The Science Behind Thermal Imaging
Thermal imaging cameras convert heat energy into an electrical signal that is used to create a visible image of an object or scene. Such cameras take temperature measurement to the next level; instead of a number, you get a visual representation of the temperature over a surface in the image. If the sensor is capable, you can even get radiometrically accurate temperatures with variation below 30 millikelvins.
If you have any sort of motion detector, it is likely using a sensor called a thermopile that can detect infrared (IR). Anything that is warmer than its surroundings can be “seen” by the IR emission from its heat dissipation. Think of the movie "Predator" and the scenes from the alien’s perspective. Our interest is in consumer facing applications, so we will neglect the high-end scientific sensors and cameras, as apparently only aliens can afford those.
At the simplest end of the thermal imaging spectrum is the single thermopile. A thermopile is a parallel connected stack of thermocouples. When infrared radiation strikes the surface of a thermopile, it is absorbed and converted into heat, which creates a voltage in the thermocouples. The voltage output is proportional to the amount of incident infrared radiation.
This output is used by the detector to calculate the temperature, which can be displayed on the screen of an IR thermometer like one would see at the doctor. The output can also be used to simply detect warm objects. Thermopiles are frequently used in standard motion sensors to detect movement. To create something as complex as an image, however, an array of thermopiles is necessary.
At the upper (alien) end of thermal imaging are cameras made from microbolometer arrays. A microbolometer is a particular kind of heat detecting sensor element. The detector material is heated by infrared radiation with wavelengths between 7.5 and 14 um, which changes its electrical resistance. This change in resistance is monitored and converted into temperatures, which can then be used to form an image.
Microbolometers, unlike the types of infrared detecting components used in expensive scientific equipment, do not require cooling. Microbolometer array thermal cameras are generally expensive, and have limited temperature measurement capabilities, making them inappropriate for large-scale consumer adoption.
How Calumino is Bringing Thermal Imaging to Consumer Applications
For thermal imaging cameras to be effective and accessible in high volume consumer applications, the sensors must perform better than low-end thermopile arrays, and they must be significantly less expensive than high-end microbolometer arrays. The physics of the detection makes this a difficult target to hit.
Calumino has created a unique and patented technology that is comparable (or better in some cases) in performance to microbolometers at the price point of thermopiles. Their products and systems are based on coupling a standard CMOS image sensor with a novel MEMS micro mirror array invented by founder and CEO, Marek Steffanson. The company is currently shipping low resolution cameras for use in occupancy and security applications. These cameras come with unique advantages for movement monitoring with computer vision and machine learning that can track and identify subjects while maintaining identity privacy. These cameras are capable of better stability and accuracy than typical microbolometer thermal cameras without requiring calibration in the field.
Effective and accessible thermal imaging can truly help people, and Calumino is making that transition possible. From COVID-19 frontline safety solutions in healthcare to building maintenance and smart buildings, affordable thermal imaging and detection can transform businesses and make the world safer.