Self-imaging process at the near field of cylindrical convex gratings (Vol. 46 No. 4)

Diffraction gratings have become one of the most used optical elements. Their behaviour has been extensively analysed from many diverse points of view. From a general sight, diffraction gratings produce diffraction orders at the far field and self-images at the near field. The applicability of diffraction gratings is quite extensive. They can be found as fundamental parts of many different devices such as telescopes, spectrometers, optical encoders, etc.

One particular kind of optical encoder uses cylindrical convex gratings. The authors show the near-field diffraction of cylindrical convex gratings illuminated by a general source that can be punctual or finite, monochromatic or polychromatic. They analyse how the size and polychromatism of the source affect the self-imaging process of cylindrical convex gratings. A decrease in the self-images contrast is produced for finite non-punctual sources. On the other hand, polychromaticity of the source produces quasi-continuous diffraction fringes from a certain distance forward.

All the results have been proven by experiments and could be helpful in applications that include convex diffraction gratings.

F. J. Torcal-Milla, L. M. Sanchez-Brea and E. Bernabeu,, Near field diffraction of cylindrical convex gratings, J. Opt., 17, 035601 (2015)
[Abstract]