Optical system for developing point coordinate information

TL;DR: In this article, a method and apparatus for defining coordinates of an object intersecting a predefined plane is presented, where each light beam is swept across the plane by a rotating reflective surface.

Abstract: A method and apparatus for defining coordinates of an object intersecting a predefined plane. More particularly, the invention provides a means for generating first and second light beams and a means for sweeping the first and second light beams across the predefined plane. A continuous optical sensor, which could be a plurality of solar cells, is provided around a portion of the periphery of the predefined plane so that each light beam when swept across the plane intersects a portion of the optical sensor. Each light beam is swept across the plane by a rotating reflective surface. The reflective surfaces are rotated by respective motors which have control systems configured so that both light beams cannot simultaneously irradiate the optical sensor. A means for generating timing pulses when each light beam defines a predetermined reference angle is provided. The invention discloses a means whereby the interruption of each of the swept light beams by the intersecting object generates an interruption pulse which, in conjunction with its associated timing pulse, is used to define the angle of the light beam at the time of intersection with respect to its predetermined reference. The coordinates of the intersecting object can then be determined from the two angles. In the exemplary embodiment, the predefined plane is substantially coincident with a video monitor display surface, and the coordinate information is utilized to generate a visually identifiable cursor which appears on the video monitor.