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Near field diffraction of cylindrical convex gratings Torcal Milla, Francisco José Sánchez Brea, Luis Miguel Bernabeu Martínez, Eusebio © 2015 IOP Publishing Ltd. The authors thank Jose Maria Herrera-Fernandez for his help with graphics. This work has been supported by the project DPI2011-27851 of the Ministry of Science and Innovation of Spain and the project Fagor Automation-UCM Ref. 92/2014. We analyze the field produced by a cylindrical convex diffraction grating at the Fresnel regime for several kinds of light sources, including a monochromatic quasipunctual source, finite size, and polychromatic sources. These results can help one understand the functioning of rotary optical encoder technology. A decrease in the self-image contrast is produced for finite nonpunctual sources. In addition, the polychromaticity of the source affects the smoothness of the self-images, making them quasicontinuous from a certain distance from the grating forward. Finally, we experimentally validate the obtained analytical predictions. 2023-06-19T14:59:07Z 2023-06-19T14:59:07Z 2015 journal article 2040-8978 10.1088/2040-8978/17/3/035601 https://hdl.handle.net/20.500.14352/35041 http://dx.doi.org/10.1088/2040-8978/17/3/035601 http://iopscience.iop.org/ eng DPI2011-27851 92/2014 open access IOP Publishing