Abstract: 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.

Abstract: A form of the disclosed invention employs data validation and screening based on the proximity of sequentially measured data points. Another form of the invention detects noisy conditions manifested in a pilot signal measurement, and discards data taken just after (and/or, if desired, just before) detection of the condition.

Abstract: An apparatus is disclosed for digitizing positions on a transparency. The apparatus includes a cool light box and an acoustic digitizer.

Abstract: An apparatus is disclosed for determining the position of a moveable element in a three-dimensional workspace near a mounting surface. A sound source is provided in the moveable element. A plurality of at least three housing units are adapted to be secured to said mounting surface in spaced relationship to one another. A sound sensor is mounted on each of the units, and a sound source is mounted on at least some of the units. The positions of the sound sensor and the sound source of said at least some of the units can be adjusted. Means are provided which are responsive to the sound from the sound source of at least one of the units and received at the sound sensor of another of the units, for computing the distance between the sound source of said one of the units and the sound sensor of said another of said units.

Abstract: The disclosure is directed to a microprocessor-based apparatus and method for determining the distance between an object and a reference position. An embodiment of a graphical digitizer is set forth in which a microprocessor system is adapted to generate and store a count that depends upon the number of instruction cycles that the microprocessor system performs during a time interval that is a function of the travel time of acoustic wave energy traveling between the object and the reference position. In a disclosed embodiment, acoustic receivers are mounted with their axes parallel, and each receiver has a generally circular receptivity pattern.