US Patent 9251708 Forward collision warning trap and pedestrian advanced warning system

A method for providing a forward collision warning using a camera mountable in a motor vehicle. The method acquires multiple image frames at known time intervals. A patch may be selected in at least one of the image frames. Optical flow may be tracked between the image frames of multiple image points of the patch. Based on the fit of the image points to a model, a time-to collision (TTC) may be determined if a collision is expected. The image points may be fit to a road surface model and a portion of the image points is modeled to be imaged from a road surface. A collision is not expected based on the fir of the image points to the road surface model.