Binocular Waveguide Display Alignment Tracking for MR Color Stability
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Solution Overview
Problem
Mixed-reality HMD devices experience visual discomfort and fatigue due to misalignments between virtual and real content, binocular disparities, and inaccurate color rendering, exacerbated by thermal expansion and mechanical shocks, leading to user discomfort and reduced immersion.
Innovation Solution
A binocular near-eye display system with separate waveguide-based optical combiners for each eye, utilizing a display alignment tracker to adjust alignment and color fidelity through optical alignment signals captured by cameras, ensuring precise binocular and color alignment using input and output couplers and a display engine controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a see-through waveguide-based optical combiner is used to display virtual images, then the user can view both virtual and real-world content simultaneously, but misalignments between virtual and real content cause visual discomfort and fatigue
Solution Approach 1:
The patent implements a feedback mechanism where a camera captures images through the waveguide combiner, these images are processed to determine misalignment between virtual and real content, and control signals are generated to adjust the display engine accordingly. This closed-loop feedback system continuously monitors and corrects alignment errors, resolving the technical contradiction by maintaining proper alignment while preserving mixed-reality display capability.
Solution Approach 2:
The patent replaces mechanical alignment adjustment mechanisms with an optical-electronic system. Instead of physically adjusting the waveguide combiner or display components, the system uses a camera to detect misalignment and electronically controls the display engine to correct positioning. This substitution eliminates mechanical complexity and enables precise, dynamic alignment correction without physical movement of optical components.
2Object-affected harmful factors
If display alignment is adjusted to improve binocular alignment, then visual comfort improves, but device complexity increases due to additional tracking and control components
Solution Approach 1:
The patent makes the camera serve multiple functions: it captures images for both alignment detection and potential other system functions. The same imaging sensor is used to monitor binocular alignment, color alignment, and can potentially track user gaze or environmental features. This multi-functionality reduces the need for separate dedicated alignment sensors, thereby limiting the increase in device complexity while maintaining visual comfort improvements.
Solution Approach 2:
The system uses the device's own camera and display system to perform alignment detection and correction, rather than requiring external alignment tools or separate specialized sensors. The display engine and waveguide combiner that potentially cause misalignment are themselves used to detect and correct it. This self-service approach minimizes additional components and keeps the system relatively simple while improving visual comfort.
3Measurement precision
If color fidelity is optimized through display alignment tracking, then color rendering improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements preliminary action by pre-calibrating the system during manufacturing to establish baseline alignment parameters. The camera and control system are pre-configured to understand the expected optical paths and alignment relationships. This preliminary setup allows the runtime alignment tracking to focus on detecting deviations from the calibrated state rather than determining absolute alignment from scratch, thereby achieving high color fidelity without requiring extremely tight manufacturing tolerances.
Solution Approach 2:
The feedback mechanism continuously monitors color alignment by capturing images through the waveguide combiner and analyzing the relative positions of virtual and real content. When color misalignment is detected, the system generates control signals to adjust the display engine's color channels or positioning. This real-time feedback compensates for manufacturing variations and maintains high color fidelity without requiring precision beyond normal manufacturing capabilities.
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
Improves user experience by minimizing visual discomfort and enhancing immersion through precise alignment and color rendering, reducing fatigue and maintaining a seamless mixed-reality environment.
Implementation Method 1
a see-through waveguide-based optical combiner for respective eyes
Implementation Method 2
An input coupler on the waveguide combiner is configured to in-couple virtual image light from the display engine
Implementation Method 3
A virtual image output coupler on the waveguide combiner out-couples virtual images over the user's views of the real world
Implementation Method 4
The display alignment tracker uses a camera to capture alignment signals from virtual image light that is out-coupled by a display alignment tracker output coupler
Data Source
AI summary
A mixed-reality near-eye display system in a head-mounted display (HMD) device includes a display alignment tracker configured for monitoring virtual image pixels in binocular waveguide-based displays and providing adjustments to a display engine to reduce binocular and color misalignments that can occur from thermal expansion of HMD device components and mechanical shock and vibration during device use. Surface relief gratings, located on waveguide combiner plates guiding separate display colors, are configured to in-couple and guide virtual image light from a projector-based display engine and simultaneously out-couple light for the near-eye display and alignment tracking.