Head-Up Display Light-Mixing Geometry Homogenizes LED Illumination
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Solution Overview
Problem
Current head-up displays in vehicles face challenges in achieving homogeneous brightness and color across the eyebox due to inefficiencies in light utilization and sensitivity to LED positioning variations, leading to illumination inhomogeneities and reduced light efficiency.
Innovation Solution
A head-up display system incorporating a light-mixing geometry with reflective boundary surfaces and a diffuser to homogenize light from multiple LEDs, combined with a condenser system for efficient projection onto the windshield, allowing for large production tolerances and effective use of light power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If lens and/or reflector arrays are used to collimate LED radiation, then light direction control is improved, but production and positioning accuracy requirements increase significantly
Solution Approach 1:
A light-mixing element is introduced as an intermediary component between the LED and the collimating optics. This element homogenizes the light distribution before it reaches the collimating lenses or reflectors, reducing the sensitivity to positioning inaccuracies and manufacturing tolerances of the subsequent optical components.
Solution Approach 2:
The invention changes the optical parameters by using light-mixing elements that modify the angular distribution and spatial coherence of the LED light before collimation. This parameter transformation allows the system to tolerate larger variations in component positioning while maintaining acceptable collimation quality.
2Illumination intensity
If diffusers are used to scatter light homogeneously, then illumination homogeneity is improved, but light efficiency decreases
Solution Approach 1:
Instead of using a single strong diffuser that scatters light in all directions, the invention employs light-mixing elements with specific local optical properties that provide homogeneous light distribution while maintaining directional control. The mixing is achieved through controlled reflections and refractions rather than complete diffusion, preserving light efficiency.
3Loss of energy
If the homogeneous scattering angle range is limited, then light is efficiently directed into the eyebox, but light from inaccurately positioned LEDs is lost
Solution Approach 1:
The light-mixing element performs a preliminary homogenization of the LED light before it enters the collimating optics. This preliminary action ensures that even if the LED position varies within tolerance ranges, the light distribution entering the collimating system remains sufficiently uniform, preventing significant light loss and maintaining reliable operation.
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 a homogeneous and efficient backlighting system that ensures consistent brightness and color across the eyebox, reducing illumination inhomogeneities and maximizing light usage, resulting in a more effective and reliable head-up display.
Implementation Method 1
The light-mixing geometry has boundary surfaces, each of which is reflective on the inner side, in order to mix and/or homogenize the light of the corresponding light sources
Implementation Method 2
The green and the red beams are merged by a dichroitic mirror DS and scattered homogeneously by a diffuser S
Implementation Method 3
an imaging device for imaging the light falling on the display onto the windshield
Data Source
AI summary
A head-up display includes an image-generating device for generating an image and an optical system for projecting the image onto a windshield of a vehicle. A lighting system illuminates the image-generating device. The lighting system includes at least one light source, downstream of which a light-mixing geometry is disposed. The light-mixing geometry has boundary surfaces, each of which has light-reflecting inner sides, in order to homogenize the light of the at least one light source.