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Pen-shaped handwriting input apparatus using accelerometers and gyroscopes and an associated operational device for determining pen movement

  • US 5,902,968 A
  • Filed: 02/20/1997
  • Issued: 05/11/1999
  • Est. Priority Date: 02/20/1996
  • Status: Expired due to Term
First Claim
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1. An input apparatus comprising:

  • a pen-shaped device having a tip end for contacting a surface and defining a pen shaft x, y, z coordinate system with the Z axis being defined by a pen shaft axis,three acceleration sensors for respectively detecting accelerations in the X-axis direction, the Y-axis direction, and the Z-axis direction of the pen shaft,three gyroscopes for respectively detecting the angular velocities around the X axis, the Y axis, and the Z axis of the pen shaft,an operational calculating section for determining the movement of said pen-shaped device on said surface, said operational calculating section comprising an initial inclination angle calculating section, an inclination angle variation calculating section, a handwriting inclination angle calculating section, a coordinates conversion calculating section, and a movement amount calculating section,wherein said initial inclination angle calculating section calculates the initial value of the inclination angle of the pen shaft in a gravity coordinate system having an axis extending in the gravity acceleration direction as the Z axis thereof, on the basis of the acceleration detected by said three acceleration sensors when said pen shaped device is grasped by an operator but not in a state of writing,wherein said inclination angle variation calculating section calculates the variation of the inclination angle in the gravity coordinate system of the pen shaft, on the basis of the angular velocity detected by said three gyroscopes when said pen shaped device is in a state of handwriting,wherein said handwriting inclination angle calculating section calculates the inclination angle in the gravity coordinate system of the pen shaft, on the basis of the initial value of the inclination angle calculated by said initial inclination angle calculating section and the inclination angle variation calculated by said inclination angle variation calculating section,wherein said coordinates conversion calculating section converts the accelerations in the pen shaft coordinate system detected by the acceleration sensors to the acceleration in the gravity coordinate system, on the basis of the inclination angle in the gravity coordinate system of the pen shaft detected by said handwriting inclination angle calculating section, andwherein said movement amount calculating section calculates the movement direction and the movement distance of the pen'"'"'s tip end over said surface, on the basis of the acceleration converted by said coordinates conversion calculating section.

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