In recent years there has been considerable growth in the use of optical methods for evaluating surfaces. Conventional stylus techniques, though powerful, have their own limitations. These include the resolution of the stylus, and the damage caused by the moving diamond stylus when tracing profiles on soft materials. Hence non-contact methods of measuring surface finish of often required. One approach in this direction is the use of an optical diffraction technique. The unique properties of the diffraction phenomenon make this technique useful and the validity of this technique in the evaluation of surface finish is investigated in this paper.