Bidirectional raster scanning to increase time for vector writing in avionics see‐through displays

Abstract

AbstractSee‐through displays (STD) like head‐up displays (HUD) play major role in providing aircraft data to pilot through a visual interface. The data is displayed in form of symbology in pilot's line of sight using vector scanning technique and is deciphered to get flight and mission information. Contrast ratio required to see against bright sunlight at high altitudes is given only by luminance of cathode ray tube (CRT). Therefore, CRT is still used as display source in avionic HUDs, although other devices are also being explored for these applications. Aircraft's night mode operation requires raster display of external scene information along with vector data display due to low visibility during night. It reduces time available for writing vector data during night mode resulting in reduced symbology. Conventionally used raster scanning methods are unidirectional scanning methods. Bidirectional raster scanning (BRS) is an unconventional approach which scans display screen from both directions. In present work, an algorithm for BRS has been developed in VHDL providing more time for vector writing by increasing vertical retrace period (VRP) of raster scanning. Functional verification of design has been performed by simulations carried out through test‐bench and VRP is increased to 5.8304 ms from conventional 1.2800 ms per field.