Design of DTMS operational software for high-precision flatness measurement in cryogenic chamber

For giant telescopes using mosaic technology, the flatness of the Mosaic Focal Plane Arrays (MFPAs) is an important determinant of their image quality. In order to measure the flatness through the flat dewar window of cryogenic chamber, a measurement system called differential triangulation measurement system (DTMS) is designed. The DTMS mainly includes four parts: a displacement platform, two laser triangulation sensors, the connecting structure and an optical flat as reference surface. To operate DTMS, an operational software system is developed. The operational software consists of the control and processing software developed by QT, the displacement platform control module realized by PLC and the sensor control module. Through the operational software, users can easily operate the DTMS to scan the MFPAs and calculate the flatness. As for data processing, it is implemented based on the Progressive Sample Consensus (PROSAC) algorithm which can reduce the effect of anomalous data points on flatness calculation. The DTMS and its operational software have been used to measure the flatness of the Wide Field Survey Telescope (WFST).