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Lock-in thermography (LIT) is a non-destructive testing technique with a broad spectrum of applications, spanning from detection of manufacturing defects in industrial samples to early diagnosis of diseases in hard and soft tissues. Nevertheless, commercialization and wide-spread adaption of LIT has long been impeded by the cost (usually $10k-$100k) and size of infrared cameras. In this paper, we demonstrate that this cost and size limitation can be overcome using cell-phone attachment infrared cameras/sensors. Developed low-cost and portable LIT systems use an intensity-modulated near infrared light for illumination while detecting thermal signatures by the low-cost cellphone attachment infrared camera (Seek thermal compact; Android). While the nominal frame rate of camera is less than 9fps, we have deciphered the communication protocol and frame information structure of the camera and set up packets of information and send them to the camera’s default endpoint address and, subsequently, acquire frame data from camera through a corresponding pipe. As such, the developed platform can control camera attributes through a simple USB interface while achieving a stable high frame rate of 33fps. To demonstrate performance of developed low-cost and portable system, two types of LIT experiments were conducted: (i) in response to the recent legalizations of marijuana in Canada, we interrogated photothermal responses of commercially available oral fluid latral flow immunoassays (LFAs), demonstrating reliable detection of THC (the psychoactive substance of cannabis) at concentrations as low as 2 ng/ml. (ii) To demonstrate ability of the system in early detection of dental caries, artificially induced early caries were created on healthy enamel surfaces and imaged with the low cost and portable system at different stages of formation. Results, suggest ability of the system in detection of caries at very early stages when neither x-ray nor visual-tactile inspection can detect them. Both sets of experiments clearly demonstrate the promise of the developed low-cost and portable LIT system in producing reliable LIT images, paving the way for translation of this technology to industry.
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