准同心广义经纬相机的成像模型及高精度标定

Imaging Model and High-Precision Calibration of Quasi-Concentric General Theodolite-Camera

对于大尺度运动目标的参数测量,固定相机存在着视场与空间分辨率之间的矛盾,并且当测量空中或海上目标时相机的标定也十分困难。跟踪式相机(如光电经纬仪)能解决此问题,但存在体积大、成本高和操作复杂等缺点。结合两者特点取长补短,将相机固定在二维旋转平台上,尽可能实现同心放置,组成准同心广义经纬相机进行中远场高精度测量,测量过程中转台实时跟踪目标并为相机提供外参数。此方法并没有光电经纬仪非常严格的同心同轴的安装要求。在合理假设基础上建立了经纬相机成像模型,提出了线性求解及平差优化相机参数的方法。大量仿真与实际测量验证了模型和标定方法的正确性和高精度。广义经纬相机测量系统组合巧妙、装拆和操作简单、体积小、成本低、可全视场测量且测量精度高,有广泛且重要的应用前景。

There is a contradiction between field of view and spatial resolution in still-camera-based measurement when the motion range of object is large, and the corresponding calibration procedure is difficult when the object is in the sky or sea. Measuring equipment like photoelectric theodolite can resolve this problem, but its volume is big, it costs very much, and the operation is relatively complicated. To combine the advantages of still camera and photoelectric theodolite, CCD camera is fixed to the two-dimensional （2D） rotation platform as concentrically as possible, constructing a quasi-concentric general theodolite-camera, to conduct high-accuracy measurement. The 2D rotation platform can rotate horizontally and vertically to track object in real time, and provide camera with rotation angle information to update its extrinsic parameters in real time. Photoelectric theodolite requires its optical center and optical axis to coincide with its rotation center and rotation axis respectively. However, no such assembling requirement is imposed on the general theodolite-camera. Theodolite-camera imaging model is constructed based on reasonable hypotheses, and linear solution and adjustment strategy for camera parameters are proposed. The correctness and high accuracy of the proposed imaging model and calibration strategy have been proved by both simulation data and experimental data. Measurement system based on general theodolite-camera possesses many advantages, for example simple structure and assembly, relatively small volume, low costs, panoramic measurement capability and high measuring accuracy. It has a wide and important application prospect.