Optoelectronic hit/miss transform for real-time defect detection by moire image analysis

In this contribution, we propose an optoelectronic hit/miss morphological transform for real-time quality control by image moire analysis, that integrates a VanderLugt optical correlator and a digital signal processor associated to a vector co-processor. The procedure for real-time defect detection is a three stage process. The first step is to enhance the moire image, using the wavelet decomposition and a multiresolution approach. The second step is to automatically segment the enhanced moire image, using the moment preserving thresholding algorithm. The third step is to apply the morphological hit/mass transform to directly recognize moire images that correspond to defectuous objects. This new procedure of defect detection by global analysis of moire image data has been compared to another new technique that is based on multidimensional supervised classification of optical correlations between the test object moire image and reference moire images.