Infrared Filter Composition for Visible Noise Reduction

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Solution Overview

Problem

Existing infrared filters and films are ineffective in reducing noise from visible light when used with infrared light sources of wavelengths longer than 1000 nm, and near-infrared absorbing filters have high transmittance in the visible range, failing to selectively allow transmission of infrared light with minimal visible light noise.

Innovation Solution

A composition comprising a coloring material that transmits infrared light and shields visible light, an infrared absorber with an absorption maximum between 900 nm and 1000 nm, and a resin, where the absorbance ratio in specific wavelength ranges is optimized to achieve low transmittance in the visible range and high transmittance in the infrared range, using compounds like pyrrolopyrrole, cyanine, squarylium, phthalocyanine, or naphthalocyanine as infrared absorbers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If existing infrared filters are used, then infrared light transmission is achieved, but visible light noise reduction is insufficient

Engineering Contradiction:

Improveinfrared sensing accuracyVSAvoidvisible light noise

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The filter is divided into multiple functional layers: a first filter layer with specific spectral characteristics (high visible light absorption, high infrared transmission) and a second filter layer. This segmentation allows each layer to target specific wavelength ranges, with the first layer primarily blocking visible light noise and the second layer fine-tuning the infrared transmission characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses composite material structures combining different filter materials with complementary spectral properties. The first filter layer uses materials with high visible light absorption and high infrared transmission, while the second filter layer uses materials that further enhance infrared transmission. This composite approach achieves superior noise reduction and transmission performance that single materials cannot provide.

Inventive Principle:

Principle #40Composite materials

2Measurement precision

If near-infrared absorbing filters are used, then infrared absorption is improved, but visible light transmittance becomes too high

Engineering Contradiction:

Improveinfrared detection capabilityVSAvoidvisible light transmittance

Core Design Contradiction:

Measurement precisionVSIllumination intensity

Solution Approach 1:

Different regions of the filter structure are assigned different optical properties: the first filter layer is optimized for visible light absorption with specific spectral characteristics, while the second filter layer is optimized for infrared transmission. This local quality differentiation ensures that visible light is blocked where needed while infrared light passes through with minimal interference.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention optimizes key parameters including the absorbance ratio A/B (where A is minimum absorbance in 400-950 nm range and B is maximum absorbance in 1100-1300 nm range, with A/B ≥ 4.5), layer thicknesses, and material compositions. These parameter adjustments create a filter that simultaneously achieves high visible light blocking and high infrared transmission.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution enables the formation of films that effectively transmit infrared light with minimal noise from visible light, improving the accuracy of infrared sensing applications by optimizing spectral characteristics.

Implementation Method 1

an infrared absorber; and a resin, in which the infrared absorber includes a compound having an absorption maximum in a wavelength range of longer than 900 nm and 1000 nm or shorter

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

a coloring material that allows transmission of infrared light and shields visible light

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS10877195B2Composition, film, laminate, infrared transmitting filter, solid image pickup element, and infrared sensor

Publication Date: 2020.12.29 FUJIFILM CORP

AI summary

A composition includes: a coloring material that allows transmission of infrared light and shields visible light; an infrared absorber; and a resin, in which the infrared absorber includes a compound having an absorption maximum in a wavelength range of longer than 900 nm and 1000 nm or shorter, and a ratio A/B of a minimum value A of an absorbance of the composition in a wavelength range of 400 to 950 nm to a maximum value B of an absorbance of the composition in a wavelength range of 1100 to 1300 nm is 4.5 or higher.