Device and method for measuring numerical aperture of optical fiber image transmission array

Abstract

The invention relates to an optical fiber image transmission array numerical aperture measuring device and method, the optical fiber image transmission array numerical aperture measuring device comprises an ambient light shielding cover, a guide rail is arranged in the ambient light shielding cover, and a laser used for outputting laser beams, a convex lens, a high-precision mobile platform and a fixed platform are sequentially arranged on the guide rail; a detected optical fiber image transmitting array is arranged on the high-precision moving platform, a high-precision moving platform is arranged on the fixed platform, and a detector is arranged on the high-precision moving platform. The optical fiber numerical aperture is detected by directly utilizing the optical fiber scattering angle theta of the optical fiber image transmission array.

Description

Technical Field

[0001] This invention relates to the field of fiber optic measurement technology, and in particular to a numerical aperture measurement device and method for fiber optic image arrays. Background Technology

[0002] Fiber optic image arrays are optical components made of tens of millions of micron-sized optical fibers arranged and fused together in a regular pattern. They are widely used in the field of high-precision optical transmission. Their working principle mainly includes three key steps: input, distribution, and output of optical signals. Each fiber acts as an independent image transmission unit, featuring high light transmission efficiency, low coupling loss, clear and realistic images, and zero optical thickness.

[0003] Numerical aperture (NA) is an important parameter of fiber optic imaging arrays, characterizing their ability to receive and transmit light. It is defined as the product of the sine of the maximum incident angle (acceptance angle) that an optical fiber can receive and transmit light from, and the refractive index of the fiber end face. The size of the numerical aperture is closely related to the structure of the optical fiber (the refractive indices of the core and cladding), reflecting the range of light that the fiber can receive and transmit.

[0004] The size of the numerical aperture (NAP) depends on the refractive index difference between the fiber core and cladding. A larger refractive index difference results in a larger NAP, which in turn strengthens the fiber's ability to receive light. A larger NAP allows the fiber to receive a wider range of light, meaning it can receive incident light at larger angles. A larger NAP can improve the fiber's coupling efficiency, but an excessively large NAP may lead to multimode transmission, affecting signal quality and transmission distance. In imaging applications such as fiber optic image arrays, NAP affects image sharpness and resolution. A larger NAP can increase image brightness but may introduce more optical distortion.

[0005] Fiber optic imaging arrays are commonly used for optical coupling in imaging, fiber optic sensors, or optical communications. A larger numerical aperture (NAP) allows the fiber optic imaging array to receive more light, resulting in higher coupling efficiency. In fiber optic imaging arrays, the NAP determines the resolution and sharpness of the image. A larger NAP may lead to increased light loss during propagation in the fiber, thus requiring a trade-off between receiving capability and transmission loss. Therefore, NAP is one of the important parameters for evaluating the optical performance of fiber optic imaging arrays, directly affecting the light-gathering capability and transmission efficiency of the fiber. In practical applications, the selection of the NAP needs to be optimized according to specific requirements to balance factors such as receiving capability, image quality, and transmission loss.

[0006] Traditional numerical aperture measurement methods typically rely on complex optical systems and cumbersome operating procedures, and their measurement accuracy is limited. Therefore, developing a high-precision, easy-to-operate fiber optic image array numerical aperture measurement device is of significant practical importance. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a device and method for measuring the numerical aperture of an optical fiber image array. The technical problem to be solved is to detect the numerical aperture of an optical fiber by directly utilizing the optical fiber scattering angle θ of the optical fiber image array.

[0008] The objective of this invention and the technical problem it solves are achieved by the following technical solution. A numerical aperture measurement device for fiber optic image transmission arrays, according to this invention, includes an ambient light shield, a guide rail disposed within the ambient light shield, and a laser for outputting a laser beam, a convex lens, a high-precision moving platform, and a fixed platform sequentially disposed on the guide rail; the fiber optic image transmission array under test is disposed on the high-precision moving platform, and the high-precision moving platform is disposed on the fixed platform, with a detector disposed on the high-precision moving platform.

[0009] Preferably, in the aforementioned fiber optic image array numerical aperture measurement device, the laser is a micro-beamwidth laser with an output laser beam width ≤ 1 mm and an output power of 1-150 mW.

[0010] Preferably, in the aforementioned fiber optic image array numerical aperture measurement device, the laser and the convex lens are on the same optical axis.

[0011] Preferably, in the aforementioned fiber optic image array numerical aperture measurement device, the high-precision moving platform has an accuracy of 0.1 μm, a maximum moving speed of not less than 1 mm / s, and a vibration isolation frequency > 200 Hz.

[0012] Preferably, in the aforementioned fiber optic image array numerical aperture measurement device, the detector is formed by coupling an optical fiber panel and a complementary metal-oxide-semiconductor detector.

[0013] Preferably, in the aforementioned fiber optic image array numerical aperture measurement device, the limiting resolution of the detector is 150 lp / mm.

[0014] Preferably, in the aforementioned fiber optic image array numerical aperture measurement device, the laser, convex lens, high-precision moving platform, and fixed platform are all housed within an ambient light shield.

[0015] Preferably, in the aforementioned fiber optic image array numerical aperture measurement device, the extinction ratio of the ambient light shield is >60 dB.

[0016] The objective of this invention and the technical problem it solves can also be achieved using the following technical solutions. A method for measuring the numerical aperture of an optical fiber imaging array according to this invention includes the following steps: The laser and convex lens are aligned along the same optical axis. The laser outputs a laser beam with an initial beam width, which is then converted by the convex lens into a laser beam with a beam width lower than the initial beam width. The fiber optic imaging array is placed on a high-precision moving platform. By adjusting the high-precision moving platform, the converted laser beam is directly irradiated onto the end face of the fiber under test. The laser beam transmitted through the fiber under test is received by the detector of the fiber panel and the complementary metal-oxide-semiconductor (CMOS) detector. The distance between the fiber panel and the detector and the image size are calculated through the imaging on the CMOS detector. The scattering angle of the fiber optic imaging array under test is then calculated, and the numerical aperture of the fiber optic imaging array under test is determined.

[0017] Preferably, in the aforementioned method for measuring the numerical aperture of a fiber optic imaging array, the laser beam output by the laser and the convex lens are on the same optical axis.

[0018] Preferably, in the aforementioned method for measuring the numerical aperture of a fiber optic imaging array, the laser beam width output by the laser is ≤1mm.

[0019] Preferably, in the aforementioned method for measuring the numerical aperture of an optical fiber imaging array, the converted laser beam width is 0.1-800 μm.

[0020] By employing the above technical solutions, the fiber optic image array numerical aperture measurement device and method proposed in this invention have at least the following beneficial effects: The numerical aperture measurement device and method for fiber optic image transmission arrays proposed in this invention can directly detect the numerical aperture values ​​of fiber optic image transmission arrays with different compositions and refractive indices, with higher efficiency.

[0021] The numerical aperture measurement device and method for fiber optic image transmission arrays proposed in this invention can focus on a specific fiber filament on the fiber optic image transmission array to measure the numerical aperture, accurate to the specific fiber filament, rather than the traditional coarse calculation.

[0022] The fiber optic imaging array numerical aperture measurement device and method proposed in this invention can directly solve the problems of indistinct core-skin boundaries caused by core-skin penetration due to the manufacturing process, and inaccurate numerical aperture calculation based solely on glass composition and refractive index, as well as large errors. The measurement range is wider and the numerical aperture measurement is more accurate.

[0023] Compared with the ±5% error of the traditional refractive index method, the numerical aperture measurement device and method proposed in this invention reduce the measurement uncertainty to within ±1%, which can cover the core diameter range of 0.5-200 μm. The numerical aperture measurement range is large, which meets the full spectrum detection needs from conventional imaging optical fibers to special microstructure optical fibers.

[0024] The numerical aperture measurement device and method for fiber optic image transmission arrays proposed in this invention are applicable to the detection of highly integrated image transmission fibers with a core diameter of <10 μm and a packing density of >1000 filaments / mm. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the numerical aperture measuring device of the present invention; Figure 2 This is a schematic diagram of the numerical aperture measurement mechanism provided in an embodiment of the present invention.

[0026] Explanation of reference numerals in the attached diagram: 1-Laser; 2-Laser beam; 3-Lens; 4-Fiber optic image array; 5-Fiber optic panel; 6-CMOS; 7-High-precision moving platform 1; 8-High-precision moving platform 2; 9-Fixed platform; 10-Guide rail (including bracket); 11-Ambient light shield; 12-Converted laser beam; 13-Fiber optic cable under test; 14-Scattering angle. Detailed Implementation

[0027] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, features, and effects of a fiber optic imaging array numerical aperture measurement device and method proposed according to the present invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features or characteristics in one or more embodiments can be combined in any suitable form.

[0028] It should be noted that all directional indicators (such as up, down, left, right, etc.) in this invention are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicator will also change accordingly. The connection can be a direct connection or an indirect connection.

[0029] Traditional optical fiber numerical aperture is mainly calculated based on the refractive indices of the core and cladding. The formula based on the refractive indices of the core and cladding is as follows: Where n1 is the refractive index of the fiber core; n2 is the refractive index of the cladding.

[0030] The refractive index difference between the fiber core and cladding determines the size of the numerical aperture. A larger refractive index difference results in a larger numerical aperture and a stronger light-receiving capability. However, because the fiber filament undergoes multiple processes of fiber assembly, melting, and drawing to obtain the desired fiber imaging array, the fiber core and cladding undergo interpenetration during this process, altering the degree of refractive index gradient change between the cladding and core. Therefore, theoretical characterization of the fiber numerical aperture based on the refractive indices of the core and cladding glass will deviate from the actual effective numerical aperture. Thus, this invention considers directly utilizing the fiber scattering angle θ of the fiber imaging array to detect the fiber numerical aperture.

[0031] like Figure 1 As shown, some embodiments of the present invention provide a numerical aperture measurement device for fiber optic image arrays, including an ambient light shield 11. Background light introduces DC bias and shot noise; the ambient light shield 11 can directly avoid background light interference, and the extinction ratio of the ambient light shield 11 is >60 dB. An extinction ratio greater than 60 dB can reduce the background count / current to the order of one millionth of the signal, significantly reducing the noise floor and improving the measurability of weak power and high spatial frequency details; it can also maintain the effective contrast of the MTF at high frequencies, ensuring that the "limit resolution" index is not limited by the external light environment. A guide rail 10 is provided inside the ambient light shield 11, and a laser 1 for outputting a laser beam 2, a convex lens 3, a high-precision moving platform 8, and a fixed platform 9 are sequentially arranged on the guide rail 10; the fiber optic image array 4 under test is arranged on the high-precision moving platform 8, and a high-precision moving platform 7 is arranged on the fixed platform 9, with a detector arranged on the high-precision moving platform 7. The high-precision moving platform 8 enables the movement of the fiber optic imaging array 4 under test in three-dimensional space. Specifically, along the X and Y axes (the plane containing the fiber optic imaging array 4), the single fiber filament to be measured within the array can be moved to the position of the central axis of the laser beam. Along the guide rail direction (Z-axis), adjustments can be made according to the diameter of the single fiber filament to be measured within the different fiber filaments of the fiber optic imaging array 4 under test, ensuring that the focused laser beam hits and completely covers the fiber filament under test. This platform can measure the numerical aperture of the fiber optic imaging array 4 with different materials, fiber diameters, and positions. This measuring device can accurately measure the numerical aperture of optical fibers and features simple operation and high measurement accuracy.

[0032] In some optional embodiments, the laser 1 is a micro-beamwidth laser with an output laser beam width ≤ 1 mm and an output power of 1-150 mW. The laser power closed-loop control system maintains output fluctuation < 0.5% (the laser beam required for measuring the fiber optic imaging array is relatively small). The micro-beamwidth laser 1, with a beam width below 1 mm, can be further combined with the convex lens 3 to achieve further laser focusing, enabling the measurement of micron-level fiber filaments and lowering the lower limit of the device's measurement range. An excessively high beam width, such as greater than 1 mm, will significantly reduce the device's measurement range and also result in an excessively large focused beam width, reducing measurement accuracy. The 1-150 mW power range covers the needs from low-power calibration and linear region verification to medium-power coupling and end-face characterization. The upper limit of 150 mW provides redundancy for cases with small beam spot power density, while the lower limit of 1 mW also meets the testing and safety debugging requirements of more fragile panels.

[0033] In some optional embodiments, the laser beam 2 emitted by the laser 1 and the convex lens 3 are on the same optical axis. The laser beam 2 and the convex lens 3 must remain on the same optical axis; coaxial normal incidence ensures the wavefront remains rotationally symmetrical, resulting in a minimum, circularly symmetrical, high-energy-density focal spot. Any eccentricity or tilt will introduce coma and astigmatism, causing the focal spot to become larger, shifted, and less efficient, even posing safety risks. The lens 3 further focuses the laser; adjusting the distance between the laser 1 and the lens 3 converts it into a laser with a narrower beam width. There are no specific limitations on the refractive index and focal length of the lens; since the platform for the sample under test is located at the principal focal length of the lens, the structure of the measuring device can be matched with the lens selection.

[0034] In some optional embodiments, the high-precision moving platform 8 is configured with an accuracy of 0.1 μm, a maximum moving speed of no less than 1 mm / s, and a vibration isolation frequency of >200 Hz, providing vibration isolation functionality. The 0.1 μm moving accuracy and closed-loop control ensure that the landing point error is much smaller than the typical fiber core scale (μm level), improving the coverage accuracy of the laser beam on the fiber optic imaging array 4 and achieving repeatable "just-complete coverage." The vibration isolation natural frequency greater than 200 Hz significantly attenuates environmental and equipment self-excited vibrations (mostly less than 100 Hz) on the sample surface, avoiding resonance amplification. A maximum speed greater than 1 mm / s, combined with optimized trajectory, increases scanning throughput without sacrificing settling time, improving consistency in multiple batches of repeated testing; excessively low maximum moving speeds, such as below 1 mm / s, are unsuitable for multiple batch testing. The high-precision moving platform 8 is used to place and adjust the fiber optic image transmission array. By adjusting the fiber optic image transmission array 4 in the x, y, and z axes (the maximum displacement in each direction is not limited, but is generally not less than 5 mm), the converted micro laser beam 12 is directly irradiated onto the end face of the fiber under test. The high-precision moving platform 8 can precisely adjust the position of the fiber optic image transmission array, ensuring that the laser accurately hits the fiber filament under test.

[0035] In some optional embodiments, the detector may be formed by coupling an optical fiber panel 5 and a complementary metal-oxide-semiconductor (CMOS) detector 6. The optical fiber panel 5 has high resolution, reaching the μm level, enabling precise detection of the size of the light spot striking the detector, significantly improving the detection accuracy of the device. The coupled CMOS detector 6 can convert the light spot size into a corresponding electrical signal, directly reading the precise value of the light spot size. The detector can receive the laser light transmitted through the optical fiber and project an image onto a CMOS sensor.

[0036] In some optional embodiments, the detector's limiting resolution is set to no less than 150 lp / mm. This 150 lp / mm limiting resolution enables the device to resolve fringe details with a period of 6.7 μm and a linewidth of 3.3 μm, ensuring measurement accuracy. Too low a limiting resolution would introduce unnecessary measurement errors. Furthermore, the micron-level pose correction of the platform 8 can eliminate off-axis aberrations such as astigmatism and coma in terms of both lateral eccentricity and angular tilt, ensuring the detector maintains recognizable contrast at a spatial frequency of 150 lp / mm, preventing MTF degradation. The high-precision moving platform 8 at the bottom of the detector allows for fine-tuning; the distance from the fiber optic output to the optical power meter receiver is generally no more than 1000 mm to avoid excessive distances that could degrade imaging and affect measurement accuracy.

[0037] In some optional embodiments, the laser 1, convex lens 3, high-precision moving platform 8, and fixed platform 9 are all housed within an ambient light shield 11. The ambient light shield 11 directly prevents interference from background light, and its extinction ratio is >60 dB. Background light introduces DC bias and shot noise, while an extinction ratio greater than 60 dB reduces the background count / current to the order of one millionth of the signal, significantly reducing the noise floor and improving the measurability of weak power and high spatial frequency details; furthermore, it maintains effective contrast of the MTF at high frequencies, ensuring that the "limit resolution" is not limited by the external light environment.

[0038] Some embodiments of the present invention also provide a method for measuring the numerical aperture of an optical fiber imaging array, comprising the following steps: Laser 1 and convex lens 3 are aligned with the same optical axis. The laser output beam with a beam width ≤ 1 mm is converted into a laser beam of 0.1-800 μm by convex lens 3, ensuring that the wavelength of the laser beam is suitable for measuring the numerical aperture of the fiber optic imaging array 4. The fiber optic imaging array 4 is placed on a high-precision moving platform 8. By adjusting the high-precision moving platform 8, the converted laser beam 12 is directly irradiated onto the end face of the fiber optic cable 13 under test. The detector formed by the coupling of fiber optic panel 5 and complementary metal-oxide-semiconductor (CMOS) detector 6 receives the laser beam transmitted through the fiber optic cable 13 under test. Through the imaging on the CMOS detector 6, the distance between the fiber optic panel 4 under test and the detector, as well as the image size, are calculated, and then the scattering angle 14 of the fiber optic cable under test is calculated. Figure 2 Then, the numerical aperture of the fiber under test can be determined.

[0039] In the above technical solution, the laser light passing through the optical fiber diverges at intervals, striking the fiber optic imaging array of the detector and ultimately forming an image on the CMOS. The scattering angle of the light is calculated by determining the distance between the panel under test and the detector, as well as the image size on the CMOS, and the numerical aperture (NA) of the optical fiber under test is then calculated. This is combined with a multimode fiber calibration reference module to homogenize and calibrate the standard NA values ​​of at least five measurement fibers.

[0040] In some optional embodiments, the converted laser beam 12 has a beamwidth of 0.1-800 μm. A smaller beamwidth results in higher spatial resolution, allowing for the measurement of smaller fiber filament diameters, but also a shallower depth of field (DOF); conversely, a larger beamwidth has the opposite effect. The 0.1-800 μm range facilitates trade-offs between resolution and stability / throughput optimization. Furthermore, the focused laser power per unit area is increased by an order of magnitude, and the larger beamwidth range allows for selection based on the damage threshold of the material / end-face coating, avoiding thermal damage and ensuring measurement within the linear response region. This range is also compatible with most wavelength bands (UV / visible / NIR) and different numerical aperture (NA) objectives / focusing lenses, simplifying device selection and improving the platform's versatility.

[0041] The laser is focused near the sample placement position of the fiber optic imaging array 4 under test, and subsequent measurements can be performed by fine-tuning the high-precision moving platform 8.

[0042] In some optional embodiments, the relationship between the numerical aperture and the scattering angle θ is as follows: Where D is the distance the beam deviates from the original measurement position (i.e., the size of the imaging spot on the complementary metal-oxide-semiconductor detector 6), and L is the distance from the fiber output end to the optical power meter receiver end.

[0043] Once the scattering angle θ is measured, the numerical aperture NA can be calculated using the following formula: NA = sin(θ) Where 0°≤θ≤89°.

[0044] Therefore, by using a micro-laser beam to measure the scattering angle θ of the optical fiber in the optical fiber imaging array under test, the actual numerical aperture of the optical fiber under test can be directly calculated.

[0045] The present invention will be further described below with reference to specific embodiments, but this should not be construed as a limitation on the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention still fall within the scope of protection of the present invention.

[0046] In this embodiment, a calibrated standard optical fiber is used as an example. The calibrated optical fibers involve different numerical apertures and are not intended to limit the measurement range of the invention patent.

[0047] Example 1 Example 1 uses calibration fiber A (commercially available), with NAA = 0.120 ± 0.003 @ 1310 nm and a test wavelength λ of 1310 nm. The end face of the fiber is polished using APC. The calibration fiber A is then tested using the device of this invention, following the test procedure described above. The test is performed three times, with 10 sets of data measured each time. The results are compared to see if there is a significant error. If not, the average value is taken as NAA' = (0.1210 ± 0.0015); the deviation from the calibration result is Δ = −0.0010, and |Δ| = 0.83%.

[0048] The default measurement result is considered acceptable if Δ ≤ 0.01 and |Δ| ≤ 5%. Example 1 shows that the device of the present invention has high measurement accuracy in the lower NA range.

[0049] Example 2 Example 2 uses calibration fiber B (commercially available), with NAB = 0.320 ± 0.002 @ 1310 nm and a test wavelength λ of 1310 nm. The end face of the fiber is polished using APC. The calibration fiber B is then tested using the device of this invention, with three tests performed and ten sets of data collected each time. The results are compared to check for significant errors; if no large errors are found, the average value is taken as NAB' = (0.3200 ± 0.0020). The deviation from the calibration result is Δ = 0, and |Δ| = 0%.

[0050] The default measurement result is considered acceptable if Δ ≤ 0.01 and |Δ| ≤ 5%. The measurement results of Example 2 show that the device of the present invention also has high measurement accuracy in the medium NA range.

[0051] Example 3 Example 3 uses calibration fiber C (commercially available), with NAC = 0.520 ± 0.005 @ 1310 nm. The device of this invention tests the calibration fiber C and takes the average value as NAC' = (0.5210 ± 0.0010); the deviation from the calibration result is Δ = -0.0010, and |Δ| = 0.19%.

[0052] The measurement results show that Δ≤0.01 and |Δ|≤5%, indicating that the measurement results are qualified. The measurement results of Example 3 show that the device of the present invention also has high measurement accuracy in the larger NA range.

[0053] Example 4 Example 4 verifies the repeatability of the equipment measurement results. The same operator, using calibrated fibers A, B, and C as the experimental subjects, repeated the equipment operations described in Examples 1-3. The results of the two tests were compared. The two measurement results were NAA'=(0.1200±0.0010), NAB'=(0.3200±0.0010), and NAC'=(0.5200±0.0015). All remeasurement results met the condition that Δ≤0.01 and |Δ|≤1%, indicating that the equipment has excellent repeatability.

[0054] Example 5 Example 5 verifies the reproducibility of the equipment's measurement results. Two other operators were selected and, using the same calibration fibers A, B, and C (commercially available), repeated the equipment operations described in Examples 1-3, comparing the results of the two tests. The first operator obtained measurement results of NAA'=(0.1200±0.0015), NAB'=(0.3200±0.0015), and NAC'=(0.5200±0.0010), while the second operator obtained results of NAA'=(0.1200±0.0010), NAB'=(0.3210±0.0010), and NAC'=(0.5210±0.0005). Both remeasurement results met the criteria of Δ≤0.01 and |Δ|≤1%, indicating that the equipment exhibits excellent reproducibility.

[0055] Example 6 Example 6 verifies the measurement capability and resolution limit of single-filament micro-regions (core diameter <3μm) in the array. The fiber array used was calibrated to NA==0.370±0.005 @1310 nm. Then, the device was used to measure the fiber under test in the array, and the result was NA==0.3700±0.0010. The measurement result Δ≤0.01 and |Δ|≤5%, which is considered a qualified measurement result. Repeated measurements of other fibers also met the requirements of Δ≤0.01 and |Δ|≤1%, which is also considered a pass.

[0056] Comparative Example 1 The difference between this comparative example and Example 1 is that the ambient light shield is removed in this comparative example, while the remaining steps and parameters are the same as in Example 1. Compared with Example 1, it was found that the R measurement fluctuation of the optical fiber under test in this comparative example increased, the SD of NA reached 0.008, which was significantly improved, and |Δ|=0.017 (>0.01), resulting in a failed test.

[0057] This reveals that a shielding cover (extinction ratio > 60 dB) is an indispensable condition for ensuring low uncertainty.

[0058] Comparative Example 2 The difference between this comparative example and Example 1 is that the coaxial calibration step is omitted, resulting in a non-coaxial or slightly tilted spatial relationship between the laser and the fiber under test. Observation and testing revealed that astigmatism caused by the non-coaxial relationship resulted in a non-circular light spot, and the spot radius extraction was direction-dependent. The R-value difference measured from different orientations was >5%, and the maximum NA deviation reached 8%.

[0059] This reveals that the coaxial calibration step cannot be omitted; otherwise, the measurement spot error will be large, and the results will not be accurate.

[0060] Comparative Example 3 The difference between this comparative example and Example 1 is that the distance L in this comparative example was not calibrated. Subsequent comparisons revealed that L deviated from the actual value by 1.8%, which was amplified into a NA systematic error in the large angle region, with |Δ| increasing to 0.118.

[0061] This reveals that each remeasurement of L is a prerequisite for the accuracy of the measurement result.

[0062] Comparative Example 4 The difference between this comparative example and Example 1 is that the laser beam width in this comparative example is 30 μm. The sample under test has a filament diameter of 10 μm. When the laser beam width is set to 30 μm, the beam width is too large, directly covering two or more filaments. Operation revealed multi-filament crosstalk and spot saturation. The NA (Navierian Array) deviated significantly from that of Example 1, and the fluctuations in multiple measurements increased significantly.

[0063] Comparative Example 5 The difference between this comparative example and Example 1 is that the laser beam width in this comparative example is 2 μm. When the laser beam width is selected to be 2 μm, the beam width is too small, resulting in insufficient energy and failure to effectively cover the end face of the fiber under test. Operation revealed an indistinct light spot and light spot distortion, leading to significant deviations in the measurement of the light spot size. The NA (Navierian Array) deviated significantly from that of Example 1, and the fluctuations in the results of multiple measurements increased significantly.

[0064] Comparative Example 6 The difference between this comparative example and Example 1 is that the laser beam in this comparative example is 10 μm and the beam spot is irregular. When the laser beam spot is non-circular and exhibits significant distortion and irregularity, it was found that the final obtained beam spot showed a large amount of random distortion, and the beam spot size fluctuated greatly, resulting in significant deviations, high randomness, and poor reliability. The NA (Neural Aspect Ratio) deviated significantly from that of Example 1, and the fluctuations in multiple measurements increased significantly.

[0065] This revealed that the key to the successful single-filament measurement of this device lies in its wide beam width, precise laser coverage of the fiber cross-section under test, and positioning capability.

[0066] Examples 1-6 demonstrate that this device achieves precise excitation and mode field analysis of a single fiber filament through microscopic laser coupling and high-precision displacement control. Employing a long-distance (500 mm) optical path design, the angle measurement sensitivity is improved to the 0.001° level. Compared to the ±5% error of the traditional refractive index method, this method reduces the measurement uncertainty to within ±1%. With optimized optical path configuration (conventional-extended-microscopic) and upgraded detection technology (CMOS-InGaAs-sCMOS), this measurement device can cover a core diameter range of 0.5-200 μm and has a large numerical aperture measurement range, meeting the full spectrum detection needs from conventional imaging fibers to special microstructure fibers; it is also suitable for detecting highly integrated imaging fibers with core diameters <10 μm and packing densities >1000 filaments / mm.

[0067] Numerous specific details are set forth in this specification. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some embodiments, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0068] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0069] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A numerical aperture measurement device for fiber optic image transmission arrays, characterized in that, The device includes an ambient light shield, inside which is a guide rail. On the guide rail are arranged a laser for outputting a laser beam, a convex lens, a high-precision moving platform, and a fixed platform. The high-precision moving platform is equipped with a fiber optic image transmission array under test, and the fixed platform is equipped with a high-precision moving platform and a detector.

2. The numerical aperture measurement device for fiber optic image transmission arrays as described in claim 1, characterized in that, The laser is a micro-beamwidth laser, with an output laser beam width ≤ 1 mm and an output power of 1-150 mw; the laser and the convex lens are on the same optical axis.

3. The numerical aperture measurement device for fiber optic image transmission arrays as described in claim 1, characterized in that, The high-precision moving platform has an accuracy of 0.1μm, a maximum moving speed of not less than 1mm / s, and a vibration isolation frequency >200 Hz.

4. The numerical aperture measurement device for fiber optic image transmission arrays as described in claim 1, characterized in that, The detector is composed of an optical fiber panel and a complementary metal-oxide-semiconductor detector coupled together; the detector's limiting resolution is 150 lp / mm.

5. The numerical aperture measurement device for fiber optic image transmission arrays as described in claim 1, characterized in that, The laser, convex lens, high-precision moving platform, and fixed platform are all housed within an ambient light shield; the extinction ratio of the ambient light shield is >60 dB.

6. A method for measuring the numerical aperture of a fiber optic image transmission array, characterized in that, Includes the following steps: The laser and convex lens are aligned along the same optical axis. The laser outputs a laser beam with an initial beam width, which is then converted by the convex lens into a laser beam with a beam width lower than the initial beam width. The fiber optic imaging array is placed on a high-precision moving platform. By adjusting the high-precision moving platform, the converted laser beam is directly irradiated onto the end face of the fiber under test. The laser beam transmitted through the fiber under test is received by the detectors of the fiber panel and the complementary metal-oxide-semiconductor (CMOS) detector. The distance between the fiber panel and the detector, as well as the image size, are calculated through the imaging on the CMOS detector. The scattering angle of the fiber optic imaging array under test is then calculated, and the numerical aperture of the fiber optic imaging array under test is determined.

7. The method for measuring the numerical aperture of an optical fiber image transmission array as described in claim 6, characterized in that, The laser beam output by the laser is on the same optical axis as the convex lens.

8. The method for measuring the numerical aperture of a fiber optic image transmission array as described in claim 6, characterized in that, The laser beam width output by the laser is ≤1mm.

9. The method for measuring the numerical aperture of an optical fiber image transmission array as described in claim 6, characterized in that, The converted laser beam width is 0.1-800μm.

10. The method for measuring the numerical aperture of an optical fiber imaging array as described in claim 6, characterized in that, The relationship between the numerical aperture and the scattering angle θ is as follows: Where D is the distance the beam deviates from its original measurement position, and L is the distance from the fiber optic output end to the optical power meter receiver end.

11. The method for measuring the numerical aperture of an optical fiber imaging array as described in claim 10, characterized in that, The numerical aperture NA is calculated using the following formula: NA = sin(θ), where θ is the scattering angle.

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