The article illustrates the use of Fourier optics to describe the operation of two-beam scanning laser interferometers. It deals with the effect of diffraction on the spatial periodicity of a monochromatic and coherent beam. Particular attention is given to the analysis of systematic errors in high-accuracy laser metrology. The article reviews the special case of plane wave and Gaussian illuminations, examines how beam truncation affects the period of traveling fringes and presents a general relation between the relative wavelength deviation and the impulse standard deviation of the photons
We have developed a null laser interferometer capable of picometer resolution in fringe division for the measurement of the silicon (220) lattice spacing by X-ray interferometry., With a view to achieving 10(-9) measurement uncertainty, we hale given special attention to the effects of diffraction, An analysis of the measurements which has brought to Light wavefront astigmatism? the effect of which had so far been overlooked, is presented, This article show's how astigmatism affects measurements, describes how we determine beam parameters, and compares theoretical and experimental results
A new translation device has been developed at the Istituto di Metrologia ''G. Colonnetti'' (IMGC) to improve the measurement of the (220) lattice spacing in silicon by X-ray/optical interferometry, It is capable of millimeter linear displacement and servo controls ensure picometer and nanoradian resolutions in crystal position and attitude, It has been successfully used to drive a scanning X-ray interferometer over a 2 mm displacement, thus extending by more than one order of magnitude the maximum crystal movement obtained before
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