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26 March 2019 Modulated dark-field phasing detection for automatic optical inspection
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Abstract
Dark-field illumination is a simple yet elegant imaging technique that can be used to detect the presence of particles on a specular surface. However, the sensitivity of dark-field illumination to initial conditions affects its repeatability. This is problematic in cases where automation is desired. We present an improvement to the current method of using a modulation field that relies on phase calculations rather than intensity. As a result, we obtain a computational method that is insensitive to noise and provides clearly defined particle information, allowing a global threshold to be set for autonomous measurement purposes. After introducing the theory behind our method, we present experimental results for various scenarios and compare them to those obtained using the dark-field approach.
© 2019 Society of Photo-Optical Instrumentation Engineers (SPIE) 0091-3286/2019/$25.00 © 2019 SPIE
Heejoo Choi, John Mineo Kam, Joel David Berkson, Logan Rodriguez Graves, and Dae Wook Kim "Modulated dark-field phasing detection for automatic optical inspection," Optical Engineering 58(9), 092603 (26 March 2019). https://doi.org/10.1117/1.OE.58.9.092603
Received: 13 January 2019; Accepted: 4 March 2019; Published: 26 March 2019
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