Using a computer controlled photodiode array a one-dimensional pseudo hologram is registered as a result from the interference of a reference light beam and focused beams diffracted from a random rough surface (RRS). The profile function of the RRS is expanded in a Fourier series, i.e. the RRS is considered as a sum of harmonic diffraction gratings. The total diffraction field thus is a summation effect of the fields from the separate gratings, the multiple diffraction being neglected. As the hologram provides information about the phase and the amplitude of the harmonic gratings, the RRS profile can be reconstructed there from by a computer and the mean roughness can be determined in a standard way. The results are shown to be in satisfactory agreement with those obtained by using the contact pin method.
