Author Affiliations
1 Laboratory of Information Optics and Opto-Electronic Technology, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China2 University of Chinese Academy of Sciences, Beijing 100049, China3 State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, Jilin 130033, Chinashow less
Fig. 1. Schematic of magnification measurement
Fig. 2. Schematic diagram of object plane fibers spacing measurement system
Fig. 3. Mathematical model of fiber spacing measurement
Fig. 4. Wavefront and its Zernike coefficient obtained from ideal and non-ideal conditions. (a) Ideal wavefront; (b) ideal wavefront (without tilt); (c) Zernike coefficient of ideal wavefront; (d) non-ideal wavefront; (e) non-ideal wavefront (without tilt); (f) Zernike coefficient of non-ideal wavefront
Fig. 5. Quantitative relationship among point source separation distance, spatial location parameter of the CCD camera, and the Zernike polynomial coefficient. (a) Quantitative relationship between point source spacing and Z2 term coefficient; (b) quantitative relationship between vertical distance and Z7 term coefficient; (c) quantitative relationship between CCD rotation angle and Z2 term coefficient; (d) quantitative relationship between CCD rotation angle and Z3 term coefficient; (e) quantitative re
Fig. 6. Flow chart of fiber spacing measurement algorithm
Fig. 7. Schematic diagram of image plane fibers’ imaging points separation distance measurement system
Fig. 8. Spot center recognition results. (a),(b) Object location results; (c),(d) image location results
Fig. 9. Experimental wavefront and its Zernike coefficient values. (a) Object plane wavefront; (b) object plane wavefront (without tilt term); (c) Zernike coefficient of object plane wavefront; (d) image plane wavefront; (e) image plane wavefront (without tilt term); (f) Zernike coefficient of image plane wavefront
Fig. 10. Measurement repeatability of Zernike polynomial coefficient. (a) Object plane measurement result; (b) image plane measurement result
Magnification measurement error /10-6 | Fiber separation distance measurement error /nm |
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1 | 0.0620 | 5 | 1.5509 | 10 | 6.2035 |
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Table 1. Error requirement of fiber spacing measurement
Simulation parameter | Ideal condition | Non-ideal condition |
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Light source wavelength λ /nm | 532 | 532 | Interference region produced by fiber /(pixel×pixel) | 400×400 | 400×400 | Pixel size /μm | 9.9×9.9 | 9.9×9.9 | d /μm | 254 | 254 | z /mm | 32.941 | 32.941 | θ /(°) | 0 | 3 | γx /(°) | 0 | 2 | γy /(°) | 0 | 1 |
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Table 2. Settings of simulation conditions
Initial parameter setting of iterative calculation | Setting value |
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d | Estimating rough value d0 according to the position of fiber end | z | Using the tool to measure the rough value z0 | θ | Calculation according to the formula:θ=tan-1(-Z03/Z02) | γx | Setting to 0° | γy | Setting to 0° |
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Table 3. Initial parameter setting of iterative calculation
Parameter | Term of Zernike polynomial | Quantitative relationship type | Calculation formula |
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d | Z2 | Linear relationship | dcal=dcur+(Z02-Z2cur)/ | z | Z7 | Linear relationship | zcal=zcur+(Z07-Z7cur)/ | θ | Z2 | Cosine relationship | θcal=θcur+(Z03-Z3cur)/ | | Z3 | Sine relationship | | γx | Z4 | Linear relationship | | | Z6 | Linear relationship | | γy | Z4 | Uncorrelated | | | Z6 | Linear relationship | |
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Table 4. Quantitative relationship among two fibers separation distance, spatial position parameters of the CCD camera, and the Zernike polynomial coefficient, and its calculation formula
| Average value | Standard deviation | Maximum value | Minimum value |
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Number of iterations | 14.6000 | 0.4900 | 15.0000 | 14.0000 | Measurement error of fiber separation distance /nm | 0.5500 | 0.9337 | 5.0000 | 0 |
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Table 5. Simulation results of the effectiveness of the method for measuring the separation distance between two fibers
Parameter | Initial value | 1 | 2 | 3 | … | 10 | 11 |
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d /μm | 297.000 | 315.307 | 272.399 | 267.318 | … | 264.818 | 264.817 | z /μm | 30000.000 | 25877.260 | 25380.070 | 25219.260 | … | 25140.380 | 25140.350 | θ /(°) | 2.231 | 1.925 | 2.188 | 2.217 | … | 2.231 | 2.231 | γx /(°) | 0 | -3.050 | -3.411 | -3.433 | … | -3.444 | -3.444 | γy /(°) | 0 | 0.015 | -0.015 | -0.018 | … | -0.020 | -0.020 |
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Table 6. Iterative calculation results of object plane separation distance between fibers
Parameter | Initial value | 1 | 2 | 3 | … | 6 | 7 |
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d /μm | 49.500 | 51.011 | 50.911 | 50.843 | … | 50.810 | 50.809 | z /μm | 6600.000 | 6584.231 | 6575.157 | 6572.180 | … | 6570.711 | 6570.667 | θ /(°) | 2.357 | 2.352 | 2.354 | 2.356 | … | 2.357 | 2.357 | γx /(°) | 0 | 1.633 | 1.633 | 1.634 | … | 1.635 | 1.635 | γy /(°) | 0 | 0.249 | 0.249 | 0.249 | … | 0.250 | 0.250 |
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Table 7. Iterative calculation results of image plane separation distance between fiber image points