Patent ID: 7259754

Claim:
A pen sensor coordinate narrowing method for determining a position indicated by a pen sensor when scanning a display screen by said pen sensor, said pen sensor coordinate narrowing method comprising: dividing said display screen into two areas when starting to scan said display screen by said pen sensor; displaying the two areas by respective, different colors or brightnesses as a first display, and in the first display, continuously moving a boundary line formed by the two areas along a vertical axis or a horizontal axis of said display screen, and from an edge of said display screen in a direction perpendicular to the boundary line, thereby increasing a size of one of the two areas while decreasing a size of another of the two areas; detecting a change of color or brightness along movement of the boundary line with the pen sensor, and determining a horizontal coordinate or a vertical coordinate of a position indicated by the pen sensor on the display screen based on the change detected by the pen sensor; further dividing said display screen into a plurality of areas along the vertical axis or the horizontal axis of the display screen as a next scan area, and displaying the plurality of areas by respective, mutually different colors or brightnesses as a second display; and judging which of the plurality of areas the position of the pen sensor on the display screen is at, based on a single color or brightness of the areas detected by the pen sensor, wherein; the judged area is used as a next scan area, and the second displaying and the judging are repeated several times so as to determine the horizontal coordinates or the vertical coordinates of the first position indicated by the pen sensor.