Coaxial monitoring with a CMOS camera for CO2 laser welding

High precision, repeatability, and quality are the three vital requirements in laser welding production. For accurate real-time tracking and inspecting the laser welding process, the high-performance sensors are extremely demanded. Monitored signal reliability can be significantly increased by using high resolution, digital CMOS sensors and high-speed, real-time image processing technologies. This feature presents the latest developments in high-performance optical joint tracking systems and optical inspection systems based on these technologies. Using a coaxially aligned CMOS imaging detector, the optical signals emission of the plasma during CO2 laser welding was studied. The camera images taken from the process were analyzed with image-processing algorithms. Compared with the lateral systems, coaxial arrangement of the camera allows observing the significant process characteristics. Experimental evidence shows that the system can monitor the instability of the keyhole, the gap caused by the welding distortion, and the deviations from the desired welding path. By the image analysis, the spatially distribution intensity of the plasma emission was analyzed, and it can be correlated to the penetration state and the penetration depth. Thus the laser welding process and the weld quality can be evaluated.