Waveguide HUD Luminance Compensation via Eye-Tracking
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Solution Overview
Problem
Current head-up display systems fail to provide uniform luminance across the eyebox, leading to varying brightness and intensity of images at different positions, which can affect the clarity and visibility of projected information for drivers.
Innovation Solution
A system that includes a laser projector, spatial light modulator, exit pupil replicator, diffuser, and controller, which projects a dot pattern onto the diffuser, captures and characterizes intensity distribution, maps driver eye locations, and adjusts image intensity by adjusting the power of the laser, grey levels, or gamma curve to ensure consistent image intensity across the eyebox.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a waveguide-based exit pupil replicator is used to project augmented reality images, then the system can provide accurate prescription of reflectivity or diffraction efficiency at each replication, but manufacturing limitations result in luminance non-uniformity across the eyebox
Solution Approach 1:
The system performs preliminary characterization of the dot pattern intensity distribution using a camera before actual operation. The controller measures and stores the intensity distribution data, then uses this pre-acquired information to calculate compensation factors that will be applied during normal operation to ensure uniform luminance across the eyebox.
Solution Approach 2:
The system implements feedback by continuously monitoring the actual intensity distribution of the projected dot pattern and comparing it against the target uniform distribution. The controller adjusts the holographic image parameters based on the measured deviations, creating a closed-loop control system that compensates for manufacturing variations and ensures consistent luminance.
2Measurement precision
If the system projects augmented reality images with accurate reflectivity prescription, then image quality is improved, but luminance non-uniformity causes varying brightness at different eye positions
Solution Approach 1:
The system applies local quality compensation by calculating and applying different intensity adjustment factors to different regions of the eyebox. The controller determines the specific intensity deviation at each measured eye position and applies targeted compensation only where needed, rather than applying uniform adjustment across the entire field of view.
Solution Approach 2:
The system changes the parameters of the holographic image projection dynamically. The controller adjusts the amplitude, phase, or other parameters of the holographic image in real-time based on the measured intensity distribution and the specific eye position, thereby compensating for luminance non-uniformity and ensuring consistent image brightness.
3Reliability
If the system compensates for luminance non-uniformity by adjusting image intensity, then visibility is improved, but the system complexity increases
Solution Approach 1:
The system uses existing components for multiple functions: the same camera used for driver monitoring also characterizes the dot pattern intensity distribution. The controller performs both the calibration measurement and the real-time compensation control. This multi-functionality reduces the need for separate dedicated calibration hardware, thereby limiting the increase in system complexity.
4Measurement precision
If the system characterizes and stores intensity distribution data, then compensation accuracy is improved, but data processing requirements increase
Solution Approach 1:
The system performs the intensive data acquisition and characterization tasks during an initial calibration phase before normal operation begins. Once the intensity distribution is characterized and stored in the controller, subsequent operation requires only lightweight lookup and adjustment operations, significantly reducing the time and processing requirements during actual use.
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 system effectively compensates for luminance non-uniformity by adjusting the projected image intensity at the driver's eye location, ensuring consistent and clear visibility of information, reducing driver distraction and improving road safety.
Implementation Method 1
a laser adapted to project a holographic image
Implementation Method 2
projecting augmented reality images, such as optimal travel paths or navigation arrows
Implementation Method 3
a spatial light modulator
Implementation Method 4
an exit pupil replicator, a diffuser adapted to be positioned within a x-y plane at a center point of a vehicle eyellipse
Implementation Method 5
a diffuser adapted to be positioned within a x-y plane at a center point of a vehicle eyellipse
Data Source
AI summary
A head-up display system includes a laser adapted to project a holographic image, a spatial light modulator, an exit pupil replicator, a diffuser adapted to be positioned within a x-y plane at a center point of a vehicle eyellipse, the hologram projector adapted to project a dot pattern onto the diffuser, and a controller adapted to characterize an intensity distribution of the dot pattern, store the intensity distribution therein, acquire a location of a driver's eyes, map the location of the driver's eyes to the intensity distribution of the dot pattern, and implement corrective action based on the intensity distribution at the location of the driver's eyes.