High-dynamic-resolution optical edge detection based on liquid crystal diffractive moiré lenses with a tunable focal length.

Abstract

In this Letter, we experimentally demonstrate liquid crystal-based moiré lenses with a wide and tunable focal length by direct-writing photoalignment. Our moiré lenses, which consist of two cascaded diffractive optical elements, have a large range of refractive power between $\pm 0.85\;{{\rm m}^{- 1}}$ at 532 nm and a mutual rotation between $\pm 90^\circ$ with high diffraction efficiency ($\gt\!{75}\%$). Based on the as-designed moiré lenses, we propose high-dynamic-resolution optical edge detection without any axial shift or substitution of components. The minimum edge width is 13.2 µm and can be adjusted within 100 µm by mutual rotation of this device, which has great potential to be used in adaptive and compact optical systems.