CN117146736B - A method for measuring double-surface shape of optical element - Google Patents

Abstract

The invention relates to the field of optical element surface shape measurement, in particular to a method for measuring the surface shape of a double surface of an optical element, which comprises the following steps: establishing a basic measuring device of the surface shape of the double surfaces of the optical element; calibrating the basic measuring device to obtain a measuring device of the surface shape of the double surfaces of the optical element; obtaining reflection stripe data of an optical element to be measured by using the measuring device; and obtaining a measurement result of the surface shape of the two surfaces of the optical element according to the reflection stripe data of the optical element to be measured, and completing calculation by shooting a single image by a camera. Finally, the method is very sensitive to the surface shape of the double surfaces of the large-size optical element because the method is calculated based on the reflection law, and can reach the measurement accuracy of micron and even submicron.

Description

A method for measuring double-surface shape of optical element

Technical Field

The invention relates to the field of optical element surface shape measurement, and in particular to a method for measuring the double-surface surface shape of an optical element.

Background Art

Optical components are widely used in various fields of military, aerospace, optics and automobiles, such as lenses, Google Glass, car windshields, etc. The reflection and refraction effects of optical components are usually used to adjust the light path to achieve the controllability of the direction of the light. Generally speaking, these optical devices need to ensure a certain surface accuracy to avoid quality problems during use. For example, if there is a large surface deviation in the head-up display (HUD) used by pilot helmets and Google Glasses, it is easy to cause distortion and blurring of the displayed image and text. If the surface quality of the car glass with HUD is poor, the image of the external scene is easily distorted, the transmittance decreases, and driving safety is affected. Therefore, in order to ensure the optical performance and imaging quality of optical components, high-precision three-dimensional measurement of both the upper and lower surfaces is required.

Generally speaking, manufacturing accuracy alone cannot meet the accuracy requirements of the optical component surface, so measurements are required after manufacturing to prevent defective products from being put into use. However, optical components are transparent parts, and there are many difficulties in measuring transparent parts. First, for transparent parts, traditional reflective optical measurement methods often cannot obtain reflected light information of sufficient intensity, such as line structured light[1], grating structured light[2], etc., and cannot be used for transparent surface measurement; secondly, the surface of transparent parts also has certain reflective characteristics, which can easily cause strong light interference to the transmission optical measurement method, resulting in overexposure. At the same time, in order to improve detection efficiency, fast measurement is often required, so contact measurement methods, such as three-coordinate measuring machines, profilometers and other measurement methods, cannot meet the speed requirements. In addition to the difficulty of measuring optical components, there is also a need for high measurement accuracy, which further brings challenges to their profile measurement.

Chinese patent application CN201980049399.3 discloses a glass surface measurement method based on line structured light, which uses ultraviolet structured light scanning to achieve glass surface measurement. However, first of all, this method can only measure the upper surface of optical components. Secondly, since this method is based on line structured light scanning, the measurement accuracy is restricted by the displacement stage, and the introduction of a large-stroke displacement stage will inevitably increase the cost. At the same time, line structured light scanning takes a certain amount of time and is difficult to meet the needs of high-speed measurement. Finally, line structured light is a method based on the principle of optical triangulation, and it is difficult to achieve high optical-level measurement accuracy.

Chinese patent application CN202010795714.1 discloses a method for measuring the three-dimensional shape of a reflective surface based on fringe deflection. Specifically, a fringe display module displays sinusoidal fringes, and a camera is used to capture the deformed fringes generated by the fringes after reflection on the mirror surface to be measured. The relationship between the fringe phase and the height is used to perform fast and high-precision three-dimensional measurement of the mirror object. However, this method can only be used to measure the upper and lower surfaces of the reflective surface. For transparent optical elements, the reflected images of the upper and lower surfaces will be mixed together, resulting in measurement failure.

In view of the above existing known technologies, there is an urgent need for a fast and high-precision measurement method that can be applied to the upper and lower surfaces of optical components.

Summary of the invention

In view of the deficiencies in the prior art, the present invention provides a method for measuring the double-surface shape of an optical element, which accurately obtains the shape measurement result of the optical element through a calibrated image acquisition device.

To achieve the above object, the present invention provides a method for measuring the double-surface shape of an optical element, comprising:

Establish a basic measurement device for the double-surface shape of optical elements;

Calibrate the basic measuring device to obtain a measuring device for the double-surface shape of an optical element;

Acquiring the reflection fringe data of the optical element to be measured by using the measuring device;

The double-surface shape measurement result of the optical element is obtained according to the reflection fringe data of the optical element to be measured.

Preferably, the basic measuring device for establishing the double-surface profile of an optical element comprises:

Cameras are arranged opposite to each other on both sides of the optical element to be measured;

The discrete fringe image display devices are connected to the cameras respectively.

Preferably, the measuring device for calibrating the basic measuring device to obtain the double-surface shape of the optical element comprises:

A reflective marking point is set on a standard plane mirror as a reflective marking plane mirror;

The basic measuring device is used to collect multi-angle reflection stripe images of the reflective marking plane mirror;

Utilizing the multi-angle reflection fringe image to calculate the coordinates of the reflective marking point based on the binocular vision principle;

Obtaining the corresponding surface equation using the coordinates of the reflective marking points;

The basic measuring device is calibrated according to the surface shape equation to obtain a measuring device for the double-surface surface shape of an optical element.

Furthermore, the coordinates of the reflective marking points are calculated using the multi-angle reflected fringe image based on the binocular vision principle as follows:

Among them, _Ai , _Bi , _Ci , _Di are the coordinates of the reflective marking points set on the standard plane mirror, _ni is the normal vector of the i-th group of standard plane mirrors, _di is the distance between the i-th group of standard plane mirrors and the coordinate origin, and h is the thickness of the reflective marking point.

Preferably, obtaining the double-surface shape measurement result of the optical element according to the reflection fringe data of the optical element to be measured includes:

Using the reflection fringe data of the optical element to be measured to perform separation processing to obtain reflection fringe separation data;

Acquire the topological relationship of the reflection fringe separation data;

Performing phase resolution processing according to the topological relationship to obtain a resolution result of the reflection fringe data;

The calculation result of the reflection fringe data is used to obtain the double-surface shape measurement result of the optical element.

Furthermore, obtaining the topological relationship of the reflection fringe separation data includes:

Using the camera corresponding feature points of the basic measurement device as reference points;

Based on the reference point, searching in a single contour direction respectively obtains a topological relationship between an upper surface of the reflection fringe image and discrete reflection fringe and a topological relationship between a lower surface of the reflection fringe image and discrete reflection fringe;

The topological relationship between the upper surface of the reflection fringe image and the discrete reflection fringe and the topological relationship between the lower surface of the reflection fringe image and the discrete reflection fringe are used as the topological relationship of the reflection fringe separation data.

Furthermore, obtaining the double-surface shape measurement result of the optical element using the solution result of the reflection fringe data includes:

Obtaining the normal direction vectors of the upper surface and the lower surface of the reflection fringe image based on the reflection law according to the solution result of the reflection fringe data;

The surface shape measurement results of the double surfaces of the optical element are obtained by performing surface shape reconstruction processing based on numerical integration using the normal direction vectors of the upper surface and the lower surface.

Furthermore, the calculation formula for obtaining the double-surface surface measurement result of the optical element by performing surface reconstruction processing based on numerical integration using the normal direction vectors of the upper surface and the lower surface is as follows:

Wherein, ( _Px , _Py , _Pz ) are the normal direction vectors of the upper surface and the lower surface, and z is the double-surface shape measurement result of the optical element.

Compared with the closest prior art, the present invention has the following beneficial effects:

This method is based on discrete fringe patterns as features, so the points after reflection on the upper and lower surfaces can be distinguished based on image processing, which is an effective method for measuring the upper and lower surfaces of optical components. Secondly, this method can complete the calculation by taking a single image with a camera, which has a significant detection speed advantage over all existing methods. Finally, since this method is based on the law of reflection for calculation, it is very sensitive to the double-surface shape of large-size optical components and can achieve micron or even sub-micron measurement accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a method for measuring the double-surface shape of an optical element provided by the present invention;

FIG2 is a schematic diagram of a basic measuring device of a method for measuring the double-surface shape of an optical element provided by the present invention;

3 is a schematic diagram of the imaging principle of a discrete fringe image of a method for measuring the double-surface shape of an optical element provided by the present invention;

FIG4 is a schematic diagram of the mutual interference between the upper and lower surfaces when measuring an uncoated HUD in a method for measuring the double-surface shape of an optical element provided by the present invention;

FIG5 is a fringe diagram of upper and lower surfaces separated based on image processing in a method for measuring the double-surface shape of an optical element provided by the present invention;

6 is a schematic diagram showing the principle of determining rows and columns of discrete stripes based on path search in a method for measuring the double-surface shape of an optical element provided by the present invention;

7 is a schematic diagram of a method for measuring the double-surface shape of an optical element provided by the present invention, which is based on the surface normal vector to restore the surface shape;

Reference numerals:

1. HUD reflector to be tested; 2. Discrete stripe image display device; 3. Binocular camera group; 4. Single discrete stripe on the stripe display device; 5. Single discrete stripe image reflected from the upper surface; 6. Upper surface of HUD reflector to be tested; 7. Lower surface of HUD reflector to be tested; 8. Single discrete stripe image reflected from the lower surface; 9. Discrete stripe image reflected from the upper surface captured by the camera; 10. Discrete stripe image reflected from the lower surface captured by the camera; 11. Incident light emitted by discrete stripes; 12. Calculated reflection point; 13. Outgoing light after surface reflection; 14. Optical center of camera; 15. Coordinates of discrete stripes in camera pixels; 16. Surface normal vector; 17. Calculated surface profile to be tested.

DETAILED DESCRIPTION

The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Embodiment 1:

The present invention provides a method for measuring the double-surface shape of an optical element, as shown in FIG1 , comprising:

S1. Establish a basic measurement device for the double-surface shape of optical elements;

S2, calibrating the basic measuring device to obtain a measuring device for the double-surface shape of an optical element;

S3, using the measuring device to obtain reflection fringe data of the optical element to be measured;

S4. Obtaining a double-surface shape measurement result of the optical element according to the reflection fringe data of the optical element to be measured.

S1 specifically includes:

S1-1, cameras are arranged opposite to each other on both sides of the optical element to be measured;

S1-2, using discrete fringe image display devices to connect with cameras respectively.

S2 specifically includes:

S2-1, setting a reflective marking point on a standard plane mirror as a reflective marking plane mirror;

S2-2, using the basic measurement device to collect multi-angle reflection fringe images of the reflective marking plane mirror;

S2-3, using the multi-angle reflection fringe image to calculate the coordinates of the reflective marking point based on the binocular vision principle;

S2-4, using the coordinates of the reflective marking points to obtain the corresponding surface equation;

S2-5. According to the surface shape equation, the basic measuring device is calibrated to obtain a measuring device for the double-surface surface shape of the optical element.

The calculation formula of S2-3 is as follows:

Among them, _Ai , _Bi , _Ci , _Di are the coordinates of the reflective marking points set on the standard plane mirror, _ni is the normal vector of the i-th group of standard plane mirrors, _di is the distance between the i-th group of standard plane mirrors and the coordinate origin, and h is the thickness of the reflective marking point.

S4 specifically includes:

S4-1, performing separation processing on the reflection fringe data of the optical element to be measured to obtain reflection fringe separation data;

S4-2, obtaining the topological relationship of the reflection fringe separation data;

S4-3, performing phase solution processing according to the topological relationship to obtain a solution result of the reflection fringe data;

S4-4. Obtain the double-surface shape measurement results of the optical element using the solution results of the reflection fringe data.

S4-2 specifically includes:

S4-2-1, using the camera corresponding feature points of the basic measurement device as reference points;

S4-2-2, searching in a single contour direction based on the reference point to obtain a topological relationship between the upper surface of the reflection fringe image and the discrete reflection fringe and a topological relationship between the lower surface of the reflection fringe image and the discrete reflection fringe;

S4-2-3. Using the topological relationship between the upper surface of the reflection fringe image and the discrete reflection fringe and the topological relationship between the lower surface of the reflection fringe image and the discrete reflection fringe as the topological relationship of the reflection fringe separation data.

S4-4 specifically includes:

S4-4-1. Obtaining the normal direction vectors of the upper surface and the lower surface of the reflection fringe image according to the solution result of the reflection fringe data based on the law of reflection;

S4-4-2. Utilize the normal direction vectors of the upper surface and the lower surface to perform surface reconstruction based on numerical integration to obtain the double-surface surface measurement results of the optical element.

The calculation formula of S4-4-2 is as follows:

Wherein, ( _Px , _Py , _Pz ) are the normal direction vectors of the upper surface and the lower surface, and z is the double-surface shape measurement result of the optical element.

In this embodiment, a method for measuring the double-surface shape of an optical element is provided, as shown in FIG2 , and the setting and specific calibration process of the basic measuring device are as follows:

It consists of three parts: a discrete fringe projection device 2, a HUD reflector to be tested 1, and a binocular camera group 3. Discrete stripes can be generated in the form of a screen display pattern, or in the form of a backlight source irradiating a glass projection printed with a discrete fringe feature map. The binocular camera group is used to capture the effect of the reflected stripes of the test piece from two angles, and calculate the specific coordinates of the surface points of the test piece that reflect the discrete stripes. As shown in Figure 3, this process strictly abides by the law of geometric optics reflection. The shooting principle of the system is shown in Figure 4. The upper and lower surfaces of the HUD reflector have certain reflective properties. The light reflected by the upper surface 6 of the HUD reflector to be tested undergoes only one mirror reflection, while the light reflected by the lower surface 7 of the HUD reflector to be tested undergoes two refractions and one mirror reflection. The discrete fringe patterns reflected by the upper and lower surfaces are formed into a single discrete fringe mirror image 5 reflected by the upper surface and a single discrete fringe mirror image 8 reflected by the lower surface in the equivalent plane mirror, and the camera captures these images. To meet the requirements of high-precision measurement, the system parameters are set according to the following steps:

(1) First, design the light source and camera layout according to the surface characteristics and accuracy requirements of the surface to be measured. Generally, the sampling point density of the surface to be measured is required to be greater than 1/mm, and the field of view of a single camera is required to be less than 200mm to ensure measurement accuracy. In addition, within the field of view of each camera, the surface of the HUD reflector is basically covered by the discrete fringe pattern, and then the camera is controlled to tilt 45° to shoot.

(2) Based on the camera imaging formula and the ideal surface shape equation of the surface to be measured, the intersection point of the incident light and the surface to be measured and the outgoing light are calculated in theory. The position and density of the discrete fringes are adjusted so that there is no overlapping of fringes in the reflected fringe pattern collected by the camera and the interval is appropriate. Based on this density, the layout and generation of the discrete fringe pattern are performed.

(3) The Zhang calibration method is used to calibrate two cameras to form a binocular stereo vision system. A discrete fringe pattern is displayed using a fringe display device, and several reflective markers are randomly pasted on a standard plane mirror. The plane mirror is moved to fifteen to twenty different positions and postures to ensure that in each posture, the corresponding fringe image and markers reflected by the plane mirror can be captured by both cameras. Based on the principle of binocular vision, the coordinates of the feature points pasted on the plane mirror can be calculated, and then the changed coordinates are used as constraints to optimize the posture relationship between the plane mirror and the camera, and the posture relationship between the fringe display device and the binocular vision system.

In this embodiment, a method for measuring the double-surface shape of an optical element is provided, and the specific process of phase resolution is as follows:

(1) In the specific measurement process, a discrete fringe pattern after layout is first displayed on a fringe display device, and then the fringe pattern reflected on the HUD reflector to be tested is photographed by a binocular vision system.

(2) The fringe images captured by the two cameras are separated. According to the two principles that the fringe reflected by the lower surface is always on the same side as the fringe reflected by the upper surface and that the brightness of the fringe reflected by the lower surface is lower than that of the fringe reflected by the upper surface, the reflected fringe on the two surfaces is identified and separated on the image. As shown in Figure 5, the fringe image captured by each camera is separated into two reflected fringe images of the upper and lower surfaces.

(3) Based on the separated discrete fringe pattern, as shown in FIG6 , starting from the reference fringe, searching along a specific path, the discrete fringe is identified in which column and row it is located, which serves as a basis for subsequent phase unwrapping.

(4) Encode the columns and rows of discrete stripes, unwrap the phase in each discrete stripe, calculate the stripe order according to the rows and columns of different discrete stripes, unwrap them, and obtain the real phase.

(5) Determine the correspondence between the sampling points on the surface of the test piece and the pattern captured by the camera based on the real phase. Based on the position between the fringe display device and the binocular vision device, as shown in Figure 7, the normal vector at each sampling point is calculated by using the reflection law and ray tracing, and the gradient is calculated and integrated from the normal vector. The upper and lower surfaces are both executed from (3) to (5), and finally the heights at each sampling point on the upper and lower surfaces of the test piece are obtained, and the three-dimensional contour of the test piece is obtained by interpolation.

In this embodiment, a method for measuring the double-surface shape of an optical element is specifically implemented and applied as follows:

(1) Build a measuring device, install a discrete fringe pattern display device and two cameras on the same side of the optical element to be measured, so that both cameras can capture the fringe pattern through reflection from the upper surface of the transparent member. The device for providing the discrete fringe pattern can be a screen, or a backlight source and glass printed with a discrete fringe feature pattern, which is determined according to the size of the surface to be measured.

(2) Calibrate the measurement device. Use Zhang’s calibration method to calibrate the binocular stereo vision device, and use the pinhole camera imaging model to calculate the corresponding parameters. The model is expressed in matrix form as follows:

in,

Where [u,v] is the pixel coordinate, _xc , _yc , _zc are the coordinates of the point to be photographed in the camera coordinate system. _ax , _ay are the normalized distances between the equivalent optical center of the lens in the x and y directions and the CCD target surface, _u0 , _v0 are the pixel coordinates of the CCD principal point, and s is the tilt correction of the camera lens.

In the specific imaging process, the screen first forms a virtual image in the plane mirror, and the camera is equivalent to directly photographing this virtual image. The plane mirror imaging model calculated according to the camera imaging matrix is:

Where _Ps ' is the coordinate of the feature point on the screen virtual image, _Pc is the camera pixel coordinate, R and T are the transformation matrices from the screen virtual image coordinate system to the camera coordinate system, which can be calculated by homography matrix decomposition. Since it is mirrored by the screen mirror, the determinant of R is -1.

A discrete fringe pattern is displayed using a fringe display device. Several reflective marking points are randomly pasted on a standard plane mirror. The plane mirror is moved at multiple angles, and the corresponding fringe image reflected by the plane mirror is photographed by a camera. Based on the principle of binocular vision, the coordinates of the feature points pasted on the plane mirror can be calculated, and then the surface shape equation at the corresponding plane mirror position can be calculated.

Where A _i , B _i , C _i , D _i are the coordinates of the feature points pasted on the surface, _ni is the normal vector of the i-th group of plane mirrors, di _is the distance between the i-th group of plane mirrors and the origin of the coordinates, and h is the thickness of the pasted reflective marking point. Combining the camera imaging model with the plane mirror imaging model, the mapping equation between the left and right camera pixels and the screen pixels can be obtained.

(3) Separate the upper and lower surface reflection stripe information. The brightness of the upper surface reflection feature is often greater than that of the lower surface reflection feature and is located on the same side of the upper surface reflection feature. The upper and lower surface reflection features are separated based on grayscale information and position information.

(4) Calculate the topological relationship between the upper and lower surface reflection stripes respectively, and use the stripe display device to display a stripe diagram with feature points. As shown in FIG5, taking the feature point captured by the two cameras as the reference, search from this point in the discrete stripe diagram along the direction of the single contour to obtain the second feature point, and then update the search direction based on the connection line between the two feature points, and obtain the third feature point based on the new search direction, and so on, so as to search and obtain a column of points, which is equivalent to obtaining a single contour data. Next, use this column of points as the reference to perform a horizontal search to obtain the topological relationship between several feature points on adjacent contours. Repeat the above steps multiple times until all points are searched, and determine the topological relationship between the discrete reflection stripes in the upper table and the topological relationship between the discrete reflection stripes on the lower surface.

(5) Phase solution: Based on the topological relationship calculated in (4), the approximate position and order of each phase peak are determined to help the phase unwrapping process unfold and obtain the correspondence between the camera pixels and the screen pixels after reflection from the upper and lower surfaces of the optical element.

(6) Calculate the gradient of the upper and lower surfaces of the reflector, and combine the corresponding relationship obtained in (5) to calculate the normal direction vectors of the upper and lower surfaces respectively according to the law of reflection, which are recorded as (P _x ,P _y ,P _z ). After obtaining the surface normal vector to be calculated, use numerical integration operation

Perform surface reconstruction and complete the three-dimensional profile measurement of the upper and lower surfaces of optical components.

Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

The present invention is described with reference to the flowchart and/or block diagram of the method, device (system), and computer program product according to the embodiment of the present application. It should be understood that each process and/or box in the flowchart and/or block diagram, as well as the combination of the process and/or box in the flowchart and/or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for implementing the functions specified in one process or multiple processes in the flowchart and/or one box or multiple boxes in the block diagram.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device that implements the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

These computer program instructions may also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims (6)

1. A method for measuring the double-surface shape of an optical element, comprising: S1. Establish a basic measurement device for the double-surface shape of optical elements; S2, calibrating the basic measuring device to obtain a measuring device for the double-surface shape of an optical element; S3, using the measuring device to obtain reflection fringe data of the optical element to be measured; S4, obtaining a double-surface shape measurement result of the optical element according to the reflection fringe data of the optical element to be measured; S4-1, performing separation processing on the reflection fringe data of the optical element to be measured to obtain reflection fringe separation data; S4-2, obtaining the topological relationship of the reflection fringe separation data; S4-2-1, using the camera corresponding feature points of the basic measurement device as reference points; S4-2-2, searching in a single contour direction based on the reference point to obtain a topological relationship between the upper surface of the reflection fringe image and the discrete reflection fringe and a topological relationship between the lower surface of the reflection fringe image and the discrete reflection fringe; S4-2-3, using the topological relationship between the upper surface of the reflection fringe image and the discrete reflection fringe and the topological relationship between the lower surface of the reflection fringe image and the discrete reflection fringe as the topological relationship of the reflection fringe separation data; S4-3, performing phase solution processing according to the topological relationship to obtain a solution result of the reflection fringe data; S4-4. Obtain the double-surface shape measurement results of the optical element using the solution results of the reflection fringe data. 2. A method for measuring the double-surface shape of an optical element as claimed in claim 1, characterized in that the basic measuring device for establishing the double-surface shape of an optical element comprises: Cameras are arranged opposite to each other on both sides of the optical element to be measured; The discrete fringe image display devices are connected to the cameras respectively. 3. The method for measuring the double-surface shape of an optical element according to claim 1, wherein the step of calibrating the basic measuring device to obtain the double-surface shape of the optical element comprises: A reflective marking point is set on a standard plane mirror as a reflective marking plane mirror; The basic measuring device is used to collect multi-angle reflection stripe images of the reflective marking plane mirror; Utilizing the multi-angle reflection fringe image to calculate the coordinates of the reflective marking point based on the binocular vision principle; Obtaining the corresponding surface equation using the coordinates of the reflective marking points; The basic measuring device is calibrated according to the surface shape equation to obtain a measuring device for the double-surface surface shape of an optical element. 4. A method for measuring the double-surface shape of an optical element as claimed in claim 3, characterized in that the coordinates of the reflective marking points are calculated using the multi-angle reflected fringe image based on the binocular vision principle as follows: Among them, _Ai , _Bi , _Ci , _Di are the coordinates of the reflective marking points set on the standard plane mirror, _ni is the normal vector of the i-th group of standard plane mirrors, _di is the distance between the i-th group of standard plane mirrors and the coordinate origin, and h is the thickness of the reflective marking point. 5. The method for measuring the double-surface shape of an optical element according to claim 1, wherein obtaining the double-surface shape measurement result of the optical element using the solution result of the reflection fringe data comprises: Obtaining the normal direction vectors of the upper surface and the lower surface of the reflection fringe image based on the reflection law according to the solution result of the reflection fringe data; The surface shape measurement results of the double surfaces of the optical element are obtained by performing surface shape reconstruction processing based on numerical integration using the normal direction vectors of the upper surface and the lower surface. 6. A method for measuring the double-surface shape of an optical element as claimed in claim 5, characterized in that the calculation formula for obtaining the double-surface shape measurement result of the optical element by performing shape reconstruction processing based on numerical integration using the normal direction vectors of the upper surface and the lower surface is as follows: Wherein, ( _Px , _Py , _Pz ) are the normal direction vectors of the upper and lower surfaces, and z is the double-surface shape measurement result of the optical element.