Automotive Lamp Lightguide Geometry for Hot-Spot-Free Outcoupling
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Solution Overview
Problem
Thin lightguides with constant cross-sections in the automotive industry often create illumination hot-spots due to the first outcoupling element reflecting significantly more light than subsequent elements, leading to uneven lighting.
Innovation Solution
A lightguide with a first outcoupling element featuring an elongated bottom part and diverging side walls, where the side walls are closer near the bottom and farther apart at their ends, and the bottom part is inclined towards the optical axis, reducing the brightness and spreading the light more evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the first outcoupling element is made as a simple indentation or cut in the lightguide surface, then the manufacturing is simple, but it creates a hot-spot with excessive brightness and uneven light distribution
Solution Approach 1:
The first outcoupling element is designed with a specific geometric structure comprising an elongated bottom part and two diverging side walls, creating different local optical properties at different positions. This localized structural differentiation causes light to be reflected and distributed more evenly, preventing hot-spot formation while maintaining manufacturing feasibility through standard molding or machining processes.
Solution Approach 2:
The invention changes the geometric parameters of the first outcoupling element by introducing an elongated bottom part and diverging side walls with specific angles. These parameter modifications alter the light reflection characteristics, spreading light over a larger area on the light-exit surface and reducing peak brightness, thereby eliminating the hot-spot effect.
2Use of energy by moving object
If the first outcoupling element reflects significantly more light than subsequent elements, then light extraction at the entry region is enhanced, but it creates visual inhomogeneity and hot-spot defects
Solution Approach 1:
The first outcoupling element is designed with a specific geometric structure comprising an elongated bottom part and two diverging side walls, creating different local optical properties at different positions. This localized structural differentiation causes light to be reflected and distributed more evenly, preventing hot-spot formation while maintaining manufacturing feasibility through standard molding or machining processes.
Solution Approach 2:
The invention changes the geometric parameters of the first outcoupling element by introducing an elongated bottom part and diverging side walls with specific angles. These parameter modifications alter the light reflection characteristics, spreading light over a larger area on the light-exit surface and reducing peak brightness, thereby eliminating the hot-spot effect.
3Illumination intensity
If the side walls of the first outcoupling element are made diverging with a smaller width at the bottom part, then light reflection area is increased and hot-spot is reduced, but the element geometry becomes more complex
Solution Approach 1:
The invention changes the geometric parameters of the first outcoupling element by introducing an elongated bottom part and diverging side walls with specific angles. These parameter modifications alter the light reflection characteristics, spreading light over a larger area on the light-exit surface and reducing peak brightness, thereby eliminating the hot-spot effect.
Solution Approach 2:
The diverging side walls create a tapered or conical geometry that gradually increases in width from the bottom part toward the opening. This curved or angled transition smoothly distributes light reflection across a larger area, reducing hot-spot brightness while maintaining a manufacturable form that can be achieved through standard molding or machining operations.
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 limits or eliminates the hot-spot, providing a more uniform light distribution across the light-exit surface by controlling the amount and area of light reflection.
Implementation Method 1
Each outcoupling element from the row is formed as an indentation on the lightguide's surface, e.g., a cut, depression, recess etc., having at least one wall or surface adapted to reflect light by total internal reflection
Implementation Method 2
The angled surfaces of the side walls limit the amount of the outcoupled light and/or spread the light over a larger area on the lightguide's light-exit surface, so the hot-spot is less bright
Data Source
Figure 1~2B
Figure 3
Figure 4A~4B
AI summary
A lightguide (1) for an automobile lamp. The lightguide (1) comprises a I ight-entry surface and a row of outcoupling elements oriented along the lightguide's (1) optical axis (2). The first outcoupling element (3) in the row, which is closest to the light-entry surface, comprises an elongated bottom part (4) and two diverging side walls (5) attached to the bottom part (4). The bottom part (4) is oriented with its length (6) extending along the optical axis (2) and the width of the first outcoupling element (3) is the smallest at the bottom part (4).