Computational lensless metrology of freeform optics: large-area optical testing with nanometre-scale precision

Characterizing wavefront of free-form optical elements is challenging. Existing interferometric techniques are accurate but not suitable for freeform elements. We propose a computational metrology technique using a coded sensor to capture diffraction measurements. Our calibration process achieves remarkable accuracy with less than 10 nm error over a 40 mm² field of view. This technique allows water-immersion operation and can characterize steep surfaces with up to 30 degrees slope. With a large field of view, nanometer precision, and a non-interferometric configuration, it has the potential to revolutionize optical metrology in manufacturing.