## 3 Results and Discussion
### Optical Experimental Setup and Results
ISO 11145:2018 standard, with the requirement for the roundness of the static pulse ablation with the ratio of minimum and maximum beam diameter to be greater than 87%, is used. To meet industrial standards, a roundness of micro-holes of greater than 90% was used for comparison. Their mean roundness and standard deviation are shown in Figure 13a for the conventional 2D scanning system, and Figure 13b for the proposed 1D scanning system using a galvanometer deflection in the range of \(\pm\)25 mm. At the non-galvanometer deflection, the averaged roundness of the ablation is achieved (95.03 \(\pm\) 0.396)%. The average roundness of the ablation will be changed to be 95% from the original 96% after the laser beam passes through the central position of the f-theta lens, shown in Figure 13. The average roundness of the ablations decreased by 0.254%, 2.099%, 4.319%, and 7.139%, corresponding to the distances of \(-\)5/5 mm, \(-\)10/10 mm, \(-\)15/15 mm, and \(-\)20/20 mm. The average roundness of the ablations decreased at the galvanometer deflections that are far away from the center position. At a position with a distance of more than 20 mm from the center position, the roundness of the static pulsed ablations does not meet the ISO standard. This effect can be attributed to insufficient centric and parallel propagation of the laser beam through the f-theta lens. A working length to  
Figure 8:0 Results of measuring the roundness of silicon ablation when using (**a**) a conventional 2D scanning system and (**b**) a 1D scanning system using two galvanometers at attenuator transmission of 30%. (**c**) and (**d**) Comparison results of two scanning systems at attenuator transmission of 55%. meet ISO standards can be determined based on the limited portion of the intersection of the solid blue line and the dashed cyan line, highlighted by the transparent green area on the graph. The roundness of the ablation is greater than 87% to meet the ISO standard. It is then easy to determine the working lengths extending from \(-\)22.86 to 21.85 mm. The total length for laser material processing that can meet the standard is 44.71 mm, which corresponds to 59.61% of the effective scanning length of the f-theta lens. An overview of the analysis results of the roundness of the resection when using 1D with two galvanometer scanners shows symmetry. The spot size change has a minor fluctuation compared to the conventional 2D scanning system. In the range of \(\pm\)5 mm, the roundness of the ablation is above 95% with a slight circularity deviation. This is because the telecentricity compensation helps to minimize aberration near the center of the lens, which corresponds to 13.3% of the scan length of the F-theta. The roundness of the ablations at the center position reached 95.4%. At positions away from the center of the workpiece, these values decrease with an average beam spot roundness of 0.112%, 1.813%, 4.114%, and 6.475%, corresponding to the distances of \(-\)5/5 mm, \(-\)10/10 mm, \(-\)15/15 mm, and \(-\)20/20 mm. Thus, a 1D scanning system using two galvanometer scanners can add an average of 3.6 mm, equivalent to 8.1% of the working length, to meet ISO standards. The total length achieved for the ISO compliance of a 1D scanning system using two galvanometers is 48.3 mm. The similarity between the extended working length of the simulation and the experiments was 87%. This can be explained in the following ways: differences in f-theta lens design and real lenses, laser beam profile, and measurement inaccuracies. For Figure 13c,d, the results measured with a laser power of the attenuator transmission of 55% also show an increase in the effective working length when using the proposed scanning system. The laser power is limited to the appearance of the thermal effect acting on the surrounding area of the micro-hole. Through comparison, we see that after increasing the power, the field of view is reduced to 7.8% compared to the micro-holes ablated with 30% of the power of the laser source.