Measurement of the spatial intensity distribution at the focal point of a converging/diverging laser beam

Abstract

In laser welding, two fundamentally important parameters are beam “diameter” or “spot size”, and spatial distribution of power intensity. These parameters have been shown to be major factors in controlling the welding mode and weld pool dimensions. In this paper, application of a rotating-wire type Laser Beam Analyser (LBA) device to measure both the intensity distribution and beam diameter of a converging/diverging beam is discussed. Analyses of the LBA are performed to determine the sampling path through the beam, the spatial resolution of the LBA, and the transformation relationship between the intensity versus time signal produced by the LBA and the desired intensity versus spatial position data. These analyses show the operation and correct interpretation of measured results from this device to be strongly dependent upon the relative position of the laser focal point and the plane of rotation of the LBA rod. Examples of the application of the LBA for measurement of spatial intensity profiles at and about the focal point of a pulsed Nd:YAG welding laser are presented.In laser welding, two fundamentally important parameters are beam “diameter” or “spot size”, and spatial distribution of power intensity. These parameters have been shown to be major factors in controlling the welding mode and weld pool dimensions. In this paper, application of a rotating-wire type Laser Beam Analyser (LBA) device to measure both the intensity distribution and beam diameter of a converging/diverging beam is discussed. Analyses of the LBA are performed to determine the sampling path through the beam, the spatial resolution of the LBA, and the transformation relationship between the intensity versus time signal produced by the LBA and the desired intensity versus spatial position data. These analyses show the operation and correct interpretation of measured results from this device to be strongly dependent upon the relative position of the laser focal point and the plane of rotation of the LBA rod. Examples of the application of the LBA for measurement of spatial intensity profiles at and a...