Optics: measuring and testing – For size of particles – By particle light scattering
Reexamination Certificate
1999-11-19
2001-05-22
Font, Frank G. (Department: 2877)
Optics: measuring and testing
For size of particles
By particle light scattering
C250S574000
Reexamination Certificate
active
06236458
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a particle size distribution measuring apparatus, and more particularly to an array detector used in the measuring apparatus of a configuration to maximize production yield and a manufacturing method for forming a plurality of array detectors.
2. Description of Related Art
A particle size distribution measuring apparatus has been provided with a limited array detector having a plurality of light detecting elements (devices) for detecting an intensity of scattering light at various scattering angles when a laser beam from a laser beam source is irradiated onto dispersed particles.
FIG. 4
schematically shows the principal parts of a conventional particle size distribution measuring apparatus. A circulating type cell
1
(flow cell) comprising a transparent container, receive a sample solution
2
prepared by dispersing a particle group of a sample target for measurement in a proper dispersion medium. A laser beam source section
3
is located on one side (rear side) of the cell
1
. The laser beam source section
3
is composed of a laser beam source
5
comprising a He-Ne laser emitting a parallel laser beam
4
, towards mirrors
6
and
7
for changing a traveling direction of the laser beam
4
by an angle of 90°, and a beam expander
8
for properly enlarging the parallel laser beam
4
in a light (beam) flux direction.
A collective (condenser) lens
9
is located on the other side (front side) of the cell
1
, and a ring-like array detector
10
is arranged on a focal position. As shown in
FIG. 5
, the array detector
10
comprises a transmitted light detecting element
11
which is formed on a position corresponding to an optical axis of the collective lens
9
, and a scattering light detecting element group
12
for detecting scattered light
4
A. The scattering light detecting group
12
comprises a plurality of circular-arc scattering light receiving elements
12
,
12
b
, . . .
12
n
, which are formed coaxially with the transmitted light detecting element
11
so as to have a wider width as they are positioned remote from the transmitted light detecting element
11
. Incidentally, a reference numeral
13
denotes an isolation gap between detecting elements. The aforesaid array detector
10
receives the light scattered/diffracted at a relatively small angle of the laser beam
4
A as it is diffracted or scattered by the particles in the cell
1
for various scattering angles, and then, measures their light intensity. The transmitted light detecting element
11
is used for adjusting a position optical axis and for measuring a concentration of the sample solution
2
.
A reference numeral
14
denotes a multiplexor which successively captures an output (scattering light intensity signal) of the array detector
10
, and successively transmits it to an A/D converter
15
, and a computer
16
which functions as a processor to which an output of the A/D converter
15
is inputted. The computer
16
stores a program for processing the output of the array detector, converted into a digital signal, on the basis of a Fraunhofer diffraction theory or a Mie scattering theory, and for determining a particle size distribution of the particle group. A reference numeral
17
denotes a color display for displaying the processed results or the like.
In the aforesaid particle size distribution measuring apparatus, where the sample solution
2
is supplied to the cell
1
, and the laser beam
4
from the laser beam source is irradiated to the sample cell
1
, the laser beam
4
is diffracted or scattered by the particles in the cell
1
. A diffracted or scattered laser beam
4
A is incident upon the array detector
10
by means of the collective lens
9
, and then, each output from the scattering light receiving elements
12
a
,
12
b
. . .
12
n
constituting the array detector
10
, is amplified by means of a pre-amplifier (not shown), and thereafter, is inputted to the multiplexor
14
.
In the multiplexor
14
, a light intensity data for each scattering angle obtained by the array detector
10
, that is, an analog electric signal is successively captured in a predetermined order. The analog electric signal captured by the multiplexor
14
is made into a serial signal, and then, is successively converted into a digital signal, and further, is inputted to the computer
16
. The computer
16
processes the light intensity data for each scattering angle obtained by the array detector
10
on the basis of a Fraunhofer diffraction theory or a Mie scattering theory, and thus, determines a particle size distribution of the particle in the sample solution
2
. Then, the result is displayed on the color display
17
, or is stored in a memory device (not shown).
The aforesaid array detector
10
is manufactured by cutting a wafer into a predetermined shape. In the conventional case, an open (sector) angle of each element
12
a
to
12
n
constituting the scattering light detecting element group
12
has been set to a fixed angle, for example, an angle of 90°. For this reason, the array detector
10
has the following problems. More specifically, in the array detector
10
, there is a need to mutually make equal the scattering light detecting characteristics of the scattering light detecting elements
12
a
to
12
n
. For this reason, as shown in
FIG. 5
, the array detector
10
is formed in a manner that a dimension of the respective scattering light detecting elements
12
a
to
12
n
is gradually increased in its radius direction and circumferential direction from the transmitted light detecting element
11
, and also, an area thereof is increased in an exponential function. In this case, if each open (sector) angle of the scattering light detecting elements
12
a
to
12
n
is held constant, as a radius distance from the transmitted light detecting element
11
gradually becomes larger, an area of each effective light collection portion (portion shown by a symbol “a” in
FIG. 5
) of the scattering light detecting elements
12
a
to
12
n
is increased. For this reason, the array detector
10
is required to be of a relatively large size, and also, any equipment for holding the array detector
10
becomes large, as a result, the particle size distribution measuring apparatus will be of a large size.
Moreover, the number of the array detectors
10
capable of being manufactured from a single wafer
18
is four (4) as shown in
FIG. 5
, in the case where the detector element sector angle is 90°. Therefore, the number of array detectors
10
capable of being manufactured from a single wafer is limited as number; for this reason, there is an increase in cost, and as a result, the particle size distribution measuring apparatus becomes expensive.
Examples of conventional array detectors can be seen in U.S. Pat. No. 5,164,787 and U.S. Pat. No. 5,185,641.
The prior art is still seeking improved and cost efficient array detectors.
SUMMARY OF THE INVENTION
The present invention has been made taking the aforesaid problems of the prior art into consideration. It is, therefore, a first object of the present invention to provide a small and compact particle size distribution measuring apparatus which includes a compact array detector section on an improved configuration.
A second object of the present invention is to provide a compact array detector to be used in a particle size distribution measuring apparatus, which can reduce an occupancy area in the measuring apparatus.
A third object of the present invention is to provide a manufacturing method of making an array detector, which can optimize the number of array detectors from a single wafer.
To achieve the above first object, the invention defined in a first aspect provides a particle size distribution measuring apparatus which includes an array detector having a plurality of scattering light detecting elements for detecting an intensity of scattering light generated when a laser beam is irradiated from a laser beam source to a dispersed particle group for each s
Igushi Tatsuo
Togawa Yoshiaki
Font Frank G.
Horiba Ltd.
Nguyen Sang H.
Price and Gess
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