Conversion Element with Radial Property Gradient for Homogeneous Illumination
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Solution Overview
Problem
Irradiation apparatuses with constant conversion or scattering properties across the emission surface lead to inhomogeneities, resulting in varying color impressions and inefficient light distribution, particularly in motor vehicle headlights, where disproportionate conversion radiation is present at the edge, causing a yellowish tint.
Innovation Solution
A conversion element with varying degrees of conversion and scattering, where the central portion of the pump radiation beam experiences higher conversion and scattering than the edge portion, ensuring a consistent color locus and reduced inhomogeneity across the emission surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conversion element with constant conversion or scattering properties is used, then the device structure is simple, but inhomogeneities occur in the emission surface leading to varying color impressions and inefficient light distribution
Solution Approach 1:
The conversion element is designed with spatially varying conversion and scattering properties. The scattering coefficient and/or conversion coefficient are made dependent on the radial distance from the beam center, creating local property variations that compensate for the non-uniform pump radiation intensity distribution. This results in a homogeneous emission surface with consistent color impression.
2Ease of manufacture
If constant conversion properties are used across the emission surface, then manufacturing is simplified, but edge regions exhibit disproportionate conversion radiation causing yellowish tint
Solution Approach 1:
The patent applies parameter changes by making the conversion coefficient and scattering coefficient spatially variable rather than constant. Specifically, these coefficients are designed to decrease with increasing radial distance from the beam center, compensating for the higher pump radiation intensity at the center and the lower intensity at the edges, thereby achieving uniform color output.
3Device complexity
If uniform conversion is applied across the beam, then the conversion element design is straightforward, but light losses increase due to inefficient distribution
Solution Approach 1:
By implementing local quality variations in the conversion element, the patent optimizes the conversion and scattering processes at different radial positions. This ensures that pump radiation is more efficiently converted and distributed, reducing unnecessary light losses while maintaining a relatively simple conversion element design.
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 achieves a homogeneous illumination with a consistent color impression and reduced light losses, simplifying downstream optical units and allowing for more compact designs, while maintaining high light density and efficiency.
Implementation Method 1
a conversion element for the at least partial conversion of the pump radiation to a conversion radiation
Implementation Method 2
a normalized degree of conversion and/or a normalized degree of scattering is lower for the second portion of the pump radiation than for the first portion of the pump radiation
Data Source
AI summary
An irradiation unit includes a pump radiation source for the emission of pump radiation; and a conversion element for the at least partial conversion of the pump radiation to a conversion radiation. During operation of the irradiation unit, the pump radiation is incident in the form of a beam from the pump radiation source on an incidence surface of the conversion element. A first portion of the pump radiation is incident on the conversion element in a central segment of the beam and a second portion of the pump radiation is incident on the conversion element in an edge segment of the beam surrounding the central segment. The conversion element is provided in such a way that a normalized degree of conversion and/or a normalized degree of scattering is lower for the second portion of the pump radiation than for the first portion of the pump radiation.