Calcomp Inc.

Dana Doubrava

James S Watson

Waldo L Landmeier

Methods and apparatus are shown for correcting velocity-induced offset errors in a digitizing system when the cursor is moved diagonally across a sensing grid. Primarily, this is a system for reducing the offset error in the actual and depicted cursor position when a pen cursor is moved rapidly over a digitizing screen of a pen-driven computer. It also provides double the number of positional outputs for added accuracy. A triplet of data is formed by taking two samples from one axis and one from the second axis. The two samples are averaged to form one component of the cursor position and then the average along with the single sample from the other axis are output as the positional coordinates. A second sample is then taken from the second axis to form a new data triplet. The averaging process is repeated with the two data points from the second axis and the average along with the second sample from the first axis are output as a next position of the cursor. The process of inputting a next data point from the axis other than the last sampled to form sequential data triplets is repeated to track the movement of the cursor and output its position.

Digitizer cursor velocity offset error correction system

Methods and apparatus for setting the signal-sampling period of each grid wire in a digitizing tablet having grid wires that are sequentially and repetitively scanned to develop a positional signal related to a cursor so as to reduce jitter associated with non-movement of the cursor and signal error associated with rapid movement of the cursor. The method comprises setting the signal-sampling period of each grid wire to a longest signal-sampling period the digitizer tablet is designed to employ if the cursor is not moving and setting the signal-sampling period of each grid wire to a value inversely related to the present speed of movement of the cursor such that the faster the present speed of movement of the cursor the shorter the signal-sampling period of each grid wire as compared to the longest signal-sampling period the digitizer tablet is designed to employ. The present position of the cursor is then saved as the prior position of the cursor for the next time the steps of the method are performed. The method can also be applied to other positional determination devices in which a cursor is moved over a scanned sensing surface. The apparatus performs the method.

Dynamically-adjustable scanning rate in digitizers

A loopback conductor arrangement for a digitizer grid employs rotation sequencing of the conductors. The conductors in each of the X- and Y-directions are looped back and forth in a parallel, spaced relationship across the active grid area so as to provide a plurality of crossing conductor segments, with the positions of selected conductors (e.g., alternate conductors) in each successive loop shifting in sequential positions by a constant offset with respect to the other conductors in those loops.

Digitizer employing loopback conductor pattern using rotation sequencing

In a digitizer tablet system employing a tablet having equally spaced parallel grid wires disposed in a plane along an axis parallel to the tablet's upper surface and a pen cursor having a sensing coil disposed concentric with and perpendicular to a longitudinal axis of the pen cursor to develop a characteristic output waveform from electromagnetic inductance between the grid wires and the sensing coil, this invention is the method of compensating a calculation of the position of the pen's tip on the tablet's upper surface and along the axis determined from an interpolation of the characteristic output waveform to find its zero voltage crossing point for tilt of the pen cursor longitudinal axis from perpendicular to the tablet's upper surface comprising using voltage values from grid wires next on opposite sides of the zero crossing point to calculate a pen tilt compensation factor.

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Phoenix, AZ, United States of America

Dana Doubrava