Variable Transmittance Visor Development Program.
Abstract
This project's objective was to develop a technology for varying the transmittance of conventional flight helmet visors under electronic control for the purpose of enhancing the contrast of helmet mounted displays. The specifications required a 10:1 attenuation range with a clear-state transmittance of 70% or better and no visible coloration, haze, or optical distortion. Two technologies were studied: polymer dispersed liquid crystal (PDLC) and suspended particles. Several low birefringence PDLCs with neutral dye in a guest-host arrangement were tested; they produced excessive haze, apparently because their birefringence, although relatively low, was still too high for the project's purpose. The suspended-particle technology was tested in two forms: fluid and polymer-dispersed. Both forms showed a strong blue coloration in the dark state and neither proved to be compatible with conventional visors; instead, they must be sandwiched between mating halves of custom-built visors. Furthermore, over time, the fluid form developed streaks and dark spots; the polymer-dispersed form developed crazing lines and spatial non-uniformities. We conclude that the suspended-particle technology is not promising, but guest-host PDLC deserves further exploration if PDLCs having lower birefringence become available. (MM)
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1994
- Accession Number
- ADA297264
Entities
People
- Birenda Bahadur
- David J. Lewis
- Kam Wan
- Willard Young