Imaging system
An imaging system is described for measuring the position or movement of a particle having a size of less than about 20 microns. The system comprises an optional sample holder configured to hold a sample with a particle, an optional illumination source configured to illuminate the sample, a lens having a magnification ratio from about 1:5 to about 5:1 and configured to generate the image of the sample, an image sensor having a pixel size of up to about 20 microns and configured to sense the image of the sample, and an image processor operatively connected to the image sensor to process the image of the particle in order to determine the position or movement of the particle. The dimension of the image of each particle is at least about 1.5 times the dimension of the particle multiplied by the magnification ratio of the lens, and the image of each particle is distributed on at least two pixels of the sensor. The imaged area of the sample is at least about one millimeter squared.
1. An imaging system, comprising:
a. a sample holder configured to hold a sample containing a particle;
b. an illumination source configured to illuminate the sample;
c. a lens having a magnification ratio of from about 1:5 to about 5:1 and configured to generate a blurred image of the particle in the sample, wherein a dimension of the blurred image of the particle is greater than the dimension of the particle multiplied by the magnification ratio of the lens, and wherein a field of view in an image plane of the lens is larger than twice a size of the particle;
d. an image sensor having a pixel size of less than about the dimension of the blurred image of the particle and senses the blurred image of the particle, wherein an intensity of the blurred image of the particle is distributed on at least two pixels of the image sensor to form an intensity distribution; and
e. an image processor operatively connected to the image sensor to process the blurred image of the particle and to find a center of an intensity distribution for multiple pixels of the image sensor within a high precision, sub-pixel particle position measurement resolution in order to determine a position or a movement of the particle, wherein a size of the particle is less than a dimension of about five pixels and wherein the center of the intensity distribution is found by at least one of a two dimensional fit to the intensity distribution and a geometric center of a bead image based on a threshold of the intensity distribution.
2. The imaging system of claim 1 , wherein the sample holder is present and comprises a capillary or a glass slide.
3. The imaging system of claim 1 , wherein the size of the particle is from about 0.5 microns to about 2 microns.
4. The imaging system of claim 1 , wherein there are from about 100 particles to about 1 million particles in an imaged area of the sample.
5. The imaging system of claim 1 , wherein the illumination source is present and provides a bright-field illumination or a dark-field illumination.
6. The imaging system of claim 1 , wherein the illumination source is present and comprises an LED ring light.
7. The imaging system of claim 1 , wherein the lens comprises a single lens, or a compound lens comprising several simple lenses, or an objective lens.
8. The imaging system of claim 1 , wherein the lens comprises a telecentric lens.
9. The imaging system of claim 8 , wherein the lens comprises an object-space telecentric lens.
10. The imaging system of claim 8 , wherein the lens comprises a double telecentric lens.
11. The imaging system of claim 1 , wherein the pixel size of the image sensor is less than about 5 microns.
12. The imaging system of claim 1 , wherein the image sensor comprises a CCD chip or a CMOS chip.
13. The imaging system of claim 1 , wherein the image processor comprises a computer or an embedded processor in an embedded system.
14. The imaging system of claim 1 , wherein the image processor associates the position of the particle with the center of the intensity distribution for multiple pixels of the image sensor.
15. The imaging system of claim 14 , wherein a center of the particle is calculated by fitting a Gaussian surface to an intensity profile of an image of the particle.
16. The imaging system of claim 14 , wherein a center of the particle is obtained as a geometric center of a binary image of the particle.
17. The imaging system of claim 1 , wherein the image processor is configured to determine the movement of the particle by determining a first position and a second position of the particle, and calculating a displacement between said first position and the second position.
18. A method of determining a position or a movement of a particle in a sample, comprising the steps of:
a. providing a sample having a particle, wherein a size of the particle is less than about 20 microns;
b. optionally illuminating the sample;
c. optionally positioning the sample along an optical axis of a lens at a distance from a focal plane of the lens that is greater than a depth of field of the lens;
d. generating a blurred image of the particle with the lens having a magnification ratio of from about 1:5 to about 5:1, wherein a dimension of the blurred image of the particle is greater than the dimension of the particle multiplied by the magnification ratio of the lens, and wherein a field of view in an image plane of the lens is larger than twice the size of the particle;
e. sensing the blurred image of the particle on at least two pixels of an image sensor having a pixel size of less than about the dimension of the blurred image of the particle wherein an intensity of the blurred image of the particle is distributed on at least two pixels of the image sensor to form an intensity distribution; and
f. processing an image of the sample, including finding a center of an intensity distribution for at least two pixels within a high precision, sub-pixel particle position measurement resolution, to measure the position or the movement of the particle, wherein a size of the particle is less than a dimension of about five pixels and wherein finding the center of the intensity distribution comprises at least one of finding a two dimensional fit to the intensity distribution and finding a geometric center of a bead image based on a threshold of the intensity distribution.
19. The method of claim 18 , wherein the sample is located on a capillary or a glass slide.
20. The method of claim 18 , wherein the size of the particle is from about 0.5 microns to about 2 microns.
21. The method of claim 18 , wherein there are from about 100 particles to about 1 million particles in an imaged area of the sample.
22. The method of claim 18 , wherein the sample is illuminated with a bright-field illumination or a dark-field illumination.
23. The method of claim 18 , wherein the sample is illuminated with an LED ring light.
24. The method of claim 18 , wherein the lens comprises a single lens, or a compound lens comprising several simple lenses, or an objective lens.
25. The method of claim 18 , wherein the lens comprises a telecentric lens.
26. The method of claim 25 , wherein the lens comprises an object-space telecentric lens.
27. The method of claim 25 , wherein the lens comprises a double telecentric lens.
28. The method of claim 18 , wherein the magnification ratio of the lens is from about 1:10 to about 10:1.
29. The method of claim 18 , wherein the pixel size of the image sensor is less than about 5 microns.
30. The method of claim 18 , wherein the image sensor comprises a CCD chip or a CMOS chip.
31. The method of claim 18 , wherein processing an image of the sample comprises using a computer or an embedded processor in an embedded system.
32. The method of claim 18 , wherein a center of the particle is calculated as the position of the particle.
33. The method of claim 32 , wherein the center of the particle is calculated by fitting a Gaussian mode to an intensity profile of an image of the particle.
34. The method of claim 32 , wherein the center of the particle is obtained as a geometric center of a binary image of the particle.
35. The method of claim 18 , wherein the movement of the particle is determined by using steps a through f to determine a first position and a second position of the particle, and calculating a displacement between the first position and the second position of the particle.