Investigation of five types of switchable retroreflector films for enhanced visible and infrared conspicuity applications

Abstract

We report on the physics, design, characterization, and demonstration of five viable techniques for switchable retroreflectors, including integrated electrowetting scattering, integrated and external electrowetting light valves, external liquid crystal light valve, and external liquid crystal scattering. All techniques were evaluated for use in conspicuity applications spanning wavelengths in the visible and IR (night vision). Achieved performance includes high optical efficiencies up to nearly 30% (out of a maximum 35%), visibly fast switching speeds of <100 ms, low to moderate operating voltages ranging from 5 to 60 V, more than ±45 deg of operation angle, and implementation with pressure-sensitive, adhesive-backed films of 0.7 to 1 mm thickness for flexibility and impact resistance. Each approach has unique strengths and weaknesses, which will also be discussed for applications ranging from commercial to military conspicuity.

Tag system with low-powered tag and depth sensing camera

“…It is often used as an electrically controlled screen [11] or privacy glass and has been applied as a programmable window [28]. PDLC can be applied as a shutter [9,25], and an investigation of several types of switchable retroreflector including a PDLC with a retroreflector has been reported [33].…”

Retroreflective Janus Microparticle as a Nonspectroscopic Optical Immunosensing Probe

“…Interestingly, the retroreflector responds to various light sources, including visible light, infrared light, and even nonmonochromatic light. 16,19,20 Thus, retroreflectorassociated retroreflection can be easily induced and detected Figure 1. Schematic illustration of a typical light path in retroreflection.…”

An embedded microretroreflector-based microfluidic immunoassay platform

“…Retroreflectors are highly detectable structures that efficiently reflect light back to its source over a broad range of angles. Arrays of spherical (transparent high-refractive index spheres partially coated with a reflective surface) or corner-cube retroreflectors (with three mutually perpendicular reflective surfaces) with dimensions on the order of 100 μm to several millimeters find applications in road markings and personnel or vehicle conspicuity (as retroreflective tape or paint), 38,39 remote sensing of air pollutants, 40 lunar laser ranging, 41 and as components of laser interferometers. 42 We have previously reported the fabrication of suspended 5 μm corner cube retroreflectors 43 and their use as optical immunoassay labels.…”