Large Field of View Space-Based Optical Detection System Based on Freeform Surfaces

Dongwei Ni; Xuyang Li; Mingyang Yang; Zhiguang Ren

doi:10.3788/AOS201838.1122003

Acta Optica Sinica, Volume. 38, Issue 11, 1122003(2018)

Large Field of View Space-Based Optical Detection System Based on Freeform Surfaces

Dongwei Ni^1,2、*, Xuyang Li^1、*, Mingyang Yang^1,2, and Zhiguang Ren³

¹ Laboratory of Space Optics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an, Shaanxi 710119, China

² University of Chinese Academy of Sciences, Beijing 100049, China

³ School of Physics and Information Technology, Shaanxi Normal University, Xi'an, Shaanxi 710119, China

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Figures & Tables(16)

Fig. 1. Structural diagram of space-based detection optical system

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Fig. 2. Profile of Zernike freeform surface of primary mirror. (a) Two-dimensional; (b) three-dimensional

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Fig. 3. Profile of XY freeform surface of tertiary mirror. (a) Two-dimensional; (b) three-dimensional

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Fig. 4. Spot diagram of system

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Fig. 5. Encircled energy distributions under different field views. (a) Field view of 0.5; (b) field view of 0.7; (c) edge field of view

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Fig. 6. Detecting optical path. (a) CGH detecting optical path of freeform surface; (b) CGH unit in detecting optical path

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Fig. 7. Lithography linear density of CGH and wave aberration of detecting system. (a) Lithographic linear density; (b) wave aberration

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Table 1. Corresponding relationship between Zernike polynomials and aberration

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Table 1. Corresponding relationship between Zernike polynomials and aberration

No.	Polynomial		Aberration
No.		Polar coordinate system	Cartesian coordinate system
1	1	1	Piston
2	ρcos θ	x	x-tilt
3	ρsin θ	y	y-tilt
4	ρ²cos(2θ)	x²-y²	0° or 90° astigmatism
5	2ρ²-1	2(x²+y²)-1	Defocus
6	ρ²sin(2θ)	2xy	45° astigmatism
7	ρ³cos(3θ)	x(x²-y²)-2xy²	x-trefoil
8	(3ρ²-2)ρcos θ	x[3(x²+y²)-2]	x-coma
9	(3ρ²-2)ρsin θ	y[3(x²+y²)-2]	y-coma

Table 2. Performance parameters of detector
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Table 2. Performance parameters of detector
Parameter Value
B 8
N_c 46
τ 0.8
Integration time /s 0.02
E_ph /(10^-19 J) 3.4
f_QE /% 55

Table 3. Main technical indexes of space-based optical detection system
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Table 3. Main technical indexes of space-based optical detection system
System parameter Value
Focal length /mm 64
Field of view /[(°) ×(°)] 30×30
Entrance aperture /mm 51
Equivalent visual magnitude 9
Spectral band /nm 400-900

Table 4. Initial structural parameters of optical system
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Table 4. Initial structural parameters of optical system
Surface Radius /mm Thickness /mm
Primary mirror 175.4386 -150
Secondary mirror 333.3333 150
Tertiary mirror -330.3704 -125

Table 5. Mirror parameters of optical system after optimization

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Table 5. Mirror parameters of optical system after optimization

Mirror	Radius /mm	Distance /mm	Constant ofquadric surface	Y decenter /mm	x tilt /(°)
Primary mirror	398.39	-297.29	-2.73	117.55	22.60
Secondary mirror	1165.19	287.29	0	19.03	0
Tertiary mirror	-770.05	-267.70	-6.82	-22.21	3.15

Table 6. Parameters of Zernike freeform surface of primary mirror

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Table 6. Parameters of Zernike freeform surface of primary mirror

No.	Term	Coefficient
1	Z₁	3.703732952805
2	Z₂	-0.005921378239
3	Z₃	1.074318956926
4	Z₄	-0.000844676164
5	Z₅	0.000225724509
6	Z₆	-7.298797621080×10^-6
7	Z₇	5.336916645650×10^-8
8	Z₈	-2.419364792778×10^-8
9	Z₉	2.566383909345×10^-6
10	Z₁₀	-1.197484299545×10^-6
11	Z₁₁	4.052592425289×10^-10
12	Z₁₂	-2.946732238365×10^-9

Table 7. Parameters of XY freeform surface of tertiary mirror

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Table 7. Parameters of XY freeform surface of tertiary mirror

Item	Coefficient	Item	Coefficient
Y	0.0657280763771848	X⁴Y	-1.508575293882×10^-13
X²	0.000526216242287311	X²Y³	-1.246876764365×10^-12
Y²	0.000529147800335145	Y⁵	1.859610071502×10^-12
X²Y	-2.14467235342657×10^-8	X⁶	8.860132888429×10^-15
Y³	-3.04871515062429×10^-8	X⁴Y²	2.549695693063×10^-14
X⁴	-1.89146570020516×10^-9	X²Y⁴	1.780628633470×10^-14
X²Y²	-3.7733664377066×10^-9	Y⁶	1.292338859180×10^-14
Y⁴	-1.69502835366705×10^-9	-	-

Table 8. Distribution of system tolerance

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Table 8. Distribution of system tolerance

Mirror	Manufacture tolerance			Alignment tolerance
Mirror	ΔR /mm	ΔK	RMS of shapeerror /λ	Decenter /mm	Tilt /rad	DisplacementΔY /mm
Primary mirror	0.02	0.01	1/50	0.02	3×10^-4	0.02
Second mirror	0.005	0.002	1/50	0.01	1.5×10^-4	0.02
Tertiary mirror	0.02	0.008	1/50	0.02	3×10^-4	0.08

Table 9. Performance of system tolerance

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Table 9. Performance of system tolerance

Field No.	Sagittal direction /(°)	Tangential direction /(°)	Design value /μm	Design tolerance /μm
1	0	-5	0.015416	0.023123
2	0	-20	0.010510	0.018538
3	0	-35	0.010699	0.018867
4	5	-5	0.009367	0.016026
5	5	-20	0.013022	0.022765
6	5	-35	0.007800	0.014165
7	10	-5	0.009585	0.017063
8	10	-20	0.013478	0.021934
9	10	-35	0.006847	0.012299
10	15	-5	0.009996	0.018456
11	15	-20	0.007032	0.012354
12	15	-35	0.006425	0.016219

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Dongwei Ni, Xuyang Li, Mingyang Yang, Zhiguang Ren. Large Field of View Space-Based Optical Detection System Based on Freeform Surfaces[J]. Acta Optica Sinica, 2018, 38(11): 1122003

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