JP2009106373A - Sensing apparatus for biological surface tissue - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure the S-N ratio of measurement signals with safe near infrared rays of low energy density, while miniaturizing and reducing the cost for the sensing apparatus. <P>SOLUTION: The sensing apparatus includes a light emitting means 22 for emitting light to irradiate biological surface tissue, and a light receiving means 23 for receiving diffused reflection light from the biological surface tissue. The light receiving means 23 is layered on the light emitting means 22 disposed on a board 24, and a reflector 27 for reflecting the light output from a side face of the light emitting means 22, which is an end face light emitting type light emitting diode, in the right-angled direction is disposed on a side of the light emitting means. The distance for receiving/emitting light, appropriate for securing the selectivity in the direction of depth of the skin, can be obtained between the reflector and the light receiving means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is directed to qualitative / quantitative analysis of biological components and properties, in particular, to measure the blood glucose level of a living body using a change in the glucose concentration of the skin tissue as a substitute characteristic. The present invention relates to a sensing device for living body surface tissue that performs irradiation with near-infrared light and reception of diffusely reflected light from the living body surface tissue.

  A technique represented by near-infrared spectroscopy that qualitatively and quantitatively analyzes biological tissue from signals and spectra obtained by irradiating the biological surface tissue with near-infrared light and receiving diffusely reflected light within the biological surface tissue. In addition to being able to obtain various in-vivo areas in a non-invasive manner on the spot and without the need for reagents, it has been attracting attention in many applications in the medical field. Is widely used.

  Japanese Unexamined Patent Publication No. 2006-87913 (Patent Document 3) discloses a method for estimating blood glucose level by spectroscopic analysis using a glucose specific absorption wavelength in the near infrared region. FIG. 6 shows an example corresponding to this method. Near-infrared light emitted from the halogen lamp 1 enters the living tissue 6 through the heat shielding plate 2, the pinhole 3, the lens 4, and the optical fiber bundle 5. Is done. One end of the measurement optical fiber 7 and one end of the reference optical fiber 8 are connected to the optical fiber bundle 5, and the other end of the measurement optical fiber 7 is connected to the measurement probe 9. The other end is connected to the reference probe 10. Furthermore, the measurement probe 9 and the reference probe 10 are connected to the measurement-side emitter 11 and the reference-side emitter 12 via optical fibers, respectively.

  When the near-infrared spectrum measurement is performed by bringing the tip surface of the measurement probe 9 into contact with the surface of the living tissue 6 such as the forearm of the human body at a predetermined pressure, the near-infrared light incident on the optical fiber bundle 5 from the light source 1 is measured. As shown in FIG. 6 (b), the surface of the living tissue 6 is irradiated from 12 optical fibers 20 arranged concentrically on the distal end surface of the measurement probe 9, as shown in FIG. . The measurement light applied to the living tissue 6 is diffusely reflected in the living tissue, and then a part of the measurement light is received by the light receiving side optical fiber 19 located at the center of the optical fiber 20. After being incident on the diffraction grating 14 through the lens 13 and separated, it is detected by the light receiving element 15.

  The optical signal detected by the light receiving element 15 is AD converted by the A / D converter 16 and then input to the arithmetic unit 17 such as a personal computer. The blood glucose level is calculated by analyzing the spectrum data thus obtained.

  In the reference measurement, light reflected from the reference plate 18 such as a ceramic plate is measured, and this is used as reference light. That is, near-infrared light incident on the optical fiber bundle 5 from the light source 1 is applied to the surface of the reference plate 18 from the tip of the reference probe 10 through the reference optical fiber 8. The reflected light of the light irradiated on the reference plate is emitted from the reference-side emitting body 12 through the light receiving optical fiber 19 disposed at the tip of the reference probe 10. A shutter 22 is disposed between the measurement-side emitting body 11 and the lens 13 and between the refanless-side emitting body 12 and the lens 13, respectively. One of the light from the refanless side emitter 12 selectively passes. The distance L from the 12 light-emitting side optical fibers 20 arranged on the circle on the end face of the measurement probe 9 to the one light-receiving side optical fiber 19 located at the center is 0.65 mm.

  Here, the reason why the optical fiber is disposed at the distance L (0.65 mm) is to selectively measure the spectrum of the dermis part from the skin tissue having a layered structure of epidermis, dermis, and subcutaneous tissue, When the light-emitting side optical fiber 20 and the light-receiving side optical fiber 19 incident optical fiber are arranged at the above interval, the near-infrared light irradiated from the light-emitting side optical fiber 20 is diffusely reflected in the skin tissue and received light-side optical fiber 19. , The propagation path takes a path called “banana shape” and propagates around the dermis part, so that an absorption signal with a good S / N ratio can be obtained.

  As described above, with regard to blood glucose measurement technology using near infrared light having a wavelength of 1100 to 2500 nm, there has been a case in which a signal is measured by using a halogen lamp as a light source and introducing near infrared light to a living body via an optical fiber. Many. By using an optical fiber, it is possible to avoid physical problems such as burns by securing a physical distance between the halogen lamp light source that is heated and the living body, and by taking advantage of the flexible characteristics of the optical fiber, This is because the biological signal can be measured under free conditions. However, if many optical fibers and lens systems are interposed between the light source and the living body (skin tissue), the optical loss increases accordingly, resulting in the consumption of the light source. The power and device size will be large. In addition, since the radius of the optical fiber that can be bent cannot be made very small, there is a limitation in handling.

  Similarly, for the light receiving system, it is necessary to increase the light receiving sensitivity due to optical loss. For example, in the case of light receiving elements such as indium, gallium, and arsenic, cool the element to lower the dark current (dark noise). The necessity to use has arisen, and this becomes the factor of the enlargement of a light receiving unit and the increase in power consumption. In addition, when a halogen lamp is used as a light source as described above, a large power supply capacity is required, and thus a large-sized device configuration is inevitably used, and it is assumed that the blood glucose trend is continuously monitored. Can not.

On the other hand, if a semiconductor element such as a light emitting diode or a diode laser is used as the light emitting means, the amount of heat generated is not large, so the temperature does not rise, and the light emitting means can be placed in the immediate vicinity of the living body. Both can build a measurement system. In addition, it is possible to reduce the size to the size of a wristwatch, and the use expands in terms of blood glucose level management.
JP 2006-87913 A

  The present invention has been made in view of the above points, and can reduce the size and cost of the living body and can secure the SN ratio of the measurement signal with near-infrared light having a low energy density that is safe for the living body. It is an object to provide a sensing device for surface tissue.

  In order to solve the above problems, a sensing device for living body surface tissue according to the present invention comprises a light emitting means for irradiating light to irradiate the living body surface tissue and a light receiving means for receiving diffusely reflected light from the living body surface tissue. A tissue sensing device, wherein a light receiving means is stacked on the light emitting means arranged on a substrate, and light output from a side surface of the light emitting means, which is an end face light emitting type light emitting diode, is perpendicular to the light emitting means. It is characterized in that a reflecting plate for reflecting light is disposed on the side of the light emitting means.

  Skin tissue is generally composed of three layers of epidermis, dermis, and subcutaneous tissue. From the viewpoint of blood glucose measurement, epidermal tissue is composed of capillaries in the tissue. Therefore, even if the glucose concentration in the blood fluctuates, the glucose concentration in the epidermal tissue does not follow. In addition, although the subcutaneous tissue has developed blood vessels, it is mainly composed of adipose tissue and is not suitable as a tissue for measuring a water-soluble glucose signal. On the other hand, dermal tissue develops capillaries in order to supply nutrients for creating cells in the basal layer of the epidermis from the blood, and active physiological activities are performed, and biological components such as glucose are tissue Since it has high permeability in the skin, it can be estimated that the glucose concentration in the tissue of the dermis changes following the blood glucose level in the same manner as the interstitial fluid (ISF).

  Therefore, accurate information on blood glucose level can be expected by avoiding information from epidermal tissue and subcutaneous tissue and selectively obtaining information on glucose concentration from dermal tissue. By setting the interval between 0.2 mm and 2 mm (more preferably 0.35 mm or more and 0.8 mm or less), selectivity for the dermis tissue in the depth direction of the skin can be ensured.

  Here, the light receiving / emitting interval is preferably 0.2 mm to 2 mm as described above. However, even if a semiconductor element is used as both the light receiving means and the light emitting means, the light receiving / emitting interval is arranged at the light receiving / emitting interval as long as the outer dimensions are large. It may be difficult to do this, and a light-receiving element and a light-emitting element having external dimensions that match the light receiving and emitting intervals may have to be prepared.

  On the other hand, in the present invention, an edge-emitting light emitting diode is used as the light emitting means, and the light output from the side surface of the light emitting means is reflected at right angles by the reflecting plate, and the light receiving means is laminated on the light emitting means. Since the diffuse reflected light from the living body can be received, the limit of the element size for setting the light receiving / emitting interval to the above distance is reduced, and a preferable light receiving / emitting interval can be easily obtained. .

  As the light receiving means, a surface incident type light receiving element can be suitably used, but the light receiving means is not limited to this, and any light emitting diode may be used as long as it is stacked on the light emitting diode.

  In addition, it is preferable that the light receiving means is arranged away from the sensing surface to be brought into contact with the surface of the living tissue so that the light receiving means is less susceptible to the influence of heat from the living body in terms of preventing the SN ratio from being lowered.

  As the reflection plate, a rectangular or circular outer shape can be suitably used. In particular, in the case of a circular shape, the light receiving and emitting intervals can be made substantially equal in all directions, which is effective in improving measurement accuracy. At this time, if the light receiving means uses a light receiving element having a circular light receiving surface. Further preferable results can be obtained.

  As the light emitting means, a stack of a plurality of edge-emitting light emitting diodes may be used. Since the amount of light can be increased, the SN ratio can be improved. When using a plurality of light emitting diodes, it is possible to perform measurement at a plurality of wavelengths by using light emitting diodes having different emission wavelengths and simultaneously shifting the light emission timing.

  6. The light emitting device according to claim 1, wherein the light emitting device and the light receiving device are both square-shaped, and the light receiving device is laminated so that the direction of the corner is aligned with the direction of the corner of the light emitting device. You may arrange | position four light emission means which each laminated | stacked the said light-receiving means in the shape of a rice field. The amount of light can be increased and the number of wavelengths can be increased, and the influence of non-uniform light paths in the living tissue can be reduced.

  If the light emitting means and the light receiving means are connected to the substrate by a three-dimensional wiring, it is advantageous for miniaturization as compared to wiring using bonding wires.

  According to the present invention, in keeping the distance between the light emitting means and the light receiving means within a preferable range in terms of selectivity with respect to the depth direction of the skin tissue, it depends on the size of the element used for the light emitting means and the light receiving means. The limitation can be reduced, and for this purpose, it is advantageous to accurately perform the intended measurement. Moreover, since the light emitting means is a light emitting diode, it is possible to configure the sensing part of the apparatus with a size of about several millimeters, and it does not require a large power source capacity as in the case of using a halogen lamp as a light source. Therefore, it can be combined into a size like a wristwatch, can easily cope with non-invasive continuous measurement of biological information such as blood glucose level, and is medical in terms of application to blood glucose level management. The above advantages are extremely large.

  Hereinafter, the present invention will be described based on an embodiment shown in the accompanying drawings. A living body tissue sensing device according to the present invention targets a skin tissue, in particular, a dermis layer, and substitutes for a glucose concentration change in the dermis tissue. As a non-invasive measurement of blood glucose level, and by selectively transmitting near-infrared light to the dermal tissue to detect changes in the scattering coefficient associated with changes in glucose concentration as a signal and to estimate blood glucose level An example configured for this purpose is shown in FIG.

  In the figure, reference numeral 24 denotes a substrate, on which a light emitting diode 22 as a light emitting and emitting means is mounted, and a light receiving element 23 such as a photodiode is laminated on the light emitting diode 22 as a light receiving means. . Further, an outer wall 26 is erected on the peripheral portion of the substrate 24, and a cover glass transparent in the near infrared band constituting the sensing surface 25 is provided.

  Here, the light emitting diode 22 is of an end surface light emitting type in which a PN junction portion serving as a light emitting portion is provided around the entire end surface portion and emits light toward the side, and the light receiving element 23 stacked on the light emitting diode 22 has a surface. Incident type. A reflecting plate 27 is disposed around the light emitting diode 22. A reflection plate 27 having a reflection surface forming an angle of 45 ° with respect to the substrate 24 and directing the reflection surface toward the light emitting diode 22 side senses light output from the side surface of the end surface light emitting diode 22. The light is reflected toward the surface 25 and projected onto the living body tissue that is in contact with the sensing surface 25.

  The light emitting diode 22 emits near-infrared light having a center wavelength of 1300 nm, has a height and width height of 0.6 mm × 0.6 mm × 0.25 mm, and a thickness of the PN junction of about 0.05 mm. The light receiving element 23 has a height and width height of 0.3 mm × 0.3 mm × 0.2 mm and a light receiving surface of 0.2 mm square. In addition, the light emitting diode 22 is not limited to the said wavelength, What is necessary is just to light-emit the light of a 1000-2500 nm near-infrared wavelength range.

  The light receiving element 23 may be in a position in contact with the inner surface side of the sensing surface 25 (cover glass), but here, in order to avoid being affected by the thermal effect of the living body via the sensing surface 25, the sensing surface. It is about 0.1 to 1 mm away from 25.

  The reflection plate 27 has a reflective surface formed by vapor-depositing a metal film that reflects near infrared rays on the surface of a resin material having a triangular cross section. In order to provide a distance from the element 23, the light emitting diode 22 is arranged on the outer periphery of the light emitting diode 22 at a position that satisfies the condition of the light emitting / receiving interval.

  1 uses a reflector 27 having a rectangular outer shape parallel to each side surface of the edge-emitting light emitting diode 22 having a square planar shape, as shown in FIG. Alternatively, a reflecting plate 27 having a circular outer shape may be used, and this can reduce variations in the light receiving and emitting intervals. Moreover, although the reflecting surface of the reflecting plate 27 is a flat surface, it may be a curved surface.

  FIG. 3 shows another example. In this example, two edge-emitting light emitting diodes 22 are stacked on a substrate 24, and a light receiving element 23 is further disposed thereon. Of course, the reflecting plate 27 can reflect both the light emitted from the side surfaces of the light emitting diodes 22 and 22. The light quantity can be increased by causing the plurality of light emitting diodes 22 and 22 to emit light having the same wavelength. In addition, both may emit light of different wavelengths, and in this case, measurement with different wavelengths can be performed by shifting the light emission timings of the light emitting diodes 22 and 22. In any case, since the light receiving / emitting interval is determined by the interval between the reflecting plate 27 and the light receiving element 23, increasing the number of the light emitting diodes 22 does not affect the light receiving / emitting interval.

  FIG. 4 shows another example. In this example, four edge-emitting light-emitting diodes 22 each having a light-receiving element 23 laminated on the upper surface are mounted on the substrate 1 in a square shape, and a reflector 27 surrounds the light-emitting diodes 22 group. Are arranged as follows. Also in this case, the wavelength of the light output from each light emitting diode 22 may be the same or different.

  FIG. 5 shows an example in which the wiring 29 between the light emitting diode 22 and the light receiving element 23 and the substrate 24 is a three-dimensional wiring. Incidentally, the wiring 29 on the sensing surface 25 (cover glass) side is made of an electric circuit pattern formed on the inner surface of the cover glass, and the wiring from the cover glass to the light emitting diode 22 and the light receiving element 23 may be a wire, but it is conductive. It is good to carry out by interposing resin.

1 illustrates an example of an embodiment of the present invention, where (a) is a cross-sectional view and (b) is a plan view. It is a top view of other examples. Furthermore, it is sectional drawing of another example. It is a top view of another example. It is sectional drawing of another example. 1 shows a conventional example, in which (a) is a schematic diagram of a system configuration, and (b) is a schematic diagram of a probe configuration thereof.

Explanation of symbols

22 Light emitting diode 23 Light receiving element 24 Substrate 27 Reflector

Claims (7)

A sensing device for living body surface tissue comprising a light emitting means for irradiating light to irradiate a living body surface tissue, and a light receiving means for receiving diffusely reflected light from the living body surface tissue,
A light receiving means is disposed on the light emitting means arranged on the substrate, and a reflecting plate for reflecting light output from the side surface of the light emitting means, which is an end face light emitting diode, in a right angle direction is a light emitting means. A living body surface tissue sensing device, characterized by being arranged on the side of the body.   2. The living body surface tissue sensing device according to claim 1, wherein the light receiving means is a surface incident type light receiving element.   The living body surface tissue sensing device according to claim 1, wherein the light receiving means is disposed apart from a sensing surface to be brought into contact with the surface of the living tissue.   The living body surface tissue sensing device according to any one of claims 1 to 3, wherein the reflecting plate has a quadrangular or circular outer shape.   The living body surface tissue sensing device according to any one of claims 1 to 4, wherein the light emitting means is formed by laminating a plurality of edge-emitting light emitting diodes.   The living body surface tissue sensing device according to any one of claims 1 to 5, wherein four light emitting means each having the light receiving means stacked thereon are arranged in a square shape.   The living body surface tissue sensing device according to any one of claims 1 to 6, wherein the light emitting means and the light receiving means are connected to the substrate by a three-dimensional wiring.

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