Extraction of Laser Spot Centroid of Turbulent Disturbance Based on Ellipse Fitting Method

Jianbing Wang; Haifeng Yao; Zhi Liu; Keyan Dong; Shutong Liu

doi:10.3788/LOP231987

Laser & Optoelectronics Progress, Volume. 61, Issue 13, 1312003(2024)

Extraction of Laser Spot Centroid of Turbulent Disturbance Based on Ellipse Fitting Method

Jianbing Wang¹, Haifeng Yao^2、**, Zhi Liu^3、*, Keyan Dong³, and Shutong Liu¹

¹School of Electronic and Information Engineering, Changchun University of Science and Technology, Changchun 130022, Jilin , China

²School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China

³National and Local Joint Engineering Research Center of Space and Optoelectronics Technology, Changchun University of Science and Technology, Changchun 130022, Jilin , China

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Abstract Get PDF(in Chinese)

Figures & Tables(16)

Fig. 1. Free space laser communication diagram

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Fig. 2. Flow chart of proposed algorithm

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Fig. 3. Weight coefficient selection process

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Fig. 4. Comparison between the phase structure function and the theoretical structure function of different phase screen generation methods

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Fig. 5. Spot distortion under different turbulence intensities. (a) $C_{n}^{2} = 3 \times 10^{- 17} m^{- 2 / 3}$ ; (b) $C_{n}^{2} = 4.5 \times 10^{- 15} m^{- 2 / 3}$ ;(c) $C_{n}^{2} = 6 \times 10^{- 14} m^{- 2 / 3}$ ; (d) $C_{n}^{2} = 3.5 \times 10^{- 13} m^{- 2 / 3}$

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Fig. 6. Mean gray intensity within the mask under different turbulence intensities. (a) $C_{n}^{2} = 4.5 \times 10^{- 16} m^{- 2 / 3}$ ; (b) $C_{n}^{2} = 2.5 \times 10^{- 13} m^{- 2 / 3}$

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Fig. 7. Simulation system

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Fig. 8. Centroid extraction by different algorithms under weak turbulence. (a) Segmentation results of OTSU; (b) variable threshold segmentation; (c) edge of spot;(d) different algorithms for centroid extraction

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Fig. 9. Mean gray intensity change curve of different spot centroid extraction methods with the change of mask radius R under different turbulence. (a) Weak turbulence; (b) moderate turbulence; (c) strong turbulence

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Fig. 10. Real scene communication link

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Fig. 11. Laser spot for real scene communication. (a) Original image; (b) segmented image; (c) centroid extraction

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Fig. 12. Mean gray intensity with the change of mask radius

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Table 1. Turbulent phase screen simulation parameters
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Table 1. Turbulent phase screen simulation parameters
Parameter Numerical value
Wavelength $λ / n m$ $1550$
Coherence length $r_{0}$ 0.1
Internal scale $l_{0} / m$ 0.0001
Outer scale $L_{0} / m$ 100
Phase screen size $L / m$ 1
Complex matrix dimension $N$ 512

Table 2. Main simulation parameters

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Table 2. Main simulation parameters

Parameter	Weak turbulence	Strong turbulence
Wavelength $λ / n m$	1064
$C_{n}^{2} / m^{- 2 / 3}$	$4.5 \times 10^{- 16}$	$2.5 \times 10^{- 13}$
Facula gridle $ω_{0}$ /m	0.02
Phase screen size $L / m$	1
Transmission distance	2000
Number of phase screens	10
Weight coefficient $(ω_{1}, ω_{2})$	$(5,2.4)$	$(1.8,1.42)$

Table 3. Centroid shift under different atmospheric turbulence

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Table 3. Centroid shift under different atmospheric turbulence

Method	Weak turbulence		Moderate turbulence		Strong turbulence
Method	$σ_{Δ x}$ /pixel	$σ_{Δ y}$ /pixel	$σ_{Δ x}$ /pixel	$σ_{Δ y}$ /pixel	$σ_{Δ x}$ /pixel	$σ_{Δ y}$ /pixel
Proposed method	6.95	7.27	12.27	10.51	13.12	12.64
Ellipse fitting	7.21	8.51	13.65	12.54	17.71	16.95
Gray centroid method	8.71	9.65	25.82	31.14	37.73	29.74
Gravity center method	7.60	7.38	23.41	27.16	33.31	25.08

Table 4. Centroid shift under different centroid extraction algorithms
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Table 4. Centroid shift under different centroid extraction algorithms
Method $σ_{Δ x}$ /pixel $σ_{Δ y}$ /pixel
Proposed method 4.30 19.15
Ellipse fitting 4.45 19.17
Gray centroid method 4.69 19.18
Gravity center method 4.57 19.16

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Jianbing Wang, Haifeng Yao, Zhi Liu, Keyan Dong, Shutong Liu. Extraction of Laser Spot Centroid of Turbulent Disturbance Based on Ellipse Fitting Method[J]. Laser & Optoelectronics Progress, 2024, 61(13): 1312003

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