COORDINATE INPUT DEVICE

摘要

PURPOSE:To attain high-speed detection of coordinates with a small number of conductors and high image resolution by providing a movable detection coil which produces the induction voltage by a current flowing through conductors onto the surface of an input board containing conductors arranged in a matrix form. CONSTITUTION:Conductors 1 are arranged in a matrix form on an input board 3, and a control circuit 15 selects these conductors one by one and flows a modulated high frequency signal through a driver circuit 4. A detection coil 2 attached to the tip of an input pen detects the induced induction voltage and sends it to a reception level deciding circuit 5. The induction voltage is compared with the threshold voltage at the circuit 5, and a conductor detection signal is delivered when the induction voltage is higher than the threshold voltage. An area deciding circuit 6 stores the conductor number corresponding to the conductor detection signal and then changes the level of stored current if the combination of stored conductor numbers does not satisfy the prescribed conditions. Then the circuit 6 delivers a current level signal and a conductor selection signal to perform decision again. This action is repeated until the conditions are satisfied.