Annular stepped three-dimensional scanning method and device for rotationally symmetrical aspheric optical element

Abstract

The invention provides an annular stepped three-dimensional scanning method and device for a rotational symmetric aspheric optical element, and belongs to the technical field of optical scanning. The method provided by the invention comprises the following steps: determining a rotational symmetry center of an optical element, and calculating curvature change information of an aspheric surface according to the rotational symmetry center; determining a distortion parameter of the scanning sub-aperture according to the size of the scanning sub-aperture and the curvature change information, wherein the distortion parameter is in direct proportion to the curvature value; dividing the surface of the aspheric surface into a plurality of annular areas according to the curvature change information by taking the rotational symmetry center as a central point; determining an optimal annular scanning path in each annular area according to the distortion parameters; the optical element is scanned from the center point from inside to outside according to the optimal annular scanning paths, and different optimal annular scanning paths correspond to different scanning field depths. The invention provides an annular stepped three-dimensional scanning method and an annular stepped three-dimensional scanning device for a rotational symmetric aspheric optical element. The method and the device are used for realizing accurate scanning of the surface of the aspheric optical element.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical scanning technology, in particular to a rotating symmetric aspheric optical element annular stepped three-dimensional scanning method and device. BACKGROUND

[0002] At present, with the rapid development of laser technology, the demand for rotating symmetric aspheric optical elements in the field of laser weapons is increasing. Such elements are widely used in core components such as laser launch systems and beam shaping modules because they can effectively optimize the transmission and focusing performance of laser beams. In order to ensure that the surface precision of optical elements meets the high-power and high-stability requirements of laser weapons, high-precision three-dimensional scanning technology is needed to detect the 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 surfaces.

[0003] Currently, the dynamic change characteristics of the curvature of the aspheric surface along the radial direction are not considered, which leads to the problem that areas with sharp curvature changes are prone to insufficient or excessive scanning coverage, affecting detection accuracy. On the other hand, arranging scanning paths according to fixed path intervals can easily result in missed area detection. Either forcibly arranging incomplete paths according to the original path interval, which cannot guarantee the effectiveness of detection, or losing control of the repetition degree, which reduces scanning efficiency, and the imaging distortion of sub-apertures in areas with large curvature can also affect the accuracy of detection data. SUMMARY

[0004] Therefore, the present application provides a rotating symmetric aspheric optical element annular stepped three-dimensional scanning method and device to realize accurate scanning of the surface of an aspheric optical element.

[0005] Specifically, the present application is realized by the following technical solutions:

[0006] The first aspect of the present application provides a rotating symmetric aspheric optical element annular stepped three-dimensional scanning method, which comprises:

[0007] determining the center of rotation symmetry of the optical element, and calculating the curvature change information of the surface of the aspheric surface according to the center of rotation symmetry;

[0008] determining the distortion parameters of the scanning sub-aperture according to the scanning sub-aperture size and the curvature change information, wherein the distortion parameters are in direct proportion to the curvature value;

[0009] dividing the surface of the aspheric surface into multiple annular regions according to the curvature change information, with the center of rotation symmetry as the center point;

[0010] determining the optimal annular scanning path in each annular region according to the distortion parameters;

[0011] The optical element is scanned from the center point outwardly according to the optimal annular scanning path, and different optimal annular scanning paths correspond to different scanning depths.

[0012] The second aspect of the application provides an annular stepped three-dimensional scanning device for a rotationally symmetric aspheric optical element, the device comprising a calculation module, a division module and a scanning module; wherein,

[0013] The calculation module is configured to determine the rotationally symmetric center of the optical element, and calculate the curvature variation information of the surface of the aspheric surface according to the rotationally symmetric center;

[0014] The calculation module is further configured to determine the distortion parameter of the scanning sub-aperture according to the scanning sub-aperture size and the curvature variation information, and the distortion parameter is in direct proportion to the curvature value;

[0015] The division module is configured to divide the surface of the aspheric surface into a plurality of annular regions according to the curvature variation information with the rotationally symmetric center as the center point;

[0016] The scanning module is configured to determine the optimal annular scanning path in each annular region according to the distortion parameter;

[0017] The scanning module is further configured to scan the optical element from the center point outwardly according to the optimal annular scanning path, and different optimal annular scanning paths correspond to different scanning depths.

[0018] The annular stepped three-dimensional scanning method and device for a rotationally symmetric aspheric optical element provided by the application plan the scanning path in an annular manner, adjust the width of the annular path based on the curvature information of the scanning surface, ensure full coverage of the scanning area, adapt the scanning path to the surface curvature, and achieve high-precision and high-efficiency scanning of the rotationally symmetric aspheric optical element. Specifically, the rotationally symmetric center is taken as the reference, the curvature variation information is calculated and associated with the distortion parameter of each scanning sub-aperture, the accurate adaptation of the scanning strategy to the geometric characteristics of the aspheric surface is ensured, and the detection error caused by the sub-aperture distortion is avoided; the annular regions are divided on the aspheric surface of the optical element based on the curvature variation information, the regions with different curvature characteristics can be adapted to the differential scanning scheme, the optimal annular scanning path is determined in combination with the distortion parameter, the detection accuracy and scanning efficiency are taken into account, the clarity of the scanning imaging of each region is ensured, the scanning sequence from the inside to the outside reduces the invalid movement of the equipment between different regions, and the overall scanning efficiency is improved. The scanning adaptation problem caused by the complex curvature variation of the rotationally symmetric aspheric surface is solved, the detection efficiency is taken into account on the premise of ensuring the detection accuracy, and reliable technical support is provided for the quality detection of high-precision optical elements 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 the aspheric surface refers to a continuous surface formed by rotating around the rotationally symmetric axis, which does not satisfy the spherical surface equation, and the core feature is that the curvature changes regularly and dynamically along the radial direction, and there is no uniform radius of curvature. The aspheric surface may be formed by rotating a quadratic curve (such as a parabola or a hyperbola) around the symmetry axis, or a complex curved surface containing high-order terms, for example, the parabolic mirror surface in the laser weapon launching system, the central area of which has a gentle curvature, and the curvature gradually increases along the radial direction outward, which can accurately project the laser beam in parallel; for example, the hyperbolic lens surface in the beam shaping module, the curvature changes along the radial direction in a non-uniform gradient, which can effectively correct the aberration of the laser beam; the aspheric surface has no fixed curvature center, and the bending degree at different radial positions is different, and the whole presents a rotationally symmetric geometric shape. It is the core structure of the rotationally symmetric aspheric optical element to realize the function of beam transmission and focusing optimization.

[0028] Specifically, at least three non-collinear feature points on the surface of the optical element to be detected are selected, and the feature points are uniformly 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, and a three-dimensional coordinate system with the placement plane of the optical element as the reference is established; according to the geometric characteristics of the rotationally symmetric figure, the centers of the circumscribed circles corresponding to the plurality of feature points are solved, and the centers of the circumscribed circles are taken as the rotationally symmetric center of the optical element; taking the rotationally symmetric center as the origin, a plurality of sampling points are set along the radial direction of the optical element, i.e. perpendicular to the rotationally symmetric axis, and the radial distance of each sampling point is not greater than half of the minimum effective size of the scanning sub-aperture; the three-dimensional coordinates of each sampling point are collected, the curvature radius at each sampling point is calculated based on the surface fitting algorithm, and the curvature value corresponding to each sampling point is obtained through the conversion relationship between the curvature radius and the curvature value, and then the curvature change information of the aspheric surface along the radial direction is formed.

[0029] Further, the rotationally symmetric center is the reference core of all subsequent scanning operations, and its positioning accuracy directly affects the accuracy of the annular region division and the scanning path layout. Selecting the edge non-collinear feature points can more intuitively reflect the rotationally symmetric profile of the optical element, and avoid positioning deviation caused by possible machining errors in the central region. The rotationally symmetric aspheric optical element refers to a high-precision optical element with a complete curved surface structure formed by rotating around a certain central axis (rotationally symmetric axis), and the curved surface profile does not satisfy the regular curved surface equation such as spherical surface and cylindrical surface; the curvature change information refers to the rotationally symmetric center of the rotationally symmetric aspheric optical element as the reference, reflecting the change of the curvature of the element surface along the radial direction (perpendicular to the rotationally symmetric axis) of the element.

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

[0031] S102, determine the distortion parameter of the scanning sub-aperture according to the scanning sub-aperture size and the curvature change information, the distortion parameter is in direct proportion to the curvature value.

[0032] Specifically, the original size of the preset scanning sub-aperture is determined, the original size is the standard effective size of the sub-aperture in the plane detection; for each sampling point, the curvature value corresponding to the point is extracted, and a correlation model of 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, and the difference between the actual effective size and the original size is the distortion parameter corresponding to the sampling point.

[0033] The distortion of the scanning sub-aperture is essentially caused by the existence of the tilt angle of the aspheric surface, which causes the difference between the actual coverage area of the sub-aperture on the curved surface and the flat surface. For example, when the sub-aperture is aligned with a region with large curvature, the included angle between the curved surface and the sub-aperture plane increases, the actual coverage range of the sub-aperture along the radial direction is stretched and deformed, while the coverage range along the circumferential direction remains basically unchanged, thereby generating radial distortion.

[0034] Further, the specific implementation steps of determining the distortion parameter of the scanning sub-aperture include:

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

[0036] Specifically, a two-dimensional coordinate system is established with the center of rotational symmetry as the origin, which provides a unified reference for subsequent angle and size calculation. The X and Y axes of the two-dimensional coordinate system are located in the plane perpendicular to the axis of rotational symmetry, 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 aspheric surface, which can associate the radial position of the aspheric surface with the spatial attitude of the sub-aperture, ensure that the subsequent calculation parameters such as the included angle and the diameter are based on the rotational symmetry characteristics of the element, and avoid quantitative errors caused by confusion of the coordinate reference.

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

[0038] Specifically, the curvature change information directly reflects the bending degree of the aspheric surface, the normal vector direction of the scanning sub-aperture is determined by the surface shape at the position where the scanning sub-aperture is located, the greater the surface curvature, the greater the deviation angle of the sub-aperture normal vector and the rotation symmetry axis. The surface tangent direction of the sub-aperture center point can be derived from the curvature change information, and then the normal vector direction perpendicular to the tangent is obtained, and finally the included angle between the normal vector and the rotation symmetry axis is calculated.

[0039] Further, the surface geometric parameters of the target scanning position are extracted from the curvature change information. For any to-be-calculated sub-aperture center point on the aspheric surface, the corresponding axial coordinate is calculated by substituting the radial coordinate of the sub-aperture center point into the surface equation obtained by fitting with multiple sampling points in the early stage, and the corresponding curvature radius is obtained from the curvature change information. The bending degree is determined according to the curvature radius. The smaller the curvature radius, the greater the curvature value, and the more significant the surface inclination. The tangent direction of the sub-aperture center point is calculated by deriving the surface equation. The first order derivative of the surface equation along the radial direction is calculated, the radial coordinate is substituted into the derivative formula of the surface equation, and the tangent slope of the surface is obtained. The tangent direction vector is determined according to 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, and the included angle between the normal vector and the rotation symmetry axis is calculated based on the inverse cosine function.

[0040] (3) calculating a distortion diameter of the scanning sub-aperture according to 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 in plane detection, and when the scanning sub-aperture is fitted on the aspheric surface, the size distortion will be caused due to the inclination of the curved surface. Specifically, when the scanning sub-aperture is projected onto the curved surface along the direction parallel to the normal vector, the projection length along the radial direction of the aspheric surface will be stretched or compressed, while the projection length along the circumferential direction remains basically unchanged. Combined with the trigonometric function relationship, the original diameter is divided by the cosine value of the included angle to obtain the distortion diameter along the radial direction. The distortion diameter along the circumferential direction is consistent with the original diameter.

[0042] (4) calculating a distortion parameter according to the difference between the distortion diameter and the diameter.

[0043] Specifically, the distortion parameter along the radial direction is the difference between the radial distortion diameter and the original diameter, and the distortion parameter along the circumferential direction 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] Further, the scanning sub-aperture is usually circular, i.e. the standard shape in planar detection, and the original diameter is set as D. When the circular sub-aperture is fitted to a region with large curvature, the sub-aperture will be stretched radially and distorted circumferentially due to the inclination of the curved surface, and finally present an elliptical shape. For example, a circular sub-aperture with an original diameter D = 4 mm, at a radial position with a curvature corresponding to an angle θ = 30°, the radial distortion diameter is equal to D / cosθ = 4 mm / 0.866 ≈ 4.62 mm according to the trigonometric function, and there is no circumferential distortion. Therefore, the circumferential distortion diameter is 4 mm. At this time, the radial distortion parameter is equal to 4.62 mm-4 mm = 0.62 mm, and the circumferential distortion parameter is equal to 0. The elliptical size of the distorted sub-aperture (major axis 4.62 mm, minor axis 4 mm) can be uniquely determined by the two distortion parameters, and the actual coverage of the sub-aperture on the curved surface can be accurately quantified.

[0045] The angle between the scanning sub-aperture normal vector and the rotationally symmetric axis is determined based on the curvature variation information, which realizes the accurate conversion of the curvature characteristics of the aspherical surface to the spatial angle parameter, and establishes a correlation bridge between the curvature variation and the spatial attitude of the sub-aperture. The distortion diameter is calculated by combining the angle and the original diameter of the sub-aperture, which can accurately quantify the size deformation of the sub-aperture caused by the inclination of the curved surface, and fit the curvature difference 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, which not only accurately quantifies the distortion degree of the sub-aperture, but also makes the distortion parameter naturally meet the core requirement of being proportional to the curvature value due to the positive correlation between the angle and the curvature value. This provides a quantifiable distortion basis for subsequent division of annular regions according to curvature and optimization of annular scanning paths, and ensures the accuracy and adaptability of the scanning of rotationally symmetric aspherical optical elements from the source.

[0046] S103. Dividing the surface of the aspherical surface into a plurality of annular regions according to the curvature variation information with the rotationally symmetric center as the center point.

[0047] Specifically, the curvature variation information is processed, the curvature value distribution range of the aspherical surface along the radial direction is counted, and the maximum value, the minimum value and the change inflection point of the curvature value are determined. According to the curvature value distribution range, at least two curvature interval thresholds are preset, and the curvature value is divided into a low curvature interval, a medium curvature interval and a high curvature interval. All sampling points are traversed along the radial direction from the rotationally symmetric center, and the continuous radial range with the same curvature interval is marked as a to-be-divided region. The radial continuity of each to-be-divided region is verified, and if there is a discontinuous radial range with the same curvature interval, the to-be-divided regions adjacent to each other and with a curvature interval difference less than a preset threshold are merged, and finally a plurality of annular regions with the rotationally symmetric center as the center are formed. The curvature value in each annular region is in the same curvature interval.

[0048] It should be noted that the preset curvature interval threshold needs to be combined with the adaptation ability of the scanning sub-aperture, for example, the low curvature interval corresponds to a small surface inclination angle and a low sub-aperture distortion degree, and a larger scanning path spacing can be used; the high curvature interval corresponds to a large surface inclination angle and a high sub-aperture distortion degree, and a smaller scanning path spacing needs to be used to ensure the coverage accuracy. The discontinuous same curvature interval is combined in order to avoid the complexity of the scanning operation caused by too many annular regions, and to ensure that the curvature uniformity of each annular region meets the scanning requirements.

[0049] Further, the specific implementation steps of dividing the plurality of annular regions include:

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

[0051] Specifically, taking the rotation symmetry center as the origin, a radial coordinate is set along the direction perpendicular to the rotation symmetry axis of the aspherical surface, and the numerical value of the radial coordinate is used to represent the distance from the coordinate point to the rotation symmetry center; along the range of the radial coordinate from the rotation symmetry center to the maximum radial dimension of the aspherical surface, a plurality of sampling points are selected at a preset interval; based on the curvature change information, the curvature value corresponding to each sampling point is extracted, and the curvature change rate at each sampling point is calculated by the ratio of the difference between the curvature values of adjacent sampling points to the difference between the radial coordinates.

[0052] (2) Based on the curvature change rate threshold, a plurality of curvature change rate intervals are divided, and the curvature change rate of each radial coordinate is traversed along the radial direction from inside to outside, and the continuous radial range with the same curvature change rate interval is divided into the same annular region.

[0053] Specifically, a plurality of curvature change rate thresholds are preset to divide the curvature change rate into a plurality of level intervals; the curvature change rate of each sampling point is sequentially traversed along the radial direction from inside to outside, and the starting radial coordinate at which the curvature change rate first enters a certain interval and the terminal radial coordinate at which the curvature change rate first leaves the interval are recorded; the continuous radial range between the starting radial coordinate and the terminal radial coordinate is divided into an annular region corresponding to the curvature change rate interval; if there is a discontinuous radial range in the same curvature change rate interval, and the radial spacing between adjacent discontinuous ranges is less than a preset threshold, the discontinuous radial ranges are combined into the same annular region.

[0054] The abstract curved surface shape is converted into calculable radial position- curvature change rate data, which provides objective data support for regional division and avoids division deviation caused by ambiguous curvature data; then, by dividing intervals based on the curvature change rate threshold and traversing to determine the continuous radial range as the annular region, the aspherical surface can be classified according to the complexity of the curvature change, so that the curvature change law of the annular region is consistent, which not only adapts to the geometric characteristics of the rotationally symmetric aspherical surface, but also lays a foundation for the subsequent targeted design of scanning strategies for different regions, and finally realizes the scientificity and accuracy of annular region division, and takes into account the accuracy and efficiency of subsequent scanning.

[0055] S104, determining an optimal annular scanning path in each annular region according to the distortion parameters.

[0056] Specifically, the distortion parameters of all sampling points in each annular region are traversed, and the minimum distortion parameter in the region is extracted; the minimum effective size of the scanning sub-aperture in the annular region is determined according to the minimum distortion parameter, the minimum effective size being the maximum usable size of the sub-aperture without excessive distortion in the region; a repetition requirement of the preset scanning path is set, the repetition being the overlap ratio of the coverage range of adjacent scanning paths, the optimal interval of the annular scanning path in the annular region is calculated according to the minimum effective size and the repetition requirement; the annular scanning path is uniformly arranged in the annular region with the rotationally symmetric center as the center and at the optimal interval, so as to ensure that the overlap ratio of adjacent paths meets the repetition requirement and all paths completely cover the annular region; if there is an uncovered region at the edge of the annular region after arrangement, the corresponding supplementary path parameters of the uncovered region are calculated, the repetition of the supplementary path and the adjacent path is adjusted until the annular region is completely covered.

[0057] Further, first, for each divided annular region, the distortion parameters corresponding to all preset sampling points in the region are extracted one by one, and the distortion parameter with the smallest value is selected through data comparison. The sub-aperture size corresponding to the smallest distortion parameter is the maximum usable size of the sub-aperture in the region under the premise of no excessive distortion, that is, the minimum effective size. If a sub-aperture larger than this size is used, it will cause the distortion of some high-curvature sampling points to exceed the allowed range, affecting the accuracy of the data. According to the repetition requirement of the preset scanning path combined with the detection accuracy requirement, the path spacing is calculated by the formula that the optimal spacing is the product of the difference between the minimum effective size and one and the repetition. For example, the minimum effective size is 4 mm, and the repetition is 30%. The optimal spacing is 2.8 mm, which ensures that the overlap ratio of the coverage of adjacent paths meets the preset requirement. Taking the center of rotational symmetry as the center, starting from the radial starting coordinate of the annular region, the annular scanning path is arranged in sequence according to the calculated optimal spacing. Whether the coverage of each arranged path is within the radial start and end coordinates of the annular region is verified, and the path coverage approaches the radial end coordinate of the region. If there is an uncovered area with a width less than the optimal spacing at the edge of the final annular region (for example, the radial end coordinate of the region is 20 mm, and the last arranged path covers 18 mm, leaving 2 mm uncovered), the radius of the supplementary path is first determined (for example, 19 mm, so that the coverage of the supplementary path can completely cover the remaining 2 mm area), and then the actual spacing of the supplementary path and the adjacent previous path (for example, the 18 mm path) is calculated. The actual repetition of the supplementary path is calculated by the actual repetition equaling 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 repetition to ensure that the overlap ratio of the adjacent paths meets the detection accuracy requirement and completely covers the edge uncovered area, finally realizing the non-missing and high-precision path arrangement of the entire annular region.

[0058] Further, the specific implementation steps include:

[0059] (1) For each annular region, traverse the distortion parameters of all scanning sub-apertures in 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 divided annular region, the distortion parameters corresponding to all preset scanning sub-apertures in the region are extracted. All extracted distortion parameters are compared in value, 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 needs to meet the requirement that when all scanning sub-apertures are arranged according to this width, no distortion parameter of any sub-aperture exceeds the allowed threshold.

[0061] Further, the scanning sub-aperture candidate positions in the annular region are determined according to the radial start and end coordinates of the region, and the candidate points are arranged at intervals not greater than the original diameter of the sub-aperture. Then, the distortion parameters of the sub-aperture at each candidate position are calculated based on the curvature change information obtained in the previous step. The original diameter of the sub-aperture corresponding to the minimum distortion parameter is the basic width of the region. This width is selected because if a larger width is used, the distortion parameters of the sub-aperture at some high-curvature positions may exceed the detection requirements. If a smaller width is used, although the distortion can be reduced, the number of scanning paths will increase, which will reduce the detection efficiency. Therefore, this width can strike a balance between excessive distortion and optimal efficiency.

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

[0063] (3) calculating the optimal annular scanning paths with the center of rotational symmetry as the center and in combination with the radial start and end coordinates of the annular region.

[0064] Specifically, the actual width of the current annular region is calculated by multiplying the basic width by one minus 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. Starting from the radial start coordinate, the center radius of each annular scanning path is calculated in sequence according to the actual width, and the center radius of each subsequent path is the center radius of the previous path plus the actual width. The center radius of the last path is verified. If the coverage range of the path does not exceed the end coordinate of the region, the path arrangement is complete. If the coverage range exceeds the region, the center radius of the last path is adjusted to ensure that the coverage range does not exceed the region. The annular trajectories corresponding to the center radii of all the calculated paths are defined as the optimal annular scanning paths of the current annular region, and all the paths must completely cover the radial range of the region.

[0065] Further, the paths are arranged uniformly according to the actual width to ensure that the region is completely covered. For example, the radial start coordinate of the annular region is five millimeters, the radial end coordinate is ten millimeters, the actual width is one point four millimeters, and the total radial length of the region is five millimeters. The center radius of the first path is calculated starting from the radial start coordinate plus half of the actual width, and the center radius of each subsequent path is the center radius of the previous path plus the actual width. The coverage range of each path extends to both sides of its center radius. If the coverage range of the last path exceeds the end coordinate of the region, the center radius of the last path is adjusted to the end coordinate of the region minus half of the actual width to ensure that the coverage range does not exceed the region. Finally, all the arranged paths must ensure that the overlap ratio of adjacent paths meets the preset requirements and completely covers the radial range of the region, forming optimal annular scanning paths with no omissions and high precision.

[0066] By traversing the distortion parameters of all scanning sub-apertures in the annular region and selecting the sub-aperture diameter corresponding to the minimum distortion parameter as the region width, it can be ensured that the width adapts to the curvature characteristics in the region, avoids excessive distortion of the sub-aperture due to improper width, and lays the foundation for scanning accuracy; based on the width and the preset overlap ratio, the actual width is determined, which can ensure that the adjacent scanning paths cover without omission while avoiding excessive repeated coverage that leads to waste of efficiency; then taking the center of rotational symmetry as the center, the optimal annular scanning path is calculated in combination with the radial start and end coordinates of the annular region, which not only fits the geometric characteristics of the rotationally symmetric aspheric surface, but also can realize the uniform arrangement of the scanning path in the region, and finally achieves the balance between scanning accuracy and efficiency of each annular region, ensuring comprehensive and accurate coverage of the surface of the rotationally symmetric aspheric optical element.

[0067] In addition, the method provided by the embodiment further includes:

[0068] (1) determining the remaining width of the annular region according to the difference between the radial start and end coordinates and the optimal annular scanning path;

[0069] (2) setting a new annular scanning path with the remaining width as the radius, and calculating the width difference between the new annular scanning path and the adjacent optimal annular scanning path;

[0070] (3) calculating the actual overlap ratio of the new annular scanning path based on the width difference;

[0071] (4) calculating an increase value according to the difference between the actual overlap ratio and the preset overlap ratio;

[0072] (5) adjusting the overlap ratio of the new annular scanning path and the adjacent optimal annular scanning path based on the increase value, and completing the scanning coverage of the annular region.

[0073] Specifically, the radial start coordinate and the radial end coordinate of the annular region are called, the coverage of all the laid optimal annular scanning paths is combined, the difference between the radial end coordinate and the coverage end point of the last optimal path is calculated to obtain the remaining width of the annular region; the newly added annular scanning path is set according to the radial position corresponding to the remaining width with the center of rotational symmetry as the center, to ensure that the coverage of the path can completely cover the area corresponding to the remaining width; the center distance between the newly added 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 newly added path and the adjacent optimal path, combined with the basic width of the annular region, the actual overlap ratio corresponding to the newly added path is obtained by calculation; the increase value of the overlap ratio is obtained by subtracting the preset overlap ratio from the actual overlap ratio; the position of the newly added path is adjusted according to the increase value, so that the overlap ratio of the newly added path and the adjacent optimal path reaches the actual overlap ratio, to ensure that the remaining area is completely covered, and the scanning coverage of the entire annular region is complete without omission or excessive repetition.

[0074] Further, the coverage end points (the maximum radial position of the coverage range of each path) of all the laid optimal annular scanning paths are sorted, and then compared with the radial end coordinate of the annular region. The difference between the two is the remaining width. For example, if the radial end coordinate of the annular region is ten millimeters and the coverage end point of the last optimal path is nine point two millimeters, then the remaining width is zero point eight millimeters. The coverage range of the path is set to cover the area corresponding to the remaining width with the center of rotational symmetry as the center. Usually, the center radius of the newly added path is set to be half of the basic width minus the radial end coordinate, to ensure that the maximum radial position of the path coverage range does not exceed the annular region and the minimum radial position can overlap with the adjacent optimal path. Then measure the center distance between the newly added path and the adjacent previous optimal path, which is the width difference. For example, if the center radius of the newly added path is nine point six millimeters and the center radius of the adjacent optimal path is eight point eight millimeters, then the width difference is zero point eight millimeters. The overlap width of the two paths is obtained by subtracting the width difference from the basic width, and the actual overlap ratio is obtained by dividing the overlap width by the basic width. The increase value of 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, the newly added path needs to be moved in the direction of the adjacent optimal path according to the increase value, so that the overlap ratio of the two reaches the actual overlap ratio. Through such adjustment, the newly added path can accurately cover the area corresponding to the remaining width, while ensuring a reasonable overlap ratio, avoiding omission of the remaining area and excessive overlap that may lead to a decrease in scanning efficiency, and finally achieving complete coverage of the entire annular region.

[0075] Thus, the uncovered residual range at the edge of the annular region can be accurately processed without readjusting the optimal path interval of the entire annular region, and the region can be completely covered by adding a supplemental path and optimizing the overlap ratio, which balances the scanning accuracy and efficiency. Meanwhile, the increase value calculation and adjustment process of the overlap ratio ensures that the supplemental coverage does not have excessive repetition, so that the scanning coverage of the entire annular region is more scientific and reasonable, further ensuring the comprehensiveness and accuracy of the surface scanning of the rotationally symmetric aspheric optical element.

[0076] S105, from the center point, scanning the optical element according to the optimal annular scanning path from inside to outside, and different optimal annular scanning paths correspond to different scanning depths of field.

[0077] Specifically, the initial position of the scanning device is adjusted so that the scanning sub-aperture is aligned with the rotationally symmetric center; the surface data acquisition of all annular scanning paths in the innermost annular region where the rotationally symmetric center is located is completed according to the optimal annular scanning path; the scanning device is moved radially outward to enter each annular region in turn, and the data acquisition is completed according to the optimal annular scanning path corresponding to each region, until all annular regions are scanned; during the scanning of each annular region, the Z-direction position (along the rotationally symmetric axis direction) of the scanning sub-aperture is adjusted in real time according to the curvature change information of the region, so that the sub-aperture is always in focus; the curvature changes of different annular regions are different, and the adjustment range of the Z-direction position is different, that is, 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 to form a complete aspheric surface three-dimensional data model.

[0078] Scanning from the center point to the outside is because the inner annular region usually has smaller curvature and lower sub-aperture distortion, and the scanning operation is easier to control, which can be used as a reference for subsequent scanning of the outer region to reduce the overall scanning error caused by initial positioning deviation. Different scanning paths correspond to different scanning depths of field, which is essentially due to the different curvatures of different annular regions, resulting in different Z-direction adjustment ranges of the sub-aperture. In the region with large curvature, the fluctuation of the curved surface along the Z-direction is more intense, and the sub-aperture needs a larger Z-direction adjustment range to maintain focus; in the region with small curvature, the Z-direction fluctuation is gentle, and the Z-direction adjustment range of the sub-aperture is small. Real-time adjustment of the Z-direction position and recording of the data are to ensure the imaging clarity and accuracy of each scanning point, and to provide high-quality three-dimensional data support for subsequent surface defect identification and accuracy evaluation.

[0079] Further, the implementation steps of scanning the optical element according to the optimal annular scanning path from inside to outside include:

[0080] (1) traversing each annular region, calculating 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 in order from inside to outside, the radial start and end coordinates of the current annular region and the center radius of the optimal annular scanning path are called, and based on the center radius of each scanning path, the three-dimensional spatial coordinates of all scanning sub-apertures on the path are calculated in combination with the curvature change information of the annular region.

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

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

[0084] Further, the implementation steps of calculating the best focusing position of the scanning sub-aperture based on the spatial coordinates include:

[0085] Further, the specific implementation steps of calculating the best focusing position of the current sub-aperture based on the spatial coordinates include:

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

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

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

[0089] Specifically, the Z coordinate of the center point of the sub-aperture on the curved surface model is obtained, the normal direction of the point is derived through the gradient calculation of the curved surface model, and for a parameterized curved surface model, the gradient vector is the normal direction of the curved surface at the point, pointing to the outside of the surface of the element to be scanned and consistent with the imaging direction of the detection system. The normal direction depth refers to the distance from the center point of the sub-aperture on the curved surface model along the normal direction to the imaging lens focal plane of the detection system, the reference working distance of the sensor, i.e. the distance from the lens focal plane to the reference position of the sensor, is determined, and the actual distance from the center point of the sub-aperture along the normal direction to the reference position of the sensor is calculated, and then the normal direction depth is calculated according to the difference between the distance from the lens focal plane to the reference position of the sensor and the actual distance.

[0090] 2.3 The normal direction depth is taken as the best focus position of the current sub-aperture.

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

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

[0093] Further, the calculated Z-axis best focus position is converted into Z-axis motion instructions of the three-dimensional displacement table based on the spatial coordinate system. For example, if the XY plane coordinates of the center point of the current sub-aperture are (X0, Y0), the Z-axis best focus position is Z0, and the current Z-axis position of the displacement table is Z_current, the displacement table needs to move along the Z-axis by a distance of ΔZ = Z0-Z_current. Since the spatial coordinates of the sub-aperture include the XY plane position and the Z-axis focus position, the displacement table needs to first drive the sample table to move along the X-axis and the Y-axis to move the center point of the current sub-aperture to the center of the field of view of the detection system; then move along the Z-axis to make the center point of the sub-aperture reach the best focus position along the normal direction of the curved surface. After the movement is completed, the distance feedback signal of the center point of the sub-aperture is collected in real time by the spectral confocal sensor. If the deviation between the actual distance of the feedback and the Z-axis best focus position meets the requirements, the focusing is qualified. If the deviation exceeds the range, the Z-axis movement distance needs to be recalculated and the Z-axis position needs to be fine-tuned until the focusing accuracy requirements are met.

[0094] Further, after focusing, the illumination light source is turned on and the parameters are adjusted to ensure that the light source uniformly covers the current sub-aperture region, ensuring stable illumination intensity and avoiding gray deviation in the sub-aperture image due to uneven illumination, which affects the subsequent defect recognition accuracy; the imaging device is controlled to capture the current sub-aperture region to obtain a high-resolution gray-scale image of the sub-aperture; at the same time, the three-dimensional spatial coordinates of the current sub-aperture and the shooting time, illumination parameters and other metadata are associated and stored, providing a coordinate reference for subsequent full-aperture image stitching and defect positioning; the captured sub-aperture image is transmitted to the software analysis unit for preprocessing operation to ensure that the image quality meets the defect recognition requirements. Then, based on the defect recognition algorithm, the preprocessed image is analyzed to determine whether the preprocessed image has defects, and the defect recognition results of the current sub-aperture image are associated and stored in the database with the three-dimensional coordinates, completing the scanning of a single sub-aperture.

[0095] (3) Focus scanning of the scanning sub-aperture according to the best focus position.

[0096] Specifically, the displacement mechanism of the scanning device is controlled to move the scanning sub-aperture to the best focus position, and the illumination light source and the imaging unit are started to complete the focus scanning and surface data acquisition of the sub-aperture; the above steps are repeated until all scanning sub-apertures in the current annular region complete focus scanning, and then the same operation is performed in the next annular region.

[0097] By calculating the spatial coordinates of the sub-aperture based on the annular region position information, the scanning position is accurately adapted to the geometric characteristics of the aspherical surface; the best focus position is determined based on the spatial coordinates and the curved surface model, ensuring that each sub-aperture can obtain clear imaging in regions with different curvatures, avoiding detection errors caused by inaccurate focusing; focus scanning is performed according to the best focus position, ensuring the accuracy and reliability of the collected data. The entire procedure closely integrates position positioning, focus calculation and scanning execution, which not only adapts to the characteristics of the rotationally symmetric aspherical surface along the radial curvature, but also improves the detection data quality through accurate focusing, laying a solid foundation for subsequent three-dimensional image stitching and defect recognition.

[0098] Further, after scanning the optical element according to the optimal annular scanning path from the inside to the outside, the method provided in this embodiment includes:

[0099] (1) Extracting feature points based on the overlapping area of adjacent scanning images and calculating the spatial coordinate deviation of the feature points;

[0100] Specifically, all collected scanning images are traversed, and adjacent scanning image pairs are screened according to the scanning order of the annular sub-regions; for each adjacent scanning image pair, the overlapping region of the two images, i.e., the surface range covered by both sub-apertures, is identified, a plurality of stable feature points are extracted from the overlapping region, and the actual coordinates of each feature point in the three-dimensional space are calculated based on the pixel coordinates of the feature point in the two images and the spatial coordinate data of the corresponding sub-aperture, and then the spatial coordinate deviation of the same feature point in the two images is obtained.

[0101] Further, adjacent image pairs are matched according to the scanning order to ensure that the splicing order is consistent with the actual scanning path and to avoid logical confusion. When identifying the overlapping region, the search range is determined according to the overlap ratio of the scanning path to reduce invalid calculations. When extracting the feature points, details with strong stability and less susceptible to light, such as the endpoints of surface micro scratches and texture spots left by processing, are selected. The pixel position of the feature point is converted into a three-dimensional coordinate through the mapping relationship between the image pixel coordinates and the sub-aperture spatial coordinates. The spatial coordinate deviation is calculated according to the difference between the feature points, and the spatial coordinate deviation reflects the degree and direction of the misalignment of the two images.

[0102] (2) Geometrically correcting the adjacent scanning images according to the spatial coordinate deviation;

[0103] Specifically, the spatial coordinate deviations of all feature points are statistically analyzed, and a geometric correction matrix is obtained by least squares fitting. The pixel coordinates of the scanning image with larger deviation are adjusted using the geometric correction matrix to make the spatial coordinates of the feature points in the overlapping region of the two images consistent, and the geometric correction is completed.

[0104] (3) Splicing all the corrected scanning images according to the scanning order of the annular sub-regions to form a three-dimensional image of the surface of the optical element.

[0105] Specifically, all the corrected scanning images are spliced in sequence according to the scanning order of the annular sub-regions, aligned and fused through the overlapping region, and the gaps between the images are filled to finally form a complete three-dimensional image covering the surface of the optical element.

[0106] By extracting the feature points in the overlapping region of adjacent images and calculating the spatial coordinate deviation, the image misalignment caused by device displacement and positioning error during the scanning process is accurately located. Based on the deviation data, the geometric correction is performed to effectively eliminate the positional deviation of adjacent images and ensure the accurate alignment of the overlapping region. All the corrected images are spliced according to the scanning order to realize the complete three-dimensional reconstruction of the surface of the optical element. The whole set of steps not only solves the problem of limited coverage of a single sub-aperture image, but also guarantees the spatial consistency and accuracy of the spliced image through deviation correction. The final three-dimensional image can completely and truly restore the aspherical surface morphology and provide complete and reliable data support for subsequent surface defect identification and precision detection.

[0107] The annular stepped three-dimensional scanning method of the rotationally symmetric aspherical optical element provided in the embodiment calculates the curvature variation information and the proportional distortion parameter based on the rotationally symmetric center, accurately adapts the aspherical geometric characteristics, and avoids detection errors caused by the distortion of the sub-aperture; the annular areas are divided according to the curvature variation information, the optimal annular scanning path of each area is determined in combination with the distortion parameter, a supplementary path is added for the remaining edge area and the overlap ratio is adjusted, and no omission is covered; the scanning is pushed from inside to outside, the best focusing position is calculated based on the spatial coordinates of the sub-aperture and the Z-direction posture is dynamically adjusted, the different paths adapt to the differentiated depth of field, the sub-apertures with approximately consistent height are divided into the same sub-area, and the stepped Z-direction moving strategy is used, so that the mechanical moving stroke is effectively reduced. Compared with the conventional snake scanning scheme, the detection efficiency is greatly improved in the three-dimensional scanning detection; meanwhile, the three-dimensional reconstruction is completed through image feature point extraction, geometric correction and sequential splicing, and finally the scanning precision is ensured and the aspherical surface is fully covered on the premise of reducing invalid movement and excessive repetition, the detection efficiency is taken into account, and reliable technical support is provided for the quality detection of high-precision optical elements in the field of laser weapons.

[0108] Corresponding to the foregoing embodiment of the annular stepped three-dimensional scanning method of the rotationally symmetric aspherical optical element, the present application also provides an embodiment of an annular stepped three-dimensional scanning device of a rotationally symmetric aspherical optical element.

[0109] Figure 2 The structure diagram of the embodiment two of the annular stepped three-dimensional scanning device of the rotationally symmetric aspherical optical element provided in the present application is shown in FIG. 2. Please refer to Figure 2 The device provided in the embodiment includes a calculation module 210, a division module 220 and a scanning module 230; wherein,

[0110] The calculation module 210 is configured to determine the rotationally symmetric center of the optical element, and calculate the curvature variation information of the surface of the aspherical surface according to the rotationally symmetric center;

[0111] The calculation module 210 is further configured to determine the distortion parameter of the scanning sub-aperture according to the scanning sub-aperture size and the curvature variation information, and the distortion parameter is proportional to the curvature value;

[0112] The division module 220 is configured to divide the surface of the aspherical surface into a plurality of annular areas according to the curvature variation information with the rotationally symmetric center as the center point;

[0113] The scanning module 230 is configured to determine the optimal annular scanning path in each annular area according to the distortion parameter;

[0114] The scanning module 230 is further configured to scan the optical element according to the optimal annular scanning path from the center point to the outside, and different optimal annular scanning paths correspond to different scanning depths of field.

[0115] The device of the embodiment can be used to execute Figure 1 The steps of the method embodiment are similar to the implementation principle and process, and thus will not be described here.

[0116] The implementation process of the functions and roles of each unit in the device is specifically described in the implementation process of the corresponding steps in the above method, and thus will not be described here.

[0117] For the device embodiment, since it basically corresponds to the method embodiment, the related parts can be referred to the part of the method embodiment. The device embodiment described above is only schematic, and the units described as separate components can or can not be physically separate, and the components displayed as units can or can not be physical units, that is, they can be located in one place, or distributed on multiple network units. According to the actual needs, some or all of the modules can be selected to achieve the purpose of the scheme of the present application. Those skilled in the art can understand and implement it without creative labor.

[0118] The above is only the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for annular step-and-scan three-dimensional scanning of a rotationally symmetric aspheric optical element, characterized in that The method comprises: determining the center of rotational symmetry of the optical element, calculating the curvature variation information of the surface of the aspheric surface according to the center of rotational symmetry; determining the distortion parameter of the scanning sub-aperture according to the scanning sub-aperture size and the curvature variation information, the distortion parameter being in direct proportion to the curvature value; dividing the surface of the aspheric surface into a plurality of annular regions according to the center of rotational symmetry as the center point and the curvature variation information; determining the optimal annular scanning path in each annular region according to the distortion parameter; scanning the optical element according to the optimal annular scanning path from inside to outside from the center point, and the scanning depth corresponding to different optimal annular scanning paths being different.

2. The method of claim 1, wherein, The method comprises: establishing a two-dimensional coordinate system with the center of rotational symmetry as the origin; determining the included angle between the normal vector of the scanning sub-aperture and the axis of rotational symmetry based on the curvature variation information; calculating the distortion diameter of the scanning sub-aperture according to the included angle and the diameter of the scanning sub-aperture; calculating the distortion parameter according to the difference between the distortion diameter and the diameter.

3. The method of claim 1, wherein, The method comprises: setting a radial coordinate along the radial direction of the aspheric surface with the center of rotational symmetry as the origin, and obtaining the curvature variation rate of different radial coordinates on the aspheric surface; dividing a plurality of curvature variation rate intervals based on the curvature variation rate threshold, traversing the curvature variation rate of each radial coordinate from inside to outside along the radial direction, and dividing the continuous radial range with the same curvature variation rate interval into the same annular region.

4. The method of claim 1, wherein, The method comprises: traversing the distortion parameter of all scanning sub-apertures in each annular region, taking the diameter of the scanning sub-aperture with the smallest distortion parameter as the width of the annular region, determining the optimal annular scanning path of each annular region based on the width and a preset overlap ratio; calculating the actual width of the annular region based on the width and the preset overlap ratio; calculating the optimal annular scanning path with the center of rotational symmetry as the center and in combination with the radial start and end coordinates of the annular region.

5. The method of claim 4, wherein, The method further comprises: determining the remaining width of the annular region according to the difference between the radial start and end coordinates and the optimal annular scanning path; setting a new annular scanning path with the remaining width as the radius, calculating the width difference between the new annular scanning path and the adjacent optimal annular scanning path; calculating the actual overlap ratio of the new annular scanning path based on the width difference; calculating an increase value according to the difference between the actual overlap ratio and the preset overlap ratio; adjusting the overlap ratio of the new annular scanning path and the adjacent optimal annular scanning path based on the increase value to complete the scanning coverage of the annular region.

6. The method of claim 1, wherein, The method comprises: traversing each annular region, calculating the spatial coordinates of the scanning sub-aperture based on the position information of the current annular region; calculating the best focusing position of the scanning sub-aperture based on the spatial coordinates. Focus scan the scanning sub-aperture according to the best focus position.

7. The method of claim 6, wherein, The best focus position of the scanning sub-aperture is calculated based on the spatial coordinates; comprising: A curved surface model of the optical element is established under a spatial coordinate system of the spatial coordinates; A normal direction depth of a current sub-aperture center point on the curved surface model is determined based on the spatial coordinates; The normal direction depth is taken as the best focus position of the current sub-aperture.

8. The method of claim 1, wherein, The method is realized based on a detection device, which comprises an illumination light source, a data acquisition unit, a control unit, a sample table, a three-axis displacement table, and a spectral confocal sensor. The illumination light source is used to emit a light source 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 three-axis displacement table, the sample table is used to place the optical element, the sample table is installed on the three-axis displacement table, the three-axis displacement table is used to drive the movement of the sample table, and the spectral confocal sensor is used to measure the relative position between the surface of the optical element and the sensor.

9. The method of claim 1, wherein, After scanning the optical element according to the optimal annular scanning path from inside to outside; comprising: Feature points are extracted based on the overlapping area of adjacent scanning images, and the spatial coordinate deviation of the feature points is calculated; Adjacent scanning images are geometrically corrected according to the spatial coordinate deviation; All corrected scanning images are spliced in the scanning order of annular sub-regions to form a three-dimensional image of the surface of the optical element.

10. A rotationally symmetric aspheric optical element annular stepped three-dimensional scanning device, characterized by, The device comprises a calculation module, a division module, and a scanning module; wherein, The calculation module is used to determine the rotationally symmetric center of the optical element, and calculate the curvature variation information of the surface of the aspheric surface according to the rotationally symmetric center; The calculation module is also used to determine the distortion parameter of the scanning sub-aperture according to the scanning sub-aperture size and the curvature variation information, and the distortion parameter is in direct proportion to the curvature value; The division module is used to divide the surface of the aspheric surface into a plurality of annular regions according to the curvature variation information with the rotationally symmetric center as the center point; The scanning module is used to determine the optimal annular scanning path in each annular region according to the distortion parameter; The scanning module is also used to scan the optical element from inside to outside according to the optimal annular scanning path from the center point, and the scanning depth corresponding to different optimal annular scanning paths is different.

Images