The core of the power inductor is made by powder metallurgy. By its nature, the powder-formed part has inherent nonuniform porosity pattern and parallel tool marks on the metal surface. In the past, the surface inspection of core is usually performed by using human eyes. However, the larger uncertainty of inspection will be induced while observing the defect image using human eyes. In the automated optical inspection process, the feature of defect is not easily separated from the image background by using the simple binarization method. This study develops an image processing method and employs a uniform diffuse illumination to build up a surface defect inspection system. Experiment result shows the distinguish rate is 95.5%, therefore it is clear that this system can successfully detects a set defect of the core of inductor.
The near-field recording mechanism of the super resolution near-field structure, glass/ZnS-SiO2/AgOx/ZnS-SiO2, has been studied experimentally. Near-field optical effects of the glass/ZnS-SiO2/AgOx/ZnS-SiO2 have been observed by a tapping mode tuning-fork near-field scanning optical microscope (TMTF-NSOM) on the transmitting light spot. Laser-excited surface plasmon at the interfaces of AgOx/ZnS-SiO2 thin film was detected by this technique. Results showed that the transmitting focused light through the AgOx type super resolution near-field structure consists of a propagating term and an evanescent one resulted from the localized surface plasmon of the AgOx thin film. A strong enhancement of the near-field intensity and the dynamic localized enhancement of the transmitting focused light were observed as well.