Analysis of Speckle Influence on Image Quality of Interference Picture in Examination of Large-Sized Optical Surfaces at Stages of Grinding

Statistic characteristics of the field scattered by the examined rough optical surface are investigated, and expressions are derived for the speckle contrast depending on the monochromaticity degree of radiation of the IR-interferometer laser. A method of partial suppression of the speckle in the recorded images is proposed which is based on using the spatial filtering and the operation of averaging over an ensemble of the cross sections running through the energy center of gravity of the images remained after filtering-off. The results of experimental studies of a prototype of the laser IR-interferometer are given which is built according to the modified functional Twyman–Green scheme with a working wavelength of radiation of λ = 10.6 μm, and recommendations on selection of its element base are formulated.