Manufacturing Super-Flat Optical Flats Using SSI and MRF

Case Study Summary

QED Technologies combined Subaperture Stitching Interferometry (SSI) with Magnetorheological Finishing (MRF) to manufacture a fused silica optical flat with peak-to-valley flatness of λ/75. High-resolution stitched metrology from the ASI platform was used to accurately characterize surface irregularity and remove reference wave error, providing precise input data for the MRF correction process.

Using a Q-flex 300 system with a 20 mm polishing wheel and D11 MR fluid, deterministic figure correction was performed in just two polishing runs totaling approximately three hours. Surface RMS error improved by nearly 100×, and mid-spatial-frequency errors were efficiently suppressed. Surface roughness measurements confirmed improvement to approximately 1.9 Å RMS.

This case study highlights the importance of high-quality metrology in achieving extreme flatness. By tightly integrating SSI measurement and MRF correction, QED Technologies enables predictable fabrication of ultra-flat optical reference surfaces.