Patent ID: 6498602
Filing Date: 2002-12-24
Classification: G06F

Abstract:
An optical digitizer with a function to recognize kinds of pointing instruments for detecting pointing position coordinates of the pointing instrument on a coordinate plane, said pointing instruments including a first pointing instrument not equipped with a retroreflective material at a tip of said first pointing instrument, and a second pointing instrument equipped with a retroreflective material at a tip of said second pointing instrument, said optical digitizer comprising:a light source means which emits a light ray; an image taking means which is positioned at a periphery of said coordinate plane, and which is adapted to use said light ray of said light source to take an image of said pointing instrument and to convert it into an electrical signal; a computing means which processes said electrical signal converted by said image taking means, and which computes said pointing position coordinates of said pointing instrument; a polarizing means which is installed at said light source means, and which is adapted to make said light ray emitted from said light source means as one of a first polarized light ray and a second polarized light ray; a switching means which switches said light ray emitted to said coordinate plane into one of said first polarized light ray and said second polarized light ray; a retroreflective means which is installed at a frame of said coordinate plane, and which has retroreflective characteristics; a polarizing film which is installed in front of said retroreflective means, and which has a transmitting axis to cause said first polarized light ray to be transmitted; and a judging means which judges said pointing instrument as said first pointing instrument if said image of said pointing instrument is taken by said first polarized light ray, and which judges said pointing instrument as said second pointing instrument if said image of said pointing instrument is taken by said second polarized light ray.