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Liquid crystal displays
Published in John P. Dakin, Robert G. W. Brown, Handbook of Optoelectronics, 2017
Operating with TFT removes steepness of the electro-optic transition as a critical design issue. This enables LCD modes to be chosen that meet the more stringent optical requirements for large area monitor and televisual displays. The crucial weakness of TN LCDs was the viewing angle, even with optical compensation. Viewing angle is particularly important for large area displays, where images must appear uniform from the center of viewing to the corners. The viewing angle target is harsher still if the image is to satisfy multiple viewers. The television market also requires fast response times not just for black to white transitions but also between adjacent gray levels. Extremely high contrast ratios are needed to compete with emissive technologies such as CRT, PDP, and, most recently (OLED).
Visual Displays
Published in Julie A. Jacko, The Human–Computer Interaction Handbook, 2012
Christopher M. Schlick, Carsten Winkelholz, Martina Ziefle, Alexander Mertens
When an LCD display is viewed from an angle, it appears darker and color representation is distorted (see Section 8.3.2). It is worth mentioning here that the restricted viewing angle has a positive effect on privacy, as in the case of automated teller machines (ATMs). Technologies such as inplane switching, multidomain vertical alignment, and TFTs have improved the size of the viewing angle. Typically only the color becomes less saturated when viewing at extreme angles. Although many technical improvements to viewing angles have been done on lateral angles, vertical angles still often lead to non-negligible distortion. The nominal screen diagonal of an LCD is equivalent to the effective screen diagonal. In contrast, CRT nominal screen diagonals are smaller than the effective ones.
Vision
Published in Anne McLaughlin, Richard Pak, Designing Displays for Older Adults, 2020
Viewing angle is the maximum angle of the observer relative to the display surface at which a display still appears acceptably clear and bright. The optimal location to view a display is directly in front (Figure 2.11); however, that may not always be possible. The viewing angle measurement identifies the point (from either side) at which the visual display will start to degrade from the viewer’s perspective. This is often called the viewing “cone.” In addition to the spatial degradation of the image, other measures of the display degrade with increasing viewing angle (contrast ratio, brightness). LCDs can have a medium to low viewing angle whereas e-paper displays have a very high viewing angle.
Low gamma shift blue-phase liquid crystal display with electric field induced multi-domain electrode structure
Published in Liquid Crystals, 2020
Yuqiang Guo, Xiaoshuai Li, Yan Sun, Chi Zhang, Yanling Yang, Hui Zhang, Hongmei Ma, Yubao Sun
Large-area LCD is suitable for multi-audience to watch. Thus, the wide viewing angle has been regarding as a key indicator for high-performance large-area LCD. People usually study the gamma shift of LCD at 60° polar angle. However, the available viewing angle should cover 85° polar angle for commercial LCD (170° horizontal and vertical viewing angle). Thus, the low gamma shift should also cover the full viewing-cone, no longer just at θ = 60°. Based on the above analysis, the MD protrusion BPLCD with H1 = 4 μm has the relatively better comprehensive properties, including operating voltage, gamma shift and transmittance. Moreover, the thinner electrodes are easier to prepare in etching process. Thus, this electrodes’ parameter is selected to investigate the viewing angle characteristics.
A simple transflective liquid crystal display with composite dielectric layer
Published in Liquid Crystals, 2019
Fan Chu, Hu Dou, Li-Lan Tian, Rui Li, Wen-Yi Hou, Lei Li, Qiong-Hua Wang
Figure 9(a,b) shows the simulated iso-contrast contour plots of the T and R regions at λ = 550 nm after phase compensation. A relative symmetrical viewing angle is achieved. In the T region, the 1000:1 contrast ratio (CR) is over 25° viewing cone and 10:1 CR is over 50°. In the R region, the 200:1 CR is over 25° viewing cone and CR in normal viewing angle is over 10:1. These contrast ratio and viewing angles are applicable to most personal privacy display and mobile display, after all a hand-held LCD is usually viewed by only one person.
Directional modulated light-emitting technology based on airborne display
Published in Liquid Crystals, 2022
Hu Dou, Lu Wang, Luo-Peng Xu, Xin Mao, Jia-Yi Ou, Jia-Yi Nie, Shi-Rui Wang, Shuai Wang, You-Quan Dan
Nowadays, the study of viewing angle problem has been a hot spot in display areas. In order to achieve large viewing angle, the multi-domain LC cell technology can be used for LCDs [4–9]. The colour shift and grey-scale defect of display are improved through the design of liquid crystal molecular orientation angle, electrode structure or main and sub-pixel structure [10] , etc. However, the display brightness under large viewing angle cannot be increased, and the viewing angle performance is ineffective under high ambient light. After applying a compensation film [11–19] on polarisers, the dark light leakage, contrast and colour shift under large viewing angle can be reduced. However, the brightness reduction in large viewing angles is not improved effectively, and the problem of brightness loss under large viewing angle is still remained. By applying a specially designed diffusion film to the backlight module [20–24], the brightness of backlight and light uniformity are increased, so as the brightness of the display viewing angle. Whereas, for ultra high definition displays with denser arrangement of non-transparent areas such as smaller pixel structure and black matrix, the effect is not improved sufficiently. So this technology can not solve the problem of colour shift under large viewing angle to some extent. Some light-mixing devices such as liquid crystal lens or prism can change the light transmission direction to improve the brightness and decrease the colour shift at large viewing angle [4,25–29]. However, the enhancement under specific angle (pilot viewing angle) is limited. The improvement of the display is positively related to the viewing angle. Therefore, in some specific situations such as when viewing angle is relatively small (such as less than 30°), the quality of display will not be enhanced, but the negative effects of brightness and contrast reduction may occur [4] .