Patent ID: 7855000

Claim:
An optical element, comprising: a substrate; an anti-reflective unit on a surface of the substrate, the anti-reflective unit comprising a first coating layer having a low refractive index, a second coating layer having a high refractive index, a third coating layer having a low refractive index, a fourth coating layer having a high refractive index, and a fifth coating layer having a low refractive index arranged sequentially, wherein the first coating layer is the innermost of the layers, the fifth coating layer is the outermost of the layers, each of the first, the third and the fifth coating layers is made of SiO 2 , each of the second and the fourth coating layers is made of TiO 2 , the thickness of the first coating layer is approximately 8.822 nanometers, the thickness of the second coating layer is approximately 15.566 nanometers, the thickness of the third coating layer is approximately 36.654 nanometers, the thickness of the fourth coating layer is approximately 131.999 nanometers, and the thickness of the fifth coating layer is approximately 97.785 nanometers.