Acta Photonica Sinica, Volume. 50, Issue 12, 1222004(2021)
Design of Airborne Infrared Dual-band Imaging Optical System Based on Harmonic Diffraction and Free-form Surface
Figures & Tables(19)
Fig. 11. The MTF of the system at different temperatures in the 3~5 μm band
Fig. 12. The MTF of the system at different temperatures in the 8~12 μm band
Table 1. Main technical indicators of the system
View tableView in ArticleTable 1. Main technical indicators of the system
Technical index Index requirements Focal length 1 200±5 mm Effective caliber 300±5 mm Working band Medium wave/long wave Half field of view ≥2° Root Mean Square （RMS） of the radius of the diffuse spot ≤25 μm Modulation Transfer Function （MTF） Medium/long wave bands are both greater than 0.4（10 lp/mm） Operating temperature -60℃~+60℃ Total length of the system ≤750 mm
Table 2. Resonant wavelengths of different design wavelengths
View tableView in ArticleTable 2. Resonant wavelengths of different design wavelengths
Design wavelength/μm 8 10 12 p=2 Resonance order 2 3 4 5 6 7 2 3 4 5 6 7 2 3 4 5 6 7 Resonance wavelength/μm 8 5.3 4 3.2 2.7 2.2 10 6.7 5 4 3.3 2.9 12 8 6 5 4 3.4 p=3 Resonance order 2 3 4 5 6 7 2 3 4 5 6 7 2 3 4 5 6 7 Resonance wavelength/μm 12 8 6 4.8 4 3.4 15 10 7.5 6 5 4.2 18 12 9 7.2 6 5.1
Table 3. Performance of optional mirror substrate materials
View tableView in ArticleTable 3. Performance of optional mirror substrate materials
Material Density/（g Elastic modmodulus/GPa Specific modulus of elasticity/（× Thermal conductivity/（W·m-1·K-1） Thermal expansion coefficien/（ Thermal deformation coefficient / （SiC 3.05 400 12.6 185 2.5 1.4 Be 1.85 280 15.1 160 11.4 7.2 Low-expansion glass-ceramic 2.5 92 3.7 1.46 0.05 3 Low expansion fused silica 2.2 67 3.1 1.3 0.03 2.3
Table 4. Performance analysis of optional refractive/refractive diffractive lens materials
View tableView in ArticleTable 4. Performance analysis of optional refractive/refractive diffractive lens materials
Material Transmission band/μm Theoretical transmittance/% Refractive index n Elastic modulus/GPa Thermal conductivity/（W·m-1·K-1） Thermal expansion coefficient/（ Knoop hardness/（kg· Breaking strength/MPa Si 1.1~9 53.9 3.426 130.91 596 （125 K）
163 （313 K）
105.1 （400 K）
-0.5 （75 K）
2.5 （293 K）
4.6 （1400 K）
1 150 70~340 Ge 1.8~23 47.1 4.003 2 103 165.8 （125K）
59 （293 K）
43.95 （400 K）
2.4 （100 K）
6.1 （298 K）
8.0 （1 200 K）
780 90~100 Standard ZnS 1-13 75 2.20 74.5 17 （296 K） 4.6 （173 K）
6.6 （273 K）
7.7 （473 K）
230~250 97.95 Standard ZnSe 0.5~20 71 2.40 70.3 18 （300 K） 5.6 （173 K）
7.1 （273 K）
8.3 （293 K）
105 52.55 GaAs 0.9~15 55.85 3.276 82.68 55 （300 K） 0.9 （75 K）
5.7 （300 K）
7.3 （1 000 K）
- 130 CaF2 0.13~12 94 1.43 75.79 8.4 18.7 158 37
Table 5. Final tolerance distribution
View tableView in ArticleTable 5. Final tolerance distribution
Operand Surface1 Surface2 Value Minimum Maximum COMP 16 — -50 -50 50 TWAV — — — 4（10） — TRAD 3 — -1999.900 -0.02 0.02 TRAD 6 — -666.652 -0.02 0.02 TRAD 9 — -999.950 -0.02 0.02 TRAD 11 — 2728.675 -0.2 0.2 TRAD 12 — 2406.081 -0.2 0.2 TRAD 13 — 1054.373 -0.2 0.2 TRAD 14 — 916.156 -0.2 0.2 TRAD 15 — 1439.644 -0.2 0.2 TRAD 16 — 1112.167 -0.2 0.2 TETX 3 3 — -0.018 0.018 TETX 6 6 — -0.018 0.018 TETX 9 9 — -0.018 0.018 TTHI 1 2 600.000 -0.2 0.2 TTHI 4 5 -499.975 -0.2 0.2 TTHI 7 8 499.975 -0.2 0.2 TTHI 10 12 -600.000 -0.2 0.2 TTHI 11 12 -13.166 -0.2 0.2 TTHI 12 14 -11.801 -0.2 0.2 TTHI 13 14 -13.855 -0.2 0.2 TTHI 14 16 -27.165 -0.2 0.2 TTHI 15 16 -23.399 -0.2 0.2
Table 6. Tolerance analysis results
View tableView in ArticleTable 6. Tolerance analysis results
Test wavelength/μm Nomimol/μm Best/μm The surface for the best results Worst/μm The surface of the worst results 90%>/μm 80%>/μm 50%>/μm 20%>/μm 10%>/μm 4 9.932 9.966 11 28.964 19 24.032 22.089 15.796 11.907 11.544 10 9.076 9.839 3 31.187 14 22.770 19.863 14.095 11.403 11.012
Table 7. Comparison of design results and corresponding technical indicators
View tableView in ArticleTable 7. Comparison of design results and corresponding technical indicators
The main parameters Technical index Design result System focal length/mm 1 200±5 1 200 Effective caliber/mm 300±5 300 Half field of view/（°） ≥±2 ±2 Working band/μm Medium wave/long wave 3~5 μm/8~12 μm MTF@10 lp/mm ≥0.4 ≥0.6（3~5 μm）
≥0.45（8~12 μm）
Diffuse spot radius（RMS）/μm ≤25 18.335（3~5 μm）
15.811（8~12 μm）
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Jie LI, Hui LUO, Jincheng LI, Hanping WU. Design of Airborne Infrared Dual-band Imaging Optical System Based on Harmonic Diffraction and Free-form Surface[J]. Acta Photonica Sinica, 2021, 50(12): 1222004
Paper Information
Category: Optical Design and Fabrication
Received: May. 21, 2021
Accepted: Sep. 22, 2021
Published Online: Jan. 26, 2022
The Author Email: WU Hanping (wuhanping601@sina.com)
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