This is the first of a two-part paper on measurement of displacement and profile using changes in the farfield diffraction patterns of a slit aperture formed between a test and reference object. When applied to displacement measurement the method is very accurate over a considerable range, noncontacting, linear, and easy to use. In addition to the measurement considerations involved in this diffractographic technique, three unique applications are discussed. These are: simultaneous deflection measurement along a line, deflection measurement of a surface relative to an edge, and vibration amplitude measurement using time-averaged fringes.
T. R. Pryor, O. L. Hageniers, and W. P. T. North, "Diffractographic Dimensional Measurement. Part 1: Displacement Measurement," Appl. Opt. 11, 308-313 (1972)