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

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conference contribution
posted on 2019-07-03, 10:31 authored by Jorge Garcia Armenta, Pablo RuizPablo Ruiz, Charles R. Coggrave, Ian S. Park, Jeremy M. Coupland
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.

Funding

Epigem Ltd, the National Physical Laboratory, the CDT-EI and the EPSRC.

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Published in

Optical Measurement Systems for Industrial Inspection XI Optical Measurement Systems for Industrial Inspection XI

Citation

GARCIA ARMENTA, J. ... et al, 2019. High-NA lensless coherent imager as a building block for a synthetic aperture interferometry array. Proceedings of SPIE volume 11056, Optical Measurement Systems for Industrial Inspection XI, 1105607 (21 June 2019); https://doi.org/10.1117/12.2526153.

Publisher

© Society of Photo-Optical Instrumentation Engineers (SPIE)

Version

  • VoR (Version of Record)

Publication date

2019

Notes

Copyright 2019 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

ISSN

0277-786X

eISSN

1996-756X

Language

  • en