High-speed identification of trace chemicals on conveyor-driven parcels

Abstract

A standoff trace chemical detection system (TCD) based on LWIR hyperspectral imaging has been developed to detect and identify a wide range of trace chemicals on a variety of shipping-related materials and surfaces. The system is able to perform the detection on a continuous stream of parcels as they move along a conveyor at speeds up to 400 ft/minute. Optical illumination is provided by miniature, widely tunable external-cavity quantum cascade lasers (EC-QCLs) and the reflected light is captured using a high-speed HgCdTe camera. The acquired images are combined into a hyperspectral image cube (i.e., hypercube) by taking into account the velocity of the parcels. The system was mounted on a gantry looking down onto the parcels. A motorized camera lens with fast focusing of <0.1 s enabled the system to focus on the top surface of each parcel. The resulting hypercubes were then analyzed using efficient image segmentation and detection algorithms to identify and map the trace surface chemicals. Applications include the detection of trace amounts of explosives and opioids on parcels in shipping, sorting, and customs screening scenarios.