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Using a helmet-mounted display computer simulation model to evaluate the luminance requirements for symbology

As the Army increases its reliance upon and continues to develop helmet mounted displays (HMDs) or head-up displays (HUDs), it is paramount that displays are developed that meet the operational needs of the warfighter. During the development cycle, questions always arise concerning the operational requirements of the HMD. These include questions concerning luminance, contrast, color and resolution. To provide intelligent answers to these operational questions, a method has been devised to evaluate these issues. Integral to this method is an HMD simulation model that was previously presented at this meeting. The model is continually undergoing improvements with additional features and improved accuracy. The model allows for the simulation of see-through images with overlaid symbology. In this study, symbology was overlaid over eight natural images, one uniform field, and one artificial background composed of moderate to high spatial frequencies. Observers graded the quality of symbology on a scale of 1 to 7, with 7 representing symbology of high contrast and excellent quality. In all, observers graded 200 images (20 images per background scene). These images ranged from an average Michaelson contrast value of about 0.09 to 0.93. We found, as have others, that the complexity of the backgrounds greatly affected the observer’s rating. The simulated images were analyzed and statistical correlates were developed that could relate to the observer’s ratings. Metrics were developed that could help predict the luminance requirements for HMD or HUD symbology.