JP2008039428A - Optical measurement unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein, although an optical measuring method is known as a method for measuring a sugar content of a part to be measured, measurement accuracy and miniaturization of a device have not been improved. <P>SOLUTION: Three types of laser beams of a single wavelength (laser beams of three wavelengths) are applied to a part to be measured so as to measure absorptance with respect to each wavelength. A quadratic differential value is obtained from three discrete absorptances to calculate a sugar content from a conversion function of the quadratic differential value and blood-sugar level. A highly-accurate and compact optical measurement unit capable of measuring a sugar content in a noninvasive manner is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical measurement unit, and more particularly to a non-invasive optical measurement unit that achieves miniaturization and high accuracy.

  There are invasive methods and non-invasive methods as methods for detecting the sugar content inside the measurement site.

  As an example of detecting the sugar content, a blood collection method (invasive method) and a non-blood collection method (non-invasive method) are methods for measuring a blood glucose level in a living body. As a blood sampling method, a method is generally used in which the collected blood is reacted with a reagent usually by glucose oxidase method, and a blood glucose level is obtained from the reaction color using a colorimetric method. Various methods have been reported for the bloodless method. For example, a method for optical measurement as described below is known.

  As a method for measuring glucose concentration (blood glucose level), there is a method of calculating blood glucose level by irradiating near-infrared light (800 nm to 2500 nm), obtaining an absorbance at a specific wavelength from transmitted light (see, for example, Patent Document 1). .) In addition, a method by spectroscopic analysis and a method of performing spectral analysis by Fourier transform (Fourier Transform infrared Spectrometer: FTIR) and obtaining from a change in the spectrum and a statistical method have been proposed. The optical system of the FTIR analyzer constitutes, for example, a Michelson interferometer (see, for example, Patent Document 2).

Further, the method by spectroscopic analysis and the method by FTIR analysis do not damage the measurement site, and are used, for example, for detecting the sugar content of fruits and vegetables (especially fruits) before shipment.
Patent Publication 2002-202258 Patent publication 2006-512979

  However, in the case of measuring the blood sugar level by the blood sampling method, the pain due to blood sampling is very large. Further, since the puncture needle is a consumable item, there is a problem that, for example, the financial burden on a diabetic patient is large.

  Further, for example, in a method of irradiating near infrared light as in Patent Document 1 and obtaining a blood glucose level from an absorbance at a specific wavelength, a blood vessel is used as a site to be measured, and it is very difficult to measure accurately. There's a problem. That is, the transmitted light is strongly influenced by components other than glucose (specifically, hemoglobin) as a blood component, and the absorbance of glucose is very small, which is a major issue for achieving high accuracy. .

  On the other hand, the method using spectral analysis is said to ensure a certain degree of measurement accuracy. However, the spectroscope used for the spectrum analysis needs to secure a certain optical path length, and there is a limit to downsizing the measuring apparatus. Moreover, it can be said that the method using the FTIR analyzer as in Patent Document 2 cannot be miniaturized because of the presence of movable parts such as an optical path and a mirror.

  The spectral analysis method is not originally a method for measuring blood sugar levels but a method for analyzing physical properties of materials. Therefore, the analysis spectrum range is very wide. However, considering only the measurement of the blood glucose level, the light absorption characteristic of glucose is known, and it is only necessary to measure only the light absorption characteristic for the spectrum of that portion.

  That is, in the spectral analysis methods such as the spectroscopic analysis method and the FTIR analysis method, it takes a long time to measure the extra area, and since the movable part is actually driven, a certain amount (waste) time is required for the measurement. And

  Furthermore, when considering the use environment of blood glucose level measurement, improvement in portability due to downsizing of the measuring device is a market requirement, and a measuring device having an optical path and a movable part has a serious problem in terms of portability.

  On the other hand, knowing the sugar content of fruits before shipment can be convenient for both producers and consumers. For fruits and vegetables, human injury before shipment is fatal, and invasive measurement is not desirable. Further, as described above, the apparatus using the spectrum analysis is large and is not portable. For this reason, for example, it is necessary to perform measurement after harvesting, and the effectiveness of sugar content detection is lost for those that lack sugar content.

  The present invention has been made in view of the various circumstances described above. First, the optical measurement unit includes a light emitting unit, a light receiving unit, and a control unit, and measures sugar content at a measurement site, and includes the light emitting unit. Outputs the near-infrared laser beams having emission wavelengths of the first wavelength, the second wavelength, and the third wavelength, respectively, to the measurement site, and the light receiving unit reflects the laser reflected by the measurement site The reflected light is detected respectively, and the control unit includes an arithmetic processing unit, and the arithmetic processing unit transmits the reflected light to the laser beam having the first wavelength, the second wavelength, and the third wavelength. Converted to the first absorbance, the second absorbance, and the third absorbance, which are proportions absorbed by the sugars, respectively, and calculate the second derivative values of the first absorbance, the second absorbance, and the third absorbance. , The second derivative value and the measured value based on the first, second and third extinction values. It solves by calculating the sugar content at the site.

  Second, an optical measurement unit that includes a light emitting unit, a light receiving unit, and a control unit, and measures sugar content at a measurement site, wherein the light emission unit has an emission wavelength that is a first wavelength with respect to the measurement site. The near-infrared laser beams of the second wavelength and the third wavelength are individually output, the light receiving unit detects the reflected light of the laser beam reflected by the measurement site, and the control unit is an arithmetic processing unit The arithmetic processing unit includes a first absorptance, a second absorptance, which is a ratio of the laser light having the first wavelength, the second wavelength, and the third wavelength absorbed by the sugar in the measurement site. Converting to an absorptivity and a third absorptance, calculating a second derivative value of the first absorptivity, a second absorptivity, and a third absorptance, and calculating the first absorptivity and the second absorptance to the third absorptivity The first corrected absorbance and the second corrected absorbance are calculated by correcting with a predetermined reference value, and the secondary fine absorbance is calculated. Value and, the first, it solves by calculating second correction absorptivity, and sugar content in the measurement site based on the third absorption rate.

  In addition, the first wavelength, the second wavelength, and the third wavelength are adjacent wavelengths, and the wavelengths become longer in this order. The third wavelength has a very large absorbance by pure water, and is almost only absorbed by pure water. The second wavelength is a wavelength having a large absorbance due to the sugar, and the first wavelength is a wavelength having a small absorbance due to the sugar.

  The arithmetic processing unit holds first, second, and third reference absorbances for the first, second, and third absorbances, respectively, and is based on the third absorbance and the third reference absorbance. A shift amount is calculated, and the first and second reference correction absorbances are calculated by correcting the first and second absorbances according to the reference shift amount, and the first and second reference correction absorbances are calculated. The first corrected absorbance and the second corrected absorbance are calculated by correcting the absorbance with the first and second reference absorbances, respectively.

  Further, the first, second, and third reference absorbances are the absorbances of the laser beams of the first, second, and third wavelengths measured in advance with pure water.

  Moreover, it has a temperature detection part, The temperature correction of said 1st wavelength, 2nd wavelength, and 3rd wavelength is performed by this temperature detection part, It is characterized by the above-mentioned.

  In addition, the temperature of the measurement site is measured by the temperature detection unit, and the temperature or driving current of the laser beam is changed based on the temperature-dependent characteristic of the light absorption characteristic of the sugar to control the emission wavelength of the laser beam. It is characterized by this.

  The light emitting unit outputs the laser light at an irradiation angle at which the laser light incident from the measurement site is diffusely reflected at a depth suitable for the sugar content measurement.

  Further, the light emitting unit and the light receiving unit are arranged adjacent to each other through a light shielding plate in the housing.

  In addition, the control unit detects that the light shielding plate has come into contact with the part to be measured, and starts a measurement process.

  The focus point to which the laser beam is irradiated is characterized in that a position at which diffusely reflected light from the sugar is efficiently obtained is selected.

  Further, the light receiving unit is characterized in that the reflected light is selected, and a focus point and a light collection angle are selected so as to efficiently collect the reflected light.

  According to the present embodiment, it is possible to provide a non-invasive optical measurement unit that has high sugar content measurement accuracy and is downsized.

  That is, first, by irradiating the measurement site with laser light and measuring the reflected light to obtain the absorbance, it is possible to improve convenience with high accuracy compared to the case of using transmitted light. For example, in an optical measurement unit employed in a blood sugar level measuring device, a method of measuring transmitted light by irradiating a blood vessel as a measurement site with near infrared light is strongly affected by blood components (hemoglobin), In addition to the change in transmitted light, the absorbance is very small as a characteristic of glucose, so that accurate measurement is difficult.

  In the present embodiment, the irradiation angle of the laser beam and the focus point are set to the optimal positions for sugar content measurement. Therefore, for example, in the case of blood glucose level measurement, the dermis layer can be used as a site to be measured for reflected light. By measuring the glucose concentration in the dermis layer from the reflected light from the dermis layer, measurement that is hardly affected by blood components other than glucose becomes possible.

  In addition, the action of measuring a blood glucose level is different from the case of measuring a blood pressure, and there is a high possibility that the place to measure after a meal is not constant. Therefore, the blood glucose meter is small and requires portability. For the same reason, the place to be measured must be a part that can be measured immediately, and it is desirable not to limit normal life so much. That is, in the present embodiment, portability can be improved as compared with the case where transmitted light is used in consideration of the usage state of such a blood glucose level measuring apparatus.

  Further, three single wavelengths are used as the laser light to be irradiated. Thereby, compared with the spectrum analysis method, the apparatus can be downsized and the measurement time can be shortened. The spectroscope used for spectrum analysis needs to secure a certain optical path length, and the FTIR analyzer cannot be miniaturized due to the presence of movable parts such as an optical path and a mirror.

  However, according to the present embodiment, the optical path length as that of the spectroscope is unnecessary, and the movable part is also unnecessary, so that the apparatus can be downsized. Specifically, for example, it can be miniaturized to the extent that it can be handled and carried with one hand.

  Therefore, for example, by adopting a sugar content detection apparatus for fruits, sugar content before harvesting can be detected, and harvesting and shipping can be performed according to the sugar content.

  Furthermore, in order to calculate the absorptance of the laser light of three wavelengths and to calculate these secondary differential values, the measured value can be obtained as the change rate (change amount) from the two points before and after the central wavelength as the apex. . For example, in the case of blood glucose level measurement, since the absorbance of glucose is very small as described above, it is difficult to distinguish between cases where the blood glucose level is actually high and measurement errors. Compared with the case where measured values of reflected light or transmitted light) are employed, calculation is easier and errors can be reduced.

  In addition, since the calculation is performed as the amount of change using the secondary differential value, the magnitude of the reference amount (the amount of deviation from the value that is normally measured) becomes irrelevant, and fluctuations such as fluctuations can be absorbed. Can be reduced.

  Second, the first wavelength has a small absorbance due to sugar, the second wavelength has a large absorbance due to sugar, and the third wavelength has a very large absorbance due to pure water, and a wavelength at which only the absorbance due to pure water can be measured. By selecting and measuring in advance the absorbance of each wavelength with pure water as a reference value and holding it as data, a quantitative numerical value can be obtained without using a physical correction reference.

  Third, since laser light is used as near-infrared light, the temperature of the laser output condition can be corrected. That is, even when the light absorption characteristics of the sugar at the site to be measured change due to fluctuations in body temperature and temperature, the temperature of the laser can be controlled by the temperature detection unit, so that an accurate blood glucose level can be measured.

  Fourth, since the laser beam is output at an irradiation angle that diffusely reflects at a position optimal for the detection of sugar content, the dermis layer can be used as a site to be measured, for example, in the case of blood glucose level measurement. The absorbance can be measured. The dermis layer has very little influence of blood hemoglobin, which is the most obstructive factor when measuring blood glucose levels with near infrared light. Further, since the first and second reference absorbances are the absorbances of the first and second wavelengths by pure water, the absorbance by glucose is obtained quantitatively by comparing these with the first and second absorbances. be able to.

  Further, for example, when detecting the sugar content of a fruit, the light emitting unit and the light receiving unit can be set so that the pulp part from which the average sugar content of the fruit is obtained becomes the measurement site. Furthermore, since it measures by contacting an optical measuring unit, a to-be-measured site | part can be stabilized regardless of the magnitude | size and shape of a fruit.

  Further, by providing a predetermined angle, it is possible to prevent the reflected light from returning to the laser oscillation point.

  Fifth, since the light emitting unit and the light receiving unit of the optical measuring unit are arranged adjacent to each other, only the diffusely reflected light to be measured can be accurately received. Moreover, since it arrange | positions via a light-shielding plate, it can prevent that the directly reflected light in the surface of a to-be-measured part reaches | attains a light-receiving part.

  Sixth, since the light emitting unit and the light receiving unit are provided in the partitioned space by the light shielding plate, the light emitting unit can stably oscillate the laser beam and reduce the measurement noise. In addition, the light receiving portion can be made less susceptible to electrical noise.

  Furthermore, since it is non-invasive, for example, it is painless when employed in a blood glucose level measuring device, and since there is no need for consumables such as a puncture needle, it is accompanied by physical and financial pain of the subject. Absent. In addition, when used for measuring the sugar content of fruits and vegetables, it can be measured before harvesting without artificially damaging the fruits and vegetables.

  Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 1 to 10. First, as a first embodiment, a case where the optical measurement unit 1 of the present embodiment is employed in a blood glucose level measuring apparatus 100 will be described as an example.

  FIG. 1 is a diagram illustrating an example of a blood sugar level measuring apparatus according to the present embodiment, in which FIG. 1A is an external view, FIG. 1B is a cross-sectional view taken along the line aa in FIG. (C) and (D) are internal plan views.

  1A and 1B, for example, a power switch 4, a measurement start / stop button 5, a display unit 2 and the like are provided on one main surface of the external casing 8 of the blood glucose level measuring apparatus 100. An attachment 3 serving as a contact portion with the measurement site is provided on the upper portion of the external housing 8. The attachment 3 is provided continuously with the optical measurement unit 1. In this embodiment, as an example, the attachment 3 has a shape (for example, a cylindrical shape) and a material so that light output from the light emitting unit in the optical measurement unit 1 and light received by the light receiving unit do not leak to the outside. It constitutes a part of the external housing of the measurement unit 1.

  As shown in FIG. 1C, the optical measurement unit 1 includes a light emitting unit, a light receiving unit (not shown here), and a control unit 6, and measures a blood glucose level at a measurement site of a living body. The control unit 6 is configured by, for example, a semiconductor integrated circuit integrated on a printed circuit board, and includes an arithmetic processing unit.

  As shown in FIG. 1D, the display unit 2 in the internal structure is connected to a display driver which is a part of the control unit 6. The display unit 2 is, for example, an LCD (Liquid Crystal Display) panel, an organic EL (Electronic Luminescent) display panel, etc., and displays a blood glucose level and other measurement information (for example, notification of measurement error, date and time) so that the measurer can recognize it. Anything can be used. A power supply unit 7 connected to the control unit 6 is provided. The power source is charging by an AC adapter, a battery, or a combination thereof.

  FIG. 2 is a schematic diagram showing a site to be measured for blood glucose level. FIG. 2A is a diagram showing the blood sugar level measuring apparatus 100 and a site to be measured, and FIG. 2B is a schematic cross-sectional view of the site to be measured.

  As shown in FIG. 2 (A), the blood glucose level measuring apparatus 100 performs measurement by attaching the attachment 3 to the inside of the arm or wrist.

  As shown in FIG. 2B, the blood sugar level measuring apparatus 100 uses a dermal layer 252 of a living body as the measurement site 25. There is a dermis layer 252 in the lower layer (inside) of the epidermis 251 of the living body, and a subcutaneous tissue 253 exists in the lower layer.

  In the present embodiment, the laser light 20 emitted from the optical measurement unit 1 is diffusely reflected by the dermis layer 252. That is, the laser light 20 is output from the light emitting unit at an irradiation angle θ at which the laser light 20 incident from the skin 251 is diffusely reflected by the dermis layer 252.

  In order to measure the blood glucose level, it is efficient to detect the blood glucose concentration. In addition, when measuring blood sugar levels non-invasively (without blood sampling), light in a wavelength band that is transparent to the human body is used. In the case of glucose, some spectra of near-infrared light are used. It is known to have light absorption characteristics. Therefore, the conventional optical blood sugar level measuring apparatus measures the blood sugar level by transmitting near infrared rays through the blood vessel and detecting the absorption rate by glucose.

  However, in addition to glucose, there are various substances in the blood, and the absorbance of glucose is very small. In particular, in the case of transmitted light, there is a problem that the blood glucose level cannot be accurately measured as a result of the strong influence of hemoglobin, which is a component in blood, to change the amount of light.

  Therefore, in this embodiment, glucose in the dermis layer 252 is measured so as not to be affected by blood components (hemoglobin). Since the dermis layer 252 is located at a very shallow position from the outside of the living body (skin 251), it is sufficient to calculate the blood glucose level by appropriately selecting the aperture angle (lens aperture diameter NA) and the irradiation angle of the laser light 20 beam. Reflected light can be obtained. In addition, since measurement using reflected light does not pass through the subcutaneous tissue 253, measurement errors due to components other than glucose can be avoided, which is more advantageous than using transmitted light.

  3A and 3B are diagrams illustrating the optical measurement unit 1, in which FIG. 3A is a top view and FIG. 3B is a cross-sectional view taken along line bb in FIG. 3A.

  The optical measurement unit 1 includes a light emitting unit 11 and a light receiving unit 12. The light emitting unit 11 is a semiconductor laser that individually outputs near-infrared laser beams having emission wavelengths of the first wavelength λ1, the second wavelength λ2, and the third wavelength λ3, respectively, to the measurement site. The laser beam 20 is condensed by a condenser lens 11a having a lens aperture diameter NA, and irradiated to a measurement site with a small spot (FIG. 2A). In FIG. 2B, although two condensing lenses 11a are provided, the number is not limited to this.

  Here, the first wavelength λ1, the second wavelength λ2, and the third wavelength λ3 are near-infrared lights of neighboring wavelengths, and the wavelengths become longer in this order (λ1 <λ2 <λ3). The third wavelength λ3 is a wavelength at which only a light absorption by pure water is measurable, and the second wavelength λ2 is a wavelength at which the light absorption by glucose is large, and the first wavelength λ1 is glucose. This is a wavelength with a small extinction coefficient. The reason for selecting these wavelengths will be described later.

  The light receiving unit (Photo Detector) 12 is, for example, a photodiode that detects the reflected light 21 of the laser light reflected from the measurement site.

  The reflected light 21 is also condensed by the condensing lens 12 a having the lens aperture diameter NA ′ and detected by the light receiving unit 12. Since it is desirable to collect as much reflected light 21 as possible in the light receiving unit 12, the spot diameter is set larger than that of the light emitting unit 11 (FIG. 2A).

  The light emitting unit 11 and the light receiving unit 12 are arranged adjacent to each other with a light shielding plate 17 interposed therebetween. For example, as shown in FIG. 2B, the light emitting unit 11 and the light receiving unit 12 are arranged in the same housing (a part of the attachment 3 in this embodiment), and a light shielding plate 17 is arranged in the center. The light shielding plate 17 is provided at least at the same height as the outer periphery of the attachment 3. When the attachment 3 is brought into contact with the measurement site 25 and the measurement site 25 is irradiated with the laser beam 20, a part of the laser beam 20 is reflected by the skin 251. In order to prevent such directly reflected light from reaching the light receiving unit 12, a light shielding plate 17 is provided. The light-emitting unit 11 and the light-receiving unit 12 are arranged in separate spaces by the light-shielding plate 17.

  The light shielding plate 17 is, for example, a material that has a black surface and absorbs near-infrared without transmitting or reflecting.

  More specifically, for example, a metal plate whose surface is coated, specifically, a metal plate whose surface is coated with a black brushed painted material may be mentioned. Examples of the light shielding plate 17 include a resin plate formed by using a resin material containing at least one resin selected from the group consisting of acrylic and polycarbonate resins. In that case, in order to improve light-shielding properties, it is preferable to use a resin plate in which at least one black filler selected from the group consisting of carbon fiber and graphite is contained in the resin material. Further, as the light shielding plate 17, for example, a black polarizing plate may be used. In that case, it is preferable to use the board | substrate which used glass as a base material as a polarizing plate, for example. Further, as the light shielding plate 17, for example, a stone material or the like may be used.

  The laser light 20 is affected by the return light, but the light shielding plate 17 can reduce the influence. Therefore, the laser beam 20 can be stably oscillated, and measurement noise can be reduced.

  Furthermore, by using the light receiving unit 12 in a space partitioned by the light shielding plate 17, it is possible to make it less susceptible to the influence of electrical noise.

  In addition, the light shielding plate 17 of the present embodiment also functions as a contact detection sensor. That is, the light shielding plate 17 is movable in the vertical direction and protrudes from the surrounding attachment 3 when not measuring. On the other hand, when the attachment 3 is brought into contact with the measurement site 25 at the time of measurement, the light shielding plate 17 is brought into contact with the measurement site 25 with a certain degree of tension and is pressed into the optical measurement unit 1, and below the light shielding plate 17. The switch 18 is activated. That is, the switch 18 can detect that the attachment 3 has normally contacted the measurement site, and can start the measurement process in a normal state (in a state where external light is shielded).

  When the light shielding plate 17 functions as a contact detection sensor and the measurement apparatus is operated after detecting normal contact, the light shielding plate 17 may be provided at a position lower than the attachment 3. For example, the attachment 3 side is movable, a contact sensor with a contacted part is provided at the upper end of the light shielding plate 17, and is connected to the switch 18 via wiring in the light shielding plate 17. By making contact with the measurement site 25 with a predetermined tension, the attachment 3 is pressed down, and the light shielding plate 17 and the attachment 3 have the same height. In this state, if the contact sensor on the upper part of the light shielding plate 17 detects contact and the switch 18 for operating the measuring device is turned on, the measuring device can be operated in a state where the outside light is shielded.

  Furthermore, when providing a contact sensor at the upper end of the light shielding plate 17, the height of the light shielding plate 17 and the attachment 3 may be the same, and both may be fixed.

  In order to avoid the intrusion of external light, the attachment 3 is also selected from a material having a light shielding property. Further, although the laser spot from the light emitting unit 11 is very small and the light receiving unit 12 is large, the spread of diffuse reflected light is about 1 mm (for example, about 0.1 mm to 0.5 mm on the photodiode surface). It is. In order to improve the measurement accuracy, it is desirable to avoid the intrusion of external light. If a sufficient opening for allowing the laser light 20 and the reflected light 21 to pass through is secured, the upper surface of the attachment 3 continues from the side surface without any gaps, A shape that covers the interior as much as possible.

  The laser beam 20 of the light emitting unit 11 is focused by an appropriate lens opening diameter NA, and irradiated to the measurement site 25 (dermis layer 252) at an angle θ. This angle θ is an angle formed by the center line in the vertical direction (up and down on the paper surface) of the light shielding plate 17 and the optical axis of the laser light 20, and is set to an angle most suitable for measuring the glucose concentration of the dermis layer 252 and irradiated. The beam focus points D and W are set to the points where the reflected light (diffuse reflected light) from glucose of the dermis layer 252 can be obtained most efficiently. Here, the focus point D is a depth from the epidermis 251 and is a point in the dermis layer 252 suitable for glucose measurement. The focus W is a distance from the light shielding plate 17 and is a point indicating how far away from the center or the end of the light shielding plate 17 at the depth of the focus point D.

  Another reason for making the laser beam 20 incident at a predetermined angle θ is to prevent the reflected beam 21 from returning as much as possible to the laser oscillation point.

  On the other hand, on the light receiving unit 12 side, the angle θ ′ and the focus points D ′ and W ′ for efficiently selecting the reflected light 21 are set. The angle θ ′ is an angle formed by the vertical center line of the light shielding plate 17 and the optical axis of the reflected light 21, and the focus points D ′ and W ′ are the depth from the skin 251 and the center or edge of the light shielding plate 17, respectively. The distance from the part.

  Since the diffusely reflected beam basically has reflected light from all layers, the reflected light from the dermis layer 252 is selectively collected by the angle θ ′, the focus points D ′, W ′, and the lens aperture diameter NA ′. Set to shine.

  The optical measurement unit 1 of the present embodiment does not require an optical path length required by a spectroscopic analyzer, an FTIR analyzer, or the like, or a movable part such as a mirror. In addition, since the reflected light of a single wavelength laser is received, it is not necessary to separate the light with a diffraction grating or the like, and the light receiving unit 12 can be configured with only a lens and a photo detector. Therefore, the blood sugar level measuring apparatus 100 can be reduced in size and weight, and the portability can be greatly improved. The size is small enough to fit in the palm of the hand and can be carried and operated with one hand.

  Next, the principle of the blood sugar level measuring apparatus according to this embodiment will be described with reference to FIG.

  In FIG. 4, the horizontal axis represents the emission wavelength λ of the laser light, and the vertical axis represents the absorbance I. A broken line is a spectrum spectrum curve that is actually measured (or a theoretical value) under a reference condition.

  In the present embodiment, laser light is used. The spectrum of the laser light is very narrow and is almost single wavelength light. Then, the laser beam of at least three different wavelengths (λ1, λ2, λ3) is individually irradiated to measure the absorbance I for each wavelength, and these secondary differential values are obtained from the three absorbances corresponding to the three wavelengths. Ask.

  The absorptance I can be obtained from the amount of laser light irradiated from the light emitting unit and the amount of received light reflected from the dermis layer. That is, if the intensity of the light having the wavelength λ incident on the measurement site is L0 (λ) and the intensity of the reflected light of the received wavelength λ is L (λ), the light absorption rate I (λ) of the measurement site 25 is ln (L (λ) / L0 (λ)) (Note that, when the incident light is constant, the received light intensity itself is equivalent to the absorbance).

  However, as described above, the extinction rate due to glucose is very small, and the blood glucose level is about 100 mg / dl, so there is a case where it is not known whether the actual blood glucose level has fluctuated or it is a measurement error. is there.

  Therefore, a secondary differential value is used. The second-order differential value of the present embodiment uses the fact that light absorption by glucose varies depending on the wavelength of light, and selects three adjacent wavelengths including a wavelength region where the variation due to this wavelength appears as large as possible. It is defined as a value corresponding to the derivative of the second derivative of the rate I and the wavelength λ.

  Obtaining the next differential value of the three points of data means obtaining the amount of change in data from the three points of wavelengths λ1, λ2, and λ3 to the center point (second data: λ2). That is, since the light absorption rate I at the center wavelength λ2 is used as the apex, the amount of change from the light absorption rate I at the two surrounding points (λ1, λ3) is obtained. The sensitivity can be improved.

  Further, since the secondary differential value is obtained as an amount of change, the magnitude of the reference (actually measured value) is irrelevant, and it is possible to absorb fluctuations such as fluctuations (fluctuation). Therefore, the same result as that obtained when the blood glucose level is measured by the spectrum analysis method (broken line) can be obtained.

  Furthermore, in the present embodiment, only the absorption spectrum of glucose is measured and unnecessary spectrum is not measured, so that the measurement time can be shortened.

  More specific description will be given with reference to FIGS. 5 and 6. 5 and 6, the horizontal axis represents the laser emission wavelength λ, and the vertical axis represents the absorbance I.

  First, the laser is driven at the first wavelength λ1, the measurement site is irradiated, and the first absorbance I1 is measured from the reflected light (FIG. 5A). Next, the laser is driven at the second wavelength λ2, the measurement site is irradiated, the second absorbance I2 is measured from the reflected light (FIG. 5B), and the third wavelength λ3 is similarly measured. The rate I3 is measured (FIG. 5C). Here, if the light emission output of the laser is constant, these secondary differential values can be calculated as discrete differential processing from the first extinction coefficient I1, the second extinction coefficient I2, and the third extinction coefficient I3.

  As described above, glucose has absorption characteristics for several spectra with respect to near-infrared light. In the case of pure water, it has been found that there is very strong absorption for wavelengths near 2000 nm.

  FIG. 6 is a diagram showing these characteristics, where the horizontal axis represents the wavelength λ and the vertical axis represents the absorbance I. The solid line is a spectrum spectrum curve of pure water measured in advance, and the broken line is a spectrum spectrum curve of a mixture of pure water and glucose measured in advance. From these spectral curves, it can be said that a wavelength having a larger light absorption rate I than a solid line is a wavelength at which the light absorption rate of glucose is high.

  When the wavelength λ is around 2000 nm, the absorption by pure water is very large, and the solid line and the broken line are superimposed. Therefore, there are almost no molecules or substances that absorb light other than pure water in this wavelength band, and the absorption by pure water. Only can be measured. In addition, since the extinction coefficient in this wavelength band is very high, even if there is absorption of other molecules and substances, it becomes relatively very small and can be ignored.

  In the present embodiment, the wavelength closest to 2000 nm at which the absorbance by pure water is the highest and the wavelength at which the absorbance by glucose is increased is the center of the laser oscillation wavelength, that is, the second wavelength λ2. As an example, the second wavelength λ2 is 1870 nm. The wavelengths before and after (λ1, λ3), that is, the first wavelength λ1 and the third wavelength λ shown in FIG. 6 are selected as follows.

  The third wavelength λ3 is a region where the absorption by pure water is high, glucose is not absorbed, and the wavelength is away from the second wavelength λ2. The first wavelength λ1 is a wavelength lower than the second wavelength λ2, and a wavelength that does not absorb light by glucose is selected.

  Here, assuming that the absorbance measured at the first wavelength λ1, the second wavelength λ2, and the third wavelength λ3 are the absorbance I1, the second absorbance I2, and the third absorbance I3, respectively, the series S is It is as follows.

S = {I1, I2, I3}
And the secondary differential value i by these discrete differential processes is expressed by the following equation.

i = Δ ² S / (Δ ² Λ) = 2 × I 2 − (I 1 + I 3)
The value of the secondary differential value i corresponds to the amount of change. Therefore the reference value is required to identify whether the amount of change from where, thus obtaining the quantitative numerical this reference value.

  Therefore, the absorbance of the laser light having the third wavelength λ3 by pure water is used as the overall reference value (third reference absorbance Ib3). Further, the absorbance of pure water of each laser beam having the first wavelength λ1 and the second wavelength λ2 is also a reference value (first reference absorbance Ib1 when correcting the absorbance actually measured (blood glucose level measurement) at each wavelength. And used as the second reference extinction coefficient Ib2).

  As the third wavelength λ3, a wavelength at which the absorbance by the pure water (third reference absorbance Ib3) is very high and the absorbance by the pure water only is selected. That is, if the displacement of the actually measured third absorbance I3 with respect to the third reference absorbance Ib3 is measured, the value is the overall displacement amount (reference shift amount Sf). Accordingly, the absorbances measured at the first wavelength λ1 and the second wavelength λ2 (first absorbance λ1, second absorbance λ2) can also be quantitatively corrected by the reference shift amount Sf, and the first reference corrected absorbance Ibr1 Then, the second reference corrected absorbance Ibr2 is obtained.

  Furthermore, since the first absorbance I1 and the second absorbance I2 include the amount of fluctuation due to the glucose absorption characteristic (broken line in FIG. 6), the first reference corrected absorbance Ibr1 and the second reference corrected absorbance Ibr2 are By comparing with the first reference absorbance Ib1 and the second reference absorbance Ib2 which are absorbances with respect to pure water, the amount of displacement of the absorbance due to glucose can be specified, and finally the quantitatively corrected first corrected absorbance Ir1 And the 2nd correction | amendment light absorbency Ir2 can be calculated.

  Then, the blood sugar level is converted by the blood sugar level conversion function using the first corrected absorbance Ir1, the second corrected absorbance Ir2, and the third absorbance I3 as reference values for setting the secondary differential value i as a quantitative value as a parameter. Ask for.

  That is, the blood glucose level can be measured by measuring the absorbance of each wavelength in pure water in advance and holding it as a reference value (data). Therefore, for example, a physical reference body that is regarded as a measurement site is not necessary.

  Further, the reference shift amount Sf from the absorption rate by pure water is obtained from the third absorbance I3 that is an actual measurement value of the third wavelength λ3 and the third reference absorbance Ib3. The third absorbance I3 is 2 It is also used as data for obtaining the second derivative value, and contributes to simplification of the amount of data handled in the arithmetic processing.

  FIG. 7 is an example of a circuit block diagram showing an outline of the optical measurement unit 1 of the blood sugar level measuring apparatus 100 of the present embodiment.

  The light emitting unit (semiconductor laser) 11 is driven by a laser driver 63 of the control unit 6 and sequentially outputs three laser beams 20 having a first wavelength λ1, a second wavelength λ2, and a third wavelength λ3 as described. A part of the laser beam 20 is input to an APC (Auto Power Control) 13 via a mirror 15 and an FMD (Front Monitor Diode). The APC 15 performs control such as keeping the power of the laser light 20 constant for each wavelength or keeping the power of the laser light 20 uniform for all three wavelengths. The laser beam 20 is irradiated onto the measurement site 25 at a predetermined irradiation angle and a beam aperture angle (lens aperture diameter NA).

  The light detector (Photo Detector) 12 is, for example, an InGaAs photodiode or the like, and receives the reflected light 21 from the dermis layer 252 of the measurement site 25 and converts it into an electrical signal. The electrical signal is proportional to the intensity of the received light, is amplified by the amplifier 14, and is output to an A / D converter (not shown here) of the control unit 6.

  Further, the optical measurement unit 1 includes a temperature detection unit (for example, a temperature sensor) 16. The temperature sensor 16 measures the temperature of the measurement site 25 (or in addition to the outside air temperature). The light absorption characteristics of glucose vary with temperature. Therefore, the temperature is measured by the temperature sensor 16 before the blood glucose level is measured, and the wavelength of the laser beam 20 is corrected within a minute range from the measurement result. Specifically, since the laser light 20 has a characteristic that the oscillation wavelength changes depending on the current or temperature, the temperature of the laser light 20 or the drive current is controlled based on the temperature dependence of the glucose absorption characteristic measured in advance. For example, when controlling with the drive current of the laser beam 20, the laser drive amount is calculated and fed back to the laser driver 63. As a result, the first wavelength λ1 to the third wavelength λ3 are selected as the most efficient wavelengths within the range satisfying the wavelength condition of the present embodiment according to the temperature of the measurement site 25, and are shifted by, for example, several nm. The Thereby, an accurate blood glucose level can be measured.

  FIG. 8 is an example of a circuit block diagram illustrating an outline of the control unit 6 of the optical measurement unit 1 of the present embodiment.

  The control unit 6 includes a DSP (Digital signal processor) 61, an A / D conversion circuit 62, a laser driver 63, and an arithmetic processing unit 65. Further, a display driver 64 for outputting data such as measurement results to the display unit, a desired circuit (not shown) necessary for other control, and the like are also provided.

  A signal (reception signal) based on the amount of received light amplified by the optical measurement unit 1 is converted into a digital signal by the A / D conversion circuit 62 and input to the arithmetic processing unit 65 in the DSP 61.

  The arithmetic processing unit 65 receives the received signals at the first wavelength λ1, the second wavelength λ2, and the third wavelength λ3 from the first absorbance I1, which is the ratio at which the laser light of the wavelength is absorbed by glucose at the measurement site, It converts into the 2nd light absorbency I2 and the 3rd light absorbency I3. Further, second derivative values of the first absorbance I1, the second absorbance I2, and the third absorbance I3 are calculated.

  Also, the first corrected absorbance Ir1 and the second corrected absorbance Ir2 are calculated by correcting the first absorbance I1 and the second absorbance I2 that are actually measured values with the third absorbance I3 and a predetermined reference value.

  That is, the arithmetic processing unit 65 calculates the absorbance by pure water at the first wavelength λ1, the second wavelength λ2, and the third wavelength λ3 measured in advance as the first reference absorbance Ib1, the second reference absorbance Ib2, and the third reference. The reference shift amount Sf is calculated based on the third absorption rate I3, which is an actually measured value, and the third reference absorption rate Ib3, which is a reference value. The third wavelength λ3 is a wavelength in the vicinity of the wavelength at which the extinction rate in pure water is highest, and other components are hardly absorbed. Therefore, the reference shift amount Sf is a variation amount of the overall reference value.

  Accordingly, the first absorbance I1 and the second absorbance I2 are corrected by the reference shift amount Sf, and the first reference corrected absorbance Ibr1 and the second reference corrected absorbance Ibr2 are calculated, respectively.

  In addition, since the first absorbance λ1 and the second absorbance λ2 include fluctuation amounts due to glucose, the first reference corrected absorbance Ibr1 and the second reference corrected absorbance Ibr2 are respectively set to the first reference absorbance Ib1 and the first absorbance. The first corrected light absorption rate Ir1 and the second corrected light absorption rate Ir2 are calculated with correction based on the second reference light absorption rate Ib2. Thereby, it is possible to quantitatively correct the actually measured absorbance of each wavelength.

  Then, the arithmetic processing unit 65 calculates blood glucose level data using a blood glucose level conversion function using the second derivative value, the first corrected absorbance rate Ir1, the second corrected absorbance rate Ir2, and the third absorbance rate I3 as parameters.

  The control unit 6 causes the display driver 64 to display the blood glucose level data on the display unit 2 as a measurement result. Furthermore, when the control unit 6 detects normal contact, such as when the switch 18 (see FIG. 2) in the optical measurement unit 1 is pressed by the light shielding plate 17 of the optical measurement unit 1 that is a contact detection sensor, Processing related to detection of the contact state, such as starting measurement processing (for example, temperature measurement, laser driving, etc.) is performed. In addition to this, the measurement unit 6 performs various known controls corresponding to pressing of a measurement start / stop button, monitoring of a measurement state, and the like.

  Next, an example of a blood sugar level measuring method using the optical unit 1 of the present embodiment will be described with reference to FIGS.

  FIG. 9 is a flowchart showing an example of the blood sugar level measuring method of the present embodiment, and FIG. 10 is a diagram showing sampling of the received light signal. This will be described below with reference to these.

  First step (step S1): A step of individually irradiating near-infrared laser beams having emission wavelengths of the first wavelength, the second wavelength, and the third wavelength to the measurement site.

  First, the body temperature (and outside air temperature) of the measurement site is measured (step S11). Based on the measurement temperature and the temperature dependence characteristics of glucose, a laser drive amount that emits a wavelength that satisfies the conditions of the specified laser wavelength (in this embodiment) or is closest to the conditions is calculated (step S12).

  In the present embodiment, three single wavelengths of the first wavelength λ1, the second wavelength λ2, and the third wavelength λ3 are used. The prescribed laser wavelength is a wavelength that satisfies the following conditions. That is, the first wavelength λ1, the second wavelength λ2, and the third wavelength λ3 are wavelengths in the vicinity, and the wavelength becomes longer in this order (λ1 <λ2 <λ3), and the third wavelength λ3 has an absorbance with respect to pure water. It is a wavelength that is very large and can only be measured for absorption by pure water. The second wavelength λ2 is a wavelength having a large absorbance due to glucose, and the first wavelength λ1 is a wavelength having a small absorbance due to glucose.

  First, the semiconductor laser having the first wavelength λ1 is pulse-driven in accordance with the calculated laser drive amount, and the temperature-corrected first wavelength λ1 is irradiated to the measurement site (step S13 and FIG. 10A).

  Second step (step S2): a step of detecting the reflected light of the laser light reflected from the measurement site.

  The laser beam having the first wavelength λ1 irradiated to the measurement site is diffusely reflected by the dermis layer. That is, the laser light is output from the light emitting unit at an irradiation angle at which the dermis layer diffusely reflects. The reflected light is detected by the light receiving unit. The light receiving unit converts the detected amount of received light into an analog light reception signal and outputs it to the amplifier (step S21 and FIG. 10B). The amplifier amplifies the received light signal as an AC signal by turning on / off the laser (step S22 and FIG. 10C). Thereafter, the analog light reception signal is subjected to digital filter processing by an A / D converter and converted into a digital light reception signal. Sampling data S is acquired and stored a predetermined number of times (for example, several thousand times) for each pulse period for this digital received light signal (step S23 and FIG. 10D).

  Third step: (Step S3): a first absorptance and a second absorptance, which are ratios in which the laser light of the first wavelength, the second wavelength, and the third wavelength is absorbed by the glucose at the measurement site from the reflected light, respectively. And calculating a third absorbance.

  The sampling data S for the first wavelength λ1 is averaged to obtain one digital received light signal (step S31). A first light absorption rate I1, which is a ratio at which the first wavelength λ1 is absorbed by glucose, is calculated from the digital received light signal with the irradiated laser light amount being constant (step S32).

  Similarly, for the second wavelength λ2 and the third wavelength λ3, the first step to the third step are performed, and the second absorbance I2 and the third absorbance I3, which are ratios absorbed by glucose, are calculated.

  Fourth step (step S4): a step of calculating a second derivative of the first absorbance, the second absorbance, and the third absorbance.

  The secondary differential value i is calculated by using the first absorbance I1, the second absorbance I2, and the third absorbance I3 as discrete data. As a result, it is possible to obtain the amount of change in the absorbance from the two surrounding points with the absorbance at the second wavelength λ2 (the second wavelength λ2) being the center wavelength as the apex.

  Fifth step (step S5): A step of correcting the first absorbance and the second absorbance based on the third absorbance and a predetermined reference value, and calculating the first corrected absorbance and the second corrected absorbance.

  The first, second, and third reference absorbances Ib1 to Ib3 for the first, second, and third absorbances λ1 to λ3 are measured in advance. The first, second, and third reference absorbances Ib1 to Ib3 are absorbances of pure water at each of the first wavelength λ1 to the third wavelength λ3. As the third wavelength λ3, the vicinity of the wavelength having the highest absorbance by pure water is selected, and the actually measured absorbance at that wavelength (third absorbance I3) is substantially the absorbance of only pure water (third reference absorbance). The value is close to the rate Ib3).

  Therefore, the reference shift amount Sf is calculated from the third absorbance I3 and the third reference absorbance Ib3 (step S51), and the first and second absorbances are corrected by the reference shift amount Sf, thereby correcting the first reference. The absorbance Ibr1 and the second reference corrected absorbance Ibr2 are calculated (step S52).

  Since the first light absorption rate I1 and the second light absorption rate I2 include fluctuation amounts due to glucose, a quantitative value can be obtained by comparing with the characteristics of these pure waters. That is, the first and second reference corrected absorbances Ib1 and Ib2 are corrected by the first and second reference absorbances Ib1 and Ib2, respectively, and the first corrected absorbance Ir1 and the second corrected absorbance are quantitative values. Ir2 is calculated (step S53).

  Sixth step (step S6): a step of calculating a blood glucose level using the first and second corrected absorbances, the third absorbance, and the second derivative value.

  The first corrected absorbance Ir1, the second corrected absorbance Ir2, and the third absorbance I3 are used as parameters for quantifying the secondary differential value i, and the blood glucose level is obtained by a blood glucose level conversion function using these as parameters. .

  Next, a second embodiment of the present invention will be described. 2nd Embodiment shows the case where the optical measurement unit 1 is used for sugar content detection, such as fruits and vegetables, For example, the case where the fructose of fruits is detected is demonstrated.

  That is, referring to FIG. 3 for explaining the optical measurement unit 1, the laser beam 20 is emitted at the first wavelength λ1, the second wavelength λ2, and the third wavelength λ3, and each wavelength is near-infrared light having a nearby wavelength. In this order, the wavelength becomes longer (λ1 <λ2 <λ3). The third wavelength λ3 is a wavelength at which only the absorbance by pure water is very large, and the second wavelength λ2 is a wavelength at which the absorbance by fructose is large. The first wavelength λ1 is fructose. This is a wavelength with a small extinction coefficient.

  The laser beam 20 of the light emitting unit 11 is focused by an appropriate lens aperture diameter NA, and irradiated to the measurement site 25 (fruit part) in the lower layer (inside) of the skin 251 at an angle θ. This angle θ is an angle formed by the center line in the vertical direction (up and down on the paper surface) of the light shielding plate 17 and the optical axis of the laser light 20, and is set to the most suitable angle for measuring the fructose concentration in the flesh part and irradiated. The focus points D and W of the beam are set to the points where the reflected light (diffuse reflected light) from the fructose of the flesh part can be obtained most efficiently. Here, the focus point D is a depth from the epidermis 251 and a depth suitable for the measurement of fructose is selected.

  For example, in the case of peach fruit, a part where the sugar content can be detected efficiently is specified to some extent depending on the type (shape) of the fruit, such as the fruit equator (abdomen) perpendicular to the suture line shows the average sugar content.

  Therefore, based on these, the focus points D and W and the angle θ suitable for the measurement of fructose are appropriately selected.

  Moreover, although the optical measurement unit 1 of this embodiment is a non-invasive system, it is used in contact with a measurement site. For example, in the measurement of sugar content by the reflection method of spectrum analysis, there is a problem that the irradiation position of near-infrared light varies depending on the shape and size of the fruit, but in this embodiment, it is possible to irradiate a desired position with laser light. .

  The light receiving unit 12 side is set to an angle θ ′ and focus points D ′ and W ′ for efficiently selecting the reflected light 21. The angle θ ′ is an angle formed by the vertical center line of the light shielding plate 17 and the optical axis of the reflected light 21, and the focus points D ′ and W ′ are the depth from the skin 251 and the center or edge of the light shielding plate 17, respectively. The distance from the part.

  Since the diffusely reflected beam basically has reflected light from all layers, reflection from a position where the average sugar content of the flesh is obtained by the angle θ ′, the focus points D ′, W ′, and the lens aperture diameter NA ′. It is set to selectively collect light.

Although detailed description other than this is omitted, since fructose is also a sugar component like glucose, the glucose of the first embodiment is fructose, and the measurement site is a flesh part from which the average sugar content of the fruit is obtained. It can be implemented in the same manner as in the first embodiment.

It is (A) external view, (B) sectional drawing, (C) top view, (D) top view for demonstrating this invention. It is (A) outline figure and (B) sectional view for explaining the present invention. It is (A) top view and (B) sectional drawing for demonstrating this invention. It is a characteristic view for demonstrating this invention. It is a characteristic view for demonstrating this invention. It is a characteristic view for demonstrating this invention. It is a circuit block diagram for demonstrating this invention. It is a circuit block diagram for demonstrating this invention. It is a flowchart for demonstrating this invention. It is a signal waveform diagram for demonstrating this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical measurement part 2 Display part 3 Attachment 4 Power switch 5 Measurement start / stop button 6 Control part 7 Power supply part 8 External housing 11 Light emission part 11a Condensing lens 12 Light receiving part 12a Condensing lens 13 APC
14 Amplifier 16 Temperature Sensor 17 Light-shielding Plate 18 Switch 20 Laser Light 21 Reflected Light 25 Measured Part 61 DSP
62 A / D Conversion Circuit 63 Laser Driver 64 Display Driver 65 Arithmetic Processing Unit 100 Blood Glucose Level Measuring Device 251 Epidermis 252 Dermis Layer 253 Subcutaneous Tissue λ1 First Wavelength λ2 Second Wavelength λ3 Third Wavelength I1 First Absorption Rate I2 Second Absorption Rate I3 Third Absorbance Ib1 First Reference Absorbance Ib2 Second Reference Absorbance Ib3 Third Reference Absorbance Ibr1 First Reference Corrected Absorbance Ibr2 Second Reference Corrected Absorbance Ir1 First Corrected Absorbance Ir2 Second Corrected Absorbance i Second derivative

Claims (12)

An optical measurement unit that has a light emitting unit, a light receiving unit, and a control unit, and measures sugar content in a measurement site,
The light emitting unit individually outputs near-infrared laser beams having an emission wavelength of a first wavelength, a second wavelength, and a third wavelength, respectively, with respect to the measurement site,
The light receiving unit detects reflected light of the laser beam reflected by the measurement site,
The control unit includes an arithmetic processing unit, and the arithmetic processing unit is a ratio in which the reflected light is absorbed into the sugar of the measurement site by the laser light having the first wavelength, the second wavelength, and the third wavelength. Converting the first absorbance, the second absorbance, and the third absorbance, calculating the second derivative of the first absorbance, the second absorbance, and the third absorbance, the second derivative, and the An optical measurement unit characterized in that the sugar content at the measurement site is calculated from values based on the first, second, and third absorbances. An optical measurement unit that has a light emitting unit, a light receiving unit, and a control unit, and measures sugar content in a measurement site,
The light emitting unit individually outputs near-infrared laser beams having an emission wavelength of a first wavelength, a second wavelength, and a third wavelength, respectively, with respect to the measurement site,
The light receiving unit detects reflected light of the laser beam reflected by the measurement site,
The control unit includes an arithmetic processing unit, and the arithmetic processing unit is a ratio in which the reflected light is absorbed into the sugar of the measurement site by the laser light having the first wavelength, the second wavelength, and the third wavelength. It converts into the 1st light absorbency, the 2nd light absorbency, and the 3rd light absorbency, computes the 2nd derivative of the 1st light absorbency, the 2nd light absorbency, and the 3rd light absorbency, and the 1st, 2nd light absorbency Is corrected with the third absorbance and a predetermined reference value to calculate a first corrected absorbance and a second corrected absorbance, and the second derivative value, the first and second corrected absorbances, and the An optical measurement unit that calculates sugar content at the measurement site based on a third absorbance.   The first wavelength, the second wavelength, and the third wavelength are adjacent wavelengths, and the wavelengths become longer in this order. The third wavelength has a very large absorbance by pure water, and only the absorbance by pure water is measured. The wavelength according to claim 1 or 2, wherein the second wavelength is a wavelength having a large absorbance due to the sugar, and the first wavelength is a wavelength having a small absorbance due to the sugar. The optical measurement unit described.   The arithmetic processing unit holds first, second, and third reference absorbances for the first, second, and third absorbances, respectively, and a reference shift amount is determined by the third absorbance and the third reference absorbance. The first and second reference corrected absorbances are calculated by correcting the first and second absorbances according to the reference shift amount, and calculating the first and second reference corrected absorbances. 3. The optical measurement unit according to claim 2, wherein the first corrected absorbance and the second corrected absorbance are calculated by correcting the values with the first and second reference absorbances, respectively.   The said 1st, 2nd, 3rd reference | standard light absorbency is the light absorbency of the said laser beam of the said 1st, 2nd, 3rd wavelength by the pure water measured previously, The 4th aspect is characterized by the above-mentioned. Optical measurement unit.   The optical measurement unit according to claim 1, further comprising a temperature detection unit, wherein the temperature detection unit performs temperature correction of the first wavelength, the second wavelength, and the third wavelength.   Measuring the temperature of the measurement site by the temperature detection unit, changing the temperature or driving current of the laser beam based on the temperature-dependent characteristic of the light absorption characteristic of the sugar, and controlling the emission wavelength of the laser beam The optical measurement unit according to claim 6.   The said light emission part outputs the said laser beam with the irradiation angle which diffusely reflects the said laser beam which injected from the said to-be-measured site | part by the depth suitable for the measurement of the said sugar content, The Claim 1 or Claim 2 characterized by the above-mentioned. The optical measurement unit described in 1.   The optical measurement unit according to claim 1, wherein the light emitting unit and the light receiving unit are disposed adjacent to each other through a light shielding plate in a housing.   The optical measurement unit according to claim 9, wherein the control unit detects that the light shielding plate is in contact with the measurement target part and starts a measurement process.   The optical measurement unit according to claim 1 or 2, wherein a position at which diffusely reflected light from the sugar is efficiently obtained is selected as the focus point to which the laser light is irradiated.   3. The optical according to claim 1, wherein the light receiving unit selects the reflected light, and a focus point and a condensing angle are selected so as to efficiently collect the reflected light. Measuring unit.

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