Accession Number : ADA297264

Title :   Variable Transmittance Visor Development Program.

Descriptive Note : Final rept. Jul 91-Oct 94,

Corporate Author : LITTON SYSTEMS (CANADA) LTD REXDALE (ONTARIO)

Personal Author(s) : Bahadur, Birenda ; Young, Willard ; Wan, Kam ; Lewis, David

PDF Url : ADA297264

Report Date : NOV 1994

Pagination or Media Count : 70

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)

Descriptors :   *SHUTTERS(OPTICS), *HELMET MOUNTED DISPLAYS, *VISORS, *ELECTROPHORETIC COATINGS, OPTICAL PROPERTIES, DISPERSING, POLYMERS, ILLUMINATION, LIQUID CRYSTALS, TRANSMITTANCE, DARKNESS, BIREFRINGENCE, AVIATION GOGGLES, DYES, OPTICAL COATINGS, DISTORTION, HAZE, LUMINANCE, FLIGHT HELMETS.

Subject Categories : Coatings, Colorants and Finishes
      Optics
      Protective Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE