Immersed LED Reflector Collimation for Optical Efficiency
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Solution Overview
Problem
Light emitting diodes (LEDs) immersed in a glass-like medium suffer from total internal reflection, leading to low optical efficiency and uncontrolled glare due to light being absorbed or scattered at high densities, which is unacceptable for illumination purposes.
Innovation Solution
Incorporating a reflective collimator with a shape such as a truncated cone or compound parabolic concentrator within the LED package to collimate light, reducing total internal reflection and directing light emission within a preferred angular range, thereby increasing optical efficiency and reducing glare.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LEDs are immersed in a glass-like medium (supporting layer with refractive index > 1), then the construction durability and integration in transparent surfaces are improved, but total internal reflection occurs at the interface between the supporting layer and surrounding air, causing light to be reflected and absorbed, which reduces optical efficiency
Solution Approach 1:
The patent introduces a reflector as an intermediary element between the LED and the supporting layer interface. This reflector captures light that would otherwise undergo total internal reflection at the glass-air interface and redirects it back into the LED package, converting the harmful reflected light into useful emitted light and thereby improving optical efficiency while maintaining the durable immersed construction
Solution Approach 2:
The patent converts the harmful effect of total internal reflection into a beneficial effect by using the reflected light to illuminate the reflector's inner surface. The reflector then redirects this previously wasted light back toward the viewing direction, transforming energy loss into useful light output and improving overall system efficiency
2Illumination intensity
If LEDs are arranged at high densities (>0.5 cm−2) in the glass stack, then the light emission intensity is improved, but totally reflected light scatters at neighbouring packages, leading to unpredictable light outcoupling and uncontrolled glare
Solution Approach 1:
The patent applies local quality by giving each LED package its own dedicated reflector with specific geometric properties. This localized reflector ensures that light from each LED is collimated and directed in a controlled manner, preventing light from one package from interfering with adjacent packages even at high densities, thereby maintaining predictable light outcoupling and controlled glare
Solution Approach 2:
The patent segments the light management function by providing individual reflectors for each LED package rather than using a common light management structure. This segmentation isolates the optical paths of adjacent LEDs, preventing cross-interference and enabling high LED densities while maintaining controlled glare through predictable, package-specific light outcoupling
3Device complexity
If no light management structure is used for immersed LEDs, then the construction simplicity is improved, but there are no means to stop light from exiting the LED-array system in unwanted directions, resulting in unacceptable glare for illumination purposes
Solution Approach 1:
The patent changes the geometric parameters of the reflector (such as its angle, height, and shape) to control the directionality of emitted light. By optimizing these parameters, the reflector collimates light within a desired angular range while preventing light from exiting in unwanted directions, thereby controlling glare without requiring complex additional light management structures
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 significantly enhances optical efficiency and controls glare, ensuring that light is emitted within a desired directional cone, maintaining acceptable luminance levels below 500 cd/m2, while also providing a durable and aesthetically pleasing transparent luminaire.
Implementation Method 1
total internal reflection (TIR) occurs at the interface between the glass surface and the surrounding air. A consequence is that light with angles larger than the critical angle is totally reflected at the glass/air interface
Implementation Method 2
a reflector having a reflective surface for collimating the light emitted by the LED
Data Source
AI summary
The present invention relates to a LED-array system (202) comprising at least one LED package (200), said at least one LED package comprising a LED (204) and being arranged on a substrate (206) provided with means (208) for supplying the LED package (200) with a drive voltage, wherein said at least one LED package is immersed in a supporting layer (212) covering the substrate plate (206). In order to improve optical efficiency and reduce glare the LED package also comprises a reflector (220) having a reflective surface for collimating the light emitted by the LED (204). The invention also relates to lighting systems comprising the LED-array system and a method for producing said LED-array system.