impact of diffraction on the intensity profile around a straight edge. A digital calibration technique follows, which objectifies the imaging parameters even under diffraction. Finally a gauging method is described which utilizes the theory of diffracted imaging when telecentric optics is used for dimensional measurements.

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