Existing galvanometer-based laser scanning systems are challenging to apply in multi-scale 3D reconstruction because of the difficulty in achieving a balance between high reconstruction accuracy and a wide reconstruction range. This paper presents a novel method that synchronizes laser scanning by switching the field-of-view (FOV) of a camera using multi-galvanometers. In addition to the advanced hardware setup, we establish a comprehensive mathematical model of the system by modeling dynamic camera, dynamic laser, and their combined interaction. We then propose a high-precision and flexible calibration method by constructing an error model and minimizing the objective function. Finally, we evaluate the performance of the proposed system by scanning standard components. The evaluation results demonstrate that the accuracy of the proposed 3D reconstruction system achieves 0.3 mm when the measurement range is extended to 1100 mm $\times$ 1300 mm $\times$ 650 mm. With the same reconstruction accuracy, the reconstruction range is expanded by a factor of 25, indicating that the proposed method simultaneously allows for high-precision and wide-range 3D reconstruction in industrial applications.