Metrologic Assessment of High Power Laser Generated Surface Roughness by Confocal Laser Scanning Microscopy-Elena

Laser ablation process covers a great diversity of particular applications in. Which mass removal of laser irradiated materials is the essence of the final required process. Even more than previously mentioned cutting and welding processes. Physical mechanisms involved in laser ablation are extremely complex (Von Allmen 1987). Besides, depending on the particular ablation technique considered (molten material ablation, vaporization phase ablation, sublimation techniques, non thermal ablation, etc.).

Quality control in laser ablation implies surface final state characterization, including. If possible, estimation of ablated mass, walls morphology in ablation fronts and layer behaviour in multilayer laser ablation. That is also the case in laser cleaning (Meja 2001), and other process as laser lithography (Lamda Physics 2001) and surface modification (Kaplan 1998) very well known in the frame of micromachining techniques. However even for fully commercial laser ablation applications as laser marking and engraving CLSM offers complete assessment. Including marking depth, walls slope, pattern homogeneity, etc.

process Another good example of CLSM capabilities in laser ablation assessment is laser paint stripping process in ship building industry.

Laser advantages with respect to other paint removal techniques as sand blasting and water jets are an enhanced cleanliness. And environmental impact and an improved final surface quality allowing a better surface maintenance. Figure 7 shows confocal reconstruction and realistic images of the steplike transition zone between clean material and residual painted areas in laser stripping of shipbuilding steel coated with two layers of different epoxy paints (transitions zone appears in white colour in Fig. 7 digital images). A sharp step is related with nonthermal ablation effects and non well defined steps prove strong thermal interaction. Images show clearly that operation in cw for high power diode lasers leads to strong thermal interaction mechanism (corresponding to soft height gradients) while pulse laser dynamic (with short peak power pulses) leads to important gradients that implies a less thermal affection of base material and better layer removal control.