Applications of SSI™: High Precision Sphere Measurements

Case Study Summary

This study highlights the exceptional measurement repeatability and accuracy of QED’s Subaperture Stitching Interferometry (SSI) technology. Through rigorous testing on a small, fast reference sphere, the SSI system demonstrated sub-nanometer repeatability with a mean RMS value of 5.60 nm and a variation range as low as 0.025 nm. Cross-validation between different measurement sets revealed only a 0.09 nm difference—well within the noise floor of the Zygo interferometer used in testing. These results validate the system’s ability to deliver consistent, high-precision results even when comparing pixel-by-pixel subtractions across multiple stitched measurements.