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Laser-line scanning speckle reduction based on a one-dimensional beam homogenizer

: Nelsen, Bryan; Jacobs, P.; Hartmann, Peter

Volltext urn:nbn:de:0011-n-4643872 (3.7 MByte PDF)
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Copyright Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Erstellt am: 5.1.2018

Lehmann, Peter H. (Ed.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Optical Measurement Systems for Industrial Inspection X : Munich, Germany; 25 June 2017
Bellingham, WA: SPIE, 2017 (Proceedings of SPIE 10329)
ISBN: 978-1-5106-1103-0
Art. 103292I, 6 S.
Conference "Optical Measurement Systems for Industrial Inspection" <10, 2017, Munich>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer IWS ()
laser brazing with beam scanning; Line scanner; 1D homogenizer; Speckle reduction; Rotating diffuser; laser scanning

Laser-line scanners have become ubiquitous in many forms of automation and measurement systems. Despite this fact, these systems are still susceptible to speckle or interference on rough scattering surfaces. Many scanning systems must be calibrated to the material being analyzed to obtain their full potential. In general, post-processing algorithms are used in most modern line-scanning devices in order to smooth out speckle and enhance the resolution through sub-pixel interpolation. However, these post-processing techniques come at a cost of increased CPU time and a subsequent decrease in bandwidth and resolution. in this paper, a low-cost, high-resolution solution to generating speckle-free sharply focused laser lines is presented. The key to this technique relies on only removing the spatial coherence in one dimension using a 1-D cylindrical lens array as a beam homogenizer. This beam homogenizer is then wrapped around and rotated about a central axis in order to remove the temporal component on the laser's coherence. Since the plane-wave-like behavior is maintained along one dimension, this beam can still be sharply focused to a line. however,the spatial coherence and temporal coherence are reduced to the point that speckle is minimally visible.