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Abstract

Described is an image tracking device that includes an array of light-sensitive elements. A row and a plurality of columns define the array, and an intersection of the row with one of the columns defines a cell frame. The row and columns are arranged in non-rectilinear geometry. Each cell frame has a frame area, and one of the light-sensitive elements is disposed in each cell frame. Each light sensitive element has an active area that generates an electrical signal indicative of light from a portion of an image that is incident within the cell frame containing that element. A fill-factor is defined by the ratio of the active area in a cell frame to the frame area of that cell frame. Two-dimensional motion of an image that is incident on the array can be tracked by whole-frame correlations between successive images from the array thereby eliminating the need for localized correlations throughout the array and subsequent curvilinear transformation algorithms to convert motion data throughout the image from an otherwise rectilinear array into data that is representative of the actual two-dimensional motion of the object. Geometric distortions produced by an optical system that focuses an image on the array or by curved object surfaces can be corrected or compensated for by arranging the array in a non-rectilinear shape that matches the geometric distortion in the image. For example, the array can have a pincushion shape or a barrel shape to compensate for pincushion distortion or barrel distortion respectively. Moreover, the flexible sizing of the active area in each cell frame can be used to compensate for fixed illumination gradients in an image incident on the array. The pitch of cell frames can be made to effect an image resolution that is dependent on position within the array. Active area shapes and positions within cell frames can be varied to reduce errors caused by aliasing.

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