Measurements of the small tilt-angle variation of an object surface using moire interferometry and digital image processing

A method of measuring the small tilt-angle variation of an object surface by using moire interferometry based on the Talbot effect and a moire technique is described. The object surface is placed in the middle of a set of two gratings. A monochromatic plane wave illuminates the first grating producing the magnified Talbot image. The moire fringe is generated by superimposing this Talbot image on the second grating. The inclination angle of the moire fringes is ameasure of the tilt angle of the object surface. The inclination angles are measured with a digital image processor.