Variable Planar Light Guide Module for Inclined Automotive Lamps
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Solution Overview
Problem
Current planar light guide technologies suffer from low optical efficiency when the output wall is not perpendicular to the longitudinal axis of a vehicle, as they rely on Fresnel reflection instead of total internal reflection, leading to inefficient light directionality in automotive lamps that are not oriented perpendicular to the vehicle's axis.
Innovation Solution
A variable planar light guide module with prismatic structures on both walls of the light guide, using the principle of total internal reflection to redirect light towards the longitudinal axis, combined with an array of reflectors and LEDs for efficient light distribution, allowing placement in any orientation while maintaining directional light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the output wall of the light guide is placed perpendicular to the longitudinal axis of the vehicle, then the optical efficiency is high with TIR reflection, but the lamp cannot be placed in inclined orientations required by automotive lighting functions
Solution Approach 1:
The light guide is divided into multiple functional segments: an input wall for light coupling, an output wall for light emission, and at least one intermediate wall with decoupling elements (prismatic structures) positioned between them. This segmentation allows the output wall to be oriented at inclined angles while intermediate walls with TIR-based decoupling elements maintain efficient light extraction regardless of the output wall's orientation relative to the vehicle's longitudinal axis.
Solution Approach 2:
The patent introduces intermediate walls with decoupling elements as a new dimensional layer between the input and output walls. These intermediate structures provide TIR-based light extraction in a direction perpendicular to the output wall's orientation, effectively decoupling the light extraction function from the output wall's angular position and enabling inclined placements while maintaining optical efficiency.
2Adaptability or versatility
If the light guide is placed at an inclined angle to the longitudinal axis, then the lamp can fulfill automotive lighting functions, but the optical efficiency drops rapidly due to Fresnel reflection instead of TIR
Solution Approach 1:
The light guide is divided into multiple functional segments: an input wall for light coupling, an output wall for light emission, and at least one intermediate wall with decoupling elements (prismatic structures) positioned between them. This segmentation allows the output wall to be oriented at inclined angles while intermediate walls with TIR-based decoupling elements maintain efficient light extraction regardless of the output wall's orientation relative to the vehicle's longitudinal axis.
Solution Approach 2:
Intermediate walls with TIR-based decoupling elements act as intermediary structures between the light source and the output wall. These intermediaries extract light via total internal reflection at angles optimized for TIR, independent of the output wall's orientation, thereby maintaining high light extraction efficiency even when the output wall is inclined relative to the vehicle's longitudinal axis.
3Adaptability or versatility
If prismatic structures are designed for Fresnel reflection to handle inclined orientations, then the lamp can be placed at various angles, but only 5%-20% of light is reflected to the output wall
Solution Approach 1:
The patent replaces Fresnel reflection-based decoupling with total internal reflection-based decoupling using prismatic structures on intermediate walls. TIR provides near-100% light reflection efficiency compared to only 5%-20% with Fresnel reflection, thereby substituting a low-efficiency optical mechanism with a high-efficiency one while maintaining the capability to handle inclined orientations through proper geometric design of the intermediate walls.
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 light emission efficiency in non-perpendicular orientations, meeting legal requirements for rear position lights by ensuring 100% reflection via total internal reflection, even at inclined angles, thereby improving the overall optical system performance.
Implementation Method 1
Light guide techniques are based on the total internal reflection (TIR) principle, which is caused by two materials with different refractive indices. coupled light 201 from a light source 200 goes through a translucent light guide 202 by TIR
Implementation Method 2
In the case of Fresnel reflection, only approximately 5%-20% of the light is reflected to the output wall
Data Source
AI summary
A light guide and module for motor vehicles that directs light generally along a horizontal axis. The module includes an array of light sources, an array of reflectors and a light guide. The light guide defines a body having opposed upper and lower walls. Formed in the lower wall is at least one prismatic structure having a reflecting surface oriented to reflect light based the principle of total internal reflection and to redirect light toward the upper wall. Formed in the upper wall is at least one decoupling prism element. The decoupling prism elements corresponding in number to the prismatic structures and are located in the upper wall so as to receive redirected light from its corresponding prismatic structures. The decoupling prism element includes a second reflecting surface that reflects light redirected from the first reflecting surface. This second reflecting surface reflects light toward an output surface of the decoupling prism element based on the principle of total internal reflection and defines a vertical spread of light. With the present invention, light emitted from the output surface of the decoupling prism element can be directed generally along the horizontal axis when the upper surface is oriented significantly less than 90° relative to the horizontal axis.