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Laser & Optoelectronics Progress, Volume. 62, Issue 4, 0412004(2025)

Surface Topography Measurement of Coal Block Based on Improved Multi-Exposure Image Fusion Digital Grating Projection Method

Jingfa Lei1,2,3、*, Yuanhang Miao1,2, Miao Zhang1,2, Yongling Li1,2,3, and Ruhai Zhao1,2
Author Affiliations
  • 1School of Mechanical and Electrical Engineering, Anhui Jianzhu University, Hefei 230601, Anhui , China
  • 2Anhui Key Laboratory of Intelligent Manufacturing of Construction Machinery, Anhui Jianzhu University, Hefei 230601, Anhui , China
  • 3Sichuan Key Laboratory of Process Equipment and Control Engineering, Zigong 643000, Sichuan , China
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    AbstractGet PDF(in Chinese)
    Figures&Tables (16)
    Equations (13)
    References (27)
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    Figures & Tables(16)
    Schematic diagram of binocular fringe projection

    Fig. 1. Schematic diagram of binocular fringe projection

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    Flowchart of adaptive multi-exposure image fusion binocular digital grating projection method

    Fig. 2. Flowchart of adaptive multi-exposure image fusion binocular digital grating projection method

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    Physical diagram of the measurement system

    Fig. 3. Physical diagram of the measurement system

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    Initial images of the measured objects. (a) Coal block 1; (b) coal block 2; (c) coal block 3

    Fig. 4. Initial images of the measured objects. (a) Coal block 1; (b) coal block 2; (c) coal block 3

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    Images of the measured objects after segmentation. (a) Coal block 1; (b) coal block 2; (c) coal block 3

    Fig. 5. Images of the measured objects after segmentation. (a) Coal block 1; (b) coal block 2; (c) coal block 3

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    Local stripe images captured by the left and right cameras under different exposure time for coal block 1. (a)‒(f) Images captured by left camera; (g)‒(l) images captured by right camera

    Fig. 6. Local stripe images captured by the left and right cameras under different exposure time for coal block 1. (a)‒(f) Images captured by left camera; (g)‒(l) images captured by right camera

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    Stripe images of coal block 1 processed by proposed method. (a) Image of left camera; (b) image of right camera

    Fig. 7. Stripe images of coal block 1 processed by proposed method. (a) Image of left camera; (b) image of right camera

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    Point cloud images of coal block 1 processed by different methods. (a) Projection phase method; (b) method in Ref. [21]; (c) method in Ref. [23]; (d) proposed method

    Fig. 8. Point cloud images of coal block 1 processed by different methods. (a) Projection phase method; (b) method in Ref. [21]; (c) method in Ref. [23]; (d) proposed method

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    Point cloud images of coal block 2 processed by different methods. (a) Projection phase method; (b) method in Ref. [21]; (c) method in Ref. [23]; (d) proposed method

    Fig. 9. Point cloud images of coal block 2 processed by different methods. (a) Projection phase method; (b) method in Ref. [21]; (c) method in Ref. [23]; (d) proposed method

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    Point cloud images of coal block 3 processed by different methods. (a) Projection phase method; (b) method in Ref. [21]; (c) method in Ref. [23]; (d) proposed method

    Fig. 10. Point cloud images of coal block 3 processed by different methods. (a) Projection phase method; (b) method in Ref. [21]; (c) method in Ref. [23]; (d) proposed method

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    Measurement result of standard step blocks

    Fig. 11. Measurement result of standard step blocks

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    • Table 1. K-value corresponding to the clustering analysis of different measured objects

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      Table 1. K-value corresponding to the clustering analysis of different measured objects

      Measured objectK-value
      Coal block 16
      Coal block 25
      Coal block 36

    • Table 2. Average grayscale value of each pixel cluster after image segmentation in clustering analysis of measured objects

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      Table 2. Average grayscale value of each pixel cluster after image segmentation in clustering analysis of measured objects

      Measured objectLeft cameraRight camera
      Coal block 16.15， 16.51， 33.13， 54.71， 86.37， 135.636.23， 18.03， 32.11， 60.09， 92.25， 136.45
      Coal block 25.11， 16.42， 37.42， 64.08， 110.836.21， 17.81， 40.36， 71.36， 121.67
      Coal block 36.26， 20.32， 31.74， 43.92、61.94， 159.677.01， 22.43， 30.45， 43.25， 67.74， 148.51

    • Table 3. Exposure time corresponding to each pixel cluster of different measured objects

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      Table 3. Exposure time corresponding to each pixel cluster of different measured objects

      Measured objectLeft cameraRight camera
      Coal block 1206504， 76923， 38334， 23213， 14704， 9364203852， 70438， 39552， 21135， 13767， 9307
      Coal block 2248532， 77345， 33939， 19819， 11459204509， 71308， 31467， 17797， 10438
      Coal block 3202875， 62500， 40013， 28916， 20504， 7954181170， 56621， 41708， 29364， 18748， 8552

    • Table 4. Point cloud numbers and reconstruction rates of the three coal blocks processed by different methods

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      Table 4. Point cloud numbers and reconstruction rates of the three coal blocks processed by different methods

      MethodNumber of point cloudRebuild rate /%
      Coal block 1Coal block 2Coal block 3Coal block 1Coal block 2Coal block 3
      Reference value184331379718477———
      Projection phase method14487113451634778.5982.2388.47
      Method in Ref. ［21］17796120341754496.5487.2294.95
      Method in Ref. ［23］17453130211739794.6894.3894.15
      Proposed method18268137191832999.1099.4399.20

    • Table 5. Measured errors of standard step blocks

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      Table 5. Measured errors of standard step blocks

      Standard step blockHeight /mmHeight error /mmRelative error /%
      14.9519-0.04810.962
      24.9539-0.04610.922
      34.9521-0.04790.958
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    Jingfa Lei, Yuanhang Miao, Miao Zhang, Yongling Li, Ruhai Zhao. Surface Topography Measurement of Coal Block Based on Improved Multi-Exposure Image Fusion Digital Grating Projection Method[J]. Laser & Optoelectronics Progress, 2025, 62(4): 0412004

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    Paper Information

    Category: Instrumentation, Measurement and Metrology

    Received: Jun. 3, 2024

    Accepted: Jul. 9, 2024

    Published Online: Feb. 10, 2025

    The Author Email:

    DOI:10.3788/LOP241409

    CSTR:32186.14.LOP241409

    Topics

    laser devices and laser physics
    Lasers and Laser Optics
    Laser physics
    laser manufacturing
    Instrumentation, Measurement and Metrology