In this talk, we will introduce a novel photo-alignment material that has been specifically developed for use in liquid crystal optical devices. These materials contain molecules that have at least one anchoring group and one α,β-unsaturated carbonyl group. These groups can include derivatives of carboxylic acid, amides, nitriles, or ketones. When these materials are dip-washed onto the substrate surface of the transparent electrode, such as an ITO layer, the anchoring group, in this case, phosphonic acid, forms a single molecular self-assembled layer. Excellent LC alignment was achieved by these alignment layers when exposed to linearly polarized light.
The increasing demand from large-scale high-density sensing arrays also raises new requirements for sensors such as higher sensitivity, more comprehensive response range but lower cost, smaller size, etc. For example, in large-scale structure health monitoring, [1-3] a sensing array can significantly decrease the cost and effort of manpower and provide a real-time and precise diagnosis of buildings. However, the power supply of the sensing probe is a vital problem to be solved: the maintenance of batteries or energy harvesters for such a large number of sensors is a considerable challenge. Besides, the low cost of sensing array is the foundation of a large-scale high-density sensing network. When we deploy these sensors below the ground or on the seabed, the problem becomes multi-fold complicated. A passive sensing technique can be a perfect solution, which needs no additional power during energy transduction. The power supply and signal process components are removed from the passive sensing probe. Thus, the cost of the sensing array can be significantly dropped while the structural complexity is reduced, and the lifetime can be much longer. [4]
In this talk, we will discuss the 3D depth mapping system using the Electrically Suppressed Helix Ferroelectric Liquid Crystal (ESHFLCs) Dammann grating. We used a photo-alignment approach to align the ESHFLC in patterns to create the Dammann grating profile. The ESHFLC Dammann grating projects an equal-intensity point array onto the scene from where we can extract the depth information from the scene. We achieved a cm-scale resolution using the proposed depth mapping system with a very high framerate >50k frames/s. The proposed ESHFLC Dammann grating replaces iterative scanning and enables LiDAR as a one-shot capturing system. The proposed device shows a fast-switching speed (approximately 5μs) with precise measurement of translational and rotational movement. Furthermore, low fabrication cost, lightweight, and small size make these devices suitable for modern Light Detection and Ranging (LiDAR)/3D depth mapping systems.
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