High-precision lightweight mirror micro-stress assembly method

Abstract

This invention discloses a high-precision, lightweight micro-stress assembly method for a reflector, relating to the field of space optical remote sensing technology. The method includes: calculating the minimum total adhesive area to ensure reliable connection between the primary mirror and the central axis based on the dynamic conditions of the optical lens, and obtaining the initial adhesive spot length for each corresponding adhesive spot; establishing a parameterized finite element model of the components including the primary mirror, central axis, structural frame, and adhesive layer, and equivalently simulating the adhesive stress generated by the curing shrinkage of the adhesive layer; parametrically adjusting the actual adhesive spot length of each spot, starting from the initial adhesive spot length, and simulating the root mean square (RMS) value of the primary mirror surface shape error caused by adhesive stress at each actual adhesive spot length; and determining the optimal adhesive spot length based on the curve of the RMS value changing with the actual adhesive spot length. This invention overcomes the problem in the bonding process between the primary mirror and the central axis where the adhesive area design only considers the lower limit requirement of mechanical strength, neglecting the negative impact of adhesive stress on the primary mirror surface shape.

Description

Technical Field

[0001] This invention relates to the field of space optical remote sensing technology, and in particular to a high-precision, lightweight micro-stress assembly method for reflectors. Background Technology

[0002] The primary mirror of a space camera is the core component of its optical system, and the surface accuracy of the primary mirror directly determines its image quality. For lightweight primary mirrors with medium and small apertures (diameter less than 1 meter), ensuring the structural connection strength while minimizing assembly stress and maintaining nanometer-level surface accuracy has been a long-standing technical challenge in the field of optical assembly and adjustment.

[0003] Currently, passive support solutions for lightweight primary mirrors include two types: multi-point back support and central axis support. While multi-point back support provides sufficient rigidity, the concentrated stress at the support points can directly lead to deterministic deformation of the mirror surface that is difficult to eliminate. Central axis support is the mainstream support method for high-precision primary mirrors. This solution uses an integrated central axis to strictly constrain only the translational degree of freedom of the primary mirror along the optical axis while controlling the release of other degrees of freedom, thereby effectively avoiding the concentration of harmful stress.

[0004] In central axis support systems, the primary mirror and central axis are typically connected by adhesives. The shrinkage stress generated during adhesive curing is a key factor affecting the final surface shape of the primary mirror. Existing technologies address this issue primarily by selecting the appropriate adhesive and optimizing the adhesive layer geometry. However, the bonding area (specifically, the adhesive spot length), as a direct control parameter for connection strength and the magnitude of introduced stress, lacks a systematic guiding method for optimization. In engineering practice, the bonding area is often designed only based on the lower limit of mechanical strength requirements, failing to fully consider its negative impact on the optical surface shape. This results in a high risk of exceeding the surface shape accuracy after the primary mirror and central axis are assembled, and incurs significant costs from repeated trial assembly.

[0005] Therefore, there is an urgent need for a mirror assembly method that can scientifically quantify and optimize the adhesive spot length, thereby actively minimizing the surface deterioration caused by adhesive stress while meeting mechanical constraints. Summary of the Invention

[0006] This invention provides a high-precision, lightweight micro-stress assembly method for a reflector, which overcomes the problem that in the bonding process between the primary mirror and the central axis, the bonding area design only considers the lower limit requirement of mechanical strength, while ignoring the negative impact of bonding stress on the surface shape of the primary mirror.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a high-precision, lightweight micro-stress assembly method for a reflector, which includes the following steps: After determining the bonding position between the primary mirror and the central axis, the minimum total bonding area to ensure the reliability of the connection between the primary mirror and the central axis is calculated based on the dynamic conditions of the optical lens, and the initial adhesive spot length of each adhesive spot corresponding to the minimum total bonding area is obtained; the dynamic conditions include sinusoidal vibration, random vibration or impact conditions; A parametric finite element model of the components, including the main mirror, the central axis, the structural frame, and the adhesive layer, is established, and the adhesive stress generated by the curing shrinkage of the adhesive layer is simulated accordingly. Starting from the initial adhesive spot length, the actual adhesive spot length of each adhesive spot is adjusted parametrically in the parameterized finite element model of the component, and the root mean square value of the principal mirror surface shape error caused by adhesive stress is calculated under each actual adhesive spot length. The optimal adhesive spot length is determined based on the curve of the change of the root mean square value with the actual adhesive spot length; the optimal adhesive spot length is the actual adhesive spot length corresponding to the inflection point where the root mean square value enters the plateau region in the curve.

[0008] In one possible implementation, the minimum total bonding area required to ensure reliable connection between the primary mirror and the central axis is calculated based on the dynamic conditions of the optical lens, specifically as follows: Based on the worst-case dynamic conditions of the optical lens under mechanical conditions, the minimum total bonding area that ensures the reliability of the connection between the primary lens and the central axis is calculated using a first calculation formula. The first calculation formula is as follows: ; in, It is the minimum total adhesive area. It is the acceleration under the worst dynamic conditions. It's the safety factor. It refers to tensile or shear strength.

[0009] In one possible implementation, starting from the initial adhesive spot length, the actual adhesive spot length of each adhesive spot is parametrically adjusted in the parameterized finite element model of the component, and the root mean square value of the principal mirror shape error caused by adhesive stress is simulated and calculated for each actual adhesive spot length, specifically including: Taking the initial adhesive spot length of each adhesive spot corresponding to the minimum total bonding area as the starting point of the analysis, in the parameterized finite element model of the component, the bonding layout of the bonding position remains unchanged, and the actual adhesive spot length of each adhesive spot is increased parametrically to increase the total bonding area between the primary mirror and the central axis proportionally. Static simulation was performed on each actual adhesive spot length to extract the surface shape error data of the primary mirror optical surface caused by adhesive stress, and the root mean square value of the surface shape error data was calculated.

[0010] In one possible implementation, the optimal glue spot length is determined based on the curve showing the change of the root mean square value with the actual glue spot length, specifically as follows: Plot the curve of the root mean square value as the actual glue spot length increases, and take the actual glue spot length corresponding to the inflection point where the root mean square value decreases into the plateau region in the curve as the optimal glue spot length.

[0011] In one possible implementation, the total adhesive area corresponding to the optimal adhesive spot length is greater than the minimum total adhesive area.

[0012] In one possible implementation, the equivalent simulation of the adhesive stress generated by the curing shrinkage of the adhesive layer specifically includes: The temperature gradient method is used to apply a negative thermal expansion system to the adhesive layer in the parameterized finite element model of the component and apply a virtual cooling field to the adhesive layer to achieve an equivalent bonding stress generated by the curing shrinkage of the adhesive layer.

[0013] In one possible implementation, after determining the optimal spot length, the method further includes: The actual amount of adhesive injected into the primary mirror and the central axis is calculated based on the optimal adhesive spot length, and the primary mirror and the central axis are then bonded together using adhesive based on the actual amount of adhesive injected.

[0014] In one possible implementation, after applying adhesive to bond the primary mirror to the central axis according to the actual amount of adhesive applied, the method further includes: After the adhesive has fully cured, an interferometer is used to detect the actual surface shape of the primary mirror in multiple directions, and the assembly qualification is verified based on the root mean square value of the actual surface shape error and the preset surface shape error value.

[0015] In one possible implementation, the actual surface shape detection of the primary mirror is performed in at least two symmetrical directions about the optical axis of the primary mirror.

[0016] In one possible implementation, the primary mirror is a silicon carbide or microcrystalline glass mirror with an aperture greater than 200 mm and a weight reduction rate greater than 70%.

[0017] The high-precision, lightweight micro-stress assembly method for reflectors provided by this invention, in practical applications, first determines the minimum total bonding area to ensure the reliability of the connection between the primary mirror and the central axis, and obtains the initial adhesive spot length for each adhesive spot corresponding to this minimum total bonding area; then, a parameterized finite element model of the primary mirror assembly is established to equivalently simulate the bonding stress generated by the curing shrinkage of the adhesive layer, and the influence of different adhesive spot lengths on the surface shape of the primary mirror is systematically simulated and analyzed; subsequently, by analyzing the curve of the change of the root mean square value of the surface shape error with the adhesive spot length, the actual adhesive spot length corresponding to the inflection point where the root mean square value enters the plateau region is taken as the optimal adhesive spot length; applying the optimal adhesive spot length determined by this invention to the actual bonding process can ensure the connection strength between the primary mirror and the central axis while actively controlling the deterioration of the primary mirror surface shape caused by bonding stress to the lowest level.

[0018] This invention provides a method for quantitatively determining the optimal adhesive spot length, thereby achieving high-precision, lightweight, and low-stress assembly of the primary mirror. This method overcomes the problem in the bonding process between the primary mirror and the central axis, where the bonding area design only considers the lower limit requirement of mechanical strength, while ignoring the negative impact of bonding stress on the surface shape of the primary mirror.

[0019] This invention solves the contradiction between bonding strength and precision in traditional bonding processes, and realizes the transformation of high-precision lightweight primary lens assembly from "experience-based trial and error" to "predictive optimization", which significantly improves the assembly success rate and assembly efficiency. Attached Figure Description

[0020] Figure 1 A flowchart illustrating the steps of a high-precision, lightweight micro-stress assembly method for a reflective mirror provided in this embodiment of the invention; Figure 2 This is a schematic diagram of the primary mirror structure in a high-precision, lightweight micro-stress assembly method for a reflective mirror provided in an embodiment of the present invention. Figure 2 In the diagram, (a) and (b) represent the front and back structures of the primary mirror, respectively. Figure 3 This invention provides a high-precision, lightweight micro-stress assembly method for a reflective mirror, which uses simulation to solve the variation curves of the RMS change of the primary mirror surface shape and the actual adhesive spot length. Figure 4 The pattern obtained by simulation solution of the micro-stress assembly method for a high-precision lightweight mirror provided in the embodiment of the present invention is the change in the shape of the primary mirror surface under an actual adhesive spot length of 28mm; Figure 5 This invention provides an embodiment of a high-precision, lightweight micro-stress assembly method for a reflective mirror, which includes an interferogram for detecting the surface shape of the primary mirror after actual bonding. Figure 5In the diagram, (a) represents the evaluation result of the core index of the primary mirror surface quality, (b) represents the fitting calculation result of the interferometer, and (c) represents the real-time monitoring result of the interferometer detector. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more. Furthermore, the use of "based on" or "according to" implies openness and inclusiveness, because processes, steps, calculations, or other actions "based on" or "according to" one or more of the stated conditions or values ​​may in practice be based on additional conditions or beyond the stated values.

[0023] To overcome the problem that in the bonding process between the primary mirror and the central axis, the bonding area design only considers the lower limit requirement of mechanical strength, while ignoring the negative impact of bonding stress on the surface shape of the primary mirror, this invention provides a high-precision, lightweight micro-stress assembly method for reflectors.

[0024] like Figure 1 As shown, this embodiment of the invention provides a high-precision, lightweight micro-stress assembly method for a reflector, which includes the following steps: Step 101: After determining the bonding position between the primary lens and the central axis, calculate the minimum total bonding area to ensure the reliability of the connection between the primary lens and the central axis based on the dynamic conditions of the optical lens, and obtain the initial adhesive spot length of each adhesive spot corresponding to the minimum total bonding area.

[0025] The dynamic conditions include sinusoidal vibration, random vibration, or impact conditions.

[0026] Furthermore, the primary mirror is a silicon carbide or microcrystalline glass mirror with an aperture greater than 200mm and a weight reduction rate greater than 70%.

[0027] Step 102: Establish a parametric finite element model of the components, including the main mirror, central axis, structural frame, and adhesive layer, and simulate the bonding stress generated by the curing shrinkage of the adhesive layer.

[0028] Specifically, equivalent simulation methods can include the temperature gradient method, the direct application of forced displacement or equivalent nodal force method, the adhesive layer equivalent shrinkage method, and the initial strain method, etc.

[0029] The temperature gradient method, in particular, applies a negative coefficient of thermal expansion to the adhesive layer and a virtual temperature drop to approximate its shrinkage effect. The adhesive used in the adhesive layer is a low-shrinkage, high-elasticity silicone rubber adhesive, such as XM-31 silicone rubber.

[0030] The principle behind directly applying forced displacement or equivalent nodal force is as follows: the essence of adhesive layer curing shrinkage is its volume reduction, which pulls on two adjacent structures (e.g., the primary mirror and the central axis) to produce a relative displacement tendency. The operational methods include: calculating the linear shrinkage strain of the adhesive layer in the thickness or tangential direction based on the volume shrinkage rate of the adhesive layer; in the component parametric finite element model, fixing the contact surface between the adhesive layer and one component (e.g., the primary mirror), and applying a forced displacement pointing inwards towards the adhesive layer (displacement amount = adhesive layer thickness × linear shrinkage rate) on the contact surface between the adhesive layer and another component (e.g., the central axis); or calculating the equivalent tension generated by shrinkage and applying it as a surface load on the adhesive layer interface.

[0031] The principle behind the adhesive layer equivalent shrinkage method is as follows: using nonlinear analysis in finite element software, the "shrinkage strain" of the material is defined. The operational method includes: directly defining the "curing application" of the adhesive layer, and defining different shrinkage coefficients based on the different shrinkage rates of the adhesive layer in the thickness and tangential directions.

[0032] The principle behind the initial strain method is as follows: In the first step of the finite element method solution, an initial strain field is directly assigned to the adhesive layer. This initial strain value is equal to the strain value due to curing shrinkage. The operation method is as follows: Before the analysis step begins, the strain state is predefined by modifying the element integration point data in the input file or software interface. Subsequently, the solver will calculate the internal stress generated to counteract this initial strain.

[0033] Step 103: Starting from the initial adhesive spot length, adjust the actual adhesive spot length of each adhesive spot in the parameterized finite element model of the component in a parameterized manner, and simulate and calculate the root mean square value of the main mirror surface shape error caused by adhesive stress under each actual adhesive spot length.

[0034] Among them, the parameterized adjustment of the actual glue spot length of each glue spot refers to the parameterized gradual increase or decrease of the actual glue spot length of each glue spot.

[0035] Step 104: Determine the optimal adhesive spot length based on the curve of the root mean square value changing with the actual adhesive spot length.

[0036] The optimal gel spot length is the actual gel spot length corresponding to the inflection point where the root mean square value enters the plateau region in the variation curve.

[0037] The high-precision, lightweight micro-stress assembly method for reflectors provided by this invention, in practical applications, first determines the minimum total bonding area to ensure the reliability of the connection between the primary mirror and the central axis, and obtains the initial adhesive spot length for each adhesive spot corresponding to this minimum total bonding area; then, a parameterized finite element model of the primary mirror assembly is established to equivalently simulate the bonding stress generated by the curing shrinkage of the adhesive layer, and the influence of different adhesive spot lengths on the surface shape of the primary mirror is systematically simulated and analyzed; subsequently, by analyzing the curve of the change of the root mean square value of the surface shape error with the adhesive spot length, the actual adhesive spot length corresponding to the inflection point where the root mean square value enters the plateau region is taken as the optimal adhesive spot length; applying the optimal adhesive spot length determined by this invention to the actual bonding process can ensure the connection strength between the primary mirror and the central axis while actively controlling the deterioration of the primary mirror surface shape caused by bonding stress to the lowest level.

[0038] This invention provides a method for quantitatively determining the optimal adhesive spot length, thereby achieving high-precision, lightweight, and low-stress assembly of the primary mirror. This method overcomes the problem in the bonding process between the primary mirror and the central axis, where the bonding area design only considers the lower limit requirement of mechanical strength, while ignoring the negative impact of bonding stress on the surface shape of the primary mirror.

[0039] This invention solves the contradiction between bonding strength and precision in traditional bonding processes, and realizes the transformation of high-precision lightweight primary lens assembly from "experience-based trial and error" to "predictive optimization", which significantly improves the assembly success rate and assembly efficiency.

[0040] Furthermore, based on the dynamic conditions of the optical lens, the minimum total bonding area required to ensure reliable connection between the primary mirror and the central axis is calculated, specifically as follows: Based on the worst-case dynamic conditions of the optical lens under mechanical conditions, the minimum total bonding area that ensures the reliability of the connection between the primary lens and the central axis is calculated using the first calculation formula. The first calculation formula is as follows: ; in, It is the minimum total adhesive area. It is the acceleration under the worst dynamic conditions. It's the safety factor. It refers to tensile or shear strength.

[0041] The worst dynamic conditions refer to the extreme and multi-factor coupled mechanical loads and environmental effects applied to materials, structures or systems in a specific engineering or physical environment, causing them to be in a state close to or exceeding the design limits and service safety boundaries.

[0042] The worst-case dynamic acceleration refers to the maximum acceleration response that the adhesive layer can withstand under extreme or ultimate mechanical conditions.

[0043] Furthermore, starting from the initial adhesive spot length, the actual adhesive spot length of each spot is parametrically adjusted in the parameterized finite element model of the component, and the root mean square value of the principal mirror surface shape error caused by adhesive stress is simulated and calculated for each actual adhesive spot length, specifically including: The initial adhesive spot length of each adhesive spot corresponding to the minimum total adhesive area is taken as the starting point for analysis.

[0044] In the component parametric finite element model, the bonding layout at the bonding position remains unchanged, and the actual adhesive spot length of each adhesive spot is parametrically increased to proportionally increase the total bonding area between the primary mirror and the central axis.

[0045] In other words, the actual glue spot length is greater than the initial glue spot length.

[0046] Static simulation was performed on each actual adhesive spot length to extract the surface shape error data of the primary mirror optical surface caused by adhesive stress, and the root mean square value (RMS) of the surface shape error data was calculated.

[0047] Furthermore, based on the curve of the root mean square value changing with the actual glue spot length, the optimal glue spot length is determined, specifically as follows: Plot the curve of the root mean square value as the actual glue spot length increases, and take the actual glue spot length corresponding to the inflection point where the root mean square value decreases into the plateau region in the curve as the optimal glue spot length.

[0048] Among them, the optimal adhesive spot length simultaneously satisfies the dual objectives of adhesive mechanical strength requirements and the optimization of the main mirror surface shape accuracy.

[0049] In this embodiment, the curve showing the change of the root mean square (RMS) value with the increase of the actual adhesive spot length exhibits a trend where the RMS value rapidly decreases from a high point and then gradually flattens out as the actual adhesive spot length increases. In other words, the curve showing the change of the RMS value with the increase of the actual adhesive spot length is not monotonically changing, but rather there exists an optimal adhesive spot length that minimizes the surface shape error of the primary mirror.

[0050] Furthermore, provided that the optimal adhesive spot length is greater than the initial adhesive spot length, the total bonding area corresponding to the optimal adhesive spot length is greater than the minimum total bonding area.

[0051] In this embodiment of the invention, the adhesive stress equivalently simulated by the curing shrinkage of the adhesive layer is specifically as follows: The temperature gradient method is used to apply a negative thermal expansion system to the adhesive layer in the parameterized finite element model of the component and apply a virtual cooling field to the adhesive layer to achieve the equivalent adhesive stress generated by curing shrinkage.

[0052] Furthermore, after determining the optimal gel spot length, the method also includes: The actual amount of adhesive injected into the primary mirror and the central axis is calculated based on the optimal adhesive spot length, and the primary mirror and the central axis are then bonded together using adhesive based on the actual amount of adhesive injected.

[0053] Specifically, the actual amount of adhesive injected is calculated according to the second calculation formula, which is as follows: ; in, Indicates the actual amount of adhesive injected. Indicates the volume of the central shaft injection hole. This indicates the volume of glue injected into the central shaft glue groove.

[0054] Furthermore, after applying adhesive to bond the primary mirror to the central axis according to the actual amount of adhesive used, the method also includes: After the adhesive has fully cured, an interferometer is used to detect the actual surface shape of the primary mirror in multiple directions, and the assembly qualification is verified based on the root mean square value of the actual surface shape error and the preset surface shape error value.

[0055] Furthermore, the actual surface shape detection of the primary mirror is performed in at least two symmetrical directions around the optical axis of the primary mirror.

[0056] In this embodiment, as Figure 2 As shown, taking the assembly of a φ212mm diameter SiC lightweight primary mirror for a space camera as an example, the target's root mean square (RMS) value on the orbital plane needs to be better than 0.025λ. The specific assembly process is as follows: (1) Determine the bonding location and minimum bonding area Specifically, refer to Figure 2 In (a) and (b), the bonding position between the primary mirror and the central axis is located between the central hole of the primary mirror and the titanium alloy support shaft (central axis). Three annular injection grooves are spaced apart at the bonding position, and each layer is injected with adhesive through eight injection points into the corresponding injection grooves. Based on the dynamic analysis of this optical lens, to ensure the fundamental frequency requirement of the optical lens, the minimum total bonding area S_min = 1600mm² is calculated based on the first calculation formula to ensure the reliability of the connection between the primary mirror and the central axis.

[0057] Among the multiple adhesive spots corresponding to the obtained minimum total adhesive area, the initial adhesive spot length (theoretical minimum length) of each adhesive spot is L_min = 20 mm.

[0058] (2) Establish a parametric finite element model of the optical lens components to analyze the optimal speckle length. A parametric finite element model of the components, including the main mirror, central axis, structural frame, and adhesive layer, was established using finite element analysis software. In this model, the adhesive layer was finely meshed; a gravity load was used to simulate the side-hanging state; the adhesive stress caused by the curing shrinkage of the adhesive layer was simulated using the "temperature gradient method," and the simulation calculations resulted in a virtual temperature drop in the adhesive layer equivalent to the actual curing shrinkage rate of XM-31 adhesive.

[0059] Starting with L_min = 20 mm as the analysis starting point, simulations were performed by sequentially increasing the actual adhesive spot length to 22 mm, 24 mm, 26 mm, 28 mm, 30 mm, and 32 mm. Data on the principal mirror shape error caused solely by adhesive stress at each actual adhesive spot length were extracted, and the root mean square (RMS) value of the principal mirror shape error data for each actual adhesive spot length was calculated. The fitting results of the adhesive spot's influence on the principal mirror shape are as follows: Figure 4 As shown, the RMS increment of the surface shape is 0.007λ.

[0060] Table 1. Root Mean Square (RMS) values ​​of the principal mirror shape corresponding to different actual glue spot lengths.

[0061] Table 1 shows the root mean square (RMS) values ​​of the primary mirror surface corresponding to different actual glue spot lengths. Based on Table 1, a curve showing the change of the RMS value with the increase of the actual glue spot length is plotted.

[0062] like Figure 3 As shown, the RMS value of the primary mirror shape decreases rapidly with the increase of the actual spot length, but when the actual spot length reaches 28mm, the change curve clearly enters a plateau region, and the gain is no longer significant.

[0063] Therefore, the optimal adhesive spot length L_opt = 28 mm was determined. At this point, the corresponding minimum total bonding area has exceeded the minimum mechanical requirement of bonding strength, and the introduced principal mirror surface shape error is only 0.008λ, achieving the best balance between bonding strength and the accuracy of the bonded component.

[0064] (3) Process implementation and verification The actual amount of adhesive injected into the primary mirror and central axis is calculated using the second calculation formula based on the optimal adhesive spot length. In this embodiment, when L_opt = 28 mm, 0.06 ml of XM-31 adhesive is required for each injection hole.

[0065] Afterwards, the bonding and curing of the primary mirror and the central axis were completed according to the process specifications. After the XM-31 adhesive was completely cured, the surface shape of the primary mirror was detected in four directions: 0°, 90°, 180°, and 270° using a phase-shifting interferometer.

[0066] In this embodiment, as Figure 5As shown in (a), (b), and (c), the measured RMS values ​​of the surface shape in all four directions are better than 0.025λ. Given that the average RMS value of the bare primary mirror surface shape is 0.018λ, the actual increment introduced by the bonding process is approximately 0.007λ, which is highly consistent with the simulation prediction of 0.008λ. This result fully verifies the accuracy and effectiveness of this method.

[0067] And in Figure 5 In (a), PV represents the peak-to-valley value, which refers to the height difference between the highest point (peak) and the lowest point (valley) on the primary mirror surface. RMS represents the root mean square value, which is the average deviation of each point on the mirror surface from the ideal surface shape. By comparing the evaluation results of the core indicators in the detection interferogram of the primary mirror surface shape with the preset target, the quality of the primary mirror can be determined.

[0068] In addition, through observation Figure 5 The surface color transition in (b) and observation Figure 5 The surface pattern of (c) is examined to determine whether it meets the design requirements and whether the next process route can be carried out.

[0069] The high-precision, lightweight reflector micro-stress assembly method of this invention, through systematic simulation analysis, clearly reveals that in the central axis bonding process, the RMS value of the surface shape error caused by bonding stress does not change monotonically with the increase of the adhesive spot length, but rather has a distinct "optimal value" range. This result corrects the one-sided perception in traditional thinking that "the larger the bonding area, the more reliable" or "the smaller the bonding area, the less stress," and provides a key theoretical basis for resolving the contradiction between strength and precision.

[0070] The high-precision, lightweight micro-stress assembly method for reflectors of this invention transforms the adhesive spot length from a passive, experience-based process parameter into a design variable that can be predicted in advance and actively optimized. It enables precise prediction of the post-assembly surface shape during the bonding process design stage, transforming the traditional "assembly-test-rework" model into a new "prediction-optimization-first-success" model.

[0071] The high-precision, lightweight reflector micro-stress assembly method of this invention can minimize the surface shape error introduced by the bonding process while ensuring mechanical reliability. Actual measurement data shows that for the SiC primary mirror with a φ212mm diameter and a weight reduction rate of 78% in this embodiment, after optimization using this method, the RMS increment of the surface shape introduced by bonding can be reduced from 0.04λ (λ=632.8nm) to below 0.008λ, providing a larger margin for surface shape accuracy for the primary mirror and significantly saving the time and cost of repeated assembly and adjustment caused by surface shape deviations.

[0072] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-precision, lightweight micro-stress assembly method for a reflective mirror, characterized in that, include: After determining the bonding position between the primary mirror and the central axis, the minimum total bonding area to ensure the reliability of the connection between the primary mirror and the central axis is calculated based on the dynamic conditions of the optical lens, and the initial adhesive spot length of each adhesive spot corresponding to the minimum total bonding area is obtained; the dynamic conditions include sinusoidal vibration, random vibration or impact conditions; A parametric finite element model of the components, including the main mirror, the central axis, the structural frame, and the adhesive layer, is established, and the adhesive stress generated by the curing shrinkage of the adhesive layer is simulated accordingly. Starting from the initial adhesive spot length, the actual adhesive spot length of each adhesive spot is adjusted parametrically in the parameterized finite element model of the component, and the root mean square value of the principal mirror surface shape error caused by adhesive stress is calculated under each actual adhesive spot length. The optimal adhesive spot length is determined based on the curve of the change of the root mean square value with the actual adhesive spot length; the optimal adhesive spot length is the actual adhesive spot length corresponding to the inflection point where the root mean square value enters the plateau region in the curve.

2. The high-precision lightweight reflector micro-stress assembly method according to claim 1, characterized in that, The minimum total bonding area required to ensure reliable connection between the primary mirror and the central axis is calculated based on the dynamic conditions of the optical lens. Specifically: Based on the worst-case dynamic conditions of the optical lens under mechanical conditions, the minimum total bonding area that ensures the reliability of the connection between the primary lens and the central axis is calculated using a first calculation formula. The first calculation formula is as follows: ； in, It is the minimum total adhesive area. It is the acceleration under the worst dynamic conditions. It's the safety factor. It refers to tensile or shear strength.

3. The high-precision lightweight reflector micro-stress assembly method according to claim 1, characterized in that, Starting from the initial adhesive spot length, the actual adhesive spot length of each adhesive spot is parametrically adjusted in the parameterized finite element model of the component, and the root mean square value of the principal mirror surface shape error caused by adhesive stress is simulated and calculated for each actual adhesive spot length, specifically including: Taking the initial adhesive spot length of each adhesive spot corresponding to the minimum total bonding area as the starting point of the analysis, in the parameterized finite element model of the component, the bonding layout of the bonding position remains unchanged, and the actual adhesive spot length of each adhesive spot is increased parametrically to increase the total bonding area between the primary mirror and the central axis proportionally. Static simulation was performed on each actual adhesive spot length to extract the surface shape error data of the primary mirror optical surface caused by adhesive stress, and the root mean square value of the surface shape error data was calculated.

4. The high-precision lightweight reflector micro-stress assembly method according to claim 3, characterized in that, The optimal adhesive spot length is determined based on the curve showing the change of the root mean square value with the actual adhesive spot length, specifically as follows: Plot the curve of the root mean square value as the actual glue spot length increases, and take the actual glue spot length corresponding to the inflection point where the root mean square value decreases into the plateau region in the curve as the optimal glue spot length.

5. The high-precision lightweight reflector micro-stress assembly method according to claim 4, characterized in that, The total bonding area corresponding to the optimal adhesive spot length is greater than the minimum total bonding area.

6. The high-precision lightweight reflector micro-stress assembly method according to claim 1, characterized in that, The equivalent simulation of the adhesive stress generated by the curing shrinkage of the adhesive layer is specifically as follows: The temperature gradient method is used to apply a negative thermal expansion system to the adhesive layer in the parameterized finite element model of the component and apply a virtual cooling field to the adhesive layer to achieve an equivalent bonding stress generated by the curing shrinkage of the adhesive layer.

7. The high-precision lightweight reflector micro-stress assembly method according to claim 1, characterized in that, After determining the optimal gel spot length, the method further includes: The actual amount of adhesive injected into the primary mirror and the central axis is calculated based on the optimal adhesive spot length, and the primary mirror and the central axis are then bonded together using adhesive based on the actual amount of adhesive injected.

8. The high-precision lightweight reflector micro-stress assembly method according to claim 7, characterized in that, After applying adhesive to bond the primary mirror to the central axis according to the actual amount of adhesive injected, the method further includes: After the adhesive has fully cured, an interferometer is used to detect the actual surface shape of the primary mirror in multiple directions, and the assembly qualification is verified based on the root mean square value of the actual surface shape error and the preset surface shape error value.

9. The high-precision lightweight reflector micro-stress assembly method according to claim 8, characterized in that, The actual surface shape detection of the primary mirror is performed in at least two symmetrical directions around the optical axis of the primary mirror.

10. The high-precision lightweight reflector micro-stress assembly method according to claim 1, characterized in that, The primary mirror is a silicon carbide or microcrystalline glass reflector with an aperture greater than 200mm and a weight reduction rate greater than 70%.

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