Optical soft aperture and use thereof

摘要

A soft aperture allows gradual attenuation of a light beam dependent upon its location away from the center of a diffractive optical element. Such an optical element may be provided by decreasing a number of phase levels, increasing a number of phase levels, increasing a density of metal patches or diffractive gratings, or decreasing a blaze height and/or duty cycle, all radially from the center. Alternatively, the soft aperture may be defined by a photolithographic process. Such a soft aperture is particularly useful in aiding circularizing of an elliptical light beam. The soft aperture may be used alone or integrated with other optical elements.