The Spatial Resolution Enhancement for a Thermogram Enabled by Controlled Subpixel Movements

Abstract

The measurement accuracy and reliability of thermography are largely limited by a relatively low spatial resolution of the thermal imager. Using a high-end camera to achieve high spatial resolution can be expensive or infeasible as a high sample rate is required. Furthermore, system miniaturization becomes an inevitable trend with the continuous development of the Internet of Things (IoT) and their suitability to in situ inspection scenarios. However, a miniaturized sensor usually suffers from low spatial resolution. Addressing this challenge, this article reports a novel spatial resolution enhancement for a thermogram (SRE4T) system to significantly improve the spatial resolution without upgrading the sensor. A high-resolution (HR) thermal image is reconstructed by fusing a sequence of low-resolution (LR) images with subpixel movements. To achieve the best image quality, instead of benefiting from natural movements of the existing studies, this article proposes to use an HR xy translation stage to produce a sequence of controlled subpixel movements. The performance of the proposed system was tested on both high-end and low-end thermal imagers. Both visual and quantitative results successfully demonstrated the considerable improvement of the quality of thermal images [up to 30.5% improvement of the peak signal-to-noise ratio (PSNR)]. This technique allows improving the measurement accuracy of thermography inspection without upgrading sensors. It also has potential to be applied on other imaging systems.