30 October 2001 Active industrial surface inspection with the inverse projected-fringe technique
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Proceedings Volume 4596, Advanced Photonic Sensors and Applications II; (2001) https://doi.org/10.1117/12.447369
Event: International Symposium on Photonics and Applications, 2001, Singapore, Singapore
A technique is introduced for the industrial surface inspection of workpieces in production lines. This procedure is based on an active technology in optical shape measurement, the so called inverse projected-fringe-technique. After a precise reconstruction of the object shape with respect to the known weak points in the projected fringe technique, a new fringe pattern can be computed and projected using a free-programmable fringe modulator. The objective is to compensate the shape dependent distortions of the fringes. Such an inverse projection can be used for the comparison between a sample and its master piece in quality control. Having a test object that completely fits in shape with the master piece the inverse projection delivers an equidistant and non-distorted fringe pattern under the same observation direction. However, every faulty object area of the sample causes distortions relatively to this known model and can be consequently detected very fast by means of suitable correlation techniques. Especially the simplicity of the master pattern (straight and uniform fringes) offers the possibility of very simple optical filters and the rapid evaluation using an OASLM with an optical correlator (analog) or by applying the spatial heterodyne-technique (digital).
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Michael K. Kalms, Michael K. Kalms, Wolfgang Osten, Wolfgang Osten, Werner P. O. Jueptner, Werner P. O. Jueptner, } "Active industrial surface inspection with the inverse projected-fringe technique", Proc. SPIE 4596, Advanced Photonic Sensors and Applications II, (30 October 2001); doi: 10.1117/12.447369; https://doi.org/10.1117/12.447369

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