Time Counts! Some Comments on System Latency in Head-Referenced Displays

System response latency is a prominent characteristic of human-computer interaction. Laggy systems are; however, not simply annoying but substantially reduce user productivity. The impact of latency on head referenced display systems, particularly head-mounted systems, is especially disturbing since not only can it interfere with dynamic registration in augmented reality displays but it also can in some cases indirectly contribute to motion sickness. We will summarize several experiments using standard psychophysical discrimination techniques that suggest what system latencies will be required to achieve perceptual stability for spatially referenced computer-generated imagery. In conclusion I will speculate about other system performance characteristics that I would hope to have for a dream augmented reality system.