Remote Phosphor Light Emitting Device with Optical Redirect Structure
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Solution Overview
Problem
The efficacy of light emitting devices is reduced due to the absorption of secondary light emitted by phosphors back into the primary light source, which is not optimally addressed by existing technologies that rely on intermediate layers or materials for reflection.
Innovation Solution
A light emitting device design featuring a primary light source, a light converting medium with a curved or dome-shaped configuration, and an optical structure that redirects secondary light away from the primary light source, eliminating the need for intermediate layers and enhancing luminous efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If phosphor is placed close to LED die for conversion, then device structure is simplified, but secondary light absorption by LED die increases significantly
Solution Approach 1:
A transparent intermediate layer with optimized refractive index is introduced between the LED die and phosphor. This intermediary layer reduces total internal reflection at the interfaces, enabling more secondary light to escape the phosphor layer without being absorbed by the LED die, thus resolving the contradiction between structural simplicity and energy loss.
Solution Approach 2:
The refractive index of the intermediate layer is specifically optimized to match the optical properties of adjacent layers. By changing this physical parameter, the optical impedance mismatch is reduced, minimizing light reflection and absorption losses while maintaining the compact device structure.
2Loss of energy
If additional reflective layer is added between LED die and phosphor, then secondary light absorption is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The transparent intermediate layer serves multiple functions simultaneously: it acts as an optical impedance matcher to reduce reflection, provides mechanical support, and facilitates phosphor deposition. This multi-functionality eliminates the need for separate reflective layers, reducing device complexity while still preventing secondary light absorption.
3Productivity
If phosphor layer thickness is increased to improve conversion, then light conversion efficiency improves, but secondary light emission in all directions increases absorption losses
Solution Approach 1:
The transparent intermediate layer with optimized refractive index acts as an optical mediator that enables preferential escape of secondary light in forward directions while suppressing backward emission toward the LED die. This allows thicker phosphor layers to be used for improved conversion efficiency without proportionally increasing absorption losses from isotropic emission.
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
This design significantly reduces absorption losses by redirecting secondary light away from the primary light source, thereby improving the overall efficacy of the light emitting device without requiring additional materials or layers.
Implementation Method 1
The light converting medium is arranged for converting at least a part of the primary light to secondary light of a wavelength different from the wavelength of the primary light
Implementation Method 2
The optical structure is arranged for receiving a part of the secondary light from the light converting medium and is configured for redirecting the part of the secondary light in a direction towards the first plane and away from the primary light source
Implementation Method 3
The reflector is provided on or over the first plane for receiving the part of the secondary light redirected by the optical structure
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4B
AI summary
The invention relates to a light emitting device (2) comprising a primary light source (10), a light converting medium (14) and an optical structure (16). The primary light source is disposed on a substrate (11). The light converting medium comprising phosphors (14) is arranged for converting at least a part of the primary light to secondary light (II) of a different wavelength. The light converting medium is in a remote phosphor configuration. The optical structure is arranged for receiving a part of the secondary light (II) from the light converting medium and is configured for redirecting the part of the secondary light in a direction towards the first plane but away for the primary light source (10). By providing an optical structure redirecting the secondary light away from the primary light source, absorption of the secondary light by the primary light source can be substantially reduced or eliminated. The luminous efficacy is improved by redirecting this secondary light in a direction such that it is transmitted from the light emitting device.