JP4925278B2 - Optical biological information measuring method and apparatus - Google Patents

Description

  The present invention relates to an optical biological information measuring method and apparatus for measuring biological information such as blood component concentration using light such as near infrared light.

Near-infrared spectroscopy, which irradiates a substance with near-infrared light and analyzes it from the spectrum of transmitted or reflected light, has recently begun to be used in various fields including the agricultural field. It is attracting attention as an invasive and harmless analytical technique. This near-infrared spectroscopy does not damage the sample because it uses low-energy electromagnetic waves, and can be applied to samples in various states such as solids, powders, fibers, liquids, and gases. In comparison with infrared light, near-infrared light has a weaker water absorption intensity, so it has the advantage that analysis in aqueous solution is possible. Quantitative and qualitative analysis of biological information such as blood component concentration such as glucose It can be done non-invasively.

   However, when using near-infrared light, the absorption signal is very weak compared to infrared light in order to deal with harmonics, and the band assignment is not clear. In the near-infrared spectroscopic analysis, a technique called “chemometrics” is used for quantification and qualification. This is a method of performing chemical analysis using multivariate analysis methods and statistical analysis methods, and has evolved with the development of computers. In recent near infrared spectroscopy, multivariate analysis methods such as principal component regression analysis or PLS regression analysis are used. Often used.

  By the way, the skin tissue in the living tissue is composed of an epidermis having a thickness of about 100 μm, a dermis having a thickness of about 1 mm under the epidermis, and a subcutaneous tissue containing a large amount of fat cells in the lower layer. And, when trying to quantitatively and qualitatively analyze blood component concentrations such as glucose in biological information using near-infrared spectroscopy, the near-infrared light is selectively transmitted through the dermis or selectively diffusely reflected at the dermis. It is necessary to do.

  Here, Patent Document 1 (Japanese Patent Laid-Open No. 11-70101) discloses a light projection point for guiding near-infrared light to the skin tissue surface of a living body, and transmission or diffuse reflection inside the skin tissue to exit from the skin tissue surface. It is shown that light that is selectively diffusely reflected at the dermis is taken out by setting the distance from the light detection point for detecting near-infrared light to 2 mm or less. In this case, the light projection point and the light detection point must be configured to face the tip surface of the probe to be brought into contact with the skin tissue surface, and the contact pressure between the probe and the skin tissue surface can be appropriately managed. Without it, the variation in light intensity detected at the light detection point is large, and it is difficult to measure with high accuracy.

In addition , it is desirable from the viewpoint of ease of measurement that light only needs to be applied without contacting the skin tissue surface. In this case, the reflected light from the skin tissue surface is reflected by the dermis part in the skin tissue. The masked light is masked and the two cannot be separated, so that measurement cannot be performed on the dermis.
Japanese Patent Laid-Open No. 11-70101

  The present invention was invented in view of the above points, and provides an optical biological information measuring method and apparatus capable of measuring biological information from a desired portion in skin tissue simply and accurately. Is an issue.

  In order to solve the above problems, an optical biological information measuring method according to the present invention irradiates light on a surface tissue of a living body, receives reflected light from the surface tissue through a spectroscopic means, and performs biological information by spectroscopic analysis. In order to obtain the above, a linearly polarized light is used as a light to irradiate the surface tissue of the living body, and the reflected light is received through a polarizing plate having a variable polarization angle to obtain a spectrum distribution, and the polarization angles are different. Based on the spectral distribution, the depth of light reaching the surface tissue is analyzed, and the polarization angle of the polarizing plate is set according to the analysis result to receive light for spectroscopic analysis. ing. Based on spectral distributions with different polarization angles, the depth of light reaching the surface tissue is analyzed, and by performing spectroscopic analysis with the polarizing plate set at the appropriate polarization angle, the reflected light from the desired depth is derived. It measures biological information.

  When the target biological information is the glucose concentration in the blood component, the present invention can be suitably used, but the present invention can also be applied to other biological information.

  Moreover, as a part which irradiates light, the part inside a human hand, especially the inner side of a finger | toe, and between a 1st joint and a 2nd joint is preferable.

  In particular, it is preferable to irradiate light on the surface tissue surface of the living body from an oblique direction and to use s-polarized light as light to be irradiated on the surface tissue surface of the living body. Reflected light containing a large amount of information in the surface tissue can be obtained, and more accurate and stable biological information measurement can be performed.

  The optical biological information measuring apparatus according to the present invention includes a light irradiating unit that irradiates light on a surface tissue of a living body, a spectral light receiving unit that spectrally receives reflected light from the surface tissue, and biological information by spectroscopic analysis. An optical biological information measuring device comprising: a measuring means for measuring the light, wherein the light irradiating means irradiates linearly polarized light, and the spectral light receiving means comprises a polarizing plate having a variable polarization angle. In addition to analyzing the depth of arrival of the light to the surface tissue based on the spectral distribution with different polarization angles obtained from the light reception via the polarizing plate, Accordingly, the present invention is characterized in that an analysis means for setting or indicating the polarization angle of the polarizing plate for spectroscopic analysis is provided.

  As said light irradiation means, what irradiates s-polarized light with respect to the to-be-irradiated surface can be used suitably for the surface tissue surface of a living body.

  The optical biological information measuring method according to the present invention analyzes the depth of light reaching the surface tissue based on the spectral distributions having different polarization angles. From this analysis result, the reflected light (transmitted light) from an appropriate depth is analyzed. ), The biological information can be measured based on the reflected light from the desired depth. Moreover, the living body can be configured to be non-contact with the human body simply by irradiating light and receiving reflected light, and is not affected by contact pressure or the like.

  In the optical biological information measuring device according to the present invention, the measurement by the measurement method can be easily performed.

  Hereinafter, the present invention will be described based on an embodiment shown in the accompanying drawings. In FIG. 1, a light source 1 capable of irradiation time control, a polarizing plate 2 using light emitted from the light source 1 as linearly polarized light, and a polarizing plate Spectral light receiving means 4 for spectrally receiving and receiving reflected or transmitted light when the surface tissue surface of the human body 9 is irradiated with light that has been linearly polarized through 2 and disposed immediately in front of the spectral light receiving means 4 Polarizing angle control when rotating the polarizing plate 3 by the rotating stage 5 that rotates the polarizing plate 3, the rotating stage 5 that rotates the polarizing plate 3 around the optical axis by driving the motor, and the spectral distribution data obtained from the spectral light receiving means 4. Analysis means 6 for performing analysis on the basis of spectrum distribution data for each polarization angle composed of data, and biological information from the spectrum distribution data obtained from the spectral light receiving means 4 by a multivariate analysis technique, And a measuring means 7 for calculating the glucose concentration in blood For example.

  Since the measuring means 7 for calculating biological information by the multivariate analysis method is known as shown in the above publications, the use of polarized light and the analyzing means 6 will be described here.

  When light that has been linearly polarized by using the polarizing plate 2 is applied to the living body 9, for example, the belly of a finger at an incident angle of 45 °, and the reflected light having a reflection angle of 45 ° is received by the spectral light receiving means 4, the polarizing plate 3 is When the spectral distribution is observed by changing the polarization angle by rotating, the polarization angle is 0 ° (the polarization direction of the received reflected light is the same as the incident light) and the polarization angle is 90 ° (the polarization of the received reflected light). When the direction is orthogonal to the incident light), a difference was observed as shown in FIG.

  In the figure, α is a fat absorption peak, β is a water absorption peak, and γ is a protein absorption peak. The human skin tissue is composed of the epidermis, dermis and subcutaneous tissue as described above. The dermis is a layer rich in protein (collagen), the subcutaneous tissue is a layer rich in fat, and the light reflected by the epidermis is The polarization angle is 0 °.

  When the spectral distribution shown in FIG. 2 is observed based on this point, when the polarization angle is 90 °, the absorption by fat is increased compared to the case where the polarization angle is 0 °, and thus the fat-containing layer is transmitted. I understand that. In addition, since the light absorption by the protein increases when the polarization angle is 90 ° than when the polarization angle is 0 °, it can be seen that the reflected light having the polarization angle of 90 ° is transmitted more through the layer containing the protein. .

  Since the change in the polarization angle is caused by the scattering phenomenon and the polarization phenomenon by the biological tissue, the arrival depth of light with respect to the surface tissue is changed by the polarization angle. Based on such knowledge, the present invention receives the reflected light from the reflected light spectrum distribution in a state where the polarization angle is different by receiving the light through the polarizing plate 3 having a variable polarization angle. Analyzing means 6 for analyzing the depth of arrival is provided. Whether the depth of light reaches the epidermis is determined based on the change in absorbance due to fat and the change in absorbance due to protein due to the change in polarization angle. It analyzes whether it is a dermis part or a subcutaneous tissue, and outputs a polarization angle corresponding to the dermis part as an analysis result.

  The measuring means 7 receives the polarization angle output from the analyzing means 6 and rotates the rotating stage 5 so that the polarizing plate 3 has the polarization angle. In this state, the received light data for the spectral analysis of biological information. Thus, the calculation for obtaining the biological information as described above is performed.

  Therefore, in this optical biological information measuring apparatus, biological information can be obtained from a desired depth in the surface tissue (skin tissue) of the living body without bringing a member for measurement into contact with the living body. In obtaining biological information such as blood component concentration, more accurate information can be obtained.

  Here, as the light, it is effective to use light having a wavelength of 600 nm to 2000 nm in order to eliminate the influence of light absorption of oxyhemoglobin having a high absorbance around 400 nm and around 500 nm to 600 nm. It is.

  In addition, here, the polarization angle of the polarizing plate 3 at the time of spectroscopic analysis is automatically set by the output of the analysis means 6, but the polarization angle based on the analysis result of the analysis means 6 is displayed on the display unit, The person engaged in the measurement based on the display or the person to be measured may manually set the polarization angle of the polarizing plate 3.

  The measurement site to be irradiated with light is preferably the inner side (palm) of the hand having few skin grooves that cause irregular reflection on the skin surface, and particularly the first joint and the inner side of the human finger (abdomen). The part between the two joints is preferred. This is because when data was actually irradiated on each part of the human body and the reflected light was observed, the data obtained in the part between the joints had the highest stability.

  By the way, when irradiating an object with linearly polarized light from an oblique direction, the result varies depending on whether the polarization direction of the irradiated light is s-polarized light or p-polarized light with respect to the irradiated surface of the object. It is well known that, for this reason, edible ham is also used as sample 90 as shown in FIG. 4, and p-polarized light, s-polarized light, and Was incident at an incident angle of 45 °, and the reflected light was received by the spectroscopic / light receiving means 4 via the condenser lens 8 and the polarizing plate 3. Incidentally, the spectroscopic / light receiving means 4 used was composed of a transmissive quartz diffraction grating and a 512-pixel CCD element and capable of measuring in the wavelength range of 900 nm to 1700 nm. As the light source 1, a halogen lamp was used.

  The result of taking out and separating the parallel component and the vertical component by rotating the polarizing plate 3 and changing the polarization angle in the case where the light from the light source 1 is converted into p-polarized light by the polarizing plate 2 and in the case where the light is converted into s-polarized light. Are shown in FIGS. FIG. 5 shows the case of p-polarized light, FIG. 6 shows the case of s-polarized light. In the figure, “e” indicates that the light is received without passing through the polarizing plate 3, “f” indicates the case where the polarization angle is 0 °, The case of 90 ° orthogonal detection is shown, and H in the figure shows the case where the transmitted light transmitted through the sample 90 is received without passing through the polarizing plate 3.

  The absorption spectra of both polarized lights are similar when the sample 90 is transmitted (h in the figure) and close to the spectrum of water alone. In the orthogonal detection (G in the figure) of the reflection spectrum at the time of incidence of p-polarized light, the protein-related absorption and scattering are effective around 1500 to 1650 nm as shown in FIG. It can be seen that is not seen. On the other hand, in the case of s-polarized light incidence shown in FIG. 6, the spectrum is considerably different from that of p-polarized light, absorption close to the water spectrum is observed, and the same result as the transmitted light detection result (h) is obtained. ing.

  This indicates that there is reflection from a deeper position in the sample 90 in the case of s-polarized light than in the case of p-polarized light. Therefore, in the case of s-polarized light, information inside the sample 90 is more than in the case of p-polarized light. As can be seen from FIG. 6, the water component becomes more prominent by capturing the diffused light of the incident and vertical components.

  On the other hand, FIG. 7 shows the result of measuring the spectrum of reflected light by irradiating the palm of the human body with s-polarized light and changing the polarization angle from 0 ° (deg0 in the figure) to 90 ° (deg90 in the figure) every 10 °. Is shown. It can be seen that the profile becomes sharper as it approaches the orthogonal deg 90. In particular, at 80 ° (deg 80) and 90 ° (deg 90), the water spectrum at 970 nm and the spectrum of the carbon compound of the living organism near 1200 nm are prominent. From this, it is possible to accurately measure the light absorbed by the tissue in the skin by using s-polarized light which is polarized in the direction parallel to the layers in the skin structure. The estimation accuracy of is improved.

It is a block diagram of an example of an embodiment of the invention. It is explanatory drawing of an example of the data about a polarization angle and an absorbance. It is explanatory drawing of the data of the light absorbency of oxyhemoglobin. It is a schematic perspective view which shows a test state. It is explanatory drawing of the near-infrared absorption spectrum in the case of p polarization | polarized-light. It is explanatory drawing of the near-infrared absorption spectrum in the case of s polarized light. It is explanatory drawing which shows the polarization angle dependence of the spectral reflection spectrum when s-polarized light is irradiated to the palm.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Polarizing plate 3 Polarizing plate 4 Spectral light receiving element 6 Analyzing means 7 Measuring means 9 Human body

Claims (6)

  In order to obtain biological information by spectroscopic analysis by irradiating light on the surface tissue of the living body and receiving reflected light from the surface tissue through the spectroscopic means, linearly polarized light is irradiated as light to irradiate the surface tissue of the living body. Using and receiving the reflected light through a polarizing plate with a variable polarization angle to obtain a spectral distribution, analyzing the depth of arrival of the light to the surface tissue based on the spectral distribution having a different polarization angle, An optical biological information measuring method, wherein the light for spectral analysis is received by setting the polarization angle of the polarizing plate according to the analysis result.   2. The optical biological information measuring method according to claim 1, wherein the target biological information is a glucose concentration in a blood component.   3. The optical biological information measuring method according to claim 1, wherein light is irradiated to a portion inside the finger of the human body and between the first joint and the second joint.   The light according to any one of claims 1 to 3, wherein the surface of the living body tissue is irradiated with light from an oblique direction, and s-polarized light is used as the light applied to the surface of the living body surface tissue. Biological information measurement method.   Optical biological information comprising light irradiating means for irradiating light on the surface tissue of a living body, spectral light receiving means for spectrally receiving reflected light from the surface tissue, and measuring means for measuring biological information by spectroscopic analysis In the measuring apparatus, the light irradiating means irradiates linearly polarized light, and the spectral light receiving means receives the reflected light through a polarizing plate having a variable polarization angle. Analyzing the depth of arrival of the light to the surface layer structure based on spectral distributions with different polarization angles obtained from the light received through the polarizing plate, and depending on the analysis result, the polarizing angle of the polarizing plate for spectroscopic analysis An optical biological information measuring device comprising an analyzing means for setting or indicating a polarization angle.   6. The optical biological information measuring device according to claim 5, wherein the light irradiating means irradiates the surface of the living body with s-polarized light on the surface to be irradiated.

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