05317140 is referenced by 250 patents and cites 42 patents.

Systems and methods for optically determining the direction of an object, such as a pointer, relative to an imaging system, particularly systems where triangulation is employed to determine the location of a pointer within a generally planar viewing field, such as a touch screen. Rather than employing focused imaging systems to produce a sharp image at the plane of a photodetector, and to thus define the visual pen for finger position, a deliberately diffuse or blurred image is employed. The diffusion produces a characteristic "bell-shaped" or Gaussian intensity distribution. By recognizing the characteristic intensity distribution, the position of the maximum intensity, and thus the direction of the object, can be determined to a small fraction of the distance between sample points, with an accordingly much higher resolution than focused systems. In a preferred embodiment, the position location system is incorporated into a computer system as a touch screen apparatus and a cursor is displayed on the screen as soon as a pointer is detected above the display.

Title
Diffusion-assisted position location particularly for visual pen detection
Application Number
7/980915
Publication Number
5317140
Application Date
November 24, 1992
Publication Date
May 31, 1994
Inventor
David I Dunthorn
908 W. Outer Dr., Oak Ridge, 37830
TN, US
Agent
Luedeka Neely & Graham
IPC
G01V 9/04
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