Comparison of speckle reduction diversity tools for active millimeter-wave imaging.

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.

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

Active millimeter-wave images typically exhibit characteristic speckle noise, due to the coherence of artificial millimeter-wave sources. We study the Hadamard speckle contrast reduction (SCR) technique, which has been successfully used in laser projection systems, in the context of millimeter-wave imaging. We show the impact of Hadamard pattern order and size and of image and pattern resolution on speckle reduction efficiency.