Diffusive Reflector for Light Guide Panel
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Solution Overview
Problem
Current methods for creating light extraction features on light guides, such as laser machining, screen printing, and injection molding, are expensive, serial in nature, and restrict the design and thickness of light panels, leading to high manufacturing costs and limitations in achieving uniform illumination.
Innovation Solution
A diffusive reflector with optically transmissive interface material and protrusions is used to increase the critical angle for total internal reflection, allowing for efficient light extraction without surface patterning on the light guide panel, utilizing a backing part with a diffusively reflective surface and interface material that reduces interfacial energy to drive air out and optically couple with the light guide panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If laser machining, screen printing, or injection molding is used to create light extraction features on the light guide panel surface, then light extraction is achieved, but manufacturing cost increases and production becomes serial and time-consuming
Solution Approach 1:
The invention extracts the light extraction function from the light guide panel surface itself and relocates it to a separate diffusive reflector component. This allows the light guide panel to be manufactured without time-consuming surface patterning, while the diffusive reflector handles light extraction through its inherently diffusive material properties.
Solution Approach 2:
The invention segments the lighting system into distinct functional components: a smooth light guide panel for light transmission and a separate diffusive reflector for light extraction and diffusion. This segmentation allows each component to be manufactured independently using optimized processes, eliminating the need for serial surface patterning operations.
2Loss of energy
If surface patterning is applied to the light guide panel, then light extraction features are created, but manufacturing complexity and cost increase
Solution Approach 1:
The invention extracts the light extraction function from the light guide panel surface itself and relocates it to a separate diffusive reflector component. This allows the light guide panel to be manufactured without time-consuming surface patterning, while the diffusive reflector handles light extraction through its inherently diffusive material properties.
Solution Approach 2:
Instead of modifying the light guide panel surface to extract light, the invention inverts the approach by using a separate component with inherently diffusive properties to perform the extraction function. The smooth light guide panel maintains total internal reflection, while the diffusive reflector positioned at the rear handles light extraction through its material characteristics.
3Illumination intensity
If traditional light extraction methods are used, then light can be extracted from the panel, but achieving uniform illumination becomes difficult and expensive
Solution Approach 1:
The diffusive reflector incorporates local variations in diffusive properties through its protrusion structure, creating zones of different light extraction efficiency. This allows optimization of light distribution across the panel surface to achieve uniform illumination without complex manufacturing processes.
Solution Approach 2:
The diffusive reflector acts as an intermediary between the light guide panel and the final illumination output. It receives concentrated light from the panel and redistributes it uniformly through its diffusive properties and protrusion geometry, simplifying the path to uniform illumination.
4Length of moving object
If the light guide panel is made thinner to reduce size, then compactness is improved, but manufacturing and handling become more difficult with traditional methods
Solution Approach 1:
By segmenting the light extraction function into a separate diffusive reflector component, the invention eliminates the need for complex surface patterning on thin light guide panels. This allows the panel to be manufactured as a simple, thin, smooth component that is easier to handle and process.
Solution Approach 2:
The invention changes the operational parameters of the light guide panel by maintaining a smooth surface without patterning, which simplifies manufacturing and allows for thinner designs. The light extraction parameters are instead controlled by the diffusive reflector's material properties and geometric structure.
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 approach enables effective light extraction and uniform illumination with reduced manufacturing costs and increased flexibility in panel design, allowing for thinner and more uniform light panels with improved brightness and efficiency.
Implementation Method 1
the interface part(s) comprises an optically transmissive interface material arranged to form said contact interface such that the interfacial energy thereof is reduced so that air is driven from the contact interface
Implementation Method 2
Light from one or more linear arrays/strips of multiple LEDs is injected into the slab at its edge from a single, multiple or all sides through simple butt coupling. Light guided within the panel by total internal reflection (TIR) is transmitted out of the panel
Implementation Method 3
The critical angle is defined by Snells law of specular reflection in terms of the refractive index (n1) of the panel material and the refractive index (n2) of the medium in immediate interface with the external surface of the panel adjacent the location of light reflection/transmission internally: θc=sin−1(n2/n1)
Implementation Method 4
A reflector sheet is placed at a back surface of light guiding panel. This reflects the light which has been transmitted out of the light guiding panel through its rear surface, back towards the front surface of the panel. A diffuser is placed at the front surface of the light guiding panel to receive the back-reflected light. It diffuses the transmitted light to create a substantially uniform illumination
Data Source
AI summary
A diffusive reflector for a lighting apparatus comprising a backing part upon a surface of which is disposed an interface part(s) wherein the interface part(s) is at least partially diffusively reflective optically and/or the backing part is diffusively reflective optically. The interface part(s) is formed with a plurality of separate protrusions each adapted for making a separate respective contact interface with a surface of a light guide panel of the lighting apparatus to optically couple the backing part to the light guide panel via the interface part(s). The interface part(s) comprises an optically transmissive interface material arranged to form said contact interface such that the interfacial energy thereof is reduced so that air is driven from the contact interface. Consequently, the critical angle for total internal reflection of light guided by the light guide panel is increased at said contact interface.