JP2012254194A - Biosensor and biological information detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a faint optic element with high accuracy by a biosensor provided with a light emitting element 24 and a light receiving element 26.SOLUTION: The biosensor includes a board 22 that has optical transparency, the light emitting element 24 that irradiates a subject with a light through the board 22, and the light receiving element 26 that receives the light from the subject through the board 22 and outputs a signal corresponding to the received light. The board 22 has anti-reflectiveness on an opposite surface to the light emitting element 24 and the light receiving element 26. To impart the anti-reflectiveness, the biosensor may have a structure in which an anti-reflection film 30, for example, is stuck on the opposite surface of the board 22.

Description

  The present invention relates to a technique for detecting biological information such as pulse wave number and oxygen saturation.

  In recent years, there has been known a biological sensor that emits light to a living body by a light emitting element, receives light reflecting biological information such as a pulse rate and oxygen saturation by a light receiving element, converts the light into an electric signal, and outputs the electric signal ( For example, see Patent Document 1). Since the light emitting element and the light receiving element that constitute the biosensor are physically different elements, they must be arranged in a state of being separated from each other. If light from the light emitting element directly enters the light receiving element in this state, the directly incident light becomes noise with respect to light reflecting biological information. Therefore, a technique has been proposed in which a light shielding element is provided between the light emitting element and the light receiving element (see, for example, Patent Document 2).

JP 2009-231577 A JP 2007-202893 A

By the way, when providing a light-shielding object between the light emitting element and the light receiving element, a certain amount of space is required, which makes it difficult to reduce the size of the sensor.
The present invention has been made in view of the above-described problems, and one of its purposes is a biological sensor and a biological information detection device that can easily be miniaturized and can accurately detect a weak light component. Is to provide.

In order to solve the above problems, in the biosensor according to the present invention, a light-transmitting counter substrate, a light-emitting element that irradiates light to the subject via the counter substrate, and the subject A light receiving element that receives the light through the counter substrate and outputs a signal corresponding to the received light, and the opposing surface of the counter substrate that faces the light emitting element and the light receiving element is antireflective. It is characterized by having.
In the present invention, even if a light shielding element is not provided between the light emitting element and the light receiving element, the component of the light emitted from the light emitting element reflected by the counter substrate and incident on the light receiving element is reduced. Therefore, according to the present invention, since it is not necessary to provide a light blocking object, the size can be easily reduced correspondingly, and a weak light component can be detected with high accuracy.

  In the present invention, a configuration in which the antireflection film is attached to the facing surface is preferable. According to this configuration, a weak light component can be accurately detected with a simple configuration. Here, as the antireflection film, a thin film is formed on the film surface, a plurality of thin films made of a dielectric are laminated on the film surface, and adjacent dielectrics have different refractive indexes, What is uneven | corrugated toward the said light emitting element and a light receiving element is preferable.

  Moreover, in order to give the said opposing surface anti-reflective property, it is good also as a structure which processes the said opposing surface directly. For example, a thin film may be formed on the facing surface of the counter substrate, or a plurality of thin films made of dielectrics may be stacked on the facing surface, and adjacent dielectrics may have different refractive indexes. Alternatively, the facing surface may have a concavo-convex shape toward the light emitting element and the light receiving element.

On the other hand, in the present invention, the light emitting element and the light receiving element may be formed on a sensor substrate, and the sensor substrate and the counter substrate may be bonded to each other with a sealing material while maintaining a predetermined gap.
It should be noted that the present invention can also be conceptualized as a biological information detection apparatus having an arithmetic processing circuit that outputs biological information based on a signal output from such a biological sensor.

It is a figure showing a living body information detecting device containing a living body sensor concerning a 1st embodiment. It is principal part sectional drawing which shows the structure of a biometric information detection apparatus. It is a top view showing the living body sensor concerning a 1st embodiment. It is sectional drawing cut | disconnected by the Aa line in FIG. It is a figure which shows reflection of the light in an antireflection film. It is a figure which shows the emission / incident of the light in a biosensor. It is a figure which shows the structure at the time of making a reflection preventing film into a laminated body. It is a figure which shows the structure which affixed the antireflection film on the opposing surface of a board | substrate. It is a figure which shows the structure of the case where it shape | molds in an uneven | corrugated shape on the opposing surface of a board | substrate. It is a block diagram which shows the structure of a biometric information detection apparatus.

Hereinafter, a biosensor according to a first embodiment of the present invention will be described with reference to the drawings.
In each of the following drawings, the scales may be varied in order to make each part, particularly each layer, recognizable.

FIG. 1 is a diagram illustrating a biological information detection apparatus to which the biological sensor according to the first embodiment is applied. This biological information detection apparatus 1 detects and outputs, for example, a pulse rate as biological information of a subject.
As shown in FIG. 1, the housing 10 of the biological information detection device 1 has a shape imitating a wristwatch. One end and the other end of the wristband 12 wound around the left wrist of the subject are attached to portions facing each other across the center portion of the outer peripheral portion of the housing 10. As a result, the housing 10 is mounted with the back side in contact with the subject. Although omitted in FIG. 1, an arithmetic processing circuit described later executes various processes and outputs the processing results.

FIG. 2 is a cross-sectional view illustrating a configuration of a main part of the biological information detection apparatus 1. As shown in the drawing, the inside of the housing 10 has a shape having a hollow portion 15, and the biosensor 20 is attached to the hollow portion 15 on the side attached to the subject. The biosensor 20 includes substrates 21 and 22 and a light emitting element 24 and a light receiving element 26 formed on the substrate 21. Here, when the housing 10 is attached to the subject, the substrate 22 comes into contact with the back side of the housing 10.
The hollow portion 15 is also provided with the arithmetic processing circuit and the like described above, although not shown.

FIG. 3 is a plan view of the configuration of the biosensor 20 as viewed from the wearing side of the subject, and FIG. 4 is a cross-sectional view taken along line Aa in FIG.
As shown in these drawings, when the biosensor 20 is viewed in a plan view, the rectangular substrates 21 and 22 having substantially the same size are kept at a certain gap with the adhesive 28 applied along the periphery. It is the structure which stuck together.

As shown in FIG. 4, the substrate 21 is located on the back side (upper side in the figure) and the substrate 22 is located on the near side (lower side in the figure) when viewed from the side worn by the subject (wearing side). . A light emitting element 24 and a light receiving element 26 are formed on a surface of the substrate 21 facing the substrate 22 so as to be separated from each other. For this reason, the board | substrate 21 turns into a sensor board | substrate with which the light emitting element 24 and the light receiving element 26 were formed.
As shown in FIG. 3, the light emitting surface of the light emitting element 24 is substantially square as shown in FIG. 3. Similarly, the light receiving surface of the light receiving element 26 is also substantially square. The planar shapes of the substrates 21 and 22 are arbitrary, and the shape of the light emitting surface of the light emitting element 24 and the shape of the light receiving surface of the light receiving element 26 are also arbitrary.

The light emitting element 24 and the light receiving element 26 are formed, for example, by laminating various thin films on the opposing surface of the substrate 21. Specifically, when an organic light emitting diode is formed as the light emitting element 24, the reflective layer, the light-transmitting anode layer, the organic layer including the light emitting layer, the light transmitting property are sequentially formed starting from the substrate 21. In addition, a structure in which a reflective cathode layer is stacked may be used. In the light emitting element 24 having such a configuration, when a forward bias is applied from the anode to the cathode, holes injected from the anode side and electrons injected from the cathode side are combined in the light emitting layer, Light having a spectrum corresponding to the material of the light emitting layer is generated. Since this light is emitted to the subject through the substrate 22 on the opposite side of the substrate 21 on which the light is formed, the light emitting element 24 has a so-called top emission structure.
For this reason, the substrate 22 is made of light-transmitting glass or the like. Here, the light transmissive property means a property of transmitting a light component included in a wavelength band of light emitted from the light emitting element 24. On the other hand, the substrate 21 does not need optical transparency, but it is preferable that the substrates 21 and 22 are made of the same material from the viewpoint of uniform expansion coefficient when bonded to the substrate 22.

  On the other hand, when a light absorption type organic photodiode is formed as the light receiving element 26, for example, a reflective cathode layer, a light receiving layer, and a light transparent anode layer are stacked in this order starting from the substrate 21. What is necessary is just to make it the structure. In such a configuration, when light enters the light receiving layer through the substrate 22 from the mounting side, a pair of electrons and holes is generated. Here, when a bias is applied in the opposite direction between the cathode and the anode, electrons and holes are separated and moved, so that a current corresponding to the amount of incident light flows through the light receiving element 26.

  The sealing layer (material) 27 is provided so as to cover the light emitting element 24 and the light receiving element 26 in order to prevent the light emitting element 24 and the light receiving element 26 from being deteriorated by moisture or oxygen. The sealing layer 27 is configured so as to fill the space sandwiched between the substrates 21 and 22 in FIG. 4, and its main role is to prevent the light emitting element 24 and the light receiving element 26 from being deteriorated. . For this reason, the space sandwiched between the substrates 21 and 22 may be provided to cover the light emitting element 24 and the light receiving element 26, and the remaining space may be filled with air. However, in the direction from the light emitting element 24 toward the substrate 21, it is preferable that the number of interfaces that reflect light is smaller, and thus the filled configuration as described above is preferable.

On the other hand, the substrate 22 as the counter substrate is provided mainly for improving the adhesion with the wrist of the subject. An antireflection film 29 is provided on the surface of the substrate 22 facing the substrate 21. The antireflection film 29 is formed by forming a single-layer thin film made of an inorganic compound such as magnesium fluoride (MgF ₂ ) or silicon dioxide (SiO ₂ ) on the opposite surface of the substrate 22 by vapor deposition or sputtering. .

FIG. 5 is a diagram showing a configuration in the vicinity of the antireflection film 29 attached to the substrate 22.
Light is emitted from the light emitting element 24 downward in the figure. Of the light emitted from the light emitting element 24, the wavelength of the light S incident obliquely on the opposing surface of the substrate 21 is λ. Further, the refractive index of the sealing layer 27 (or air) on the incident side is n _1, and the refractive index of the substrate 22 is n ₃ .
Further, when the thickness of the thin film in the antireflection film 29 is d and the refractive index is n ₂ , the phase condition represented by the following formula (1) and the amplitude condition represented by the formula (2) are respectively satisfied. The thin film is formed.
d = (1/4) × (λ / n ₂ ) (1)
n ₂ = (n ₁ × n ₃ ) ^1/2 (2)

  The light S from the light emitting element 24 is converted into light R1 reflected on the surface of the antireflection film 29 and light R2 that has passed through the antireflection film 29 and reflected on the back surface (interface between the antireflection film 29 and the substrate 22). Divided. When the antireflection film 29 is formed so as to satisfy the expressions (1) and (2), the light R1 and the light R2 cancel each other because they have a phase inversion relationship in which the phases are shifted by 180 degrees. For this reason, as shown in FIG. 6, in the present embodiment, the component of the light emitted from the light emitting element 24 that is reflected by the substrate 22 and goes directly to the light receiving element 26 can be reduced.

  On the other hand, in FIG. 6, among the light emitted from the light emitting element 24, light that has passed through the sealing layer 27, the antireflection film 29, and the substrate 22 in order enters the subject's skin. The light that has entered the skin reaches a blood vessel (not shown) and is absorbed and reflected by blood flowing through the blood vessel or passes through the blood. The light reflected by the blood flowing in the blood vessel enters the light receiving element 26 through the substrate 22, the antireflection film 29 and the sealing layer 27 in this order. For this reason, the light receiving element 26 outputs a current corresponding to the amount of incident light. Since the blood vessels of the subject repeat expansion and contraction in the same cycle as the heartbeat, the amount of reflected light increases and decreases in the same cycle as the blood vessel expansion and contraction cycle. Accordingly, a change in the current output from the light receiving element 26 indicates a change in the volume of the blood vessel.

Here, the light component reflected by the blood vessel, that is, the light component reflecting the biological information is weak with respect to the emitted light. For this reason, the light component other than the light reflected by the blood vessel is nothing other than noise for the light receiving element 26.
When the opposing surface of the substrate 22 is not provided with antireflection properties, the light emitted from the light emitting element 24 is reflected by the opposing surface of the substrate 22 and is directed directly to the light receiving element 26. And a weak light component reflecting biological information cannot be detected with high accuracy.
On the other hand, in the present embodiment, since the antireflection film 29 formed on the opposite surface of the substrate 22 provides antireflection properties, the component reflected by the substrate 22 and directed directly to the light receiving element 26 is greatly increased. Reduced. Therefore, according to this embodiment, noise components are reduced, and accordingly, a weak light component reflecting biological information can be detected with high accuracy.

  In the present embodiment, since there is no need to provide a light shielding material as described in the background art between the light emitting element 24 and the light receiving element 26, the production yield of the biosensor 20 can be reduced by providing the light shielding material. In addition to avoiding an increase in cost, the structure is simplified, which makes it easy to reduce the size and thickness.

The antireflection film 29 formed on the opposing surface of the substrate 22 is not limited to a single-layer thin film, and may be a laminate of a plurality of thin films. When the antireflection film 29 is formed of such a laminated body, the reflectance can be reduced with respect to a wider band of wavelengths as compared with a single-layer thin film.
For example, when the reflectance of light in the visible light region having a wavelength of 350 nm to 750 nm is reduced, as shown in FIG. 7, relatively high refractive index dielectric films 291, 293, 295, The low refractive index dielectric films 292, 294, and 296 may be a laminated body in which a total of six layers are alternately laminated.

Further, the opposing surface itself of the substrate 22 may be a structure having an effect equivalent to that of the antireflection film 29. For example, as shown in FIG. 9A, the substrate 22 is made of a light-transmitting resin such as plastic, and a fine concavo-convex shape 297 is integrally formed on the surface of the opposing surface at intervals equal to or less than the wavelength of light. Thus, a structure in which the refractive index of light changes in accordance with the thickness direction of the substrate 22 (moth eye structure) may be used.
Specifically, in this structure, since the proportion of the light-transmitting resin is substantially zero at the convex apex, the sealing layer 27 (or air if the sealing layer 27 is not filled) On the other hand, in the concave valley, the ratio of the sealing layer 27 (or air) is almost zero, so that the refractive index of the resin material constituting the substrate 22 is equal. Note that, at the intermediate point between the convex apex and the concave trough, the ratio of the light-transmitting resin is determined according to the height of the intermediate point, and therefore the refractive index is in accordance with the ratio.
Therefore, in such a structure, the refractive index of light ranges from the refractive index of the sealing layer 27 (air) at the apex of the convex shape to the refractive index of the resin material at the concave valley portion in the thickness direction of the substrate 22. Therefore, it changes continuously. For this reason, the antireflection property superior to the laminated body of the thin film of multiple layers can be expected.

  Next, the biosensor according to the second embodiment will be described. In the first embodiment, one or a plurality of layers of thin films are formed on the substrate 22 or the surface of the substrate 22 is molded to provide antireflection properties to the facing surface. In the second embodiment, the same applies. An antireflection film having a good antireflection property is applied to the opposite surface of the substrate 22.

Moreover, FIG. 8 is a figure which shows the principal part structure of the biosensor which concerns on 2nd Embodiment, and attaches the antireflection film 30 to the opposing surface of the board | substrate 22 through the adhesion layer (illustration omitted). . The antireflection film 30 is obtained by forming an antireflection film 29 made of a single-layer thin film on the surface of a film substrate 301 made of a light-transmitting plastic or the like.
Here, the refractive index n ₃ is replaced with the refractive index of the film substrate 301 in the above formula (2), and the antireflection film 29 of the antireflection film 30 is formed so as to satisfy the formulas (1) and (2). The As a result, the antireflection film 30 attached to the substrate 21 has antireflection properties equivalent to the configuration in which the antireflection film 29 is directly formed on the opposing surface of the substrate 22, so that the weak reflection reflecting biological information is applied. It is possible to accurately detect a light component.
In addition, in the second embodiment, it is only necessary to attach the antireflection film 30 without directly processing the facing surface of the substrate 22, so that a biosensor can be configured more simply.

In the antireflection film 30, a multilayered structure of a plurality of thin films similar to that shown in FIG. 7 may be formed on the surface of the film substrate 301 instead of a single-layer thin film. Thereby, a reflectance can be made small with respect to a wider band wavelength.
Further, as shown in FIG. 9B, an antireflection film 30 may be formed by forming a fine uneven shape 297 on the surface of the film substrate 301. According to this antireflection film 30, as described above, more excellent antireflection properties can be expected.

FIG. 10 is a block diagram showing an electrical configuration of the biological information detection apparatus 1. Note that this configuration is only briefly described.
In this figure, the drive circuit 40 drives the light emitting element 24 by supplying a current constantly or intermittently in accordance with an instruction from the arithmetic processing circuit 50. Here, it is preferable to drive the current intermittently in order to reduce power consumption. On the other hand, the conversion circuit 45 converts the current flowing through the light receiving element 26 into a voltage and converts the voltage into digital data at a predetermined sampling interval.

  When the light emitting element 24 is driven, the arithmetic processing circuit 50 processes the digital data converted by the conversion circuit 45. That is, when light from the light emitting element 24 is emitted, the signal received by the light receiving element 26 is processed. For example, the arithmetic processing circuit 50 calculates the pulse rate from the digital data, or records the pulse rate in association with the time measured by the internal timer. The information and data may be transferred to an external computer, displayed on a display unit (not shown), or output by speech synthesis.

The present invention can be variously applied and modified in addition to the above-described embodiments.
The light emitting element 24 and the light receiving element 26 may be configured such that the light emitting element 24 emits light toward the subject via the substrate 22, and the light receiving element 26 receives light from the subject via the substrate 22. For example, the arrangement and the number are arbitrary.
For example, a plurality of light emitting elements 24 and a plurality of light receiving elements 26 may be alternately arranged in a matrix. According to this configuration, since the area of the emitted light is widened by the plurality of light emitting elements 24 and the area of the incident light is widened by the plurality of light receiving elements 26, the light component reflecting the biological information can be more accurately obtained. Can be detected.
Further, the light emitting element 24 and the light receiving element 26 are not necessarily formed on the same surface with respect to the substrate 21 and may be formed on different surfaces. For example, the light emitting element 24 may be formed on the inner surface (upper surface in FIG. 4) of the substrate 21 when viewed from the mounting side, and a bottom emission structure in which light is emitted through the substrate 21 on which the light emitting element 24 is formed. Further, for example, the light emitting element 24 and the light receiving element 26 may be formed on different substrates positioned on the back side of the substrate 22 when viewed from the mounting side.

  In the embodiment, the measurement site of the subject is the left wrist, but the fingertip may be set as the measurement site by incorporating a biosensor in the cuff body, for example. In other words, the finger plethysmogram may be detected.

Although the biological sensor 20 has exemplified the configuration for detecting the pulse wave, it can also be applied to a sensor for detecting the oxygen saturation of arterial blood. The hemoglobin in blood has different absorbances for red light and infrared light depending on the presence or absence of binding to oxygen. Therefore, while preparing multiple sets of elements with different emission and reception wavelengths, such as elements that emit and receive red light and elements that emit and receive infrared light, measure the reflected light. The oxygen saturation can be detected by analysis.
The blood vessel may be an artery or a vein.
The biological information may be a blood vessel pattern of the living body, and can also be applied to an authentication device that authenticates the living body from this blood vessel pattern.
Of course, the measurement target is not limited to a human but may be an animal.

DESCRIPTION OF SYMBOLS 1 ... Biological information detection apparatus, 20 ... Biosensor, 21, 22 ... Board | substrate, 24 ... Light emitting element, 26 ... Light receiving element, 27 ... Sealing layer, 28 ... Adhesive material, 29 ... Antireflection film, 30 ... Antireflection film , 50... Arithmetic processing circuit, 291 to 296... Dielectric film, 297.

Claims (10)

A counter substrate having optical transparency;
A light emitting element that irradiates the subject with light through the counter substrate;
A light receiving element that receives light from the subject via the counter substrate and outputs a signal corresponding to the received light;
With
The biosensor according to claim 1, wherein a surface of the counter substrate facing the light emitting element and the light receiving element has antireflection properties. The biosensor according to claim 1, wherein the antireflection film is affixed to an opposing surface of the counter substrate. The antireflection film is
The biosensor according to claim 2, wherein a thin film is formed on the film surface. On the film surface, a plurality of thin films made of a dielectric are laminated,
The biological sensor according to claim 3, wherein the refractive indexes of adjacent dielectrics are different from each other. The antireflection film is
The biosensor according to claim 2, wherein the film surface has an uneven shape toward the light emitting element and the light receiving element. The biosensor according to claim 1, wherein a thin film is formed on an opposing surface of the counter substrate. A plurality of thin films made of a dielectric are laminated on the facing surface,
The living body sensor according to claim 6, wherein adjacent dielectrics have different refractive indexes. The biosensor according to claim 1, wherein the facing surface has a concavo-convex shape toward the light emitting element and the light receiving element. The light emitting element and the light receiving element are formed on a sensor substrate,
The biosensor according to any one of claims 1 to 8, wherein the sensor substrate and the counter substrate are bonded with a sealing material while maintaining a predetermined gap. The biological sensor according to any one of claims 1 to 9,
An arithmetic processing circuit that outputs biological information based on a signal output from the light receiving element;
A biological information detection device comprising:

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