Laser Speckle Optical Flow Tracking for Stable AR Headgear
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Solution Overview
Problem
Existing augmented reality headgear systems face challenges in accurately tracking the motion of virtual objects relative to the real world due to inaccuracies in gyroscopes and environmental surface limitations, leading to virtual objects drifting when the user moves.
Innovation Solution
The system employs upward, sideways, and front-facing lasers to project coherent light onto environmental surfaces, which creates speckle patterns detected by 2D optical sensor arrays to track six degrees of freedom motion, using optical flow methods to adjust virtual content positioning relative to the real environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gyroscopes are used to track headgear orientation, then motion tracking is achieved, but drift occurs causing virtual objects to slowly drift relative to the real world
Solution Approach 1:
The patent introduces an intermediary measurement system (optical sensors detecting speckle patterns from laser illumination) to mediate between the headgear motion and the virtual object positioning. This intermediary system provides absolute position references that correct the drift inherent in direct gyroscope integration, thereby resolving the contradiction between achieving motion tracking and maintaining virtual object stability.
Solution Approach 2:
The system implements feedback by continuously monitoring speckle pattern changes and using this information to correct gyroscope drift. The optical measurement system provides feedback signals that are integrated with gyroscope data through sensor fusion algorithms, allowing the system to maintain accurate virtual object positioning by compensating for accumulated drift over time.
2Measurement precision
If speckle defocus imaging is used for motion sensing, then 6 DOF ego-motion can be detected, but accuracy is limited when environmental surfaces are not appropriate
Solution Approach 1:
The patent employs multiple lasers with different wavelengths (e.g., red, green, blue) that can illuminate various environmental surfaces effectively. Each wavelength interacts differently with surface materials, allowing the system to maintain speckle pattern detectability across diverse environmental conditions. This multi-functional illumination approach enables the system to adapt to different surface types while maintaining motion detection accuracy.
Solution Approach 2:
The system changes illumination parameters by using multiple laser wavelengths and adjusting illumination intensity to optimize speckle pattern generation for different environmental surfaces. By varying these parameters, the system can maintain adequate contrast and detectability of speckle patterns even on surfaces that are not ideal for a single wavelength, thereby improving both accuracy and environmental adaptability.
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
Accurately maintains virtual content in a fixed position relative to the real world, compensating for user movements, enhancing the immersion and realism of augmented reality experiences.
Implementation Method 1
upward, sideways, and front-facing lasers to project coherent light onto environmental surfaces
Implementation Method 2
upward, sideways, and front-facing lasers to project coherent light
Implementation Method 3
surfaces, which creates speckle patterns detected by 2D optical sensor arrays
Data Source
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AI summary
Augmented reality headgear includes a first optical sensor having a first surface normal pointed in a first direction and operable to receive light reflected from a first surface; a second optical sensor having a second surface normal pointed in a second direction and operable to receive light reflected from a second surface; a set of coherent light sources operable to project light onto the first surface and the second surface; and electronic circuitry configured to sense translation of a first speckle pattern formed on the first optical sensor by light reflected from the first surface, wherein the translation of the first speckle pattern is along at least one of the second direction or a direction azimuthal to the first direction; and sense translation of a second speckle pattern formed on the second optical sensor by light reflected from the second surface, wherein the translation of the second speckle pattern is along at least one of the first direction or a direction azimuthal to the second direction.