Conventional stereoscopic displays present images at a single focal plane. As a result, the focal distance to points in the image is usually inconsistent with the depicted scene, resulting in a mismatch or conflict between the stimulus to accommodation and the stimulus to vergence. This causes two significant problems. First, distance information from accommodation specifies the properties of the display surface, not the depicted scene, which can lead to distortions in perceived depth (Hoffman, Girshick, Akeley, & Banks,
2008; Watt, Akeley, Ernst, & Banks,
2005). Second, because the focal distance and vergence-specified distance typically differ, observers frequently have to accommodate at one distance while converging at another in order to see a single, sharp binocular image. Accommodation and vergence responses are synergistically coupled (Fincham & Walton,
1957; Martens & Ogle,
1959), and attempting to decouple them has been shown to lead to visual fatigue (Hoffman et al.,
2008; see also Emoto, Niida, & Okano,
2005; Ukai,
2007; Ukai & Howarth,
2008; Wann & Mon-Williams,
1997; Yano, Emoto, & Mitsuhashi,
2004), difficulty fusing stereoscopic images (Akeley, Watt, Girshick, & Banks,
2004; Watt, Akeley, Girshick, & Banks,
2005), reduced stereoacuity (Hoffman et al.,
2008), and unstable accommodation responses (Fukushima, Torii, Ukai, Wolffsohn, & Gilmartin,
2009).