Patent ID: 7508585

Claim:
A diffraction optical element in which an element having an n-step staircase shape and an element having an m-step staircase shape (n>m) are formed on one substrate, wherein a first step of the m-step staircase shape is formed to the same height as a second step of the n-step staircase shape, and wherein phase correction between the n-step staircase shape and the m-step staircase shape is (1/m−1/n)π, the phase correction in a step direction is Aπ (direction toward a lower step being positive), the phase correction in a direction orthogonal to the step direction is Bπ (direction in which the m-step staircase shape is brought close to the n-step staircase shape being positive), A>(1/m−1/n), and A+B=1m−1/n.