Optimum pseudo random sequence determining method, position detection system, position detection method, transmission device and reception device

A position detection system including at least one transmission device and a reception device for detecting a position of said transmission device, wherein

• said transmission device transmits a first ultrasonic signal modulated by data of a pseudo random sequence having high self-correlativity,
• said reception device generates an ultrasonic model waveform of a pseudo random sequence of said first ultrasonic signal received, obtains a correlation value between a waveform of said first ultrasonic signal received and said ultrasonic model waveform generated, determines data which defines an optimum pseudo random sequence with which a secondary peak of said correlation value becomes the smallest and assigns the data to said transmission device,
• said transmission device simultaneously sends a trigger signal indicative of transmission timing and a second ultrasonic signal modulated by data of a pseudo random sequence generated based on data which defines an optimum pseudo random sequence assigned by said reception device, and
• said reception device executes correlation processing between a waveform of a second ultrasonic signal received and an ultrasonic model waveform of a pseudo random sequence of said second ultrasonic signal to specify an arrival time of said ultrasonic signal and calculates a propagation time of the ultrasonic from an arrival time point of said trigger signal and the specified arrival time to detect a position of said transmission device based on said ultrasonic propagation time calculated.

A position detection method, wherein

• at at least one transmission device, transmitting a first ultrasonic signal modulated by data of a pseudo random sequence having high self-correlativity,
• at a reception device for detecting a position of said transmission device, generating an ultrasonic model waveform of a pseudo random sequence of said first ultrasonic signal received, obtaining a correlation value between a waveform of said first ultrasonic signal received and said ultrasonic model waveform generated, determining data which defines an optimum pseudo random sequence with which a secondary peak of said correlation value becomes the smallest and assigning the data to said transmission device,
• at said transmission device, simultaneously sending a trigger signal indicative of transmission timing and a second ultrasonic signal modulated by data of a pseudo random sequence generated based on data which defines an optimum pseudo random sequence assigned by said reception device, and
• at said reception device, executing correlation processing between a waveform of a second ultrasonic signal received and an ultrasonic model waveform of a pseudo random sequence of said second ultrasonic signal to specify an arrival time of said ultrasonic signal, calculating a propagation time of the ultrasonic from an arrival time point of said trigger signal and the specified arrival time and detecting a position of said transmission device based on said ultrasonic propagation time calculated.