Optical camouflage filters

Patent metadata

Field	Value
Publication number	US-11269121-B2
Application number	US-201616071544-A
Country	US
Kind code	B2
Filing date	May 6, 2016
Priority date	Jan 21, 2016
Publication date	Mar 8, 2022
Grant date	Mar 8, 2022

Abstract

A system may include one or both of a light emitter (46) and a light receiver (40), and an optical filter (10). The optical filter (10) includes a wavelength selective scattering layer (14). The wavelength selective scattering layer (14) may have a near-infrared scattering ratio of less than about 0.9. The filter (10) may have a visible reflective haze ratio of greater than about 0.5. A method may include disposing the wavelength selective scattering layer (14) adjacent one or both of the light emitter (46) and the light receiver (40). The optical filter (10) may include a wavelength selective reflective layer (16). The optical filter (10) may include a wavelength selective absorbing layer (34). An article may include the optical filter (10). The wavelength selective scattering layer (14) may have an average near-infrared scattering of less than 60%, an average visible scattering of greater than 10%, and a difference between the % total visible reflectance and the % diffuse visible reflectance of less than 20.

First claim

The invention claimed is:

1. A system comprising:
one or both of a light emitter or a light receiver; and
an optical filter adjacent one or both of the light emitter or the light receiver and configured to provide high clarity near-infrared transmission such that a near-infrared pattern can be sensed through the optical filter, wherein the optical filter comprises a wavelength selective scattering layer, wherein the wavelength selective scattering layer has a near-infrared scattering ratio of less than about 0.9, the near-infrared scattering ratio being a ratio of an average near-infrared scattering to an average visible scattering, and wherein the wavelength selective scattering layer has a visible reflective haze ratio of greater than about 0.5, the visible reflective haze ratio being a ratio of an average visible diffusive reflectance to an average visible total reflectance.

2. The system of claim 1 , wherein the wavelength selective scattering layer has a near-infrared scattering ratio of less than about 0.7.

3. The system of claim 1 , wherein the wavelength selective scattering layer has a near-infrared scattering ratio of less than about 0.6.

4. The system of claim 1 , wherein the wavelength selective scattering layer has a visible reflective haze ratio of greater than about 0.6.

5. The system of claim 1 , wherein the wavelength selective scattering layer has a visible reflective haze ratio of greater than about 0.7.

6. The system of claim 1 , wherein one or both of the light emitter or the light receiver have an operating wavelength within a near-infrared range.

7. The system of claim 1 , wherein the wavelength selective scattering layer transmits less than about 50% of incident visible light, and wherein the wavelength selective scattering layer transmits greater than about 50% of incident near-infrared light.

8. The system of claim 1 , wherein the wavelength selective scattering layer scatters greater than about 50% of incident visible light.

9. The system of claim 1 , wherein the wavelength selective scattering layer scatters greater than about 50% of incident visible light as white light.

10. The system of claim 1 , wherein the wavelength selective scattering layer comprises an optical medium have a first refractive index, wherein the optical medium comprises a plurality of particles, wherein the plurality of particles has a second refractive index and an average particle size of less than about 5 μm, and wherein an absolute difference between the first refractive index and the second refractive index is less than about 0.1.

11. The system of claim 1 , wherein the wavelength selective scattering layer comprises an optical medium have a first refractive index, wherein the optical medium comprises a plurality of particles, wherein the plurality of particles has a second refractive index and an average particle size of less than about 1 μm, and wherein an absolute difference between the first refractive index and the second refractive index is less than about 0.2.

12. The system of claim 1 , wherein the wavelength selective scattering layer comprises an optical medium have a first refractive index, wherein the optical medium comprises a plurality of particles, wherein the plurality of particles has a second refractive index and an average particle size of less than about 0.5 μm, and wherein an absolute difference between the first refractive index and the second refractive index is less than about 0.4.

13. The system of claim 1 , wherein the wavelength selective scattering layer comprises an optical medium have a first refractive index, wherein the optical medium comprises a plurality of particles, wherein the plurality of particles has a second refractive index and an average particle size of less than about 0.3 μm, and wherein an absolute difference between the first refractive index and the second refractive index is less than about 0.6.

14. The system of claim 1 , wherein the wavelength selective scattering layer comprises an optical medium have a first refractive index, wherein the optical medium comprises a plurality of particles, wherein the plurality of particles has a second refractive index and an average particle size of less than about 0.2 μm, and wherein an absolute difference between the first refractive index and the second refractive index is less than about 1.8.

15. The system of claim 1 , wherein the wavelength selective scattering layer comprises an optical medium have a first refractive index, wherein the optical medium comprises a plurality of particles, wherein the plurality of particles has a second refractive index, wherein an average particle size of the plurality of particles, the first refractive index, and the second refractive index are selected from a region under a line representing a near-infrared scattering ratio of 0.2 in a contour plot of near-infrared scattering ratio for wavelength selective scattering layers comprising media and particles, a vertical axis of the contour plot being particle diameter, a horizontal axis of the contour plot being a refractive index difference between the media and particles, wherein the refractive index difference is between −1.8 to 1.8.

16. The system of claim 1 , wherein the wavelength selective scattering layer comprises an optical medium have a first refractive index, wherein the optical medium comprises a plurality of particles, wherein the plurality of particles has a second refractive index, wherein an average particle size of the plurality of particles, the first refractive index, and the second refractive index are selected from a region under a line representing a near-infrared scattering ratio of 0.4 in a contour plot of near-infrared scattering ratio for wavelength selective scattering layers comprising media and particles, a vertical axis of the contour plot being particle diameter, a horizontal axis of the contour plot being a refractive index difference between the media and particles, wherein the refractive index difference is between −1.8 to 1.8.

17. The system of claim 1 , wherein the wavelength selective scattering layer comprises an optical medium have a first refractive index, wherein the optical medium comprises a plurality of particles, wherein the plurality of particles has a second refractive index, wherein an average particle size of the plurality of particles, the first refractive index, and the second refractive index are selected from a region under a line representing a near-infrared scattering ratio of 0.6 in a contour plot of near-infrared scattering ratio for wavelength selective scattering layers comprising media and particles, a vertical axis of the contour plot being particle diameter, a horizontal axis of the contour plot being a refractive index difference between the media and particles, wherein the refractive index difference is between −1.8 to 1.8.

18. The system of claim 1 , wherein the wavelength selective scattering layer comprises an optical medium have a first refractive index, wherein the optical medium comprises a plurality of particles, wherein the plurality of particles has a second refractive index, wherein an average particle size of the plurality of particles, the first refractive index, and the second refractive index are selected from a region under a line representing a near-infrared scattering ratio of 0.8 in a contour plot of near-infrared scattering ratio for wavelength selective scattering layers comprising media and particles, a vertical axis of the contour plot being particle diameter, a horizontal axis of the contour plot being a refractive in

Assignees

• 3M Innovative Properties Co

Inventors

• Du Guanglei
• Wheatley John A
• Lv yi hang
• Renstrom Anthony M
• Sharma Neeraj
• Xu Fuguo

Classifications

• G02F1/21

  by interference · CPC title

• G02B5/26 Primary

  Reflecting filters (G02B5/28 takes precedence) · CPC title

• G02B5/208

  for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation · CPC title

• G02B5/204 Primary

  in which spectral selection is performed by means of a conductive grid or array, e.g. frequency selective surfaces (for use with wavelengths longer than the infrared light H01Q15/0006) · CPC title

• G02B5/22

  Absorbing filters {(G02B5/201 - G02B5/208 take precedence)} · CPC title