JP2012148034A - Apparatus for measuring component concentration in object to be measured - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for measuring component concentration in an object to be measured, capable of measuring, with high accuracy, the component concentration such as glucose concentration in the object to be measured that shows light scattering by particulates in a medium of a human living body or the like.SOLUTION: The apparatus 1 for measuring component concentration in the object to be measured includes a semiconductor laser 2 emitting linearly polarized light; a phase modulator 3 temporally changing the polarized state of the linearly polarized light incident thereto from the semiconductor laser 2; a polarization beam splitter 5 for polarizing and separating the light changed in its polarized state by the phase modulator 3, radiated to the object 4 to be measured that shows light scattering by particulates in the medium, and transmitted through the object 4 to be measured; first and second photodetectors 6 and 7 detecting two polarized-separated polarized beams of light, respectively; and a differential amplifier 8 for differentially computing detection signals for the two polarized-separated polarized beams of light. A differential signal obtained by the differential amplifier 8 is used as a measurement signal.

Description

  The present invention relates to a device for measuring a concentration of a component in a measurement object, and more particularly to a noninvasive measurement device suitable for measuring a blood glucose concentration in blood in a human biological tissue.

  In recent years, with the arrival of an aging society, the number of patients with diabetes has been increasing every year. In addition, diabetics must measure blood glucose levels in order to control the blood glucose concentration in the blood. Particularly in severe patients, blood glucose levels in blood need to be controlled in near real time, so that frequent blood glucose level measurement is required several times a day.

  Currently, blood glucose measurement methods that are in practical use include a chemical analysis method that chemically measures the sugar concentration of plasma obtained by removing red blood cells from blood collected from veins, and an electrical method that uses only the sugar content using an enzyme electrode. There is an enzyme electrode method for selectively measuring conductivity.

  However, in any case, measuring blood glucose levels with invasion in this way not only imposes pain and mental burden on patients, but also various types of patients with reduced immunity. It is also a cause of infectious diseases. In addition, since a disposable needle tip is required for each measurement, not only resource and economic problems occur, but also a problem of safe recovery processing of the needle tip to which blood has adhered occurs.

  Thus, recently, a blood glucose level (glucose concentration) measuring apparatus using a polarization preserving component (photon) detection method that is non-invasive and does not require blood collection has been proposed (for example, see Patent Document 1).

Patent Document 1 discloses the following. That is,
(1) Patent Document 1 discloses a method using a change in light scattering coefficient due to blood glucose level. In this case, since absorption is not used, light having a wavelength near 800 nm, which is called a living body window, can be used. This also facilitates measurement without being affected by the absorption of water present in the background of glucose absorption.

  (2) The scattering coefficient that determines the light scattering characteristics in the living body depends on the difference in refractive index between the minute biological material (red blood cells, white blood cells, platelets, cell membrane, etc.) that is a scatterer and the medium (plasma). It is known that the refractive index of a minute biological material is larger than the refractive index of plasma as a medium. As the concentration of glucose (sugar) dissolved in plasma increases, the refractive index of the medium (plasma) increases. As a result, it is considered that the difference in refractive index between the scatterer and the medium is reduced, and the scattering coefficient of the living body with respect to light transmitted through the living body is reduced. Therefore, if the change in the scattering coefficient is measured, the glucose concentration can be estimated.

  (3) It is known that the intensity of light passing through a scattering material follows the Lambert-Beer law with respect to the scattering coefficient. Therefore, if this rule is used, a change in the scattering coefficient can be detected.

  However, in a medium with a high scattering coefficient such as a living body, the influence of wraparound light appears, and the Lambert-Beer law is not satisfied in a region having a scattering coefficient larger than a certain scattering coefficient value.

  Therefore, in order to suppress the influence of the reflected light, a polarization preserving photon detection method effective for extracting a quasi-straight light component according to the Lambert Beer rule from the scattered light component is used. The quasi-straight light component is light that has passed through a path that travels substantially linearly toward the detector in the scattering medium with a small number of scattering times until reaching the detector. Thus, the quasi-straight light component has a small number of scattering times and a small degree of depolarization received during scattering. Therefore, the quasi-straight light component preserves the polarization state of the light irradiated to the object to be measured. On the other hand, since the wraparound component has a large number of scattering times, the degree of depolarization is large and non-polarized light. In this way, by extracting only the component that preserves the polarization state (quasi-straight light component) from the light transmitted through the object to be measured, the change in the scattering coefficient is measured by the intensity of the quasi-straight light component, The glucose concentration can be estimated.

Japanese Patent No. 4269079

  However, in the blood glucose level measuring apparatus proposed by Patent Document 1, the measurement signal includes light source noise and noise derived from local fluctuations of the living body (pulse wave, respiration, etc.), and the signal quality. There is a problem that it causes a decrease in

  The present invention has been made in order to solve the above-mentioned problems in the prior art, and the concentration of components such as glucose concentration in a measured object that shows light scattering by fine particles in a medium such as a human living body can be accurately determined. An object of the present invention is to provide an apparatus for measuring the concentration of a component in a measurement object that can be measured.

  In order to achieve the above object, the configuration of the component concentration measuring device in the object to be measured according to the present invention includes a light source that emits linearly polarized light, linearly polarized light from the light source, and a polarization state of the incident light. Is changed with time, means for irradiating the object to be measured which shows light scattering by fine particles in the medium, means for polarizing and separating the light transmitted through the object to be measured, and the two polarization-separated polarized lights It comprises a photodetector for detecting each of them, and means for differentially calculating the detection signals of the two polarized lights separated from each other, and a differential signal obtained by the means for differentially calculating is used as a measurement signal. To do.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to measure component concentrations, such as glucose concentration, for example with high precision using the light which permeate | transmitted the to-be-measured object which shows the light scattering by microparticles | fine-particles in media, such as a human body. Therefore, according to the present invention, a highly accurate non-invasive blood sugar level sensor can be realized.

FIG. 1 is a schematic configuration diagram showing an apparatus for measuring a component concentration in an object to be measured according to Embodiment 1 of the present invention. FIG. 2 is a graph showing temporal changes in the detected intensities of the quasi-straight light component and the sneak component in the embodiment of the present invention. FIG. 3 is a schematic configuration diagram showing an apparatus for measuring a component concentration in a measurement object in Embodiment 2 of the present invention. FIG. 4 is a schematic configuration diagram showing an apparatus for measuring a component concentration in a measurement object in Embodiment 3 of the present invention. FIG. 5 is a schematic configuration diagram illustrating another example of a component concentration measuring device in a measurement object according to Embodiment 3 of the present invention. FIG. 6 is a schematic configuration diagram showing a component concentration measuring apparatus in a measurement object in Embodiment 4 of the present invention. FIG. 7 is a schematic configuration diagram illustrating another example of a component concentration measuring device in a measurement object according to Embodiment 4 of the present invention.

  An apparatus for measuring a concentration of a component in a measurement object according to the present invention includes a light source that emits linearly polarized light, linearly polarized light from the light source, and changes the polarization state of the incident light with time, so that Means for irradiating an object to be measured that exhibits light scattering by the fine particles, means for polarizing and separating the light transmitted through the object to be measured, a photodetector for detecting each of the two polarized lights separated from each other, and the polarization Means for differentially calculating the detection signals of the two separated polarizations. In the measurement apparatus, a differential signal obtained by the means for performing the differential operation is used as a measurement signal. Then, the measurement signal obtained in this way is input to, for example, a personal computer, and a change in scattering coefficient and further a component concentration are obtained by subsequent signal processing.

  The object to be measured is, for example, a finger or an earlobe in blood glucose level measurement (glucose concentration measurement). In this case, the “fine particles in the medium” are red blood cells, white blood cells, platelets, cell membranes and the like in plasma. A scattering coefficient that determines scattering characteristics in a living body depends on a difference in refractive index between a minute biological substance (erythrocyte, white blood cell, platelet, cell membrane, etc.) as a scatterer and a medium (plasma). It is known that the refractive index of a minute biological material is larger than the refractive index of plasma as a medium. As the concentration of glucose (sugar) dissolved in plasma increases, the refractive index of the medium (plasma) increases. As a result, it is considered that the difference in refractive index between the scatterer and the medium is reduced, and the scattering coefficient of the living body with respect to light transmitted through the living body is reduced. Therefore, if the change in the scattering coefficient is measured, the glucose concentration can be estimated. However, the component concentration measuring device in the object to be measured according to the present invention is not limited to the glucose concentration measuring device (blood glucose level sensor), and for example, measures the concentration of a specific fiber in a textile product. It can also be used as a device or the like.

  According to the apparatus for measuring the concentration of a component in the object to be measured according to the present invention, the difference signal obtained by polarization-separating the light transmitted through the object to be measured and differentially calculating the detection signals of the two polarization-separated lights is obtained. Since it is used as a measurement signal, the signal intensity can be doubled. Also, it is possible to provide a highly accurate measurement device for measuring the concentration of a component in a measurement object that suppresses sneak light and suppresses noise derived from light source noise and local fluctuations (pulse wave, respiration, etc.) of a living body. Is possible.

  In the configuration of the component concentration measuring device in the object to be measured according to the present invention, the light source is preferably a semiconductor laser or a light emitting diode provided with a polarizer. Since the semiconductor laser is small and highly efficient, the measurement apparatus can be stabilized and downsized. Further, if a light emitting diode provided with a polarizer is used as the light source, a cheaper measuring device can be provided.

  In the configuration of the component concentration measuring apparatus in the object to be measured according to the present invention, the object to be measured which shows light scattering by the fine particles in the medium by temporally changing the polarization state of the incident light. Preferably, the means for changing the polarization state of the incident light with respect to time is a phase modulator. In this case, it is preferable to further include a synchronous detection means for extracting a component that changes in synchronization with the phase modulator from the measurement signal. According to this preferable example, the sneak light and the noise of the detection system can be suppressed with higher accuracy. A lock-in amplifier can be used as the synchronous detection means.

  In the configuration of the component concentration measuring apparatus in the object to be measured according to the present invention, the object to be measured which shows light scattering by the fine particles in the medium by temporally changing the polarization state of the incident light. In the means for irradiating the light, it is preferable that the means for temporally changing the polarization state of the incident light is a rotating phase plate. In this case, it is preferable to further include a synchronous detection means for extracting a component that changes in synchronization with the rotation of the rotating phase plate from the measurement signal. A lock-in amplifier can be used as the synchronous detection means.

  Further, in the configuration of the component concentration measuring device in the object to be measured according to the present invention, the means for polarizing and separating the light transmitted through the object to be measured includes a polarization beam splitter, a polarization diffraction grating, a Glan-Thompson prism, Wollaston It is preferably one selected from the group consisting of a prism, a lotion prism, and a beam displacer. In particular, by using a polarization diffraction grating, it is possible to provide a smaller and cheaper component concentration measuring apparatus.

  In the configuration of the component concentration measuring device in the object to be measured according to the present invention, it is preferable that the means for performing the differential operation is a differential amplifier.

  Hereinafter, the present invention will be described more specifically with reference to preferred embodiments. However, the following embodiments are merely examples embodying the present invention, and the present invention is not limited thereto.

[Embodiment 1]
FIG. 1 is a schematic configuration diagram showing an apparatus for measuring a component concentration in an object to be measured according to Embodiment 1 of the present invention.

  As shown in FIG. 1, a component concentration measuring device (hereinafter also simply referred to as “measuring device”) 1 in an object to be measured according to the present embodiment includes a semiconductor laser 2 as a light source that emits linearly polarized light, and a semiconductor Linearly polarized light from the laser 2 is incident, and polarization of the incident light is performed in a means for irradiating the object to be measured 4 that shows light scattering by fine particles in the medium by changing the polarization state of the incident light with time. A phase modulator 3 as means for temporally changing the state, a polarization beam splitter 5 as means for polarizing and separating the light transmitted through the object 4 to be measured, and a first for detecting two polarization-separated polarized lights. And the second photodetectors 6 and 7 and a differential amplifier 8 as means for differentially calculating the detection signals of the two polarized lights separated from each other. In the measurement apparatus 1, the differential signal obtained by the differential amplifier 8 is used as a measurement signal. The measurement signal obtained by the differential amplifier 8 is input to the personal computer 9, where signal processing is performed.

  In the present embodiment, the semiconductor laser 2 is used as a light source that emits linearly polarized light. Since the semiconductor laser 2 is small and highly efficient, the measurement apparatus 1 can be stabilized and downsized. In the present embodiment, a polarizer 10 is disposed between the semiconductor laser 2 and the phase modulator 3 as shown in FIG. 1 in order to remove the spontaneous emission component and increase the accuracy. Yes. However, the polarizer 10 is not an essential component of the measuring apparatus 1. As a light source that emits linearly polarized light, a light emitting diode including a polarizer can also be used. In this case, light from the light emitting diode is converted into linearly polarized light through a polarizer. And if a light emitting diode provided with a polarizer is used as a light source that emits linearly polarized light in this way, it becomes possible to provide a cheaper measuring apparatus.

  Further, since it is desirable that the light incident on the phase modulator 3 is collimated light, in this embodiment, as shown in FIG. 1, a collimating lens 11 is provided between the semiconductor laser 2 and the phase modulator 3. Has been placed. However, the collimating lens 11 is not an essential component of the measuring device 1.

  The wavelength of the light emitted from the semiconductor laser 2 is desirably 600 nm to 1200 nm, through which light called a biological light window is easily transmitted.

  As the phase modulator 3, for example, an electro-optic crystal such as lithium niobate or BSO (bismuth silicon oxide) or a liquid crystal can be used. This phase modulator 3 is controlled by the phase modulator. Controlled by circuit 12. As a result, the linearly polarized light incident on the phase modulator 3 can be changed to elliptically polarized light and further to linearly polarized light having a 90 ° polarization plane rotated from the polarization plane of the incident linearly polarized light.

  As the 1st and 2nd photodetectors 6 and 7, photoelectric conversion elements, such as a photodiode and a photomultiplier tube, can be used, for example.

  In the present embodiment, the polarization beam splitter 5 is used as means for polarizing and separating the light transmitted through the DUT 4, but in addition, a polarization diffraction grating, a Glan-Thompson prism, a Wollaston prism, a lotion prism, A beam displacer or the like can also be used.

  In addition, after the polarizing beam splitter 5, immediately before the first and second photodetectors 6, 7, the light transmission position of the object 4 to be measured has a diameter similar to the diameter of the light that irradiates the object 4 to be measured. A pinhole (not shown) may be provided for removing scattered light.

  Next, a method for obtaining a measurement signal using the measurement apparatus 1 having the above configuration will be described with reference to FIG.

  The linearly polarized light from the semiconductor laser 2 is collimated by the collimating lens 11, passes through the polarizer 10, and then enters the phase modulator 3. The light whose polarization state has been temporally changed by the phase modulator 3 is irradiated to the object to be measured 4 (such as a finger or earlobe in blood glucose level measurement (glucose concentration measurement)). The light that has passed through the DUT 4 is polarized and separated by the polarization beam splitter 5, and the two polarized lights that have been separated by polarization are detected by the first and second photodetectors 6 and 7, respectively. The detection signals detected by the first and second photodetectors 6 and 7, respectively, are input to the differential amplifier 8. From the differential amplifier 8, a difference signal between the two polarization-detected detection signals is separated. Output as measurement signal.

  The light detected by the first and second photodetectors 6 and 7 after passing through the DUT 4 and polarized and separated includes a “quasi-straight light component” and a “wraparound component”. Here, the quasi-straight light component is light that has passed through a path that travels substantially linearly in the scattering medium toward the detector with a small number of scattering times until reaching the detector. Thus, the quasi-straight light component has a small number of scattering times and a small degree of depolarization received during scattering. Therefore, the quasi-straight light component preserves the polarization state of the light irradiated to the object to be measured. On the other hand, since the wraparound component has a large number of scattering times, the degree of depolarization is large and non-polarized light.

  Therefore, the sneak component is polarized and separated and then oscillated in the polarization component (p-polarized light) oscillating in the incident plane of the polarization splitting surface of the polarization beam splitter 5 and in the plane orthogonal to the incident plane. Along with the polarization component (s-polarized light), the first and second signal components are polarized light of the object 4 to be measured, that is, as signal components having a constant intensity regardless of time modulation of the polarization state in the phase modulator 3. Detected by photodetectors 6 and 7.

  On the other hand, the quasi-straight light component is a modulated signal whose intensity changes in synchronization with the polarization of the light irradiated on the object 4 to be measured, that is, in synchronization with the time modulation of the polarization state in the phase modulator 3 Detected by the first and second photodetectors 6 and 7.

  That is, in both the first photodetector (p-polarized light detector) 6 and the second photodetector (s-polarized light detector) 7, the quasi-straight light is converted into a signal component having a constant intensity due to the wraparound component. A signal carrying a component modulation signal is detected (the signals detected by the respective detectors are referred to as “p-polarization side optical signal” and “s-polarization side optical signal”).

  Here, the linearly polarized light (linearly polarized light of incident light) from the semiconductor laser 2 is changed from the linearly polarized light corresponding to p-polarized light to the linearly polarized light corresponding to s-polarized light through elliptical polarized light at time t in the phase modulator 3. When the polarization state is changed, for example, at the moment when the linearly polarized light of the incident light becomes linearly polarized light corresponding to the p-polarized light, all the quasi-straight light components of the light transmitted through the DUT 4 are polarized and separated to the p-polarized light side. At the moment when the linearly polarized light of the incident light becomes the linearly polarized light corresponding to the s-polarized light, all the quasi-straight light components of the light transmitted through the DUT 4 are polarized and separated to the s-polarized light side. The intensity change of the quasi-straight light component obtained by the first photodetector (p-polarized photodetector) 6 and the second photodetector (s-polarized photodetector) 7 provided on the s-polarization side is The strength is reversed (represented by the dashed line in FIG. 2). Referring to the represented waveform by the waveform and two-dot chain line).

  Therefore, if the difference between the p-polarization side optical signal and the s-polarization side optical signal is taken, a wraparound component is canceled and a signal in which the amplitude (intensity) of the quasi-straight light component is doubled can be obtained (by the solid line in FIG. 2). (See waveform shown).

  Here, when a laser noise or a local variation (pulse wave, respiration, etc.) of a living body occurs, the influence thereof is the first photodetector (p-polarized photodetector) 6, the second photodetector ( The same amount of noise is superimposed on both the s-polarized light detectors 7 at the same time. These noises can be canceled by taking the difference between the signal from the first photodetector (p-polarized light detector) 6 and the signal from the second photodetector (s-polarized light detector) 7. it can. As a result, the influence of the noise can be reduced, and a higher-quality quasi-straight light component signal can be obtained.

  The difference signal obtained as described above is input to the personal computer 9, and a change in the scattering coefficient and further a component concentration such as a glucose concentration are obtained by subsequent signal processing.

  FIG. 2 shows a case where the polarization state of the incident light is changed with time so that the temporal change of the intensity of the quasi-straight light component becomes a sine wave. Is not to be done. For example, the polarization state of the incident light may be temporally changed so that the temporal change in the intensity of the quasi-straight light component is a rectangular wave or a triangular wave.

[Embodiment 2]
FIG. 3 is a schematic configuration diagram showing an apparatus for measuring a component concentration in a measurement object in Embodiment 2 of the present invention.

  The configuration of the measurement apparatus 13 shown in FIG. 3 performs synchronous detection of the differential signal from the differential amplifier 8 using a lock-in amplifier 14 that is synchronized with the phase modulator control circuit 12 that controls the phase modulator 3. In the above embodiment, only the component (quasi-straight light component) that changes in synchronization with the polarization change in the phase modulator 3 is extracted from the differential signal (measurement signal) from the differential amplifier 8. 1 is different from the configuration of the measuring device 1 (see FIG. 1). Therefore, the same members as those constituting the measuring apparatus 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  For example, noise generated in the first and second photodetectors 6 and 7 and the differential amplifier 8 is removed by extracting the quasi-straight light component from the differential signal using the lock-in amplifier 14. Thus, a higher quality signal can be obtained.

  An output signal from the lock-in amplifier 14 is input to the personal computer 9, and a change in the scattering coefficient and further a component concentration such as a glucose concentration are obtained by subsequent signal processing.

[Embodiment 3]
FIG. 4 is a schematic configuration diagram showing an apparatus for measuring a component concentration in a measurement object in Embodiment 3 of the present invention.

  The configuration of the measurement apparatus 15 shown in FIG. 4 is that the polarization diffraction grating 16 is used in place of the polarization beam splitter 5 as means for polarizing and separating the light transmitted through the object 4 to be measured. This is different from the configuration of the apparatus 1 (see FIG. 1). Therefore, the same members as those constituting the measuring apparatus 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. As described above, by using the polarization diffraction grating 16 as a means for polarizing and separating the light transmitted through the DUT 4, it is possible to provide a smaller and cheaper measurement apparatus for component concentration.

  The polarization diffraction grating 16 is a diffraction grating with different diffraction efficiencies that are diffracted into each diffracted light depending on the direction of incident polarized light.

  The polarization diffraction grating 16 is obtained by alternately arranging an optical medium having birefringence and an isotropic medium. Examples of the material of the optical medium having birefringence include liquid crystal molecules. The material of the isotropic medium includes transparent glass, plastic, or ultraviolet curable resin.

For example, in an isotropic medium refractive index is the same as the ordinary refractive index n _o of the liquid crystal having birefringence, the phase difference of the ordinary light polarization and abnormal light polarization is serrated a 1 [lambda (lambda is the wavelength used) Polarization diffraction grating that forms grooves and fills the grooves with liquid crystal molecules so that the major axis direction of the liquid crystal molecules is aligned. 16 can be obtained. Not limited to the above configuration, the isotropic medium average value in the form of the refractive index of the ordinary refractive index n _o and extraordinary refractive index n _e, the phase difference of the ordinary light polarization and abnormal light polarization is 2 [lambda] (lambda is used A triangular groove having a wavelength) may be formed, and the liquid crystal may be filled in the groove so that the major axis directions of the liquid crystal molecules are aligned. In this case, the ordinary light polarization and the extraordinary light polarization are diffracted so as to be diffracted light of one different diffraction order.

  In the measuring device 15 shown in FIG. 4, a lens 17 is provided immediately after the polarization diffraction grating 16. The lens 17 and the first and second photodetectors 6 and 7 are arranged such that the distance from the lens 17 to the first and second photodetectors 6 and 7 is the focal length of the lens 17. According to this configuration, the polarized lights separated by the polarization diffraction grating 16 can be condensed at different positions, and the first and second photodetectors 6 and 7 can be downsized. .

  In addition, in the measurement apparatus 15 shown in FIG. 4, two photodetectors (first and second photodetectors 6 and 7) are used. May be detected respectively.

  Similarly to the second embodiment, the differential signal from the differential amplifier 8 is subjected to synchronous detection using the lock-in amplifier 14 synchronized with the phase modulator control circuit 12 that controls the phase modulator 3. A component (quasi-straight light component) that changes in synchronization with the polarization change in the phase modulator 3 may be extracted from the differential signal (measurement signal) from the differential amplifier 8 (see FIG. 5). .

  For example, noise generated in the first and second photodetectors 6 and 7 and the differential amplifier 8 is removed by extracting the quasi-straight light component from the differential signal using the lock-in amplifier 14. Thus, a higher quality signal can be obtained.

  An output signal from the lock-in amplifier 14 is input to the personal computer 9, and a change in the scattering coefficient and further a component concentration such as a glucose concentration are obtained by subsequent signal processing.

[Embodiment 4]
FIG. 6 is a schematic configuration diagram showing a component concentration measuring apparatus in a measurement object in Embodiment 4 of the present invention.

  The configuration of the measuring device 18 shown in FIG. 6 is that the rotating phase plate 19 is used instead of the phase modulator 3 as means for temporally changing the polarization state of incident light. This is different from the configuration of the measuring apparatus 1 (see FIG. 1). Therefore, the same members as those constituting the measuring apparatus 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  For example, a half-wave plate can be used as the rotating phase plate 19, and the rotation of the phase plate 19 is controlled by a motor 20.

  When the linearly polarized light from the semiconductor laser 2 is incident on the half-wave plate at an azimuth angle of θ ° with respect to the main direction of the half-wave plate, the polarization plane remains linearly polarized. Rotates 2 × θ °. Therefore, when the phase plate (1/2 wavelength plate) 19 rotates once, the polarization plane rotates twice.

  Similarly to the second embodiment, the differential signal from the differential amplifier 8 is subjected to synchronous detection using a lock-in amplifier 21 synchronized with the motor 20 that controls the rotating phase plate 19 to obtain a differential signal. A component (quasi-straight light component) that changes in synchronization with the polarization change at the rotating phase plate 19 may be extracted from the difference signal (measurement signal) from the amplifier 8 (see FIG. 7).

  In this case, the intensity of the polarized light separated from each polarization changes in four periods with respect to one rotation of the phase plate (1/2 wavelength plate) 19, so the number of rotations of the phase plate (1/2 wavelength plate) 19. Is used as a reference signal for the lock-in amplifier 21 to perform synchronous detection.

  For example, noise generated in the first and second photodetectors 6 and 7 and the differential amplifier 8 is removed by extracting a quasi-straight light component from the difference signal using the lock-in amplifier 21. Thus, a higher quality signal can be obtained.

  The apparatus for measuring the concentration of a component in the measurement object of the present invention is useful when measuring the concentration of a component in the measurement object that shows light scattering by fine particles in the medium. In particular, according to the present invention, it is possible to realize a non-invasive measurement device (blood glucose level sensor) suitable for measuring the blood glucose concentration in blood in a human biological tissue.

1, 13, 15, 18 Device concentration measuring device 2 to be measured 2 Semiconductor laser 3 Phase modulator 4 Device to be measured 5 Polarization beam splitter 6 First photodetector 7 Second photodetector 8 Differential amplifier DESCRIPTION OF SYMBOLS 9 Personal computer 10 Polarizer 11 Collimating lens 12 Phase modulator control circuit 14, 21 Lock-in amplifier 16 Polarization diffraction grating 17 Lens 19 Rotating phase plate 20 Motor

Claims (9)

A light source that emits linearly polarized light;
Means for irradiating an object to be measured which shows light scattering by fine particles in a medium by linearly polarized light from the light source being incident, changing the polarization state of the incident light with time, and
Means for polarizing and separating the light transmitted through the object to be measured;
A photodetector for detecting each of the two polarized lights separated from each other;
Means for differentially calculating a detection signal of the two polarized lights separated from each other,
An apparatus for measuring a concentration of a component in an object to be measured, wherein a differential signal obtained by the means for performing a differential operation is used as a measurement signal.   The apparatus for measuring a component concentration in an object to be measured according to claim 1, wherein the light source is a semiconductor laser or a light emitting diode having a polarizer.   Means for changing temporally the polarization state of the incident light in the means for irradiating the object to be measured showing light scattering by the fine particles in the medium by temporally changing the polarization state of the incident light. The apparatus for measuring the concentration of a component in the object to be measured according to claim 1 or 2, wherein is a phase modulator.   The apparatus for measuring a component concentration in a measurement object according to claim 3, further comprising synchronous detection means for extracting a component that changes in synchronization with the phase modulator from the measurement signal.   Means for changing temporally the polarization state of the incident light in the means for irradiating the object to be measured showing light scattering by the fine particles in the medium by temporally changing the polarization state of the incident light. The apparatus for measuring the concentration of a component in the object to be measured according to claim 1 or 2, wherein is a rotating phase plate.   6. The apparatus for measuring a concentration of a component in a measurement object according to claim 5, further comprising synchronous detection means for extracting a component that changes in synchronization with the rotation of the rotating phase plate from the measurement signal.   The apparatus for measuring a concentration of a component in a measurement object according to claim 4 or 6, wherein the synchronous detection means is a lock-in amplifier.   The means for polarizing and separating the light transmitted through the object to be measured is one selected from the group consisting of a polarizing beam splitter, a polarizing diffraction grating, a Glan-Thompson prism, a Wollaston prism, a lotion prism, and a beam displacer. The measuring apparatus of the component density | concentration in the to-be-measured object of any one of 1-7.   The device for measuring a concentration of a component in a measurement object according to any one of claims 1 to 8, wherein the means for performing a differential operation is a differential amplifier.

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