Patent ID: 7773300
Filing Date: 2010-08-10
Classification: G02B

Abstract:
1. An optical filter comprising: a substrate; a first plurality of hard-coating layers provided on the substrate and including alternating first and second layers, the first layers having a first refractive index and the second layers having a second refractive index greater than the first refractive index; a second plurality of hard-coating layers including a repeating sequence of a third layer and a first instance of a first layer group and a fourth layer and a second instance of a first layer group provided on the substrate, each third layer having a third refractive index, each first layer group comprising at least one of a first intermediate index layer and a first Herpin equivalent layer, said first intermediate index layer having a first intermediate refractive index, and said first Herpin equivalent layer having a first effective refractive index substantially equivalent to said first intermediate refractive index, and each fourth layer having a fourth refractive index, the first intermediate refractive index being greater than the third refractive index and less than the fourth refractive index; and a third plurality of hard-coating layers including a repeating sequence of a fifth layer and a first instance of a second layer group and a sixth layer and a second instance of a second layer group provided on the substrate, each fifth layer having a fifth refractive index, each second layer group comprising at least one of a second intermediate index layer and a second Herpin equivalent layer, said second intermediate index layer having a second intermediate refractive index, and said second Herpin equivalent layer having a second effective refractive index substantially equivalent to said second intermediate refractive index, and each sixth layer having a sixth refractive index, the second intermediate refractive index being greater than the fifth refractive index and less than the sixth refractive index, wherein each instance of the first layer group is said first Herpin equivalent layer, said first Herpin equivalent layer comprising at least one first sub-layer and at least one second sub-layer and each instance of the second layer group is said second Herpin equivalent layer, said second Herpin equivalent layer comprising at least one third sub-layer and at least one fourth sub-layer, wherein the thickness of each of said first, second, third, and fourth sub-layers is substantially less than the thickness of at least one of said first, second, third, fourth, fifth, and sixth layers.