On liquid crystal diffractive optical elements utilizing inhomogeneous alignment

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

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.

Full-color holographic display with increased-viewing-angle [Invited]

Among the important features of holographic displays are the wide viewing angles and the full color of the reconstructed images. The present work focuses on achievement of both features. We propose an increased-viewing-angle full-color holographic display using two tiled phase-only spatial light modulators (SLMs), a 4f concave mirrors system, and a temporal-spatial multiplexing method. The 4f optical system consists of two concave mirrors and serves to increase the viewing angle. A temporal-spatial multiplexing synchronization control (TSMSC) method is developed to achieve a full-color image and to remove the color crosstalk of the image. We calculate RGB phase-only holograms of a computer-generated color pyramid by using a slice-based Fresnel diffraction algorithm. The experimental results indicate that the proposed display system is feasible to reconstruct a full-color holographic 3D image with a viewing angle of 12.8°, which is about 3.8 times wider than the viewing angle formed by a single SLM.

UV-treated ZnO films for liquid crystal alignment

UV treatment has applied to modify the surface wettability of ZnO films for controlling the liquid crystal alignment.

Assessment of minimum permissible geometrical parameters of a near-to-eye display

Light weight and small dimensions are some of the most important characteristics of near-to-eye displays (NEDs). These displays consist of two basic parts: a microdisplay for generating an image and supplementary optics in order to see the image. Nowadays, the pixel size of microdisplays may be less than 4 μm, which makes the supplementary optics the major factor in defining restrictions on a NED dimensions or at least on the distance between the microdisplay and the eye. The goal of the present work is to find answers to the following two questions: how small this distance can be in principle and what is the microdisplay maximum resolution that stays effective to see through the supplementary optics placed in immediate vicinity of the eye. To explore the first question, we consider an aberration-free magnifier, which is the initial stage in elaboration of a real optical system. In this case, the paraxial approximation and the transfer matrix method are ideal tools for simulation of light propagation from the microdisplay through the magnifier and the human eye's optical system to the retina. The human eye is considered according to the Gullstrand model. Parameters of the magnifier, its location with respect to the eye and the microdisplay, and the depth of field, which can be interpreted as the tolerance of the microdisplay position, are determined and discussed. The second question related to the microdisplay maximum resolution is investigated by using the principles of wave optics.