Abstract

Imaging concealed objects with millimeter-wave coherent radiation is accompanied by speckle. Like all interference phenomena, speckle depends on three light parameters of the millimeter-wave laser beam—phase, wavelength, and angle of incidence—and can be reduced by the diversity of these three parameters. Diversity tools to improve images of concealed objects have been compared. We report measurements, simulations, and image reconstruction results over the whole W-band $(75–110\mathrm{GHz})$ and demonstrate where each tool works the best. Multiphase diversity is successful in reducing speckle contrast: multiangle to improve the image quality, and multispectral to recognize a small object’s features. A simple postprocessing eliminates the areas still covered by interference.

© 2008 Optical Society of America

Study of active millimeter-wave image speckle reduction by Hadamard phase pattern illumination

Gaetan Koers, Ilja Ocket, Qi Feng, Vahid Tavakol, Irina Jäger, Bart Nauwelaers, and Johan Stiens
J. Opt. Soc. Am. A 25(2) 312-317 (2008)

Multimode illumination for speckle reduction and angle neutrality in millimeter wave active imaging: range and time-resolved mode averaging

Mark A. Patrick, Colin D. Joye, and Frank C. De Lucia
J. Opt. Soc. Am. A 31(10) 2135-2141 (2014)

Elimination of speckle and target orientation requirements in millimeter-wave active imaging by modulated multimode mixing illumination

Mark A. Patrick, Jennifer A. Holt, Colin D. Joye, and Frank C. De Lucia
J. Opt. Soc. Am. A 29(12) 2643-2656 (2012)

Range resolved mode mixing in a large volume for the mitigation of speckle and strategic target orientation requirements in active millimeter-wave imaging

Mark A. Patrick, Jennifer A. Holt, Colin D. Joye, and Frank C. De Lucia
J. Opt. Soc. Am. A 32(4) 637-646 (2015)

Multispectral illumination and image processing techniques for active millimeter-wave concealed object detection

Lixiao Zhang, Johan Stiens, Amna Elhawil, and Roger Vounckx
Appl. Opt. 47(34) 6357-6365 (2008)