Stereo Camera-based Pre-Focusing Method and Its Application to Detection of Pedestrians Entering The Street

Abstract

For mobile stereo camera systems, constructing three-dimensional (3D) surroundings was an important process to ensure safe navigation; however, it was very time consuming. To decrease the number of traffic accidental deaths, pedestrians entering the street needed to be efficiently detected. Thus, a pre-focusing method (PFM) was proposed to decrease the time required to retrieve matching pixel pairs in stereo pair images. The method PFM provided pre-focused stereo pair images in which an object at a pre-determined distance displays no disparity between images. Pre-focusing was performed by applying a perspective transformation to the image pair, whose coefficients were obtained via a calibration stage of the PFM. An object at the distance was extracted by evaluating the spatial similarity between the pre-focused stereo pair images without scanning in order to find matching point pairs. To avoid errors due to edges and uniform areas, the smooth test, which was a nonparametric test, was introduced to evaluate the spatial similarity. A watching window was introduced to detect the pedestrians. In this study, the method PFM was successfully applied to actual video data captured by a stereo video camera mounted on a bicycle.