Research And Application Of The Coded Points Based On Concentric Circles

Coded point is widely used in stereo vision and photogrammetry. The design and identification of the coded point is an important issue in stereo vision and photogrammetry. It needs urgently to find the solution which could be able to expand the amount of the coded points as well as to improve the location accuracy of them and enhance the capabilities of data processing to ensure the accuracy and efficiency of the measuring system.The existing coded point has low locating accuracy as it usually adopts single circle pattern, and mostly use the centroid method or ellipse fitting method to detect the center of the circle. So, the concentric circles pattern which has rich projective constraints is introduced in coded point, and the corresponding detection method is proposed to improve the location accuracy of the coded point.Many works have been done in study of coded point by scholars all over the world. The thesis summarizes the existing coded points scheme and analyses its merit and disadvantages. Then two kinds of improved coded points scheme are proposed based on existing coded point scheme, which are improved point-array coded point scheme and improved pentagon coded point scheme respectively. Both of the two kinds of improved coded points scheme adopt concentric circle pattern which has high detection accuracy. The two kinds of coded points scheme are both simple and easy to recognize, they both have high rate of correct decoding, high locating accuracy and large encoding capacity to meet the demands of the actual measurement.Finally, the two types of coded point are applied to the practical measurement based on stereo vision. The coded points are placed at the key position of the hoop-rib deployable antenna and several images which include the coded points are obtained by a nikon camera, then the decoding and identification of the coded points have been done and stereo matching is completed. The 3D coordinates of the coded points are obtained through camera calibration and projective matrix computing etc, and the measurement results are compared with the results obtained by the Tian Yuan photogrammetry system to prove the rationality and practicability of the coded points schemes.The experiments demonstrate the rationality and practicability of the coded points scheme based on concentric circles in the thesis.