The Research Of Space Points Localized In Operation System Based On Binocular Stereovision

3D localizer of the optical position sensor in surgical navigation determines the positions and orientations of all the surgical devices in operating theater. Its accuracy, reliability and convenience are important for a surgery to complete an operation successfully. In this paper, after reviewing of the localizing technology used in surgical navigation system (SNS), directing against the location difficulty of distal screw on interlocking of tibial or femoral intramedullary nails in SNS, binocular stereovision is applied to acquire coordinates of objects, which imitate the man's feeling distance to know 3D world with eyes. In the method tow cameras are used to take pictures to the same objects from 2 different positions, then disparity of feature point is calculated to get Z coordinate. Much research focused on the principle of stereovision reconstruction, the segmentation and distills of character points, the definition of relative position and orientation among different space points and development of prototype. According to the actual environments in operating theater, the method that lighting LEDs are used as sign points is brought forward. The positions of space points can be received with the method of untouched optical localization. The coordinations of space points in virtual world coordinate are calculated after a series of steps such as the cameras calibration, image segments, the calculation of the center of objects. The algorithms of localization, which is untouched and no-trauma, is programmed. It is efficient and effective in structural less circumstance. In terms of the situation of operation tool and diagnostic, the relationship among the intramedullary nail coordinate system, the drill coordinate system, and the world coordinate system is confirmed through transform. Then the relative positions and orientations of them are analyzed. In order to evaluate the performance of the proposed method in this paper, experiment system by correspond principle was set up base on the current condition in the laboratory. Both software and hardware of prototype are described here. Then the experiments were done and the errors produced in experiment were analyzed. The conclusion is drawn that the error of the coordination of space points will be larger along with the distance between the ranges of calibration and object points increased. These are the bases for the definition of the ranges of calibration. The paper has made a systematic and independent study on space point localizer with the technology of binocular stereovision. It not only tests the feasibility of operation navigation location and realizes a prototype using stereovision. It also gives some helps to the research of operation navigation system. The algorithms as well as scheme are proved to be clear, simple and efficient in practice. It localizes successfully in sur gical navigation. The algorithms and experiments are useful in researching for surgical navigation system as well as object identifying, work pieces localizing, robot self-piloting etc.