High resolution light pen for use with graphic displays

Abstract From the Canadian patent

A high resolution light pen is disclosed for use with graphic displays. More particularly a light pen is, disclosed having a collimation tube slidably mounted within a housing, The collimation tube includes an axially extending channel having a non-reflective surface. A photodetector is fixably mounted within the housing aligned with the channel. A lens is mounted adjacent the front end of the channel and has a focal length equal to the spacing between the lens and an aligned pixel of the video screen. By this arrangement all, light rays emanating from an aligned pixel and passing through the lens are refracted axially along the channel and directed to the photodetector thereby maximizing …