Wearable Display Throughput Calibration for Waveguide Distortion
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Solution Overview
Problem
Head-mounted displays (HMDs) face challenges in reducing size and weight, particularly due to bulk optics, which can cause distortions, non-uniformity, and unwanted coloring in wearable optical display systems.
Innovation Solution
A near-eye display system that includes a waveguide pupil expander and a controller, which adjusts optical power density based on eye position and orientation using an eye-tracking system to offset angular and color-dependent throughput variations, thereby minimizing distortions and color transfer function issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If compact planar optical components (waveguides, gratings, Fresnel lenses) are used to reduce size and weight, then the size and weight of the optics block are reduced, but distortions, non-uniformity, ghosting, and residual coloring occur
Solution Approach 1:
The patent applies preliminary calibration to measure and store the optical characteristics (throughput, angular distribution, color transfer function) of the compact planar optics before actual use. This pre-characterization allows the system to compensate for distortions and non-uniformities by adjusting the displayed content in advance, thereby maintaining image quality while using lightweight optics
Solution Approach 2:
The patent modifies display parameters (brightness, color, angular distribution) based on the measured optical characteristics of the compact planar components. By dynamically adjusting these parameters according to the specific optical path and viewer position, the system compensates for the inherent non-uniformities and distortions of lightweight optics
2Manufacturing precision
If bulk optics (refractive lenses, cube beamsplitters) are used, then optical quality is maintained, but size and weight of the optics block increase
Solution Approach 1:
The patent applies local quality by implementing position-dependent and angle-dependent calibration. Different regions of the optical field are characterized and compensated individually, allowing compact planar optics to achieve uniform optical quality across the viewing area. The calibration data is used to adjust local display parameters to match the specific optical path characteristics
3Manufacturing precision
If throughput calibration is performed to offset angular and color-dependent variations, then image quality is improved, but device complexity and calibration time increase
Solution Approach 1:
The patent creates a digital model (copy) of the optical system's characteristics through measurement and stores it as calibration data. This digital representation allows the system to simulate and compensate for optical variations without requiring physical modification of the optics or complex real-time measurements during operation
Solution Approach 2:
The patent implements feedback by using the measured optical characteristics to continuously adjust the display output. The calibration process establishes a feedback loop where the actual optical performance informs the display corrections, ensuring that the perceived image quality matches the intended content
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 enhances image quality by reducing distortions and color variations, providing a more comfortable and immersive experience by compensating for the limitations of waveguide-based optics in HMDs.
Implementation Method 1
a waveguide pupil expander coupled to the projector for relaying the image light to an eyebox of the display device
Implementation Method 2
The controller is operably coupled to the electronic display and configured to modify the image data to at least partially offset the dependence of the throughput on the beam angle and the coordinate
Data Source
AI summary
A wearable display device and a calibration method for the wearable display device are provided. The wearable display device or its component(s) may exhibit optical throughput dependent on beam angle or beam coordinate at the eyebox. The linear or angular dependencies of throughput may be accounted for when generating an image to be displayed, to lessen or offset these dependencies during operation of the wearable display.