社会への普及が進むLED照明とスマートフォン等に搭載される汎用動画カメラを用いた高速高精度時刻同期技術を提案する。 理論的解析を通して、カメラのシャッタースピードをパラメータとする最適変調照明についての数式表現を導出した。 1つのLED光源と60fpsのカメラを用いた実環境での評価実験では、観測時間0.067秒(4フレーム画像)で90 percentile誤差 26.3 μsを達成した。コンピュータシミュレーションによる比較実験では、 最適変調照明を用いることで時刻同期の計算量が抑えられることも明らかになった。 提案手法の特徴を利用したアプリケーションとして、高速可視光通信システム等の実装を進めている。


  For rapid indoor 3D localization of smartphones, a new method called Frequency Division Multiplexing Phase Accordance Method (FDM-PAM) is proposed. The method uses a beat called a sync pattern composed of a pair of sinusoidal waves whose frequencies are slightly different, which is the same way as our original ultrasound ranging technique called the Phase Accordance Method (PAM). By generating multiple sync patterns whose central frequencies are different and transmitting each of them from different speakers, FDM-PAM conducts time-difference-of-arrival (TDOA) multilateration. In the current implementation of FDM-PAM, four sync patterns are generated by using two out of eight sinusoidal waves whose frequencies range from 14.75 kHz to 18.25 kHz (frequency interval: 500 Hz). Through experiments using four speakers in short baseline intervals (10-14 cm), it is confirmed that FDM-PAM achieves accuracy range around 10 to 30 centimeters using only a transmission of a short burst (4 ms), which indicates a sufficiently rapid indoor localization for smartphones.

Rapid Optical Ranging Technique

  The proposed optical ranging technique called LT-PAM (Long-Term Phase Accordance Method) transmits multiple sync patterns composed of two sinusoidal waves with different frequencies. Unlike chirp modulation techniques, LT-PAM transmits the two waves simultaneously and thus enables the shortening of measurement time. We have conducted experiments using two types of light sources, collimated and diffused light.
The experimental results indicated that the proposed method showed a moderate level of accuracy by adjusting the measurement time.

Compact 3D Tracking System

  We propose a novel technique for 3D localization that integrates a single camera and ultrasound. We use the Extended Phase Accordance Method and the ultrasound to measure accurately the distance to a moving target and we use the camera to identify the target’s 2D position on the image plane. A prototype system consists of a transmitter unit mounting one ultrasound transmitter and three infrared LEDs around it, and a receiver unit with one inexpensive camera and one ultrasound receiver.

Ultrasound Motion Capture System

  We propose an innovative motion capture system using ultrasonic communications. Compared with existing commercial motion-capture systems that use optical or magnetic sensing, the proposed system can provide a cost effective solution for industrial and entertainment applications. To improve the capture rate of the proposed system, the EPAM algorithm was implemented in a field-programmable gate array (FPGA).


  複数のユーザ間の相対的な位置データを、超音波通信を用いて取得する研究です。近年では、モバイルデバイスの普及が急速に進んでいるため、本研究はモバイ ルデバイス向けに実装を進めています。従来の位置認識手法よりも高精度の測定が、外部の機器を必要とせずに実現可能です。本技術が実装されれば、様々なア プリケーションに応用できると考えています。