Measurement for far-field focal spot of high power laser based on the diffraction inversion of sidelobe beam

Zhengzhou WANG; Li WANG; Jitong WEI; Wei WANG; Gang LI; Dongchi YI; Yajun WANG

doi:10.37188/OPE.20223004.0380

Optics and Precision Engineering, Volume. 30, Issue 4, 380(2022)

Measurement for far-field focal spot of high power laser based on the diffraction inversion of sidelobe beam

Zhengzhou WANG*... Li WANG, Jitong WEI, Wei WANG, Gang LI, Dongchi YI and Yajun WANG |Show fewer author(s)

Author Affiliations

Xi’an Institute of Optics and Precision Mechanics， Chinese Academy of Sciences， Xi'an710119， China

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Abstract Get PDF(in Chinese)

Figures & Tables(25)

$Optical design for far-field focal spot measurement using schlieren method based on diffraction inversion of sidelobe beam$

Fig. 1. Optical design for far-field focal spot measurement using schlieren method based on diffraction inversion of sidelobe beam

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Fig. 2. Schematic diagram of different area of far-field focal reconstruction

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Fig. 3. Flow chart of data processing

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Fig. 4. Generated experimental data of far field focal spot obtained by simulated parameters

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Fig. 5. Original image

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Fig. 6. Preprocessing result of mainlobe and sidelobe beam of focal spot image

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$Diffraction image of sidelobe beam z=200 mm$

Fig. 7. Diffraction image of sidelobe beam z=200 mm

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Fig. 8. Images of adding random noise

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Fig. 9. Denoising result of add noise images

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$Denoising image of sidelobe beam diffraction inversion z=200 mm$

Fig. 10. Denoising image of sidelobe beam diffraction inversion z=200 mm

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Fig. 11. Intensity distribution reconstructed result of far-field focal spot

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$Simulated data processing flow of sidelobe beam diffraction inversion$

Fig. 12. Simulated data processing flow of sidelobe beam diffraction inversion

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$Sidelobe beam diffraction inversion results in simulated error environment$

Fig. 13. Sidelobe beam diffraction inversion results in simulated error environment

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$Inverse curve of sidelobe diffraction beam with different distance error （y=256）$

Fig. 14. Inverse curve of sidelobe diffraction beam with different distance error （y=256）

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$Analysis the influence of phase error on diffraction inversion of sidelobe beam$

Fig. 15. Analysis the influence of phase error on diffraction inversion of sidelobe beam

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$Effect of phase measurement error on diffraction inversion of sidelobe beam$

Fig. 16. Effect of phase measurement error on diffraction inversion of sidelobe beam

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$Denoise effect of improve DnCNN algorithm on sidelobe diffraction beam addnoise image$

Fig. 17. Denoise effect of improve DnCNN algorithm on sidelobe diffraction beam addnoise image

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$Comparison of sidelobe diffraction image of denoising effect （y=256）$

Fig. 18. Comparison of sidelobe diffraction image of denoising effect （y=256）

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$Comparison between no diffraction and denoise and addnoise inverse curve of sidelobe diffraction laser beam （δ=25）$

Fig. 19. Comparison between no diffraction and denoise and addnoise inverse curve of sidelobe diffraction laser beam （δ=25）

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$Inverse curve of denoise sidelobe diffraction beam when noise MSE is different （y=256）$

Fig. 20. Inverse curve of denoise sidelobe diffraction beam when noise MSE is different （y=256）

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Fig. 21. Reconstructed accuracy analysis of far-field focal spot

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Fig. 22. Comparison of logarithm transform result of intensity distribution between original and reconstructed horizontal curve（y=256） of far-field focal spot

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Table 1. Simulated experimental parameters of far-field focal spot to obtain intensity distribution
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Table 1. Simulated experimental parameters of far-field focal spot to obtain intensity distribution
No. Parameter Name Value Unit
1 lmda Wavelength 6.350 0×10^-4 mm
2 a Radius of the sphere 0.5 mm
3 f Focal length of telecentric lens 100 mm
4 Am Magnification 1 mm
5 pixel Pixel size 0.005 6 mm

Table 2. Error statistics of sidelobe beam diffraction inversion experiment

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Table 2. Error statistics of sidelobe beam diffraction inversion experiment

Error name	Unit	Symbol	Theoretical value	Error value
Transmission distance error	mm	z	200	2
Average phase error of sidelobe beam	degree	$ϕ$	0	10
Noise mean square error		$σ$	0	25
Radius error of schlieren sphere	mm	d	0.4480	0.056

Table 3. Comparison of dynamic range ratio errors between original and reconstructed far-field focal spot

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Table 3. Comparison of dynamic range ratio errors between original and reconstructed far-field focal spot

Beam		Org. Max （y=256）	Merge Max （y=256）	Error of log10 curve	Error of gray curve	Dynamic range
Beam		Org. Max （y=256）	Merge Max （y=256）	Error of log10 curve	Error of gray curve	Used	Org. Image	Merge Image	Error
Mainlobe		$C_{m a x}^{}$ =5.8554	$M_{m a x}^{}$ =5.8481	-0.0073	11875	Yes	1 286.3	1 328.9	3.22%
Side- lobe	Peak 1	$S_{m a x}^{1}$ =4.091	$M_{m a x}^{1}$ =3.904	0.1870	4314	No
	Peak 2	$S_{m a x}^{2}$ =3.474	$M_{m a x}^{2}$ =3.184	0.2900	1452	No
	Peak 3	$S_{m a x}^{3}$ =3.06	$M_{m a x}^{3}$ =3.056	0.0040	11	No
	Peak 4	$S_{m a x}^{4}$ =2.746	$M_{m a x}^{4}$ =2.725	0.0210	26	Yes

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Zhengzhou WANG, Li WANG, Jitong WEI, Wei WANG, Gang LI, Dongchi YI, Yajun WANG. Measurement for far-field focal spot of high power laser based on the diffraction inversion of sidelobe beam[J]. Optics and Precision Engineering, 2022, 30(4): 380

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Paper Information

Category: Modern Applied Optics

Received: Jul. 10, 2021

Accepted: --

Published Online: Mar. 4, 2022

The Author Email: WANG Zhengzhou (azhou_china@126.com)

DOI:10.37188/OPE.20223004.0380

Topics

laser devices and laser physics

Lasers and Laser Optics

Laser physics

laser manufacturing

Instrumentation, Measurement and Metrology

Table 1. Simulated experimental parameters of far-field focal spot to obtain intensity distribution

Table 1. Simulated experimental parameters of far-field focal spot to obtain intensity distribution

Table 2. Error statistics of sidelobe beam diffraction inversion experiment

Table 2. Error statistics of sidelobe beam diffraction inversion experiment

Table 3. Comparison of dynamic range ratio errors between original and reconstructed far-field focal spot

Table 3. Comparison of dynamic range ratio errors between original and reconstructed far-field focal spot

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