3.) Inducing Freeform Shape and Correcting MSF


mrf application 7 pict3Goals:

  • Start from a “standard” best-fit sphere
  • Induce mild “OAP-like” freeform shape (~13 λ PV)
  • Finish to extremely high precision: λ/30


Part details:

  • Size: ~150 mm Φ
  • Radius: ~210 mm (concave)
  • Material: soft optical glass


Q-flex 300 configuration:

  • Raster “free-form” polishing mode
  • 150mm wheel, 50mm wheel and 20mm wheel
  • D11 Fluid and C30 Fluid


Process Overview:

  • Use “ultra-fine” MRF to finish to extremely high precision, including reduction of mid-spatial frequency errors
  • Use “standard” MRF to reach high precision
  • Use “aggressive” MRF to induce freeform shape
  • Start from a best-fit sphere


Ion Beam Finishing (IBF) is often used for the “ultra-fine” finishing step, but is too slow to induce microns of freeform shape –
now MRF can do both!






Two new features of the Q-flex platform enable powerful new MRF capabilities

Modularity of Polishing Wheels (MRF Heads) and Delivery System (MRF FCM) allows:

  • Rapid configuration changeover: Change wheels quickly and  Change fluids quickly

  • Multiple wheel orientations: Traditional (rotational polishing) and  Rotated 90º, which enables full freeform raster polishing


In this case study, we combine these new features to create a mild freeform optic with

  • Ultra-high precision

  • Ultra-low levels of mid-spatial frequencies