The work described here is part of the U.S. Air Force-sponsored Operational Based Vision Assessment (OBVA) program that has been tasked with developing a high-fidelity flight simulation laboratory to determine the relationship between human vision and performance in simulated operationally relevant tasks. The OBVA simulator was designed and built to provide the Air Force School of Aerospace Medicine (USAFSAM) with a scientific testing laboratory to study human vision and testing standards.
The exceptional visual acuities of Air Force pilots required the simulator to present significantly greater pixel density than was currently available in existing technologies. This necessitated the development of a higher-fidelity image generator system, based on emerging technologies, than systems currently available as a complete solution. This innovation resulted in a 150-megapixel, synchronized, continuous display system driving real-time computer-generated imagery at a 60-Hz refresh rate.
The most significant requirement of the OBVA simulator is that it should generate observer-limited imagery. That is, visually dependent performance measured during simulated operational tasks must be limited by the observer’s visual system and not the generated imagery or the display hardware. In the spatial domain, this requires a pixel pitch of about 0.5 arcminute and imagery that matches the display sampling rate. The temporal sampling requirements are less well defined. Although the human visual system is not sensitive to stationary temporal modulation that exceeds approximately 60 Hz, simulation of moving objects requires higher frame rates in order to avoid visible motion artifacts due to sampling or hold properties.
With the possible exception of high sampling requirements, the OBVA simulator design goals are similar to those of many flight simulators. Because of the need to tile multiple projectors on a spherical screen with high accuracy, tools were used that would automate and simplify the setup for required warping and blending operations. Further, quantifying and minimizing system latency for the various subsystems and devising methods to measure total system latency within the simulator became important objectives to properly characterize the system. Finally, in order to minimize cost and leverage commercially available solutions, commercial off-the shelf (COTS) hardware and software components were used when possible.
There are three key parts of the OBVA simulator: a real-time computer image generator, various COTS technologies used to construct the simulator, and a spherical dome display and real-time distortion correction subsystem. The utilization and selection of the right COTS tools and components (hardware and software) for the OBVA image generator have proven successful thus far.