Particle measuring device, calibration method, and measuring device
For an easy calibration using calibration particles, provided is a measuring device to capture images of target objects. An image analyzer acquires multiple images obtained at a predetermined time interval, (a) specifies the mean-square displacement of a bright point of a calibration particle based on the displacement of the bright point of the calibration particle in the multiple images in a calibration mode, and (b) specifies the mean-square displacement of a bright point of the target particle based on the displacement of the bright point of the target particle in the multiple images in a measurement mode. A particle size analyzer (c) derives the particle size of the target particle from the mean-square displacement of the bright point of the target particle based on the mean-square displacement of the bright point of the calibration particle and the particle size of the calibration particle in an analysis mode.
1. A particle measuring device for measuring a particle size of a target particle in a dispersion medium, comprising:
an image analyzer configured to acquire multiple images obtained at a predetermined time interval, (a) specify a mean-square displacement of a bright point of a calibration particle based on a displacement, in terms of a pixel unit, of the bright point of the calibration particle in the multiple images in a calibration mode, and (b) specify a mean-square displacement of a bright point of the target particle based on a displacement, in terms of a pixel unit, of the bright point of the target particle in the multiple images unit in a measuring mode; and
a particle size analyzer configured to (c) derive the particle size of the target particle from the mean-square displacement of the bright point of the target particle based on the mean-square displacement of the bright point of the calibration particle and a particle size of the calibration particle in an analysis mode.
2. The particle measuring device according to claim 1 , wherein
the image analyzer (a) corrects the displacement of the bright point of the calibration particle based on flow velocity distribution of the dispersion medium to specify the mean-square displacement of the bright point of the calibration particle in the calibration mode, and (b) corrects the displacement of the bright point of the target particle based on the flow velocity distribution of the dispersion medium to specify the mean-square displacement of the bright point of the target particle in the measuring mode.
3. The particle measuring device according to claim 1 , wherein
the particle size analyzer sorts the derived particle size into any of multiple predetermined particle size ranges to count the number of particles in each of the multiple predetermined particle size ranges.
4. The particle measuring device according to claim 1 , wherein
the image analyzer acquires the multiple images obtained at the predetermined time interval, (a) specifies the mean-square displacement of the bright point of the calibration particle based on the displacement, in terms of the pixel unit, of the bright point of the calibration particle in the multiple images to calculate, as a device constant, a product of the mean-square displacement of the bright point of the calibration particle and a particle size of the calibration particle in the calibration mode, and (b) specifies the mean-square displacement of the target particle based on the displacement, in terms of the pixel unit, of the bright point of the target particle in the multiple images in the measuring mode, and
the particle size analyzer (c) derives the particle size of the target particle by dividing the device constant by the mean-square displacement of the bright point of the target particle in the analysis mode.
5. The particle measuring device according to claim 4 , wherein
the image analyzer specifies the mean-square displacement of the bright point of the calibration particle at each of multiple positions in the images, and
the particle size analyzer derives the particle size at a position of the bright point of the target particle in the images based on two-dimensional distribution of the device constant at the multiple positions in the images.
6. A method for calibrating a particle measuring device for capturing an image of a target particle in a dispersion medium by an imaging device to measure a particle size of the target particle, comprising:
specifying, by the particle measuring device, a mean-square displacement of a bright point of a calibration particle based on a displacement, in terms of a pixel unit, of the bright point of the calibration particle in multiple images obtained at a predetermined time interval; and
enabling the particle measuring device, based on the mean-square displacement of the bright point of the calibration particle and on a particle size of the calibration particle, to calculate the particle size of the target particle from a mean-square displacement of a bright point of the target particle specified based on a displacement, in terms of the pixel unit, of the bright point of the target particle in the multiple images obtained at the predetermined time interval.
7. The calibration method according to claim 6 , wherein
the displacement of the bright point of the calibration particle is corrected based on flow velocity distribution of the dispersion medium, and the mean-square displacement of the bright point of the calibration particle is specified accordingly.
8. A measuring device for capturing an image of a target object by an imaging device to measure the target object,
a mean-square displacement, in terms of a physical unit, of a calibration particle of which viscosity is acquired in a dispersion medium being derived according to a Stokes-Einstein expression, and
a mean-square displacement, in terms of a pixel unit, of a bright point of the calibration particle being specified based on a displacement, in terms of the pixel unit, of the bright point of the calibration particle in multiple images obtained in such a manner that an image of the calibration particle in the dispersion medium is captured multiple times at a predetermined time interval by the imaging device, comprising:
a scale calibrated according to a correspondence between the mean-square displacement, in terms of the physical unit, of the calibration particle and the mean-square displacement, in terms of the pixel unit, of the bright point of the calibration particle.