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Claims  |
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What is claimed is:
1. A glucose concentration measuring method, comprising the steps of:
i) splitting a low coherence light beam, which has been radiated out of a
predetermined light source, into a signal light beam and a reference light
beam, each of which travels along one of two different optical paths,
ii) modulating at least either one of said signal light beam and said
reference light beam such that a slight difference in frequency may occur
between them,
iii) irradiating said signal light beam to the eyeball lying at a
predetermined position,
iv) causing a first backward scattered light beam of said signal light beam
having been irradiated to the eyeball, said first backward scattered light
beam coming from an interface between the cornea and the anterior aqueous
chamber of the eyeball, and said reference light beam to interfere with
each other by adjusting an optical path length of said reference light
beam, a first interference light beam being thereby obtained,
v) measuring an intensity of said first interference light beam,
vi) calculating an intensity of said first backward scattered light beam
from the intensity of said first interference light beam,
vii) causing a second backward scattered light beam of said signal light
beam having been irradiated to the eyeball, said second backward scattered
light beam coming from an interface between the anterior aqueous chamber
and the crystalline lens of the eyeball, and said reference light beam to
interfere with each other by adjusting the optical path length of said
reference light beam, a second interference light beam being thereby
obtained,
viii) measuring an intensity of said second interference light beam,
ix) calculating an intensity of said second backward scattered light beam
from the intensity of said second interference light beam,
x) obtaining light absorption characteristics of constituents of the
aqueous humor, which fills the anterior aqueous chamber, from the
intensity of said first backward scattered light beam and the intensity of
said second backward scattered light beam,
xi) obtaining light absorption characteristics of the constituents of the
aqueous humor with respect to each of a plurality of other low coherence
light beams, which are of wavelength bands different from the wavelength
band of said low coherence light beam, in the same manner, and
xii) calculating a concentration of glucose in the constituents of the
aqueous humor from the light absorption characteristics, which have been
obtained with respect to the plurality of said low coherence light beams.
2. A method as defined in claim 1 wherein each of said low coherence light
beams is selected as a portion of light, which is of an emission
wavelength band wider than the wavelength band of each low coherence light
beam.
3. A method as defined in claim 1 wherein each of said low coherence light
beams is radiated out of one of a plurality of different light sources.
4. A glucose concentration measuring method, comprising the steps of:
with respect to concentrations of glucose in the constituents of the
aqueous humor, which concentrations have been measured with a method as
defined in claim 1, invasively measuring the corresponding concentrations
of glucose in the blood, correlation between the concentrations of glucose
in the constituents of the aqueous humor and the concentrations of glucose
in the blood being thereby determined previously, and
thereafter non-invasively determining a concentration of glucose in the
blood from a concentration of glucose in the constituents of the aqueous
humor, which concentration is newly measured with a method as defined in
claim 1, and said correlation.
5. A glucose concentration measuring apparatus, comprising:
i) a light source device for radiating out a plurality of low coherence
light beams, which are of different emission wavelength bands,
ii) an optical path splitting means for splitting each of the low coherence
light beams, which has been radiated out of said light source device, into
a signal light beam irradiated to the eyeball and a reference light beam,
each of which travels along one of two different optical paths,
iii) a modulation means, which is located in at least either one of the two
different optical paths and modulates at least either one of said signal
light beam and said reference light beam such that a slight difference in
frequency may occur between them,
iv) an optical path length adjusting means for adjusting the length of the
optical path, along which said reference light beam travels,
v) a wavefront matching means for:
matching a wave front of a first backward scattered light beam of said
signal light beam having been irradiated to the eyeball, said first
backward scattered light beam coming from an interface between the cornea
and the anterior aqueous chamber of the eyeball, and a wave front of said
reference light beam with each other, and
matching a wave front of a second backward scattered light beam of said
signal light beam having been irradiated to the eyeball, said second
backward scattered light beam coming from an interface between the
anterior aqueous chamber and the crystalline lens of the eyeball, and a
wave front of said reference light beam with each other,
vi) a photodetector for photoelectrically detecting an intensity of a first
interference light beam, which is obtained from the matching of the wave
front of said first backward scattered light beam and the wave front of
said reference light beam with each other, and an intensity of a second
interference light beam, which is obtained from the matching of the wave
front of said second backward scattered light beam and the wave front of
said reference light beam with each other,
vii) a heterodyne operation means for calculating an intensity of said
first backward scattered light beam from the intensity of said first
interference light beam, and calculating an intensity of said second
backward scattered light beam from the intensity of said second
interference light beam,
viii) a light absorption characteristics analyzing means for obtaining
light absorption characteristics of constituents of the aqueous humor,
which fills the anterior aqueous chamber, from the intensity of said first
backward scattered light beam and the intensity of said second backward
scattered light beam, and
ix) a glucose concentration calculating means for calculating a
concentration of glucose in the constituents of the aqueous humor from the
light absorption characteristics, which have been obtained with respect to
the plurality of said low coherence light beams.
6. An apparatus as defined in claim 5 wherein said light source device
comprises a single light source for radiating out low coherence light,
which is of an emission wavelength band wider than the wavelength band of
each of said low coherence light beams, and a wavelength selecting means
for selecting each of said low coherence light beams with respect to the
wavelength from said low coherence light, which is of the wide emission
wavelength band.
7. An apparatus as defined in claim 5 wherein said light source device
comprises a plurality of light sources, each of which radiates out one of
said low coherence light beams.
8. A glucose concentration measuring apparatus, comprising a table
representing correlation between concentrations of glucose in the
constituents of the aqueous humor, which concentrations have been measured
with an apparatus as defined in claim 5, and concentrations of glucose in
the blood, which have been measured previously,
wherein a concentration of glucose in the blood is non-invasively
determined from a concentration of glucose in the constituents of the
aqueous humor, which concentration is newly measured with an apparatus as
defined in claim 5, and said table. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for measuring a
concentration of glucose in a living body. This invention particularly
relates to a method and apparatus for measuring non-invasively the
concentration of glucose in the aqueous humor in the anterior aqueous
chamber of the eyeball, and a method and apparatus for measuring
non-invasively the concentration of glucose in the blood in accordance
with the concentration of glucose in the aqueous humor.
2. Description of the Prior Art
The mean level of glucose in the blood varies for different persons and is
an important index for determining whether drugs are to be or are not to
be administered to diabetic patients.
The concentration of glucose in the blood has the characteristics such that
it fluctuates markedly within a very short time in accordance with food
intake, physical activity, a complication by another disease, or the like.
Urgent dosage is often required due to a sharp increase in concentration
of blood glucose.
Therefore, as for patients having such a disease, it is desired that the
concentration of glucose in the blood can be monitored at as short
intervals as possible. Ordinarily, monitoring of the concentration of
glucose in the blood is carried out by lancing the finger of the patient
in order to obtain a drop of blood, analyzing the drop of blood, and
thereby measuring the concentration of glucose in the blood. Since the
lancing of the finger is painful, it is difficult to compel the patients
to undergo the measurement procedure many times per day.
Accordingly, recently, in lieu of the invasive measurements having the
drawbacks described above, various non-invasive measuring methods, which
are not accompanied by pain, have been proposed.
The non-invasive measuring methods are primarily based upon the findings in
that the concentration of glucose in the aqueous humor, which fills the
anterior aqueous chamber located between the cornea and the crystalline
lens of the human eyeball, has strong correlation with the concentration
of glucose in the blood, though the level of correlation varies for
different persons. With the non-invasive measuring methods, the
concentration of glucose in the aqueous humor is measured non-invasively.
For example, a glucose sensor system, wherein the angle of rotation of
infrared radiation having impinged upon the aqueous humor is measured, and
the concentration of glucose having relationship with the angle of
rotation is thereby determined, is proposed in, for example, U.S. Pat. No.
3,958,560.
Also, a technique for measuring stimulated Raman light from glucose is
disclosed in, for example, WO 92/10131.
Further, a device for measuring the optical properties of light reflected
from the crystalline lens of the eye is described in, for example, U.S.
Pat. No. 5,535,743. Furthermore, a method for measuring the concentration
of glucose in the aqueous humor is described in, for example, U.S. Pat.
No. 5,433,197.
However, with the device described in U.S. Pat. No. 5,535,743, light
reflected from the interface between the cornea and the aqueous humor
cannot be eliminated, and information representing absorption at the
cornea is detected together with the necessary information. Therefore, the
accuracy, with which the concentration of glucose in the aqueous humor is
determined, cannot be kept high.
Further, in U.S. Pat. No. 5,535,743, nothing is disclosed as to technical
means to be used for measuring a minute change in absorbance. Therefore,
the device described in U.S. Pat. No. 5,535,743 cannot be appropriately
used in practice.
As for the glucose sensor system proposed in U.S. Pat. No. 3,958,560, many
compounds other than glucose in the aqueous humor are optically active and
take part in rotation of the plane of polarization. Also, the cornea
exhibits birefringence and therefore causes rotation of the plane of
polarization to occur. Accordingly, with the glucose sensor system
proposed in U.S. Pat. No. 3,958,560, wherein the concentration of glucose
in the aqueous humor is determined from the angle of rotation, the
measurement accuracy cannot be kept high.
With the technique disclosed in WO 92/10131, in order for stimulated Raman
light from glucose to be measured, a pump laser beam having a high
intensity is introduced into the anterior aqueous chamber and in a
direction normal to the vision line optical axis. Therefore, a practical
measuring system cannot be constituted easily.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a glucose
concentration measuring method, wherein the concentration of glucose in
the aqueous humor is measured non-invasively and with a high accuracy.
Another object of the present invention is to provide a glucose
concentration measuring method, wherein the concentration of glucose in
the blood is measured non-invasively from the non-invasively obtained
concentration of glucose in the aqueous humor.
Another object of the present invention is to provide an apparatus for
carrying out the glucose concentration measuring method.
The present invention provides a first glucose concentration measuring
method, comprising the steps of:
i) splitting a low coherence light beam, which has been radiated out of a
predetermined light source, into a signal light beam and a reference light
beam, each of which travels along one of two different optical paths,
ii) modulating at least either one of the signal light beam and the
reference light beam such that a slight difference in frequency may occur
between them,
iii) irradiating the signal light beam to the eyeball lying at a
predetermined position,
iv) causing a first backward scattered light beam of the signal light beam
having been irradiated to the eyeball, the first backward scattered light
beam coming from an interface between the cornea and the anterior aqueous
chamber of the eyeball, and the reference light beam to interfere with
each other by adjusting an optical path length of the reference light
beam, a first interference light beam being thereby obtained,
v) measuring an intensity of the first interference light beam,
vi) calculating an intensity of the first backward scattered light beam
from the intensity of the first interference light beam,
vii) causing a second backward scattered light beam of the signal light
beam having been irradiated to the eyeball, the second backward scattered
light beam coming from an interface between the anterior aqueous chamber
and the crystalline lens of the eyeball, and the reference light beam to
interfere with each other by adjusting the optical path length of the
reference light beam, a second interference light beam being thereby
obtained,
viii) measuring an intensity of the second interference light beam,
ix) calculating an intensity of the second backward scattered light beam
from the intensity of the second interference light beam,
x) obtaining light absorption characteristics of constituents of the
aqueous humor, which fills the anterior aqueous chamber, from the
intensity of the first backward scattered light beam and the intensity of
the second backward scattered light beam,
xi) obtaining light absorption characteristics of the constituents of the
aqueous humor with respect to each of a plurality of other low coherence
light beams, which are of wavelength bands different from the wavelength
band of the low coherence light beam, in the same manner, and
xii) calculating a concentration of glucose in the constituents of the
aqueous humor from the light absorption characteristics, which have been
obtained with respect to the plurality of the low coherence light beams.
In the first glucose concentration measuring method in accordance with the
present invention, as the light source for producing each of the low
coherence light beams, a super-luminescent diode (SLD), a light emitting
diode (LED), or the like, which produces a light beam having a coherence
length of as short as approximately several tens of microns, may be
employed. Practically, an SLD having a high directivity should preferably
be used.
The term "measuring an intensity of an interference light beam" as used
herein means the measurement of the intensity of the beat signal (i.e.,
the interference light beam), the intensity of which repeatedly becomes
high and low at a frequency equal to the difference between the
frequencies of the backward scattered light beam (i.e., the signal light
beam) and the reference light beam.
In the first glucose concentration measuring method in accordance with the
present invention, each of the low coherence light beams may be selected
as a portion of light, which is of an emission wavelength band wider than
the wavelength band of each low coherence light beam. Alternatively, each
of the low coherence light beams may be radiated out of one of a plurality
of different light sources.
In cases where a plurality of different light sources, which produce the
low coherence light beams of different wavelength bands, are employed, the
low coherence light beams may be radiated successively out of the
plurality of the light sources, and the interference light beams
corresponding to the low coherence light beams may be detected with a
single photodetector.
The present invention also provides a second glucose concentration
measuring method, comprising the steps of:
i) splitting a coherent light beam (e.g., a laser beam), which has been
radiated out of a predetermined light source and the frequency of which is
swept temporally in a sawtooth-like form (e.g., as illustrated in FIG. 6),
into a signal light beam and a reference light beam, each of which travels
along one of two different optical paths,
ii) irradiating the signal light beam to the eyeball lying at a
predetermined position,
iii) causing a first backward scattered light beam of the signal light
beam, the first backward scattered light beam coming from an interface
between the cornea and the anterior aqueous chamber of the eyeball, and
the reference light beam to interfere with each other, the reference light
beam being constituted of the coherent light beam, which has been radiated
out of the light source with a difference in time in accordance with a
difference between an optical path length of the signal light beam
(traveling from the position, at which the signal light beam is split from
the reference light beam, to the interface between the cornea and the
anterior aqueous chamber of the eyeball) and the first backward scattered
light beam (traveling from the interface between the cornea and the
anterior aqueous chamber of the eyeball to the position, at which the
first backward scattered light beam interferes with the reference light
beam) and an optical path length of the reference light beam (traveling
from the position, at which the reference light beam is split from the
signal light beam, to the position, at which the reference light beam
interferes with the first backward scattered light beam), and which has a
difference in frequency with respect to the first backward scattered light
beam, a first interference light beam being thereby obtained,
iv) measuring an intensity of the first interference light beam,
v) calculating an intensity of the first backward scattered light beam from
the intensity of the first interference light beam,
vi) causing a second backward scattered light beam of the signal light
beam, the second backward scattered light beam coming from an interface
between the anterior aqueous chamber and the crystalline lens of the
eyeball, and the reference light beam to interfere with each other, the
reference light beam being constituted of the coherent light beam, which
has been radiated out of the light source with a difference in time in
accordance with a difference between an optical path length of the signal
light beam (traveling from the position, at which the signal light beam is
split from the reference light beam, to the interface between the anterior
aqueous chamber and the crystalline lens of the eyeball) and the second
backward scattered light beam (traveling from the interface between the
anterior aqueous chamber and the crystalline lens of the eyeball to the
position, at which the second backward scattered light beam interferes
with the reference light beam) and an optical path length of the reference
light beam (traveling from the position, at which the reference light beam
is split from the signal light beam, to the position, at which the
reference light beam interferes with the second backward scattered light
beam), and which has a difference in frequency with respect to the second
backward scattered light beam, a second interference light beam being
thereby obtained,
vii) measuring an intensity of the second interference light beam,
viii) calculating an intensity of the second backward scattered light beam
from the intensity of the second interference light beam,
ix) obtaining light absorption characteristics of constituents of the
aqueous humor, which fills the anterior aqueous chamber, from the
intensity of the first backward scattered light beam and the intensity of
the second backward scattered light beam,
x) obtaining light absorption characteristics of the constituents of the
aqueous humor with respect to each of a plurality of other coherent light
beams, which have wavelengths different from the wavelength of the
coherent light beam, in the same manner, and
xi) calculating a concentration of glucose in the constituents of the
aqueous humor from the light absorption characteristics, which have been
obtained with respect to the plurality of the coherent light beams.
In the second glucose concentration measuring method in accordance with the
present invention, the reference light beam, which is caused to interfere
with the first backward scattered light beam, has a difference in
frequency with respect to the first backward scattered light beam. The
reasons for this will be described hereinbelow.
The optical paths are set such that the sum of the length of the optical
path, along which the signal light beam travels, and the length of the
optical path, along which the first backward scattered light beam travels,
may be different from the length of the optical path, along which the
reference light beam travels. (The optical path length of the reference
light beam may be shorter than the sum of the optical path lengths of the
signal light beam and the first backward scattered light beam.
Alternatively, the optical path length of the reference light beam may be
longer than the sum of the optical path lengths of the signal light beam
and the first backward scattered light beam.) Due to the difference in
optical path length, for example, in cases where the optical path length
of the reference light beam is shorter than the sum of the optical path
lengths of the signal light beam and the first backward scattered light
beam, the reference light beam arrives at the position, at which the
wavefront matching (the interference) is effected, with an earlier timing
than the first backward scattered light beam does.
Specifically, at the time at which the first backward scattered light beam
arrives at the position of interference, the reference light beam, which
was split from the signal light beam that formed the first backward
scattered light beam, has already passed through the position of
interference, and the reference light beam, which is a portion of the
coherent light beam radiated out of the light source with a later timing
than the signal light beam was, arrives at the position of interference.
The frequency of the coherent light beam, which is radiated out of the
light source with a later timing than the signal light beam was, is swept
temporally. Therefore, there is a slight difference in frequency between
the reference light beam, which is caused to interfere with the first
backward scattered light beam, and the first backward scattered light
beam.
The reference light beam, which is caused to interfere with the second
backward scattered light beam, has a frequency different from the
frequency of the reference light beam, which is caused to interfere with
the first backward scattered light beam. Specifically, the first backward
scattered light beam comes from the interface between the cornea and the
anterior aqueous chamber, and the second backward scattered light beam
comes from the interface between the anterior aqueous chamber and the
crystalline lens, the latter interface being located at a position in the
eyeball deeper than the former interface. Therefore, a difference in time,
which corresponds to the difference in optical path length between the
first backward scattered light beam and the second backward scattered
light beam (the difference being two times as long as the thickness of the
anterior aqueous chamber), occurs between when the first backward
scattered light beam arrives at the position of interference and when the
second backward scattered light beam arrives as the position of
interference. As a result, the reference light beam, which is caused to
interfere with the second backward scattered light beam, is the one
constituted of a portion of the coherent light beam, which is radiated out
of the light source with a later timing than the reference light beam
caused to interfere with the first backward scattered light beam is.
In the second glucose concentration measuring method in accordance with the
present invention, the coherent light beams may be selectively radiated
out of a single light source. Alternatively, each of the coherent light
beams may be radiated out of one of a plurality of different light
sources.
The present invention further provides a third glucose concentration
measuring method, comprising the steps of:
i) irradiating an ultrashort pulsed light beam, which has been radiated out
of a predetermined light source, to the eyeball,
ii) measuring each of an intensity of a first backward scattered light beam
of the ultrashort pulsed light beam, the first backward scattered light
beam coming from an interface between the cornea and the anterior aqueous
chamber of the eyeball, and an intensity of a second backward scattered
light beam of the ultrashort pulsed light beam, the second backward
scattered light beam coming from an interface between the anterior aqueous
chamber and the crystalline lens of the eyeball,
iii) obtaining light absorption characteristics of constituents of the
aqueous humor, which fills the anterior aqueous chamber, from the
intensity of the first backward scattered light beam and the intensity of
the second backward scattered light beam,
iv) obtaining light absorption characteristics of the constituents of the
aqueous humor with respect to each of a plurality of other ultrashort
pulsed light beams, which have wavelengths different from the wavelength
of the ultrashort pulsed light beam, in the same manner, and
v) calculating a concentration of glucose in the constituents of the
aqueous humor from the light absorption characteristics, which have been
obtained with respect to the plurality of the ultrashort pulsed light
beams having different wavelengths.
The term "ultrashort pulsed light beam" as used herein means the pulsed
light beam, which is emitted for a very short time (e.g., on the order of
femtoseconds to picoseconds) such that the intensity of the first backward
scattered light beam and the intensity of the second backward scattered
light beam coming from the interface between the anterior aqueous chamber
and the crystalline lens can at least be separated temporally and measured
respectively. The ultrashort pulsed light beam may be produced by a mode
locked Ti:sapphire laser, or the like. In cases where the ultrashort
pulsed light beam is employed, the second backward scattered light beam,
which lags behind the first backward scattered light beam by a length of
time corresponding to the distance two times as long as the thickness of
the anterior aqueous chamber, can be detected separately from the first
backward scattered light beam by using a photodetector capable of
effecting time resolution, such as a streak camera.
In the third glucose concentration measuring method in accordance with the
present invention, the ultrashort pulsed light beams may be selectively
radiated out of a single light source. Alternatively, each of the
ultrashort pulsed light beams may be radiated out of one of a plurality of
different light sources.
The present invention still further provides a fourth glucose concentration
measuring method, comprising the steps of:
with respect to concentrations of glucose in the constituents of the
aqueous humor, which concentrations have been measured with the aforesaid
first, second, or third glucose concentration measuring method in
accordance with the present invention, invasively measuring the
corresponding concentrations of glucose in the blood, correlation between
the concentrations of glucose in the constituents of the aqueous humor and
the concentrations of glucose in the blood being thereby determined
previously, and
thereafter non-invasively determining a concentration of glucose in the
blood from a concentration of glucose in the constituents of the aqueous
humor, which concentration is newly measured with the aforesaid first,
second, or third glucose concentration measuring method in accordance with
the present invention, and the correlation.
The present invention also provides an apparatus for carrying out the
aforesaid first glucose concentration measuring method in accordance with
the present invention. Specifically, the present invention also provides a
first glucose concentration measuring apparatus, comprising:
i) a light source device for radiating out a plurality of low coherence
light beams, which are of different emission wavelength bands,
ii) an optical path splitting means for splitting each of the low coherence
light beams, which has been radiated out of the light source device, into
a signal light beam irradiated to the eyeball and a reference light beam,
each of which travels along one of two different optical paths,
iii) a modulation means, which is located in at least either one of the two
different optical paths and modulates at least either one of the signal
light beam and the reference light beam such that a slight difference in
frequency may occur between them,
iv) an optical path length adjusting means for adjusting the length of the
optical path, along which the reference light beam travels,
v) a wavefront matching means for:
matching a wave front of a first backward scattered light beam of the
signal light beam having been irradiated to the eyeball, the first
backward scattered light beam coming from an interface between the cornea
and the anterior aqueous chamber of the eyeball, and a wave front of the
reference light beam with each other, and
matching a wave front of a second backward scattered light beam of the
signal light beam having been irradiated to the eyeball, the second
backward scattered light beam coming from an interface between the
anterior aqueous chamber and the crystalline lens of the eyeball, and a
wave front of the reference light beam with each other,
vi) a photodetector for photoelectrically detecting an intensity of a first
interference light beam, which is obtained from the matching of the wave
front of the first backward scattered light beam and the wave front of the
reference light beam with each other, and an intensity of a second
interference light beam, which is obtained from the matching of the wave
front of the second backward scattered light beam and the wave front of
the reference light beam with each other,
vii) a heterodyne operation means for calculating an intensity of the first
backward scattered light beam from the intensity of the first interference
light beam, and calculating an intensity of the second backward scattered
light beam from the intensity of the second interference light beam,
viii) a light absorption characteristics analyzing means for obtaining
light absorption characteristics of constituents of the aqueous humor,
which fills the anterior aqueous chamber, from the intensity of the first
backward scattered light beam and the intensity of the second backward
scattered light beam, and
ix) a glucose concentration calculating means for calculating a
concentration of glucose in the constituents of the aqueous humor from the
light absorption characteristics, which have been obtained with respect to
the plurality of the low coherence light beams.
In the first glucose concentration measuring apparatus in accordance with
the present invention, the light source device may comprise a single light
source for radiating out low coherence light, which is of an emission
wavelength band wider than the wavelength band of each of the low
coherence light beams, and a wavelength selecting means for selecting each
of the low coherence light beams with respect to the wavelength from the
low coherence light, which is of the wide emission wavelength band.
Alternatively, the light source device may comprise a plurality of light
sources, each of which radiates out one of the low coherence light beams.
The present invention further provides an apparatus for carrying out the
aforesaid second glucose concentration measuring method in accordance with
the present invention. Specifically, the present invention further
provides a second glucose concentration measuring apparatus, comprising:
i) a light source device for radiating out a plurality of coherent light
beams, which have different wavelengths and the frequencies of which are
swept temporally in a sawtooth-like form (e.g., as illustrated in FIG. 6),
ii) an optical path splitting means for splitting each of the coherent
light beams, which has been radiated out of the light source device and
the frequency of which is swept, into a signal light beam irradiated to
the eyeball and a reference light beam, each of which travels along one of
two different optical paths,
iii) a wavefront matching means for:
matching a wave front of a first backward scattered light beam of the
signal light beam, the first backward scattered light beam coming from an
interface between the cornea and the anterior aqueous chamber of the
eyeball, and a wave front of the reference light beam with each other, the
reference light beam being constituted of the coherent light beam, which
has been radiated out of the light source device with a difference in time
in accordance with a difference between an optical path length of the
signal light beam and the first backward scattered light beam and an
optical path length of the reference light beam, and which has a
difference in frequency with respect to the first backward scattered light
beam, and
matching a wave front of a second backward scattered light beam of the
signal light beam, the second backward scattered light beam coming from an
interface between the anterior aqueous chamber and the crystalline lens of
the eyeball, and a wave front of the reference light beam with each other,
the reference light beam being constituted of the coherent light beam,
which has been radiated out of the light source device with a difference
in time in accordance with a difference between an optical path length of
the signal light beam and the second backward scattered light beam and an
optical path length of the reference light beam, and which has a
difference in frequency with respect to the second backward scattered
light beam,
iv) a photodetector for photoelectrically detecting an intensity of a first
interference light beam, which is obtained from the matching of the wave
front of the first backward scattered light beam and the wave front of the
reference light beam, the reference light beam having the slight
difference in frequency with respect to the first backward scattered light
beam, with each other, and an intensity of a second interference light
beam, which is obtained from the matching of the wave front of the second
backward scattered light beam and the wave front of the reference light
beam, the reference light beam having the slight difference in frequency
with respect to the second backward scattered light beam, with each other,
v) a heterodyne operation means for calculating an intensity of the first
backward scattered light beam from the intensity of the first interference
light beam, and calculating an intensity of the second backward scattered
light beam from the intensity of the second interference light beam,
vi) a light absorption characteristics analyzing means for obtaining light
absorption characteristics of constituents of the aqueous humor, which
fills the anterior aqueous chamber, from the intensity of the first
backward scattered light beam and the intensity of the second backward
scattered light beam, and
vii) a glucose concentration calculating means for calculating a
concentration of glucose in the constituents of the aqueous humor from the
light absorption characteristics, which have been obtained with respect to
the plurality of the coherent light beams.
In the second glucose concentration measuring apparatus in accordance with
the present invention, the light source device may comprise a single light
source capable of selectively radiating out each of the plurality of the
coherent light beams, and a control means for controlling the light source
such that the light source may selectively radiate out one of the
plurality of the coherent light beams. Alternatively, the light source
device may comprise a plurality of light sources, each of which radiates
out one | | |
