Windshield Holographic HUD Calibration Using Phase Feedback
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Solution Overview
Problem
Holographic head-up displays (HUDs) suffer from system-generated errors due to spatial light modulator, pupil replicator, and windshield surface imperfections, leading to obscurities in the reconstructed graphics image.
Innovation Solution
A calibration method and system using holographic phase modulation, where an initial hologram is projected onto the windshield, captured by a camera, and an optimization algorithm corrects the image to minimize noise and enhance contrast, with the differences stored as a lookup table for application during vehicle operation, and an eye tracker determines the appropriate lookup table based on the driver's eye position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an initial hologram is projected onto the windshield, then the graphics are displayed in the eyellipse, but system-generated errors from the SLM, pupil replicator, and windshield surface roughness cause obscurities in the reconstructed image
Solution Approach 1:
The patent captures the actual degraded image produced by the system and uses it as the basis for generating correction holograms. The optimization algorithm processes this real degraded image to compute phase modulations that will compensate for the specific errors introduced by the SLM, pupil replicator, and windshield, effectively converting the harmful system errors into useful calibration information
Solution Approach 2:
The system uses a camera to capture the actual displayed graphics and feeds this information back to an optimization algorithm. The algorithm compares the captured image with the intended display and generates corrected holograms that compensate for the observed errors. This closed-loop feedback process iteratively refines the hologram phase to minimize system-generated errors
2Reliability
If an optimization algorithm is used to correct the initial hologram, then the contrast in the final output is enhanced, but the processing time and computational complexity increase
Solution Approach 1:
The patent performs the computationally intensive optimization algorithm and phase modulation calibration during the manufacturing or initial setup phase, before the vehicle is delivered to the customer. The resulting correction lookup tables are stored in memory and applied in real-time during normal operation, separating the heavy computational work from the time-critical display operation
Solution Approach 2:
The system implements a dynamic lookup table mechanism where pre-computed correction data for different eye positions and display conditions is stored in memory. During operation, the appropriate correction table is quickly retrieved and applied based on the current eye tracker position, enabling real-time adaptation without performing full optimization calculations
3Measurement precision
If multiple look up tables are created for multiple eyellipse positions, then the calibration accuracy is improved for different driver positions, but the memory storage requirements and system complexity increase
Solution Approach 1:
The patent divides the calibration space into multiple discrete eyellipse positions, creating separate lookup tables for each position. The eye tracker determines which segment (position) the driver's eyes occupy and applies the corresponding correction table. This segmentation allows high calibration accuracy for each position while keeping the system manageable through modular organization
Solution Approach 2:
The same optimization algorithm and phase modulation framework is used universally across all eyellipse positions and different display content types. The system creates a unified calibration approach that handles multiple positions, eye trackers, and graphics types through a single multi-functional lookup table mechanism rather than requiring separate specialized systems for each case
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 method effectively minimizes system-generated errors and enhances the image quality of holographic HUDs by adaptively modifying the hologram phase and creating optimized lookup tables for various eye positions, resulting in improved image clarity and contrast.
Implementation Method 1
modulating a phase of a light beam generating the initial graphics using the loss function value to generate an updated graphics
Implementation Method 2
The light beam carrying the graphics information then reflects off the windshield to create an image in the eyellipse
Data Source
AI summary
A method for holographic display calibration using phase modulation includes projecting an initial graphic on a windshield of a vehicle, capturing an image of the initial graphic with a camera inside a vehicle, determining a loss function value between the image of the initial graphic captured by the camera and a target graphic, modulating a phase of a light beam generating the initial graphic using the loss function value to generate an updated graphic, and displaying the updated graphic on the windshield of the vehicle.