空间飞行器上普遍具有星箭对接环部件，可以提供单圆特征，但基于单个空间圆的单目视觉位姿估计有两个位姿解，无法应用到实际工程中。为了有效剔除虚假解的干扰，利用对接环平面外一参考点到圆心距离的欧氏不变性作为约束，提出一种虚假解剔除方法，给出了在该约束条件下有唯一解的证明，并对位姿求解方法进行了误差仿真分析，给出了提高测量精度的可行策略。根据空间圆在图像上的投影计算出空间圆位姿的两个解；利用参考点到圆心的距离已知且不变作为约束剔除虚假解，得到星箭对接环的真实位姿；对该方法的有效性进行了仿真和实验验证。实验结果表明，该方法可有效剔除虚假解，计算过程简单，结果稳定可靠，对接环圆心计算误差小于0.5%，姿态角误差小于0.8°。

Docking ring is a typical component on space vehicle, which can provide a single circle feature. But monocular vision pose estimation based on single circle with two solutions, which can not be applied to practical engineering application. In order to exclude the interference of false solution, a new method of removing the false solution using Euclidean distance invariance as a constraint is proposed to solve the pose ambiguity, and the paper gives the proof of a unique solution under the constraint. The error simulation analyses of the method are done, and feasible strategies to improve the measurement accuracy are given. According to the projection of the circle on the image, two pose solutions of the circle are calculated. Then a reference point on the circle supporting plane outside the circle is selected. The distance between the reference point and circle center is Euclidean invariant and prior knowledge, which can be used for a constraint to exclude the false solution to get the uniquely correct solution. The effectiveness and superiority of the method are verified by numerical simulation and experiments. Experimental results indicate that the method is robust to the noise, can get the right solution, requires least constraint conditions for the circle, and the calculation process is simple. Pose results are stable and reliable, and more accurate. The relative error of the circle center is less than 0.5%, and the absolute error of pose angle is less than 0.8°.