A method for detecting the end face of an optical fiber

Abstract

The present application mainly relates to the field of automation detection, and particularly to a kind of optical fiber end face detection method, optical fiber, the optical fiber has optical fiber end face, the optical fiber end face has center of circle;The optical fiber end face is the optical fiber end face after fusion treatment, the edge of the optical fiber end face has arc transition to end face main body, several point light sources;In axial direction, several the point light source is located in the front of the optical fiber end face, in the projection on axial direction, several the point light source is located on the concentric circle of the center of circle;The point light source can produce light reflection area in the edge of the side corresponding to the optical fiber end face;Several the point light source is sequentially lighted, obtains the image of optical fiber end face when several single point light source is lighted;The light reflection area of image in optical fiber end face is detected and the quantity information of light reflection area is obtained, if the quantity of light reflection area in optical fiber end face is detected greater than or equal to two, then determine that the optical fiber end face is unqualified.

Description

Technical Field

[0001] This invention mainly relates to the field of automated testing, and in particular to a method for testing the end face of optical fibers. Background Technology

[0002] Existing technology, such as patent application number 201410713984.8 entitled "Optical Fiber End-Face Inspection Method and Optical Fiber End-Face Polishing and Inspection Equipment," discloses "an optical fiber end-face polishing and inspection equipment, including a power supply device, a light source, a camera device, an image processing device, an image display device, a motor drive device, a discharge device, and an optical fiber clamping device. The power supply device is connected to the light source, camera device, image processing device, image display device, motor drive device, and discharge device respectively; the image processing device is connected to the camera device, image display device, motor drive device, and discharge device; the discharge device consists of an electrode group; the optical fiber clamping device is connected to the motor drive device; the optical fiber clamping device is provided with an optical fiber fixing slot, and the light source is opposite to the optical fiber fixing slot." This patent is a melting treatment device for optical fiber end faces. It melts the optical fiber end face using a discharge device and then images the optical fiber end face using a camera device. This patent defines some data that needs to be collected for end-face inspection, but it does not disclose a specific end-face inspection method.

[0003] For example, patent application number 201910430030.9, entitled "Fiber Optic End-Face Polishing Inspection Equipment and Method," discloses "a fiber optic end-face polishing inspection equipment that performs electro-thermal melting treatment on the cut end face of the fiber optic cable to ensure the consistency of cleanliness, damage, and end-face curvature radius of the fiber optic end face. After electro-thermal melting treatment, the equipment acquires images of the fiber optic end face in real time and transmits them to a display screen for observation. Simultaneously, it transmits these images to an image processing device for black-and-white binarization processing to calculate the cleanliness, damage, and curvature radius of the fiber optic end face. Based on the principle of optical reflection, the image processing device automatically determines the electro-thermal melting status of the fiber optic end face to determine whether an additional electro-thermal melting is needed to ensure that the deposits on the fiber optic end face are cleaned, the cut damage is repaired, and a suitable curvature radius is formed… The inspection steps include: acquiring images of the fiber optic end face; the image processing device acquiring images from the camera device…" The process involves: first, foreground segmentation of the received image to obtain an image of the fiber optic end face; second, binarization processing, where the image of the fiber optic end face captured by the camera is transmitted to an image processing device for black-and-white binarization; and third, calculation and comparison, where the radius of curvature of the fiber optic end face is calculated and compared with a standard range parameter of the radius of curvature of the fiber optic end face preset in the image processing device. If the comparison result meets the predefined value, the operation ends; otherwise, an additional polishing step is added, and the steps of capturing the fiber optic end face image and binarization are repeated, followed by recalculation and comparison, until the radius of curvature of the fiber optic end face is lower than a preset minimum value, at which point the operation ends. A radius of curvature meeting the predefined value means that the inner diameter of the formed bright ring is within the range between a circle with a preset radius R1 and a circle with a preset radius R2. This patent discloses the general process of detection when the melting processing device uses a ring light source, but it does not disclose the specific judgment method or the method for detecting end face burrs.

[0004] Before optical fibers are processed by the aforementioned melting equipment, they need to be cut, typically by a cleaver. For example, patent application number 202120851945.X, entitled "An Optical Fiber Cutter," discloses a "optical fiber cleaver body comprising an optical cable fixing part, an optical fiber fixing platform, an inner cavity, a blade holder, and a slide rod; the optical cable fixing part is used to fix the stripped optical cable and position the stripped optical fiber on the optical fiber fixing platform; the bottom of the optical fiber fixing platform has the inner cavity, and the slide rod is disposed within the inner cavity, with a spring sleeved on the slide rod; the blade holder is equipped with a cleaver, the blade holder slidably disposed on the slide rod, and the blade holder has an extension arm; when the blade holder approaches one end of the slide rod, the spring is compressed, and the extension arm engages with the bayonet of the optical fiber cleaver body through a locking point, thus fixing the blade holder relative to the optical fiber cleaver body..." The cover is also equipped with a breaking device, which includes a breaking spring, an extension platform, and a breaking arm. During the closing process of the cover, the extension platform abuts against the surface of the blade holder and compresses the breaking spring, causing the extension platform and the breaking arm to retract. When the blade holder is pushed out by the compressed spring and moves to the other end of the slide rod, the blade holder disengages from the extension platform, and the breaking arm extends to strike and break the optical fiber. An optical fiber cleaver is a commonly used tool. Its working principle is to make a cut on the optical fiber with a blade, and then break the fiber by breaking it. However, this breaking method may cause a burr to form at the end of the optical fiber away from the cut due to the breaking force or accidental factors, i.e., a tear-like protrusion at the edge of the optical fiber end face. This protrusion may still exist after melting, and existing melting equipment does not have a corresponding detection method. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for detecting the end face of an optical fiber, which is achieved through the following technical solution:

[0006] A method for inspecting the end face of an optical fiber, comprising an optical fiber having an end face with a center; the end face is a fused-face end face, and the edge of the end face has an arc-shaped transition towards the end face body.

[0007] Acquire an axially captured image of the fiber end face;

[0008] A plurality of point light sources; in the axial direction of the fiber end face, the plurality of point light sources are located in front of the fiber end face; when the projection direction is the axial direction of the fiber end face, and the plane where the image of the fiber end face is located is the projection plane, the projection of the plurality of point light sources is located on the concentric circles of the projection of the center of the circle.

[0009] The point light source can generate a reflective area on the edge of one side corresponding to the end face of the optical fiber, and the reflective area is imaged onto the end face of the optical fiber.

[0010] Several point light sources emit light sequentially, and an image of the fiber end face is obtained when several individual point light sources emit light.

[0011] The system detects the reflective areas of the image within the fiber endface and obtains the number of reflective areas. If the number of reflective areas detected within the fiber endface is greater than or equal to two, the fiber endface is deemed unqualified.

[0012] Preferably, the reflective area of ​​the image within the fiber end face includes:

[0013] S1: Obtain image information representing the brightness and darkness pixel values ​​at the fiber end face;

[0014] S2: Perform edge detection to obtain the fiber end face contour information and the information of the reflective area within the fiber end face in the image.

[0015] Preferably, the number of point light sources is configured to be four.

[0016] Preferably, when the number of pixels in the bright area of ​​the detected image within the fiber endface exceeds a set threshold, it is identified as a reflective area.

[0017] This invention also provides a method for detecting the end face of an optical fiber. The optical fiber has an end face with a center point. The end face is a fused-to-metal fiber end face, and its edge has an arc-shaped transition towards the main body of the end face.

[0018] Acquire an axially captured image of the fiber end face;

[0019] A plurality of point light sources; in the axial direction of the fiber end face, the plurality of point light sources are located in front of the fiber end face; when the projection direction is the axial direction of the fiber end face, and the plane where the image of the fiber end face is located is the projection plane, the projections of the plurality of point light sources are located on the concentric circles of the projection of the center of the circle; in the projection plane, they are located on the virtual straight line formed by the projection of the point light sources and the projection of the center of the circle, and the straight line forms two intersection points with the outline of the projection of the fiber end face, the intersection point closer to the point light source is the near intersection point, and the intersection point farther away from the point light source is the far intersection point.

[0020] Several point light sources emit light sequentially, and an image of the fiber end face is obtained when several individual point light sources emit light.

[0021] The image at the far intersection point within the fiber optic endface is detected. If a reflective area is detected in the area within the fiber optic endface at the far intersection point, the fiber optic endface is deemed unqualified.

[0022] Preferably, the region where the image at the far intersection point within the fiber endface is detected includes:

[0023] S1: Obtain image information representing the brightness and darkness pixel values ​​at the fiber end face;

[0024] S2: Perform edge detection to obtain the fiber end face contour information in the image and whether there is a reflective area in the fiber end face at the far intersection point.

[0025] Preferably, the number of point light sources is configured to be four.

[0026] Preferably, the image is divided into equal parts along the circumference with the physical center of the image or with the center of the circle as the center. The number of equal parts is the same as the number of point light sources, and the intersection point is located in the middle of the arc of a single equally divided region.

[0027] Preferably, when the number of pixels in the bright area of ​​the detected image within the fiber endface exceeds a set threshold, it is identified as a reflective area.

[0028] The beneficial effects of the present invention are as follows: The fiber end face detection method provided by the present invention can be applied to the fusion splicing equipment. The fiber end face is illuminated by a polling method of sequentially lighting several point light sources to obtain an image of the fiber end face. Since the fused fiber end face will inevitably have a crescent-shaped reflective area near the point light source, if reflection is detected in areas other than the crescent-shaped reflective area, it proves that the fiber end face has a burr protrusion. The end face with the burr protrusion is a defective end face. Attached Figure Description

[0029] Figure 1 A schematic diagram showing the relative positions of the optical fiber, point light source, and camera is provided.

[0030] Figure 2 This shows a side view of the fiber end face when it has a burr.

[0031] Figure 3 A schematic diagram showing an image of an optical fiber end face without burrs is displayed;

[0032] Figure 4 A schematic diagram showing an image of an optical fiber end face with a burr is shown;

[0033] Figure 5 A schematic diagram of the line image of the optical fiber end face without burrs is shown. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] The equipment used in this method is such as Figure 1As shown, optical fiber 1 has an end face with a center. The end face is a fiber end face treated with existing fusion processing technology. The edge of the end face has an arc-shaped transition towards the main body of the end face. The fusion processing eliminates impurities such as burrs and dust particles caused by fiber optic cutting. Figure 2 As shown, if the fiber end face has a burr, this burr 4 may not disappear after melting. Here Figure 2 The image shows a side view of the fiber 1 with the burr 4. The camera 3 used in this patent is facing the end face of the fiber and is photographing the forward end face of the fiber. Therefore, it cannot directly photograph the burr 4 extending from the side.

[0036] Along the axial direction of the optical fiber or its end face, several point light sources 2 are located in front of the fiber end face. In the axial projection, these point light sources 2 are located on concentric circles around the center of the optical fiber. The point light sources 2 can be uniformly or non-uniformly distributed on these concentric circles. Since the relative position of the optical fiber is fixed, its relative coordinates on the image are also fixed, and the positions of the point light sources 2 are also fixed. Although the optical fiber is manually inserted into the device, even if there is a slight error in the relative position of the fiber, this error is small and does not affect the detection results. Furthermore, to prevent this error from becoming too large, the aspect ratio information can be obtained from the contour information of the fiber end face, thereby obtaining the coordinates of the center.

[0037] The fiber optic end face is placed in a closed, dark space. The point light source 2 illuminates the fiber optic end face. Here, the point light source's function is to generate reflection at the curved edge of the fiber optic end face, rather than illuminating the entire end face. For example... Figure 3 As shown, since it is a point light source and the fiber optic end face is a circular cross-section, the camera 3 located on the front of the fiber optic end face can only receive the reflection generated by the curved part of the fiber optic end face, which is a crescent-shaped reflective area. The reflection generated on the end face portion that is roughly parallel to the CCD plane of the camera 3 will not be received by the camera 3. The illumination of the point light source 2 on the background far away from the fiber optic end face will form a white background during imaging. In addition to the crescent-shaped reflection, the remaining end face portion of the fiber optic end face will form a dark fiber optic end face image.

[0038] Theoretically, two or more point light sources are sufficient, but in practice, four are generally used. Although this patent uses the term "point light source," it can also refer to a parallel light source facing the fiber optic end face. The burr on the end face must have a certain length and width. When a point light source illuminates the burr from the front side, a reflective area will also be formed on the fiber optic end face image; this reflective area is the second reflective area. Although a single point light source may not be able to cause the burr to reflect light at a certain angle, the point light sources will be lit sequentially, ensuring that at least one light source can produce a second reflective area on the fiber optic end face image. Theoretically, the point light sources do not need to be uniformly distributed, as long as the angle of illumination is sufficient to cause the burr to reflect light onto the image. Uniform distribution of point light sources is mainly to avoid visual discrepancies in the image affecting the user during device imaging.

[0039] During fiber optic end-face inspection, several point light sources emit light sequentially, allowing camera 3 to capture images of the fiber optic end-face when each point light source is emitting light. This image can be displayed on a splicing device, where its processor and memory process the image. The pixel data acquired by the camera is copied to an designated computational area, and the grayscale values ​​of the pixels are binarized. Grayscale values ​​exceeding a set threshold are considered bright spots, while those below the threshold are considered black spots, thus forming a black-and-white image of the fiber optic end-face. Edge detection provides the image's contour information, thus obtaining the region information of the inner fiber optic end-face. Simultaneously, edge detection within the fiber optic end-face region yields information about reflective areas. A bright region is defined as a group of connected bright pixels. The maximum connected component algorithm can be used to determine the connectivity of reflective regions, thus obtaining the number of reflective regions. When calculating the number of reflective regions, noise caused by equipment noise, error interference, or the external environment is discarded. For example, regions with fewer than a specified number of pixels are defined as noise points and are not included in the count of reflective regions. Meanwhile, edge detection can also scan from the center outwards or scan line by line to detect whether there are coordinates or areas representing bright spots inside the fiber end face. Since the relative position of the crescent-shaped reflective area generated by a point light source to the point light source is fixed, an area can be set to represent the area where reflection must exist. If a bright spot is detected inside the photoelectric end face by scanning line by line outside the area, it can be determined that the fiber end face has a burr.

[0040] The system detects the reflective areas within the fiber optic endface and obtains the number of reflective areas. If the number of reflective areas detected is greater than or equal to two, the fiber optic endface is deemed unqualified. When a point light source emits light, the fiber optic endface will inevitably produce a crescent-shaped reflection on the side closest to the light source. Figure 4As shown, if there is still reflective area 5 in the image, it indicates that the image shows a raised burr on the fiber end face. If the fiber end face is qualified, as shown... Figure 3 As shown, without a burr, the image will only show one reflective area.

[0041] Since a single point light source can only produce a limited reflection angle, when several point light sources are evenly distributed and lit up in turn, there will inevitably be at least one point light source that can cause the flare to form a reflective area on the image.

[0042] Another embodiment provided by this patent is that when a point light source emits light, a crescent-shaped reflective area will inevitably be generated on the side of the optical fiber end face closest to that light source. Since the fringe is generally located at the edge of the optical fiber end face, theoretically, the reflective area is most obvious in the image when the fringe is located at the farthest end relative to the point light source. Because several point light sources are used, at least one point light source must be the farthest from the fringe. Therefore, to reduce computational load, it is sufficient to detect only whether there is a reflective area in the far end region of the optical fiber end face corresponding to the crescent-shaped reflective area formed by a single point light source.

[0043] To simplify the explanation of relative positions, a virtual model is used here. Specifically, for example... Figure 5 As shown, in the projection plane, on the virtual straight line formed by the point light source and the center of the circle, the straight line intersects the edge of the fiber end face at two points. The intersection point closer to the point light source is the near intersection point, and the intersection point farther away from the point light source is the far intersection point 5. When the point light source is lit, the area of ​​the fiber end face near the near intersection point will inevitably generate a reflective area formed by the point light source. Therefore, it is not necessary to detect the reflection.

[0044] At this point, only the region at the far intersection point 5 of the image within the fiber optic endface needs to be detected. Since the relative positions of the light sources are fixed, a fixed detection area 'a' can be set in the corresponding region at the far intersection point 5. If a reflective area or several reflective points are detected in the region within the fiber optic endface at the far intersection point 5, the fiber optic endface is deemed unqualified. Because the position and number of point light sources within the image are physically fixed, their relative positions within the image can be predicted after the equipment is manufactured. If there are three point light sources, the image can be pre-divided into three equal parts along the circumference, with the region at the far intersection point located in the middle of the arc of each division. Thus, during detection, only the region within the fiber optic endface of the image at the corresponding far intersection point can be detected, significantly reducing the computational load.

[0045] The above method involves a pre-defined detection area within the equipment. If a real-time detection method is used to divide the area, it is necessary to detect the center of the fiber end face within the fiber end face image. After obtaining the outline information of the fiber end face through edge detection, the coordinates of the center are found based on the aspect ratio of the image. Then, based on the coordinates of the center and the coordinates of the pre-known point light source, the corresponding far intersection point is found. A pre-set threshold is used to detect whether there is a reflective area at the far intersection point. If a reflective area is detected, it proves that the fiber end face has a burr; if no reflective area is detected, it proves that the fiber end face is qualified.

Claims

1. A method for detecting the end face of an optical fiber, comprising an optical fiber having an end face with a center; the end face being a fused end face, and the edge of the end face having an arc-shaped transition towards the end face body, characterized in that: Acquire an axially captured image of the fiber end face; A plurality of point light sources; in the axial direction of the fiber end face, the plurality of point light sources are located in front of the fiber end face; when the projection direction is the axial direction of the fiber end face, and the plane where the image of the fiber end face is located is the projection plane, the projection of the plurality of point light sources is located on the concentric circles of the projection of the center of the circle. The point light source can generate a reflective area on the edge of one side corresponding to the end face of the optical fiber, and the reflective area is imaged onto the end face of the optical fiber. Several point light sources emit light sequentially, and an image of the fiber end face is obtained when several individual point light sources emit light. The system detects the reflective areas of the image within the fiber endface and obtains the number of reflective areas. If the number of reflective areas detected within the fiber endface is greater than or equal to two, the fiber endface is deemed unqualified.

2. The fiber optic end-face detection method according to claim 1, characterized in that: The reflective areas of the image within the fiber optic end face include: S1: Obtain image information representing the brightness and darkness pixel values ​​at the fiber end face; S2: Perform edge detection to obtain the fiber end face contour information and the information of the reflective area within the fiber end face in the image.

3. The fiber optic end-face detection method according to claim 1, characterized in that: The number of point light sources is configured to be four.

4. The fiber optic end-face inspection method according to any one of claims 1 to 3, characterized in that: When the number of pixels in the bright area of ​​the detected image within the fiber endface exceeds a set threshold, it is identified as a reflective area.

5. A method for detecting the end face of an optical fiber, comprising an optical fiber having an end face with a center; the end face being a fused-to-metal end face, and the edge of the end face having an arc-shaped transition towards the end face body, characterized in that: Acquire an axially captured image of the fiber end face; A plurality of point light sources; in the axial direction of the fiber end face, the plurality of point light sources are located in front of the fiber end face; when the projection direction is the axial direction of the fiber end face, and the plane where the image of the fiber end face is located is the projection plane, the projections of the plurality of point light sources are located on the concentric circles of the projection of the center of the circle; in the projection plane, they are located on the virtual straight line formed by the projection of the point light sources and the projection of the center of the circle, and the straight line forms two intersection points with the outline of the projection of the fiber end face, the intersection point closer to the point light source is the near intersection point, and the intersection point farther away from the point light source is the far intersection point. Several point light sources emit light sequentially, and an image of the fiber end face is obtained when several individual point light sources emit light. The image at the far intersection point within the fiber optic endface is detected. If a reflective area is detected in the area within the fiber optic endface at the far intersection point, the fiber optic endface is deemed unqualified.

6. The fiber optic end-face inspection method according to claim 5, characterized in that: The region where the far intersection point of the image within the fiber endface is detected includes: S1: Obtain image information representing the brightness and darkness pixel values ​​at the fiber end face; S2: Perform edge detection to obtain the fiber end face contour information in the image and whether there is a reflective area in the fiber end face at the far intersection point.

7. The fiber optic end-face inspection method according to claim 5, characterized in that: The number of point light sources is configured to be four.

8. The fiber optic end-face inspection method according to claim 5, characterized in that: The image is divided into equal parts along the circumference, with the physical center of the image or the center of the circle as the center. The number of equal parts is the same as the number of point light sources. The intersection point is located in the middle of the arc of a single equally divided region.

9. The fiber optic end-face inspection method according to any one of claims 5 to 8, characterized in that: When the number of pixels in the bright area of ​​the detected image within the fiber endface exceeds a set threshold, it is identified as a reflective area.

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