We're finally starting to see practical thermal imaging sensors (microbolometers) entering the consumer market. However, they are still vastly more expensive than comparable visible imaging sensors. 384x288 17µm pixel (i.e., 32mm2) thermal imagers with a fixed manual-focus lens run about $500, whereas $500 will get a 6000x4000 2µm pixel (i.e., 96mm2) CMOS sensor ... plus 5-axis sensor stabilization and a nice zoom lens.
My question: Are there physical constraints that would prevent large-scale production of thermal imagers from achieving price levels comparable to visible-light cameras?
I think there are two significant differences that need consideration: Sensors and lenses.
First is the sensor: Thermal imaging looks for radiation with wavelengths between 7-14µm, whereas visible light is in the range 0.4-0.7µm. Based on the physics alone, at the diffraction limit microbolometer pixels will have an order of magnitude greater surface area. Apparently commercial sensors are at the diffraction limit for both visible light (at 1 micron pixels) and thermal light (at 17 micron pixels). So, to make it fair, we would compare a 1" 24Mpx visible sensor with a 1" 300kpx thermal sensor. Microbolometers can be made from silicon using a CMOS process. Their structure looks a little trickier than state-of-the-art visible spectrum CMOS sensors, requiring a thermal bridge for each pixel as well as vacuum encapsulation of the sensor. But I know little of large-scale manufacturing processes, so are these variables significant in the limit on a per-unit basis? Update: This question now answered here.
Second is the lens: Thermal radiation requires lenses of different materials – typically silicon or germanium. Because of its longer wavelength, I would imagine thermal lens systems would be less sensitive to flaws than are visible optics, but maybe thermal attenuation is so high that it's just not possible to put a significant number of elements in front of the sensor, and maybe these lenses are intrinsically more expensive to manufacture?