JP4724559B2 - Optical sensor and sensor unit thereof - Google Patents

Description

  The present invention relates to an optical sensor such as a blood flow meter that measures blood flow volume, blood volume, blood flow velocity, pulse, etc. in a target biological tissue using scattered light from the biological tissue.

  There is Patent Document 1 as a document describing a conventional blood flow meter. 7 and 8 are diagrams showing the configuration of the sensor chip of the conventional blood flow meter shown in the same document. FIG. 7 (a) is a top view, FIG. 7 (b) is a cross-sectional view along AA ′, and FIG. a) is a BB ′ sectional view, and FIG. 8B is a CC ′ sectional view. As shown in FIGS. 7A and 7B, the sensor chip according to the prior art has an electrode 122 on a semiconductor substrate (silicon substrate 121: silicon bench using a (100) silicon substrate) made of surface-oxidized silicon. A semiconductor laser (LD) 123, which is a light emitting element, is formed on the electrode 122 in the concave portion formed and surrounded by the inclined surface via a solder film (not shown). Similarly, an electrode 124 is formed on the same silicon substrate 121, and a photodiode (surface incident PD 125) as a light receiving element is formed on the electrode 124 in a recess surrounded by an inclined surface via a solder film. Further, a cover substrate 126 is provided on the silicon substrate 121.

  Here, synthetic quartz is used for the cover substrate 126. The cover substrate 126 is manufactured by dicing a 6-inch synthetic quartz wafer. For example, a surface emitting laser is used as the semiconductor laser. The semiconductor laser 123 and the photodiode 125 are bonded to the silicon substrate 121 via a solder film. By forming the light emitting element and light receiving element on the same semiconductor substrate, each optical element need only be two-dimensionally positioned and does not require three-dimensional alignment, thus reducing the adjustment process and enabling mass production. Thus, cost reduction can be realized.

As shown in FIGS. 7A and 7B, a metal (TiPtAu) film is patterned as a light shielding film 127 on the silicon substrate on the side where the photodiode 125 is mounted by a conventional technique. As a result, stray light entering the photodiode 125 from the semiconductor laser 123 through the silicon substrate 121 can be prevented. If the light shielding film is not provided, light may reach the photodiode 125 from the semiconductor laser without passing through the living tissue. Then, the scattered light component whose intensity is modulated by scattered light (Doppler-shifted light) from the red blood cells in the capillary blood vessels received by the sensor chip is very weak, about several hundred pW. The S / N ratio becomes worse. Therefore, in the absence of the light shielding film 127, the intensity of the weak Doppler shifted scattered light component is buried, and the blood flow velocity cannot be detected.
As shown in FIG. 7A and FIG. 8A, in this prior art, a surface emitting semiconductor laser 161 is used as a light emitting element. Here, a (100) silicon substrate is fabricated by wet anisotropic etching. Further, the surface emitting LD 161 is connected to the electrode 122 by a wire 129.

  Further, as shown in FIG. 8A, since the refractive lens 162 is formed on the cover substrate 126, the light from the LD 161 is irradiated to an external living tissue in the state of diverging light, convergent light, and parallel light. Is possible. The lens formed on the cover substrate 126 is not limited to the refractive lens 130 but may be a binary lens or a Fresnel lens that can be formed using a semiconductor process.

  In addition, as shown in FIG. 8B, the conventional technology uses a surface incident PD 125. In addition, a light shielding film 131 that blocks unnecessary scattered light is formed by patterning on the upper and lower surfaces of the cover substrate 126 by photolithography, and the scattered light from the biological tissue is incident on the surface incident PD 125 from the opening in the light shielding film. This light-shielding film 131 can efficiently detect scattered light (Doppler-shifted light) from red blood cells in the moving capillary in the living tissue. Further, the surface incident PD 125 is connected to the electrode 124 by a wire 132.

  Further, as is clear from this document, a light emitting element and a light receiving element can be directly mounted on a semiconductor substrate by a combination using a surface emitting LD as a light emitting element and a surface incident PD as a light receiving element.

In such a blood flow meter, scattered light from a stationary biological tissue and scattered light from red blood cells (scattering particles) moving in the capillary of the biological tissue (subject to Doppler shift Δf depending on the blood flow). By detecting interference light (scattered light) (heterodyne detection), blood flow volume, blood volume, blood flow velocity, and pulse are measured. This measurement principle is known and is described in, for example, Non-Patent Document 1.
JP 2004-229920 A JP 2002-330936 A MDStern: “In vivo evaluation of microcirculation by coherent light scattering” Nature, col. 254, pp. 56-58 (1975)

  However, in order to actually use such a conventional blood flow meter, as shown in FIG. 8B, a light shielding film for selecting unnecessary scattered light is formed vertically on the surface incident PD portion. Needed a cover substrate that is. Since the light shielding film pattern on the upper side of the cover substrate is constantly in contact with a living tissue such as a finger during blood flow measurement, the light shielding film pattern is easily peeled off, and the light shielding is deteriorated and the measurement accuracy is lowered.

  Further, in the manufacturing process, it is necessary to perform etching processing on the semiconductor substrate, which increases the manufacturing cost. Furthermore, it is necessary for the electrical wiring pattern to reach the concave portion on the silicon substrate, and it is necessary to form the electrical wiring pattern on the inclined surface, which is difficult to manufacture, has a low success rate, and often breaks. there were.

  Furthermore, wire bonding is required for mounting, which takes time and labor, and has been a factor in increasing manufacturing costs.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical sensor that is easy to manufacture, that realizes low cost and high accuracy, and a sensor unit thereof.

The above problem is that a light-emitting element and a light-receiving element are installed on a transparent substrate, and light emitted from the light-emitting element is emitted toward an external biological tissue through the substrate and scattered from the biological tissue. A sensor unit in an optical sensor that receives light by a light receiving element and measures a value related to blood flow in a living tissue, wherein each of the light emitting element and the light receiving element is formed on a wiring pattern formed on the same plane of the substrate. A sensor unit that arranges a light-shielding structure made of an opaque material that can electrically connect each of the light-emitting element and the light-receiving element to a wiring pattern, and can block unnecessary scattered light in the light-receiving element ; The light shielding structure has a cap shape. Further, the light shielding structure is electrically conductive and can be solved by a sensor unit that serves both as electromagnetic noise shielding and stray light shielding .

  Further, the present invention includes the above-described sensor unit, a circuit that drives the light emitting element, and a circuit that has a function of amplifying a signal received from the sensor unit and processing to calculate a value related to the blood flow. It can also be configured as an optical sensor characterized by having.

  According to the present invention, the sensor unit is formed by installing the light emitting element, the light receiving element, and the light shielding structure on an inexpensive flat substrate provided with an electrical wiring pattern. Thus, an optical sensor with high measurement accuracy can be realized at a low manufacturing cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, a blood flow meter is used as an example of the optical sensor. However, the sensor unit of the present invention can be applied not only to a blood flow meter but also to a blood pressure monitor and other optical sensors.

[First embodiment]
A first embodiment of the present invention will be described with reference to FIG. FIG. 1A is a top view of the optical sensor according to the first embodiment, and FIG. 1B is a cross-sectional view taken along a broken line in FIG.

  In the first embodiment, electric wiring patterns 12, 13, 14, and 15 are formed on a quartz glass substrate 11 that is an insulating and transparent material, and a photodiode 16 and a light emitting element that are light receiving elements are formed on the electric wiring pattern. The photodiode 16 is covered with a photodiode shielding cap 18, and the laser diode 17 is covered with a laser shielding cap 19.

  The electrical wiring pattern 12 is an anode for a photodiode, and the electrical wiring pattern 13 is a cathode for a photodiode, each connected to a photodiode 16 and each connected to a preamplifier 20 for detecting a minute signal. The electrical wiring pattern 14 is a cathode for a laser diode, and the electrical wiring pattern 15 is an anode for a semiconductor laser. The electrical wiring pattern 14 is connected to a laser diode 17 and connected to a laser driving power source 21. The preamplifier 20 and the laser drive power source 21 are schematically shown and are built in the circuit unit 24. All these components are built in a housing 25 that serves both as an electric shield and internal protection.

  Further, the circuit unit 24 has a function of calculating a blood flow rate from the amplified signal in the same manner as the configuration described in Patent Document 1. That is, in addition to the preamplifier 20 and the laser driving power source 21 (including the laser driving circuit), the circuit unit 24 is an A / D converter and a digital signal processor that performs an operation for obtaining a value related to blood flow from the received signal. (DSP), including an interface with the outside.

  Each part will be described below.

  FIG. 2 is a top view for explaining the electric wiring pattern on the quartz glass substrate 11 and corresponds to a state before mounting the cap, the PD 16 and the LD 17. There is a hole 26 for partially blocking the light from the outside that has passed through the glass substrate and transmitting only the central portion, and the electric wiring pattern 14 transmits the light of the semiconductor laser 17 through the quartz glass substrate to the outside. There is a hole 27 for radiation.

  An electrode 28 is formed on the anode electrical wiring pattern 12 of the photodiode, and electrodes 29, 30, and 31 are formed on the cathode electrical wiring pattern 13 of the photodiode. Electrodes 32, 33, and 34 are formed on the cathode electrical wiring pattern 14 of the laser diode, and electrodes 35 are formed on the anode electrical wiring pattern 15 of the laser diode. When connecting to a photodiode or laser diode, a solder ball (not shown) is placed on the electrodes 28, 29, 30, 31, 32, 33, 34, and 35, on which a photodiode and a laser are mounted. A diode is installed and is responsible for electrical and mechanical connection with the photodiode and laser diode after the solder ball is heated and melted. In this way, wire bonding is not required for electrical connection with the solder balls.

  FIG. 3 is a top view (a), an oblique sectional view (b), and a bottom view (c) of the photodiode 16. In the center of the lower surface of the photodiode, there are a light receiving surface 36, an anode electrode 37, and cathode electrodes 38, 39, 40 penetrating to the upper surface.

  FIG. 4 is a top view (a) and an oblique sectional view (b) and a bottom view (c) of the laser diode 17. At the center of the lower surface of the laser diode 17, there are a light emitting portion 41, an anode electrode 42, and cathode electrodes 43, 44, 45 that penetrate to the upper surface.

  FIG. 5 is a perspective view of the photodiode shielding cap 18 and the semiconductor laser diode shielding cap 19. These caps are made of metal-coated plastic and have electrical conductivity. When installed on the electrical wiring pattern, each is connected to the electrical wiring pattern of the cathode and has the same potential as the cathode. These caps are electrically conductive and opaque, and serve as both electromagnetic noise and stray light shielding. There are also cutouts to avoid contact with the electrical wiring pattern of the anode. A sensor chip as shown in FIG. 1 is formed by picking up the above components.

  The scattered light component whose intensity is modulated by scattered light (Doppler-shifted light) from the red blood cells in the capillaries received by the sensor chip is very weak, about several hundreds pW. Therefore, if the stray light shielding cap 18 is not provided, the laser The direct light from the diode 17 enters the photodiode 16 and the S / N ratio of the signal is deteriorated. In the absence of the stray light shielding cap 18, the intensity of the weak Doppler shifted scattered light component is buried and the blood flow velocity cannot be detected.

  The sensor chip is configured to use the quartz glass substrate as described above, the electrical wiring pattern on the quartz glass substrate, and the stray light shielding cap. Can be formed with an inexpensive material and a small number of processes, and the manufacturing cost is low.

  The operation of the sensor chip will be described next.

  When a current is injected from the electrode 15 into the semiconductor laser 17, the semiconductor laser 17 oscillates. The light emitted from the semiconductor laser 17 passes through the holes 27 on the electric wiring pattern, passes through the quartz glass substrate 11, and is irradiated to an external living tissue. When this sensor chip is brought close to a living tissue such as skin, light scattering occurs, and the scattered light passes through the quartz glass substrate 11 again and enters the photodiode 16 through the hole 26 on the electric wiring pattern 13. This scattered light includes interference components of scattered light from a stationary biological tissue and scattered light (Doppler-shifted light) from moving red blood cells in capillaries of the biological tissue. Therefore, the blood flow velocity can be obtained by frequency analysis of this signal. The experiment confirmed that a linear relationship was established between the fluid velocity and the Doppler shift frequency using a solution in which fine particles were dispersed in a fluid. Further, the intensity of the scattered light corresponds to the amount of blood that is moving, and the blood flow volume is obtained by the product of the blood flow velocity and the blood volume.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG. The second embodiment is different from the first embodiment only in the part relating to the photodiode, and is otherwise the same. 6A is a top view of a portion including the photodiode 50, FIG. 6B is a cross-sectional view taken along the broken line shown in FIG. 6A, and FIG. 4 is a bottom view of only the diode chip 50. FIG.

  In the drawing, the PD cap 18 and the housing 25 are omitted. In the present embodiment, the light receiving surface 51 of the photodiode is substantially at the center of the upper surface, is electrically connected to the through electrode 52, and is connected to the anode electrical wiring pattern 12. Further, the lower surface of the photodiode chip is covered with metal, and there is a hole 53 through which light can be transmitted at a position facing the light receiving surface. There are three electrodes 54, 55, and 56 for connecting to the cathode, which are electrically connected to the metal pattern 13 on the lower surface. The through electrode 52 from the upper surface reaches the lower surface, but is not electrically connected to the metal pattern 13 on the lower surface, and an electrode for connecting to the anode electric wiring pattern 12 is formed. The electrical wiring pattern for photodiodes is the same as that in the first embodiment.

  Next, the operation of this embodiment will be described. Light from an external living body passes through the quartz glass substrate 11 and reaches the light receiving surface 51 through the hole 26 of the electric wiring pattern and further through the hole 53 on the lower surface of the PD. Light from the outside passes through both the hole 26 of the electrical wiring pattern and the hole 53 on the lower surface of the photodiode before reaching the light receiving surface, and the distance of the thickness of the photodiode from the hole on the lower surface of the photodiode to the light receiving surface is increased. Since the light must be transmitted, the solid angle of light that can be received by the light receiving surface is limited. For this reason, there is a disadvantage that the amount of light that can be received is small compared to the first embodiment, but there is an advantage that the S / N ratio of the signal is improved in order to shield light from the background. Other basic operations are the same as those in the first embodiment.

  In the second embodiment, a material that is transparent to the wavelength of the laser diode is used as the material of the photodiode. The InP material is transparent to infrared rays having a wavelength of 1 μm or more. In this embodiment, a surface emitting laser diode having an oscillation wavelength of 1.3 μm is used, and an InGaAs photodiode formed on an InP substrate is used as the photodiode. ing.

  In addition, although the flat quartz glass substrate which gave the electrode pattern was used as a board | substrate used in 1st, 2nd embodiment, the light and light which are object, such as a sapphire glass board | substrate, are an insulator and surface The same effect can be obtained by using a material capable of forming an electrode pattern. Further, as the substrate, a semiconductor substrate that transmits target light and has a non-conductive material formed on the surface thereof can be used.

  The present invention is not limited to the above-described embodiments, and various modifications and applications are possible within the scope of the claims.

It is a figure explaining 1st embodiment of this invention. It is a figure explaining 1st embodiment of this invention. It is a figure explaining 1st embodiment of this invention. It is a figure explaining 1st embodiment of this invention. It is a figure explaining 1st embodiment of this invention. It is a figure explaining 2nd embodiment of this invention. It is the top view and sectional drawing which show the sensor chip of the conventional blood flow meter. It is sectional drawing which shows a part of sensor chip of the conventional blood flow meter.

Explanation of symbols

11 Quartz glass substrate 12 PD anode electrical wiring pattern 13 PD cathode electrical wiring pattern 14 LD cathode electrical wiring pattern 15 LD anode electrical wiring pattern 16 Photodiode chip 17 Laser diode chip 18 PD cap 19 LD cap 20 Preamplifier 21 Laser drive power supply 24 Circuit unit 25 Case 26 PD light receiving hole 27 LD hole 36 PD light receiving surface 37 PD anode electrode 38 PD cathode through electrode 39 PD cathode through electrode 40 PD cathode through electrode 41 LD Light emitting part 42 LD anode electrode 43 LD cathode through electrode 44 LD cathode through electrode 45 LD cathode through electrode 50 Photodiode chip 51 Light receiving part 52 PD anode through electrode 53 PD light receiving bottom hole 54 PD light Over de electrode 55 PD cathode electrode 56 PD cathode electrode 121 silicon substrate 122 electrode 124 electrode 125 faces incident PD
126 Cover substrate 127 Light shielding film 128 Metal film for mirror 129 Wire 161 Surface emitting LD
162 Refractive lens

Claims (9)

A light emitting element and a light receiving element are installed on a transparent substrate, light emitted from the light emitting element is emitted toward an external biological tissue through the substrate, and scattered light from the biological tissue is received by the light receiving element. A sensor unit in an optical sensor that receives light and measures a value related to blood flow in a living tissue,
Each of the light emitting element and the light receiving element is disposed on a wiring pattern formed on the same plane of the substrate, and each of the light emitting element and the light receiving element is electrically connected to the wiring pattern, and unnecessary scattering is performed on the light receiving element. It is a sensor part that arranges a light shielding structure made of an opaque material that can block light ,
The sensor portion is characterized in that the light shielding structure has a cap shape, and further, the light shielding structure has electrical conductivity and serves both as electromagnetic noise shielding and stray light shielding .   The sensor unit according to claim 1, wherein the substrate is made of a non-conductive material.   The sensor unit according to claim 1, wherein the substrate is a semiconductor substrate having a non-conductive material formed on a surface thereof. Sensor unit according to any one of claims 1 to 3, characterized by using a surface emitting semiconductor laser as the light emitting element. 5. The sensor unit according to claim 4 , wherein the surface emitting semiconductor laser has a through electrode and can be electrically connected only by connection from the substrate side. Sensor unit according to any one of claims 1 to 5, characterized in that a surface illuminated photodiode as the light receiving element. The sensor unit according to claim 6 , wherein the surface incident photodiode has a through electrode and can be electrically connected only from the substrate side. The light-shielding shape is formed in the back surface on the opposite side to the light-receiving part in the said light receiving element, Light is injected from the back surface, The light-shielding performance is improved, The any one of Claim 1 thru | or 7 characterized by the above-mentioned. Sensor part. A function of amplifying a signal received from the sensor unit according to any one of claims 1 to 8 , a circuit for driving the light emitting element, and processing and calculating a value related to the blood flow And an optical sensor.

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