twang006/rifta

Robust Iterative Fourier Transform based dwell time Algorithm (RIFTA) for deterministic optics fabrication

Introduction

RIFTA is the Robust Iterative Fourier Transform based dwell time Algorithm (RIFTA) for deterministic optics fabrication. RIFTA was proposed and developed at the National Synchrotron Light Source II (NSLS-II), NY, USA, for the Ion Beam Figuring (IBF) of synchrotron X-ray mirrors. It can be generally applied to any Computer Controlled Optical Surfacing (CCOS) processes. Both the MATLAB and Python implementations of the algorithm are open sourced in this repository.

Implemented algorithms

• Surface height-based RIFTA [1]
• Surface slope-based RIFTA
• Thresholded inverse filtering assisted by direct search [1]
• 2D convolution using Fast Fourier Transform (FFT)

RIFTA example results

Note

• All the units used in the code are metres unless otherwise specified.
• The common arguments that are required for IBFest dwell time calculation include:
  • Tool Influence Function (TIF): the TIF can come from either the measurement or model, by choosing avg or model, respectively. If model is chosen, the parameters for a 2D Gaussian should be set, includeing the Peak Removal Rate (PRR) A, the Sigma, the diameter d, and the centers u. If avg is chosen, Xtif, Ytif, and Ztif should be provided.
  • Zd: the desired height to be removed.
  • ca_range: the range of the Clear Aperture (CA), which is a struct contains x_s, y_s, x_e, and y_e, which are the start and end coordinates (units are meters) of the CA.
  • dg_range: the range of the Dwell Grid (DG), which should be larger than ca_range at least the radius of the BRF on each side.

Reference

[1] Wang, T., Huang, L., Kang, H. et al. RIFTA: A Robust Iterative Fourier Transform-based dwell time Algorithm for ultra-precision ion beam figuring of synchrotron mirrors. Sci Rep 10, 8135 (2020). https://doi.org/10.1038/s41598-020-64923-3.