In this paper a simplified "1.5D" modeling approach is presented which can be used to characterize and optimize an
entire active millimeter wave imaging system for concealed weapon detection. The method uses Huygens' Principle to
compute one field component on selected planes of the imaging set-up. The accuracy of the method is evaluated by
comparing it to a rigorous 2D method of moments approach. The model includes the effects of lenses, diffusers, mirrors,
object and any other component present in the system. The approach allows fast determination of the influence of each
of the system components on the image projected onto the sensor, including effects such e.g. speckle. Also, the
effectivity of different speckle reduction techniques, e.g. using a Hadamard diffuser or a multifrequency approach are
evaluated in this paper.