Multilayer diffractive optical element

1. A multilayer diffractive optical element, comprising:

a first substrate;

a second substrate;

a first resin layer having a first diffraction grating pattern disposed on the first substrate; and

a second resin layer having a second diffraction grating pattern disposed on the second substrate,

wherein the first diffraction grating pattern and the second diffraction grating pattern oppose each other in adhesion to each other,

wherein the first resin layer includes a first region provided at a peripheral portion adjacent to a portion of the first diffraction grating pattern, the first region satisfying 1≦h R1 /hd, wherein h R1 represents a thickness of the first resin layer in a direction normal to a surface of the first substrate, and hd represents an average grating height of the first diffraction grating pattern,

wherein the first resin layer includes a second region provided at a peripheral portion adjacent to the first region, the second region satisfying h R2 /h 1 ≦0.34, wherein hR 2 represents a thickness of the second region in a direction normal to a surface of the first substrate, and h 1 represents an average thickness of the first region, and

wherein Expression (1) below is satisfied,

50≦w 1 /hd and 0.5≦w 2 /w 1 (1), wherein w 1 represents a width of the first region in a radial direction along a plane parallel to the surface of the first substrate, and w 2 represents a width of the second region in the radial direction along a plane parallel to the surface of the first substrate, and

wherein the first resin layer and the second resin layer are in adhesion to each other at the first region and the second region.

2. The multilayer diffractive optical element according to claim 1 ,

wherein the first region satisfies 1≦h R1 /hd≦1.4 and 50≦w 1 /hd≦160, and

wherein the second region satisfies 0.04≦h R2 /h 1 ≦0.34 and 0.5≦w 2 /w 1 ≦1.

3. The multilayer diffractive optical element according to claim 1 ,

wherein the multilayer diffractive optical element is an optical lens.

4. The multilayer diffractive optical element according to claim 1 ,

wherein one of the first resin layer and the second resin layer includes an indium tin oxide fine particle.

5. The multilayer diffractive optical element according to claim 1 ,

wherein the first resin layer has an average thickness of greater than 1 μm and less than 3 μm at a portion other than the first diffraction grating pattern, and includes an indium tin oxide particle dispersed therein, the indium tin oxide particle having a number-average particle size of greater than 1 nm and less than 100 nm.

6. The multilayer diffractive optical element according to claim 1 ,

wherein the first resin layer has a refractive index of no less than 1.54 and no greater than 1.63 and an Abbe number of no less than 42 and no greater than 57, and

wherein the second resin layer has a refractive index of no less than 1.48 and no greater than 1.57 and an Abbe number of no less than 14 and no greater than 28.

7. The multilayer diffractive optical element according to claim 1 ,

wherein the first resin layer and the second resin layer contain energy-curable resin.

8. The multilayer diffractive optical element according to claim 1 , wherein the second resin layer covers an outer peripheral portion of the first resin layer, and is in adhesion with the first substrate.