Chemistry: analytical and immunological testing – Optical result
Reexamination Certificate
2000-06-27
2003-09-16
Warden, Jill (Department: 1743)
Chemistry: analytical and immunological testing
Optical result
C356S364000, C356S367000, C356S368000, C250S225000
Reexamination Certificate
active
06620622
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of polarimetry for use in the identification, examination on purity, determination of the concentration and the like of a solute in a liquid specimen, and a method of urinalysis using the same.
A polarimeter is employed as an optical rotation detecting type saccharimeter for detecting the concentrations of fructose, sucrose, glucose, and the like contained in an aqueous solution. It can also determine especially the concentrations of optical active substances such as glucose and protein in a urine. Therefore, it is expected to come into wide use as a urinalysis equipment which requires no consumable articles such as test papers.
FIG. 6
shows a conceptual constitution of one example of conventional polarimeters. The polarimeter is for determining the magnitude of spontaneous optical rotatory power, i.e., an angle of rotation attributed to a spontaneous optical rotatory power of a spontaneous optical active substance in a specimen to be detected. In concrete, the angle of spontaneous optical rotation is determined based on an angle of magnetorotation (compensated value) by an optical Faraday effect when the spontaneous optical rotation attributed to the spontaneous optical active substance is canceled (compensated) by the magnetorotation.
A semiconductor laser module
21
configured with a sodium lamp, a band-pass filter, a lens, a slit, and the like projects a substantially parallel light composed of a sodium D ray having a wavelength of 589 nm. A polarizer
23
transmits only a component that has a specific plane of vibration out of the light projected from the semiconductor laser module
21
. A sample cell
25
for holding a specimen to be detected has a pair of mutually opposing transparent transmission surfaces, and is arranged so that the light projected from the semiconductor laser module
21
can transmit through the inside thereof. An analyzer
26
transmits only a component that has another specific plane of vibration out of the light transmitted through the sample cell
25
. The relative angle &THgr; formed between the transmission axis of the polarizer
23
and the transmission axis of the analyzer
26
is fixed at &pgr;/2. A photosensor
27
detects the component transmitted through the analyzer
26
out of the light projected from the semiconductor laser module
21
. A Faraday cell
24
modulates and controls the plane of vibration of the light projected from the semiconductor laser module
21
based on a modulation signal outputted from a signal generator
30
and a control signal outputted from a computer
22
. The Faraday cell
24
is driven by a Faraday cell driver
29
. A lock-in amplifier
28
performs a phase sensitive detection on the output signal from the photosensor
27
by using the modulation signal outputted from the signal generator
30
as a reference signal. The computer
22
calculates the angle of rotation attributed to the specimen to be detected accommodated in the sample cell
25
based on the control signal, and the output signal from the lock-in amplifier
28
.
As described above, by sweeping the angle of the plane of vibration by the Faraday cell, it becomes possible to achieve simplification and compactness thereof as compared with apparatuses using other means for modulating the plane of vibration.
Below, the principle of the conventional polarimeter will be described.
The Faraday cell
24
modulates the plane of vibration of the light projected from the semiconductor laser module
21
and transmitted through the polarizer
23
with an amplitude of “&dgr;” and an angular frequency of “&ohgr;”. In this step, the intensity “I” of the light that has reached the photosensor
27
is represented by the following equation (1):
I=T×I
0
×{cos[&THgr;−&agr;+&bgr;+&dgr;×sin(&ohgr;×
t
)]}
2
(1)
where T: transmittance of the specimen,
I
0
: intensity of the light incident upon the specimen,
&THgr;: relative angle formed between the transmission axis of the polarizer
23
and the transmission axis of the analyzer
26
,
&agr;: angle of rotation attributed to the specimen,
&bgr;: angle of rotation of light due to the Faraday cell
24
, and
t: time.
It is noted that the transmission loss and the reference loss of the sample cell
25
and the analyzer
26
respectively are ignored.
Since the relative angle &THgr; between the transmission axis of the polarizer
23
and the transmission axis of the analyzer
26
is &pgr;/2, the following equation (2) is given from the equation (1).
I=T×I
0
×{sin[&bgr;−&agr;+&dgr;×sin (&ohgr;×
t
)]}
2
(2)
In case of &bgr;−&agr;=0, in other words, when it is assumed that the angle of rotation attributed to the specimen is canceled (compensated) by the angle of rotation due to the Faraday cell
24
, the equation (2) is expressed as the following equation (3):
I
=
(
1
/
2
)
×
T
×
I
0
×
{
1
-
cos
[
2
×
δ
×
sin
(
ω
×
t
)
]
}
=
(
1
/
2
)
×
T
×
I
0
×
{
1
-
[
J
0
(
2
×
δ
)
+
2
×
J
2
(
2
×
δ
)
×
cos
(
2
×
ω
×
t
)
+
…
]
}
(
3
)
where J
n
(X) is an nth-degree Bessel function.
The equation (3) indicates that the intensity “I” of the light detected by the photosensor
27
does not contain the frequency component &ohgr; of the modulation signal alone.
When it is assumed that the angle of rotation attributed to the specimen and the amplitude of the modulation are small, that is, |&bgr;−&agr;|<<1, and &dgr;<<1, the equation (3) is approximated to the following equation (4):
I
≅
T
×
I
0
×
(
β
-
α
+
δ
×
sin
(
ω
×
t
)
)
2
=
T
×
I
0
×
{
(
β
-
α
)
2
+
2
(
β
-
α
)
×
δ
×
sin
(
ω
×
t
)
+
[
δ
×
sin
(
ω
×
t
)
]
P
2
}
=
T
×
I
0
×
{
(
β
-
α
)
2
+
2
(
β
-
α
)
×
δ
×
sin
(
ω
×
t
)
+
[
δ
2
/
2
×
{
[
1
-
cos
(
2
×
ω
×
t
)
]
}
]
(
4
)
This indicates that the output signal “I” from the photosensor
27
contains components with angular frequencies of 0 (DC), “&ohgr;”, and “2×&ohgr;”, respectively. By the phase sensitive detection of the value “I” using the modulation signal as a reference signal in the lock-in amplifier
28
, it is possible to pick up the component of the angular frequency “&ohgr;”, i.e., the signal “S” shown by the following equation (5):
S=T×I
0
×2×(&bgr;−&agr;)×&dgr; (5)
This signal “S” equals zero only when &bgr;=&agr;. This point is the extinction point. In the process of rotating the plane of vibration of light by the Faraday cell
24
, in other words, sweeping “&bgr;”, the value of “&bgr;” when “S” becomes zero corresponds to the angle “&agr;” of rotation. The same is also true for the case where this process is considered based on the equation (3). Namely, upon the phase sensitive detection of the value “I”, the output “I” from the photosensor
27
becomes zero when &bgr;=&agr;.
As described above, by modulating the angle of plane of vibration of light, it is possible to pick up only the signal “S” of the modulated frequency component selectively while separating the signal from noises attributed to an intensity of the light source, a fluctuation in the power source, a radiation and the like, thereby deriving a signal with a high S/N ratio. Therefore, the extinction point can be determined accurately by using this value of the signal “S”, and hence the angle “&agr;” of rotation can be determined with high accuracy.
However, in the above-described polarimetry, it is requi
Cross LaToya
Matsushita Electric - Industrial Co., Ltd.
Warden Jill
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