Micron resolution particle image velocimeter

• US 6,653,651 B1
• Filed: 12/02/1999
• Issued: 11/25/2003
• Est. Priority Date: 12/09/1998
• Status: Expired due to Term

• Current Assignee: Carl D. Meinhart, Juan G. Santiago, Ronald J. Adrian, Steve T. Wereley
• Original Assignee: Carl D. Meinhart, Juan G. Santiago, Ronald J. Adrian, Steve T. Wereley
• Inventors: Santiago, Juan G., Meinhart, Carl D., Wereley, Steve T., Adrian, Ronald J.
• Primary Examiner(s): Le, Que T.
• Assistant Examiner(s): Luu, Thanh X.
• Application Number:
  US09/453,138
• Time in Patent Office: 1,454 Days
• Field of Search: 290/573-577, 290/356.1, 290/356.2, 356/335, 356/348, 356/441, 356/442, 356/243.2, 356/27, 356/28, 356/28.5, 738/61, 738/610.4, 738/610.5
• US Class Current: 250/573
• CPC Class Codes: G01F 1/712 using auto-correlation or cross-correlation detection means
• CPC Class Codes: G01N 15/1427 with the synchronisation of components, a time gate for operation of components, or suppression of particle coincidences
• CPC Class Codes: G01N 15/1433 using image recognition
• CPC Class Codes: G01N 15/1459 the analysis being performed on a sample stream
• CPC Class Codes: G01N 2015/1027 Determining speed or velocity of a particle
• CPC Class Codes: G01N 2015/1447 Spatial selection

Abstract

A method and apparatus for measuring fluid motion with micron scale spatial resolution has been developed. Here, micron or submicron solid fluorescent particles are injected into the fluid body. The particles are chosen to closely follow the motion of the fluid. Pulses of light, at the excitation wavelength, broadly illuminate the test device and the fluorescent particles, The flourescent particles absorb the excitation light and emit pulses of fluorescent light, at the emission wavelength. The fluorescent light is collected by a microscope objective lens, and relayed through a fluorescent filter to an image recording device, such as a CCD camera. Subsequently, discrete images of discrete particles at two or more instances in time are recorded. These images can then be analyzed using correlation analysis to obtain velocity measurements. Since the illumination light broadly illuminates the test section, the depth of field of the objective lens is used to define the thickness of the two-dimensional measurement plane.

Claims

1. A test apparatus for measuring with approximately microscale spatial resolution the velocity of fluid flow in a passageway, comprising:

(a) a test device having a passageway through which a fluid to be tested is flowing;

(b) the fluid to be tested containing solid particles having a fluorescent dye with a known excitation wavelength and a known emission wavelength, and wherein the solid particles approximately follow the motion of the flowing fluid;

(c) the passageway in the test device having a transparent wall through which the solid particles in the flowing fluid may be observed;

(d) a light source for repetitively delivering closely spaced pulses of light, with the pulses of light having a known duration, and a known time delay between the pulses;

(e) a mirror positioned between the light source and the test device and being positioned to reflect light from the light source to the test device, the mirror being coated to reflect light at the excitation wavelength;

(f) a microscope objective lens positioned between the mirror and the test device for receiving light at the excitation wavelength reflected from the mirror and transmitting it to the test device, so as to broadly illuminate the test device with pulses of light at the excitation wavelength, such that the fluorescent dye contained within the solid particles absorbs pulses of light at the excitation wavelength and emits pulses of fluorescent light at the emission wavelength;

(g) the microscope objective lens having a known depth of field and being positioned to image fluorescent light emitted from the solid particles within the flowing fluid;

(h) the mirror being coated to transmit the fluorescent light at the emission wavelength received through the microscope objective lens from the solid particles;

(i) a barrier filter for receiving fluorescent light passing through the mirror at the emission wavelength while rejecting light at the excitation wavelength;

(j) an image recording device positioned to receive fluorescent light transmitted from the test device through the microscope objective lens, the mirror and the barrier filter, thereby recording discrete images of discrete particles; and

(k) the solid particles lying within the known depth of field of the microscope objective lens emitting fluorescent light that produce in-focus particle images, such that the depth of field of the microscope objective lens defines a two-dimensional measurement plane within the flowing fluid in which fluid velocity can be determined from the in focus discrete images of discrete particles.

2. The apparatus of claim 1 wherein the duration of said pulses of light is of the order of five nanoseconds, and the known time delay between the spaced pulses is in the approximate range of several nanoseconds to several seconds.

3. The apparatus of claim 1 which further includes average correlation analysis means associated with the image recording device.

4. A method of measuring with approximately microscale spatial resolution the velocity of a flowing fluid, the method comprising the steps of:

(a) injecting into the fluid a plurality of solid particles that approximately follow the motion of the flowing fluid, with the solid particles containing fluorescent dye having a known excitation wavelength and a known emission wavelength;

(b) selecting a light source for repetitively delivering closely spaced pulses of light at the excitation wavelength having a known duration and a known time delay between the pulses;

(c) positioning a microscope objective lens having a known depth of field to transmit pulses of light from the light source into the flowing fluid and positioned to image within the flowing fluid;

(d) gathering pulses of fluorescent light, emitted by the solid particles contained within the flowing fluid, through said microscope objective lens;

(e) relaying the gathered pulses of fluorescent light from the objective lens through a barrier filter to an image recording device, thereby recording discrete images of discrete particles;

(f) wherein only fluorescent light from the solid particles lying within the depth of field of the objective lens will produce well-focused discrete images of discrete particles that are recorded by the image recording device, thereby determining a two-dimensional measurement plane in the flowing fluid; and

(g) analyzing the recorded discrete images of discrete particles to determine the velocity of the particles, and therefore determine the velocity of the flowing fluid.

5. The method of claim 4 wherein the duration of said pulses of light is of the order of five nanoseconds, and the known time delay between the spaced pulses is in the approximate range of several nanoseconds to several seconds.

6. The method of claim 4 which further includes the step of analyzing a successively recorded time sequence of discrete images of discrete fluorescent particles by average correlation analysis at multiple points within the image field to determine the average fluid velocities at multiple respective points within the two-dimensional measurement plane.

7. A test apparatus for measuring with approximately microscale spatial resolution the velocity of fluid flow in a passageway, comprising:

(a) a test device having a passageway through which a fluid to be tested is flowing;

(b) the fluid to be tested containing solid particles having a fluorescent dye with a known excitation wavelength and a known emission wavelength, and wherein the solid particles approximately follow the motion of the flowing fluid;

(c) the passageway in the test device having a transparent wall through which the solid particles in the flowing fluid may be observed;

(d) a light source for repetitively delivering closely spaced pulses of light, with the pulses of light having a known duration of the order of five nanoseconds, and the known time delay between the spaced pulses being in the approximate range of several nanoseconds to several seconds;

(e) a mirror positioned between the light source and the test device and being positioned to reflect light from the light source to the test device, the mirror being coated to reflect light at the excitation wavelength;

(f) a microscope objective lens positioned between the mirror and the test device for receiving light at the excitation wavelength reflected from the mirror and transmitting it to the test device, so as to broadly illuminate the test device with pulses of light at the excitation wavelength, such that the fluorescent dye contained within the solid particles absorbs pulses of light at the excitation wavelength and emits pulses of fluorescent light at the emission wavelength;

(g) the microscope objective lens having a known depth of field and being positioned to image fluorescent light emitted from the solid particles within the flowing fluid;

(h) the mirror being coated to transmit the fluorescent light at the emission wavelength received through the microscope objective lens from the solid particles;

(i) a barrier filter for receiving fluorescent light passing through the mirror at the emission wavelength while rejecting light at the excitation wavelength;

(j) an image recording device positioned to receive fluorescent light transmitted from the test device through the microscope objective lens, the mirror and the barrier filter, thereby recording discrete images of discrete particles;

(k) the solid particles lying within the known depth of field of the microscope objective lens emitting fluorescent light that produce in-focus particle images, such that the depth of field of the microscope objective lens defines a two-dimensional measurement plane within the flowing fluid in which fluid velocity can be determined from the in focus discrete images of discrete particles; and

(l) which further includes average correlation analysis means associated with the image recording device.

8. A method of measuring with approximately microscale spatial resolution the velocity of a flowing fluid, the method comprising the steps of:

(a) injecting into the fluid a plurality of solid particles that approximately follow the motion of the flowing fluid, with the solid particles containing fluorescent dye having a known excitation wavelength and a known emission wavelength;

(b) selecting a light source for repetitively delivering closely spaced pulses of light at the excitation wavelength having a known duration of the order of five nanoseconds, and a known time delay between the spaced pulses in the approximate range of several nanoseconds to several seconds;

(c) positioning a microscope objective lens having a known depth of field to transmit pulses of light from the light source into the flowing fluid and positioned to image within the flowing fluid;

(h) gathering pulses of fluorescent light, emitted by the solid particles contained within the flowing fluid, through said microscope objective lens;

(i) relaying the gathered pulses of fluorescent light from the objective lens through a barrier filter to an image recording device, thereby recording discrete images of discrete particles;

(j) wherein only fluorescent light from the solid particles lying within the depth of field of the objective lens will produce well-focused discrete images of discrete particles that are recorded by the image recording device, thereby determining a two-dimensional measurement plane in the flowing fluid; and

(k) which further includes the step of analyzing a successively recorded time sequence of discrete images of discrete fluorescent particles by average correlation analysis at multiple points within the image field to determine the average fluid velocities at multiple respective points within the two-dimensional measurement plane.

9. A method of measuring motion within a fluid body comprising the steps of:

(a) selecting fluorescent particles having an excitation wavelength and an emission wavelength;

(b) injecting a plurality of the fluorescent particles into the fluid body in dispersed relation to move therewith;

(c) repetitively applying a short pulse of light at the excitation wavelength at periodic intervals to broadly illuminate the fluid body;

(d) after each pulse of the impinging light, observing light emitted from the individual particles at the emission wavelength through an objective lens, whereby the depth of field of the objective lens defines a measurement field within the fluid body; and

(e) then comparing successively observed discrete images of discrete particles at the emission wavelength as a function of time to determine the motion of the fluid body.

10. The method of claim 9 wherein the pulses of impinging light are applied through an objective lens having a high numerical aperture, and the emitted light is observed through the same objective lens.

11. The method of claim 9 wherein the images of discrete particles at the emission wavelength are observed to determine two vectorial components of the measurement field.

12. The method of claim 10 wherein the images of discrete particles at the emission wavelength are observed to determine two vectorial components of the measurement field.