Robust beam width estimation with sub-pixel resolution in uncontrolled imaging conditions

Estimating the laser beam widths from a single image of numerous laser beams, which have a spatial extent of only a few pixels on the sensor, is not straightforward. Various beam width estimation methods are described in literature but the presence of image noise or background signals can heavily distort their estimated beam width. In this paper, we examine the feasibility of an image analysis method, proposed in the field of laser eye safety, to determine a laser’s beam width. Here, the estimated beam width corresponds to the size of the evaluation window for which the ratio, referred to as the MTH ratio, between the beam power encircled by the evaluation window and its diameter is maximal. Based on simulations and experimental data, we show that this method yields accurate beam width estimations for different transverse beam profiles. We also demonstrate that the method is robust to noisy imaging conditions or the presence of background illumination. Moreover, we expand this method to make precise and accurate sub-pixel resolution beam width estimations on an image of multiple beams which are only of a few pixels large each.