Passive Euro-American Terahertz Camera (PEAT-CAM): Passive indoors THz imaging at video rates for security applications

摘要

The objective of this program is to demonstrate a system capable of passive indoors detection and identification of concealed threat items hidden underneath the clothing of non-cooperative subjects from a stand-off distance of several meters. To meet this difficult task, we are constructing an imaging system utilising superconducting ultrawideband antenna-coupled microbolometers, coupled to innovative room temperature read-out electronics, and operated within a cryogen-free pulse tube refrigerator. Previously, we have demonstrated that these devices are capable of a Noise Equivalent Temperature Difference (NETD) of 125 mK over a pre-detection bandwidth from 0.2-1 THz using a postdetection integration time of 30 ms. Further improvements on our devices are reducing this number to a few tens of mK. Such an exquisite sensitivity is necessary in order to achieve the undoubtedly stringent requirements for low false positive alarm rate combined with high probability of detection dictated by the application. Our technological approach allows for excellent per frame NETD (objective 0.5 K or below at 30 Hz frame rate), and is also amenable to multispectral (colour) imagery that enhances the discrimination of innocuous objects against real threats. In the paper we present results obtained with an 8-pixel subarray from our linear array of 128 pixels constructed using a modular approach. Two-dimensional imaging will be achieved by the use of conical scanning.