Light Source Secondary Emitter Uniform Color Temperature
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Solution Overview
Problem
Conventional high flux density solid state light generators, particularly LEDs with luminescent phosphor coatings, struggle to maintain a constant correlated color temperature across different viewing angles due to non-uniform phosphor coating application, leading to varying color temperatures when viewed straight on versus wider angles.
Innovation Solution
A light source comprising a primary excitation source emitting electromagnetic radiation at a first peak wavelength, a secondary emitter conversion element that absorbs and emits radiation at a longer peak wavelength, and a non-imaging optical coupler to ensure consistent correlated color temperature white light emission, utilizing a ceramic substrate with phosphor materials for uniform light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a luminescent phosphor coating is applied on the LED die to convert light wavelength, then the light can be converted from one peak wavelength to another, but the correlated color temperature varies with viewing angle due to non-uniform coating application
Solution Approach 1:
The invention divides the phosphor conversion function into two separate components: a primary phosphor coating on the LED die and a secondary phosphor coating on a separate substrate. This segmentation allows each phosphor layer to be optimized independently, with the secondary phosphor layer compensating for angular color temperature variations and achieving uniform correlated color temperature across different viewing angles.
Solution Approach 2:
The invention introduces a secondary phosphor coating on a separate substrate as an intermediary element between the LED die and the viewer. This intermediary layer acts as a color temperature equalizer, absorbing excess blue light at certain angles and re-emitting it to maintain consistent correlated color temperature regardless of viewing angle.
2Ease of manufacture
If conventional phosphor coating methods are used on LED dice, then the manufacturing process is simple, but it is difficult to apply the coating uniformly resulting in varying color temperature
Solution Approach 1:
The invention separates the phosphor conversion function into two independent coating applications: one on the LED die and another on a separate substrate. This allows each coating to be applied using simple conventional methods while achieving overall uniformity through the combined effect of both layers, rather than requiring a single complex uniform coating.
Solution Approach 2:
The invention changes the spatial distribution parameters of the phosphor coating by applying it in two separate locations (on the LED die and on a separate substrate). This parameter change allows the system to achieve uniform correlated color temperature output without requiring either individual coating to be perfectly uniform, thus maintaining ease of manufacture while improving precision.
3Use of energy by moving object
If LEDs are used to provide specific peak wavelengths, then the light generation is efficient, but it has been difficult to maintain a constant correlated color temperature radiation
Solution Approach 1:
The invention segments the color temperature control function into two independent phosphor layers, allowing the LED die to maintain its efficient wavelength conversion while the secondary phosphor layer on the separate substrate compensates for angular variations. This segmentation preserves the high efficiency of LED light generation while achieving constant correlated color temperature radiation across different viewing angles.
Solution Approach 2:
The invention changes the angular distribution parameters of the phosphor conversion by using a secondary coating on a separate substrate. This allows the system to maintain the efficient peak wavelength conversion of the LED while adjusting the overall correlated color temperature output to remain constant regardless of viewing angle, resolving the contradiction between efficiency and constancy.
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 highly consistent correlated color temperature white light source across various angles by using a secondary emitter conversion element with a ceramic substrate and non-imaging optical coupler, enhancing color rendering index and maintaining uniformity in light output regardless of LED die variations.
Implementation Method 1
Light having a first peak wavelength ('primary light') can be converted into light having a longer peak wavelength ('secondary light') using a process known as luminescence. The luminescent process involves absorbing the primary light by a photoluminescent phosphor material, which excites the atoms of the phosphor material, and emits the secondary light.
Implementation Method 2
The luminescent process involves absorbing the primary light by a photoluminescent phosphor material, which excites the atoms of the phosphor material, and emits the secondary light.
Data Source
AI summary
A light source is disclosed. The light source includes a primary excitation source configured to emit electromagnetic radiation at a first peak wavelength and a band of wavelengths around the first peak wavelength. A secondary emitter conversion element is optically coupled to the primary excitation source and is configured to absorb at least a portion the electromagnetic radiation at the first peak wavelength from the primary excitation source and emit electromagnetic radiation at a second peak wavelength and a band of wavelengths around the second peak wavelength. The second peak wavelength is longer than the first peak wavelength. A non-imaging optical coupler is optically coupled to the secondary emitter conversion element. An optical system includes the light source optically coupled to a transparent rod.