Quick Shot

Ph.D. candidate Sivan Salzman is shown nulling fringes on the white-light interferometer’s NewView 100 live-image screen. She is measuring the surface texture of a polycrystalline, chemical-vapor–deposited (CVD) zinc sulfide (ZnS) that was polished with an advanced acidic magnetorheological finishing (MRF) fluid developed at LLE. A 5× Michelson objective was used to provide 1.0-mm × 1.4-mm false-color 2-D and 3-D maps, along with a black and white image of the measured surface. CVD ZnS is an important material for producing infrared windows and domes. MRF polishing of such material, where a magnetic material stiffens a fluid suspension in contact with a workpiece, opens the opportunity to produce complex and aerodynamic shapes. The acidic MR fluid is composed of zirconia-coated carbonyl-iron particles, a procedure invented by Professor Stephen Jacobs and his Materials Group at LLE during 2007–2008 and patented in 2014.