Advances in eSWIR imaging

The eSWIR band of the electromagnetic spectrum, approximately (1.7 – 2.5) μm, lies beyond the upper range of traditional InGaAs SWIR imagers and below the cut-on wavelength of most commercially available MWIR cameras. Despite the combination of high atmospheric transmission and the ability to see through most commercial glasses, this waveband has been largely neglected due to the high costs associated with detectors optimized for this region. Offering a combination of both standard reflective image data and (high temperature) thermal data, the eSWIR region lends itself well to a range of novel surveillance applications which remain to be fully exploited. The advantages and disadvantages of mature detector materials are discussed along with a range of emerging detector technologies. In this paper we present performance characterization data from two state of the art detectors targeting this waveband, comparing and contrasting both their merits and limitations. The total dark noise measured for these sensors is dominated by dark current shot noise at higher FPA temperatures. The temperature dependence of dark current is presented for each sensor type, allowing a determination of the cooling required by each device to be made. Laboratory based test data is supplemented with real world images, demonstrating the powerful and unique capabilities of imaging within the eSWIR waveband.