Field of view: not just a number

Near-eye display users universally request larger fields of view for enhanced immersion, presence, and device utility. Unlike frame rate or device weight, field of view cannot be represented precisely as a single number. Quoting field of view as a diagonal, a carry-over from the display industry, could refer to either the monocular or stereo field of view and gives no indication of the field of view boundary shape. This work defines an unambiguous metric evaluation of field of view based on solid angle, accounting for eye relief, interpupillary distance, eye rotation, and device alignment. The approach allows optical system designers to identify weak points in the optics/display/rendering pipeline. To accompany modeling, a measurement scheme was developed to metrically compare field of view over various real-world user conditions. Best practices for visualizing and communicating field of view are also presented. This work reviews the methods used to increase field of view, with discussion of the monocular and binocular artifacts that arise in large field of view systems. The limitations and advantages of optical tiling, canting, and extreme distortion are described, using relevant examples in the commercial VR space. The fundamental tradeoffs between resolution, field of view, and optical quality over field are discussed, including a review of methods to maximize field of view without sacrificing on-axis resolution. Until display and optics technology can fully match the human visual system, the intermediate objective is to find the best experience match in field of view, resolution, and optical quality given existing hardware limitations. Qualitative assessments of the relative value of different regions of the human visual field will be provided.