Multi-pitch self-calibration measurement using a nano-accuracy surface profiler for X-ray mirror metrology

Area of Science:

• Optics and Metrology
• Surface Science
• Instrument Calibration

Background:

• High-accuracy X-ray mirror measurement demands meticulous analysis and correction of systematic instrument errors.
• The nano-accuracy surface profiler (NSP) utilizes autocollimators (AC) for precise surface profiling, with the sample-beam AC at a fixed distance from the mirror.

Purpose of the Study:

• To apply and validate the multi-pitch self-calibration method for reconstructing both mirror slope and instrument errors in an NSP.
• To demonstrate the method's effectiveness on a working-distance-fixed slope scanner.

Main Methods:

• Introduction of the multi-pitch self-calibration principle and discussion of its ambiguities.
• Application of regularization techniques illustrated with simulations.
• Experimental verification using a spherical mirror with a 10-mrad total slope.

Main Results:

• Successful reconstruction of mirror slope and sample-beam AC instrument error using the multi-pitch self-calibration method.
• Demonstration of the technique's effectiveness in compensating for instrument errors in NSP measurements.
• Analysis of low- and high-frequency instrument error signals, assessing repeatability, reproducibility, and self-consistency.

Conclusions:

• The multi-pitch self-calibration method is technically sound and effective for NSP instruments.
• The technique enables accurate reconstruction of mirror slope and systematic instrument errors.
• Experimental results confirm the method's capability for enhancing X-ray mirror metrology accuracy.