| CPC G02C 7/104 (2013.01) [A61F 9/022 (2013.01); G02B 1/02 (2013.01)] | 20 Claims |

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1. An optical filter, wherein the filter comprises a Bragg grating; the Bragg grating comprises alternating layers of a first material having a first index of refraction and a second material having a second index of refraction, wherein the first index of refraction is higher than the second index of refraction; and the filter reflects at least 80% of light with a wavelength below 560 nm, and transmits at least 80% of light with a wavelength above 570 nm.
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