We describe a quantitative method of measuring film thickness profiles as deposited by plasma beams. Film thickness profiles are usually closely related to the plasma density profile of the depositing beam. The technique relies on the deposition of a semiopaque film over a large area transparent mediumin situand thus is particularly suitable for plasma systems used for thin film deposition. A simple and fast technique for quantifying the optical density versus position in the deposited film using a scanner and image processing software is described. The ability to quantify the relative optical density between different deposition profiles makes this a powerful tool for the study of the effects of process parameters on plasma density profiles and for the optimization of deposition systems. ©1998 American Institute of Physics.