We present new imaging techniques for the detection and classification of particulate contamination on structured surfaces.This allows for cleanliness inspection directly on the sample.Classical imaging techniques for particle detection, such as dark-field imaging, are typically limited to flat surfaces becausestructures, scratches, or rough surfaces will give similar signals as particles. This problem is overcome using stimulateddifferential imaging. Stimulation of the sample, e.g. by air blasts, results in displacement of only the particles while samplestructures remain in place. Thus, the difference of images before and after stimulation reveals the particles with highcontrast.Cleanliness inspection systems also need to distinguish (often harmful) metallic particles from (often harmless) nonmetallicparticles. A recognized classification method is measuring gloss. When illuminated with directed light, theglossy surface of metallic particles directly reflects most parts of the light. Non-metallic particles, in contrast, typicallyscatter most of the light uniformly. Here, we demonstrate a new imaging technique to measure gloss. For this purpose,several images of the sample with different angles of illumination are taken and analyzed for similarity.
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