Patent ID: 7893924

Claim:
A data input device comprising: an illuminator operative to illuminate at least one engagement surface; a two-dimensional imaging sensor viewing said at least one engagement surface from a location outside said at least one engagement surface for sensing engagement of a data entry object with said at least one engagement surface; and a data entry processor receiving an output from said two-dimensional imaging sensor and providing a data entry input to utilization circuitry, said data entry processor employing shadow analysis, said data entry processor comprising the following functionality: as each pixel value is acquired, determining, using the pixel coordinates, whether that pixel lies within a predefined keystroke region and within predefined left and right keystroke subregions therewithin; acquiring pixel values for various pixel coordinates; obtainining the derivative of each pixel value along an X axis; summing said derivatives for each said subregion; subtracting the summed derivatives for the two subregions in each keystroke region, one from the other to provide a difference; comparing said difference with a current key actuation threshold; if the difference exceeds the key actuation threshold for a given keystroke region in a given frame and in the previous frame the pixel total did not exceed the key actuation threshold for that keystroke region, providing a key actuation output; and if the difference does not exceed the key actuation threshold for a given keystroke region in a given frame and in the previous frame the pixel total did exceed the key actuation threshold for that keystroke region, providing a key deactuation output.