A simple optical coupling method for water-jet guided laser machining system

In this paper a simple optical coupling method for water-jet guided laser machining system is introduced and its characteristics are studied. By the introduced method the output spot pattern behind the water-jet was observed instead of the laser focus. In order to acquire the pattern a piece of glass was used to block the water-jet but let the laser through, and a light screen was placed behind the glass in a certain distance to display the pattern image. Since the image scale could be adjusted by changing the distance between the glass and the light screen, the CCD magnifying system was no longer needed. It is found that the pattern varied while the coupling condition changed. Only in small chance the pattern was a tiny spot but more commonly it was in a ring-like shape which could be easily recognized. So such ring-like patterns could be signals for optical coupling guidance. Furthermore a series of study to analyze the correlation between the pattern shape and coupling parameters was carried out by simulation with the help of Zemax.