Asymmetrically anchored liquid crystal (LC) cells have different anchoring energies between the top and bottom substrates. A substrate with patterned electrodes has comparatively weak anchoring energy. Therefore, asymmetrically anchored LC cells exhibit more twisted deformation in the on-state than conventional in-plane switching or fringe-field switching cells. In this study, we introduced asymmetrically anchored LC cells for display and photonic applications. We first introduced asymmetrically anchored LC cells to achieve high transmittance for LC displays. The LC molecules can rotate between the two substrates more easily because one of the two substrates has weaker anchoring energy. This resulted in a significant increase in transmittance. Three-terminal electrodes can be used to provide a vertical trigger pulse to an LC cell, thereby overcoming the delayed turn-off switching of an asymmetrically anchored cell without reducing transmittance. Next, we introduced an adjustable polarisation rotator with an asymmetrically anchored LC cell. To offer optical waveguiding, the arrangement of LC molecules can be controlled into a twisted configuration. During the cover of the wavelength range of 400–800 μm, we confirmed that the proposed LC cell can rotate the polarisation axis of linearly polarised light by up to 90°.
Anisotropic Mechanochromism In article number 2310658, Suk-kyun Ahn and co-workers create cholesteric liquid crystal elastomers (CLCEs) with slanted helices via direct ink writing. Notably, the anisotropic mechanochromic response of the printed CLCE to being stretched relative to the printing direction is observed. The anisotropic mechanochromism enables the creation of a unique strain sensor displaying intricate and programmable color patterns upon stretching.
In the current commercial automotive market, the need for intelligent headlight control systems has increased more and more. Camera-based night-time vehicle detection has become a crucial issue in determining the performance of such control systems. The purpose of this paper is to offer an answer to the question, 'Which thresholding method is suitable in terms of detection performance for a night-time vehicle candidate selection process?' For such purposes, two local adaptive thresholding methods are introduced and tested. One is local maximum-based thresholding, and the other is local mean-based thresholding. Efficient implementation methodologies are also introduced for real-time processing. Through the simulations tested on road image sequences with different exposure times, we prove that local adaptive thresholding methods have better performance than other well-known global thresholding methods. In particular, the simulations show that the proposed mean-based thresholding method has better performance on both long- and short-exposure sequences.
We introduce a simple method for fast switching of vertically-aligned nematic liquid crystals (LCs). When an electric field is applied to a patterned vertical alignment (PVA) LC cell, virtual walls are formed in the middle of the gaps between and at the center of the patterned electrodes. These virtual walls formed in a PVA cell results in the turn-off time being dependent on the pitch of the patterned electrodes as well as the cell gap. Therefore, a short response time can be achieved by fine patterning of pixel electrodes without requiring additional fabrication steps or complicated drive schemes. A similar behavior has been observed in switching of vertically-aligned LCs with positive dielectric anisotropy by an in-plane electric field.
We introduce a twisted-nematic LC cell, which can rotate the polarization angle of the polychromatic light. We used interdigitated electrodes to apply an in-plane field to control the twist angle. Thanks to the asymmetrical anchoring in the LC cell, the twist angle could be rotated continuously by increasing the applied electric field. The linearly polarized light incident on the LC cell can be rotated following the twist direction. Since it does not require an additional retardation film such as QWP, there is no degradation of the performance at a specific wavelength even for the polychromatic light.
A dye-doped LC/polymer light shutter with a polymer structure that is formed using the thermally-induced phase separation (TIPS) method is demonstrated. The TIPS method relies on the difference in solubility between thermoplastic polymer and solvent, and thus there is no degradation of the dye during the fabrication process. The light shutter can be fabricated quickly because the optical properties are not affected by the cooling time. The fabricated TIPS cell shows a superior black color with excellent optical properties, such as a low haze value of 0.5% in the transparent state, and a high haze value of 99.1% in the opaque state. This result can be applied for the high image quality of see-through displays using organic light-emitting diodes.
We investigated the two-dimensional (2-D) confinement effect of liquid crystals (LCs) on the switching of vertically aligned LCs by an in-plane electric field. When an in-plane field is applied to a vertical alignment (VA) cell, virtual walls are built at the center of the interdigitated electrodes and at the middle of the gaps between them. The LC molecules are confined not only by the two substrates but also by the virtual walls so that the turn-off time of a VA cell driven by an in-plane field is dependent on the pitch of the interdigitated electrodes as well as the cell gap. Therefore, the turn-off time of a VA cell driven by an in-plane field can be reduced simply by decreasing the pitch of the interdigitated electrodes as a result of the enhanced anchoring provided by the virtual walls. The experimental results showed good agreement with a simple model based on the 2-D confinement effect of LCs.
A tunable liquid crystal (LC) polarization rotator that can rotate the polarization axis of linearly-polarized broadband light is achieved by using an asymmetrically-anchored negative LC cell. Interdigitated electrodes are used to apply an in-plane field to control the twist angle. The use of the asymmetrical anchoring in the LC cell enables continuous change of the twist angle by increasing the applied electric field. For uniform transmission, we used an LC that has negative dielectric anisotropy to avoid tilting of LC molecules by the vertical component of the electric field. We theoretically and experimentally confirmed that the fabricated LC cell could continuously change the twist angle and rotate the polarization axis of the linearly-polarized broadband incident light.
When an electric field is applied to in-plane switching (IPS) and fringe-field switching (FFS) cells with zero rubbing angle, virtual walls are built such that the switching speed can be increased several-fold. In this study, we investigate the dependence on the interdigitated electrode structure of the electro-optical characteristics of IPS and FFS cells with zero rubbing angle. We found that when the rubbing angle is zero, the single-layered IPS electrode structure provides a higher transmittance than the double-layered FFS electrode structure because of the reduced width of dead zones at domain boundaries between interdigitated electrodes. Single-layered IPS electrodes not only minimize the transmittance decrease but also provide a shorter response time than double-layered FFS electrodes, although the operating voltage is higher and fabrication requires a more precise rubbing process. The transmittance decrease due to the zero rubbing angle in an IPS cell can be minimized using optimization of the electrode structure while retaining a short response time.
'%3e%3cg id='b'%3e%3cpath id='a' stroke='%23000' stroke-width='2' d='M-6-25H6m-12 3H6m-12 3H6'/%3e%3cuse xlink:href='%23a' y='44'/%3e%3c/g%3e%3cpath stroke='%23fff' d='M0 17v10'/%3e%3ccircle r='12' fill='%23cd2e3a'/%3e%3cpath fill='%230047a0' d='M0-12A6 6 0 0 0 0 0a6 6 0 0 1 0 12 12 12 0 0 1 0-24z'/%3e%3c/g%3e%3cg transform='rotate(-123.69)'%3e%3cuse xlink:href='%23b'/%3e%3cpath stroke='%23fff' d='M0-23.5v3M0 17v3.5m0 3v3'/%3e%3c/g%3e%3c/svg%3e)