Brownian motion correction method for particle measurement
A flow passage is irradiated with irradiation light, and light scattered from a particle contained in a sample passing through a detection region that is formed in a prescribed section is condensed at a position obtained by extending the prescribed section in a flow direction of the sample and captured at a prescribed frame rate. Then movement amount of the particle due to Brownian motion in directions perpendicular to the flow direction on the basis of captured plural frame images. Furthermore, a particle size of the particle is determined by correcting the movement amount using correction values that were obtained in advance corresponding to each of defocus positions for correcting errors of movement amount in the images caused by magnification.
1 . A particle measuring method comprising:
irradiating a sample flowing through a flow passage with irradiation light;
condensing light scattered from a particle contained in the sample passing through a detection region that is formed in a prescribed section of the flow passage by irradiation with the irradiation light, at a position obtained by extending the prescribed section in a flow direction of the sample;
capturing, by a camera, the condensed scattered light at a prescribed frame rate;
calculating movement amount of the particle due to Brownian motion in two-dimensional directions on a basis of captured plural frame images;
correcting the calculated movement amount using correction values that were obtained in advance so as to correspond to each of defocus positions of frame images captured the condensed scattered light to correct for a magnification error that occurs due to defocusing at condensing the scattered light;
determining a particle size of the particle on the basis of the corrected movement amount;
outputting a result of the determination of the particle size to one of a display screen, a printer, a storage unit, and a network,
wherein the correcting the calculated movement amount comprises using a correction map that stores the correction values corresponding to respective positions on a light receiving surface of the camera, and
wherein the correction values are obtained by optical simulation software that calculates magnification errors for predetermined object heights at different defocus positions in the flow direction.
2 . The particle measuring method according to claim 1 , implement by a particle measuring device that comprises:
a flow cell having the flow passage inside;
a light source which emits the irradiation light;
an irradiation optical system which irradiates the sample flowing through the flow passage with the irradiation light;
a condensing optical system which condenses light scattered from the particle contained in the sample passing through the detection region that is formed in the prescribed section of the flow passage by irradiation with the irradiation light, at a position downstream of the prescribed section in the flow direction of the sample; and
the camera which captures condensed scattered light at the prescribed frame rate.
3 . The particle measuring method according to claim 1 , wherein the correction values are expressed in a unit of velocity.
4 . A correction method of a particle measuring device which condenses light scattered from a particle contained in a sample passing through a detection region that is formed in a prescribed section of a flow passage by irradiation with irradiation light, at a position obtained by extending the prescribed section in a flow direction of the sample, and captures, by a camera, the scattered light at a prescribed frame rate, and which calculates movement amount of the particle due to Brownian motion in two-dimensional directions on a basis of captured plural frame images, and determines a particle size, the correction method comprising:
correcting the movement amount using correction values to correct for a magnification error that occurs due to defocusing at the condensing the scattered light, where the correction values being obtained in advance so as to correspond to each of defocus positions of the captured frame images;
determining a particle size of the particle on the basis of the corrected movement amount;
outputting a result of the determination of the particle size to one of a display screen, a printer, a storage unit, and a network,
wherein the correcting the calculated movement amount comprises using a correction map that stores the correction values corresponding to respective positions on a light receiving surface of the camera, and
wherein the correction values are obtained by optical simulation software that calculates magnification errors for predetermined object heights at different defocus positions in the flow direction.