Summagraphics Corporation

Science Accessories Corp.

Robert L Davis

Joseph A Howells

Stephen L Domyan

A digitizer having a pointer or cursor driven by an alternating carrier signal and a grid of sequentially enabled parallel spaced conductors inductively coupled to the cursor in which enabling of the conductors is initiated at an origin conductor and continues with a serial scan of the conductors until a phase change is detected when the cursor is between the origin conductor and an enabled conductor. The grid is sub-divided into overlapping sections which are scanned in sequence until the pointer is located. After the pointer is located, the conductor enabling scans begin at a conductor enabling device a predetermined distance from the enabling device actuated when pointer position was detected. Means are provided for re-initiating conductor enabling scans at the origin conductor in the absence of detection of the pointer.

Digitizer with floating scan

A position coordinate determination device wherein data generation lines are displaced from the edges of a data surface, and a sensing device is movably located on the surface. Erroneous detection of data resulting from reflection of signals at the edge of the sheet is inhibited by summing the times required for waves to pass between the sensor and both data generation lines. When this sum exceeds a predetermined level, an erroneous detection is indicated and the processing of the data may be inhibited.

Position coordinate determination device

An apparatus for determining the position of a movable element or stylus which is movable in a data space. In accordance with the invention there are provided first and second spaced receivers, each receiver comprising a hollow shell of piezoelectric material, which may be cylindrical or spherical in shape, and resilient conductive means coupled across the inner and outer surfaces of the shell. Means are provided for periodically generating a source of sound waves for travel between the stylus and the first and second receivers. Timing means are coupled to the receivers and synchronized with the generation of the sound waves for measuring transit time of the sound waves between the source and receivers. Computing means are employed to determine the positional coordinates of the stylus in a desired coordinate system, such as rectangular coordinates. In an embodiment of the invention the first and second receivers have conductive mesh loaded within the shell and in contact with the inner surface of the shell. In this embodiment a spring contact is coupled to the outer surface of the shell. In an embodiment of the invention the movable element or stylus is passive and means are provided for periodically generating sound waves at a source position spaced from the movable element. This eliminates the need for an 'active' stylus and the problems associated therewith.

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Prospect, CT, United States of America

Robert L Davis