Structured laser light improves tripping hazard recognition for people with visual impairments

Abstract

Purpose: Using a geometrically derived model and a virtual curb simulator, we quantify the degree to which a wearable device that projects a laser line onto tripping hazards in a pedestrian’s path improves visual recognition for people with visual impairments (VI). We confirm this with subjects’ performance on computer simulations of low contrast curbs. Methods: We derive geometric expressions quantifying the visual cue users perceive when a single laser line is projected from their hip onto a curb. We show how the efficacy of this cue changes with the angle of the laser line relative to the subject’s walking trajec-tory. We confirm this result with data from three subjects with VI in a simulated curb recognition task in which subjects classified computer images as an “Ascending,” “Flat,” or “Descending” curb. Results: The derived model predicts that human recognition performance depends strongly on the laser line angle and the subject data confirms this (r2 = 0.86, P < 0.001). The laser line cue improved subject accuracy from a chance level of 33% to 95% for a simulated, one-inch, low-contrast curb at a distance of five feet. Conclusions: Recognition of curbs in low light can be improved by augmenting the scene with a single laser line projected from a user’s hip, if the angle of laser line is appro-priately selected. Translational Relevance: A majority of people with VI rely on their impaired residual vision for mobility, rather than a mobility aid, resulting in increased injury for this population. Enhancing residual vision could promote safety, increase independence, and reduce medical costs.