Patent ID: 8068214

Claim:
In an optical tracking system, a method for tracking a distorted optical image using centroiding, comprising the steps of: projecting a laser pencil beam towards the source of the distorted optical image; projecting a portion of the projected beam on a focal plane array comprising a number of pixels; detecting from the output of selected pixels of the focal plane array the center of energy of the projected laser beam to establish a precise aiming direction of the laser beam; imaging the distorted optical image on the focal plane array; detecting from the output of selected pixels of the focal plane array to the center of energy of the distorted optical image; and, moving the direction of the projected laser beam such that the center of energy of the distorted optical image is coincident with the center of energy of the projected laser beam on the focal plane array, thus to provide laser pointing accuracy commensurate with sub-pixel level resolution, the center of energy of either the distorted optical image on the focal plane array or the center of energy of the portion of the projected laser beam on the focal plane array being ascertained by: taking a small array of adjacent pixels of the focal plane array that constitute a subset of the pixels in the array and ascertaining for each column passing through vertically arranged pixels in the subset of pixels the sum of the energies in the vertically-arranged columns, and for each horizontal row through horizontally arranged pixels in the subset of pixels the sum of the energies in the horizontal rows; and dividing both of the sums by the sum of the energy in the horizontally arranged pixels and the sum of the energy in the vertically arranged pixels, thus to provide in the horizontal and vertical directions the position of the center of energy of the image on the focal plane array.