19 May 2015 Toward a real time stand-off submillimeter-wave imaging system with large field of view: quasi-optical system design considerations
Author Affiliations +
In the frame-work of the European project CONSORTIS, a stand-off system for concealed object detections working at submillimeter-wave frequencies is being developed. The system is required to perform real-time image acquisition over a large field of view at a short range using both an active and a passive sensor operating in the frequency range from 250 to 600 GHz. In this contribution, the main trade-offs associated with the quasi-optical system design are presented. The imaging distance is from 2 m to 5 m range with a spatial resolution lower than 2 cm. Focal plane arrays will be used to achieve high imaging frame rates. Two configurations are considered in CONSORTIS: a sparse array of active transceivers and incoherent passive staring array with a large number of elements. Both cases use mechanical scanning to achieve the required field of view. This paper presents an in-depth analysis of the different trade-offs driving the quasi-optical design: from the mechanical scanner considerations to the optical beam quality required over the whole field of view. This analysis starts from the fundamental limitations of the quasi-optical mechanical systems. The limitations of the optics are discussed considering a canonical elliptical reflector as a reference. After this fundamental analysis, we compare the performances of several practical standard implementations, based on dual-reflectors and lenses, with canonical geometries. It is shown that, at short ranges, the main limitation of the optical system is the poor beam quality associated with the wide angular field of view and none of the standard implementation fulfills the requirements. In the last section, a technique to overcome this limitation is investigated. In particular, the use of optics with oversized reflectors can significantly improve the performance over a larger field of view if the coma aberrations are limited by a good angular filter.
© (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Erio Gandini, Erio Gandini, Nuria Llombart, Nuria Llombart, "Toward a real time stand-off submillimeter-wave imaging system with large field of view: quasi-optical system design considerations", Proc. SPIE 9462, Passive and Active Millimeter-Wave Imaging XVIII, 946205 (19 May 2015); doi: 10.1117/12.2177038; https://doi.org/10.1117/12.2177038


Real-time passive millimeter-wave imaging
Proceedings of SPIE (August 20 1998)
Techniques for millimetre-wave imaging
Proceedings of SPIE (December 07 2004)
Review of imaging architecture
Proceedings of SPIE (July 28 2002)

Back to Top