This study aims to expand a measuring range of stereovision system. In the previous paper, the authors achieved a 3D motion capture system by using one camera with triangle markers, named as Mono-MoCap (MMC). MMC has two features. One is that MMC can measure 3D positions of subjects by using one camera on the basis of the perspective n point (PnP) problem. Another is that MMC does not need to recalibrate the camera parameters. In this paper, the authors apply MMC to binocular stereovision system for expanding its measurement range. MMC will solve the problem that stereovision system can not measure 3D positions of objects when even one camera does not capture the objects. In this study, 3D positions of three points where a geometrical relation each other is already-known will be measured by a stereovision. 3D position measurement by the stereovision is enabled by secondarily using MMC when a part of the object is hidden with one camera of the stereovision. Simulation and experimental results will show the effectiveness of the proposed method for expanding the measuring range of stereovision system.
This study aims to realize a motion capture for measuring 3D human motions by using single camera. Although motion capture by using multiple cameras is widely used in sports field, medical field,
engineering field and so on, optical motion capture method with one camera is not established. In this paper, the authors achieved a 3D motion capture by using one camera, named as Mono-MoCap (MMC), on the basis of two calibration methods and triangle markers which each length of side is given. The camera calibration methods made 3D coordinates transformation parameter and a lens distortion parameter with Modified DLT method. The triangle markers enabled to calculate a coordinate value of a depth direction on a camera coordinate. Experiments of 3D position measurement by using the MMC on a measurement space of cubic 2 m on each side show an average error of measurement of a center of gravity of a triangle marker was less than 2 mm. As compared with conventional motion capture method by using multiple cameras, the MMC has enough accuracy for 3D measurement. Also, by putting a triangle marker on each human joint, the MMC was able to capture a walking motion, a standing-up motion and a bending and stretching motion. In addition, a method using a triangle marker together with conventional spherical markers was proposed. Finally, a method to estimate a position of a marker by measuring the velocity of the marker was proposed in order to improve the accuracy of MMC.