Optical fiber sensor

Abstract

The utility model provides an optical fiber sensor capable of inhibiting the incidence of interference light to a light receiving element for monitoring the luminous quantity of a light-emitting element so as to realize miniaturization and high coupling of light. An optical fiber sensor is provided with: a substrate; a light-emitting element which is mounted on the substrate and projects light to the optical fiber; a light-receiving element which is mounted on the substrate and monitors the amount of light emitted by the light-emitting element; and an optical fiber holding member that holds the optical fiber. The optical fiber holding member includes: a hole into which an optical fiber is inserted; an opening between the light emitting element and the hole; and a light shielding part which is located on the outer side of the opening in the radial direction and is located between the light receiving element and the hole.

Description

Technical Field

[0001] The present disclosure relates to an optical fiber sensor. Background Art

[0002] Fiber optic sensors are used to connect various optical fibers to devices such as fiber amplifiers. They consist of a hole for inserting the optical fiber, a light-emitting element that projects light onto the end face of the inserted optical fiber, and a monitoring light-receiving element that monitors the light-emitting element's emission intensity. By monitoring whether the light-emitting element maintains an appropriate emission intensity, the monitoring light-receiving element enables the fiber optic sensor to transmit appropriate signals.

[0003] Patent Document 1 discloses a photoelectric sensor as a fiber optic sensor. The photoelectric sensor's light-projecting components include a light-emitting element, a monitoring light-receiving element, and a reflector. The monitoring light-receiving element detects the amount of light emitted by the light-emitting element and performs feedback control of the light-emitting element to maintain the detected light-emission amount at a predetermined value.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-170394 Utility Model Content

[0007] Issues to be solved by the utility model

[0008] The reflector, positioned between the light-emitting element and the end face of the optical fiber, guides light from the light-emitting element toward the optical fiber, maintaining a specified distance between them. To minimize the overall device size and improve the optical coupling efficiency, the optical fiber end face is preferably placed close to the light-emitting element. However, if the distance is too close, unintended interference light, such as reflected light from the optical fiber end face, may enter the monitoring light-receiving element, potentially preventing accurate monitoring of the light emission level. For example, this could cause unintended feedback, potentially reducing the brightness of the light-emitting element, making stable sensing difficult.

[0009] The present disclosure provides an optical fiber sensor capable of suppressing the incidence of disturbance light on a light-receiving element for monitoring the light emission amount of a light-emitting element, thereby achieving miniaturization and high optical coupling.

[0010] Solutions to Problems

[0011] One embodiment of the present disclosure is an optical fiber sensor, wherein the optical fiber sensor comprises: a substrate; a light-emitting element mounted on the substrate for projecting light onto the optical fiber; a light-receiving element mounted on the substrate for monitoring the amount of light emitted by the light-emitting element; and an optical fiber holding component for holding the optical fiber, the optical fiber holding component comprising: a hole for inserting the optical fiber; an opening located between the light-emitting element and the hole; and a light-shielding portion located radially outside the opening and between the light-receiving element and the hole.

[0012] Utility model effect

[0013] According to the present disclosure, it is possible to suppress the incidence of disturbance light on a light-receiving element for monitoring the light emission amount of a light-emitting element, thereby achieving miniaturization and high optical coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a perspective view of an optical fiber sensor according to an embodiment of the present disclosure.

[0015] Figure 2 These are stereograms of fiber optic sensors, (A) is a stereogram of the finished product, and (B) is an exploded stereogram.

[0016] Figure 3 It is a perspective view of the optical fiber holding component.

[0017] Figure 4 This is a perspective view of the optical fiber holding component viewed from the light projecting module side. Figure 2 (B) Enlarged view of part B.

[0018] Figure 5 This is a perspective view of the optical fiber holding member viewed from the side of the hole for inserting the optical fiber.

[0019] Figure 6 yes Figure 1 Enlarged cross-sectional view of part A on the XZ plane.

[0020] Figure 7 It shows Figure 6 A perspective cutaway view of a portion of a .

[0021] Figure 8 yes Figure 6 The C1 part and Figure 7 An enlarged cross-sectional view of the C2 portion.

[0022] Figure 9 Therefore Figure 1 An enlarged cross-sectional view of the XZ plane of the optical fiber sensor.

[0023] Description of Reference Numerals

[0024] 1: Fiber optic sensor, 10: Main body, 31: PCB substrate (an example of a substrate), 50: Fiber holding component, 51: Main body block, 52: Clamping member, 53: Clamping rod, 54: Light projecting module, 55: Light receiving module, 56: Molded portion, 57: Lens, 58: LED (an example of a light-emitting element), 62: Hole, 62a: First abutting portion, 63: Opening, 63a: Second abutting portion, 64: Light-shielding wall, 80: Monitoring light receiving element (an example of a light receiving element), 90: Screw, 101: First optical fiber (an example of an optical fiber), 102: Second optical fiber (an example of an optical fiber), 120: Other optical fibers, L1, L2, L3: Light, L3A: Reflected light. DETAILED DESCRIPTION

[0025] The following describes the embodiments in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming too lengthy and to make it easier for those skilled in the art to understand. It should be noted that the drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure and are not intended to limit the subject matter described in the technical solution.

[0026] Figure 1 It is a perspective view of the optical fiber sensor 1 according to the embodiment of the present disclosure.

[0027] The optical fiber sensor 1 has a thin, box-like shape and has holes 62 and 70 on one side for inserting optical fibers (described later). The optical fiber sensor 1 is configured as follows: a light projector and a light receiver are connected to corresponding optical fibers, with the tips of the light projector and light receiver positioned so they can detect an object. In this example, light emitted from the light projector propagates through the optical fiber connected to hole 62 and exits from the other end. Light reflected from the object propagates through the optical fiber connected to hole 70 and enters the light receiver. Light entering the photoelectric converter element of the light receiver is converted into an electrical signal and amplified by a light receiving amplifier. For example, the optical fiber sensor 1 uses a comparator circuit to compare this electrical signal with a predetermined threshold value to determine the presence of an object, measure the amount of received light, or perform processing based on the amount of received light. The results of the object determination, light measurement, or processing based on the amount of received light can be output to a PLC (Programmable Logic Controller) device, for example.

[0028] It should be noted that coordinates are defined and used in the following description, including the X-axis along the length direction of the optical fiber sensor 1, the Y-axis along the width direction of the optical fiber sensor 1, and the Z-axis along the height direction of the optical fiber sensor 1. The positive side of the Z-axis is referred to as "up," and the negative side of the Z-axis is referred to as "down."

[0029] Figure 2 These are stereograms of fiber optic sensors, (A) is a stereogram of the finished product, and (B) is an exploded stereogram. Figure 3 It is a perspective view of the optical fiber holding component. Figure 4 This is a perspective view of the optical fiber holding component viewed from the light projecting module side. Figure 2 (B) Enlarged view of part B. Figure 5 This is a perspective view of the optical fiber holding member viewed from the side of the hole for inserting the optical fiber.

[0030] like Figure 2 As shown in (B), the optical fiber sensor 1 includes a main body 10 and an optical fiber holding member 50. The main body 10 primarily generates and processes electrical signals. It includes a first housing 21, a second housing 22, an indicator 23, a display cover 24, a cover 25, a NET (Network) lens 26, a guide rail stopper 27, a display 28, a shield substrate 29, screws 30, a PCB (Printed Circuit Board) substrate 31, a pin header 32, and a resin cable 33.

[0031] like Figure 3 As shown in FIG. 1 and FIG. 2 , the optical fiber holding member 50 is an integrated module member. Figure 4 Too Figure 2 (B) Enlarged view of part B. Figure 4 as well as Figure 5 As shown, the optical fiber holding component 50 includes a main body block 51, a clamping member 52 and a clamping rod 53. It should be noted that, Figure 3 The perspective view shows a state where the clamping rod 53, the light projecting module 54, and the light receiving module 55 are removed.

[0032] The main body block 51 is the main component of the optical fiber holding component 50, and a through hole 62A constituting a part of the hole 62 is formed inside. In addition, it includes a hole for assembling the optical fiber holding component 50 to the first shell 21. The optical fiber holding component 50 is positioned by pressing the convex portion of the first shell 21 into the hole. The clamping member 52 acts as a cover for one side of the optical fiber sensor 1 when installed on the main body 10. A through hole 62B constituting a part of the hole 62 is formed inside the clamping member 52. When the main body block 51 and the clamping member 52 are combined, the through hole 62A is connected to the through hole 62B to form the hole 62. As shown in FIG. Figure 1As shown, the hole 62 is exposed from one side surface of the optical fiber sensor 1 formed by the clamping member 52. The main body block 51 is made of, for example, a conductive resin.

[0033] A clamping lever 53 is provided at one end of the main body block 51. The clamping lever 53 is used to lock the optical fiber after it has been inserted into the holes 62 and 70. When the clamping lever 53 is open (unlocked), the optical fiber is inserted into the holes 62 and 70. When the clamping lever 53 is closed (locked), the clamping lever 53 is secured to the optical fiber by friction, preventing it from falling out of the holes 62 and 70.

[0034] The light projecting module 54 functions as a light projecting unit that projects light to the optical fiber connected to the hole 62. Figure 5 As shown, the light projecting module 54 includes a lens 57 and a light-emitting element, namely an LED (Light Emitting Diode) 58, which serves as a light source. Lens 57 is positioned approximately in the center of the light projecting module 54 by forming a molded portion 56 made of a light-projecting resin. The molded portion 56 includes a portion shaped like lens 57, which enables light to be concentrated and highly coupled. LED 58 is mounted on the PCB substrate 31 by soldering or other means and is electrically connected to the light projecting module 54 via a cable or other means. The light receiving module 55 functions as a light receiving unit, which receives light from an optical fiber connected to another hole 70 provided in the optical fiber holding component 50.

[0035] Figure 6 yes Figure 1 An enlarged cross-sectional view of the XZ plane of part A, Figure 7 It shows Figure 6 A stereogram of a portion of . Figure 6 、 Figure 7 The connection between the optical fiber holding member 50 and the optical fiber will be described in detail.

[0036] like Figure 6 As shown by the dotted line, the first optical fiber 101 or the second optical fiber 102 is inserted into the innermost portion of the hole 62 (the innermost portion in the X-axis direction, the positive end). The first optical fiber 101 and the second optical fiber 102 are flexible. The diameters of the first optical fiber 101 and the second optical fiber 102 differ (described later). The tip of the first optical fiber 101 or the second optical fiber 102 faces the lens 57 of the light projection module 54 at the innermost portion of the hole 62. An LED 58 is disposed behind the lens 57, and light emitted from the LED 58 passes through the lens 57 and reaches the tip of the first optical fiber 101 or the second optical fiber 102.

[0037] The other optical fiber 120 is inserted into the innermost portion (the innermost portion in the X-axis direction) of the hole 70 . At the innermost portion of the hole 70 , the tip of the other optical fiber 120 faces the light receiving module 55 , and light emitted from the tip of the other optical fiber 120 reaches the light receiving module 55 .

[0038] Figure 8 yes Figure 6 The C1 part and Figure 7 Enlarged cross-sectional view of portion C2 of the PCB substrate 31. The LED 58 is mounted on the PCB substrate 31 and projects light toward the first optical fiber 101 or the second optical fiber 102. In addition, a monitoring light receiving element 80 that monitors the light emission of the LED 58 is mounted on the PCB substrate 31. The monitoring light receiving element 80 monitors whether the LED 58 maintains an appropriate light emission by receiving the light projected by the LED 58 toward the optical fiber. The monitoring light receiving element 80 feeds back the light emission of the LED 58, that is, the light emission brightness, to a prescribed control circuit such as an APC (Automatic Power Control) control circuit. The control circuit controls the LED 58 based on the feedback signal so as to maintain a constant light emission (constant brightness). Through such control, the optical fiber sensor 1 is able to send an appropriate signal. The APC control circuit is, for example, mounted on the PCB substrate 31.

[0039] At least one of the LED 58 , the monitoring light receiving element 80 , and the APC control circuit may be directly mounted on the PCB substrate 31 , or may be connected to the PCB substrate 31 when mounted on the light projecting module 54 .

[0040] The LED 58 projects light, for example, from the surface (i.e., the top surface) of the optical fiber retaining member 50 facing the hole 62. In this case, the LED 58 emits light, for example, from the top surface toward the negative side of the X-axis, with a light emission range of approximately 180 degrees. It should be noted that the light intensity is higher in the direction along the X-axis (the top surface), i.e., the amount of light is higher, while the light intensity decreases in the direction away from the X-axis (the side surface), i.e., the amount of light decreases. This allows the optical fiber sensor 1 to perform stable sensing while maintaining high light coupling to the optical fiber.

[0041] As described above, the optical fiber holding member 50 includes the hole 62 for inserting the optical fiber. The optical fiber holding member 50 further includes an opening 63 located between the LED 58 and the hole 62, and a light-shielding wall 64 located radially outward of the opening 63 and between the monitoring light-receiving element 80 and the hole 62. In this embodiment, the optical fiber holding member 50 includes a light-shielding portion having a light-shielding function between the monitoring light-receiving element 80 and the hole 62, and the light-shielding wall 64 is illustrated as an example of the light-shielding portion.

[0042] The opening 63 is a space portion formed continuously from the innermost portion of the hole 62. The light shielding wall 64 is formed in an annular shape to surround the opening 63 radially outward. In this embodiment, the light shielding wall 64 is formed integrally with the main body of the optical fiber holding member 50, and no additional component is used for the light shielding wall 64.

[0043] The light-shielding wall 64 also includes a first abutting portion 62a, which faces the innermost portion of the hole 62 and is capable of abutting the first fiber end face of the first optical fiber 101. Furthermore, the opening 63 is formed continuously with the hole 62, closer to the LED 58 than the hole 62. The light-shielding wall 64 also includes a second abutting portion 63a, which faces the opening 63 and has a smaller diameter than the first abutting portion 62a. The second fiber end face of the second optical fiber 102, which has a smaller diameter than the first optical fiber 101, can abut the second abutting portion 63a. The diameter of the first optical fiber 101 is, for example, 2.2 mm (φ2.2). The diameter of the second optical fiber 102 is, for example, 1.0 mm (φ1.0) or 0.75 mm (φ0.75). By having the first abutting portion 62a and the second abutting portion 63a of different diameters in the optical fiber holding member 50, the optical fiber sensor 1 can position optical fibers of varying diameters at desired locations without requiring special positioning components. It should be noted that the LED 58 of the light projection module 54 is arranged so as to face the first contact portion 62 a and the second contact portion 63 a .

[0044] Thus, the optical fiber holding member 50 can hold optical fibers of various diameters and can realize a fiber stopper function of fixing the optical fiber at a constant position, thereby realizing stable sensing.

[0045] It should be noted that while the example illustrates a stepped structure formed by the first abutting portion 62a located near the front and the second abutting portion 63a located in the back (closer to the LED 58) when viewed from the optical fiber side, a stepped structure may also be formed by three or more abutting portions. For example, by configuring the optical fiber sensor 1 so that the diameter of the abutting portion decreases as it approaches the LED 58, it can accommodate optical fibers of various diameters.

[0046] Next, the behavior of light projected from the LED 58 will be described.

[0047] Light L1 projected directly upward from LED 58 travels straight ahead without being reflected by the optical fiber. Furthermore, light L2, which enters the end face of the optical fiber at a relatively low angle of incidence, mostly travels within the fiber, with a portion reflected as indicated by the dashed line. However, since the reflection angle is also relatively low, reflected light L2A, as indicated by the dashed line, does not reach the monitoring light receiving element 80.

[0048] On the other hand, light L3 that enters the end face of the optical fiber at a large incident angle partially propagates within the optical fiber, while a portion is reflected as indicated by the dashed line. In this case, due to the large reflection angle, if light-shielding wall 64 were not present, reflected light L3A could potentially reach monitoring light-receiving element 80 as indicated by the dashed line. Since reflected light L3A is not the light originally emitted by LED 58, if reflected light L3A reaches monitoring light-receiving element 80, it may not be able to accurately monitor the light emission of LED 58, and the control circuit may not be able to correctly control the light emission of LED 58.

[0049] In this embodiment, the light-shielding wall 64 serves to block light, such as reflected light L3A, projected from the LED 58 that is not intended to reach the monitoring light-receiving element 80. Therefore, even when the optical fiber is brought close to the LED 58, the reflected light L3A projected from the LED 58 and reflected from the end face of the optical fiber inserted into the hole 62 is blocked by the light-shielding wall 64, thereby preventing the LED 58 from receiving light. Specifically, the reflected light L3A stops at a predetermined position P on the inner surface of the light-shielding wall 64, i.e., at the opening 63. Furthermore, since the distance between the optical fiber and the LED 58 can be kept close, optical coupling can be ensured while miniaturizing the optical fiber sensor 1.

[0050] Furthermore, the presence of the light shielding wall 64 eliminates the need to excessively reduce the opening 63, thereby suppressing a decrease in the coupling force of light from the LED 58 to the optical fiber. Furthermore, in the embodiment, there is no need to provide any other components, such as a light guide member for guiding light to the monitoring light receiving element 80, and a portion of the optical fiber holding member 50 required to hold the optical fiber serves as the light shielding wall 64, thereby enabling the optical fiber sensor 1 to be miniaturized and costs to be suppressed.

[0051] Furthermore, the optical fiber retaining member 50 is formed, for example, from an optically opaque material. An optically opaque color is one that does not transmit light (is not translucent), such as black. Furthermore, the LED 58 is located along an extension of the length of the hole 62. In other words, the LED 58 and the optical fiber are coaxially arranged.

[0052] Thus, since the optical fiber holding member 50 has an optically opaque color, leakage of light from the LED 58 toward the monitoring light receiving element 80 or leakage of light from the optical fiber toward the monitoring light receiving element 80 can be suppressed by the optical fiber holding member 50. Furthermore, since the LED 58 and the optical fiber are coaxially arranged, high optical coupling can be achieved.

[0053] Next, the light projection module 54 will be described.

[0054] The light projecting module 54 includes (at least a portion of) the PCB substrate 31, an LED 58, and a monitoring light receiving element 80. Furthermore, the light projecting module 54 includes a molded portion 56, which is formed from a light-transmitting resin and has light-transmitting properties. This molded portion 56 molds the PCB substrate 31, the LED 58, and the monitoring light receiving element 80. A portion of the light projected from the LED 58, such as light L4, is reflected off the inner surface of the molded portion 56 and directed to the monitoring light receiving element 80.

[0055] Thus, light from LED 58 reaches monitoring light receiving element 80 by being reflected once or more on the inner surface of mold portion 56 of light projecting module 54 , and thus can be received by monitoring light receiving element 80 .

[0056] The surface of the PCB substrate 31 on which the LED 58 and the monitoring light-receiving element 80 are mounted is, for example, optically opaque. This allows the optical fiber sensor 1 to absorb a certain amount of light through the PCB substrate 31, thereby suppressing light leakage from the PCB substrate 31 to the outside of the PCB substrate 31 or diffuse reflection within the light projection module 54. The optically opaque color of the PCB substrate 31 can be achieved, for example, by applying a black coating or black resist.

[0057] Next, the positional relationship between the LED 58 and the monitoring light-receiving element 80 will be described.

[0058] like Figure 8 As shown, let D be the radial distance between the LED 58 and the monitoring light-receiving element 80, d be the distance from the LED 58 to the light-shielding wall 64 along the axial direction (insertion direction) of the optical fiber, the critical angle θc at which light projected from the LED 58 enters the light-shielding wall 64, the refractive index of the molded portion 56 be n1, and the refractive index of the light-shielding wall 64 be n2 (n1>n2). Under these conditions, it is preferable to set the radial distance D between the LED 58 and the monitoring light-receiving element 80 to be longer than the shortest distance Dmin expressed by the following (Equation 3). The shortest distance Dmin is the shortest radial distance between the LED 58 and the monitoring light-receiving element 80. The shortest distance Dmin is the shortest distance that light projected from the LED 58 can reach the monitoring light-receiving element 80 after undergoing a single total internal reflection at the boundary between the molded portion 56 and the light-shielding wall 64.

[0059] Specifically, when light enters the light-shielding wall 64 (fiber holding member 50) from the molded portion 56, if n1 > n2 and the incident angle θ is greater than the critical angle θc, the light does not enter the light-shielding wall 64 from the molded portion 56 but is totally reflected at the boundary between the molded portion 56 and the light-shielding wall 64. According to Snell's law, the following (Equation 1) holds.

[0060]

[0061] Meanwhile, the relationship between the distance d from the LED 58 to the light shielding wall 64 in the axial direction of the optical fiber, the shortest distance Dmin between the LED 58 and the monitoring light receiving element 80 , and the critical angle θc is expressed by the following (Equation 2).

[0062]

[0063] Therefore, when the incident angle θ is the critical angle θc, the shortest distance Dmin along the radial direction between the LED 58 and the monitoring light receiving element 80 is expressed by the following (Formula 3). ” represents the multiplication sign.

[0064]

[0065] Furthermore, when the critical angle θc is expressed using the refractive index n1 and the refractive index n2, it is expressed by the following (Formula 4).

[0066]

[0067] As described above, the shortest distance Dmin can be defined using the critical angle θc (sinθc=n2 / n1) for total reflection of light projected from LED 58. Distance D is longer than the shortest distance Dmin. Therefore, the following (Equation 5) is satisfied.

[0068]

[0069] That is, the monitoring light receiving element 80 is arranged at a position farther than the position on the PCB substrate 31 where the light projected from the LED 58 reaches when it is reflected once at the critical angle θc on the surface of the light shielding wall 64 (the inner surface of the mold portion 56 ).

[0070] Through such a configuration relationship between LED58 and the monitoring light receiving element 80, the optical fiber sensor 1 can prevent any light that passes through the opening 63 and is reflected at the end face of the optical fiber from reaching the monitoring light receiving element 80, and can allow light reflected by the molded part 56 or the light shielding wall 64 of the light projection module 54 to be incident on the monitoring light receiving element 80.

[0071] Thus, the optical fiber sensor 1 can prevent reflected light from the optical fiber end face from reaching the monitoring light receiving element 80. Therefore, the optical fiber sensor 1 can accurately measure only the amount of light projected from the LED 58 and reflected by the light shielding wall 64, thereby accurately controlling the LED 58 and performing stable sensing.

[0072] Next, the electrical connection of each component in the optical fiber sensor 1 will be described.

[0073] Figure 9 Therefore Figure 1 The XZ plane of the optical fiber sensor is an enlarged cross-sectional view of the cross section. Figure 9 , a portion of the optical fiber sensor 1 on the negative side of the X axis is shown.

[0074] The optical fiber holding member 50 is made of, for example, a conductive resin and has conductivity. In addition, the PCB substrate 31 and the screw 90 also have conductivity. The screw 90 is, for example, a self-tapping screw. The screw 90 passes through the through hole of the PCB substrate 31. Figure 9 As shown, screws 90 sandwich the ground electrode pad (not shown) on the PCB substrate 31 and the optical fiber holder 50, securing them to the housing of the optical fiber sensor 1. This allows the optical fiber holder 50 to be electrically connected to the ground of the PCB substrate 31, thereby ensuring stable electrical connection to components on the PCB substrate 31 (e.g., the LED 58 and the monitoring light-receiving element 80). Consequently, by electrically connecting the optical fiber holder 50 to the ground of the PCB substrate 31 via screws 90, the optical fiber sensor 1 can reduce electrical noise through a shielding effect.

[0075] As described above, the optical fiber sensor 1 of this embodiment uses the light-shielding wall 64 to block reflected light from the end face of the optical fiber inserted into the hole 62, thereby preventing the monitoring light-receiving element 80 from receiving light other than the light from the LED 58. Furthermore, the end face of an optical fiber may not be a desired flat surface. For example, it may have uneven surfaces due to cleaving, or may be oriented obliquely relative to the direction of the optical fiber's extension. Even in such cases, the optical fiber sensor 1 can prevent the monitoring light-receiving element 80 from receiving extra light using the light-shielding wall 64.

[0076] Furthermore, the presence of the light-shielding wall 64 in the optical fiber sensor 1 eliminates the need to excessively reduce the opening 63, thereby suppressing a decrease in the coupling force of light from the LED 58 to the optical fiber. Furthermore, as detection targets (workpieces) become increasingly smaller, the SN ratio tends to decrease when detecting smaller workpieces. However, the optical fiber sensor 1 can suppress a decrease in the coupling force of light, enabling stable detection of workpieces.

[0077] Furthermore, the optical fiber holding member 50 has a light-shielding function due to the light-shielding wall 64. This eliminates the need for a dedicated light-shielding component on, for example, the surface of the monitoring light-receiving element 80. This increases design freedom and contributes to the miniaturization of the optical fiber sensor 1. Furthermore, the optical fiber holding member 50 is also conductive, eliminating the need for a dedicated electromagnetic shielding component and stabilizing the electrical characteristics.

[0078] Furthermore, in the optical fiber sensor 1, the light-shielding wall 64, which faces the innermost portion of the hole 62 and the opening 63, also serves as a stopper. This allows the optical fiber sensor 1 to maintain a constant insertion distance of the optical fiber (e.g., the first optical fiber 101 or the second optical fiber 102) into the hole 62, thereby securing the optical fiber at a constant position and stabilizing optical coupling.

[0079] In addition, the optical fiber holding component 50 is optically opaque and conductive, so through the ground electrical connection with the PCB substrate 31, it can electromagnetically shield the entire optical fiber sensor 1 and suppress the interference of electrical noise on the monitoring light receiving element 80.

[0080] By forming the optical fiber holding member 50 having such a function as an integral component, the optical fiber sensor 1 can improve assemblability, reduce the number of components, and further achieve cost reduction.

[0081] While various embodiments have been described above with reference to the accompanying drawings, the present invention is not limited to such examples. It is apparent that those skilled in the art will be able to devise various variations or modifications within the scope of the technical solution, and will understand that these variations and modifications also fall within the technical scope of the present invention. Furthermore, the various components of the above embodiments may be arbitrarily combined without departing from the spirit of the present invention.

[0082] <Overview of this embodiment>

[0083] Based on the above, at least the following matters are described in this disclosure. It should be noted that, although the corresponding components and the like in the above embodiment are exemplified in parentheses, the present invention is not limited thereto.

[0084] (Item 1)

[0085] An optical fiber sensor (optical fiber sensor 1) having:

[0086] Substrate (PCB substrate 31);

[0087] a light emitting element (LED 58 ) mounted on the substrate and projecting light toward the optical fibers (the first optical fiber 101 and the second optical fiber 102 );

[0088] a light receiving element (monitoring light receiving element 80 ) mounted on the substrate to monitor the amount of light emitted by the light emitting element; and

[0089] An optical fiber holding member (optical fiber holding member 50) that holds the optical fiber.

[0090] The optical fiber holding component comprises:

[0091] a hole (hole 62) for inserting the optical fiber;

[0092] an opening (opening 63 ) located between the light emitting element and the hole; and

[0093] The light shielding portion (light shielding wall 64 ) is located radially outside the opening and between the light receiving element and the hole.

[0094] Thus, even when the optical fiber is brought close to the light-emitting element, the light reflected from the light-emitting element and reflected by the end face of the optical fiber inserted into the hole is blocked by the light shield, thereby preventing the light-receiving element from receiving light. Furthermore, the presence of the light shield eliminates the need to excessively reduce the opening, thereby preventing a reduction in the coupling force of light from the light-emitting element to the optical fiber. Furthermore, since no additional components are required, and a portion of the optical fiber retaining member required to retain the optical fiber serves as the light shield, miniaturizing the optical fiber sensor.

[0095] (Item 2)

[0096] Based on the optical fiber sensor described in item 1,

[0097] The optical fiber sensor also has a light projection module.

[0098] The light projection module has:

[0099] The substrate, the light emitting element, the light receiving element, and a mold portion (mold portion 56 ) having light transparency and molding the substrate, the light emitting element, and the light receiving element,

[0100] Light projected from the light emitting element is guided to the light receiving element by reflection at the inner surface of the molded portion.

[0101] Thus, light from the light emitting element reaches the light receiving element due to reflection at the inner surface of the mold portion of the light projecting module, and the light receiving element can receive the light.

[0102] (Item 3)

[0103] In the optical fiber sensor described in item 1 or 2, wherein:

[0104] The surface of the substrate on which the light emitting element and the light receiving element are mounted has an optically opaque color.

[0105] This can suppress light from leaking from the substrate side to the outside of the substrate.

[0106] (Item 4)

[0107] In the optical fiber sensor according to any one of items 1 to 3,

[0108] The light shielding portion has:

[0109] a first abutting portion (first abutting portion 62 a ) facing the innermost portion of the hole and capable of abutting against a first fiber end face of a first optical fiber (first optical fiber 101 ) serving as the optical fiber; and

[0110] The second abutment portion (second abutment portion 63a) is opposite to the opening and is formed continuously with the first abutment portion. The radius of the second abutment portion is smaller than that of the first abutment portion, and the second optical fiber end face of the second optical fiber (second optical fiber 102) having a smaller radius than that of the first optical fiber can abut against it.

[0111] Thus, the optical fiber sensor can hold optical fibers of various diameters, and the light shielding portion can realize a fiber stopping function in addition to the light shielding function, thereby preventing the light shielding portion from contacting the light emitting element.

[0112] (Item 5)

[0113] In the optical fiber sensor according to any one of items 1 to 4,

[0114] The optical fiber sensor further includes a lens (lens 57 ) disposed between the opening and the light emitting element.

[0115] Thus, in the optical fiber sensor, the first and second abutment portions abut the optical fiber, preventing it from reaching the lens further inward than the opening. Consequently, the optical fiber end face of the optical fiber does not contact the lens, preventing damage to the lens and breakage of the light-emitting element, thereby enabling stable detection. Furthermore, the optical fiber sensor can use the lens to focus light projected from the light-emitting element, increasing its intensity and allowing it to enter the optical fiber.

[0116] (Item 6)

[0117] In the optical fiber sensor according to any one of items 1 to 5,

[0118] The optical fiber holding member is formed of an optically opaque and conductive member, and the light emitting element is located on an extension line of the hole in the longitudinal direction.

[0119] Thus, because the optical fiber retaining member has an optically opaque color, it can suppress light leakage from the light-emitting element to the light-receiving element, or light leakage from the optical fiber to the light-receiving element. Furthermore, because the optical fiber retaining member is conductive, it can be electrically connected to, for example, the ground of the substrate, thereby ensuring stable electrical connection to components on the substrate (e.g., the light-emitting element, the light-receiving element, etc.).

[0120] (Item 7)

[0121] In the optical fiber sensor according to any one of items 1 to 6,

[0122] The light emitting element and the light receiving element are arranged on the same plane.

[0123] As a result, in the optical fiber sensor, the light emitting element and the light receiving element can be efficiently arranged, so that light from the light emitting element can be easily incident on the light receiving element.

[0124] (Item 8)

[0125] In the optical fiber sensor according to any one of items 1 to 7,

[0126] The distance from the light emitting element to the light shielding portion along the length direction of the hole is d, and the angle when the incident angle of the light projected from the light emitting element to the light shielding portion is the critical angle is θc. Under the condition of multiplication sign, the distance D between the light emitting element and the light receiving element is greater than 2d The distance of Tanθc (the shortest distance Dmin) is the longest distance.

[0127] This prevents reflected light from the optical fiber end face from reaching the light-receiving element. Therefore, the amount of light projected from the light-emitting element and reflected by the light-shielding portion can be accurately measured, enabling accurate control of the light-emitting element and stable sensing.

[0128] (Item 9)

[0129] In the optical fiber sensor according to any one of items 1 to 8,

[0130] The light emitting element projects light only from a surface of the optical fiber holding member on the hole side.

[0131] As a result, the optical fiber sensor can perform stable sensing while keeping costs low while maintaining high coupling of light to the optical fiber.

[0132] Industrial Applicability

[0133] The present disclosure is useful in an optical fiber sensor or the like that can suppress the incidence of disturbance light on a light-receiving element for monitoring the light emission amount of a light-emitting element, thereby achieving miniaturization and high optical coupling.

Claims

1. An optical fiber sensor, characterized in that: The optical fiber sensor has: substrate; a light emitting element mounted on the substrate and projecting light toward the optical fiber; a light receiving element mounted on the substrate to monitor the light emission of the light emitting element; as well as an optical fiber holding component for holding the optical fiber, The optical fiber holding component comprises: a hole for inserting the optical fiber; an opening located between the light emitting element and the hole; and The light shielding portion is located outside the opening in a radial direction and between the light receiving element and the hole.

2. The optical fiber sensor according to claim 1, wherein The optical fiber sensor also has a light projection module. The light projection module includes: the substrate, the light emitting element, the light receiving element, and a light-transmitting mold portion that molds the substrate, the light emitting element, and the light receiving element. Light projected from the light emitting element is guided to the light receiving element by reflection at the inner surface of the molded portion.

3. The optical fiber sensor according to claim 1 or 2, characterized in that The surface of the substrate on which the light emitting element and the light receiving element are mounted has an optically opaque color.

4. The optical fiber sensor according to claim 1 or 2, characterized in that The light shielding portion has: a first abutting portion, which is opposite to the innermost portion of the hole and can be abutted by a first optical fiber end face of a first optical fiber serving as the optical fiber; as well as The second abutting portion is opposite to the opening, is formed continuously with the first abutting portion, has a smaller radius than the first abutting portion, and can be abutted by a second fiber end face of a second optical fiber having a smaller radius than the first optical fiber.

5. The optical fiber sensor according to claim 3, wherein: The optical fiber sensor further includes a lens disposed between the opening and the light emitting element.

6. The optical fiber sensor according to claim 1 or 2, characterized in that: The optical fiber holding member is formed of an optically opaque and conductive member, and the light emitting element is located on an extension line of the hole in the longitudinal direction.

7. The optical fiber sensor according to claim 1 or 2, characterized in that: The light emitting element and the light receiving element are arranged on the same plane.

8. The optical fiber sensor according to claim 7, wherein: The distance from the light emitting element to the light shielding portion along the length direction of the hole is d, and the angle when the incident angle of the light projected from the light emitting element to the light shielding portion is the critical angle is θc. Under the condition of a multiplication sign, the distance D between the light emitting element and the light receiving element satisfies: 。 9. The optical fiber sensor according to claim 1 or 2, characterized in that: The light emitting element projects light only from a surface of the optical fiber holding member on the hole side.

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