18‐4: Invited Paper : Digital Modulation on Micro Display and Spatial Light Modulator

Liao²,

Chen

et al. 2018

Applied Sciences

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.

Section: Response Timementioning

confidence: 99%

Liquid-Crystal-on-Silicon for Augmented Reality Displays

Liao²,

Chen

et al. 2018

Applied Sciences

“…The challenge for enabling a high frame rate depends on the driving scheme. For digital driving, a maximum voltage, say Vmax ~5V, is applied and the grayscale is controlled by the pulse width modulation [3]. Digital driving offers a better gray scale accuracy in amplitude modulators and a faster response time.…”

Section: Introductionmentioning

confidence: 99%

44‐4: New Liquid Crystals Enabling High‐Frame‐Rate LCoS for Augmented Reality Displays

Symp Digest of Tech Papers

2018

We report three new liquid crystal mixtures enabling 240-Hz spatial light modulators and 1080-Hz amplitude modulators for augmented reality displays. Experimentally, at 40°C it achieves 2 phase change, 2.08 ms average gray-to-gray response time, and 5.38 V operation voltage on a reflective homogeneous cell, as well as 0.90 ms average gray-to-gray response time, 5 V operation voltage, and 2097:1 contrast ratio on a reflective 90° MTN cell. This outstanding performance paves the way to color-sequential augmented reality displays.

“…The challenge for enabling a high refresh rate depends on the driving scheme. For digital driving, a maximum voltage, say V max ~6 V, is applied and the grayscale is controlled by the pulse width modulation technique [8]. Digital driving offers good grayscale accuracy and fast response time for amplitude modulators, but for phase modulation it suffers from digital flicker noise the high power consumption.…”

Section: Introductionmentioning

confidence: 99%

Fast-response liquid crystal phase modulators for augmented reality displays

2017

Opt. Express

We report three new liquid crystal mixtures optimized for the phase modulator of an augmented reality display. The mixtures exhibit a relatively high birefringence (Δn) yet low viscosity, modest dielectric anisotropy (Δε), and acceptable resistivity and UV stability. High Δn enables a thin cell gap (d≈1.7 μm) for achieving 2π phase change with a reflective Liquid-Crystal-on-Silicon (LCoS) device and ~2 ms average phase-to-phase response time at 40°C. The modest Δε helps lower the operation voltage to 5V. To improve the response time of a full-color LCoS, we propose a new driving method by shifting the operation voltage away from the threshold. We also applied such a high Δn LC mixture to LCoS based amplitude modulators and achieved submillisecond response time. Widespread applications of these materials for the emerging augmented reality displays are foreseeable.