Fringe visibility analysis on silica glass based on automated Michelson interferometry system

A non-contact measurement method based on fringes produced from Michelson interferometry for fringe visibility analysis of transparent silica (SiO2) glass has been developed. An automatic micro-controlled stepper motor is implemented on the Michelson Interferometer to provide small micro displacement on the movable mirror and enable fringe shift. Through fringe visibility measurement, fringe shifting through micro-controlled stepper motor allows consistent and precise measurement. Analysis of fringe visibility was conducted on several samples etched with Hydrofluoric (HF) acid. The main fringe visibilities obtained after the silica glass were etched with HF ranged from 0.67-0.73. Fringe visibility of the silica glass samples increased when the time of etching of HF was reduced. Based on the results obtained the automatic fringe shift with micro-controlled stepper motor reduced human error and has better resolution in intensity measurement which allows fringe visibility to be measured more accurately. The fringe visibility analysis can also assist in surface profiling of other transparent and reflective thin films.