Laser Activated Remote Phosphor Homogeneity via Radial Gradient
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Solution Overview
Problem
Laser Activated Remote Phosphor (LARP) systems in vehicle headlights suffer from color inhomogeneity due to blue-yellow rings and spatial dependence of color location, leading to undesirable color variations on irradiated surfaces.
Innovation Solution
A LARP system with a symmetrical excitation radiation source and a conversion element, where the central excitation spot exceeds the conversion element's boundary, ensuring a homogeneous light emission by balancing unconverted and converted radiation ratios across the emission area, and optionally using a transmission element with passage cutouts or a non-transparent structure to enhance homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a laser diode is used as excitation source with a conversion element (phosphor) to generate useful light, then the system achieves high efficiency and compact design, but color inhomogeneity (blue-yellow rings) occurs due to spatial variation in conversion efficiency
Solution Approach 1:
The patent applies local quality by varying the phosphor concentration or composition in different regions of the conversion element. Specifically, the phosphor concentration is adjusted radially to compensate for the excitation intensity distribution, ensuring uniform color output across the emission surface despite the non-uniform laser excitation profile.
Solution Approach 2:
The patent changes physical parameters of the conversion element, particularly the phosphor concentration distribution and particle size distribution, to optimize the conversion efficiency spatially. By controlling these parameters during manufacturing, the system achieves homogeneous color output while maintaining high overall conversion efficiency.
2Productivity
If the excitation spot is focused tightly on the conversion element to maximize conversion efficiency, then energy efficiency improves, but color locus variation increases due to non-uniform excitation distribution
Solution Approach 1:
The patent implements local quality by creating radial gradients in phosphor concentration within the conversion element. The central region has different phosphor concentration compared to the peripheral regions, matching the excitation intensity profile to achieve uniform color output across the emission surface.
Solution Approach 2:
The patent uses composite materials with spatially varying composition - specifically, a phosphor matrix with non-uniform distribution of phosphor particles or varying phosphor concentration. This composite structure enables different local conversion efficiencies to compensate for the non-uniform excitation light distribution.
3Power
If optical elements (reflectors and lenses) are added to focus excitation radiation, then conversion efficiency improves, but device complexity increases
Solution Approach 1:
The patent applies self-service by designing the conversion element itself to perform the function of uniformizing the light output. The non-uniform phosphor distribution within the conversion element automatically compensates for the non-uniform excitation profile, eliminating the need for additional optical homogenization elements and reducing system complexity.
4Quantity of substance
If the conversion element size is increased to cover the excitation spot, then conversion efficiency improves, but color locus dependence on viewing angle increases
Solution Approach 1:
The patent applies local quality by varying phosphor concentration radially across the conversion element. This radial gradient in phosphor distribution compensates for the geometric effects that cause viewing angle dependence, maintaining consistent color output across different observation angles.
Solution Approach 2:
The patent transitions from considering only the two-dimensional excitation plane to incorporating the third dimension of viewing angle. By designing the phosphor distribution in three-dimensional space (radial and axial variations), the system achieves viewing angle independence while maintaining efficient conversion across the entire phosphor volume.
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 a low spatial variance in color coordinates, reducing the blue-yellow ring issue and improving light homogeneity, thereby minimizing color locus variations and simplifying optical system design with reduced efficiency loss.
Implementation Method 1
a conversion element, which is arranged at a distance from a radiation source and comprises or consists of a phosphor, is irradiated with an excitation radiation... The excitation radiation of the excitation beam is at least partially absorbed by the phosphor and at least partially converted into conversion radiation
Implementation Method 2
The excitation radiation of the excitation beam is at least partially absorbed by the phosphor and at least partially converted into conversion radiation
Data Source
Figure 1~4
AI summary
A Laser Activated Remote Phosphor (LARP) system is disclosed, featuring a radiation source that emits excitation radiation. A conversion element containing a phosphor is provided for the partial conversion of the excitation radiation. The diameter of the excitation spot is larger than the diameter of the conversion element.