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Frank S Werblin, Robert W Massof, Nicole C Ross, Danielle Natale, Chris Bradley, Boger Yuval, David Teitelbaum; Gaze-Directed Magnification: Developing a Head-Mounted, Wide Field, Immersive Electronic Low Vision Aid . Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2226.
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© ARVO (1962-2015); The Authors (2016-present)
Design, develop and test a mobile head-mounted electronic low vision enhancement device with immersive wide field of view integrated with a region-of-interest gaze-directed magnification "bubble" locked to the patient's preferred retinal locus (PRL).
System has 120 degree binocular field of view in HMD with 70 deg binocular overlap. We use two 5 inch 1080p smartphone displays, one for each eye with resolution of 3 arcmin/pixel. The images from a HMD-mounted central field camera resolution of 2 arcmin/pixel and a peripheral field camera resolution of 5 arcmin/pixel, are “stitched” together to create a panoramic montage. The magnification bubble is positioned and maintained at the patient's PRL by tracking pupil position. Eye tracker is NTSC miniature IR-sensitive video camera placed below each eye illuminated with IR. The display is enriched with edge and contrast enhancement, ambient illumination level control, and additional image remapping.
The sensor and processing systems minimize processing delays so that eye tracking and natural image motion with head movements run essentially in real-time. Pupils are tracked at 30 fps (with an angular resolution of 7 arcmin) providing bubble position coordinates within 33 msec (one frame).The magnification bubble is processed within ~10 msec, then rendered into the scene and displayed in the HMD within 16 msec. Therefore, the overall processing for repositioning the bubble in the scene, locked on the PRL, is less than 60 msec, a delay short enough that subjects do not experience motion of the bubble when making saccades.
Our proof-of-principle prototype demonstrates that it is feasible to build a wide field of view head-worn low vision enhancement device that can perform gaze-directed image remapping and other forms of real time image processing. Currently, this apparatus is being used to test the visual performance of low vision patients while navigating and viewing with gaze-directed bubble magnification
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