Combining SSI & MRF to Reach
λ/75 PV on a Plano


High precision optical flat surfaces are used in a number of applications, including reference surfaces, stage mirrors, and laser cavities.  Manufacturing a plano surface to λ/75 peak-to-valley (PV) can be challenging for many reasons.

  • Conventional polishing methods usually are not deterministic enough to reach this level of precision for various part sizes and aperture shapes with predictable throughput.

  • Magnetorheological Finishing (MRF™) is a computer-controlled subaperture polishing process, that is deterministic. However, computer controlled processes like MRF need sufficiently-accurate, full-aperture metrology to “drive” the process, i.e. to tell the software where the highs & lows of the surface error are.

  • Metrology needs to be accurate enough in two (2) key quality areas:
    • Vertical resolution/accuracy – the ability for the instrument to resolve and accurately quantify the amplitude of the highs & lows of the surface error
    • Lateral resolution/accuracy – the ability of the instrument to accurately represent the position of the highs & lows of the surface error


Download a PDF of the the full Case Study, "Polishing Super Flat Flats".