A real-time automatic ranging algorithm for vision systems

A high-speed algorithm has been devised to determine the range from a video camera to objects in its field-of-view. As the camera focus control is adjusted, the algorithm will detect each object feature as it comes into sharpest focus. The range from the image plane to the object can then be computed from the corresponding lens-to-image distance, which is known. The level-of-focus (LOF) algorithm is computationally simple, and may be performed in hardware in real-time for reasonable frame rates and pixel densities. The spatial resolution of the ranging information is a function of the lens F-stop, the sensitivity of the video sensors, the S/N ratio of the observed scene, and the range to the object. The LOF algorithm has been validated by simulating a variable parameter camera which views objects whose shapes, S/N ratios, and ranges may be varied.