Camera-less Optical Motion Capture Using Light-Direction Detectors
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Solution Overview
Problem
Current motion-capture systems relying on cameras can be cumbersome, require multiple expensive cameras, and often fail to accurately capture six degrees of freedom (6 DoF) motion data, especially when markers are close together or poorly positioned, leading to data contamination and unrealistic animations.
Innovation Solution
A camera-less motion tracking system using light-direction detectors (LDDs) mounted on substrates at varying angles to detect light intensity and transmit current signals to a computing device, allowing for 6 DoF motion analysis without the need for cameras, and can be hybridized with camera-based systems for redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple expensive digital cameras are used to detect infrared signals, then motion capture capability is improved, but system cost and complexity increase
Solution Approach 1:
The patent replaces camera-based optical detection with a direct infrared signal detection system using photodetectors. Instead of using multiple expensive digital cameras to capture and process visual information, the system uses infrared-emitting markers that directly transmit motion data to photodetectors, eliminating the need for complex camera systems while maintaining motion capture precision.
2Measurement precision
If three or more passive markers are applied to track a single point for 6 DoF data, then rotational movement tracking is improved, but data contamination and measurement accuracy deteriorate
Solution Approach 1:
The patent segments the motion tracking function into independent infrared-emitting markers placed at specific anatomical points, each detected by dedicated photodetectors. This segmentation allows each marker to provide independent 6 DoF data without the merging and contamination issues that occur when multiple passive markers are clustered together, thereby improving both accuracy and data reliability.
Solution Approach 2:
The patent introduces infrared radiation as an intermediary between the markers and detectors. Instead of relying on passive reflective markers that require complex camera systems and multiple marker clusters, infrared-emitting markers directly transmit their position and orientation information through infrared signals to photodetectors, eliminating data contamination from marker merging.
3Measurement precision
If passive markers are placed close together physically or at similar angles, then spatial resolution is improved, but marker identification and data accuracy worsen
Solution Approach 1:
The patent uses infrared emission characteristics as a unique identifier for each marker, analogous to color changes. Each infrared-emitting marker can be distinguished by its unique infrared signal properties, allowing clear identification even when markers are placed close together or at similar angles, thereby maintaining spatial resolution while improving marker identification accuracy.
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
Enables accurate and consistent 6 DoF motion capture with reduced equipment complexity and cost, improving data quality and realism in applications like virtual reality and animation by eliminating the need for multiple cameras and enhancing marker placement issues.
Implementation Method 1
The light-direction detectors may be configured to detect, at two optically isolated points, the intensity of a light from a light source. The light-direction detectors may be configured to generate a current signal representing the photodiode differential and proportional to the intensity of the light
Data Source
AI summary
According to some embodiments, a motion tracker device can include a substrate and a plurality of light-direction detectors mounted on the substrate. Each light-direction detector may be configured to: detect, at two optically isolated points, the intensity of a light from a light source; generate a current signal representing the photodiode differential and proportional to the intensity of the light; and transmit the current signal to a computing device. Each of the plurality of light-direction detectors can be mounted on the substrate at an angle selected such that the computing device can use the transmitted signal to determine the motion of a motion tracker with six degrees of freedom.