Netsu Sokutei, 41 (4), p. 148, (2014)


Thermal Imaging, a Potential Method for Microscale Quantitative Thermal Analysis – On Occasion of the 50th Anniversary of JCCTA Meeting –

Infrared (IR) cameras have been used to visualize the thermal image in IR wavelength. IR sensors are assembledinto focal–plane arrays (FPAs) and categorized in the photon (InSb, MCT) and thermal (pyroelectric or ferroelectriccrystals, amorphous silicon, VOx) detectors. The photon detectors are superior in speed and sensitivity in thermal andlong IR wavelength (LWIR), and microscale thermography has been usually operated with InSb detectors combinedwith the optical lens design optimized for 3 micro-m to 5 micro-m wavelengths. However, the photon detector must be cooled byliquid nitrogen or a Stirling cycle cooler in order to get the high-quality image with high sensitivity and low noise. It iscostly, and a cooling device takes a space. Recently, the performance of thermal detectors, as called micro-bolometers,has been developed with a smaller pixel pitch and larger pixel numbers of FPA, obtaining Noise EquivalentTemperature Difference (NETD) 50 mK and pixel size 17 micro-m, with reducing the cost. It is attractive to the micro-scalethermography, if the time response is improved, and the micro-lens is optimized for the wavelength ofmicro-bolometers, to realize a concept of a common and wide use apparatus for a high-quality thermal imaging. Inorder to realize the mobile type quantitative microscale thermography apparatus using a micro-bolometer, thefollowing idea is proposed; an achromatic lens design for a micro-scale image, a video signal superimposed for the realtime emissivity correction, and a pseudo acceleration of a timeframe. The total size of the instrument is designed as itis put in the 17 cm x 28 cm x 26 cm size carrying box. We have developed a quantitative microscale thermal imagingsystem that can be used as a portable instrument. Our apparatus has the potential to improve the spatial and timeresolutions of uncooled IR cameras. We are now planning to make our instrument design for the general purposes inthermal characterization of materials, with energy transport and storage applications. We are targeting spectroscopicand 3D thermal imaging for the next generation of our technology.