JP5206944B2 - Optical module and medical optical measurement system using the same - Google Patents

Description

  The present invention relates to an optical module including a semiconductor laser element and a light receiving element in a package, and more particularly to an optical module for optically measuring blood flow of a human body.

  In the technical fields such as optical measurement and optical communication, interest in a light source of a surface-emitting semiconductor laser (Vertical-Cavity Surface-Emitting Laser: hereinafter referred to as VCSEL) is increasing. The VCSEL has excellent features not found in edge emitting semiconductor lasers, such as low threshold current and low power consumption, and a circular light spot can be easily obtained. Taking advantage of these features, VCSELs are expected as light sources in technical fields such as optical communication and optical measurement (Patent Document 1).

  Patent Document 2 discloses a blood flow meter in which a light emitting element and a light receiving element are integrated on the same substrate, and a light shielding plate is provided between the light emitting element and the light receiving element. Patent Document 3 discloses a technique related to a blood flow sensor unit in which a light emitting element and a light receiving element are arranged in a concave portion on the same substrate surface, and a cover substrate having a light shielding film formed on the upper surface of the substrate is arranged.

JP-A-5-164553 JP 2002-330936 A JP2004-229920A

  The present invention provides an optical module that can be manufactured at a low cost and can perform optical measurement with high accuracy, and a medical optical measurement system using the optical module, as compared with the case where a concave portion is formed on a light shielding plate or a substrate. The purpose is to provide.

  An optical module according to the present invention includes a surface emitting semiconductor laser element that emits laser light, a light receiving element that receives reflected light of the laser light emitted from the surface emitting semiconductor laser element, and the surface emitting semiconductor laser element. And a supporting member that supports the light receiving element, and a sealing member that is attached to the supporting member and that forms an internal space for housing the surface emitting semiconductor laser element and the light receiving element on the supporting member. The sealing member is formed with an emission window for emitting laser light to the outside and an incident window for receiving reflected light of the laser light from the outside, and the surface emitting semiconductor laser element is formed in the internal space A light reception suppressing member is provided that suppresses light reception to the light receiving element of internally reflected light generated when the laser light emitted from the laser beam is reflected by the internal space.

  Preferably, the light reception suppressing member includes a light shielding wall formed between the surface emitting semiconductor laser element and the light receiving element. Preferably, the light shielding wall is integrally formed on a substrate on which the surface emitting semiconductor laser element is formed or on a substrate on which the light receiving element is formed. Alternatively, the wall is formed on the support member.

  Preferably, the surface-emitting type semiconductor laser element includes a mesa for emitting laser light on a substrate, and the wall includes a semiconductor layer adjacent to the mesa and the same semiconductor layer as that constituting the mesa. . Preferably, the light reception suppressing member includes an antireflection film formed in the internal space of the exit window. Preferably, an optical lens is attached to the exit window, and the antireflection film covers the optical lens exposed to the internal space. Preferably, an optical filter for removing light having a wavelength other than a specific wavelength is attached to the incident window. A filter having a pinhole may be attached to the exit window.

  Preferably, the sealing member includes a mask in which the exit window and the entrance window are formed, and a cylindrical cap fixed on the support member, and one surface of the cap transmits laser light to the outside. In addition, an opening through which reflected light from the outside is transmitted is formed, and the mask is mounted on the one surface so as to cover the opening.

  An optical module according to the present invention includes a surface emitting semiconductor laser element that emits laser light, a light receiving element that receives reflected light of the laser light emitted from the surface emitting semiconductor laser element, and the surface emitting semiconductor laser. A support member that supports the element and the light receiving element, and a sealing member that is attached to the support member and that forms an internal space for accommodating the surface emitting semiconductor laser element and the light receiving element on the support member. The sealing member is formed with an emission window for emitting laser light to the outside and an incident window for receiving reflected light of the laser light from the outside, and the light receiving surface of the light receiving element is the surface emitting type The semiconductor laser element side is inclined so as to be higher.

  Preferably, the support member includes a mount member for inclining the light receiving surface of the light receiving element. The light receiving surface forms an angle of, for example, 30 degrees or more with respect to the surface of the support member. Preferably, the surface emitting semiconductor laser element emits a single mode laser beam. The surface emitting semiconductor laser element may include a laser array in which a plurality of light emitting units are arranged in an array. Further, the surface emitting semiconductor laser element emits laser light having a wavelength of 780 nm to 850 nm.

  The medical optical measurement system according to the present invention outputs an optical module having the above-described features, a measurement unit that measures blood flow based on a light reception signal from the light receiving element, and a result measured by the measurement unit. Output means.

  According to the present invention, by providing the light reception suppressing member for suppressing the reception of the internally reflected light of the surface emitting semiconductor laser element in the internal space, the reception of unnecessary internal reflected light to the light receiving element is suppressed, Noise to the element is reduced, and the S / N ratio of the received light signal can be improved. As a result, more accurate optical measurement can be performed. Furthermore, the provision of a light reception suppressing member and the inclination of the light receiving surface of the light receiving element do not significantly increase the number of steps for the existing optical module and do not require advanced mounting technology. An optical module can be manufactured at low cost.

  The best mode for carrying out the present invention will be described below with reference to the drawings. The optical module according to the present embodiment will be described by taking a medical optical module for irradiating a living tissue with laser light, receiving the reflected light, and measuring blood flow as an example.

  FIG. 1A is a plan view of a medical optical module according to the first embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along the line XX of FIG. The medical optical module 10 includes a metal disc-shaped stem 12, a submount 14 attached to the upper surface of the stem 12, a VCSEL 16 mounted on the submount 14, and a light receiving element 18 that receives laser light. A cylindrical cap 20 fixed to the stem 12 and a plurality of lead terminals 22 made of a conductive metal attached to the bottom surface side of the stem 12 are included.

  The stem 12 is formed with a through hole (not shown) for inserting a plurality of lead terminals 22. The inner wall of each through hole is coated with glass, and the lead terminal 22 is thereby electrically insulated from the stem 12. One end of the lead terminal 22 extends into the internal space where it is electrically connected to the electrodes of the VCSEL 16 and the light receiving element 18 using connection means such as a bonding wire.

  On the upper surface of the cap 20, a circular emission window 20a for emitting laser light from the VCSEL 16 to the external biological tissue and a circular incident window for receiving reflected light scattered and reflected by the external biological tissue. 20b.

  A ball lens 24 is fitted into the exit window 20a. The optical axis of the ball lens 24 coincides with the light emitting point of the VCSEL 16, and the laser light having the divergence angle θ emitted from the VCSEL 16 is condensed by the ball lens 24. In this example, a ball lens is used, but other plano-convex lenses and other optical members may be used. Alternatively, the exit window 20a may be sealed with flat glass, and the ball lens may be disposed outside the cap.

  An optical filter 26 is preferably attached to the incident window 20b for removing light of a specific wavelength from the light reflected by the external biological tissue. By removing light having an unnecessary wavelength, for example, accuracy in blood flow measurement processing can be improved. However, when it is not always necessary to remove the wavelength by the optical filter, a flat glass or other optical lens may be attached to the incident window 20b.

  The cap 20, the ball lens 24, and the optical filter 26 preferably form an airtightly sealed internal space on the stem 12, and protect the VCSEL 16 and the light receiving element 18 disposed in the internal space from the external environment. For example, when the medical optical module 10 measures the blood flow of a human body, the surface of the cap 20 is in direct contact with the skin, but moisture such as sweat generated from the skin is prevented from entering the inside.

  FIG. 2 is a cross-sectional view showing the configuration of the VCSEL shown in FIG. The present embodiment illustrates a single spot VCSEL in which one light emitting spot is formed, but this is an example, and a multi spot VCSEL in which a plurality of light emitting spots are formed may be used.

  As shown in FIG. 2, the VCSEL 18 has an n-side electrode 102 formed on the back surface of an n-type GaAs substrate 100, and n-type GaAs buffer layers 104 and AlGaAs layers having different Al compositions are alternately formed on the substrate 100. Stacked n-type lower DBR (Distributed Bragg Reflector) 106, active region 108, current confinement layer 110 made of p-type AlAs including an oxidized region on the periphery, and AlGaAs layers having different Al compositions are alternately arranged. A stacked p-type upper DBR 112 and a p-type GaAs contact layer 114 are stacked. A cylindrical post (or mesa) P is formed on the substrate by etching the stacked semiconductor layers.

  An interlayer insulating film 116 such as SiON or SiOx is formed on the entire substrate so as to cover a part of the bottom, side and top of the post P. In the interlayer insulating film 116 on the top of the post P, a circular contact hole 116a exposing the contact layer 114 is formed. A p-side electrode 118 made of a conductive material is formed on the top of the post P, and the p-side electrode 118 is ohmically connected to the contact layer 114 through a contact hole 116a. A circular emission window for emitting laser light is formed at the center of the p-side electrode 118. The exit window may expose the contact layer 114, but the exit window may be protected by a dielectric film.

  The lower DBR 106 and the upper DBR 112 form a resonator structure, and the active region 108 and the current extraction layer 110 are interposed therebetween. The current exploitation layer 110 includes an oxidized region in which AlAs is selectively oxidized from the side surface of the post P and a circular conductive region surrounded by the oxidized region, and confines current and light in the conductive region. . The center of the conductive region coincides with the center of the emission window of the p-side electrode 118. By injecting a forward drive current into the p-side electrode 118 and the n-side electrode 102, a laser beam of, for example, 850 nm is emitted from the emission window of the post P in a direction perpendicular to the substrate. The emitted laser light is collected on the ball lens 24.

  A submount 14 is fixed on the flat surface of the stem 12 with an adhesive or the like. The submount 14 includes a flat bottom surface bonded to the stem 12 and a surface opposite to the bottom surface, and is preferably made of an insulating ceramic substrate (for example, aluminum nitride) having high thermal conductivity and excellent heat dissipation. The A thin film pattern such as Ti / Pt / Au is formed on the surface of the submount 14, and the VCSEL 16 is mounted thereon.

  Further, a light receiving element mount 14 a is fixed on the surface of the ab mount 14 adjacent to the VCSEL 16. The light receiving element mount 14a has a bottom surface fixed to the surface of the submount 14 and a flat surface inclined so as to descend in a direction away from the VCSEL 16 side, and has a triangular cross-sectional shape. The light receiving element 18 is fixed to the surface of the light receiving element cloak 14a with a conductive adhesive or the like, and the light receiving surface of the light receiving element 18 forms a certain angle with the flat surface of the stem 12 or the flat surface of the submount 14. It is inclined to. Preferably, the angle formed by the light receiving surface and the flat surface of the stem 12 is 30 degrees or more. The light receiving element mount 14a is not necessarily separate from the submount 14, and may be integrally formed with the submount. Further, the shape of the light receiving element mount 14a is not limited as long as the light receiving surface of the light receiving element 18 can be inclined. For example, the light receiving element mount 14a may have a trapezoidal shape with an inclined surface or a shape with irregularities on the surface.

Next, the operation of the medical optical module will be described. When a forward drive current is applied to the VCSEL 16 via the lead terminal 22, laser light is emitted from the VCSEL 16, and this laser light irradiates the external living tissue as emitted light L via the ball lens 24. The emitted light L is scattered or reflected by blood cells or the like of the external biological tissue, and the external reflected light _LR is received by the light receiving element 18 through the optical filter 26. The light received by the light receiving element 18 is converted into an electrical signal and output from the lead terminal 22.

Most of the laser light emitted from the VCSEL 16 is incident on the ball lens 24, but a part of the laser light is reflected by the ball lens 24 or the inner wall surface of the cap 20, and undesired internally reflected light L _N in the cap 20. Occurs. Since the light receiving surface of the light receiving element 16 is inclined so as to become lower in the direction away from the VCSEL 16 or the ball lens 24, it is effective that the internally reflected light _{LN from} the ball lens 24 is incident on the light receiving surface. It is suppressed. As a result, the light receiving element 18, the external reflected light L _R that has passed through the entrance window 20b exclusively received, reception of internally reflected light L _N which can be a noise is eliminated to improve the S / N ratio of the received light signal, the light Measurement accuracy can be improved.

Further, when measuring the blood flow velocity of the external living tissue, the wavelength of the external reflected light _LR is shifted by Doppler shift, but light having a wavelength other than the assumed wavelength is cut by the optical filter 24, and noise is generated. It is possible to prevent unnecessary external reflected light from being received by the light receiving element 18 and improve the S / N ratio of the received light signal.

  In addition, by setting the laser light from the VCSEL to a single mode, the S / N ratio can be improved and high-precision optical measurement can be performed. Further, when a multi-spot VCSEL array is used as a light source, high output of laser light can be achieved. Furthermore, when laser light having a wavelength of 780 to 850 nm is used, the optical module is suitable for blood flow measurement of an external living tissue because the laser light has high skin transmittance and low water absorption.

  Next, FIG. 3 shows a medical optical module according to the second embodiment of the present invention. The medical optical module 10A according to the second embodiment uses a light shielding unit for preventing the internally reflected light from being received by the light receiving element, instead of inclining the light receiving surface of the light receiving element.

The optical module 10 </ b> A illustrated in FIG. 3A forms the light shielding unit 30 in the VCSEL 16. As shown in FIG. 2, in the VCSEL, a plurality of semiconductor layers are stacked on a GaAs substrate and etched to form a post P serving as a light emitting portion. In the second embodiment, as shown in FIG. 2B, a light shielding portion P1 having a semiconductor layer similar to the post P adjacent to the post P is formed. Thus, the light shielding portion P1 is interposed between the post P of the VCSEL and the light receiving element 18 to prevent the internally reflected light _LN generated by the ball lens 24 or the like from being received by the light receiving element 18. Further, an extension part P2 made of an insulating film, a conductive film or the like may be laminated on the light shielding part P1, so that the light shielding part P1 is made higher. By integrating the light shielding part P1 monolithically, it is possible to reduce the size, and there is an advantage that advanced mounting is not required.

  In the optical module 10 </ b> A shown in FIG. 3B, the light shielding element 18 a is formed monolithically on the light receiving element 18. The light receiving element 18 is formed using, for example, a silicon substrate, and a light shielding portion 18a having a certain height between the VCSEL 16 and the light receiving surface by laminating an insulating layer, a conductive film, or the like on the silicon substrate. Form.

In the optical module 10 </ b> A shown in FIG. 3C, a light shielding member 30 is formed between the VCSEL 16 and the light receiving element 18. The light shielding member 30 is preferably formed with a light absorption film on the surface for absorbing the internally reflected light _LN . The light shielding member 30 can be fixed on the submount 14 with an adhesive or the like. Further, the light shielding member 30 may be integrally formed with the submount 14.

The optical module 10 </ b> A illustrated in FIG. 3D includes a light shielding member 32 that extends downward from the top of the cap 20. The light shielding member 32 is located between the VCSEL 16 and the light receiving element 18. The light shielding member 32 is preferably coated on the surface with a light absorbing film that absorbs the internally reflected light _LN . The light shielding member 32 can be fixed to the cap 20 with an adhesive or the like. The light shielding member 32 may be integrally formed with the cap 20.

Next, FIG. 4 shows a medical optical module according to a third embodiment of the present invention. Medical optical module 10B according to the third embodiment, in order to suppress the generation of internal reflection light L _N of the laser beam from the VCSEL 16, reflecting a part of the back surface of the ball lens 24 and the cap 20 is exposed in the cap The prevention film 40 is formed. Thereby, the laser beam reflected by the ball lens 24 is reduced, the internal reflection light _LN received by the light receiving element 18 is reduced, and the reduction of the S / N ratio of the received light signal can be suppressed. Even when an optical member other than a ball lens is attached to the exit window 20a, an antireflection film is formed on the surface thereof.

Next, a medical optical module according to a fourth embodiment of the present invention is shown in FIG. Medical optical module 10C according to the fourth embodiment is fitted with an optical lens 42 for effectively condensing the external reflected light L _R from an external biological tissue on the surface of the entrance window 20b of the cap 20. Further, a slit member 44 is attached to the back surface of the incident window 20 b of the cap 20. The slit member 44 is substantially central to the pinhole 44a is formed, pinholes 44a passes through the external reflected light L _R condensed by the optical lens 42. The slit 44a can transmit only scattered light having a specific wavelength, like the optical filter, according to the aperture. Thus, when measuring the external reflected light L _R, suppressing the loss of the light receiving signal, thereby improving the S / N ratio.

  Next, a medical optical module according to the fifth embodiment of the present invention will be described. FIG. 6 is a cross-sectional view of a medical optical module 10D according to a fifth embodiment, FIG. 7A is a plan view of a cap, and FIG. 7B is a plan view of a mask.

As shown in FIG. 7A, a circular opening 20c is formed in the center of the cap 20. As shown in FIG. The opening 20c is large enough to expose at least the laser light emitting region and the light receiving region of the VCSEL 16 and the light receiving element 18.
A circular flat glass 50 is preferably fitted into the opening 20c, thereby hermetically sealing the internal space. A mask 52 is fixed with an adhesive or the like so as to cover the surface of the cap 20. The mask 52 is a thin plate-like circular member made of, for example, metal or a sealing material, and the diameter of the mask 52 is substantially equal to the diameter of the cap 20. In the mask 52, a circular emission window 52 a is formed at a position where the laser light of the VCSEL 16 is emitted, and a circular incident window 52 b is formed at a position corresponding to the light receiving element 18. Preferably, an optical spatial filter 54 that selectively transmits a specific wavelength is fitted into the incident window 52b. Further, an antireflection film 56 may be attached to the back surface of the cap 20 in order to suppress the generation of the internally reflected light _LN of the laser light emitted from the VCSEL 16. More preferably, the surface of the mask 52 is coated with a color (for example, black) that absorbs stray light unnecessary for optical measurement, for example, light other than laser light.

  By preparing such a mask 52, the cap can be easily manufactured, and the manufacturing cost of the optical module can be reduced. Furthermore, by attaching the mask 52, stray light from the outside is blocked by the incident window 52 b, and unwanted light that can become noise is prevented from entering the optical module, thereby improving the sensitivity of the light receiving element 18. Can do.

  Further, when it is desired to converge the laser light emitted from the VCSEL 16, a convex lens or a spherical lens 58 may be attached to the emission window 52a of the mask 52 as shown in FIG. Note that the mask 52 may be fixed to the surface of the cap 20 using means other than an adhesive. For example, the mask 52 may be fixed to the cap 20 by means such as mechanical fitting.

  Although various optical modules have been described as described in the first to fifth embodiments, the optical modules may be configured to combine the first to fifth features. For example, the optical module may be one in which the light receiving surface of the light receiving element is inclined and a light shielding unit is provided between the VCSEL and the light receiving element.

  Further, the configuration of the can package used in the first to fifth embodiments is a combination of a stem 12 having a recess and a flat cap 20 covering the recess, as shown in FIG. 8, for example. It may be. The external lead terminal does not necessarily have a pin shape, and may have a shape such as a bump or an electrode land. Furthermore, the package of the optical module may be a ceramic package or a resin sealed package.

  Next, FIG. 9 shows a configuration example of a medical optical measurement system using the optical module according to the present embodiment. The medical optical measurement system shown in the figure preferably measures the blood flow of the human body and outputs the result. The medical optical measurement system 200 shown in FIG. 9A includes an optical module 10 including the VCSEL 16 and the light receiving element 18, a drive circuit 210 that supplies a drive current to the VCSEL 16 via the lead terminal 22 of the optical module 20, and A signal processing circuit 220 that processes a light reception signal photoelectrically converted by the light receiving element 18, a control unit 230, and a display unit 240 are included.

  The signal processing circuit 220 includes an amplification circuit that amplifies a light reception signal from the light receiving element 18, an A / D conversion circuit that converts the amplified signal into a digital signal, and a wavelength of laser light emitted from the VCSEL 16 based on the converted digital signal. A circuit for calculating the shift amount, a circuit for calculating the blood flow velocity from the calculated wavelength, and the like are included. The control unit 230 causes the display unit 240 to display the calculated blood flow velocity.

  In the medical optical measurement system illustrated in FIG. 9B, the optical module 10 </ b> E includes the VCSEL 16 and the integrated circuit device 300. The integrated circuit device 300 includes a drive circuit 210 and a signal processing circuit 220 on a silicon substrate, for example. The control unit 230 displays the blood flow velocity on the display unit 240 based on the signal obtained via the lead terminal of the optical module 10E.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to specific embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims. Deformation / change is possible.

  The optical module according to the present invention can be used in the field of medical devices such as a blood flow meter and a blood oxygen concentration meter, and in other optical measurement fields.

FIG. 1A is a plan view of a medical optical module according to the first embodiment of the present invention, and FIG. 1B is a sectional view taken along line XX. 2A is a schematic cross-sectional view showing a configuration example of the VCSEL shown in FIG. 1, and FIG. 2B is a cross-sectional view showing a configuration of the VCSEL used in the second embodiment. It is sectional drawing of the medical optical module which concerns on the 2nd Example of this invention. It is sectional drawing of the medical optical module which concerns on the 3rd Example of this invention. It is sectional drawing of the medical optical module which concerns on the 4th Example of this invention. It is sectional drawing of the medical optical module which concerns on the 5th Example of this invention. FIG. 7A is a plan view of the cap, and FIG. 7B is a plan view of the metal mask. It is sectional drawing which shows the other structural example of a package. It is a block diagram which shows the structural example of the blood-flow measurement system using the optical module which concerns on the Example of this invention.

Explanation of symbols

10: medical optical module 12: stem 14: submount 14a: light receiving element mount 16, 16a: VCSEL 18: light receiving element 20 cap 20a: exit window 20b: entrance window 22: lead terminal 24: ball lens 26: optical filter 30, 32: light shielding member 40: antireflection film 42: optical lens 44: slit member 50: flat glass 52: mask 52a: exit window 52b: entrance window 54: spatial optical filter 56: antireflection film 58: spherical lens

Claims (12)

A surface emitting semiconductor laser element that emits laser light;
A light receiving element for receiving reflected light of the laser light emitted from the surface emitting semiconductor laser element;
A support member for supporting the surface emitting semiconductor laser element and the light receiving element;
A sealing member that is attached to the support member and that forms an internal space for accommodating the surface-emitting type semiconductor laser element and the light receiving element on the support member;
The sealing member is formed with an emission window for emitting laser light to the outside and an incident window for receiving reflected light of the laser light from the outside,
The internal space is provided with a light reception suppression member that suppresses light reception to the light receiving element of internally reflected light generated when the laser light emitted from the surface emitting semiconductor laser element is reflected by the internal space,
The light reception suppressing member includes a light shielding wall formed between the surface emitting semiconductor laser element and the light receiving element, and the light shielding wall is integrally formed on a substrate on which the surface emitting semiconductor laser element is formed. The surface emitting semiconductor laser element includes a mesa for emitting laser light in a direction perpendicular to the substrate, and the light shielding wall between the mesa and the light receiving element, and the light shielding wall includes the mesa. An optical module including the same semiconductor layer as a semiconductor layer to be formed . The optical module according to claim 1, wherein the light shielding wall includes an extension that extends a height of the light shielding wall from a height of the mesa. The optical module according to claim 2, wherein the extension includes an insulating film or a conductive film. The optical module according to claim 1, wherein the light reception suppressing member further includes an antireflection film formed in the internal space of the exit window. Wherein the exit window, an optical lens is mounted, the antireflection film, covering the optical lens exposed to at least the internal space, the optical module according to claim 1. The optical module according to claim 1, wherein an optical filter that removes light having a wavelength other than a specific wavelength is attached to the incident window. The optical module according to claim 1, wherein a slit member having a pinhole is attached to the exit window. The sealing member includes a mask in which the exit window and the entrance window are formed, and a cylindrical cap fixed on the support member. One surface of the cap transmits laser light to the outside, and The optical module according to claim 1, wherein an opening that transmits light reflected from the outside is formed, and the mask is attached on the one surface so as to cover the opening. 2. The optical module according to claim 1 , wherein a light receiving surface of the light receiving element is inclined so that the surface emitting semiconductor laser element side becomes higher. The optical module according to claim 1 , wherein the support member includes a mount member for inclining a light receiving surface of the light receiving element. The optical module according to claim 8 , wherein a color capable of absorbing light other than laser light is attached to a surface of the mask. An optical module according to any one of claims 1 to 11 ,
Measuring means for measuring blood flow based on a light receiving signal from the light receiving element;
Output means for outputting the result measured by the measuring means;
Medical optical measurement system.

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