Fiducial Dot Patterns for Optical Element Pose Estimation
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Solution Overview
Problem
Fiducial patterns that generate Barker Code-like diffraction patterns are complex and expensive, making them unsuitable for certain applications that require localization using cameras, particularly in head-mounted devices where precise alignment and calibration of optical elements are necessary.
Innovation Solution
The use of fiducial patterns comprising sub-patterns of dot-like markers etched or applied on transparent glass or plastic materials, such as cover glasses and lens attachments, to create diffraction patterns that can be analyzed by cameras to estimate the pose and alignment of these elements, allowing for precise calibration and encoding of information like prescription details.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Barker Code-like diffraction patterns are used for localization, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The fiducial pattern is segmented into multiple sub-patterns, each containing dot-like markers arranged in specific geometric configurations. This segmentation allows the system to achieve precise localization through simpler individual sub-patterns rather than requiring a single complex Barker Code pattern, thereby reducing manufacturing complexity while maintaining measurement precision.
Solution Approach 2:
The patent replaces expensive, complex Barker Code fiducials with simpler, cheaper dot-like marker sub-patterns that can be easily manufactured on transparent optical elements. These simplified fiducial patterns achieve sufficient localization precision without the high manufacturing costs associated with Barker Code optimization for each camera.
2Ease of operation
If fiducial patterns are made visible for naked eye detection, then ease of operation is improved, but signal attenuation increases
Solution Approach 1:
The patent introduces video stream integration as an intermediary mechanism to detect fiducial patterns. Instead of relying on naked eye visibility, the system captures multiple video frames and integrates the signal computationally, allowing the use of low-attenuation fiducial patterns that are barely visible or invisible to the naked eye while still enabling reliable detection through digital signal processing.
Solution Approach 2:
The patent replaces the mechanical/optical approach of making fiducials visible to the naked eye with a digital signal processing approach. By substituting human visual detection with camera-based capture and computational integration of video frames, the system can use minimal-attenuation fiducial patterns that would otherwise be undetectable, thereby reducing light loss while maintaining detection capability.
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
This solution enables accurate alignment and calibration of optical elements in head-mounted devices, allowing for precise localization and adaptation to individual lenses, while being cost-effective by using low-attenuation fiducial patterns that are barely visible to the naked eye, facilitating integration into video streams for signal recovery.
Implementation Method 1
a fiducial pattern configured to affect light received from an object field to cause a diffraction pattern in images formed by the camera lens at a surface of the image sensor
Data Source
AI summary
Fiducial patterns that include sub-patterns of dot-like markers are generated or applied on or in transparent glass or plastic material, for example an optical element such as a cover glass or lens attachment. A camera may capture multiple images through the glass or plastic element that include diffraction patterns caused by the fiducial patterns. The diffraction patterns from multiple images may be processed and analyzed to extract information including but not limited to centroids of the sub-patterns of the fiducial patterns. This information may, for example, be used to estimate location of the fiducial 10 patterns with respect to the camera, and thus to estimate pose of the glass or lens element with respect to the camera. Information such as serial numbers and prescriptions can also be encoded in the fiducial patterns and extracted from the respective diffraction patterns.