Diffractive-refractive method for design of diffractive optical elements for uniform illumination

The diffractive optical element is one of the main solutions to achieve uniform illumination, which is achieved through the pure phase element. There are sub-diffraction spots because of the discontinuity of pure phase element, which makes the beam lose 15% or more energy. Thus a diffractive-refractive method based on the traditional input-output algorithm is developed to design the diffractive optical element. This method makes part of a diffractive optical element continuous in phase, which reduces the light intensity in the discontinuous region of the element, therefore reduces the intensity of sub-diffraction spots. Through studying the influence of spherical phase factor on output light intensity, the phase parameter can be optimized to increase the diffraction efficiency of the incid