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Liquid Crystal Cells
Published in Russell A. Chipman, Wai-Sze Tiffany Lam, Garam Young, Polarized Light and Optical Systems, 2018
Russell A. Chipman, Wai-Sze Tiffany Lam, Garam Young
Figure 24.29 shows the configuration for a typical projector. Light from the lamp is shaped by illumination optics and the color is modulated by a spinning color wheel. Since the LCoS is a reflective device, it is generally illuminated on-axis using a polarizing beam splitter (PBS). The illuminating light passes through a pre-polarizer and is reflected from the PBS. The LCoS is illuminated with linear polarized light, which transmits through the ITO and liquid crystal layer, reflects, and then makes a second pass through the liquid crystal and ITO before exiting the device. The change in polarization state introduced by the LCoS panel is transformed into intensity variations by an analyzer following the LCoS. In the dark state, the light reflects without polarization change and is reflected back into the illumination system by the PBS. In the on state, the LCoS rotates the polarization 90°, and this reflected light transmits through the PBS and onto the viewing screen. The PBS is typically a MacNeille-type cube beam splitter or a wire grid beam polarizing splitter. Other projector configurations may utilize one, two, or three panels for different wavelengths in a variety of configurations.
Visual Displays
Published in Julie A. Jacko, The Human–Computer Interaction Handbook, 2012
Christopher M. Schlick, Carsten Winkelholz, Martina Ziefle, Alexander Mertens
The well-known liquid crystal on silicon (LCoS) displays are also nonemitter displays. The advantages of LCoS technology are high luminance, high resolution, high contrast, relatively low production costs, and economy of weight. Unlike LCD technology, LCoS displays do not use light transmission through glass layers to create an image on a screen. Instead, an active array of pixels with liquid crystals is directly mounted on silicon that has been coated with aluminum. This additional layer consists of a reflective passivation layer that reflects the incoming RGB light toward a prism. The prism directs the light at a projection target, such as a flat screen or projection field. The crystals’ orientation relative to the reflective surface can be controlled using an electric current. The current either brings the crystals into a reflective state or aligns them so that no light is reflected.
Polarization and Polarizing Optical Devices
Published in Daniel Malacara-Hernández, Brian J. Thompson, Fundamentals and Basic Optical Instruments, 2017
Rafael Espinoza-Luna, Qiwen Zhan
The Liquid Crystal Display (LCD)-based variable retarders use nematic liquid crystal molecules contained in cells with parallel faces made of high quality transparent glass with Indium Tin Oxide thin films. Applying an external direct voltage changes the orientation of the nematic molecules, generating the desired birefringence along a preferred direction within the cell. The birefringence induces a phase difference between the orthogonal components of a transmitted beam of light, proportional to the DC voltage applied. The Liquid Crystal on Silicon (LCoS) Displays are the basis for the Spatial Light Modulators (SLM), which are some of the most successful devices employed to manipulate the polarized light with control at a pixel-microscale.
Recent progress of organic light-emitting diode microdisplays for augmented reality/virtual reality applications
Published in Journal of Information Display, 2022
Microdisplays have received much attention as main display engines of augmented reality/virtual reality (AR/VR) devices due to their small size and high resolution [1–4]. There are many types of microdisplays such as liquid crystal display (LCD)-based microdisplays that use high-temperature polysilicon (HTPS) technology [5], liquid crystal on silicon (LCoS) [4,6], digital micromirror device (DMD) [6,7], organic light-emitting diode (OLED)-based microdisplays including OLED on silicon (OLEDoS) [8–16], quantum dot-based microdisplays [17], and microLED-based microdisplays [18,19]. LCoS and DMD have already been used in various applications such as projectors, projection TVs, night vision for military use, and AR/VR glasses. LCoS microdisplays have high luminance and simple fabrication processes, but low response time, low contrast ratio, and relatively large volume and weight due to their external lighting sources. DMD microdisplays have a complex fabrication process and need additional light sources. Advanced technologies are required for high-resolution and low-cost full-color quantum dot-based and microLED-based microdisplays.
Reflective blue phase liquid crystal displays with double-side concave-curved electrodes
Published in Liquid Crystals, 2018
Yufei Xing, Zhengbo Guo, Qing Li
Field sequential colour displays with reflective liquid-crystal-on-silicon (LCoS), as a key trend of LCD technology, have outstanding advantages in high-resolution display and micro-display technologies. A fast response time is required for realise colour sequential driving mode. However, to achieve a fast response, the current common approaches based on LCoS such as mixed-mode twisted nematic cell [1], vertical alignment nematic cell [2] and ferroelectric LC cell [3] require uniformity of thin cell gap, which is difficult to fabricate [4].