Digital image correlation method is a high-precision non-contact modern optical mechanics method whose measurement accuracy is directly affected by the quality of the speckle pattern used. In this paper, a numerical simulation experiment is designed to measure and analyze the accuracy of DIC method using speckle patterns which are generated with different speckle densities. The results show that the measurement error of DIC decreases first and then increases with the increase of speckle density, and the error is minimum when the duty ratio is about 60% to 70%. The result show that in practical application the duty ratio of speckle on the specimen surface should be appropriately high, preferably between 60% and 70%. This study is helpful for speckle selection and related research in practical application.

The relative pose estimation of uncooperative spacecraft is an essential technology in space missions. However, lacking the prior knowledge of uncooperative targets brings great challenges to accurately measure their pose, which hinders their application in space. To overcome these problems, an accurate and robust pose estimation approach for uncooperative spacecraft is proposed based on a time-of-flight camera coupled with a gray-scale camera. We reconstruct the target model using our hierarchical registration strategy by the ToF camera and extract 2D lines from image sequences captured by the gray-scale camera. We attempt to establish 2D–3D line correspondences for pose estimation, which effectively associates the 2D image information with the reconstructed 3D model. Experimental results manifest that, when dealing with a completely unknown model, our method computes its relative position and attitude with significantly high accuracy.

An important aspect of space exploration and situational awareness involves the characterization of the surface geometry of space objects. This paper puts forward a precise three-dimensional (3D) reconstruction method for uncooperative spacecraft based on a low-resolution time-of-flight (ToF) depth camera coupled with a high-resolution optical texture camera. In the proposed approach, a texture-guided depth upsampling algorithm is adopted to reconstruct high-resolution 3D shapes with high-precision geometry and detailed textures, in which the low-resolution depth map upsampling is guided by the high-resolution texture image. Then, in order to build a globally consistent 3D surface model, a scale estimator-based iterative closest point algorithm is put forward to align the 3D shapes of the uncooperative spacecraft from different views. The experimental results demonstrate both quantitatively and qualitatively that our approach achieves a significant improvement in reconstruction results compared to ToF-based solutions.