Environment monitoring system

An environment monitoring system for monitoring a relative relation between one's own vehicle and another surrounding vehicle comprising:

• image pick-up means for picking up two early and later images which are located at a front, rear or diagonal-rear position from one's own vehicle at two early and later timings and on the basis of the images thus picked-up, detecting white lines of one's own vehicle lane on which one's own vehicle runs;
• monitoring region setting means for setting a monitoring region in one's own vehicle lane or an adjacent lane on the basis of the white lines thus detected;
• and
• optical-flow detecting means for detecting an optical flow generated from another surrounding vehicle within the monitoring region, wherein said optical-flow detecting means comprises:
• means for reverse-projection converting said early image on the basis of a predetermined optical arrangement of said image pick-up means onto an x-z plane in parallel to a road surface in a real space to acquire a road surface image;
• means for computing a moving distance of one's own vehicle between the two timings on the basis of a time interval between said two timings and speed information of one's own vehicle;
• means for parallel-shifting the road surface image by the moving distance thus computed;
• means for projection-converting the road surface image after parallel-shifted to acquire an estimated image of the later image in timing;
• means for acquiring a differential image between the later image and its estimated image to extract a feature point;
• and
• means for searching a corresponding point of the feature point extracted, thereby-detecting the optical flow.