High-resolution optical see-through vari-focal-plane head-mounted display using freeform Alvarez lenses

With recent developments in the manufacturing of freeform surfaces, Alvarez lenses have recently surfaced as an attractive method to achieve large focal ranges rapidly while still maintaining a compact structure. These characteristics make Alvarez lenses ideal for rendering correct focus cues in virtual/augmented reality (AR/VR), solving the vengeance- accommodation conflict. This paper presents a novel design combining a compact eyepiece with two lateral shifting freeform Alvarez lenses to create a compact, high-resolution, tunable optical see-through head-mounted display (OST- HMD) design capable of optical power shifts from ~ 0-3 diopters. Currently limited by the speed of the actuators that mechanically translates the Alvarez lenses for optical power tuning, the display system is capable of achieving the entire range of focus shift with an update rate of 50Hz. The proposed design renders near-accurate focus cues with high image quality and a large undistorted see-through field of view (FOV), utilizing an 1920x1080 color resolution organic LED (OLED) microdisplay to achieve virtual display FOV greater than 30 degrees diagonally, with an angular resolution less than 0.85 arcminutes per pixel and an average optical performance of > 0.4 contrast over the full field and a contrast above 0.2 at the Nquist frequency of 63 cycles/mm.