Patent ID: 6781756
Filing Date: 2004-08-24
Classification: G02B

Abstract:
A diffractive optical element comprising:a first optical region made of a first optical material which is substantially transparent to light within a wavelength range to be used and has a refractive index n1; a second optical region made of a second optical material which is substantially transparent to said light but is different from said first optical material and has a refractive index n2; a third optical region made of a third optical material which is transparent to said light but is different from said second optical material and has a refractive index n3, said first, second and third optical regions being arranged to be brought into contact with each other or being arranged close to each other; a first relief pattern formed in a boundary surface between said first and second optical regions and having a first pitch distribution and a first depth; and a second relief pattern formed in a boundary surface between said second and third optical regions and having a second pitch distribution and a second depth, said second pitch distribution being substantially identical with said first pitch distribution of the first relief pattern, wherein said first and second pitch distributions and first and second depths of the first and second relief patterns are set to diffract said light, said first and second relief patterns are arranged such that tops and bottoms of the first relief pattern are aligned with tops and bottoms of the second relief pattern, respectively viewed in a direction of an optical axis, and said refractive indices n1, n2 and n3 of the first, second and third optical materials satisfy the following condition: n1, n3>n2.