Method and system for counting particles in a laminar flow with an imaging device
AssigneeUniversity of Wyoming
InventorPaul E. Johnson
Life of this patent
Estimating the term…
Abstract
An invention is described which allows measurement of the concentration of fluorescent particles in a flowing (laminar) fluid by imaging the flow with a video camera. A beam of illumination is used to illuminate the target particles. Imaging optics are arranged to view the focal plane to form an image of the multiple fluorescent sample particles in the flow stream; a camera records the image formed by the imaging optics, and a counting algorithm enumerates the particles. Operational parameters of the system are adjusted according to an initial estimate of particle density, for example flow rate, exposure time, and sampling interval. In addition, the counting algorithm is selected according to the estimated particle density.
Claims9
A method of enumerating particles in a flow wherein the flow is monitored by an imaging system including an imaging device having a focal plane that images an illuminated cross-section of the flow, the method comprising the steps of:
- (a) imaging one or more frames with the imaging device;
- (b) making a preliminary estimate of particle density, using a default counting algorithm, based upon an imaged frame;
- (c) determining into which of two or more predetermined categories of density the particle density of the imaged frame falls;
- (d) adjusting at least one of the following elements according to the determined density category—
- the counting algorithm;
- a parameter of the imaging system;
- and/or
- the flow speed;
- and
- (e) enumerating particles in the flow after making the adjustment of step (d);
- wherein the adjusting step adjusts the counting algorithm by selecting between counting algorithms designed to operate at different particle density categories;
- wherein the counting algorithms comprise a Lower Particle Density Algorithm and a High Particle Density Algorithm;
- and
- wherein the Lower Particle Density Algorithm implements the steps of—
- differencing two successive image frames;
- flagging groups of pixels above a predetermined threshold of intensity;
- counting flagged groups as particles;
- and
- correcting counts for spatial confusion.
A method of enumerating particles in a flow wherein the flow is monitored by an imaging system including an imaging device having a focal plane that images an illuminated cross-section of the flow, the method comprising the steps of:
- (a) imaging one or more frames with the imaging device;
- (b) making a preliminary estimate of particle density, using a default counting algorithm, based upon an imaged frame;
- (c) determining into which of two or more predetermined categories of density the particle density of the imaged frame falls;
- (d) adjusting at least one of the following elements according to the determined density category
- the counting algorithm,
- a parameter of the imaging system;
- and/or
- the flow speed;
- and
- (e) enumerating particles in the flow after making the adjustment of step (d);
- wherein the adjusting step adjusts the counting algorithm by selecting between counting algorithms designed to operate at different particle density categories;
- wherein the counting algorithms comprise a Lower Particle Density Algorithm and a High Particle Density Algorithm;
- and
- wherein the High Particle Density Algorithm includes the steps of—
- flagging groups of pixels above a predetermined threshold of intensity;
- counting flagged groups as particles;
- and
- applying a spatial confusion correction factor to the count according to a formula based upon the count.
Dependencies are inferred from the claim text.