Abstract:

Objective: In response of the issue of errors in measuring slab height using line laser in the production of ultra-thin high-density fiberboard (HDF), a blind-zone compensation and surface-morphology distortion correction method was proposed. The method can compensate for measurement blind zones caused by excessive height variations on the slab surface, reduce height-measurement errors induced by installation misalignment of a line-laser 3D profile sensor, and correct distortions in the reconstructed surface-morphology map to improve slab height measurement accuracy. The proposed approach aims to improve slab height measurement accuracy, thereby providing theoretical support for quantitatively evaluating slab forming uniformity and enhancing the precision of defect localization. Method: Based on the principle of line-laser triangulation, a quadratic-curve blind-zone compensation algorithm for slab height measurement was developed. Lagrange interpolation was used to reconstruct slab height data within the blind zone, and a corrected height map (height point-cloud color map) was established. The effects of sensor rotational misalignment about the x-axes, y-axes, and z-axes on both slab height readings and surface-morphology distortions were further analyzed, deriving corresponding distortion-correction formulations for rotations about each axis. Region-of-interest (ROI) cropping was then applied to extract the corrected mat area. Result: The proposed quadratic-curve blind-zone compensation algorithm effectively compensated for missing height data in blind zones during line-laser measurement. The x-axis rotation error of the laser 3D contour imaging instrument led to overestimation of slab height, the y-axis rotation error caused an overall widening trend in the surface-morphology map, and the z-axis rotation error produced a parallelogram-type distortion. Within the tested installation-error range of 0°–30°, the proposed correction methods achieved good rectification performance for height maps obtained under x-axis, y-axis, and z-axis rotational errors. To avoid substantial information loss in the corrected 3D point-cloud data, the sensor installation tilt angle should be controlled within 10°. Conclusion: The proposed blind-zone compensation and surface-morphology distortion correction method can effectively reconstruct missing height data on the slab surface blind zones and correct slab height measurement errors caused by installation misalignment of a line-laser 3D profile sensor. The method improves the accuracy and reliability of mat surface morphology measurement, strengthens the quantitative evaluation of forming uniformity for ultra-thin HDF mats, and helps to enhance defect localization precision. These outcomes are of significant research and practical value for improving the quality of ultra-thin HDF products.

Key words: ultra-thin high-density fiberboard, surface profile scanning, blind zone compensation, line laser correction