As a core component of the opto-mechanical structure in large-scale optoelectronic equipment, the optical workbench directly affects the imaging quality of optical systems. The workbench must possess sufficient structural rigidity and a high lightweight ratio to minimize gravitational deformation, enhance portability, and improve maneuverability. In addition, it must exhibit high dimensional stability and minimal thermal deformation to ensure adaptability in ground environments. Utilizing new structures and materials has significant potential to refine large-size opto-mechanical designs and enhances the performance of ground-based optoelectronic equipment. In this paper, we propose the design of an optical workbench with honeycomb sandwich structure for a 430 mm clear aperture telescope, aiming to improve its lightweight ratio and thermal stability.

An equivalent modeling approach is developed to ensure high simulation accuracy for opto-mechanical components. In this method, carbon fiber reinforced plastic (CFRP) facepanels and aluminum honeycomb cores are modeled as shell elements with in-plane anisotropy and solid elements with orthogonal anisotropy, respectively. Equivalent physical properties of the facepanels are derived from the laminate theory, while those of the honeycomb cores are derived using the cellular geometry and material mechanics principles (Tables 1 and 2). Facepanels, prepared with M40J/cyanate ester prepreg at a thickness of 0.10 mm, feature a quasi-isotropic symmetric layup of [0°/±45°/90°]_S to reduce moisture absorption and enhance long-term dimensional stability. Three types of aluminum alloy inserts, heavy-load, edge, and light-load, are designed to meet the various installation interfaces while maintaining the structure’s stiffness and reliability (Fig. 4). Based on simulations, the facepanel thickness is determined to be 1.6 mm and the workbench height to be 40 mm, resulting in a final design weight of 3.03 kg for the 490 mm workbench (Fig. 3). The two parameters, facepanel thickness, and workbench height, together determine the stiffness of the workbench, which in turn affects the static and dynamic characteristics of the telescope (Fig. 5). To manufacture the complex honeycomb sandwich structure reliably, a combined hot bonding and cold bonding process is developed (Fig. 6). The main body is formed using hot bonding under high temperature and high pressure in an autoclave, while the inserts are bonded to the facepanels using an adhesive that cures at room temperature, completing the process.

Simulations show that under horizontal optical axis gravity, the relative displacement and angle between the primary and secondary mirrors are 8.09 μm and 2.21″, respectively, meeting the design requirements (Table 3). The quasi-isotropic CFRP facepanels exhibit low coefficients of thermal expansion, effectively minimizing in-plane thermal deformation. Under a 10 ℃ uniform temperature change, the RMS value of primary mirror surface accuracy deviation is 12.655 nm, well within the design requirements (RMS≤λ/30, λ=632.8 nm). Maximum stresses in the facepanels (8 MPa) and honeycomb core (0.4 MPa) are significantly below material strength limits. A forced displacement of 0.05 mm results in a negligible RMS surface accuracy deviation of 0.745 nm, confirming the workbench’s capacity to uniformly transfer external loads. The proposed workbench with honeycomb sandwich structure exhibits good stiffness, thermal stability, and insensitivity to manufacturing errors and assembly stresses. Dimensional stability is verified through coordinate measuring machine (CMM) measurements of the facepanel inserts over six months, showing stable flatness with fluctuations below 5 μm (ranging from 0.020 mm to 0.035 mm) (Fig. 7). To evaluate the system stability of the telescope, a mechanical prototype is constructed, and a high-precision photoelectric theodolite is used to monitor the relative elevation angles between the reference prisms on each component (Fig. 8). The test spans 1.5 months, during which the relative angles between the prisms remain stable, with a maximum drift of only 2.88″. Following alignment and assembly (Fig. 9), the system wavefront error of the actual telescope at the center field of view is measured to be RMS 36.45 nm at normal temperature (20 ℃), RMS 36.58 nm at relative low temperature (18 ℃), and RMS 36.64 nm at relative high temperature (23 ℃) (Fig. 10). These results demonstrate that the telescope consistently maintains excellent imaging quality within the ambient temperature range of 18?23 ℃.

The monitoring data from the CMM confirms that the developed workbench has excellent long-term dimensional stability in conventional ground environments. The proposed honeycomb sandwich structure design is both feasible and reliable in terms of its preparation processes. Mechanical prototype testing further demonstrate that the optical system of the telescope, with the workbench as its core component, remains in a stable state, with no significant degradation in mechanical performance observed under ground conditions. In addition, the CFRP facepanels prepared with M40J/cyanate ester prepreg exhibit low moisture absorption, contributing to the workbench’s stability. System wavefront error data shows that the telescope equipped with this workbench achieves good thermal stability and maintains accurate relative positioning between the primary and secondary mirrors, even as ambient temperature fluctuates within a certain range. The honeycomb sandwich workbench we proposed demonstrates high specific stiffness and stability, meeting the demands of high-performance opto-mechanical structures. This technical approach can also be applied to enhance the performance of similar equipment operating in conventional ground environments.