Accommodation to multiple-focal-plane displays: Implications for improving stereoscopic displays and for accommodation control.
Most stereoscopic displays present images at a single focal plane, resulting in "conflicts" between the stimuli to vergence and accommodation. Minimizing these conflicts is beneficial because they can cause distorted depth percepts, visual fatigue, and reduced stereoscopic performance. One proposed solution is to present a sum of images at multiple focal planes and to vary focal depth continuously by distributing image intensity across planes-a technique referred to as depth filtering. We evaluated this digital approximation to real-world variations in focal depth by measuring accommodation responses to depth-filtered stimuli at various simulated distances. Specifically, we determined the maximum image-plane separation that supported accurate and reliable accommodation. We used an analysis of retinal-image formation to predict when responses might be inaccurate. Accommodation to depth-filtered images was accurate and precise for image-plane separations up to ∼1 diopter, suggesting that depth filtering can be used to precisely match accommodation and vergence demands in a practical display. At larger plane separations, responses broke down in a manner consistent with our analysis. We develop this approach to consider how different spatial frequencies contribute to accommodation control. The results suggest that higher spatial frequencies contribute less to the accommodation response than has previously been thought.