Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1998-04-18
2001-02-06
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S458100, C356S073000, C356S335000
Reexamination Certificate
active
06184517
ABSTRACT:
BACKGROUND OF THE INVENTION
1 Field of Invention
This invention relates to a particle analyzer system that analyzes elements of fine particles, for example, suspended in a clean room or contained in purified water; and more particularly, to such a system which is of reduced size and cost.
2 Description of the Prior Art
FIG. 1
shows a conventional particle component analyzer system using a microwave induced plasma, and comprising a dispersion chamber
51
in which a filter
52
is provided. Solid particles (not shown) to be measured adhere to filter
52
. An aspirator
53
draws in solid particles which are stuck on filter
52
and supplies them to discharge tube
54
. In dispersion chamber
51
, after the air is discharged with a suction pump (not shown), helium gas is introduced and maintained at a pressure which is slightly higher than atmospheric pressure. A microwave source
55
introduces microwaves into a cavity
56
.
A detection window
57
is provided at the other end of the discharge tube
54
and four optical fibers
58
introduce the beam emitted from the detection window
57
into a plurality of spectometers (four Czerny-Turner monochromators in
FIG. 1
)
59
. The outputs of the spectrometers
59
are applied to signal processor (CPU)
60
.
When the microwaves of frequency 2.45 GHz are introduced into cavity
56
from source
55
, plasma at a temperature of approximately 4000 K is generated in discharge tube
54
. Solid particles, which are introduced into discharge tube
54
from the dispersion chamber
51
are atomized and ionized in the plasma. The particles emit light when they fall to the ground state after further excitation. This emission spectrum is taken out from the discharge tube
54
in the axial direction and are then subjected to spectrometric analysis by spectrometers
59
. Then, the output signals from the spectrometers
59
are processed by the CPU
60
to measure and display the elements contained in the samples being measured.
In addition, a photoelectric converter (not shown) is provided for each spectrometer
59
to output electrical signals corresponding to the intensity of the light beams of selected wavelengths. Amplifiers (not shown) may be provided to amplify the output signals of the photoelectric converters. The amplifiers may be provided in the latter stages of each photoelectric converter. The sizes of the particles are, for example, classified into three types, by size, such as large, medium and small, corresponding to the values of the output signals from the amplifiers. The filter
52
has a predetermined area and aspirator
53
scans the filter
52
a plurality of times to draw in the same quantity of particles with each scan.
FIG. 2
shows the relationship between the emission wavelengths of the elements and the emission intensities and in practice about
50
elements are the object of the measurement. As seen in
FIG. 2
, for example, manganese (Mn) has an emission wavelength near 2600 Angstrom, and Aluminum (Al), fluorine (F), and oxygen (O) have emission wavelengths near 3950, 6900, and 7800 Angstrom, respectively.
Since photo emission is introduced into a plurality of spectrometers (e.g. four spectrometers) whose measuring wavelengths are fixed, only four components can be captured in one emission. Because the particles may contain a number of various elements, such as described above, the measurement may have to be carried out a plurality of times with the wavelength settings of the spectrometers being changed for each measurement. Thus, measurement with prior art devices takes a long time. Although the problem may be solved with use of a larger number of spectrometers to shorten the measuring time, this requires a very large system, and also increases the cost of such system,since spectrometers are expensive.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to overcome and resolve the aforementioned deficiencies, disadvantages and problems of the prior art.
Another object is to provide a particle analyzer system wherein the measuring time is shortened and the system is made smaller and the cost thereof is lowered.
REFERENCES:
patent: 4710025 (1987-12-01), Wyatt et al.
patent: 4957363 (1990-09-01), Takeda et al.
patent: 4986657 (1991-01-01), Ohe
patent: 5106187 (1992-04-01), Bezanson
patent: 5194913 (1993-03-01), Myrick et al.
patent: 5443793 (1995-08-01), Ehrlich et al.
patent: 5491344 (1996-02-01), Kenny et al.
patent: 5825485 (1998-10-01), Cohn et al.
patent: 5862273 (1999-01-01), Pelletier
Kitamori Takehiko
Naitou Seiichi
Sawada Tsuguo
Takahara Hisao
Takamatsu Yukihiko
Kojima Monnray
Le Que T.
Luu Thanh X.
Yokogawa Electric Corporation
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