Two-wavelength lateral shearing interferometry

We propose a two-wavelength interferometric system based on a single optical element, i.e., a shear plate. The observation of beat formation phenomenon and the measurement of phase at synthetic wavelength are demonstrated for the first time using two wavelengths simultaneously in a lateral shearing interferometer. Shearing interferograms are recorded both at individual wavelength and at synthetic wavelength. The phase map at synthetic wavelength is obtained by means of subtracting the phase maps at individual wavelength as well as directly from the synthetic interferogram, and the results are found in good agreement. The validity of the principle is applied for collimation testing and reconstructing the phase map of transparent objects. The main advantages of the present system over the previous systems based on two-wavelength interferometry are high stability, nearly common path interferometry, single optical element (shear plate) requirement, compactness, and low Cost. (c) 2005 Society of Photo-Optical Instrumentation Engineers.