IMAGE RECONSTRUCTION BY MEANS OF KALMAN FILTERING IN PASSIVE MILLIMETRE-WAVE IMAGING

Passive millimetre-wave (PMMW) imaging is a technique that detects thermal radiation emitted and reflected by metallic and non-metallic objects. While visual and infra-red (IR) emissions are attenuated by atmospheric constituents, PMMW emissions are transmitted, resulting in consistent contrast between objects from day to night even in low-visibility conditions. The use of a PMMW imaging system on an unmanned aerial vehicle (UAV) has applications for airborne surveillance, but the size of the UAV precludes optical or mechanical scanning. One solution is a long, thin antenna fitted under the UAV. This antenna has a narrow beam along the plane perpendicular to the flight path, but a broad beam along the plane of the flight path blurs the image, making it difficult to determine the position of objects or to differentiate between objects. This paper proposes a technique of image reconstruction based on the Kalman filter to reconstruct an accurate image of the target area from such a detected signal. It is shown that given a simulated target area, the Kalman filter is able to reconstruct the image using the measured antenna pattern to model the scanning process and reverse the blurring effect.