Automated diffraction interferometer with scatter plate

Vladimir S. Obraztsov; Vladimir I. Podoba

doi:10.1117/12.357774

17 August 1999 Automated diffraction interferometer with scatter plate

Vladimir S. Obraztsov, Vladimir I. Podoba

Proceedings Volume 3745, Interferometry '99: Applications; (1999) https://doi.org/10.1117/12.357774
Event: International Conference on Optical Metrology, 1999, Pultusk Castle, Poland

Abstract

The automated diffraction interferometer with scatter plate (DISP) is described. Special feature of the interferometer optical scheme is a special construction of an illuminator which permits to suppress speckle structure of interferometric picture. The basic part of the illuminator is a vibrating fiber bundle made from multimode optical fibers different lengths. The difference in fiber lengths overcomes the coherent length of multimode laser used as a radiation source in the interferometer. Mathematical model of DISP is presented. Mathematical model of DISP interferogram was derived from refined calculation of ray path. The model allows to evaluate errors of measurement in relation to parameters of a detail under control and size of scatter plate. It is shown that the finite size of scatter plate causes an additional phase shift. This additional phase shift we can be considered as a DISP systematic error. The procedure for calibration of DISP instrumental error is proposed. It is based on the analysis of an interferogram set made from the only optical detail under different orientation about interferometer optical axis. Experimental data on DISP error calibration is presented. DISP root mean square error is not over 0.005(lambda) for detail under control with relative aperture 1:7. The production procedure of a scatter plate with uniform high aperture scattering indicatrix is described. It is based on photoregistration of coherent radiation scattered on round diffuser with central obscuration. The obscuration is performed by transparency with inverse Gauss function transmission.

Citation Download Citation

Vladimir S. Obraztsov and Vladimir I. Podoba "Automated diffraction interferometer with scatter plate", Proc. SPIE 3745, Interferometry '99: Applications, (17 August 1999); https://doi.org/10.1117/12.357774

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