title: Optical techniques for real-time penetration monitoring for laser welding.
abstract: Optical techniques for real-time full-penetration monitoring for Nd:YAG laser welding have been investigated. Coaxial light emission from the keyhole is imaged onto three photodiodes and a camera. We describe the spectral and statistical analyses from photodiode signals, which indicate the presence of a full penetration. Two image processing techniques based on the keyhole shape recognition and the keyhole image intensity profile along the welding path are presented. An intensity ratio parameter is used to determine the extent of opening at the rear of a fully opened keyhole. We show that this parameter clearly interprets a hole in formation or a lack of penetration when welding is performed on workpieces with variable thicknesses at constant laser power.
authors: School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK. f.bardin@hw.ac.uk
authors: Fabrice
authors: F
authors: Bardin
authors: Adolfo
authors: A
authors: Cobo
authors: Jose M
authors: JM
authors: Lopez-Higuera
authors: Olivier
authors: O
authors: Collin
authors: Pascal
authors: P
authors: Aubry
authors: Thierry
authors: T
authors: Dubois
authors: Mats
authors: M
authors: Högström
authors: Per
authors: P
authors: Nylen
authors: Peter
authors: P
authors: Jonsson
authors: Julian D C
authors: JD
authors: Jones
authors: Duncan P
authors: DP
authors: Hand