Author Affiliations
1School of Electronic and Electrical Engineering, Wuhan Textile University, Wuhan, Hubei 430200, China2Institute of Engineering & Technology, Hubei University of Science and Technology, Xianning, Hubei 437100, China;3Hubei Xiangcheng Intelligent Electromechanical Industry Technology Research Institute Limited Company, Xianning, Hubei 437100, Chinashow less
Fig. 1. Sketch maps of phase unwrapping. (a) Wrapped phases ϕ1 and ϕ2; (b) wrapped phase ϕ2 and unwrapped phase φ
Fig. 2. Unwrapped phases of 4 step method and 16 step method
Fig. 3. Error of unwrapped phase of 4 step method
Fig. 4. Mean filtering templates. (a) Normal 3×3 mean filtering template; (b) a kind of one-dimension mean filtering template; (c) mean filtering template to decrease phase error
Fig. 5. New mean filtering templates. (a) Mean filtering template for head of each row of pixels; (b) mean filtering template for end of each row of pixels
Fig. 6. Experimental device and image collection. (a) Experimental device of structure light measurement; (b) projected fringes on background plane; (c) projected fringes on carton
Fig. 7. Frequency spectra. (a) Frequency spectrum of phase error (displayed frequency range is 0--150); (b) frequency spectrum of unwrapped phase obtained by 4 step method (displayed frequency range is 0--150)
Fig. 8. Phase error and restrained phase error of pixels in 100th row
Fig. 9. Three dimensional (3D) point cloud measurement results (height from carton to reference plane). (a) 4 step method; (b) 4 step method with error compensation by LUT method; (c) 4 step method with phase error restraining; (d) 16 step method
Fig. 10. Cross sections of measured 3D point cloud (1500th row). (a) 4 step method; (b) 4 step method with phase error compensation by LUT method; (c) 4 step method with phase error restraining; (d) 16 step method
Phase error | Maximum /rad | Minimum /rad | Average error /(rad·pixel-1) |
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Withoutphase error restraining | 0.2079 | -0.2076 | 0.1019 | 1st restraining (T=84) | 0.0526 | -0.0488 | 0.0127 | 2nd restraining (T=42) | 0.0471 | -0.0597 | 0.0075 | 3rd restraining (T=28) | 0.0253 | -0.0548 | 0.0057 |
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Table 1. Experimental result of phase error restraining
Experiment No. | Average error /(rad·pixel-1) | Decline rate/% |
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Without error restraining | LUT method | Proposed method | LUT method | Proposed method |
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① | 0.0998 | 0.0179 | 0.0034 | 82.0641 | 96.5932 | ② | 0.1021 | 0.0203 | 0.0057 | 80.1175 | 94.4172 | ③ | 0.1065 | 0.0231 | 0.0089 | 78.3099 | 91.6432 | ④ | 0.1068 | 0.0218 | 0.0049 | 79.5880 | 91.6667 | ⑤ | 0.1060 | 0.0211 | 0.0076 | 80.0943 | 92.8302 |
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Table 2. Statistics of results of 5 phase error restraining experiments