Thermal error analysis and compensation of a LED-CMOS camera 3D measuring system

Photogrammetry measuring systems using LED targets and CCD/CMOS cameras are gaining application in industry. Compared with conventional CMMs (coordinate measuring machines), they are easily portable, versatile and convenient to use. Like most precise measuring devices, these camera systems also suffer from performance degradation when temperature deviates from standard condition. This paper introduces research work performed on a twin-camera 3D measuring system regarding its measurement performance during environment temperature fluctuations. An artefact is developed to provide stable reference for drift identification and performance verification. This artefact is used together with temperature sensors to study the thermal drift behaviours of the camera system. A thermal drift model is built to calculate and compensate the thermal drifts. After compensation, the thermal drifts (of 3D length measurements) are reduced to approximately 30% of their original sizes in a temperature range of 9 centigrade (16.5 ̊C ~ 25.5 ̊C), which enables the measuring system to work with enhanced performance under typical industrial environments.