FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
COMPONENT MEASUREMENT DEVICE AND COMPONENT MEASUREMENT
METHOD;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
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DESCRIPTION
Component Measurement Device and Component Measurement Method
5 TECHNICAL FIELD
[0001] The present invention relates to a component measurement device and a
component measurement method, and specifically relates to a component measurement
device and component measurement method for measuring a component in a living
body.
10 BACKGROUND ART
[0002] In applications to various fields, particularly to chemistry, biology, and medical
science, a component measurement device for measuring a component contained in a
sample is known. For example, a component measurement device for measuring a
component contained in a living body is known. Most of component measurement
15 devices are invasive devices using chemical analysis. In the case of such an invasive
component measurement device, a substance changes due to partial separation or
chemical reaction during measurement. For example, for measurement of a blood
glucose level in a living body, an invasive sensor is widely used. In this case, blood is
sampled using a needle and is reacted with a reagent.
20 [0003] When an invasive component measurement device is used for, for example,
blood glucose level measurement, a patient feels pain due to needling. Therefore,
particularly in the fields of medical science and health care, there have been demands
for non-invasive component measurement devices.
[0004] A non-invasive component measurement device based on optothermal
25 spectroscopy is known which performs measurement based on interstitial fluid to which
biological components are to be transported from blood. For example, Patent
Literature 1 discloses a non-invasive component measurement device to perform, as
biometric measurement, measurement of a component such as blood glucose level or
lipid based on interstitial fluid to which biological components are to be transported
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from blood. Interstitial fluid is fluid that is contained in cells and is present also in an
area closer to the skin surface than the blood vessels, and is therefore suitable for use in
measurement from outside of the body.
CITATION LIST
5 PATENT LITERATURE
[0005] PTL1: Japanese National Patent Publication No. 2017-519214
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0006] However, stratum corneum that is the outermost surface of the skin is a layer of
10 dead cells. Interstitial fluid is not contained in stratum corneum that is the outermost
surface of the skin as a layer of dead cells, and is present in stratum granulosum under
stratum corneum and in layers deeper than stratum granulosum. The thickness of
stratum corneum generally depends on the part of a living body, and may be different
between a part such as an arm, wrist, forehead, or abdomen and a part that frequently
15 comes into contact with external substances, such as a finger, palm, or feet bottom.
Therefore, in the case of such a non-invasive component measurement device as
described above to perform measurement based on interstitial fluid, measurement may
be performed on the basis of information from a portion containing no interstitial fluid.
For this reason, such a non-invasive component measurement device as described
20 above is required to be improved in component measurement accuracy.
[0007] In order to solve the above problem, it is an object of the present invention to
provide a non-invasive component measurement device and component measurement
method having improved component measurement accuracy.
SOLUTION TO PROBLEM
25 [0008] A component measurement device according to one aspect of the present
invention is a component measurement device for measuring a given component
contained in a sample, the component measurement device including: an optical
medium portion on which the sample is stationarily placed; an excitation light source to
emit excitation light onto the optical medium portion; a probe light source to emit
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probe light onto the optical medium portion; an intensity modulation unit to perform
intensity modulation on the excitation light emitted by the excitation light source based
on stratum corneum information about stratum corneum of the sample to generate
intensity-modulated excitation light and emit the generated intensity-modulated
5 excitation light onto the optical medium portion; and a measurement unit to measure
the given component based on a difference between the probe light emitted from the
optical medium portion in a first state where the excitation light is emitted and the
probe light emitted from the optical medium portion in a second state where the
intensity-modulated excitation light is emitted.
10 [0009] A component measurement method according to one aspect of the present
invention is a component measurement method for measuring a given component
contained in a sample, the component measurement method including: a stationarily
placing step of stationarily placing the sample on an optical medium portion, an
excitation light emitting step of emitting excitation light from an excitation light source
15 onto the optical medium portion, a probe light emitting step of emitting probe light
from a probe light source onto the optical medium portion, a stratum corneum
information acquisition step of acquiring stratum corneum information about stratum
corneum of the sample, an intensity modulation step of performing intensity
modulation on the excitation light emitted by the excitation light source based on the
20 stratum corneum information acquired in the stratum corneum information acquisition
step to generate intensity-modulated excitation light and emit the generated intensitymodulated excitation light onto the optical medium portion, and a measurement step of
measuring the given component based on a difference between the probe light emitted
from the optical medium portion in a first state where the excitation light is emitted and
25 the probe light emitted from the optical medium portion in a second state where the
intensity-modulated excitation light is emitted.
ADVANTAGEOUS EFFECTS OF INVENTION
[0010] According to one aspect of the present invention, it is possible to provide a noninvasive component measurement device and component measurement method having
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improved component measurement accuracy.
BRIEF DESCRIPTION OF DRAWINGS
[0011] Fig. 1 is a diagram showing the configuration of a component measurement
device according to a first embodiment.
5 Fig. 2 is a top view of an optical medium portion of the component
measurement device according to the first embodiment.
Fig. 3 is a graph showing the relationship between a modulation frequency used
for measurement and a diffusion length of heat generated inside the skin.
Fig. 4 is a diagram showing the configuration of a component measurement
10 device according to a second embodiment.
DESCRIPTION OF EMBODIMENTS
[0012] Hereinbelow, an example of a component measurement device for measuring a
blood glucose level in a living body as a component contained in a sample will be
described with reference to the drawings. However, needless to say, the component
15 measurement device according to the present invention can be applied also to
measurement of a component other than blood glucose level.
[0013] First Embodiment
Fig. 1 is a diagram showing the configuration of a component measurement
device 100 according to a first embodiment. Component measurement device 100
20 according to the first embodiment includes an excitation light source 1, a probe light
source 2, an optical medium portion 3, a light position detector 4, an optical chopper 9,
a lock-in amplifier 10, a stratum corneum information acquisition unit 11, and an
operation unit 20.
[0014] Excitation light source 1 includes at least one infrared light source. Excitation
25 light source 1 is a component to emit, as excitation light 6, infrared light in the entire
wavelength range from 8 m to 10 m including the wavelength of a fingerprint
spectrum by which glucose can be identified to measure a blood glucose level or in part
of such a wavelength range. Excitation light source 1 includes a broadband quantum
cascade laser. Excitation light source 1 is configured to include wavelengths used for
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measurement, such as wavelengths 1 and 2 absorbed by glucose in a human body
and a wavelength 3 not absorbed by glucose in a human body and used as a reference
wavelength. Excitation light source 1 may be configured to include 4 or more
wavelengths used for measurement.
5 [0015] Probe light source 2 is a laser to output, as probe light 7, light in a wavelength
range that passes through optical medium portion 3 that will be described later. Probe
light source 2 is preferably configured as a laser to output light having a wavelength in
a wavelength range from visible light to near-infrared. This is because light having a
wavelength in a wavelength range from visible light to near-infrared is easily generated
10 for output and detected, and therefore the burden of assembling component
measurement device 100 can be reduced.
[0016] Optical medium portion 3 is a sample stage on which a sample 5 containing
glucose used to measure a blood glucose level is stationarily placed. In component
measurement device 100 of the first embodiment according to an example of the
15 present invention, a finger is stationarily placed as sample 5 on optical medium portion
3 as a sample stage. Optical medium portion 3 is formed using, as an optical medium,
a material that is highly permeable to light in the infrared wavelength range, such as
zinc sulfide (ZnS), zinc selenide (ZnSe), germanium (Ge), silicon (Si), or chalcogenide
glass so as to have a predetermined refractive index gradient 8. Refractive index
20 gradient 8 is changed by excitation light 6 emitted by excitation light source 1.
[0017] Light position detector 4 is a light detection sensor to detect light from probe
light source 2 emitted from optical medium portion 3. By such detection, light
position detector 4 detects the pathway of light emitted from probe light source 2 and
passed through optical medium portion 3. Light position detector 4 is configured to
25 be able to detect emitted probe light 7a and emitted probe refracting light 7b which will
be described later. Light position detector 4 detects the position of light entering light
position detector 4. Light position detector 4 is configured using, for example, a
quadrant photodiode.
[0018] Optical chopper 9 is a component to perform intensity modulation on light
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passing therethrough using a specific frequency component. Optical chopper 9 is
disposed between excitation light source 1 and optical medium portion 3 and is
configured to perform intensity modulation on excitation light 6 emitted from
excitation light source 1 and send intensity-modulated excitation light 6’ to optical
5 medium portion 3. Optical chopper 9 includes a rotary blade. The rotation of the
rotary blade periodically blocks excitation light 6 as continuous light so that intensity
modulation is performed on excitation light 6.
[0019] Refractive index gradient 8 of optical medium portion 3 at the time when
excitation light 6 not subjected to intensity modulation is emitted is different from
10 refractive index gradient 8 of optical medium portion 3 at the time when intensitymodulated excitation light 6’ is emitted. Light position detector 4 detects a difference
between the pathway of emitted probe light 7a at the time when excitation light 6 not
subjected to intensity modulation is emitted and the pathway of emitted probe
refracting light 7b at the time when intensity-modulated excitation light 6’ is emitted.
15 [0020] Lock-in amplifier 10 is connected to light position detector 4 and optical
chopper 9. Lock-in amplifier 10 reads, among signals measured by light position
detector 4, a signal synchronized with the modulation frequency component of
excitation light 6. Therefore, component measurement device 100 can perform
measurement with high accuracy.
20 [0021] A measured signal includes a noise including various frequency components,
and the amount of noise increases as the frequency reduces. When excitation light is
modulated using an optical chopper to have a frequency f, a desired measured signal is
a modulated signal that is the same as modulated excitation light in frequency and
phase but different in amplitude from the modulated excitation light. At this time,
25 when the excitation light and the measured signal are multiplied, a signal is obtained
which has a frequency component obtained by performing addition (2f) on their
respective frequency components f and a frequency component obtained by subtraction
(0 = direct current component) on their respective frequency components f. When the
measured signal includes a noise including a large amount of different frequency
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components, measured signals corresponding to the modulation frequency of excitation
light and the frequency of a noise are added. However, a necessary component is
contained only in a direct current component. Therefore, only a direct current
component is measured using a low-pass filter, which makes it possible to remove a
5 noise component even from a weak signal to perform measurement with high accuracy.
[0022] Stratum corneum information acquisition unit 11 is a component to acquire
stratum corneum information about the stratum corneum of sample 5 stationarily placed
on optical medium portion 3. For example, stratum corneum information acquisition
unit 11 is an input device to acquire stratum corneum information input by a user of
10 component measurement device 100.
[0023] The thickness of stratum corneum may be different depending on a
measurement method used or from person to person in a precise sense, but can
generally depend on the part of a living body. It is known that the stratum corneum of
a part that frequently comes into contact with external substances, such as a finger,
15 palm, or feet bottom, is as thick as 100 to 300 m whereas the thickness of stratum
corneum of a part such as an arm, wrist, forehead, or abdomen is about 20 m.
Therefore, stratum corneum information acquisition unit 11 according to the first
embodiment is a numeric input device such as a numeric keyboard and acquires, as
stratum corneum information, a thickness value such as 20 m from a user.
20 [0024] As Stratum corneum information acquisition unit 11 according to an example of
the present invention described above, a numeric input device is exemplified.
However, the present invention is not limited to this example. An input device may
be used which can select a target part corresponding to sample 5 from among parts such
as an arm, wrist, forehead, abdomen, finger, palm, and feet bottom. The thickness
25 value of stratum corneum corresponding to each part such as an arm, wrist, forehead,
abdomen, finger, palm, or feet bottom may be stored in a memory unit so that the
thickness value corresponding to a part selected using stratum corneum information
acquisition unit 11 can be acquired. Such a configuration makes it possible to
increase design flexibility of component measurement device 100.
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[0025] Operation unit 20 is a component to calculate a blood glucose level to measure
glucose contained in sample 5. Operation unit 20 is connected to lock-in amplifier 10.
Operation unit 20 calculates a blood glucose level based on a signal acquired by lock-in
amplifier 10.
5 [0026] Operation unit 20 is also a component to further perform adjustment based on
the stratum corneum of sample 5. Operation unit 20 is connected not only to lock-in
amplifier 10 but also to stratum corneum information acquisition unit 11. Operation
unit 20 performs intensity modulation on excitation light 6 emitted from excitation light
source 1 based on stratum corneum information acquired by stratum corneum
10 information acquisition unit 11. Specifically, operation unit 20 controls the rotation
speed of optical chopper 9 to set a modulation frequency that will be described later.
The modulation frequency herein means the frequency of intensity modulation of
excitation light.
[0027] As shown in Fig. 1, component measurement device 100 is configured so that
15 probe light 7 emitted from probe light source 2 enters optical medium portion 3 as
incident probe light and is emitted toward light position detector 4 as emitted probe
light 7a. When excitation light source 1 emits excitation light 6 toward optical
medium portion 3 so that absorption heat is generated in sample 5, the generated
absorption heat is conducted to optical medium portion 3 so that a temperature gradient
20 is formed in optical medium portion 3 and refractive index gradient 8 of optical
medium portion 3 changes. When passing through optical medium portion 3 whose
refractive index gradient 8 has been changed, probe light 7 is emitted toward light
position detector 4 as emitted probe refracting light 7b whose light path is different
from that of emitted probe light 7a because the refractive index of optical medium
25 portion 3 also changes due to a change in refractive index gradient 8. Component
measurement device 100 is configured to perform component measurement by
allowing light position detector 4 to detect a gap between emitted probe light 7a and
emitted probe refracting light 7b and allowing operation unit 20 to perform an
operation on a detection result passed through lock-in amplifier 10. Above-described
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light position detector 4, lock-in amplifier 10, operation unit 20, and a combination
thereof relate to an example of a measurement unit to measure a given component
based on a difference between emitted probe light 7a emitted from optical medium
portion 3 at the time when excitation light 6 is emitted and emitted probe refracting
5 light 7b emitted from optical medium portion 3 at the time when intensity-modulated
excitation light 6’ is emitted.
[0028] Optical chopper 9 performs intensity modulation based on the modulation
frequency set by operation unit 20 so that excitation light 6 emitted from excitation
light source 1 has a modulation frequency corresponding to stratum corneum
10 information acquired by stratum corneum information acquisition unit 11.
Specifically, intensity modulation is performed on excitation light 6 by rotating the
rotary blade at a rotation speed corresponding to the modulation frequency set by
operation unit 20. That is, optical chopper 9 corresponds to an example of an intensity
modulation unit according to the present invention. Intensity-modulated excitation
15 light 6’ after passing through optical chopper 9 passes through optical medium portion
3 and enters sample 5. In the case of blood glucose level measurement, sample 5
corresponds to a part of a subject, such as a finger, wrist, arm or earlobe. Operation
unit 20 calculates absorption by a glucose component contained in interstitial fluid of
sample 5 where probe light 7 enters through the skin.
20 [0029] Fig. 2 is a top view of optical medium portion 3 of component measurement
device 100 according to the first embodiment. Excitation light source 1 and probe
light source 2 are configured so that the light path of probe light 7 intersects excitation
light 6 from excitation light source 1 in an excitation light radiation site on the plan
view shown in Fig. 2. When the range of a refractive index gradient generation area 
25 generated in optical medium portion 3 is taken into consideration, the beam width of
excitation light 6 emitted by excitation light source 1 is preferably the same as or
greater than that of probe light 7 emitted by probe light source 2. If the beam width of
excitation light is small, the refractive index gradient generation area  may be smaller
than the beam width of probe light 7. If the refractive index gradient generation area
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 is smaller than the beam width of probe light 7, only part of probe light is influenced,
which makes it difficult to measure a change in the light path of probe light 7. On the
other hand, if the beam width of excitation light is excessively large, the density of
excitation light may reduce or the refractive index gradient generation area  may
5 widen. If the density of excitation light is lower than necessary or the refractive index
gradient generation area  is wider than necessary, the refractive index gradient itself
may reduce. If the refractive index gradient itself reduces, the refractive index
gradient may have no effect of changing the light path of probe light 7. Therefore,
specifically, it is preferred that the beam width of excitation light is 50 m and the
10 beam width of probe light is 30 m.
[0030] The operation of blood glucose level measurement in component measurement
device 100 will be described. The description will be made with reference to a case
where a state where light output of excitation light source 1 is zero is defined as a
reference state. In the reference state, the internal state of optical medium portion 3 is
15 considered to be uniform. Therefore, probe light 7 output from the probe light source
2 is refracted only when entering and exiting optical medium portion 3. Here, a
position where emitted probe light 7a enters light position detector 4 in the reference
state is defined as a reference position. In an example according to the first
embodiment, as shown in Fig. 1, component measurement device 100 is configured so
20 that probe light 7 is totally reflected once by the contact surface with sample 5 at the
excitation light radiation site. Refractive index gradient 8 generated in an optical
medium that will be described later is generated near the surface of optical medium
portion 3, and particularly, the gradient is larger as it is closer to the surface in contact
with an area where heat is generated. As described above, since the probe light source
25 is disposed, the incidence angle of probe light 7 can be made shallow, and therefore the
pathway through which probe light 7 passes is located near the surface of the optical
medium. This makes it possible to efficiently change the light path. Probe light 7 is
refracted by passing through refractive index gradient 8 so that its light path changes.
Therefore, for example, component measurement device 100 may be configured so that
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the pathway is one such that probe light 7 is totally reflected twice or more in optical
medium portion 3 or probe light 7 passes near the contact surface with sample 5 in
parallel with the contact surface.
[0031] After probe light source 2 emits probe light 7, excitation light source 1 outputs,
5 as excitation light 6, infrared light with a fingerprint spectrum wavelength of glucose.
Optical chopper 9 performs intensity modulation on excitation light 6 output by
excitation light source 1. Excitation light 6 subjected to intensity modulation by
optical chopper 9 passes through optical medium portion 3 and enters sample 5.
Excitation light 6 that is infrared light and has entered sample 5 is absorbed by glucose
10 contained in interstitial fluid present near the surface of sample 5. When excitation
light 6 is absorbed by glucose, absorption heat is generated inside sample 5. The
generated absorption heat is conducted to optical medium portion 3 from sample 5.
When the absorption heat is conducted to optical medium portion 3, a temperature
gradient is generated in optical medium portion 3. The refractive index of optical
15 medium portion 3 generally has temperature dependency. Therefore, when a
temperature gradient is generated in optical medium portion 3, a refractive index
gradient is generated so that refractive index gradient 8 is formed. The following
description will be made with reference to a case where a state where refractive index
gradient 8 is formed is defined as a state A.
20 [0032] When excitation light 6 emitted onto sample 5 penetrates up to about 50 to 100
m inside sample 5 so that absorption heat is generated, heat diffusion length L, which
is the length of diffusion of generated heat, is represented by the following formula (1)
using the frequency f which corresponds to the modulation frequency of excitation light
6 and at which absorption heat is generated and the thermal diffusion coefficient  of
25 sample 5. When sample 5 is a part of a subject, such as a finger, wrist, arm, or
earlobe, the thermal diffusion coefficient of skin of such a part is about 0.13 to 0.17
mm2
/s.
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... Formula (1)
[0033] Fig. 3 is a graph showing the relationship between a modulation frequency used
for measurement and a diffusion length of heat generated inside the skin. Fig. 3
5 shows the heat diffusion length inside the skin with respect to the modulation frequency
when the thermal diffusion coefficient is 0.15 mm2
/s. Specifically, when the
modulation frequency is 100 Hz, 30 Hz, or 5 Hz, the heat diffusion length is about 20
m, about 40 m, and about 100 m, respectively. In order to measure a component
contained in interstitial fluid, the heat diffusion length needs to be larger than the
10 thickness of stratum corneum. Therefore, the modulation frequency f is set to satisfy f
< /(d2
 ). More preferably, the heat diffusion length is in the range of one to three
times the thickness of stratum corneum, and therefore the modulation frequency f is set
to satisfy /{(3d)2
 } < f < /(d2
 ). In order to increase the heat diffusion length,
the modulation frequency needs to be reduced. However, noise generated during
15 measurement is usually greater in a lower frequency range. Therefore, when the
modulation frequency is low, the S/N ratio of a signal may be reduced even using a
lock-in amplifier. For this reason, the frequency to be used is preferably as high as
possible in a range such that interstitial fluid can be measured. Specifically, when a
finger or palm whose skin has a thick stratum corneum of 100 m or more is measured,
20 operation unit 20 sets the rotation speed of optical chopper 9 via lock-in amplifier 10 so
that the modulation frequency of excitation light 6 is 0.5 to 5 Hz. Similarly, when a
part, such as an arm, wrist, or forehead, whose skin has a stratum corneum of about 20
m is measured, operation unit 20 sets the rotation speed of optical chopper 9 via lockin amplifier 10 so that the modulation frequency of excitation light 6 is 15 to 100 Hz.
25 Such a configuration as described above makes it possible, when stratum corneum is
relatively thin, to perform measurement using a higher modulation frequency.
[0034] When passing through refractive index gradient 8 in which the gradient of
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refractive index is not generated in the reference state, probe light 7 is refracted
according to a refractive index at a position in optical medium portion 3 where probe
light 7 passes. Refracting probe light 7 is emitted from optical medium portion 3 as
emitted probe light 7a and enters light position detector 4. In the reference state, the
5 light position detector detects a position where emitted probe light 7a enters light
position detector 4 as a reference position.
[0035] When passing through refractive index gradient 8 in which the gradient of
refractive index is generated in the state A, probe light 7 is refracted according to a
refractive index in refractive index gradient 8 at a position in optical medium portion 3
10 where probe light 7 passes. Refracting incident probe light 7 is emitted from optical
medium portion 3 as emitted probe refracting light 7b and enters light position detector
4. In the state A, the light position detector detects a position where emitted probe
refracting light 7b enters light position detector 4 as a displaced position.
[0036] Lock-in amplifier 10 reads the value of a signal based on a difference between
15 the reference position and the displaced position detected by light position detector 4.
Operation unit 20 acquires the signal about the difference read by lock-in amplifier 10
and calculates a blood glucose level as a component.
[0037] As described above, component measurement device 100 according to the first
embodiment can efficiently measure absorption heat generated by a given component
20 in interstitial fluid contained in layers deeper than stratum corneum by driving optical
chopper 9 based on stratum corneum information acquired by stratum corneum
information acquisition unit 11. Specifically, the diffusion length of heat generated in
a living body during measurement is about 1 to 3 times the thickness of stratum
corneum, and therefore absorption heat generated by a glucose component in interstitial
25 fluid contained in layers deeper than stratum corneum can efficiently be measured. In
other words, it is possible to provide a non-invasive component measurement device
which reduces the risk of performing measurement on the basis of information from a
portion containing no interstitial fluid and therefore achieves improved component
measurement accuracy.
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[0038] A component measurement method for measuring a blood glucose level as a
given component contained in sample 5 will be described using component
measurement device 100 according to the first embodiment. In the component
measurement method, a stationarily placing step is first performed in which sample 5 is
5 stationarily placed on optical medium portion 3. In the component measurement
method, after the stationarily placing step is performed, an excitation light emitting step
is performed in which excitation light 6 is emitted from excitation light source 1 onto
optical medium portion 3. In the component measurement method, after the
stationarily placing step is performed, a probe light emitting step is also performed in
10 which probe light 7 is emitted from probe light source 2 onto optical medium portion 3.
In the component measurement method, a stratum corneum information acquisition
step is also performed in which stratum corneum information about the stratum
corneum of sample 5 is acquired.
[0039] In the component measurement method described above, after stratum corneum
15 information is acquired in the stratum corneum information acquisition step, an
intensity modulation step is performed in which intensity modulation is performed on
excitation light 6 emitted by excitation light source 1 based on the acquired stratum
corneum information to generate intensity-modulated excitation light and the generated
intensity-modulated excitation light is emitted onto optical medium portion 3. In the
20 component measurement method, after the intensity modulation step is performed, a
measurement step is performed in which a blood glucose level as a given component is
measured based on a difference between emitted probe light 7a emitted from optical
medium portion 3 at the time when excitation light 6 is emitted and emitted probe
refracting light 7b emitted from optical medium portion 3 at the time when the
25 intensity-modulated excitation light is emitted.
[0040] As described above, the component measurement method according to the first
embodiment performs the intensity modulation step by driving optical chopper 9 based
on the stratum corneum information acquired by stratum corneum information
acquisition unit 11, which makes it possible to efficiently measure absorption heatgenerated by a given component in interstitial fluid contained in layers deeper than
stratum corneum. Specifically, the diffusion length of heat generated in a living body
during measurement is about 1 to 3 times the thickness of stratum corneum, and
therefore absorption heat generated by a glucose component in interstitial fluid
5 contained in layers deeper than stratum corneum can efficiently be measured. In other
words, it is possible to provide a non-invasive component measurement method which
reduces the risk of performing measurement on the basis of information from a portion
containing no interstitial fluid and therefore achieves improved component
measurement accuracy.
10 [0041] In the above-described first embodiment, an example of component
measurement device 100 to calculate a blood glucose level has been described.
However, the present invention is not limited to such an example described above.
For example, the component measurement device according to the present invention
may be one to measure and calculate protein, amino acid, sugar, fatty acid, hormone,
15 neurotransmitter, or the like contained in interstitial fluid of a living body. Therefore,
the component measurement device according to the present invention can be applied
to measurement of various biological information.
[0042] Second Embodiment
Fig. 4 is a diagram showing the configuration of a component measurement
20 device 101 according to a second embodiment. Component measurement device 101
according to the second embodiment is different from component measurement device
100 according to the first embodiment in that optical chopper 9 is not provided.
Component measurement device 101 according to the second embodiment includes,
instead of optical chopper 9, a modulator 22 to perform modulation on a power source
25 of excitation light source 1. In component measurement device 101 according to the
second embodiment, modulator 22 periodically sends a modulated signal to excitation
light source 1 to perform intensity modulation on excitation light 6. That is,
modulator 22 corresponds to an example of the intensity modulation unit according to
the present invention.
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[0043] Modulator 22 is configured using, for example, a signal generator to output an
intensity-modulated pulse signal according to a set frequency. However, the present
invention is not limited to this example. A device capable of modulating an electric
signal may be used. Signal modulation may be performed using a periodic function
5 such as a sine wave, a square wave, or a saw-tooth wave. The power source of
excitation light source 1 supplies power to excitation light source 1 by current output or
voltage output modulated according to the signal of modulator 22. However, the
present invention is not limited to this example. A configuration in which a power
source having a modulation function is integrated with modulator 22 may be used.
10 [0044] In component measurement device 101 according to the second embodiment,
lock-in amplifier 10 is connected to modulator 22. Modulator 22 determines the
operation frequency of the lock-in amplifier so that the modulation frequency of
excitation light source 1 and the operation frequency of the lock-in amplifier are
synchronized with each other. The other configuration of component measurement
15 device 101 is the same as that of component measurement device 100 according to the
first embodiment.
[0045] Component measurement device 101 according to the second embodiment is
different from component measurement device 100 according to the first embodiment
in that optical chopper 9 is not provided. Therefore, the modulation frequency can be
20 measured without using a physical drive mechanism to externally perform laser
intensity modulation. This makes it possible to provide a non-invasive component
measurement device which not only reduces the risk of performing measurement on the
basis of information from a portion containing no interstitial fluid and achieves
improved component measurement accuracy but also can be reduced in size by space25 saving.
REFERENCE SIGNS LIST
[0046] 1: excitation light source, 2: probe light source, 3: optical medium portion, 4:
light position detector, 5: sample, 6: excitation light, 7: probe light, 7a: emitted probe
light, 7b: emitted probe refracting light, 8: refractive index gradient, 9: optical chopper,
- 18 -
10: lock-in amplifier, 11: stratum corneum information acquisition unit, 20: operation
unit, 22: modulator, 100, 101: component measurement device

- 19 -
We Claim :
[Claim 1] A component measurement device for measuring a given
component contained in a sample, characterized in that the component measurement
5 device comprising:
an optical medium portion on which the sample is stationarily placed;
an excitation light source to emit excitation light onto the optical medium
portion;
a probe light source to emit probe light onto the optical medium portion;
10 an intensity modulation unit to perform intensity modulation on the excitation
light emitted by the excitation light source based on stratum corneum information about
stratum corneum of the sample to generate intensity-modulated excitation light and
emit the generated intensity-modulated excitation light onto the optical medium
portion; and
15 a measurement unit to measure the given component based on a difference
between the probe light emitted from the optical medium portion in a first state where
the excitation light is emitted and the probe light emitted from the optical medium
portion in a second state where the intensity-modulated excitation light is emitted.
20 [Claim 2] The component measurement device according to claim 1,
characterized in further comprising a stratum corneum information acquisition unit to
acquire stratum corneum information about stratum corneum of the sample,
wherein the intensity modulation unit is configured to perform the intensity
modulation based on the stratum corneum information acquired by the stratum corneum
25 information acquisition unit.
[Claim 3] The component measurement device according to claim 2,
characterized in that
when a modulation frequency of the intensity-modulated excitation light is
- 20 -
defined as f, a thickness of the stratum corneum indicated by the stratum corneum
information acquired by the stratum corneum information acquisition unit is defined as
d, and a thermal diffusion coefficient of the sample is defined as , the intensity
modulation unit performs the intensity modulation so that f, d, and  satisfy f < /(d2).
5
[Claim 4] The component measurement device according to claim 3,
characterized in that
the intensity modulation unit performs the intensity modulation so that f, d, and
 further satisfy /{(3d)2} < f.
10
[Claim 5] The component measurement device according to any one of claims
2 to 4, characterized in that
the intensity modulation unit includes a rotary blade that rotates at a
predetermined rotation speed,
15 the intensity modulation unit is disposed between the excitation light source and
the optical medium portion,
the excitation light source is configured to emit the excitation light onto the
optical medium portion through the rotary blade, and
the intensity modulation unit changes the rotation speed of the rotary blade
20 based on the stratum corneum information acquired by the stratum corneum
information acquisition unit.
[Claim 6] The component measurement device according to any one of claims
2 to 4, characterized in that
25 the intensity modulation unit includes a modulator to perform modulation on a
power source of the excitation light source, and
the intensity modulation unit changes the modulation performed by the
modulator based on the stratum corneum information acquired by the stratum corneum
information acquisition unit.
- 21 -
[Claim 7] A component measurement method for measuring a given
component contained in a sample, characterized in that the component measurement
method comprising:
5 a stationarily placing step of stationarily placing the sample on an optical
medium portion,
an excitation light emitting step of emitting excitation light from an excitation
light source onto the optical medium portion,
a probe light emitting step of emitting probe light from a probe light source onto
10 the optical medium portion,
a stratum corneum information acquisition step of acquiring stratum corneum
information about stratum corneum of the sample,
an intensity modulation step of performing intensity modulation on the
excitation light emitted by the excitation light source based on the stratum corneum
15 information acquired in the stratum corneum information acquisition step to generate
intensity-modulated excitation light and emit the generated intensity-modulated
excitation light onto the optical medium portion, and
a measurement step of measuring the given component based on a difference
between the probe light emitted from the optical medium portion in a first state where
20 the excitation light is emitted and the probe light emitted from the optical medium
portion in a second state where the intensity-modulated excitation light is emitted.