Optical camouflage filters

Patent metadata

Field	Value
Publication number	US-12474514-B2
Application number	US-202217583553-A
Country	US
Kind code	B2
Filing date	Jan 25, 2022
Priority date	Jan 21, 2016
Publication date	Nov 18, 2025
Grant date	Nov 18, 2025

Abstract

A system may include one or both of a light emitter and a light receiver, and an optical filter. The optical filter includes a wavelength selective scattering layer. The wavelength selective scattering layer may have a near-infrared scattering ratio of less than about 0.9. The filter may have a visible reflective haze ratio of greater than about 0.5. A method may include disposing the wavelength selective scattering layer adjacent one or both of the light emitter and the light receiver. The optical filter may include a wavelength selective reflective layer. The optical filter may include a wavelength selective absorbing layer. An article may include the optical filter. The wavelength selective scattering layer 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 . An article comprising an optical filter, the optical filter configured to provide 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 an average visible scattering of greater than 10%, a wavelength selective reflective layer, and at least one wavelength selective absorbing layer, wherein each wavelength selective layer is configured to transmit near-infrared wavelengths, wherein the optical filter has a visible transmittance of less than 5% and a near-infrared transmittance of greater than 75% for wavelengths greater than 900 nm.

2 . The article of claim 1 , wherein the optical filter has a visible transmittance of less than 1%.

3 . The article 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.

4 . The article of claim 1 , wherein the wavelength selective scattering layer comprises a binder, a plurality of particles, and a plurality of interconnected voids, wherein a volume fraction of the plurality of interconnected voids in the wavelength selective scattering layer is not less than about 20%, and wherein a weight ratio of the binder to the plurality of the particles is not less than about 1:2.

5 . The article of claim 1 , wherein the at least one wavelength selective absorbing layer is between the wavelength selective scattering layer and the wavelength selective reflective layer, and wherein the at least one wavelength selective absorbing layer is configured to reduce a total visible reflectance of the optical filter by a predetermined magnitude.

6 . The article of claim 5 , wherein the optical filter has a near-infrared transmittance at 830-900 nm of greater than 50%.

7 . The article of claim 1 , wherein the wavelength selective reflective layer is between the wavelength selective scattering layer and the at least one wavelength selective absorbing layer, and wherein the at least one wavelength selective absorbing layer is configured to reduce a total visible reflectance uniformly over an area of a major surface of the optical filter.

8 . The article of claim 7 , wherein the optical filter has a near-infrared transmittance at 830-900 nm of greater than 50%.

9 . A system comprising the article of claim 1 and one or both of a light emitter or a light receiver, the optical filter disposed adjacent one or both of the light emitter or the light receiver, wherein the optical filter is configured to at least partially camouflage one or both of the light receiver or the light emitter from a visual perception.

Assignees

• 3M Innovative Properties Company

Inventors

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

Classifications

• G02B5/281

  designed for the infrared light · CPC title

• G02B5/223

  containing organic substances, e.g. dyes, inks or pigments · 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

• G02B5/206

  comprising particles embedded in a solid matrix · CPC title

• G02B5/22

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