Planar Lightguide Arc Return Edge for Intense Linear Beam

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Solution Overview

Problem

Conventional lighting and signaling devices for motor vehicles using light guides fail to produce high-intensity light beams due to random and unordered light ray guidance, resulting in inhomogeneous light distribution and significant light losses, making them unsuitable for functions requiring intense light, such as compliance with regulations.

Innovation Solution

The lighting device employs a light guide sheet with angular sectors around the source axis, where each sector's return edge is shaped as an arc of a circle centered on the axis, and the return edge is inclined to reflect light rays towards the optical axis, forming a linear light beam, with a flat section and a disk shape to optimize light propagation and emission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a conventional cylindrical light guide with irregularities is used to guide light rays, then the device structure is simple and easy to manufacture, but the light beam intensity is weak and highly inhomogeneous

Engineering Contradiction:
Improvelight beam intensityVSAvoidguide sheet structure complexity
Core Design Contradiction:
Illumination intensityVSDevice complexity

Solution Approach 1:

The guide sheet is divided into multiple angular sectors around the source axis, with each sector having a specific return edge configuration. This segmentation allows controlled light ray paths in different angular regions, transforming the random light guidance into an ordered system that maintains intensity while simplifying the overall design.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The return edge of each angular sector is shaped as an arc of a circle centered on the source axis. This curved geometry naturally guides light rays through controlled reflections, creating a homogeneous light beam with high intensity without requiring complex irregularities or scattering structures.

Inventive Principle:
Principle #14Spheroidality (Curvature)

2Illumination intensity

If light rays are guided in a random and unordered manner inside the light guide, then the guide structure is simple, but the light beam intensity remains weak due to unordered propagation

Engineering Contradiction:
Improvelight beam intensityVSAvoidmanufacturing complexity
Core Design Contradiction:
Illumination intensityVSEase of manufacture

Solution Approach 1:

Different angular sectors of the guide sheet are assigned different return edge configurations, with each sector optimized for its specific angular range. This local differentiation creates ordered light propagation in each sector while maintaining overall manufacturing simplicity through repetitive modular patterns.

Inventive Principle:
Principle #3Local quality

3Stability of the object's composition

If the light guide material causes absorption of light rays, then the device structure remains simple, but luminosity becomes inhomogeneous with greater losses at distance from the source

Engineering Contradiction:
Improveluminosity homogeneityVSAvoidlight ray absorption loss
Core Design Contradiction:
Stability of the object's compositionVSLoss of energy

Solution Approach 1:

The guide sheet geometry is designed to reflect and redirect light rays before they can be significantly absorbed by the material. By creating controlled reflection paths through the angular sector divisions and curved return edges, the system minimizes the distance light rays travel through the absorbing material while maintaining uniform luminosity distribution.

Inventive Principle:
Principle #10Preliminary action

4Stability of the object's composition

If part of the light rays directly reach the opposite face of the light guide, then the device structure is simple, but a very bright point appears causing high inhomogeneity

Engineering Contradiction:
Improveluminosity homogeneityVSAvoidreturn edge configuration
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The return edge is configured as an arc of a circle that naturally redirects light rays through controlled reflections. This curved geometry prevents direct transmission of light rays to the opposite face, eliminating bright spots and ensuring homogeneous luminosity distribution without requiring complex additional optical elements.

Inventive Principle:
Principle #14Spheroidality (Curvature)

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 enhances light beam intensity by ensuring efficient light ray reflection and distribution, achieving an intensity up to 10 times greater than conventional devices while maintaining homogeneity, with minimal light loss.

Implementation Method 1

the portion of the return edge is inclined so that the light rays are generally reflected in the direction of the optical axis by crossing one of the guide faces to form the light beam

Methodology Applied
Scientific EffectLight reflection: Reflection

Implementation Method 2

the light rays propagating by successive reflections between the guide faces in the direction of the deflection edge

Methodology Applied
Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentEP1881265B1Lighting device comprising a planar lightguide with a light reflecting portion having the shape of an arc of a circle
Publication Date: 2009.12.23 VALEO VISION SA
  • EP1881265B1 patent drawingFigure 1~3
  • EP1881265B1 patent drawingFigure 4~6
  • EP1881265B1 patent drawingFigure 7~8

AI summary

The device (10) has a flat transversal light guiding sheet (12) including an angular sector around a point light source e.g. side-emitter type LED, axis (S). The sector forms an elementary portion of an outer return edge (18), where the portion is conformed in a manner so that a meridian propagation plane (M) of a light ray reaching the portion is perpendicular to points at the portion. The portion is inclined in a manner so that the ray is totally reflected in a direction of a longitudinal optical orientation axis by traversing light ray guiding surfaces (14, 16) to form a linear light beam.