Summagraphics Corporation

Science Accessories Corp.

Thomas L Stone

Seymour J Sindeband

An apparatus is disclosed for determining the position of a moveable element over the surface of a solid medium. First and second transducer devices are provided and are moveable for placement at selected respective first and second locations on the surface for coupling with said surface. A third transducer device, for coupling with said surface, is mounted with the moveable element. Ultrasonic energy is transmitted, in either direction, between the third transducer device and the first and second transducer devices, the ultrasonic energy travelling through said solid medium. The transit times of the ultrasonic energy propagating, in either direction, between the third transducer device and the first and second transducer devices are determined, the transit times being indicative of the position of the third transducer device with respect to the first and second transducer devices. In a disclosed embodiment, the first and second transducer devices have tips that are feet of a housing and contact the surface over an area that is less than 2 mm.sup.2 and preferably, less than 0.5 mm.sup.2. A reflection reducer is provided at at least some of the edges of the solid medium.

Position determining apparatus

A digitizer tablet with a cordless transducer which is capable of providing to the tablet information relating not only to the position of the pointing device but also with respect to the status of any button switches on the transducer. This is obtained by providing a plurality of oscillators, connected in circuits in which the relative ratio of the signal frequency outputs of the oscillators can be varied in response to activation of a switch while at the same time the sum of the amplitudes of the oscillating signals remain constant. Thus, the determination of the sum can be used as a indication of the position of the pointing device with respect to the tablet, whereas by determining the differences in the signal intensities of the different frequency oscillating signals, it is possible to determine the status of the button switches on the pointing device. The invention is typically used with a stylus or cursor driven tablet.

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Beacon Falls, CT, United States of America

Thomas L Stone