Object detection device

Abstract

To obtain, for example, an improved new object detection device.SOLUTION: The object detection device comprises: an optical fiber that includes at least partly a sensor optical fiber that transmits light with a loss, for example, of 0.3 [dB / m] or more; and a light receiving unit for receiving light received by the sensor optical fiber from the optical fiber. An object is detected on the basis of the intensity of light received by the light receiving unit. The sensor optical fiber may include a core, of which at least a portion of outer circumference is exposed. A rugged structure of the size of 1 / 100 to 1 / 10 of the wavelength of light received by the light receiving unit may be provided to the outer circumference of the core. Furthermore, the length of the sensor optical fiber may be 10 times the wavelength of light received by the light receiving unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an object detection device. [Background technology]

[0002] Conventionally, object detection devices having optical fibers are known (for example, Patent Document 1). In the object detection device of Patent Document 1, test light is coupled to an end face in the longitudinal direction of the optical fiber. However, the end face is narrow. For this reason, a focusing lens is provided so that light from a wider detection range is coupled to the end face of the optical fiber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-063920 Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of object detection device, it would be beneficial to have a new and improved object detection device that, for example, allows a wider detection range to be set with a simpler configuration.

[0005] Therefore, one object of the present invention is to provide, for example, a novel and improved object detection device. [Means for solving the problem]

[0006] The object detection device of the present invention comprises, for example, an optical fiber that at least partially includes a sensor optical fiber that transmits light with a loss of 0.3 [dB / m] or more, and a light receiving unit that receives light received by the sensor optical fiber from the optical fiber, and detects an object based on the intensity of the light received by the light receiving unit.

[0007] In the object detection device, the sensor optical fiber may have a core with at least a part of its outer periphery exposed.

[0008] In the object detection device, the outer periphery may be provided with an uneven structure having a size not less than 1 / 100 and not more than 1 / 10 of the wavelength of light received by the light receiving section.

[0009] In the object detection device, the length of the sensor optical fiber may be ten times or more the wavelength of the light received by the light receiving section.

[0010] In the object detection device, the sensor optical fiber may have a curved portion.

[0011] In the object detection device, the sensor optical fiber may have a plurality of curved portions as the curved portion.

[0012] In the object detection device, the core of the sensor optical fiber may have an exposed end surface that intersects with a longitudinal direction.

[0013] In the object detection device, the sensor optical fiber may include a plurality of nanostructures, each of which has a cross-sectional diameter of 100 nm or less in a cross section perpendicular to a longitudinal direction of the sensor optical fiber.

[0014] In the object detection device, the nanostructure may be a particle, a tube, or a void.

[0015] In the object detection device, the sensor optical fiber may be a plastic fiber.

[0016] The object detection device may include a light source that inputs test light to one end of the optical fiber, and the light receiving unit may receive the test light output from the other end of the optical fiber.

[0017] In the object detection device, the optical fiber may include the sensor optical fiber, and a delivery optical fiber connected to the sensor optical fiber and having a smaller transmission loss than the sensor optical fiber.

[0018] In the object detection device, an effective relative refractive index difference of the delivery optical fiber may be larger than an effective relative refractive index difference of the sensor optical fiber.

[0019] The object detection device includes a light source that inputs test light into the optical fiber, and at the wavelength of light received by the light receiving unit, the sensor optical fiber is a single-mode optical fiber, and the delivery optical fiber interposed between the light source and the sensor optical fiber may be a multi-mode optical fiber.

[0020] In the object detection device, a pressure acting on the sensor optical fiber may be detected based on the intensity of the light received by the light receiving section.

[0021] In addition, the object detection device of the present invention, for example, includes an optical fiber including a sensor unit to which light is input from the outer periphery, and a light receiving unit that receives the light input to the sensor unit from the optical fiber, and detects an object based on the intensity of the light received by the light receiving unit.

[0022] In the object detection device, an outer periphery of a core may be at least partially exposed in the sensor unit.

[0023] In the object detection device, the optical fiber may have a section having a lower transmission loss than the sensor unit.

[0024] In the object detection device, the optical fiber may have a section in which an effective relative refractive index difference is larger than that of the sensor unit.

[0025] In addition, the object detection device of the present invention includes, for example, an optical fiber having a partially exposed outer periphery of a core, and a light receiving unit that receives light input from the outer periphery from the optical fiber, and detects an object based on the intensity of the light received by the light receiving unit. Effect of the Invention

[0026] According to the present invention, for example, a novel and improved object detection device can be obtained. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is an exemplary schematic configuration diagram of an object detection device according to the first embodiment. [Diagram 2] FIG. 2 is a schematic diagram illustrating an exemplary configuration of an optical fiber according to an embodiment. [Diagram 3] FIG. 3 is an exemplary schematic cross-sectional view taken along the longitudinal direction of a part of a sensor unit according to an embodiment. [Figure 4] FIG. 4 is an illustrative schematic cross-sectional view perpendicular to the longitudinal direction of a sensor unit according to an embodiment. [Diagram 5] FIG. 5 is an exemplary schematic configuration diagram of the sensor unit of the object detection device of the first embodiment, illustrating a state in which no object to be detected is present. [Figure 6] FIG. 6 is an exemplary schematic configuration diagram of the sensor unit of the object detection device of the first embodiment, illustrating a state in which an object to be detected is present. [Figure 7] FIG. 7 is an exemplary graph showing the change over time in the received light intensity at the light receiving unit of the object detection device of the first embodiment, which is a graph showing a case where a state where a detection target is present relative to the sensor unit is switched to a state where it is not present. [Figure 8] FIG. 8 is an exemplary schematic configuration diagram of the sensor unit of the object detection device of the first embodiment, illustrating a state in which an object to be detected is present at a position farther away from the sensor unit than in FIG. [Figure 9] FIG. 9 is an exemplary schematic configuration diagram of an object detection device according to the second embodiment. [Figure 10] FIG. 10 is an illustrative schematic cross-sectional view of a portion of the optical fiber of the first modified example. [Figure 11] FIG. 11 is an illustrative schematic cross-sectional view of a portion of the optical fiber of the second modified example. [Figure 12] FIG. 12 is an illustrative schematic cross-sectional view of a portion of the optical fiber of the third modified example. [Figure 13] FIG. 13 is an exemplary schematic diagram of a portion of an optical fiber according to the fourth modification. [Figure 14] FIG. 14 is an exemplary schematic perspective view of a portion of an optical fiber according to the fifth modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Exemplary embodiments and modifications of the present invention are disclosed below. The configurations of the embodiments and modifications shown below, as well as the actions and results (effects) brought about by the configurations, are merely examples. The present invention can be realized by configurations other than those disclosed in the following embodiments and modifications. 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.

[0029] The embodiments and modifications shown below have similar configurations. Therefore, according to the configurations of the embodiments and modifications, similar actions and effects based on the similar configurations can be obtained. In the following, the similar configurations are given the same reference numerals, and duplicated descriptions may be omitted.

[0030] In addition, in this specification, ordinal numbers are given for the sake of convenience to distinguish between parts, members, portions, etc., and do not indicate priority or order.

[0031] [First embodiment] 1 is a schematic configuration diagram of an object detection device 10A according to a first embodiment. The object detection device 10A is an active detection device that outputs test light and detects an object based on the state in which the output test light is received.

[0032] As shown in FIG. 1, the object detection device 10A includes an optical fiber 11A, a light source 21, a light receiving unit 22, and a control unit 30.

[0033] An end 11e1 in the longitudinal direction of the optical fiber 11A is optically connected to the light source 21, and an end 11e2 in the longitudinal direction of the optical fiber 11A is optically connected to the light receiving unit 22. The test light output from the light source 21 is input into the optical fiber 11A from the end 11e1, transmitted through the optical fiber 11A including the sensor unit 11a, output from the end 11e2 to the outside of the optical fiber 11A, and received by the light receiving unit 22. The end 11e1 is an example of one end, and the end 11e2 is an example of the other end.

[0034] The light source 21 has, for example, a laser diode and outputs light having a wavelength of, for example, 400 [nm] or more and 500 [nm] or less. The light source 21 may also output pulsed light intermittently at a predetermined time interval.

[0035] The light receiving unit 22 has, for example, a photodiode, and detects the intensity of the light input from the optical fiber 11A, that is, the intensity of the light that has passed through the sensor unit 11a. The light receiving unit 22 may also be referred to as a detection unit.

[0036] The control unit 30 can acquire the intensity of light received by the light receiving unit 22. The control unit 30 can also switch between outputting and stopping the output of the test light from the light source 21, and change the output state of the test light. The control unit 30 can also be referred to as a calculation processing unit.

[0037] FIG. 2 is a schematic diagram of the optical fiber 11A. As shown in FIG. 2, the optical fiber 11A has a sensor unit 11a and two delivery optical fibers 11d. The sensor unit 11a is an optical fiber interposed between the two delivery optical fibers 11d. In other words, one delivery optical fiber 11d, the sensor unit 11a which is an optical fiber, and the other delivery optical fiber 11d are mechanically and optically connected in series. The transmission loss of the delivery optical fiber 11d is lower than that of the sensor unit 11a. The effective relative refractive index difference of the delivery optical fiber 11d is larger than that of the sensor unit 11a. The substantial relative refractive index difference is determined depending on the refractive index distribution in the radial direction. In addition, at the boundary 11f between the sensor unit 11a and the delivery optical fiber 11d, the sensor unit 11a and the delivery optical fiber 11d are fusion-spliced. The sensor unit 11a is an example of a sensor optical fiber. Moreover, the delivery optical fiber 11d is an example of a section of the optical fiber 11A that has a lower transmission loss and a larger effective relative refractive index difference than the other sections (in this case, the sensor section 11a). In other words, the sensor section 11a is a section of the optical fiber 11A that has a higher transmission loss and a smaller effective relative refractive index difference than the other sections (in this case, the delivery optical fiber 11d).

[0038] In the sensor unit 11a, light (in this embodiment, reflected light Lr) is input from the outer periphery.

[0039] The sensor portion 11a also has a curved portion 11a1 that is bent back into a U-shape. The curved portion 11a1 can also be called a bent portion or a folded back portion.

[0040] FIG. 3 is a cross-sectional view taken along the longitudinal direction of a portion of the sensor unit 11a, and FIG. 4 is a cross-sectional view taken perpendicular to the longitudinal direction of the sensor unit 11a.

[0041] As is clear from FIGS. 3 and 4, the sensor portion 11a has a core 11b and a cladding 11c that surrounds the core 11b and has a lower refractive index than the core 11b.

[0042] The diameter of the core 11b and the relative refractive index difference of the core 11b with respect to the cladding 11c are set so that the sensor unit 11a can transmit the test light in a single mode. The cladding 11c may be surrounded by a coating (not shown). In this case, the coating has transparency to the test light.

[0043] As an example, the cladding diameter, i.e., the outer diameter of the core, is the same between the sensor unit 11a and the delivery optical fiber 11d. The core diameter (outer diameter) may be the same or different between the sensor unit 11a and the delivery optical fiber 11d. As an example, the core diameter of the delivery optical fiber 11d may be larger than the diameter of the core 11b of the sensor unit 11a. The delivery optical fiber 11d may be a multimode optical fiber that transmits the test light in multiple modes.

[0044] The sensor unit 11a and the delivery optical fiber 11d are so-called plastic fibers made of synthetic resin materials that are transparent to the test light, such as methacrylic resin or fluororesin. However, the present invention is not limited to this, and the sensor unit 11a and the delivery optical fiber 11d may be glass optical fibers made of a silica-based glass material. The sensor unit 11a and the delivery optical fiber 11d may also be made of different materials.

[0045] Also, as shown in Figs. 3 and 4, the sensor section 11a may include a plurality of nanostructures 11p near the interface between the core 11b and the clad 11c. However, such a distribution of the nanostructures 11p is an example, and the nanostructures 11p may be present throughout the entire radial direction of the clad 11c in the sensor section 11a. The nanostructures 11p may each include a filler (e.g., particles such as fine particles or cylindrical tubes) or a void (e.g., a tube or a minute space of air other than fine particles), or may include at least two of these examples. For example, the cross-sectional diameter of the nanostructure 11p in a cross section perpendicular to the longitudinal direction of the sensor section 11a is 100 [nm] or less. In this case, the loss of the sensor section 11a is likely to increase compared to a case in which the filler or void is not included. The filler or void may be included in the clad 11c more than in the core 11b of the sensor section 11a.

[0046] Through intensive research by the inventors, it has been found that in the sensor unit 11a having such a configuration, the test light is scattered by the nanostructure 11p, so that the test light is less likely to be confined in the core 11b than in a configuration without the nanostructure 11p, in other words, the test light is more likely to leak from the core 11b. The fact that the test light is more likely to leak from the core 11b means that light is more likely to be input from the outside into the core 11b. As an example, it has been found that such a characteristic becomes prominent when the transmission loss for the test light in the sensor unit 11a is 0.3 [dB / m] or more.

[0047] 2, the sensor unit 11a has a curved portion 11a1 that is bent back into a U-shape. The curved portion 11a1 can also be called a bent portion or a folded back portion.

[0048] In the object detection device 10A having such a configuration, as shown in Fig. 1, a part of the test light leaks from the sensor unit 11a and becomes the emitted light Le. In addition, at least a part of the emitted light Le is reflected by the object A to be detected, and the reflected light Lr is input into the sensor unit 11a.

[0049] 5 is a side view of the sensor unit 11a when there is no object A facing the sensor unit 11a. In this case, the emitted light Le output from the sensor unit 11a is not reflected by the object A. Therefore, the reflected light Lr of the emitted light Le by the object A is not input to the sensor unit 11a.

[0050] 6 is a side view of the sensor unit 11a when an object A faces the sensor unit 11a. In this case, the emitted light Le output from the sensor unit 11a is reflected by the object A. At least a part of the reflected light Lr of the emitted light Le from the object A is input to the sensor unit 11a.

[0051] Fig. 7 is a graph showing the change over time in the received light intensity at the light receiving unit 22, and the thick solid line indicates the transition from the state in Fig. 6 to the state in Fig. 5 at time t1. It is clear from Fig. 7 that in the state in Fig. 6 before time t1, the received light intensity at the light receiving unit 22 is high, and in the state in Fig. 5 after time t1, the received light intensity at the light receiving unit 22 is low. Note that the thick dashed line in Fig. 7 indicates the change over time in the received light intensity when the state in Fig. 6 is maintained.

[0052] Therefore, the control unit 30 can detect the presence or absence of the object A based on the received light intensity at the light receiving unit 22. As an example, the control unit 30 can determine that the object A is present when the received light intensity is equal to or greater than a predetermined value Th (threshold value), and can determine that the object A is not present when the received light intensity is less than the predetermined value Th.

[0053] 8 is a side view of the sensor unit 11a in a case where the object A facing the sensor unit 11a is positioned farther away from the sensor unit 11a than in FIG. 6. In this case as well, the emitted light Le output from the sensor unit 11a is reflected by the object A, and at least a part of the reflected light Lr of the emitted light Le from the object A is input to the sensor unit 11a. However, the intensity of the reflected light Lr at the sensor unit 11a is smaller than in FIG. 6. Therefore, the received light intensity of the test light at the light receiving unit 22 is also smaller than in FIG. 6.

[0054] Therefore, the control unit 30 can determine whether the object A is far or close to the sensor unit 11a based on the received light intensity at the light receiving unit 22. As an example, the control unit 30 can determine based on the received light intensity that the greater the received light intensity, the closer the object A is located to the sensor unit 11a, and the smaller the received light intensity, the farther the object A is located from the sensor unit 11a. In addition, the control unit 30 can detect the distance of the object A from the sensor unit 11a. As an example, in a case where a correlation between the position of the target object A and the received light intensity is acquired in advance, the control unit 30 can estimate the position of the object A corresponding to the received light intensity at the light receiving unit 22 from the correlation. Furthermore, the control unit 30 can estimate the moving speed of the object A from the change over time in the estimated position of the object A.

[0055] Furthermore, through intensive research by the inventors, it was found that in such a configuration, the greater the external force acting on the sensor unit 11a, the more the leakage of the test light from the sensor unit 11a increases, in other words, the transmission loss in the sensor unit 11a increases. Furthermore, it was also found that in the sensor unit 11a in which the test light is likely to leak from the core 11b, when an external force is applied, the transmission loss changes more sensitively in response to the external force.

[0056] From such characteristics of the sensor unit 11a, the control unit 30 can calculate the external force acting on the sensor unit 11a corresponding to the light receiving intensity at the light receiving unit 22 based on the correlation between the light receiving intensity at the light receiving unit 22 and the external force acting on the sensor unit 11a, which is obtained in advance by experiment. The external force may be a force or a pressure.

[0057] Furthermore, through the inventors' intensive research, it was found that, with regard to the sensor unit 11a, the length L (see FIG. 2) of the sensor unit 11a is preferably 10 times or more the wavelength of the test light (light received by the light receiving unit 22) from the viewpoint of the size (length) of the detection range, and more specifically, is preferably 0.01 cm or more and 100 cm or less. It was also found that the radius of curvature R of the curved portion 11a1 (see FIG. 2, the radius of the central axis of the sensor unit 11a) is preferably 50 μm or more and 200 μm or less from the viewpoint of transmission loss.

[0058] As described above, in this embodiment, the light receiving unit 22 receives light input from the outer periphery of the sensor unit 11a via the optical fiber 11A. The control unit 30 detects the object A based on the intensity of the light received by the light receiving unit 22.

[0059] According to such a configuration, for example, the object detection device 10A can be realized with a more compact and simple configuration based on optical fiber. Also, in the sensor unit 11a, light is input into the sensor unit 11a from the outer periphery of the sensor unit 11a. Therefore, compared to a configuration in which light is input to the end face of an optical fiber, a wider detection range can be ensured with a simpler configuration.

[0060] Furthermore, as in this embodiment, the length L of the sensor portion 11a may be ten times the wavelength of the light received by the light receiving portion 22 or more.

[0061] According to such a configuration, for example, the detection range of the sensor unit 11a can be set larger.

[0062] Also, as in this embodiment, the sensor unit 11a may be an optical fiber that transmits the test light with a loss of 0.3 [dB / m] or more.

[0063] Furthermore, as in this embodiment, the sensor portion 11a may have a curved portion 11a1.

[0064] Furthermore, as in this embodiment, the sensor unit 11a may include a plurality of nanostructures 11p.

[0065] As in this embodiment, the sensor portion 11a may be a plastic fiber.

[0066] In this embodiment, the delivery optical fiber 11d between the sensor unit 11a and the light source 21 may be a multimode optical fiber, and the sensor unit 11a may be a single mode optical fiber.

[0067] In this embodiment, the sensor section 11a may be a section having a higher transmission loss than the delivery optical fiber 11d.

[0068] In this embodiment, the sensor section 11a may be a section having an effective relative refractive index difference smaller than that of the delivery optical fiber 11d.

[0069] According to such a configuration, for example, the transmission loss in the sensor unit 11a becomes higher, which makes it easier for light from the outside to be input to the sensor unit 11a, and increases the detection sensitivity of the sensor unit 11a.

[0070] Furthermore, as in this embodiment, the transmission loss of the delivery optical fiber 11d may be smaller than the transmission loss of the sensor unit 11a.

[0071] Furthermore, as in this embodiment, the effective relative refractive index difference of the delivery optical fiber 11d may be larger than the effective relative refractive index difference of the sensor section 11a.

[0072] According to such a configuration, for example, the delivery optical fiber 11d can confine and transmit light, and the sensor section 11a can perform the functions of leaking or receiving light and detecting it.

[0073] Furthermore, as in this embodiment, the light receiving unit 22 may receive test light input from the light source 21 to the optical fiber 11A via the end 11e1 (one end), passed through the sensor unit 11a, and output from the end 11e2 (the other end).

[0074] According to such a configuration, for example, an active object detection device 10A can be realized with a relatively simple configuration. Also, since it is not necessary to provide the light source 21 at a position separate from the optical fiber 11A, it is easy to configure the object detection device 10A to be compact overall. Furthermore, in a configuration in which the sensor unit 11a has a curved portion 11a1, the emitted light Le is easily emitted radially outward from the curved portion 11a1, so that the object A can be easily detected radially outward from the curve.

[0075] Furthermore, the control unit 30 may detect the external force acting on the sensor unit 11a based on the intensity of the light received by the light receiving unit 22, as in this embodiment.

[0076] According to such a configuration, the configuration can be further simplified compared to, for example, a case where a separate device for detecting an external force is provided.

[0077] The object detection device 10A of the present embodiment may be a passive detection device that does not have the light source 21.

[0078] [Second embodiment] 9 is a side view of an object detection device 10B according to the second embodiment. In this embodiment, the object detection device 10B is also an active detection device.

[0079] As shown in Fig. 9, the sensor portion 11a may not have a curved portion and may extend linearly. Also, the sensor portion 11a may include a plurality of nanostructures 11p, similar to the first embodiment.

[0080] 9, the light source 21 may be provided at a position away from the optical fiber 11B. In this case, the light source 21 and the sensor unit 11a are arranged so that the output light Le output from the light source 21 is input to the sensor unit 11a from its outer periphery as test light.

[0081] 9, a light receiving unit 22 may be provided at each end in the longitudinal direction of the optical fiber 11B. In this case, the control unit 30 may detect the object A based on the sum or average of the light receiving intensities at the two light receiving units 22. The control unit 30 may also estimate the position of the object A in the direction along the longitudinal direction of the optical fiber 11B (the left-right direction in FIG. 9) from the difference between the light receiving intensities at the two light receiving units 22.

[0082] A reflector or a filter may be provided instead of one of the two light receiving sections 22. The reflector keeps the light within the optical fiber 11B. The filter allows the light to exit the optical fiber 11B and prevents the light from entering the optical fiber 11B.

[0083] According to this embodiment, the same effects as those of the above-mentioned embodiment can be obtained. Note that, in this embodiment, the object detection device 10B may be a passive detection device that does not have the light source 21.

[0084] [First Modification of Optical Fiber] 10 is a side view of a portion of an optical fiber 11C of the first modified example. The optical fiber 11C can be incorporated into an object detection device in place of the optical fiber of the above-described embodiment.

[0085] As shown in FIG. 10, the sensor unit 11a may have only the core 11b without the cladding. In other words, the cladding may be removed from the sensor unit 11a. With this configuration, the outer periphery 11b1 of the core 11b is exposed in the sensor unit 11a. This makes it easier for light from the outside to be input to the sensor unit 11a, and the detection sensitivity of the sensor unit 11a is increased. Note that the core 11b does not need to be exposed in the entire section of the sensor unit 11a, and it is sufficient that the outer periphery 11b1 of the core 11b is exposed in at least a part of the sensor unit 11a. The outer periphery 11b1 may also be referred to as the outer periphery surface.

[0086] In this case, the outer periphery 11b1 may be provided with an uneven structure (not shown) including recesses or protrusions. If the size of the uneven structure, for example, the length and interval in the longitudinal direction, the height difference in the radial direction, etc., is 1 / 10 or less of the wavelength of light entering the core 11b from the outside through the outer periphery 11b1, Rayleigh scattering occurs at the outer periphery 11b1, which is the interface, and the light from the outside easily enters the core 11b. If the size of the uneven structure is smaller than 1 / 100 of the wavelength of light, the outer periphery 11b1 is smoothed, making it difficult for Rayleigh scattering to occur at the outer periphery 11b1. Therefore, it is preferable that the size of the uneven structure is 1 / 100 or more and 1 / 10 or less of the wavelength of light entering the core 11b from the outside through the outer periphery 11b1, i.e., the light received by the light receiving unit 22.

[0087] The delivery optical fiber 11d has a core 11d1 and a clad 11d2 surrounding the core 11d1. The core 11b of the sensor unit 11a is optically connected to the core 11d1 of the delivery optical fiber 11d. Specifically, the core 11b and the core 11d1 are connected by, for example, fusion splicing.

[0088] [Second Modification of Optical Fiber] 11 is a side view of a portion of an optical fiber 11D of Modification 2. The optical fiber 11D can be incorporated into an object detection device in place of the optical fiber of the above embodiment.

[0089] 11, the sensor unit 11a in which the outer periphery 11b1 of the core 11b is at least partially exposed may have a curved portion 11a1. With such a configuration, the core 11b is curved, so that light from the outside can more easily enter the core 11b, thereby increasing the detection sensitivity of the sensor unit 11a.

[0090] [Third Modification of Optical Fiber] 12 is a side view of a portion of an optical fiber 11E of Modification Example 3. The optical fiber 11E can be incorporated into an object detection device in place of the optical fiber of the above-described embodiments.

[0091] As shown in FIG. 12, the sensor unit 11a, in which the outer periphery 11b1 of the core 11b is at least partially exposed, may be cut in the middle to expose the end face 11b2 in the longitudinal direction (optical axis direction). The end face 11b2 is a surface intersecting the longitudinal direction and is an example of an exposed end face. The end faces 11b2 of the two cores 11b face each other. The two cores 11b are optically connected, although the transmission loss between them is high. With this configuration, light can enter the core 11b from the end face 11b2 in addition to the outer periphery 11b1. Therefore, light from the outside can enter the core 11b more easily, and the detection sensitivity of the sensor unit 11a is higher. The sensor unit 11a of this modification may be made by cutting the core 11b, or may be made of two parts made separately. The two end faces 11b2 may be in contact with each other. The core 11b may be partially connected and partially separated, so that the end face 11b2 is partially exposed.

[0092] [Fourth Modification of Optical Fiber] 13 is a side view of a portion of an optical fiber 11F of the fourth modified example. The optical fiber 11F can be incorporated into an object detection device in place of the optical fiber of the above-described embodiments.

[0093] 13, the sensor unit 11a may have a plurality of curved portions 11a1. With such a configuration, the number of curved portions 11a1 increases, so that light from the outside can more easily enter the core 11b, and the detection sensitivity of the sensor unit 11a is increased.

[0094] [Fifth Modification of Optical Fiber] 14 is a side view of a portion of an optical fiber 11G of the fifth modified example. The optical fiber 11G can be incorporated into an object detection device in place of the optical fiber of the above-described embodiments.

[0095] As shown in FIG. 14, the sensor unit 11a may be configured in a coil shape. The coil may be elliptical or oval when viewed in the direction of the winding axis of the coil. The coil may also be configured by being wound around a core member (not shown). In this case, the core member may be a strip-shaped member having rounded edges. In this modification, the sensor unit 11a also has a plurality of curved portions 11a1. Thus, with such a configuration, the increased number of curved portions 11a1 allows light from the outside to enter the core 11b more easily, and the detection sensitivity of the sensor unit 11a is increased.

[0096] Although the embodiment of the present invention has been illustrated above, the above embodiment is merely an example and is not intended to limit the scope of the invention. The above embodiment can be implemented in various other forms, and various omissions, substitutions, combinations, and modifications can be made without departing from the gist of the invention. In addition, 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 changed and implemented.

[0097] For example, in the above embodiments and variants, the optical fiber is formed by connecting the sensor portion (sensor optical fiber) and the delivery optical fiber to each other, but this is not limited to this, and the sensor portion may be created in a part of the optical fiber by performing a localized process on the optical fiber.

[0098] In addition, for example, optical fibers having different mode transmission states may be applied to the sensor unit (sensor optical fiber) and the delivery optical fiber between the sensor unit and the light source so that mode conversion occurs at the connection point (boundary) between the sensor unit and the delivery optical fiber. [Explanation of symbols]

[0099] 10A, 10B...Object detection device 11A~11G...Optical fiber 11a...sensor section (sensor optical fiber) 11a1…Bend 11b…Core 11b1…outer circumference 11b2...End face (exposed end face) 11c…Clad 11d…Delivery optical fiber 11d1…Core 11d2…Clad 11e1...End (one end) 11e2...End (other end) 11f…boundary 11p…Nanostructure 21…Light source 22...Light receiving section 30...Control unit (arithmetic processing unit) A...object L…Length Le...Emitted light Lr…Reflected light R…curvature radius Th...predetermined value (threshold value) t1…Time

Claims

1. An optical fiber including at least a portion of a sensor optical fiber that includes a core and a cladding and transmits light with a loss of 0.3 [dB / m] or more; a light receiving unit that receives the light received by the sensor optical fiber from the optical fiber; Equipped with the sensor optical fiber includes a plurality of nanostructures near an interface between the core and the cladding, each of which has a cross-sectional diameter of 100 nm or less in a cross section perpendicular to a longitudinal direction of the sensor optical fiber; An object detection device that detects an object based on the intensity of light received by the light receiving unit.

2. The object detection device according to claim 1 , wherein the sensor optical fiber has a core with at least a part of its outer periphery exposed.

3. The object detection device according to claim 2 , wherein the outer periphery is provided with an uneven structure having a size not less than 1 / 100 and not more than 1 / 10 of the wavelength of the light received by the light receiving portion.

4. 4. The object detection device according to claim 1, wherein the length of the sensor optical fiber is 10 times or more the wavelength of the light received by the light receiving section.

5. 5. The object detection device according to claim 1, wherein the sensor optical fiber has a curved portion.

6. The object detection device according to claim 5 , wherein the sensor optical fiber has a plurality of curved portions as the curved portion.

7. 7. The object detection device according to claim 1, wherein the core of the sensor optical fiber has an exposed end surface that intersects with the longitudinal direction.

8. The object detection device according to claim 1 , wherein the nanostructure is a particle, a tube, or a void.

9. 9. The object detection device according to claim 1, wherein the sensor optical fiber is a plastic fiber.

10. a light source for inputting a test light into the optical fiber; 10. The object detection device according to claim 1, wherein the light receiving section receives a test light output from the other end of the optical fiber.

11. 11. The object detection device according to claim 1, wherein the optical fiber comprises: the sensor optical fiber; and a delivery optical fiber connected to the sensor optical fiber and having a smaller transmission loss than the sensor optical fiber.

12. The object detection device according to claim 11 , wherein an effective relative refractive index difference of the delivery optical fiber is greater than an effective relative refractive index difference of the sensor optical fiber.

13. a light source for inputting a test light into the optical fiber; 13. The object detection device according to claim 11 or 12, wherein, at a wavelength of light received by the light receiving unit, the sensor optical fiber is a single-mode optical fiber, and the delivery optical fiber interposed between the light source and the sensor optical fiber is a multi-mode optical fiber.

14. 14. The object detection device according to claim 1, further comprising: a light receiving section configured to receive a light beam from the light receiving section, the light receiving section receiving the light beam from the light receiving section, and detecting an external force acting on the sensor optical fiber based on the intensity of the light beam.

15. An optical fiber including a core and a cladding, and including a sensor portion into which light is input from an outer periphery; a light receiving unit that receives the light input to the sensor unit from the optical fiber; Equipped with the sensor portion includes a plurality of nanostructures in the vicinity of an interface between the core and the cladding, each of which has a cross-sectional diameter of 100 nm or less in a cross section perpendicular to a longitudinal direction of the sensor portion; An object detection device that detects an object based on the intensity of light received by the light receiving unit.

16. The object detection device according to claim 15 , wherein an outer periphery of the core is at least partially exposed in the sensor unit.

17. 17. The object detection device according to claim 15, wherein the optical fiber has a section having a lower transmission loss than the sensor unit.

18. 18. The object detection device according to claim 15, wherein the optical fiber has a section in which an effective relative refractive index difference is larger than that of the sensor portion.

19. An optical fiber including a core and a cladding, the outer periphery of the core being partially exposed; a light receiving unit that receives light input from the outer periphery through the optical fiber; Equipped with the core includes a plurality of nanostructures near the exposed outer periphery, each of which has a cross-sectional diameter of 100 nm or less in a cross section perpendicular to a longitudinal direction of the optical fiber; An object detection device that detects an object based on the intensity of light received by the light receiving unit.

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