Measuring total film thickness: an experimental procedure

A simple optical procedure for obtaining a representative value of fluid film thickness is described which is designed for use in conjunction with the moire fringe technique to allow the complete determination of the fluid film thickness distribution. The geometrical arrangement of the test equipment used in this procedure is illustrated, and expressions are obtained which constitute the system of equations for finding the value of the fluid film thickness at a particular point. Application of the general theory for moire contouring will then give the fluid thickness at all other points in the film.