HUD Microlens Diffuser Layout for Efficient LED Light Coupling
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Solution Overview
Problem
Conventional HUDs face challenges in efficiently coupling LED light sources into HUD optics due to their broader and more directional optical output, leading to image quality degradation and reduced brightness, necessitating optical filtering that further diminishes performance.
Innovation Solution
Employing a microlens array with alternating convex and concave microlenses, decentred to minimize surface discontinuities and improve manufacturing tolerance, thereby enhancing light coupling efficiency into HUD optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LED light sources are used in HUD systems, then the system becomes more modern and energy-efficient, but the broader and more directional optical output degrades image quality
Solution Approach 1:
The patent divides the waveguide into multiple sections, each containing a microlens array that processes light from different regions of the LED source. This segmentation allows each microlens array to be optimized for its specific region, managing the directional and spectral characteristics of LED light while maintaining overall image quality.
Solution Approach 2:
Different regions of the waveguide are equipped with microlens arrays having different optical properties tailored to local requirements. The microlenses are designed with specific focal lengths and spacing to handle the broader spectrum and directional output of LEDs in different areas, ensuring optimal performance throughout the display.
2Manufacturing precision
If optical filtering is applied to reduce bandwidth, then image quality is maintained, but optical intensity and brightness are reduced
Solution Approach 1:
Instead of using traditional optical filters that reduce intensity, the patent changes the approach by using microlens arrays with specifically designed focal lengths and spacing parameters. These parameters are optimized to work with the broader LED spectrum without requiring aggressive filtering, thereby maintaining both image quality and brightness.
3Device complexity
If conventional waveguide designs are used, then the system is simpler, but the waveguides are larger and produce stray light paths
Solution Approach 1:
The patent introduces microlens arrays positioned at specific distances from the waveguide surface, creating a three-dimensional optical structure. This dimensional approach allows for more efficient light coupling and guidance, reducing the waveguide size and eliminating stray light paths while maintaining system functionality.
4Ease of manufacture
If microlens surfaces are not aligned, then manufacturing is easier, but light coupling efficiency is reduced
Solution Approach 1:
The microlens arrays are designed with asymmetric positioning and orientation relative to the waveguide surface. The microlenses are tilted at specific angles and positioned at optimized distances to maximize light coupling efficiency. This asymmetric design maintains manufacturing feasibility while significantly reducing light loss compared to conventional symmetric alignments.
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 microlens array design reduces light loss and improves optical efficiency, maintaining image quality and brightness by aligning microlens surfaces for optimal light direction, addressing the inefficiencies of conventional systems.
Implementation Method 1
a microlens array, wherein surfaces of adjacent microlenses are aligned to minimise surface discontinuities
Data Source
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AI summary
A diffuser for use in a head up display formed of an array of microlenses. The microlenses comprises both concave and convex microlenses to reduce surface discontinuities between adjacent lenses.