Vergence accommodation conflict: breaking the near-vision barrier with focus tuneable lenses

The optical architecture of VR/AR devices usually puts the image plane of the display 1.5 – 2.0 meters from the eyes, whilst stereoscopy is used to give an impression of depth. The resulting mismatch in where the crystalline lens of the eye focuses (accommodation) and the vergence of the eye, is unnatural to the visual system and causes an imbalance that can lead to nausea. Developer guidelines from manufacturers advise against placing content closer than the image plane to avoid VAC induced discomfort. A similar problem is more apparent with AR headsets, where content shown on the display is not in focus if the eyes are focused on a real-world target closer than about 1.5 meters. This focal rivalry presents challenges for the many new applications utilising hand tracking to stimulate interaction with virtual objects. Focus tuneable lenses can be used to move the focal plane of the display to match the plane of accommodation. This presentation will compare the approaches to mitigate VAC and assess focus tuneable lenses in more detail, along with some details of a study using voice-coil actuated Alvarez lenses.