HMD Calibration via Encoded Frame Metrics
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Solution Overview
Problem
Head-mounted display (HMD) systems struggle to accurately synchronize virtual or augmented elements with real-world environments, leading to a degraded user experience due to synchronization errors between the display and the user's movements.
Innovation Solution
A method and system for calibrating HMD systems by rendering performance metrics within frames, recording their display times, measuring performance aspects, and calibrating the system based on these measurements to ensure accurate synchronization with the user's movements and environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the HMD system displays artificial or augmented scenes based on head position and orientation, then the user experience becomes more immersive, but synchronization errors occur between the display and user movements
Solution Approach 1:
The system performs preliminary calibration by displaying test frames with encoded performance metrics before actual use. The calibration process measures actual display times and compares them with predicted display times in advance, establishing correction factors that are then applied during normal operation to maintain synchronization accuracy.
Solution Approach 2:
The system incorporates feedback mechanisms by encoding performance metrics (such as actual display times and synchronization values) within displayed frames. These metrics are captured by a camera, decoded, and used to measure and correct synchronization errors, creating a closed-loop system that continuously improves timing accuracy.
2Productivity
If the HMD system renders frames at high frequency to improve synchronization, then the frame rate increases, but the complexity of measuring and calibrating display timing increases
Solution Approach 1:
The system uses its own display output to provide calibration information. By encoding performance metrics directly within the displayed frames, the system self-measures its display timing characteristics without requiring external measurement equipment, simplifying the calibration process while supporting high frame rates.
Solution Approach 2:
The patent introduces an intermediary calibration process that mediates between the high-frequency frame rendering and the measurement system. Test frames with encoded metrics serve as intermediaries that carry timing information through the display pipeline, enabling accurate measurement without disrupting the high frame rate operation.
3Measurement precision
If the system captures frames using a camera to measure display timing, then measurement precision improves, but the system requires additional hardware and calibration steps
Solution Approach 1:
The system creates a copy of the display output by capturing frames with a camera. This optical copy allows precise measurement of display timing by analyzing when specific framedata appears in the captured image, providing accurate timing measurements without requiring direct electrical access to the display circuitry.
Data Source
AI summary
The disclosed computer-implemented method may include directing a head-mounted display system to render, within a frame generated by the head-mounted display system, at least one performance metric for the frame. The method may also include recording when the frame containing the performance metric is displayed by a display of the head-mounted display system, measuring, based at least in part on when the frame containing the performance metric was displayed, at least one aspect of the head-mounted display system's performance, and calibrating the head-mounted display system based on the measurement. Various other methods, calibration systems, and computer-readable media are also disclosed.