Eliminating Pupil Swim Effect in AR/VR Displays
The geometry-deforming effect inherent to head-mounted display optics is removed using advanced computational imaging along with custom optical profiling tools.
Every near-eye display optical system has geometry distortions, which are computationally pre-corrected before the image is projected (so-called “pre-warp”). That distortion, however, changes as the eye moves, so the pre-warp works well only in the tiny sweet spot – with the user looking straight and the display sitting in the ideal position on the head.
With even a slight display misalignment, or with eyeball movement – quite a natural part of the vision – the geometry of the XR scene gets distorted and “flowing”. This effect called Pupil Swim greatly spoils the visual experience, making it unnatural and even causing dizziness and nausea. The effect inevitably becomes more apparent and annoying as the field of view of the displays gets wider.
Almalence Digital Lens, a complete solution for near-eye display optics correction, now includes the correction of the Pupil Swim effect. The pure computational solution adds no extra size, weight, or cost to the optical system, at the same time, drastically improving the visual experience and removing the fundamental roadblock on the way to achieve a realistic look and feel of Virtual Reality.
The video below shows pupil swim elimination on the latest-and-greatest displays at the moment, Pico 3 Neo:
Besides the image pre-processing algorithm itself, the elimination of geometry distortion and deforming requires precise profiling of the optical system properties depending on the eye pupil position.
Almalence has developed its custom optical profiling hardware and software, an essential part of which is the Human Eye Simulator. By both copying the optical properties of the human eye and mimicking a human eye to eye-tracking systems, it allows precise profiling and testing of every aspect of the near-eye display optics – from blur and smear to chromatic aberrations to geometry distortions.
The wide-angle configuration of the Human Eye Simulator with a large entrance pupil captures the entire field of view at once and was specifically designed for geometry distortion correction. It allows us to measure the distortions at all eye pupil positions and to pre-calculate the image transformation that keeps the ideal geometry of the scene even outside of the sweet spot.