考虑测绘相机调焦会影响相机的主点位置, 从而改变相机的内方位元素, 降低立体测绘精度, 故本文分析了空间相机常用的3种调焦方式(镜组调焦、平面反射镜调焦、焦面调焦)对测绘相机主点位置的影响。简要介绍3种调焦方式的工作原理, 研究了理想情况下3种调焦方式对主点位置的影响。在考虑系统装调误差的情况下, 建立了主点位置变化量与调焦量之间的数学模型, 通过实例计算得出焦面调焦易满足测绘相机主点定位精度＜0.2 pixel, 是最适合的调焦方式。最后, 以某一型号相机调焦机构为实验对象, 对平面反射镜方式对主点的位置变化进行了实验量测, 结果证明了提出的主点位置变化量理论计算公式的准确性和分析得到的不同调焦方式对主点位置影响的正确性, 该公式可以用于指导测绘相机调焦方式的选择, 以满足高精度测绘的需要。

The focusing of a mapping camera affects its principal point, which will change the inner orientation elements and affect the mapping accuracy. Therefore, this paper analyzes in detail the effects of three usual focusing methods(lens focusing, plane mirror focusing, focal plane focusing) on the principal point position of aerospace mapping camera. First, the principles of three usual focusing methods were introduced briefly, and the effects of these focusing methods on the principal points were studied under an ideal condition. Then, through considering the assembly error, the mathematical model between the principal point offset and the focusing distance was built, and the focal plane focusing was proved to be the best focusing method through the example computation in which the positional error of principal point was less than 0.2 pixel. Finally, by taking the focusing mechanism designed for some cameras as the experiment object, the principal point changes of plane mirror focusing and focal plane focusing were measured. The results show that the computing formula proposed is accurate, and the analysis about the principal point based on different focusing methods is right. The results can be used for choosing the focusing mode of the mapping camera and can meet the needs of high precision mapping.