Adjustable Lens Feedback Calibration for Stable HMD Optical Power
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) with adjustable lenses face calibration issues due to changes in atmospheric pressure, actuator sag, stress, and hysteresis, leading to inaccuracies in optical power adjustment, causing visual fatigue and nausea if vergence and accommodation conflicts are not correctly managed.
Innovation Solution
An optical system with dynamically-generated feedback for the adjustable lens, using an illumination layer with point light sources, an active optics block, and a camera to capture calibration images, allowing for real-time adjustment of actuation to maintain desired optical power, compensating for distortions caused by environmental changes and actuator variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional adjustable lenses are used in HMDs, then the system can provide focus adjustment capability, but calibration inaccuracies occur due to atmospheric pressure changes, actuator sag, stress, and hysteresis
Solution Approach 1:
The patent implements a feedback mechanism where a camera captures images of calibration targets through the adjustable lens, and the captured images are processed to determine actual optical power. This feedback loop allows the system to detect calibration deviations caused by atmospheric pressure changes, actuator sag, stress, and hysteresis, and subsequently correct these inaccuracies by adjusting actuator commands based on the difference between desired and actual optical power.
Solution Approach 2:
The system dynamically changes operational parameters by measuring actual optical power through image processing and using this information to adjust actuator commands in real-time. This parameter change approach compensates for environmental variations and actuator characteristics, maintaining calibration accuracy despite changes in atmospheric pressure, temperature, or mechanical stress.
2Measurement precision
If dynamic calibration feedback is implemented, then optical power accuracy is improved, but device complexity increases due to additional components
Solution Approach 1:
The patent integrates multiple functions into existing HMD components. The display layer serves both as a visual output device and as a mounting substrate for calibration light sources. The camera, already present for other HMD functions, is utilized for capturing calibration images. This multi-functionality approach minimizes additional hardware while achieving accurate optical power measurement and feedback.
Solution Approach 2:
The system merges the calibration functionality with the existing display and imaging components. Calibration light sources are integrated into the display layer, and the calibration imaging process utilizes the existing camera and optical path. This consolidation reduces the need for separate dedicated calibration hardware, thereby limiting the increase in device complexity.
3Measurement precision
If calibration light sources are added to the display layer, then optical calibration becomes possible, but user noticeability of calibration elements increases
Solution Approach 1:
The patent positions calibration light sources at specific locations within the display layer where they serve their calibration function effectively. By strategically placing these light sources and configuring their optical characteristics, the system achieves sufficient calibration image quality while minimizing the visibility of calibration elements to the user during normal operation.
Solution Approach 2:
The calibration imaging operation is performed periodically or on-demand rather than continuously. The system captures calibration images at appropriate intervals or when calibration is needed, keeping calibration light sources active only during these brief calibration periods. This periodic operation reduces user noticeability of calibration elements while still maintaining measurement precision when calibration is performed.
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 and dynamic adjustment of the adjustable lens, reducing visual fatigue and nausea by maintaining correct optical power alignment with minimal user noticeability of the calibration light sources, enhancing the overall HMD performance in providing augmented and virtual reality experiences.
Implementation Method 1
an adjustable lens configured to dynamically adjust a focus of the display light in response to actuator application
Implementation Method 2
an illumination layer disposed behind the adjustable lens and including a plurality of point light sources arranged in an array
Implementation Method 3
a camera configured to generate a calibration image in response to the calibration light
Data Source
AI summary
An optical system includes an illumination layer, an optical combiner, and an active optics block. The illumination layer includes an array of point light sources configured to emit calibration light. The optical combiner is configured to pass visible light to a front side of the optical system and to direct the calibration light to a camera that generates an image in response to the calibration light. The image includes an array of points corresponding to the array of point light sources. The active optics block includes an adjustable lens disposed between the illumination layer and the optical combiner and is configured to pass the calibration light to the optical combiner and to focus the visible light. The active optics block is further configured to adjust an optical power of the adjustable lens based on the image of the array of points.