LED Brightness via Angular Light Recycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High power LED sources emit light in random directions, leading to significant light loss due to limited light collection capability, making them unsuitable for projection systems without enhancement.
Innovation Solution
An LED package design that includes an edge filter and diffuser to recycle light emitted at angles greater than a certain threshold, redirecting it back into the package and re-emitting it after changing its angle, combined with collimation optics like Compound Parabolic Concentrators or Brightness Enhancement Films to enhance brightness by matching light distribution with collection optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LED emits light in random directions to maximize total output flux, then the total light output is improved, but the collectible light within the projection aperture is lost
Solution Approach 1:
The patent converts the harmful effect of light emitting in unwanted directions into a beneficial recycling process. High-angle light that would normally be wasted is reflected by the edge filter and diffuser back toward the LED chip, where it has a chance to be re-emitted in a collectible direction. This transforms energy loss into a useful resource.
Solution Approach 2:
The patent implements a light recycling mechanism where light that would normally be discarded (high-angle emission) is recovered through reflection and diffusion. The edge filter and diffuser work together to capture and redirect this discarded light back into the optical path, allowing it to be reused and increasing the overall system efficiency.
2Device complexity
If collection optics are designed to capture light within a limited aperture, then the optical system is simplified, but significant light from the LED cannot be collected
Solution Approach 1:
The patent segments the light emission into two categories: low-angle light that passes through the edge filter directly, and high-angle light that is reflected and recycled. This segmentation allows the system to handle different light paths differently, maximizing collection efficiency without requiring complex optics for the entire system.
Solution Approach 2:
The edge filter and diffuser act as intermediary elements between the LED chip and the collection optics. These intermediaries modify the light distribution pattern, redirecting high-angle light into the collectible range without requiring the collection optics themselves to be complex or have a large aperture.
3Illumination intensity
If LED current density is increased to improve brightness, then the LED brightness is improved, but heat generation and efficiency degradation worsen
Solution Approach 1:
The patent implements an optical feedback loop where light that misses the collection aperture on its first emission is reflected back to the LED chip and given another chance to be emitted in a collectible direction. This feedback mechanism increases the effective utilization of generated light, allowing the system to achieve higher effective brightness without proportionally increasing current density and heat generation.
Solution Approach 2:
The recycling process extends the useful life of photons that would otherwise be lost. Instead of a single emission opportunity, light undergoes multiple potential emission cycles, continuously contributing to the useful light output. This increases overall system efficiency and reduces the need for higher current densities to achieve the same effective brightness.
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
Increases the apparent brightness of the LED source by recycling and re-directing previously wasted light into the projection system's aperture, enhancing the brightness and efficiency of LED light sources for projection systems.
Implementation Method 1
an edge filter that transmits light emitted from the LED chip having a first angle of incidence or less relative to the LED chip, and reflects light emitted from the LED chip having an angle of incidence relative to the LED chip greater than the first angle of incidence
Implementation Method 2
a diffuser disposed to receive light reflected from the edge filter
Data Source
AI summary
Light that is emitted from an LED chip at a first angle of incidence or less relative to the LED chip is permitted to leave the LED package. Light emitted from the LED chip at an angle of incidence greater than that is kept from leaving the LED package and is recycled back within the LED package. The recycled light is reemitted from the LED package after its angle of incidence relative to the LED chip has been changed, for example by passing it through a diffuser.