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Coordinate reader

  • US 5,228,124 A
  • Filed: 12/03/1991
  • Issued: 07/13/1993
  • Est. Priority Date: 03/22/1989
  • Status: Expired due to Fees
First Claim
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1. A display apparatus comprising:

  • a display screen for displaying an original image on a display screen surface thereof, said display screen surface having an X-axis dimension and a Y-axis dimension which is perpendicular to the X-axis dimension, wherein locations on said display screen surface are defined by corresponding X-axis and Y-axis coordinates;

    a generally flat transparent tablet having an image projection surface having an X-axis dimension and a Y-axis direction which is perpendicular to the X-axis direction, wherein locations on said image projection surface are defined by corresponding X-axis and Y-axis coordinates;

    means for enlarging said original image displayed on said display screen and projecting the thus enlarged image from said image projection surface of said transparent tablet, wherein there is a one-to-one correspondence of said X-axis and Y-axis coordinates defining locations on said display screen surface and said X-axis and Y-axis coordinates defining locations on said image projection surface, and wherein a location of said original image is defined by X-axis and Y-axis coordinates of said display screen surface which correspond to the X-axis and Y-axis coordinates of said image projection surface that define the location of said enlarged image;

    first and second cursor devices for respectively generating electric signals when placed in contact with said image projection surface of said transparent tablet;

    a reading means, operatively coupled to said transparent tablet, for receiving said electric signals and for determining the X-axis and Y-axis coordinates of said image projection surface at which a one of said first and second cursor devices operatively coupled to said reading means is placed in contact with said image projection surface, said reading means further for generating a position signal denoting the thus determined X-axis and Y-axis coordinates of said image projection surface;

    a switch means for selectively operatively coupling either one of said first and second cursor devices to said reading means;

    a central processing unit, operatively coupled to said reading means and said switch means, for receiving said position signal from said reading means and for controlling a switching operation of said switch means; and

    ,a timer, operatively coupled to said central processing unit, for establishing a timing of the switching operation of said switch means controlled by said central processing unit.

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