Alignment Method for Off-Axis Optical Systems Based on CGH Multi-Mirror Attitude Determination

Yifan Wu; Jianfa Chen; Zeyao Cui; Haoyang Huang

doi:10.3788/AOS231547

Acta Optica Sinica, Volume. 44, Issue 3, 0322002(2024)

Alignment Method for Off-Axis Optical Systems Based on CGH Multi-Mirror Attitude Determination

Yifan Wu^1,2, Jianfa Chen^1,2、*, Zeyao Cui^1,2, and Haoyang Huang^1,2

¹Luoyang Institute of Electro-Optical Equipment, Aviation Industry Corporation of China, Ltd., Luoyang 471009, Henan, China

²National Key Laboratory of Space Based Information Perception and Fusion, Luoyang 471009, Henan, China

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Figures & Tables(16)

Fig. 1. CGH design flow

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Fig. 2. Trends in stripe linewidth of CGH. (a) Effect of raidus of curvature; (b) effect of envelope aperture

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Fig. 3. Adjustment flow diagram

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Fig. 4. Drawing of the lighpath of off-axis TMA system

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Fig. 5. Drawing of CGH design. (a) Drawing of CGH design; (b) drawing of the lighpath for two mirrors locating

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Fig. 6. Simulation results of CGH shape detection for primary mirror and third mirror. (a) Result of primary mirror; (b) result of third mirror

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Fig. 7. Simplified CGH model

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Fig. 8. Results of transmitted wavefront of CGH. (a) Result of primary mirror holographic region; (b) result of third mirror holographic region

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Fig. 9. Lightpath of optical system attitude determination using CGH

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Fig. 10. Result of wavefront error measurement of center field of view

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Table 1. Designed system parameters

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Table 1. Designed system parameters

Parameter	Value
Light aperture of primary mirror	$210 m m$
Light aperture of third mirror	$120 m m$
Operating band	Near infrared（NIR）band：0.7-0.9 μm； Long wave infrared（LWIR）band：8-12 μm
Field of view（FoV）	NIR band： $0.4 ° \times 0.4 °$ ； LWIR band： $2 ° \times 2 °$
Imaging quality	Full FoV of NIR RMS： $< 0.10 λ$ ； Full FoV of LWIR RMS： $< 0.23 λ$

Table 2. Influence on wavefront by primary error in CGH fabrication
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Table 2. Influence on wavefront by primary error in CGH fabrication
Type Tolerance RMS / $λ$
Stripe linewidth $0.2 μ m$ 0.011
Etching depth $1 %$ 0.005
Duty cycle $1 %$ —

Table 3. Error of physical CGH
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Table 3. Error of physical CGH
Type Error RMS / $λ$
Primary area RMS $7.8 n m$ 0.0123
Third area RMS $6.7 n m$ 0.0106
Duty cycle $0.4 %$ 0.0032

Table 4. CGH locating accuracy
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Table 4. CGH locating accuracy
Mirror α /（″） β /（″） γ /（″） X decenter $/ μ m$ Y decenter $/ μ m$ Z $/ μ m$
Primary mirror $13.68$ $10.08$ $92.16$ $26.1$ $35.0$ $2.1$
Third mirror $12.24$ $26.64$ $483.80$ $51.9$ $65.8$ $3.0$

Table 5. Value range of various tolerances
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Table 5. Value range of various tolerances
Tolerance type Primary mirror Third mirror
X decenter $/ μ m$ $\pm 50$ $\pm 100$
Y decenter $/ μ m$ $\pm 50$ $\pm 100$
Z $/ μ m$ $\pm 5$ $\pm 5$
Tilt /（″） $\pm 100$ $\pm 500$

Table 6. Results of wavefront error measurement of full field of view

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Table 6. Results of wavefront error measurement of full field of view

Elevation angle α /（°）		WFE RMS of full FoV $/ λ$
Elevation angle α /（°）		β=-1°	β=-0.2°	β=0°	β=0.2°	β=1°
	-1	0.126	—	0.118	—	0.089
	-0.2	—	0.083	0.084	0.080	—
	0	0.096	0.093	0.079	0.085	0.078
	0.2	—	0.087	0.088	0.082	—
	1	0.084	—	0.113	—	0.080

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Yifan Wu, Jianfa Chen, Zeyao Cui, Haoyang Huang. Alignment Method for Off-Axis Optical Systems Based on CGH Multi-Mirror Attitude Determination[J]. Acta Optica Sinica, 2024, 44(3): 0322002

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