WO2022254866A1 - 光電容積脈波センサー及び脈波の検出方法 - Google Patents
光電容積脈波センサー及び脈波の検出方法 Download PDFInfo
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Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
- A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb
Definitions
- the present invention relates to a photoelectric volumetric pulse wave sensor and a pulse wave detection method, and more particularly to a photoelectric volumetric pulse wave sensor that has a small number of parts, can reduce costs, and can more accurately detect body motion and pulse waves. .
- a Photo Plethysmo Graphy sensor (hereinafter, also simply referred to as a "PPG sensor”) has attracted particular attention as it is employed in pulse oximeters and smart watches.
- a PPG sensor is composed of a light-emitting element and a light-receiving element.
- the light from the light-emitting element irradiates the light-receiving element, a photoelectric effect occurs, and the light is converted into electricity to obtain a signal from the object to be measured.
- the object to be measured is a living tissue containing blood vessels, a pulse wave due to pulsation of the blood vessels can be detected when the tissue is transmitted or reflected inside the living body.
- a sensor for detecting body motion is provided separately from the PPG sensor, and a method of extracting only the pulse wave signal by processing the PPG signal and the body motion signal has been adopted. Acceleration sensors, capacitance sensors, and optical sensors are used as sensors for detecting body movements. Also, it is known that a clearer pulse waveform can be obtained by preferably applying an appropriate pressure to the measuring part.
- Patent Document 1 discloses a method of removing noise from a PPG sensor using a PPG sensor and a capacitive body motion sensor.
- An object of the present invention is to provide a sensor and a pulse wave detection method.
- the present inventor used at least one of the electrodes constituting the light-emitting element or the light-receiving element as an electrode for detecting body movement in the process of examining the causes of the above-mentioned problems. , the number of parts is small, the cost can be reduced, and body motion and pulse wave can be detected more accurately, leading to the present invention. That is, the above problems related to the present invention are solved by the following means.
- a photoelectric volumetric pulse wave sensor comprising a light-emitting element and a light-receiving element
- a photoelectric volumetric pulse wave sensor in which the electrodes constituting the light-emitting element or the light-receiving element are surface electrodes, and at least one of these electrodes is used as an electrode for detecting body movement.
- the electrodes constituting the light-emitting element or the light-receiving element are surface electrodes, and at least one of the electrodes is used in combination to detect body movement,
- the perfusion index (PI) represented by the following formula (1) is 0.0. 5.
- Formula (1): PI (%) AC/DC x 100
- a light-transmissive elastic dielectric layer that contacts the measurement site is provided on the surface of the electrode for detecting body movement, and the pulse wave and body movement are detected. 6. The method of detecting a pulse wave according to claim 4 or 5, wherein the pulse wave is detected.
- the photoelectric volume pulse wave sensor of the present invention uses at least one of the electrodes constituting the light emitting element or the light receiving element as an electrode for detecting body movement, a separate body movement sensor is provided as in the conventional art. Therefore, the number of parts can be reduced, and the pulse wave and body motion can be detected at low cost. In addition, since the position where the pulse wave is detected and the position where the body movement is detected match, accurate body movement can be detected. pulse waves can be detected with high accuracy.
- Sectional view showing an example of the configuration of the reflection type photoelectric volume pulse wave sensor of the present invention Cross-sectional view showing the details of the configuration of the reflective photoelectric volume pulse wave sensor of FIG.
- a cross-sectional view showing an example of the configuration of the transmission type photoelectric volume pulse wave sensor of the present invention Cross-sectional view showing the details of the configuration of the transmission type photoelectric volume pulse wave sensor in FIG.
- Schematic cross-sectional view of an organic EL element Schematic cross-sectional view showing an example of the configuration of an organic EL element
- Schematic cross-sectional view of an organic photodiode Schematic cross-sectional view showing an example of the configuration of an organic photodiode
- Schematic cross-sectional view of the reflective photoelectric volume pulse wave sensor attached to the measurement site Schematic cross-sectional view of the reflective photoelectric volume pulse wave sensor attached to the measurement site
- Schematic cross-sectional view of the reflective photoelectric volume pulse wave sensor attached to the measurement site Perspective view of a biological information measurement device using a reflective photoelectric volumetric pulse wave sensor that can be wrapped around the wrist Diagram showing an example of the functional configuration of the biological information measuring device Flowchart showing an example of pulse wave detection processing The figure which showed the drive method in a light emitting element, a light receiving element, and a body motion detection electrode.
- a diagram showing an example of the functional configuration of an information processing device Planar cross-sectional view for explaining the contact area in the body motion detection electrode The figure which showed the result of an Example The figure which showed the result of an Example The figure which showed the result of an Example The figure which showed the result of an Example The figure which showed the result of an Example The figure which showed the result of an Example The figure which showed the result of an Example The figure which showed the result of an Example The figure which showed the result of an Example
- the photoelectric volumetric pulse wave sensor of the present invention is a photoelectric volumetric pulse wave sensor comprising a light-emitting element and a light-receiving element, the electrodes constituting the light-emitting element or the light-receiving element are planar electrodes, and among these electrodes At least one electrode is also used as an electrode for detecting body movement.
- This feature is a technical feature common to or corresponding to each of the following embodiments.
- the light irradiated to the living body is incident on the light-receiving element by being transmitted through the living body or being reflected in the living body, and the pulse wave can be detected by photoelectric conversion, that is, Preferably, either the reflective type or the transmissive type can be effectively used.
- a light-transmissive elastic dielectric layer that contacts the measurement site is provided on the surface of the electrode that detects the body movement, This is preferable in that the detection accuracy of body motion and pulse wave can be improved.
- the pulse wave detection method of the present invention is a pulse wave detection method using the photoelectric volume pulse wave sensor, wherein the electrode constituting the light emitting element or the light receiving element is a surface electrode, and among these electrodes Body motion is also detected using at least one electrode, and the difference between the pulse wave data and the body motion data obtained by using the photoelectric volume pulse wave sensor is optimized and the difference is obtained. As a result, the number of parts can be reduced, the cost can be reduced, and the body motion and pulse wave can be detected more accurately.
- the perfusion index (PI) represented by the above formula (1) is It is preferable to display an error when it is less than 0.5%, and judge and measure as normal when it is 0.5% or more, in that the detection accuracy of body motion and pulse wave can be improved.
- a light-transmissive elastic dielectric layer that contacts the measurement site is provided on the surface of the electrode for detecting body movement, and the pulse wave and body movement are detected. is preferable in that the detection accuracy of body motion and pulse wave can be improved.
- the contact area of the portion that overlaps with the electrode that detects the body movement is 200 mm 2 or more. It is preferable in that it has good adhesion and can reduce measurement variations. Further, the pressure applied to the measurement site of the living body to which the photoelectric volume pulse wave sensor is attached is in the range of 0.02 N/cm 2 to (systolic blood pressure [N/cm 2 ]+0.4 [N/cm 2 ]). is preferable in that the measurement can be performed without applying excessive pressure to the living body.
- the photoelectric volumetric pulse wave sensor of the present invention is a photoelectric volumetric pulse wave sensor comprising a light-emitting element and a light-receiving element, the electrodes constituting the light-emitting element or the light-receiving element are planar electrodes, and among these electrodes At least one electrode is also used as an electrode for detecting body movement.
- a “plane electrode” is a planar flat plate electrode.
- Body motion is a change due to movement or vibration of the subject's body
- body motion data is waveform data of an electrical signal obtained by capturing the change as a waveform.
- Pulse wave is a waveform that captures changes in the volume of blood vessels that occur as the heart pumps out blood. Waveform data of a signal.
- the photoelectric volume pulse wave sensor of the present invention can be used either as a reflective type or as a transmissive type.
- the light emitted from the light-emitting element to the living body is reflected in the living body, enters the light-receiving element, and is photoelectrically converted, so that the pulse wave can be detected.
- the light applied to the living body passes through the living body, is incident on the light receiving element, and is photoelectrically converted to detect a pulse wave.
- FIG. 1 is a cross-sectional view showing an example of the configuration of the reflective photoelectric volumetric pulse wave sensor of the present invention
- FIG. 2 is a cross-sectional view showing the details of the configuration of the reflective photoelectric volumetric pulse wave sensor of FIG. be.
- a reflective photoelectric volumetric pulse wave sensor (hereinafter also referred to as a “reflective photoelectric volumetric pulse wave sensor”) 100A is attached to a measurement site of a living body E.
- the measurement site of the living body E consists of the epidermis, dermis and subcutaneous tissue in this order from the surface side.
- the reflective photoelectric volume pulse wave sensor 100A includes a light emitting element 500 and a light receiving element 400, and further has a light-transmissive elastic dielectric layer 600.
- the reflective photoelectric volume pulse wave sensor 100A is provided with an elastic dielectric layer 600, a light receiving element 400, and a light emitting element 500 in this order from the upper surface of the measurement site of the living body E.
- the measurement site in this case includes, for example, a site (wrist) that cannot transmit light.
- the light receiving element 400 is embedded substantially in the center of the elastic dielectric layer 600 in a plan view, but it is not limited to this.
- a light-emitting element 500 is provided on the elastic dielectric layer 600 in which the light-receiving element 400 is embedded. It is preferable that the light emitting element 500 and the elastic dielectric layer 600 have approximately the same size in plan view, and the light receiving element 400 has a smaller size in plan view than the light emitting element 500, and The light receiving element 400 is preferably sized to fit within the light emitting element 500 . Furthermore, the light-emitting element 500 , the light-receiving element 400 and the elastic dielectric layer 600 are housed inside the housing 700 .
- the shape of the light-emitting element 500 and the light-receiving element 400 in plan view may be rectangular, circular, or other shapes.
- reference numeral 50 denotes a light emitting portion and reference numeral 40 denotes a light receiving portion in FIG.
- the “light-emitting portion 50” refers to layers 50a (light-emitting functional layers (specifically, electron injection layer 53, electron transport layer 54, light-emitting layer 55, A hole-transporting layer 56 and a hole-injecting layer 57 (see FIGS.
- the “light-receiving portion 40” means a region having a layer 40a (light-receiving functional layer) inside the light-receiving element 400 that actually functions for light reception and electrodes (the anode 42 and the cathode 46) overlapping the layer 40a. do. Details of the configurations of the light emitting element 500 and the light receiving element 400 (FIGS. 2, 5A, 5, 6A, and 6B) will be described later.
- At least one of the electrodes (52, 58, 42 and 46) constituting the light-emitting element 500 or the light-receiving element 400 is also used as a body motion detection electrode for detecting body motion.
- the anode of the light-emitting element together as the body motion detection electrode.
- the body movement detection electrode functions as a capacitive pressure sensor with the living body E as the other electrode, and detects body movement of the measurer. That is, an alternating current is passed through the body motion detection electrodes, and a change in capacitance between the body motion detection electrodes and the measurement site of the living body is detected based on the value of the current flowing through the body motion detection electrodes.
- the contact area of the photoelectric volume pulse wave sensor with respect to the measurement site changes, or the pressure applied to the measurement site and the body movement detection electrode changes, the capacitance between the body movement detection electrode and the measurement site changes, The changed capacitance information is output as body motion data.
- FIG. 3 is a cross-sectional view showing an example of the configuration of the transmission type photoelectric volumetric pulse wave sensor of the present invention
- FIG. 4 is a cross-sectional view showing the details of the configuration of the transmission type photoelectric volumetric pulse wave sensor of FIG. be.
- a transmissive photoelectric volumetric pulse wave sensor also referred to as a “transmissive photoelectric volumetric pulse wave sensor”
- 100B is attached to a measurement site of a living body E.
- the transmission-type photoelectric volumetric pulse wave sensor 100B also preferably includes a light-emitting element 500 and a light-receiving element 400 in the same manner as the reflection-type photoelectric volumetric pulse wave sensor 100A, and further has a light-transmitting elastic dielectric layer 600. .
- the light emitting element 500 is provided on the upper surface of the measurement site of the living body E via the elastic dielectric layer 600, and the elastic dielectric layer 600 is provided on the lower surface of the measurement site.
- a light receiving element 400 is provided therebetween.
- the light-emitting element 500 and the light-receiving element 400 are arranged facing each other, and the measurement site of the living body E is arranged between the light-emitting element 500 and the light-receiving element 400 .
- the measurement site in this case includes, for example, a site through which light can be transmitted (a fingertip or an earlobe).
- the light emitting element 500 and the light receiving element 400 preferably have approximately the same size in plan view, and at least the light receiving element 400 preferably has a size that fits within the light emitting element 500 in plan view.
- the light emitting element 500 , the elastic dielectric layer 600 , the light receiving element 400 and the elastic dielectric layer 600 are housed inside the housing 700 .
- the shape of the light-emitting element 500 and the light-receiving element 400 in plan view may be rectangular, circular, or other shapes. Details of the configurations of the light emitting element 500 and the light receiving element 400 (FIGS. 4, 5A, 5B, 6A, and 6B) will be described later.
- At least one of the electrodes (the anode 42 and the cathode 46) constituting the light emitting element 500 or the light receiving element 400 is used as a body movement detection electrode for detecting body movement. used together. In particular, it is preferable to use the anode of the light-emitting element together as the body motion detection electrode.
- the photoelectric volume pulse wave sensor of the present invention uses a light-emitting element such as a light-emitting diode as a light source to irradiate light to the measured part of the biological tissue, and a light-receiving element such as a photodiode as a light detection sensor detects the measurement of the biological tissue. It detects the light reflected or transmitted by the part to be measured, and measures changes in the volume pulse wave, etc. of the living tissue based on the detected signal.
- a light-emitting element such as a light-emitting diode
- a light-receiving element such as a photodiode
- the photoelectric volume pulse wave sensor of the present invention can detect body movement by using either the light emitting element or the light receiving element as a body movement detection electrode, and the body movement data can be obtained from the pulse wave data obtained above. By taking the difference of , it is possible to extract only the pulse wave data from which noise etc. have been removed.
- the light emitted from the light emitting element passes through the epidermis and reaches the blood vessels behind it.
- Light reaching a blood vessel is absorbed, reflected, or transmitted through the blood flowing through the blood vessel.
- the light scattered by the vascular tissue and blood enters the light receiving element. Therefore, the light receiving element outputs a photocurrent corresponding to the amount of incident light.
- blood vessels repeat expansion and contraction in the same cycle as the heartbeat. Therefore, since the amount of reflected light increases and decreases in the same period as the period of expansion and contraction of the blood vessel, the change in the photocurrent output from the light receiving element indicates the volume change of the blood vessel.
- the photoelectric volume pulse wave sensor of the present invention can also be applied as a sensor for detecting the oxygen saturation of arterial blood.
- Hemoglobin in blood has different absorbances of red light and infrared light depending on the presence or absence of bonding with oxygen. Therefore, while preparing multiple sets of elements with different emission wavelengths and light reception wavelengths, such as elements that emit and receive red light and elements that emit and receive infrared light, the reflected light from these is measured and received.
- Oxygen saturation can be detected by analysis. Also when detecting the oxygen saturation in this way, it is possible to detect the oxygen saturation more accurately by subtracting the above-described body movement data.
- the blood vessel is an artery.
- volume pulse wave is a waveform when pressure changes in blood vessels due to pulsation cause changes in volume, and it is possible to directly grasp changes in blood vessels.
- a “photoelectric pulse wave” is a waveform detected by utilizing light transmission or reflection of blood to detect a pulse wave.
- the photoelectric volume pulse wave sensor (pulse oximeter) is used to measure oxygen saturation in blood.
- a pulse oximeter irradiates a finger with two wavelengths of light in the red to near-infrared wavelength range and measures the transmittance and reflectance.
- blood hemoglobin (Hb) exists in four states: oxygenated hemoglobin (O 2 Hb), reduced hemoglobin (HHb), methemoglobin (MetHb), and carboxyhemoglobin (COHb).
- MetHb and COHb are abnormal hemoglobins that increase in methemoglobinemia and carbon monoxide poisoning. Therefore, oxygen saturation is usually determined by the ratio of O 2 Hb and O 2 Hb+HHb.
- the red light absorbance of HHb When red light is transmitted through hemoglobin (Hb), the red light absorbance of HHb is significantly higher than the red light absorbance of O 2 Hb, and varies greatly depending on the wavelength of red light. Further, when near-infrared light is transmitted through hemoglobin (Hb), the near-infrared light absorbance of HHb is slightly lower than the near-infrared light absorbance of O 2 Hb. Therefore, the ratio R between the absorbance of red light and the absorbance of near-infrared light of hemoglobin (the absorbance of red light/the absorbance of near-infrared light) is the ratio of O 2 Hb and O 2 Hb+HHb in blood. Varies with saturation.
- the signal corresponding to the absorbance detected by the light-receiving element can be broadly divided into a signal due to the pulsation of arterial blood (also referred to as “pulsation component” or “AC”), non-pulsation part of arterial blood, venous blood, living tissue, and bone. and the like (also referred to as “non-pulsatile component” or “DC”).
- the absorbance when the absorbance is measured by irradiating red light and near-infrared light on fingers, wrists (e.g., ulnar side, radial side), the instep of the arm, the chest, and the chest, the change in absorbance over time is measured by the pulse wave. measured as a waveform that reflects Therefore, the AC component of the absorbance can be specified by calculating the difference between the maximum value and the minimum value of the change in absorbance over time, and the DC component of the absorbance can be specified by calculating the average value of the change in absorbance over time. can be done.
- the perfusion index (PI) represented by the following formula (1) using the pulsatile component (AC) and the non-pulsatile component (DC) identified in this way is 0.5% or more. It is preferable because it is less susceptible to noise during measurement. In particular, when the oxygen saturation is calculated, the PI value is more preferably 1.0% or more.
- Formula (1): PI (%) AC/DC x 100
- a light emitting element that is driven to blink at a frequency higher than the frequency of the volume pulse wave of the living body and emits light, and the light emitted from the light emitting element and the external light are measured.
- a light-receiving element that receives light reflected or transmitted by a target living tissue and generates a signal having a signal level corresponding to the amount of received light, and extracts an external light signal component due to the external light from the signal generated by the light-receiving element.
- body motion detection means for detecting a body motion signal component due to body motion; the external light signal component extracted by the external light extraction means and the body motion detection signal detected by the body motion detection means a noise signal caused by external light and body movement in the signal generated by the light-receiving element by subtracting the component from the signal generated by the light-receiving element; means for generating a signal representing the volume pulse wave of the living body to be measured, based on the signal after the noise signal component caused by body motion or the like has been reduced.
- the light-emitting element is used as a light source for irradiating living tissue.
- an organic light-emitting diode (OLED) or an inorganic light-emitting diode (LED) can be used, and the light-emitting element according to the present invention is not particularly limited.
- OLED organic light-emitting diode
- LED inorganic light-emitting diode
- the use of an organic electroluminescent diode (also referred to as "OLED”, “organic EL element” and “organic photodiode”), which is a light-emitting element, is flexible, comfortable to wear, and has wavelength variations. This is preferable in that luminance variation can be reduced.
- a wavelength conversion filter for converting visible light of the organic EL element into near-infrared light (IR) is arranged on the organic EL element emitting red light.
- IR near-infrared light
- a display backlight employs a method in which LEDs are arranged at the edge of a light guide plate and light is incident from the side edge of the light guide plate.
- a micro LED may be used with a resolution that can be regarded as a plane. It is more preferable to provide a scattering layer in order to reduce the local increase in brightness directly above the LED.
- FIG. 5A is a schematic plan cross-sectional view of an organic EL element
- FIG. 5B is a schematic cross-sectional view showing an example of the configuration of the organic EL element.
- an organic EL device 500 suitable for the present invention for example, as shown in FIGS.
- a configuration in which a group of light-emitting functional layers 50a (also referred to as “organic functional layers” or “organic layers”) is sandwiched between an anode 58 and a cathode 52 at opposing positions can be mentioned.
- the sealing member 59, and functional layers such as a gas barrier layer and a light extraction layer (not shown) may be combined as appropriate.
- FIG. 5B is a cross-sectional view showing the case of the following configuration (7).
- anode/light-emitting layer/cathode (2) anode/light-emitting layer/electron-transporting layer/cathode (3) anode/hole-transporting layer/light-emitting layer/cathode (4) anode/hole-transporting layer/light-emitting layer/electron transport layer/cathode (5) anode/hole transport layer/light emitting layer/electron transport layer/electron injection layer/cathode (6) anode/hole injection layer/hole transport layer/light emitting layer/electron transport layer/cathode ( 7) Anode 58/hole injection layer 57/hole transport layer 56/(electron blocking layer/) luminescent layer 55/(hole blocking layer/) electron transport layer 54/electron injection layer 53/cathode 52 Further, reference numeral 501 in FIG. 5A represents an extraction electrode.
- An electric field is applied to the organic EL element from the outside, holes are injected into the hole transport layer from the anode, and electrons are injected into the electron transport layer from the cathode.
- the injected carriers move by hopping between molecules. Holes and electrons recombine in the light-emitting layer to form electrically neutral excitons. Excitons emit light and are radiatively deactivated according to the emission quantum efficiency. Light generated in the organic layer is extracted into the air from the light extraction surface.
- the organic EL device according to the present invention is preferably provided with a wavelength conversion filter for converting visible light of the organic EL device into near-infrared light.
- the wavelength conversion filter according to the present invention preferably contains a luminous body (for example, a luminescent dye, etc.) having wavelength conversion ability.
- a luminous body for example, a luminescent dye, etc.
- the wavelength conversion filter according to the present invention is not particularly limited in terms of form, production method, etc., as long as it contains a luminescent dye having wavelength conversion ability, and can be appropriately determined according to the intended use.
- the wavelength conversion filter according to the present invention is a visible light region (380 to 780 nm) including a near red light region, preferably a green to red region (495 to 750 nm) including a near red light region, particularly preferably a red region (600 to 750 nm).
- 700 nm absorbs light from an organic EL element that emits light within the range of near-infrared light, e.g. It preferably has a function of converting to near-infrared light.
- the wavelength conversion filter and the organic EL element may be manufactured separately and laminated together, or the wavelength conversion filter may be directly coated and laminated on the organic EL element. good. Moreover, if necessary, a cut filter may be laminated or included to exclude light emitted without being wavelength-converted.
- the thickness of the wavelength conversion filter according to the present invention is preferably in the range of 0.01 to 1000 ⁇ m, more preferably in the range of 1 to 500 ⁇ m, from the viewpoint of miniaturization and maintaining flexibility. , and more preferably within the range of 10 to 300 ⁇ m.
- a coloring agent in addition to the luminescent dye, if necessary, a coloring agent, a light stabilizer, an antioxidant, a surfactant, a flame retardant, an inorganic additive, a transparent agent, an ultraviolet absorber, a filler Various well-known additives such as agents and light-scattering particles may also be included.
- the light-receiving element functions as a sensor that detects light reflected by the living tissue among the light emitted from the light-emitting element to the living tissue and converts the light into electricity.
- a planar inorganic or organic photodiode (OPD) or organic photovoltaics (OPV) can be used, and in particular, the use of OPD is flexible and comfortable to wear.
- OPD organic photodiode
- OCV organic photovoltaics
- Organic Photodiode A conventionally known organic photodiode (also referred to as “OPD” or “organic PD”) can be used as the light receiving element according to the present invention.
- FIGS. 2, 4, 6A, and 6B are schematic diagrams of an organic photodiode, where FIG. 6A is a plan cross-sectional view and FIG. 6B is a cross-sectional view showing an example of the configuration.
- the organic photodiode 400 is a metal layer formed on a substrate 41 such as a light-transmissive resin or glass by a sputtering method, a resistance heating vapor deposition method, or the like.
- each functional layer such as the sealing member 47 may be appropriately combined.
- reference numeral 401 in FIG. 6A represents an extraction electrode.
- the light-receiving functional layer can consist of a single layer or multiple layers.
- Light-receiving functional layers include, for example, an intrinsic layer (I layer), p-type layer/I layer, I layer/n-type layer, p-type layer/I layer/n-type layer, p-type layer/n-type layer, etc. can have various combinations of
- Organic thin-film solar cell As the light-receiving element according to the present invention, conventionally known various types of organic thin-film solar cells (OPV) can be used.
- OOV organic thin-film solar cells
- a bulk heterojunction organic photovoltaic device having a basic configuration in which an anode as a transparent electrode, a hole transport layer, a photoelectric conversion layer as a bulk heterojunction layer, an electron transport layer and a cathode are sequentially stacked on one surface of a substrate. Conversion elements can be used.
- other layers such as a hole blocking layer, an electron blocking layer, an electron injection layer, a hole injection layer, or a smoothing layer may be included.
- the photoelectric conversion layer is a layer that converts light energy into electrical energy, and includes a bulk heterojunction layer in which a p-type semiconductor material and an n-type semiconductor material are uniformly mixed.
- the p-type semiconductor material acts relatively as an electron donor (donor) and the n-type semiconductor material relatively acts as an electron acceptor (acceptor).
- an electron donor and an electron acceptor are defined as "an electron donor in which electrons move from an electron donor to an electron acceptor upon absorption of light to form a pair of holes and electrons (charge separation state). and "electron acceptor", which does not simply donate or accept electrons like an electrode, but donates or accepts electrons by a photoreaction.
- a tandem configuration having multiple bulk heterojunction layers in which such photoelectric conversion elements are stacked may be used.
- Examples of p-type semiconductor materials include various condensed polycyclic aromatic compounds and conjugated compounds.
- Examples of n-type semiconductor materials include fullerene, octaazaporphyrin, p-type semiconductor perfluoro compounds, naphthalenetetracarboxylic acid anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, perylenetetracarboxylic acid diimide, and the like.
- a polymer compound containing an aromatic carboxylic acid anhydride or an imidized product thereof as a skeleton can be mentioned.
- the elastic dielectric layer serves as a capacitor in a capacitive pressure sensor in which at least one electrode (body motion detection electrode) among the electrodes constituting the light emitting element or the light receiving element and the other electrode is the measurement site of the living body. Function.
- 7A to 7C are schematic cross-sectional views of the reflective photoelectric volume pulse wave sensor attached to the measurement site.
- 7A to 7C have the same meanings as those in FIG. 2, so description thereof will be omitted.
- S is the contact area of the portion overlapping with the body movement detection electrode in the contact area of the elastic dielectric layer 600 that contacts the measurement site when viewed from above
- the following formula clearly shows:
- the capacitance C increases as the contact area S increases.
- the thickness d of the elastic dielectric layer 600 is assumed to be d
- the capacitance C increases as the thickness d of the elastic dielectric layer 600 decreases due to pressure.
- FIG. 7A of the contact area M of the elastic dielectric layer 600 that contacts the measurement site, the portion where the elastic dielectric layer 600 and the body movement detection electrode (for example, the anode 58 of the light emitting element 500) overlap when viewed from above. refers to the area portion S corresponding to Also in the case of FIGS. 7B and 7C, when the body motion detection electrode is the anode 58 of the light emitting element 500, the area indicated by symbol S in the elastic dielectric layer 600 is the contact area S.
- FIG. 7A of the contact area M of the elastic dielectric layer 600 that contacts the measurement site, the portion where the elastic dielectric layer 600 and the body movement detection electrode (for example, the anode 58 of the light emitting element 500) overlap when viewed from above. refers to the area portion S corresponding to Also in the case of FIGS. 7B and 7C, when the body motion detection electrode is the anode 58 of the light emitting element 500, the area indicated by symbol S in the elastic dielectric layer 600 is the contact area S.
- the body motion detection electrode is the anode 58 of the light emitting element 500
- the body motion detection electrode may be the cathode 52 of the light emitting element 500 or the anode 42 or the cathode 46 of the light receiving element 400.
- the contact area S is defined as the area corresponding to the overlapping portion of the elastic dielectric layer 600 and each electrode.
- the "thickness d of the elastic dielectric layer” refers to the distance from the surface of the elastic dielectric layer 600 in contact with the measurement site to the surface of the elastic dielectric layer 600 in contact with the substrate 41. (Part d in FIGS. 7A to 7C). In addition, in FIG. 2 as well, the symbol d portion is referred to. Further, in the case of the transmission type photoelectric volume pulse wave sensor of FIG.
- the thickness is the "thickness d of the elastic dielectric layer" in the above formula
- the body motion detection electrode is the electrode (anode 42 or cathode 46) of the light receiving element 400
- the elastic dielectric layer on the side of the light receiving element Let the thickness of 600 be the "thickness d of the elastic dielectric layer" in the above formula.
- FIG. 7A the entire surface of the elastic dielectric layer 600 is in contact with the measurement site, there is no adhesion failure, and no pressure is applied.
- FIG. 7B compared with the elastic dielectric layer 600 in FIG. 7A, the contact area with respect to the measurement site is small, resulting in poor adhesion. Also, it is in a non-pressurized state. Therefore, due to poor adhesion, the living body is irradiated with external light, and the area S is reduced, so that the light is reflected on the skin surface, so that the pulsation component (AC) in the pulse wave data is less likely to increase. That is, the non-pulsating component (DC) increases and the capacitance decreases.
- AC pulsation component
- DC non-pulsating component
- the thickness d1 of the elastic dielectric layer 600 and the thickness d2 of the living tissue up to the artery D are reduced by applying pressure from the state of FIG. 7A. Therefore, the absorption of light by the living body is reduced and the capacitance is increased.
- the elastic dielectric layer 600 and the body motion detection electrode can detect the adhesion and pressure to the measurement site from the change in the capacitance C.
- the contact area S is preferably 200 mm 2 or more, more preferably in the range of 200 to 600 mm 2 .
- the pressure applied to the measurement site of the living body is preferably 0.02 N/cm 2 or more, more preferably 3 N/cm 2 or less.
- the pressure applied to the measurement site of the living body can be controlled by changing the thickness d of the elastic dielectric layer 600, for example. Specifically, the thickness d is preferably in the range of 0.1 to 1 mm.
- polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, cellulose acetate propionate (CAP), cellulose acetate
- PET polyethylene terephthalate
- PEN polyethylene naphthalate
- TAC cellulose triacetate
- CAP cellulose acetate propionate
- Cellulose esters such as phthalate, cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyetherketone, polyimide, polyethersulfone ( PES), polyphenylene sulfide, polysulfones, polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, silicone
- the photoelectric volumetric pulse wave sensor of the present invention can be applied to various forms of biological information measuring devices depending on the purpose. Application examples will be described below.
- FIG. 8 is a perspective view of a biological information measuring device using a reflective photoelectric volumetric pulse wave sensor that can be wrapped around the wrist.
- the biological information measurement device 1 has a main body 10 that is worn on a patient's wrist like a wristwatch.
- the main body 10 includes a belt 20 and can be worn on the patient's wrist by means of the belt 20 .
- the detecting section 14 including the light emitting element 500, the light receiving element 400, the elastic dielectric layer 600, etc. is arranged, and the detecting section 14 and the main body section 10 are electrically connected. ing.
- the main body part 10 is formed in a flat shape, and the operation part 12 and the display part 15 are provided on its peripheral surface and surface.
- an electric circuit and the like that perform functions corresponding to the control section 11, the recording section 13, and the like are housed inside.
- the operation unit 12 is configured with, for example, a power switch 12a, a timing switch (operation switch) 12b, and the like.
- FIG. 9 is a diagram showing a functional configuration example of the biological information measuring device 1.
- the biological information measuring apparatus 1 includes a control unit 11, an operation unit 12, a recording unit 13, a detection unit 14, a display unit 15, a wireless communication unit 16, a power supply unit 18, and the like.
- the control unit 11 includes a CPU (Central Processing Unit), a RAM (Random Access Memory) ), etc.
- the CPU of the control unit 11 reads various programs such as a system program and a processing program recorded in the recording unit 13, develops them in the RAM, and executes various processes according to the developed programs.
- the control unit 11 performs a pulse wave detection process (see FIG. 10), which will be described later. Specifically, the light emitted from the light emitting element 500 into the living body is reflected in the living body and is incident on the light receiving element 400, resulting in pulse wave data, and the body motion detection electrode and the capacitance at the measurement site. A process of optimizing the body motion data obtained by the change and taking the difference is performed.
- control unit 11 sets the pulsatile component in the signal corresponding to the absorbance of the light detected by the light receiving element 400 to AC and the non-pulsatile portion to DC, the perfusion index represented by the above formula (1) When (PI) is less than 0.5%, an error is displayed.
- the operation unit 12 is a detection unit that detects an operator's instruction, and includes various switches, various function buttons, etc., and outputs these operation signals to the control unit 11 .
- the recording unit 13 is composed of a semiconductor non-volatile memory or the like.
- the recording unit 13 records system programs and various programs necessary for the function of the biological information measuring device 1 according to the present embodiment, parameters and files necessary for executing the programs, and the like.
- the recording unit 13 continuously records measured vital data from the start of measurement to the end of measurement. Vital data may be recorded at fixed time intervals from the start of measurement to the end of measurement.
- the detection unit 14 is a data acquisition unit that acquires patient vital data by applying the photoelectric volume pulse wave sensor 100A or 100B (see FIGS. 2, 4, etc.) of the present invention. It preferably includes the element 500 and the light-receiving element 400, and further includes an elastic dielectric layer 600, and is configured to be attachable to a measurement site such as the wrist.
- the photoelectric volume pulse wave sensor in this case is of a reflective type, but may be of a transmissive type.
- the detection unit 14 controls the light-emitting element driving circuit 14b by the measurement control unit 14a, and emits red light and infrared light toward the living body part by the light-emitting element 500 provided in the detection unit 14.
- An analog signal of reflected light from the measurement site received by the light receiving element 400 is sent to the analog front end circuit 14c.
- the detection unit 14 controls the body motion detection electrode control circuit 14e by the measurement control unit 14a, and selects at least one electrode (body detection electrode), and an analog signal of body movement detected by the body movement detection electrode is sent to the analog front end circuit 14c. Then, based on the analog signals of the reflected light and body movement, noise removal and signal amplification are performed, and after preparing a voltage signal to be input to the AD converter 14d, the AD converter 14d converts it into digital data.
- the control unit 11 After being converted into digital data by the AD converter 14d, the control unit 11 calculates vital data such as SpO2 , pulse rate, and arteriosclerosis based on this digital data. The calculated vital data is recorded in the recording unit 13 .
- the display unit 15 is configured with, for example, an LCD (Liquid Crystal Display) or the like, and performs display by, for example, a dot matrix method, and performs display according to instructions of display signals input from the control unit 11.
- LCD Liquid Crystal Display
- the wireless communication unit 16 has a wireless interface for transmitting and receiving data to and from the information processing device 3 through wireless communication such as Bluetooth (registered trademark) and Wi-Fi (registered trademark).
- the power supply unit 18 supplies power required for the operation of each part of the biological information measurement device 1 to each part.
- the power supply unit 18 supplies power output from a battery (not shown) at the operating voltage of each unit.
- FIG. 10 is a flowchart showing an example of pulse wave detection processing.
- 11A and 11B are diagrams showing a driving method for the light emitting element, the light receiving element, and the body motion detection electrode.
- the control unit 11 drives the light-emitting element 500 and the light-receiving element 400 to measure a pulse wave (PPG) (step S1, see step (a) in FIG. 11). That is, pulse wave data is obtained by the light emitted from the light emitting element 500 entering the living body and being reflected in the living body and incident on the light receiving element 400 .
- PPG pulse wave
- step S2 the body movement is measured (step S2, see step (c) in FIG. 11). That is, body motion data is obtained from changes in the body motion detection electrodes and capacitance at the measurement site.
- step S3 it is determined whether or not the required number of samples of pulse wave data and body motion data has been obtained. If it is determined that the required number of samples has not been obtained (step S3; NO), steps (a) to (c) in FIG. 11 are regarded as one cycle until the required number of samples is obtained. ) repeat the process (steps S1 and S2). Note that the periods between steps (a) and (b) and between steps (b) and (c) in FIG. 11 are periods for avoiding the effects of charging and discharging due to transient phenomena.
- step S4 When it is determined that the required number of samples has been obtained (step S3; YES), the following signal processing is performed (step S4). Specifically, from the pulse wave data obtained in the step (a) of FIG. 11, external light data obtained by receiving only the light due to the external light obtained in the step (b) of FIG. Subtraction processing is performed (external light removal processing). Furthermore, using image processing filters such as band-pass filters and moving average filters, smoothing processing to remove electrical noise, pulse wave data obtained optically, and body movement data obtained by capacitance method Perform preprocessing such as processing to equalize the signal strength of each. A process of obtaining the difference of the body motion data from the pulse wave data thus preprocessed is performed. As a result, accurate pulse wave data with body motion data removed can be obtained.
- image processing filters such as band-pass filters and moving average filters
- PI perfusion index
- the information processing device 3 is a device capable of analyzing vital data transmitted from the biological information measurement device 1 .
- the information processing device 3 for example, a smart phone, a tablet, a PC (Personal Computer), or the like can be applied, but the device is not particularly limited.
- the information processing device 3 includes, for example, a control section 31, an operation section 32, a recording section 33, a display section 34, a communication section 35, and the like.
- the control unit 31 is composed of a CPU, a RAM, and the like.
- the CPU of the control unit 31 reads various programs such as a system program and a processing program recorded in the recording unit 33, develops them in the RAM, and executes various processes according to the developed programs. Specifically, the control unit 31 performs a process of analyzing vital data obtained based on light emitted from the light emitting element 500 in the biological information measuring device 1 .
- the operation unit 32 includes various switches, various function buttons, a touch panel, etc., and outputs these operation signals to the control unit 31.
- the recording unit 33 is composed of a semiconductor non-volatile memory or the like.
- the recording unit 33 records system programs, various programs, parameters and files necessary for executing the programs, and the like.
- the recording unit 33 records vital data output from the biological information measurement device 1 .
- the display unit 34 is configured with a monitor such as a CRT (Cathode Ray Tube) or LCD (Liquid Crystal Display), for example, and displays various screens according to the display signal instructions input from the control unit 31.
- a monitor such as a CRT (Cathode Ray Tube) or LCD (Liquid Crystal Display), for example, and displays various screens according to the display signal instructions input from the control unit 31.
- the communication unit 35 has an interface for transmitting/receiving data to/from the biological information measuring device 1 by wireless communication such as Bluetooth or Wi-Fi.
- the communication unit 35 may have a wired interface such as USB.
- Example 1 Capacitance change by body motion sensor
- An organic EL element "A9F4C0A (manufactured by Konica Minolta)" is used as the light emitting element
- a silicon photodiode "KPD30S (manufactured by Kyoto Semiconductor)” is used as the light receiving element
- the anode of the organic EL element is attached to the "Arduino uno R3”.
- a reflective photoelectric volume pulse wave sensor having the configuration shown in FIG. 2, which was connected as a motion detection electrode and used silicone resin as an elastic dielectric layer, was prepared.
- the area of the body movement detection electrode (the anode of the organic EL element) in plan view was 15.25 mm ⁇ 15.6 mm.
- the measurement site is the wrist position (radial artery position), the light emitting element does not emit light, current is passed through the body movement detection electrode, and the capacitance is measured under the following conditions (1) to (6).
- the results are shown in FIG. Note that the capacitance value is automatically converted to an arbitrary signal strength and displayed.
- FIG. 13 is a plan sectional view showing the body motion detecting electrode and the substrate.
- Condition (1) The elastic dielectric layer is not brought into contact with the measurement site (non-contact), no pressure is applied. The corresponding elastic dielectric layer is brought into contact with the measurement site, and no pressure is applied.
- Condition (5) The elastic dielectric layer corresponding to an area (see FIG. 13) equivalent to (one time) the area of the body motion detection electrode is brought into contact with the measurement site, and the wrist is bent.
- condition (1) by bringing the body movement detection electrode into contact with the measurement site, the signal strength becomes stronger, and the larger the contact area (condition (2) to condition (4)) It can be seen that the signal strength increases. Moreover, it can be seen that the signal intensity is further increased by applying pressure (conditions (5) and (6)).
- Example 2 Change in pulse wave due to pressure
- the reflective photoelectric volume pulse wave sensor used in Example 1 was prepared.
- the wrist position (radial artery position) was used as the measurement site, and pulse waves were measured using the reflection-type photoelectric volumetric pulse wave sensor while alternately repeating the state in which the wrist was placed straight and the state in which the wrist was bent.
- the results are shown in FIG. 15B shows the details of the b portion of FIG. 15A, and FIG. 15C shows the details of the c portion of FIG. 15A.
- FIG. 16 is a diagram showing the pulse wave data and body motion data shown in FIG.
- the data indicated by broken lines are pulse wave data
- the data indicated by solid lines are body motion data.
- the capacitance increases due to the application of pressure, and the capacitance when the reflective photoelectric volume pulse wave sensor is in close contact with the measurement site is set as a threshold, and the case of the threshold or more can be measured normally. It was determined that the Then, the obtained pulse wave data is subjected to preprocessing such as the above-described external light removal processing and smoothing processing.
- AC/DC was calculated from the data, and it was determined whether AC/DC was 0.5% or more, and if it was 0.5% or more, it was measured as a normal pulse wave.
- the number of parts can be reduced, the cost can be reduced, and the body movement and pulse wave can be detected more accurately. can be detected.
- the present invention can be used for a photoelectric volumetric pulse wave sensor and a pulse wave detection method that can reduce the number of parts, reduce costs, and more accurately detect body motion and pulse waves.
- detection unit 40 light receiving unit 40a light receiving functional layer 42 anode 46 cathode 50 light emitting unit 50a light emitting functional layer 52 cathode 58 anode 100A reflection type photoelectric volumetric pulse wave sensor 100B transmission type photoelectric volumetric pulse wave sensor 400 light receiving element 500 Light emitting element 600 Elastic dielectric layer 700 Housing D Artery E Living body d Elastic dielectric layer thickness S Contact area
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Abstract
Description
特に、(1)非侵襲測定が可能で、(2)デバイスの装着性が良く、(3)高精度で安定測定でき、バイタルデータを取得できるユーザーライクなデバイスが求められている。中でも、光電容積脈波(Photo Plethysmo Graphy)センサー(以下、単に「PPGセンサー」ともいう。)は、パルスオキシメーターやスマートウォッチで採用されるなど、特に注目されている。
PPGセンサーは、発光素子と受光素子で構成され、発光素子の光が受光素子に照射されることで光電効果が生じ、光を電気に変換することで測定対象から信号を得るセンサーである。例えば、測定対象が血管を含む生体組織の場合、生体内を透過又は反射する際に、血管の脈動による脈波を検知できる。
そこで、従来はPPGセンサーとは別に、体動を検知するセンサーを設け、PPG信号と体動信号を処理することで、脈波信号のみを抽出する方法を採用していた。体動を検知するセンサーとして、加速度センサー、静電容量センサー、光学式センサーが用いられる。また、好ましくは測定部に適切な圧力をかけることで、より明瞭な脈波形を得られることが知られている。
しかし、これらのセンサーはPPGセンサーとは別に体動センサーを設けているため、部品点数が多く、コストアップに繋がったり、PPGセンサーと体動センサーの位置が一致していないことにより正確な体動を検知できないといった問題があった。
例えば、特許文献1では、PPGセンサーと静電容量式の体動センサーにより、PPGセンサーからノイズを除去する方法が開示されている。
すなわち、本発明に係る上記課題は、以下の手段により解決される。
前記発光素子又は前記受光素子を構成する電極が面電極であり、これらの前記電極のうち少なくとも一つの電極を、体動を検知する電極として併用する光電容積脈波センサー。
前記発光素子又は前記受光素子を構成する電極を面電極とし、これらの前記電極のうち少なくとも一つの電極を併用して体動も検知し、
前記光電容積脈波センサーを用いて得られる脈波データと、体動データをそれぞれ最適化して差分を取る脈波の検出方法。
式(1):PI(%)=AC/DC×100
本発明の効果の発現機構又は作用機構については、明確にはなっていないが、以下のように推察している。
本発明の光電容積脈波センサーは、発光素子又は受光素子を構成する電極のうち少なくとも一つの電極を、体動を検知する電極として併用するので、従来のように別途、体動センサーを設けることなく、部品点数を減らせ、安価に、脈波及び体動を検知することができる。
また、脈波を検出する位置と体動を検出する位置とが一致することから、正確な体動を検知でき、ノイズ等を含む脈波データから体動データを差し引くことで、体動を除いた脈波を高い精度で検出することができる。
この特徴は、下記各実施形態に共通又は対応する技術的特徴である。
また、前記光電容積脈波センサーを装着した前記生体の測定部位に加わる圧力を、0.02N/cm2から(最高血圧[N/cm2]+0.4[N/cm2])の範囲とすることが、生体に過度な圧力をかけず測定できる点で好ましい。
本発明の光電容積脈波センサーは、発光素子と受光素子を備えた光電容積脈波センサーであって、前記発光素子又は前記受光素子を構成する電極が面電極であり、これらの前記電極のうち少なくとも一つの電極を、体動を検知する電極として併用する。
また、「体動」とは、測定者の体の動きや振動による変化であり、「体動データ」とは、その変化を波形としてとらえた電気信号の波形データである。
「脈波」とは、心臓が血液を送り出すことに伴い発生する、血管の容積変化を波形として捉えたものであり、「脈波データ」とは、前記血管の容積変化を波形として捉えた電気信号の波形データをいう。
また、本発明の光電容積脈波センサーは、反射型又は透過型のいずれでも使用することができる。反射型は、発光素子から生体に照射された光が、生体内で反射することで受光素子に入射して、光電変換されることで脈波を検知できるもので、透過型は、発光素子から生体に照射された光が、生体内を透過することで前記受光素子に入射して、光電変換されることで脈波を検知できるものである。
以下に、反射型の光電容積脈波センサー、透過型の光電容積脈波センサーの順で、各構成について説明する。
図1は、本発明の反射型の光電容積脈波センサーの構成の一例を示した断面図、図2は、図1の反射型の光電容積脈波センサーの構成の詳細を示した断面図である。
図1に示すように、生体Eの測定部位に反射型の光電容積脈波センサー(以下、「反射型光電容積脈波センサー)ともいう。)100Aが装着されている。
生体Eの測定部位は、図示しないが、表面側から順に表皮、真皮及び皮下組織からなり、表皮と真皮の間に毛細血管が流れ、真皮及び皮下組織には細動脈が流れ、細動脈の下方には動脈Dが流れている。
前記反射型光電容積脈波センサー100Aは、発光素子500と受光素子400を備え、さらに光透過性の弾性誘電体層600を有することが好ましい。
具体的に、反射型光電容積脈波センサー100Aは、生体Eの測定部位の上面から弾性誘電体層600、受光素子400及び発光素子500の順に設けられている。この場合の測定部位としては、例えば、光透過できない部位(手首)などが挙げられる。
図1において、受光素子400は、平面視において弾性誘電体層600の略中央に埋設されているが、これに限定されるものではない。
また、受光素子400が埋設された弾性誘電体層600上に、発光素子500が設けられている。発光素子500及び弾性誘電体層600の平面視の大きさは、同程度であることが好ましく、受光素子400の平面視の大きさは発光素子500の平面視の大きさよりも小さく、平面視において受光素子400は発光素子500内に収まる大きさとなっていることが好ましい。
さらに、このような発光素子500、受光素子400及び弾性誘電体層600は、筐体700内に収納されている。なお、発光素子500及び受光素子400の平面視の形状は、矩形状や円形状であってもそのほかの形状であってもよい。
また、「受光部40」とは、受光素子400内部の実際に受光のために機能する層40a(受光機能層)及び当該層と重なっている電極(陽極42及び陰極46)を有する領域を意味する。
なお、発光素子500及び受光素子400の構成の詳細(図2、図5A、図5、図6A、図6B)については後述する。
体動検知電極は、生体Eを他方の電極として、静電容量式の圧力センサーとして機能し、測定者の体動を検知する。すなわち、体動検知電極に交流の電流を流し、当該体動検知電極を流れる電流値に基づいて、体動検知電極及び生体の測定部位間における静電容量の変化を検出する。光電容積脈波センサーの測定部位に対する接触面積が変化したり、測定部位及び体動検知電極にかかる圧力が変化することで、体動検知電極と測定部位との間における静電容量が変化し、変化した静電容量情報を体動データとして出力する。
図3は、本発明の透過型の光電容積脈波センサーの構成の一例を示した断面図、図4は、図3の透過型の光電容積脈波センサーの構成の詳細を示した断面図である。
図3に示すように、生体Eの測定部位に透過型の光電容積脈波センサー(「透過型光電容積脈波センサー」ともいう。)100Bが装着されている。
前記透過型光電容積脈波センサー100Bも、前記した反射型光電容積脈波センサー100Aと同様に、発光素子500と受光素子400を備え、さらに光透過性の弾性誘電体層600を有することが好ましい。
具体的に、透過型光電容積脈波センサー100Bは、生体Eの測定部位の上面には弾性誘電体層600を介して発光素子500が設けられ、測定部位の下面には弾性誘電体層600を介して受光素子400が設けられている。すなわち、発光素子500と受光素子400が対向して配置され、これら発光素子500及び受光素子400の間に生体Eの測定部位が配置されている。この場合の測定部位としては、例えば、光透過できる部位(指先や耳朶)などが挙げられる。
図3において、発光素子500及び受光素子400の平面視における大きさは同程度であることが好ましく、少なくとも、平面視において受光素子400は発光素子500内に収まる大きさとなっていることが好ましい。
さらに、このような発光素子500、弾性誘電体層600、受光素子400及び弾性誘電体層600は、筐体700内に収納されている。なお、発光素子500及び受光素子400の平面視の形状は、矩形状や円形状であってもそのほかの形状であってもよい。なお、発光素子500及び受光素子400の構成の詳細(図4、図5A、図5B、図6A、図6B)については後述する。
本発明の光電容積脈波センサーは、光源としての発光ダイオード等の発光素子により、生体組織の被測定部に光を照射して、光検出センサーとしてのフォトダイオード等の受光素子により、生体組織の被測定部で反射又は透過した光を検出し、この検出した信号に基づいて、生体組織の容積脈波等の変化を測定するものである。
特に本発明の光電容積脈波センサーは、発光素子又は受光素子のいずれかの電極を体動検知電極として併用することで、体動を検知でき、前記で得られた脈波データから体動データの差分を取ることにより、ノイズ等を除去した脈波データのみを抽出することができる。
このうち、血管組織、血液によって散乱された光は、受光素子に入射する。このため、受光素子は、入射光量に応じた光電流を出力する。ここで、血管は、心拍と同じ周期で膨張・収縮を繰り返している。したがって、血管の膨張・収縮の周期と同じ周期で光の反射量が増減するので、受光素子から出力される光電流の変化は、血管の容積変化を示すことになる。
このように酸素飽和度を検出する際にも、前記した体動データを差し引くことで、より正確な酸素飽和度を検出することができる。
なお、血管としては、動脈である。
また、「光電容積脈波」とは、容積脈波を検出するために血液の光の透過又は反射を利用して検出した波形である。
一般的に、血液中の酸素飽和度を計測するためには、前記光電容積脈波センサー(パル
スオキシメーター)が使用される。パルスオキシメーターは、指に赤色~近赤外の波長域に含まれる二つの波長の光を照射し、その透過率や反射率を測定する。
具体的には、血中ヘモグロビン(Hb)は、酸素化ヘモグロビン(O2Hb)、還元ヘモグロビン(HHb)、メトヘモグロビン(MetHb)、一酸化炭素ヘモグロビン(COHb)の4種類の状態で存在する。MetHb及びCOHbは、メトヘモグロビン血症や一酸化炭素中毒で増加する異常ヘモグロビンである。そのため、酸素飽和度は、通常、O2HbとO2Hb+HHbとの比によって決定される。ヘモグロビン(Hb)に赤色光を透過させた場合、HHbの赤色光の吸光度はO2Hbの赤色光の吸光度より著しく大きく、赤色光の波長によって大きく変化する。また、ヘモグロビン(Hb)に近赤外光を透過させた場合、HHbの近赤外光の吸光度はO2Hbの近赤外光の吸光度よりよりわずかに低い。そのため、ヘモグロビンの赤色光の吸光度と近赤外光の吸光度との比率R(赤色光の吸光度/近赤外光の吸光度)は、血液中のO2HbとO2Hb+HHbとの比である酸素飽和度によって変化する。
受光素子で検出する吸光度に対応する信号は、大きく分けて動脈血の拍動による信号(「拍動成分」又は「AC」ともいう。)と、動脈血非拍動部分、静脈血、生体組織、骨等により吸収された信号(「非拍動成分」又は「DC」ともいう。)の2つに分類される。
そして、例えば、波長660nmの赤色光の吸光度の拍動成分をAC660、DC成分をDC660とし、例えば、波長940nmの近赤外光の吸光度のAC成分をAC940、DC成分をDC940とすると、赤色光の吸光度と近赤外光の吸光度との比率R(赤色光の吸光度/近赤外光の吸光度)は以下の(I)式で表される。
このようにして特定した拍動成分(AC)と、非拍動成分(DC)を用いた下記式(1)で表される灌流指標(PI)は、0.5%以上であることが、測定時のノイズ影響を受けにくく好ましい。特に、酸素飽和度を算出する用途の場合には、PI値が1.0%以上であることがより好ましい。
式(1):PI(%)=AC/DC×100
光電容積脈波センサーの全体的構成としては、種々の形態・態様を採り得る。
例えば、基本的全体構成としては、発振器の信号に基づいて、生体の容積脈波の周波数よりも高い周波数により点滅駆動され発光する発光素子と、当該発光素子から発光された光及び外光が測定対象の生体組織により反射又は透過した光を受光し、受光光量に対応した信号レベルを有する信号を生成する受光素子と、当該受光素子が生成した信号から、前記外光による外光信号成分を抽出する外光抽出手段と、体動による体動信号成分を検知する体動検知手段と、前記外光抽出手段により抽出された外光信号成分及び前記体動検知手段により検知された体動検知信号成分を、前記受光素子が生成した信号から減算することにより、前記受光素子が生成した信号中の外光及び体動等に起因するノイズ信号を低減する低減手段と、前記低減手段により外光及び体動等に起因するノイズ信号成分が低減された後の信号に基づいて、測定対象の生体の容積脈波を表す信号を生成する手段とを備えた構成であることが好ましい。
光電容積脈波センサーの各種構成要素のうち、主要な要素である、発光素子、受光素子及び弾性誘電体層について説明する。
本発明において、発光素子は、生体組織に照射する光の光源として用いる。
発光素子としては、有機発光ダイオード(OLED)も無機系の発光ダイオード(LED)も使用でき、特に限定されるものではないが、本発明に係る発光素子としては、面状の有機層で構成される発光素子である有機エレクトロルミネッセンス素子(organic electroluminescent diode:「OLED」、「有機EL素子」及び「有機フォトダイオード」ともいう。)を用いることが、フレキシブルで装着感が良好で、かつ波長ばらつきや輝度ばらつきを低減できる点で好ましい。
特に、赤色発光する有機EL素子上に、有機EL素子の可視光を近赤外光(IR)に変換する波長変換フィルターを配置した構成であることが好ましい。
また、面状の発光素子として、LEDと導光板を用いてもよい。ディスプレイ用バックライトでは、LEDを導光板のエッジに配置し、導光板のサイドエッジから光を入射する方式が取られている。
さらに、面とみなせる程度の解像度でマイクロLEDを用いてもよい。LED直上の輝度が局所的に高くなることを緩和するために、散乱層を設けることがより好ましい。
図5Aは、有機EL素子の模式平断面図、図5Bは有機EL素子の構成の一例を示した模式断面図である。
(2)陽極/発光層/電子輸送層/陰極
(3)陽極/正孔輸送層/発光層/陰極
(4)陽極/正孔輸送層/発光層/電子輸送層/陰極
(5)陽極/正孔輸送層/発光層/電子輸送層/電子注入層/陰極
(6)陽極/正孔注入層/正孔輸送層/発光層/電子輸送層/陰極
(7)陽極58/正孔注入層57/正孔輸送層56/(電子阻止層/)発光層55/(正孔阻止層/)電子輸送層54/電子注入層53/陰極52
また、図5Aにおいて符号501は、引き出し電極を表す。
本発明に係る有機EL素子は、有機EL素子の可視光を近赤外光に変換する波長変換フィルターが設けられていることが好ましい。
本発明に係る受光素子は、発光素子から生体組織に照射された光のうち、前記生体組織によって反射された光を検出し、電気に変換するセンサーとして機能する。
受光素子としては、平面状の無機又は有機フォトダイオード(organic photo diode:OPD)、有機薄膜太陽電池(organic photovoltaics:OPV)を用いることができ、特にOPDを用いることが、フレキシブルで装着感が良好で、かつ波長ばらつきや輝度ばらつきを低減できる点で好ましい。
本発明に係る受光素子としては、従来公知の有機フォトダイオード(「OPD」又は「有機PD」ともいう。)を用いることができる。
図6A及び図6Bは、有機フォトダイオードの模式図であり、図6Aは平断面図、図6Bは構成の一例を示した断面図である。
例えば、有機フォトダイオード400は、図2、図4、図6A、図6Bに示すように、光透過性の樹脂、ガラス等の基材41にスパッタリング法や抵抗加熱蒸着法等により形成された金属からなる陰極46と、陰極46に受光機能層40aをそれぞれ抵抗加熱蒸着法等によって成膜してなる構成と、さらに受光機能層40aに、同じく抵抗加熱蒸着法等により形成されたITO(Indium-Tin Oxide)等の透明な導電性膜からなる陽極42とを基本的構成要素としている。また、目的に応じて、封止部材47等の各機能層を適宜組み合わせて構成して良い。また、図6Aにおいて符号401は、引き出し電極を表す。
本発明に係る受光素子としては、従来公知の種々の形態の有機薄膜太陽電池(OPV)を用いることもできる。
例えば、基板の一方面上に、透明電極である陽極、正孔輸送層、バルクヘテロジャンクション層の光電変換層、電子輸送層及び陰極が順次積層されている基本的構成を有するバルクヘテロジャンクション型の有機光電変換素子を用いることができる。
なお、正孔ブロック層、電子ブロック層、電子注入層、正孔注入層、又は平滑化層等の他の層を有していてもよい。
p型半導体材料は、相対的に電子供与体(ドナー)として機能し、n型半導体材料は、相対的に電子受容体(アクセプター)として機能する。
ここで、電子供与体及び電子受容体は、“光を吸収した際に、電子供与体から電子受容体に電子が移動し、正孔と電子のペア(電荷分離状態)を形成する電子供与体及び電子受容体”であり、電極のように単に電子を供与又は受容するものではなく、光反応によって、電子を供与又は受容するものである。
n型半導体材料の例としては、フラーレン、オクタアザポルフィリン、p型半導体のパーフルオロ体、ナフタレンテトラカルボン酸無水物、ナフタレンテトラカルボン酸ジイミド、ペリレンテトラカルボン酸無水物、ペリレンテトラカルボン酸ジイミド等の芳香族カルボン酸無水物やそのイミド化物を骨格として含む、高分子化合物が挙げられる。
弾性誘電体層は、発光素子又は受光素子を構成する電極のうち少なくとも一つの電極(体動検知電極)と、生体の測定部位を他方の電極とした静電容量式の圧力センサーにおいて、コンデンサーとして機能する。
ここで、平面視したときに、前記測定部位に接触する前記弾性誘電体層600の接触面積のうち、前記体動検知電極と重なる箇所の接触面積をSとしたとき、下記式から明らかなとおり、接触面積Sが大きくなると静電容量Cが増加する。また、弾性誘電体層600の厚さをdとしたとき、加圧により弾性誘電体層600の厚さdが小さくなると静電容量Cが増加する。
C=ε・S/d
[ε:空間の誘電率(F/m)、d:弾性誘電体層の厚さ(距離)(m)、S:平面視したときに、測定部位に接触する弾性誘電体層の接触面積のうち、体動検知電極と重なる箇所の接触面積(m2)]
一方、図4に示す透過型光電容積脈波センサーの場合においても、平面視したときに、弾性誘電体層600と体動検知電極(例えば、発光素子500の陽極58)とが重なる箇所に相当する面積部分Sをいう。
なお、前記の説明では、体動検知電極を発光素子500の陽極58とした場合について説明したが、体動検知電極を、発光素子500の陰極52や、受光素子400の陽極42又は陰極46とした場合には、弾性誘電体層600と各電極とが重なる箇所に相当する面積部分を前記接触面積Sとする。
さらに、前記式において、「弾性誘電体層の厚さd」とは、弾性誘電体層600の測定部位に接触する面から弾性誘電体層600の基材41に接触する面までの距離をいう(図7A~図7C中、符号d部分)。なお、図2においても、符号d部分をいう。
また、図4の透過型光電容積脈波センサーの場合には、体動検知電極を発光素子500の電極(陽極58又は陰極52)とした場合には、発光素子側の弾性誘電体層600の厚さを、前記式における「弾性誘電体層の厚さd」とし、体動検知電極を受光素子400の電極(陽極42又は陰極46)とした場合には、受光素子側の弾性誘電体層600の厚さ
を、前記式における「弾性誘電体層の厚さd」とする。
図7Bでは、図7Aの弾性誘電体層600に比べて、測定部位に対する接触面積が少なく、密着不良となっている。また、加圧していない状態である。したがって、密着不良により、外光が生体に照射されて、面積Sが小さくなるため、皮膚表面で反射することから、脈波データにおける拍動成分(AC)は増加しにくくなる。すなわち、非拍動成分(DC)が増加し、静電容量が減少する。
図7Cでは、図7Aの状態から加圧することにより、弾性誘電体層600の厚さd1と動脈Dまでの生体組織の厚さd2が薄くなる。そのため、生体による光の吸収が減少し、静電容量が増加する。
ここで、前記接触面積Sは、200mm2以上とすることが好ましく、200~600mm2の範囲内であることがより好ましい。
また、生体の測定部位に加わる圧力を0.02N/cm2以上とすることが好ましく、3N/cm2以下であることがより好ましい。
なお、生体の測定部位に加わる圧力は、例えば、弾性誘電体層600の前記厚さdを変えることによって制御することができる。具体的に、前記厚さdとしては、0.1~1mmの範囲内であることが好ましい。
本発明の光電容積脈波センサーは、目的に応じて種々の形態の生体情報測定装置に適用できる。
以下において、適用例について説明する。
生体情報測定装置1は、腕時計のように患者の手首に対して装着される本体部10を有する。具体的には、本体部10はベルト20を備え、ベルト20により患者の手首に装着可能である。また、ベルト20の内側には、前記した発光素子500及び受光素子400、弾性誘電体層600等を備えた検出部14が配置され、当該検出部14と本体部10とが電気的に接続されている。
)等により構成される。制御部11のCPUは、記録部13に記録されているシステムプログラムや処理プログラム等の各種プログラムを読み出してRAMに展開し、展開されたプログラムに従って各種処理を実行する。
制御部11は、後述するような脈波の検出処理(図10参照。)を行う。具体的には、発光素子500から生体内に照射された光が生体内で反射することで受光素子400に入射することで得られる脈波データと、体動検知電極及び測定部位における静電容量変化により得られる体動データをそれぞれ最適化して差分を取る処理を行う。
さらに、制御部11は、受光素子400によって検出された光の吸光度に対応する信号における拍動成分をACとし、非拍動部分をDCとしたとき、前記式(1)で表される灌流指標(PI)が、0.5%未満のときはエラーを表示し、0.5%以上のときは正常であると判定し測定する処理を行う。
例えば、記録部13は、測定開始から測定終了までの間、測定しているバイタルデータを連続的に記録する。なお、測定開始から測定終了までの間、一定時間ごとにバイタルデータが記録されることとしても良い。
検出部14は、測定制御部14aによって発光素子駆動回路14bを制御し、検出部14に備えられた発光素子500によって赤色光と赤外光を生体部位に向けて発光し、検出部14に備えられた受光素子400により受光した測定部位の反射光のアナログ信号を、アナログ・フロント・エンド回路14cに送る。また、検出部14は、測定制御部14aによって体動検知電極制御回路14eを制御し、検出部14に備えられた発光素子500又は受光素子400を構成する電極のうち少なくとも一つの電極(体動検知電極)に電流を流し、当該体動検知電極により検知した体動のアナログ信号を、アナログ・フロント・エンド回路14cに送る。そして、前記反射光及び体動のアナログ信号を元に、ノイズ除去や信号増幅を行い、ADコンバーター14dに入力するための電圧信号に整えた後、ADコンバーター14dによってデジタルデータに変換する。
まず、制御部11は、発光素子500及び受光素子400を駆動させて、脈波(PPG)を測定する(ステップS1、図11の(a)工程参照。)。すなわち、発光素子500から生体内に照射された光が生体内で反射することで受光素子400に入射することで脈波データを得る。
また、発光素子500及び受光素子400を駆動させて脈波データを得た後、受光素子400のみを駆動させる。これにより、発光素子500は駆動させていないため、外光による光のみを受光素子400で受光し測定する(図11の(b)工程参照。)。
なお、図11の(a)工程及び(b)工程の間や、(b)工程及び(c)工程の間は、過渡現象による充放電の影響を受けないための期間とする。
具体的には、前記した図11の(a)工程で得た脈波データから、図11の(b)工程で得た外光による光のみを受光素子で受光して得た外光データを差し引く処理を行う(外光除去処理)。さらに、バンドパスフィルターや移動平均フィルターなどの画像処理フィルターを用いて、電気的なノイズを除去する平滑化処理や、光学式で得た脈波データと、静電容量式で得た体動データの信号強度を揃える処理などの前処理を行う。このようにして前処理された脈波データから体動データの差分を取る処理を行う。これにより、体動データを除去した正確な脈波データが得られる。
そして、PIが0.5%以上であるか否かを判定し(ステップS6)、0.5%未満である場合には(ステップS6;NO)、エラー表示を行い、PPG測定を再度行い(ステップS1)、0.5%以上である場合には(ステップS6;YES)、正常であると判定し測定を終了する。
情報処理装置3は、生体情報測定装置1から送信されたバイタルデータの解析を行うことの可能な装置である。情報処理装置3としては、例えば、スマートフォンやタブレット、PC(Personal Computer)等が適用可能であるが、特に限定されない。
具体的には、制御部31は、生体情報測定装置1において、発光素子500から発せられる光に基づいて得られたバイタルデータを解析する処理を行う。
例えば、記録部33には、生体情報測定装置1から出力されたバイタルデータが記録されている。
発光素子として有機EL素子「A9F4C0A(コニカミノルタ社製)」を用い、受光素子としてシリコンフォトダイオード「KPD30S(京都セミコンダクタ社製)」を用い、「Arduino uno R3」に前記有機EL素子の陽極を体動検知電極として接続し、弾性誘電体層としてシリコン樹脂を使用した、図2に示す構成の反射型光電容積脈波センサーを準備した。体動検知電極(有機EL素子の陽極)の平面視における面積は15.25mm×15.6mmであった。
測定部位は、手首位置(橈骨動脈位置)とし、発光素子は発光させずに、体動検知電極に電流を流して、下記の条件(1)~(6)で静電容量を測定し、その結果を図14に示した。なお、静電容量値は自動的に任意の信号強度に自動変換して表示される。また、図13は、体動検知電極及び基材を示した平断面図である。
条件(2):体動検知電極の前記面積のうち1/4倍の面積部分(図13参照)に相当する弾性誘電体層を測定部位に接触、加圧なし
条件(3):体動検知電極の前記面積のうち1/2倍の面積部分(図13参照)に相当する弾性誘電体層を測定部位に接触、加圧なし
条件(4):体動検知電極の前記面積と同等(1倍)の面積部分(図13参照)に相当する弾性誘電体層を測定部位に接触、加圧なし
条件(5):体動検知電極の前記面積と同等(1倍)の面積部分(図13参照)に相当する弾性誘電体層を測定部位に接触、手首を反った状態とする。
条件(6):体動検知電極の前記面積と同等(1倍)の面積部分(図13参照)に相当する弾性誘電体層を測定部位に接触、手首を反り、指で外圧を加えた状態とする。
実施例1で使用した反射型光電容積脈波センサーを準備した。
測定部位は、手首位置(橈骨動脈位置)とし、前記反射型光電容積脈波センサーを用いて手首をまっすぐに置いた状態と手首を反った状態を交互に繰り返したときの脈波を測定した。その結果を図15に示した。なお、図15Bは図15Aのb部分、図15Cは図15Aのc部分の詳細を示している。
このように発光素子又は受光素子を構成する電極のうち少なくとも一つの電極を、体動を検知する電極として併用することにより、部品点数が少なく、コストを低減でき、より正確に体動及び脈波を検出することができる。
14 検出部
40 受光部
40a 受光機能層
42 陽極
46 陰極
50 発光部
50a 発光機能層
52 陰極
58 陽極
100A 反射型光電容積脈波センサー
100B 透過型光電容積脈波センサー
400 受光素子
500 発光素子
600 弾性誘電体層
700 筐体
D 動脈
E 生体
d 弾性誘電体層の厚さ
S 接触面積
Claims (8)
- 発光素子と受光素子を備えた光電容積脈波センサーであって、
前記発光素子又は前記受光素子を構成する電極が面電極であり、これらの前記電極のうち少なくとも一つの電極を、体動を検知する電極として併用する光電容積脈波センサー。 - 生体に照射された光が、生体内を透過又は生体内で反射することで前記受光素子に入射して、光電変換されることで脈波を検知できる請求項1に記載の光電容積脈波センサー。
- 前記光電容積脈波センサーを生体の測定部位に装着したとき、当該測定部位に接触する光透過性の弾性誘電体層を、前記体動を検知する前記電極の表面に設けた請求項1又は請求項2に記載の光電容積脈波センサー。
- 請求項1から請求項3までのいずれか一項に記載の光電容積脈波センサーを用いた脈波の検出方法であって、
前記発光素子又は前記受光素子を構成する電極を面電極とし、これらの前記電極のうち少なくとも一つの電極を併用して体動も検知し、
前記光電容積脈波センサーを用いて得られる脈波データと、体動データをそれぞれ最適化して差分を取る脈波の検出方法。 - 前記受光素子によって検出された光の吸光度に対応する信号における拍動成分をACとし、非拍動成分をDCとしたとき、下記式(1)で表される灌流指標(PI)が、0.5%未満のときはエラー表示をし、0.5%以上のときは正常であると判定し測定する請求項4に記載の脈波の検出方法。
式(1):PI(%)=AC/DC×100 - 前記光電容積脈波センサーを生体の測定部位に装着したとき、当該測定部位に接触する光透過性の弾性誘電体層を、前記体動を検知する電極の表面に設けて、脈波と体動を検知する請求項4又は請求項5に記載の脈波の検出方法。
- 平面視したときに、前記測定部位に接触する前記弾性誘電体層の接触面積のうち、前記体動を検知する前記電極と重なる箇所の接触面積を、200mm2以上とする請求項6に記載の脈波の検出方法。
- 前記光電容積脈波センサーを装着した生体の測定部位に加わる圧力を、0.02N/cm2以上とする請求項4から請求項7までのいずれか一項に記載の脈波の検出方法。
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JP2010264126A (ja) * | 2009-05-15 | 2010-11-25 | Konica Minolta Sensing Inc | 生体情報測定装置 |
JP2013000157A (ja) * | 2011-06-13 | 2013-01-07 | Seiko Epson Corp | 生体センサーおよび生体情報検出装置 |
WO2015129843A1 (ja) * | 2014-02-27 | 2015-09-03 | 京セラ株式会社 | センサ,センサ装置およびセンサ装置の駆動方法 |
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