Abstract
Five modern encoding methods for diffractive optical elements are compared in terms of diffraction efficiency for an f/1 focusing element. It is shown that all five produce similar results for a given value of the minimum feature size δ and number of phase levels N when the grating period is larger than Nδ. In contrast, when the grating period is smaller than Nδ, the analytic quantization method cannot be employed. When this condition is met, it is shown that the radially symmetric iterative discrete on-axis method can result in diffraction efficiencies as much as 30% higher than those obtained with direct sampling. It is also shown that performance advantages of iterative algorithms improve as the target region in the focal plane increases.
© 1997 Optical Society of America
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