Opto-Electronic Engineering, Volume. 52, Issue 5, 250006(2025)
Structure design of flat mirror with large aspect ratio for space camera
Figures & Tables(17)
Fig. 4. Influence of three-point back support position on gravitational deformation of mirror. (a) δy=50 mm; (b) δy=80 mm; (c) δy=110 mm
Fig. 5. Gravitational deformation of flat mirror under typical support positions. (a) Dx=610 mm; (b) Dx=650 mm; (c) Dx=690 mm
Fig. 6. Back three-point support structure for flat mirror. (a) Assembly relationship; (b) Component physical object
Fig. 7. Flexure support with biaxial orthogonal hinge. (a) Main flexure parameters; (b) Optimization of hinge structure parameters; (c) Relation between hinge position and mirror deformation
Fig. 8. Fitting nephograms of mirror deformation under typical conditions. (a) 1 G, -Y gravity; (b) 4 ℃ temperature change; (c) 0.02 mm forced displacement; (d) Compound
Fig. 10. Surface accuracy test of flat mirror. (a) Schematic of surface zoning; (b) Test scene using large aperture interferometer
Fig. 11. Zonal surface nephograms of flat mirror. (a) Left, RMS of 0.0203λ; (b) Middle, RMS of 0.0197λ; (c) Right, RMS of 0.0204λ
Table 1. Main design metrics for flat mirror assembly
View tableView in ArticleTable 1. Main design metrics for flat mirror assembly
No. Item Requirement 1 Clear aperture 1220 mm×198 mm 2 Testing attitude Optical axis horizontal 3 Gravitational deformation Tilt: θM≤10″ 4 Working temperature (20±4) ℃ 5 Surface accuracy RMS≤1/50λ over sub-aperture of Φ140 mm (λ=632.8 nm) 6 Mass ≤40 kg 7 Frequency ≥100 Hz
Table 2. Properties of spatial reflector materials in main visible light band
View tableView in ArticleTable 2. Properties of spatial reflector materials in main visible light band
Property SiC ULE Zerodur Density ρ/(kg·m−3) 3050 2210 2530 Elastic modulus E/GPa 340 67 91 Specific stiffness E/ρ 111.5 30.3 36 Thermal conductivity λ1/(W·K−1·m−1) 155 1.31 1.64 Thermal expansion coefficient α/(10−6·K−1) 2.50 0.03 0.05 Thermal stability λ1/α 62 43.7 32.8
Table 3. Main parts materials and their physical properties
View tableView in ArticleTable 3. Main parts materials and their physical properties
Parameter Main parts material Mirror Cone Flexure Base Material SiC Invar TC4 SiC/Al Density ρ/(kg·m−3) 3050 8100 4400 3000 Elastic modulus E/Gpa 340 141 114 180 Poisson ratio μ 0.27 0.25 0.34 0.18 Thermal expansion coefficient α/(10−6·K−1) 2.5 2.5 9.1 8.4
Table 4. Deformation data of the flat mirror assembly under typical conditions
View tableView in ArticleTable 4. Deformation data of the flat mirror assembly under typical conditions
Typical condition RMS/nm θX/″ Condition 1 Gravity/(1 G, −Y) 1.812 3.639 Condition 2 Temperature change/4 3.302 / Condition 3 Forced displacement/0.02 mm 0.948 / Condition 1+2+3 Compound 5.044 / Requirement ≤1/50λ (λ=632.8 nm) ≤10
Table 5. Modal analysis results of flat mirror assembly
View tableView in ArticleTable 5. Modal analysis results of flat mirror assembly
No. Frequency/Hz Vibration mode 1 129.1 Mirror rotation around Y-axis 2 134.6 Mirror rotation around X-axis 3 174.9 Mirror rotation around Z-axis 4 178.5 Mirror translation along Y-axis 5 193.3 Mirror translation along X-axis 6 201.5 Mirror translation along Z-axis
Table 6. Surface accuracy data of flat mirror before and after overturn
View tableView in ArticleTable 6. Surface accuracy data of flat mirror before and after overturn
Zone RMS/λ Left Before 0.0203 After 0.0213 Middle Before 0.0197 After 0.0204 Right Before 0.0204 After 0.0207
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Jian Yuan, Lei Zhang, Siyu Pei, Xiaotao Li, Guanchen Zhang. Structure design of flat mirror with large aspect ratio for space camera[J]. Opto-Electronic Engineering, 2025, 52(5): 250006
Paper Information
Category: Article
Received: Jan. 8, 2025
Accepted: Mar. 24, 2025
Published Online: Jul. 18, 2025
The Author Email: Lei Zhang (张雷)
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