Fluorescence Light Source With Periodic Structure Aspect Ratio
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Solution Overview
Problem
Fluorescence light source devices face issues with temperature rise, excitation light reflection, and inefficient fluorescence emission due to the use of phosphors with low thermal conductivity and complex structures, leading to poor luminous efficacy and limited etendue.
Innovation Solution
A fluorescence light source device with a phosphor member having a periodic structure layer made of high refractive index material, featuring conical or truncated projections with an aspect ratio of 0.5 to 0.9, formed by etching, which reduces temperature rise and excitation light reflection while enhancing fluorescence extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phosphor is dispersed in a sealing material with low thermal conductivity, then the phosphor can be protected and positioned, but the heat generated in the phosphor cannot be transmitted effectively, resulting in elevated temperature and temperature quenching
Solution Approach 1:
The wavelength conversion member is divided into distinct functional layers: a phosphor layer containing the phosphor particles, and a separate heat-dissipating member with high thermal conductivity. This segmentation allows the phosphor to be protected in its own layer while heat is efficiently conducted away through the dedicated heat-dissipating member, resolving the contradiction between protection and heat transmission.
Solution Approach 2:
A heat-dissipating member with high thermal conductivity is introduced as an intermediary between the phosphor and the external environment. This intermediary component specifically addresses the heat transmission problem by providing a thermal conduction path without interfering with the phosphor's protective encapsulation, enabling effective heat removal while maintaining phosphor integrity.
2Device complexity
If excitation light is irradiated onto a flat surface of a fluorescence member, then the structure is simple, but excitation light reflects off the surface, causing insufficient light introduction and poor luminous efficacy
Solution Approach 1:
The flat surface of the wavelength conversion member is replaced with a curved surface having a specific radius of curvature. This curvature causes incident excitation light to be reflected at various angles rather than uniformly, reducing the amount of light reflected back and increasing the portion that enters the phosphor layer. This resolves the contradiction by maintaining structural simplicity while significantly reducing energy loss through reflection.
3Quantity of substance
If the wavelength conversion member has a large size to accommodate the phosphor, then the phosphor can be fully utilized, but the etendue is limited and fluorescence cannot be used effectively
Solution Approach 1:
The curved surface with specific radius of curvature refracts and directs fluorescence light at optimized angles, improving light extraction efficiency. This allows effective utilization of fluorescence from a compact phosphor layer without requiring a large overall device size, thereby maintaining small etendue while fully utilizing the phosphor material.
Solution Approach 2:
The radius of curvature parameter is optimized to balance phosphor utilization and etendue. By carefully selecting this geometric parameter, the device achieves high phosphor utilization efficiency while maintaining a compact form factor with small etendue, resolving the contradiction between quantity and adaptability.
4Device complexity
If a heat-dissipating member is provided only on the peripheral part of the back surface, then the structure is simple, but the contact area is small and heat transmission distance is long, resulting in insufficient heat dissipation
Solution Approach 1:
The entire back surface of the wavelength conversion member is made to have high thermal conductivity, making the whole back surface functional for heat dissipation. This multi-functional approach allows the back surface to simultaneously serve as both the structural support and the heat-dissipating interface, eliminating the need for separate heat-dissipating components while achieving superior heat dissipation efficiency.
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 effectively suppresses temperature increase, reduces excitation light reflection, and improves fluorescence emission efficiency, resulting in high luminous efficacy and effective use of generated fluorescence.
Implementation Method 1
an uneven structure is formed on an excitation-light receiving surface of a wavelength conversion member. This uneven structure reduces the reflection of excitation light off the excitation-light receiving surface
Implementation Method 2
the phosphor in the wavelength conversion member generates light in the green region upon irradiation of the wavelength conversion member with laser light in the blue region
Implementation Method 3
the substrate 42 is a Mo—Cu substrate, and a heat-dissipating fin 45 is disposed on the back surface of the substrate 42
Implementation Method 4
the heat generated in the phosphor upon irradiation with excitation light is less likely to be transmitted, which results in an elevated temperature of the phosphor itself
Data Source
AI summary
The fluorescence light source device of the present invention includes a fluorescence member formed from a phosphor composed of single crystal or polycrystal and excited by excitation light. A periodic structure layer made of a high refractive index material having a refractive index of not less than the refractive index of the fluorescence member is formed on the surface of the fluorescence member. The periodic structure layer has a surface with a periodic structure having a periodic array of conical or truncated projections and formed by an etching process. The aspect ratio which is a ratio of the height of the projections to the pitch in the periodic structure is within a range of 0.5 to 0.9.