Shih-Ping Liou and Jain 1989 : Presents an analysis of existing motion detectors for determining desirable characteristics of a motion detector. A spatio-temporal surface type inseparable model is then proposed for motion detection. Based on this model, the authors analyzed mathematically how the geometry of the intensity hypersurface gives information about motion in image. The local motion information, obtained from the parameters of the Monge patch approximating the intensity hypersurface in the spatio-temporal space, may be used for segmentation of dynamic scenes. Motion detection results for real sequences show the robustness of this detector.