Add-on optical mask to declutter visual information based on depth for visual prostheses.

Abstract

One of the challenges in retinal and cortical visual prostheses is decluttering the visual information of the scene. Current device use brightness information, therefore, bright faraway targets can dominate the perception and nearby obstacles may be missed. Therefore, the aim is to ensure that visual information of interest is delivered to the implant. To achieve this, it is essential to obtain information regarding the distance of each object in a scene. Owing to limited power requirements, it is problematic to use an active depth sensor such as Lidar, which requires strong illumination. specifically, in outdoor environments. Depth sensors based on stereo imaging require heavy computational resources, which is also problematic in wearable devices. There is a need for simple passive and robust depth sensor. Herein, we demonstrate the usability of an optical mask that can be placed in front of any RGB camera to create a depth sensor. The mask introduces chromatic aberrations and artificially separates the colors by creating pre-defined phase errors that shift the focal plane as a function of the wavelength. We designed and fabricated a mask that, in combination with the lens of the camera, allows each color to be in focus at a different distance. The red channel produces a focused image for objects that are in the near range, the green channel focuses objects at the mid-range, and the blue channel focuses distant objects. Because realistic targets contain radiation at all wavelengths, they appear in focus at the color channel that matches their distance. Finally, a standard deviation image filter is used to extract only the information that is in focus and to convert the color information to depth information. Clinical Relevance-The proposed method can enhance the usability and functionality of current and future visual prostheses, specifically in outdoor environments, by providing depth information using a passive miniature optical device.