Compact passive millimeter wave (PMMW) camera

A passive millimeter wave (PMMW) camera includes: a lens forming an entrance aperture for the camera, the lens configured to receive millimeter wave (MMW) radiation from a scene so as to form an image at its focus; a polarization beamsplitter positioned behind the lens, the polarization beamspiltter configured to substantially reflect only one polarization of the radiation, and to substantially pass through other polarizations without reflection; a twist reflector configured to receive the reflected radiation from the beamsplitter, and to reflect the MMW radiation back towards the beamsplitter, the twist reflector further configured to rotate the polarization of the incident MMW radiation by 90 degrees, the twist reflector further configured to swivel back and forth around an axle in a plane of the twist reflector so as to move the image back and forth; and a focal plane array (FPA) of millimeter wave receivers configured to receive the radiation passed through the beamsplitter after its polarization was rotated by the twist reflector.