Diffusion-assisted position location particularly for visual pen detection

A method for optically determining the direction of an object, said method comprising:

• projecting a diffuse image of the object onto a photodetector having a plurality of detector elements extending in at least one dimension such that each of the detector elements produces an output signal corresponding to the intensity of that portion of the diffuse image which is projected onto the particular detector element, the diffuse image having a characteristic intensity distribution;
• locating the position of the diffuse image on the photodetector by recognizing the characteristic intensity distribution of the diffuse image.

A system for optically determining the position of an object within a generally planar viewing field, said system comprising:

• at least a pair of detector systems in the same plane as the viewing field and arranged to view the object within the viewing field from different angular positions, each of said detector systems including a photodetector having a plurality of detector elements extending in at least one dimension, and elements for projecting a diffuse image of the object onto said photodetector such that each of said detector elements produces an output signal corresponding to the intensity of that portion of the diffuse image which is projected onto the particular detector element, the diffuse image having a characteristic intensity distribution;
• a data analyzer connected for receiving the output signals from said detector elements, and operable to locate the position of the diffuse image on each of said photodetectors by recognizing the characteristic intensity distribution of the diffuse image and thereby to determine the direction of the object relative to each of said detector systems, and to determine the position of the object by triangulation based on the determined directions.

A system for determining the position of an object adjacent to a surface of a display having a perimeter, said system comprising:

• at least a pair of detector systems positioned outside of and adjacent to the perimeter of the display and arranged to view the object from different angular positions and to view the object when it is positioned on the surface of the display and when the object is positioned adjacent to the surface of the display, but spaced apart from the display, each of said imaging systems including a photodetector and elements for projecting a light pattern corresponding to the object onto said photodetector such that said photodetector produces output signals corresponding t the intensity distribution of the light pattern;
• and
• a data analyzer connected for receiving the output signals and operable to locate the position of the light pattern on each of said photodetectors and thereby to determine the direction of the object relative to each of said imaging systems, to determine the position of the object by triangulation based on the determined directions, and to display a cursor on the display at a position corresponding to the position of the object, said cursor being displayed when the object is adjacent to, but spaced apart from, the display.