Patent ID: 9395476
Filing Date: 2016-07-19
CPC Classification: C03C,G02B

Claim Text:
1. An infrared cut-off optical filter, comprising: a substrate having a thickness and allowing incoming lights to enter the optical filter at an incidence angle; a film structure formed on the substrate to reduce an angle dependence of the optical filter with respect to the incoming lights, wherein: the film structure contains a plurality of first type thin films with a first refractive index and a plurality of second type thin films with a second refractive index; the first type thin films and the second type thin films are arranged alternately; and thickness of individual films of the first type thin films and the second type thin films are controlled individually such that a substantial number of the first type thin films and the second type thin films have different thickness, wherein the film structure is formed in a format of “a1Hb1La2Hb2L . . . a(i−1)Hb(i−1)LaiH”, provided that ‘i’ is a number of film layer, ‘a’ stands for the first type, ‘H’ stands for high-refractive-index film, ‘b’ stands for the second type, and ‘L’ stands for low-refractive-index film, a pass-through rate change for 600-700 nm red-light spectral band over an entire incident angle range of 0-30 degrees of the optical filter is less than 20%, and the pass-through rate change is calculated as (initial pass-through rate-final pass-through rate)/initial pass-through rate, the initial pass-through rate is light transmission at 0 degree incident angle, and the final pass-through rate is light transmission at an incident angle larger than 0 degree but equal to or smaller than 30 degrees, wherein a total number of the first type thin films and the second type thin films is greater than about 40.