Abstract
Thanks to the laser, which offers high energy and monochromatism. as well as temporal and spatial coherence, optics enjoyed an expansion ; and new application fields were opened in several areas such as telecommunications or information storage and processing. To tackle these applications several optical elements have been designed for use under coherent illumination. In this paper, we show how to use the self-imaging properties of periodic structures to generate light coherence. To be specific, we use the Lau effect observed at fractional distances to convert a periodic structure, composed of mutually incoherent light sources,into spatially coherent sources.