Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2000-03-17
2002-10-15
Allen, Stephone (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C356S442000
Reexamination Certificate
active
06465802
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flow cell for forming an irradiation region therein, as a particle detector portion, and to a particle measurement apparatus for obtaining particle information, including a diameter of particles and so on, which are suspended in sample fluid passing through the irradiation region by using the flow cell.
2. Description of Relevent Art
As shown in
FIG. 8
, a conventional flow cell
100
is made of a transparent material, and is constructed to have a straight flow path or passage of a predetermined length, having a square cross-section thereof. And, an outer wall surface
101
a
and an inner wall surface
101
b
of a wall portion
101
, constructing the flow cell
100
through which a laser beam La passes, are formed to be parallel each other.
Also, as shown in
FIG. 9
when the laser beam La from a laser light source is irradiated upon the flow cell
100
, the laser beam La is incident upon a boundary surface between air and the outer wall surface
101
a
at an incident angle &thgr;
11
(&thgr;
11
≠0°) and is refracted at an refraction angle &thgr;
12
.
This is because, when the laser beam La is incident upon the outer wall surface
101
a
of the flow cell
100
at right angle by setting the incident angle &thgr;
11
to be zero (&thgr;
11
≠0°), the laser beam La is reflected on the outer wall surface
101
a
, so as to return a portion of the reflection light back to the laser light source. Therefore, it is prevented from superposing on the laser beam La as return or feedback noise.
However, depending on the refractive index of sample fluid
102
(i.e., a solvent of the sample fluid) flowing inside the flow cell
100
, the refraction angle of the laser beam La changes at the boundary surface between the inner wall surface
101
b
and the sample fluid
102
, therefore the laser beam La propagating within the sample fluid
102
comes to be La
1
(in a case where the refractive index of the sample fluid is n
2
) or La
2
(in a case where the refractive index of the sample fluid is n
3
). As a result of this, the irradiation region M, being provided at the center of the flow passage as the detection portion of particles, is shifted in the position thereof.
Namely, according to Snell's law, when the laser beam La is incident upon the boundary surface between the inner wall surface
101
b
and the sample fluid
102
at the incident angle &thgr;
13
(the outer wall surface
101
a
and the inner wall surface
101
b
are parallel each other, therefore &thgr;
13
=&thgr;
12
), the refraction angle comes to be &thgr;
14
if the refractive index of the sample fluid is n
2
, and it comes to be &thgr;
15
if the refractive index of the sample fluid is n
3
.
Then, a light collecting means, which is provided to fit to the position of the irradiation region M corresponding to the sample fluid of refractive index n
2
, is shifted or not properly aligned in the position thereof in the case where the sample fluid has a refractive index n
3
. In such a situation, the light collecting means cannot detect light scattered by particles passing through the irradiation region M.
Accordingly, there is a problem that particle information, including a particle diameter and so on, cannot be detected accurately, due to the the difference in the kinds of sample fluids being analyzed.
Furthermore, depending on the shape of the wall portion
101
constructing the flow cell
100
, the laser beam La passing through the irradiation region M is reflected on the boundary surface between the sample fluid
102
and the inner wall surface
101
c
and/or between the outer wall surface
101
d
and air, to be turned or reflected back toward the laser light source in a part thereof. Therefore, there are problems that the portion of the reflection light superposes on the laser beam La as feedback noise, and that the portion of the reflection light passes through the irradiation region M again, thereby increasing noise.
SUMMARY OF THE INVENTION
According to the present invention, for overcoming the problems mentioned above, there is provided a flow cell for obtaining particle information, including a diameter of particles and so on, suspended in sample fluid, wherein an irradiation region, through which the sample fluid passes, is defined in said flow cell for functioning as a detection portion to be irradiated with light, and a wall portion of said flow cell is so adapted and arranged that when said light is incident upon an outer wall surface of the flow cell at a predetermined incident angle &thgr; (&thgr;≠0°), said light exits from an inner wall surface into said sample fluid at a refraction angle of almost or approximately 0°.
With this flow cell and arrangement according to the invention, it is possible to keep the irradiation region functioning as a particle detection portion at a constant position, independent of and influence by a value or magnitude of refractive index of the sample fluid.
Further, according to the present invention, there is also provided a flow cell for obtaining particle information, including a diameter of particles, suspended in sample fluid, wherein an irradiation region, through which the sample fluid passes, is defined in said flow cell for functioning as a detection portion to be irradiated with light, and a wall portion of said flow cell is so adapted and arranged that said light becomes incident upon a boundary surface between said sample fluid and an inner wall surface of the flow cell at a predetermined incident angle &agr; (&agr;≠0°) after being passing through said irradiation region.
With this flow cell and arrangement according to the invention, after light passes through the irradiation region functioning as a particle detection portion, the light can be prevented from being reflected on the boundary surface between the sample fluid and the inner wall surface back into a direction of the light source, independent of and influence by a value or magnitude of refractive index of the sample fluid. This advantageously prevents superposing of the feedback noise onto the light due to self action a portion of the light, as well as avoiding an increase of the noise due to the portion of reflection light passing through the irradiation region again.
It is preferable that, in the flow cell as defined above, the wall portion of the flow cell is so arranged that the light is incident upon a boundary surface between an outer wall surface of the flow cell and air at a predetermined incident angle &agr;′ (&agr;′≠0°).
With this additional feature, after light passes through the irradiation region functioning as a particle detection portion, the light can be prevented from being reflected on the boundary surface between the sample fluid and the inner wall surface into a direction of, the light source, independent of any influence by a value or magnitude of the refractive index of the sample fluid, and in addition, the light can also be prevented from being reflected on the boundary surface between the outer wall surface and air back into a direction reflected portion of the the light source, superposing of the feedback noise onto the light due to turn-back of light, as well as avoiding an increase of the noise due to the portion of reflection light passing through the irradiation region again.
Furthermore, according to the present invention, there is also provided a flow cell for obtaining particle information, including a diameter of particles, suspended in sample fluid, wherein an irradiation region, through which the sample fluid passes, is defined in said flow cell for functioning as a detection portion to be irradiated with light, and a wall portion of said flow cell is so adapted and arranged that said light becomes incident upon a boundary surface between said sample fluid and an inner wall surface of the flow cell at approximately 0°, and then becomes incident upon a boundary surface between an outer wall surface of the flow cell and air at a predetermined incident a
Allen Stephone
Blackman William D.
Carrier Joseph P.
Carrier Blackman & Associates P.C.
Hill Bradford
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