Abstract
Laser welding has been applied to various industries, in particular, automotive, aerospace and microelectronics. However, traditional off-line testing of the welds is costly and inefficient. Therefore, on-line inspection systems with low cost have being developed to increase productivity and maintain high welding quality. This paper presents the applications of acoustic, optical, visual, thermal and ultrasonic techniques and latest development of laser welding monitoring. The advantages and limitations of these techniques are also discussed.