Possibility of detecting the information on weld line or groove shape near molten pool in TIG arc welding process by combination of He-Ne laser and interference filter with narrow width at half maximum (WHM: 1.0 nm) is shown experimentally for in-process control of arc welding process.
Relative light intensity ratio of laser light reflected or scattered from surface of object and light emitted from arc or molten pool can be easely calculated theoretically on the assumpution that transmittance of interference filter is expressed as Gauss's error distribution function with wave length, and then it is shown theoretically that relative light intensity ratio increase with decrease of half width (WHM) of the filter.
On other hand, adoptig the interference filter with extrem narrow half width, or max transmittance of the filter is easely influenced by the change of temperature, humidity, incident angle of laser and so on. As the result, optimum half width on interference filter exists for improving the relative light intensity ratio.
It is clarified experimentally that the light scattered from projected laser spot near molten pool can easely detected without disturbance of powerful arc light, and furthermore, it's method can be applied to get the information on behaviour of the molten pool in TIG arc welding process, by using combination of He-Ne laser and the interference filter with narrow band pass (WHM: 1.0nm.)
