Ultrasonic distance measuring device

  • Inventors: DOI KOJI
  • Assignees: Canon Inc
  • Publication Date: December 06, 1991
  • Publication Number: JP-H03276222-A

Abstract

PURPOSE: To accurately decide whether an input is regular or not and to prevent the wrong input by invalidating the measurement of distance when it is estimated the pressing force is less than a prescribed level. CONSTITUTION: A coordinate pointing device 1 is provided together with a sensor 2, a pen drive circuit 100, a driving waveform generating circuit 101, a t g /t p detection circuit 200, a counter circuit 201, a CPU 300, etc. Then a signal level is read out and at the same time the distance is measured between a vibration generating means and the sensor 2. Based on the relation between the result of the distance measurement and the signal level, the pressing force of the vibration generating means is estimated. Then the result of the distance measurement is validated only when the pressing force of the vibration generating means is larger than a prescribed level. Thus it is possible to evade the input of an extreme tilt state of the vibration generating means regardless of the distance relation between the vibration generating means and the means 2. Then the measurement of distance is always attained with the constant pressing force. COPYRIGHT: (C)1991,JPO&Japio

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