Optical Filter for Ambient Light Sensor with Low Incident Angle Dependence

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Solution Overview

Problem

Ambient light sensors in information terminal devices face challenges in accurately detecting illuminance and color tone due to reduced visible light transmission, especially at large incident angles, which affects the accuracy of screen brightness and color correction.

Innovation Solution

An optical filter with a light absorbing layer having maximum absorption in the 750-1150 nm range, using compounds like squarylium and phthalocyanine, and a dielectric multilayer film, ensuring high visible light transmittance and near-infrared cut performance even at oblique angles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a metal multilayer thin film near infrared cut filter is used, then near infrared cut performance is improved, but optical characteristics change greatly according to incident angle

Engineering Contradiction:

Improvenear infrared cut performanceVSAvoidincident angle dependence

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the material parameter from metal multilayer thin film to organic dye compound, which fundamentally alters the optical characteristics to be less sensitive to incident angle while maintaining near infrared cut performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite structure by combining the organic dye compound with a transparent resin or glass substrate, achieving both near infrared absorption and visible light transmission with reduced incident angle dependence

Inventive Principle:

Principle #40Composite materials

2Measurement precision

If near infrared absorbing particles are increased to achieve sufficient near infrared cut performance, then near infrared cut performance is improved, but visible light transmittance decreases

Engineering Contradiction:

Improvenear infrared cut performanceVSAvoidvisible light transmittance

Core Design Contradiction:

Measurement precisionVSIllumination intensity

Solution Approach 1:

The patent changes the concentration parameter by using a very small amount of dye compound (0.01-15.0 parts by weight per 100 parts resin), which is significantly lower than conventional particle-based solutions, achieving near infrared cut without compromising visible light transmittance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The dye compound exhibits selective absorption properties, strongly absorbing near infrared light while remaining transparent to visible light, creating localized optical functionality without bulk material interference

Inventive Principle:

Principle #3Local quality

3Length of stationary object

If the distance from light incidence window to ambient light sensor is reduced, then device height is reduced, but proportion of incident light from large incident angle increases

Engineering Contradiction:

Improvedevice heightVSAvoidincident angle insensitivity

Core Design Contradiction:

Length of stationary objectVSAdaptability or versatility

Solution Approach 1:

The patent changes the optical material parameter to use dye compounds with specific absorption characteristics that are inherently less sensitive to incident angle, allowing the sensor to maintain performance even with increased oblique light incidence due to reduced device height

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 maintains high accuracy in illuminance and color tone detection across various angles, preventing erroneous operations and improving screen luminance and color correction in ambient light sensors.

Implementation Method 1

the light absorbing layer has a maximum absorption in a wavelength range of 750 to 1,150 nm

Methodology Applied

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

Implementation Method 2

a dielectric multilayer film is provided on at least one surface of the base material (i)

Methodology Applied

Scientific EffectInterference: Interference

Data Source

PatentUS10996105B2Optical filter having low incident angle dependence of incident light, ambient light sensor, sensor module and electronic device

Publication Date: 2021.05.04 JSR CORPORATION

AI summary

One object of the present disclosure is to show an optical filter capable of realizing both an excellent visible light transmittance and an excellent near-infrared ray-shielding performance even if an incident angle becomes large. The optical filter of the present disclosure has a base material (i) including a light absorbing layer, and transmits visible light, wherein the light absorbing layer has a maximum absorption in a wavelength range of 750 nm to 1,150 nm, and in a wavelength range of 850 nm to 1,050 nm, an average OD value measured in a direction perpendicular to the optical filter is 2.0 or more, and an average OD value measured at an angle of 60° with respect to the direction perpendicular to the optical filter is 2.0 or more.