The ability to track eye movements with eyewear has aroused the interest of AR headset developers and developers of mixed reality systems. This is allowing system designers to improve image confidentiality and contrast across the entire length of view without not much demand on the power of projection system. Resultantly, this leads to extended battery life and improved utility of AR system.
In fact, a slew of eye-tracking systems have been studied that have problems of either being bulky or low resolution. Meanwhile, holographic optical elements have been showcased to be suitable for AR eyewear. Holographic optical elements are characteristic of being able to be fabricated for complex optical functions. This includes high efficiency and relatively svelte films that can be placed on curved or flat surfaces.
Dry-processed Covestro photopolymers and dichromated gelatin have emerged to be promising materials for holographic optical elements for AR eyewear. However, the sensing operations in AR systems eyewear require near-infrared wavelengths in the range between 750 and 900 nm. This is beyond the normal sensitivity range of dichromated gelatin from 350 to 550 nm and of PP materials between 450 and 650 nm. This limitation complicates the design of optical elements with focusing power because significant alterations occur when there is difference between reconstruction wavelength and construction wavelength.
Recently, a team of researchers at the University of Arizona devised a holographic input coupling lens for experimentation purpose. To undertake this, the researchers used photopolymer placed on a glass substrate of 0.6 mm thickness and a refractive index of 1.80 that fixes major alterations due to change in the reconstruction wavelength. Additionally, a holographic optical elements out-coupling waveguide multiplexed with five gratings designed and fabricated to magnify the field of view.