Liquid-Crystal-on-Silicon for Augmented Reality Displays

Yuge Huang,Ran Chen,Shin-Tson Wu,Engle Liao

doi:10.3390/app8122366

Yuge Huang, Ran Chen + Show 2 more

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https://doi.org/10.3390/app8122366

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Abstract

In this paper, we review liquid-crystal-on-silicon (LCoS) technology and focus on its new application in emerging augmented reality (AR) displays. In the first part, the LCoS working principles of three commonly adopted LC modes—vertical alignment and twist nematic for amplitude modulation, and homogeneous alignment for phase modulation—are introduced and their pros and cons evaluated. In the second part, the fringing field effect is analyzed, and a novel pretilt angle patterning method for suppressing the effect is presented. Moreover, we illustrate how to integrate the LCoS panel in an AR display system. Both currently available intensity modulators and under-developing holographic displays are covered, with special emphases on achieving high image quality, such as a fast response time and high-resolution. The rapidly increasing application of LCoS in AR head-mounted displays and head-up displays is foreseeable.

Highlights

Dating from the 1970s, Hughes research labs creatively combined liquid crystal (LC) with semiconductor substrates, enabling optically addressed liquid crystal light valves [1,2], which paved the way for the invention of liquid-crystal-on-silicon (LCoS) display technology [3,4,5]
We review the LCoS technology intended for augmented reality (AR) displays
1 μm is desirable for AR displays; (3) new LC materials with a submillisecond response time for intensity modulation [46,58,59] and ~2 ms response time for phase modulation at 40 ◦ C [46,47] are available, enabling high-frame-rate LCoS with both analog and digital driving; (4) new methods are proposed to suppress the fringing field effect from a large-pixel design to the accommodation of small pixels [78]

Summary

Introduction

Dating from the 1970s, Hughes research labs creatively combined liquid crystal (LC) with semiconductor substrates, enabling optically addressed liquid crystal light valves [1,2], which paved the way for the invention of liquid-crystal-on-silicon (LCoS) display technology [3,4,5]. The emergence of LCoS is jointly contributed by the application of liquid crystal (LC) electro-optic response behaviors and the development of the silicon complementary metal oxide semiconductor (CMOS). The structure of a typical reflective LCoS panel is shown in Figure 1: an LC layer is sandwiched between an indium tin oxide (ITO)-coated glass and a CMOS backplane. The Aluminum (Al) electrodes on the Silicon CMOS backplane are pixelated to provide independent voltage control. When an incident linearly polarized light traversing through the LC layer twice, its polarization state or phase is modulated depending on the LC alignment mode

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