Error Analysis Of Optical Surface Flaws Detection Scan Stitching

Sub-aperture scanning stitching is used for surface defects detecting of large aperture optical components, and it plays an important part in the optical components detecting in Inertial Confinement Fusion system. This paper analyses all the stitching errors of the large aperture optical components surface defect detecting, and proposes the method how to reduce these errors. By using this method, The full-aperture can be stitched without any stitching errors , so the evaluation of defects can be improved greatly.Errors of full-aperture stitching include positional error of the translating system, the perpendicular error of scanning trace and the angle between the coordinate of CCD and coordinate of scanning trace. The paper esdablishes a mathematical model of error analysis, and calculats the mathematical expectation of accumulated error of asymmetry and symmetry error, which have a greet importance for the error analysing of full-aperture stitching.A CCD rotating system is established to adjust the angel between CCD coordinate and scanning coordinate when the angle is calculated. By using these methods, full-aperture could be stitched without any stitching errors. With the feature of randomness and asymmetry, positional error of the translating system could be reduced by stitching along scanning trace. the perpendicular error of scanning trace is belong to systematic error, and it affects full-aperture stitching by its asymmetry. The perpendicular error of scanning trace is measured accuracily in order to reduce it by the software compensation.A software which is used for automatic collection of sub-aperture is programmed. The software contains the picture collection of picketage, sub-aperture collection and the automatic adusting for the angle between CCD coordinate and scanning trace. Thus, the system can collect M×N sub-aperture arrays automatically, and it plays an basement part in defects detecting of large aperture components.