Experimental Research On Large Aperture Thin Beam Auto-collimation System Based On Single Mode Fiber Light Source

In Synchrotron radiation light source,X-ray free electron laser and other related fields,Large-sized mirrors are usually one of the optical elements that realize X-ray reflection,focusing and other functions.Since the surface profile quality of these large size mirrors directly affects the quality of the reflected beam,a very high-precision inspection technique is required to detect the surface profile,and the detection accuracy needs to reach the order of nanometer(height detection)or nano-arc(slope detection).Therefore,the high-precision detection of the surface profile of large size optical components become an important aspect that needs to be studied.The appearance of long trace profiler(LTP)and nano-optical-measurement machine(NOM)provides an important high-precision detection method for large size optical components.In particular,NOM technology adopts the idea of combining LTP and commercial autocollimator,which greatly improves the measurement accuracy of surface profile.NOM uses a small aperture diaphragm to obtain a collimated thin beam with a diameter of the order of millimeters to achieve point-by-point measurement of the surface of the optical element.But the commercial autocollimator is designed for a full-aperture with wide beam(usually the lens aperture is 20 ~ 30mm).According to current theoretical calculations and simulations,when the commercial autocollimator performs measurement in the thin beam mode,the measurement error will be caused by factors such as the aberration of the f-? lens at different incident angles and the thin beam divergence.So the research group studied the optimization of pencil f-? lens,and designed the scheme of large aperture thin beam auto-collimation measurement system based on single mode fiber light source,and the error sources of the system are calculated and analyzed.In order to make the autocollimator more suitable for measurement in the thin beam mode,based on the preliminary design of the research group,this paper has carried out relevant experimental research.According to the characteristics of single mode fiber light source,the beam collimation process of the system is further calculated,analyzed and verified by software simulation.The experimental optical path of the large aperture thin beam auto collimation measurement system was built,and the collimated thin beam that meets the measurement needs of the system is obtained in the experiment.And the main error sources affecting the system measurement were experimentally studied.The results show that the experimental data is in good agreement with the theoretical calculation,which provides an important reference for the experimental determination of the error sources of the large aperture thin beam auto collimation measurement system.