Fig 1.
Types of defects to be detected.
(a) gasket pleat; (b) gasket missing;(c) dark point;(d) scratch.
Fig 2.
The structure of the bottle cap to be detected.
(a) 3D schematic of the bottle cap; (b) commonly used high-angle ring light detection method; (c) the image brightness of the side wall region of the cap is dark, and the image of the inner circle region also has the problem of uneven background; (d) the image brightness of the side wall region is dark, but the brightness of the inner circle region is overexposed.
Fig 3.
The detection system of LALDA.
(a) system schematic; (b) basic principles of low-angle incident light illumination; (c)(d) images of bottle caps in different colors captured by the system.
Fig 4.
Algorithm flow.
Fig 5.
Direct grayscale operation of different objects to be detected, as well as conversion to HSV color space: (a) the conversion of blue bottle cap; (b) the conversion of red bottle cap; (c) the conversion of pink bottle cap.
Fig 6.
Different colors and H-channel images after HSV.
Fig 7.
Sample with dark point and the V-channel in the side wall region.
Fig 8.
Sample with dark point and the V-channel in the inner circle region.
Fig 9.
Sample with scratch and the V-channel in the inner circle region.
Fig 10.
Sample without defect and sample with gasket missing in the inner circle region.
Fig 11.
Sample without defect and sample with gasket pleat in the inner circle region.
Fig 12.
The actual built detection system based on LALDA.
(a) the main components of the detection system; (b), (c), (d) imaging results of the light source at different working distances (d1, d2, d3).
Fig 13.
Comparison of different light intensities in the LASA.
(a) the light source controller is set to 40;(b) the light source controller is set to 70; (c)the light source controller is set to 140; (d)the light source controller is set to 200.
Fig 14.
Comparison of traditional detection systems.
(a) the High-angle Light Detection Method;(b)the Coaxial lighting mode with the light source controller set to 90 degrees;(c) the High-angle Light Detection Method;(b)the Coaxial lighting mode with the light source controller set to 140 degrees.
Fig 15.
Detection of dark points and color mixing in the interior of cap.
Fig 16.
Detection of scratch in the inner circle region.
Fig 17.
Detection of gasket missing in the inner circle region.
Fig 18.
Detection of gasket pleat in the inner circle region.
Fig 19.
Detection of different defects in bottle caps of different sizes and colors.
Fig 20.
Comparison of results: Small black spots and scratches, as well as the shape, direction, and curvature of the scratches, have a certain randomness, leading to missed detections.
Table 1.
Comparison of detection accuracy of different detection methods.