High-NA lensless coherent imager as a building block for a synthetic aperture interferometry array

Jorge Garcia-Armenta; Pablo D. Ruiz; Charles R. Coggrave; Ian S. Park; Jeremy Coupland

doi:10.1117/12.2526153

21 June 2019 High-NA lensless coherent imager as a building block for a synthetic aperture interferometry array

Jorge Garcia-Armenta, Pablo D. Ruiz, Charles R. Coggrave, Ian S. Park, Jeremy Coupland

Proceedings Volume 11056, Optical Measurement Systems for Industrial Inspection XI; 1105607 (2019) https://doi.org/10.1117/12.2526153
Event: SPIE Optical Metrology, 2019, Munich, Germany

Abstract

In digital holography, the field of view (FOV) and lateral resolution are limited by the pixel pitch and sensor dimensions, respectively. A large numerical aperture can be synthesized to increase the FOV and spatial resolution by coherently combining low resolution holograms obtained for different illumination and/or observation directions. This is known as Synthetic Aperture Interferometry (SAI) and in this work we describe the design, construction, calibration and testing of high numerical aperture compact coherent imagers (CI) which constitute the optical building block of a multi-sensor SAI array. The CIs consist of a photodetector array, a highly divergent reference beam close to it and an aperture that acts as a spatial filter to prevent aliasing of the digital holograms. We explore different optical designs to produce a highly divergent reference beam close to the sensor, including bulk optics, micro-optics, and ion beam milled optical fibres. An optimization approach is used to characterize the reference wavefront for accurate digital reconstructions of the scattered field first at the aperture plane and then at the object plane. The performance of a compact CI is demonstrated by reconstructing an object 76 mm wide at 80 mm from the sensor, which corresponds to a numerical aperture NA>0.5.

Conference Presentation

Citation Download Citation

Jorge Garcia-Armenta, Pablo D. Ruiz, Charles R. Coggrave, Ian S. Park, and Jeremy Coupland "High-NA lensless coherent imager as a building block for a synthetic aperture interferometry array", Proc. SPIE 11056, Optical Measurement Systems for Industrial Inspection XI, 1105607 (21 June 2019); https://doi.org/10.1117/12.2526153

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