Patent ID: 6595834
Filing Date: 2003-07-22
Classification: B24B,C09G

Abstract:
A method of making a <200 nm light transmitting optical fluoride crystal for transmitting less than 200 nm light, said method comprising:providing an optical fluoride crystal preform, said preform having a first and second initial finished parallel flat optical transmission surfaces, said initial finished surfaces having a &lE;50 angstrom RMS surface roughness with an initial finished mid-spatial frequency roughness with 1-1000 &mgr;m spatial wavelengths and an initial finished high-spatial frequency roughness with <1 &mgr;m spatial wavelengths, said initial finished preform having a low initial finish &lgr;<200 nm transmission LT (%/cm); providing a final surface processing colloidal nonfriable spherical abrasive particle solution, said final surface processing solution having a pH&gE;9 and a plurality of colloidal nonfriable spherical abrasive particles, said particles having a mean particle size in the range from 20 to 300 nm, final polishing said initial finished surfaces with said final surface processing colloidal particle solution into a final polished optical transmissions surface with said final polishing final surface processing colloidal particle solution removing said initial finished mid-spatial frequency roughness 1-1000 &mgr;m spatial wavelengths and said initial finished high-spatial frequency roughness<1 &mgr;m spatial wavelengths to provide a final finished optical fluoride crystal having a final finish polished high optical transmission surface with a final finish &lgr;<200 nm high transmission HT (%/cm), with HT>LT.