Slope error evaluation method for interferometric test results of X-ray mirrors

Evaluation of the corresponding slope error from interferometric test results of X-ray mirrors is essential for assessing fabrication accuracy and enabling comparisons between interferometers and slope profilers. By analyzing the effects of point spread function (PSF) and sampling interval on the form measurements of both systems, a slope error evaluation model is established based on the ISO Gaussian filter, with the cut-off wavelength determined by the ITFs of the interferometer and profiler, and the truncation constant defined by the profiler's spot intensity distribution. Verification experiments involved transforming stitched height error data from two interferometers into slope errors, which were compared with results measured by two LTPs. This model, aligned with ISO standards on Gaussian filtering and ITF calibration, provides a standardized procedure for slope error evaluation and promotes consistency across advanced light sources and X-ray mirror manufacturing.