JP2019007824A - Optical acoustic measurement probe - Google Patents

Abstract

To provide an optical acoustic measurement probe that can detect an optical acoustic wave more sensitively.SOLUTION: In an optical acoustic wave detection unit 14 of the optical acoustic measurement probe, a cantilever 29 is arranged. The cantilever 29 is formed into a thin film and has a piezo-resistance layer on the front surface of a silicon layer. An acoustic impedance matching material 27 is formed in the inside of the probe closer to the contact surface than to the cantilever 29, and the vibration of the cantilever 29 is detected as a change of a resistance value. The cantilever 29 is arranged between a gas layer 38 and a liquid layer 39.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a photoacoustic measurement probe.

  The photoacoustic measurement device detects a photoacoustic wave (elastic wave) that is generated when the molecule inside the measurement target absorbs the pulsed light that is irradiated and instantaneously expands, and based on the photoacoustic wave In addition, a photoacoustic measurement apparatus that can determine the concentration of molecules that have absorbed pulsed light is known (see, for example, Patent Document 1). The photoacoustic measurement device includes a photoacoustic measurement probe. The photoacoustic measurement probe is a light irradiation unit that irradiates a measurement target with pulsed light, and a photoacoustic that detects a photoacoustic wave from inside the measurement target. It has a wave detector.

JP 2002-328116 A

  By the way, it cannot be said that the photoacoustic wave detection part of the photoacoustic measurement probe has sufficient detection sensitivity. For this reason, photoacoustic measurement that can be detected with higher sensitivity is desired.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a photoacoustic measurement probe capable of detecting a photoacoustic wave with higher sensitivity.

  The photoacoustic measurement probe of the present invention is housed in a first housing part, and is irradiated with intensity-modulated light toward the measurement object, and is housed in the second housing part, and light from the measurement object. A photoacoustic wave detection unit for detecting an acoustic wave, the photoacoustic wave detection unit, a cavity formed inside the second housing part, a base part that partitions the inside and the outside of the cavity, and A communication hole that is formed in the base and connects the inside and the outside of the cavity, and is arranged in the communication hole. The base end is formed in a plate shape that is supported by the base, and is formed in the penetrating direction of the communication hole. A cantilever having flexibility and a resistance layer made of a semiconductor on the surface layer, a gas layer provided on the first surface side of the cantilever, and an acoustic impedance matching provided on the measurement object side from the cantilever With materials That.

  According to the present invention, since the photoacoustic wave is detected by the cantilever and the acoustic impedance matching material is provided between the cantilever and the measurement target, the photoacoustic wave can be detected with higher sensitivity.

It is explanatory drawing which shows the structure of the photoacoustic measuring device which concerns on 1st Embodiment. It is explanatory drawing which decomposes | disassembles and shows the structure of a photoacoustic measuring probe. It is a perspective view which shows the external appearance of the sensor part in which the cantilever was formed. It is sectional drawing which expands and shows the principal part of a photoacoustic wave detection part. It is a circuit diagram which shows the example of a circuit structure of a detection circuit. It is sectional drawing which shows the photoacoustic measurement probe of 2nd Embodiment. It is sectional drawing which shows the structure of a variable focus lens. It is sectional drawing which shows a state with a large curvature of a variable focus lens. It is sectional drawing which shows the photoacoustic measuring probe of 3rd Embodiment. It is sectional drawing which expands and shows the principal part of the photoacoustic measurement probe of 3rd Embodiment. It is sectional drawing which shows the photoacoustic measuring probe of 4th Embodiment. It is sectional drawing which shows the photoacoustic measuring probe of 5th Embodiment.

[First Embodiment]
In FIG. 1, a photoacoustic measurement device (hereinafter simply referred to as a measurement device) 10 includes a photoacoustic measurement probe (hereinafter simply referred to as a probe) 11 and a circuit unit 12. The probe 11 includes a light irradiation unit 13 and a photoacoustic wave detection unit 14 and is accommodated in a housing 15. The circuit unit 12 includes a drive unit 16, a detection circuit 17, a concentration calculation unit 18, and a control unit 19 that comprehensively controls them.

  The measuring apparatus 10 irradiates the measurement target 21 with light from the light irradiation unit 13, and the photoacoustic wave detection unit 14 generates photoacoustic waves (elastic waves) generated by the photoacoustic effect inside the measurement target 21 due to the light irradiation. Detect with. In this example, the measurement target 21 is a living body, and the blood glucose concentration in the blood vessel 22 inside the measurement target 21 is measured as a measurement component from the detection result of the photoacoustic wave. Note that the measurement target and the measurement component are not limited to this.

  The housing 15 has a structure in which a first housing portion 15 a that houses the light irradiation unit 13 and a second housing portion 15 b that houses the photoacoustic wave detection unit 14 are integrated. A plate 25 and a sealing film 26 are provided. At the time of measurement, the contact surface 11 a of the probe 11 is brought into close contact with the surface of the measurement object 21. In this example, the outer surface of the sealing film 26 that prevents leakage of the acoustic impedance matching material 27 accommodated in the housing 15 is the contact surface 11a. The probe 11 is, for example, a small piece having a casing 15 of about several millimeters square and a thickness of about several millimeters. For example, the probe 11 is arranged on the surface of the measurement target 21, and the probe 11 is placed on the measurement target 21 from above. It can be used by sticking with adhesive tape or the like to hold down. For example, the probe 11 may be attached to the surface of the measurement target 21 by interposing a gel used for ultrasonic inspection between the probe 11 and the measurement target 21. In the following, for convenience, the direction in which the contact surface 11a exists in the vertical direction will be described below the probe 11, but the direction of the probe 11 is not limited.

  The drive unit 16 drives the light source 28 provided in the light irradiation unit 13 and outputs light whose intensity is modulated from the light source 28. In this example, the drive unit 16 outputs pulsed light from the light source 28 as intensity-modulated light, and outputs the pulsed light a plurality of times, for example, about 5 times in one measurement. The intensity-modulated light is not limited to light that completely blocks the output of light, such as pulsed light, and for example, the light may be modulated so as to reduce the intensity to a predetermined level (> 0). The detection circuit 17 converts the detection result of the photoacoustic wave detected as a change in the resistance value of a cantilever 29 (see FIG. 2), which will be described in detail later, into a detection signal and outputs the detection signal. The concentration calculation unit 18 calculates the blood glucose concentration based on the detection signal.

  In FIG. 2, a first cavity 31 is provided inside the housing body 24 on the first housing portion 15a side, and a second cavity 32 is provided inside the second housing portion 15b side. In addition, a housing chamber 33 for housing the acoustic impedance matching material 27 is provided in the lower portion of the housing body 24. The 1st cavity 31 and the 2nd cavity 32 are each opened to the storage chamber 33 side. The partition plate 25 is disposed above the accommodation chamber 33 and partitions the first cavity 31 and the second cavity 32 from the accommodation chamber 33. The partition plate 25 is bent in a V shape and includes a first plate portion 25a on the first housing portion 15a side and a second plate portion 25b on the second housing portion 15b side. The upper portion of the storage chamber 33 is defined by the partition plate 25, so that the storage chamber 33 has a groove shape with a V-shaped cross section. The partition plate 25 prevents the acoustic impedance matching material 27 from entering the first cavity 31 and the second cavity 32 even when the acoustic impedance matching material 27 is a liquid.

  The light irradiation unit 13 includes the above-described light source 28 and a lens 34 as a light collecting unit, both of which are arranged in the first cavity 31. The light source 28 is fixed to the upper surface of the first cavity 31 parallel to the first plate portion 25a. As the light source 28, a light source that outputs light having a wavelength corresponding to a component to be measured is used, and the wavelength is not limited. Light in the near-infrared to mid-infrared region (having a wavelength of about 0.7 to 4 to 5 μm) is useful and preferable for quantifying the molecular stoichiometry because it becomes the absorption wavelength of many molecules.

  In this example, as the light source 28, a laser diode that outputs laser light having a wavelength of about 1.6 μm, in which blood glucose has an absorption wavelength, is used. In addition, as the light source 28, you may use things other than a laser diode, for example, LED, organic EL, etc. In addition to the light source 28 that outputs a single wavelength, a light source that outputs light including light components of a plurality of wavelengths may be used. Further, a light source 28 having a variable wavelength of light to be output may be used so that light having a wavelength corresponding to a component to be measured can be irradiated.

  The lens 34 is provided on the surface of the first plate portion 25a on the first cavity 31 side. This lens 34 is a plano-convex lens and condenses light from the light source 28. In this example, the curvature, refractive index, and the like of the lens 34 are determined so that light is collected in the blood vessel 22 inside the measurement target 21.

  Light from the light source 28 is applied to the measurement target 21 through the lens 34, the first plate portion 25 a, the acoustic impedance matching material 27, and the sealing film 26. Therefore, the lens 34, the first plate portion 25 a, the acoustic impedance matching material 27, and the sealing film 26 are made of a material that is transmissive to light from the light source 28, and they absorb light from the light source 28. A low rate is preferred.

  The photoacoustic wave detection unit 14 constitutes a part of the housing and has a second plate part 25b in which a communication hole 36 is formed, a sensor part 37 including a cantilever 29, a gas layer 38, a liquid layer 39, and acoustic impedance matching. A material 27 is provided. The communication hole 36 penetrates through the second plate portion 25b in the thickness direction so as to communicate the inside of the second cavity 32 and the storage chamber 33 (outside of the second cavity 32). A sensor unit 37 is disposed inside.

  In the photoacoustic wave detection unit 14, the photoacoustic wave propagating through the acoustic impedance matching material 27 is transmitted from the second plate portion 25 b to the cantilever 29 to vibrate the cantilever 29. The second plate portion 25b is configured to efficiently transmit the photoacoustic wave to the cantilever 29. For this reason, it is preferable that the 2nd board part 25b is formed with hard materials, for example, semiconductor materials, such as Si, SiC, GaAs, GaN, Ge, or a metal. In this example, the second plate portion 25b is a base portion.

  The sensor unit 37 is provided at a position close to the second cavity 32 side in the communication hole 36. As will be described in detail later, the cantilever 29 provided in the sensor unit 37 vibrates with a photoacoustic wave as indicated by a two-dot chain line in FIG. 4 and changes its resistance value due to deformation during the vibration. is there. Since the cantilever 29 is a thin film having a thickness of, for example, about 0.3 μm, the cantilever 29 is easily vibrated by a weak photoacoustic wave, and high detection sensitivity is obtained.

  The gas layer 38 is formed as a space between the cantilever 29 and the storage chamber 33 in the communication hole 36. That is, the gas layer 38 is a space in which the second cavity 32 side is closed with the cantilever 29 and the liquid layer 39 and the accommodation chamber 33 side is closed with the acoustic impedance matching material 27. Although air is used as the gas constituting the gas layer 38, the present invention is not limited to this. For example, an inert gas such as nitrogen may be used. As will be described later, the gas layer 38 is composed of the liquid constituting the liquid layer 39, the surface tension and viscosity of the acoustic impedance matching material 27, the pressure difference between them and the gas layer 38, and the like. The impedance matching material 27 is maintained by not flowing into the communication hole 36.

  The liquid layer 39 is provided on the surface of the second plate part 25b on the second cavity 32 side, and the liquid constituting the liquid layer 39 is held on the second plate part 25b by being covered with the holding film 39a. . The liquid layer 39 is disposed in the second cavity 32. As the liquid constituting the liquid layer 39, it is desirable to select a liquid that has a large surface tension, has a certain degree of viscosity, and is chemically stable. For example, as the liquid constituting the liquid layer 39, silicone oil is used, and the holding film 39a is formed by forming a paraxylylene-based polymer (for example, parylene (registered trademark)) on the surface of the liquid layer 39 by a CVD method. The liquid constituting the liquid layer 39 may be a non-conductive liquid and is not limited to silicone oil. In addition, as the liquid constituting the liquid layer 39, a liquid substance such as gel can be used. Examples of the liquid constituting the liquid layer 39 include liquid paraffin, glycerin and the like in addition to silicone oil. The holding film 39a may be any film that can hold the liquid constituting the liquid layer 39 without leaking.

  The gas layer 38 and the liquid layer 39 efficiently vibrate the cantilever 29 with photoacoustic waves to improve detection sensitivity, particularly detection sensitivity for high-frequency photoacoustic waves. That is, the cantilever 29 is vibrated by the photoacoustic wave propagated to the second plate portion 25b, and the cantilever 29 is vibrated efficiently by the configuration in which the cantilever 29 is arranged at the boundary between the gas layer 38 and the liquid layer 39.

  The inside of the second cavity 32 may be filled with a liquid constituting the liquid layer 39, or a space other than the liquid layer 39 may be filled with a gas as in this example. When the space other than the liquid layer 39 is filled with gas, the surface of the liquid layer 39 opposite to the cantilever 29 is in contact with the gas in the second cavity 32, and the gas in the second cavity 32 and the liquid layer 39 are in contact with each other. A boundary is formed. Since the photoacoustic wave is reflected at this boundary and the photoacoustic wave is collected at or near the cantilever 29, higher detection sensitivity can be achieved.

  The acoustic impedance matching material 27 is for reducing reflection when the photoacoustic wave from the measurement target 21 enters the probe 11 and is accommodated in the accommodation chamber 33 as described above. In this example, water is used as the acoustic impedance matching material 27. As the acoustic impedance matching material 27, a material having an acoustic impedance intermediate between the measurement target 21 and the second plate portion 25b is selected. The acoustic impedance matching material 27 may be a liquid such as silicone oil other than water, a solid, a solid or gel substance, or an elastic body such as silicone rubber.

  The acoustic impedance matching material 27 is accommodated in the accommodation chamber 33 after the partition plate 25 provided with the lens 34, the sensor unit 37, and the liquid layer 39 is attached to the housing body 24. The sealing film 26 closes the lower opening of the accommodation chamber 33. The sealing film 26 prevents leakage of the acoustic impedance matching material 27 from the bottom of the housing 15. The sealing film 26 is formed in a thin film shape using, for example, an epoxy resin. Thus, since the thin sealing film 26 hardly reflects the photoacoustic wave, it is not particularly necessary to consider its acoustic impedance. As the sealing film 26, a material having flexibility (flexibility) is preferable in order to bring the probe 11 into close contact with the surface of the measurement target 21 without a gap between the measurement target 21.

  When the acoustic impedance matching material 27 is solid and can be fixed to the housing 15, the sealing film 26 can be omitted. When the sealing film 26 is omitted in this way, the contact surface 11 a of the probe 11 becomes the lower surface of the acoustic impedance matching material 27.

  In this example, both the light irradiation unit 13 and the photoacoustic wave detection unit 14 are inclined and arranged in the housing 15 so as to be directed to the position where the measurement component in the measurement target 21 is measured. The light is irradiated in that direction, and the photoacoustic wave detector 14 effectively detects the photoacoustic wave from that direction (measurement position). Specifically, the photoacoustic wave detection unit 14 is tilted so that the normal direction of the communication hole 36 of the second plate portion 25b and the surface portion around the communication hole 36 is directed to the measurement position.

  As shown in FIG. 3, the sensor unit 37 includes a cantilever 29 and a frame 43 that are integrally formed. The cantilever 29 has a plate shape with a thickness of about 0.3 μm, for example, and is provided in a hole penetrating the center of the frame 43. The sensor unit 37 has a layer structure including a silicon substrate 45, an insulating layer 46, a silicon layer 47, and a piezoresistive layer 48 that is a semiconductor, and the cantilever 29 includes the silicon layer 47 and the piezoresistive layer 48. Further, electrodes 49 a and 49 b are formed in the frame 43 on the upper layer of the piezoresistive layer 48.

  The cantilever 29 has a pressure receiving portion 29 a and a pair of beam portions 29 b connecting the pressure receiving portion 29 a and the frame 43. The pair of beam portions 29b extend from one side of the pressure receiving portion 29a toward the frame 43, and the base ends thereof are connected to the frame 43, and each support the pressure receiving portion 29a in a cantilever state. A part of the frame 43 protrudes in a rectangular shape between the pair of beam portions 29b. A gap 51 is formed between the frame 43 and the cantilever 29 including the protruding portion. The gap 51 is formed in such a size that the liquid of the liquid layer 39 does not flow into the opposite side of the cantilever 29 due to its surface tension, for example, a width of about 0.02 μm to 10 μm.

  The piezoresistive layer 48 in the cantilever 29 is formed in a substantially U shape connected by a path from one beam portion 29b through the pressure receiving portion 29a to the other beam portion 29b. One beam portion 29b of the piezoresistive layer 48 is connected to the electrode 49a, and the other beam portion 29b is connected to the electrode 49b. Accordingly, the resistance value of the piezoresistive layer 48 between the one beam portion 29b and the other beam portion 29b can be detected as the resistance value of the cantilever 29 through the electrodes 49a and 49b. The resistance value of the piezoresistive layer 48 increases or decreases by compression or expansion. Reference numeral 52 denotes a groove for electrically separating the electrodes 49a and 49b and the piezoresistive layer 48 immediately below them.

  The cantilever 29 has flexibility. That is, the cantilever 29 is elastically deformable so as to move the end portion which is the free end of the pressure receiving portion 29a around the base end of each beam portion 29b in the normal direction (vertical direction in the drawing) of the surface. It is. Due to the deformation of the cantilever 29, each beam portion 29b is bent, whereby the resistance value of the piezoresistive layer 48 increases or decreases, and the resistance value of the cantilever 29 changes. When the cantilever 29 is vibrated by the photoacoustic wave, the beam portion 29b is curved and deformed in this way, and thus its resistance value changes.

  In order to manufacture the sensor unit 37, an SOI (Silicon On Insulator) substrate in which a silicon substrate 45, an insulating layer 46, and a silicon layer 47 are stacked is prepared. The thicknesses of the silicon substrate 45, the insulating layer 46, and the silicon layer 47 are, for example, 300 μm, 0.4 μm, and 0.3 μm in this order. Doping is performed on the silicon layer 47 of this SOI substrate to form a piezoresistive layer 48 on the surface layer of the silicon layer 47. After forming metal layers to be the electrodes 49a and 49b on the piezoresistive layer 48, the metal layer, the silicon layer 47, and the piezoresistive layer 48 are sequentially etched to form the gap 51 and the groove 52. Further, the metal layer is etched to form electrodes 49a and 49b. Finally, the silicon substrate 45 and the insulating layer 46 are etched from the bottom side to form a through hole, thereby forming the sensor portion 37 including the cantilever 29.

  A through hole 54 is formed in the second plate portion 25 b, and the frame 43 is fixed to a step provided in the hole 54. Thereby, the communication hole 36 in which the hole provided in the frame 43 and the hole 54 are integrated is formed. Further, the cantilever 29 is arranged in the communication hole 36 in such a posture that the surface of the cantilever 29 is perpendicular to the direction of penetration of the communication hole 36. A gap 51 between the cantilever 29 and the frame 43 becomes a gap between the cantilever 29 and the inner surface of the communication hole 36.

  As shown in FIG. 4, the cantilever 29 is located close to the second cavity 32 in the communication hole 36. In this example, the cantilever 29 is almost the same height as the surface of the second plate portion 25b on the second cavity 32 side. Arranged in position. By disposing the cantilever 29 in the communication hole 36 in this way, one surface (second surface) of the cantilever 29 is covered with the liquid layer 39, and the one surface is in contact with the liquid constituting the liquid layer 39. And In addition, a space is provided in the communication hole 36 on the other surface (first surface) side of the cantilever 29, and a gas layer 38 is formed by confining gas in the space, and the other surface of the cantilever 29 is placed on the gas layer 38. Keep in contact with gas.

  In the gap 51, a gas-liquid interface is formed by the gas layer 38 and the liquid layer 39. Assuming that the gap 51 is a minute gap, the gas-liquid interface is maintained by the surface tension and viscosity of the liquid in the liquid layer 39, the pressure difference between the gas layer 38 and the liquid layer 39, and the like. Even if the position of the gap 51 is moved or the width thereof is changed due to the deformation of the cantilever 29, the state in which the gas-liquid interface is formed is maintained, and the liquid in the liquid layer 39 flows into the communication hole 36 or gas. The gas in the layer 38 does not flow into the liquid layer 39. In addition, the liquid layer 39 of this example covers a part of the surface of the second plate portion 25b in addition to the range of the cantilever 29 and the gap 51 as described above.

  Further, in this example, a gas-liquid interface is formed by the acoustic impedance matching material 27 that is water and the gas layer 38 in the vicinity of the opening of the communication hole 36 on the accommodation chamber 33 side. This gas-liquid interface is maintained by the surface tension and viscosity of the acoustic impedance matching material 27, the pressure difference between the acoustic impedance matching material 27 and the gas layer 38, and the like.

  In order to maintain the gas-liquid interface as described above, the surface of the cantilever 29, the surfaces of the electrodes 49a and 49b, the inner surface of the communication hole 36, and the lower surface of the frame 43 may be subjected to hydrophobic or oleophobic surface treatment. . For example, when the liquid layer 39 and the acoustic impedance matching material 27 are aqueous liquids, hydrophobic treatment may be performed.

  As shown in FIG. 5, the detection circuit 17 includes a bridge circuit 55 and a differential amplifier 56. The bridge circuit 55 has a circuit configuration in which a series circuit of resistors 57a and 57b and a series circuit of resistors 58 and 57c are connected in parallel between the power supply voltage Vs and the ground. The resistor 58 is a resistance between the electrodes 49 a and 49 b, that is, a resistance due to the piezoresistive layer 48 of the cantilever 29. The differential amplifier 56 is supplied with the potential difference between the connection point of the resistors 57a and 57b and the connection point of the resistors 58 and 57c as an input voltage, and the output voltage of the differential amplifier 56 is output as a detection signal.

  The bridge circuit 55 is adjusted so that the ratio of the resistance values of the resistors 58 and 57c when the cantilever 29 is not deformed is the same as the ratio of the resistance values of the resistors 57a and 57b. As a result, when the cantilever 29 is deformed, the input voltage of the differential amplifier 56 changes according to the deformation amount of the cantilever 29, and a voltage detection signal corresponding to the input voltage is output. As a result, a detection signal corresponding to the magnitude of vibration of the cantilever 29 is obtained.

  Next, the operation of the above configuration will be described. When measuring the blood glucose concentration, the contact surface 11a of the probe 11 is brought into close contact with the surface of the measuring object 21 where the blood vessel 22 is present near the surface. Thereafter, the light source 28 is driven by the driving unit 16 and the pulsed light is output a plurality of times. The pulsed light passes through the lens 34, the partition plate 25, the acoustic impedance matching material 27, and the sealing film 26 and is irradiated to the measurement target 21. The pulsed light reaches the inside of the measurement object 21 and is collected in the blood vessel 22 by the action of the lens 34. Every time pulse light is irradiated, glucose in the blood absorbs the pulse light and instantaneously expands to generate a photoacoustic wave (elastic wave). A larger photoacoustic wave is generated as the glucose concentration is higher.

  The photoacoustic wave propagates inside the measurement target 21, and a part of the photoacoustic wave enters the probe 11 from the measurement target 21 and is detected by the cantilever 29. At this time, the photoacoustic wave from the measurement target 21 is incident on the sealing film 26, the acoustic impedance matching material 27, and the second plate portion 25b in this order, but the change in acoustic impedance before and after the incidence is not increased. Therefore, both when the photoacoustic wave is incident on the probe 11 (acoustic impedance matching material 27) from the measurement target 21, and also when the photoacoustic wave is incident on the second plate portion 25b from the acoustic impedance matching material 27. The reflection of is small.

  The photoacoustic wave transmitted to the second plate portion 25b is transmitted from the second plate portion 25b to the cantilever 29 and vibrates the cantilever 29. The photoacoustic wave transmitted to the second plate portion 25b, particularly the high frequency component thereof, acts on the cantilever 29, and the cantilever 29 vibrates. At this time, since the surface of the cantilever 29 opposite to the gas layer 38 is suppressed by the liquid layer 39, the vibration of the photoacoustic wave from the second plate portion 25b effectively acts on the cantilever 29, and the cantilever 29 is Vibrate more.

  When the cantilever 29 vibrates as described above, the resistance value of the cantilever 29 changes, and the detection signal from the detection circuit 17 changes according to the change in the resistance value. If the photoacoustic wave generated inside the measurement object 21 is large, the vibration of the cantilever 29 increases and the amplitude of the detection signal also increases. The detection signal is input to the concentration calculation unit 18 to perform various arithmetic processes, and the blood glucose concentration is calculated based on the amplitude of the detection signal.

  As described above, in the probe 11, the photoacoustic wave from the measurement target 21 is detected by the cantilever 29, and the acoustic impedance matching material 27 is provided between the cantilever 29 and the measurement target 21. The attenuation due to reflection of the photoacoustic wave when entering the probe 11 is small, and the photoacoustic wave is detected with higher sensitivity. Further, since the cantilever 29 is arranged at the boundary between the gas layer 38 and the liquid layer 39 and the cantilever 29 is vibrated effectively by the photoacoustic wave, the photoacoustic wave detection sensitivity by the cantilever 29 is further enhanced. As a result, a highly accurate blood glucose concentration can be obtained non-invasively.

[Second Embodiment]
In the second embodiment, a condensing position by a lens as a condensing unit is made variable. As described below, the lens is the same as in the first embodiment except that the lens is different. The same components are denoted by the same reference numerals, and detailed description thereof is omitted.

  A probe 60 shown in FIG. 6 is provided with a variable focus lens 61 as a condensing unit of the light irradiation unit 13. The variable focus lens 61 can change the curvature of the lens. Thereby, the condensing position of the light from the light source 28 can be adjusted to an arbitrary position between the first measurement position P1 deepened from the surface of the measurement object 21 and the second measurement position P2 shallow from the surface. In the case of the first measurement position P1, as shown by a solid line in FIG. 6, the curvature of the variable focus lens 61 is reduced, and in the case of the second measurement position P2, as shown by a two-dot chain line in FIG. In addition, the curvature of the variable focus lens 61 is increased. Thereby, the condensing position of the light from the light source 28 can be appropriately adjusted according to the distance from the surface of the measurement target 21 to the blood vessel 22.

  As shown in FIG. 7, in the variable focus lens 61, an ITO (Indium Tin Oxide) electrode 63 is formed on the surface of a transparent substrate 62. In the center of the ITO electrode 63, a placement region 63a for placing transparent silicone oil is formed in a disc shape, and a plano-convex lens-like silicone oil bulging portion 65 is formed on the placement region 63a. Is provided. The silicone oil bulging portion 65 can be formed into a shape bulging into a convex lens shape due to the surface tension of the silicone oil by forming a highly oleophobic film 66 that repels silicone oil on the outside of the placement region 63a. . The protective film 67 is formed on the surface of the substrate 62, the ITO electrode 63, and the silicone oil bulging portion 65, and fixes the silicone oil bulging portion 65 to the substrate 62. A transparent gold film 68 having a thickness of about 5 nm is formed on the surface of the protective film 67.

  The ITO electrode 63 and the gold film 68 are connected to a power supply unit 69 and a voltage from the power supply unit 69 is applied. By applying this voltage, an electrostatic force is generated between the ITO electrode 63 and the gold film 68, and the curvature of the silicone oil bulging portion 65, that is, the curvature of the variable focus lens 61 is changed by the electrostatic force. By increasing or decreasing the voltage applied from the power supply unit 69 by operating the operation unit (not shown), the curvature of the silicone oil bulging unit 65 increases or decreases. For example, by increasing the voltage from the power supply unit 69 from the state shown in FIG. 7, the curvature of the variable focus lens 61 is increased as shown in FIG. Such a variable focus lens 61 is described in, for example, Japanese Patent Application Laid-Open No. 2008-197611. The configuration of the variable focus lens 61 is an example, and a variable focus lens having another configuration may be used.

  According to this example, the curvature of the varifocal lens 61 can be adjusted by increasing or decreasing the voltage from the power supply unit 69 so that the light from the light source 28 is condensed at the position of the blood vessel 22. High measurement can be made.

[Third Embodiment]
In the third embodiment, a sound collecting member is provided in the probe on the contact surface side of the sensor unit, and a gas layer is provided on the cavity side of the cantilever. In addition, except being demonstrated below, it is the same as 1st Embodiment, The same code | symbol is attached | subjected to the same structural member, and the detailed description is abbreviate | omitted.

  As shown in FIG. 9, the first cavity 31 and the second cavity 32 provided in the housing 75 of the probe 71 are separated by a first partition plate 76 and a second partition plate 77 as a base, respectively, on the contact surface side. And partitioned. A lens 34 is formed on the first partition plate 76. In this example, the lens 34 may be provided on any surface of the first partition plate 76. However, by arranging the lens 34 in the first cavity 31 as shown in FIG. Adhesion can be prevented. The lower part of the first housing part 75 a that houses the light irradiation unit 13 is open, and the light irradiation unit 13 irradiates the measurement target 21 with light from the light source 28 through the lens 34 and the first partition plate 76.

  The photoacoustic wave detection unit 14 in this example includes a second partition plate 77 having a communication hole 36 (see FIG. 10), a sensor unit 37, an acoustic impedance matching material 27, a sound collecting member 78, and a gas layer 38 (FIG. 10). Reference) etc. In the second housing part 75 b that houses the photoacoustic wave detection unit 14, a sound collecting member 78 is disposed below the second partition plate 77. The sound collecting member 78 collects photoacoustic waves from the measurement target 21 in the sensor unit 37, and the bottom (contact surface 71a side) opening is larger than the upper (sensor unit 37 side) opening. It is cylindrical. The sound collecting member 78 is a reflecting surface 78 a having a curved inner peripheral surface so that the photoacoustic wave from the measurement target 21 is collected and incident on the second partition plate 77 around the sensor unit 37. Yes. The reflecting surface 78a is, for example, an ellipsoid, and one focus of the ellipse is located at or near the position of the sensor unit 37, and the other focus is a condensing position of light from the light source 28, that is, a measurement position. The shape is determined.

  In order to effectively reflect the photoacoustic wave, it is preferable to increase the difference in acoustic impedance between the sound collecting member 78 and the acoustic impedance matching material 27. Moreover, the structure which formed the thin wall surface of the sound collection member 78 used as the reflective surface 78a, and provided the cavity filled with gas on the outer side (opposite side to the acoustic impedance matching material 27) of the wall surface may be sufficient. Even with such a configuration, the photoacoustic wave can be reflected by the difference in acoustic impedance between the gas in the cavity of the sound collecting member 78 and the acoustic impedance matching material 27.

  The hollow interior of the sound collection member 78 (the space surrounded by the reflection surface 78 a) is a storage chamber for storing the acoustic impedance matching material 27. The opening below the sound collection member 78 is closed by a sealing film 79. In this example, a liquid is used as the acoustic impedance matching material 27. As the liquid of the acoustic impedance matching material 27, for example, silicone oil having no conductivity is used because it contacts the sensor unit 37. As with the liquid constituting the liquid layer 39 of the first embodiment, the liquid of the acoustic impedance matching material 27 is not limited to silicone oil. For example, liquid paraffin, glycerin, or the like may be used. It is also possible to use liquid substances such as gel.

  As shown in FIG. 10, a communication hole 36 is formed in the second partition plate 77. The sensor unit 37 is provided at a position close to the contact surface 71a side (the lower side in the drawing) in the communication hole 36, and one surface (second surface) of the cantilever 29 is a liquid acoustic impedance matching material 27. And the acoustic impedance matching material 27 is in contact with it. This acoustic impedance matching material 27 functions as a liquid layer. A gas layer 38 is provided in the communication hole 36 on the other surface (first surface) side of the cantilever 29, and the other surface of the cantilever 29 is in contact with the gas in the gas layer 38. The gas layer 38 is integrated with the space of the second cavity 32.

  In the gap 51, a gas-liquid interface is formed by the acoustic impedance matching material 27 and the gas layer 38. As in the case of the first embodiment, the gas-liquid interface is maintained by the surface tension and viscosity of the acoustic impedance matching material 27, the pressure difference between the acoustic impedance matching material 27 and the gas layer 38, and the like.

  As in this example, even if the cantilever 29 and the gap 51 are covered with the liquid acoustic impedance matching material 27 on the contact surface 71a side and the gas layer 38 is disposed on the opposite surface side, Similarly, the cantilever 29 can be more effectively vibrated by the photoacoustic wave, and the photoacoustic wave detection sensitivity is increased. Moreover, since the photoacoustic wave from the measuring object 21 is collected at the position of the cantilever 29 by the reflecting surface 78a, the detection sensitivity can be further increased.

[Fourth Embodiment]
4th Embodiment uses a concave mirror as a condensing part. As described below, except that a concave mirror is used in place of the lens, it is the same as in the first embodiment, and the same components are denoted by the same reference numerals and detailed description thereof is omitted.

  As shown in FIG. 11, the light irradiation part 13 of the probe 84 in this example is provided with a concave mirror 85 as a condensing part. A concave part having the same shape as the concave mirror 85 is formed in the first cavity 86, and the concave mirror 85 is formed, for example, by depositing a reflective film on the inner surface of the concave part. The surface shape of the concave mirror 85 is, for example, an ellipsoid, and the shape is determined so that the light source 28 is disposed at one focal point and the other focal point is a measurement position. The light source 28 outputs light toward the concave mirror 85. The light source 28 is supported by a stay (not shown).

  According to this example, the light from the light source 28 is reflected by the concave mirror 85 and collected inside the measurement target 21. In the case of reflection, high reflectance can be obtained in a wide wavelength range including wavelengths in the mid-infrared range. Therefore, it is advantageous in reducing attenuation of light from the light source 28.

[Fifth Embodiment]
In the fifth embodiment, the light irradiation unit and the photoacoustic wave detection unit are accommodated in separate housing units. In addition, except being demonstrated below, it is the same as 1st Embodiment, The same code | symbol is attached | subjected to the same structural member, and the detailed description is abbreviate | omitted.

  As shown in FIG. 12, the probe 91 in this example includes a first housing portion 92 that houses the light irradiation unit 13 and a second housing portion 93 that houses the photoacoustic wave detection unit 14. The first housing part 92 and the second housing part 93 are independent of each other.

  The opening of the first cavity 31 formed in the first housing portion 92 is closed by the first partition plate 94. A lens 34 is formed on the surface of the first partition plate 94 on the first cavity 31 side. Light from the light source 28 is applied to the measurement target 21 through the lens 34 and the first partition plate 94. The first housing portion 92 causes the outer surface of the first partition plate 94 to be in close contact with the measurement target 21 during measurement.

  In the second housing part 93, the second cavity 32 is formed, and the second partition plate 95 in which the communication hole 36 is formed, the acoustic impedance matching material 27, the sealing film 96, the sensor part 37, and the gas layer 38. A liquid layer 39 is provided. The configuration of the second casing portion 93 is the same as that accommodated in the second casing portion 15b in the first embodiment. The second partition plate 95 and the sealing film 96 correspond to the second plate portion 25b and the sealing film 26 of the first embodiment, respectively. The second housing portion 93 causes the outer surface of the sealing film 96 to be in close contact with the measurement target 21 during measurement.

  In the measurement of the probe 91 in this example, the first casing 92 and the second casing 93 are arranged on the opposite sides of the measurement target 21 as shown in the figure. As a result, the photoacoustic wave detection unit 14 of the second housing unit 93 transmits the photoacoustic wave propagating in the measurement target 21 in the same direction as the light irradiation direction from the light irradiation unit 13 of the first housing unit 92. To detect. Since the photoacoustic wave propagates in all directions from the condensing position (measurement position) of the laser beam that is the source of the photoacoustic wave, the arrangement of the second casing portion 93 is a measurement in which the photoacoustic wave propagates. Any location on the surface of the object 21 may be used.

DESCRIPTION OF SYMBOLS 10 Photoacoustic measuring device 11, 60 Photoacoustic measuring probe 13 Light irradiation part 14 Photoacoustic wave detection part 15a, 75a, 92 1st housing | casing part 15b, 75b, 93 2nd housing | casing part 25b 2nd board part 27 Acoustic impedance Matching material 28 Light source 29 Cantilever 31 First cavity 32 Second cavity 34 Lens 36 Communication hole 37 Sensor part 38 Gas layer 39 Liquid layer 48 Piezoresistive layer 51 Gap 61 Variable focus lens 77 Second partition plate 78 Sound collecting member 85 Concave mirror

Claims (10)

A light irradiating unit that is accommodated in the first housing unit and irradiates intensity-modulated light toward the measurement target;
A photoacoustic wave detection unit that is housed in a second housing part and detects a photoacoustic wave from the measurement object,
The photoacoustic wave detector is
A cavity formed in the second housing part;
A base that separates the inside and the outside of the cavity;
A communication hole formed in the base and connecting the inside and the outside of the cavity;
A cantilever that is arranged in the communication hole, has a base end formed in a plate shape supported by the base, has flexibility in the direction of penetration of the communication hole, and has a resistance layer made of a semiconductor on the surface layer; ,
A gas layer provided on the first surface side of the cantilever;
A photoacoustic measurement probe comprising: an acoustic impedance matching material provided closer to the measurement object than the cantilever.   Provided on the second surface side of the cantilever opposite to the first surface, covers the gap between the cantilever and the inner surface of the communication hole and the second surface, and interfaces with the gas layer at the position of the gap The photoacoustic measurement probe according to claim 1, further comprising a liquid layer that forms a layer. The liquid layer is disposed in the cavity;
In the cavity, a space other than the liquid layer is filled with gas,
The photoacoustic measurement probe according to claim 2, wherein a surface of the liquid layer opposite to the cantilever is in contact with the gas in the cavity.   The acoustic impedance matching material is a liquid, is provided on the second surface side of the cantilever opposite to the first surface, and covers the gap between the cantilever and the inner surface of the communication hole and the second surface. The photoacoustic measurement probe according to claim 1, wherein an interface is formed with the gas layer at the position of the gap.   5. The photoacoustic measurement probe according to claim 1, wherein the light irradiation unit includes a light source and a lens that collects light from the light source.   The photoacoustic measurement probe according to claim 5, wherein the lens is a variable focus lens.   The photoacoustic measurement probe according to any one of claims 1 to 4, wherein the light irradiation unit includes a light source and a concave mirror that collects light from the light source.   The said photoacoustic wave detection part is provided with the sound collection member which has the reflective surface which collects the photoacoustic wave from the said measuring object side in the vicinity of the said cantilever on the said measuring object side rather than the said cantilever. The photoacoustic measurement probe according to any one of 1 to 7.   The photoacoustic measurement probe according to any one of claims 1 to 8, wherein the first housing portion and the second housing portion are integrally connected.   The photoacoustic measurement probe according to any one of claims 1 to 8, wherein the first housing portion and the second housing portion are independent of each other.

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