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Liquid Crystal Displays
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
The display row and column IC drivers are attached to the row and column bond pads of the display either by tape-automated bonding (TAB) using an ACA (anisotropic conductive adhesive), or chip on glass (COG) approaches. For backlighting transmissive LCDs, a fluorescent lamp is generally used. The R, G, B emission spectrum of the backlight and transmission spectrum of the R, G, B color filters are tuned together to achieve the desired color coordinates for the primary colors. Also, a diffuser is used to achieve uniform backlighting of the display. The backlight system may also use brightness enhancement films to tailor the light intensity distribution in the viewing cone. In addition to the earlier components, LCDs for specialized applications requiring enhanced performance may use a cover glass with EMI and antireflection coatings at the front, and a heater glass at the back side (between the backlight and the LCD) that facilitates low-temperature operation.
Visual Displays
Published in Julie A. Jacko, The Human–Computer Interaction Handbook, 2012
Christopher M. Schlick, Carsten Winkelholz, Martina Ziefle, Alexander Mertens
The contrast ratio represents the factor by which one pixel is brighter than another pixel. For electronic information displays, maximum contrast ratio is used to determine the range of gray levels that can be displayed. Modern LCDs have a contrast ratio of 500:1 or more. Because LCDs do not emit light, the luminance in Equation 8.4 for contrast refers to the luminance of light either passing through the display (for a backlit transmissive type) or the luminance of the light that is reflected off the display’s surface (for a reflective LCD). In multiplexed LCDs, the contrast is affected by the viewing angle. Therefore, the contrast should be indicated by referring to the solid angle, known as the “viewing cone” (Castellano 1992).
Low-gamma shift asymmetrical double-side blue-phase liquid crystal display
Published in Liquid Crystals, 2020
Yuqiang Guo, Xiaoshuai Li, Yanling Yang, Chi Zhang, Yan Sun, Hui Zhang, Yubao Sun
The commercial LCD has a wide viewing angle, which generally covers 170° (±85º polar angle), thus the characteristics of the proposed BPLCD at full viewing angles should be investigated [3,49]. Figure 9(a) shows the ideal contrast plot of the asymmetrical double-side BPLCD with w = l/3 = 2 μm, here the contrast is the ratio between the on-state and off-state transmittances. In the voltage-off state, BPLC is regarded as the isotropic material, and one biaxial compensation film has been added to further reduce the light intensities at oblique viewing angles. Thus, the off-state transmittances are same for three kinds of BPLCDs. Compared with the inner figures of Figure 3(b) and 3(d), the on-state transmittances at various oblique viewing angles are higher for the asymmetrical double-side BPLCD. Thus, the asymmetrical double-side BPLCD has a higher contrast ratio compared with the conventional IPS-BPLCD. The results show that the peak contrast ratio at normal direction is higher than 10,000:1, and the average contrast ratio is ~5000:1 for the asymmetrical double-side BPLCD. Figure 9(a) further indicates that the contrast ratios are all higher than 200:1 at full viewing-cone, and the contrast ratio of 1000:1 can cover 60° viewing-cone.
High performance LCD for augmented reality and virtual reality displays
Published in Liquid Crystals, 2019
Javed Rouf Talukder, Yuge Huang, Shin-Tson Wu
As Figure 3(b) shows, the gaps (white areas) between electrodes exhibit zig-zag structure. That means, each pixel actually exists multi-domain structure, which helps to widen the viewing angle. We use a positive A-plate and a positive C-plate as compensation films. Their refractive indices and film thickness are listed as follows: ne, +A = 1.5110, no, +A = 1.5095, ne, +C = 1.5110, no,+C = 1.5095, d+A = 92.59 µm, and d+C = 60.09 µm. Figure 9(a,b) depicts the simulated isocontrast contour of our d-FFS LCD with compensation films at α = 0° and α = 1.5°, respectively. For α = 1.5°, maximum contrast ratio over 5000:1 is obtained and it expands to a larger zone when compared to α = 0° where maximum contrast ratio is 3357:1. In both cases, the contrast ratio over 500:1 expands to ~70° viewing cone and it remains over 100:1 in the entire viewing cone.
Low voltage blue-phase liquid crystal display with insulating protrusion sandwiched between dual-layer electrodes
Published in Liquid Crystals, 2019
Yuqiang Guo, Yifei Wang, Chi Zhang, Qihui Mu, Xiaoshuai Li, Hu Dou, Fan Chu, Hongmei Ma, Hui Zhang, Yubao Sun, Qionghua Wang
The iso-contrast ratio is a significant performance for large-area LCD, which is the luminance ratio between voltage-on and voltage-off states [65,66]. Figure 10(a,b) shows the iso-contrast plot of the proposed BPLCD without and with zigzag electrode structure. The viewing cone of contrast ratio larger than 1,000:1 is over 50º, and the contrast ratio is larger than 150:1 for full-viewing cone. For straight electrode structure, the light leakage appears at bisector directions of polarisers (45º+ 90nº) [67]. Moreover, the light leakage appears at 22.5º± 45nº as a half-wave biaxial film is used. Thus, the low contrast ratio area occurs at 22.5º± 45nº, and the large contrast ratio area occurs at 0º+ 90nº, as shown in Figure 10(a). For zigzag electrode structure, the absorption axes of two crossed polarisers are 0ºand 90º, and the optic axis of half-wave biaxial film is 90º. Thus, the low contrast ratio area occurs at 22.5º± 45nº, and the large contrast ratio area occurs at 45º+ 90nº, as shown in Figure 10(b). Figure 10(b) shows that the area of contrast ratio > 1,000:1 is a little smaller than that of the proposed BPLCD with straight electrode structure. Moreover, the average contrast ratio of the proposed BPLCD with zigzag electrode structure is 3,141 which is smaller than that of straight electrode structure (4,025). This is owing to the lower transmittance for BPLCD with zigzag electrode structure. Fortunately, the viewing cone of contrast ratio > 1,000:1 is also over 50º.