|
The Diamond-NOM slope profilometer has been in operation for more than 15 years in the Optics Metrology Lab at Diamond. It is an established instrument for accurate characterisation of x-ray optics for synchrotron and XFEL beamlines. However, continuous improvements in the fabrication quality of x-ray optics now means that polishing errors are comparable in magnitude to instrumental systematic errors. For x-ray optics with slope errors << 100 nrad rms and height errors < 1 nm, repeated measurements in multiple configurations are typically required to obtain accurate metrology data. To tackle such issues, we have developed a new instrument: the Diamond-VeNOM (velocity-NOM). VeNOM utilizes multiple autocollimators, synchronized with motion stages, to simultaneously measure the optical surface and monitor parasitic motion errors. A significant increase in measurement speed is achieved using 10x faster Elcomat5000 autocollimators. Motion trajectories are aligned with autocollimator data by temporarily blocking the beam paths using electronic shutters, based on triggering signals from positional encoders. Enhanced motion control capabilities allow user-defined velocity profiles of the scanning stage, coordinated with motorised pitch of the optic under test throughout the scan. This enables innovative dynamic scanning strategies, including on-the-fly, free-form, automated nulling of the optical surface throughout the scan to reduce systematic errors.
|
