Binocular Distance Measurement System And Calibration Method

Binocular CCD passive distance measurement with good concealment has been widely used in military field. This paper completed the design of binocular distance measurement on the basis of stereo vision. The CCD cameras of4.65μm pixel size and500mm focal lenses have been chosen. The high precision measurement of remote distance is realized within a comprehensive analysis of baseline length, pixel size, lens focal, image matching and calibration. This system is more convenient by the turntable of adjusting rotation and pitch.This paper proposes a calibration method of cameras with binocular distance measurement system. The image pairs of high precision HALCON plate are obtained by binocular distance meters, and the coordinates of feature points on HALCON plate are extracted by SURF algorithm. Then, left camera and right camera are both calibrated. The coordinate of principal point on the image is calibrated by a brand new method which is based on the invariance of point on the optical axis. The other camera parameters are calibrated by linear algorithm on the basis of Tsai’s two step method. Finally, the baseline of binocular distance measurement system, the angles between optical axis of two cameras and the two relative position between two camera coordinate system are all calibrated. The calibration method of binocular distance measurement system in this paper is proved to be with high precision through the experiments.This paper completed the target image matching for sub-pixel level, using the gray correlation matching algorithm on the basis of template matching. The fast matching method is used not only to reduce the data for calculation, but also to save matching time. The peak point of correlation function is obtained through the three-times surface fitting algorithm, which can reach image matching with sub-pixel level.The formula for distance calculation is corrected in order to make the result of binocular distance measurement more accurate. The calibration parameters are put into the modified formula to make the calculation result more accurate, so that the precision is improved.Two experiments of distance measurement for targets nearly3km are done by using the calibrated binocular distance measurement system. The results are obtained after sub-pixel image matching and distance calculation, of which the precision is reaching1%. This paper realizes the high precision distance measurement for remote target by using binocular distance measurement system.