Reducing the minimum range of a RGB-depth sensor to aid navigation in visually impaired individuals

The introduction of RGB-depth (RGB-D) sensors harbors a revolutionary power in the field of navigational assistance for the visually impaired. However, RGB-D sensors are limited by a minimum detectable distance of about 800 mm. This paper proposes an effective approach to decrease the minimum range for navigational assistance based on a RGB-D sensor of RealSense R200. A large-scale stereo matching between two infrared (IR) images and a cross-modal stereo matching between one IR image and RGB image are incorporated for short-range depth acquisition. The minimum range reduction is critical not only for avoiding obstacles up close, but also in the enhancement of traversability awareness. Overall, the minimum detectable distance of RealSense is reduced from 650 mm to 60 mm with qualified accuracy. A traversable line is created to give feedback to visually impaired individuals through stereo sound. The approach is proved to have usefulness and reliability by a comprehensive set of experiments and field tests in real-world scenarios involving real visually impaired participants.