Quantitative thermal imaging using single-pixel Si APD and MEMS mirror

Accurate quantitative temperature measurements are difficult to achieve using focal-plane array sensors. This is due to reflections inside the instrument and the difficulty of calibrating a matrix of pixels as identical radiation thermometers. Size-of-source effect (SSE), which is the dependence of an infrared temperature measurement on the area surrounding the target area, is a major contributor to this problem and cannot be reduced using glare stops. Measurements are affected by power received from outside the field-of-view (FOV), leading to increased measurement uncertainty. In this work, we present a micromechanical systems (MEMS) mirror based scanning thermal imaging camera with reduced measurement uncertainty compared to focal-plane array based systems. We demonstrate our flexible imaging approach using a Si avalanche photodiode (APD), which utilises high internal gain to enable the measurement of lower target temperatures with an effective wavelength of 1 µm and compare results with a Si photodiode. We compare measurements from our APD thermal imaging instrument against a commercial bolometer based focal-plane array camera. Our scanning approach results in a reduction in SSE related temperature error by 66 °C for the measurement of a spatially uniform 800 °C target when the target aperture diameter is increased from 10 to 20 mm. We also find that our APD instrument is capable of measuring target temperatures below 700 °C, over these near infrared wavelengths, with D* related measurement uncertainty of ± 0.5 °C

Evaluation of High Resolution Thermal Imaging to Determine the Effect of Vertebral Fractures on Associated Skin Surface Temperature in Children with Osteogenesis Imperfecta

Vertebral fractures are common in children with osteogenesis imperfecta (OI). Current imaging methods for fracture detection (X-ray and DXA) use ionising radiation. This pilot study explored whether the alteration in blood flow in vertebral fractures results in skin temperature changes that may be detected using high resolution thermal imaging (HRTI) and thus assist diagnosis and monitoring of fractures in OI patients. Eleven participants aged 5-18 years with OI and known vertebral fractures were enrolled. Small metal discs were placed on the skin surface alongside the vertebrae before participants had DXA and X-ray scans and thermal imaging of their backs. Visibility of the discs on the DXA and X-ray scans and thermal images allowed the temperatures of the skin surface above vertebrae without (healthy) and with fractures to be compared to their respective adjacent skin surface regions (Region of Reference, ROR) by calculating the temperature percentage change (TPC). The TPC between the skin temperature over the fractured thoracic vertebrae (n=11) and the ROR was significant (1.44%, p=0.002, 95% confidence). TPC between the skin temperature over healthy thoracic vertebrae and ROR was not (0.97%, p=0.15, 95% confidence). HRTI may provide a novel tool for assisting in detection of vertebral fractures in OI. Keywords: Computerised medical diagnosis, thermal imaging, vertebral fracture detection, osteogenesis imperfecta

Detecting hot spots in photovoltaic panels using low-cost thermal cameras

One of the most important challenges to mitigate global climate change is to move towards replacing petroleum-based energy sources. In this idea, non-conventional renewable energy sources such as photovoltaic (PV) solar and wind power are the most used worldwide. In the case of the massification of PV solar generation systems due to its low cost, it has resulted in the use of large-scale supervision techniques that allow a quick and effective determination of the health status of its main components. This study, performs an analysis of the performance of different low-cost cameras for thermography. The analysis compares the accuracy of the thermal images obtained and the error is quantified by means of an image dispersion analysis in each of them. Three-dimensional meshes and contours figures are also made to determine the temperature of a faulty cell. The study shows that the performance obtained with low-cost cameras presents errors below 10% in costs and less than 0.015 USD/pixel. © Springer Nature Switzerland AG 2020.One of the most important challenges to mitigate global climate change is to move towards replacing petroleum-based energy sources. In this idea, non-conventional renewable energy sources such as photovoltaic (PV) solar and wind power are the most used worldwide. In the case of the massification of PV solar generation systems due to its low cost, it has resulted in the use of large-scale supervision techniques that allow a quick and effective determination of the health status of its main components. This study, performs an analysis of the performance of different low-cost cameras for thermography. The analysis compares the accuracy of the thermal images obtained and the error is quantified by means of an image dispersion analysis in each of them. Three-dimensional meshes and contours figures are also made to determine the temperature of a faulty cell. The study shows that the performance obtained with low-cost cameras presents errors below 10% in costs and less than 0.015 USD/pixel. © Springer Nature Switzerland AG 2020.Sori