Camera-Based Structural Motion Measurement Using Optical Flow
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional methods for monitoring structural motion, such as using motion sensors and camera-based systems, face challenges like laborious setup, noise interference, and low accuracy, especially in measuring small vibrations from a distance.
Innovation Solution
A method and device that utilize video cameras to measure structural motion by calculating the global optical flow field and correcting for camera motion using a reference object, allowing for high signal-to-noise ratio measurements without the need for sensors attached to the structure or camera, and enabling detection of motions one order of magnitude smaller than previously possible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If motion sensors are attached to the structure to be monitored, then measurement precision is improved, but device complexity and ease of operation deteriorate due to laborious setup, wiring, and maintenance requirements
Solution Approach 1:
The patent replaces mechanical motion sensors attached to the structure with an optical measurement system using a camera to capture video images. The camera-based system measures structural motion by analyzing pixel displacement of reference objects in the video sequence, eliminating the need for physical sensor attachment, wiring, and maintenance while achieving comparable or superior measurement precision for small vibrations
Solution Approach 2:
The patent creates an optical copy (video image) of the structure and measures motion in the copy rather than the physical object itself. By analyzing pixel positions in the video sequence, the system determines structural motion without physical contact, simplifying the measurement process and eliminating sensor installation complexity
2Ease of operation
If video cameras are used to measure structural motion from a distance, then ease of operation is improved, but measurement precision deteriorates due to noise from camera motion
Solution Approach 1:
The patent introduces a reference object as an intermediary to separate camera motion from structural motion. The reference object, which is rigid and does not move with the structure, serves as a stable reference frame. By measuring the apparent motion of the reference object, the system calculates and removes camera-induced noise from the structural motion measurements, restoring measurement precision while maintaining the ease of remote operation
Solution Approach 2:
The patent implements a feedback mechanism where the measured apparent motion of the reference object is used to correct the structural motion measurements. The system continuously monitors reference object displacement and uses this information to compensate for camera motion in real-time, eliminating noise and improving measurement accuracy without requiring the camera to be stationary
3Device complexity
If traditional camera-based measurement methods are used, then device complexity is reduced, but measurement precision deteriorates because noise from camera motion cannot be effectively removed
Solution Approach 1:
The patent segments the motion measurement into two independent components: structural motion and camera motion. By separately measuring the apparent motion of the reference object (which captures only camera motion) and the total motion of the structure, the system can isolate and remove camera-induced noise through subtraction, achieving high measurement precision while keeping the device complexity low
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 measurement of structural vibrations from a distance with minimized noise, facilitating long-term monitoring of structural integrity and health with improved sensitivity and reduced setup complexity.
Implementation Method 1
a sequence of images of the scene including representations of the target object and the reference object
Implementation Method 2
measuring an apparent, sub-pixel motion of the reference object with respect to an imaging plane of the camera
Data Source
AI summary
A method and corresponding apparatus for measuring object motion using camera images may include measuring a global optical flow field of a scene. The scene may include target and reference objects captured in an image sequence. Motion of a camera used to capture the image sequence may be determined relative to the scene by measuring an apparent, sub-pixel motion of the reference object with respect to an imaging plane of the camera. Motion of the target object corrected for the camera motion may be calculated based on the optical flow field of the scene and on the apparent, sub-pixel motion of the reference object with respect to the imaging plane of the camera. Embodiments may enable measuring vibration of structures and objects from long distance in relatively uncontrolled settings, with or without accelerometers, with high signal-to-noise ratios.