Optics: measuring and testing – By polarized light examination
Reexamination Certificate
2000-10-04
2002-10-15
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
By polarized light examination
C356S368000, C600S316000
Reexamination Certificate
active
06466320
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of measuring an angle of rotation usable for identifying, examining a purity and determining a concentration of a solute in the solution, and a polarimeter using the method, and more particularly to a method and an apparatus for urinalysis in which the angle of rotation of urine sampled from a man or other animal for examining the concentration of glucose, protein, etc. contained in the urine.
BACKGROUND ART
A healthy adult person usually voids 1000-1500 ml of urine every day. The total amount of solid components thereof is 50-70 g. About 25 g of the solid components is inorganic substances mainly composed of sodium chloride, potassium chloride and phosphoric acid, most of which are dissolved in the form of ions. The remains are organic substances mainly composed of urea and uric acid, and slight amounts of sugar and protein also exist therein. The concentrations of sugar and protein in the urine reflect the health conditions of the adult.
The sugar contained in the urine, i.e., glucose is discharged usually at a rate of 0.13-0.5 g per day into the urine. From this figure and the amount of urine, the concentration, i.e., the urine glucose level can be estimated at not more than 50 mg/dl on the average. The corresponding value is several hundred mg/dl, or sometimes as high as several thousand mg/dl. In other words, the value for diabetics can increase by a factor of ten or hundred as compared with the normal value.
On the other hand, the protein contained in urine, i.e., albumin is smaller in amount than glucose, and discharged at the rate of 3-60 mg into the urine. By taking the amount of the urine into account, average concentration is about 6 mg/dl or less. If a kidney is suffered, the albumin concentration reaches 100 mg/dl or more. That is, the value is increased to ten times the normal value or more.
Ordinally, as a conventional method of examining such sugar or protein in the urine, a test paper impregnated with an agent is dipped into the urine and a color reaction thereof is measured by spectrophotometer or the like.
In this method, however, different kinds of test paper were required to use for different items of examination including sugar, protein, etc. Also, a new test paper is required for each test, thereby leading to the disadvantage of a high running cost. Further, automation for labor saving has its own limit.
In addition, in a case of home use, a layman is demanded to set and change the test paper. This process is comparatively annoying and forms a stumbling block to the extension of the domestic use of the urinalysis apparatus.
Now, the conventional polarimeter will be explained. The conventional polarimeter had the problems described below.
An example of the conventional polarimeter is shown in FIG.
20
.
In
FIG. 20
, a light source
121
is configured of a sodium lamp, a band-pass filter, a lens, a slit, etc. for projecting a substantially parallel light composed of a sodium D ray having a wavelength of 589 nm. A polarizer
122
is arranged in the direction of advance of the light projected from the light source
121
in such a position as to transmit only a component in a specific direction, which has a plane of vibration coincident with a transmission axis thereof, of the light projected from the light source
121
. A sample cell
123
for holding a specimen is arranged in the direction of advance of the light transmitted through the polarizer
122
. Further, an analyzer
124
is arranged, like the polarizer
122
, in such a position as to transmit only the component of the light in a specific direction. An analyzer rotator
125
is for rotating the analyzer
124
on an axis parallel with the direction of advance of the light projected from the light source
121
under the control of a computer
127
. A light sensor
126
is for detecting the light projected from the light source
121
and transmitted through the polarizer
122
, the sample cell
123
and the analyzer
124
. The computer
127
controls the analyzer rotator
125
while recording and analyzing a signal from the light sensor
126
.
The principle of this conventional example will be explained with reference to FIG.
21
. In the figure the abscissa represents the relative angle &thgr; formed between the plane of vibration of the light transmitted through the polarizer
122
and the plane of vibration of the light transmitted through the analyzer
126
. Herein, &thgr; is assumed to take zero when the angle between these two planes of vibration reaches &pgr;/2, i.e., in the orthogonal nicol state. The ordinate represents an intensity I of the light that has reached the light sensor
126
based on an output signal of the light sensor
126
. Herein, the solid line indicates the output signal in the case where the specimen exhibits no optical rotatory power. Under this condition, the relation between &thgr; and I is shown by equation (1) mentioned below. Herein, a transmission loss and a reference loss of the sample cell
123
and the analyzer
122
respectively are ignored.
I=T×I
o
×(cos &thgr;)
2
(1)
where,
T: transmittance of specimen
I
o
: intensity of light incident to specimen
As apparent from equation (1), I changes with a change of &thgr;, i.e., with the rotation of the analyzer
126
, so that an extinction point with a minimum I appears for each &pgr;.
In the case where the specimen has an optical rotatory power and its angle of rotation=&agr;, on the other hand, the light intensity is represented by dashed line in FIG.
21
and given by equation (2).
I=T×I
o
×{cos(&thgr;−&agr;)}
2
(2)
As seen from this, a specimen having an optical rotatory power, as compared with a specimen having no optical rotatory power, has the angle associated with the extinction point displaced by &agr;. The angle of rotation can be measured by finding the displacement &agr; of the angle associated with the extinction point by the computer
127
.
In this method, however, S/N ratio of the output signal of the light sensor
126
is comparatively inferior for lack of a modulated component and it is difficult to accurately determine the extinction point. As a result, a specimen with a small &agr; cannot be measured with high accuracy.
For this reason, a polarimeter shown in
FIG. 22
is also used in order to improve an accuracy of determining the extinction point. In
FIG. 22
, a light source
141
is configured of a sodium lamp, a band-pass filter, a lens, a slit, etc. for projecting a substantially parallel light of sodium D ray having a wavelength of 589 nm. A polarizer
142
and an analyzer
144
are arranged in the direction of advance of the light projected from the light source
141
aligning their transmission axes with the direction of advance of the light projected from the light source
141
, with a sample cell holding a specimen interposed therebetween. An analyzer rotator
145
is for rotating the analyzer
144
on the transmission axis thereof as a rotation shaft under the control of a computer
147
. A light sensor
146
detects the light projected from the light source
141
and transmitted through the polarizer
142
, the sample cell
143
and the analyzer
144
. The computer
147
controls the analyzer rotator
145
, and records and analyzes the signal of the light sensor
146
. An optical Faraday modulator
151
vibrates the direction of polarization. A signal generator
152
drives the optical Faraday modulator
151
. A lock-in amplifier
143
is for phase sensitive detection of an output signal of the light sensor
146
with reference to the vibration-modulated signal from the optical Faraday modulator
151
.
The operating principle of the polarimeter will be explained below with reference to FIG.
23
.
In
FIG. 23
, the abscissa and the ordinate represent, as same in
FIG. 21
, &thgr; and I, respectively, with the extinction point and the neighborhood thereof shown in an enlarged view. The optical Faraday modulator
151
vibration-modulates the direction
Kawamura Tatsurou
Onishi Hiroshi
Sonoda Nobuo
Matsushita Electric - Industrial Co., Ltd.
McDermott & Will & Emery
Pham Hoa Q.
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