An alignment processing device and an alignment processing method for long optical fiber laser focusing processing

Abstract

The present invention discloses an alignment processing device for long optical fiber laser focusing processing, including a turntable, a displacement stage, a rotating table and a placing table, the displacement stage translates along the x, y and z directions respectively, and the turntable rotates along the θz direction and the θy direction. The alignment processing method thereof is that the turntable tightens the optical fiber to the processing area, the displacement stage moves along the y-axis direction to align the optical fiber with the common objective lens for processing / imaging, the rotating turntable makes the optical fiber parallel to the x-z plane where the displacement stage is located, the turntable is rotated along the θy direction according to the pitch angle of the optical fiber, so that the optical fiber is parallel to the processing plane, the displacement stage moves along the z-axis direction until the camera is clearly focused on the optical fiber core, and the displacement stage moves along the x-axis direction to the processing starting position for processing. The alignment method in the present invention performs leveling and direction correction on the optical fiber, and the processing process is completed simultaneously by the turntable and the high-precision displacement stage, which is more conducive to the long-distance processing of the optical fiber while ensuring the high precision of the processing, and the processing length can be extended to the kilometer level.

Description

Technical Field

[0001] The invention belongs to the field of integrated photonics, and in particular relates to an alignment processing device and an alignment processing method for long optical fiber laser focusing processing. Background Art

[0002] Since the invention of optical fiber in the 1970s, it has been the most widely used optical waveguide device, applied in many important fields of production and life. In order to increase the application scenarios and functional properties of optical fiber, a variety of new optical fibers have been invented, such as multimode optical fiber, multi-core optical fiber, polarization-maintaining optical fiber, sapphire optical fiber, etc. However, when various optical fibers are applied to the field of sensing, they still have disadvantages such as weak modulation capability, single modulation mode, and few detectable signal types.

[0003] In order to overcome the above shortcomings, people try to process various micro-nano structures in optical fiber structures to expand the functions and applications of optical fibers and increase the detection capabilities of optical fibers as sensor devices. One of the most typical processing methods is to process periodic Bragg gratings in optical fibers. The earliest method to process such gratings was to use ultraviolet light irradiation and mask projection to write various parameter gratings. At present, although this method has a relatively mature processing technology and can achieve large-scale industrial production, it still has complex processes, high investment costs, the types of processed micro-nano structures are limited by the mask, it is impossible to achieve three-dimensional processing inside the optical fiber, and the processed structure cannot withstand high temperatures.

[0004] In recent years, femtosecond laser processing technology has developed rapidly. Using femtosecond laser to process micro-nano structures in optical fibers has also become an emerging processing method. Using femtosecond laser to process optical fibers can be done by mask processing or by direct writing without a mask, directly forming various micro-nano structures. When processed without a mask, femtosecond processing has the advantages of simple and flexible process and is not restricted by masks. More importantly, after focusing the femtosecond laser, true three-dimensional processing can be achieved on the surface, end face, and inside of the optical fiber, not just limited to general periodic grating structures. Moreover, the sensing structure processed by femtosecond laser has better high temperature resistance, and its failure temperature is much higher than the structure produced by traditional UV processing.

[0005] Unlike traditional mask projection processing, femtosecond focusing direct writing processing of optical fibers requires precise alignment and positioning of the fiber core, and uses the positioning surface as a reference to accurately process the structure at a specific position inside the optical fiber. The objective lens used in laser direct writing optical fiber processing has a large numerical aperture, a small depth of focus, and a longitudinal size of the spot of only micrometers. Its positioning accuracy needs to reach hundreds of nanometers, which places high demands on the alignment of the optical fiber before processing. The alignment scheme proposed in the present invention integrates the alignment device with the laser processing device. Using this equipment and the corresponding alignment method, precise alignment can be achieved during laser direct writing processing of long optical fibers, meeting the alignment requirements of various optical fiber microstructure processing. Summary of the invention

[0006] The purpose of the present invention is to propose an alignment processing device and an alignment processing method for long optical fiber laser focusing processing. Using the device and method, high-precision three-dimensional positioning processing can be performed at any position within the core range using focused laser.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] An alignment processing device for long optical fiber laser focusing processing comprises two turntables, two ends of the optical fiber are respectively wound on the turntables, a motion feedback mechanism arranged between the two turntables comprises a translation table, a turntable and a placement table, the translation table is mounted with a turntable, the turntable is mounted with a placement table, the translation table translates along the x-axis direction, the y-axis direction and the z-axis direction respectively, the turntable rotates along the θz direction and the θy direction, the θz direction is the rotation of the turntable with the z-axis direction as the rotation axis, the θy direction is the rotation of the turntable with the y-axis direction as the rotation axis, a processing / alignment imaging structure is arranged above the placement table, the processing / alignment imaging structure comprises a processing / imaging common objective lens and an alignment imaging camera, the position and direction of the alignment imaging camera are relatively fixed with the position and direction of the translation table, and the optical fiber is processed by the processing / alignment imaging structure through the placement table.

[0009] An alignment processing method for long fiber laser focusing processing comprises the following steps:

[0010] (1) The optical fiber is moved to the processing area 5 by two turntables and the optical fiber is tightened;

[0011] (2) The translation stage moves along the y-axis direction to align the optical fiber with the common processing / imaging objective lens, and the turntable is rotated to make the optical fiber parallel to the xz plane where the translation stage is located, and the optical fiber core is in the center of the field of view;

[0012] (3) According to the fiber pitch angle, the turntable is rotated in the θy direction to make the fiber parallel to the processing plane;

[0013] (4) The translation stage moves along the z-axis until the camera is clearly focused on the fiber core;

[0014] (5) The translation stage moves along the x-axis direction to the processing starting position for processing;

[0015] (6) After processing is completed, the optical fiber is released, and the two turntables rotate in the same direction to move the optical fiber to the next processing position, and steps (2) to (6) are repeated.

[0016] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0017] (1) When focusing the optical fiber core, the single-point alignment accuracy of the optical fiber processing position can reach hundreds of nanometers through imaging with a high numerical aperture objective lens and feedback adjustment with a high-precision translation stage with nanometer resolution, which is much higher than the micron-level alignment accuracy required for traditional optical fiber processing.

[0018] (2) The alignment method used in the present invention also adopts a multi-point alignment technology during the alignment process. The pitch attitude of the optical fiber is calculated through the feedback movement in the multi-point alignment. The yaw direction attitude of the optical fiber is calculated through image recognition and corresponding corrections are made, thereby realizing multi-dimensional alignment of optical fiber processing.

[0019] (3) The processing is completed simultaneously by a turntable and a high-precision translation stage. Therefore, while ensuring high processing precision, long-distance processing of optical fibers is achieved, and the processing length can be extended to kilometers. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings.

[0021] Figure 1 The figure is a schematic diagram of the structure of an alignment processing device for long fiber laser focusing processing.

[0022] Figure 2 To adjust the processing light spot imaging at the center of the camera field of view.

[0023] Figure 3 The optical fiber appears in the camera's field of view.

[0024] Figure 4 This is the situation after the optical fiber is calibrated.

[0025] Figure 5 The fiber core is aligned with the center of the field of view, and the fiber core is out of focus in the z-axis direction at the current position.

[0026] Figure 6 This is the situation where the optical fiber core at the current position has completed focusing in the z-axis direction.

[0027] Figure 7 Schematic diagram of the optical fiber core defocusing in the z-axis direction at position x1.

[0028] Figure 8 Schematic diagram of the optical fiber focusing along the z-axis at the core at position x1.

[0029] Fig. 9 Schematic diagram of the optical fiber core defocusing in the z-axis direction at position x2.

[0030] Fig.10 Schematic diagram of the optical fiber focusing along the z-axis at the core at position x2.

[0031] Fig.11 Schematic diagram of the defocusing of the fiber core in the z-axis direction after the optical fiber is leveled.

[0032] Fig.12 Schematic diagram of focusing the fiber core in the z-axis direction after optical fiber leveling. DETAILED DESCRIPTION

[0033] like Figure 1 The alignment processing device for long optical fiber laser focusing processing shown in the figure includes a left turntable 1 and a right turntable 2, and the two ends of the optical fiber 12 are respectively wound on the left turntable 1 and the right turntable 2, and the optical fiber 12 passes through the tension sensor 18. When working, the left turntable 1 and the right turntable 2 rotate in opposite directions to tighten the optical fiber 12. The motion feedback mechanism provided between the left turntable 1 and the right turntable 2 includes a displacement table 3, a turntable 4 and a placement table 16. The displacement table 3 can translate along the x-axis direction, the y-axis direction and the z-axis direction, respectively, and the turntable 4 rotates along the θz direction and the θy direction. The turntable 4 in the θz direction rotates with the z-axis as the rotation axis, and the turntable 4 in the θy direction rotates with the y-axis as the rotation axis. A turntable 4 is placed on the translation stage 3, and a placement table 16 is installed on the turntable 4. A processing / alignment imaging structure is arranged above the placement table 16, including a common objective lens 10 for processing / alignment imaging and an alignment imaging camera 11. The position and direction of the alignment imaging camera 11 are relatively fixed to the position and direction of the translation stage 3. The focusing spot of the processing beam is adjusted to be imaged at the center of the camera field of view. Figure 2 shown.

[0034] A processing area 5 and two optical fiber holding mechanisms are provided on the placement table 16. The optical fiber holding mechanism includes a V-groove 6, a V-groove 7, a clamping device 8 and a clamping device 9. The optical fiber 12 is placed in the V-groove 6 and the V-groove 7, and the optical fiber 12 is pressed downward by the clamping device 8 and the clamping device 9.

[0035] An alignment processing method for long fiber laser focusing processing comprises the following steps:

[0036] (1) Move the position of the optical fiber 12 to be processed to the processing area 5 by the left turntable 1 and the right turntable 2 and tighten the optical fiber 12. The specific steps are as follows:

[0037] (1.1) The left turntable 1 and the right turntable 2 rotate in the same direction. After the optical fiber 12 to be processed is moved to the processing area 5, the left turntable 1 and the right turntable 2 stop moving, and the optical fiber 12 remains in a taut state.

[0038] (1.2) The clamping device 8 and the clamping device 9 press the optical fiber 12 downward so that the optical fiber 12 is pressed tightly in the V-groove 6 and the V-groove 7. After clamping, the optical fiber 12 can move along with the translation stage 3 and the turntable 4.

[0039] (1.3) The left turntable 1 on the starting end of the processing direction rotates to release the fiber, leaving room for the translation stage 3 to move the optical fiber 12. At this time, the optical fiber 12 to be processed area between the V-grooves 6 and 7 is still in a taut state.

[0040] (2) The translation stage 3 moves along the y-axis direction so that the processing / alignment imaging common objective lens 10 is aligned with the optical fiber 12. The rotating turntable 4 rotates the optical fiber 12 to be parallel to the xz plane where the translation stage 3 is located, and the optical fiber core is at the center of the field of view. The specific steps are as follows:

[0041] (2.1) The translation stage 3 moves along the y-axis direction, so that the optical fiber 12 appears in the field of view, and the translation stage 3 stops moving, as shown in FIG. Figure 3 shown.

[0042] (2.2) By aligning the imaging camera 11 to image, the edge of the core of the optical fiber 12 is identified, such as Figure 3 As shown by the arrow in the middle, the center line of the core of the optical fiber 12 is located by calculating the edge of the core of the optical fiber 12, as shown in FIG. Figure 3 As shown by the dotted line, the angle between the fiber core and the x-axis direction of the translation stage 3 is calculated as θz based on the center line. According to the identified angle θz, the turntable 4 rotates -θz to compensate for the angle, so that the optical fiber 12 is parallel to the xz plane where the x-axis direction of the translation stage 3 is located, and the yaw direction calibration of the optical fiber 12 is completed, as shown in FIG. Figure 4 shown.

[0043] (2.3) The processing spot position corresponds to the center position of the camera field of view. The y-axis direction of the optical fiber deviates from the center of the field of view, that is, deviates from the processing spot position, such as Figure 4 According to the imaging diagram, the core edge of the optical fiber 12 is identified, as shown in FIG. Figure 4 As shown by the middle arrow, the pixel position N of the core center in the image is calculated by the core edge position of the optical fiber 12. y , get the number of pixels △N that the current core center pixel position deviates from the center y The actual size of a pixel is d pix , the magnification of the imaging system is M, and the actual distance of the fiber core from the center of the field of view is △y=△N y d pix / M. The translation stage 3 moves -△y along the y-axis direction to align the fiber core with the center of the field of view, such as Figure 5 shown.

[0044] (3) There is a pitch angle between the optical fiber of the imaging camera 11 and the x-axis of the translation stage 3. According to the pitch angle of the optical fiber 12, the turntable 4 is rotated along the θy direction to make the optical fiber 12 parallel to the processing plane. The specific steps are as follows:

[0045] (3.1) The left turntable 1 and the right turntable 2 rotate counterclockwise, and the translation stage 3 moves along the x-axis direction to the front end of the processing area 5 of the optical fiber 12, and the x-axis position x1 of the translation stage 3 is recorded. The optical fiber is in a defocused and misaligned state in the z-axis direction, such as Figure 5 and Figure 7 shown. Figure 7 The process includes a common objective lens 10 for processing / aligning imaging, an optical fiber 12, a fiber core 13, an imaging beam 14, and an imaging alignment focal plane 15. The translation stage 3 moves along the z-axis direction, and the imaging camera 11 is aligned with the imaging clarity of the fiber core 13 to determine whether the optical fiber 12 is in focus in the z-axis direction at this position. Figure 6 and Figure 8 Stop the movement of the translation stage 3 and record the current focus height z1;

[0046] (3.2) The left turntable 1 and the right turntable 2 rotate clockwise, and the translation stage 3 moves along the x-axis direction to the rear end of the optical fiber 12 processing area 5. The x-axis position x2 of the translation stage 3 is recorded. The optical fiber 12 is in a defocused and misaligned state in the z-axis direction, as shown in FIG. Figure 5 and Fig. 9 The translation stage 3 moves along the z-axis direction, and while moving, it is aligned with the imaging camera 11 to judge whether the optical fiber 12 is in focus in the z-axis direction at this position by imaging the fiber core 13 clearly. Figure 6 and Fig.10 As shown, the movement of the translation stage 3 is stopped, and the current focus height z2 is recorded;

[0047] (3.3) According to the two z-axis focusing height differences △z=z2-z1 and the x-axis displacement distance △x=x2-x1 at the front and rear ends of the optical fiber 12, the pitch angle of the optical fiber 12 is calculated. , and rotate the turntable 4 along the θy direction according to the calculated angle, the rotation angle is -△φ, and the pitch angle is compensated. After compensation, the optical fiber 12 is parallel to the processing plane, and the pitch adjustment of the optical fiber 12 processing is completed. After the pitch angle compensation, the angle offset is corrected. The optical fiber is parallel to the x-axis direction of the translation stage, and there is still a defocus offset in the z-axis direction. Figure 5 and Fig.11 shown.

[0048] (4) The translation stage 3 moves again along the z-axis direction, and is aligned with the imaging camera 11 while moving. The imaging clarity of the core of the optical fiber 12 is used to determine whether the optical fiber 12 is in focus in the z-axis direction. When in focus, the state is as follows: Figure 6 and Fig.12 The movement of the translation stage 3 is stopped, and the z-axis direction compensation alignment of the processing position of the optical fiber 12 is finally completed.

[0049] (5) After the θy direction and the z-axis direction are aligned, the translation stage 3 moves along the x-axis direction to the processing starting position for processing;

[0050] (6) After the processing is completed, the left turntable 1 and the right turntable 2 move to tighten the optical fiber 12, and the clamping devices 8 and 9 are loosened to allow the optical fiber 12 to leave the placement table 16. The left turntable 1 and the right turntable 2 rotate in the same direction to move the optical fiber 12 to the next processing position, and repeat steps (2) to (6).

[0051] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. An alignment method for long fiber laser focusing processing, It is characterized in that An alignment processing device is used, the alignment processing device includes two turntables, two ends of the optical fiber are respectively wound on the turntables, the motion feedback mechanism provided between the two turntables includes a displacement table, a turntable and a placement table, the displacement table is installed with the turntable, the placement table is installed with the turntable, the displacement table translates along the x-axis direction, the y-axis direction and the z-axis direction respectively, the turntable rotates along the θz direction and the θy direction, the θz direction is the rotation of the turntable with the z-axis direction as the rotation axis, the θy direction is the rotation of the turntable with the y-axis direction as the rotation axis, a processing / alignment imaging structure is provided above the placement table, the processing / alignment imaging structure includes a processing / imaging common objective lens and an alignment imaging camera, the position and direction of the alignment imaging camera are relatively fixed with the position and direction of the displacement table, the optical fiber is processed by the processing / alignment imaging structure through the placement table, including the following steps: (1) The optical fiber is moved to the processing area through two turntables and the optical fiber is tightened; (2) The translation stage moves along the y-axis direction so that the common objective lens for processing / alignment imaging is aligned with the optical fiber. The rotating turntable rotates the optical fiber to be parallel to the xz plane where the translation stage is located, and the optical fiber core is at the center of the field of view. The specific steps are as follows: 2.1 The translation stage moves along the y-axis direction until the optical fiber appears in the field of view, and the translation stage stops moving; 2.2 Identify the edge of the fiber core by aligning the imaging camera, locate the center line of the fiber core by calculating the edge of the fiber core, calculate the angle between the fiber core and the x-axis direction of the translation stage as θz based on the center line, and rotate the turntable -θz to compensate for the angle based on the identified angle θz, so that the fiber is parallel to the xz plane where the x-axis direction of the translation stage is located, and complete the fiber yaw direction calibration; 2.3 The processing spot position corresponds to the center position of the camera field of view. The fiber y-axis direction deviates from the center of the field of view, that is, deviates from the processing spot position. The fiber core edge is identified according to the imaging image, and the pixel position N of the fiber core center in the image is calculated by the fiber core edge position of the fiber. y , get the number of pixels △N that the current core center pixel position deviates from the center y , the actual size of the pixel is d pix , the magnification of the imaging system is M, and the actual distance of the fiber core from the center of the field of view is △y=△N y d pix / M, the translation stage moves -△y along the y-axis direction to align the fiber core to the center of the field of view; (3) There is a pitch angle between the optical fiber of the imaging camera and the x-axis of the translation stage. According to the pitch angle of the optical fiber, the turntable is rotated along the θy direction to make the optical fiber parallel to the processing plane. The specific steps are as follows: 3.1 The translation stage moves along the x-axis direction to the front end of the optical fiber processing area, and the x-axis position x1 of the translation stage is recorded. The translation stage moves along the z-axis direction. While moving, the camera determines whether the optical fiber is in focus at this position in the z-axis direction by imaging the optical fiber core clearly. When it is in focus, the translation stage stops moving and the current focus height z1 is recorded. 3.2 The translation stage moves along the x-axis direction to the rear end of the optical fiber processing area, and the x-axis position x2 of the translation stage is recorded. The translation stage moves along the z-axis direction. While moving, the camera determines whether the optical fiber is in focus at this position in the z-axis direction by imaging the optical fiber core clearly. When in focus, the translation stage stops moving and the current focus height z2 is recorded. 3.3 According to the two focusing height differences in the z-axis direction △z=z2-z1 and the displacement distance in the x-axis direction of the front and rear ends of the optical fiber △x=x2-x1, the optical fiber pitch angle ∆φ=arctan(∆z / ∆x) is calculated, and the turntable -△φ is rotated along the θy direction according to the calculated angle to compensate for the pitch angle. After compensation, the optical fiber is parallel to the processing plane, and the optical fiber processing pitch adjustment is completed; (4) The translation stage moves along the z-axis until the camera is clearly focused on the fiber core; (5) The translation stage moves along the x-axis direction to the processing starting position for processing; (6) After the processing is completed, the optical fiber is released, and the two turntables rotate in the same direction to move the optical fiber to the next processing position, and steps (2) to (6) are repeated.

2. According to claim 1, an alignment processing method for long fiber laser focusing processing, Features: The placement table is provided with an optical fiber holding mechanism, and the optical fiber holding mechanism includes a V-shaped groove and a pressing device provided on the placement table. The optical fiber is placed in the V-shaped groove and the pressing device is used to press the optical fiber.

3. According to claim 2, an alignment processing method for long fiber laser focusing processing, It is characterized in that The specific steps in step (1) include: 1.1 The two turntables rotate in the same direction. After the optical fiber to be processed is moved to the processing area, the two turntables stop moving and the optical fiber remains taut; 1.2 The pressing device presses the optical fiber downward so that the optical fiber is pressed tightly in the V-groove. After pressing, the optical fiber moves along with the translation stage and the turntable; 1.3 The turntable on the starting end of the processing direction rotates to release the fiber, leaving room for the placement table to move the optical fiber. At this time, the optical fiber processing area between the two V-grooves is still in a taut state.

4. According to claim 1, an alignment processing method for long fiber laser focusing processing, It is characterized in that The specific steps in step (4) include: the translation stage moves again along the z-axis direction, and while moving, the camera determines whether the optical fiber is in focus in the z-axis direction by imaging the clarity of the optical fiber core, and stops moving the translation stage after it is in focus, thereby finally completing the z-axis alignment of the optical fiber processing position.

5. According to claim 1, an alignment processing method for long fiber laser focusing processing, It is characterized in that The specific steps in step (6) include: after the processing is completed, the turntable moves to tighten the optical fiber, loosens the clamping device to make the optical fiber leave the placement table, the two turntables rotate in the same direction, move the optical fiber to the next processing position, and repeat steps (2) to (6).

6. According to claim 1, an alignment processing method for long fiber laser focusing processing, Features: A tension sensor is provided between the translation platform and one of the turntables, and the optical fiber passes through the tension sensor.

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