The Effect of Viewing Angle on Detection of Landmines from Thermal Time Series Images Using Active Thermography

Abstract

Use of landmines in soils is a significant international threat facing the world today. There are no safe and highly reliable methods or inspection systems capable of detecting landmines in all situations. The use of infrared thermography is one of the promising methods for mine detection tasks. In infrared thermography, the investigation is done in either way: actively or passively. In this study, thermal signatures of the active infrared time difference images of buried mines and sand are investigated for different camera angles. It is aimed to find the effects of shot angles of the thermal camera on the performance of landmine detection. The experiments are performed at a sandbox emplaced in an indoor laboratory environment. A metal and a plastic antipersonnel mine are buried at 2 cm depth in sandbox. The sand surface is initially heated homogeneously by an infrared heater (2400 W) for 10 minutes on different days. During the cooling phase of the surface, a sequence of images are captured with an LWIR (8-12 µm band) camera (FLIR T 650 SC), which is 280 cm away from the detection area at different angles (90°, 60° and -60°). Images of the size of 480×640 pixels are taken at 15 seconds intervals during one hour. “Thermal signatures” of the buried mines and soil in three viewing angles are compared in MATLAB® environment. The results show that the locations of landmines are easily detected from the captured images during the cooling phase of the surface since observable differences develop between temperature signatures of landmines and sand, but the observation angle of camera has little effects on the detection performance. In addition, it is found that one hour measurement period is adequate for the detection of landmines at 2 cm depth in active thermography.

Keywords

• Landmine detection,Thermal infrared imagery,Active thermography

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