OPTICAL INTERFERENCE BLOCKING FILTER Russian patent published in 2023 - IPC G02B5/28 

FIELD: optical filters.

SUBSTANCE: invention can be used for protection against infrared radiation in visual surveillance equipment. The optical interference blocking filter includes a substrate with a low refractive index and alternating layers with low and high refractive indices located on it, the first and last layers have a low refractive index, representing 3 groups, where the first group located on the substrate includes 3 matching layers, the second group, which forms the filter blocking zone and is located on the first group, is made with optical thicknesses of the layers equal to λ₀/4, where λ₀ is the wavelength of the middle of the filter blocking zone, and the third group, in contact with air, includes 2 matching layers. The first group includes additionally 2 matching layers, the optical thicknesses of the layers, starting from the substrate, are equal to: K₃⋅λ₀/4, K₄⋅λ₀/4, L₅⋅λ₀/4, K₆⋅λ₀/4, K₇⋅λ₀/4, where K₃=K₄=(0.13÷0.23); K₅=(0.08÷0.18); K₆=K₇=(1.05÷4.15), and the third group additionally includes one matching layer, the first upper layer having an optical thickness of K₁₀⋅λ₀/4, the second and third layers have optical thicknesses K ₉⋅λ₀/4, K₈⋅λ₀/4, where K₁₀=(0.45-0.55), and K₈=K₉=(1.05-1.15).

EFFECT: broadening the blocking zone of long-wave radiation, increasing the filter transmittance in the visible region of the spectrum, the possibility of implementing a filter design for almost any pair of two film materials in the visible and near regions of the spectrum.

1 cl, 3 dwg