Torcal Milla, Francisco JoséSánchez Brea, Luis MiguelBernabeu Martínez, Eusebio2023-06-192023-06-1920152040-897810.1088/2040-8978/17/3/035601https://hdl.handle.net/20.500.14352/35041© 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.engjournal articlehttp://dx.doi.org/10.1088/2040-8978/17/3/035601http://iopscience.iop.org/open access535Rotary encoderÓptica (Física)2209.19 Óptica Física