Wavelength-Converting Device Brewster Angle Optimization
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Solution Overview
Problem
Conventional wavelength-converting devices, such as phosphor wheels, face challenges with high optical loss due to light leakage caused by the Brewster angle effect, especially when incidence angles exceed 35.5 degrees, leading to inefficient light reflection and increased fabrication complexity.
Innovation Solution
A wavelength-converting device is designed with a transmissive substrate and an optical layer, where the refraction coefficients satisfy the conditions θC=sin−1(namb/ns) and nr>2(namb^2)/ns, ensuring the Brewster angle is greater than the critical angle, allowing for total reflection and reducing light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional phosphor wheel with a reflection layer is used to convert laser light into color light, then wavelength conversion is achieved, but light leakage occurs due to the Brewster angle effect causing energy loss
Solution Approach 1:
The patent changes the refractive index parameter of the substrate material to satisfy the condition nr>2(namb2)/ns, which ensures the Brewster angle is greater than the critical angle. This parameter change eliminates the Brewster angle light leakage problem while maintaining total internal reflection for omnidirectional light emission from the phosphor layer.
2Reliability
If a multilayer reflection mirror structure is used to reflect light at large incidence angles, then reflection capability is improved, but fabrication complexity significantly increases
Solution Approach 1:
The patent extracts and eliminates the complex multilayer reflection mirror structure by using a single substrate with specifically selected refractive index. The substrate alone provides both total internal reflection for omnidirectional light and proper reflection at large incidence angles, removing the need for additional multilayer mirror components.
3Use of energy by moving object
If the Brewster angle effect is considered in the reflection layer design, then P-polarized light transmission is improved, but light leakage occurs at incidence angles greater than or equal to the Brewster angle
Solution Approach 1:
The patent changes the substrate refractive index to satisfy nr>2(namb2)/ns, which ensures the Brewster angle is greater than the critical angle. This parameter change allows P-polarized light transmission at smaller angles while preventing light leakage at larger angles through total internal reflection, eliminating the energy loss problem.
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
This configuration enhances light reflection efficiency, simplifies the fabrication process, and reduces material selection difficulties by minimizing light loss and optimizing the reflection of broad incidence angles.
Implementation Method 1
a phosphor layer for converting first waveband light into second waveband light
Implementation Method 2
the Brewster angle is greater than the critical angle, allowing for total reflection
Implementation Method 3
considering the Brewster angle (θB=tan−1(n2/n1)) effect of the incident environment n1 and the transmissive environment n2
Data Source
AI summary
An illumination device includes a solid-state light-emitting element, and a wavelength-converting device with a transmissive substrate, a phosphor layer and a reflective optical layer. The transmissive substrate has a refraction coefficient ns greater than an ambient refraction coefficient namb. The phosphor layer is disposed over a side of the transmissive substrate and the reflective optical layer is disposed over a side of the transmissive substrate opposite to the phosphor layer. The reflective optical layer has an effective refraction coefficient nr. The relation between ns, namb and nr is given by nr>2(namb2)/ns.