Diffractive optical element, projection device and measuring device

A diffractive optical element having a convexo-concave pattern to generate two-dimensional phase distribution, which two-dimensionally diffracts incident light into plural diffracted light rays,

• which comprises a transparent substrate, a convexo-concave portion formed on one surface of the transparent substrate and a filling portion with which concave portions of the convexo-concave portion are filled and which covers top surfaces of convex portions of the convexo-concave portion for planarizing the convexo-concave portion,
• wherein the convexo-concave portion has at least two stages on the surface of the transparent substrate;
• the top surfaces of the respective stages are parallel to one another;
• among the transparent substrate, the convexo-concave portion and the filling portion, the refractive indexes of at least the convexo-concave portion and the filling portion are different with respect to the incident light which enters from the normal direction of the surface of the transparent substrate;
• the diffractive optical element has a refractive index-controlling layer between the convexo-concave portion and the filling portion or between the transparent substrate and the convexo-concave portion;
• and
• the refractive index-controlling layer is a monolayer refractive index-controlling layer which satisfies the following equation (A) with respect to both interfaces of the refractive index-controlling layer or a refractive index-controlling layer consisting of at least one layer which satisfies a theoretical reflectivity R<4% by a multilayer structure, wherein nm is a refractive index of a medium which forms an incident side interface, no is a refractive index of a medium which forms an emergent side interface, nr is a refractive index of the refractive index-controlling layer or each layer, and dr is the thickness:
• (n0×nm)0.5−α<nr<(n0×nm)0.5+α, and
• (1−β)×λ/4<nr×dr<(1+β)×λ/4, equation (A)
• wherein α=0.25, β=0.6.

A diffractive optical element having a convexo-concave pattern to generate two-dimensional phase distribution, which two-dimensionally diffracts incident light into plural diffracted light rays,

• which comprises a transparent substrate, a convexo-concave portion formed so as to be in contact with one surface of the transparent substrate and a filling portion with which concave portions of the convexo-concave portion are filled and which covers top surfaces of convex portions of the convexo-concave portion for planarizing the convexo-concave portion, wherein the convexo-concave portion has at least two stages on the surface of the transparent substrate;
• the top surfaces of the stages are parallel to one another;
• among the respective stages of the convexo-concave portion, at least a stage having height is constructed by stacking at least one base block, when the base block is a multilayer film consisting of at least 2 layers having a predetermined refractive index and thickness,
• wherein the base block satisfies a theoretical reflectivity R<4% in the multilayer structure.