FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
BIOLOGICAL COMPONENT MEASUREMENT DEVICE AND BIOLOGICAL
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.
- 2 -
DESCRIPTION
TITLE OF INVENTION
Biological Component Measurement Device and Biological Component
Measurement Method5
TECHNICAL FIELD
[0001] The present disclosure relates to a biological component measurement device
and a biological component measurement method.
BACKGROUND ART
[0002] Japanese National Patent Publication No. 2017-519214 (PTL 1) discloses a10
noninvasive analysis system including an optical medium, an infrared light source, a
probe light source, and a photodiode. Specifically, a biological sample is placed on a
surface of the optical medium. The infrared light source emits infrared light. The
infrared light travels through the optical medium to illuminate the biological sample.
The infrared light is absorbed by the biological sample to cause the biological sample15
to generate heat. The amount of absorption heat of the biological sample varies in a
manner that depends on the amount or concentration of a biological component present
in the sample or on the surface of the sample.
[0003] The probe light source emits, toward the optical medium, probe light that is
visible light. The probe light is totally internally reflected at an interface between the20
optical medium and the biological sample to outgo from the optical medium. The
absorption heat of the biological sample transfers to the optical medium to change a
refractive index of the optical medium. The change in refractive index of the optical
medium affects total internal reflection of the probe light at the interface between the
optical medium and the biological sample to change a traveling direction of the probe25
light that outgoes from the optical medium. The photodiode detects a change in the
traveling direction of the probe light. The amount or concentration of a biological
component is measured based on the change in the traveling direction of the probe light
detected by the photodiode. For example, when the sample is a skin of a patient, a
- 3 -
blood glucose level of the patient is measured as a biological component.
CITATION LIST
PATENT LITERATURE
[0004] PTL 1: Japanese National Patent Publication No. 2017-519214
SUMMARY OF INVENTION5
TECHNICAL PROBLEM
[0005] In the noninvasive analysis system described in PTL 1, an optical chopper is
disposed between the infrared light source and the optical medium. Infrared light
(continuous light) emitted from the infrared light source is intensity-modulated by the
optical chopper, and the biological sample is irradiated with the infrared light. The10
biological sample is irradiated with pulsed light that is turned on and off at a cycle
corresponding to a chopping frequency of the optical chopper.
[0006] In PTL 1, the biological sample is irradiated with the infrared light intensity-
modulated at a different adjustment frequency. The adjustment frequency of the high
frequency results in an absorption process in a region closer to the surface of the15
biological sample, while the adjustment frequency of the low frequency results in the
absorption process in a deeper layer of the biological sample. The noninvasive
analysis system is configured to analyze different layers of the skin of the patient based
on the change in the traveling direction of the probe light detected at each of the
different adjustment frequencies.20
[0007] In the above noninvasive analysis system, in order to accurately measure the
biological component, the biological sample is required to be disposed at an optimum
position where the absorption heat of the biological sample is stably and efficiently
transmitted to the optical medium. Accordingly, at a start of measurement, the
position of the biological sample on the surface of the optical medium is adjusted. In25
the position adjustment of the biological sample, a change in the traveling direction of
the probe light is detected using a photodiode while the biological sample is irradiated
with the infrared light intensity-modulated at a predetermined frequency. However,
because the absorption heat of the biological sample becomes smaller as the adjustment
- 4 -
frequency becomes higher, the absorption heat of the biological sample is not
sufficiently transmitted to the optical medium, and it becomes difficult to determine
whether the position of the biological sample is optimal. As a result, there is a
possibility that measurement accuracy is degraded.
[0008] Furthermore, in the configuration in which the optical chopper is used for the5
intensity modulation of the infrared light like PTL 1, there is a problem that it takes
more time to adjust the modulation frequency in a case where the modulation frequency
is changed from a high frequency to a low frequency than in a case where the
modulation frequency is changed from the low frequency to the high frequency due to a
structure of the optical chopper.10
[0009] The present disclosure has been made to solve the above problems, and an
object of the present disclosure is to provide a biological component measurement
device and a biological component measurement method capable of measuring the
biological component with high accuracy and high efficiency.
SOLUTION TO PROBLEM15
[0010] A biological component measurement device according to the present
disclosure includes: an optical medium to include a sample placement surface; an
excitation light source to emit excitation light traveling in the optical medium toward a
sample placed on the sample placement surface; a probe light source to emit probe light
traveling in the optical medium; a light position detector to detect a position of the20
probe light emitted from the optical medium; a biological component acquisition unit
connected to the light position detector; and a modulation unit to modulate intensity of
the excitation light and to make the excitation light incident on the optical medium. In
plan view of the sample placement surface, an optical path of the probe light in the
optical medium overlaps a part of the sample placement surface irradiated with the25
excitation light. The modulation unit is configured to switch a plurality of modulation
frequencies in order from a low frequency to a high frequency. The plurality of
modulation frequencies include a first frequency and a second frequency higher than
the first frequency. The light position detector detects the position of the probe light
- 5 -
when the sample is irradiated with the excitation light intensity-modulated at the first
frequency. The light position detector detects the position of the probe light when the
sample is irradiated with the excitation light intensity-modulated at the second
frequency. The biological component acquisition unit measures a biological
component of the sample based on the position of the probe light at the first frequency5
and the position of the probe light at the second frequency.
[0011] A biological component measurement method according to the present
disclosure is a biological component measurement method for measuring a biological
component of a sample. The biological component measurement method includes:
setting a modulation frequency in intensity modulation of excitation light to a first10
frequency; detecting a position of probe light emitted from an optical medium while
emitting probe light traveling in the optical medium and irradiating the sample placed
on a sample placement surface of the optical medium with the excitation light intensity-
modulated at the first frequency; changing the modulation frequency in the intensity
modulation from the first frequency to a second frequency higher than the first15
frequency; detecting the position of the probe light emitted from the optical medium
while emitting the probe light traveling in the optical medium and emitting the
excitation light intensity-modulated at the second frequency toward the sample placed
on the sample placement surface of the optical medium; and measuring the biological
component of the sample based on the position of the probe light at the first frequency20
and the position of the probe light at the second frequency.
ADVANTAGEOUS EFFECTS OF INVENTION
[0012] According to the present disclosure, the biological component measurement
device and the biological component measurement method capable of measuring the
biological component with high accuracy and high efficiency can be provided.25
BRIEF DESCRIPTION OF DRAWINGS
[0013] Fig. 1 is a view illustrating a configuration of a biological component
measurement device according to a first embodiment.
Fig. 2 is a flowchart illustrating a basic concept of the biological component
- 6 -
measurement method of the first embodiment.
Fig. 3 is a flowchart illustrating the biological component measurement method
of the first embodiment.
Fig. 4 is a view illustrating the biological component measurement method of
the first embodiment.5
Fig. 5 is a view illustrating a configuration of a biological component
measurement device according to a second embodiment.
DESCRIPTION OF EMBODIMENTS
[0014] With reference to the drawings, an embodiment of the present disclosure will be
described in detail below. In the drawings, the same or corresponding portion is10
denoted by the same reference numeral, and the description will not be repeated in
principle.
[0015] First embodiment
Fig. 1 is a view illustrating a configuration of a biological component
measurement device according to a first embodiment. A biological component15
measurement device 100 of the first embodiment is a device that non-invasively
measures a biological component of a sample 5.
[0016] As illustrated in Fig. 1, biological component measurement device 100 of the
first embodiment includes an excitation light source 1, a probe light source 2, an optical
medium 3, a light position detector 4, a biological component acquisition unit 9, a20
recording unit 10, an optical chopper 11, a lock-in amplifier 12, an oscillator 13, and a
power supply 14.
[0017] Optical medium 3 includes a first surface 31, a second surface 32 located on
than opposite side of first surface 31, a third surface 33 connecting first surface 31 and
second surface 32, and a fourth surface 34 that connects first surface 31 and second25
surface 32 and is located on an opposite side of third surface 33.
[0018] First surface 31 of optical medium 3 is an incident surface of excitation light 6
emitted from excitation light source 1. Second surface 32 is a sample placement
surface. A sample 5 is placed on second surface 32 and is in contact with second
- 7 -
surface 32. Sample 5 is, for example, a skin or a body fluid of a patient. When a
liquid is to be measured, sample 5 is a liquid contained in a transparent sample holder.
Third surface 33 is an incident surface of probe light 7 emitted from probe light source
2. A normal direction of third surface 33 is inclined with respect to the incident
direction of probe light 7. Fourth surface 34 is an emission surface of probe light 7.5
Fourth surface 34 is inclined with respect to the emission direction of probe light 7.
For example, optical medium 3 may be a total internal reflection prism (TIR prism).
[0019] Optical medium 3 is transparent to excitation light 6. In the present
specification, the fact that optical medium 3 is transparent to excitation light 6 means
that light transmittance of optical medium 3 with respect to excitation light 6 is greater10
than or equal to 25%. The light transmittance of optical medium 3 with respect to
excitation light 6 may be greater than or equal to 50%, may be greater than or equal to
75%, or may be greater than or equal to 90%.
[0020] Optical medium 3 is transparent to probe light 7. In the present specification,
the fact that optical medium 3 is transparent to probe light 7 means that the light15
transmittance of optical medium 3 with respect to probe light 7 is greater than or equal
to 25%. The light transmittance of optical medium 3 with respect to probe light 7 may
be greater than or equal to 50%, may be greater than or equal to 75%, or may be greater
than or equal to 90%.
[0021] Optical medium 3 is formed from a material having thermal conductivity of less20
than or equal to 15.0 W/(m·K). The thermal conductivity of the material of optical
medium 3 may be less than or equal to 10.0 W/(m·K), less than or equal to 5.0
W/(m·K), less than or equal to 3.0 W/(m·K), less than or equal to 2.0 W/(m·K), or less
than or equal to 1.0 W/(m·K). The thermal conductivity of the material of optical
medium 3 is greater than or equal to 0.5 times the thermal conductivity of sample 5.25
The thermal conductivity of the material of optical medium 3 may be greater than or
equal to 0.75 times the thermal conductivity of sample 5, may be greater than or equal
to the thermal conductivity of sample 5, may be greater than or equal to 1.5 times the
thermal conductivity of sample 5, or may be greater than or equal to 2.0 times the
- 8 -
thermal conductivity of sample 5.
[0022] Optical medium 3 is formed from chalcogenide glass. For example, the
chalcogenide glass contains greater than or equal to 2 mol% and less than or equal to
22 mol% of germanium (Ge), greater than or equal to 6 mol% and less than or equal to
34 mol% of at least one element selected from the group consisting of antimony (Sb)5
and bismuth (Bi), greater than or equal to 1 mol% and less than or equal to 20 mol% of
tin (Sn), and greater than or equal to 58 mol% and less than or equal to 70 mol% of at
least one element selected from the group consisting of sulfur (S), selenium (Se), and
tellurium (Te). The chalcogenide glass has a thermal conductivity of 0.36 W/(m·K).
[0023] Excitation light source 1 receives power supply from power supply 14 and10
emits excitation light 6 toward sample 5 placed on the sample placement surface
(second surface 32). Excitation light 6 is emitted from excitation light source 1 and is
incident on optical medium 3 from first surface 31. Excitation light 6 travels through
optical medium 3 and enters sample 5 from second surface 32. Excitation light 6 is
absorbed by a biological component existing in sample 5 or on a surface 51 of sample15
5. For example, when a blood glucose level of a patient is measured using biological
component measurement device 100, the biological component is glucose existing in an
interstitial fluid in epidermis. The absorption of excitation light 6 by the biological
component generates absorption heat in sample 5. The absorption heat of sample 5
transfers to optical medium 3. When a temperature gradient region is generated in20
optical medium 3, a refractive index gradient region 8 is generated in optical medium 3.
[0024] A wavelength of excitation light 6 is determined according to an absorption
wavelength of the biological component existing in sample 5 or on surface 51 of
sample 5. The wavelength of excitation light 6 may be longer than the wavelength of
probe light 7. For example, the wavelength of excitation light 6 is greater than or25
equal to 6.0 μm. The wavelength of excitation light 6 may be greater than or equal to
8.0 μm. For example, the wavelength of excitation light 6 is less than or equal to 13.0
μm. The wavelength of excitation light 6 may be less than or equal to 11.0 μm.
Excitation light 6 may be light having a plurality of wavelengths. For example, when
- 9 -
the blood glucose level of the patient is measured using biological component
measurement device 100, the wavelength of excitation light 6 falls within a wavelength
range including a wavelength of a fingerprint spectrum of glucose (for example, a
wavelength range of greater than or equal to 8.5 μm to less than or equal to 10 μm).
For example, excitation light source 1 is a quantum cascade laser capable of emitting5
broadband infrared light. In the following description, it is assumed that excitation
light 6 is light having three wavelengths λ1, λ2, λ3. The light having wavelengths λ1,
λ2 is absorbed by a biological component existing in sample 5 or on surface 51 of
sample 5. The light having wavelength λ3 is not absorbed by the biological
component but is used as reference light.10
[0025] Probe light source 2 emits probe light 7. Probe light 7 is incident on optical
medium 3 from third surface 33 of optical medium 3. Probe light 7 is refracted by
third surface 33 and travels through optical medium 3 toward the interface between
optical medium 3 (second surface 32) and sample 5. In planar view of the sample
placement surface (second surface 32), an optical path of probe light 7 in optical15
medium 3 overlaps a portion of the sample placement surface (second surface 32)
irradiated with excitation light 6. Probe light 7 is totally internally reflected at the
interface between optical medium 3 (second surface 32) and sample 5. While probe
light 7 is traveling through optical medium 3, probe light 7 travels through refractive
index gradient region 8 generated in optical medium 3 by the absorption heat of sample20
5. Probe light 7 is refracted by refractive index gradient region 8, and the traveling
direction of probe light 7 changes accordingly. Probe light 7 (first emission probe
light 7a and second emission probe light 7b) is emitted from fourth surface 34 of
optical medium 3.
[0026] For example, the wavelength of probe light 7 is greater than or equal to 110025
nm. The wavelength of probe light 7 may be greater than or equal to 1300 nm. For
example, the wavelength of probe light 7 is less than or equal to 1700 nm.
Accordingly, an inexpensive semiconductor laser for use in optical communication
such as an InGaAsP-based semiconductor laser or an InGaNAs-based semiconductor
- 10 -
laser may be used as probe light source 2. Furthermore, probe light 7 is not visible
light, so that a risk of damage to human eyes caused by probe light 7 can be reduced.
For example, the output of probe light 7 is less than or equal to 5 mW. This makes it
possible to reduce the risk of the damage to the human eyes caused by probe light 7.
[0027] Light position detector 4 detects the position of probe light 7 emitted from5
optical medium 3. Fig. 1 illustrates a first position 71a of the probe light (first
emission probe light 7a) when sample 5 is not irradiated with excitation light 6 and a
second position 71b of the probe light (second emission probe light 7b) when sample 5
is irradiated with excitation light 6.
[0028] In a state where sample 5 is not irradiated with excitation light 6 (hereinafter,10
also referred to as a “reference state”), no absorption heat is generated in sample 5.
Accordingly, a temperature gradient region is not generated in optical medium 3, and
refractive index gradient region 8 is not generated in optical medium 3.
Consequently, as indicated by a solid line in the figure, probe light 7 (first emission
probe light 7a) in optical medium 3 is emitted from fourth surface 34 of optical medium15
3 without being refracted in refractive index gradient region 8. First position 71a of
the probe light (first emission probe light 7a) is the position of probe light 7 in the
reference state and corresponds to the “reference position”.
[0029] Light position detector 4 detects second position 71b of the probe light (second
emission probe light 7b) when sample 5 is irradiated with excitation light 6. In the20
state where sample 5 is irradiated with excitation light 6, refractive index gradient
region 8 is generated in optical medium 3 as described above. Therefore, as indicated
by a broken line in the figure, the probe light (second emission probe light 7b) is
refracted by refractive index gradient region 8 in optical medium 3 and emitted from
fourth surface 34 of optical medium 3. Second position 71b of probe light 7 (second25
emission probe light 7b) is a position of probe light 7 detected by light position detector
4 when sample 5 is irradiated with excitation light 6. When sample 5 is irradiated
with excitation light 6, the position of probe light 7 detected by light position detector 4
is displaced from first position 71a (reference position) to second position 71b.
- 11 -
[0030] Light position detector 4 outputs a signal related to second position 71b of
probe light 7 (second emission probe light 7b) when sample 5 is irradiated with
excitation light 6. For example, light position detector 4 is a photodiode or a
semiconductor position detection element.
[0031] Biological component acquisition unit 9 is connected to light position detector5
4. Biological component acquisition unit 9 acquires a displacement amount δ of probe
light 7, which is the distance between first position 71a (reference position) and second
position 71b, and obtains the amount or concentration of the biological component in
sample 5 or on surface 51 of sample 5 from acquired displacement amount δ.
Recording unit 10 records the amount or concentration of the biological component10
obtained by biological component acquisition unit 9. For example, biological
component acquisition unit 9 and recording unit 10 are one of functions implemented
by an arithmetic processing unit.
[0032] Optical chopper 11 is disposed in the optical path of excitation light 6. Optical
chopper 11 chops excitation light 6 (continuous light) emitted from excitation light15
source 1 at an arbitrary frequency. Excitation light 6 becomes intermittent light (pulse
light) that is turned on and off at the cycle corresponding to the chopping frequency
(frequency at which light is turned on and off) of optical chopper 11, and is incident on
optical medium 3. Optical chopper 11 corresponds to an example of the “modulation
unit” that modulates the intensity of excitation light 6. The chopping frequency of20
optical chopper 11 corresponds to an example of the “modulation frequency” that
modulates the intensity of excitation light 6.
[0033] A known configuration can be applied to optical chopper 11. For example,
optical chopper 11 includes a rotating disk in which an opening that allows the passage
of excitation light 6 and a light shielding portion that blocks excitation light 6 are25
arranged in a circumferential direction, and a motor that rotates the rotating disk.
When the rotary disk is periodically rotated by the motor, whether to irradiate sample 5
with excitation light 6 can be switched. That is, excitation light 6 undergoes intensity
modulation at the chopping frequency of optical chopper 11. The chopping frequency
- 12 -
of excitation light 6 is determined by a rotation speed of the rotating disk.
[0034] Oscillator 13 is connected to optical chopper 11 and lock-in amplifier 12.
Oscillator 13 sets the chopping frequency (modulation frequency) of optical chopper
11. Oscillator 13 generates a control signal for chopper control of excitation light 6,
and gives the generated control signal to optical chopper 11 and lock-in amplifier 12.5
The control signal includes the chopping frequency of optical chopper 11.
[0035] Lock-in amplifier 12 is connected to oscillator 13 and light position detector 4.
Lock-in amplifier 12 selectively amplifies a signal synchronized with the chopping
frequency (modulation frequency) of optical chopper 11 among the signals related to
the position of probe light 7 output from light position detector 4 based on the control10
signal given from oscillator 13.
[0036] Specifically, lock-in amplifier 12 outputs the signal obtained by amplifying a
difference between the position of probe light 7 in an on-period of a chopping cycle of
optical chopper 11 and the position of probe light 7 in an off-period of the chopping
cycle.15
[0037] The on-period of the chopping cycle corresponds to a period in which excitation
light 6 is emitted. Therefore, the position of probe light 7 during the on-period
corresponds to second position 71b. The off-period of the chopping cycle corresponds
to a period in which excitation light 6 is not emitted. Accordingly, the position of
probe light 7 in the off-period corresponds to first position 71a (reference position).20
Lock-in amplifier 12 generates the signal related to displacement amount δ of probe
light 7, which is the distance between first position 71a (reference position) and second
position 71b, based on the output signal of light position detector 4.
[0038] The output signal of lock-in amplifier 12 is obtained by removing a noise
included in the signal related to the position of probe light 7 output from light position25
detector 4. This enables biological component measurement device 100 to measure
the biological component with improved accuracy.
[0039] The operation frequencies of optical chopper 11 and lock-in amplifier 12 may
be synchronized by directly connecting optical chopper 11 and lock-in amplifier 12
- 13 -
without using oscillator 13 and exchanging signals with each other.
[0040] A biological component measurement method using biological component
measurement device 100 in Fig. 1 will be described below.
Fig. 2 is a flowchart illustrating a basic concept of the biological component
measurement method of the first embodiment.5
[0041] The biological component measurement method of the first embodiment
includes step (S1) of adjusting the position of sample 5 on the sample placement
surface (second surface 32) while irradiating sample 5 with excitation light 6. This is
because sample 5 is required to be disposed at an optimum position where the
absorption heat of sample 5 is stably and efficiently transferred to optical medium 3 in10
order to accurately measure the biological component of sample 5. In particular,
when sample 5 is a finger of the patient and has a minute bump such as a fingerprint on
the surface of the finger, the position of sample 5 is required to be adjusted also from
the viewpoint of securing the contact pressure of sample 5 to optical medium 3.
[0042] In step (S1), the position of sample 5 with respect to excitation light 6 and probe15
light 7 in the traveling direction of probe light 7 is adjusted using light position detector
4 while irradiating sample 5 with excitation light 6.
[0043] As described above, excitation light 6 with which sample 5 is irradiated is
absorbed by the biological component in sample 5 or on surface 51 of sample 5. The
absorption of excitation light 6 by the biological component generates absorption heat20
in sample 5. When the absorption heat of sample 5 is conducted to optical medium 3,
the temperature gradient region is generated in optical medium 3. Accordingly,
refractive index gradient region 8 is generated in optical medium 3. Probe light 7 is
refracted by refractive index gradient region 8 and emitted from optical medium 3.
[0044] Light position detector 4 detects second position 71b of probe light 7 (second25
emission probe light 7b). When sample 5 is irradiated with excitation light 6, the
position of probe light 7 detected by light position detector 4 is displaced from first
position 71a (reference position) to second position 71b. Lock-in amplifier 12
generates the signal related to displacement amount δ of probe light 7, which is the
- 14 -
distance between first position 71a (reference position) and second position 71b, based
on the output signal of light position detector 4.
[0045] In step (S1), an operation of acquiring displacement amount δ of probe light 7
based on the output signal of lock-in amplifier 12 is repeatedly executed while the
position of sample 5 is changed along the traveling direction of probe light 7, thereby5
searching for the position where displacement amount δ of probe light 7 is maximized.
As a result of this search, the position where displacement amount δ of probe light 7 is
maximized is determined as the position of sample 5.
[0046] The biological component measurement method of the first embodiment
includes step (S2) of detecting displacement amount δ of probe light 7 using light10
position detector 4 while irradiating sample 5 with excitation light 6. In step (S2),
sample 5 adjusted to the optimum position is irradiated with excitation light 6. Probe
light 7 is refracted by refractive index gradient region 8 generated in optical medium 3
and emitted from optical medium 3. Light position detector 4 detects second position
71b of probe light 7 (second emission probe light 7b). Lock-in amplifier 12 generates15
the signal related to displacement amount δ of probe light 7, which is the distance
between the reference position and second position 71b, based on the output signal of
light position detector 4. The process of step (S2) can be performed continuously with
the process of step (S1).
[0047] The biological component measurement method of the first embodiment20
includes step (S3) of obtaining the amount or concentration of the biological
component existing in sample 5 or on surface 51 of sample 5 based on displacement
amount δ of probe light 7. For example, recording unit 10 stores a data table in which
the type of the biological component, displacement amount δ of probe light 7, and the
amount or concentration of the biological component are associated with each other.25
Biological component acquisition unit 9 refers to the data table stored in recording unit
10 to obtain the amount or concentration of the biological component corresponding to
the type of the biological component and displacement amount δ of probe light 7.
[0048] In biological component measurement device 100 of the first embodiment, the
- 15 -
intensity of excitation light 6 is modulated by optical chopper 11, and sample 5 is
irradiated with excitation light 6. Excitation light 6 is intermittent light (pulse light)
that is turned on and off at the cycle corresponding to the modulation frequency (the
chopping frequency of optical chopper 11). An irradiation time per cycle of excitation
light 6 changes according to the modulation frequency. The lower the modulation5
frequency, the longer the irradiation time per cycle.
[0049] On the other hand, a penetration depth of excitation light 6 into sample 5
changes as the irradiation time per cycle changes. Specifically, as the irradiation time
becomes longer, the penetration depth of excitation light 6 becomes deeper.
Accordingly, the lower the modulation frequency, the longer the irradiation time per10
cycle, so that the penetration depth of excitation light 6 into sample 5 becomes deeper.
[0050] For example, when sample 5 is a skin of the patient, sample 5 is composed of an
epidermal tissue, a dermal tissue existing in a lower layer of the epidermal tissue, and a
subcutaneous tissue existing in a lower layer of the dermal tissue. The epidermal
tissue contains the keratin as a main component, the dermal tissue contains interstitial15
fluid and cells as components, and the subcutaneous tissue contains fat as a main
component. When the modulation frequency is high, the irradiation time per cycle is
short, so that the penetration depth of excitation light 6 into sample 5 becomes shallow.
Accordingly, the information obtained by the measurement is mainly information about
the epidermal tissue.20
[0051] On the other hand, when the modulation frequency is low, because the
irradiation time per cycle is long, the penetration depth of excitation light 6 with respect
to sample 5 becomes deeper. Accordingly, the information obtained by the
measurement is information obtained by synthesizing the information about the
epidermal tissue and the information about the dermal tissue. As the modulation25
frequency decreases, the irradiation time per cycle becomes longer, and the penetration
depth of excitation light 6 becomes deeper, so that a ratio of the information about the
dermal tissue included in the information obtained by the measurement increases.
[0052] When the blood glucose level of the patient is measured using biological
- 16 -
component measurement device 100, because the biological component is a sugar
existing in the tissue interstitial fluid in the dermal tissue, the information about the
dermal tissue is required to be acquired. However, as described above, the
information obtained by the measurement includes the information about the epidermal
tissue, and the information about the epidermal tissue may be noise with respect to the5
information about the dermal tissue.
[0053] Accordingly, in the biological component measurement method of the first
embodiment, the intensity modulation of excitation light 6 is performed for each
modulation frequency by switching a plurality of modulation frequencies. Then, the
information about the dermal tissue required for blood glucose level measurement is10
acquired based on a plurality of pieces of information obtained corresponding to the
plurality of modulation frequencies.
[0054] Fig. 3 is a flowchart illustrating the biological component measurement method
of the first embodiment. Fig. 4 is a view illustrating the biological component
measurement method of the first embodiment.15
[0055] As described in Fig. 2, first, step (S1) of adjusting the position of sample 5 on
the sample placement surface (second surface 32) is performed while irradiating sample
5 with excitation light 6.
[0056] Step (S1) includes a step of setting the chopping frequency (modulation
frequency) of optical chopper 11 to a first frequency f1 using oscillator 13 (S11).20
Oscillator 13 generates a control signal based on the set chopping frequency (first
frequency f1), and gives the generated control signal to optical chopper 11 and lock-in
amplifier 12. Excitation light 6 undergoes the intensity modulation at the chopping
frequency (first frequency f1) of optical chopper 11.
[0057] Step (S1) includes step (S12) of adjusting the position of sample 5 using light25
position detector 4 while irradiating sample 5 with excitation light 6 intensity-
modulated at first frequency f1. Fig. 4(A) is a view illustrating the optical path of
probe light 7 (second emission probe light 7b) when sample 5 is irradiated with
excitation light 6 intensity-modulated at first frequency f1.
- 17 -
[0058] As illustrated in Fig. 4(A), excitation light 6 intensity-modulated at first
frequency f1 is absorbed by the biological component in sample 5 or on surface 51 of
sample 5. When the absorption heat of sample 5 is conducted to optical medium 3,
refractive index gradient region 8 is generated in optical medium 3. Probe light 7 is
refracted by refractive index gradient region 8 and emitted from optical medium 3.5
Light position detector 4 detects second position 71b of probe light 7 (second emission
probe light 7b). Lock-in amplifier 12 generates the signal related to displacement
amount δ of probe light 7, which is the distance between first position 71a (reference
position) and second position 71b, based on the output signal of light position detector
4.10
[0059] In step (S12), the position of sample 5 is changed along the traveling direction
of probe light 7 while the excitation light intensity-modulated at first frequency f1 is
emitted, and the operation of acquiring displacement amount δ of probe light 7 based
on the output signal of lock-in amplifier 12 is repeatedly executed, so that the position
where displacement amount δ of probe light 7 is maximized is searched. As a result15
of this search, the position where displacement amount δ of probe light 7 is maximized
is determined as the position of sample 5.
[0060] After the position of sample 5 is adjusted in step (S1), step (S2) of detecting
displacement amount δ1 of probe light 7 using light position detector 4 while
irradiating sample 5 with excitation light 6 is performed.20
[0061] Step (S2) includes step (S21) of detecting displacement amount δ1 of probe
light 7 using light position detector 4 while irradiating sample 5 with excitation light 6
intensity-modulated at first frequency f1. That is, in step (S21), sample 5 is irradiated
with excitation light 6 intensity-modulated at first frequency f1 that is the same as the
chopping frequency used for the position adjustment of sample 5. Lock-in amplifier25
12 generates the signal related to displacement amount δ1 of probe light 7 when sample
5 is irradiated with excitation light 6 intensity-modulated at first frequency f1 based on
the output signal of light position detector 4.
[0062] Displacement amount δ1 of probe light 7 is displacement amount δ of probe
- 18 -
light 7 when sample 5 is irradiated with excitation light 6 intensity-modulated at first
frequency f1. Displacement amount δ1 of probe light 7 corresponds to the
information about the amount or concentration of the biological component in sample 5
or on surface 51 of sample 5. Displacement amount δ1 of probe light 7 is stored in
recording unit 10.5
[0063] Step (S2) includes step (S22) of setting the chopping frequency (modulation
frequency) of optical chopper 11 to a second frequency f2 using oscillator 13. Second
frequency f2 is higher than first frequency f1 (f2 > f1). Oscillator 13 generates the
control signal based on the set chopping frequency (second frequency f2), and gives the
generated control signal to optical chopper 11 and lock-in amplifier 12. Excitation10
light 6 undergoes the intensity modulation at the chopping frequency (second frequency
f2) of optical chopper 11.
[0064] Step (S2) includes step (S23) of detecting a displacement amount δ2 of probe
light 7 using light position detector 4 while irradiating sample 5 with excitation light 6
intensity-modulated at second frequency f2. Fig. 4(B) is a view illustrating the optical15
path of probe light 7 (second emission probe light 7b) when sample 5 is irradiated with
excitation light 6 intensity-modulated at second frequency f2.
[0065] As illustrated in Fig. 4(B), excitation light 6 intensity-modulated at second
frequency f2 is absorbed by the biological component in sample 5 or on surface 51 of
sample 5. The absorption of excitation light 6 by the biological component generates20
absorption heat in sample 5. When the absorption heat of sample 5 is conducted to
optical medium 3, refractive index gradient region 8 is generated in optical medium 3.
Probe light 7 (second emission probe light 7b) is refracted by refractive index gradient
region 8 and emitted from optical medium 3. Light position detector 4 detects second
position 71b of probe light 7 (second emission probe light 7b). Lock-in amplifier 1225
generates the signal related to displacement amount δ2 of probe light 7 based on the
output signal of light position detector 4.
[0066] Displacement amount δ2 of probe light 7 is displacement amount δ of probe
light 7 when sample 5 is irradiated with excitation light 6 intensity-modulated at second
- 19 -
frequency f2. Displacement amount δ2 of probe light 7 corresponds to the
information about the amount or concentration of the biological component in sample 5
or on surface 51 of sample 5. Displacement amount δ2 of probe light 7 is stored in
recording unit 10.
[0067] Step (S2) includes step (S24) of setting the chopping frequency (modulation5
frequency) of optical chopper 11 to a third frequency f3 using oscillator 13. Third
frequency f3 is higher than second frequency f2 (f3 > f2). Oscillator 13 generates the
control signal based on the set chopping frequency (third frequency f3), and gives the
generated control signal to optical chopper 11 and lock-in amplifier 12. Excitation
light 6 undergoes the intensity modulation at the chopping frequency (third frequency10
f3) of optical chopper 11.
[0068] Step (S2) includes step (S25) of detecting a displacement amount δ3 of probe
light 7 using light position detector 4 while irradiating sample 5 with excitation light 6
intensity-modulated at third frequency f3.
[0069] Excitation light 6 intensity-modulated at third frequency f3 is absorbed by the15
biological component in sample 5 or on surface 51 of sample 5. The absorption of
excitation light 6 by the biological component generates absorption heat in sample 5.
When the absorption heat of sample 5 is conducted to optical medium 3, refractive
index gradient region 8 is generated in optical medium 3. Probe light 7 (second
emission probe light 7b) is refracted by refractive index gradient region 8 and emitted20
from optical medium 3. Light position detector 4 detects second position 71b of probe
light 7 (second emission probe light 7b). Lock-in amplifier 12 generates the signal
related to displacement amount δ3 of probe light 7 based on the output signal of light
position detector 4.
[0070] Displacement amount δ3 of probe light 7 is displacement amount δ of probe25
light 7 when sample 5 is irradiated with excitation light 6 intensity-modulated at third
frequency f3. Displacement amount δ3 of probe light 7 corresponds to the
information about the amount or concentration of the biological component in sample 5
or on surface 51 of sample 5. Displacement amount δ3 of probe light 7 is stored in
- 20 -
recording unit 10.
[0071] Subsequently, step (S3) of obtaining the amount or concentration of the
biological component in sample 5 or on surface 51 of sample 5 from the displacement
amounts δ1, δ2, δ3 of probe light 7 obtained in steps S21, S23, S25 is performed. In
this step (S3), Biological component acquisition unit 9 refers to the data table stored in5
recording unit 10 to obtain the amount or concentration of the biological component
corresponding to the type of the biological component and displacement amounts δ1,
δ2, δ3 of probe light 7.
[0072] As illustrated in Fig. 3, in the biological component measurement method of the
first embodiment, the modulation frequency (the chopping frequency of optical chopper10
11) is switched at a plurality of frequencies (first frequency f1, second frequency f2,
and third frequency f3), second position 71b of probe light 7 (second emission probe
light 7b) is detected while sample 5 is irradiated with excitation light 6 of each
modulation frequency, and displacement amounts δ1, δ2, δ3 of the plurality of pieces of
probe light 7 are obtained. The number of modulation frequencies is not limited to15
three, and may be two or greater than or equal to four.
[0073] As described above, because the irradiation time of excitation light 6 per cycle
is different by changing the modulation frequency, the penetration depth of excitation
light 6 with respect to sample 5 is different. In the example of Fig. 4, because first
frequency f1 is lower than second frequency f2, the penetration depth of excitation light20
6 into sample 5 becomes deeper. Because the absorption heat generated in sample 5
increases as the penetration depth of excitation light 6 increases, refractive index
gradient region 8 generated in optical medium 3 also increases. As a result,
displacement amount δ1 of probe light 7 becomes larger than displacement amount δ2
of probe light 7.25
[0074] When sample 5 is the skin of the patient, displacement amount δ1 (first
information) of probe light 7 is obtained by measurement in which sample 5 is
irradiated with excitation light 6 intensity-modulated at first frequency f1. The first
information is information in which the information about the epidermal tissue and the
- 21 -
information about the dermal tissue are synthesized. Furthermore, displacement
amount δ2 (second information) of probe light 7 is obtained by measurement in which
sample 5 is irradiated with excitation light 6 intensity-modulated at second frequency
f2 lower than first frequency f1. The second information includes a lot of information
about the epidermal tissue. In step S3, the information about the dermal tissue can be5
obtained by removing the second information from the first information. For
example, the sugar amount corresponding to displacement amount δ1 and the sugar
amount corresponding to displacement amount δ2 are obtained by referring to the data
table stored in recording unit 10. Then, the information about the dermal tissue can be
obtained by subtracting the sugar amount corresponding to displacement amount δ210
from the sugar amount corresponding to displacement amount δ1 or by dividing the
two sugar amounts.
[0075] Furthermore, in the biological component measurement method of the first
embodiment, the plurality of modulation frequencies are changed in order from the low
frequency to the high frequency. In the example of Fig. 3, the three modulation15
frequencies are changed in the order of first frequency f1, second frequency f2, and
third frequency f3. As illustrated in Fig. 1, in the configuration in which optical
chopper 11 is used to modulate the intensity of excitation light 6, there is a problem that
it takes more time to adjust the chopping frequency when the chopping frequency is
changed from the high frequency to the low frequency than when the chopping20
frequency is changed from the low frequency to the high frequency due to a structure of
a motor or the like in optical chopper 11. In one example, it takes about several
seconds to change the chopping frequency from the low frequency to the high
frequency, whereas it takes about several 10 seconds to change the chopping frequency
from the high frequency to the low frequency. In the first embodiment, the25
modulation frequency is changed in the order from the low frequency to the high
frequency, so that the modulation frequency can be quickly changed. Thus, the
measurement efficiency of the biological component can be improved.
[0076] Furthermore, in order to accurately measure the biological component, sample 5
- 22 -
is required to be disposed at the optimum position where the absorption heat of sample
5 is stably and efficiently transferred to optical medium 3. Accordingly, at the start of
measurement, step (S1) of adjusting the position of sample 5 on second surface 32
(sample placement surface) of optical medium 3 is performed.
[0077] In the position adjustment of sample 5, displacement amount δ of probe light 75
is obtained using light position detector 4 while sample 5 is irradiated with excitation
light 6 intensity-modulated at a predetermined frequency. The optimum position of
sample 5 on the sample placement surface is determined by searching for the position
where obtained displacement amount δ is maximized. At this point, because the
absorption heat of sample 5 becomes smaller as the modulation frequency becomes10
higher, the absorption heat of sample 5 is not sufficiently transmitted to optical medium
3, and it becomes difficult to determine whether the position of sample 5 is optimal.
As a result, there is a possibility that measurement accuracy is degraded.
[0078] In the biological component measurement method of the first exemplary
embodiment, at the start of measurement, excitation light 6 is intensity-modulated at15
the low modulation frequency (first frequency f1 in the example of Fig. 3), whereby the
absorption heat of sample 5 can be increased. Accordingly, whether the position of
sample 5 is optimal can be easily determined based on displacement amount δ of probe
light 7. When sample 5 is disposed at the optimum position, the measurement
accuracy can be improved.20
[0079] Second embodiment
Fig. 5 is a view illustrating a configuration of a biological component
measurement device according to a second embodiment. Biological component
measurement device 100 of the second embodiment is different from biological
component measurement device 100 in Fig. 1 in that a modulator 15 is provided instead25
of optical chopper 11 and oscillator 13.
[0080] Modulator 15 is connected to power supply 14 and lock-in amplifier 12.
Modulator 15 generates the intermittent signal (pulse signal) that is turned on and off at
the cycle corresponding to the set modulation frequency. Power supply 14 controls
- 23 -
power supply and interruption to excitation light source 1 according to the output signal
provided from modulator 15. Specifically, power supply 14 supplies the power to
excitation light source 1 during the on period of the output signal of modulator 15, and
interrupts the supply of the power to excitation light source 1 during the off period of
the output signal. Excitation light source 1 generates the intermittent light (pulse5
light) at the cycle corresponding to the modulation frequency by the power
intermittently supplied from power supply 14.
[0081] For example, a signal generator is applied to modulator 15. However,
modulator 15 is not limited to the signal generator, but may be any device capable of
modulating an electric signal. Although the configuration in which power supply 1410
supplies the current or the voltage modulated according to the output signal of
modulator 15 to excitation light source 1 has been exemplified, power supply 14 and
modulator 15 may be integrated using a power supply having a modulation function.
[0082] Lock-in amplifier 12 selectively amplifies the signal synchronized with the
modulation frequency among signals related to the position of probe light 7 output from15
light position detector 4 based on the signal given from modulator 15. This makes it
possible to remove the noise contained in the signal related to the position of probe
light 7 output from light position detector 4. Thus, similarly to biological component
measurement device 100 of the first embodiment, the biological component can be
measured with improved accuracy.20
[0083] Because biological component measurement device 100 in Fig. 1 includes
optical chopper 11 and the drive mechanism thereof, there is a concern that biological
component measurement device 100 becomes large in size and occupies a large
installation space.
[0084] According to biological component measurement device 100 of the second25
embodiment, because the configuration in which the output signal of power supply 14
to excitation light source 1 is modulated is adopted, optical chopper 11 is not required
to be provided between excitation light source 1 and optical medium 3. As a result,
miniaturization and space saving of biological component measurement device 100 can
- 24 -
be implemented.
[0085] It should be considered that the disclosed embodiment is an example in all
respects and not restrictive. The scope of the present disclosure is defined by not the
description above, but the claims, and it is intended that all modifications within the
meaning and scope of the claims and their equivalents are included in the present5
invention.
REFERENCE SIGNS LIST
[0086] 1: excitation light source, 2: probe light source, 3: optical medium, 4: light
position detector, 5: sample, 6: excitation light, 7: probe light, 71a: first position, 71b:
second position, 8: refractive index gradient region, 9: biological component10
acquisition unit, 10: recording unit, 11: optical chopper, 12: lock-in amplifier, 13:
oscillator, 14: power supply, 15: modulator, 100: biological component measurement
device, δ: displacement amount
- 25 -
We Claim :
[Claim 1] A biological component measurement device comprising:
an optical medium to include a sample placement surface;
an excitation light source to emit excitation light traveling in the optical5
medium toward a sample placed on the sample placement surface;
a probe light source to emit probe light traveling in the optical medium;
a light position detector to detect a position of the probe light emitted from the
optical medium;
a biological component acquisition unit connected to the light position detector;10
and
a modulation unit to modulate intensity of the excitation light and to make the
excitation light incident on the optical medium,
wherein
in plan view of the sample placement surface, an optical path of the probe light15
in the optical medium overlaps a portion of the sample placement surface irradiated
with the excitation light,
the modulation unit is configured to switch a plurality of modulation
frequencies in order from a low frequency to a high frequency, and the plurality of
modulation frequencies include a first frequency and a second frequency higher than20
the first frequency,
the light position detector detects a position of the probe light when the sample
is irradiated with the excitation light intensity-modulated at the first frequency, and
detects a position of the probe light when the sample is irradiated with the excitation
light intensity-modulated at the second frequency, and25
the biological component acquisition unit measures a biological component of
the sample based on the position of the probe light at the first frequency and the
position of the probe light at the second frequency.
- 26 -
[Claim 2] The biological component measurement device according to claim
1, wherein the modulation unit includes an optical chopper disposed in an optical path
of the excitation light,
the biological component measurement device further comprising:
a lock-in amplifier connected to the optical chopper and the light position5
detector; and
an oscillator to set operating frequencies of the optical chopper and the lock-in
amplifier.
[Claim 3] The biological component measurement device according to claim10
1, wherein the modulation unit includes a modulator to modulate an output signal of a
power supply to the excitation light source,
the biological component measurement device further comprising a lock-in
amplifier connected to the modulator and the light position detector.
15
[Claim 4] The biological component measurement device according to claim
2 or 3, wherein
the lock-in amplifier generates a signal related to a displacement amount of the
probe light, the displacement amount being a distance between a first position of the
probe light when the sample is not irradiated with the excitation light and a second20
position of the probe light when the sample is irradiated with the excitation light, and
the biological component acquisition unit measures the biological component of
the sample based on a first displacement amount of the probe light that is a distance
between the first position and the second position at the first frequency and a second
displacement amount of the probe light that is a distance between the first position and25
the second position at the second frequency.
[Claim 5] A biological component measurement method for measuring a
biological component of a sample, the biological component measurement method
- 27 -
comprising:
setting a modulation frequency in intensity modulation of excitation light to a
first frequency;
detecting a position of probe light emitted from an optical medium while
emitting the probe light traveling in the optical medium and irradiating the sample5
placed on a sample placement surface of the optical medium with the excitation light
intensity-modulated at the first frequency;
changing the modulation frequency in the intensity modulation from the first
frequency to a second frequency higher than the first frequency;
detecting the position of the probe light emitted from the optical medium while10
emitting the probe light traveling in the optical medium and emitting the excitation
light intensity-modulated at the second frequency toward the sample placed on the
sample placement surface of the optical medium; and
measuring the biological component of the sample based on the position of the
probe light at the first frequency and the position of the probe light at the second15
frequency.
[Claim 6] The biological component measurement method according to claim
5, further comprising adjusting a position of the sample on the sample placement
surface while emitting the probe light traveling in the optical medium and irradiating20
the sample placed on the sample placement surface of the optical medium with the
excitation light intensity-modulated at the first frequency.
[Claim 7] The biological component measurement method according to claim
5 or 6, further comprising:25
detecting a first displacement amount of the probe light, the first displacement
amount being a distance between a first position of the probe light when the sample is
not irradiated with the excitation light and a second position of the probe light when the
sample is irradiated with the excitation light intensity-modulated at the first frequency;
- 28 -
detecting a second displacement amount of the probe light, the second
displacement amount being a distance between the first position and the second
position of the probe light when the sample is irradiated with the excitation light
intensity-modulated at the second frequency; and
measuring the biological component of the sample based on the first5
displacement amount and the second displacement amount.