Variable-Transmittance Visor for Helmet-Mounted Display.

摘要

Efficient operation of HMD's (helmet-mounted displays) requires the use of VTV's (Variable-transmittance visors) to maintain constant visual contrast between projected images and their backgrounds. No VTV's responding controllably or reversibly with rapidity had been developed prior to this program. A high-priority military objective was to encourage the design and development of such VTV's. An unsolicited proposal to the USAF, based on a new concept, suggested the use of a liquid optronic medium in a sandwich-cell visor configuration with automatic control of variable transmittance. Three such units were installed in flight helmets and delivered to the customer as airborne feasibility demonstrators. These accommodated variations in external brightness over a range greater than 80:1. Automatic regulation was provided from light sensors, behind the visors, connected to closed-loop, electronic controllers using 28-vdc aircraft power. Controllers were packaged as pocket-size units with self-contained batteries for emergency operation. Most effort was directed toward solving critical problems involved in the selection, processing, and fabrication of materials suitable for this application. Among the many mathematical relationships, both optical and optronic, put to practical use in the VTV design were several derived.