Patent ID: 7212336
Filing Date: 2007-05-01
Classification: G02B

Abstract:
1. An optical filter for screening out infrared and ultraviolet light, comprising: a transparent substrate having a first surface and an opposite second surface; a first film stack formed on the first surface of the substrate; and a second film stack formed on the second surface of the substrate, the first and second film stacks each comprising a plurality of high refractive index layers and a plurality of low refractive index layers alternately stacked one on another, wherein the first film stack is defined as follows: wherein H represents a high refractive index layer having a base optical thickness equal to one fourth of a first reference wavelength associated with the optical filter, L represents a low refractive index layer having a base optical thickness equal to one fourth of said first reference wavelength associated with the optical filter, the expression enclosed in each parenthesis represents a filter cavity, and superscripts represent the number of repetitions of the expression enclosed in the parenthesis; the second film stack is defined as follows: wherein, H represents a high refractive index layer having a base optical thickness equal to one fourth of a second reference wavelength associated with the optical filter, L represents a low refractive index layer having a base optical thickness equal to one fourth of said second reference wavelength associated with the optical filter, the expression enclosed in each parenthesis represents a filter cavity, and the superscript represents the number of repetitions of the expression enclosed in the parenthesis.