Tech Trends: Thermal Imagers Feeling the Shrink

Nearly everything about infrared is decreasing — including size and, most importantly, cost


In the last several years, thermal imaging cameras have become mainstream, finding their way into several front-line manufacturers’ IP camera offerings. At the Association for Unmanned Vehicle Systems International Conference in August, FLIR revealed a prototype camera small enough to fit into a smartphone — further proof that the technology is normalizing in the security and consumer markets.

It probably won’t stop there — as FLIR CEO Andy Teich explains, the evolution of thermal imaging parallels GPS, following a cost and adoption curve that began with the military, proceeded through dual military-commercial use, followed by broad commercial use, and, eventually commoditization.

Teich says thermal has now entered the broad commercial use phase and expects continuing adoption: “Our mantra is ‘Infrared Everywhere,’” Teich says, “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.”

 

Charting the Thermal Evolution
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 applications where IR illuminators 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 μm — 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 that can 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 called a microbolometer, a detector based on micro-electromechanical (MEMS) technology that detects changes in temperature caused by the incoming 8 – 12 μm heat radiation which affects its electrical resistance. Importantly, the device requires no external cooling to create useful sensitivity. Back in 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.

 

Innovation Lowers Costs
We are now seeing the price decrease in the market in a now-familiar pattern — military-based technology meets consumer-driven costs. New families of lower-cost camera cores are opening the door to new products and affordable applications.

The 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 Noise Equivalent Temperature Difference (NETD) of < 50 mK. NETD is the common measure of sensitivity for these devices, where a change of one degree K is equal to a one-degree C differential. The THC-36 camera manufactured by Zistos (www.zistos.com) employs the FLIR Quark. 

That these new imaging devices are small, low-power and less expensive does not mean that high performance sensing systems will shun them; in fact, adoption will continue in Unmanned Aerial Vehicle (UAV) areas, the battlefield and other defense and security applications, while broader commercial applications become more apparent. “(The technology is) not yet cheap enough to become ubiquitous, but it will get there,” Teich says.

Speaking of getting there, passive IR technology is becoming available for the masses, as we are beginning to see in various blog pages and early-stage company offerings. MikroSens (www.mikrosens.com.tr) has developed a QCIF (160x120) infrared sensor with NETD < 280 mK and USB output. Mμ Optics (www.muoptics.com) launched in January with plans to sell a similar imaging device. 

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