Waveguide Alignment Scanning for Stable HMD Image and Eye Tracking
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Solution Overview
Problem
The alignment of stacked waveguides in head-mounted displays (HMDs) can change due to wear, position, and age, affecting the delivery of virtual images and eye-tracking systems.
Innovation Solution
A scanner is used to scan light into a display waveguide and an array of reflectors for alignment monitoring, with a detection module measuring returning light to generate alignment data, allowing adjustments to the display and eye-tracking systems based on these measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If stacked waveguides are used in HMDs, then virtual image delivery and eye-tracking functionality are enabled, but alignment changes occur due to wear, position, and age
Solution Approach 1:
The system performs preliminary alignment measurements using a scanner and detection module to establish baseline alignment data before actual use. This allows the system to proactively detect and compensate for alignment changes rather than reacting to them after they affect performance.
Solution Approach 2:
The patent implements a feedback mechanism where alignment measurements are continuously or periodically taken, and the system adjusts waveguide positions or scanner parameters based on measured deviations. This closed-loop control maintains alignment accuracy despite wear, position changes, or aging.
2Measurement precision
If alignment measurements are performed continuously, then alignment accuracy is maintained, but device complexity and power consumption increase
Solution Approach 1:
Instead of continuous monitoring, the system performs alignment measurements periodically or at key moments (e.g., when the device is first worn, after detected shifts, or at scheduled intervals). This reduces the operational burden on the scanner and detection module while maintaining sufficient alignment accuracy.
Solution Approach 2:
The system uses existing optical components (scanner, waveguides, output couplers) for alignment measurements rather than adding completely separate measurement hardware. The same optical paths and components used for display and eye-tracking are leveraged for alignment detection, minimizing additional complexity.
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
Ensures accurate alignment of waveguides, improving the delivery of virtual images and eye-tracking functionality in HMDs by adjusting positions and illumination based on real-time alignment data.
Implementation Method 1
directing light to reflectors disposed along a boundary of an eye-tracking waveguide
Implementation Method 2
a detection module is configured to receive and measure returning light reflected by the reflectors
Implementation Method 3
A display waveguide delivers a virtual image to an eyebox region
Implementation Method 4
an output coupler of the display waveguide directs the returning light to the scanner
Data Source
AI summary
A near-eye system includes a display waveguide, an eye-tracking waveguide, and a scanner. The display waveguide is configured to present a virtual image to an eyebox region. The eye-tracking waveguide is configured to illuminate the eyebox region with illumination light. The scanner is configured to be driven to varying image scan angles to direct image light to the display waveguide to present the virtual image to the eyebox region. The scanner is also configured to be driven to one or more alignment scan angles to sense an alignment between the display waveguide and the eye-tracking waveguide.