Focus-tunable and Fixed Lenses and Stereoscopic 3D Displays

International audienceStereoscopic 3D (S3D) displays provide an enhanced sense of depth by sending different images to the two eyes. But these displays do not reproduce focus cues (blur and accommodation) correctly. Specifically, the eyes must accommodate to the display screen to create sharp retinal images even when binocular disparity drives the eyes to converge to other distances. This mismatch causes discomfort, reduces performance, and distorts 3D percepts. We developed two techniques designed to reduce vergence-accommodation conflicts and thereby improve comfort, performance, and perception. One uses focus-tunable lenses between the display and viewer’s eyes. Lens power is yoked to expected vergence distance creating a stimulus to accommodation that is consistent with the stimulus to vergence. This yoking should reduce the vergence-accommodation mismatch. The other technique uses a fixed lens before one eye and relies on binocularly fused percepts being determined by one eye and then the other, depending on simulated distance. This is meant to drive accommodation with one eye when simulated distance is far and with the other eye when simulated distance is near. We conducted performance tests and discomfort assessments with both techniques and with conventional S3D displays. We also measured accommodation. The focus-tunable technique, but not the fixed-lens technique, produced appropriate stimulus-driven accommodation thereby minimizing the vergence-accommodation conflict. Because of this, the tunable technique yielded clear improvements in comfort and performance while the fixed technique did not. The focus-tunable lens technique therefore offers a relatively easy means for reducing the vergence-accommodation conflict and thereby improving viewer experience