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Proceedings Paper

Development of a 3D dynamic measurement system using a high-speed camera with white light scanning interference microscopy associated with real-time FPGA image processing
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Paper Abstract

White light scanning interference microscopy is used for measuring the surface morphology of materials and devices more and more widely in many areas of research and industry. However, a limiting requirement is that the surface to be analysed be kept static during measurement, which can typically take from several seconds to several minutes. As industries such as MEMS manufacturing mature and create more complex dynamic devices, it becomes increasingly important to be able to characterize structures that undergo periodic or transitory motion. In this paper we present the architecture of a 4D (3D + time) interference microscopy system that is being developed based on continuous fringe scanning over the depth of the sample. The simulation of results using real time detection of the peak fringe intensity (PFSM, Peak Fringe Scanning Microscopy) or the maximum of the fringe visibility (FSA, Five Sample Adaptative non linear algorithm) is discussed. During scanning, a high speed CMOS camera provides images at a rate of 500 i/s (1280x1024 pixels) that are processed using a FPGA (Field Programmable Gate Array) to extract the 4D measurements. At a bit stream rate of 625 Mbyte/second, it is reasonable to expect a measurement rate of nearly 1 i/s at full frame size over a 20 &mgr;m depth and 9 i/s over a depth of 2 &mgr;m. By reducing the image size to 128x128 pixels, the rate is increased to 16 i/s over a 20 &mgr;m depth and 600 i/s over 2 &mgr;m. These values could be increased further using under sampling or by means of higher speed reference mirror scanning.

Paper Details

Date Published: 18 June 2007
PDF: 9 pages
Proc. SPIE 6616, Optical Measurement Systems for Industrial Inspection V, 661633 (18 June 2007); doi: 10.1117/12.726394
Show Author Affiliations
Gyasi Johnson, Institut d'Electronique du Solide et des Systemes, CNRS (France)
Paul Montgomery, Institut d'Electronique du Solide et des Systemes, CNRS (France)
Freddy Anstotz, Institut d'Electronique du Solide et des Systemes, CNRS (France)
Renaud Kiefer, Lab. des Systemes Photoniques, INSA de Strausberg (France)


Published in SPIE Proceedings Vol. 6616:
Optical Measurement Systems for Industrial Inspection V
Wolfgang Osten; Christophe Gorecki; Erik L. Novak, Editor(s)

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