A commercial device was more recently introduced, i.e., the thermal boroscope Vividia (by Oasis Scientific), which has a flexible arm with diameter of 17mm or 18.5mm mounting LWIR sensors of 80圆0 or 160x120 pixel, respectively. When developing our project since 2016, ,, the state-of-the-art technology did not report imaging devices for endoscopic thermography. Recent advances in sensor technology has lead to the availability of small and cost-effective LWIR camera cores, mounting uncooled microbolometers, allowing researchers to prototype thermal vision systems tailored to very peculiar applications and specific environments, such as the endoscopic thermal inspection proposed in this paper. The thermal cameras available on the market include portable medium-sized devices for on field measurements, up to more recent and compact devices suitable for machine vision and drone applications. For measuring objects around room temperature ( ∼ 300 K), uncooled Long Wave Infrared (LWIR) sensors with spectral sensitivity in the range from 8 μm to 15 μm are typically used.
A thermal camera, therefore, is a calibrated device that provides, in non-contact way, a 2D map of the temperature field on the object surface. The technique is based on the use of proper imaging systems for the acquisition of the thermal radiation that every body at a given temperature emits from this radiation, knowing the thermal emissivity, it is possible to calculate the temperature of the body. Infrared (IR) thermography is an important nondestructive technique with applications in different fields, ranging from engineering to industry, from bio-medicine to emergency relief, up to heritage conservation, as extensively reviewed in, ,.
The thermal endoscope was designed with dimensions also compatible for robotic-assisted/traditional minimally-invasive surgery. In general, the device enables to perform thermography in applications in which traditional larger equipment cannot be employed, as nondestructive diagnostics in confined space in the engineering field. The Infrared Vision Software is provided for controlling the acquisition of thermal frames, and for the thermographic calculation of the object temperature from the input parameters on object surface emissivity and environment. The thermal endoscope unit is controlled by a Raspberry external unit. Two PCBs were developed for assembling the endoscope in two different schemes, to enable frontal or lateral thermal vision setup. The sensor and the PCB can be inserted into a cylindrical protective case of diameter down to 15mm, inox tube or plastic, 3D printable envelope, with an optical window in Germanium. The implementation of a thermal endoscope based on the LWIR camera cores Lepton and a custom miniaturized electronics is reported.
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