Object detection device
The object detection device uses a sensor optical fiber with exposed outer circumference and nanostructures to enhance detection range and sensitivity, addressing the limitations of existing devices by enabling wider detection with increased sensitivity and compact design.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- FURUKAWA ELECTRIC CO LTD
- Filing Date
- 2025-01-09
- Publication Date
- 2026-07-03
AI Technical Summary
Existing object detection devices using optical fibers face challenges in achieving a wider detection range with a simpler configuration, as the end face of the optical fiber is narrow and limits the detection capabilities.
The object detection device incorporates a sensor optical fiber with exposed outer circumference, nanostructures, and a curved portion, along with a light receiving unit to detect objects based on light intensity, utilizing a single-mode optical fiber for detection and a multimode optical fiber for delivery, allowing for a wider detection range with increased sensitivity.
The device achieves a more compact and efficient object detection with a simpler configuration, enabling a wider detection range and sensitivity to external forces, including the ability to detect objects and measure distances based on light intensity variations.
Smart Images
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Abstract
Description
Technical Field
[0007]
[0001] The present invention relates to an object detection device.
Background Art
[0002] Conventionally, an object detection device having an optical fiber has been known (for example, Patent Document 1). In the object detection device of Patent Document 1, the test light is coupled to the end face in the longitudinal direction of the optical fiber. However, the end face is narrow. Therefore, a condenser 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
Summary of the Invention
Problems to be Solved by the Invention
[0004] In this type of object detection device, for example, it would be beneficial to obtain an improved and novel object detection device that can set a wider detection range with a simpler configuration.
[0005] Therefore, one of the problems of the present invention is to obtain, for example, an improved and novel object detection device.
Means for Solving the Problems
[0006] The object detection device of the present invention includes, 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 the 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 in which at least a portion of the outer circumference is exposed.
[0008] In the object detection device, the outer circumference may be provided with an uneven structure having a size of 1 / 100 or more and 1 / 10 or less of the wavelength of the light received by the light receiving unit.
[0009] In the object detection device, the length of the sensor optical fiber may be 10 times or more the wavelength of the light received by the light receiving unit.
[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 sections as the curved section.
[0012] In the object detection device, the core of the sensor optical fiber may have an exposed end face that intersects the longitudinal direction.
[0013] In the object detection device, the sensor optical fiber may include a plurality of nanostructures, each having a cross-sectional diameter of 100 nm or less in a cross-section perpendicular to the longitudinal direction of the sensor optical fiber.
[0014] In the object detection device, the nanostructure may be fine particles, tubes, or voids.
[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 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 lower transmission loss than the sensor optical fiber.
[0018] In the object detection device, the effective relative refractive index difference of the delivery optical fiber may be larger than the effective relative refractive index difference of the sensor optical fiber.
[0019] The object detection device includes a light source for inputting test light into the optical fiber. At the wavelength of the 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, the pressure acting on the sensor optical fiber may be detected based on the intensity of the light received by the light receiving unit.
[0021] Further, the object detection device of the present invention includes, for example, an optical fiber including a sensor unit into 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, at least part of the outer periphery of the core may be exposed in the sensor unit.
[0023] In the object detection device, the optical fiber may have a section with a lower transmission loss than the sensor unit.
[0024] In the object detection device, the optical fiber may have a section with an effective relative refractive index difference larger than that of the sensor unit.
[0025] Further, the object detection device of the present invention includes, for example, an optical fiber with a partially exposed outer circumference of the core, and a light receiving unit that receives light input from the outer circumference from the optical fiber, and detects an object based on the intensity of the light received by the light receiving unit.
Advantages of the Invention
[0026] According to the present invention, for example, an improved and novel object detection device can be obtained.
Brief Description of the Drawings
[0027] [Figure 1] FIG. 1 is an exemplary schematic configuration diagram of the object detection device according to the first embodiment. [Figure 2] FIG. 2 is an exemplary schematic configuration diagram of the optical fiber according to the embodiment. [Figure 3] FIG. 3 is an exemplary and schematic cross-sectional view along the longitudinal direction of a part of the sensor unit according to the embodiment. [Figure 4] FIG. 4 is an exemplary and schematic cross-sectional view perpendicular to the longitudinal direction of the sensor unit according to the embodiment. [Figure 5] FIG. 5 is an exemplary schematic configuration diagram of the sensor unit of the object detection device according to the first embodiment, showing a state where no object to be detected exists. [Figure 6] FIG. 6 is an exemplary schematic configuration diagram of the sensor unit of the object detection device according to the first embodiment, showing a state where an object to be detected exists. [Figure 7] FIG. 7 is an exemplary graph showing the change over time of the light reception intensity in the light receiving unit of the object detection device according to the first embodiment, showing a case where the detection target for the sensor unit switches from a state where it exists to a state where it does not exist. [Figure 8] FIG. 8 is an exemplary schematic configuration diagram of the sensor unit of the object detection device according to the first embodiment, showing a state where an object to be detected exists at a position farther from the sensor unit than in FIG. 6. [Figure 9] FIG. 9 is an exemplary schematic configuration diagram of the object detection device according to the second embodiment. [Figure 10] Figure 10 is an exemplary and schematic cross-sectional view of a portion of the optical fiber of the first modified example. [Figure 11] Figure 11 is an illustrative and schematic cross-sectional view of a portion of an optical fiber in the second modified example. [Figure 12] Figure 12 is an exemplary and schematic cross-sectional view of a portion of an optical fiber in the third modified example. [Figure 13] Figure 13 is a schematic diagram illustrating a portion of the optical fiber in the fourth modified example. [Figure 14] Figure 14 is an illustrative and schematic perspective view of a portion of the optical fiber in the fifth modified example. [Modes for carrying out the invention]
[0028] Illustrative embodiments and modifications of the present invention are disclosed below. The configurations of the embodiments and modifications shown below, as well as the functions and results (effects) brought about by such configurations, are examples only. The present invention can also 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 derived effects) that can be obtained by the configuration.
[0029] The embodiments and modifications shown below have similar configurations. Therefore, the configurations of each embodiment and modification yield similar functions and effects based on those similar configurations. In the following, similar components are denoted by the same reference numerals, and redundant explanations may be omitted.
[0030] Furthermore, in this specification, ordinal numbers are assigned for convenience to distinguish parts, components, and other components, and do not indicate priority or order.
[0031] [First Embodiment] Figure 1 is a schematic diagram of the object detection device 10A according to the first embodiment. The object detection device 10A is an active detection device that outputs test light and detects objects based on the reception state of the output test light.
[0032] As shown in Figure 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] The longitudinal end 11e1 of the optical fiber 11A is optically connected to the light source 21, and the longitudinal end 11e2 of the optical fiber 11A is optically connected to the light receiving unit 22. Test light output from the light source 21 is input into the optical fiber 11A from end 11e1, transmitted within the optical fiber 11A including the sensor unit 11a, output outside the optical fiber 11A from end 11e2, and received by the light receiving unit 22. End 11e1 is an example of one end, and end 11e2 is an example of the other end.
[0034] The light source 21, for example, has a laser diode and outputs light with 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 predetermined time intervals.
[0035] The light-receiving unit 22, for example, has a photodiode and detects the intensity of light input from the optical fiber 11A, that is, the intensity of light that has passed through the sensor unit 11a. The light-receiving unit 22 may also be referred to as the detection unit.
[0036] The control unit 30 can acquire the light intensity received by the light receiving unit 22. The control unit 30 can also switch the output and stop of the test light from the light source 21, and change the output state of the test light. The control unit 30 may also be referred to as the arithmetic processing unit.
[0037] Figure 2 is a schematic diagram of the optical fiber 11A. As shown in Figure 2, the optical fiber 11A has a sensor section 11a and two delivery optical fibers 11d. The sensor section 11a is an optical fiber interposed between the two delivery optical fibers 11d. In other words, one delivery optical fiber 11d, the optical fiber sensor section 11a, 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 the transmission loss of the sensor section 11a. The effective specific refractive index difference of the delivery optical fiber 11d is greater than the effective specific refractive index difference of the sensor section 11a. The actual specific refractive index difference is determined by the refractive index distribution in the radial direction. Furthermore, at the boundary 11f between the sensor section 11a and the delivery optical fiber 11d, the sensor section 11a and the delivery optical fiber 11d are fusion spliced together. The sensor section 11a is an example of a sensor optical fiber. Furthermore, the delivery optical fiber 11d is an example of a section of the optical fiber 11A that has lower transmission loss and a larger effective specific refractive index difference than 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 higher transmission loss and a smaller effective specific refractive index difference than other sections (in this case, the delivery optical fiber 11d).
[0038] In the sensor unit 11a, light (reflected light Lr in this embodiment) is input from its outer periphery.
[0039] Furthermore, the sensor portion 11a has a curved portion 11a1 that is folded back in a U-shape. The curved portion 11a1 may also be referred to as a bend or a folded portion.
[0040] Figure 3 is a cross-sectional view of a portion of the sensor unit 11a along its longitudinal direction, and Figure 4 is a cross-sectional view of the sensor unit 11a perpendicular to its longitudinal direction.
[0041] As is clear from Figures 3 and 4, the sensor unit 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 difference in refractive index between the core 11b and the cladding 11c are set so that the sensor unit 11a can transmit the test light in single mode. The cladding 11c may also be surrounded by a covering (not shown). In this case, the covering has transparency to the test light.
[0043] Furthermore, as an example, the cladding diameter, i.e., the outer diameter of the core wire, is the same for the sensor unit 11a and the delivery optical fiber 11d. Also, the core diameter (outer diameter) of the sensor unit 11a and the delivery optical fiber 11d may be the same or different. For example, the core diameter of the delivery optical fiber 11d may be larger than the core diameter of the core 11b of the sensor unit 11a. In addition, the delivery optical fiber 11d may be a multimode optical fiber that transmits test light in multimode.
[0044] The sensor unit 11a and the delivery optical fiber 11d are so-called plastic fibers made of a synthetic resin material that is transparent to test light, such as methacrylic resin or fluororesin. However, they are not limited to this, and the sensor unit 11a and the delivery optical fiber 11d may also be glass optical fibers made of silica-based glass material. Furthermore, the sensor unit 11a and the delivery optical fiber 11d may be made of different materials.
[0045] Furthermore, as shown in Figures 3 and 4, the sensor portion 11a may include multiple nanostructures 11p near the interface between the core 11b and the cladding 11c. However, this distribution of nanostructures 11p is just an example, and the nanostructures 11p may exist throughout the entire radial direction of the cladding 11c within the sensor portion 11a. Each nanostructure 11p may include fillers (e.g., particles such as fine particles or cylindrical tubes) or voids (e.g., tubes, minute spaces of air other than fine particles), and at least two of these examples may be included. For example, the cross-sectional diameter of the nanostructure 11p in a cross-section perpendicular to the longitudinal direction of the sensor portion 11a is 100 [nm] or less. In this case, the loss of the sensor portion 11a is more likely to increase compared to the case where fillers or voids are not included. Note that fillers and voids may be present in greater quantities in the cladding 11c than in the core 11b of the sensor portion 11a.
[0046] Through diligent research by the inventors, it was discovered that in a sensor unit 11a with this configuration, the test light is scattered by the nanostructure 11p, making it more difficult to confine the test light within the core 11b compared to 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 easily input into the core 11b from the outside. For example, it was found that this characteristic becomes more pronounced when the transmission loss for the test light in the sensor unit 11a is 0.3 [dB / m] or more.
[0047] Furthermore, as shown in Figure 2, the sensor portion 11a has a curved portion 11a1 that is folded back in a U-shape. The curved portion 11a1 may also be referred to as a bend or a folded portion.
[0048] In an object detection device 10A with this configuration, as shown in Figure 1, a portion of the test light leaks from the sensor unit 11a and becomes the emitted light Le. In addition, at least a portion 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] Figure 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 object A. Therefore, the reflected light Lr of the emitted light Le from object A is not input to the sensor unit 11a.
[0050] Figure 6 is a side view of the sensor unit 11a when an object A is facing the sensor unit 11a. In this case, the emitted light Le from the sensor unit 11a is reflected by object A. At least a portion of the reflected light Lr from object A is input to the sensor unit 11a.
[0051] Figure 7 is a graph showing the change in light reception intensity at the light receiving unit 22 over time. The thick solid line represents the transition from the state in Figure 6 to the state in Figure 5 at time t1. From Figure 7, it is clear that the light reception intensity at the light receiving unit 22 is high in the state in Figure 6 before time t1, and decreases in the state in Figure 5 after time t1. The thick dashed line in Figure 7 shows the change in light reception intensity over time if the state in Figure 6 is maintained.
[0052] Therefore, the control unit 30 can detect the presence or absence of object A based on the light intensity received by the light receiving unit 22. For example, the control unit 30 can determine that object A is present if the light intensity is equal to or greater than a predetermined value Th (threshold), and that object A is not present if the light intensity is less than the predetermined value Th.
[0053] Furthermore, Figure 8 is a side view of the sensor unit 11a when object A facing the sensor unit 11a is located further away from the sensor unit 11a than in Figure 6. In this case as well, the emitted light Le output from the sensor unit 11a is reflected by object A, and at least a portion of the reflected light Lr of the emitted light Le at 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 the case of Figure 6. Consequently, the light intensity of the test light received by the light receiving unit 22 is also smaller than in the case of Figure 6.
[0054] Therefore, the control unit 30 can determine whether object A is far from or near the sensor unit 11a based on the light intensity received by the light receiving unit 22. For example, the control unit 30 can determine that the greater the light intensity, the closer object A is to the sensor unit 11a, and the smaller the light intensity, the further away object A is from the sensor unit 11a. The control unit 30 can also detect the distance of object A from the sensor unit 11a. For example, if a correlation between the position of the target object A and the light intensity has been obtained in advance, the control unit 30 can estimate the position of object A corresponding to the light intensity received by the light receiving unit 22 from this correlation. Furthermore, the control unit 30 can also estimate the movement speed of object A from the change in the estimated position of object A over time.
[0055] Furthermore, through diligent research by the inventors, it was found that in such a configuration, the greater the external force acting on the sensor unit 11a, the greater the leakage of test light from the sensor unit 11a; in other words, the transmission loss in the sensor unit 11a increases. Moreover, it was found that in a sensor unit 11a from which test light is easily leaked from such a core 11b, the transmission loss changes more sensitively in response to the external force applied.
[0056] Based on these 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 intensity at the light receiving unit 22, based on the correlation between the light intensity at the light receiving unit 22 and the external force acting on the sensor unit 11a, which has been experimentally acquired in advance. The external force may be a force or a pressure.
[0057] Furthermore, through diligent research by the inventors, it was found that, from the viewpoint of the size (length) of the detection range, the length L of the sensor section 11a (see Figure 2) is preferably 10 times or more the wavelength of the test light (light received by the light receiving section 22), and specifically, it is preferably 0.01 [cm] or more and 100 [cm] or less. In addition, it was found that, from the viewpoint of transmission loss, the radius of curvature R of the curved section 11a1 (see Figure 2, radius of the central axis of the sensor section 11a) is preferably 50 [μm] or more and 200 [μm] or less.
[0058] As described above, in this embodiment, the light receiving unit 22 receives light input from its outer periphery at the sensor unit 11a via the optical fiber 11A. The control unit 30 detects object A based on the light intensity received by the light receiving unit 22.
[0059] With this configuration, for example, the object detection device 10A can be realized with a more compact and simpler configuration based on optical fibers. Furthermore, in the sensor unit 11a, light is input into the sensor unit 11a from its outer periphery. Therefore, compared to a configuration in which light is input to the end face of the optical fiber, a wider detection range can be secured with a simpler configuration.
[0060] Furthermore, as in this embodiment, the length L of the sensor portion 11a may be 10 times or more the wavelength of the light received by the light receiving portion 22.
[0061] With this configuration, for example, the detection range of the sensor unit 11a can be set to be larger.
[0062] Furthermore, as in this embodiment, the sensor unit 11a may be an optical fiber that transmits 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 portion 11a may include a plurality of nanostructures 11p.
[0065] Furthermore, as in this embodiment, the sensor portion 11a may be made of plastic fiber.
[0066] Furthermore, in this embodiment, the delivery optical fiber 11d between the sensor unit 11a and the light source 21 is a multimode optical fiber, and the sensor unit 11a may be a single-mode optical fiber.
[0067] Furthermore, in this embodiment, the sensor unit 11a may be located in a section with higher transmission loss than the delivery optical fiber 11d.
[0068] Furthermore, in this embodiment, the sensor section 11a may be a section where the effective specific refractive index difference is smaller than that of the delivery optical fiber 11d.
[0069] With this configuration, for example, the transmission loss in the sensor unit 11a becomes higher. As a result, external light is more easily input to the sensor unit 11a, and the detection sensitivity of the sensor unit 11a becomes higher.
[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 greater than the effective relative refractive index difference of the sensor unit 11a.
[0072] With this configuration, for example, the delivery optical fiber 11d can perform its respective function of confining and transmitting light, while the sensor unit 11a can perform detection by leaking or receiving light.
[0073] Furthermore, as in this embodiment, the light receiving unit 22 may receive test light that is input from the light source 21 to the optical fiber 11A via end 11e1 (one end), passes through the sensor unit 11a, and is output from end 11e2 (the other end).
[0074] With this configuration, for example, an active object detection device 10A can be realized with a relatively simple configuration. Furthermore, since it is not necessary to provide a light source 21 in a location separate from the optical fiber 11A, the object detection device 10A can be made more compact overall. In addition, in a configuration in which the sensor unit 11a has a curved portion 11a1, the emitted light Le is more likely to be emitted radially outward from the curved portion 11a1, making it easier to detect an object A radially outward from the curve.
[0075] Furthermore, as in this embodiment, the control unit 30 may detect an external force acting on the sensor unit 11a based on the light intensity received by the light receiving unit 22.
[0076] With this configuration, for example, the setup can be simplified compared to a case where a separate device for detecting external forces is provided.
[0077] In addition, the object detection device 10A in this embodiment may be a passive detection device that does not have a light source 21.
[0078] [Second Embodiment] Figure 9 is a side view of the object detection device 10B of the second embodiment. In this embodiment as well, the object detection device 10B is an active detection device.
[0079] As shown in Figure 9, the sensor portion 11a may not have a curved portion and may extend in a straight line. Also, the sensor portion 11a may include a plurality of nanostructures 11p, similar to the first embodiment described above.
[0080] Furthermore, as shown in Figure 9, the light source 21 may be located at a distance from the optical fiber 11B. In this case, the light source 21 and the sensor unit 11a are arranged such that the emitted light Le from the light source 21 is input to the sensor unit 11a from its outer periphery as test light.
[0081] Furthermore, as shown in Figure 9, a light-receiving unit 22 may be provided at each of the longitudinal ends of the optical fiber 11B. In this case, the control unit 30 may detect object A based on the sum or average of the light-receiving intensities of the two light-receiving units 22. Alternatively, the control unit 30 may estimate the position of object A in the direction along the longitudinal direction of the optical fiber 11B (left-right direction in Figure 9) from the difference in light-receiving intensities of the two light-receiving units 22.
[0082] Alternatively, one of the two light-receiving units 22 may be replaced with a reflector or a filter. The reflector keeps the light within the optical fiber 11B. The filter allows light to escape from the optical fiber 11B while preventing light from entering the optical fiber 11B.
[0083] This embodiment also provides the same effects as the above embodiment. In this embodiment as well, the object detection device 10B may be a passive detection device that does not have a light source 21.
[0084] [First modified example of optical fiber] Figure 10 is a side view of a portion of the optical fiber 11C of the first modified example. The optical fiber 11C can be incorporated into the object detection device in place of the optical fiber of the above embodiment.
[0085] As shown in Figure 10, the sensor portion 11a may have no cladding and only a core 11b. In other words, the cladding may be removed from the sensor portion 11a. With this configuration, the outer periphery 11b1 of the core 11b is exposed in the sensor portion 11a. This makes it easier for light from the outside to be input to the sensor portion 11a, and increases the detection sensitivity of the sensor portion 11a. Note that the core 11b does not need to be exposed over the entire length of the sensor portion 11a; it is sufficient for the outer periphery 11b1 of the core 11b to be exposed in at least a part of the sensor portion 11a. The outer periphery 11b1 may also be called the outer surface.
[0086] In this case, the outer periphery 11b1 may also be provided with an uneven structure (not shown) including recesses or protrusions. If the size of the uneven structure, for example, the length and spacing 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 via the outer periphery 11b1, Rayleigh scattering will occur at the interface of the outer periphery 11b1, making it easier for the light from the outside to enter the core 11b. Also, if the size of the uneven structure is less than 1 / 100 of the wavelength of light, the outer periphery 11b1 will be smoothed, making it less likely 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 via the outer periphery 11b1, i.e., the wavelength of light received by the light receiving unit 22.
[0087] The delivery optical fiber 11d has a core 11d1 and a cladding 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, for example, by fusion splicing.
[0088] [Second variation of optical fiber] Figure 11 is a side view of a portion of the optical fiber 11D of the second modified example. The optical fiber 11D can be incorporated into the object detection device in place of the optical fiber of the above embodiment.
[0089] As shown in Figure 11, the sensor portion 11a, in which at least a portion of the outer periphery 11b1 of the core 11b is exposed, may have a curved portion 11a1. With such a configuration, the curvature of the core 11b allows external light to enter the core 11b more easily, and the detection sensitivity of the sensor portion 11a is increased.
[0090] [Third modified example of optical fiber] Figure 12 is a side view of a portion of the optical fiber 11E of the third modified example. The optical fiber 11E can be incorporated into the object detection device in place of the optical fiber of the above embodiment.
[0091] As shown in Figure 12, the sensor portion 11a, in which at least a portion of the outer periphery 11b1 of the core 11b is exposed, may be divided in the middle, exposing the end face 11b2 in the longitudinal direction (optical axis direction). The end face 11b2 is a surface that intersects 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 portion 11a becomes higher. In this modified example, the sensor portion 11a may be made by cutting the core 11b, or it may be composed of two separately made parts. Also, the two end faces 11b2 may be in contact with each other. Furthermore, the core 11b may be partially connected and partially separated, with the end face 11b2 partially exposed.
[0092] [Fourth variation of optical fiber] Figure 13 is a side view of a portion of the optical fiber 11F of the fourth modified example. The optical fiber 11F can be incorporated into the object detection device in place of the optical fiber of the above embodiment.
[0093] As shown in Figure 13, the sensor unit 11a may have multiple curved sections 11a1. With such a configuration, as the number of curved sections 11a1 increases, external light can enter the core 11b more easily, and the detection sensitivity of the sensor unit 11a becomes higher.
[0094] [Fifth variation of optical fiber] Figure 14 is a side view of a portion of the optical fiber 11G of the fifth modified example. The optical fiber 11G can be incorporated into the object detection device in place of the optical fiber of the above embodiment.
[0095] As shown in Figure 14, the sensor portion 11a may be configured in a coil shape. The coil may be elliptical or oblong when viewed in the direction of the winding axis of the coil. The coil may also be configured by winding it around a core member (not shown). In this case, the core member may be a strip-shaped member with a rounded edge. In this modified example as well, the sensor portion 11a has a plurality of curved portions 11a1. Therefore, with this configuration, as the number of curved portions 11a1 increases, external light can enter the core 11b more easily, and the detection sensitivity of the sensor portion 11a becomes higher.
[0096] Although embodiments of the present invention have been illustrated above, these 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, each configuration, shape, and other specifications (structure, type, orientation, model, size, length, width, thickness, height, number, arrangement, position, material, etc.) can be modified as appropriate.
[0097] For example, in the above embodiment and its modifications, the optical fiber is formed by connecting the sensor part (sensor optical fiber) and the delivery optical fiber to each other, but it is not limited to this, and the sensor part may be created in a part of the optical fiber by performing local processing on the optical fiber.
[0098] Furthermore, for example, optical fibers with 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, such 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 unit (sensor optical fiber) 11a1...Curved section 11b... Core 11b1…outer circumference 11b2...End face (exposed end face) 11c...Clad 11d... Delivery Fiber Optic 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) t1…Time
Claims
1. An optical fiber that includes at least a portion of the sensor portion of a sensor optical fiber including a core and cladding, The optical fiber comprises a first light-receiving unit and a second light-receiving unit, which are located at each of the longitudinal ends of the optical fiber. A calculation processing unit that estimates the position or movement speed of the object in the longitudinal direction of the optical fiber based on the difference between the light reception intensity at the first light receiving unit and the light reception intensity at the second light receiving unit of the light input to the sensor unit via the object, Equipped with, The transmission loss of the sensor unit to the input light is 0.3 [dB / m] or more. An object detection device in which the outer circumference of the core is at least partially exposed.
2. An optical fiber comprising at least a portion of a sensor portion of a sensor optical fiber including a core and a cladding, The optical fiber comprises a first light-receiving unit and a second light-receiving unit, which are located at each of the longitudinal ends of the optical fiber. A calculation processing unit that detects the object based on the sum or average of the light intensity received by the first light receiving unit and the light intensity received by the second light receiving unit, which are input to the sensor unit via the object, Equipped with, The transmission loss of the sensor unit to the input light is 0.3 [dB / m] or more. An object detection device in which the outer circumference of the core is at least partially exposed.
3. The object detection device according to claim 2, wherein the calculation processing unit estimates the position or moving speed of the object in the longitudinal direction of the optical fiber based on the difference between the light reception intensity at the first light receiving unit and the light reception intensity at the second light receiving unit.
4. The object detection device according to any one of claims 1 to 3, wherein the length of the sensor optical fiber is 10 times or more the wavelength of the light received by the first light receiving unit and the second light receiving unit.
5. The object detection device according to any one of claims 1 to 4, wherein a light source that inputs test light to the optical fiber is arranged away from the sensor unit.
6. An object detection device according to any one of claims 1 to 4, which is a passive detection device that does not have a light source for inputting test light to the optical fiber.