U.S. patent application number 09/805208 was filed with the patent office on 2001-12-13 for particle measurement apparatus and method.
Invention is credited to Shinabe, Seiya, Ueno, Kunio.
Application Number | 20010050562 09/805208 |
Document ID | / |
Family ID | 18589206 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010050562 |
Kind Code |
A1 |
Shinabe, Seiya ; et
al. |
December 13, 2001 |
Particle measurement apparatus and method
Abstract
A particle measurement apparatus includes: a particle signal
detector for detecting a particle signal; a false signal generator
for generating a false signal corresponding to the particle signal;
a selector for selecting the particle signal or the false signal, a
non-linear amplifier; a first calculator for receiving the signal
selected by the selector through the non-linear amplifier to
calculate a characteristic parameter; a second calculator for
receiving the signal selected by the selector not through the
non-linear amplifier to calculate the characteristic parameter; a
comparator for including the characteristic parameters calculated
by the first and second calculators respectively when the selector
selects the false signal; a memory for storing a comparison result
of the comparator; and a compensator for compensating the
characteristic parameter calculated by the first calculator on the
basis of the comparison result when the selector selects the
particle signal.
Inventors: |
Shinabe, Seiya; (Kobe-shi,
JP) ; Ueno, Kunio; (Kakogawa-shi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
18589206 |
Appl. No.: |
09/805208 |
Filed: |
March 14, 2001 |
Current U.S.
Class: |
324/710 |
Current CPC
Class: |
G01N 2015/1087 20130101;
G01N 2015/1493 20130101; G01N 15/12 20130101; G01N 15/1227
20130101; G01N 15/1459 20130101 |
Class at
Publication: |
324/710 |
International
Class: |
G01R 027/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2000 |
JP |
2000-070479 |
Claims
What is claimed is:
1. A particle measurement apparatus comprising: a particle signal
detecting section for detecting a particle signal with respect to a
plurality of particles, the particle signal representing
characteristics of each particle; a false signal generating section
for generating a false signal corresponding to the particle signal;
a selecting section for selecting the particle signal or the false
signal, a non-linear amplifier; a first calculating section for
receiving the signal selected by the selecting section through the
non-linear amplifier to calculate a characteristic parameter; a
second calculating section for receiving the signal selected by the
selection section not through the non-linear amplifier to calculate
the characteristic parameter; a comparison section for comparing
the characteristic parameters calculated by the first and second
calculating sections respectively when the selecting section
selects the false signal; a storage section for storing a
comparison result of the comparison section; and a compensating
section for compensating the characteristic parameter calculated by
the first calculating section on the basis of the comparison result
when the selection section selects the particle signal.
2. The particle measurement apparatus of claim 1, wherein the
particle signal detecting section comprises an electric
measurement-type particle detector.
3. The particle measurement apparatus of claim 1, wherein the
non-linear amplifier comprises a logarithmic amplifier.
4. The particle measurement apparatus of claim 1, wherein the false
signal generating section comprises a pulse generating circuit and
a gain variable amplifier.
5. The particle measurement apparatus of claim 1, wherein the
selecting section comprises an analog switch.
6. The particle measurement apparatus of claim 1, wherein the
second calculating section calculates the characteristic parameter
using a mathematical non-linear function.
7. The particle measurement apparatus of claim 1, wherein the
characteristics parameter comprises a pulse height and pulse width
or a particle volume and particle diameter calculated on the basis
thereof.
8. The particle measurement apparatus of claim 1, wherein the
storage section comprises a ROM.
9. The particle measurement apparatus of claim 1, wherein the
comparison result is stored as a correction curve on a rectangular
coordinates.
10. The particle measurement apparatus of claim 1, further
comprising a first A/D converter for beforehand converting the
signal input to the first calculating section into a digital signal
and a second A/D converter for beforehand converting the signal
input to the second calculating section into a digital signal.
11. A method of measuring particles, comprising the steps of:
making a preparation for measurement by sucking a sample liquid
containing particles to introduce the same into a particle signal
detector; generating a false signal corresponding to a particle
signal which really represents characteristics of a plurality of
particle; calculating a first characteristic parameter by receiving
the false signal through a non-linear amplifier; calculating a
second characteristic parameter by receiving the false signal not
through the non-linear amplifier; comparing the first
characteristic parameter with the second characteristic parameter;
storing a comparison result; detecting a particle signal by the
particle detector; calculating a third characteristic parameter by
receiving the detected particle signal through the non-linear
amplifier; and correcting the third characteristic parameter on the
basis of the comparison result.
12. The method of claim 4, wherein the steps from the false signal
generating step to the storing step are carried out along with the
measurement preparations step.
13. The method of claim 4 which is carried out by the apparatus of
claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is related to Japanese Patent Application
No. 2000-70479 filed on Mar. 14, 2000, whose priority is claimed
under 35 USC .sctn. 119, the disclosure of which is incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a particle measurement
apparatus and method and more particularly to an apparatus and
method for calculating a characteristic parameter by processing a
signal representative of particle characteristics through a
nonlinear amplifier.
[0004] 2. Description of the Related Art
[0005] Particle measurement apparatuses usually employ a linear
amplifier for amplifying an electrical signal obtained from
particles, i.e., a particle signal to be measured.
[0006] The linear amplifier used in such apparatuses is required to
maintain the precision of linearity for accurate measurements.
Therefore some techniques to compensate or correct the
amplification characteristics of the linear amplifier are
conventionally proposed (see, Japanese unexamined patent
publication Nos. Hei 7(1995)-145718 and Hei 2(1990)-206905).
[0007] On the other hand, in case the particle measurement
apparatuses measure industrial particles, the apparatuses use a
non-linear amplifier, e.g., a logarithmic amplifier rather than the
linear amplifier. It is because the industrial particles have a
wide range of diameter from submicrons to hundreds of microns and
the non-liner amplifier can conveniently cover the wide range.
[0008] However, few techniques for compensating the amplification
characteristics of the non-linear amplifier have been known.
SUMMARY OF THE INVENTION
[0009] In view of such circumstances, it is an object of the
present invention to provide a particle measurement apparatus and
method in which the characteristics of the non-linear amplifier
used for processing the particle signal are compensated so as to
permit a wide range particle measurement with high precision.
[0010] The object of the present invention is attained by providing
a particle measurement apparatus comprising: a particle signal
detecting section for detecting a particle signal with respect to a
plurality of particles, the particle signal representing
characteristics of each particle; a false signal generating section
for generating a false signal corresponding to the particle signal;
a selecting section for selecting the particle signal or the false
signal, a non-linear amplifier; a first calculating section for
receiving the signal selected by the selecting section through the
non-linear amplifier to calculate a characteristic parameter; a
second calculating section for receiving the signal selected by the
selection section not through the non-linear amplifier to calculate
the characteristic parameter; a comparison section for comparing
the characteristic parameters calculated by the first and second
calculating sections respectively when the selecting section
selects the false signal; a storage section for storing a
comparison result of the comparison section; and a compensating
section for compensating the characteristic parameter calculated by
the first calculating section on the basis of the comparison result
when the selection section selects the particle signal.
[0011] In other words, the apparatus of the present invention is so
constituted as to check an input-output characteristics of the
non-linear amplifier using a false signal beforehand so that when a
real particle signal is amplified by the non-linear amplifier to
calculate the characteristic parameter of the particle, a result of
the calculation may be compensated using the aforesaid input-output
characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A preferred embodiment of the present invention will be
illustrated, and not by way of limitation, in conjunction with the
accompanying drawings, in which:
[0013] FIG. 1 is a block diagram of a particle measurement
apparatus embodying the present invention.
[0014] FIG. 2 is a correction curve in the embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] The object particles to be measured in the present invention
include a toner, graphite, silica, abrasive material, ceramic
powder, pigment, powder paint, cultured cell, blood cell, yeast,
plankton and magnetic powder. The particle size in diameter ranges
from submicrons to hundreds of microns.
[0016] In the present invention, the particle signal detecting
section which individually detects the characteristics of a
plurality of particles and convert them into a particle signal may
be an optical flow cytometer-type detector in which a solution
containing particles is flowed into a sheath flow cell to detect
optical information from the particles or an electric
measurement-type detector wherein a solution containing particles
is flowed through an orifice (microscopic hole) to detect a change
in electrical impedance of the particle-contained solution, for
example.
[0017] The detecting section detects and converts the
characteristics of particles into a particle signal. This particle
signal is an analog pulse signal, for example. In case the optical
flow cytometer-type detector is used as the detecting section, the
signal shows a change in time of the intensity of such light rays
as forward scattered, side scattered and fluorescent lights from
the particles. In case the electric measurement-type detector is
used as the detecting section, its signal shows a change in time of
the electric impedance.
[0018] In the false signal generating section for generating false
signals, a signal generator may be used that generates an analogue
signal, for example, a pulse-formed signal corresponding to a
plurality of particles different in size and kind to be detected by
the particle signal detecting section.
[0019] The selecting section is provided with a switching function,
for which an analog switch, for example, may be used. As non-linear
amplifier may be used a logarithmic amplifier TL441 (Texas
Instruments), for example. Some of the same type amplifiers may be
combined (for example, by cascade connection) to expand its
input-output range.
[0020] The first calculating section receives a signal (particle
signal or false signal) selected by the selecting section through
the non-linear amplifier and calculates the characteristic
parameters. The second calculating section receives a signal
selected by the selecting section not through the non-linear
amplifier and calculates the characteristic parameters. The
calculated parameters may include sampling values such as, for
example, a signal peak value (pulse height) and pulse width, or a
particle volume and particle diameter calculated on the basis
thereof.
[0021] Since the first calculating section calculates the
characteristic parameters on the basis of the particle signal or
false signal through the non-linear amplifier, the calculated
parameters will be values that require to be corrected depending on
the input-output characteristics of the non-linear amplifier. On
the other hand, the second calculating section calculates the
characteristic parameters from a false signal not through the
non-linear amplifier, and therefore, the calculated parameters will
be highly accurate values. But the calculation has to be performed
using a mathematical non-linear function instead of the non-linear
amplifier. Thus, the calculation process is complicated and takes
longer than the process of the first calculating section.
[0022] The comparison section compares two kinds of characteristic
parameters calculated by the first and second calculating sections
respectively when the selecting section selects the false signal.
In that case, the two kinds of characteristic parameters may be
compared by converting them into a correction curve on a
rectangular coordinates. Also, a correction table or the like may
be prepared to calculate a difference between the two kinds of
parameters for comparison.
[0023] The storage section preferably comprises rewritable memory
such a RAM, since the storage section stores renewably the
aforesaid correction curve or correction table.
[0024] It is noted that the first and second calculating sections,
comparison section, storage section, compensating section may be
integrally formed using a personal computer or microcomputer.
[0025] In another aspect, the present invention provides a method
of measuring particles, comprising the steps of: making a
preparation for measurement by sucking a sample liquid containing
particles to introduce the same into a particle signal detector;
generating a false signal corresponding to a particle signal which
really represents characteristics of a plurality of particle;
calculating a first characteristic parameter by receiving the false
signal through a non-linear amplifier; calculating a second
characteristic parameter by receiving the false signal not through
the non-linear amplifier; comparing the first characteristic
parameter with the second characteristic parameter; storing a
comparison result; detecting a particle signal by the particle
detector; calculating a third characteristic parameter by receiving
the detected particle signal through the non-linear amplifier; and
correcting the third characteristic parameter on the basis of the
comparison result.
[0026] The step of making the measurement preparation may include
sampling, that is, sucking a sample liquid to introducing it into
the particle detector, and processing the sample liquid, for
example, diluting or reacting it with a reagent. If the step of
storing the comparison results is completed during the step of
making the measurement preparation, the step of correcting the
parameter can be carried out conveniently and efficiently. The
effect of the ambient temperature on the non-linear amplifier can
be properly corrected.
[0027] Configuration and operation of particle signal detecting
section
[0028] In the present embodiment, an electric measurement
(electrical sensing zone method) is used for a particle signal
detecting section 1. The particle signal detecting section 1 is
composed of a flow cell 2, a container 3 for storing a sample
liquid containing particles to be tested, a suction nozzle 4 for
sucking the sample liquid, valves 5, 6, 7, a syringe 8 actuated by
a motor 9 and a sheath liquid container 10. The flow cell 2 is
formed of a first cell 2a, a second cell 2b, an orifice section 2c
having a micro through hole (orifice) through which the first cell
2a communicates with the second cell 2b and a sample nozzle 2d for
jetting the sample liquid into the orifice section 2c. Furthermore,
the first cell 2a is provided with a inlet port 2e which accepts a
sheath liquid from the sheath liquid container 10 through the valve
7. And the second cell 2b is provided with a outlet port 2f which
discharges the sheath liquid together with the sample liquid.
[0029] Furthermore, the first cell 2a and the second cell 2b are
provided with electrodes 11, 12 respectively. A power source 13 is
provided for supplying a constant d.c. current to the liquid
between the electrodes 11 and 12. When a voltage is generated
between the electrode 12 and the electrode 11, a d.c. component of
the voltage is cut out by a capacitor 14 and a resistor 15, and an
a.c. component (fluctuating component) alone is outputted as a
particle signal V1.
[0030] In the particle signal detecting section 1, if the valves 5,
6 are first opened for a predetermined period of time, the sample
liquid is sucked through the suction nozzle 4 under a negative
pressure until a flow path between the valves 5, 6 is filled with
the sample liquid. Then, the sample liquid is discharged into the
first cell 2a through the sample nozzle 2d when the syringe 8
presses out the sample liquid between the valves 5, 6 to the sample
nozzle 2d at a constant rate.
[0031] If the valve 7 is opened at the same time, the sheath liquid
is supplied to the first cell 2a. Thus, the sample liquid is
sheathed with the sheath liquid, and further squeezed by the
orifice section 2c to form a sheath flow.
[0032] The formed sheath flow allows the particles contained in the
sample liquid to be aligned and flowed in a line through the
orifice section 2c. The sample liquid and the sheath liquid that
have passed through the orifice section 2c are discharged through
the outlet port 2f of the second cell 2b.
[0033] The electric impedance of the liquid between the electrodes
11 and 12 is determined by an electrical conductivity of the sheath
liqiud, a size (sectional area) of the orifice in the orifice
section 2c, an electrical conductivity of the sample liquid and a
diameter of the flow of the sample liquid.
[0034] As mentioned above, the d.c. current is supplied to the
liquid between the electrode 12 and the electrode 11 from the power
source 13, a d.c. voltage is generated that is determined by an
electrical resistance and electric current value between the
electrode 12 and the electrode 11. Furthermore, if the particles
pass through the orifice section 2c, an electric resistance at both
ends of the orifice section 2c changes. Therefore, the voltage
generated between the electrode 12 and the electrode 11 changes in
the form of pulse every time a particle passes. The maximum value
of change (peak value of the pulse) is proportional with a size of
the particle passing through the orifice section 2c. Thus, the
particle signal V1 represents such pulses.
[0035] Configuration and operation of false signal generating
section
[0036] Meanwhile, a false signal generating section 20 is provided
with a pulse generating circuit 20a and a gain variable amplifier
20b. The amplifier 20 changes pulse waveforms outputted from the
pulse generating circuit 20a and generates a false signal V2
including a plurality of serial pulse waveforms corresponding to
the particle signal V1.
[0037] The particle signal V1 and false signal V2 are selected by a
selecting section 30 and processed in the following way.
[0038] Step of measuring false signal
[0039] In the particle measurement apparatus of the present
embodiment, the selecting section 30 first selects the false signal
V2, and the step of measuring the false signal V2 is carried out.
The false signal V2 can be corresponds to a particle signal
representative of a plurality of particles of all sizes from the
largest to the smallest to be detected in the step of measuring the
particle signal, which will be described later. That is, the false
signal V2 corresponds to a plurality of saw-tooth pulses with
different peak values which will be obtained from particles within
a volume range of 10 to 10.sup.5 fl.
[0040] Then, the false signal V2 selected by the selecting section
30 is amplified by a linear amplifier 41 and its peak value is
sampled and hold by a peak hold circuit 42 and converted into a
digital value P by an A/D converter 43, then inputted into a
particle size calculating section 44.
[0041] Meanwhile, if the particle is spherical, then the relation
between a volume V and a particle diameter D is given by the
following equation:
V=(.pi./6).multidot.D.sup.3 (1)
[0042] Since the peak value P corresponds to the particle
volume,
V=k.sub.1.multidot.P (2)
[0043] From (1) and (2),
D=k.sub.2.multidot.P.sup.1/3 (3)
[0044] (3) is transformed as follows.
D=k.sub.3.multidot.LOGP+k.sub.4 (4)
[0045] (k.sub.1, k.sub.2, k.sub.3, k.sub.4: constants)
[0046] Therefore, the particle size calculation secting 44 receives
the output P from the A/D converter 43, calculates the particle
diameter D using equation (4) and outputs a result A to a
comparison section 45.
[0047] Also, the false signal amplified by the linear amplifier 41
is logarithmically converted by an LOG amplifier (logarithmic
amplifier) 46, and peak values are sampled and hold by the peak
hold circuit 47, converted into a digital value Q by the A/D
converter 43 and inputted into a particle size calculating section
49.
[0048] The particle size calculating section 49 calculates a
particle diameter D by equation (4). In this case, the LOG
amplifier 46 allows an output Q of the A/D converter 48 to be given
as follows:
Q=LOGP (5)
[0049] Therefore, from equations (4), (5),
D=k.sub.3.multidot.Q+k.sub.4 (6)
[0050] Then, the particle size calculating section 49 calculates
the particle diameter D using equation (6) and outputs a result
value B to a comparison section 45.
[0051] With regard to n pieces of false pulses outputted from the
false signal generating section 20, as shown in FIG. 2, the
comparison section 45 plots on A-B two-dimensional coordinates n
points representative of particle diameter A.sub.1, A.sub.2, . . .
A.sub.n, and B.sub.1, B.sub.2 . . . B.sub.n obtained from the
particle size calculating sections 44 and 49, respectively and
prepares a correction curve (a) by linear interpolation between the
plotted points and stores it in a storage section 50.
[0052] Step of measuring particle signal
[0053] In this step, the sample liquid is flowed into the flow cell
2 while the selecting section 30 selects the particle signal V1.
Thus, the measurement of the particle signal is carried out. The
particle signal V1 is amplified by the linear amplifier 41 and
logarithmically converted by the LOG amplifier 46. The peak values
is sampled and hold by the peak hold circuit 47, converted into a
digital value Q by the A/D converter 43 and inputted into the
particle size calculating section 49.
[0054] The particle size calculating section 49 calculates the
particle diameter D using the equation (6) and outputs its value as
B into the compensating section 51. The compensating section 51
corrects m pieces of particle diameters B obtained from the
particle size calculating section 49, that is, particle diameters B
are converted into particle diameters A respectively using the
correction curve in FIG. 2. An output section 52 prepares a
particle size distribution on the basis of m pieces of the
corrected particle diameters and displays it.
[0055] Also, the particle signal V1 is amplified by the linear
amplifier 41, its peak values are sampled and hold by the peak hold
circuit 42 and is converted into digital values P by the A/D
converter 43 to be inputted into a volume calculating section 53.
The volume calculating section 53 converts m pieces of peak values
P into respective volumes V using the equation (2). The output
section 52 prepares a particle volume distribution on the basis of
m pieces of particle volumes and displays it.
[0056] As set forth above, the particle diameters D can be
calculated by the simple linear equation (6) at a high speed, and
the calculated values are speedily corrected by the correction
curve in FIG. 2. That is, the input-output characteristics of the
LOG amplifier 46 can be easily and precisely compensated.
Therefore, a wide range of particle sizes can be calculated with
high precision and at a high speed.
[0057] The input-output characteristics of the logarithmic
amplifier tend to be affected by the ambient temperature, and
therefore it is desirable to renew the correction curve in FIG. 2
beforehand by carrying out the false signal detecting step before
the particle signal detecting step.
[0058] It is noted that the present embodiment uses two peak hold
circuits and two A/D converters. But if it is so arranged that a
signal to be inputted into the peak hold circuits 42, 47 is
selected by a switch, one peak hold circuit and one A/D converter
can be omitted.
[0059] The gain variable amplifier 20b may be provided within
linear amplifier 41. In that case, the gain variable amplifier 20b
can have two functions, one being for changing the peak values of
the false signal and the other being for varing the gain in
measuring the particle signal.
[0060] According to the present invention, even if the particle
signal is amplified through the non-linear amplifier, the
input-output characteristics of the non-linear amplifier are
compensated sufficiently, permitting measurement of particles over
a wide size range with high accuracy.
* * * * *