Calibration of graphic data-acquisition tracking system

Abstract

A system and method for calibrating and monitoring the height of an electromagnetic radiation expanse above a writing surface is described. An electromagnetic-radiation-generating structure is disposed adjacent produce an expanse of radiation in a substantially planar zone near the writing surface. At least one object is located at a first point in the zone remote from the structure. The object is capable of interacting with the expanse to effect the production of quantitative data correlating to the relative distance between the expanse and the writing surface at the first point. A processor receives and processes the data and allows the position of the expanse relative to the writing surface to be monitored. In a preferred embodiment, four calibration strips are placed near the corners of a writing surface in a system employing two beam-generating scanners to provide X, Y and Z information concerning the location of a writing implement relative to a writing surface. Each of the calibration strips has a 'Z' pattern of slots which allow quantitative reflectance information to be produced when the laser beam impinges the face of the strip at a preferred angle of approximately ninety (90) degrees. The strip also has a pair of angled slots which are designed to interact with a diagonally impinging beam which is out of alignment, i.e., too low or too high above the writing surface.