Particle measuring apparatus
An object of the invention is to provide a particle measuring device capable of determining a type of a particle. The particle measuring device according to the invention repeatedly scans a focal position of light along an optical axis direction in a three-dimensional region in a sample, calculates two or more of (a) one or more parameters that are obtained based on a maximum intensity of reflected light from particles, the maximum intensity being acquired from each focal position in a scanning process, and that indicate a type of the particles and (b) one or more parameters that are obtained based on positions of the particles acquired by continuously tracking the particles and that indicate a type of the particles, and outputs a calculation result.
1 . A particle measuring device for measuring a particle contained in a sample containing a solvent and the particle, the particle measuring device comprising:
a light source configured to emit light;
a condenser lens configured to condense the light and irradiate the sample with the light;
a two-dimensional scanner configured to repeatedly scan a focal position of the light in a three-dimensional region in the sample;
a photodetector configured to detect reflected light from the particle;
an image generation unit configured to generate a three-dimensional image of the sample based on a signal detected by the photodetector; and
an analysis unit configured to analyze the three-dimensional image, wherein
the analysis unit calculates two or more of
one or more parameters that are obtained based on a maximum intensity of the reflected light from the focal position during a process of repeatedly scanning the focal position along an optical axis direction of the light in the three-dimensional region, and that indicate a type of the particle, and
one or more parameters that are obtained based on a position of the particle acquired by continuously tracking the particle and that indicate a type of the particle, and
outputs a calculation result;
wherein the analysis unit outputs, as the parameters, two or more of
the maximum intensity,
a sphericity of the particle calculated based on the maximum intensity obtained by causing the focal position to repeatedly reciprocate in the three-dimensional region along the optical axis direction,
a diffusion constant of the particle calculated based on a change in time in a position of the particle, or a size of the particle calculated based on the diffusion constant, and
a sedimentation velocity of the particle calculated based on a change in time in a position of the particle in a gravity direction.
2 . The particle measuring device according to claim 1 , wherein
the analysis unit calculates a size of the particle as the parameter according to a relationship among the maximum intensity, a refractive index of the particle, a refractive index of the solvent, and a size of the particle.
3 . The particle measuring device according to claim 1 , wherein
the two-dimensional scanner repeatedly causes the focal position to reciprocate along the optical axis direction in the three-dimensional region,
the analysis unit acquires, for each reciprocation, the maximum intensity obtained from the focal position in a process of causing the focal position to reciprocate, and
the analysis unit calculates, as the parameter, a numerical value representing a sphericity of the particle using a maximum value and a minimum value among maximum intensities in all repeated reciprocations.
4 . The particle measuring device according to claim 1 , wherein
when t is a time required for the two-dimensional scanner to scan the three-dimensional region once, n is a concentration of a maximum particle to be measured, D is a diffusion constant of a minimum particle to be measured, and a is a constant of one or more,
t
<
n
-
2
/
3
24
α
2
D
is satisfied.
5 . The particle measuring device according to claim 1 , wherein
the two-dimensional scanner repeatedly scans the focal position of the light in the three-dimensional region by repeating a step of scanning the focal position of the light in a two-dimensional plane perpendicular to the optical axis and a step of moving a position of the focal point of the light relative to the sample along the optical axis direction at an interval p z , and
when L z is a width of the three-dimensional region along the optical axis direction, Δt is a time required for the two-dimensional scanner to scan the two-dimensional plane once, n is a concentration of a maximum particle to be measured, D is a diffusion constant of a minimum particle to be measured, and a is a constant of one or more,
Δ
t
<
n
-
2
/
3
p
z
24
α
2
DL
z
is satisfied.
6 . The particle measuring device according to claim 1 , wherein
when L x and L y are respectively widths in vertical and horizontal directions of the three-dimensional region in a plane perpendicular to the optical axis, L z is a width in the optical axis direction of the three-dimensional region, t is a time required for the two-dimensional scanner to scan the three-dimensional region once, N is the number of times the two-dimensional scanner repeatedly scans the three-dimensional region, D is a diffusion constant of a minimum particle to be measured, α is a constant of one or more, ρ p is a density of the particle, ρ s is a density of the solvent, n is a viscosity of the solvent, g is a gravitational acceleration, and d is a diameter of the particle,
L
x
≥
2
α
2
DNt
L
y
≥
2
α
2
DNt
L
z
≥
max
d
,
ρ
p
-
ρ
s
>
0
{
α
2
DNt
+
❘
"\[LeftBracketingBar]"
(
ρ
p
-
ρ
s
)
g
18
η
d
2
❘
"\[RightBracketingBar]"
Nt
}
+
max
d
,
ρ
p
-
ρ
s
<
0
{
α
2
DNt
+
❘
"\[LeftBracketingBar]"
(
ρ
p
-
ρ
s
)
g
18
η
d
2
❘
"\[RightBracketingBar]"
Nt
}
is satisfied.
7 . The particle measuring device according to claim 1 , wherein
when L x and L y are respectively widths in vertical and horizontal directions of the three-dimensional region in a plane perpendicular to the optical axis, L z is a width in the optical axis direction of the three-dimensional region, t is a time required for the two-dimensional scanner to scan the three-dimensional region once, N is the number of times the scanning unit two-dimensional scanner repeatedly scans the three-dimensional region, D is a diffusion constant of a minimum particle to be measured, and a is a constant of one or more,
L
x
≥
2
α
2
DNt
L
y
≥
2
α
2
DNt
L
z
≥
2
α
2
DNt
is satisfied.
8 . The particle measuring device according to claim 1 , wherein
the two-dimensional scanner repeatedly scans the focal position of the light in the three-dimensional region by repeating a step of scanning the focal position of the light in a two-dimensional plane perpendicular to the optical axis and a step of moving a position of a focal point of the light relative to the sample along the optical axis direction at an interval p z , and
when L x and L y are respectively widths in vertical and horizontal directions of the three-dimensional region in a plane perpendicular to the optical axis, L z is a width in the optical axis direction of the three-dimensional region, Δt is a time required for the two-dimensional scanner to scan the two-dimensional plane once, N is the number of times the two-dimensional scanner repeatedly scans the three-dimensional region, D is a diffusion constant of a minimum particle to be measured, and a is a constant of one or more,
L
x
≥
2
α
2
DNt
L
y
≥
2
α
2
DNt
L
z
>
8
α
2
DN
Δ
t
p
z
is satisfied.
9 . The particle measuring device according to claim 1 , wherein
the analysis unit calculates a diffusion coefficient of the particle as the parameter based on a change in time in a position of the particle.
10 . The particle measuring device according to claim 9 , wherein
the analysis unit calculates a size of the particle as the parameter based on the diffusion coefficient of the particle.
11 . The particle measuring device according to claim 1 , wherein
the analysis unit calculates a sedimentation velocity of the particle as the parameter based on a change in time in a position of the particle in a gravity direction.
12 . The particle measuring device according to claim 11 , wherein
the analysis unit classifies a type of the particle by using a signal amplitude of the reflected light and the sedimentation velocity as the parameters.
13 . The particle measuring device according to claim 1 , further comprising:
a polarized beam splitter configured to split light emitted from the light source to generate signal light and reference light; and
an interference optical system configured to combine the signal light reflected from the sample with the reference light to generate three or more beams of interference light having different phase relationships from one another, wherein
the photodetector detects the interference light and outputs the interference light as an electric signal.
14 . The particle measuring device according to claim 1 , wherein
the analysis unit determines a type of the particle using the two or more parameters and outputs a determination result.