Black point focusing based optical axis perpendicularity error judgment, correction method and device

Abstract

The application relates to a light axis perpendicularity error judgment and correction method and equipment based on black point focusing, the error judgment method first performs coarse focusing, sequentially completes three groups of calibration sample structures in the form of a right triangle, determines accurate focusing distances of three calibration sample machining positions through black point testing, calculates plane tilt rates of a machining plane along X and Y directions by combining the side length of adjacent calibration sample structures, and judges whether the light axis perpendicularity has errors according to the size of the plane tilt rate. The error judgment and correction method solves the problem of incomplete structure caused by the misalignment of a laser focus and a machining plane in a two-photon polymerization machining process, has the advantages of simplicity, convenience and high precision, and can further realize machining plane flatness, that is, light axis perpendicularity error judgment and correction.

Description

Technical Field

[0001] This invention relates to the field of femtosecond laser micro-nano processing, and in particular to a method for judging the perpendicularity error of the optical axis based on black dot focusing, a method for correcting the perpendicularity error of the optical axis, and a two-photon polymerization processing device that applies the judgment method and the correction method. Background Technology

[0002] 3D laser printing based on femtosecond laser two-photon polymerization has become a promising option for micro- and nano-fabrication due to its versatility, flexibility, and tunability. Two-photon polymerization offers unique advantages such as high resolution, three-dimensional formability, and wide applicability to a broad range of materials, making it widely applicable in fields like micro-optics, micromechanics, and MEMS. These micro- and nano-devices demand high precision and integrity in the fabricated structures; however, in actual processing, misalignment between the laser focus and the processing plane often leads to structural defects or loss, thus affecting the overall functionality of the structure.

[0003] In ultrafast laser processing, processing is achieved through the relative motion between the material being processed and the laser focus. The problem of misalignment between the laser focus and the processing plane includes defocusing from the initial processing position and deviation of the focal plane from the processing plane during processing due to unevenness of the processing plane. Unevenness of the processing plane can be caused by factors such as a non-flat substrate, uneven stage support, and insufficient stability of the three-dimensional moving stage leading to Z-axis deviation during horizontal X / Y movement. Figure 1 As shown, under the conditions of initial processing laser focus and processing plane focusing, Figure 1 a and 1b are respectively caused by the base surface moving up during the processing and the stage 5 moving the base 4 up, causing the laser focus to fall into the interior of the base 4, resulting in bottom defects in the subsequent array structure; Figure 1 c is due to the downward deviation in the Z direction caused by the parallelism error when the three-dimensional moving stage 6 moves horizontally in the X / Y direction. The laser focus falls into the material to be processed above the substrate 4, resulting in the loss of all other array structures after processing and development.

[0004] Currently, the main methods for achieving laser focus and the plane to be processed during two-photon processing are automatic focusing technology and optical judgment. Automatic focusing technology relies on a photoelectric detection module on the laser and an algorithm-controlled backend to automate the focusing process. Optical judgment determines the focus position by observing the brightness and size of the laser spot formed by photopolymerization. Automatic focusing technology requires sophisticated photoelectric instruments and complex control programs, making it expensive. Optical judgment, on the other hand, is greatly affected by laser energy and the content of fluorescent substances in the polymer material, relying on experience gained from multiple processing operations, and is considered a coarse focusing method. Summary of the Invention

[0005] Based on this, unlike autofocus technology which relies on expensive detection modules and complex control programs, and optical judgment methods which rely on processing experience and can only achieve coarse focusing, this invention proposes a simple, convenient, and high-precision focusing method based on black spot testing, and realizes the judgment and correction of optical axis perpendicularity error through triangular tilt gradient calculation.

[0006] This invention discloses a method for judging the perpendicularity error of the optical axis based on black dot focusing, which is used to judge the error of the flatness of the processing plane, i.e., the perpendicularity of the optical axis, of a two-photon polymerization processing device. The two-photon polymerization processing device includes a substrate, a stage, and a three-dimensional moving stage. The material to be processed is dropped onto the upper surface of the substrate, and the lower surface is placed on the stage. The three-dimensional moving stage is used to move the stage along the X, Y, and Z axes during movement, wherein the Z-axis is perpendicular to the horizontal plane where X and Y are located. The error judgment method includes the following steps:

[0007] S1. Move the three-dimensional moving stage along the Z-axis to complete coarse focusing and record the Z-axis moving distance z to ensure that the calibration sample structure can be processed onto the substrate.

[0008] S2. Control the movement of the three-dimensional moving stage according to the pre-configured calibration sample processing file to process the structure of the first calibration sample.

[0009] S3. After the structural processing of the first calibration sample is completed, control the three-dimensional moving stage to return to the coarse focusing position of the first calibration sample.

[0010] S4. Control the three-dimensional moving stage to move the preset horizontal movement distance along the Y and X directions respectively, so as to reach the coarse focusing position of the second calibration sample and the third calibration sample in turn, and process the structure of the second calibration sample and the third calibration sample in the manner of S2.

[0011] In this process, after each calibration sample structure is processed, a black spot test is performed on the current calibration sample to obtain the precise focusing distance of each of the three calibration samples at their respective processing positions.

[0012] S5. Combining the three precise focusing distances and the horizontal movement distance between adjacent calibration samples, calculate the plane inclination rate of the processing plane along the X and Y directions respectively.

[0013] S6. Determine whether there is an error in the perpendicularity of the optical axis based on the magnitude of the plane inclination.

[0014] As a further improvement to the above scheme, the specific process of performing black spot testing on the current calibration sample in S4 is as follows:

[0015] S41. Starting from the coarse focusing position corresponding to the current calibration sample, control the three-dimensional moving stage to move slightly along the Z direction, and collect the black dot pattern at the horizontal plane where the laser focus is located in real time when moving to different focusing distances.

[0016] S42. Determine the clearest black dot pattern based on the clarity and blackness of each black dot pattern, and record the Z-axis micro-movement distance corresponding to the clearest black dot pattern. At this time, the Z-axis is exactly located at the junction of the substrate and the calibration sample structure, that is, the focal plane of the laser processing, so as to obtain the precise focusing distance of the current calibration sample processing position.

[0017] As a further improvement to the above scheme, in S5, the formula for calculating the plane inclination rate of the machining plane is as follows:

[0018] Kx=(z3-z2) / x

[0019] Ky=(z2-z1) / y

[0020] In the formula, Kx represents the plane inclination rate of the machining plane along the X direction. Ky represents the plane inclination rate of the machining plane along the Y direction. x and y represent the preset horizontal movement distances of the three-dimensional moving platform along the X and Y directions, respectively. z+z1, z+z2, and z+z3 represent the precise focusing distances of the machining positions of the first, second, and third calibration samples, respectively.

[0021] As a further improvement to the above scheme, in S6, if z1=z2=z3 or Kx=Ky=0, then the processing plane is determined to be flat, that is, there is no optical axis perpendicularity error.

[0022] As a further improvement to the above scheme, in S1, coarse focusing is achieved through optical observation.

[0023] As a further improvement to the above scheme, the calibration sample adopts a micropillar array structure.

[0024] This invention also discloses a method for correcting the perpendicularity error of the optical axis in two-photon processing. This method is used to add correction to a structure to be processed when an error in the perpendicularity of the optical axis is determined using any of the aforementioned error judgment methods. The correction method includes the following steps:

[0025] By adding the same tilt gradient to the structure to be processed based on the plane tilt rate of the processing plane along the X and Y directions, the bottom of the structure to be processed can be made to coincide with the base surface of the substrate after the black dot focusing processing.

[0026] The present invention also discloses a two-photon polymerization processing device, which includes: a light source, a substrate, a stage and a three-dimensional moving stage.

[0027] The light source includes a femtosecond laser and an optical system. The femtosecond laser is used to generate the laser beam. The optical system is used to transmit the laser beam and adjust its parameters. The material to be processed is dropped onto the upper surface of the substrate. The stage is used to support and fix the substrate. The three-dimensional moving stage is used to move the stage along the X, Y, and Z axes during movement.

[0028] During the preparation stage of the two-photon polymerization processing equipment, any of the above error judgment methods are used to determine whether there is an error in the perpendicularity of the optical axis. When it is determined that there is an error in the perpendicularity of the optical axis, the above correction method is used to add correction to a structure to be processed.

[0029] As a further improvement to the above solution, the processing equipment also includes an image acquisition module. The image acquisition module is used to acquire images of the horizontal plane where the laser focus is located.

[0030] As a further improvement to the above solution, the image acquisition module uses a CCD camera.

[0031] Compared with the prior art, the technical solution disclosed in this invention has the following beneficial effects:

[0032] The error judgment and correction method disclosed in this invention involves coarse focusing and processing a triangular calibration sample structure. The precise focusing distance of the three calibration sample processing positions is determined through black spot testing. A three-value comparison is used to judge the flatness of the processing plane, i.e., the magnitude of the optical axis perpendicularity error during processing. After processing, the black spot pattern is observed. Only when the CCD observation surface and the focal plane of the laser processing focus coincide can the clearest and darkest black spot pattern be observed. This allows for finding the most suitable laser processing focus at this location, with an accuracy within ±0.5μm. This solves the structural defects caused by misfocusing between the laser focus and the processing plane during two-photon polymerization processing. It has the advantages of simplicity, convenience, and high precision, and can further achieve judgment of the flatness of the processing plane, i.e., the optical axis perpendicularity error, and finally, indirect correction. Attached Figure Description

[0033] Figure 1 This diagram illustrates three scenarios in the prior art where unevenness of the machining plane causes a perpendicularity error between the optical axis and the machining reference plane, resulting in the machining reference plane deviating from the focal plane during the machining process.

[0034] Figure 2 This is a flowchart of the optical axis perpendicularity error judgment method based on black dot focusing in Embodiment 1 of the present invention;

[0035] Figure 3 This is a schematic diagram of the black dot focusing process in two-photon polymerization processing according to Embodiment 1 of the present invention;

[0036] Figure 4 This is a schematic diagram of the triangular tilt gradient used to determine the perpendicularity error of the optical axis in two-photon polymerization processing in Embodiment 1 of the present invention.

[0037] Figure 5 This is a schematic diagram of the tilt gradient correction of optical axis perpendicularity error in two-photon polymerization processing in Embodiment 1 of the present invention;

[0038] Figure 6This is a schematic diagram of the overall structure of the two-photon polymerization processing equipment in Embodiment 2 of the present invention;

[0039] Figure 7 This is a schematic diagram of the calibration sample structure used in the experiment in Embodiment 2 of the present invention;

[0040] Figure 8 The black dot patterns at different focusing distances in Embodiment 2 of the present invention;

[0041] Figure 9 This is a schematic diagram and actual optical image of the triangular machining calibration sample structure in Embodiment 2 of the present invention.

[0042] Explanation of main component symbols

[0043] 1. First calibration sample; 2. Second calibration sample; 3. Third calibration sample; 4. Substrate; 5. Stage; 6. Three-dimensional moving stage; 7. Laser focal plane; 8. Laser; 9. Dichroic mirror; 10. Image acquisition module; 11. Processing plane; 12. Objective lens; 13. Processing module; 14. Material to be processed.

[0044] The above description of the main component symbols, together with the accompanying drawings and specific embodiments, provides a more detailed explanation of the present invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] It should be noted that when a component is said to be "installed on" another component, it can be directly on the other component or it may be in a component that is centered on it. When a component is said to be "set on" another component, it can be directly set on the other component or it may also be in a component that is centered on it. When a component is said to be "fixed to" another component, it can be directly fixed to the other component or it may also be in a component that is centered on it.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0048] Example 1

[0049] This embodiment provides a method for judging the optical axis perpendicularity error based on black dot focusing, which is used to judge the flatness of the processing plane 11 of a two-photon polymerization processing device, i.e., the optical axis perpendicularity error.

[0050] The two-photon polymerization processing equipment includes a substrate 4, a stage 5, and a three-dimensional moving stage 6. The material to be processed 14 is dropped onto the upper surface of the substrate 4, and the lower surface is placed on the stage 5. The three-dimensional moving stage 6 is used to move the stage 5 along the X, Y, and Z axes during movement to complete the focusing and processing operations.

[0051] Please see Figure 2 The judgment method includes the following steps:

[0052] S1. Move the three-dimensional moving stage 6 along the Z-axis direction. The Z-axis moving distance z can be roughly focused and recorded by optical observation to ensure that the calibration sample structure can be processed onto the substrate 4.

[0053] S2. Control the movement of the three-dimensional moving stage 6 according to the pre-configured calibration sample processing file to process the structure of the first calibration sample 1.

[0054] S3. After the structural processing of the first calibration sample 1 is completed, control the three-dimensional moving stage 6 to return to the coarse focusing position of the first calibration sample 1.

[0055] S4. Control the three-dimensional moving stage 6 to move the preset horizontal movement distance along the Y and X directions respectively, so as to reach the coarse focusing position of the second calibration sample 2 and the third calibration sample 3 in turn, and process the structure of the second calibration sample 2 and the third calibration sample 3 in the manner of S2.

[0056] After each calibration sample structure is manufactured, a black spot test is performed on the current calibration sample to obtain the precise focusing distance of each of the three calibration samples at its respective manufacturing position. Specifically, the black spot test process for the current calibration sample is as follows:

[0057] S41. Starting from the coarse focusing position corresponding to the current calibration sample, control the three-dimensional moving stage 6 to move slightly along the Z direction, and collect the black dot pattern at the horizontal plane where the laser focus is located in real time when moving to different focusing distances. The black dot pattern is a unique optical phenomenon caused by the change in the refractive index of the aggregated calibration sample.

[0058] S42. Determine the clearest black dot pattern based on the clarity and blackness of each black dot pattern, and record the Z-axis micro-movement distance corresponding to the clearest black dot pattern. At this time, the Z-axis is exactly located at the junction of the substrate and the calibration sample structure, that is, the focal plane of the laser processing, so as to obtain the precise focusing distance of the current calibration sample processing position.

[0059] Please see Figure 3 , Figure 3 Figure a shows a schematic diagram of the two-photon polymerization processing equipment. Figure 3 b represents the virtual position of the calibration sample structure during coarse focusing. In this embodiment, after the calibration sample processing is completed, the top view morphology of the processed sample can be observed using a CCD within a certain Z-axis movement range of the coarse focusing surface, such as... Figure 3 As shown in c, 3d, and 3e. However, only when the Z-axis is moved to a position where the machining surface is parallel to the laser focal plane 7 ( Figure 3 d) Because the laser connects the sample to the substrate 4 at this position, the refractive index change after the photosensitive polymer polymerization creates a unique optical phenomenon. The clearest and darkest black dot pattern can be obtained at this interface. Let the Z-axis movement distance be z1, and thus a more precise focusing distance z+z1 is found. When the focusing distance is less than this, i.e., when the CCD observation surface and the laser focal plane 7 are located within the substrate 4 ( Figure 3 c), the black pattern is the morphology of the calibration sample transmitted from the substrate 4, showing an outward blurring of size and a lighter degree of blackness; when the movement is greater than this focusing distance, the CCD observation surface and the laser focal plane 7 are located within the calibration sample structure. Figure 3 e) At this point, the black pattern is a structural cross-sectional view of the calibration sample at this location, showing a size-reduced blurring, and the degree of blackness is between the two cases above.

[0060] S5. Combining the three precise focusing distances and the horizontal movement distance between adjacent calibration samples, calculate the plane inclination rate of the processing plane 11 along the X and Y directions respectively.

[0061] The formula for calculating the inclination rate of machining plane 11 is as follows:

[0062] Kx=(z3-z2) / x

[0063] Ky=(z2-z1) / y

[0064] In the formula, Kx represents the inclination rate of the machining plane 11 along the X direction. Ky represents the inclination rate of the machining plane 11 along the Y direction. x and y represent the preset horizontal movement distances of the three-dimensional moving platform along the X and Y directions, respectively. z+z1, z+z2, and z+z3 represent the precise focusing distances of the machining positions of the first calibration sample 1, the second calibration sample 2, and the third calibration sample 3, respectively.

[0065] S6. Determine whether there is an error in the perpendicularity of the optical axis based on the magnitude of the plane inclination. If z1 = z2 = z3 or Kx = Ky = 0, then the processing plane 11 is determined to be flat, i.e. there is no error in the perpendicularity of the optical axis.

[0066] Please see Figure 4 The specific process for determining the perpendicularity error of the optical axis using the triangular tilt gradient calculation method proposed in this invention is as follows:

[0067] like Figure 4As shown in (a), three calibration sample structures are processed by optical coarse focusing. The three calibration samples are distributed in a right-angled triangle in space. First, calibration sample 1 is processed. Then, calibration sample 2 is processed after moving a distance y along the Y direction by a three-dimensional moving stage 6. Finally, calibration sample 3 is processed after moving a distance x along the X direction.

[0068] like Figure 4 As shown in (b) and (c), the more precise focusing distances of the three calibration samples at their respective processing positions are determined using the black dot method during the processing: z+z1, z+z2, and z+z3.

[0069] Based on the focusing distance of each of the three calibration samples and the horizontal movement distance between each pair, the plane inclination rates along the X and Y directions are calculated respectively: Kx=(z3-z2) / x, Ky=(z2-z1) / y.

[0070] If z1 = z2 = z3 or Kx = Ky = 0, then the machining plane 11 is flat, meaning there is no optical axis perpendicularity error; otherwise, Kx and Ky represent the tilt gradients of the machining plane 11 in the X and Y directions. It should be noted that the machining plane 11 mentioned here is a holistic representation of the levelness of the base 4, the flat support of the stage 5, and the stability in the Z direction when the three-dimensional moving stage 6 moves in the X / Y directions.

[0071] It should be noted that the triangular calibration sample used in this embodiment is for the convenience of calculation and explanation in the X / Y direction. In fact, as long as it is a point-based form, it can be used to determine the inclination or flatness of any axis or plane.

[0072] This embodiment also provides a method for correcting the perpendicularity error of the optical axis in two-photon processing. This method is used to add correction to a structure to be processed when the above-mentioned error judgment method determines that there is an error in the perpendicularity of the optical axis. The correction method includes the following steps:

[0073] Based on the plane inclination rate of the processing plane 11 along the X and Y directions, the same tilt gradient is added to the structure to be processed, so that after the black dot focusing processing, the bottom of the structure to be processed can coincide with the base surface of the base 4.

[0074] Specifically, the method for correcting optical axis perpendicularity error using tilt gradient proposed in this invention is as follows: Figure 5 As shown, Figure 5 a. Viewed from both the X and Y directions, the machining plane 11 slopes upwards, causing part of the calibration sample structure to be printed below the base plane, resulting in structural defects. For example... Figure 5 b. After calculating the tilt gradients of the machining plane 11X and Y directions using trigonometric methods, add the same tilt gradients to the designed horizontal structure array. For example... Figure 5 c. Since the processing structure array and the processing plane 11 have the same tilt gradient, the bottom can be made to coincide with the base surface after the black dot is focused and processed, and the processed structure is not damaged or lost.

[0075] Example 2

[0076] Please see Figure 6 This embodiment provides a two-photon polymerization processing device, which includes: a light source, a substrate 4, a stage 5 and a three-dimensional moving stage 6, and may also include an image acquisition module 10, a processing module 13, etc.

[0077] The light source includes a femtosecond laser and an optical path system. The femtosecond laser is used to generate laser light 8. The optical path system is used to transmit the laser light and adjust its parameters. The optical path system includes a dichroic mirror 9 and an objective lens 12. The dichroic mirror 9 allows the 800nm ​​wavelength laser light to be highly reflected into the objective lens 12 and allows auxiliary light from the processing area to be transmitted downwards into the image acquisition module 10. The objective lens 12 focuses the light for processing.

[0078] The material to be processed 14 is dropped onto the upper surface of the substrate 4. In this embodiment, the substrate 4 can be a cover glass. Of course, in addition to rigid substrates 4 such as cover glass, various soft material substrates 4 (such as PDMS) that are spin-coated or stretched can also be used in the implementation of this invention. The material to be processed 14 can be SZ2080 solid photoresist. In addition, other materials that can undergo refractive index changes during photoprocessing, such as NOA61 liquid photoresist and hydrogels, can also be used in the implementation of the two-photon polymerization process of this invention.

[0079] The stage 5 is used to support and fix the base 4.

[0080] The three-dimensional moving stage 6 is used to drive the stage 5 to move along the X, Y, and Z axes during movement.

[0081] The processing module 13 can be a computer, which can install control programs and software to control the movement of the three-dimensional moving stage 6, and can establish a signal connection with the light source and image processing module 13.

[0082] The image acquisition module 10 is used to acquire images of the horizontal plane where the laser focal point is located. The image acquisition module 10 can be a CCD camera, which is aligned with the laser processing focal plane and displayed on a computer screen.

[0083] Implementation process:

[0084] (1) Open the optical path and adjust the laser processing parameters such as power. Import the processing file of the calibration sample into the control software. Use a pipette to drop the photoresist onto the coverslip and place it on the stage 5 for fixation.

[0085] (2) Move the three-dimensional moving stage 6 downwards and gradually move the cover glass closer to the laser focus. At the same time, use CCD optical observation for coarse focusing. Coarse focusing must ensure that the calibration sample can be processed and fixed on the surface of the substrate 4, even if there are some structural defects at the bottom.

[0086] Please see Figure 7 To enhance the black spot recognition effect, such as Figure 7 As shown in a, this experiment used a 3×3 array of 9 micropillars (4μm long, 4μm wide, and 12μm high) as the calibration sample. Figure 7 b and 7c are scanning electron microscope images of the processed calibration sample taken from different angles (45° oblique angle and top view).

[0087] (3) After coarse focusing is determined, record the Z-axis movement distance z, and then process the calibration sample. After completion, temporarily block the laser and return to the coarse focusing position of processing the first calibration sample 1 to perform a black spot test: use the control software to micro-move the three-dimensional moving stage 6 along the Z-axis, stop when the clearest black spot pattern is observed, and record the Z-axis micro-movement distance z1. This gives z+z1 the most accurate focusing distance processed at this position. Figure 8 As shown, Figure 8 a represents the black dot pattern at the optimal focusing distance found in the experiment; Figure 8 b represents the black dot pattern at a focal distance of 1μm, which is blurred overall; Figure 8 c represents the black dot pattern when the focusing distance is greater than 1μm. The overall boundary has a certain sense of compression, and the interior gradually becomes blurred.

[0088] (4) Return to the coarse focusing position of the first calibration sample 1, and move the three-dimensional moving stage 6 a distance y (y = 10 μm) along the Y direction to reach the coarse focusing position of the second calibration sample 2. Turn on the laser, process the second calibration sample 2, and perform a black spot test as described in step (3) above to determine the optimal focusing distance z + z2.

[0089] (5) Return to the coarse focusing position of calibration sample 2, and move the three-dimensional moving stage 6 a distance x (x = 40 μm) along the X direction to reach the coarse focusing position of the third calibration sample 3. Turn on the laser, and after processing the third calibration sample 3, perform a black spot test to determine the optimal focusing distance z + z3. Figure 9 As shown, Figure 9 A schematic diagram of the three calibration sample structures processed in experiment a. Figure 9 b is the actual optical image (objective lens 12 (50X)).

[0090] (6) Compare whether z1=z2=z3. If so, it means that the processing plane 11 is flat and there is no optical axis perpendicularity error; otherwise, calculate the plane inclination rate along the X and Y directions respectively: Kx=(z3-z2) / x, Ky=(z2-z1) / y.

[0091] (7) If there is an optical axis perpendicularity error, the obtained plane tilt gradient is introduced into the structural space design to indirectly realize the optical axis perpendicularity error correction.

[0092] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for judging the perpendicularity error of the optical axis based on black dot focusing, used to judge the error of the flatness of the processing plane, i.e., the perpendicularity of the optical axis, of a two-photon polymerization processing device; the two-photon polymerization processing device includes a substrate, a stage, and a three-dimensional moving stage; the upper surface of the substrate is coated with the material to be processed, and the lower surface is placed on the stage; the three-dimensional moving stage is used to drive the stage to move along the X, Y, and Z three dimensions during movement, wherein, The Z-axis is perpendicular to the horizontal plane containing the XY axes; the error judgment method is characterized by the following steps: S1. Move the three-dimensional moving stage along the Z-axis to complete coarse focusing and record the Z-axis moving distance z to ensure that the calibration sample structure can be processed onto the substrate; S2. Control the movement of the three-dimensional moving stage according to the pre-configured calibration sample processing file to process the structure of the first calibration sample; S3. After the structural processing of the first calibration sample is completed, control the three-dimensional moving stage to return to the coarse focusing position of the first calibration sample; S4. Control the three-dimensional moving stage to move a preset horizontal distance along the Y and X directions respectively, so as to reach the coarse focusing position of the second calibration sample and the third calibration sample in turn, and process the structure of the second calibration sample and the third calibration sample in accordance with the method of S2; In this process, after each calibration sample structure is processed, a black spot test is performed on the current calibration sample to obtain the precise focusing distance of each of the three calibration samples at their respective processing positions. S5. Combining the three precise focusing distances and the horizontal movement distance between adjacent calibration samples, calculate the plane inclination rate of the processing plane along the X and Y directions respectively; S6. Determine whether there is an error in the perpendicularity of the optical axis based on the magnitude of the plane inclination rate; In S4, the specific process of performing a black spot test on the current calibration sample is as follows: S41. Starting from the coarse focusing position corresponding to the current calibration sample, control the three-dimensional moving stage to move slightly along the Z direction, and collect the black dot pattern at the horizontal plane where the laser focus is located in real time when moving to different focusing distances; S42. Determine the clearest black dot pattern based on the clarity and blackness of each black dot pattern, and record the Z-axis micro-movement distance corresponding to the clearest black dot pattern. At this time, the Z-axis is located at the junction of the substrate and the calibration sample structure, i.e., the focal plane of the laser processing, so as to obtain the precise focusing distance of the current calibration sample processing position.

2. The method for judging the perpendicularity error of the optical axis based on black dot focusing according to claim 1, characterized in that, In S5, the formula for calculating the plane inclination rate of the processing plane is as follows: Kx=(z3-z2) / x Ky=(z2-z1) / y In the formula, Kx represents the plane inclination rate of the processing plane along the X direction; Ky represents the plane inclination rate of the processing plane along the Y direction; x and y represent the preset horizontal movement distances of the three-dimensional moving stage along the X and Y directions, respectively; z+z1, z+z2 and z+z3 represent the precise focusing distances of the processing positions of the first calibration sample, the second calibration sample and the third calibration sample, respectively.

3. The method for judging the perpendicularity error of the optical axis based on black dot focusing according to claim 2, characterized in that, In S6, if z1=z2=z3 or Kx=Ky=0, then the processing plane is determined to be flat, that is, there is no optical axis perpendicularity error.

4. The method for judging the perpendicularity error of the optical axis based on black dot focusing according to claim 1, characterized in that, In S1, coarse focusing is achieved through optical observation.

5. The method for judging the perpendicularity error of the optical axis based on black dot focusing according to claim 1, characterized in that, The calibration sample adopts a micropillar array structure.

6. A method for correcting optical axis perpendicularity error based on black dot focusing, characterized in that, It is used to add correction to a structure to be processed when the error judgment method as described in any one of claims 1 to 5 determines that there is an error in the perpendicularity of the optical axis; the correction method includes the following process: By adding the same tilt gradient to the structure to be processed according to the plane tilt rate of the processing plane along the X and Y directions, the bottom of the structure to be processed can be made to coincide with the base surface of the substrate after the black dot focusing processing.

7. A two-photon polymerization processing apparatus, comprising: The light source includes a femtosecond laser and an optical path system; The femtosecond laser is used to generate laser light; the optical path system is used to transmit the laser light and adjust the laser parameters. A substrate on which the material to be processed is dripped; A stage for supporting and securing the base; as well as A three-dimensional moving stage, used to drive the platform to move along the X, Y, and Z axes during movement; The feature is that, during the processing preparation stage, the two-photon polymerization processing equipment uses the error judgment method as described in any one of claims 1 to 5 to determine whether there is an error in the perpendicularity of the optical axis, and when it is determined that there is an error in the perpendicularity of the optical axis, it uses the correction method as described in claim 6 to add correction to a structure to be processed.

8. The two-photon polymerization processing equipment according to claim 7, characterized in that, The processing equipment also includes: The image acquisition module is used to acquire images of the horizontal plane where the laser focus is located.

9. The two-photon polymerization processing equipment according to claim 8, characterized in that, The image acquisition module uses a CCD camera.

Images