Metrology of large optical components at sub-nanometric level accuracy

Abstract:

Next-generation synchrotron beamlines and coronagraphs rely on improved optical systems, particularly those with optics of superior surface quality. Because metrology is essential to producing such optics, this thesis aims to improve their fabrication by investigating the limitations of the Long Trace Profiler (LTP), a deflectometer capable of nanoradian-level accuracy. Through a combination of experiments, analytical modelling, and full 3D optical simulations, the work evaluates multiple LTP configurations, examines challenges in measuring sideways- and downward-facing optics, identifies some of the major error sources—such as height biases from sensor defocus and aberrations in the Fourier Transform lens—and demonstrates how techniques like AB-BA averaging can mitigate them. As a practical outcome of this research, the deployment of a new LTP in an underground low-noise laboratory (LSBB) is planned, supporting mirror manufacturing and contributing to the development of the next generation of optical components.