Stereo imaging velocimetry system and method
AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorMark McDowell
Life of this patent
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Abstract
A system and a method is provided for measuring three-dimensional velocities at a plurality of points in a fluid employing at least two cameras positioned approximately perpendicular to one another. Image frames captured by the cameras may be filtered using background subtraction with outlier rejection with spike-removal filtering. The cameras may calibrated to accurately represent image coordinates in a world coordinate system using calibration grids modified using warp transformations. The two-dimensional views of the cameras may be recorded for image processing and particle track determination. The tracer particles may be tracked on a two-dimensional basis and then stereo matched to obtain three-dimensional locations of the particles as a function of time so that velocities can be measured therefrom.
Claims23
A method for measuring three-dimensional velocities at a plurality of points in a fluid, comprising the steps of:
- a) positioning at least two cameras to view a fluid with the cameras being approximately perpendicular to one another;
- b) capturing a plurality of image frames of the fluid seeded with tracer particles with each camera;
- c) filtering the image frames using time-averaged background subtraction with outlier rejection;
- and
- d) determining three dimensional coordinates of tracer particle tracks in the filtered image frames;
- e) calculating velocities at a plurality of points in the fluid responsive to the three dimensional coordinates of the tracer particle tracks and time durations between image frames.
A system for measuring three-dimensional velocities at a plurality of points in a fluid, comprising:
- a chamber, wherein the chamber includes a fluid seeded with tracer particles;
- at least two cameras positioned to view the fluid seeded with the tracer particles, wherein the at least two cameras being positioned approximately perpendicular to one another, wherein the at least two cameras are operative to provide a plurality of image frames which include views of the tracer particles seeded in the fluid;
- at least one computer in operative connection with the at least two cameras, wherein the at least one computer is operatively programmed to filter the image frames using time-averaged background subtraction with outlier rejection, wherein the computer is further operatively programmed to determine three dimensional coordinates of tracer particle tracks in the filtered image frames and calculate responsive to three dimensional coordinates and time durations between the image frames, velocities at the plurality of points in the fluid.
A system for measuring three-dimensional velocities at a plurality of points in a fluid, comprising:
- a chamber, wherein the chamber includes a fluid seeded with tracer particles;
- at least two cameras positioned to view the fluid seeded with the tracer particles, wherein the at least two cameras being positioned approximately perpendicular to one another, wherein the at least two cameras are operative to provide a plurality of image frames which include views of the tracer particles seeded in the fluid;
- at least one computer in operative connection with the at least two cameras, wherein the at least one computer includes:
- means for processing the image frames using time-averaged background subtraction with outlier rejection and spike removal filtering
- means for identifying particle tracks for common particles in multiple image frames for each camera;
- means for stereo matching the particle tracks associated with each camera to determining three dimensional coordinates for the tracer particle tracks;
- and
- means for calculating velocity for a plurality of points in the fluid responsive to the three dimensional coordinates of particle tracks and time durations between the image frames.
Dependencies are inferred from the claim text.