Tech Trends: Thermal Imagers: Shrink Wrapped

Thermal imaging is based on heat sensing from a surveillance target

In the last several years, thermal imaging cameras have gone main stream, finding their way into several front-line manufacturers’ IP camera offerings.

Thermal imaging is based on heat sensing from a surveillance target, where feature discrimination is based on temperature differences and does not rely on external source lighting. This is known as passive IR, in contrast to those situations which employ IR illuminators to enhance the low light performance of standard monochrome or day/night cameras. The technology has its roots in military applications, where IR seekers and imagers have been used in weapons and reconnaissance systems. Most passive IR systems, including PIR intrusion sensors, work in the long wavelength IR (LWIR) range of 8 - 14 m, far out of the visible range. A significant advantage of passive IR in this range is that elements in the atmosphere, such as fog or smoke, which obscure or block visibility in the visible and the near IR bands, are almost transparent to LWIR.

The increasing commercialization of thermal imagers has been made possible by developments in a device with an odd-sounding name. The microbolometer, a detector based on micro-electromechanical (MEMS) technology, detects changes in temperature caused by the incoming 8 – 12 m heat radiation which affects its electrical resistance. Importantly, the device requires no external cooling to create useful sensitivity. In January 2011, I wrote that the increasing use of silicon in these imagers, coupled with advancements in packaging, would lead to less expensive, more compact optics and cameras. We are now seeing this in the market in a now familiar pattern - military-based technology and consumer driven costs. New families of lower cost camera cores are opening the door to new products and affordable applications.

At the Association for Unmanned Vehicle Systems International Conference in August, FLIR Corporation revealed a prototype camera small enough to fit into a smartphone. FLIR has been a major supplier of infrared equipment to the military and security market for years, so it’s interesting that they’ve revealed a smartphone application. But, as CEO Andy Teich explained, FLIR sees a parallel between IR and GPS, following a cost and adoption curve beginning with military, proceeding through dual military-commercial use, followed by broad commercial use, and, eventually commoditization. He maintains that we have now entered the broad commercial use phase and expects continuing adoption of thermal imaging. “Our mantra is ‘Infrared Everywhere’”, Teich said, “and we really view infrared becoming the sixth sense for human activity to ‘see’ what’s out there in ways the human eye can’t.” The new FLIR Quark core measures just three-quarters of an inch thick (7.5 cc volume), comes in resolutions from 80 - 640 lines (0.3 megapixels, dissipates about .7 Watt and has a NEDT <50 mK. Noise Equivalent Temperature Difference (NEDT) is the common measure of sensitivity for these devices, where a change of 1o K is equal to a 1o C differential. That these new imaging devices are small, low-power, and less expensive does not mean that high performance sensing systems will shun them. These adoption will continue in Unmanned Aerial Vehicle (UAV), battlefield, and other defense and security applications, while broader commercial applications become more apparent. As Teich admits, the technology is “not yet cheap enough to become ubiquitous, but it will get there.”

This content continues onto the next page...