Light Guide Glare Reduction in LED Filament Devices
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Solution Overview
Problem
LED-based lighting devices often produce uncomfortable glare when the intensity of the light emitted by the LED filament is high, which limits their use in applications where a softer brightness transition is desired, such as decorative lighting.
Innovation Solution
A light-emitting device comprising a transparent light exit window and a light guide with incoupling and outcoupling features that control the luminous flux, allowing the light guide to appear frosted and reducing glare by superimposing a second light output onto the first, thereby creating a softer brightness transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the intensity of light emitted by the LED filament is increased, then the luminous flux is improved, but glare is produced for the viewer
Solution Approach 1:
A light guide is introduced as an intermediary between the LED filament and the viewer. The light guide receives light from the LED filament via total internal reflection and outcouples it along its entire length, transforming the point-source glare into a distributed, softer light output that maintains high luminous flux without causing uncomfortable glare
Solution Approach 2:
The light output is transformed from a concentrated directional beam (1D/2D) into a distributed linear source along the light guide (1D extension). This dimensional transformation spreads the light over a larger spatial area, reducing intensity concentration and eliminating glare while preserving total luminous flux
2Object-affected harmful factors
If the LED filament emits light at low intensity, then glare is reduced, but the luminous flux is limited
Solution Approach 1:
The light guide acts as a mediator that decouples the relationship between LED intensity and perceived brightness. It allows the LED to operate at high intensity for maximum luminous flux while the light guide distributes this light softly along its length, preventing glare and enabling simultaneous achievement of high flux and comfortable viewing
Solution Approach 2:
The light output is segmented and distributed along the entire length of the light guide rather than concentrated at a single point. This segmentation of the light source into multiple outcoupling points along the guide creates a softened, diffuse appearance that reduces glare while maintaining high overall luminous flux
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 effectively reduces glare and contrast between the light emitted by the LED filament and its surroundings, enabling the light-emitting device to operate at higher luminous flux levels without causing discomfort, while maintaining a soft appearance similar to a frosted lamp.
Implementation Method 1
The light guide comprises at least one internal surface adapted for internal reflection of the incoupled light within the light guide
Data Source
AI summary
A light-emitting device (1) is provided. The light-emitting device (1) comprises a transparent light exit window (10), and a light-emitting diode, LED, filament (2) adapted for emitting a first light output along one or more light output directions through the transparent light exit window (10). The light-emitting device (1) comprises a light guide (3). The light guide (3) comprises an incoupling feature (4), configured for receiving light emitted by a light source (2, 7) and for coupling of the light emitted by the light source (2, 7) into the light guide (3). The light source (2, 7) comprises or is constituted by at least one of the LED filament (2) or a separate light source (7) comprised in the light-emitting device (1). The light guide (3) further comprises at least one internal surface (5) adapted for internal reflection of the incoupled light within the light guide (3), and an outcoupling feature (6) configured for outcoupling of light having been internally reflected within the light guide (3) from the light guide (3) thereby emitting a second light output, the second light output being superimposed onto the first light output when viewed along the one or more light output directions.