A compact, low-cost, passive MMW security scanner

We describe a low-cost passive millimeter wave (MMW) scanning camera for detecting concealed weapons and contraband. It is based on a focal plane array of 64 radiometric channels that employ MMICs operating at 94 GHz. Equipped with a 125 mm primary optic, the camera achieves a 26 x 26 degrees field of view by means of a rotating optic that performs 10 conical scans of the scene per second. The resulting 10 Hz rate images are of size 28 by 28, yielding a spatial resolution of 5 cm at a range of 1.6 meters from the camera. The radiometric sensitivity, at the maximum frame rate, is given by a median Delta T of under 3 Kelvin. With a size of 8 in. x 8 in. x 22 in. and a weight of 26 lbs., the camera is very compact and portable. This development may constitute the first affordable, commercially available passive MMW scanning camera. When operated at the slower frame rate of 1 Hz, the resulting time integration improves the image Delta T to less than 1 Kelvin, making the camera well suited for the detection of a wide variety of threats at security checkpoints. At finer camera sensitivity levels, the possibility arises of the exposure of anatomic details of the scanned subjects. In view of this, we have developed specialized display software that allows the presentation of the MMW scanning results in a manner that overcomes privacy concerns.