Stabilization of Magnified Videos on a Mobile Device for Visually Impaired

The camera function in smart phones has a great potential to help visually impaired people with discerning scene details. Many apps have been developed to turn a smart phone into a handy video magnifier using digital zoom. As digital zoom normally cannot provide sufficient magnification for distant objects, optical telescopic devices attached to the smart phone cameras can be used to increase magnification power. However, image jitter of hand held phone cameras is greatly enlarged too, and can impair patients´ reading efficiency, especially for distant objects. Gyro-sensor based stabilization methods are not effective for this application due to the limited precision of the gyro-sensor in common mobile devices. We have implemented an image motion based video stabilization method on iOS that is more sensitive than the gyro-sensor. The image motion based stabilization not only appeared to be able to remove most of the image jitter visually, it also improved the performance of human subjects, including 2 visually impaired, at discerning distant details.