The opto-mechanical structure is a critical component of the space camera, which requires sub-micron accuracy. The fabrication and testing of the space camera occur under earth gravity, while its on-orbit operation takes place in a microgravity environment. The change in gravity conditions causes deformation of the opto-mechanical structure, which can alter the relative position of the mirror. This, in turn, affects the imaging performance of the space camera. Therefore, we study the effect of gravity load on the consistency of the opto-mechanical structure between ground and space.

We propose a non-contact optical measurement method, considering measurement error, to test the deformation of the opto-mechanical structure. This method is based on the self-collimation technique and is implemented by combining cubic prisms and a theodolite. The cubic prisms are attached to the load-bearing structure of the opto-mechanical system, and a theodolite with a self-collimating lamp is used to measure the normal direction of each cubic prism, thus representing the deformation of the assembly plane. Furthermore, the accuracy of the experimental results is verified through simulation by comparing the positive and negative gravity conditions. Moreover, the influence of gravity load on the consistency of the opto-mechanical structure between ground and space is comprehensively evaluated by combining the results from both the test and simulation.

It can be seen from the test that the angular deviation of each mirror assembly plane of the opto-mechanical structure under the gravity condition is within 1″, and the dimensional deviation is within 1 μm (Table 5). Since the measured angular deviation is smaller than the measurement error of the theodolite, it is necessary to take into account the influence of measurement error on the results. The deformation obtained after considering the measurement error is within 3 μm, which is much smaller than the accuracy requirement (Table 1). Numerical simulation is used to extract and calculate the relative deformation of the mirror assembly planes, and the deformation obtained from the simulation is within 5 μm (Table 6). Comparing the experimental and simulation results (Fig. 5), the results show that the accuracy of the non-contact optical measurement method is verified. The deformations of the designed front frame and rear frame are less than 5 μm, which verifies the designed support structure’s high stiffness and stability.

In this paper, we propose a non-contact optical measurement method, considering the measurement error, for testing and analyzing the effect of gravity on the consistency of the opto-mechanical structure between ground and space. Additionally, the deformation of the structure is characterized by the relative position change of the assembly planes. The method of mutual verification between testing and simulation is introduced to verify the feasibility and accuracy of the proposed measurement method. The proposed non-contact measurement method, combining cubic prisms and the theodolite, can be used to test the deformation of large opto-mechanical structures under gravity loading, which requires consideration of the influence of measurement errors. The deformation of the opto-mechanical structure under both positive and negative gravity conditions can be obtained through experiments and simulations as mutual verification. Simultaneously, the accuracy of the established simulation model and the feasibility of the test method can also be verified. Through the combination of experimental and simulation results, it can be concluded that the deformations of the designed large opto-mechanical structures under gravity conditions are all within 5 μm, and the deformations of the front and rear frames are less than 5 μm. This verifies that the consistency of the opto-mechanical structure between ground and space under gravity conditions meets the tolerance requirements of the optical system.