| 摘要 |
A diffraction grating lens according to the present invention is a diffraction grating lens 11 including: a lens body 12; and a plurality of diffraction steps relative to a base shape and a plurality of diffraction gratings 13 interposed between the diffraction steps, provided on a surface of the lens body 12. The lens body 12 is made of a first material having a refractive index n1(λ) at a used wavelength λ; the diffraction grating 13 is in contact with air; and the relationship of an inequality below is satisfied, where d is a design step length of the diffraction steps, and m is an order of diffraction. Each of the plurality of annular zones includes an intermediate portion and a pair of end portions sandwiching the intermediate portion along a radial direction, and in at least one of the plurality of annular zones, either one of a recess 18 and a protrusion 19 is provided in at least a portion of one of the pair of end portions, and the other one of the recess 18 and the protrusion 19 is provided in at least a portion of the other of the pair of end portions. Between two kinds of diffraction steps 17A and 17B of the diffraction grating 13, one is provided at a position where the phase difference from the base shape given the design wavelength λ0 is not 2 nm&pgr;. 0.9  d ≤ m · λ n 1  ( λ ) - 1 ≤ 1.1  d |
