Fast-response liquid crystal phase modulators for augmented reality displays

Abstract

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.

66‐3: Submillisecond‐Response 10‐Megapixel 4K2K LCoS for Microdisplay and Spatial Light Modulator

“…High pixel density (~7000 ppi) 4K2K LCoS IC backplane suffers from low driving voltage (<3.3 V) limitations. The recently reported fast response time LCoS with PCM-2-01, L1, MCRI or UCF-L1 also requires at least 4~6 V driving voltage [22][23][24][25][26]. In this paper, we revealed a novel 1.2-inch 4K2K TN amplitude-type LCoS microdisplay (PCU-3-02-MD) with 1-ms RT under 5.0 V for displays.…”

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

“…1 (c Photo-stability is a common problem on high-birefringent LC materials. After 120 J/cm 2 UV exposure, the Δn of LC-1 drops by 3.1%, while γ1/K11 fluctuates within 1.6% variation [10]. Though this change is already small on a high-birefringent LC mixture, we still recommend covering the LC area in the UV sealing process.…”

“…In this paper, we report three new nematic LC mixtures [10] optimized for phase-only LCoS. Their high birefringence (Δn~0.25 at T=25°C and λ=550 nm) and low rotational viscosity (γ1~130 mPaꞏs) jointly contribute to a fast response time (2.08 ms), which enables 240-Hz frame rate without the annoying image flickering.…”

“…, the red color with the longest λ and the lowest Δn has the highest V2π =5 V. More than 2π phase change can be obtained within 5 V in green and blue. By employing a shifting voltage driving method, the response time for R/G/B colors are [2.99, 3.81, 3.10] ms, respectively[10].…”

Analog LCOS SLM devices for AR display applications

“…The LC response time is also an important parameter for the LCOS SLMs [7]. By cooperating with major LC vendors, we are able to reduce the cell gap to 1.8um while still reaching 2π phase change for 633nm wavelength.…”