A solid-state hyperspectral imager for real-time standoff explosives detection using shortwave infrared imaging

Abstract

We present a new and innovative shortwave infrared (SWIR) hyperspectral imaging focal plane array (FPA) concept for bulk and trace standoff explosives detection. The proposed technology combines conventional uncooled InGaAs based SWIR imaging with the wavelength selectivity of a monolithically integrated solid-state Fabry-Perot interferometer. Each pixel of the array consists of a group of sub-pixels in which each sub-pixel is tuned to absorb a separate wavelength. The relative responses from the sub-pixels (i.e. wavelengths) are compared to the spectral characteristics of explosives in the SWIR to detect and locate them within an imaged scene among various background materials. The novel technology will be compact, and consume low power such that it can be used as a handheld device or mounted for persistent surveillance of crowded areas and checkpoints. The technology does not use any scanning nor tuning apparatuses such as MEMS devices, and is therefore fast, compact, lightweight and not susceptible to vibration. The technology is therefore ideal for man portable applications and unmanned vehicle platforms. An eyesafe (covert) illuminator may be used to provide illumination in situations when ambient light conditions are not sufficient. We will present a detailed design of the novel focal plane array and a theoretical standoff distance and false rates study.

Sensors and Systems for the Detection of Explosive Devices - An Overview

“…The main factors determining the signal power are the following ones: mean power of laser radiation, efficiency of the radiation interaction with the matter, solid angle within the scattered radiation, and efficiency of the receiving optics and electronics. As shown in literature [60,61], the standoff optical methods have quite high sensitivity detecting low amounts of chemical substances.…”

“…DIAL lasers transmit into the atmosphere pulses of radiation at two wavelengths: one of which is absorbed by the gas to be measured and one is not. The difference between the return signals from atmospheric backscattering on the absorbed and non-absorbed wavelengths is used as a direct measure of the concentration of the absorbing species [61]. Sometimes a differential reflectance lidar is used.…”

Active spectral imaging for standoff detection of explosives

“…To implement the SI technology, Onat et al [34] proposed an original unified solid monolithic sensor, composed of an uncooled InGaAs photodetector array, a solid Fabry - Perot interferometer, and an integrated circuit for reading and processing signals from sensitive elements. Each element (pixel) of the photodetector array is a group of subpixels, and each subpixel is tuned to absorb radiation at a certain wavelength.…”

“…The approach to remote detection of explosive traces based on the SI technique, which was developed in [34,52], differs from those described above and is based on measuring the reflectance of explosives in the eye-safe wavelength range of 1500 - 1800 nm, which falls in one of the transparency windows of atmosphere. In this spectral range the reflected IR radiation dominates over thermal radiation; therefore, the contrast of separate regions of an object will be determined by the changes in its optical properties in the aforementioned range.…”

Towards optoelectronic detection of explosives

“…The interaction yields an optical response, which is collected by an optical receiver. As were described in li− teratures the standoff optical methods deliver the sensi− tivities reaching even the ppb level [56][57][58].…”