A device and method for detecting the geometry of a fiber coating

Abstract

The application belongs to the technical field of optical fiber detection, and relates to a device and method for detecting the geometric parameters of an optical fiber coating layer. The detection device comprises a support module, a motion control module, a limiting module, an illumination light source, an imaging module and an image analysis module. The motion control module is used to drive one end of the optical fiber to rotate around an axis, and the limiting module is used to limit the other end of the optical fiber in the radial direction. The interface between the coated section and the bare section of the optical fiber is taken as a to-be-measured section. The illumination light source is used to emit a light beam from one side of the optical fiber, so that the light beam is projected into the imaging module to form image information after passing through the to-be-measured section. The image analysis module is used to collect and analyze the image information of the optical fiber at multiple rotation angles in the process of rotating the optical fiber by the motion control module, so as to obtain the coating geometry and concentricity information of the optical fiber. The detection device can effectively measure the coating geometry of non-transparent coating optical fibers and colored optical fibers.

Description

Technical Field

[0001] This application belongs to the field of optical fiber testing technology, and relates to a device and method for detecting the geometric parameters of optical fiber coating. Background Technology

[0002] With the rapid development of communication technology, optical fiber, as a key carrier of information transmission, directly affects communication quality due to its performance. The fiber coating, as an important structure protecting the core of the fiber, has geometric parameters such as coating thickness and concentricity that play a decisive role in the mechanical, optical, and long-term reliability of the fiber. For example, uneven coating thickness may lead to uneven stress distribution when the fiber is bent or stretched, increasing the risk of fiber breakage; while poor concentricity can cause scattering and attenuation of the optical signal during transmission, reducing communication efficiency.

[0003] Currently, there are numerous methods for testing the geometry of optical fiber coatings, including contact mechanical measurement, optical microscopy, and laser scanning. For example, the traditional optical microscopy method obtains coating parameters and concentricity parameters by cutting the optical fiber sample and observing the cross-sectional image under a microscope. However, this method is not only cumbersome, requiring specialized personnel for meticulous sample preparation, but its measurement accuracy is also easily affected by human factors, resulting in low efficiency.

[0004] Based on the measurement principle of fiber end-face geometry under a microscope, various fiber end-face geometry measurement systems and methods have been further developed. For example, Chinese patent document CN107941466A describes a special fiber end-face geometry testing system and method. By injecting a light source from one end and imaging the other end onto the focal plane of the microscope system, the geometric parameters of the fiber under test are obtained through processing by an industrial control computer. Its advantage is that it can test the end-face geometry parameters of circular, elliptical, and polygonal clad fibers. For example, Chinese patent document CN215725709U describes a geometric parameter testing system for large-core optical fibers. This system uses a single-wavelength beam injected at one end, with a cladding stripper controlling the output ratio of the cladding light in the middle of the fiber. The single-wavelength beam output from the other end is used for spot imaging. Its advantage lies in forming a high-contrast imaging spot during geometric parameter measurements of large-core optical fibers (such as double-clad fibers with diameters of 250μm, 400μm, 550μm, 600μm, 800μm, and 1000μm), ensuring the stability of the measurement results. However, all of these methods require processing the fiber end face to obtain a defect-free, coated fiber end face for multi-parameter testing. This processing often requires different fiber cleavers and clamps, making it difficult to obtain defect-free (no chipping, no cracks, and no core loss) fiber end faces, resulting in cumbersome and costly operations.

[0005] Another Chinese patent document with publication number CN103115568A describes a method for detecting the geometric parameters of an optical fiber coating. By peeling off the coating at a suitable length backward from the end face of the optical fiber coating, and shining a light source into the peeled area, the end face image of the optical fiber coating is projected onto an imaging system. This method avoids the optical fiber end face preparation based on microscopy, but it can only be used for testing optical fibers after traditional optical fiber coating. After the optical fiber is colored, it does not have light-guiding properties, making it difficult to use this method for testing.

[0006] Laser scanning measurement technology utilizes a rotating multifaceted mirror or galvanometer system to emit a laser beam that scans an optical fiber. A photodetector receives the obstruction signal to calculate the diameter. This method enables non-contact measurement, but it can only obtain the projected diameter in a single direction, cannot detect concentricity or out-of-roundness, and the laser reflection signal is easily interfered with, leading to significant measurement deviations. This is especially true when measuring multi-layered coated optical fibers, where signal interference between different layers makes accurate measurement of the geometric parameters of each coating layer extremely difficult. For example, patent document CN103673906A describes a laser scanning diameter gauge and a method for measuring the outer diameter of a workpiece. The laser beam emitted by the laser passes through a high-speed rotating multifaceted mirror to obtain a scanning beam. The workpiece is placed within the scanning beam, and the diameter is calculated using the signal obstructed by the workpiece received by a receiver. The drawbacks of this method are that the laser signal is easily interfered with when measuring transparent objects, and it can only test the outer diameter of the optical fiber, unable to simultaneously detect multiple parameters.

[0007] Measurement methods based on the principle of interference, using white light or laser interference, can resolve the surface morphology of coatings at the nanometer level. However, these methods require sophisticated testing equipment, are expensive, and their accuracy is significantly affected by factors such as fiber material and ambient temperature. They are only suitable for laboratory environments and are difficult to widely apply in actual production and testing. For example, patent document CN107401988A describes a fiber coating concentricity monitoring system. This system uses two mutually perpendicular light sources to test concentricity. After the light sources illuminate the fiber, they form alternating bright and dark interference fringes on the receiver. The receiver converts and processes the received light signal and displays the concentricity result on a monitor. This method has high accuracy, but it suffers from drawbacks due to severe influence from environmental vibrations and temperature, resulting in indistinct fringes.

[0008] In summary, existing methods for testing the geometry of optical fiber coatings have several limitations in terms of accuracy, efficiency, cost, and applicability: 1. High-precision testing methods are inefficient, while high-efficiency methods lack sufficient accuracy; 2. Most techniques can only measure a single diameter parameter, making it difficult to simultaneously acquire key parameters such as concentricity and out-of-roundness; 3. Current measurement techniques are mostly based on measuring the geometric parameters of optical fiber coatings after traditional transparent coatings, with limited research on the geometric measurement of non-transparent coated fibers and colored fibers with special applications. These limitations prevent existing technologies from meeting the current demands for high-quality, rapid, and comprehensive testing in optical fiber manufacturing and specialized applications. Therefore, developing an innovative, efficient, accurate, and cost-effective optical fiber coating geometry testing technology is of significant practical importance. Summary of the Invention

[0009] In view of the deficiencies or improvement needs of the prior art, this application provides a device and method for detecting the geometric parameters of optical fiber coating, which aims to improve the problem that traditional measurement methods are difficult to effectively measure the coating geometry of non-transparent coated optical fibers and colored optical fibers.

[0010] This application provides a device for detecting the geometric parameters of an optical fiber coating, specifically including a support module, a motion control module, a limiting module, an illumination source, an imaging module, and an image analysis module, wherein: The motion control module and the limiting module are arranged side by side on the support module. The motion control module is used to drive one end of the optical fiber to rotate around the axis, and the limiting module is used to form a radial limit on the other end of the optical fiber. The optical fiber includes a coated section with a coating layer and a bare section with the coating layer removed to expose the cladding. The section where the interface between the coated section and the bare section is located is between the limiting module and the motion control module, and is used as the section to be tested. The illumination source and the imaging module are located on opposite sides of the optical fiber. The imaging module is connected to the image analysis module. The illumination source is used to emit a light beam from one side of the optical fiber, so that the light beam passes through the section of the optical fiber to be tested and is projected into the imaging module to form image information. The image analysis module is used to collect and analyze image information of the optical fiber at multiple rotation angles during the rotation of the optical fiber by the motion control module, so as to obtain the optical fiber coating geometry and concentricity information.

[0011] As a further preferred embodiment, the optical fiber coating geometry and concentricity information includes: cladding diameter, cladding non-circularity, coating diameter, coating non-circularity, and the concentricity of the cladding and coating.

[0012] As a further preferred embodiment, the lighting source is a uniformly diffused light source.

[0013] As a further preferred embodiment, the imaging module includes a camera body, on which a magnification-adjustable objective lens is disposed.

[0014] As a further preferred embodiment, the support module includes a multi-degree-of-freedom motion platform, and the limiting module and the motion control module are arranged side by side on the motion platform of the multi-degree-of-freedom motion platform.

[0015] As a further preferred embodiment, the motion control module includes a clamping fixture with an adjustable clamping range and a drive mechanism for driving the clamping fixture to rotate.

[0016] As a further preferred embodiment, the limiting module includes a linear limiting channel, the inner peripheral wall of which is fitted to the outer peripheral surface of the optical fiber.

[0017] The detection method provided in the second aspect of this application adopts the following technical solution: A detection method, performed using a detection device based on any of the optical fiber coating geometric parameters described in the first aspect, includes the following steps: S1. Install the optical fiber into the motion control module and the limiting module, and control the section where the interface between the coated section and the bare section of the optical fiber is located between the motion control module and the limiting module, so as to serve as the section to be tested; S2. The motion control module drives the optical fiber to rotate around the axis with a preset rotation angle value. The image analysis module collects the image information in the imaging module. This image information is formed by the illumination source emitting a beam of light from one side of the optical fiber and projecting it from the section of the optical fiber to be tested into the imaging module. S3. Repeat step S2 until the fiber rotates one full turn. The image analysis module analyzes the image information of the fiber at multiple rotation angles to obtain the fiber coating geometry and concentricity information.

[0018] As a further preferred embodiment, the image analysis module uses an edge detection method to fit the cross-section of the fiber cladding and coating layer based on image information from multiple rotation angles, in order to obtain the fiber coating geometry and concentricity information.

[0019] As a further preferred embodiment, in step S2, after the motion control module drives the optical fiber to rotate around the axis at a preset rotation angle value, the image analysis module acquires image information and performs median filtering, threshold segmentation, boundary positioning, bilateral edge positioning, edge parallelism adjustment, center positioning, and coordinate transformation on the acquired image information to obtain coordinate information for edge fitting.

[0020] In summary, compared with the prior art, the technical solutions conceived in this application have the following main technical advantages: 1. Under this design scheme, only a portion of the coating layer needs to be removed from the optical fiber to expose the cladding, enabling efficient and high-precision simultaneous detection of optical fiber coating geometry and concentricity information without the need for complex optical fiber end-face processing. Furthermore, the detection device is not only suitable for detecting the geometric parameters of conventional communication optical fibers but also for detecting optical fibers with other special coating processes, especially those coated with non-transparent coatings for special purposes.

[0021] 2. In this design, the motion control module and the image analysis module can work together to output multiple parameters, including fiber cladding diameter, cladding non-circularity, coating diameter, coating non-circularity, and concentricity of the cladding and coating, which is beneficial for achieving nanometer-precision measurement of optical fibers. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the optical fiber coating geometry parameter detection device provided in the embodiments of this application; Figure 2 This is a projection image of the coated and bare sections of the optical fiber provided in the embodiments of this application; Figure 3 This is a fitted image of the cross-sectional edge morphology of the fiber cladding and coating layer in an embodiment of this application; Figure 4 This is a flowchart of the detection method provided in the embodiments of this application; Figure 5 This is a schematic diagram of the boundary positioning principle provided in the embodiments of this application; Figure 6 This is a schematic diagram of the positioning principle of the second boundary provided in the embodiments of this application; Figure 7 This is a schematic diagram illustrating the principle of determining boundary parallel lines provided in an embodiment of this application; Figure 8 This is a schematic diagram illustrating the principle of determining the radius values ​​of the cladding and coating layers at the current angle, as provided in the embodiments of this application. Figure 9 This is a coordinate graph based on coordinate transformation provided in the embodiments of this application; Figure 10 This is a fitted image based on data reconstruction provided in the embodiments of this application; Figure 11 This is an example diagram of the edge model provided in the embodiments of this application; Figure 12 It is a function image generated by the first-order operator detection model provided in the embodiments of this application; Figure 13 It is a function image generated by the second-order operator detection model provided in the embodiments of this application.

[0023] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1. Support module; 2-1. Clamping fixture; 2-2. Drive mechanism; 3. Limiting module; 4. Illumination source; 5-1. Objective lens; 5-2. Camera body; 6. Image analysis module; 7. Fiber cladding fitting circle; 8. Fiber coating fitting circle; 10. Fiber; 10-1. Coated section; 10-2. Exposed section. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0025] The following is in conjunction with the appendix Figures 1-7 This application will be described in further detail.

[0026] This application discloses a device for detecting the geometric parameters of an optical fiber coating. (Refer to...) Figures 1-2 The optical fiber coating geometry parameter detection device includes a support module 1, a motion control module, a limiting module 3, an illumination source 4, an imaging module, and an image analysis module 6. The motion control module and the limiting module 3 are arranged side-by-side on the support module 1. The motion control module drives one end of the optical fiber 10 to rotate around its axis, and the limiting module 3 provides radial restraint to the other end of the optical fiber 10. The optical fiber 10 includes a coated section 10-1 with a coating layer and a bare section 10-2 with the coating layer removed to expose the cladding. The coated section 10-1 and the bare section 10-2... The section containing the interface of fiber 10 is located between the limiting module 3 and the motion control module, serving as the section to be tested. The illumination source 4 and the imaging module are located on opposite sides of the optical fiber 10. The imaging module is connected to the image analysis module 6. The illumination source 4 emits a light beam from one side of the optical fiber 10, which passes through the section to be tested and is projected into the imaging module to form image information. The image analysis module 6 collects and analyzes image information of the optical fiber 10 at multiple rotation angles during the rotation of the optical fiber 10 by the motion control module, simultaneously obtaining the optical fiber coating geometry and concentricity information. The optical fiber coating geometry and concentricity information includes: cladding diameter, cladding non-circularity, coating diameter, coating non-circularity, and the concentricity of the cladding and coating.

[0027] Under this design, only the coating layer of optical fiber 10 needs to be removed to expose the cladding, allowing for simultaneous detection of optical fiber coating geometry and concentricity information without the need for complex end-face processing. Furthermore, this device is simple, easy to integrate, and inexpensive, facilitating equipment miniaturization and portability.

[0028] Moreover, this design scheme is not only suitable for the geometric parameter detection of conventional communication optical fibers 10, but also applicable to the detection of optical fibers 10 with other special coating processes, especially optical fibers 10 coated with non-transparent coatings for special purposes. Among them, the motion control module and the image analysis module 6 can work together to achieve automatic focusing and automatic detection, and output multiple parameters such as fiber cladding diameter, cladding non-circularity, coating diameter, coating non-circularity, and concentricity of cladding and coating.

[0029] More preferably, the support module 1 includes a multi-degree-of-freedom motion platform, and the limiting module 3 and motion control module are arranged side by side on the motion table of the multi-degree-of-freedom motion platform. The multi-degree-of-freedom motion platform includes, but is not limited to, an electrically powered three-axis displacement stage.

[0030] Further preferably, the light beam emitted by the illumination source 4 is a parallel light beam, and the illumination source 4 is preferably a highly uniform and high-quality surface light source. In this design, a highly uniform and high-quality surface light source is used as the illumination source 4. The area to be tested of the optical fiber 10 is imaged onto the focal plane of the objective lens 5-1 through side illumination and projection imaging. Then, it is connected to the image analysis module 6 through the imaging module. This eliminates the need for complex end-face processing of the optical fiber 10, simplifies the device and operation process, and facilitates the miniaturization, portability, and operation of the entire device, making it suitable for different working environments and on-site testing needs.

[0031] Further preferably, the motion control module includes a clamping fixture 2-1 with an adjustable clamping range, preferably 40μm-1000μm, used to fix the optical fiber 10 (preferably to fix the coating layer of the optical fiber 10). Additionally, the control module includes a drive mechanism 2-2, which may include, but is not limited to, a rotary motor. The drive mechanism 2-2 is mounted on the support module 1 and is used to drive the clamping fixture 2-1 to rotate the optical fiber 10 around its axis. The drive mechanism 2-2 can be angle-set and rotate automatically according to a program. Preferably, the rotational concentricity error of the motion control module is ≤3 micrometers.

[0032] Among them, the motion control module and the imaging module have the characteristics of high precision and high stability, which is conducive to achieving nanometer-level repeatability measurement.

[0033] More preferably, the limiting module 3 includes a funnel-shaped fixture with a linear limiting channel that extends axially. The inner peripheral wall of the linear limiting channel fits into the outer peripheral surface of the optical fiber 10 to limit the radial movement of the optical fiber 10 and allow the optical fiber 10 to rotate circumferentially within the linear limiting channel.

[0034] Generally, a portion of the coating is peeled off one end of the optical fiber 10, so that one axial end of the optical fiber 10 is a coated section 10-1 with the coating, and the other end is a bare section 10-2 with the coating removed to expose the cladding. The cleaned optical fiber 10 is then fixed in the motion control module and the limiting module 3 for detection.

[0035] The exposed section 10-2 can be installed in the motion control module, while the coated section 10-1 is installed in the limiting module 3. Alternatively, the exposed section 10-2 can be installed in the limiting module 3, and the coated section 10-1 can be installed in the motion control module. The selection can be made according to the requirements.

[0036] Further preferably, the imaging module includes a camera body 5-2, on which a magnification-adjustable objective lens 5-1 is mounted. The camera body 5-2 may include, but is not limited to, a high-resolution CCD camera or a CMOS area array camera. The magnification range of the objective lens 5-1 is preferably 0.5x-100x. In actual testing, a suitable objective lens is selected based on the outer diameter of the fiber 10. With the high-magnification objective lens 5-1, even minute fluctuations (such as fluctuations less than 0.001 micrometers) at the boundary of the coating or cladding can be captured by the imaging module and converted into recognizable image signals, providing basic resolution support for fiber optic dimension measurement in the micrometer range (e.g., 40-1000 micrometers).

[0037] In a further preferred embodiment, the detection device also includes a control module, which is electrically connected to the support module 1, motion control module, imaging module, and image analysis module 6, etc., for controlling the operation of each module and for controlling the device to perform automatic focusing. The control module is existing technology and will not be described in detail here. Generally, a computer is used as the control and analysis module of the detection device; that is, the computer includes both the control module and the image analysis module 6.

[0038] In this design, the angle of rotation of the motion control module is set, and the controller controls the linkage between the motion control module and the image analysis module 6. Each rotation acquires an image and extracts the boundaries of the fiber cladding and coating, until the fiber 10 completes a 360° rotation and returns to the origin. Then, the image analysis module fits the circular shapes of the fiber cladding and coating based on the acquired images (e.g., ...). Figure 3 As shown in the figure, further analysis is performed to output multiple parameters such as cladding diameter, cladding non-circularity, coating diameter, coating non-circularity, and concentricity of cladding and coating. This design has a wide range of applications and is not affected by factors such as whether the fiber coating material is transparent or not, the size of fiber 10, or the shape of fiber 10.

[0039] In this design, images are acquired through projection imaging. Regardless of whether the fiber is colored or not, or whether the coating material is transparent or not, the cladding and coating (or colored) of the fiber will be imaged. In particular, this design method is based on a directional parallel light source, resulting in high accuracy in image boundary recognition and images containing more information. When the image analysis module 6 analyzes the image information, the analysis results can include key data such as the fiber cladding diameter, cladding non-circularity, coating diameter, coating non-circularity, and the concentricity of the cladding and coating.

[0040] This application also discloses a detection method based on any of the above-described optical fiber coating geometry parameters detection devices. The detection method includes the following steps: S1. Install the optical fiber 10 into the motion control module and the limiting module 3, and control the section where the interface between the coated section 10-1 and the bare section 10-2 of the optical fiber 10 is located between the motion control module and the limiting module 3, so as to serve as the section to be tested.

[0041] S2. The motion control module drives the optical fiber 10 to rotate around the axis with a preset rotation angle value. The image analysis module 6 collects the image information in the imaging module. The image information is formed by the illumination source 4 emitting a beam of light from one side of the optical fiber 10 and projecting it from the section of the optical fiber 10 to be measured into the imaging module.

[0042] Specifically, in step S2, after the motion control module drives the optical fiber 10 to rotate around its axis at a preset rotation angle value, the image analysis module 6 acquires image information and processes the acquired image information based on its built-in image edge algorithm. Preferably, the image information processing includes: performing median filtering, threshold segmentation, boundary positioning, bilateral edge positioning, edge parallelism adjustment, center positioning, and coordinate transformation on the image information to obtain coordinate information for edge fitting.

[0043] S3. Repeat step S2 until the fiber 10 rotates one full turn. The image analysis module 6 analyzes the image information of the fiber 10 at multiple rotation angles to obtain the fiber coating geometry and concentricity information.

[0044] Specifically, the image analysis module 6 uses image information from multiple rotation angles and employs an edge detection method to fit the edges of the cross-section of the fiber cladding and coating layer. This enables repeatable measurement accuracy at the nanometer level (0.001 micrometer level) and accurately obtains the coating geometry and concentricity information of the fiber 10.

[0045] For ease of understanding, Figure 4The flowchart of this detection method is shown. The N angles represent the pre-set total number of angles to be acquired (e.g., N = 360 angles). In practice, N can be determined based on the number of rotations and the angle of each rotation by the motion control module, or by recording the number of angle acquisitions completed using a counter or other devices. When the actual number of acquisitions reaches N, an "angle complete" signal is triggered. Then, the data from the N acquisitions are used to reconstruct the coating layer and fit the edges of the fiber cladding and coating cross-section. The fitting results are then calculated to obtain the fiber coating geometry and concentricity information, ultimately completing the test.

[0046] In this process, after each preset rotation angle, image information is acquired, image noise is removed by median filtering, and the coating (coating layer and cladding layer) and background are distinguished by threshold segmentation. Then, the coating boundary and double edges are located sequentially and the edge parallelism is adjusted to complete the center positioning and coordinate transformation, providing image data and position reference for N-angle judgment and image reconstruction.

[0047] For example, in a test, if the preset rotation angle is required to be 1°, and image information is collected every 1° of rotation, for a total rotation of 360°, then 360 images need to be collected (N=360). Once the system confirms that 360 image information from different angles has been acquired, it determines that N angles have been completed.

[0048] In this design, the image analysis module 6 uses image information from multiple rotation angles and employs an edge detection method to fit the edges of the fiber cladding and coating cross-sections, so as to simultaneously obtain the coating geometry and concentricity information of the fiber 10.

[0049] In some embodiments, image processing is a process of extracting useful information from an image and locating target features through a series of technical means, the core steps of which include: (1) Image acquisition; (2) Image preprocessing; (3) Structural feature extraction and geometric processing.

[0050] Image preprocessing includes median filtering and threshold segmentation of the image information acquired from image acquisition. Structural feature extraction and geometric processing include boundary localization, bilateral edge localization, edge parallelism adjustment, center localization, coordinate transformation, N-angle data reconstruction, and result calculation.

[0051] Specifically, such as Figures 5-10 As shown, layer edge positioning, double edge positioning, edge parallelism adjustment, center positioning, left-side conversion, data reconstruction, and result calculation include the following sub-steps; Step 1: Boundary Location: Define the unidirectional direction of the coating and cladding in the optical fiber, and determine the first boundary of the coating and cladding. The approximate location of the first boundary is as follows: Figure 5As indicated by the arrow.

[0052] Step Two: Based on the first boundary, perform a reverse search on the image to locate and determine the second boundary between the coating layer and the cladding layer. The approximate location of the relevant second boundary is as follows: Figure 6 As indicated by the arrow.

[0053] Step 3: Determine the boundary points of the first and second boundaries based on the preset coating and cladding intervals, ensuring that the boundary points are within their respective intervals (the coating and cladding intervals are preset by the equipment parameters, minimizing the need for boundary points to intersect). Perform straight line fitting based on the boundary points, and adjust the parallel lines according to the average slope of the two fitted lines for each coating and cladding layer, obtaining two sets of boundary parallel lines for each layer. The principle is roughly as follows: Figure 7 As shown.

[0054] Step 4: Based on the two parallel lines of the cladding, obtain the center line of the cladding parallel lines. Using the center line of the cladding parallel lines as the baseline, calculate the perpendicular distances between the cladding parallel lines, the coating parallel lines, and the baseline. Use these distances as the cladding radius and coating radius values ​​for the current angle. The principle is roughly as follows: Figure 8 As shown.

[0055] Step 5: Perform coordinate transformation based on the cladding radius and coating radius values ​​at the current angle to obtain the coordinates of the corresponding boundary point at the current angle.

[0056] Step Six: Repeat steps one through five to obtain multiple coordinate points (e.g., ... Figure 9 (As shown).

[0057] Step 7: Based on the radius coordinate distribution of the coating and cladding layers at N angles, reconstruct the coating and cladding layer data (ellipse fitting). The reconstruction results are roughly as follows: Figure 10 As shown, the inner circle is the fitted circle of the cladding layer, and the outer circle is the fitted circle of the coating layer.

[0058] Step 8: Calculate the results (fitting radius, out-of-roundness, concentricity, etc.) based on the data of the fitted circles of the coating and cladding layers.

[0059] Generally speaking, image edges are the most fundamental feature of an image. An edge refers to a discontinuity in the local characteristics of an image. An edge is a point where information such as grayscale or structure changes abruptly. Examples include abrupt changes in grayscale levels, color, and texture. An edge marks the end of one region and the beginning of another; this feature can be used to segment an image.

[0060] like Figure 11 As shown, when you see an object with edges, the first thing you perceive is the edges. Among them, Figure 5(a) in the diagram represents the characteristics of an ideal edge; each gray level jumps to a vertical step. However, in reality, due to factors such as the performance of the image acquisition system, the sampling rate, and the lighting conditions during image acquisition, the resulting edges are often blurred. The edges are simulated as a profile with a "sloping surface," such as... Figure 5 As shown in (b) of the model, in this model, blurred edges become “wide” and sharp edges become “narrow”.

[0061] The technical principles and application methods of edge detection can be summarized as follows: The edges of a target (such as fiber optic cable 10) in an image are regions where grayscale values ​​change abruptly. Essentially, this reflects the grayscale discontinuity between the target and the background (or different regions of the target; in this case, the coated section 10-1 and the bare section 10-2 are different regions). This abrupt change originates from physical characteristics (such as the fiber optic coating having a lower grayscale value than the background due to light scattering), manifesting as two basic attributes at the edges: direction (gradient direction) and amplitude (intensity of grayscale change). The goal of edge detection is to quantify this grayscale change to achieve accurate segmentation and feature extraction of the target region.

[0062] The core of image edge detection lies in capturing the abrupt changes in grayscale values, which can be mathematically analyzed and achieved through first-order or second-order operator detection models.

[0063] Among them, such as Figure 12 The function graph obtained by the first-order operator detection model is shown in the figure. The first derivative reflects the rate of change of gray values, and its extreme values ​​correspond to the transition regions of edges. The specific principle is as follows: by calculating the first-order gradient of the image (such as the gradient components in the horizontal and vertical directions), the local direction of the edge (gradient direction) is determined, and the maximum value of the gradient magnitude in that direction is found to locate the edge position. Typical operators include: Roberts Cross operator, Prewitt operator, Sobel operator, Kirsch operator, Canny operator, compass operator, etc. For example, in the Sobel operator, pixel values ​​in the edge region of the image will "jump". Taking the derivative of these pixels, the first derivative is extreme at the edge position. This is the principle used by the Sobel operator: "the extreme value is the edge".

[0064] Among them, such as Figure 13 The function graph calculated by the second-order operator detection model is shown. It locates and detects edges by finding the zero-crossing points (intersections where the second derivative obtained from the image changes from positive to negative or vice versa). Because the second derivative is more sensitive to abrupt changes in grayscale (single-peak response), it is suitable for accurately detecting the fine-grained locations of edges. Typical operators include the Laplacian operator and the LOG operator. If you take the second derivative with respect to the pixel value, you will find that the derivative value at the edge is 0.

[0065] Example 1: Take a section of the optical fiber 10 to be tested, peel off part of the coating layer from one end of the fiber 10, wipe the surface clean, and then limit the coated end through the limiting module 3. Insert the end of the fiber cladding without the coating layer into the clamping fixture 2-1 of the motion control module for fixation. Control the support module 1 through the computer software to move the support module 1 until the area of ​​the optical fiber 10 to be tested, projected by the illumination source 4, is focused on the focal plane of the objective lens 5-1. The image of the optical fiber 10 is then displayed on the image analysis module 6 of the computer software after being imaged by the camera.

[0066] In this process, a single image capture yields a pair of data sets representing the boundaries of the fiber cladding and coating. The motion control module of fiber 10 is set to rotate at 36°. Its automatic rotation function works in conjunction with the information processing function of the image analysis module 6, capturing image data with each rotation. After a full 360° rotation, an edge fitting map of the fiber cladding and coating cross-section is obtained. Based on this fitting map, multiple parameters can be calculated and output, including the fiber cladding diameter, fiber cladding non-circularity, fiber coating diameter, fiber coating non-circularity, and the concentricity of the cladding and coating. Table 1 below summarizes the results of 10 tests involving a single application of black coating to the fiber; the data is clear and concise.

[0067] Table 1. Test results of optical fibers coated with black paint in a single application.

[0068] Example 2: A section of colored optical fiber 10 is tested. Part of the coating is peeled off one end of the fiber 10, the surface is cleaned, and the coated end is limited by the limiting module 3. The peeled end is inserted into the clamping fixture 2-1 of the motion control module for fixation. The support module 1 is controlled by the computer software to move until the area of ​​the fiber 10 to be tested, projected by the illumination source 4, is focused on the focal plane of the objective lens 5-1. The image of the fiber 10 is then captured by the camera and displayed on the image analysis module 6 of the computer software.

[0069] In this method, a single image acquisition yields a pair of data sets representing the boundaries of the fiber cladding and coating. The motion control module of fiber 10 is set to rotate at 36°. Its automatic rotation function works in conjunction with the information processing function of the image analysis module 6, acquiring image data with each rotation. After a full 360° rotation, an edge fitting map of the fiber cladding and coating cross-section is obtained. Based on this fitting map, multiple parameters can be output, including fiber cladding diameter, fiber cladding non-circularity, fiber coating diameter, fiber coating non-circularity, and concentricity of the cladding and coating. Table 2 below summarizes the results of 10 tests on the colored fiber 10 sample.

[0070] Table 2 Test Results of Colored Fibers

[0071] Example 3: A small-sized optical fiber 10 with a conventional coating was tested. Part of the coating was peeled off one end of the fiber 10, the surface was cleaned, and the coated end was positioned using the limiting module 3. The cladding end of the fiber, now without coating, was inserted into the clamping fixture 2-1 of the motion control module for fixation. The support module 1 was controlled by computer software to move until the area of ​​the fiber 10 to be tested, projected by the illumination source 4, was focused onto the focal plane of the objective lens 5-1. The image of the fiber 10 was then displayed on the image analysis module 6 of the computer software after passing through a camera.

[0072] A single image acquisition yields a pair of data sets representing the boundaries of the fiber cladding and coating. The motion control module of fiber 10 is set to rotate at 36°. Its automatic rotation function works in conjunction with the information processing function of the image analysis module 6, acquiring image data with each rotation. After a full 360° rotation, an edge fitting map of the fiber cladding and coating cross-sections is obtained. Based on this fitting map, multiple parameters can be output, including fiber cladding diameter, fiber cladding non-circularity, fiber coating diameter, fiber coating non-circularity, and concentricity of the cladding and coating. Table 3 below summarizes the results of 10 tests on a small-sized fiber 10 sample.

[0073] Table 3 Test Results of Small-Size Optical Fibers

[0074] It should be understood that expressions such as "comprising" and "may include" as used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0075] It should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0076] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0077] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0078] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A device for detecting the geometric parameters of an optical fiber coating, characterized in that, It includes a support module (1), a motion control module, a limiting module (3), an illumination source (4), an imaging module, and an image analysis module (6), wherein: The motion control module and the limiting module (3) are arranged side by side on the support module (1). The motion control module is used to drive one end of the optical fiber (10) to rotate around the axis. The limiting module (3) is used to form a radial limit on the other end of the optical fiber (10). The optical fiber (10) includes a coated section (10-1) with a coating layer and an exposed section (10-2) with the coating layer removed to expose the cladding. The section where the interface between the coated section (10-1) and the exposed section (10-2) of the optical fiber (10) is located between the limiting module (3) and the motion control module is used as the section to be tested. The illumination source (4) and the imaging module are respectively located on both sides of the optical fiber (10). The imaging module is connected to the image analysis module (6). The illumination source (4) is used to emit a light beam from one side of the optical fiber (10), so that the light beam passes through the section to be tested of the optical fiber (10) and is projected into the imaging module to form image information. The image analysis module (6) is used to collect and analyze image information of the optical fiber (10) at multiple rotation angles during the process of the motion control module rotating the optical fiber (10) in order to obtain the coating geometry and concentricity information of the optical fiber (10).

2. The optical fiber coating geometric parameter detection device as described in claim 1, characterized in that, The optical fiber (10) coating geometry and concentricity information includes: cladding diameter, cladding non-circularity, coating diameter, coating non-circularity, and concentricity of the cladding and coating.

3. The optical fiber coating geometric parameter detection device as described in claim 1, characterized in that, The lighting source (4) is a uniformly divergent light source.

4. The optical fiber coating geometric parameter detection device as described in claim 1, characterized in that, The imaging module includes a camera body (5-2), on which a magnification-adjustable objective lens (5-1) is provided.

5. The optical fiber coating geometric parameter detection device as described in claim 1, characterized in that, The support module (1) includes a multi-degree-of-freedom motion platform, and the limiting module (3) and the motion control module are arranged side by side on the motion platform of the multi-degree-of-freedom motion platform.

6. The optical fiber coating geometric parameter detection device as described in claim 1, characterized in that, The motion control module includes a clamping fixture (2-1) with an adjustable clamping range and a drive mechanism (2-2) for driving the clamping fixture (2-1) to rotate.

7. The optical fiber coating geometric parameter detection device as described in claim 1, characterized in that, The limiting module (3) includes a linear limiting channel, the inner peripheral wall of which is fitted to the outer peripheral surface of the optical fiber (10).

8. A detection method, based on the detection device for the geometric parameters of the optical fiber coating as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Install the optical fiber (10) into the motion control module and the limiting module (3), and control the section where the interface between the coated section (10-1) and the bare section (10-2) in the optical fiber (10) is located between the motion control module and the limiting module (3) as the section to be tested; S2. The motion control module drives the optical fiber (10) to rotate around the axis with a preset rotation angle value. The image analysis module (6) collects the image information in the imaging module. The image information is formed by the illumination source (4) emitting a beam from one side of the optical fiber (10) and projecting it from the section to be measured of the optical fiber (10) into the imaging module. S3. Repeat step S2 until the fiber (10) rotates one full turn. The image analysis module (6) analyzes the image information of the fiber (10) at multiple rotation angles to obtain the coating geometry and concentricity information of the fiber (10).

9. The detection method as described in claim 8, characterized in that, The image analysis module (6) uses the edge detection method to fit the cross-section of the fiber cladding and coating layer based on the image information under multiple rotation angles, so as to obtain the coating geometry and concentricity information of the fiber (10).

10. The detection method as described in claim 8, characterized in that, In step S2, after the motion control module drives the optical fiber (10) to rotate around the axis at a preset rotation angle value, the image analysis module (6) collects image information and performs median filtering, threshold segmentation, boundary positioning, bilateral edge positioning, edge parallelism adjustment, center positioning and coordinate transformation on the collected image information to obtain coordinate information for edge fitting.

Images