| 摘要 |
A transmitter pen positioning system is provided, in which a pen, having multiple output elements, is used to accurately determine the location of the pointing tip of the pen, in relation to the writing area of a surface, such as a white board. The first output element, preferably an infrared transducer, transmits a first output signal from the transmitter pen. The second output element, preferably an ultrasonic transducer, transmits a second output signal, having a lower propagation velocity than the first output signal, from the transmitter pen to two or more receivers. In a basic embodiment, the first output signal arrives at one or more receivers generally concurrently. The second output signal, having a speed of propagation different from the speed of propagation of the first signal, is transmitted from the transmitter pen at a known time in relation to the first output signal, and arrives at each of the receivers at a time which is dependent on the velocity of the second signal and the distance between the transmitter pen and the receivers. The location of the pointing tip of the transmitter pen is then determined, by using the first signal as a boundary condition, by comparing the waveform of the second output signal to one or more stored prior second output signals to determine an accurate time of arrival, and by solving simultaneous equations. Alternative embodiments allow the transmission of supplementary information from the transmitter pen to the receivers, using either the first and/or second output signals, such as determined pen color, line color, width, and pen user identification.
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