Rotational symmetric aspherical optical element annular step three-dimensional scanning method and device

Abstract

The application provides a rotating symmetric aspheric optical element annular step three-dimensional scanning method and device, and belongs to the technical field of optical scanning. The method provided by the application comprises the following steps: determining a rotating symmetric center of an optical element, calculating curvature variation information of a surface of the aspheric optical element according to the rotating symmetric center; determining distortion parameters of a scanning sub-aperture according to the size of the scanning sub-aperture and the curvature variation information, wherein the distortion parameters are in direct proportion to the curvature values; dividing the surface of the aspheric optical element into a plurality of annular regions according to the rotating symmetric center as a center point and the curvature variation information; determining optimal annular scanning paths in each annular region according to the distortion parameters; and scanning the optical element according to the optimal annular scanning paths from the center point to the outside, wherein the scanning depths corresponding to different optimal annular scanning paths are different. The rotating symmetric aspheric optical element annular step three-dimensional scanning method and device provided by the application are used to realize accurate scanning of the surface of the aspheric optical element.

Description

Technical Field

[0001] This application relates to the field of optical scanning technology, and in particular to a method and apparatus for ring-shaped stepped three-dimensional scanning of rotationally symmetric aspherical optical elements. Background Technology

[0002] With the rapid development of laser technology, the demand for rotationally symmetric aspherical optical components in the field of laser weapons is increasing. These components are widely used in core components such as laser emission systems and beam shaping modules because they can effectively optimize the transmission and focusing performance of laser beams. To ensure that the surface accuracy of optical components meets the high-power and high-stability requirements of laser weapons, high-precision three-dimensional scanning technology is needed to inspect their surface morphology to identify defects such as surface depressions, protrusions, and scratches. The rationality of the scanning strategy directly determines the detection accuracy, efficiency, and adaptability to complex curved surfaces.

[0003] Currently, for areas where the radial curvature of aspherical surfaces is not considered, the problem of insufficient scanning coverage or excessive repetition is prone to occur, affecting detection accuracy. On the other hand, laying out scanning paths according to fixed path spacing can easily lead to missed areas in detection. Alternatively, forcibly laying out incomplete paths according to the original path spacing not only fails to guarantee detection effectiveness but may also reduce scanning efficiency due to uncontrolled repeatability. Furthermore, sub-apertures are prone to imaging distortion in areas with large curvature, which also affects the accuracy of detection data. Summary of the Invention

[0004] In view of this, this application provides a method and apparatus for ring-shaped stepped three-dimensional scanning of rotationally symmetric aspherical optical elements, so as to achieve accurate scanning of the surface of aspherical optical elements.

[0005] Specifically, this application is implemented through the following technical solution:

[0006] The first aspect of this application provides a method for ring-shaped stepped three-dimensional scanning of rotationally symmetric aspherical optical elements, the method comprising:

[0007] Determine the rotational symmetry center of the optical element, and calculate the curvature change information of the aspherical surface based on the rotational symmetry center;

[0008] The distortion parameters of the scanning sub-aperture are determined based on the size of the scanning sub-aperture and the curvature change information, and the distortion parameters are directly proportional to the curvature value.

[0009] With the rotational symmetry center as the center point, the surface of the aspherical surface is divided into multiple annular regions according to the curvature change information;

[0010] The optimal annular scan path within each annular region is determined based on the distortion parameters.

[0011] Starting from the center point, the optical element is scanned from the inside out according to the optimal circular scanning path. Different optimal circular scanning paths correspond to different scanning depths.

[0012] A second aspect of this application provides a ring-shaped stepped three-dimensional scanning device for rotationally symmetric aspherical optical elements, the device comprising a calculation module, a partitioning module, and a scanning module; wherein...

[0013] The calculation module is used to determine the rotational symmetry center of the optical element and calculate the curvature change information of the aspherical surface based on the rotational symmetry center.

[0014] The calculation module is also used to determine the distortion parameters of the scanning sub-aperture based on the size of the scanning sub-aperture and the curvature change information, wherein the distortion parameters are directly proportional to the curvature value;

[0015] The division module is used to divide the surface of the aspherical surface into multiple annular regions based on the curvature change information, with the rotational symmetry center as the center point.

[0016] The scanning module is used to determine the optimal annular scanning path within each annular region based on the distortion parameters.

[0017] The scanning module is also used to scan the optical element from the center point outwards along the optimal circular scanning path, with different optimal circular scanning paths corresponding to different scanning depths.

[0018] The ring-shaped stepped 3D scanning method and apparatus for rotationally symmetric aspherical optical elements provided in this application, based on the ring-shaped scanning path planning for rapid scanning, adjusts the width of the ring path according to the curvature information of the scanning surface to ensure full coverage of the scanning area. This makes the scanning path compatible with the surface curvature, achieving high-precision and high-efficiency scanning of rotationally symmetric aspherical optical elements. Specifically, using the rotational symmetry center as a reference, by calculating curvature change information and associating it with the distortion parameters of each scanning sub-aperture, the scanning strategy is accurately adapted to the aspherical geometry, avoiding detection errors caused by sub-aperture distortion. Based on the curvature change information, a ring-shaped region is divided on the aspherical surface of the optical element, allowing regions with different curvature characteristics to be adapted to differentiated scanning schemes. The optimal ring-shaped scanning path is determined by combining distortion parameters, balancing detection accuracy and scanning efficiency, ensuring the clarity of the scanned images in each region. The inside-out scanning sequence reduces unnecessary movement of the device between different regions, improving overall scanning efficiency. It can solve the scanning adaptation problem caused by the complex curvature changes of rotationally symmetric aspherical surfaces, and can also ensure detection accuracy while taking into account detection efficiency, providing reliable technical support for the quality inspection of high-precision optical components in the field of laser weapons. Attached Figure Description

[0019] Figure 1 A flowchart of an embodiment of the ring-shaped stepped three-dimensional scanning method for rotationally symmetric aspherical optical elements provided in this application;

[0020] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the ring-shaped stepped three-dimensional scanning device for rotationally symmetric aspherical optical elements provided in this application. Detailed Implementation

[0021] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0022] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used herein are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0023] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0024] The following specific embodiments are given to illustrate the technical solution of this application in detail.

[0025] Figure 1 This is a flowchart of an embodiment of the ring-shaped stepped three-dimensional scanning method for rotationally symmetric aspherical optical elements provided in this application. Please refer to... Figure 1 The method provided in this embodiment may include:

[0026] S101. Determine the rotational symmetry center of the optical element, and calculate the curvature change information of the aspherical surface based on the rotational symmetry center.

[0027] It should be noted that aspherical surfaces refer to continuous curved surfaces that do not satisfy the equation of a spherical surface, formed by rotating around an axis of rotational symmetry. Their core characteristic is that the curvature changes dynamically and regularly along the radial direction, without a uniform radius of curvature. Aspherical surfaces may be formed by rotating quadratic curves (such as parabolas or hyperbolas) around an axis of symmetry, or they may be complex curved surfaces containing higher-order terms. For example, the surface of a parabolic reflector in a laser weapon launching system has a gentle curvature in its central region, which gradually increases in curvature outward along the radial direction, enabling precise parallel projection of the laser beam. Another example is the surface of a hyperboloid lens in a beam shaping module, where the curvature shows a non-uniform gradual change in radial direction, which can effectively correct aberrations in the laser beam. Aspherical surfaces do not have a fixed center of curvature, and the degree of curvature varies at different radial positions. They also exhibit a rotationally symmetric geometry, making them the core structure for rotationally symmetric aspherical optical elements to achieve beam transmission and focusing optimization.

[0028] Specifically, at least three non-collinear feature points on the surface of the optical element to be tested are selected, and these feature points must be evenly distributed in the radial edge region of the optical element. A high-precision coordinate measuring device is used to collect the three-dimensional coordinates of each feature point, establishing a three-dimensional coordinate system based on the plane where the optical element is placed. Based on the geometric characteristics of rotationally symmetric figures, the centers of the circumcircles corresponding to multiple feature points are determined, and these centers are used as the rotational symmetry center of the optical element. Using the rotational symmetry center as the origin, multiple sampling points are set along the radial direction of the optical element, i.e., perpendicular to the rotational symmetry axis. The radial spacing between each sampling point is no greater than half the minimum effective size of the scanning sub-aperture. The three-dimensional coordinates of each sampling point are collected, and the radius of curvature at each sampling point is calculated based on a surface fitting algorithm. Through the conversion relationship between the radius of curvature and the curvature value, the curvature value corresponding to each sampling point is obtained, thus forming the radial curvature variation information of the aspherical surface.

[0029] Furthermore, the rotational symmetry center is the core reference for all subsequent scanning operations, and its positioning accuracy directly affects the accuracy of annular region division and scanning path layout. Selecting non-collinear feature points on the edges can more intuitively reflect the rotational symmetry contour of the optical element and avoid positioning deviations caused by possible processing errors in the central region. Rotationally symmetric aspherical optical elements refer to a class of high-precision optical elements that can form a complete curved surface structure after rotating around a central axis (rotational symmetry axis) as a reference, and whose curved surface contour does not meet the equations of regular curved surfaces such as a soccer ball or a cylinder. Curvature change information refers to the change of surface curvature of the rotationally symmetric aspherical optical element changes with radial position along the radial direction (perpendicular to the rotational symmetry axis) of the element, with the rotational symmetry center as a reference.

[0030] Optionally, the method provided in this embodiment is implemented based on a detection device, which includes an illumination source, a data acquisition unit, a control unit, a sample stage, a triaxial displacement stage, and a spectral confocal sensor. The illumination source is used to emit light to the optical element. The data acquisition unit is used to acquire a two-dimensional image of each sub-aperture on the surface of the optical element. The control unit is used to control the movement of the triaxial displacement stage. The sample stage is used to place the optical element and is mounted on the triaxial displacement stage. The triaxial displacement stage is used to drive the sample stage to move. The spectral confocal sensor is used to measure the relative position between the surface of the optical element and the sensor.

[0031] S102. Determine the distortion parameters of the scanning sub-aperture based on the size of the scanning sub-aperture and the curvature change information, wherein the distortion parameters are directly proportional to the curvature value.

[0032] Specifically, a preset original size of the scanning sub-aperture is defined, which is the standard effective size of the sub-aperture during planar detection. For each sampling point, the curvature value corresponding to that point is extracted, and a correlation model between the curvature value and the sub-aperture distortion is established. Based on the correlation model, the actual effective size of the scanning sub-aperture at each sampling point along the radial and circumferential directions of the optical element is calculated. The difference between the actual effective size and the original size is the distortion parameter corresponding to that sampling point.

[0033] The distortion of a scanning sub-aperture is essentially due to the tilt angle of the aspherical surface, which causes a difference between the curved area actually covered by the sub-aperture and the planar area. For example, when the sub-aperture is aligned with an area with greater curvature, the angle between the curved surface and the sub-aperture plane increases, and the actual coverage area of ​​the sub-aperture in the radial direction is stretched and deformed, while the coverage area in the circumferential direction remains basically unchanged, thus producing radial distortion.

[0034] Furthermore, the specific steps for determining the distortion parameters of the scanning sub-aperture include:

[0035] (1) Establish a two-dimensional coordinate system with the rotational symmetry center as the origin;

[0036] Specifically, a two-dimensional coordinate system is established with the rotational symmetry center as the origin, providing a unified reference for subsequent angle and dimension calculations. The X and Y axes of the two-dimensional coordinate system are both located in a plane perpendicular to the rotational symmetry axis, and the radial direction of the two-dimensional coordinate system (the direction extending outward from the origin) is consistent with the radial direction of the aspherical surface. This allows for the correlation between the radial position of the aspherical surface and the spatial orientation of the sub-aperture, ensuring that subsequent calculated parameters such as included angles and diameters are based on the rotational symmetry characteristics of the component, avoiding quantization errors caused by a confused coordinate reference.

[0037] (2) Determine the angle between the normal vector of the scanning sub-aperture and the axis of rotational symmetry based on the curvature change information;

[0038] Specifically, curvature variation information directly reflects the degree of curvature of the aspherical surface. The direction of the normal vector of the scanning sub-aperture is determined by the surface morphology at its location. The greater the surface curvature, the greater the deviation angle between the sub-aperture normal vector and the rotational symmetry axis. The curvature variation information can be used to deduce the direction of the surface tangent at the center point of the sub-aperture, thereby obtaining the direction of the normal vector perpendicular to the tangent, and finally calculating the angle between the normal vector and the rotational symmetry axis.

[0039] Furthermore, the surface geometric parameters of the target scanning position are extracted from the curvature variation information. For any sub-aperture center point to be calculated on the aspherical surface, the radial coordinates of the sub-aperture center point are substituted into the surface equation obtained by fitting multiple sampling points in the previous step to calculate the corresponding axial coordinates. At the same time, the corresponding radius of curvature is obtained from the curvature variation information. The degree of curvature is determined based on the radius of curvature. The smaller the radius of curvature, the larger the curvature value and the more significant the surface tilt. The tangent direction of the sub-aperture center point is calculated by differentiating the surface equation. The first derivative of the surface equation is obtained radially, and the radial coordinates are substituted into the derivative formula of the surface equation to obtain the tangent slope of the surface. The tangent direction vector is determined based on the tangent slope. Since the surface normal vector is perpendicular to the tangent direction, the normal vector direction can be derived based on the tangent direction vector. The angle between the normal vector and the rotational symmetry axis is calculated based on the inverse cosine function.

[0040] (3) Calculate the distortion diameter of the scanning sub-aperture based on the included angle and the diameter of the scanning sub-aperture;

[0041] Specifically, the original diameter of the scanning sub-aperture is the standard size for planar inspection. However, when the scanning sub-aperture is fitted to an aspherical surface, dimensional distortion occurs due to the surface's tilt. Specifically, when the scanning sub-aperture is projected onto the surface along a direction parallel to the normal vector, the radial projection length of the aspherical surface will be stretched or compressed, while the circumferential projection length remains essentially unchanged. Using trigonometric relationships, the radial distortion diameter is obtained by dividing the original diameter by the cosine of the included angle; the circumferential distortion diameter is consistent with the original diameter.

[0042] (4) Calculate the distortion parameters based on the difference between the distortion diameter and the diameter.

[0043] Specifically, the radial distortion parameter is the difference between the radial distortion diameter and the original diameter, and the circumferential distortion parameter is the difference between the circumferential distortion diameter and the original diameter. Thus, the radial distortion parameter and the circumferential distortion parameter are obtained.

[0044] Furthermore, the scanning sub-aperture is typically circular, which is the standard shape for planar inspection. The original diameter is set to D. When fitting a region with significant aspherical curvature, the circular sub-aperture will undergo radial stretching and circumferential distortion due to the surface inclination, ultimately appearing as an ellipse. For example, a circular sub-aperture with an original diameter D = 4mm has an included angle θ = 30° at a certain radial position. Using trigonometric functions, the radial distortion diameter is calculated to be D / cosθ = 4mm / 0.866 ≈ 4.62mm. There is no circumferential distortion, therefore the circumferential distortion diameter is 4mm. At this point, the radial distortion parameter is 4.62mm - 4mm = 0.62mm, and the circumferential distortion parameter is 0. These two distortion parameters uniquely determine the elliptical dimensions of the distorted sub-aperture (major axis 4.62mm, minor axis 4mm), accurately quantifying the actual coverage shape of the sub-aperture on the curved surface.

[0045] Based on curvature change information, the angle between the scanning sub-aperture normal vector and the rotational symmetry axis is determined, realizing the accurate conversion of the curvature characteristics of the aspherical surface into spatial angle parameters, and establishing a bridge between curvature change and the spatial attitude of the sub-aperture. Combining this angle with the original diameter of the sub-aperture, the distortion diameter is calculated, which can accurately quantify the dimensional deformation of the sub-aperture caused by the surface tilt, and conforms to the curvature differences at different radial positions of the aspherical surface, ensuring the accuracy of the distortion diameter calculation. Finally, the distortion parameter is obtained by the difference between the distortion diameter and the original diameter. This not only accurately quantifies the degree of distortion of the sub-aperture, but also, because the angle is positively correlated with the curvature value, the distortion parameter naturally meets the core requirement of being proportional to the curvature value. This provides a quantifiable distortion basis for subsequent division of the annular region according to curvature and optimization of the annular scanning path, ensuring the accuracy and adaptability of scanning of rotationally symmetric aspherical optical elements from the source.

[0046] S103. Using the rotational symmetry center as the center point, divide the surface of the non-spherical surface into multiple annular regions according to the curvature change information.

[0047] Specifically, the curvature variation information is processed to statistically analyze the radial distribution range of curvature values ​​on the aspherical surface, determining the maximum, minimum, and inflection points of curvature values. Based on the curvature value distribution range, at least two curvature interval thresholds are preset to divide the curvature values ​​into low, medium, and high curvature intervals. All sampling points are traversed radially from the rotational symmetry center outwards, and continuous radial ranges with curvature values ​​within the same curvature interval are marked as regions to be divided. The radial continuity of each region to be divided is verified. If discontinuous radial ranges within the same curvature interval exist, adjacent regions with curvature interval differences less than the preset threshold are merged, ultimately forming multiple annular regions centered on the rotational symmetry center, where the curvature values ​​within each annular region are within the same curvature interval.

[0048] It should be noted that the preset curvature interval threshold needs to be considered in conjunction with the adaptability of the scanning sub-aperture. For example, low curvature intervals correspond to small surface tilt angles and low sub-aperture distortion, allowing for a larger scanning path spacing; high curvature intervals correspond to large surface tilt angles and high sub-aperture distortion, requiring a smaller scanning path spacing to ensure coverage accuracy. Merging discontinuous intervals of the same curvature is to avoid an excessive number of annular regions that would complicate the scanning operation, while ensuring that the curvature uniformity of each annular region meets the scanning requirements.

[0049] Furthermore, the specific steps for dividing the region into multiple annular areas include:

[0050] (1) Taking the rotational symmetry center as the origin, set the radial coordinates along the radial direction of the aspherical surface, and obtain the curvature change rate of different radial coordinates on the aspherical surface;

[0051] Specifically, with the center of rotational symmetry as the origin, a radial coordinate is set along the direction perpendicular to the axis of rotational symmetry of the aspherical surface. The value of the radial coordinate is used to characterize the distance from the coordinate point to the center of rotational symmetry. Multiple sampling points are selected at preset intervals along the radial coordinate from the center of rotational symmetry to the maximum radial dimension of the aspherical surface. Based on the curvature change information, the curvature value corresponding to each sampling point is extracted. The curvature change rate at each sampling point is calculated by the ratio of the difference in curvature values ​​between adjacent sampling points to the difference in radial coordinates.

[0052] (2) Divide multiple curvature change rate intervals based on the curvature change rate threshold, traverse the curvature change rate of each radial coordinate from the inside to the outside along the radial direction, and divide the continuous radial range of curvature change rate in the same curvature change rate interval into the same annular region.

[0053] Specifically, multiple curvature change rate thresholds are preset to divide the curvature change rate into multiple level intervals; the curvature change rate of each sampling point is traversed radially from the inside out, and the starting radial coordinate when the curvature change rate first enters a certain interval and the ending radial coordinate when it first leaves the interval are recorded; the continuous radial range between the starting and ending radial coordinates is defined as the annular region of the corresponding curvature change rate interval; if there are discontinuous radial ranges in the same curvature change rate interval, and the radial distance between adjacent discontinuous ranges is less than the preset threshold, they are merged into the same annular region.

[0054] By transforming abstract surface morphology into calculable radial position-curvature change rate data, objective data support is provided for region division, avoiding division deviations caused by fuzzy curvature data. Furthermore, by dividing intervals based on curvature change rate thresholds and traversing and defining continuous radial ranges as annular regions, aspherical surfaces can be classified and categorized according to curvature change complexity. This ensures that the curvature change patterns of surfaces within the same annular region are consistent, which not only adapts to the geometric characteristics of rotationally symmetric aspherical surfaces but also lays the foundation for subsequent targeted design of scanning strategies for different regions. Ultimately, this achieves the scientific and accurate division of annular regions, balancing the accuracy and efficiency of subsequent scanning.

[0055] S104. Determine the optimal annular scanning path within each annular region based on the distortion parameters.

[0056] Specifically, the distortion parameters of all sampling points within each annular region are traversed, and the minimum distortion parameter within that region is extracted. Based on the minimum distortion parameter, the minimum effective size of the scanning sub-aperture within the annular region is determined. The minimum effective size is the maximum usable size of the sub-aperture within that region without excessive distortion. A preset repeatability requirement for the scanning path is established, where repeatability is the overlap ratio of adjacent scanning paths. Based on the minimum effective size and repeatability requirement, the optimal spacing of the annular scanning paths within the annular region is calculated. Using the rotational symmetry center as the center, annular scanning paths are evenly distributed within the annular region at the optimal spacing, ensuring that the overlap ratio of adjacent paths meets the repeatability requirement and that all paths completely cover the annular region. If uncovered areas exist at the edge of the annular region after distribution, the supplementary path parameters corresponding to these uncovered areas are calculated, and the repeatability of the supplementary paths with adjacent paths is adjusted until the annular region is completely covered.

[0057] Furthermore, for each pre-defined annular region, the distortion parameters corresponding to all previously preset sampling points within that region are extracted one by one. By comparing the data, the distortion parameter with the smallest value is selected. The sub-aperture size corresponding to the smallest distortion parameter is the maximum usable size of the sub-aperture within that region without excessive distortion, i.e., the minimum effective size. If a sub-aperture larger than this size is used, the distortion at some high-curvature sampling points will exceed the allowable range, affecting the accuracy of the data. Combining the detection accuracy requirements with the preset repeatability requirements of the scanning path, the path spacing is calculated using the formula that the optimal spacing is the product of the minimum effective size and the difference between the repeatability and the minimum effective size. For example, when the minimum effective size is 4mm and the repeatability is 30%, the optimal spacing is 2.8mm, ensuring that the overlap ratio of the coverage of adjacent paths exactly meets the preset requirements. Using the rotational symmetry center as the center, starting from the radial starting coordinates of the annular area, the annular scanning path is laid out sequentially according to the calculated optimal spacing. After laying each path, its coverage is verified to be within the radial starting and ending coordinates of the annular area, until the path coverage approaches the radial ending coordinates of the area. If there is an uncovered area at the edge of the final annular area with a width smaller than the optimal spacing (e.g., the radial ending coordinate of the area is 20mm, the last laid path covers 18mm, leaving 2mm uncovered), the radius of the supplementary path is first determined (e.g., 19mm, so that the coverage of the supplementary path can completely cover the remaining 2mm area). Then, the actual spacing between the supplementary path and the adjacent previous path (e.g., the path at 18mm) is calculated. The actual repeatability of the supplementary path is calculated by the actual repeatability being equal to one and the difference between the actual spacing and the minimum effective size. The position of the supplementary path is adjusted according to the actual repeatability to ensure that its overlap ratio with the adjacent path meets the detection accuracy requirements, while completely covering the uncovered edge area, ultimately achieving a complete and high-precision path layout for the entire annular area.

[0058] Furthermore, the specific implementation steps include:

[0059] (1) For each annular region, iterate through the distortion parameters of all scanning sub-apertures within the annular region, and take the diameter of the scanning sub-aperture with the smallest distortion parameter as the width of the annular region;

[0060] Specifically, for a single defined annular region, the distortion parameters corresponding to all preset scanning sub-apertures within that region are extracted; all extracted distortion parameters are compared numerically, and the distortion parameter with the smallest value is selected; the scanning sub-aperture corresponding to the smallest distortion parameter is determined, and the original diameter of the sub-aperture is retrieved; the original diameter of the sub-aperture is defined as the base width of the current annular region, and this width must satisfy the requirement that when all scanning sub-apertures within the region are laid out at this width, no sub-aperture distortion parameter exceeds the allowable threshold.

[0061] Furthermore, candidate positions for scanning sub-apertures within the annular region are clearly defined. Candidate points are placed at intervals no larger than the original diameter of the sub-aperture, based on the radial start and end coordinates of the region. The distortion parameters of the sub-aperture at each candidate position are then calculated using prior curvature change information. After selecting the minimum distortion parameter, the corresponding original diameter of the sub-aperture becomes the base width of the region. This width is chosen because a larger width would cause the distortion parameters of some highly curved sub-aperture positions to exceed detection requirements; a smaller width, while reducing distortion, would increase the number of scanning paths and decrease detection efficiency. Therefore, this width strikes a balance between avoiding excessive distortion and achieving optimal efficiency.

[0062] (2) Determine the actual width of the annular region based on the width and the preset overlap ratio;

[0063] (3) Using the rotational symmetry center as the center and the radial start and end coordinates of the annular region as the center, calculate the optimal annular scanning path.

[0064] Specifically, the actual width of the current annular region is calculated by multiplying the base width by one and subtracting the preset overlap ratio; the radial start and end coordinates of the current annular region are retrieved to determine the total radial length of the region; with the rotational symmetry center as the center, starting from the radial start coordinate, the center radius of each annular scanning path is calculated sequentially according to the actual width, and the center radius of each subsequent path is accumulated based on the actual width of the previous one; the center radius of the last path is verified. If the path coverage does not exceed the region's end coordinate, the path layout is complete; if it exceeds the region, the center radius of the last path is adjusted to ensure that its coverage does not exceed the region; the annular trajectories corresponding to all calculated path center radii are defined as the optimal annular scanning paths for the current annular region, and all paths must completely cover the radial range of the region.

[0065] Furthermore, paths are evenly distributed according to the actual width to ensure complete coverage of the area. For example, the radial starting coordinate of a ring-shaped area is 5 mm, the radial ending coordinate is 10 mm, the actual width is 1.4 mm, and the total radial length of the area is 5 mm. The center radius of the first path is calculated from the radial starting coordinate plus half of the actual width. The center radius of each subsequent path is accumulated from the previous path plus the actual width, and the coverage area of ​​each path extends to both sides from its own center radius. If the coverage area of ​​the last path exceeds the area's ending coordinate, its center radius needs to be adjusted to the area's ending coordinate minus half of the actual width to ensure that the coverage area does not exceed the area. Finally, all paths deployed must ensure that the overlap ratio of adjacent paths meets the preset requirements and completely covers the radial range of the area, forming an optimal ring-shaped scanning path with no omissions and high precision.

[0066] By traversing the distortion parameters of all scanning sub-apertures within the annular region and selecting the sub-aperture diameter corresponding to the minimum distortion parameter as the region width, it is ensured that this width adapts to the curvature characteristics within the region, avoiding excessive distortion of the sub-apertures due to inappropriate width, thus laying the foundation for scanning accuracy. Based on this width and the preset overlap ratio, the actual width is determined, ensuring that adjacent scanning paths are covered without omissions while avoiding excessive overlapping coverage that leads to wasted efficiency. Then, with the rotational symmetry center as the center, the optimal annular scanning path is calculated in combination with the radial start and end coordinates of the annular region. This not only conforms to the geometric characteristics of the rotational symmetry of the aspherical surface but also achieves a uniform layout of the scanning path within the region, ultimately achieving a balance between scanning accuracy and efficiency in each annular region, ensuring comprehensive and accurate coverage of the surface of the rotationally symmetric aspherical optical element.

[0067] In addition to the above, the method provided in this embodiment also includes:

[0068] (1) Determine the remaining width of the annular region based on the difference between the radial start and end coordinates and the optimal annular scan path;

[0069] (2) Set the new circular scanning path with the remaining width as the radius, and calculate the width difference between the new circular scanning path and the adjacent optimal circular scanning path;

[0070] (3) Calculate the actual overlap ratio of the newly added circular scanning path based on the width difference;

[0071] (4) Calculate the increase value based on the difference between the actual overlap ratio and the preset overlap ratio;

[0072] (5) Based on the increased value, adjust the overlap ratio between the newly added annular scanning path and the adjacent optimal annular scanning path to complete the scanning coverage of the annular region.

[0073] Specifically, the radial start and end coordinates of the annular region are retrieved. Combined with the coverage of all the already deployed optimal annular scanning paths, the difference between the radial end coordinate and the coverage endpoint of the last optimal path is calculated to obtain the remaining width of the annular region. Using the rotational symmetry center as the center, a new annular scanning path is set according to the radial position corresponding to the remaining width, ensuring that the coverage of this path completely covers the area corresponding to the remaining width. The center-to-center distance between the new annular scanning path and the adjacent previous optimal annular scanning path is measured to obtain the width difference between them. Based on the width difference between the new path and the adjacent optimal path, combined with the basic width of the annular region, the actual overlap ratio corresponding to the new path is calculated. The actual overlap ratio is subtracted from the preset overlap ratio to obtain the increase in the overlap ratio. The position of the new path is adjusted according to the increase to ensure that the overlap ratio between the new path and the adjacent optimal path reaches the actual overlap ratio, ensuring that the remaining area is completely covered and that the scanning coverage of the entire annular region is complete without omissions or excessive repetition.

[0074] Furthermore, the coverage endpoints of all deployed optimal circular scan paths (the maximum radial position of each path's coverage area) are analyzed, and then compared with the radial termination coordinates of the circular area. The difference between the two is the remaining width. For example, if the radial termination coordinate of the circular area is 10 mm, and the coverage endpoint of the last optimal path is 9.2 mm, then the remaining width is 0.8 mm. Using the rotational symmetry center as the center, the path's coverage area is designed to precisely cover the area corresponding to the remaining width. Typically, the center radius of the new path is set to half the radial termination coordinate minus the base width, ensuring that the maximum radial position of the path's coverage area does not exceed the circular area, and the minimum radial position overlaps with the adjacent optimal path. Then, the center distance between the new path and the adjacent previous optimal path is measured; this distance is the width difference. For example, if the center radius of the newly added path is 9.6 mm and the center radius of the adjacent optimal path is 8.8 mm, then the width difference is 0.8 mm. Subtracting the width difference from the base width gives the overlap width of the two paths. Dividing the overlap width by the base width gives the actual overlap ratio. The increase in the overlap ratio is the difference between the actual overlap ratio and the preset overlap ratio. When adjusting the position of the newly added path, it needs to be moved towards the adjacent optimal path according to the increase value, so that the overlap ratio reaches the actual overlap ratio. Through this adjustment, the newly added path can accurately cover the area corresponding to the remaining width, while ensuring a reasonable overlap ratio. This avoids missing remaining areas and prevents a decrease in scanning efficiency due to excessive overlap, ultimately achieving complete coverage of the entire annular area.

[0075] This approach allows for precise handling of uncovered residual areas at the edges of the annular region. It eliminates the need to readjust the optimal path spacing for the entire annular region; simply adding a supplementary path and optimizing its overlap ratio achieves complete coverage, balancing scanning accuracy and efficiency. Furthermore, the calculation and adjustment of the increased overlap ratio ensures that the supplementary coverage does not result in excessive repetition, making the scanning coverage of the entire annular region more scientific and reasonable. This further guarantees the comprehensiveness and accuracy of scanning the surface of rotationally symmetric aspherical optical elements.

[0076] S105. Starting from the center point, scan the optical element from the inside out according to the optimal circular scanning path. Different optimal circular scanning paths correspond to different scanning depths.

[0077] Specifically, the initial position of the scanning device is adjusted so that the scanning sub-aperture is aligned with the center of rotational symmetry. Following the optimal annular scanning path, scanning begins from the innermost annular region where the center of rotational symmetry is located, completing surface data acquisition for all annular scanning paths within that region. The scanning device is then moved radially outwards, sequentially entering each outer annular region, and data acquisition is completed according to the optimal annular scanning path for each region until all annular regions have been scanned. During the scanning of each annular region, the Z-axis position of the scanning sub-aperture (along the axis of rotational symmetry) is adjusted in real time based on the curvature changes of that region, ensuring the sub-aperture remains in focus. Different annular regions have different curvature changes, resulting in different Z-axis position adjustment ranges, meaning different optimal annular scanning paths correspond to different scanning depths of field. The three-dimensional coordinates and imaging data of each scanning point are recorded in real time during the scanning process, forming a complete three-dimensional data model of the aspherical surface.

[0078] Scanning from the center point outwards is crucial because the inner annular region typically has less curvature and lower sub-aperture distortion, making the scanning operation easier to control. It can serve as a reference for subsequent scanning of the outer region, reducing overall scanning errors caused by initial positioning deviations. Different scanning paths correspond to different depths of field, essentially due to the varying curvature of different annular regions. This results in different Z-axis adjustment ranges for the sub-aperture. In areas with greater curvature, the surface undulations along the Z-axis are more pronounced, requiring a larger Z-axis adjustment range for the sub-aperture to maintain focus; conversely, in areas with less curvature, the Z-axis undulations are gentler, resulting in a smaller Z-axis adjustment range for the sub-aperture. Real-time adjustment of the Z-axis position and data recording ensure the image clarity and coordinate accuracy of each scanning point, providing high-quality 3D data support for subsequent surface defect identification and accuracy assessment.

[0079] Furthermore, the steps for scanning the optical element from the inside out according to the optimal circular scanning path include:

[0080] (1) Traverse each of the annular regions and calculate the spatial coordinates of the scanning sub-aperture based on the position information of the current annular region;

[0081] Specifically, each annular region is traversed from the inside out, and the radial start and end coordinates of the current annular region and the center radius of the optimal annular scanning path are retrieved. Based on the center radius of each scanning path and combined with the curvature change information of the annular region, the three-dimensional spatial coordinates of all scanning sub-apertures on the path are calculated.

[0082] (2) Calculate the optimal focusing position of the scanning sub-aperture based on the spatial coordinates;

[0083] Specifically, based on the spatial coordinates of the scanning sub-aperture, a curved surface model of the optical element is established in a preset spatial coordinate system; the normal direction of the center point of each scanning sub-aperture on the curved surface model is determined, and the distance from the center point along the normal direction to the focal plane of the imaging lens of the detection system, i.e., the normal direction depth, is calculated; the normal direction depth is used as the optimal focusing position of the scanning sub-aperture.

[0084] Furthermore, the steps for calculating the optimal focusing position of the scanning sub-aperture based on the spatial coordinates include:

[0085] Furthermore, the specific steps for calculating the optimal focusing position of the current sub-aperture based on the spatial coordinates include:

[0086] 2.1 Establish the surface model of the large-aperture curved optical element in the spatial coordinate system of the aforementioned spatial coordinates;

[0087] Specifically, multiple feature sampling points on the surface of the element to be scanned are collected by the sensor, and the three-dimensional coordinates of each sampling point in the above-mentioned spatial coordinate system are obtained. Combined with the design parameters of the element, such as the radius of curvature of the spherical element and the quadratic surface coefficient of the non-spherical element, the least squares method is used to fit the coordinates of the sampling points to construct the parameterized surface model of the element.

[0088] 2.2 Determine the depth of the normal direction of the current sub-aperture center point on the surface model based on the spatial coordinates;

[0089] Specifically, the initial Z-coordinate of the sub-aperture center point on the surface model is obtained. The normal direction of this point is derived through gradient calculation of the surface model. For a parametric surface model, its gradient vector is the normal direction of the surface at that point, pointing outwards from the surface to be scanned, consistent with the imaging direction of the detection system. The normal direction depth refers to the distance from the sub-aperture center point on the surface model along the normal direction to the focal plane of the imaging lens of the detection system. The reference working distance of the sensor is determined, i.e., the distance from the lens focal plane to the sensor's reference position. Then, the actual distance from the sub-aperture center point along the normal direction to the sensor's reference position is calculated. The normal direction depth is then calculated based on the difference between the distance from the lens focal plane to the sensor's reference position and the actual distance.

[0090] 2.3 The depth in the normal direction is taken as the optimal focusing position for the current sub-aperture.

[0091] Specifically, the depth along the normal direction is directly used as the optimal focus position of the current sub-aperture in the Z-axis direction. This ensures that the focus of the scanning system can accurately fall on the surface position corresponding to the center point of the sub-aperture along the normal direction of the surface, so that the sub-aperture image acquired by the imaging device is in the clearest state, which conforms to the basic principle of focusing of optical systems. When the focus is consistent with the normal direction of the measured surface, the image quality is optimal. Based on the optimal focus position of the current sub-aperture and its spatial coordinates, the three-dimensional spatial coordinates of the current sub-aperture are obtained.

[0092] In addition, the difference between the next sub-aperture Z-axis spatial position and the current sub-aperture Z-axis spatial position can be calculated. This difference is used as the height difference. The height difference is compared with the system depth of field. If the height difference is less than the system depth of field, the next sub-aperture Z-axis spatial position remains unchanged and is the same as the current sub-aperture Z-axis spatial position. If the height difference is greater than or equal to the system depth of field, the position moves to the next sub-aperture Z-axis spatial position.

[0093] Furthermore, based on the spatial coordinate system, the calculated optimal Z-axis focus position is converted into a Z-axis motion command for the three-dimensional displacement stage. For example, if the XY plane coordinates of the current sub-aperture center point are (X0, Y0), the optimal Z-axis focus position is Z0, and the current Z-axis position of the displacement stage is Z_current, then the distance the displacement stage needs to move along the Z-axis is ΔZ = Z0 - Z_current. Since the spatial coordinates of the sub-aperture include both the XY plane position and the Z-axis focus position, the displacement stage first needs to move the sample stage along the X and Y axes to move the current sub-aperture center point to the center of the detection system's field of view; then, it needs to move along the Z-axis to bring the sub-aperture center point to the optimal focus position along the surface normal direction. After the movement is completed, the distance feedback signal of the sub-aperture center point is collected in real time by a spectral confocal sensor. If the deviation between the actual feedback distance and the optimal Z-axis focus position meets the requirements, the focus is considered qualified; if the deviation exceeds the range, the Z-axis movement distance needs to be recalculated and the Z-axis position finely adjusted until the focus accuracy requirements are met.

[0094] Furthermore, after focusing, the illumination source is turned on and its parameters are adjusted to ensure uniform coverage of the current sub-aperture area, guaranteeing stable illumination intensity and preventing grayscale deviations in the sub-aperture image due to uneven illumination, which could affect the accuracy of subsequent defect identification. The imaging device is then controlled to capture a high-resolution grayscale image of the current sub-aperture area. Simultaneously, the three-dimensional spatial coordinates of the current sub-aperture are associated and stored with metadata such as shooting time and illumination parameters, providing a coordinate reference for subsequent full-aperture image stitching and defect localization. The captured sub-aperture image is transmitted to the software analysis unit for preprocessing to ensure image quality meets defect identification requirements. The preprocessed image is then analyzed based on a defect identification algorithm to determine if defects exist. The defect identification result of the current sub-aperture image is associated with its three-dimensional coordinates and stored in the database, completing the scanning of a single sub-aperture.

[0095] (3) Perform focusing scan on the scanning sub-aperture according to the optimal focusing position.

[0096] Specifically, the displacement mechanism of the control scanning device moves the scanning sub-aperture to the optimal focusing position, activates the illumination source and imaging unit, and completes the focusing scan and surface data acquisition of the sub-aperture; repeat the above steps until all scanning sub-apertures in the current annular area have completed focusing scans, and then enter the next annular area to perform the same operation.

[0097] By calculating the spatial coordinates of sub-apertures based on the location information of the annular region, precise adaptation of the scanning position to the geometric characteristics of the aspherical surface was achieved. The optimal focusing position was determined based on the spatial coordinates and the surface model, ensuring clear imaging of each sub-aperture in areas with varying curvature, avoiding detection errors caused by inaccurate focusing. Focusing and scanning at the optimal focusing position guaranteed the accuracy and reliability of the acquired data. This entire process tightly integrates position positioning, focusing calculation, and scanning execution, adapting to the radial curvature variations of the rotationally symmetric aspherical surface and improving the quality of the detection data through precise focusing, laying a solid foundation for subsequent 3D image stitching and defect identification.

[0098] Furthermore, after scanning the optical element from the inside out according to the optimal circular scanning path, the method provided in this embodiment includes:

[0099] (1) Extract feature points based on the overlapping area of ​​adjacent scanned images and calculate the spatial coordinate deviation of the feature points;

[0100] Specifically, all acquired scanned images are traversed, and adjacent scanned image pairs are selected according to the scanning order of the annular sub-region. For each pair of adjacent scanned images, the overlapping area between the two is identified, that is, the surface range covered by both sub-apertures at the same time. Multiple stable feature points are extracted from the overlapping area. Based on the pixel coordinates of the feature points in the two images, combined with the spatial coordinate data of the corresponding sub-apertures, the actual coordinates of each feature point in three-dimensional space are calculated, and the spatial coordinate deviation of the same feature point in the two images is obtained.

[0101] Furthermore, adjacent image pairs are matched according to the scanning order to ensure that the stitching order is consistent with the actual scanning path and avoid logical confusion. When identifying overlapping areas, the search range is determined based on the overlap ratio of the scanning path to reduce invalid calculations. Feature points extracted should select details with strong stability and not easily affected by lighting, such as the endpoints of minor surface scratches or texture spots left by processing. The pixel positions of feature points are transformed into three-dimensional spatial coordinates through the mapping relationship between image pixel coordinates and sub-aperture spatial coordinates. The spatial coordinate difference is calculated based on the difference between feature points, and the spatial coordinate difference reflects the degree and direction of misalignment between the two images.

[0102] (2) Perform geometric correction on adjacent scanned images based on the spatial coordinate deviation;

[0103] Specifically, statistical analysis is performed on the spatial coordinate deviations of all feature points, and the geometric correction matrix is ​​obtained by fitting using the least squares method. The geometric correction matrix is ​​then applied to adjust the pixel coordinates of the side with the larger deviation in adjacent scanned images, so that the spatial coordinates of feature points in the overlapping area of ​​the two images are consistent, thus completing the geometric correction.

[0104] (3) All the corrected scan images are stitched together in the scanning order of the annular sub-region to form a three-dimensional image of the surface of the optical element.

[0105] Specifically, following the scanning order of the annular sub-region, all corrected scanned images are stitched together sequentially, and the overlapping areas are aligned and fused to fill the image gaps, ultimately forming a three-dimensional image that completely covers the surface of the optical element.

[0106] By extracting feature points from overlapping areas of adjacent images and calculating spatial coordinate deviations, image misalignment caused by equipment displacement and positioning errors during scanning was accurately located. Geometric correction based on the deviation data effectively eliminated positional deviations between adjacent images, ensuring precise alignment of overlapping areas. All corrected images were then stitched together in the scanning sequence, achieving a complete 3D reconstruction of the optical element's surface. This entire process not only solved the problem of limited coverage of a single sub-aperture image but also ensured spatial consistency and accuracy of the stitched images through deviation correction. The resulting 3D image completely and realistically reproduces the aspherical surface morphology, providing complete and reliable data support for subsequent surface defect identification and accuracy testing.

[0107] The ring-shaped stepped 3D scanning method for rotationally symmetric aspherical optical elements provided in this embodiment calculates curvature change information based on the rotational symmetry center and correlates it with proportional distortion parameters to accurately adapt to the geometric characteristics of the aspherical surface, avoiding detection errors caused by sub-aperture distortion. It divides the area into ring regions according to curvature change information, determines the optimal ring scanning path for each region based on distortion parameters, adds supplementary paths for remaining edge regions, and adjusts the overlap ratio to achieve complete coverage. During scanning, it advances from the inside out, calculates the optimal focus position based on the sub-aperture spatial coordinates, and dynamically adjusts the Z-axis attitude. Different paths adapt to different depths of field, classifying sub-apertures with approximately the same height as the same sub-region. Combined with a stepped Z-axis movement strategy, it effectively reduces mechanical movement. Compared with conventional serpentine scanning schemes, this method significantly improves detection efficiency in 3D scanning inspection. Simultaneously, it completes 3D reconstruction through image feature point extraction, geometric correction, and sequential stitching. Ultimately, while ensuring scanning accuracy and comprehensive coverage of the aspherical surface, it reduces invalid movement and excessive repetition, balancing detection efficiency and providing reliable technical support for the quality inspection of high-precision optical elements in the field of laser weapons.

[0108] Corresponding to the aforementioned embodiment of a ring-shaped stepped three-dimensional scanning method for rotationally symmetric aspherical optical elements, this application also provides an embodiment of a ring-shaped stepped three-dimensional scanning device for rotationally symmetric aspherical optical elements.

[0109] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the ring-shaped stepped three-dimensional scanning device for rotationally symmetric aspherical optical elements provided in this application. Please refer to... Figure 2 The apparatus provided in this embodiment includes a calculation module 210, a division module 220, and a scanning module 230; wherein,

[0110] The calculation module 210 is used to determine the rotational symmetry center of the optical element and calculate the curvature change information of the aspherical surface based on the rotational symmetry center.

[0111] The calculation module 210 is also used to determine the distortion parameters of the scanning sub-aperture based on the size of the scanning sub-aperture and the curvature change information, wherein the distortion parameters are directly proportional to the curvature value;

[0112] The division module 220 is used to divide the surface of the aspherical surface into multiple annular regions based on the curvature change information, with the rotational symmetry center as the center point.

[0113] The scanning module 230 is used to determine the optimal annular scanning path within each annular region based on the distortion parameters;

[0114] The scanning module 230 is also used to scan the optical element from the center point outwards along the optimal circular scanning path, with different optimal circular scanning paths corresponding to different scanning depths.

[0115] The apparatus of this embodiment can be used to perform... Figure 1 The steps of the method embodiment shown are similar in principle and process, and will not be repeated here.

[0116] The specific implementation process of the functions and roles of each unit in the above device can be found in the implementation process of the corresponding steps in the above method, and will not be repeated here.

[0117] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this application according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0118] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for ring-shaped stepped three-dimensional scanning of rotationally symmetric aspherical optical elements, characterized in that, The method includes: Determine the rotational symmetry center of the optical element, and calculate the curvature change information of the aspherical surface based on the rotational symmetry center; The distortion parameters of the scanning sub-aperture are determined based on the size of the scanning sub-aperture and the curvature change information, and the distortion parameters are directly proportional to the curvature value. With the rotational symmetry center as the center point, the surface of the aspherical surface is divided into multiple annular regions according to the curvature change information; The optimal annular scan path within each annular region is determined based on the distortion parameters. Starting from the center point, the optical element is scanned from the inside out according to the optimal circular scanning path. Different optimal circular scanning paths correspond to different scanning depths.

2. The method according to claim 1, characterized in that, The step of determining the distortion parameters of the scanning sub-aperture based on the size of the scanning sub-aperture and the curvature change information includes: A two-dimensional coordinate system is established with the rotational symmetry center as the origin; The angle between the normal vector of the scanning sub-aperture and the axis of rotational symmetry is determined based on the curvature change information. The distortion diameter of the scanning sub-aperture is calculated based on the included angle and the diameter of the scanning sub-aperture; The distortion parameters are calculated based on the distortion diameter and the difference between the two diameters.

3. The method according to claim 1, characterized in that, The process of dividing the surface of the aspherical surface into multiple annular regions based on the curvature change information includes: Using the rotational symmetry center as the origin, radial coordinates are set along the radial direction of the aspherical surface to obtain the curvature change rate at different radial coordinates on the aspherical surface; Based on the curvature change rate threshold, multiple curvature change rate intervals are divided. The curvature change rate of each radial coordinate is traversed from the inside to the outside along the radial direction. The continuous radial range where the curvature change rate is in the same curvature change rate interval is divided into the same annular region.

4. The method according to claim 1, characterized in that, Determining the optimal annular scan path within each annular region based on the distortion parameters includes: For each annular region, iterate through the distortion parameters of all scanning sub-apertures within the annular region, and take the diameter of the scanning sub-aperture with the smallest distortion parameter as the width of the annular region; The actual width of the annular region is determined based on the width and the preset overlap ratio; Using the rotational symmetry center as the center and combining the radial start and end coordinates of the annular region, the optimal annular scanning path is calculated.

5. The method according to claim 4, characterized in that, The method further includes: The remaining width of the annular region is determined based on the difference between the radial start and end coordinates and the optimal annular scan path; Use the remaining width as the radius to set a new circular scan path, and calculate the width difference between the new circular scan path and the adjacent optimal circular scan path; Calculate the actual overlap ratio of the newly added circular scan path based on the width difference; The increase value is calculated based on the difference between the actual overlap ratio and the preset overlap ratio; Based on the increased value, the overlap ratio between the newly added annular scanning path and the adjacent optimal annular scanning path is adjusted to complete the scanning coverage of the annular region.

6. The method according to claim 1, characterized in that, The scanning of the optical element from the inside out according to the optimal circular scanning path includes: Traverse each of the annular regions and calculate the spatial coordinates of the scanning sub-aperture based on the position information of the current annular region; Calculate the optimal focusing position of the scanning sub-aperture based on the spatial coordinates; The scanning sub-aperture is focused and scanned according to the optimal focus position.

7. The method according to claim 6, characterized in that, The calculation of the optimal focusing position of the scanning sub-aperture based on the spatial coordinates includes: A surface model of the optical element is established in the spatial coordinate system of the aforementioned spatial coordinates; Determine the depth of the normal direction of the current sub-aperture center point on the surface model based on the spatial coordinates; The depth in the normal direction is used as the optimal focus position for the current sub-aperture.

8. The method according to claim 1, characterized in that, The method is implemented based on a detection device, which includes an illumination source, a data acquisition unit, a control unit, a sample stage, a triaxial displacement stage, and a spectral confocal sensor. The illumination source is used to emit light onto the optical element. The data acquisition unit is used to acquire two-dimensional images of each sub-aperture on the surface of the optical element. The control unit is used to control the movement of the triaxial displacement stage. The sample stage is used to place the optical element and is mounted on the triaxial displacement stage. The triaxial displacement stage is used to drive the sample stage to move. The spectral confocal sensor is used to measure the relative position between the surface of the optical element and the sensor.

9. The method according to claim 1, characterized in that, After scanning the optical element from the inside out according to the optimal circular scanning path, the process includes: Feature points are extracted based on the overlapping region of adjacent scanned images, and the spatial coordinate deviation of the feature points is calculated. Geometric correction is performed on adjacent scanned images based on the spatial coordinate deviation; All the corrected scanned images are stitched together in the scanning order of the annular sub-regions to form a three-dimensional image of the surface of the optical element.

10. A ring-shaped stepped three-dimensional scanning device with rotationally symmetric aspherical optical elements, characterized in that, The device includes a calculation module, a partitioning module, and a scanning module; wherein... The calculation module is used to determine the rotational symmetry center of the optical element and calculate the curvature change information of the aspherical surface based on the rotational symmetry center. The calculation module is also used to determine the distortion parameters of the scanning sub-aperture based on the size of the scanning sub-aperture and the curvature change information, wherein the distortion parameters are directly proportional to the curvature value; The division module is used to divide the surface of the aspherical surface into multiple annular regions based on the curvature change information, with the rotational symmetry center as the center point. The scanning module is used to determine the optimal annular scanning path within each annular region based on the distortion parameters. The scanning module is also used to scan the optical element from the center point outwards along the optimal circular scanning path, with different optimal circular scanning paths corresponding to different scanning depths.

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