Light Emitting Device Slanted Incoupling Edge
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Solution Overview
Problem
Existing edge-lit light emitting devices face challenges in using thinner light guides than the smallest width of the LED light source, leading to light leakage and an uncontrolled ratio of upward and downward light flux, which increases cost, weight, and thickness.
Innovation Solution
A light emitting device with a light guide that incorporates a linear refractive and/or reflective optical element to shape and focus leaked light, allowing for controlled light leakage and configuration of light output direction, using angles less than 90 degrees for the light incoupling edge and emitting surface relative to the plane, enabling effective use of otherwise lost light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the light guide thickness is reduced to reduce cost and weight, then the luminaire thickness is reduced, but the light guide cannot be thinner than the LED width for proper light incoupling
Solution Approach 1:
The patent transforms the light incoupling problem from a two-dimensional planar interface to a three-dimensional slanted interface. By inclining the light incoupling edge at 45 degrees relative to the light guide thickness direction, the effective incoupling area increases by a factor of √2, enabling thinner light guides (3-4mm) to accommodate standard LED sizes while maintaining proper light coupling.
Solution Approach 2:
The patent changes the geometric parameters of the light incoupling edge from a vertical orientation to a slanted orientation at 45 degrees. This parameter change increases the incoupling surface area without increasing the light guide thickness, allowing the use of thinner light guides while maintaining effective light coupling from LEDs of standard sizes.
2Area of stationary object
If slanted incoupling edges are used to accommodate larger LEDs in thinner guides, then the incoupling surface area increases, but a fraction of light (1 - 1/√2) cannot be coupled into the light guide and is lost
Solution Approach 1:
The patent converts the previously harmful light leakage into a beneficial indirect lighting component. The slanted incoupling edge that causes light to leak out at 45 degrees is now utilized to create a controlled indirect light output, which can be directed to reflective surfaces or used for ambient illumination, transforming energy loss into useful lighting functionality.
Solution Approach 2:
The patent changes the orientation of the light incoupling edge to 45 degrees, which simultaneously increases the incoupling surface area by √2 and directs the leaked light at a controlled 45-degree angle. This parameter change allows the previously lost light to be systematically redirected for useful purposes rather than being wasted.
3Length of stationary object
If the light guide thickness is reduced below LED width, then cost and weight are reduced, but the ratio of upward to downward light flux becomes uncontrolled
Solution Approach 1:
The patent introduces controllable parameters (reflector geometry, diffuser properties, extraction feature distribution) that allow adjustment of the upward-to-downward light flux ratio. By modifying these parameters, the system can be tuned to achieve desired lighting distributions while maintaining thin light guide dimensions.
Solution Approach 2:
The patent introduces intermediate optical elements (reflectors, diffusers, extraction features) between the light source and the final light output. These intermediaries control and distribute the light flux in predetermined ratios, enabling versatile lighting configurations while using thin light guides.
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
Enables the use of thinner light guides without compromising light output, achieving controlled light leakage and reduced cost, weight, and thickness by utilizing the leaked light for indirect lighting or reflective surfaces, while maintaining desired light output ratios.
Implementation Method 1
a linear refractive and/or reflective optical element arranged and adapted for shaping the fraction of the light emitted by the light source which is not coupled into the light guide
Implementation Method 2
a linear refractive and/or reflective optical element arranged and adapted for shaping the fraction of the light emitted by the light source which is not coupled into the light guide
Data Source
Figure 1~2
Figure 3~5
Figure 6A~6B
AI summary
A light emitting device (1) comprising at least one light source (2) adapted for, in operation, emitting light, the at least one light source (2) comprising a light emitting surface (21), and a light guide (3) comprising a top surface (31), a bottom surface (32) and a light incoupling edge (33) extending between the top surface (31) and the bottom surface (32), where a plane (4) is defined as extending in parallel with at least one of the top surface (31) and the bottom surface (32) of the light guide (3), where the at least one light source (2) and the light guide (3) is arranged in such a way with respect to each other that the light emitting surface (21) of the at least one light source (2) and the light incoupling edge (33) of the light guide (3) face each other, that the light incoupling edge (33) of the light guide (3) extends in a first angle (α) with respect to said plane (4), and that the light emitting surface (21) of the at least one light source (2) extends in a second angle (β) with respect to said plane (4), and that at least one of the first angle (α) and the second angle (β) is less than 90°, and where the light emitting device (1) further comprises a linear refractive and/or reflective optical element (6) arranged and adapted for shaping the fraction of the light emitted by the light source (2) which is not coupled into the light guide (3) and/or which leaks out of the top surface (31) of the light guide (3) into a focused light beam propagating above the top surface (31) of the light guide (3) in an acute angle with said plane (4).