Optical inspection device and optical fiber structure

Abstract

Provided is an optical inspection device which can be inserted into a tubular body, and in which an SN ratio when receiving reflected light reflected from an object under inspection can be improved.　An optical inspection device 1 comprises a light source 23, a light emission optical fiber 2 having a first light guide portion 22 through which light emitted from the light source 23 propagates and a first light emitting portion 21 which emits the light that has propagated through the first light guide portion 22 as emitted light onto a detection target, a light reception optical fiber 3 having a first light receiving portion 31 for receiving reflected light resulting from the emitted light emitted from the first light emitting portion 21 being reflected by the detection target and a second light guide portion 32 through which the reflected light received by the first light receiving portion 31 propagates, and a light detecting portion 33 for detecting the reflected light that has propagated through the second light guide portion 32, wherein an optical fiber structure 10 is formed by arranging the first light emitting portion 21 and the first light receiving portion 31 so as to be mutually offset in the fiber axial direction.

Description

Optical inspection device and optical fiber structure

[0001] The present invention relates to an optical inspection device and an optical fiber structure.

[0002] Optical inspection devices that irradiate a detection object with light and detect the reflected light are configured to transmit light emitted from a light source to a light-emitting unit using optical fiber, irradiate the detection object from the light-emitting unit, and transmit the reflected light from the detection object received by a light-receiving unit using optical fiber to a light-detecting unit, process the light detected by the light-detecting unit, and inspect the detection object, and are used in a variety of fields including the medical field.

[0003] For example, Patent Document 1 describes a laser blood flow meter that includes a blood flow meter main body, an irradiating optical fiber and a light-receiving optical fiber connected to the blood flow meter main body, and a probe in which the tips of the irradiating optical fiber and the light-receiving optical fiber are fixed in parallel, whereby laser light is irradiated from the blood flow meter main body through the irradiating optical fiber to biological tissue, and scattered light within the biological tissue is transmitted as blood flow information to the blood flow meter main body through the light-receiving optical fiber. The optical fiber probe used in this laser blood flow meter includes a reflecting fixing plate provided with fixing means for fixing to the biological tissue, and the irradiating optical fiber and the light-receiving optical fiber are fixed in parallel to the reflecting surface of the reflecting fixing plate to form the probe, and the laser light output from the irradiating optical fiber and the scattered light within the biological tissue are reflected by the reflecting surface of the reflecting fixing plate.

[0004] Patent document 2 also describes a medical system comprising a catheter including a distal end assembly for performing medical surgery on tissue within a cavity of a patient's organ, the distal end assembly including an optical fiber configured to guide irradiated light (transmitted light) to interact with the tissue in the cavity and to guide reflected light (returned light) that has interacted with the tissue, a light source configured to generate the irradiated light, a detector configured to measure the reflected light, a circulator configured to couple the irradiated light from the light source to the optical fiber and couple the reflected light from the optical fiber to the detector, and a processor configured to identify contact of the distal end assembly with the tissue based on the reflected light measured by the detector and to indicate the identified contact to a user.

[0005] Japanese Patent Application Laid-Open No. 10-118039 Japanese Patent Application Laid-Open No. 2022-126610

[0006] When temporarily blocking blood flow in a blood vessel during surgery or other procedures, a balloon catheter is inserted into the blood vessel and the balloon is inflated to block the blood flow. In addition, in fields other than medicine, such as plumbing, a method of inserting an air bag into a pipe and inflating the air bag to block the water flow (airbag waterstop method) is also used to temporarily stop the water flow in a pipe. In these methods and techniques, an optical fiber for emitting light and an optical fiber for receiving light are placed inside the balloon catheter or airbag, and the blockage of the blood vessel or pipe is detected by utilizing the difference in light reflectance between the blood vessel wall to be detected and the blood, or the difference in light reflectance due to the presence or absence of water between the blood vessel wall to be detected and the airbag.

[0007] However, the laser blood flow meter described in Patent Document 1 measures blood flow by being fixed to a measurement surface of biological tissue such as the body surface using a reflective fixing plate, and is not intended to be inserted into a thin tube such as a blood vessel.

[0008] Furthermore, the medical system described in Patent Document 2 is configured with a single optical fiber, and uses a circulator to separate the irradiated light emitted from the light source and the reflected light from the detection target. When the irradiated light and the reflected light are propagated using only a single optical fiber, as in this medical system, reflected light due to Fresnel reflection at the tip of the optical fiber (hereinafter referred to as Fresnel reflected light) occurs, and this Fresnel reflected light becomes a large noise compared to the reflected light from the detection target, resulting in a problem of a reduced signal-to-noise ratio (SN ratio).

[0009] An object of the present invention is to provide an optical inspection device and an optical fiber structure that can be inserted into a tubular body, for example, when the object to be inspected is a tubular body, particularly a thin tubular body such as a blood vessel, and that can prevent noise due to Fresnel reflected light and improve the signal-to-noise ratio when receiving light reflected from the object to be inspected.

[0010] The inventors have discovered that by using a light-emitting optical fiber that propagates light emitted from a light source and a light-receiving optical fiber that propagates reflected light received from a detection object (inspection object), and by arranging the first light-emitting portion of the light-emitting optical fiber and the first light-receiving portion of the light-receiving optical fiber so that they are shifted from each other in the fiber axial direction X, and preferably by arranging the tip of the first light-receiving portion closer to the first light-guiding portion than the tip of the first light-emitting portion, or by arranging the tip of the first light-emitting portion closer to the second light-guiding portion than the tip of the first light-receiving portion, the first light-receiving portion of the light-receiving optical fiber can effectively receive reflected light without directly receiving irradiation light emitted from the first light-emitting portion of the light-emitting optical fiber, thereby making it possible to improve the signal-to-noise ratio when receiving reflected light, and have completed the present invention.

[0011] In order to achieve the above object, the gist of the present invention is as follows: (1) An optical inspection device including a light source, at least one light-emitting optical fiber having a first light-guiding section that propagates light emitted from the light source and a first light-emitting section that irradiates a detection object with the light propagated through the first light-guiding section as irradiation light, at least one light-receiving optical fiber having a first light-receiving section that receives reflected light of the irradiation light emitted from the first light-emitting section that is reflected by the detection object and a second light-guiding section that propagates the reflected light received by the first light-receiving section, and a light detection section that detects the reflected light that has propagated through the second light-guiding section of the light-receiving optical fiber, wherein the light-emitting optical fiber and the light-receiving optical fiber form an optical fiber structure with the first light-emitting section and the first light-receiving section shifted from each other in the fiber axial direction. (2) The optical inspection device according to (1) above, wherein the irradiation light is emitted from a side surface of the first light-emitting section. (3) The optical inspection device according to (1) or (2), wherein the length of the first light-receiving portion of the light-receiving optical fiber is longer than the length of the first light-emitting portion of the light-emitting optical fiber. (4) The optical inspection device according to any one of (1) to (3), wherein the light-emitting optical fiber and the light-receiving optical fiber form the optical fiber structure such that a portion of the first light-emitting portion and a portion of the first light-receiving portion are shifted from each other in the fiber axial direction. (5) The optical inspection device according to any one of (1) to (4), wherein the light-emitting optical fiber and the light-receiving optical fiber are respectively arranged such that a tip of the first light-emitting portion and a tip of the first light-receiving portion are at the same position in the fiber axial direction. (6) The optical inspection device according to any one of (1) to (5), wherein the light-receiving optical fiber includes a plurality of the first light-receiving portions. (7) The optical inspection device according to any one of (1) to (6), wherein the light-emitting optical fiber includes a plurality of the first light-emitting portions. (8) An optical inspection device described in any one of (1) to (7) above, wherein one or both of the first light-emitting unit and the first light-receiving unit are provided in an intermediate portion of the light-emitting optical fiber or the light-receiving optical fiber.(9) An optical inspection device according to any one of (1) to (8), wherein the light-emitting optical fiber and the light-receiving optical fiber are constituted by a quartz fiber or a plastic fiber. (10) An optical fiber structure comprising: at least one light-emitting optical fiber having a first light-guiding section that propagates light emitted from a light source and a first light-emitting section that irradiates a detection object with the light propagated through the first light-guiding section as irradiation light; and at least one light-receiving optical fiber having a first light-receiving section that receives reflected light of the irradiation light emitted from the first light-emitting section that is reflected by the detection object and a second light-guiding section that propagates the reflected light received by the first light-receiving section, wherein the light-emitting optical fiber and the light-receiving optical fiber form an optical fiber structure with the first light-emitting section and the first light-receiving section shifted from each other in the fiber axial direction.

[0012] According to the present invention, for example, when the object to be inspected is a tubular body, particularly a thin tubular body such as a blood vessel, an optical inspection device and an optical fiber structure can be provided which can be inserted into such a tubular body, and which can prevent noise due to Fresnel reflected light and improve the signal-to-noise ratio when receiving light reflected from the object to be inspected.

[0013] Fig. 1 is a plan view schematically showing the configuration of an optical inspection device and an optical fiber structure according to a first embodiment. Fig. 2 is a diagram showing the positional relationship between the optical fiber structure and a tube when the optical fiber structure of the optical inspection device according to the first embodiment is inserted into the tube to be inspected, where Fig. 2(a) is an enlarged longitudinal cross-sectional view of a main part of the optical fiber structure, and Fig. 2(b) is a cross-sectional view taken along line II' in Fig. 2(a), showing the optical paths of the irradiation light emitted from the first light-emitting unit and the reflected light from the tube received by the first light-receiving unit. Fig. 3 is a plan view showing the structure of an optical fiber structure according to a second embodiment. Fig. 4 is a cross-sectional view showing the arrangement of the light-emitting optical fiber and the light-receiving optical fiber constituting the optical inspection device and the optical fiber structure according to a third embodiment. Fig. 5 is a plan view showing the structure of an optical fiber structure according to a fourth embodiment, where Fig. 5(a) shows a case where the tip of the first light receiving portion is positioned closer to the first light guiding portion than the tip of the first light emitting portion, and Fig. 5(b) shows a case where the tip of the first light emitting portion is positioned closer to the second light guiding portion than the tip of the first light receiving portion. Fig. 6 is a plan view showing the structure of an optical fiber structure according to a fifth embodiment, where Fig. 6(a) shows a case where the length of the first light receiving portion of the light-receiving optical fiber is longer than the length of the first light emitting portion of the light-emitting optical fiber, and Fig. 6(b) shows a case where the length of the first light emitting portion of the light-emitting optical fiber is longer than the length of the first light receiving portion of the light-receiving optical fiber. Fig. 7 is a plan view showing the structure of an optical fiber structure according to a sixth embodiment, where Fig. 7(a) shows a case where the light-receiving optical fiber includes multiple first light receiving portions, and Fig. 7(b) shows a case where the light-emitting optical fiber includes multiple first light emitting portions. Fig. 8 is a plan view showing the structure of an optical fiber structure according to a seventh embodiment.Fig. 9 is a longitudinal cross-sectional view of a first light-emitting portion of a light-emitting optical fiber showing various embodiments, in which Fig. 9(a) shows a case where the first light-emitting portion is formed by forming a rough surface on the surface of the clad of the light-emitting optical fiber, Fig. 9(b) shows a case where the first light-emitting portion is formed by completely scraping off the clad of the light-emitting optical fiber in the radial direction and forming a light-diffusing resin layer on the scraped-off surface of the clad, Fig. 9(c) shows a case where the first light-emitting portion is formed by partially scraping off the clad of the light-emitting optical fiber in the radial direction and forming a light-diffusing resin layer on the scraped-off surface of the clad, and Fig. 9(d) shows a case where a coreless fiber or a light-diffusing fiber is fusion-spliced ​​to the tip of the light-emitting optical fiber. Fig. 10 is a longitudinal cross-sectional view of a first light-emitting portion of a light-emitting optical fiber showing various embodiments, in which Fig. 10(a) shows a case where the first light-emitting portion is formed by scraping off the tip of the core and clad of the light-emitting optical fiber into a conical shape, and Fig. 10(b) shows a case where the first light-emitting portion is formed by cutting the core and clad of the light-emitting optical fiber obliquely. 11A and 11B are longitudinal cross-sectional views of the first light receiving portion of a light receiving optical fiber showing various embodiments, in which FIG. 11A shows a case where the first light receiving portion is formed by forming a rough surface on the surface of the cladding of the light receiving optical fiber, and FIG. 11B shows a case where the first light receiving portion is formed by scraping off the cladding while leaving the core of the light receiving optical fiber. 12A and 12B are longitudinal cross-sectional views of the first light receiving portion of a light-receiving optical fiber showing various embodiments, in which FIG. 12A shows a case in which the first light receiving portion is formed by forming a rough surface on the surface of the cladding of the light-receiving optical fiber, FIG. 12B shows a case in which the first light receiving portion is formed by completely scraping away the cladding of the light-receiving optical fiber in the radial direction and forming a light-diffusing resin layer on the surface of the scraped-off cladding, FIG. 12C shows a case in which the first light receiving portion is formed by partially scraping away the cladding of the light-receiving optical fiber in the radial direction and forming a light-diffusing resin layer on the surface of the scraped-off cladding, and FIG. 12D shows a case in which a coreless fiber or a light-diffusing fiber is fusion-spliced ​​to the tip of the light-receiving optical fiber.

[0014] Next, optical inspection devices and optical fiber structures according to some embodiments of the present invention will be described below.

[0015] <First embodiment> Fig. 1 is a plan view that schematically shows an optical inspection device of a first embodiment. Fig. 2 is a diagram showing the positional relationship between an optical fiber structure and a tube that is a detection target (inspection target) when the optical fiber structure of the optical inspection device of the first embodiment is inserted into the tube, in which Fig. 2(a) is an enlarged vertical cross-sectional view of a main part of the optical fiber structure, and Fig. 2(b) is a cross-sectional view taken along line II' in Fig. 2(a), showing the optical paths of irradiation light emitted from a first light-emitting unit and reflected light from the tube that is received by a first light-receiving unit.

[0016] 1 , the optical inspection device 1 includes a light source 23, at least one light-emitting optical fiber 2 having a first light-guiding section 22 that propagates light emitted from the light source 23 and a first light-emitting section 21 that irradiates the light propagated through the first light-guiding section 22 as irradiation light Lt onto a detection object 6, at least one light-receiving optical fiber 3 having a first light-receiving section 31 that receives reflected light Lt′ when the irradiation light Lt emitted from the first light-emitting section 21 is reflected by the detection object 6 and a second light-guiding section 32 that propagates the reflected light Lt′ received by the first light-receiving section 31, and a light-detecting section 33 that detects the reflected light Lt′ that has propagated through the second light-guiding section 32 of the light-receiving optical fiber 3. Here, the optical inspection device 1 may further include a display section 34 that displays a detection value of the intensity of the reflected light Lt′ detected by the light-detecting section 33. The display unit 34 may be configured to perform a predetermined process on the reflected light Lt' and display the results of the process, in addition to displaying the detected value of the intensity of the reflected light Lt'.

[0017] 2(a) and 2(b), the light-emitting optical fiber 2 and the light-receiving optical fiber 3 form the optical fiber structure 10 in such a manner that the first light-emitting portion 21 and the first light-receiving portion 31 are mutually shifted in the fiber axial direction X. At this time, the first light-emitting portion 21 and the first light-receiving portion 31 are fixedly connected in a parallel arrangement state.

[0018] 2(a), the first light-emitting portion 21 of the light-emitting optical fiber 2 and the first light-receiving portion 31 of the light-receiving optical fiber 3 are arranged in parallel. By configuring the light-emitting optical fiber 2 and the light-receiving optical fiber 3 as separate optical fibers, noise due to Fresnel reflected light can be prevented. Furthermore, by reducing and preventing this noise, an improvement in the signal-to-noise ratio when receiving the reflected light Lt' reflected from the detection target 6 can be expected.

[0019] Here, in particular, by positioning the tip of the first light receiving unit 31 closer to the first light guiding unit 22 than the tip 2a of the first light emitting unit 21, or by positioning the tip of the first light emitting unit 21 closer to the second light guiding unit 32 than the tip 3a of the first light receiving unit 31, when the irradiation light Lt is irradiated onto the detection object 6, the irradiation light Lt emitted from the first light emitting unit 21 can be effectively prevented from being directly taken in by the first light receiving unit 31, and as shown in Figure 2 (b), the reflected light Lt' obtained by reflecting once or multiple times on the detection object 6 is taken in by the first light receiving unit 31, thereby reducing noise due to the intake of the irradiation light Lt in the detection value of the intensity of the reflected light Lt' taken in by the first light receiving unit 31.

[0020] [Configuration of the optical fiber structure] The optical fiber structure 10 includes a light-emitting optical fiber 2 and a light-receiving optical fiber 3. Here, the optical fiber structure 10 shown in Fig. 1 includes one light-emitting optical fiber 2 and one light-receiving optical fiber 3. This is expected to prevent noise in the reflected light Lt' due to Fresnel reflected light.

[0021] (Light-emitting optical fiber) Of these, the light-emitting optical fiber 2 has a first light-guiding section 22 that propagates light emitted from the light source 23, and a first light-emitting section 21 that irradiates the light propagated through the first light-guiding section 22 as irradiation light Lt onto the detection target 6. This allows the light emitted from the light source 23 to propagate through the first light-guiding section 22 with little loss. Furthermore, by propagating the light from the light source 23 with little loss, it is expected that more light will be irradiated as irradiation light Lt from the first light-emitting section 21 onto the inner surface of a tube, which is the detection target 6, for example.

[0022] Here, the light-emitting optical fiber 2 is configured to propagate light from the light source 23 at least in the first light guiding section 22. An example of the light-emitting optical fiber 2 is an optical fiber having a core-clad structure, in which at least in the first light guiding section 22, when viewed in a cross section perpendicular to the fiber axial direction X, the core has a core-clad structure that has a core at the center and a clad covering the entire periphery of the core. In this case, the first light guiding section 22 of the light-emitting optical fiber 2 is preferably configured using an optical fiber whose clad has not been removed. Here, by configuring the first light guiding section 22 using an optical fiber whose clad has not been removed, it is expected that light from the light source 23 will propagate with little loss. On the other hand, the first light-emitting section 21 of the light-emitting optical fiber 2 can have a shape in which part or all of the clad has been removed. Here, by configuring the first light-emitting section 21 using an optical fiber whose clad has been removed, it is expected that light from the light source 23 emitted from the part where the clad has been removed will be emitted as the irradiation light Lt. The light-emitting optical fiber 2 is not limited to a fiber-shaped one, but may be an optical waveguide formed on a substrate or the like.

[0023] From the viewpoint of shortening the optical path to the detection object 6 and reducing loss of the reflected light Lt′, it is preferable that the first light-emitting unit 21 of the light-emitting optical fiber 2 is configured so that the irradiation light Lt is emitted approximately perpendicular to the fiber axial direction X of the light-emitting optical fiber 2. From this viewpoint, it is preferable that the irradiation light Lt emitted from the first light-emitting unit 21 is emitted from the side surface of the first light-emitting unit 21.

[0024] Furthermore, at least the portion of the first light-emitting section 21 of the light-emitting optical fiber 2 that emits the irradiation light Lt may be subjected to at least one of the following treatments (a) to (d): (a) surface roughening treatment using hydrofluoric acid, an organic solvent, or the like; (b) laser patterning treatment; (c) coating treatment of the portion where the cladding has been scraped off with a transparent resin containing a light-diffusing material such as titanium oxide; and (d) fusion splicing of a coreless fiber or a light-diffusing fiber to the tip.

[0025] Of these, (d) the portion fusion-spliced ​​to the tip of the coreless fiber or light-diffusing fiber is preferably coated with a transparent resin having a high refractive index. In this case, if the light-emitting optical fiber 2 is made of a quartz fiber, for example, the transparent resin used in the coating process preferably has a refractive index higher than that of the quartz glass that constitutes the cladding 27 of the quartz fiber.

[0026] Furthermore, in order to ensure mechanical strength, the portion of the light-emitting optical fiber 2 that has been subjected to (a) surface roughening or (b) patterning may be further coated with a transparent resin. The refractive index of the transparent resin used in this case is not particularly limited.

[0027] The material of the light-emitting optical fiber 2 is not particularly limited, but it is preferably made of a quartz fiber or a plastic fiber, particularly from the viewpoint of facilitating insertion into a tubular body or the like that serves as the detection target 6. Of these, quartz fiber has tension, so by using a quartz fiber for the light-emitting optical fiber 2, it becomes possible to insert the light-emitting optical fiber 2 deep into the internal space of the tubular body, even if the tubular body that serves as the detection target 6 has a small diameter. Furthermore, since plastic fiber is flexible, by using a plastic fiber for the light-emitting optical fiber 2, it becomes possible to insert the light-emitting optical fiber 2 into the part with a high degree of curvature, even if the tubular body that serves as the detection target 6 has a part with a high degree of curvature, such as a blood vessel.

[0028] The outer diameter of the light-emitting optical fiber 2 is preferably set in accordance with the detection target 6 of the optical inspection device 1. For example, if the detection target 6 is the inner wall surface of a blood vessel, the outer diameter of the light-emitting optical fiber 2 is preferably 250 μm or less from the viewpoint of facilitating attachment to a small-diameter tube such as a balloon catheter inserted into the blood vessel.

[0029] (Light-receiving optical fiber) The light-receiving optical fiber 3 has a first light-receiving unit 31 that receives reflected light Lt' when the irradiation light Lt emitted from the first light-emitting unit 21 is reflected by the detection object 6, and a second light-guiding unit 32 that propagates the reflected light Lt' received by the first light-receiving unit 31. As a result, it is expected that the reflected light Lt' from the inner surface of a pipe, which is the detection object 6, is received by the first light-receiving unit 31 and propagates through the second light-guiding unit 32 with little loss, and is reflected in the inspection results via the light-detecting unit 33, which will be described later, etc.

[0030] Here, the light-receiving optical fiber 3 is configured to propagate the reflected light Lt' at least in the second light guiding section 32. An example of the light-receiving optical fiber 3 is an optical fiber having a fiber shape with a core-clad structure similar to the above-mentioned light-emitting optical fiber 2. In this case, the second light guiding section 32 of the light-receiving optical fiber 3 is preferably configured by an optical fiber whose cladding has not been removed. Here, by configuring the second light guiding section 32 by an optical fiber whose cladding has not been removed, it is expected that the reflected light Lt' will propagate with little loss. On the other hand, the first light receiving section 31 of the light-receiving optical fiber 3 can have a shape in which part or all of the cladding has been removed. Here, by configuring the first light receiving section 31 by an optical fiber whose cladding has been removed, it is expected that the reflected light Lt' will be received from the part where the cladding has been removed.

[0031] The first light-receiving portion 31 of the light-receiving optical fiber 3 may have a surface that is roughened with hydrofluoric acid, an organic solvent, or the like at least at the portion that receives the reflected light Lt'. Note that the light-receiving optical fiber 3 is not limited to a fiber-shaped optical fiber, and may also be an optical waveguide formed on a substrate or the like.

[0032] Furthermore, the first light receiving section 31 of the light receiving optical fiber 3 may have at least one of the following processes (a) to (d) applied to at least the portion that receives the reflected light Lt': (a) surface roughening treatment using hydrofluoric acid, an organic solvent, or the like; (b) laser patterning treatment; (c) coating the portion where the cladding has been scraped off with a transparent resin containing a light diffusing material such as titanium oxide; and (d) fusion splicing of a coreless fiber or a light diffusing fiber to the tip.

[0033] Of these, (d) the portion fusion-spliced ​​to the tip of the coreless fiber or light diffusing fiber is preferably coated with a transparent resin having a high refractive index. In this case, if the light-receiving optical fiber 3 is made of a quartz fiber, for example, the transparent resin used in the coating process preferably has a refractive index higher than that of the quartz glass that constitutes the cladding 37 of the quartz fiber.

[0034] Furthermore, in order to ensure mechanical strength, the portion of the light-receiving optical fiber 3 that has been subjected to (a) surface roughening or (b) patterning may be further coated with a transparent resin. The refractive index of the transparent resin used in this case is not particularly limited.

[0035] The material of the light-receiving optical fiber 3 is not particularly limited. However, from the viewpoint of facilitating insertion into a tubular body or the like serving as the detection target 6, it is preferable that the light-receiving optical fiber 3 be made of a quartz fiber or a plastic fiber. Among these, quartz fiber has tension. Therefore, by using a quartz fiber for the light-receiving optical fiber 3, the light-receiving optical fiber 3 can be inserted deep into the internal space of the tubular body, even if the tubular body, serving as the detection target 6, has a small diameter. Furthermore, because plastic fiber has flexibility, by using a plastic fiber for the light-receiving optical fiber 3, the light-receiving optical fiber 3 can be inserted into the highly curvatured portion of the tubular body, such as a blood vessel, even if the tubular body, serving as the detection target 6, has such a portion. Here, when the above-mentioned light-emitting optical fiber 2 is made of a quartz fiber, the light-receiving optical fiber 3 is preferably made of a plastic fiber. Furthermore, when the above-mentioned light-emitting optical fiber 2 is made of a plastic fiber, the light-receiving optical fiber 3 is preferably made of a quartz fiber. In this way, by making the light-emitting optical fiber 2 and the light-receiving optical fiber 3 out of different materials, a quartz fiber with high tension and a plastic fiber with high flexibility can be combined, thereby adjusting the tension and flexibility when a lateral force is applied to the optical fiber structure 10. Furthermore, by adjusting the tension and flexibility when a lateral force is applied to the optical fiber structure 10, it is expected that the optical fiber structure 10 will be easily mounted in a small-diameter tube, particularly in a balloon catheter that is inserted into a blood vessel. On the other hand, from the viewpoint of increasing the tension of the optical fiber structure 10 when inserting the light-emitting optical fiber 2 and the light-receiving optical fiber 3 into a catheter or the like, the light-emitting optical fiber 2 and the light-receiving optical fiber 3 may both be made of quartz optical fiber. Furthermore, from the viewpoint of increasing the flexibility of the optical fiber structure 10 when inserting the light-emitting optical fiber 2 and the light-receiving optical fiber 3 into a catheter or the like, the light-emitting optical fiber 2 and the light-receiving optical fiber 3 may both be made of plastic fiber.

[0036] In the optical inspection device 1 shown in FIG. 1, the length dimension P ２is the length dimension P of the first light emitting portion 21 of the light emitting optical fiber 2 １ In particular, in the optical inspection device 1 in which the optical fiber structure 10 is inserted into a blood vessel, the length dimension P of the first light emitting portion 21 is equal to １ and the length dimension P of the first light receiving portion 31 ２ On the other hand, when the irradiation light Lt is irradiated from the first light-emitting unit 21 at a wide angle, the length dimension P １ may be 5 mm or less.

[0037] The outer diameter of the light-receiving optical fiber 3 is preferably set in accordance with the detection target 6 of the optical inspection device 1, similar to the light-emitting optical fiber 2. For example, from the viewpoint of facilitating the installation of the optical fiber structure 10 in a small-diameter tube, the outer diameter of the light-receiving optical fiber 3 is preferably 250 μm or less. Furthermore, in the optical inspection device 1 shown in FIG. 1 , the outer diameter of the light-receiving optical fiber 3 is configured to be the same as the outer diameter of the light-emitting optical fiber 2, but these may be different.

[0038] The light-receiving optical fiber 3 preferably has a high numerical aperture from the viewpoint of propagating the reflected light Lt′ irradiated onto the first light-receiving unit 31 from a wider range of directions to the light-detecting unit 33 and increasing the amount of light received by the light-detecting unit 33. As an example, the light-receiving optical fiber 3 may have a numerical aperture higher than that of the light-emitting optical fiber 2.

[0039] The light-emitting optical fiber 2 and the light-receiving optical fiber 3 form the optical fiber structure 10 with the first light-emitting unit 21 and the first light-receiving unit 31 arranged such that they are mutually offset in the fiber axis direction X. For example, in the optical inspection device 1 shown in FIG. 1 , the optical fiber structure 10 is formed with the first light-emitting unit 21 and the first light-receiving unit 31 as a whole arranged such that they are mutually offset in the fiber axis direction X. By forming the optical fiber structure 10 in this manner with the first light-emitting unit 21 and the first light-receiving unit 31 partially or entirely arranged such that they are mutually offset, the first light-emitting unit 21 and the first light-receiving unit 31 are fixedly connected in a parallel arrangement. This effectively prevents the irradiation light Lt emitted from the first light-emitting unit 21 from being directly taken in by the first light-receiving unit 31, and is therefore expected to facilitate the attachment of the optical fiber structure 10 to a tube or insertion into the detection object 6 without changing the positional relationship between the first light-emitting unit 21 and the first light-receiving unit 31.

[0040] 1 , the light-emitting optical fiber 2 and the light-receiving optical fiber 3 are preferably configured such that the tip of the first light-receiving section 31 is located closer to the first light-guiding section 22 than the tip 2 a of the first light-emitting section 21. More preferably, as shown in the optical inspection device 1 in FIG. 2( a), the tip of the first light-receiving section 31 of the light-receiving optical fiber 3 is located closer to the first light-guiding section 22 of the light-emitting optical fiber 2 than the entire first light-emitting section 21. In this way, when the irradiation light Lt is irradiated onto the detection object 6, the irradiation light Lt emitted from the first light-emitting section 21 is irradiated onto the detection object 6 without being directly taken in by the first light-receiving section 31, and therefore, the irradiation light Lt emitted from the first light-emitting section 21 can be effectively prevented from being directly taken in by the first light-receiving section 31. 2(a) and 2(b), the illumination light Lt illuminated on the detection target 6 is reflected once or multiple times by the detection target 6 to become reflected light Lt', which is then captured by the first light receiving unit 31. In this way, the first light receiving unit 31 captures the reflected light Lt' from the detection target 6 while effectively suppressing direct capture of the illumination light Lt from the first light emitter 21, thereby reducing noise due to capture of the illumination light Lt relative to the detected value of the intensity of the reflected light Lt'. Furthermore, this noise reduction is expected to improve the signal-to-noise ratio of the detection light detected by the light detecting unit 33.

[0041] The first light-emitting unit 21 and the first light-receiving unit 31 are preferably fixed and connected in a manner that does not interfere with light emission from the first light-emitting unit 21 or light reception from the first light-receiving unit 31. As a means for fixing and connecting them, in addition to bonding with an adhesive, a means for fixing the vicinity of the first light-emitting unit 21 and the first light-receiving unit 31 with a tube such as a heat-shrink tube, or a means for fixing by crimping the vicinity of the first light-emitting unit 21 and the first light-receiving unit 31 with a ring or the like can be used.

[0042] In addition, in order to make it easier to install the optical fiber structure 10 in a tube or insert it into the object to be detected 6, it may have a fixing portion 5 that fixedly connects the light-emitting optical fiber 2 and the light-receiving optical fiber 3.

[0043] 1 , the optical inspection device 1 at least includes a light source 23, a light-emitting optical fiber 2, a light-receiving optical fiber 3, and a light detection unit 33, and the light-emitting optical fiber 2 and the light-receiving optical fiber 3 form an optical fiber structure 10 in which the first light-emitting unit 21 and the first light-receiving unit 31 are arranged so as to be shifted from each other in the fiber axis direction X. That is, the optical inspection device 1 includes at least the light source 23 and the light detection unit 33 in addition to the configuration of the optical fiber structure 10 described above.

[0044] Of these, the light source 23 is a light source of the irradiation light Lt. The light emitted from the light source 23 may be light containing a single wavelength component, such as laser light, or may be light containing multiple wavelength components.

[0045] The wavelength of the light emitted from the light source 23 is preferably selected from wavelengths that can be propagated through the light-emitting optical fiber 2 and the light-receiving optical fiber 3, depending on the material of the detection target 6 and the medium between the first light-emitting unit 21 and the detection target 6. For example, when the optical fiber structure 10 is used to block blood flow by inserting a balloon catheter with the optical fiber structure 10 disposed therein into a blood vessel and inflating the balloon, the wavelength of the light emitted from the light source 23 is preferably a wavelength in the visible range (a wavelength of 400 nm or more and 700 nm or less), which is a wavelength that is highly absorbed by blood.

[0046] Furthermore, the light emitted from the light source 23 may be a continuous wave emitted by CW oscillation, or a pulse wave emitted by pulse oscillation.

[0047] The light detecting unit 33 is a part that detects the reflected light Lt' that has propagated through the second light guiding portion 32 of the light-receiving optical fiber 3. The light detecting unit 33 is configured, for example, by an optical sensor, and is configured to measure the intensity of the reflected light Lt' and read out an electrical signal corresponding to the intensity, etc. Here, from the viewpoint of being able to detect the intensity of the reflected light Lt' for each wavelength component, there may be multiple light detecting units 33, and in this case, the light detecting unit 33 may be configured to include multiple light sensors corresponding to the respective wavelength components.

[0048] Here, in order to further increase the signal-to-noise ratio for the reflected light, the light emitted from the light source 23 may be modulated (pulsed), and the reflected light Lt' that has propagated through the second light-guiding section 32 may be passed through an appropriate frequency filter to separate the reflected light Lt' from noise, and the reflected light Lt' that has passed through the frequency filter may be detected by the light detection section 33.

[0049] The display unit 34 is a part that displays the detected value of the intensity of the reflected light Lt′ detected by the light detection unit 33. The display unit 34 is configured to display the detected value of the intensity of the received light to the person taking the measurer, based on the electrical signal from the light detection unit 33. Here, when there are multiple light detection units 33, there may also be multiple display units 34, one for each light detection unit 33.

[0050] The optical inspection device 1 may further include a light detection unit and a display unit (not shown) on the light source side of the light emitting optical fiber 2, at a position branched from the light from the light source 23. This allows the return light from the light emitting optical fiber 2 to be detected, making it possible to predict the amount of loss in the light emitting optical fiber 2 and the light receiving optical fiber 3. Furthermore, this prediction of the amount of loss is expected to improve the inspection accuracy of the optical inspection device 1.

[0051] [Regarding uses of the optical inspection device and optical fiber structure] The optical inspection device 1 and the optical fiber structure 10 can be widely used for inspection purposes by detecting reflected light Lt' from the object to be detected 6 when irradiation light Lt is irradiated from the first light receiving unit 31.

[0052] As an example, when temporarily blocking blood flow in a blood vessel during surgery or the like, a balloon catheter with the optical fiber structure 10 disposed therein can be inserted into the blood vessel and the balloon inflated to block the blood flow. This allows the presence or absence of blood between the blood vessel wall and the balloon to be detected based on the difference in light reflectance between the blood vessel wall and the blood being detected. Furthermore, by detecting the presence or absence of blood between the blood vessel wall and the balloon in this way, it is expected that the blood flow in the blood vessel can be appropriately blocked and that damage to the blood vessel due to excessive inflation of the balloon can be prevented. In this case, the optical fiber structure 10 may be inserted into a medical catheter or the like.

[0053] When the optical fiber structure 10 is disposed inside a balloon catheter, from the viewpoint of efficiently receiving the light Lt′ reflected from the blood vessel wall, it is desirable that the positions of one or both of the first light guiding portion 22 of the light-emitting optical fiber 2 and the first light receiving portion 31 of the light-receiving optical fiber 3 inside the balloon be adjustable. Here, one or both of the first light guiding portion 22 and the first light receiving portion 31 may be configured to be able to move parallel to each other along the fiber axial direction X, or may be configured to be able to rotate about the central axis of the light-emitting optical fiber 2 or the light-receiving optical fiber 3 as the rotation axis. In this case, it is more preferable that one or both of the first light guiding portion 22 and the first light receiving portion 31 have a structure that allows them to be re-fixed after their positions inside the balloon have been adjusted.

[0054] As another example, when temporarily stopping the flow of water in a pipe during plumbing work, an air bag with the optical fiber structure 10 disposed therein can be inserted into the pipe and inflated to stop the water flow in the pipe. This makes it possible to detect the presence or absence of water between the pipe wall and the air bag based on the difference in light reflectance depending on the presence or absence of water between the pipe wall and the air bag, which is the detection target. Furthermore, by detecting water between the pipe wall and the air bag in this way, it is expected that the water flow in the pipe can be stopped appropriately and that damage to the pipe or the air bag due to excessive inflation of the air bag will be less likely to occur.

[0055] <Second embodiment> Fig. 3 is a plan view showing the structure of an optical fiber structure in a second embodiment. Note that the components shown in Fig. 3 are the same as those of the optical inspection device 1 and the optical fiber structure 10 shown in Fig. 1, and are denoted by the same reference numerals.

[0056] In the optical inspection device 1 shown in FIG. 1, the length dimension P １ and the length dimension P of the first light receiving portion 31 of the light receiving optical fiber 3 ２ For example, as shown in the optical inspection device 1A of FIG. 3, the length dimension P ２ The length dimension P of the first light emitting portion 21A of the light emitting optical fiber 2A １ By configuring the first light-emitting unit 21A and the first light-receiving unit 31A in this manner, the reflected light Lt′ can be received over a wider range of the light-receiving optical fiber 3A, and the amount of light received by the light-detecting unit 33 can be increased.

[0057] In particular, in the optical inspection device 1A in which the optical fiber structure 10A is inserted into a blood vessel, the length dimension P of the first light emitting portion 21A is １ The length P of the first light receiving portion 31A can be set in the range of 5 mm to 40 mm. ２ The length dimension P of the first light-emitting portion 21A can be set in the range of 10 mm to 50 mm. １is set to 20 mm, and the length dimension P ２ Here, from the viewpoint of effectively increasing the reflected light Lt′ at the first light receiving portion 31A, the length dimension P ２ is the length dimension P of the first light-emitting portion 21A １ It is preferable that the ratio is in the range of 1.5 to 4.0 times.

[0058] The optical inspection device 1 has a length P ２ The length dimension P of the first light emitting portion 21 of the light emitting optical fiber 2 １ It may be configured to be shorter than

[0059] <Third embodiment> Fig. 4 is a cross-sectional view showing the arrangement of light-emitting optical fibers and light-receiving optical fibers constituting the optical inspection device and optical fiber structure of the third embodiment. Note that the components shown in Fig. 4 are the same as the components of the optical inspection device 1 and the optical fiber structure 10 shown in Fig. 1, and are denoted by the same reference numerals.

[0060] In the optical inspection device 1 shown in FIG. 1 , the optical fiber structure 10 includes one light-emitting optical fiber 2 and one light-receiving optical fiber 3. However, the present invention is not limited to this, and the optical fiber structure 10 may include a plurality of either or both of the light-emitting optical fiber 2 and the light-receiving optical fiber 3. For example, as shown in the optical inspection device 1B of FIG. 4 , the optical fiber structure 10B may include two or more light-receiving optical fibers 3 each having a first light-receiving unit 31. This allows the optical fiber structure 10B to receive a larger amount of reflected light Lt′ due to the multiple light-receiving optical fibers 3. Furthermore, by receiving a larger amount of reflected light Lt′ via these multiple light-receiving optical fibers 3, it is expected that the reflected light Lt′ propagating to the light detection unit 33 will be further increased.

[0061] Furthermore, in the optical inspection device 1, the optical fiber structure 10 may include two or more light-receiving optical fibers 3 each having a first light-receiving unit 31. This allows a larger amount of irradiation light Lt to be irradiated onto the detection object 6. Furthermore, by increasing the amount of irradiation light Lt irradiated onto the detection object 6, it is expected that an intensity of reflected light Lt' that can obtain highly accurate detection results in the light detection unit 33 can be obtained, especially when the reflectance of the irradiation light Lt on the detection object 6 is low.

[0062] Furthermore, the optical fiber structure 10 of the optical inspection device 1 may include two or more light-emitting optical fibers 2 and two or more light-receiving optical fibers 3 .

[0063] Here, the one or more light-emitting optical fibers 2 and the one or more light-receiving optical fibers 3 are arranged with the first light-emitting units 21 and the first light-receiving units 31 shifted from each other in the fiber axis direction X, thereby forming the optical fiber structure 10. For example, in the optical inspection device 1B of Fig. 4, the first light-receiving units 31 are arranged in parallel on one side (upper side of Fig. 4) of the light-emitting optical fiber 2 so as to be shifted from the first light-emitting units 21 in the fiber axis direction X, and the first light-receiving units 31 are also arranged in parallel on the other side (lower side of Fig. 4) of the light-emitting optical fiber 2 so as to be shifted from the first light-emitting units 21 in the fiber axis direction X, thereby forming the optical fiber structure 10B.

[0064] 5A and 5B are plan views showing the structure of an optical fiber structure according to a fourth embodiment, in which Fig. 5A shows a case in which the tip of the first light receiving portion is disposed so as to be closer to the first light guiding portion than the tip of the first light emitting portion, and Fig. 5B shows a case in which the tip of the first light emitting portion is disposed so as to be closer to the second light guiding portion than the tip of the first light receiving portion. Note that the components shown in Fig. 5 are the same as those of the optical inspection device 1 and the optical fiber structure 10 shown in Fig. 1, and are denoted by the same reference numerals.

[0065] In the optical inspection device 1 shown in FIG. 1 , the optical fiber structure 10 is formed with the first light emitter 21 and the first light receiver 31 of the light-emitting optical fiber 2 and the light-receiving optical fiber 3 being entirely displaced from each other in the fiber axis direction X. However, the present invention is not limited to this, and the optical fiber structure 10 may be formed with the first light emitter 21 and the first light receiver 31 being partially or entirely displaced from each other in the fiber axis direction X. For example, as shown in the optical inspection device 1C of FIG. 5( a), the optical fiber structure 10C may be formed with the first light emitter 21 and the first light receiver 31 of the light-emitting optical fiber 2 and the light-receiving optical fiber 3 being partially displaced from each other in the fiber axis direction X. In this case, the optical fiber structure 10C is arranged so that the first light emitter 21 and the first light receiver 31 partially overlap with each other in the fiber axis direction X.

[0066] Here, as shown in the optical inspection device 1C in Fig. 5(a), the optical fiber structure 10C may be arranged so that the tip 3a of the first light receiving portion 31 is located closer to the first light guiding portion 22 than the tip 2a of the first light emitting portion 21. On the other hand, as shown in the optical inspection device 1D in Fig. 5(b), the optical fiber structure 10D may be arranged so that the tip 2a of the first light emitting portion 21 is located closer to the second light guiding portion 32 than the tip 3a of the first light receiving portion 31.

[0067] 6A shows a case where the length dimension of the first light receiving portion of the light receiving optical fiber is longer than the length dimension of the first light emitting portion of the light emitting optical fiber, and FIG. 6B shows a case where the length dimension of the first light emitting portion of the light emitting optical fiber is longer than the length dimension of the first light receiving portion of the light receiving optical fiber. Note that the same reference numerals are used for the components shown in FIG. 6 when they are the same as the components of the optical inspection device 1 and the optical fiber structure 10 shown in FIG.

[0068] In the optical inspection device 1 shown in FIG. 5, in a configuration in which a part of the first light emitting unit 21 and the first light receiving unit 31 are shifted from each other in the fiber axis direction X, the length dimension P of the first light emitting unit 21 of the light emitting optical fiber 2 is １and the length dimension P of the first light receiving portion 31 of the light receiving optical fiber 3 ２ However, the present invention is not limited to this, and the length dimension P １ and the length dimension P of the first light receiving portion 31 of the light receiving optical fiber 3 ２ For example, as shown in the optical inspection device 1E in FIG. 6(a), in a configuration in which a part of the first light emitting unit 21E and a part of the first light receiving unit 31E are shifted from each other in the fiber axis direction X, the length dimension P ２ However, the length dimension P of the first light emitting portion 21E of the light emitting optical fiber 2E １ It may be configured to be longer than

[0069] In this case, as shown in the optical inspection device 1E in Figure 6 (a), the optical fiber structure 10E may be arranged so that the tip 2a of the first light emitting portion 21E and the tip 3a of the first light receiving portion 31E are at the same position in the fiber axis direction X for the light emitting optical fiber 2E and the light receiving optical fiber 3E.

[0070] On the other hand, as shown in the optical inspection device 1F of FIG. 6(b), the optical fiber structure 10F is arranged so that a part of the first light emitting portion 21F and the first light receiving portion 31F overlap with each other in the fiber axial direction X, and the length dimension P ２ However, the length dimension P of the first light emitting portion 21F of the light emitting optical fiber 2F １ It may be configured to be shorter than

[0071] 7A and 7B are plan views showing the structure of an optical fiber structure according to a sixth embodiment, in which Fig. 7A shows a case where the light-receiving optical fiber has a plurality of first light-receiving portions, and Fig. 7B shows a case where the light-emitting optical fiber has a plurality of first light-emitting portions. Note that the components shown in Fig. 7 are the same as those of the optical inspection device 1 and the optical fiber structure 10 shown in Fig. 1, and are denoted by the same reference numerals.

[0072] In the optical inspection device 1 shown in FIG. 1 , the light-emitting optical fiber 2 includes one first light-emitting unit 21, and the light-receiving optical fiber 3 includes one first light-receiving unit 31. However, this is not limited to this, and one or both of the first light-emitting unit 21 and the first light-receiving unit 31 may be provided in plurality. For example, as shown in the optical inspection device 1G of FIG. 7 , the light-receiving optical fiber 3G may include multiple first light-receiving units 31G, 31G. In this case, a second light-guiding unit 32G is disposed between the multiple first light-receiving units 31G, 31G. In this way, by providing multiple first light-receiving units 31G, 31G in the light-receiving optical fiber 3G, the reflected light Lt′ can be received over a wider range of the light-receiving optical fiber 3G, thereby increasing the amount of light received by the light detection unit 33.

[0073] Here, the multiple first light-receiving units 31G, 31G are preferably arranged to straddle the first light-emitting unit 21G, so that even if the first light-emitting unit 21G irradiates the irradiation light Lt on both sides in the fiber axis direction X, the reflected light Lt′ can be received by the first light-receiving units 31G, 31G on both sides of the first light-emitting unit 21G.

[0074] 7(b), an optical fiber structure 10H may have a light-emitting optical fiber 2H including a plurality of first light-emitting portions 21H, 21H. In this case, a first light-guiding portion 22H is disposed between the plurality of first light-emitting portions 21H, 21H.

[0075] <Seventh embodiment> Fig. 8 is a plan view showing the structure of an optical fiber structure according to a seventh embodiment. Note that the components shown in Fig. 8 are denoted by the same reference numerals as those of the optical inspection device 1 and the optical fiber structure 10 shown in Fig. 1.

[0076] In the optical inspection device 1 shown in FIG. 1 , the first light-emitting unit 21 is provided at the end of the light-emitting optical fiber 2, and the first light-receiving unit 31 is provided at the end of the light-receiving optical fiber 3. However, this is not limiting, and one or both of the first light-emitting unit 21 and the first light-receiving unit 31 may be provided in the intermediate portions of the optical fibers. For example, as shown in the optical inspection device 1I of FIG. 8 , in an optical fiber structure 10I, the first light-emitting unit 21 may be provided in the intermediate portion of the light-emitting optical fiber 2I. In addition, in the optical fiber structure 10I, the first light-receiving unit 31 may be provided in the intermediate portion of the light-receiving optical fiber 3I. In this case, first light-guiding units 22I, 22I are arranged on both sides of the first light-emitting unit 21 in the fiber axial direction X. In addition, second light-guiding units 32I, 32I are arranged on both sides of the first light-receiving unit 31 in the fiber axial direction X.

[0077] Here, the optical fiber structure 10I preferably has fixing portions 5I that fixedly connect the light emitting optical fiber 2I and the light receiving optical fiber 3 at the ends of the light emitting optical fiber 2I and the light receiving optical fiber 3. This allows the fixing portions 5I, 5I to be provided at positions on both sides of the first light receiving portion 31 and the first light emitting portion 21 along the fiber axis direction X, making it even easier to mount the optical fiber structure 10I in a tube or insert it into a detection target.

[0078] <Other embodiments> In the above-described embodiments, the first light-guiding section 22 of the light-emitting optical fiber 2 is configured by an optical fiber from which the cladding has not been removed, and the first light-emitting section 21 of the light-emitting optical fiber 2 has a shape in which part or all of the cladding of the optical fiber has been removed, but this is not limited to this form.

[0079] For example, as shown in FIG. 9( a) , the first light-emitting portion 21J of the light-emitting optical fiber 2J may have a shape in which a portion of the cladding 27 of the optical fiber is scraped off, and a roughened surface 27a may be formed on the scraped surface of the cladding 27. By forming the roughened surface 27a on the surface of the cladding 27 in this manner, the first light-emitting portion 21J can irradiate the irradiation light Lt in various directions, such as oblique directions relative to the fiber axial direction X of the light-emitting optical fiber 2J. The roughened surface 27a on the scraped surface of the cladding 27 of the first light-emitting portion 21J can be formed by surface roughening treatment using hydrofluoric acid or an organic solvent, laser patterning, or the like. Furthermore, since the portion of the light-emitting optical fiber 2J where the roughened surface 27a is formed tends to have low mechanical strength due to its small diameter, the portion where the roughened surface 27a is formed may be covered with a transparent resin (not shown) to increase the mechanical strength of this portion. The refractive index of the transparent resin used in this case is not particularly limited.

[0080] 9(b) and the light-emitting optical fiber 2K' in FIG. 9(c), the first light-emitting section 21K of the light-emitting optical fiber 2K (or the first light-emitting section 21K' of the light-emitting optical fiber 2K') has a shape in which all or part of the cladding 27 of the optical fiber is scraped off in the thickness direction of the optical fiber, i.e., in the radial direction of the light-emitting optical fiber 2F (or the light-emitting optical fiber 2K'), and a light-diffusing resin layer 25 having light-diffusing properties is formed on the surface of the core 26 (or the scraped-off cladding 27). Furthermore, a roughened surface 25a may be formed on the surface of the light-diffusing resin layer 25, as necessary. By forming the light-diffusing resin layer 25 on the surface of the core 26 or the cladding 27 in this way, the irradiation light Lt can be emitted from the first light-emitting section 21K (or the first light-emitting section 21K') in various directions, such as oblique directions with respect to the fiber axial direction X of the light-emitting optical fiber 2K (or the light-emitting optical fiber 2K'). This irradiation of the illumination light Lt in various directions diversifies the paths of the reflected light Lt' reflected from the detection target 6, which is expected to make it easier for the first light receiving unit 31 to receive the reflected light Lt'. Here, the light diffusion resin layer 25 formed on the surface of the core 26 or the cladding 27 is preferably made of a transparent resin containing a light diffusion material such as titanium oxide, and the light diffusion resin layer 25 can be formed by, for example, coating the scraped-off portion of the cladding 27 with a transparent resin. Furthermore, the roughened surface 25a on the surface of the light diffusion resin layer 25 can be formed by, for example, a surface roughening treatment using hydrofluoric acid or an organic solvent, or a laser patterning treatment.

[0081] 9(d) , the first light-emitting portion 21L of the light-emitting optical fiber 2L may be formed by fusion-splicing a coreless fiber or a light-diffusing fiber 28 to the tip portion of an optical fiber having a core 26 and a cladding 27. In this case, the portion where the coreless fiber or the light-diffusing fiber 28 is fusion-spliced ​​tends to have low mechanical strength. Therefore, in order to increase the mechanical strength of the fusion-spliced ​​portion, at least the fusion-spliced ​​portion may be covered with a transparent or opaque resin layer 29. Here, the resin layer 29 covering the fusion-spliced ​​portion is preferably made of a transparent resin from the viewpoint of extracting as much irradiation light Lt as possible from the coreless fiber or the light-diffusing fiber 28. In particular, from the viewpoint of increasing the signal-to-noise ratio of the extracted irradiation light Lt, it is more preferable that the resin layer 29 be made of a transparent resin having a high refractive index. Here, for example, when the optical fiber to which the coreless fiber or the light-diffusing fiber 28 is fusion-spliced ​​is made of a quartz fiber, the transparent resin having a high refractive index preferably has a refractive index higher than that of the quartz glass constituting the cladding 27 of the quartz fiber. When the resin layer 29 is made of a transparent resin, the transparent resin may contain a light diffusing material such as titanium oxide. Furthermore, it is preferable to use a material for medical use as the material for the resin layer 29, taking into consideration the possibility of the balloon bursting.

[0082] Furthermore, particularly when a reflector or the like that changes the traveling direction of the illumination light Lt to the opposite direction with respect to the fiber axial direction X is provided ahead of the tip 2a of the first light-emitting portion 21 of the light-emitting optical fiber 2, the first light-guiding portion 22 of the light-emitting optical fiber 2 may be configured with an inclined surface 21a obtained by obliquely cutting the core 26 and cladding 27 of the optical fiber, as shown in, for example, a light-emitting optical fiber 2M in Fig. 10(a). Furthermore, for example, as shown in a light-emitting optical fiber 2N in Fig. 10(b), the first light-emitting portion 21N of the light-emitting optical fiber 2N may be configured with an inclined surface 21a obtained by cutting the core 26 and cladding 27 of the optical fiber into the shape of a cone concentric with the core 26.

[0083] On the other hand, in the above-described embodiment, the second light-guiding section 32 of the light-receiving optical fiber 3 is constructed of an optical fiber whose cladding has not been removed, and the first light-receiving section 31 of the light-receiving optical fiber 3 has a shape in which part or all of the cladding of the optical fiber has been removed, but this is not limited to this form.

[0084] 11( a), the first light receiving unit 31P of the light receiving optical fiber 3P may have a shape in which a portion of the cladding 37 of the optical fiber is scraped away, and a rough surface 34a may be formed on the surface of the scraped away cladding 37. By forming the rough surface 34a on the surface of the cladding 37 in this way, the first light receiving unit 31P can receive the reflected light Lt' from various directions, such as a direction oblique to the fiber axial direction X of the light receiving optical fiber 3P. Furthermore, by having the first light receiving unit 31P receive the reflected light Lt' from various directions, it is expected that the possibility of receiving the reflected light Lt' at the first light receiving unit 31P can be increased.

[0085] As shown in FIG. 11B, the first light receiving portion 31Q of the light receiving optical fiber 3Q may have a shape in which the cladding 37 of the optical fiber is entirely removed.

[0086] 12( a), the first light receiving portion 31R of the light receiving optical fiber 3R may have a shape in which a portion of the cladding 37 of the optical fiber is scraped off, and a roughened surface 37a may be formed on the scraped surface of the cladding 37. By forming the roughened surface 37a on the surface of the cladding 37 in this manner, the first light receiving portion 31R can receive reflected light Lt′ irradiated onto the first light receiving portion 31R from various directions, such as a direction oblique to the fiber axial direction X of the light receiving optical fiber 3R. The roughened surface 37a on the scraped surface of the cladding 37 of the first light receiving portion 31R can be formed by a surface roughening treatment using hydrofluoric acid or an organic solvent, a laser patterning treatment, or the like. Furthermore, the portion of the light receiving optical fiber 3R where the roughened surface 37a is formed tends to have low mechanical strength due to its small diameter. Therefore, to increase the mechanical strength of this portion, the portion where the roughened surface 37a is formed may be covered with a transparent resin (not shown). The refractive index of the transparent resin used in this case is not particularly limited.

[0087] 12(b) and the light-receiving optical fiber 3S' in FIG. 12(c), the first light-receiving portion 31S of the light-receiving optical fiber 3S (or the first light-receiving portion 31S' of the light-receiving optical fiber 3S') has a shape in which all or part of the cladding 37 of the optical fiber is shaved off in the thickness direction of the optical fiber, i.e., in the radial direction of the light-receiving optical fiber 3S (or the light-receiving optical fiber 3S'), and a light-diffusing resin layer 35 having light-diffusing properties is formed on the surface of the core 36 (or the shaved-off cladding 37). Furthermore, a roughened surface 35a may be formed on the surface of the light-diffusing resin layer 35, as necessary. By forming the light-diffusing resin layer 35 on the surface of the core 36 or the cladding 37 in this way, the irradiation light Lt can be emitted from the first light-receiving portion 31S (or the first light-receiving portion 31S') in various directions, such as oblique directions with respect to the fiber axial direction X of the light-receiving optical fiber 3S (or the light-receiving optical fiber 3S'). This irradiation of the illumination light Lt in various directions diversifies the paths of the reflected light Lt' reflected from the detection target 6, which is expected to make it easier for the first light receiving unit 31 to receive the reflected light Lt'. Here, the light diffusion resin layer 35 formed on the surface of the core 36 or the clad 37 is preferably made of a transparent resin containing a light diffusion material such as titanium oxide, and the light diffusion resin layer 35 can be formed by, for example, coating the scraped-off portions of the core 36 or the clad 37 with a transparent resin. Furthermore, the roughened surface 35a on the surface of the light diffusion resin layer 35 can be formed by, for example, a surface roughening treatment using hydrofluoric acid or an organic solvent, or a laser patterning treatment.

[0088] 12(d), the first light receiving portion 31T of the light receiving optical fiber 3T may be formed by fusion-splicing a coreless fiber or a light diffusing fiber 38 to the tip portion of an optical fiber having a core 36 and a cladding 37. In this case, the portion where the coreless fiber or the light diffusing fiber 38 is fusion-spliced ​​tends to have low mechanical strength. Therefore, from the viewpoint of increasing the mechanical strength of the fusion-spliced ​​portion, at least the fusion-spliced ​​portion may be covered with a transparent or opaque resin layer 39. Here, the resin layer 39 covering the fusion-spliced ​​portion is preferably made of a transparent resin from the viewpoint of allowing a large amount of reflected light Lt' to be incident on the coreless fiber or the light diffusing fiber 38. In particular, from the viewpoint of increasing the signal-to-noise ratio of the incident reflected light Lt', it is more preferable that the resin layer 39 be made of a transparent resin having a high refractive index. Here, for example, when the optical fiber to which the coreless fiber or the light diffusing fiber 38 is fusion-spliced ​​is made of a quartz fiber, the transparent resin having a high refractive index preferably has a refractive index higher than that of the quartz glass constituting the cladding 37 of the quartz fiber. When the resin layer 39 is made of a transparent resin, the transparent resin may contain a light diffusing material such as titanium oxide. Furthermore, it is preferable to use a material for medical use as the material for the resin layer 39, taking into consideration the possibility of the balloon bursting.

[0089] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, but includes all aspects encompassed by the concept of the present invention and the scope of the claims, and can be modified in various ways within the scope of the present invention.

[0090] 1, 1A to 1I Optical inspection device 10, 10A to 10I Optical fiber structure 2, 2A, 2E to 2F, 2H to 2K, 2K', 2L to 2N Light-emitting optical fiber 2a Tip of light-emitting optical fiber 21, 21A, 21E to 21F, 21H, 21J, 21K, 21K', 21L to 21N First light-emitting section 21a Inclined surface 22, 22A, 22H, 22I First light-guiding section 23 Light source 25, 35 Light-diffusing resin layer 25a, 35a Rough surface of light-diffusing resin layer 26 Core of light-emitting optical fiber 27 Cladding of light-emitting optical fiber 27a Rough surface of cladding of light-emitting optical fiber 28, 38 Coreless fiber or light-diffusing fiber 29, 39 (Transparent or opaque) resin layer 3, 3E to 3G, 3I, 3P to 3S, 3S', 3T Light receiving optical fiber 3a Tip of light receiving optical fiber 31, 31A, 31E to 31G, 31P to 31S, 31S', 31T First light receiving section 32, 32A, 32G, 32I Second light guiding section 33 Light detecting section 34 Display section 36 Core of light receiving optical fiber 37 Cladding of light receiving optical fiber 37a Rough surface of cladding of light emitting optical fiber 5 Fixing section 6 Detection object Lt Irradiated light Lt' Reflected light P １ Length dimension of the first light-emitting part P ２ Length dimension of first light receiving section X fiber axis direction

Claims

1. An optical inspection device comprising: a light source; at least one light-emitting optical fiber having a first light-guiding section that propagates light emitted from the light source and a first light-emitting section that irradiates the light propagated through the first light-guiding section as irradiation light onto a detection object; at least one light-receiving optical fiber having a first light-receiving section that receives reflected light from the detection object of the irradiation light emitted from the first light-emitting section and a second light-guiding section that propagates the reflected light received by the first light-receiving section; and a light detection section that detects the reflected light that has propagated through the second light-guiding section of the light-receiving optical fiber; wherein the light-emitting optical fiber and the light-receiving optical fiber form an optical fiber structure with the first light-emitting section and the first light-receiving section shifted from each other in the fiber axial direction.

2. The optical inspection device according to claim 1, wherein the irradiated light is emitted from a side surface of the first light-emitting element.

3. The optical inspection device according to claim 1, wherein the length of the first light receiving portion of the light receiving optical fiber is longer than the length of the first light emitting portion of the light emitting optical fiber.

4. An optical inspection device as described in claim 1, wherein the light emitting optical fiber and the light receiving optical fiber form the optical fiber structure in such a manner that a portion of the first light emitting section and a portion of the first light receiving section are mutually shifted in the fiber axial direction.

5. An optical inspection device as described in claim 1, wherein the light emitting optical fiber and the light receiving optical fiber are each arranged so that the tip of the first light emitting section and the tip of the first light receiving section are at the same position in the fiber axial direction.

6. The optical inspection device according to claim 1, wherein the light receiving optical fiber comprises a plurality of the first light receiving portions.

7. The optical inspection device according to claim 1, wherein the light emitting optical fiber comprises a plurality of the first light emitting portions.

8. An optical inspection device as described in claim 1, wherein one or both of the first light emitting section and the first light receiving section are provided in an intermediate portion of the light emitting optical fiber or the light receiving optical fiber.

9. An optical inspection device according to any one of claims 1 to 8, wherein the light emitting optical fiber and the light receiving optical fiber are constituted by quartz fibers or plastic fibers.

10. An optical fiber structure comprising: at least one light-emitting optical fiber having a first light-guiding section that propagates light emitted from a light source and a first light-emitting section that irradiates the light propagated through the first light-guiding section as irradiation light onto a detection object; and at least one light-receiving optical fiber having a first light-receiving section that receives reflected light of the irradiation light emitted from the first light-emitting section that is reflected by the detection object, and a second light-guiding section that propagates the reflected light received by the first light-receiving section, wherein the light-emitting optical fiber and the light-receiving optical fiber form an optical fiber structure with the first light-emitting section and the first light-receiving section shifted from each other in the fiber axial direction.

Images