Active Marker Device Light Redirection for Tracking Accuracy
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Solution Overview
Problem
Motion tracking systems using optical markers face accuracy and performance issues due to occlusion and visibility problems with active markers, which can be mitigated by increasing the number of cameras and markers, but this is costly and time-consuming.
Innovation Solution
An active marker device with a mounting body, light emitting units, and optical elements that redirect light to improve visibility over a wide range of angles, and a control system to selectively emit light from subsets of units, allowing for unique pattern formation and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If more cameras and markers are provided to improve tracking reliability, then marker visibility and tracking accuracy are improved, but system cost and setup time increase
Solution Approach 1:
The marker device is segmented into multiple light emitting units (at least four) that can be independently controlled to emit light in different patterns. Each unit can be activated or deactivated to create unique identification patterns, allowing multiple markers to be distinguished without requiring additional physical markers or cameras.
Solution Approach 2:
The control system activates different subsets of light emitting units in different time periods or frames, creating temporal patterns of light emission. This periodic activation allows the marker to convey information about its identity and position over time, improving distinguishability without requiring more simultaneous light sources.
2Illumination intensity
If light is emitted from all light emitting units simultaneously, then marker brightness and visibility are maximized, but power consumption increases
Solution Approach 1:
Instead of activating all light emitting units simultaneously, the control system activates only the necessary subset of units required to create the current identification pattern. This partial activation maintains sufficient brightness for tracking while reducing overall power consumption compared to full activation of all units.
Solution Approach 2:
Different subsets of light emitting units are activated in different time periods or frames in a periodic manner. This allows the marker to maintain visibility through temporal patterns while reducing the instantaneous and average power consumption compared to continuous full activation.
3Reliability
If multiple markers are used on the same subject, then tracking coverage is improved, but marker distinguishability becomes difficult
Solution Approach 1:
Each marker is segmented into multiple light emitting units that can be independently controlled. This segmentation allows each marker to generate unique identification patterns through different combinations of activated units, enabling the motion tracking system to distinguish between multiple markers even when they are in close proximity or viewed from different angles.
Solution Approach 2:
The light emitting units are arranged in asymmetric patterns on each marker, and different asymmetric patterns are assigned to different markers. This asymmetry ensures that each marker produces a unique spatial pattern of light that can be easily distinguished from other markers by the motion tracking system, preventing confusion in multi-marker scenarios.
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
Enhances marker visibility and distinguishability, reducing occlusion issues and improving tracking accuracy without increasing the number of cameras or markers, while optimizing light usage and device design for efficient operation.
Implementation Method 1
each optical element is configured to redirect at least a portion of light emitted by the light emitting unit covered by the optical element in such a way as to be more parallel to the mounting portion on which the light emitting unit is mounted
Data Source
AI summary
An active marker device, and method of design thereof, for use in a motion tracking system are provided. In one arrangement, the device comprises a mounting body comprising a mounting surface. A plurality of light emitting units are mounted on respective mounting portions of the mounting surface. A control system controls the plurality of light emitting units such that light is emitted simultaneously from a selected subset of light emitting units. A plurality of optical elements are mounted on the mounting surface. Each optical element covers a different one of the light emitting units and is configured so that an inner surface of the optical element is separated from an outer surface of the light emitting unit. Each optical element redirects a portion of light emitted by the light emitting unit covered by the optical element to be more parallel to the mounting portion of the light emitting unit.