Light Guiding Part Height Variation for Color Uniformity
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Solution Overview
Problem
Conventional light emitting devices exhibit color non-uniformity, which is a challenge for applications requiring consistent luminance and color output, such as vehicular headlamps.
Innovation Solution
A light emitting device comprising a semiconductor light emitting element, a phosphor plate with an inorganic material containing phosphor, and a light guiding part with varying heights to optimize light distribution and reduce color non-uniformity, along with a direct bonding method for thermal conductivity and efficient light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional light emitting device structure is used, then the device is simple to manufacture, but color non-uniformity occurs in the light output
Solution Approach 1:
The light guiding part is designed with varying heights at different locations to optimize light extraction. Specifically, the height from the lower face of the phosphor plate to the upper face of the light guiding part is greater at both ends than at the center, creating local variations in light path length that improve color uniformity across the emission surface.
Solution Approach 2:
The light guiding part employs an asymmetric height distribution pattern where the central region has a different height compared to the end regions. This asymmetric design compensates for non-uniform light distribution, ensuring consistent color output across the entire emission area while maintaining a relatively simple overall structure.
2Illumination intensity
If the phosphor plate lower face is made larger than the light emitting element upper face, then light extraction is improved, but thermal conductivity may be reduced
Solution Approach 1:
The phosphor plate is designed with a larger lower face area compared to the upper face, creating a tapered structure. This geometric parameter change increases the light extraction area while the direct bonding method compensates for any thermal conductivity reduction by ensuring intimate contact between components.
Solution Approach 2:
The light guiding part acts as an intermediary structure between the phosphor plate and the external environment. It manages both light extraction and thermal pathways, allowing the phosphor plate to have optimized light extraction geometry while maintaining effective thermal conduction through the bonded interface with the light emitting element.
3Loss of energy
If direct bonding is used between phosphor plate and light emitting element, then thermal conductivity is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The phosphor plate is designed with predetermined larger dimensions at the lower face to facilitate direct bonding. This preliminary design consideration ensures that even with manufacturing tolerances, the bonding interface achieves sufficient contact area for effective thermal conduction while maintaining alignment with the light emitting element.
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 achieves reduced color non-uniformity and enhanced luminance by ensuring uniform light distribution and thermal conductivity, making it suitable for high-luminance applications like vehicular headlamps.
Implementation Method 1
The phosphor plate is configured with an inorganic material containing a phosphor
Implementation Method 2
The light guiding part covers the lateral faces of the light emitting element and the lower face of the phosphor plate
Implementation Method 3
The light guiding part has a height hd defined in a cross section perpendicular to the lower face that includes one of the two diagonal lines of the rectangular shape at a position farthest from the light emitting element
Implementation Method 4
bonding the lower face of the phosphor plate and the upper faces of the plurality of light emitting elements by direct bonding
Data Source
AI summary
A light emitting device including: a light emitting element, a phosphor plate, and a light guiding part. The lower face of the light emitting element has a rectangular shape. The light guiding part covers lateral faces of the light emitting element and the lower face of the phosphor plate that is exposed from the light emitting element. The light guiding part has one or more lateral faces having at least one of structures below: a height at both ends being different from the height at a central area; outer lateral faces being parallel to the lateral faces of the light emitting element.