Figure 3
From: Focus Tracking System for Femtosecond Laser Machining using Low Coherence Interferometry
(a) Bovine tooth sample. The machined regions with and without active focus tracking are highlighted (blue and green boxes, respectively), the raster pattern is illustrated in the black box and the arrows indicate the laser path. (b) Tooth surface profiles showing the curvature along the raster path with (blue) and without (green) focus tracking. There is a total axial displacement of ∼1000 μm for both regions. (c) Surface position (during raster) over time. Square dots represent the detected axial position of the sample surface (relative to the OPD). The surface curvature (axial displacements in the graph) repeats itself over time as the raster goes back and forth. The focal plane (thick solid green line at 300 μm) and its confocal parameter (lighter green lines) are shown for reference. For ease of interpretation, the dots inside confocal parameter are colored green, while those outside (faulty) are red. The vertical orange lines indicate when the raster motion changed direction, which is represented by the orange arrows. (d) Optical profilometry image showing the ceasing of the ablation process after 4000 μm of raster length, shorter than desired.
