This attenuation filter is used to optimize measurement of highly reflective parts and helps produce good fringe contrast. The filter is positioned between the test part and a standard transmission flat.
Specifications:
Quality : ≤ ƛ/10 Transmitted wavefront (PVr) Transmittance (4 in. filter) : 20 ± 4% @ 10° angle of incidence @ ƛ=632.8 nm through the pelicle