Image: Finney County in Southwestern Kansas is now irrigated cropland where once there was short grass prairie. NASA IR image with false color. Photograph Credit: NASA/GSFC/METI/Japan Space Systems, and U.S./Japan ASTER Science Team
Current Uses of Thermal Analysis Devices
One of the benefits of our space program (apart from TANG®) has been the development of Infrared Detector Technology (IR). Various thermal analysis cameras that can see from the near IR (around 800-1200 nm) to far IR (8-12 um) depending on their detector technologies have been a part of many public and not so public satellite programs that observe everything from crops, to images of your city, to Homeland Security-related stuff for decades.
The government has pumped money into IR sensor technology through various agencies and we all get to benefit as the results get to market. We can’t get our hands on the super-secret defense cameras yet, but there are some cool new things coming to Amazon real soon. Thermal analysis cameras will soon be available for purchase by consumers.
My Work With IR Cameras
I have worked on IR microscopy and thermal imaging systems and analysis for years in order to see into the workings of semiconductor devices. The systems I have worked on are complex combinations of high-accuracy motion systems, specialized optics such as Solid Immersion Lens (SIL) technology, and in the case of the most recent system, I architected a full wafer-level prober integrated with the diagnostic tool so that testing could be done at the wafer level.
Those interested in that system can see a paper I presented at the IEEE Semiconductor Wafer Test Workshop in 2012:
It turns out that silicon is largely transparent (depending on doping) to near IR wavelengths. This allows for some really interesting diagnostic opportunities. If you could see in the near infrared region and looked at the backside of a chip as it operates you would see what looks like a cityscape at night from space and depending on the magnification of the optics you could see all the way down to a single transistor blinking as it switches. Such transitions are visible because as a transistor switches it passes briefly through its linear region and emits a few photons of IR energy.
Static, bright spots can be heat signatures from power dissipation like shorts or heavy current draws. Blinking spots result from the ON-OFF-ON transitions of flip-flops as each transistor slides briefly through its linear region on its way to a stable state. With the right magnification optics it is possible to zoom in on individual cells and look for logic faults, stuck-at faults and crosstalk effects that result from subtle design rule violations. If a system adds an IR laser, it can stimulate the circuitry and then changes in operating behavior can be seen. The world of semiconductor failure analysis (FA) owes a lot to these systems.
The heart of all these systems, from diagnosing bad ICs to seeing bad guys at night from space is the IR camera. They have always been very expensive (our system camera is in the 10’s of thousands of dollars) and in order to get decent S/N on the image they typically need to be cooled. The best such cameras have traditionally used liquid nitrogen to get the sensor down to around 70K. One of the big names in IR sensor camera technology in the U.S. is Raytheon.
IR Imaging Comes to Consumers
According to a recent journal publication from Raytheon http://www.raytheon.com/newsroom/technology_today/2014_i1/nextgen.html, new breeds of IR sensors that do not require cooling are becoming available. Although sensors from Raytheon have traditionally been produced in very expensive, and very low quantities, Raytheon has partnered with Freescale Semiconductor to make these devices in mass quantities.
This means that the consumer can have a useful, lowcost thermal imaging camera system. Just this week, Seek Thermal http://www.obtainthermal.com, a Santa Barbara-based startup made a $199 IR Camera/Sensor accessory for smartphones available for purchase. Their website illustrates some intriguing applications for the camera in a consumer environment.
Specialized, high cost IR camera systems will continue to have a place in industry. When you need to see individual photons and resolve spots down to the sub-micron level, only the most cutting edge camera will do. For those of us in the industrial world, we can complete the circle by thinking of things to do with a really low cost IR camera in the factory. For the price of one so-called industrial camera you can perhaps network 20 or so cheap ones and get better results. Personally, I have a few ideas that I plan to pursue. Stay tuned.