Existing auto-focusing methods in laser processing typically include two independent modules: surface detection and z-axis adjustment. The latter is mostly implemented by mechanical z-stage motion, which is up to three orders of magnitude slower than the lateral processing speed. To alleviate this processing bottleneck, we developed a single-lens approach, using only one high-speed z-scanning optical element, to accomplish both in-situ surface detection and focus control quasi-simultaneously in a dual-beam setup. Our approach provides instantaneous surface tracking by collecting position information and executing focal control both at 140-350 kHz, which significantly accelerates the z-alignment process and offers great potential for enhancing the speed of advanced manufacturing processes in three-dimensional space.
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