Abstract
A dual-stimuli polarizer-free dye-doped liquid crystal (LC) dimmer is demonstrated. The LC composition consists of photo-stable chiral agent, photosensitive azobenzene, and dichroic dye in a nematic host with positive dielectric anisotropy. Upon UV exposure, the LC directors and dye molecules turn from initially vertical alignment (high transmittance state) to twisted fingerprint structure (low transmittance state). The reversal process is accelerated by combining a longitudinal electric field to unwind the LC directors from twisted fingerprint to homeotropic state, and a red light to transform the cis azobenzene back to trans. This device can be used as a smart dimmer to enhance the ambient contrast ratio for augmented reality displays.
Highlights
See-through augmented reality (AR) displays, such as Google Glass, HoloLens, and Magic Leap One, are emerging due to their useful applications in education, engineering design, medical, retail, transportation, automotive, aerospace, gaming, and entertainment, just to name a few [1,2,3,4,5,6,7]
A smart dimmer placed in front of the AR display helps to control the incident background light, which in turn improves the ambient contrast ratio
The electric field-induced liquid crystal (LC) director reorientation changes the absorption of dichroic dyes, which in turn alters the transmittance of the incident background light
Summary
See-through augmented reality (AR) displays, such as Google Glass, HoloLens, and Magic Leap One, are emerging due to their useful applications in education, engineering design, medical, retail, transportation, automotive, aerospace, gaming, and entertainment, just to name a few [1,2,3,4,5,6,7]. To enhance ambient contrast ratio, we could either boost the display luminance or dim the incident background light through a built-in sensor The former is called adaptive brightness control, while the latter is called smart dimmer. Dichroic dye (guest) doped LC (host) device is a potential candidate for smart dimmer due to its wide view, low cost, and polarizerfree characteristics [22,23]. In such a device, transmittance changes from high to low by exposing a UV (or blue) light, while the reversal process is carried out by a red light. Such an electric-field-assisted reversal time can be reduced from ~10 seconds to a few milliseconds, depending on the applied voltage
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