<title>Near-infrared (NIR) emitter/detector probe for sensing buried objects and land mines</title>

Abstract

The detection of landmines and buried objects requires methods that can cover large areas rapidly while providing the required sensitivity to detect the optical and spectroscopic contrasts in soil properties that can reveal their presence. These conditions on contrast and coverage can be met by capturing images of the soil at wavelengths which are sensitive to the properties modified by the presence of buried objects. In this work we investigate both NIR scanning methods which may have some utility for the detection problem. For the scanning method, we acquire data point-by-point over a two- dimensional grid with a single emitter/detector probe. The soil (or sand) above a shallow buried object can be differentiated from the surrounding soil by detecting the difference in relative water content. Moist soil absorbs more near-infrared (NIR) incident light than dry soil. A light- emitting diode (LED) operating at 900 nm and a photodiode sensitive to NIR radiation formed the emitter/detector (ED) probe used in this study. The ED probe was mounted side-by- side and scanned over a surface in a two-dimensional grid as readings were collected point-by-point. The results indicated that this simple NIR emitter/detector probe discriminated between soils of varying water contents with an imaging resolution of 4 millimeters. To illustrate how imaging techniques can be used in this application, the fluorescence image of a landmine casing is presented. The results illustrate the potential of these two approaches for detection of landmines and buried objects.