Single Detector Assemblies and Small Arrays

Today's infrared (IR) and visible sensors are used in two general configurations. One configuration, focal plane arrays (FPAs), includes thousands or millions of elements, accessed through a readout‐integrated circuit (ROIC). The other configuration includes single detectors and arrays of a few elements often 1, 2, or 4, or perhaps as many as 16 or even 64. This chapter refers to these as “single detector assemblies” with the understanding that they may include more than one element. It outlines the commonly used detector types for single detector assemblies, along with some common applications for each detector type. Fourier‐Transform IR (FTIR) spectrometers detect the emissions from target materials and use a scanned mirror to cause a time‐varying signal. The basic test for any IR detector includes measurement of the output and noise, as well as the calculations of responsivity and the composite figures of merit: noise‐equivalent irradiance (NEI) and noise‐equivalent power (NEP).