Image chopping techniques for fast measurement of irradiance distribution parameters

In several applications it is necessary to get a fast evaluation of the shape and quality of an image of a point source. Since a complete description by means of the point spread function involves time-consuming data processing, it is necessary to limit the evaluation to a set of parameters which can be measured at high rates. Such a set can be defined in terms of the first and second moments of the distribution. In this article the centroid, variance, eccentricity, and angle of the principal axes are suggested as pertinent parameters, and an image chopping technique for fast measurement of these parameters is described.