The relative fringe order in a holographic interference pattern can be measured with high accuracy by means of methods like heterodyning or phase shifting. The determination of the absolute fringe order from the interferogram has not been solved satisfactorily. In this study, the absolute fringe order is determined through the employment of several wavelengths. Two interferograms are recorded with different wavelengths of a dye-laser. The mathematical treatment and an experimental application are reported.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.