Developing bendable air bearing slide supporting long trace profiler to compensate gravity effect during measuring process

Abstract

In Taiwan photon source facilities, soft x-ray beamlines are equipped with self-developed active high-precision mirrors or gratings. It is crucial to establish more advanced optical surface metrology instruments to satisfy the demands of optical production, installation, and testing in synchrotron optics. A long trace profiler (LTP) is an instrument used to measure the optical surface’s slope. This assists in monitoring the installation processes of optical instruments to ensure that the final optical components satisfy the required specifications in terms of quality. In this study, we propose a new air-bearing slide design to achieve nanometer-level precision for the LTP. This new design replaces ceramic and granite structures and addresses rail deformation and surface imperfections. This LTP features a specially designed bendable linear slide comprising four airbrushes, two shafts, and eight end mounts. The motion stage, supported and guided by four airbrushes against two parallel steel shafts, carries the optical head. End mounts are installed on the tilting stage at both ends, using flexure guides with manually adjusted screws and fine-tuning piezo. The rail system can be bent to a third-order polynomial rail profile to compensate for the effect of gravity when moving the optical head, enabling the achievement of the desired rail pitch variation within a distance of 400 mm with 2.5 μrad (RMS). To further enhance the precision, dynamic correction methods can be employed by utilizing PZT actuators and bender mechanisms. These mechanisms enabled rail pitch variation as low as 0.2 μrad (RMS).We introduce a new design for an air-bearing slide and its corresponding performance. This slide design is employed in LTP measurements. The outcomes of our study demonstrate a correlation between the observed results and the rail pitch profile.