Light-Absorbing Optical Filter for UV and Near-IR Blocking

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Solution Overview

Problem

Existing optical filters do not adequately address the need for high transmittance in the visible and longer wavelength ranges while effectively blocking ultraviolet and infrared light, particularly in the 700 to 1000 nm range, which affects the accuracy and safety of imaging and distance measurement devices.

Innovation Solution

An optical filter with a specific transmission spectrum that includes a light-absorbing composition comprising a copper complex and alkoxy-containing compounds, achieving high transmittance in the visible and longer wavelength ranges while blocking ultraviolet and infrared light, particularly in the 700 to 1000 nm range, using a light-absorbing layer with a thickness of 100 μm to 400 μm.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a light-reflecting film is used to block infrared or ultraviolet light, then the blocking performance is improved, but ghosting and flare occur due to multiple reflections

Engineering Contradiction:

Improveinfrared and ultraviolet blocking performanceVSAvoidghosting and flare from multiple reflections

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent changes the mechanism from light reflection to light absorption by using a light absorber-including film. The absorption coefficient and thickness of the film are optimized to achieve high blocking performance (transmittance < 5% in UV and 700-1000nm ranges) while eliminating multiple reflections that cause ghosting and flare

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite structure combining a light absorber-including film with specific materials (such as copper-phosphonate complexes or organic dyes) that provide both high absorption efficiency and appropriate spectral characteristics, achieving superior performance compared to simple reflective films

Inventive Principle:

Principle #40Composite materials

2Object-generated harmful factors

If a light absorber-including film is used to block infrared and ultraviolet, then ghosting and flare are reduced, but the transmittance in longer wavelength ranges (1500 nm and above) needs to be optimized

Engineering Contradiction:

Improveghosting and flare reductionVSAvoidtransmittance in 1500 nm and above wavelength range

Core Design Contradiction:

Object-generated harmful factorsVSIllumination intensity

Solution Approach 1:

The patent applies local quality by designing the light absorber-including film with specific spectral absorption characteristics that selectively block certain wavelength ranges (UV and 700-1000nm) while maintaining high transmittance in other ranges (1500nm and above). The absorption spectrum of the light absorber is carefully selected to create this wavelength-dependent transmission profile

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent optimizes parameters including the thickness of the light absorber-including film (typically 10-100 nm) and the absorption coefficient of the light absorber material to achieve the desired balance between blocking performance in specific ranges and transmittance in the 1500nm+ range, ensuring Tmin ≥ 60% while maintaining UV and near-IR blocking

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If conventional light absorbers (phosphonic acid and copper ion) are used, then the optical filter structure is simplified, but the transmittance in longer wavelength ranges is insufficient

Engineering Contradiction:

Improveoptical filter structure simplificationVSAvoidtransmittance in wavelength ranges including 1500 nm and above

Core Design Contradiction:

Device complexityVSIllumination intensity

Solution Approach 1:

The patent modifies the conventional light absorber composition by adjusting the ratio of phosphonic acid to copper ion, adding specific organic dyes, or using modified copper complexes with tailored absorption spectra. These parameter changes enable the simplified single-layer structure to achieve both high transmittance in 1500nm+ ranges and effective blocking in UV and 700-1000nm ranges

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 optical filter provides high transmittance in the visible and infrared regions, enhancing image quality and distance measurement accuracy by reducing flare and ghosting, and ensuring safety by blocking harmful wavelengths, suitable for use in camera modules and TOF sensors.

Implementation Method 1

optical filters including a light absorber-including film have been attracting attention. The transmittance properties of optical filters including a light absorber-including film are unlikely to be dependent on the incident angle

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS20250334727A1Optical filter, optical device, and light-absorbing composition

Publication Date: 2025.10.30 NIPPON SHEET GLASS CO LTD

AI summary

An optical filter 1a has a first transmission spectrum satisfying the following requirements (i), (ii), (iii), and (iv) at 25° C. (i) A minimum of a transmittance in a wavelength range of 450 nm to 600 nm is 70% or more. (ii) A maximum of the transmittance in a wavelength range of 300 nm to 370 nm is 5% or less. (iii) A maximum of the transmittance in a wavelength range of 800 nm to 1000 nm is 5% or less. (iv) A minimum of the transmittance in a wavelength range of 1500 nm to 1700 nm is 60% or more.