Patent ID: 8902504

Claim:
A diffractive optical element configured to be usable as a lens of an optical system, the diffractive optical element comprising: a first diffractive grating that includes a first grating surface and a first grating wall surface; a reflective member disposed on the first grating wall surface; and a second diffractive grating that includes a second grating surface and a second grating wall surface, and that is disposed so that the second grating surface contacts the first grating surface and so that the second grating wall surface contacts the reflective member, wherein when off-screen light having an incident angle larger than an incident angle of off-axis light flux of the optical system enters the diffractive optical element at an incident angle ωi with reference to a surface normal of the lens, an emission angle ωo of light having a maximum intensity emitted from one of the first grating wall surface or the second grating wall surface meets the following Expression (1): ωo≧ωi (1), and wherein a maximum width W (μm) of the reflective member and a grating pitch P (μm) of each of the first diffractive grating and the second diffractive grating meet the following Expressions (2-1) and (2-2): 0< W/P< 0.04 (2-1), and 0.02<W (2-2).