Optical waveguide-type sensor

Abstract

This optical waveguide-type sensor comprises, for example, a core constituting a waveguide for guiding inspection light, a first cladding surrounding the periphery of the core, and a second cladding positioned on the opposite side of the core with respect to the first cladding or in contact with the core, having a refractive index different than the first cladding, and contacted by an inspection target object. In the optical waveguide-type sensor, the refractive index of the first cladding may be higher or lower than the refractive index of the second cladding. The refractive index of the inspection target object may be higher or lower than one of the refractive index of the first cladding and the refractive index of the second cladding. The second cladding may be capable of being adhered along the unevenness of the surface of the inspection target object.

Description

Optical Waveguide Sensor

[0001] The present invention relates to an optical waveguide sensor.

[0002] Conventionally, sensors that measure the components, concentration, etc. of a substance using the attenuated total reflection (ATR) method have been known (see, for example, Patent Document 1). This sensor enables sample inspection by utilizing the light (evanescent light) that slightly seeps out of the prism in contact with the sample when infrared light is totally reflected inside the ATR crystal prism.

[0003] Japanese Patent Application Laid-Open No. 2005-61904

[0004] For this type of sensor, it would be beneficial, for example, if the accuracy of the inspection could be improved.

[0005] Therefore, one object of the present invention is to provide a new and improved optical waveguide sensor that can further improve the accuracy of inspection, for example.

[0006] The optical waveguide sensor of the present invention comprises, for example, a core that constitutes a waveguide that guides inspection light, a first cladding that surrounds the core, and a second cladding that is located on the opposite side of the core with respect to the first cladding or that is in contact with the core, has a refractive index different from that of the first cladding, and is in contact with an object to be inspected, and is configured so that the seepage component of the inspection light leaks from the second cladding to the opposite side of the core.

[0007] In the optical waveguide sensor, the refractive index of the first cladding may be higher than the refractive index of the second cladding.

[0008] In the optical waveguide sensor, the refractive index of the first cladding may be lower than the refractive index of the second cladding.

[0009] In the optical waveguide sensor, the refractive index of the test object may be higher than either one of the refractive index of the first cladding and the refractive index of the second cladding.

[0010] In the optical waveguide sensor, the refractive index of the test object may be lower than either one of the refractive index of the first cladding and the refractive index of the second cladding.

[0011] In the optical waveguide sensor, the second clad may be capable of adhering closely to the irregularities on the surface of the inspection object.

[0012] In the optical waveguide sensor, the second clad may be a fluid.

[0013] In the optical waveguide sensor, the second clad may be flexible.

[0014] In the optical waveguide sensor, the second clad may be an adhesive.

[0015] In the optical waveguide sensor, the adhesive may be a photocurable adhesive.

[0016] The optical waveguide sensor may include a third clad interposed between the first clad and the second clad.

[0017] In the optical waveguide sensor, the core and the second clad may be in contact with each other, and the second clad may be in contact with the test object on the side opposite to the part in contact with the core.

[0018] In the optical waveguide sensor, the first clad has a first surface facing a first direction and a recess recessed from the first surface in a direction opposite to the first direction, the core extends at least partially along a bottom surface of the recess, intersecting the first direction, and the second clad is arranged to cover at least the bottom surface and may come into contact with the object to be inspected on the side opposite to the portion covering the bottom surface.

[0019] In the optical waveguide sensor, the recess may be formed to be wider than the core when viewed in a direction opposite to the first direction.

[0020] In the optical waveguide sensor, the second cladding may be provided only in the recess.

[0021] In the optical waveguide sensor, the core may extend while being curved.

[0022] In the optical waveguide sensor, the object to be inspected is positioned offset in a second direction relative to the core, and the core has a first portion that intersects with other portions of the core and a second portion that does not intersect with other portions of the core, and a first thickness in the second direction of a portion of the first cladding adjacent to the first portion in the second direction may be greater than a second thickness in the second direction of a portion of the first cladding adjacent to the second portion in the second direction.

[0023] The optical waveguide sensor may include, as the core, a plurality of first cores each constituting a waveguide for guiding the inspection light.

[0024] In the optical waveguide sensor, the first cores may have different lengths.

[0025] In the optical waveguide sensor, the second claddings corresponding to the plurality of first cores may have different refractive indices.

[0026] Furthermore, the optical waveguide sensor of the present invention comprises, for example, a core that constitutes a waveguide that guides inspection light, a first clad that surrounds the core, and a second clad that is located on the opposite side of the core with respect to the first clad, that comes into contact with the object to be inspected, and that can adhere closely to the unevenness of the surface of the object to be inspected, and is configured so that the seeping component of the inspection light leaks from the second clad to the opposite side of the core.

[0027] In the optical waveguide sensor, the first cladding and the second cladding may have different refractive indices.

[0028] In the optical waveguide sensor, the refractive index of the first cladding and the refractive index of the second cladding may be the same.

[0029] According to the present invention, for example, a new and improved optical waveguide sensor can be obtained that can further improve the inspection accuracy.

[0030] FIG. 1 is an exemplary and schematic plan view of an optical waveguide sensor according to a first embodiment. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III of FIG. 1. FIG. 4 is a cross-sectional view of an optical waveguide sensor according to a second embodiment, taken at a position equivalent to that of FIG. 3. FIG. 5 is a cross-sectional view of an optical waveguide sensor according to a third embodiment, taken at a position equivalent to that of FIG. 3. FIG. 6 is a cross-sectional view of an optical waveguide sensor according to a fourth embodiment, taken at a position equivalent to that of FIG. 3. FIG. 7 is an exemplary and schematic plan view of an optical waveguide sensor according to a fifth embodiment. FIG. 8 is a cross-sectional view taken along line VIII-VIII of FIG. 7. FIG. 9 is an exemplary and schematic plan view of an optical waveguide sensor according to a sixth embodiment. FIG. 10 is a cross-sectional view taken along line X-X of FIG. 9. FIG. 11 is an exemplary and schematic plan view of an optical waveguide sensor according to a seventh embodiment. FIG. 12 is a cross-sectional view taken along line XII-XII of FIG. 11. FIG. 13 is an exemplary and schematic plan view of an optical waveguide sensor according to an eighth embodiment. Fig. 14 is an exemplary schematic plan view of the optical waveguide sensor according to the ninth embodiment. Fig. 15 is a cross-sectional view taken along line XV-XV of Fig. 14. Fig. 16 is an exemplary schematic plan view of the optical waveguide sensor according to the tenth embodiment.

[0031] Hereinafter, several exemplary embodiments of the present invention will be disclosed. The configurations of the embodiments shown below, as well as the actions and results (effects) brought about by these configurations, are merely examples. The present invention can also be realized by configurations other than those disclosed in the following embodiments. Furthermore, according to the present invention, it is possible to obtain at least one of the various effects (including derivative effects) obtained by the configurations.

[0032] The following embodiments have similar configurations. Therefore, according to the configurations of each embodiment, similar actions and effects based on the similar configurations can be obtained. Furthermore, in the following, similar configurations are given similar reference numerals, and duplicated descriptions may be omitted.

[0033] Furthermore, each drawing is a schematic diagram, and the dimensions in the drawing may differ from the actual dimensions. In each drawing, the X direction is represented by an arrow X, the Y direction is represented by an arrow Y, and the Z direction is represented by an arrow Z. The X direction, Y direction, and Z direction intersect with each other and are perpendicular to each other. In this specification, a plan view is a line of sight seen in the opposite direction to the Z direction, and a plan view is a drawing in that plan view.

[0034] 1 is a plan view of an optical waveguide sensor 10A (10) according to a first embodiment. The optical waveguide sensor 10 has, for example, a rectangular parallelepiped shape that is relatively thin and flat in the Z direction. A surface 10a that faces the Z direction and intersects with and is substantially perpendicular to the Z direction is provided at an end of the optical waveguide sensor 10 in the Z direction. The Z direction is an example of a first direction.

[0035] The optical waveguide sensor 10 can be configured as, for example, a known planar lightwave circuit (PLC). In this case, the optical waveguide sensor 10 integrally includes a substrate extending across the Z direction and a structure stacked on the substrate in the Z direction. The substrate is a glass substrate or a silicon substrate. The structure on the substrate includes a core 12 and a clad 11 surrounding the core. The clad 11 is made of, for example, SiO ２ The core 12 is made of a silica-based glass material having a refractive index higher than that of the cladding 11. The cladding 11 is an example of a first cladding.

[0036] In the optical waveguide sensor 10, the core 12 constitutes a waveguide that guides the inspection light. As the inspection light is guided, a leaking component of the inspection light, i.e., evanescent light, is distributed in a portion of the cladding 11 that is close to the core 12.

[0037] Each core 12 extends while curving substantially along an imaginary plane intersecting the Z direction. Inspection light L is input to an incident end 12i of a core 12, transmitted along the core 12, and output from an output end 12o of the core 12. The inspection light input to the incident end 12i is referred to as incident light Li, and the inspection light output from the output end 12o is referred to as output light Lo.

[0038] 2 is a cross-sectional view of the optical waveguide sensor 10A of FIG. 1 taken along line II-II. The core 12 has the same cross-sectional shape as that of FIG. 2 from the input end 12i to the output end 12o. The cladding 11 has a surface 11a at its end in the Z direction, which intersects with and is perpendicular to the Z direction and faces the Z direction. The surface 11a is an example of a first surface. In this embodiment, the cross-sectional shape of the core 12 is rectangular as an example, but is not limited thereto and may be any shape other than rectangular.

[0039] The clad 13 is provided adjacent to the surface 11a in the Z direction. The clad 13 is located on the opposite side of the clad 11 from the core 12. The clad 13 is provided so as to cover the surface 11a with a predetermined thickness, for example, a substantially constant thickness. The clad 13 is made of, for example, SiO ２ The cladding 13 is made of, but is not limited to, a silica-based glass material including, but not limited to, the following: The cladding 13 is an example of a second cladding.

[0040] FIG. 3 is a cross-sectional view of the optical waveguide sensor 10A of FIG. 1 taken along the line III-III. As shown in FIG. 3, the cladding 11 has a recess 11b recessed in the opposite direction of the Z direction from its surface 11a toward the core 12. The recess 11b is provided so as to overlap the core 12 in the Z direction and extends along the core 12 over a section except for the vicinity of the input end 12i and the output end 12o. The recess 11b has the cross-sectional shape shown in FIG. 3, i.e., a substantially constant width and a substantially constant depth, over the entire section. The bottom surface 11b1 of the recess 11b is a plane that faces the Z direction, intersects the Z direction, and extends substantially perpendicular to it. The bottom surface 11b1 substantially overlaps the core 12 in the Z direction. The width of the bottom surface 11b1 is substantially the same as the width of the core 12 and is constant along the longitudinal direction of the recess 11b.

[0041] The clad 13 also covers the clad 11 in the recess 11b of the clad 11 to a thickness substantially equal to that on the surface 11a. That is, the clad 11 is not exposed on both the surface 10a and the recess 10b of the optical waveguide sensor 10A, but is covered with the clad 13. As shown in Figures 2 and 3, the clad 13 is located on the opposite side of the clad 11 from the core 12.

[0042] In this configuration, the recess 10b accommodates an inspection object S. The inspection object S may be, for example, a liquid, a gas, a fluid, a viscoelastic material, or a flexible or pliable solid. The surface of the recess 10b is covered with the cladding 13, so that the cladding 13 contacts the inspection object S on the side opposite to the core 12 and the cladding 11. As described above, evanescent light of the inspection light L is distributed in the claddings 11 and 13 surrounding the core 12. When the distance between the core 12 and the inspection object S is relatively short, for example, 5 μm or less, and is smaller than the mode field diameter of the inspection light L passing through the core 12, the mode fields of the inspection light L1 and L2 extend further inside the recess 11b than the bottom surface 11b1. As a result, the evanescent light of the inspection light L leaks from the bottom surface of the recess 10b and is absorbed by the inspection object S. In this case, the intensity of the output light Lo decreases relative to the intensity of the incident light Li by the amount of the inspection light L absorbed by the inspection object S. The amount of decrease in the intensity of the output light Lo relative to the incident light Li (loss intensity), i.e., the amount of absorption, varies depending on the inspection object S. Therefore, by measuring the loss intensity, it is possible to identify the inspection object S. In the cross section shown in FIG. 2, the cladding 11 around the core 12 is thick, so no leakage of evanescent light occurs.

[0043] The inventors have conducted extensive research into identifying the inspection object S using the optical waveguide sensor 10 configured as described above, and have found that the amount of evanescent light (leaked light) can be appropriately adjusted by adjusting the magnitude relationship between the refractive indices of the clad 11 and the clad 13, thereby further improving the accuracy of the inspection. The amount of leaked light depending on the magnitude of the refractive index of the clad 11 (first clad), the clad 13 (second clad), and the inspection object is as shown in Table 1. For example, if the state in which the amount of leaked light is small when the refractive index of the first cladding is higher than that of the second cladding corresponds to, for example, state (2), the amount of leaked light can be increased by increasing the refractive index of the second cladding (using an optical waveguide sensor 10 including a second cladding with a higher refractive index) to achieve state (1). This is because light spreads more strongly from the first cladding to the second cladding. Similarly, if the state in which the amount of leaked light is small when the refractive index of the first cladding is higher than that of the second cladding corresponds to, for example, state (5), the amount of leaked light can be increased by increasing the refractive index of the second cladding (using an optical waveguide sensor 10 including a second cladding with a higher refractive index) to achieve state (6). On the other hand, when the optical waveguide sensor 10 is applied to an object to be inspected that has a lower refractive index than the first cladding, increasing the refractive index of the second cladding to be higher than that of the first cladding, as in state (3), can increase the amount of leaked light compared to when there is no second cladding. This is because light spreads more strongly from the first cladding to the object to be inspected via the second cladding. Furthermore, when the optical waveguide sensor 10 is applied to an object to be inspected that has a higher refractive index than the first cladding, making the refractive index of the second cladding higher than that of the object to be inspected, as in (3), can reduce the amount of leaked light compared to when there is no second cladding. This is because the high refractive index of the second cladding suppresses the spread of light into the object to be inspected. In other cases, by changing the refractive index of at least one of the first cladding and the second cladding, the amount of leaked light can be changed from low to high in accordance with Table 1. Conversely, even when the amount of leaked light is too high, by changing the refractive index of at least one of the first cladding and the second cladding, the amount of leaked light can be changed from low to high in accordance with Table 1.

[0044] As described above, in this embodiment, the optical waveguide sensor 10A (10) includes the core 12, and the cladding 11 (first cladding) and the cladding 13 (second cladding) which have different refractive indices. Therefore, compared to an optical waveguide sensor including only the first cladding, it is easier to set the amount of leakage light to a more suitable state, and ultimately it is easier to improve the accuracy of the inspection.

[0045] Furthermore, in this embodiment, the clad 11 is provided with a surface 11a facing the Z direction and a recess 11b recessed from the surface 11a in the opposite direction to the Z direction, the core 12 extends along a bottom surface 11b1 of the recess 11b intersecting the Z direction, and the clad 13 covers the bottom surface 11b1 and comes into contact with the test object S on the side opposite to the bottom surface 11b1. This configuration makes it possible to provide a recess 10b whose bottom is covered with the clad 13, and therefore, when the test object S is placed in the recess 10b, the clad 11 and the clad 13 are interposed between the test object S and the core 12. In other words, the test object S can be held more easily and stably in a state where it can be inspected. In addition, the amount of light leaking from the core 12 into the object to be inspected S through the claddings 11 and 13 can be adjusted relatively easily depending on the depth of the recess 10b, in other words, the thickness of the claddings 11 and 13 between the object to be inspected S and the core 12.

[0046] In this embodiment, the core 12 overlapping the bottom surface 11b1 extends while curving substantially along an imaginary plane intersecting with the Z direction. This configuration makes it easier to ensure a required amount of leakage evanescent light.

[0047] The cladding 13 only needs to be located within the range of the evanescent light. Therefore, the cladding 13 does not need to cover the entire surface, including the side surfaces, of the recess 11b provided in the cladding 11, nor does it need to cover the surface 11a. The cladding 13 only needs to be located in a position that covers at least the bottom surface 11b1 of the recess 11b or in the vicinity thereof.

[0048] Second Embodiment FIG. 4 is a cross-sectional view of an optical waveguide sensor 10B (10) according to a second embodiment, taken at the same position as FIG. 3 . In this embodiment, the optical waveguide sensor 10B also includes a core 12 and clads 11 and 13, achieving the same effects as those of the first embodiment. However, in this embodiment, the clad 13 is a fluid, such as a liquid or sol, contained in the recess 11b. The liquid may be, for example, a refractive index-matching oil. If a gap were to form at the boundary between the clad 13 and the test object S, scattering of evanescent light would occur at the boundary, potentially reducing the test accuracy. In this embodiment, the clad 13 is a fluid that has fluidity and can adhere closely to the surface Sa of the test object S, conforming to the irregularities. This prevents a gap from forming at the boundary between the clad 13 and the test object S, thereby reducing the test accuracy.

[0049] The clad 13 may be a flexible or pliable solid. Examples of such a clad 13 include gels and elastomers. The gel may be, for example, a hydrogel such as polyacrylamide hydrogel. The flexible solid may be, for example, an adhesive containing an antimony compound, a fluorine compound, or the like. The clad 13 may also be an adhesive that has fluidity before solidifying and can eliminate gaps at the boundary between the clad 13 and the test object S. Examples of the adhesive include an ultraviolet-curing (photo-curing) adhesive. In this case, the adhesive may be applied to the clad 11 in a fluid state before solidifying by a method such as spin coating, and then solidified with the test object S pressed against it. The adhesive may also be one that can be dissolved or peeled off with a predetermined solvent or the like after the measurement is completed. In these cases, the clad 13 can adhere closely to the surface Sa of the test object S, at least during the measurement, following the irregularities of the surface Sa. Therefore, it is possible to prevent a gap from occurring at the boundary between the cladding 13 and the inspection object S, which would otherwise cause a decrease in inspection accuracy.

[0050] In this embodiment, the refractive indices of the claddings 11 and 13 are also set appropriately in consideration of the amount of leaked light. The refractive indices of the claddings 11, 13 and the inspection object S are set high or low according to the amount of leaked light in the same manner as in the first embodiment. The effect of eliminating gaps at the boundary can also be achieved when the refractive indices of the claddings 11, 13 are the same. In this case, the claddings 11, 13 optically function as the same cladding (first cladding).

[0051] [Third embodiment] Fig. 5 is a cross-sectional view of an optical waveguide sensor 10C (10) of a third embodiment at the same position as in Fig. 3. In this embodiment, the optical waveguide sensor 10C also includes a core 12 and clads 11 and 13, and the same effects as in the first embodiment can be obtained. However, in this embodiment, another clad 14 is provided between the clad 11 and the clad 13. The clad 14 is provided so as to cover the clad 13 with a predetermined thickness, for example, a substantially constant thickness. The clad 14 is made of, for example, SiO ２ The cladding 14 is made of a silica-based glass material including, but not limited to, SiO 2 . The cladding 14 is an example of a third cladding. With this configuration, by appropriately setting the refractive index of the cladding 14, it becomes easier to set the amount of leakage light to a more optimal state, which in turn makes it easier to further improve the accuracy of the inspection.

[0052] [Fourth Embodiment] Figure 6 is a cross-sectional view of an optical waveguide sensor 10D (10) of a fourth embodiment, taken at the same position as in Figure 3. In this embodiment, the optical waveguide sensor 10D also includes a core 12 and clads 11 and 13, and provides the same effects as those of the first embodiment. However, in this embodiment, the clad 11 is removed between the test object S and the core 12, and only the clad 13 is interposed between the test object S and the core 12. The clad 13 contacts the test object S on the side opposite to the portion where it contacts the core 12. With this configuration, the clad 11 ensures light confinement within the core 12, while the amount of evanescent light leaking into the test object S can be adjusted by setting and adjusting specifications such as the thickness of the clad 13.

[0053] 7 is a plan view of an optical waveguide sensor 10E (10) according to a fifth embodiment. In this embodiment, the optical waveguide sensor 10E also includes a core 12 and claddings 11 and 13, and provides the same effects as those of the first embodiment. However, in this embodiment, the recess 10b does not extend elongatedly along the core 12 as in the first embodiment, but is formed to be wider than the core 12 in a plan view, include the area where the curved core 12 is present, and have a rectangular shape.

[0054] 8 is a cross-sectional view of the optical waveguide sensor 10E of FIG. 7 taken along line VIII-VIII. The optical waveguide sensor 10E is configured so that the overlapping portions of the core 12 and the recesses 10b and 11b have the same cross-sectional shape as that shown in FIG. 8. The thickness and other specifications of the claddings 11 and 13 between the core 12 and the bottom surface 11b1 are appropriately set so that evanescent light leaks to the inspection target S. In this configuration, evanescent light leaks from the section of the core 12 that overlaps with the bottom surface 11b1 of the recess 11b. Therefore, the amount of leaked evanescent light is proportional to the product of the width and length of the section of the core 12 that overlaps with the bottom surface 11b1.

[0055] FIG. 9 is a plan view of an optical waveguide sensor 10F (10) according to a sixth embodiment, and FIG. 10 is a cross-sectional view of the optical waveguide sensor 10F taken along the X-X line in FIG. 9 . The optical waveguide sensor 10F is configured so that the overlapping portions of the core 12 and the recesses 10b and 11b have a cross-sectional shape similar to that shown in FIG. 10 . Also, as shown in FIG. 9 , in this embodiment, the recess 10b does not extend elongatedly along the core 12 as in the first embodiment, but is wider than the core 12 in plan view and is formed to include the area where the curved core 12 is present. However, the planar shape of the recess 10b is elliptical. Note that the shape of the recess 10b is not limited to the rectangular shape shown in FIG. 7 or the elliptical shape shown in FIG. 9 , and may be a polygonal shape other than a rectangle, a polygonal shape with rounded corners, a circle, an oval, or the like.

[0056] 10 , in this embodiment, the cladding 13 is provided so as to cover only the bottom surface 11b1 of the recess 11b, and does not cover the surface 11a or the side surfaces of the recess 11b. Since the cladding 13 only needs to be present in the region overlapping with the core 12 in the Z direction and in the vicinity thereof, this configuration also provides the same effects as the fifth embodiment. This configuration also provides the effects of reducing waste of the cladding 13 and making the optical waveguide sensor 10 lighter.

[0057] According to the fifth and sixth embodiments, the recess 10b is wider, so that an object S to be inspected that has lower fluidity and flexibility can come into contact with the bottom surface 11b1, and thus with the area of ​​the bottom surface 11b1 through which the evanescent light leaks, thereby enabling inspection. Furthermore, in the present embodiment, the shape of the recesses 10b and 11b is simplified, which may reduce the effort and cost required for manufacturing the optical waveguide sensor 10C. Another advantage is that the cladding 13 can be formed relatively easily on the wider bottom surface 11b1.

[0058] [Seventh Embodiment] Fig. 11 is a plan view of an optical waveguide sensor 10G (10) according to a seventh embodiment, and Fig. 12 is a cross-sectional view of the optical waveguide sensor 10G taken along line XII-XII in Fig. 11. The optical waveguide sensor 10G is configured so that the portion where the core 12 and the recess 11b overlap has the same cross-sectional shape as that shown in Fig. 12. This embodiment also has the same configuration as the fifth and sixth embodiments, and provides the same effects as those of the fifth and sixth embodiments.

[0059] However, as shown in FIG. 12 , in this embodiment, recesses 10b are provided only in portions 12b of the core 12 where the core 12 does not intersect with other portions. For portions 12a of the core 12 that intersect with other portions, recesses 10b are not provided, but protrusions 10c are provided instead. The top surfaces of the protrusions 10c are substantially flush with the surface 11a surrounding the recesses 10b. In this configuration, the thickness T2 of the cladding 11 on the core 12 at the protrusions 10c is greater than the thickness T1 of the cladding 11 on the core 12 within the recesses 10b. The portions 12a are an example of a first portion, and the portions 12b are an example of a second portion. Furthermore, thickness T1 is an example of a first thickness, and thickness T2 is an example of a second thickness.

[0060] If the thickness of the cladding 11 is thin at the portion 12a where the core 12 intersects with other portions, the loss of light is likely to be large. In this regard, according to this embodiment, the thickness of the cladding 11 can be made thicker at the portion 12a, thereby suppressing the loss of light at the portion 12a.

[0061] Eighth Embodiment FIG. 13 is a plan view of an optical waveguide sensor 10H (10) according to an eighth embodiment. As shown in FIG. 13 , the optical waveguide sensor 10H of this embodiment includes a plurality of cores 12A and 12B as cores 12, each of which guides an inspection light beam L. Each of the cores 12A and 12B extends while curving substantially along an imaginary plane intersecting the Z direction. The inspection light beams L1 and L2 are input to the input ends 12i of the cores 12, guided along the cores 12, and output from the output ends 12o of the cores 12. The inspection light beams input to the input ends 12i are referred to as incident light beams L1i and L2i, and the inspection light beams output from the output ends 12o are referred to as output light beams L1o and L2o. The optical waveguide sensor 10H includes cores 12A and 12B each having a configuration similar to that of the first embodiment.

[0062] However, in this embodiment, the lengths of the cores 12A and 12B are different. The amount of leakage evanescent light from each of the cores 12A and 12B varies depending on the area (width × length) of the bottom surface 11b1 (see FIG. 3 ) that overlaps with each of the cores 12A and 12B in the Z direction, and the larger the area, the greater the amount of leakage evanescent light. Therefore, the optical waveguide sensor 10A (10) of this embodiment includes two waveguides (cores 12A and 12B) that have different amounts of leakage evanescent light. With this configuration, by measuring the loss intensity in the two waveguides with different amounts of leakage evanescent light, the inspection target S can be inspected more accurately than when measuring the loss intensity in a single waveguide.

[0063] In this configuration, the refractive indexes of the claddings 13 corresponding to the cores 12A and 12B may be different from each other. This allows the optical waveguide sensor 10 to have two waveguides (cores 12) with different leaked evanescent light intensities. In this case, the cores 12A and 12B may have the same specifications, such as width, length, thickness, and shape. The number of waveguides is not limited to two and may be three or more. The optical waveguide sensor 10 may also have multiple waveguides (cores 12) with the same leaked evanescent light intensities. In this case, for example, the measurement results of multiple test objects S of different types can be compared to further improve the test accuracy. The multiple test objects S may include a reference object.

[0064] Ninth Embodiment FIG. 14 is a plan view of an optical waveguide sensor 10I (10) according to a ninth embodiment, and FIG. 15 is a cross-sectional view taken along the line XV-XV in FIG. 14 . As shown in FIG. 15 , the optical waveguide sensor 10I according to this embodiment also includes a core 12 and clads 11 and 13, achieving the same effects as those of the first embodiment. However, as shown in FIGS. 14 and 15 , the present embodiment does not include the recess 11b (10b) as in the first to eighth embodiments, and the test object S is placed on the surface 10a. Therefore, as shown in FIG. 15 , the core 12 is located relatively close to the surface 11a (10a) so that evanescent light of the test light L passing through the core 12 escapes from the surface 10a via the surface 11a of the clad 11 and the clad 13. This configuration achieves the advantage of realizing the optical waveguide sensor 10I with a relatively simple configuration without the recess 10b. 14 , the optical waveguide sensor 10I includes a protrusion 10d that protrudes from the surface 10a in the Z direction and extends in the Y direction at the end opposite the X direction where the incident end 12i and the output end 12o are provided. The protrusion 10d has a wall-like shape that extends in the Y direction with a predetermined width in the X direction and a predetermined height in the Z direction. The protrusion 10d functions as a barrier for the test object S. That is, if the test object S is a liquid, fluid, viscoelastic material, or a soft or flexible solid, the test object S can be prevented from spilling from the surface 10a onto the optical connector or optical fiber connected to the incident end 12i or the output end 12o, thereby contaminating or damaging the optical connector or optical fiber.

[0065] Tenth Embodiment Fig. 16 is a plan view of an optical waveguide sensor 10J (10) according to a tenth embodiment. As is clear from comparing Fig. 16 with Fig. 14, the optical waveguide sensor 10J of this embodiment has a configuration in which the ridge 10d is removed from the optical waveguide sensor 10I of the ninth embodiment. In cases where the test object S is a gas, or where the test object S is a liquid, fluid, viscoelastic material, or a flexible or pliable solid that does not spill off the surface 10a, or where spilling does not pose any particular problems, the ridge 10d may be omitted, as in this embodiment. This embodiment also provides the same effects as the ninth embodiment, and also provides the effect of enabling the optical waveguide sensor 10J to be realized with an even simpler configuration.

[0066] While the above describes exemplary embodiments of the present invention, the above embodiments are merely examples and are not intended to limit the scope of the invention. The above embodiments can be implemented in various other forms, and various omissions, substitutions, combinations, and modifications can be made without departing from the spirit of the invention. Furthermore, the specifications of each configuration, shape, and the like (structure, type, direction, model, size, length, width, thickness, height, number, arrangement, position, material, etc.) can be appropriately modified and implemented.

[0067] The present invention can be used in an optical waveguide sensor.

[0068] DESCRIPTION OF SYMBOLS 10, 10A to 10J...Optical waveguide sensor 10a...Surface 10b...Concave portion 10c...Protrusion 10d...Convex strip 11...Cladding (first cladding) 11a...Surface (first surface) 11b...Concave portion 11b1...Bottom surface 12...Core 12A, 12B...Core (first core) 12a...Part (first part) 12b...Part (second part) 12i...Input end 12o...Output end 13...Cladding (second cladding) 14...Cladding (third cladding) L, L1, L2...Inspection light Li, L1i, L2i...Input light Lo, L1o, L2o...Output light S...Inspection object Sa...Surface T1...Thickness (first thickness) T2...Thickness (second thickness) X...Direction Y...Direction Z...Direction (first direction)

Claims

1. An optical waveguide sensor comprising: a core that forms a waveguide that guides inspection light; a first cladding that surrounds the core; and a second cladding that is located on the opposite side of the core with respect to the first cladding or that is in contact with the core, has a refractive index different from that of the first cladding, and comes into contact with an object to be inspected, wherein the optical waveguide sensor is configured so that leaking components of the inspection light leak from the second cladding to the opposite side of the core.

2. The optical waveguide sensor according to claim 1, wherein the refractive index of said first cladding is higher than the refractive index of said second cladding.

3. The optical waveguide sensor according to claim 1, wherein the refractive index of said first cladding is lower than the refractive index of said second cladding.

4. The optical waveguide sensor according to claim 2 or 3, wherein the refractive index of the object to be inspected is higher than either one of the refractive index of the first clad and the refractive index of the second clad.

5. An optical waveguide sensor according to claim 2 or 3, wherein the refractive index of the object to be inspected is lower than either the refractive index of the first cladding or the refractive index of the second cladding.

6. The optical waveguide sensor according to claim 1, wherein the second clad is capable of adhering closely to the irregularities on the surface of the object to be inspected.

7. The optical waveguide sensor according to claim 6, wherein the second cladding is a fluid.

8. The optical waveguide sensor according to claim 6, wherein the second clad is flexible.

9. The optical waveguide sensor according to claim 6, wherein the second clad is an adhesive.

10. The optical waveguide sensor according to claim 9, wherein the adhesive is a photo-curable adhesive.

11. The optical waveguide sensor according to claim 1, further comprising a third clad interposed between said first clad and said second clad.

12. The optical waveguide sensor according to claim 1, wherein the core and the second clad are in contact with each other, and the second clad is in contact with the object to be inspected on the side opposite to the part in contact with the core.

13. The optical waveguide sensor according to claim 1, wherein the first clad has a first surface facing a first direction and a recess recessed from the first surface in a direction opposite to the first direction, the core extends at least partially along a bottom surface of the recess, intersecting the first direction, and the second clad is provided so as to cover at least the bottom surface and contacts the test object on the side opposite to the portion covering the bottom surface.

14. The optical waveguide sensor according to claim 13, wherein the recess is formed to be wider than the core when viewed in the opposite direction to the first direction.

15. The optical waveguide sensor according to claim 13, wherein the second cladding is provided only in the recess.

16. The optical waveguide sensor according to claim 1 or 13, wherein the core extends while being curved.

17. The optical waveguide sensor described in claim 16, wherein the object to be inspected is positioned offset in a second direction relative to the core, the core has a first portion that intersects with other portions of the core and a second portion that does not intersect with other portions of the core, and a first thickness in the second direction of a portion of the first cladding adjacent to the first portion in the second direction is greater than a second thickness in the second direction of a portion of the first cladding adjacent to the second portion in the second direction.

18. The optical waveguide sensor according to claim 1, wherein the cores comprise a plurality of first cores each constituting a waveguide for guiding the inspection light.

19. The optical waveguide sensor according to claim 18, wherein the lengths of the plurality of first cores are different from one another.

20. The optical waveguide sensor according to claim 18, wherein the refractive indexes of the second claddings corresponding to the plurality of first cores are different from each other.

21. An optical waveguide sensor comprising: a core that forms a waveguide for guiding inspection light; a first clad that surrounds the core; and a second clad that is located on the opposite side of the core from the first clad, that comes into contact with the object to be inspected, and that can adhere closely to the irregularities on the surface of the object to be inspected, wherein the optical waveguide sensor is configured so that seeping components of the inspection light leak from the second clad to the side opposite the core.

22. The optical waveguide sensor according to claim 21, wherein the refractive index of said first cladding and the refractive index of said second cladding are different from each other.

23. The optical waveguide sensor according to claim 21, wherein the refractive index of said first cladding is the same as the refractive index of said second cladding.

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