## 4 The Experiment and Discussion
### The Experimental Precision Analysis  
As shown in Figure 13, the 3D reconstruction experimental platform was built based on the laser triangulation test in this work. The detection object is the red laser line on the surface of the lithium battery. The laser data is collected by a CMOS array industrial camera. The grayscale center of gravity method, curve fitting method, and the method proposed in this paper are used to extract the laser center line. Because the real coordinates in the center of the bar cannot be measured, the mean \(x^{*}\) of the three methods is used to estimate the truth. The sample data of laser lines and the result deviation of extraction methods are shown in Table 3, which represents the error analysis of 21 continuous cross-sections collected. Among them, the measurement value by the grayscale center of gravity method, the curve fitting method, and the method proposed in this paper is represented as \(x_{1}\), \(x_{2}\), and \(x_{3}\), respectively. The \(\sigma_{i}\) is the absolute value of the difference between the measured value \(x_{i}\) and the estimated value \(x^{*}\), and the average absolute deviations MAE of each method are calculated, respectively. Figure 12: The size of the lithium battery. Figure 13: Experimental computer data acquisition. The above three extraction methods are used to extract the center line of the laser fringe, respectively, to verify the accuracy of the proposed method in this work. The visualization results extracted by the methods are shown in Figure 14.  
As can be seen from Figure 14, among the three methods in the experiment, the extraction effect of the method proposed in this paper is smoother than that of the grayscale center of gravity method, and can better reflect the gray characteristics than the curve fitting method. The absolute error values of sampling points extracted by the three methods are shown in Figure 15, and the MAE values of each method are calculated (Table 3). It can be seen that the average absolute deviation of the three methods after sorting was 0.060 pixels of the grayscale center of gravity method, 0.050 pixels of the curve fitting method, and 0.026 pixels of the proposed method in this work. The results show that the average absolute error of the improved laser line extraction method proposed in this paper was  
Figure 14: The light strip center line graph. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Measurement Methods**} & \multirow{2}{*}{ \begin{tabular}{c} **The Grayscale Centers** \\ **of Gravity Method** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **The Curve** \\ **Fitting Method** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **The Method Proposed** \\ **in This Paper** \\ \end{tabular}  } & \multirow{2}{*}{\ \begin{tabular}{c} **The Mean of** \\ **Three** \\ **Methods** \\ \end{tabular}  } \\ \hline \multirow{4}{*}{
\begin{tabular}{c} **Pixel** \\ **Coordinates** \\ **Fixed** \\ **Cordinates** \\ **1565** \\ **1571** \\ **1572** \\ **1573** \\ **1585** \\ **1586** \\ **1587** \\ **1588** \\ **1589** \\ **1589** \\ **1590** \\ **1591** \\ **1592** \\ **1593** \\ **1594** \\ **1595  
2.3 times lower than that of the grayscale center of gravity method, and 1.9 times lower than that of the curve fitting method, which has the better extraction effect. Since the real coordinates at the center of the laser beam cannot be measured, the average \(x^{\prime}\) of the three methods is used as the estimated true value. Residual refers to the difference between the measured value and the regression value, which is used to replace the true error in the experiment to verify and analyze the experimental accuracy.