CONTOURING USING 2-WAVELENGTH ELECTRONIC SPECKLE PATTERN INTERFEROMETRY EMPLOYING DUAL-BEAM ILLUMINATIONS

A new contouring technique using two-wavelength electronic speckle pattern interferometry (TWESPI) employing dual-beam illuminations is proposed. The optical rough surface is tested at a synthesized longer equivalent wavelength lambda(eq) = (lambda-1 lambda-2)/ (\lambda-1 - lambda-2\) so that a variable measurement sensitivity can be achieved by changing the wavelenghts lambda-1 and lambda-2. Therefore, this technique extents the measurement range of single-wavelengths electronic speckle pattern interferometry and allows the measurement of profiles of the steeper surface than has preciously been possible with a single-wavelenght, assuming that 2-pi ambiguities can be removed at equivalent wavelength lambda(eq).