PROBLEM TO BE SOLVED: To provide a light irradiation device with high heat resistance.;SOLUTION: A light irradiation device 1 includes a diffractive optical element 10 that diffracts and emits incident light and a light source unit 30 that projects light to the diffractive optical element 10, and the diffractive optical element 10 includes at least one diffractive layer 115 having a high refractive index portion 111 in which convex portions 111a are arranged side by side and a low refractive index portion 114 including a concave portion 112 formed between the convex portions 111a, and a glass layer 41 disposed on the side from which light from a light source unit 30 is emitted relative to any of the diffractive layers 115.;SELECTED DRAWING: Figure 3;COPYRIGHT: (C)2019,JPO&INPIT
展开▼
