Characterization of the error of the speckle-based wavefront metrology device at Shanghai Synchrotron Radiation Facility

Abstract

A metrology device based on the near-field speckle technique was developed in the x-ray test beamline at the Shanghai Synchrotron Radiation Facility to meet the at-wavelength detection requirements of ultra-high-precision optical elements. Different sources of error that limit the uncertainty of the instrument were characterized. Two main factors that contribute to the uncertainty of the measurements were investigated: (1) noise errors introduced by the electronics and the errors introduced by the algorithm and (2) stability errors owing to environmental conditions. The results show that the high measurement stability of the device is realized because it is insensitive to the effect of the external environment. The repetition accuracy of the device achieved 9 nrad (rms) when measuring the planar mirror that produces weak phase curvature.

X-ray optics development and metrology at Shanghai synchrotron radiation facility

“…Generally speaking, measurement only requires two images, one is recorded with the sample and the other is without the sample. The first application of the speckle technology is to measure the slope error of mirrors 11 . The scanning mode is used to improve the angular sensitivity and ultimately reduce the repeatability of the slope error in a plane mirror to 9 nrad (RMS) (Fig.…”