Binary optics and their application to imagery Self-imaging optics

Binary optics are optical components encoded, either in phase or amplitude, by a succession of patterns. Compared with conventional optical components, which use refraction or reflection to modify the direction of light rays, binary components exploit the phenomenon of diffraction, which calls on the wave aspect of light. For a long time, diffraction was seen as a limitation (optical systems are referred to as "diffraction-limited"), but it is now gradually being exploited in optical architectures.

Imaging using binary optics is particularly popular in the gamma-ray and X-ray fields, where the material is highly absorbent. This makes it tricky to create refractive lenses, which require considerable optical thickness, or to use mirrors, where the stacking of reflective dielectric layers can be problematic. With the advent of digital sensors, which enable images to be manipulated after acquisition, some research teams are now looking to take advantage of the original imaging properties of diffractive optics to replace refractive and reflective optics, in order to create lightweight, inexpensive and compact systems. Indeed, the systematic inclusion of cameras in smartphones has considerably reduced the cost of imaging sensors. The production of low-cost sensors from low-cost components for home automation applications makes binary components attractive in the visible and infrared ranges too.

This article highlights the imaging capabilities of Self-Imaging Binary Optical Components (SIBOCs). These have the property of repeating the same diffraction pattern, and some even channel light along focal lines. These COBAIs are the only optical "ingredients" needed to form an image.

The formalism of image formation will not be recalled in this article, the reader can refer to the article [E 4 045] . However, several examples of COBAI are detailed. For each, the equations used to model them are described, along with examples of their application to imaging.

Throughout the article, sidebars discuss the original effects of the various COBAIs.

Finally, a comparative table is presented summarizing the COBAIs presented with their characteristics. They are compared with the focusing binary optics developed in the article