Normalization of the scattered light from a defect illuminated by a gaussian beam.

The intensity distribution of the beam from a laser operated in the TEM(00) mode is Gaussian. In some applications it is desirable to have a uniform intensity over a certain region in space. For example, when a Gaussian beam is incident on a smooth surface containing small isolated defects the amount of light scattered by a defect will depend on the position of the defect relative to the center of the beam. In the past, several techniques have been devised to convert a Gaussian intensity profile into a uniform intensity over a specified region in space. In the present work a method of normalization is described that makes direct use of the Gaussian intensity distribution of the TEM(00) mode. By this method, the amount of light scattered by a defect can be normalized to the value that would be observed if the defect were located at the center of the beam for a defect small in size compared with the 1/e(2) diameter of the Gaussian profile. Experimental data were obtained that verify the theory.