Stepped model of smooth irregularities corrected for location of equivalent reflection surface

A stepped model of smooth irregularities is designed on the basis of the data for the location of an equivalent reflecting plane for a rectangular echelette. The correction enables the authors to improve the approximate simulation results. Although the conventional increment of step number provides, in the limit of large N, the exact solution, the approximation approach dealt with in this Letter is more preferable, because a smaller number of steps is needed to obtain practically exact results.