Optimized strategies for galvo scanning in fully synchronized mode leading to massive improvement in machining time

Abstract

With fully synchronized galvo scanners, outstanding machining quality and accuracy for 2.5-D surface structures can be achieved [1]. For this method, the structuring information is described as a black and white bitmap with, e.g., black for laser off and white for laser on. The bitmap is then machined line by line with a constant marking speed requiring an acceleration and deceleration phase at the end of the lines. In a recent work [2], a high-speed galvo scanner offering marking speeds up to 40 m/s with a 160 mm objective was investigated in synchronized mode. Due to high jerk during the acceleration phase, an additional distance after the acceleration phase had to be introduced to diminish oscillations of the scanner mirror during laser structuring.In an initial step of the current work, a bidirectional mode for the high-speed galvo scanner was introduced. Then, the acceleration and deceleration trajectory were optimized to suppress the mirror oscillations and to allow a direct jump if one or more lines in the bitmap do not need to be marked. In a final step, a new control software was developed, which analyzes the bitmap and shortens the trajectory line length if points do not have to be marked at the start and/or end of the original line of the bitmap.Due to the diminution of the jerk by the newly implemented marking trajectory, no oscillations of the mirror are observed. Thus, the scan trajectory does not need to contain any forerun and overrun segments to fade out the oscillations. The position error has been reduced from 100 µm (without forerun) or 5 µm (with forerun) to 3 µm. Further, removing of pixels that do not get machined at the beginning and end of every line, reduced the machining time, depending on the outline of the structure.