Development of a Focal Point Positioning System for Laser Sensing Instruments using Galvano Mirrors and Tunable Lens

We developed a focal positioning system for laser sensing instruments. The positioning system consists of x- and y-axis galvano mirrors and a high-speed response tunable lens. It allows for quick adjustment of the measuring position with high resolution and repeatability afforded by the galvano mirrors, which enable the plotting of 10,000 focal points per second, and the tunable lens, which allows adjustment of the focal length within 2.5 ms (10%–90% step). For laser measurements, the location information of the laser spot on the sample is the key parameter to determine the quantitative difference in chemical compositions at different locations. Furthermore, if the sample changes location systematically with some temporal variation, quick correction before changing the default position is required to prevent missing the target. The laser spot positioning system we present here can play an important role in obtaining multi-plot measurements for complicated surface topologies and dynamic micro-samples.