Light Guide Stack Display for Burn-In-Free Steering Wheel Symbols
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Solution Overview
Problem
Conventional electronic pixel matrix displays for function displays are expensive, limit design flexibility, suffer from 'burn-in' issues, and pose a risk of injury, particularly in head impacts, while being energy-inefficient.
Innovation Solution
A function display using a transparent or translucent cover layer with a light guide stack composed of superimposed light guides separated by optically thinner layers, featuring light sources and microstructures for selective symbol display, which is cost-effective, energy-efficient, and reduces injury risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If electronic pixel matrix displays are used for function display, then display functionality is achieved, but manufacturing cost increases and design flexibility is limited
Solution Approach 1:
The patent uses a light guide plate with microstructured reflection structures that copy and redirect light from a single edge-mounted LED source to create multiple visible light points across the display area. This replaces expensive electronic pixel matrices with a simple optical copying mechanism using total internal reflection and micro-geometry
Solution Approach 2:
The light guide plate serves multiple functions simultaneously: it acts as a structural component, a light distribution medium, and a display element. The same plate that guides light also creates the visible display pattern through its microstructured surface, eliminating the need for separate display electronics
2Use of energy by moving object
If electronic pixel matrix displays are used, then display content can be controlled, but power consumption increases
Solution Approach 1:
The patent extracts the light generation function from multiple electronic pixels and consolidates it into a single passive LED source. The active control electronics are removed entirely, replacing them with passive optical structures that redirect light based on pre-designed micro-geometric patterns
Solution Approach 2:
The light guide plate's microstructured surface automatically directs light to create the desired display pattern without requiring active control. The optical geometry itself performs the function of selecting and positioning light output, making the system self-regulating and energy-efficient
3Reliability
If electronic pixel matrix displays are used, then display visibility is achieved, but burn-in damage occurs
Solution Approach 1:
The patent uses inexpensive, replaceable optical components (light guide plate, adhesive layers) instead of expensive, fragile electronic displays. While the optical components may need replacement, they are much cheaper and more durable than electronic pixel matrices, especially in harsh environments
Solution Approach 2:
The patent replaces the electronic mechanical pixel matrix system with a passive optical system based on total internal reflection and micro-geometric light redirection. This mechanical/optical system has no moving parts, no electronic degradation, and is immune to burn-in phenomena
4Object-affected harmful factors
If conventional electronic displays are used in steering wheels, then information display is achieved, but injury risk in head impact increases
Solution Approach 1:
The patent uses thin, flexible light guide plates and adhesive layers that can deform under impact forces without shattering. These flexible optical components maintain display functionality while reducing the rigid structure that would cause injury in head impacts
Solution Approach 2:
The display information is created by optical copying and redirection rather than electronic emission. This passive optical approach eliminates the need for fragile electronic components while maintaining full display functionality through light redirection patterns
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 provides design flexibility, avoids 'burn-in', reduces power consumption, and minimizes injury risk, while maintaining high visibility and allowing placement on steering wheels without obstructing the view.
Implementation Method 1
a layer that is optically thinner than the light guides or a layer structure composed of several layers that are optically thinner than the light guides is provided between two light guides in order to increase the critical angle for total internal reflection within the adjacent light guide
Implementation Method 2
a light-refracting and/or light-scattering microstructure is further provided in or on each light guide, which is designed to display a backlit symbol, visible to the viewer, when the light source is activated, using the light coupled into the light guide
Implementation Method 3
a light-refracting and/or light-scattering microstructure is further provided in or on each light guide
Data Source
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AI summary
The invention relates to a function display (1) for selectively displaying symbols (18) which represent switch functions and/or switch states, in particular for a motor vehicle, having: an outer transparent or translucent cover layer (23) which defines a display surface (8); a light guide stack of at least two flat transparent or translucent light guides (13, 14, 15) which lie one over the other in a stacking direction and which are mutually spaced by a transparent or translucent layer made of an optically thinner material than that of the adjacently arranged light guides (13, 14, 15), preferably by an air gap (24), such that each of the light guides (13, 14, 15) has a main surface (H) facing a viewer (B) and in the case of at least one light guide (13, 14, 15), the main surface (H') facing away from the viewer (B) faces the next adjacent light guide (13, 14, 15) in the stacking direction; at least one light source (12) for each light guide (13, 14, 15), said light source being designed to couple light into each light guide (13, 14, 15) via an end face (S) of the corresponding light guide (13, 14, 15), wherein for each light guide (13, 14, 15), a light-refracting and/or light-scattering microstructure is provided in or on the light guide (13, 14, 15), said structure being designed to visibly display a backlit symbol (18) for the viewer (B) when the light source (12) is activated by means of the respective light being coupled into the light guide (13, 14, 15). The invention also relates to an operating element (10) which contains the function display and to a steering wheel (20).