JP2012024113A - Optical measuring probe device for organism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily operable optical measuring probe device for organism, which can detect various angle components of scattered light.SOLUTION: The optical measuring probe device for organism has: a first optical element 11, which is in contact with a part of an organism and receives scattered light from the organism; a second optical element 12, which is irradiated with light condensed by the first optical element 11; and a bundle fiber 13, which is irradiated with light condensed by the second optical element 12; wherein it is possible to measure the angle distribution of the scattered light intensity.

Description

  The present invention relates to a biological optical measurement probe device. More specifically, the present invention relates to a biological light measurement probe device in which scattered light propagates to a bundle fiber via a first optical element and a second optical element that are in contact with a living body.

  NIRS (Near Infrared Spectroscopy) is a device that non-invasively measures the inside of a living body by irradiating near infrared light from above the skin. NIRS is used as a brain function measuring device, for example. The brain function measurement device irradiates the head with near-infrared light of a plurality of wavelengths, and detects the intensity distribution of scattered light and its temporal change. Thereby, the brain function measuring device can analyze the concentration change of hemoglobin accompanying the brain activity, and can analyze the part of the brain activity and the magnitude of the activity.

As a light source of a biological light measuring device such as NIRS, near-infrared light having a wavelength of 690, 780, 800, 830 nm or the like is often used, and these wavelengths are hardly absorbed by water, and absorption by hemoglobin is remarkable. It is common in the point. There are two types of hemoglobin: oxygenated hemoglobin associated with oxygen and reduced hemoglobin not associated with oxygen. Since these absorption spectra are slightly different from each other, at least two of the above wavelengths are selected. By simultaneously measuring and solving the simultaneous equations, the concentration ratio of oxygenated hemoglobin and reduced hemoglobin can be estimated.

  A semiconductor laser is often used as the near infrared light source. When brain function is measured using near-infrared light, the output light from the semiconductor laser is guided to the desired part of the head using a single-mode fiber or a multi-mode fiber transmission fiber. The tip is brought into close contact with the surface of the scalp so as to avoid hair, and laser light is irradiated. The irradiated laser light passes through the scalp, skull, and cerebrospinal fluid to the cerebral gray matter. In the process, it is mainly absorbed by hemoglobin and strongly scattered by living tissues. For this reason, a part of the light propagating through the head tissue is emitted from the scalp to the outside as scattered light. Therefore, a light receiving probe for receiving scattered light is provided on the scalp several cm away from the light transmitting fiber. Then, this scattered light can be detected. The detected scattered light contains information on changes in hemoglobin concentration in cerebral gray matter. The brain activity of the part sandwiched between them can be measured with a pair of optical fiber and optical probe.

  Japanese Patent Laid-Open No. 11-299760 discloses a brain activity measuring device. As shown in FIG. 1 of this publication, this brain activity measuring apparatus forms an optical image of a brain surface on a CCD camera using an optical system provided with a space from the brain surface.

  Japanese Patent Application Laid-Open No. 2002-243641 discloses a biological function measuring device. As shown in FIG. 1 of this publication, this biological function measuring apparatus is configured to form an optical image of a brain surface to be measured, or a very shallow part from the brain surface, on the detection fiber end.

  Japanese Unexamined Patent Application Publication No. 2009-136434 discloses an optical measurement device. This optical measuring device has a larger number of light receiving probes than before, and measures the change in the concentration of hemoglobin based on the difference in detection signals between the light receiving probes.

JP-A-11-299760 JP 2002-243641 A JP 2009-136434 A

  A probe device for measuring biological light for measuring brain function needs to be used in a state where the tip of the light receiving probe is pressed perpendicularly to the scalp. Further, the conventional biological light measurement probe device has a structure for detecting light incident along the optical axis of the probe out of scattered light. For this reason, the conventional probe device can only detect the component of the scattered light emitted in a direction perpendicular to the scalp and cannot measure the angular distribution of the scattered light intensity.

If the angular distribution of the scattered light can be measured, more information about the position of the brain active site can be obtained with only one light receiving probe, so that the measurement accuracy of the brain active site can be improved. Therefore, an object of the present invention is to provide a biological light measurement probe device that can detect various angle components of scattered light and is easy to handle.

  In addition, the conventional probe device for measuring biological light cannot always measure the brain activity by eliminating the influence of scalp blood flow. For this reason, an apparatus having a plurality of light receiving probes with respect to one light transmission fiber has been developed as in the above-mentioned Japanese Patent Application Laid-Open No. 2009-136434. This device can measure the brain activity by eliminating the influence of scalp blood flow by measuring the difference in the output signal between the light receiving probes. However, this device needs to fix a large number of light receiving probes to the scalp. For this reason, an apparatus having a plurality of light receiving probes for one transmission fiber places a heavy burden on the subject and is difficult to handle.

Therefore, an object of the present invention is to provide a biological optical measurement probe device capable of measuring brain activity by eliminating the influence of scalp blood flow without increasing the number of probes.

  The present invention relates to a biological optical measurement probe device. The biological optical measurement probe device includes a first optical element 11, a second optical element 12, and a bundle fiber 13, as shown in FIG.

  The first optical element 11 is an optical element that contacts a part of a living body and receives scattered light from the living body. The second optical element 12 is an optical element that is irradiated with light condensed by the first optical element 11. The bundle fiber 13 has a plurality of single-core fibers 14. The bundle fiber 13 is irradiated with light collected by the second optical element 12.

  In the present invention, the scattered light propagates to the bundle fiber via the first optical element 11 and the second optical element 12 that are in contact with the living body. By using optical elements having a large numerical aperture for the optical element 11 and the optical element 12, the numerical aperture of the light receiving probe can be effectively increased as compared with the case where these optical elements are not used. As a result, the biological optical measurement probe device of the present invention can obtain higher detection efficiency than the conventional one. Furthermore, since the aperture of the first optical element 11 in contact with the living body can be reduced, the burden on the living body can be reduced.

  Further, according to the present invention, the scattered light having the incident angle θ and the azimuth angle φ to the first optical element 11 is mapped to the single fiber 14 constituting the bundle fiber 13, thereby scattering from the (θ, φ) direction. The light component can be detected, for example, as an output from a single fiber having a polar coordinate (r, φ + π) where r is a distance from the center of the bundle fiber. Thus, according to the present invention, components incident from various angles in the scattered light can be distinguished from each other and analyzed.

  In a preferred aspect of the present invention, at least the surface that contacts the living body among the surfaces of the first optical element 11 is a flat surface. Thereby, the adhesiveness of the biological skin and the 1st optical element 11 can be improved. The surface of the first optical element 11 that comes into contact with the living body is a flat surface, so that when the first optical element 11 is fixed to the living body, it is stable without applying unnecessary pressure to the living body. To do.

  In a preferred embodiment of the present invention, the diameter of the first optical element 11 is smaller than the diameter of the bundle fiber 13. The living body light measurement probe device according to this aspect can reduce the diameter of the first optical element 11 in contact with the living body, and therefore can reduce the burden on the living body.

  In a preferred embodiment of the present invention, the second optical element 12 and the tip of the bundle fiber 13 are in close contact. The surface of the second optical element 12 that is in close contact with the tip of the bundle fiber 13 is a flat surface. Since such a configuration is employed, the biological light measurement probe device is easily mechanically stable because the relative position between the second optical element 12 and the bundle fiber 13 is easily determined.

  In a preferred embodiment of the present invention, the tip end portion of the bundle fiber 13 has a shape in which the center portion is raised, whereby the tip end portion of the bundle fiber 13 functions as the second optical element 12.

  In a preferred embodiment of the present invention, the first optical element 11 is a window that transmits incident light. That is, the first optical element 11 transmits the light incident on the optical element 11 out of the scattered light to the second optical element 12 without condensing it.

  In a preferred embodiment of the present invention, the first optical element 11 and the second optical element 12 are composed of one optical element.

In a preferred embodiment of the present invention, the bundle fiber 13 has a plurality of single-core fibers 14. Then, the biological optical measurement probe device of this aspect satisfies the relationship of the following formula I, where the F value of the first optical element 11 is F ₁ and the numerical aperture of the single-core fiber 14 is NA.

F ₁ ≦ 1 / (2NA) Formula I

  A preferred embodiment of the present invention relates to a biological light measurement system including any one of the biological light measurement probe devices described above.

  In the present invention, the scattered light propagates to the bundle fiber via the first optical element 11 and the second optical element 12 that are in contact with the living body. By using optical elements having a large numerical aperture for the optical element 11 and the optical element 12, the numerical aperture of the light receiving probe can be effectively increased as compared with the case where these optical elements are not used. As a result, the biological optical measurement probe device of the present invention can obtain higher detection efficiency than the conventional one. Furthermore, since the aperture of the first optical element 11 in contact with the living body can be reduced, the burden on the living body can be reduced.

  Further, according to the present invention, the scattered light having the incident angle θ and the azimuth angle φ to the first optical element 11 is mapped to the single fiber 14 constituting the bundle fiber 13, thereby scattering from the (θ, φ) direction. The light component can be detected, for example, as an output from a single fiber having a polar coordinate (r, φ + π) where r is a distance from the center of the bundle fiber. As described above, according to the present invention, components incident from various angles can be distinguished from each other and analyzed without using a mechanically movable mechanism.

  The present invention can provide a biological optical measurement probe device capable of measuring cerebral blood flow while eliminating the influence of scalp blood flow.

  By applying the mechanism of the biological light measurement probe device of the present invention to a light transmission fiber, the irradiation direction of incident light can be changed without using a mechanically movable mechanism. By applying the mechanism of the biological light measurement probe device of the present invention not only to the light receiving probe side but also to the light transmission fiber side, a large number of measurement data with different irradiation conditions can be obtained, thereby improving the measurement accuracy. And a very useful biological light measurement system can be obtained.

FIG. 1 is a configuration diagram of a biological light measurement probe apparatus according to the present invention. FIG. 2 is a schematic view of the light receiving probe of the present invention. FIG. 3 is a diagram for explaining the coordinate system of the light receiving probe. FIG. 4 is a diagram illustrating the biological light measurement probe device according to the first embodiment. FIG. 5 is a diagram illustrating the biological light measurement probe device according to the second embodiment. FIG. 6 is a diagram illustrating the biological light measurement probe device according to the third embodiment. FIG. 7 is a diagram illustrating a biological light measurement probe device according to a fourth embodiment. FIG. 8 is a diagram showing the positional relationship between the light transmitting fiber and the light receiving fiber and the optical path distribution of the scattered light.

  FIG. 1 is a configuration diagram of a biological light measurement probe apparatus according to the present invention. As shown in FIG. 1, the biological light measurement probe device includes a first optical element 11, a second optical element 12, and a bundle fiber 13. The bundle fiber 13 includes a plurality of single-core fibers 14. Reference numeral 15 in the figure denotes a housing. The housing covers the side surface of the first optical element 11 and the second optical element 12, and prevents light from entering from other than the window surface of the first optical element 11. An example of a housing is a protective sheath. Reference numeral 16 in the figure denotes a detector. Each detector is connected to a computer (not shown), for example. Therefore, based on the information detected by the detector, the computer can perform various arithmetic processes and obtain a desired analysis result. In the figure, 17 indicates scattered light from the living body.

  The biological light measurement probe device is a probe device used in a biological light measurement system including, for example, a brain function measurement device. The biological light measurement system includes, for example, a light transmission fiber and a light receiving fiber. The probe device for biological light measurement of the present invention is provided at the tip of a light receiving fiber. On the other hand, the light transmission fiber may have the same configuration as the biological light measurement probe device of the present invention. That is, the light transmission fiber may include a first optical element, a second optical element, and a bundle fiber. Hereinafter, various aspects of the biological optical measurement probe apparatus will be described in the present specification. The optical system provided on the light transmission fiber side may have an optical system similar to a biological light measurement probe device described below.

  The first optical element 11 is an optical element that contacts a part of a living body and receives scattered light from the living body. An example of this optical element is in a light receiving probe of a brain function measuring apparatus. An example of a living organism is the subject's scalp. By fixing the biological optical measurement probe device to the scalp, for example, the state of the brain can be examined.

  An example of the first optical element 11 is a lens or an optical window. The lens preferably has a positive refractive power. If the first optical element 11 has a positive refractive power, the scattered light from the living body can be condensed toward the bundle fiber. The first optical element 11 may be a spherical lens. Further, the first optical element 11 may be an aspheric lens or a fisheye lens. Further, the first optical element 11 may be a Fresnel lens or a holographic optical element. When the first optical element 11 is an optical window, light incident on the optical window out of the scattered light is transmitted to the second optical element 12 without being collected. Examples of optical windows are glass plates and apertures.

  An example of the diameter of the first optical element 11 is not less than 1 mm and not more than 5 mm. The diameter of the first optical element 11 may be 2 mm or more and 3 mm or less.

  Of the surfaces of the first optical element 11, it is preferable that at least the surface in contact with the living body is a flat surface. Thereby, the adhesiveness of the biological skin and the 1st optical element 11 can be improved. The surface of the first optical element 11 that comes into contact with the living body is a flat surface, so that when the first optical element 11 is fixed to the living body, it is stable without applying unnecessary pressure to the living body. To do.

  The second optical element 12 is an optical element that is irradiated with light that has passed through the first optical element 11. The second optical element 12 is preferably installed at a position closer to the first optical element 11 than the focal point of the first optical element 11. And it is preferable that the light which passed the 1st optical element 11 is condensed on the front-end | tip part of the bundle fiber 13. FIG.

  The diameter of the first optical element 11 and the diameter of the second optical element 12 may be the same. On the other hand, since the second optical element 12 does not directly contact the living body, the diameter thereof may be larger than the diameter of the first optical element 11. Increasing the diameter of the second optical element 12 can guide incident light having a wider range of incident angles to the bundle fiber. An example of the diameter of the second optical element 12 is 1 to 3 times the diameter of the first optical element 11, and may be 1.5 to 2 times the diameter of the first optical element 11. The aperture of the first optical element 11 is preferably smaller than the diameter of the bundle fiber 13. The living body light measurement probe device according to this aspect can reduce the diameter of the first optical element 11 in contact with the living body, and therefore can reduce the burden on the living body.

  The bundle fiber 13 has a plurality of single-core fibers 14. The bundle fiber 13 is irradiated with light collected by the second optical element 12.

  Further, according to the present invention, the scattered light having the incident angle θ and the azimuth angle φ to the first optical element 11 is mapped to the single fiber 14 constituting the bundle fiber 13, thereby scattering from the (θ, φ) direction. For example, the optical component can be detected as an output from a single-core fiber whose polar coordinates with the distance from the center of the bundle fiber being r are (r, φ + π). Thus, according to the present invention, components incident from various angles in the scattered light can be distinguished from each other and analyzed. For this reason, it is preferable that the detection unit analyzes the position (r, φ + π) of each single fiber 14 constituting the bundle fiber 13 in association with the incident angle θ and the azimuth angle φ.

  FIG. 2 is a schematic view of the light receiving probe of the first embodiment. As shown in FIG. 2, this light receiving probe has two large and small convex lenses L1 and L2 near the tip of the bundle fiber. FIG. 3 is a coordinate system for explaining the light receiving probe. A light receiving probe is brought into contact with the scalp vertically. It is assumed that the optical axis of the light receiving probe is the ζ (zeta) axis, and that the light source is located somewhere on the negative extension of the ξ (guzai) axis. Scattered light incident on the first convex lens L1 at an incident angle θ and an azimuth angle φ is caused by the condensing action of the lens L1 so that the distance from the optical axis is r and the azimuth is φ + π on the focal plane of the lens L1. Focused.

  When the convex lens L1 is a normal convex lens, the light passes through the focal plane with an inclination of an angle θ at the focal plane of L1. For this reason, this scattered light cannot be coupled to the single-core fiber unless the refractive index of the scalp is n and the NA of the single-fiber is greater than n · sin θ. Therefore, a second convex lens L2 is provided near the focal plane of L1. When the distance d1 between the principal points of L1 and L2 is equal to the focal length f2 of L2, the optical axes of all the light beams that have passed through L2 are aligned in parallel, and are incident perpendicularly to the end face of the bundle fiber. The light beam can be effectively coupled to a single fiber having a small NA.

  For simplicity, the refractive index in the living body is regarded as 1. Then, at the end face of the bundle fiber, when L1 is a general convex lens, r = d1 · tan θ, and r = d1 · θ in the case of an equidistant projection type lens represented by an f-θ lens or a fisheye lens. In the case of an equisolid angle projection type lens represented by some fisheye lenses, the relationship r = 2 · d1 · sin (θ / 2) is approximately established. In any method, scattered light belonging to a specific incident angle / azimuth angle is mapped on a one-to-one basis on a single fiber that forms a bundle, and light incident from the directions of θ and φ has a polar coordinate ( The light is output only from a single-fiber (r, φ + π) (including a limited number of single-core fibers arranged in the vicinity of the point image due to aberration). Therefore, only the light incident on the probe is extracted from these specific directions θ and φ by taking out only the output light from these single-core fibers and making it incident on a specific photodetector and measuring the light intensity. Can be measured. If a photodetector is prepared corresponding to the desired number of single fiber groups, light from different directions can be distinguished and measured at the same time. If the light is incident on the detector in a lump, it is possible to collectively detect all the light in the range of θ and φ that can be received by the probe, as in the conventional probe. As the photodetector, a PIN photodiode, an avalanche photodiode, a CCD, a photomultiplier tube, a streak camera, or the like can be used as appropriate.

  Furthermore, by using a compound lens such as a fisheye lens in addition to a spherical lens or an aspheric lens for L1 and L2, the NA of the lens system can be easily increased to 0.5 or more, so only a bundle fiber is used. The maximum value of θ can be made larger than the case, and as a result, the light receiving efficiency of the probe is improved. In general, a light beam incident at an incident angle θ that greatly exceeds the NA of the lens system reaches the light receiving fiber with aberrations. In this case, the accuracy of mapping between θ, φ and the single fiber is reduced. , The curvature of the focal plane and astigmatism may cause a decrease in the coupling efficiency to the single fiber. However, unless a high accuracy is required for the measurement of θ, it is considered that there is almost no practical impediment, and a large incident angle θ that exceeds the NA of the optical system within the limits of the aperture of the optical system. It is also possible to efficiently capture light incident on the.

  Conversely, by making light incident on these specific single fiber groups from the opposite direction, it is possible to emit light only from the tip of the probe in the corresponding θ and φ directions.

  The light coupling performance to each single fiber is mainly determined by the F number F1 of L1 (or the numerical aperture of L1). Therefore, it is preferable to design F1 so that F1 ≦ 1 / (2 · NA), where NA is the numerical aperture of the single-core fiber. On the other hand, the maximum incident angle θmax of scattered light that can be captured by the entire bundle fiber is mainly determined by the F number F2 of L2. Therefore, when the diameter of the bundle fiber is D, it is preferable to design so that F2 = d1 / D ≦ 0.5 / tan (θmax). However, a value that takes into account the actual refractive index n in the living body is used as the value of θmax.

  In general, the focal length f1 of L1 and the focal length f2 of L2 may be different, but in order to satisfy the condition that the light beam is vertically focused on the end face of the bundle fiber, the distance between the principal points of L1 and L2 is set to d1. As shown in FIG.

d1 = f2 ≦ f1 Formula 1

  At this time, the distance d2 between the principal point of L2 and the end face of the bundle fiber is, if the thickness of the lens is ignored,

d2 = (f1-f2) f2 / f1 Equation 2
It becomes.

  Since the diameter of L1 can be made smaller than the diameter of the bundle fiber, the burden on the subject when wearing one probe can be made almost the same as in the past. The first convex lens L1 is preferably a plano-convex lens in consideration of adhesion to the skin, but any form may be used as long as it is an optical element having a positive refractive power. For example, a Fresnel lens or a holographic optical element can be used in addition to a classical convex lens having a spindle section. Furthermore, an aspherical lens or a compound lens can be used. The second convex lens L2 is preferably a plano-convex lens in consideration of the adhesion to the end face of the bundle fiber, but a Fresnel lens, a holographic optical element, an aspherical lens, and a compound lens can be used as in the case of L1.

  In addition, L1 preferably collects the light flux so that the luminance distribution is uniform on the end face of the bundle fiber, so that it is an optical element designed by an equidistant projection method or an isosolid angle projection method rather than using a normal convex lens. Is preferably used.

  Although the case where one bundle fiber is used has been described here, a plurality of bundle fibers having a small bundle diameter may be bundled and used. A plurality of single-core fibers may be bundled and used.

  According to the present invention, even if the scattered light has a large incident angle θ exceeding the NA of the light receiving bundle fiber, the scattered light can be efficiently coupled to the bundle fiber. This means that the NA of the light receiving probe is apparently increased, but the optical power that can be coupled per single fiber does not change, so in order to receive light with a large incident angle, the bundle diameter must be set accordingly. It needs to be thick. If the bundle diameter is increased by the conventional method, the contact area between the light receiving probe and the skin increases, the position resolution decreases, and the force to press the probe needs to be increased, which increases the burden on the subject. However, in the present invention, since only the lens L1 at the tip of the light receiving probe is in contact with the skin, even if the bundle diameter is increased, the position resolution does not decrease and the burden on the subject does not increase.

  According to the present invention, since the single-core fiber constituting the bundle fiber can be made to correspond to the incident angle θ and the azimuth angle φ 1: 1, the dependence of the scattered light intensity on θ and φ can be measured. It becomes like this. This makes it possible to roughly estimate the three-dimensional position of the light source and absorber using only one light receiving fiber when performing diffuse optical tomography.

  When the present invention is applied to brain function measurement, comparing the scattered light from the direction in which θ is approximately 0 radians and the scattered light from the direction in which θ is greater than 0 radians, the latter is a shallow region in the tissue. It is thought that it contains more light that passes through and is less affected by blood flow of cerebral gray matter. In addition, it is considered that the scalp blood flow is affected more strongly because it crosses the scalp diagonally. Therefore, by subtracting the former and the latter with appropriate weights, it becomes possible to selectively extract only the information of light passing through the cerebral gray matter, eliminating the influence of scalp blood flow. This eliminates the effect of scalp blood flow and enables more accurate measurement of brain activity.

  When the present invention is applied to a light transmission fiber, the irradiation direction of incident light can be made variable without introducing a mechanical movable part. As a result, even when a light receiving probe having the same structure as the conventional one is used, a lot of measurement data under irradiation conditions different from the conventional one can be obtained. Measurement can be performed, or measurement accuracy equivalent to the conventional one can be obtained with a smaller number of light receiving probes than the conventional one.

  When the present invention is applied to both the light receiving probe and the light transmitting fiber, the same number of light transmitting fibers and light receiving probes as the conventional one can be measured with higher accuracy than before, or a smaller number of light transmitting light than conventional. Measurement accuracy equivalent to the conventional one can be obtained with the number of fibers and light receiving probes.

  FIG. 4 is a diagram illustrating the biological light measurement probe device according to the first embodiment. In this biological light measurement probe device, L2 is brought into close contact with the end of the bundle fiber in order to minimize the aperture of the second optical element L2. The lens configuration corresponds to the case where the equal sign holds in Equation 1, that is, the case where d1 = f2 = f1 holds. D1 is the distance between the principal points of L1 and L2. In consideration of the adhesiveness to the skin and the adhesiveness to the end face of the bundle fiber, the two lenses disclose a plano-convex lens and disclose an arrangement in which the convex surfaces face each other. However, the direction in which the plano-convex lens is arranged is not limited to this.

  That is, a preferred embodiment of the biological optical measurement probe device of the present invention is one in which the second optical element 12 and the tip of the bundle fiber 13 are in close contact. The surface of the second optical element 12 that is in close contact with the tip of the bundle fiber 13 is a flat surface. Since such a configuration is employed, the biological light measurement probe device is easily mechanically stable because the relative position between the second optical element 12 and the bundle fiber 13 is easily determined.

  As shown in FIG. 4, in the biological optical measurement probe device of this aspect, it is preferable to make the diameter of L2 larger than the diameter of L1. As shown in FIG. 4, the distance d1 is adjusted so that the scattered light incident on L1 passes through L1 and L2 and is collected at the tip of the bundle fiber. As shown in FIG. 4, the biological light measurement probe device has a protective sheath that covers L2 from the side surface of L1 so that light does not enter from other than the L1 portion.

  FIG. 5 is a diagram illustrating the biological light measurement probe device according to the second embodiment. This biological light measurement probe device is an example in which the end surface of the bundle fiber is processed into a convex shape so that the bundle fiber itself has an L2 function. For this reason, L2 is omitted in this embodiment. However, the configuration of the optical system itself is equivalent to that of the first embodiment. The focal point of L1 is located inside the single fiber, and the focused spot is blurred on the end face. For this reason, in the living body optical measurement probe device of this embodiment, the complete correspondence between (θ, φ) and (r, φ + π) is lost. However, there is no practical problem unless a high angular resolution is required. The optical coupling efficiency of the entire bundle fiber is mainly determined by the core filling factor of the single-core fiber. For this reason, the biological light measurement probe device of this embodiment has an optical coupling efficiency equivalent to that of the biological light measurement probe device of the first embodiment. As a processing method of the end face of the bundle fiber, a method of polishing on a convex surface or a method of heating and melting and molding on a dome can be considered.

  That is, as shown in FIG. 5, in a preferred embodiment of the present invention, the end portion of the bundle fiber 13 has a shape in which the center portion is raised, so that the end portion of the bundle fiber 13 is the second optical element 12. Function as.

  FIG. 6 is a diagram illustrating the biological light measurement probe device according to the third embodiment. This biological optical measurement probe device uses a window material having a plane parallel to L1. This corresponds to the case where f1 = ∞ in Equations 1 and 2. The diameter of L2 is made larger than the diameter of the bundle fiber. Further, d1 + d2 is also doubled in the first embodiment. For this reason, this probe device for measuring biological light is larger in size than the other embodiments. However, this biological optical measurement probe device has an advantage that only one lens is required. That is, in a preferred embodiment of the present invention, as shown in FIG. 6, the first optical element L1 is a window that transmits incident light. In other words, the first optical element L1 transmits the incident light to the window among the scattered light to the second optical element 12 without condensing it.

FIG. 7 is a diagram illustrating a biological light measurement probe device according to a fourth embodiment. In the probe device for biological light measurement of the above-described embodiment, total reflection can occur at the interface between the living body and the outside of the living body (that is, the lower surface of L1). Therefore, there is a problem that the value of θmax cannot generally exceed the value of sin ⁻¹ (1 / n). This probe device for measuring biological light is an example for solving this problem, and L1 and L2 are single materials having a refractive index substantially equal to that of a living body (referred to as a “fan lens” because the cross section is a fan shape) To make). That is, in a preferred aspect of the present invention, the first optical element L1 and the second optical element L2 are made of one optical element. For example, the refractive index of the measurement site of the measurement subject may be measured in advance, and a lens made of an optical element having a refractive index within a range of 10% (or within a range of 5%) from the measured value may be employed. . In addition, even if the refractive index of the measurement site of the measurement subject is not measured each time, an average value of refractive indexes at a plurality of locations is obtained in advance for each nationality, age, and gender, and is within a range of 10% of the average value. A lens made of an optical element having a refractive index (or within a range of 5%) may be employed. The upper surface of the fan-shaped lens is a plane and is similar to the third embodiment in that it corresponds to f1 = ∞. On the other hand, the lower surface of the fan-shaped lens has a function of L2 and also serves as a refractive index interface. As long as the upper surface of the fan-shaped lens is in close contact with the skin, a light flux having any value of θ can be introduced into the fan-shaped lens. Therefore, if the center of curvature of the lower surface of the fan-shaped lens is designed to be located near the upper surface of the lens, the light beam incident on the lower surface of the fan-shaped lens will always pass through the lower surface of the lens under conditions close to normal incidence. It is possible to prevent total reflection from occurring.
In this embodiment, the first optical element L1 and the second optical element L2 are formed of one optical element.

  This embodiment is a biological light measurement system including any of the biological light measurement probe devices described above. The biological light measurement system further includes a light source and a detection device. And the light from a light source is irradiated to a part of living body via a light source system. The light from the light source may be emitted from the above-described biological light measurement probe device. Then, the biological light measurement probe device collects the light scattered from the object and guides it to the detection unit device. For example, the light source can irradiate near infrared light having two or more wavelengths. For this reason, various analysis results can be obtained by solving simultaneous equations using detection values based on two or more wavelengths in the detection unit. A biological optical measurement system is already known. As the configuration of the biological light measurement system, for example, the configurations of various devices cited in the present specification can be adopted as appropriate.

  FIG. 8 is a diagram showing the positional relationship between the light transmitting fiber and the light receiving fiber and the optical path distribution of the scattered light. By using the probe device of the present invention, it is possible to measure the intensity ratio of the scattered light incident on the light receiving fiber from the side closer to the light source (φ = π) and the opposite side (φ = 0). Is possible. Using this intensity ratio, it is possible to know the value of the incident angle θ. In addition, if the probe device of the present invention is used, it is possible to measure separately for a light beam having a relatively small incident angle θ and a light beam having a relatively large incident angle. The latter is considered to be relatively strongly affected by scalp blood flow. Therefore, the former and the latter are measured independently, and the latter is subtracted from the former by an appropriate weight. It is possible to extract a signal that reflects only the influence.

  The present invention can be used in the field of diagnostic equipment, the field of brain function measurement, the field of biological light measurement, the field of brain computer interfaces (BMI, BCI), the field of food inspection, and the like.

DESCRIPTION OF SYMBOLS 11 1st optical element 12 2nd optical element 13 Bundle fiber 14 Single fiber 15 Housing 16 Detector

Claims (9)

A first optical element (11) that contacts a part of a living body and receives scattered light from the living body;
A second optical element (12) irradiated with light that has passed through the first optical element (11);
A bundle fiber (13) irradiated with light that has passed through the second optical element (12),
A probe device for measuring biological light. Of the surfaces of the first optical element (11), at least the surface in contact with the living body is a plane,
The biological optical measurement probe device according to claim 1. The aperture of the first optical element (11) is smaller than the diameter of the bundle fiber (13),
The biological optical measurement probe device according to claim 1. The second optical element (12) and the end of the bundle fiber (13) are in close contact with each other,
Of the surfaces of the second optical element (12), the surface closely contacting the tip of the bundle fiber (13) is a plane.
The biological optical measurement probe device according to claim 1. The tip portion of the bundle fiber (13) has a shape with a raised center portion, whereby the tip portion of the bundle fiber (13) functions as the second optical element (12).
The biological optical measurement probe device according to claim 1. The first optical element (11) is a window that transmits incident light.
The biological optical measurement probe device according to claim 1. The first optical element (11) and the second optical element (12) are composed of one optical element.
The biological optical measurement probe device according to claim 1. The bundle fiber (13) has a plurality of single-core fibers (14),
A biological optical measurement probe device satisfying the relationship of the following formula I, where F is F _{1 of} the first optical element (11) and NA is the numerical aperture of the single-core fiber (14).
F ₁ ≦ 1 / (2NA) Formula I A biological light measurement system including the biological light measurement probe device according to claim 1.

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