Absolute Calibration And Repeatability Analysis Of Planar Topography

The planar optical element has a wide range of applications in optical systems and engineering instruments,and is also a basic optical and optic test object.With the rapid development of the optical industry and related technical fields,the requirements for the processing accuracy of the optical plane profile have also increased.Existing detection technologies generally use instruments based on the Fizeau interferometer system.However,the surface shape detection methods currently used still have many problems : limited discrete point data cannot replace full surface data points,the traditional relative measurement is limited by the accuracy of the reference mirror,and it is impossible to detect high-precision planar components,or using the central area of an expensive large-calibre interferometer for detection;the reference surface shape of any aperture interferometer changes with temperature and humidity.In order to solve the above problems,this paper proposes an absolute calibration study of planar topography based on a phase-shifting Fizeau laser interferometer.The objective is to eliminate the effect of the surface mirror error of the reference mirror,improve the measurement accuracy of the plane profile,and improve the detection efficiency.In order to reduce the measurement results affected by the environment and adjustment errors,this paper proposes a four-step rotation absolute measurement method,four combinations and one rotation.A rotating disk was designed to ensure that the accuracy of the flat crystal rotation angle during measurement was controlled within the level of second.In order to reduce the measurement error caused by air disturbances,an air flow isolator was designed;a planar calibration experiment was designed based on the above experimental apparatus and the method was adopted.The measurement result,measured on the plane of National Institute of Metrology in China,is close to the measurement result of the multi-rotation absolute measurement method used by the department.In order to further verify whether the absolute calibration of the interferometer has been achieved,compared with the experimental results of the absolute calibration of the interferometer.The experimental results show that the absolute calibrated interferometer can achieve the measurement result without the reference mirror surface shape error,and can form a closed-loop self-test.At the same time,measurement repeatability is also an important indicator of the quality of the interferometer system.Therefore,this paper will study the reproducibility of planar topographies and analyze the related error factors that affect the repeatability of the measurements.