| 摘要 |
The use of graphical display devices in conjunction with digital computer and data processing systems is enhanced by an acoustic coordinate determinating system providing a completely unobstructed view of the display. A transparent sheet of suitable material, such as glass, arranged in front of the display and acoustic waves are propagated in the material from a spaced pair of acoustic wave radiating elements radiating acoustic energy in the sheet at a frequency of the order of 185 kHz. An acoustic probe tuned to the frequency of the radiation is touched to the material for developing currents on arrival of the radiated waves. These currents control counting circuitry advanced by pulses derived from a 2.5 MHz oscillator under control of circuitry comprising conventional gating circuits and latches for manifesting values proportional to the distances of the probe at any given point in the display with respect to the two transducers. The conversion of counting circuitry values to r, theta or X-Y coordinates is done under programmed computer control if desired.
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