Extension of the displacement measurement range for electronic speckle-shearing pattern interferometry using carrier fringes and a temporal-phase-unwrapping method

A technique for increasing the displacement measurement range in electronic speckle-shearing pattern interferometry is proposed. The technique is based on the introduction of carrier fringes and the use of a temporal-phase-unwrapping method to obtain larger measuring ranges of out-of-plane displacements of an object without sign ambiguities. A larger measuring range is obtained by dividing the desired maximum-phase range into several subranges where the spatial synchronous detection method can be successfully applied. These phase subranges correspond to small out-of-plane displacements of the object, and a speckle pattern is recorded for each displacement. The carrier fringes are obtained by the subtraction correlation of two consecutive speckle fields with a translation of the illuminating beam between recordings. The method allows the measurement of object displacements of about 216 mu m. (C) 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)01803-1].