Wavelength Conversion Layer Structure for Higher Light Extraction

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Solution Overview

Problem

Existing wavelength conversion elements with air holes inside suffer from low use efficiency of excitation light and extraction efficiency of fluorescence due to internal scattering and reabsorption of light by the phosphor material.

Innovation Solution

A wavelength conversion element with a wavelength conversion layer that includes a scattering element no higher than 5% in volume ratio, and is configured with specific surfaces and refractive index layers to minimize internal reflection and reabsorption, thereby enhancing light emission efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If scattering elements such as air holes are included inside the wavelength conversion element, then light scattering is enhanced, but the use efficiency of excitation light and extraction efficiency of fluorescence decrease due to increased internal reflection and reabsorption

Engineering Contradiction:

Improvelight scatteringVSAvoiduse efficiency of excitation light and extraction efficiency of fluorescence

Core Design Contradiction:

Illumination intensityVSLoss of energy

Solution Approach 1:

The patent removes scattering elements (air holes) from the wavelength conversion element structure. By extracting the scattering function and replacing it with a flat, homogeneous wavelength conversion layer, the invention eliminates the harmful internal reflection and reabsorption caused by scattering elements, thereby improving light extraction efficiency while maintaining adequate light scattering through the layer's optical properties

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent employs a homogeneous wavelength conversion layer without internal scattering structures. The layer maintains uniform composition and refractive index throughout, eliminating the interfaces between phosphor material and air holes that cause total internal reflection. This homogeneity reduces light trapping and reabsorption, improving overall optical efficiency

Inventive Principle:

Principle #33Homogeneity

2Use of energy by moving object

If the wavelength conversion layer has high refractive index, then light conversion efficiency is improved, but light extraction from the layer becomes difficult due to total internal reflection at interfaces

Engineering Contradiction:

Improvewavelength conversion efficiencyVSAvoidlight extraction efficiency

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The patent introduces an intermediate layer with refractive index between that of the wavelength conversion layer and the surrounding medium. This intermediary layer acts as a refractive index bridge, reducing the abrupt refractive index mismatch at interfaces and minimizing total internal reflection, thereby improving light extraction efficiency while preserving the high refractive index benefits for wavelength conversion

Inventive Principle:

Principle #24Intermediary (Mediator)

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 proposed solution efficiently converts first light into second light with increased use efficiency of the excitation light and extraction efficiency of the fluorescence, preventing reabsorption and enhancing the overall light emission from the wavelength conversion element.

Implementation Method 1

a wavelength conversion layer configured to convert first light in a first wavelength band into second light in a second wavelength band different from the first wavelength band

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 2

an optical element including glass having a first refractive index lower than a second refractive index of the wavelength conversion layer

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 3

a low-refractive index layer having a third refractive index lower than the first refractive index of the glass

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS12321089B2Wavelength conversion element, light source device, and projector

Publication Date: 2025.06.03 SEIKO EPSON CORP

AI summary

A wavelength conversion element includes a wavelength conversion layer configured to convert first light in a first wavelength band into second light in a second wavelength band different from the first wavelength band, the wavelength conversion layer including a scattering element no higher than 5% in volume ratio and having a first surface, a second surface intersecting the first surface, and a third surface intersecting the second surface and different from the first surface, an optical element including glass having a first refractive index lower than a second refractive index of the wavelength conversion layer, the optical element having contact with the first surface and the second surface, and a low-refractive index layer having a third refractive index lower than the first refractive index of the glass, the low-refractive index layer having contact with the third surface.