Automotive Rearview Mirror Lightguide for Uniform LCD Illumination
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Solution Overview
Problem
Existing automotive rearview mirror assemblies face challenges in providing spatially uniform luminance for displays while maintaining a clear, undistorted view of the rear and peripheral scene, especially under varying ambient light conditions, and require efficient light distribution to minimize the number of light emitters and reduce heat dissipation issues.
Innovation Solution
The implementation of a light source system within the rearview mirror assembly that includes a lightguide with an elbow configuration, a reflective polarizer, and a segmented LC-cell, which channels light from emitters along a non-transverse plane to the LCD, optimizing light outcoupling and reducing the number of emitters needed, while using a reflective polarizer to enhance light distribution and reduce power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional backlighting systems with multiple LEDs are used to illuminate the LCD, then sufficient luminance is achieved, but the number of light emitters increases and heat dissipation becomes problematic
Solution Approach 1:
The patent segments the light emission function by using a single LED coupled to a lightguide that distributes light across the LCD area. The lightguide is divided into multiple light-guiding surfaces that collectively provide uniform illumination, replacing the need for multiple discrete LEDs while maintaining sufficient luminance output.
Solution Approach 2:
The patent introduces a lightguide as an intermediary component between the single LED light emitter and the LCD. The lightguide channels and redistributes the light from the single emitter across the display area, achieving uniform luminance without requiring multiple light emitters, thus reducing heat generation while maintaining illumination intensity.
2Illumination intensity
If multiple light emitters are used to provide uniform illumination, then luminance uniformity is improved, but the volume and power consumption of the light source system increases
Solution Approach 1:
The patent transitions from a planar arrangement of multiple LEDs to a three-dimensional lightguide structure that channels light along its length. The lightguide's elongated geometry allows a single LED to illuminate the entire LCD area by distributing light through its volume, reducing the overall system volume while achieving uniform luminance across the display surface.
3Power
If a conventional light source system is used, then adequate power is available for illumination, but electrical power consumption and heat dissipation increase
Solution Approach 1:
The lightguide structure passively distributes light from the single LED emitter throughout the LCD area without requiring additional active components or power consumption. The optical design enables the system to achieve uniform illumination using only the power needed for the single LED, eliminating the need for multiple powered emitters and reducing overall electrical power consumption while maintaining adequate illumination power.
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 configuration achieves a fraction of the electrical power consumption and volume compared to conventional systems, providing uniform illumination and reducing heat dissipation needs, while maintaining the required luminance and clarity for the driver's view.
Implementation Method 1
a lightguide with first and second light-guiding surfaces that channels the coupled light and outcouple the channeled light through the first light-guiding surface
Implementation Method 2
a reflective polarizer layer disposed within the light source adjacent to the LCD
Implementation Method 3
an LCD having a liquid-crystal (LC) layer oriented to be substantially parallel to the first light-guiding surface
Implementation Method 4
a transflective electrochromic (EC) mirror element disposed inside the housing
Data Source
AI summary
A vehicular rearview assembly comprising a light source illuminating the mirror system within the housing of the assembly. The light source is a layered structure including generally co-extensive optical elements such as a light-guiding element that accepts light from light emitters and distributes this light along an area that is not transverse with respect to a display of the assembly. Light distributed and outcoupled through the light-guiding element illuminates the whole display, while radiation from other emitters may traverse the light-guiding element in order to highlight respectively corresponding segments of the display. The display may be configured in a spatially-segmented fashion to increase brightness of displayed indicia.