Fluid film thickness measurement with moiré fringes.

A mathematical analysis of the application of moiré fringe contouring to fluid film thickness measurement is made. Two special cases are treated. The first considers the generation of contours with a collimated light source and distant observer. The second analyzes the fringe patterns viewed by an observer near the grid when there is a point source of light. Geometrical restrictions imposed on the experimental setup are detailed. Experimental results are included.