Patent ID: 7256939

Claim:
A diffractive optical element comprising a first element and a second element, whose materials are different from each other and which elements are bonded to each other, with a diffraction grating created on a boundary surface between said first element and said second element, wherein: at least said second element is made from a photo-setting resin, which is set by light rays incident through said first element; said diffractive optical element is set in a predetermined range of values including values that make a transmittance of said first element and a transmittance of said second element equal to each other for said light rays, so that as differences in cure shrinkage in said second element are generated by differences in intensity of said light rays caused from ups and downs of said diffraction grating created on said boundary surface of said first element, said differences in cure shrinkage are controlled within a range so as not to degrade a desired performance of said diffractive optical element; and said diffractive element satisfies the following condition 0.990≦( T 2 /T 1) H/10000) ≦1.010 where “H” (unit: μm) represents a height of said diffraction grating, and for said second element to be cured by said light rays being transmitted through said first element, “T 1 ” represents the transmittance per 10 mm through said first element and “T 2 ” represents the transmittance per 10 mm through said second element.