An electrically tunable polarization and polarization-independent liquid-crystal microlens array for imaging applications

Abstract

In this study, a polarization-independent microlens array composed of two layered nematic liquid crystal (LC) materials with orthogonal alignment and separated by a double-sided indium-tin oxide silica with a thickness of ∼500 μm, is proposed. The functioned stacking of two polarization LC microstructures lead to an electrically tuning polarization and also polarization-independent light control architecture. Experimental investigations reveal key characters such as a high beam utilization efficiency of more than 90% and a compound point spread function tuned electrically. Dual-mode imaging including the polarization mode and the polarization-independent mode can be realized based on the novel configuration with both independent voltage signals applied over two functioned LC layers. The normalized focusing intensity demonstrates a special property of no polarization dependence on beams processed. An image criteria for evaluating the quality of polarization-insensitive images based on the difference image between the horizontal and vertical polarization images, is introduced. Considering the advantages of electrically tunable composed focal length and then switching the polarization and polarization-independent mode, it can be expected that the developed devices can not only be used to measure and further tune the polarization state of beams propagating in LC layers but also acquire high quality target images.

All-In-Focus Polarimetric Imaging Based on an Integrated Plenoptic Camera with a Key Electrically Tunable LC Device

“…In general, the focal length dependence on the applied signal voltage of a LC microlens exhibits a non-monotonic behavior, that is, it will firstly decrease and then increase with increasing the voltage signals applied. The reasons are already explained in detail in previous research [43].…”

Design of polarimetric camera based on the single-layer twisted nematic liquid crystal device

“…Owing to exceptional electro-optic effect, polarization-sensitive characteristic and light beam modulation capacity of liquid crystal (LC) materials, LC devices are widely used in various optical applications [8][9][10] . The twisted nematic LC (TNLC) device is a typical choice for the light valve in LC display field owing to the merits of low cost, wide colour gamut and quick response capability.…”

Gradient pretilt angle alignment materials with different photosensitivity for tunable polarization‐independent self‐aligned liquid crystal lens

“…Common LC lenses are polarization-dependent, focusing the incident rays with an electric field corresponding to the alignment direction of the LC lens, and rays with orthogonal polarization pass through it without changes. 14 Using a polarizer in front of the LC lens allows us to select the appropriate rays with the necessary polarization and improve the characteristics of the LC device. However, this approach sacrifices brightness and reduces the efficiency of LC lenses application in optical devices; therefore, the most promising direction for the development of LC lenses is the creation of polarization-independent devices.…”

“…17 The combination of two round polarizationdependent LC lenses with a mutually perpendicular orientation direction is the technique, which raises the problem of the mutual positioning of the two lenses. 14,18 The resulting image from such lenses will consist of two images formed by each lens independently, and when the two lenses are made independently, an offset always takes place. The mutual exact combination of two lenses, or else self-alignment, is the solution to this problem.…”