A practical determination of the phase change at reflection

A Microscope-TV-Computer system has been developed to measure the radii of the Newton´s rings formed when light is reflected from contacting spherical and plane surfaces. The rings include information of the phase change of light at reflection from the surfaces. A computer program which uses a simple and accurate least squares fit of measured data to circles then calculates the phase change. An uncertainty of ±5° has been achieved in measured phase change and the values of phase change determined using this approach are compared with those obtained from several other methods.