image: Top figure illustrates advanced LC-based devices, including LCD, LCoS, and LC planar optics. These LC devices contribute to novel display technologies, including AR and VR systems. The bottom figure shows the system configurations of a, VR and b, AR. view more
Credit: by Kun Yin, En-Lin Hsiang, Junyu Zou, Yannanqi Li, Zhiyong Yang, Qian Yang, Po-Cheng Lai, Chih-Lung Lin, and Shin-Tson Wu
Augmented reality (AR) and virtual reality (VR) have potential to revolutionize the ways we perceive and interact with digital information. Since the 1990s, AR and VR experienced their first boom ushering in the dawn of evolution in display and information platforms. At one end of the spectrum is VR display, which effectively extends the field of view (FoV), blocks the entire ambient, and offers a completely immersive virtual environment. At the other end of the spectrum is AR display, which enables see-through capability while overlaying digital content to the real world. With the refreshing visual experiences, AR/VR displays have opened a new gateway for many attractive applications, including healthcare, education, engineering, manufacturing, and entertainment, just to name a few. These new display platforms are mutually reinforcing with emerging functional LC-based optics, resulting in many impressive, AR/VR-ready LC devices. Due to the unique requirements, diverse capabilities, and rapid development of LC devices in near-eye systems, it is increasingly important to discuss advanced LC-based devices in AR/VR from a comprehensive perspective to provide valuable reference for future development.
In a new paper published in Light Science & Application, a team of scientists, led by Professor Shin-Tson Wu from College of Optics and Photonics, University of Central Florida, USA, have conducted a systematic and comprehensive analysis to bridge various functional LC devices with their corresponding applications in near-eye displays. In this paper, three major LC devices, including transmissive active matrix microdisplays, reflective Liquid-Crystal-on-Silicon (LCoS), and LC planar optics, are described in detail. Figure 1 shows the classification of LC photonic devices and their structures and working principles, which have been widely used in AR/VR systems as emerging technologies to support various functionalities.
More specifically, high-dynamic-range (HDR) LCDs for VR headsets suffer from low transmittance issues caused by small aperture ratios and disclination lines blocking the backlight, achieving a high-performing VR that is compatible with directional backlight and spatial patterned beam steerer represents a promising solution. Meanwhile, LCoS spatial light modulators offer an unrivaled phase modulation to realize holographic views beyond conventional displays for near-eye system. Emerging LC planar optics provide excellent optical properties with an ultrathin formfactor and high efficiency. These advanced LC devices cover the entire AR/VR systems from light engines, imaging optics, optical combiner, to various functional elements, and play pivotal roles for systematically improving the image quality and formfactor of the AR/VR displays.
With the presented work, Wu and co-workers provided an overview of LC devices in the rapidly growing field of AR/VR systems. Taking advanced LC as the cornerstone, a variety of devices, such as HDR and high-resolution density microdisplays for VR, high-brightness and high-resolution LCoS light engines for AR, and polarization selective beam deflector and lens are discussed. Based on the specific AR/VR requirements, such as light efficiency, resolution density, ambient contrast ratio, form factor, imaging performance, FoV, and vergence-accommodation conflict, Wu’s team demonstrated several promising photonic solutions to address these challenges and provide useful guidelines for future LC device development.
Journal
Light Science & Applications