Adhesive bonding has become one of the most popular methods and a unique method sometimes for connecting optical components to their support structure in optical systems. For high-precision optical systems, the shrinkage stress caused by adhesive curing has a non-negligible influence on the mirror figure accuracy. At present, there is a lack of methods for monitoring the figure precision during the bonding, which makes the bonding process hard to control in time. The bonding process is planned to be optimized, and the dynamic monitoring problem of the bonded mirror figure should be solved to reduce the relative figure change rate before and after mirror bonding. We investigate thin glass mirror specimens with a diameter of Ф100 mm and a thickness of 10 mm to optimize the stress-relieving structure. Finally, a foundation can be laid for promoting stable opto-mechanical integration quality and widening the engineering application of light-thin mirrors.

Firstly, the principle of curing shrinkage stress of adhesive layers is analyzed. Secondly, based on the constitutive theory of adhesive materials, the viscoelastic mechanical model of the adhesive layer is introduced, and the relationship between the shrinkage stress of the adhesive layer and the curing time is analyzed. Then, the equivalent temperature loading method is adopted to simulate the influence of the adhesive shrinkage stress on the mirror figure, based on which the optimal design of the curing stress unloading structure is carried out by topology optimization. Finally, by employing the proposed adhesive bonding technique, a dynamic monitoring test platform for the curing figure of the adhesive layer is built, with the bonding process and optical tests carried out.

Based on the viscoelastic theory, the mechanical model of the adhesive layer is built, and the performance parameters of the adhesive layer are determined according to the theoretical calculation and finite element simulation, with the 0.2 mm thickness of the adhesive layer and minimum adhesive area of 300 mm². The equivalent temperature loading method is adopted to simulate the effect of the adhesive curing shrinkage on the mirror figure, and it is verified that the results of the curing shrinkage stress of the adhesive layer before optimization are consistent with those of theoretical analysis. The results show that the shrinkage stress of the adhesive layer is 0.016 MPa and the mirror figure accuracy RMS is 0.018λ after the optimized bonding structure, which indicates that the designed adhesive structure meets the application requirements. According to the whole history curves of the PV and RMS values of the mirror figure during the curing process, it is found that the curing time is recommended as 15000 s, and the final figure accuracy RMS is 0.021λ/0.018λ for the non-optimized/optimized structure respectively. The test results show that the structure of the optimized adhesive joint is better than that before optimization, and the simulation results are verified by experiments.

In studying the influence of optomechanical hetero-bonding processes on the mirror figure, the mechanical model of the adhesive layer is built by analyzing the principle of curing shrinkage stress of the adhesive layer combined with the viscoelastic theory, with the curing stability time of the adhesive layer recommended as 15000 s. By adopting the combination of viscoelastic finite element modeling method and the equivalent temperature loading method, the influence of adhesive curing shrinkage stress on the figure is simulated, and then a reasonable stress-relieving bonding structure is optimized. By conducting the optimal design of structural topology, the adhesive layer bonding area is optimized from 490 to 300 mm², a reduction of 39%, and the corresponding RMS of the optimized mirror surface is stabilized around 0.018λ. The mirror bonding equipment for monitoring the mirror figure dynamically is designed to ensure the bonding quality. The dynamic monitoring bonding process of the adhesive layer curing figure is established at room temperature. The curing time and surface deformation are tested during the curing process focusing on the mirror figure stability. As a result, we verify the effectiveness of the structural optimization, the bonding process, and the finite element model.