CN118130046A - Bessel structured light illumination special optical fiber system and online detection method - Google Patents
Bessel structured light illumination special optical fiber system and online detection method Download PDFInfo
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Abstract
The invention discloses a special optical fiber system for Bessel structured light illumination and an online detection method. The system has the characteristics of simple structure of the optical path device and clear imaging of the internal structure of the special optical fiber, and can realize real-time dynamic measurement of the internal structure of the fiber core; in the field of optical fiber side surface measurement, the method disclosed by the invention benefits from the Bessel structured light coherent illumination technology, has the characteristics of high measurement precision and clear imaging, and can be widely applied to scenes such as optical fiber preparation, optical fiber processing, optical fiber structure measurement and the like.
Description
Technical Field
The invention relates to imaging and measurement of special optical fibers, in particular to a special optical fiber system for Bessel structured light illumination and an online detection method.
Background
Multicore fibers are a promising next-generation communication carrier due to their space division multiplexing characteristics, and therefore they are widely used in the fields of large-capacity data communication and high-precision measurement. Including multi-core optical fibers, polarization maintaining optical fibers, photonic crystal optical fibers, and the like, a series of special optical fibers with internal special structures must precisely position the distribution of the core structures inside the optical fibers during processing, such as fiber splicing, fiber bundle fanning/fanning, mode coupling, grating writing, fiber drawing, and the like, because this determines the operational performance of the device, including loss, responsiveness, sensitivity, and the like.
In fiber splicing, fiber bundle fanin/fanout and mode coupling, accurate core alignment can reduce losses, thereby significantly improving the quality and capacity of the transmitted signal; the grating inscription of the multi-core optical fiber requires to precisely position each fiber core so as to facilitate multi-parameter and high-precision temperature and strain measurement; the drawing of special optical fibers requires effective on-line monitoring to minimize fiber twist and stabilize product quality.
Under these requirements, the existing technical solutions can be divided into two types of optical fiber end face imaging and optical fiber side face imaging. Fiber-optic endface imaging such as that of application nos. 201420363471.4 and 202310058392.6 require destructive manipulation of the fiber, such as cutting, which is detrimental to on-line detection during fiber drawing. There are various kinds of optical fiber side imaging, for example, patent application number 201510195930.1 provides a multi-channel digital holographic method using coherent light, which requires multi-channel coherent polarized light, and has complex structure and high cost; the 202010651411.2 patent provides a gaussian illumination aperture diffraction method using coherent light, which uses diffraction spots that do not allow visual visualization of the core structure inside the fiber.
The prior art has the following disadvantages:
1. Compared with the existing optical fiber side imaging systems in the market, the images of the optical fiber side imaging systems are blurred due to the complex structure of the special optical fiber core, and clear imaging and measurement of the internal optical fiber core structure are difficult to realize.
2. Comparison of similar patents: a digital holographic system for online nondestructive measurement of refractive index of special optical fiber and an optical fiber axial nondestructive online detection device and method. A similar point is that images of the internal structure of the fiber are obtained by illuminating the transmissive fiber with coherent light at the sides of the fiber. The technical advantages of this patent are: the patent uses the mode of single-path Bessel structured light coherent illumination, clear optical fiber internal structure imaging can be obtained, and the problems that an imaging light path structure is complex and an imaging result is not visual in similar patents are avoided.
Disclosure of Invention
The invention aims to: the invention aims to provide a special optical fiber system for Bessel structured light illumination, which has a simple optical path structure and a clear imaging result, and the other aim of the invention is to provide a special optical fiber on-line detection method for Bessel structured light illumination, so that real-time dynamic measurement of the internal structure of a fiber core is realized.
The technical scheme is as follows: the invention relates to a special optical fiber on-line detection method for Bessel structured light illumination, which comprises the following steps:
Step 1, taking a part of the optical fiber to be tested, forming a test optical fiber, and placing the test optical fiber in an optical fiber electric rotator;
The step 1 specifically comprises the following steps: cutting a section of test optical fiber from the tested optical fiber by using an optical fiber cutting knife, so that the first end face and the second end face of the test optical fiber are relatively flat; and placing the test optical fiber into an optical fiber electric rotator and fixing the test optical fiber, wherein the optical fiber electric rotator drives the test optical fiber to rotate along the axial direction of the optical fiber.
Step 2, turning on a laser light source, and transmitting coherent light along a light path to form Bessel coherent structural light to illuminate the test optical fiber;
The step 2 specifically comprises the following steps: turning on a laser source, enabling Gaussian coherent light to propagate along a light path and enter a first light spot adjusting lens and a second light spot adjusting lens, generating Bessel coherent structural light through a Bessel structural light generator, and then entering a third light spot adjusting lens and a first objective lens to form Bessel coherent structural light for illuminating a test optical fiber; the first light spot adjusting lens and the second light spot adjusting lens adopt optical lenses, and comprise one of convex lenses, concave lenses and cemented lenses; the Bessel structured light generator adopts a spatial light phase modulation device, and comprises one of a conical lens, a phase plate and a spatial light modulator.
Step 3, acquiring a light field image of the Bessel coherent structured light transmission test optical fiber by using a first camera;
The step 3 specifically comprises the following steps: the light field image of the Bessel coherent structure light side transmission test optical fiber is amplified by a second objective, and the amplified image is subjected to image acquisition by using a first camera.
Step 4, transmitting light emitted by a point light source to a first end face of the test optical fiber, collecting images of a second end face of the tested optical fiber, calculating characteristics according to the collected images, distributing unique serial numbers to the characteristics, naming the images collected by the second end face at the moment by using the serial numbers, naming the images collected by the step 3 by using the serial numbers, and rotating the test optical fiber by using an optical fiber electric rotator;
the step 4 specifically comprises the following steps: transmitting light emitted by a point light source to a first end face of a test optical fiber, coupling light into a fiber core of the test optical fiber, transmitting the light to a second end face along the fiber core of the test optical fiber, and acquiring an image of the second end face of the test optical fiber, and acquiring gray scale images of fiber core images and fiber cladding images; calculating the characteristic of the second end face image of the test optical fiber by using an image processing program, assigning a unique serial number to the characteristic, adopting an image algorithm for characteristic calculation, including the rotation angle of the characteristic points of the optical fiber, the coordinates of the characteristic points or the black-and-white structural coding of the image, naming the image acquired by the second end face at the moment by using the serial number, naming the image acquired in the step 3 by using the serial number, establishing the association of the two images by using the unique serial number, and rotating the test optical fiber by using an optical fiber electric rotator.
Step 5, repeating the step 4 until the test optical fiber is rotated 360 degrees; the rotation angle can be reduced according to the structural symmetry of the inside of the optical fiber;
Step 6, integrating all the images with the unique serial number marks obtained in the step 5 to form an image database of the optical fiber to be tested;
the step 6 specifically comprises the following steps: and (3) integrating all the obtained images with the unique serial number marks in the step (5) to form an image database of the optical fiber to be tested, wherein each group of data in the image database comprises a unique serial number, a corresponding second end face image and a corresponding optical field image of the Bessel coherent structure light transmission test optical fiber.
Step 7, placing an optical fiber to be measured in the optical fiber electric rotator; the optical fiber electric rotator (14) is replaced by other optical fiber clamps, and the optical fiber (10) to be tested and the test optical fiber are kept at the same position;
Step 8, acquiring a light field image of the Bessel coherent structure light transmission optical fiber to be measured by using a first camera;
And 9, comparing the image obtained in the step 8 with the image in the database established in the step 6 by using an image algorithm, finding out the most similar image, and deriving a corresponding unique serial number of the most similar image in the database and an associated second end face image to complete the online detection of the optical fiber internal structure.
The step 9 specifically comprises the following steps: and (3) comparing the structured light transmission image obtained in the step (8) with the structured light transmission image in the database established in the step (6) by using an image algorithm to find the most similar image, wherein the image algorithm comprises at least one of two-dimensional data similarity calculation, image feature extraction comparison or deep learning, and deriving a corresponding unique serial number of the most similar image in the database and an associated second end face image to complete the optical fiber online detection.
Before the optical fiber to be tested is tested, the positions of the laser light source, the first light spot adjusting lens, the second light spot adjusting lens, the Bessel structure light generator, the third light spot adjusting lens, the first objective lens and the second objective lens in the optical path are calibrated, so that the positions of the first objective lens and the second objective lens are located at the center of the optical axis of the optical path, the positions of the first objective lens and the second objective lens are fixed after adjustment are finished, the positions of the first objective lens and the second objective lens are not changed, and the optical fiber electric rotator platform is reset.
The special optical fiber system for Bessel structured light illumination is used for realizing the special optical fiber online detection method for Bessel structured light illumination, and comprises a laser light source, coherent Gaussian light, a first light spot adjusting lens, a second light spot adjusting lens, a Bessel structured light generator, coherent Bessel structured sightseeing, a third light spot adjusting lens, a first objective lens, an optical fiber to be detected, a second objective lens, a first camera, a point light source, an optical fiber electric rotator, a third objective lens and a second camera.
The laser light source is used for generating illumination Gaussian coherent light for imaging, and the wavelength of the laser light source is 600-650 nm, preferably 625nm; the first light spot adjusting lens and the second light spot adjusting lens are used for adjusting the light spot size and the light spot quality of Gaussian light, convex lenses, concave lenses, cemented lenses and the like can be used, and are preferably biconvex lenses with the diameter of a dimension circle of 25.4mm, and the focal lengths are 25mm and 50mm respectively; the Bessel structured light generator is used for converting incident coherent Gaussian light into emergent coherent Bessel light, and a conical lens, a phase plate, a spatial light modulator and the like can be used, and the conical lens with the diameter of a dimension circle of 25.4mm and the conical inclination angle of 5 degrees is preferable; the third light spot adjusting lens and the first objective lens are parameters for adjusting the generated Bessel structured light, the third light spot adjusting lens can use a convex lens, a cemented lens and the like, and is preferably a biconvex lens with a dimension circle diameter of 25.4mm, the focal length is 50mm, and the magnification of the first objective lens is 10 to 40 times, preferably 20 times; the optical fiber to be measured is an optical fiber to be measured, the types of the optical fiber to be measured comprise but are not limited to polarization maintaining optical fiber, multi-core optical fiber, photonic crystal optical fiber and the like, the materials of the optical fiber to be measured comprise but are not limited to quartz glass, plastic and multi-component glass, and the diameter of the optical fiber to be measured is 60 micrometers to 2 millimeters; the second objective lens and the third objective lens are used for magnifying an imaging image, and the magnification of the objective lens is 10 to 100 times, preferably 50 times and 40 times respectively; the first camera and the second camera are used for image acquisition, and linear array or area array photosensitive elements can be used; the point light source is used for illuminating the internal structure of the optical fiber to be tested, and is visible incoherent light with the wavelength of 400nm to 700nm, preferably white light; the optical fiber electric rotator is used for rotating the optical fiber to be measured, the rotating angle range of the optical fiber electric rotator is not limited, and the minimum rotating angle is 0.05-5 degrees, preferably 0.1 degrees.
The beneficial effects are that: compared with the prior art, the invention has the following advantages:
1. The system provided by the invention has the characteristics of simple structure of the optical path device and clear imaging of the internal structure of the special optical fiber, and can realize real-time dynamic measurement of the internal structure of the fiber core.
2. In the field of optical fiber side surface measurement, the method disclosed by the invention benefits from the Bessel structured light coherent illumination technology, has the characteristics of high measurement precision and clear imaging, and can be widely applied to scenes such as optical fiber preparation, optical fiber processing, optical fiber structure measurement and the like.
Drawings
Fig. 1 is a schematic diagram of generating bessel structured light in an optical path system for online detection of a special optical fiber illuminated by bessel structured light provided in embodiment 1 of the present invention;
fig. 2 is a schematic space structure diagram of an illumination light path and a fiber rotator in a light path system for online detection of special fiber illuminated by bessel structured light provided in embodiment 1 of the present invention;
FIG. 3 is a schematic diagram of imaging results of a Bessel structured light illumination specialty fiber in example 1;
FIG. 4 is a schematic diagram of the imaging result of a second end face of a point source illumination fiber first end face in example 1;
fig. 5 is a schematic flow chart of a method for online detection of special optical fibers illuminated by bessel structured light provided in embodiment 2 of the present invention.
Detailed Description
The technical scheme of the invention is further described below with reference to the accompanying drawings.
Example 1:
As shown in fig. 1 to 4, a special optical fiber system for bessel structured light illumination includes a laser light source 1, coherent gaussian light 2, a first light spot adjusting lens 3, a second light spot adjusting lens 4, a bessel structured light generator 5, a coherent bessel structured sightseeing 6, a third light spot adjusting lens 7, a first objective lens 8, an optical fiber 10 to be measured, a second objective lens 11, a first camera 12, a point light source 13, an optical fiber electric rotator 14, a third objective lens 15 and a second camera 16. The laser source 1 is used for generating illumination Gaussian coherent light 2 for imaging, and the wavelength of the laser source is 600-650 nm, preferably 625nm; the first light spot adjusting lens 3 and the second light spot adjusting lens 4 are used for adjusting the light spot size and the light spot quality of the Gaussian light 2, and convex lenses, concave lenses, cemented lenses and the like can be used, and are preferably biconvex lenses with the diameter of a dimension circle of 25.4mm, and the focal lengths are respectively 25mm and 50mm; the bessel structured light generator 5 is used for converting incident coherent gaussian light into emergent coherent bessel light 6, and conical lenses, phase plates, spatial light modulators and the like can be used, and the conical lenses with the diameter of a dimension circle of 25.4mm and the inclination angle of a cone of 5 degrees are preferable; the third flare adjusting lens 7 and the first objective lens 8 are parameters for adjusting the generated bessel structured light 6, and the third flare adjusting lens 7 can use a convex lens, a cemented lens, etc., preferably a biconvex lens with a dimension circle diameter of 25.4mm, the focal length is 50mm, and the magnification of the first objective lens 8 is 10 to 40 times, preferably 20 times; the optical fiber to be measured 10 is an optical fiber to be measured, and the types of the optical fiber to be measured 10 include, but are not limited to: polarization maintaining fiber, multi-core fiber, photonic crystal fiber, etc., in this embodiment, seven-core fiber is used as a reference, the materials of the fiber 10 to be measured include, but are not limited to, quartz glass, plastic, and multicomponent glass, in this embodiment, multicomponent glass is used as a reference, the diameter of the fiber 10 to be measured is 60 micrometers to 2 millimeters, and in this embodiment, 150 micrometers is used as a reference; the second objective lens 11 and the third objective lens 15 are used for magnifying the imaged image, and the magnification of the objective lens is 10 to 100 times, preferably 50 times and 40 times, respectively; the first camera 12 and the second camera 16 are used for image acquisition, and linear array or area array photosensitive elements can be used; the point light source 13 is used for illuminating the internal structure of the optical fiber 10 to be measured, and the point light source 13 is visible incoherent light with the wavelength of 400nm to 700nm, preferably white light; the optical fiber electric rotator 14 is used for rotating the optical fiber 10 to be measured, the rotation angle range of the optical fiber electric rotator 14 is not limited, and the minimum rotation angle is 0.05-5 degrees, preferably 0.1 degrees.
The principle of the special optical fiber internal structure imaging system for the structured light coherent illumination is as follows: the Bessel beam is light without diffraction structures, and the self-healing characteristic can provide longer focusing depth in a scattering medium, so that imaging speckles based on Bessel laser illumination are less, and an image is clearer. In addition, when a Bessel beam is transmitted through an off-axis object having a transparent medium with a refractive index change inside, one core will create two refractive paths with different curvatures.
The initial quality of the light source and the light ring inside the bessel structured light will have a certain impact on the imaging quality. The invention proposes a solution to the above-mentioned disturbances: and small holes are arranged at the focusing positions of the light spot adjusting lenses, so that the uniformity of Gaussian laser light spots is optimized. And the image processing mode is used, and part of extra Bessel light spot circular rings are eliminated through opening and closing operation and bright spot curvature identification.
Example 2:
As shown in fig. 5, the special optical fiber on-line detection method for Bessel structured light illumination comprises the following steps:
Step 1, cutting a section of test optical fiber with the length of 5-40 cm, preferably 20cm, from the tested optical fiber 10 by using an optical fiber cutting knife to enable the first end face and the second end face of the test optical fiber to be relatively flat, enabling the cutting inclination angle of the optical fiber to be smaller than 5 degrees, and removing stains on the end faces of the optical fibers by using alcohol or acetone; the test optical fiber is placed in the optical fiber electric rotator 14 and fixed, and when the test optical fiber is rotated by the optical fiber electric rotator 14, the test optical fiber only rotates along the optical fiber axial direction.
Step 2, turning on the laser source 1, wherein the Gaussian coherent light 2 propagates along the light path and enters the first light spot adjusting lens 3 and the second light spot adjusting lens 4, bessel coherent structured light 6 is generated by the Bessel structured light generator 5, and then the Bessel coherent structured light for illuminating the test optical fiber is formed after the third light spot adjusting lens 7 and the first objective lens 8 are shot; the first flare adjusting lens 3 and the second flare adjusting lens 4 can use convex lenses, concave lenses, cemented lenses and the like, and are preferably biconvex lenses with the diameter of a dimension circle of 25.4mm, and the focal lengths are 25mm and 50mm respectively; the bessel structured light generator 5 may use a conical lens, a phase plate, a spatial light modulator, etc., preferably a conical lens with a diameter of a dimension circle of 25.4mm, a conical inclination angle of 5 °; the third flare adjusting lens 7 may use a convex lens, a cemented lens, or the like, preferably a biconvex lens with a circular diameter of 25.4mm, a focal length of 50mm, and a magnification of 10 to 40 times, preferably 20 times, of the first objective lens 8;
Step 3, amplifying a light field image of the Bessel coherent structure light side transmission test optical fiber by a second objective 11, wherein the position of the light transmission test optical fiber is less than 150 microns from the end surface of the test optical fiber, the amplification factor of the second objective 11 is 10 to 100 times, preferably 50 times, and the amplified image is acquired by using a first camera 12;
step 4, transmitting the light emitted by the point light source 13 to the first end face of the test optical fiber, coupling the light into the fiber core of the test optical fiber, transmitting the light to the second end face along the fiber core of the test optical fiber, and carrying out image acquisition on the second end face of the test optical fiber, so that gray-scale images of fiber core images and fiber cladding images can be acquired, and image quality can be further improved by applying image algorithms such as wavelet noise reduction, gaussian blur, median extraction, image opening and closing operation, image binarization, edge detection and the like; the point light source 13 is visible incoherent light with a wavelength of 400nm to 700nm, preferably white light; calculating the characteristic of the second end face image of the test optical fiber by using an image processing program, assigning a unique serial number to the characteristic, wherein the characteristic can be obtained by using the rotation angle of the characteristic points of the optical fiber, the coordinates of the characteristic points or the black-and-white structural codes of the image, and the like, preferably the rotation angle of the characteristic points of the optical fiber, naming the image acquired by the second end face at the moment by using the serial number, naming the image acquired in the step 3 by using the serial number, establishing the association of the two images by using the unique serial number, rotating the test optical fiber by using the optical fiber electric rotator 14, wherein the rotation angle range of the optical fiber electric rotator 14 is not limited, and the minimum rotation angle is 0.05-5 degrees, preferably 0.1 degrees;
Step 5, repeating the step 4 until the test optical fiber is rotated 360 degrees and the stepping angle is 0.1 degrees, wherein the total step 4 is 3600 times, and the rotation angle can be reduced according to the structural symmetry in the optical fiber;
Step 6, integrating all the obtained images with the unique serial number marks in the step 5 to form an image database of the optical fiber 10 to be tested, wherein the preferred database comprises 3600 groups of data, each group of data comprises a unique serial number, and a corresponding second end face image and a corresponding optical field image of the Bessel coherent structured light transmission test optical fiber;
Step 7, placing the optical fiber 10 to be measured in the optical fiber electric rotator 14, and only keeping the optical fiber 10 to be measured and the test optical fiber at the same position without using the optical fiber electric rotator 14 or using other optical fiber clamps;
Step 8, illuminating the optical fiber 10 to be detected by using Bessel coherent structural light, and obtaining a transmission image of the Bessel coherent structural light of the optical fiber 10 to be detected;
And 9, comparing the structured light transmission image obtained in the step 8 with the structured light transmission image in the database established in the step 6 by using an image algorithm to find the most similar image, wherein the image algorithm can be two-dimensional data similarity calculation, corner detection, peak and trough characteristic value extraction, characteristic matching or deep learning, preferably two-dimensional data similarity calculation and deep learning, and deriving a unique serial number corresponding to the most similar image in the database and an associated second end face image to complete the optical fiber online detection.
Claims (10)
1. The special optical fiber on-line detection method for Bessel structured light illumination is characterized by comprising the following steps of:
Step 1, taking a part of the optical fiber to be tested (10) to form a test optical fiber, and putting the test optical fiber into an optical fiber electric rotator (14);
Step 2, turning on a laser light source (1), and transmitting coherent light along a light path to form Bessel coherent structured light to illuminate a test optical fiber;
Step 3, acquiring a light field image of the Bessel coherent structure light transmission test optical fiber by using a first camera (12);
Step 4, transmitting light emitted by a point light source (13) to a first end face of the test optical fiber, carrying out image acquisition on a second end face of the tested optical fiber, calculating characteristics according to the acquired images, assigning a unique serial number to the characteristics, naming the image acquired by the second end face at the moment by using the serial number, naming the image acquired in the step 3 by using the serial number, and rotating the test optical fiber by using an optical fiber electric rotator (14);
Step 5, repeating the step 4 until the test optical fiber is rotated 360 degrees;
Step 6, integrating all the images with the unique serial number marks obtained in the step 5 to form an image database of the optical fiber (10) to be tested;
step 7, placing an optical fiber (10) to be measured in the optical fiber electric rotator (14);
step 8, acquiring a light field image of the Bessel coherent structured light transmission optical fiber (10) to be tested by using a first camera (12);
And 9, comparing the image obtained in the step 8 with the image in the database established in the step 6 by using an image algorithm, finding out the most similar image, and deriving a corresponding unique serial number of the most similar image in the database and an associated second end face image to complete the online detection of the optical fiber internal structure.
2. The special optical fiber online detection method for Bessel structured light illumination according to claim 1, wherein before the optical fiber (10) to be tested is tested, the positions of a laser light source (1), a first light spot adjusting lens (3), a second light spot adjusting lens (4), a Bessel structured light generator (5), a third light spot adjusting lens (7), a first objective lens (8) and a second objective lens (11) in an optical path are calibrated, so that the positions of the optical fiber are located at the right center of an optical axis of the optical path, the positions of the optical fiber are fixed after adjustment are not changed, and the rotation of a platform of an optical fiber electric rotator (14) is reset.
3. The method for on-line detection of special optical fibers for Bessel structured light illumination according to claim 1, wherein the step 1 is specifically: cutting a section of test optical fiber from the optical fiber (10) to be tested by using an optical fiber cutting knife, so that the first end face and the second end face of the test optical fiber are relatively flat; and placing the test optical fiber into an optical fiber electric rotator (14) and fixing the test optical fiber, wherein the optical fiber electric rotator (14) drives the test optical fiber to rotate along the axial direction of the optical fiber.
4. The method for on-line detection of special optical fibers for Bessel structured light illumination according to claim 1, wherein the step 2 is specifically: turning on a laser light source (1), enabling Gaussian coherent light (2) to propagate along a light path and enter a first light spot adjusting lens (3) and a second light spot adjusting lens (4), generating Bessel coherent structural light (6) through a Bessel structural light generator (5), and then injecting a third light spot adjusting lens (7) and a first objective lens (8) to form Bessel coherent structural light for illuminating a test optical fiber; the first light spot adjusting lens (3) and the second light spot adjusting lens (4) adopt optical lenses, and comprise one of convex lenses, concave lenses and cemented lenses; the Bessel structured light generator (5) employs a spatial light phase modulation device comprising one of a axicon, a phase plate and a spatial light modulator.
5. The method for on-line detection of special optical fibers for Bessel structured light illumination according to claim 1, wherein the step 3 is specifically: the light field image of the Bessel coherent structure light side transmission test optical fiber is amplified by a second objective (11), and the amplified image is subjected to image acquisition by using a first camera (12).
6. The method for on-line detection of special optical fibers for illumination by Bessel structured light according to claim 1, wherein the step 4 is specifically: transmitting light emitted by a point light source (13) to a first end face of a test optical fiber, coupling the light into a fiber core of the test optical fiber, transmitting the light to a second end face along the fiber core of the test optical fiber to emit, and acquiring an image of the second end face of the test optical fiber to acquire a gray scale image of an optical fiber core image and an optical fiber cladding image; calculating the characteristic of the second end face image of the test optical fiber by using an image processing program, assigning a unique serial number to the characteristic, adopting an image algorithm for characteristic calculation, including the rotation angle of the characteristic points of the optical fiber, the coordinates of the characteristic points or the black-and-white structural coding of the image, naming the image acquired by the second end face at the moment by using the serial number, naming the image acquired in the step 3 by using the serial number, establishing the association of the two images by using the unique serial number, and rotating the test optical fiber by using an optical fiber electric rotator (14).
7. The method for on-line detection of special optical fibers for illumination by Bessel structured light according to claim 1, wherein the step 6 is specifically: and (3) integrating all the obtained images with the unique serial number marks in the step (5) to form an image database of the optical fiber (10) to be tested, wherein each group of data in the image database comprises a unique serial number, a corresponding second end face image and a corresponding optical field image of the Bessel coherent structure light transmission test optical fiber.
8. The method for on-line detection of special optical fibers for illumination of bessel structured light according to claim 1, wherein the step 9 is specifically: and (3) comparing the structured light transmission image obtained in the step (8) with the structured light transmission image in the database established in the step (6) by using an image algorithm to find the most similar image, wherein the image algorithm comprises at least one of two-dimensional data similarity calculation, image feature extraction comparison or deep learning, and deriving a corresponding unique serial number of the most similar image in the database and an associated second end face image to complete the optical fiber online detection.
9. Special optical fiber system for bessel structured light illumination, which is used for realizing the special optical fiber on-line detection method for bessel structured light illumination according to any one of claims 1-8, and is characterized by comprising a laser light source (1), coherent gaussian light (2), a first light spot adjusting lens (3), a second light spot adjusting lens (4), a bessel structured light generator (5), a coherent bessel structured sightseeing (6), a third light spot adjusting lens (7), a first objective lens (8), an optical fiber to be detected (10), a second objective lens (11), a first camera (12), a point light source (13), an optical fiber electric rotator (14), a third objective lens (15) and a second camera (16).
10. The special optical fiber system for Bessel structured light illumination according to claim 9, wherein the laser light source (1) is used for generating illumination Gaussian coherent light (2) for imaging, and the wavelength of the laser light source is 600-650 nm; the first light spot adjusting lens (3) and the second light spot adjusting lens (4) are used for adjusting the light spot size and the light spot quality of Gaussian light (2), and an optical lens comprising one of a convex lens, a concave lens and a cemented lens is adopted; the Bessel structured light generator (5) is used for converting incident coherent Gaussian light into emergent coherent Bessel light (6), and adopts a spatial light phase modulation device, and comprises one of a conical lens, a phase plate and a spatial light modulator; the third light spot adjusting lens (7) and the first objective lens (8) are used for adjusting parameters of the generated Bessel structured light (6), the third light spot adjusting lens (7) adopts an optical lens, and comprises one of a convex lens, a concave lens and a cemented lens, and the magnification of the first objective lens (8) is 10 to 40 times; the optical fiber (10) to be measured is an optical fiber to be measured, the type of the optical fiber (10) to be measured is a special optical fiber, the optical fiber comprises a polarization maintaining optical fiber, a multi-core optical fiber and a photonic crystal optical fiber, the optical fiber (10) to be measured is made of silicon dioxide or plastics, the optical fiber comprises quartz glass, plastics and multi-component glass, and the diameter of the optical fiber (10) to be measured is 60 micrometers to 2 millimeters; the second objective lens (11) and the third objective lens (15) are used for magnifying an imaging image, and the magnification of the objective lens is 10 to 100 times; the first camera (12) and the second camera (16) are used for image acquisition, and a photoelectric conversion device is adopted, wherein the photoelectric conversion device comprises a photodiode, a linear array or an area array photosensitive element; the point light source (13) is used for illuminating the internal structure of the optical fiber (10) to be detected, and the point light source (13) is visible incoherent light with the wavelength of 400nm to 700 nm; the optical fiber electric rotator (14) is used for rotating the optical fiber (10) to be detected, the rotation angle range of the optical fiber electric rotator (14) is not limited, and the minimum rotation angle is 0.05-5 degrees.
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