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.