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- Title
Evaluation of Scanner-Based Focus Finding Methods on Rough Surfaces.
- Authors
Cvecek, Kristian; Eckl, Johannes; Eiselen, Sasia; Huber, Heinz P.; Schmidt, Michael
- Abstract
Automated laser beam focus positioning for precise work piece alignment is highly important in laser processing. Ideally, the laser used for processing of the work piece should also be used for focus finding. For this a confocal camera can be used in front of a galvanometric scanner and objective. However, in typical laser processing applications the roughness of the sample in combination with the laser spot size and the coherence of the laser provide a confocal camera image with a distinct speckle pattern. This speckle pattern can impede the determination of the focal position with respect to the work piece, especially if simple evaluation algorithms are applied. In this work we investigate the performance of several more advanced image evaluation methods on confocal camera images for work pieces of different materials, different roughness under normal and tilted incidence of the laser beam. We show that two investigated algorithms provide a positioning uncertainty that is well below the Rayleigh length of the laser beam.
- Subjects
ROUGH surfaces; SCANNING systems; LASER beams; PARTICLE beam focusing; GALVANOMETER; COHERENCE (Optics)
- Publication
Journal of Laser Micro / Nanoengineering, 2015, Vol 10, Issue 3, p304
- ISSN
1880-0688
- Publication type
Article
- DOI
10.2961/jlmn.2015.03.0012