NARROWBAND FILTRATION COVER Russian patent published in 2007 - IPC G02B5/26 G02B5/28 

FIELD: narrowband filtration covers.

SUBSTANCE: narrowband filtration cover contains two systems of alternating dielectric layers with different refraction coefficients and equal optical thickness λ₀/4, in the form of high reflection mirrors, and a dielectric layer dividing them. In accordance to the invention, structure of high reflection mirrors additionally features dielectric layers with intermediate value of refraction coefficient and dividing layer has optical thickness λ₀ or one divisible by it, and sequence of layer alternation has form (CBCABA)^KD(ABACBC)^K with n_A<n_B<n_C, where refraction coefficient of dividing layer n_D is not equal to n_A (for example, n_D=n_C) and k≥1 is an integer number, where: λ₀ - maximal filtration cover throughput wave length; A, B and C - dielectric layers with values of refraction coefficient n_A, n_B and n_C respectively, and D - dividing layer.

EFFECT: increased selectivity due to expansion of high reflection bands on the sides of pass band.

5 dwg