Device for calculating diffraction efficiencies of a diffraction lens, lens with grating element, and optical system for reading

摘要

A device for calculating diffraction efficiencies of a diffraction lens divided into a plurality of regions, each region comprising at least one grating ring, comprises a first memory for storing information about diffraction efficiencies of the regions; a second memory for storing information about weights corresponding to the regions; and a first processor for retrieving information from the first and the second memory, and calculating diffraction efficiencies of the entire diffraction lens using the formulawherein:j: integer indicating the order of diffraction lightEj: diffraction efficiency for j-th order diffraction light of the diffraction lensM: positive integer (M>1) indicating the number of regions for which the diffraction efficiency is calculatedm: index of the region for which the diffraction efficiency is calculatedetamj: diffraction efficiency for the j-th order diffraction light of the m-th region (stored in the first memory)Wm: weight for the m-th region (stored in the second memory means).Thus, the diffraction efficiency of the diffraction lens can be calculated easily.