Browse Prior Art Database

Scanning Light Spot for Stylus Input to a Computer Through a Tablet

IP.com Disclosure Number: IPCOM000076532D
Original Publication Date: 1972-Mar-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Garwin, RL: AUTHOR

Abstract

A system for determining the position of an input stylus relative to an input tablet is illustrated.

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Scanning Light Spot for Stylus Input to a Computer Through a Tablet

A system for determining the position of an input stylus relative to an input tablet is illustrated.

A beam 1 from laser 2 passes through partially reflective mirror 3 and is reflected by fixed mirror 4 to rotating mirror 5, which operates to scan the beam across tablet 6 in the x direction. Rotating mirror 7 operates to scan the beam across tablet 6 in the y direction.

Sapphire or glass spheres 8 having a refractive index approximately 2 are mounted at known locations on the tablet. A one millimeter diameter sphere will return essentially all the light in a laser beam of angular aperture about 2 milliradians. A similar sphere 9 is mounted on the input end of a hand-held stylus
10.

When the scanning beam 1 strikes a sphere 8 or 9, almost the full energy of the beam is reflected back along the beam path to be deflected by mirror 3 through a lens 11 to detector 12, which measures a few millimeters in diameter. Thus detector 12 receives almost full-beam energy during the period that the beam is traversing a sphere 8 or 9.

Since the positions of spheres 8 are known, simple processing of the time of appearance of reflected light from sphere 9, relative to that from sphere 8, yields the position of the center of sphere 9 relative to the tablet.

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