JP4773390B2 - Component concentration measuring device - Google Patents

Description

  The present invention relates to a component concentration measuring apparatus that performs non-invasive component concentration measurement on an object to be measured.

  With the aging of society, dealing with adult diseases is becoming a major issue. In blood glucose level and other tests, blood collection is necessary, which places a heavy burden on the patient. Therefore, a non-invasive component concentration measurement apparatus that does not collect blood has attracted attention. As a non-invasive component concentration measuring device that has been developed so far, the skin is irradiated with electromagnetic waves and absorbed by blood molecules to be measured, for example, glucose molecules in the case of blood glucose levels, and heated locally. Photoacoustic spectroscopy (hereinafter, “photoacoustic spectroscopy” is abbreviated as “PAS”) that observes sound waves generated from the living body by causing thermal expansion has attracted attention (for example, Non-Patent Document 1 and Patents). See reference 1.)

  FIG. 1 is a schematic diagram of a component concentration measuring apparatus using PAS described in Non-Patent Document 1. The blood component concentration measuring apparatus in FIG. 1 uses light pulses as electromagnetic waves. In this example, blood glucose, that is, glucose is the measurement target as the blood component. In the component concentration measurement apparatus of FIG. 1, the drive power supply 102 supplies a pulsed excitation current to the pulse light source 103. The pulse light source 103 generates a light pulse having a sub-microsecond duration, and irradiates the living body test part 101 with the light pulse. The light pulse generates a sound wave called a pulsed photoacoustic signal inside the living body test portion 101. The generated photoacoustic signal is detected by the ultrasonic detector 104 and further converted into an electric signal proportional to the sound pressure.

  The waveform of the converted electric signal is observed by the waveform observer 105. The waveform observer 105 is triggered by a signal synchronized with the excitation current, and displays the converted electric signal on a screen or the like. Further, the waveform observer 105 can measure the converted electric signals by integrating and averaging them. By analyzing the amplitude of the electrical signal thus obtained, the blood sugar level inside the living body test portion 101, that is, the amount of glucose is measured. The component concentration measuring apparatus shown in FIG. 1 generates light pulses having a sub-microsecond pulse width at a repetition of a maximum of 1 kHz, and averages 1024 light pulses.

  However, the interaction between glucose and electromagnetic waves is small, and there is a limit to the intensity of electromagnetic waves that can be safely irradiated to a living body, so that a sufficient effect has not been achieved in measuring blood glucose levels in the living body.

  Therefore, Patent Document 1 discloses a component concentration measuring apparatus that uses a light source that is continuously intensity-modulated for the purpose of improving measurement accuracy. FIG. 2 is a schematic view of a component concentration measuring apparatus using PAS described in Patent Document 1. In this example, blood glucose is the main measurement target. In order to improve measurement accuracy, a plurality of light sources having different wavelengths are used. In order to avoid complicated explanation, the operation when the number of light sources is two will be described. In the component concentration measurement apparatus of FIG. 2, light sources having different wavelengths, that is, a first light source 201 and a second light source 202 are driven by a driving power source 203 and a driving power source 204, respectively, and output continuous light.

  The light output from the first light source 201 and the second light source 202 is intermittently driven by a chopper plate 213 that is driven by a motor 214 and rotates at a constant rotational speed. Here, the chopper plate 213 is formed of an opaque material, and a sparse number of openings are formed on the circumference through which the light of the first light source 201 and the second light source 202 passes around the axis of the motor 214. Is formed.

With the above configuration, the light output from each of the first light source 201 and the second light source 202 is intensity-modulated at a modulation frequency f ₁ and a modulation frequency f ₂ that are sparse. The multiplexer 211 multiplexes the intensity-modulated lights and irradiates the living body test part 101 as one light beam.

A photoacoustic signal having a frequency f ₁ is generated by light from the _first light source 201 and a photoacoustic signal having a frequency f ₂ is generated by light from the _second light source 202 in the living body test part 101. The acoustic sensor 212 detects these photoacoustic signals and converts them into electrical signals proportional to the sound pressure. The frequency spectrum is observed by a frequency analyzer 215. In this example, the wavelengths of the plurality of light sources are all set to the absorption wavelength of glucose, and the intensity of the photoacoustic signal corresponding to each wavelength is measured as an electrical signal corresponding to the amount of glucose contained in the blood. The

Here, the relationship between the intensity of the measured value of the photoacoustic signal and the value obtained by measuring the glucose content by separately collected blood is stored in advance, and the amount of glucose is measured from the measured value of the photoacoustic signal. Yes.
JP-A-10-000189 University of Oulu (University of Ouru, Finland) dissertation "Pulsed photoacoustic techniques and glucose determination in human blood and tissue" (IBS 951-42-6690-0, 2001/95.

  The light that has entered the object to be measured by light irradiation is absorbed by the PAS, and is attenuated in the object by being scattered. Specifically, light is attenuated to approximately 1/10 at an attenuation distance obtained from the absorbance of moisture contained in the object to be measured. However, part of the light is transmitted without being absorbed or scattered due to the finite sample thickness of the object to be measured and the amount of water content. The transmitted leakage light is absorbed by the surface and peripheral portion of the acoustic detector facing the irradiation side, and a photoacoustic signal is also generated from these. Since the photoacoustic signal from the surface of the acoustic detector and the peripheral portion becomes noise of the photoacoustic signal generated from the object to be measured, there is a problem that the measurement accuracy of the component to be measured is significantly affected. In the following description, “photoacoustic signal from the surface of the acoustic detector and its peripheral portion” is abbreviated as “acoustic noise”.

  The present invention has been made in order to solve the above-described problems, and provides a component concentration measuring apparatus that can suppress acoustic noise caused by leaked light at a place other than the object to be measured and can measure the component concentration of the object to be measured with high accuracy. The purpose is to provide.

  In order to achieve the above object, the component concentration measuring apparatus according to the present invention includes a sound wave reflecting plate that transmits light from a light source and reflects a photoacoustic signal generated in the object to be measured.

  Specifically, the component concentration measuring apparatus according to the present invention includes a light irradiating unit that irradiates a laser beam with a modulated laser beam that is electrically intensity-modulated with a modulation signal having a predetermined frequency, and the modulated laser. A sound wave reflecting plate that is in the optical axis direction of light, transmits the modulated laser light that has passed through the object to be measured, and reflects a photoacoustic signal generated on the object to be measured by the modulated laser light; and the sound wave reflecting plate A sound intensity measuring means for detecting a photoacoustic signal generated on the object to be measured by the modulated laser light and a photoacoustic signal reflected by the sound wave reflection plate from the object to be measured; Is provided.

  Since the sound wave reflection plate transmits the leakage light, the acoustic noise caused by the leakage light at a place other than the object to be measured can be suppressed.

  In the component concentration measuring apparatus according to the present invention, it is preferable that the light irradiating means modulates the intensity of two different wavelength laser beams with the same frequency and opposite phase modulation signals. It is possible to detect a difference between acoustic signals generated by the irradiation of two light waves.

  In the component concentration measurement apparatus according to the present invention, the intersection of the optical axis of the modulated laser beam from the light irradiation unit and the sound collection central axis, which is the center of the direction in which the sound wave intensity measurement unit detects a photoacoustic signal, The angle of the optical axis of the modulated laser beam with the surface of the sound wave reflecting plate on the light irradiating means side of the sound wave reflecting plate is the central axis of sound collection of the sound wave intensity measuring means. Is preferably equal to the angle formed with the surface of the sound wave reflecting plate on the light irradiation means side. Photoacoustic signal transmission from the sound source of the object to be measured to the acoustic detector can be performed efficiently.

  The component concentration measuring apparatus according to the present invention preferably further includes a dielectric mirror that reflects the modulated laser light on a surface of the sound wave reflecting plate on the light irradiation means side. In order to reduce the leaked light that has passed through the object to be measured, an effect of reducing the generation amount of acoustic noise is achieved.

  The component concentration measuring apparatus according to the present invention preferably further includes a light absorber that absorbs the modulated laser light transmitted through the sound wave reflection plate on the side opposite to the light irradiation means side of the sound wave reflection plate. It absorbs leaked light that has passed through the sonic reflector, suppresses the generation of acoustic noise due to multiple reflections of leaked light, and has an effect of improving measurement accuracy.

  The light absorber and the sound wave reflecting plate of the component concentration measuring apparatus according to the present invention transmit the modulated laser light transmitted through the sound wave reflecting plate and reflect a photoacoustic signal generated by the light absorber. It is preferable to be connected via Since the photoacoustic signal generated by the light absorber is efficiently reflected at the interface between the spacer and the light absorber and does not propagate to the object to be measured, an effect of reducing acoustic noise is achieved.

  It is preferable that the light absorber and the sound wave reflecting plate of the component concentration measuring apparatus according to the present invention are connected by a support column that forms a gap into which gas enters between the light absorber and the sound wave reflecting plate. Since the photoacoustic signal generated in the light absorber is efficiently reflected at the interface between the air and the light absorber and does not propagate to the object to be measured, an effect of reducing acoustic noise is achieved.

  The present invention provides a component concentration measuring apparatus that can suppress the acoustic noise caused by the leaked light at a place other than the object to be measured and can accurately measure the component concentration of the object to be measured because the sound wave reflection plate transmits the leaked light. Can be provided.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment. In the following description, a component concentration measuring apparatus for measuring the component concentration of a human or animal subject as the object to be measured will be described, but the object to be measured is not limited to these. In addition, in this specification and drawing, the component with the same code | symbol shall show the same thing, respectively.

  In this embodiment, there is light irradiation means for irradiating the object to be measured with modulated laser light that is electrically intensity-modulated with a modulation signal of a predetermined frequency, and in the optical axis direction of the modulated laser light. A sound wave reflecting plate that transmits the modulated laser light transmitted through the object to be measured and reflects a photoacoustic signal generated in the object to be measured by the modulated laser light; and on the light irradiation means side of the sound wave reflecting plate, A sound intensity measuring means for detecting, from the object to be measured, a photoacoustic signal generated by the modulated laser beam on the object to be measured and a photoacoustic signal reflected by the sound wave reflection plate.

  As a basic configuration example of the present embodiment, a block diagram of a component concentration measuring apparatus 1 is shown in FIG. The component concentration measurement apparatus 1 includes a light irradiation unit 301, a sound wave intensity measurement unit 302, a sound wave reflection plate 303, an oscillator 309, and a photoacoustic signal output terminal 315.

  The light irradiation means 301 irradiates the object 900 to be measured with a modulated laser light L obtained by electrically modulating the intensity of the laser light with a modulation signal having a predetermined frequency. The laser light may be one wavelength or a plurality of wavelengths. The light irradiation means 301 preferably modulates the intensity of two different wavelengths of laser light with the same frequency and opposite phase modulation signals. The component concentration measuring apparatus 1 can detect a difference between acoustic signals generated by the irradiation of two light waves, and can measure the component concentration of the detected object 900 with high accuracy. In this case, as shown in FIG. 3, the light irradiation means 301 includes a first light source 31-1, a second light source 31-2, a drive circuit 32-1, a drive circuit 32-2, a delay adjuster 33, and an optical fiber 34. -1, an optical fiber 34-2, an optical multiplexer 35, an optical fiber 36, and a light emitting portion 37.

  The drive circuit 32-1 and the drive circuit 32-2 supply current to the second light source 31-1 and the second light source 31-2, respectively. The oscillator 309 supplies a voltage to the drive circuit 32-1 and the drive circuit 32-2. The oscillator 309 has a function of generating a pulse train having an arbitrary frequency. The delay adjuster 33 adjusts the delay to a half of the cycle in order to drive the first light source 31-1 and the second light source 31-2 in opposite phases.

  The modulated laser beams generated by the first light source 31-1 and the second light source 31-2 are respectively transmitted to the optical input terminal of the optical multiplexer 35 by the optical fiber 34-1 and the optical fiber 34-2 which are light transmission means. Connected. The optical multiplexer 35 outputs the combined modulated laser light L from the optical output terminal, and supplies it to the light emitting portion 37 via the optical fiber 36 that is an optical transmission means. The light emitting unit 37 emits the modulated laser light L to the object 900 to be measured. The light emitting portion 37 may be the tip of the optical fiber 36, but may be a right-angle prism, a fiber collimator, or a ferrule that matches the shape of the measured object 900 in order to efficiently emit the modulated laser light L to the measured object 900.

  The light irradiation unit 301 controls the first light source 31-1 and the second light source 31-2, so that the modulated laser light L on which the wavelength of light from each light source is superimposed or the light from one light source is superimposed. Modulated laser light L having only a wavelength can be emitted. The modulated laser light L emitted from the light emitting unit 37 generates a photoacoustic signal by PAS inside the object to be measured 900.

  The sound wave reflection plate 303 is in the optical axis direction of the modulated laser light L from the light irradiation means 301, transmits the modulated laser light L that has passed through the measured object 900, and is generated in the measured object 900 by the modulated laser light L. Reflect photoacoustic signals.

  The sound wave reflection plate 303 transmits the modulated laser light L that passes through the object to be measured 900 and emits it into the air as leakage light. The sound wave reflecting plate 303 is not only a material having high acoustic reflection efficiency, but also needs to suppress the generation of acoustic noise of the sound wave reflecting plate 303 itself. Therefore, the sound wave reflection plate 303 needs to be small enough that the light absorption in the wavelength band of the first light source 31-1 and the second light source 31-2 is negligible compared to the DUT 900. Furthermore, the sound wave reflection plate 303 is preferably made of a material that transmits 90% or more of the light having the two wavelengths of the first light source 31-1 and the second light source 31-2. The sound wave reflection plate 303 is, for example, a glass plate or a sapphire plate.

  The sound wave intensity measuring unit 302 includes a sound wave detection unit 41, a preamplifier 42, and a phase detection amplifier 43. The sound intensity measuring means 302 is located on the light irradiating means 301 side of the sound wave reflection plate 303, and measures the photoacoustic signal generated on the measurement object 900 by the modulated laser light L and the photoacoustic signal reflected by the sound wave reflection plate 303. Detect from the object 900.

  The sound wave detection unit 41 detects a photoacoustic signal generated in the measurement object 900 directly or after reflection by the sound wave reflection plate 303. The sound wave detection unit 41 converts the detected photoacoustic signal into an electrical signal. The preamplifier 42 amplifies the electric signal from the sound wave detection unit 41. The phase detection amplifier 43 is based on the electrical signal from the oscillator 309, and the amplitude and phase of the same frequency component as the modulation frequency of the first light source 31-1 and the second light source 31-2 from the electrical signal from the preamplifier 42. Is extracted and output to the photoacoustic signal output terminal 315. By using an electrical signal from the oscillator 309, a photoacoustic signal measurement signal based on the modulated laser beam L can be output with high accuracy.

The photoacoustic signal output terminal 315 has a photoacoustic signal measurement signal (s ₁ -s ₂ ) based on the modulated laser light L on which two wavelengths are superimposed and a photoacoustic signal measurement signal s ₂ based on the modulated laser light L of only one wavelength. Is output. A calculation method for obtaining the concentration M using the measurement signal output below will be described.

Here, it is assumed that the wavelength of light output from the first light source is λ ₁ and the wavelength of light output from the second light source is λ ₂ . For each of the wavelengths λ ₁ and λ ₂ , when knowing the background absorption coefficients α ₁ ^(w) and α ₂ ^(w) and the molar absorption coefficients α ₁ ^(g) and α ₂ ^(g) of the components to be measured, The simultaneous equations including the measurement signals s ₁ and s ₂ measured at each wavelength can be expressed by Equation (1). The background absorption coefficient is, for example, the absorption coefficient of water.

Here, C is a coefficient that varies and is difficult to control or predict. For example, the unknown multiplier also depends on the acoustic coupling, the sensitivity of the ultrasonic detector, the distance r from the irradiation part to the contact part, the specific heat, the thermal expansion coefficient, the sound speed, the modulation frequency, and the absorption coefficient. Here, if the two wavelengths λ ₁ and λ ₂ are set to wavelengths with substantially the same background absorption coefficient, α ₁ ^(w) = α ₂ ^(w) , so C is deleted from Equation (1), The concentration M can be derived as shown in Equation (2).

The measurement signal s ₁ and the measurement signal s ₂ are measurement results, and the background absorption coefficients α ₁ ^(w) and α ₂ ^(w) for each of the wavelengths λ ₁ and λ ₂ and the molar absorption coefficient α ₁ ^{(g ) And} α ₂ ^(g) are known values. Therefore, the concentration M can be calculated from the measured photoacoustic signal and a known value.

  Next, the component concentration measuring apparatus 1 in FIG. 3 will be described in detail with reference to FIG. FIG. 4 is a schematic view showing a cross section of the component concentration measuring apparatus 1. FIG. 4 shows a column 434, a light absorber 435, and an optical modulation signal input terminal 409 not shown in FIG.

  The light irradiation means 301 and the sound wave intensity measuring means 302 are in contact with the boundary of the measurement object 900 at an equal angle, and are arranged at a distance where the central axes of the light irradiation means 301 and the sound wave intensity measuring means 302 intersect on the surface of the sound wave reflection plate 303. . Specifically, the intersection of the optical axis of the modulated laser light L from the light irradiation means 301 and the sound collection central axis that is the center of the direction in which the sound wave intensity measurement means 302 detects the photoacoustic signal is The angle formed by the optical axis of the modulated laser beam L and the surface of the sound wave reflection plate 303 on the light irradiation unit 301 side is on the surface of the light irradiation unit 301 side. Is equal to the angle formed with the surface on the light irradiation means 301 side. Photoacoustic signal transmission from the sound source of the object to be measured to the acoustic detector can be performed efficiently.

  The light absorber 435 is on the opposite side of the sound wave reflection plate 303 from the light irradiation means 301 side, and absorbs the leaked light T transmitted through the sound wave reflection plate 303 in the modulated laser light L. It absorbs leaked light that has passed through the sonic reflector, suppresses the generation of acoustic noise due to multiple reflections of leaked light, and has an effect of improving measurement accuracy. The light absorber 435 is desirably a foaming material having a sound absorbing effect, and examples thereof include foamed urethane and black rubber.

  The column 434 connects the light absorber 435 and the sound wave reflection plate 303 so as to form a gap for gas to enter between the light absorber 435 and the sound wave reflection plate 303. The material of the column 434 is, for example, metal, ceramics, or plastic. In normal use, the gas between the light absorber 435 and the sound wave reflector 303 is air. Since the photoacoustic signal generated by the light absorber 435 reflects the interface between the air and the light absorber with high efficiency and does not propagate to the device under test 900, there is an effect of reducing acoustic noise.

  Further, the light absorber 435 and the sound wave reflection plate 303 may be connected via a spacer instead of the support column 434. Specifically, a solid or liquid serving as a spacer may be filled between the light absorber 435 and the sound wave reflection plate 303 in FIG. The spacer is preferably one that transmits the leakage light T and efficiently reflects the photoacoustic signal generated by the light absorber 435 at the interface with the light absorber 900. The spacer is, for example, silicone rubber or an acrylic plate.

従って、被測定物９００と音波反射板３０３の音響インピーダンスの比（Ｚ_１／Ｚ_２，Ｚ_１＜Ｚ_２の場合）が小さいほど反射効率が良い。被測定物９００が水や生体の場合、音波反射板３０３の部材として音響インピーダンスが高い金属やガラスが好適である。 Next, the sound wave reflection plate 303 will be described. When the thickness of the sound wave reflection plate 303 is larger than the wavelength of the photoacoustic signal, the reflectance R can be obtained by setting the specific acoustic impedance of the DUT 900 to Z ₁ and the specific sound impedance of the sound wave reflection plate 303 to Z _2. It can obtain | require by Numerical formula (3).

Therefore, the smaller the ratio of the acoustic impedance of the DUT 900 and the sound wave reflector 303 (in the case of Z ₁ / Z ₂ , Z ₁ <Z ₂ ), the better the reflection efficiency. When the measurement object 900 is water or a living body, a metal or glass with high acoustic impedance is suitable as a member of the sound wave reflection plate 303.

ここで、Ｚ_３は空隙の音響インピーダンスである。従って、Ｚ_１＜＜Ｚ_２の場合、反射効率Ｒを高くするために、音波反射板３０３の厚みｄとしてｋｄがπの整数倍となるｄを避ける必要がある。 In addition, when the thickness of the sound wave reflection plate 303 is equal to or less than the wavelength λ (wave number k = 2π / λ) of the photoacoustic signal, the reflectance R is expressed by the equation (4) if the thickness d of the sound wave reflection plate 303 is set. )become that way.

Here, Z ₃ is the acoustic impedance of the air gap. Therefore, in the case of Z ₁ << Z ₂ , it is necessary to avoid d where kd is an integral multiple of π as the thickness d of the sound wave reflection plate 303 in order to increase the reflection efficiency R.

  The component concentration measuring apparatus 1 measures the component concentration by sandwiching the measurement object 900 between the light irradiation means 301, the sound wave intensity measuring means 302 and the sound wave reflection plate 303. Specifically, the light irradiation means 301 irradiates the device under test 900 with the modulated laser light L based on the modulation signal input to the light modulation signal input terminal 409. A photoacoustic signal A is generated inside the device under test 900 by PAS. Some of the photoacoustic signals A go directly to the sound wave intensity measuring means 302, but some of them are reflected by the sound wave reflection plate 303 and go to the sound wave intensity measuring means 302. The modulated laser light L that has not contributed to the generation of the photoacoustic signal A passes through the sound wave reflection plate 303 and is absorbed by the light absorber 435. The sound wave intensity measuring means 302 detects the photoacoustic signal from the surface of the measurement object 900 and outputs it to the photoacoustic signal output terminal 315 as described with reference to FIG.

(Example)
EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this invention is not limited by this. FIG. 5 is a schematic cross-sectional view of the component concentration measuring apparatus 2 used in this example. The component concentration measuring apparatus 2 further includes a table 11, a support column 12, a measured object fixing mechanism 13, a dielectric mirror 51, an aluminum plate 52, an optical attachment 53, and an acoustic attachment 54 in the component concentration measuring apparatus 1 of FIG. In the present embodiment, the measurement object 900 is a human body, and the component concentration measuring device 2 measures the glucose concentration in the blood.

  The aluminum plate 52 mounts a light irradiation means 301, a sound wave intensity measurement means 302, a light attachment 53, and an acoustic attachment 54. Here, the material of the aluminum plate 52 may be a metal other than aluminum or ceramics. The sound wave reflection plate 303 uses a glass plate. The material of the column 434 is aluminum. The light absorber 435 uses black rubber.

  The light irradiation means 301 incorporates a 1.38 μm band DFB-LD and a 1.61 μm band DFB-LD as the first light source 31-1 and the second light source 31-2, respectively. Each LD is appropriately temperature-controlled by a Peltier element. Although not shown in FIG. 5, the signal from the oscillator 309 described in FIG. 3 is input to the optical modulation signal input terminal 409. Each LD emits modulated laser beams having opposite phases. The average optical power was set to about 10 mW and the modulation frequency was set to 350 kHz. The modulated laser beams from the two LDs are collimated into parallel light by the ball lens and are multiplexed by the optical multiplexer 35 described with reference to FIG. The light irradiation means 301 irradiates the object 900 to be measured with the combined modulated laser light L from the light exit window via the light attachment 53. The optical attachment 53 includes a prism and a lens, and changes an optical path and sets an irradiation spot diameter. In this example, an irradiation spot having an incident angle of 30 degrees and a radius of 2 mm was formed on the surface of the measurement object 900.

A dielectric mirror 51 that reflects the modulated laser light L is further provided on the surface of the sound wave reflection plate 303 on the light irradiation means 301 side. A dielectric mirror 51 that reflects light in the 1.38 μm band and the 1.61 μm band is deposited on the sound wave reflection plate 303. On the dielectric mirror 51, SiO ₂ and TiO ₂ having different refractive indexes are deposited in a single layer or multiple layers. In order to reduce the leaked light that has passed through the object to be measured, an effect of reducing the generation amount of acoustic noise is achieved.

  The acoustic attachment 54 matches the acoustic impedance between the sound intensity measuring means 302 and the object 900 to be measured. The material and thickness of the acoustic attachment 54 are based on the mathematical formula (2), and silicone rubber is used as a material that matches the object to be measured. The thickness of the silicone rubber was 1 mm. In addition, the angle formed by the sound collection center axis of the sound intensity measuring means 302 and the surface of the object 900 is 30 degrees.

  The object to be measured 900 is fixed by being sandwiched between the aluminum plate 52 and the glass plate as the sound wave reflection plate 303. The surface may be smoothed so that the air does not enter the boundary between the aluminum plate 52 or the glass plate and the object 900 to be measured. The measured object fixing mechanism 13 includes a motor that adjusts the distance between the aluminum plate 52 and the sound wave reflecting plate 303. The measured object fixing mechanism 13 can repeatedly pinch the measured object 900 while controlling an appropriate pressure. The measured object fixing mechanism 13 is fixed to the table 11 by the support 12.

FIG. 6 shows the result of measuring the glucose concentration in the blood of the human body with a conventional component concentration measuring apparatus. FIG. 7 shows the result of measuring the glucose concentration in the blood of the human body with the component concentration measuring apparatus 2 of FIG. Photoacoustic signal are the linear to power and absorbance, when power and absorbing medium is constant, the wavelength lambda ₁ of the acoustic signal and the wavelength lambda ₁ and lambda ₂ acoustic signal obtained by subtracting the (broken line in the figure) Maintain a certain ratio in the frequency domain. As shown in FIG. 6, when measured by conventional constituent concentration measuring apparatus, unspecified acoustic noise is generated, the acoustic signal and the wavelength lambda ₁ and the acoustic signal obtained by subtracting the lambda ₂ wavelength lambda ₁ is a constant proportional relationship There wasn't. On the other hand, as shown in Figure 7, when measured at constituent concentration measuring apparatus 2, consistent across the frequency domain when the acoustic signal and the wavelength lambda ₁ and lambda ₂ wavelength lambda ₁ compares the 30-fold acoustic signals difference, acoustic noise It was not mixed. As shown in the above measurement results, the component concentration measuring apparatus 2 calculates the component concentration M of the object to be measured without mixing unspecified acoustic noise in the acoustic signal values s ₁ and s ₂ in the formula (2). I was able to.

  The component concentration measuring apparatus of the present invention can measure a human blood component with high accuracy in a non-invasive manner. Furthermore, since the component concentration measuring apparatus of this invention can measure the component density | concentration in a liquid, it can be applied also to the sugar content measurement of a fruit, for example.

It is the schematic of the conventional component concentration detection apparatus. It is the schematic of the conventional component concentration detection apparatus. It is the schematic of the component concentration detection apparatus which concerns on this invention. It is the schematic of the component concentration detection apparatus which concerns on this invention. It is the schematic of the component concentration detection apparatus which concerns on this invention. It is the result of having measured the glucose concentration in the blood of a human body with the component concentration detection apparatus. It is the result of having measured the glucose concentration in the blood of a human body with the component concentration detection apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Component density | concentration detection apparatus 101 Living body test part 102 Drive power supply 103 Pulse light source 104 Ultrasonic detector 105 Waveform observer 201 1st light source 202 2nd light source 203,204 Drive power supply 211 Multiplexer 212 Acoustic sensor 213 Chopper plate 214 Motor 215 Frequency analyzer 11 Stand 12 Support 13 Measurement object fixing mechanism 301 Light irradiation means 31-1 First light source 31-2 Second light source 32-1, 32-2 Drive circuit 33 Delay adjuster 34- 1, 34-2, 36 Optical fiber 35 Optical multiplexer 37 Light emitting unit 302 Sound wave intensity measuring means 41 Sound wave detecting unit 42 Preamplifier 43 Phase detection amplifier 303 Sound wave reflector 309 Oscillator 315 Photoacoustic signal output terminal 409 Optical modulation signal Input terminal 434 Support column 435 Light absorber 51 Dielectric mirror 52 Aluminum plate 53 Optical attachment 54 Acoustic attachment Chimento 900 DUT L modulated laser beam A photoacoustic signal T leakage light

Claims (7)

A light irradiating means for irradiating the object to be measured with modulated laser light obtained by electrically modulating the intensity of the laser light with a modulation signal of a predetermined frequency;
A sound wave reflector that is in the optical axis direction of the modulated laser light, transmits the modulated laser light transmitted through the object to be measured, and reflects a photoacoustic signal generated on the object to be measured by the modulated laser light;
The sound wave intensity that is on the light irradiation means side of the sound wave reflector and detects the photoacoustic signal generated on the object to be measured by the modulated laser light and the photoacoustic signal reflected on the sound wave reflector from the object to be measured. Measuring means;
A component concentration measuring device.   2. The component concentration measuring apparatus according to claim 1, wherein the light irradiating means modulates the intensity of two different wavelengths of laser light with modulated signals having the same frequency and opposite phases.   The intersection of the optical axis of the modulated laser light from the light irradiating means and the sound collecting central axis that is the center of the direction in which the sound intensity measuring means detects the photoacoustic signal is the light irradiating means side of the sound wave reflector. The angle formed by the optical axis of the modulated laser beam and the surface of the sound wave reflecting plate on the light irradiating means side is such that the sound collecting central axis of the sound wave intensity measuring means is the light irradiating means of the sound wave reflecting plate. The component concentration measuring apparatus according to claim 1, wherein the component concentration measuring apparatus is equal to an angle formed with a side surface.   4. The component concentration measuring apparatus according to claim 1, further comprising a dielectric mirror that reflects the modulated laser light on a surface of the sound wave reflecting plate on the light irradiation unit side. 5.   5. The light absorber according to claim 1, further comprising a light absorber that absorbs the modulated laser light transmitted through the sound wave reflection plate on a side opposite to the light irradiation unit side of the sound wave reflection plate. Component concentration measuring device.   The light absorber and the sound wave reflection plate are connected via a spacer that transmits the modulated laser light transmitted through the sound wave reflection plate and reflects a photoacoustic signal generated by the light absorber. The component concentration measuring apparatus according to claim 5, wherein:   6. The component concentration according to claim 5, wherein the light absorber and the sound wave reflecting plate are connected by a support column that forms a gap into which a gas enters between the light absorber and the sound wave reflecting plate. measuring device.

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