Patent ID: 7842893

Claim:
An electronic pen comprising: a housing comprising a longitudinal axis and a write side tip along said longitudinal axis; at least an ultrasonic wave transmitter, said ultrasonic wave transmitter being arranged near said write side tip of said housing; and a controller for detecting a sensor orientation and for controlling a transmission of an ultrasonic wave, wherein the sensor orientation comprises a rotational orientation of said housing about said longitudinal axis, said rotational orientation indicating a predetermined direction towards an ultrasonic wave sensor for receiving the ultrasonic wave that is transmitted from said ultrasonic wave transmitter, wherein said controller selectively activates a part of said ultrasonic wave transmitter such that the ultrasonic wave is transmitted from a part of said ultrasonic wave transmitter which is directed to said sensor orientation, wherein said ultrasonic wave transmitter includes a plurality of ultrasonic wave transmitting units arranged around said longitudinal axis of said housing, said ultrasonic wave transmitting units being arranged at orientations that are different from each other, and wherein said controller comprises: a sensor detecting section for detecting said sensor orientation; and a unit selecting section for selectively triggering a part of said ultrasonic wave transmitting units such that only one of said ultrasonic wave transmitting units that is arranged at an orientation that is relatively closest to said sensor orientation is triggered, wherein said sensor orientation is detected by said sensor detecting section.