Recently, optical dielectric metasurfaces, ultrathin optical skins with densely arranged dielectric nanoantennas, have arisen as next-generation technologies with merits for miniaturization and functional improvement of conventional optical components. In particular, dielectric metalenses capable of optical focusing and imaging have attracted enormous attention from academic and industrial communities of optics. They can offer cutting-edge lensing functions owing to arbitrary wavefront encoding, polarization tunability, high efficiency, large diffraction angle, strong dispersion, and novel ultracompact integration methods. Based on the properties, dielectric metalenses have been applied to numerous three-dimensional imaging applications including wearable augmented or virtual reality displays with depth information, and optical sensing of three-dimensional position of object and various light properties. In this paper, we introduce the properties of optical dielectric metalenses, and review the working principles and recent advances in three-dimensional imaging applications based on them. The authors envision that the dielectric metalens and metasurface technologies could make breakthroughs for a wide range of compact optical systems for three-dimensional display and sensing.
The moiré effect in multi-layered cylindrical objects was studied theoretically and experimentally. In theory, the central projection of double-layered convex and concave half-cylinders was considered. Based on the projected period expressed analytically in terms of the incidence angles, the period of the moiré patterns on the axis was obtained as the closed-form expression; the off-axis effect was analyzed qualitatively. The distance was discovered, where the period as the function of the angle is nearly constant. The experiments performed with two cylindrical devices confirm the theory. The results can be applied to nanoparticles and curved/flexible displays.
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