Measurement of surface shape and deformation by phase-shifting image digital holography

Abstract

Measurement of shape and deformation of diffusely reflecting surfaces by phase-shifting digital holography is presented that uses an imaging setup. The difference of the reconstructed phases before and after tilt of the object illumination beam provides the contour lines of the surface height, while before and after object deformation delivers those of object displacement. This method enables measurements of both the surface shape and deformation of 3-D objects of various sizes with the same optical system and processing software. Suppression of speckle noise is also discussed. Although the setup is the same as electronic speckle pattern interferometry with a phase-shifted reference beam, the present method is more flexible because phase information can also be used for numerical reconstruction of the defocused region of a 3-D object.