Lensless image processing based on a single-layered metasurface.

A single-layered metasurface image processor is proposed to realize the operations of addition, subtraction, and differentiation of images. The metasurface, composed of double Si nanopillars deposited on a glass substrate, effectively modulates the amplitude and phase of the light field, and it enables optical image processing without the help of lenses and other optical devices. Under circularly polarized light illumination, the proposed metasurface image processor can perform the addition and subtraction of two images, and the differentiation or edge detection of an image. The numerical simulation and experimental measurement provide verification. Compared with the multiple elements in existing image processing techniques, this metasurface image processor works independently. The normal incidence condition is more convenient than the critical incidence in practical applications. We believe the proposed metasurface image processor may expand the wider applications of integrated metasurfaces in optical computation, image processing, and image recognition.