Infrared temperature measurement of slender irregular tubes by thermal image guided scanning

Abstract Accurate infrared temperature measurement of slender irregular tubes is a significant challenge due to alignment difficulties. The current study aims to overcome these challenges by developing an automatic measurement method based on thermal image-guided scanning. The temperature measurement device comprises a thermal-imaging camera and an infrared probe with their optical axes intersecting at the target. The device is assembled on a two-dimensional motion platform to form a system that can be used for automatic scanning and aiming. A mathematical model is established to describe the aiming position of the infrared probe in the coordinate system of the thermal-imaging camera. The internal parameters characterizing the optical system are calibrated offline, whereas the aiming point position is calibrated in situ . The axis of the tube in the thermal image is located using pixel resolution based on temperature symmetry. The aiming error is dynamically calculated when moving along the horizontal axis and used for the proportional integral derivative control of motion along the vertical axis. Experiments on a Φ = 3 × 800 mm tube show that the aiming errors are less than 0.3 mm, and the temperature measurement repeatability is approximately 1.5%.