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 (Δe), 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 Δe 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.
Highlights
Liquid-Crystal-on-Silicon (LCoS) panels have found promising applications in augmented reality (AR) near-eye displays because of their low operation voltage, high resolution density, broad bandwidth, compact size, and light weight [1,2,3,4,5]
Because the information encoded in an amplitude modulator is limited, to generate high-quality 3D images in AR displays, phase-only LCoS is receiving increasing attention
The challenge for enabling a high refresh rate depends on the driving scheme
Summary
Liquid-Crystal-on-Silicon (LCoS) panels have found promising applications in augmented reality (AR) near-eye displays because of their low operation voltage, high resolution density, broad bandwidth, compact size, and light weight [1,2,3,4,5]. We report three nematic LC mixtures 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 mPa·s) jointly contribute to a fast response time (2.08 ms), which enables 240 Hz refresh rate without the annoying image flickering [18]. Their relatively large dielectric anisotropy (∆ε> 6.6) helps to lower the operation voltage to about 5 V. When used in a reflective 90° MTN cell for amplitude modulation, submillisecond response time (0.90 ms) and high contrast ratio (2097:1) are achieved at 5 V, which enables 1 kHz frame rate operation
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