Abstract
Lock-in thermography (LIT) is a thermal-wave-based, non-destructive testing, technique which has been widely utilized in research settings for characterization and evaluation of biological and industrial materials. However, despite promising research outcomes, the wide spread adaptation of LIT in industry, and its commercialization, is hindered by the high cost of the infrared cameras used in the LIT setups. In this paper, we report on the feasibility of using inexpensive cellphone attachment infrared cameras for performing LIT. While the cost of such cameras is over two orders of magnitude less than their research-grade counterparts, our experimental results on block sample with subsurface defects and tooth with early dental caries suggest that acceptable performance can be achieved through careful instrumentation and implementation of proper data acquisition and image processing steps. We anticipate this study to pave the way for development of low-cost thermography systems and their commercialization as inexpensive tools for non-destructive testing of industrial samples as well as affordable clinical devices for diagnostic imaging of biological tissues.
Highlights
Lock-in thermography (LIT) is a non-destructive testing (NDT) technique that is widely used in research settings for characterization and evaluation of materials
In existing industry standard, infrared cameras are offered in three distinct spectral ranges: Short- Wavelength InfraRed (SWIR: 1.4–3 μm), Mid- Wavelength InfraRed (MWIR: 3–8 μm), and Long- Wavelength InfraRed (LWIR: 8–15 μm)
The sensor core of research grade MWIR and LWIR cameras are usually made from Indium Antimonide (InSb) and Mercury Cadmium Telluride (MCT), respectively, and are actively cooled with an expensive and bulky internal sterling cooling mechanism to achieve minimal noise equivalent temperature difference (NETD usually better than 25mK)
Summary
Lock-in thermography (LIT) is a non-destructive testing (NDT) technique that is widely used in research settings for characterization and evaluation of materials. While the cost of these cameras can be as low as $200, their NETD can be as poor as 150mK and frame rates as low as 9Hz. In this study, we have characterized the performance of these inexpensive cellphone attachment infrared cameras and have demonstrated the feasibility of using them for lock-in thermography investigation of biological and non-biological samples.
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