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EmnDash: M-sequence Dashed Markers for High-speed Spatial Tracking


Self-position and posture estimation using a camera can be used for augmented reality and navigation, and can create a high user experience according to the user's posture information. In particular, focusing on sports such as cycling, posture information in situations where the user is moving over a wide area and at high speed is expected to have a high motor learning effect when accompanied by feedback information during the movement. However, self-pose estimation for outdoor sports requires high-speed tracking, wide-area applicability, and bright environment robustness.

We focus on a vector laser projection system using galvanometer mirrors as a means for wide applicability and bright environment countermeasures, and propose a system named EmnDash that enables high-speed spatial tracking by embedding M-sequence dashed line markers (Fig. 1). EmnDash embeds M-sequence signals, where 0 and 1 are represented by long and short dashed lines, into periodically scanned vector figures. The dashed lines are switched on and off at odd and even periods, so that they appear as dashed lines to a high-speed camera with a short exposure time, while the dashed markers become invisible and are observed as solid lines to the human eye with a long exposure time (Figs. 2, 3). Using this difference in exposure time, it is possible for the high-speed camera to recognize the M-sequence dashed line markers and perform self-pose estimation while displaying some vector-type figure on the surrounding ground to the user. Since the M-sequence is characterized by its ability to uniquely identify the position in the whole series from the observation of sub-sequences, the absolute pose of the camera can be determined from a single image, and high-speed tracking becomes robust against occlusion. The system does not require synchronization between the laser projection and the high-speed camera, and the far-field reach of the laser and the wearability of the high-speed camera make it suitable for use not only in sports such as cycling, marathon running, and skating, but also in traffic applications such as automobiles.

Fig.1 Concept of EmnDash.
Fig.2 User view and high-speed camera view.
Fig.3 M-sequence dashed line projection.


  1. Tomohiro Sueishi, Ryota Nishizono, and Masatoshi Ishikawa: EmnDash: A Robust High-Speed Spatial Tracking System Using a Vector-Graphics Laser Display with M-sequence Dashed Markers, Journal of Robotics and Mechatronics, Vol.34, No.5, pp. 1085-1095 (2022)
  2. Ryota Nishizono, Tomohiro Sueishi, and Masatoshi Ishikawa: EmnDash: M-sequence Dashed Markers on Vector-based Laser Projection for Robust High-speed Spatial Tracking, IEEE International Symposium on Mixed and Augmented Reality Adjunct (ISMAR-Adjunct2020) (Recife, 2020.11.12) pp. 195-200
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