Patent ID: 8441728

Claim:
A diffractive lens comprising: a lens base, which has a surface with a diffraction grating; and a protective coating, which is arranged on the diffraction grating of the lens base, wherein the diffraction grating has a first group of diffraction steps and a second group of diffraction steps, which is arranged farther away from an optical axis of the diffractive lens than the first group of diffraction steps is and which is lower in height than the first group of diffraction steps, wherein the lens base comprises a first material and the protective coating comprises a second material, wherein each of the first material and the second material has a corresponding Abbe number and a refractive index, wherein both the Abbe number and the refractive index of the first material are greater than or less than the respective Abbe number and the refractive index of the second material, and wherein the first group of diffraction steps is covered with the protective coating but the second group of diffraction steps is not covered with the protective coating.