Coordinate digitizing device

Abstract

Coordinate digitizers comprise a data tablet having perpendicular X and Y axes grids, which cross each other to define a data surface. Each grid has a plurality of parallel evenly-spaced-apart grid wires having their ends connected by end busses. An inductor connected to an alternating electrical input signal is movable on the data surface, and induces current flow in loops comprised of individual grid wires and end busses, with the strength of the current strongest in the grid wires near the inductor. Each grid has a receptor loop into which signals from the grid are induced, and the receptor loop is preferably deployed in a receptor area off the data surface. The receptor loops are configured such that signals induced therein correlate to inductor position on the data surface. The receptor loops are preferably composite loops providing complimentary signals to compensate for variations in the input signal or an induction-to-grid coupling. The data tablet may be translucent and backlighted to form a light-box digitizer. A microprocessor calculates inductor position from the receptor loop signals. A self-contained cursor comprising an inductor coil, signal generator means and a battery power supply in a housing for use on the data tablet eliminates input leads.