A new method to determine 3D motion and structure based on spare optical flow is presented. Motion analysis can be roughly classified as feature based or flow based

according to if the data they use are a set of features matches or an optical flow field. The proposed method integrates feature based and flow based method by using the corner points as feature points and estimating sparse optical flow field. Firstly

detecting and tracking corner points in image sequence and the locations of tracked corner points were recorded. Then

we proved that optical flow field could be replaced using displacement field approximately in theoretically

so the optical flow field was estimated at sparse locations by measuring the displacement of corner points between consecutive frames. Finally

a new linear method is derived to determine the 3D motion and structure at each corner point from known optical flow field. Experimental results using real image sequences showed that the presented method provided a good estimation of the optical flow field and 3D motion and structure.