Graphical compensation of area coverage and stitching accuracy for galvanometric laser texturing on spherical surface

This paper presents the graphical compensation of area coverage and stitching accuracy for galvanometric laser texturing on spherical surface to improve the area coverage and stitching accuracy. The spherical surface is divided into partitions based on the spherical central angle. The sphere is approximated as a UV polyhedron to examine the effect of the spherical central angle on area coverage and stitching accuracy. Based on Spherical Triangular Area Coordinate Systems (STACs), this paper proposes Single Spherical Polygonal Area Coordinate Systems (SSPACs) and Multi Spherical Triangular Area Coordinates Systems (MSTACs). The benefits of MSTACs in improving area coverage and stitching accuracy are demonstrated. Furthermore, a method for repainting bitmaps using parallel projection, contour detection, and pixel upsampling is proposed. This method reconstructs the compensated discrete pixel points into a filled bitmap. Processing on a 30 mm diameter hemisphere, the average of Relative Area Mean (RA Mean) was improved by 2.02 %, and the average of Zone Standardized Compactness Mean Absolute Error (ZSC MAE) was reduced by 73.33 % after compensation with MSTACs. The Mean Absolute Deviation (MAD) of the stitching error between the cambered patches decreased from 88.95 μm to 4.72 μm (by 94.69 %). The Root Mean Square (RMS) also reduced from 111.77 μm to 5.62 μm (a reduction of 94.97 %), and the Standard Deviation (SD) decreased from 67.9 μm to 4.39 μm (a reduction of 93.54 %). Furthermore, this paper proposes that a smaller spherical central angle from the center of the cambered patch to stitching results in higher area coverage and lower stitching errors, thereby demonstrating the impact of the proposed spherical surface partition. Therefore, the proposed graphic processing method is practical for improving area coverage and reducing stitching errors in spherical laser texturing.