Over the last 20 years Liquid Crystal Display (LCD) technology has been rapidly advancing. Next generation LCDs are utilizing transparent and flexible substrates and various polymers as supporting material instead of glass. Many of the new applications using LCDs, such as smartphones, have improved functionality and safety. In the automotive industry, displays are being used to convey information to drivers, such as calls and text messages and vehicle speed and maintenance. Although, the most important display, the windshield and windows, have changed little over the last two decades.
These transparent displays are essential for drivers to observe and navigate through their environment, while protecting them from nature and other potential hazards. However, due to the properties of these displays there exists an inherent hazard; the transmission of too much light that may cause Temporary Visual Obstruction (TVO). Sources of TVO's include natural and artificial sources, such as sunlight and vehicle headlights. Each of these sources may directly or indirectly cause occupants to experience TVO, for instance glare from roadways and other vehicles. In the past, attempts to prevent TVO's include: tinting portions of or entire windows and using Electro-Chromics (e.g., transitions lenses). Both methods have limited success due to their inability to adjust to light intensity and time-varying conditions.
From 2004-07, the National Highway Traffic Safety Administration determined 16.4% of accidents in the United States (US), attributed to roadway and atmospheric conditions, were caused by glare. In 2005 and 2012 the total number of vehicles operated (cars and commercial vans) increased by 14 million and 115 million in the US and the world, respectively. As of 2012, 1.1 billion vehicles were operated worldwide. As a result new and improved transportation safety devices are needed to prevent such accidents from occurring.
The two primary goals for this project includes: reducing vehicle accidents originating from TVO's and providing an affordable-post-manufactured insert display and modified vehicle windshields that can be installed in vehicles without requiring extensive and expensive vehicle modifications.
To accomplish these goals a three part system is being designed: a hemispherical light detector to measure the intensity of transmitted light at various angles, a control system to interpret data and output a unique signal based on a drivers location and the current lighting conditions, and a passive Polymer Dispersed LCD (PDLCD) with locally variable transmittance coordinated by an array of embedded microprocessors. Smart Shield will primarily utilize a polymer film substrate instead of traditional glass substrates. Manipulating the display's material, encapsulated liquid crystal droplet size, and display thickness the optimal transmittance during the on and off periods can be achieved. A distinct advantage to using PDLCDs is the shallow voltage threshold curve that allows the transmittance to be more easily regulated and the high efficiency light scattering ability that reduces the total power consumption. Compared to previous attempts and traditional LCDs, Smart Shield has the potential to provide increased controllability, sensitivity to light intensity and time-varying conditions, and reduce overall fabrication complexity and expense.