Concentric Spherical Cap Retroreflective Marker for Tracking Accuracy
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Solution Overview
Problem
Retroreflective marker systems in medical applications face inaccuracies due to contamination and interference from distal markers, leading to incorrect position determination of objects, especially when observation angles vary or markers are partially occluded.
Innovation Solution
The development of enhanced retroreflective markers with shapes defined by two concentric spherical caps of different radii, tuned to retroreflect light within specific entrance angles, and configured with reflective materials on select surfaces to maintain consistent intensity and accuracy, preventing marker merging and occlusion-induced inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional retroreflective markers are used, then the system is simple, but measurement precision deteriorates due to contamination and marker interference
Solution Approach 1:
The marker is divided into multiple spherical caps of different sizes arranged concentrically. This segmentation allows each cap to contribute to retroreflection at different angles, enabling the marker to maintain high measurement precision while resisting interference from distal markers and contamination, thus resolving the contradiction between precision and complexity.
Solution Approach 2:
The marker employs spherical caps of different radii rather than identical symmetric structures. This asymmetric design creates distinct retroreflection patterns that improve position determination accuracy and prevent marker merging, achieving higher measurement precision without requiring overly complex structural elements.
2Measurement precision
If markers are made highly retroreflective, then tracking accuracy improves, but susceptibility to contamination increases
Solution Approach 1:
Different spherical caps are designed with specific retroreflective properties optimized for their respective angular ranges. This local quality optimization ensures that each region of the marker provides appropriate retroreflection without excessive susceptibility to contamination, maintaining tracking accuracy while reducing the harmful effect of contamination.
Solution Approach 2:
The use of spherical caps with different radii creates curved surfaces that provide broad-angle retroreflection. This curvature-based design maintains high retroreflective performance and tracking accuracy while the distributed spherical structure reduces the impact of contamination compared to flat or highly polished surfaces.
3Measurement precision
If single spherical markers are used, then manufacturing is simple, but marker merging and occlusion interference occur
Solution Approach 1:
The marker is segmented into multiple spherical caps of different sizes that are concentrically arranged. This segmentation creates distinct retroreflection patterns for each cap, allowing the system to differentiate between multiple markers even when they are close together or partially occluded, thereby preventing marker merging interference and maintaining high measurement precision.
Solution Approach 2:
The marker structure transitions from a single spherical dimension to a multi-cap dimensional arrangement with varying radii. This dimensional complexity enables the marker to provide angularly differentiated retroreflection signals, improving the system's ability to distinguish between multiple markers and reducing occlusion-induced inaccuracies.
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
These markers improve tracking accuracy by ensuring consistent retroreflection and preventing marker interference, maintaining accurate position determination even under varying observation angles and partial occlusions.
Implementation Method 1
a first retroreflective marker having a shape that is substantially defined by two spherical caps of different radii that are disposed substantially concentric in relation to one another... The first retroreflective marker may retroreflect light when light rays emanating from the marker illuminating device enter the first retroreflective marker within entrance angles ranging between 0° and ±β°.
Data Source
AI summary
A marker-tracking system includes an object, a marker illuminating device, a marker sensing device, and a computing device. The object includes a first retroreflective marker having a shape that is substantially defined by two spherical caps of different radii that are disposed substantially concentric in relation to one another. The marker illuminating device substantially illuminates the first retroreflective marker, the marker sensing device detects the illuminated first retroreflective marker and generates first data indicative of the location of the illuminated first retroreflective marker in space, and the computing device processes the first data generated by the marker sensing device to determine a position and/or orientation of the object in space.