LOW POWER LASER BEAM PROFILE ANALYSIS BY DIGITAL PHOTOGRAPHIC TECHNIQUE

Abstract
Laser beam profile is an important physical parameter which is often not taken into account. We describe a photographic technique to study Helium-Neon (HeNe) laser beam profile, testing different film sensitivities. When laser beam strikes directly towards the camera lens, several pictures were taken at different exposition times. Negative image of laser beam spot were recorded using a video camera with a trasillumination setup thatched to an analogyc-digital converter to be computed. Laser spot diameter profiles were scanned, and the results were plotted (grey levels against beam size). The results were normalized to the film grossfog, and Gaussian behaviours were found as expected. The same procedure was repeated using different films with different sensitivities, trying to select the more suitable film for our laser power. This technique is also useful to study infrared wavelength beam profiles, and other low power lasers, choosing the optimal films. Laser beam in homogeneities can be detected, and mixed medical lasers can be checked. It is also possible to study the emergent light through different thickness tissue slices.