Continued reduction of α-Si bolometer pixel size has led to increases in array size as well as improvements in temporal response for a given level of sensitivity. Programs funded by DARPA and NVESD are developing advanced 320×240, 640×480 and 1024×768 α-Si bolometer arrays with 17μm pixels, on-chip A/D conversion, significant improvements in dynamic range, significant reductions in thermal time constant and other specialized functions. The push to 17μm is motivated not only by system size and weight, but also by improvements in performance resulting from increased resolution. Smaller pixels permit fabrication of larger arrays without subverting the field-size constraints of ordinary photolithographic processes. Reducing pixel size also reduces the effects of stress mismatches. This permits reduction of device thickness, thereby reducing thermal time constant. Improvements in bolometer material properties have served to improve responsivity while lowering 1/f noise. Because these arrays substantially reduce sensor size, they are becoming the preferred format for most applications, particularly for weapon sights and for head-mounted and UAV applications. The larger array sizes are of interest for pilotage and surveillance.