Fig. 1. Schematic diagram of two-channel laser and cross-seven-line laser

Fig. 2. Multi-line laser surface structure diagram. (a) Cross-seven-line model diagram; (b) curves of laser projection; (c) surface structure diagram of a single laser

Fig. 3. The laser lines projected on the calibration plate and numbered

Fig. 4. Intersection diagram of multi-line laser surface and calibration plane. (a) The intersection of the multi-line laser spatial quadratic surface with the calibration plate. (b) The intersection of a single laser quadratic surface with multiple positions

Fig. 5. Polar constraint diagram

Fig. 6. Schematic diagram of polar line matching

Fig. 7. Schematic diagram of geometric distance error of polar lines

Fig. 8. Handheld multi-line laser hardware

Fig. 9. Reflective calibration plate

Fig. 10. Calibration and acquisition of multi-line laser surface equation

Fig. 11. Extraction and classification of multi-line laser center

Fig. 12. Laser point matching and back-projection

Fig. 13. Comparison of point cloud effect before and after optimization based on geometric estimation. (a) Left and right multi-line laser extraction effect and box selection area; (b) the point cloud effect of box selection area before optimization; (c) geometrically estimated point cloud effect after optimization; (d) and (e) overall point cloud reconstruction effect after geometric estimation optimization

Fig. 14. Reconstruction result of standard ball.(a) Standard ball physical object; (b) point cloud effect of original match reconstruction; (c) geometrically estimated point cloud effect after optimization

Fig. 15. Comparison of 3D reconstruction results. (a) Test object; point cloud effects (b) before and (c) after optimization