Land mines, and other buried explosive devices, are widely deployed all over the world. As such, they pose a significant threat to dismounted soldiers, vehicles, and civilians. Land mines inhibit the safe movement of troops and produce chaos in countries struggling for socio-economic stability long after the cessation of hostilities. Consequently, there has been much investigation into how buried explosives might be detected and safely neutralized. Many different electro-optical and radar sensor systems have been considered for the detection of buried land mines. These include ground penetrating radars, polarization detectors, and visible/thermal infrared (IR) imagers. This paper will describe the efforts to develop a near IR/LWIR mine detection system. The core of the discussion will include highlights of a two-color LWIR QWIP sensor system designed to provide uniform, high spatial resolution, multi-color co-registered imagery and possess negligible spectral cross-talk. The current developments have been sponsored by the Defense Advanced Research Projects Agency (DARPA) for developing a visible/infrared mine detection system, which when deployed on a TUAV would increase the war fighting effectiveness of any rapid deployment force by facilitating ground penetration into hostile territory.
With increased requirements for better performance being placed on thermal imaging systems, new characterization figures of merit are being developed to assess infrared focal plane array (IRFPA) attributes. Post correction uniformity (PCU) is a parameter that determines how successfully a thermal imaging system can eliminate spatial noise from scanning and staring focal plane arrays. Requirements on PCU, particularly for the more sensitive IRFPAs and applications, are quite rigorous. Test issues of l/f noise, drift, and repeatability become critical and require a rethinking of accepted methods. As infrared sensors have become more sensitive, the need to characterize these focal plane arrays under more controlled and realistic test conditions has emerged. The U.S. Army Night Vision and Electronic SEnsors Directorate (NVESD) has attempted to address these issues by developing a unique capability to measure the PCU of IR focal plane arrays using software algorithms and a specialized mechanical modulator. The modulator is a two foot diameter, two toothed (one reflective and one emissive) blade, which is used to facilitate the real-time collection of test, gain, and offset flux levels. This paper addresses (1) the significance of PCU from a system perspective, (2) discuss the limitations of various PCU measurement techniques, (3) present the NVESD approach for measuring PCU, and (4) report PCU data collected using these techniques.
A new concept, the Direct Schottky Injection (DSI), is described for a three-dimensional construction of infrared imagers with a continuous Schottky-barrier-detector surface on one side of a thinned (10 to 25 microns) silicon substrate and p-type buried-channel CCD readout structure on the other side. The DSI structure provides a 100-percent fill factor, a large charge-handling capacity, and a high-density pixel design. The construction and operation are described for DSI imagers with frame-transfer CCD (FT-CCD) and interline-transfer CCD(IT-CCD) readout. The operation of the IT-CCD DSI imager was demonstrated with a 128 x 128 focal plane array (FPA) with 50 x 50-micron pixels.