Defect inspection by an active 3D multiresolution technique

Reliable inspection of large surfaces with low depth recovery error is needed in a wide variety of industrial applications, for example in external defect inspection in aeronautical surfaces. Active triangulation measurement systems with a rigid geometrical configuration are inappropriate for scanning large objects with low measuring tolerances due to the fixed ratio between the depth recovery error and the lateral extension. Therefore, with a rigid triangulation setup, if we are interested in defect inspection over extended surfaces then we have to assume errors proportional to the field of view that can preclude a precise local defect measurement. This problem can be solved by the use of multiresolution techniques. In this work we demonstrate the application of an active triangulation multiresolution method for defect inspection of large aeronautical panels. The technique is based on a standard camera-projector system used together with a second auxiliary camera that can move freely. The result is a global measurement with a superposed local measurement without any optimization, explicit registration or recalibration process. The presented results show that the depth recovery error of the local measurement permits the local defects measurement together with a wide-area inspection.