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Conceptual Design of a Compact Fizeau Interferomet
er
Neng-hong Zhu, Xin-yang Chen
Shanghai Astronomical Observatory23/4/20
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Background & Goal• Dream: Optical long baseline interferometer based in space• Reality: Optical interferometry of China is just in inital stage
+ limited money• Option: Compact Fizeau Space Interferometer
short baseline direct instantaneous imaging small scale
• Step 1: gound prototype with diameter equivalent to 1m
Step 2: Fizeau space Interferometer with diameter equivalent to 2~4m
future: longer baseline & more elements...
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Array configurationGeometric Array
Modulation Transfer Function: MTF=|FT(PSF)|
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
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2
3
4
5
6x 10
16
square d=0.4m L=0.3995m Deff=0.89398m
Y-3 d=0.4m L=0.39837m Deff=0.79998m
Y-4 d=0.4m L=0.65m Deff=1.0278m
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
1
2
3
4
5
6x 10
16
square d=0.4m L=0.3995m Deff=0.89398m
Y-3 d=0.4m L=0.39837m Deff=0.79998m
Y-4 d=0.4m L=0.65m Deff=1.0278m
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
1
2
3
4
5
6x 10
16
square d=0.4m L=0.3995m Deff=0.89398m
Y-3 d=0.4m L=0.39837m Deff=0.79998m
Y-4 d=0.4m L=0.65m Deff=1.0278m
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
1
2
3
4
5
6x 10
16
square d=0.4m L=0.3995m Deff=0.89398m
Y-3 d=0.4m L=0.39837m Deff=0.79998m
Y-4 d=0.4m L=0.65m Deff=1.0278m
α=0° α=10°
α=20° α=30°
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Beam combining errors (1/2)
• PSF vs. piston error
piston=-0.2λpiston=-0.4λ piston=0.2λ piston=0.4λ
MTF vs. piston
Strehl Ratio vs. piston
SR≥0.9 -----> piston P-V≤0.1λ
[Cao Fang, et al, 2008]
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Beam combining errors (2/2)
• PSF vs. tip/tilt error
X tip=0
X tip=0.2λ X tip=0.1λ X tip=0.3λ
Y tilt=0 Y tilt=0.2λ Y tilt=0.1λ Y tilt=0.3λ
MTF vs. tip/tilt
Strel Ratio vs. tip/tilt SR≥0.9 -----> tip/tilt P-V≤0.055λ≈0.
3"
[Cao Fang, et al, 2008]
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Spec. of the ground prototype
• Y-4 array -----> (1) high stability due to symmetric structure (2) optimal MTF (3) tubes modulization
• common mounting -----> without optical delay line for compensating outer OPD• C-shape board & triangle flatform -----> high stiffness & resonance freq. • wide FOV ~ ±2 '• Direct Drive -----> no backlash, high tracking accuracy ~ RMS:0.01"(Dec=45°)
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FEA of structure
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Optics design
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8 9 10 11 12 13
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19 SIT-19
子孔径望远镜主镜
场镜
准直物镜组
朱能鸿
周丹 光学系统
旋转光阑
四棱锥组件
CCD出瞳检测 相机-2反射镜
综合孔径
中国科学院上海天文台朱能鸿
( )重量 公斤
第 张
图样标记 数量
共 张
文 件 号 签 字日期标记处所
:材料日期 批 准
审 核
部件设计
设 计 比例
干涉成像望远镜
18 SIT-18
17 SIT-17
16 SIT-16-00
Tip-Tilt -2镜
CCD干涉条纹检测 相机
分光立方棱镜
反射棱镜
分光平面镜
SIT-15
SIT-14
SIT-13
SIT-12
SIT-11
SIT-10
SIT-09-00
1514131211109 合成物镜组
Piston镜
Tip-Tilt -1镜
调焦物镜
-1反射镜
CCD干涉成像 相机
子孔径望远镜副镜
SIT-08
SIT-07
SIT-06
SIT-05-00
SIT-04
SIT-03
SIT-02
SIT-01
87654321序号 件号 名称 备注总重单重材料数量
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sub-telescope optics
folding & combiner optics confusion circle Φ≤ 0.7"Primary mirror
Outer diameter(mm)
420 Inner diameter(mm)
80
Thickness(mm) 60 Weight (Kg) 20
f/D ratio 2 Eccentricity 1.020466
Secondary mirror
Outer diameter(mm)
80 Curvature radii 336
Thickness(mm) 15 Weight (Kg) 0.15
Eccentricity 2.076363
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Challenge• How to measure and eliminate co-phasing errors b
etween sub-telescopes? pyramid wavefront sensor fringe tracking
How to improve image quality? interferometric image restoration method -> better MTF
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