Method for measuring and compensating for X-ray source position drift and jitter

Abstract

The present application provides a method for measuring and compensating for the drift and jitter of the position of an X-ray light source, and relates to the field of X-ray technology. The method for measuring and compensating for the drift and jitter of the position of an X-ray light source provided by the present application includes collecting the initial position origin of the X-ray light source driven by a laser plasma accelerator; collecting the real-time jitter offset of the X-ray light source during the application time; counting the real-time jitter offset, and calculating the average jitter offset within the specified time; adjusting the position of the laser target according to the average jitter offset, thereby providing feedback and pre-compensation for the offset of the X-ray light source; and correcting the corresponding results generated by the X-ray light source through data post-processing. The present application compensates and corrects the high-frequency jitter of the average jitter offset and the real-time jitter offset generated during the application process through the synergistic effect of the method of adjusting the position of the laser target and the data post-processing, thereby improving the precision and accuracy of the obtained results.

Description

Technical Field

[0001] The present application relates to the field of X-ray technology, and in particular to a method for measuring and compensating for the drift and jitter of an X-ray light source position. Background Art

[0002] Laser plasma accelerator is a new accelerator technology that uses the ponderomotive force of ultrashort and ultra-intense laser beam pulses to accelerate charged particles in a plasma medium. It can produce an ultra-strong acceleration structure of 100GV / m in a rarefied plasma medium. It can also produce high-intensity 0.1-1GeV high-energy electron beams with ultra-fast time structures on the millimeter to centimeter scale. The scale and cost are greatly reduced compared to traditional linear accelerators. It has great development potential in the construction of a new generation of accelerator-based scientific equipment and the application of miniaturized accelerator radiation sources.

[0003] Laser plasma accelerators, while simultaneously generating high-energy electron beams, combine multiple radiation generation modes to produce versatile ultrafast, high-brightness X-ray sources, ranging from soft X-rays to high-energy gamma rays. Desktop ultrafast X-ray sources driven by laser plasma accelerators combine many key features of traditional synchrotron radiation and free electron lasers, while also being highly complementary to traditional sources in parameter space. Therefore, they hold broad application prospects in areas such as ultra-high-definition soft tissue imaging, non-destructive testing of dense samples, and analysis of ultrafast physical and chemical processes. They are expected to revolutionize the high-end application of high-brightness X-rays in industry, medicine, and scientific research.

[0004] In applications where laser plasma accelerators generate X-ray sources, the direction of the laser beam pulses can drift and experience shot-to-shot fluctuations (also known as shot-to-shot fluctuations) over long periods of operation due to mechanical vibration interference and changes in ambient temperature and humidity. This can cause the transmission direction and generation position of the electron beam generated by the laser plasma accelerator to drift and fluctuate accordingly, thereby causing the subsequent lateral source position of the X-ray source to drift and fluctuate. This lateral source position drift and fluctuate not only increases the size of the equivalent source, for example, degrading spatial resolution in imaging applications, but also shifts the center position of the equivalent source, for example, causing changes in the X-ray focusing process in applications of ultrafast near-edge absorption spectroscopy, thereby affecting spectral and temporal resolution.

[0005] Therefore, it is necessary to provide a method that can accurately measure the offset of the lateral source position of an X-ray source driven by a laser plasma accelerator and provide feedback compensation. Summary of the Invention

[0006] Based on this, the present application provides a method for measuring and compensating for the drift and jitter of the X-ray source position, so as to reduce the impact of the drift and jitter of the X-ray source position on the actual application results.

[0007] The method provided in this application for measuring and compensating for the drift and jitter of the X-ray source position includes:

[0008] Collect the initial position origin of the X-ray source driven by the laser plasma accelerator;

[0009] Synchronously collect the real-time jitter offset of the X-ray source within the application time;

[0010] Set a specified time within the application time, count the real-time jitter offset within the specified time, and calculate the average jitter offset within the specified time;

[0011] Adjust the position of the laser target according to the average jitter offset, so as to provide feedback and pre-compensation for the offset of the X-ray source within a specified time;

[0012] According to the real-time jitter offset collected, the corresponding results generated by the X-ray source are corrected through data post-processing.

[0013] Optionally, the method for measuring and compensating for the drift and jitter of the X-ray source position provided by the present application further includes:

[0014] The positioning sample is placed between the X-ray detector and the X-ray light source. The plane of the X-ray detector is perpendicular to the transmission direction of the X-ray light source. The X-ray light source projects an image of the positioning sample onto the X-ray detector.

[0015] Optionally, collecting the initial position origin of the X-ray source driven by the laser plasma accelerator includes:

[0016] The initial position information of the positioning sample projection formed by the X-ray light source penetrating the positioning sample in the initial stage is collected by the X-ray detector, thereby obtaining the initial position origin of the X-ray light source.

[0017] Optionally, synchronously collecting the real-time jitter offset of the X-ray source within the application time includes:

[0018] The X-ray detector is used to collect the offset position information of the projection of the positioning sample formed by the positioning sample after the position of the X-ray light source is offset and jittered;

[0019] The actual real-time jitter offset of the X-ray source is calculated based on the offset position information.

[0020] Optionally, calculating the actual real-time jitter offset of the X-ray source according to the offset position information includes:

[0021] The position offset Δd of the X-ray source is calculated using the following formula:

[0022] Δd=(-Δa×l) / L

[0023] Wherein, Δa is the position change of the current position of the projection imaging result of the positioning sample relative to the initial position origin of the projection imaging result, l is the distance from the X-ray light source to the positioning sample along the longitudinal direction, and L is the distance from the positioning sample to the X-ray detector plane along the longitudinal direction.

[0024] Optionally, in the step of calculating the actual real-time jitter offset of the X-ray source according to the offset position information,

[0025] Make Δa larger than the effective width of the imaging surface point spread function under the imaging magnification ratio, and the imaging magnification ratio M=(L+l) / l.

[0026] Optionally, a specified time is set within the application time, real-time jitter offset within the specified time is counted, and the average jitter offset within the specified time is calculated, including:

[0027] Set multiple consecutive specified times within the application time;

[0028] The average jitter offset within a plurality of specified time periods is measured and calculated, and a trend curve of the X-ray source offset varying with time is obtained through the average jitter offset within the plurality of specified time periods.

[0029] Optionally, adjusting the position of the laser target according to the average jitter offset, thereby providing feedback and pre-compensating for the offset of the X-ray source within a specified time, includes:

[0030] The electric optical adjustment frame is used to move the position of the laser target point by an average jitter offset and in a direction opposite to the average jitter offset direction of the X-ray source to achieve pre-compensation.

[0031] Optionally, the method for measuring and compensating for the drift and jitter of the X-ray source position provided by the present application further includes:

[0032] The positioning sample projection of the positioning sample is decomposed along any two mutually perpendicular directions in the projection plane, so that the positioning sample projection of the positioning sample has a two-dimensional attribute, thereby reducing the difficulty of extracting position information.

[0033] Optionally, the positioning sample includes a thin sheet sample with a vertical hard edge structure, a circular thin sheet sample, or a spherical sample.

[0034] This application provides a method for measuring and compensating for X-ray source position drift and jitter by acquiring the X-ray source's positional difference relative to its initial position in real time to obtain the source's real-time jitter offset. For the case of transverse source position jitter in a laser plasma accelerator-driven X-ray source, the method calculates the average jitter offset over a specified time period Δt based on the measured real-time jitter offset data.

[0035] Through data post-processing, the laser target position is initially adjusted based on the average jitter offset to eliminate the effects of the average jitter offset. This compensates for the effects of X-ray source jitter and offset on results and performance during actual applications. Through data post-processing, based on real-time jitter offset data, the corresponding data generated by the X-ray source during actual applications is further corrected for source position jitter to compensate for the effects of high-frequency jitter caused by the real-time jitter offset on the results.

[0036] By adjusting the position of the laser target and working together with data post-processing methods, the high-frequency jitter of the average jitter offset and real-time jitter offset generated during the application process are compensated and corrected respectively, thereby reducing and eliminating the impact of jitter and offset on the results and effects during actual application, and improving the precision and accuracy of the results obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without exceeding the scope of protection required by this application.

[0038] Figure 1 It is a flow chart of the method provided by this application;

[0039] Figure 2 It is a working diagram of placing the positioning sample between the X-ray detector and the X-ray light source;

[0040] Figure 3 is a flow chart of step S120;

[0041] Figure 4 is a flow chart of step S130;

[0042] Figure 5 It is a structural diagram of a thin-sheet sample with a vertical hard-edge structure;

[0043] Figure 6 It is a structural diagram of a spherical sample;

[0044] Figure 7 This is an imaging result obtained without using the method shown in this application;

[0045] Figure 8 This is an imaging result diagram obtained by using the method shown in this application.

[0046] Explanation of the accompanying symbols: 1. X-ray source; 2. Positioning sample; 3. X-ray detector. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0048] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a corresponding orientation, be constructed and operate in a corresponding orientation, and therefore cannot be understood as limiting this application. In addition, the terms "first", "second", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the said features. In the description of this application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0049] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or connections that can communicate with each other; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0050] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0051] It should be noted that in this application, the transmission direction of the X-ray source 1 is referred to as the longitudinal direction, the plane perpendicular to the transmission direction of the X-ray source 1 is referred to as the transverse plane, and the position where the light-emitting point of the X-ray source 1 falls on the plane perpendicular to the transmission direction of the X-ray source 1 is referred to as the transverse source.

[0052] refer to Figure 1 and Figure 2 The method for measuring and compensating for the drift and jitter of the position of the X-ray source 1 provided in this application includes steps S110-S150.

[0053] In step S110 , the initial position origin of the X-ray source 1 driven by the laser plasma accelerator is acquired.

[0054] The X-ray source 1 driven by the laser plasma accelerator may include a betatron ray source (a laser plasma accelerator self-generated synchrotron radiation source), an all-optical inverse Compton scattering source, and an all-optical bremsstrahlung radiation source.

[0055] In step S120 , the real-time jitter offset of the X-ray source 1 within the application time is synchronously collected, and the position difference between the real-time position of the X-ray source 1 and the initial position origin is collected. The position difference is the real-time jitter offset.

[0056] In step S130 , a designated time Δt is set within the application time, the real-time jitter offset within the designated time Δt is counted, and the average jitter offset within the designated time Δt is calculated.

[0057] The designated time Δt is selected to be as small as possible based on the statistically valid average jitter offset. For example, the designated time Δt is selected to be as small as possible based on the fact that the statistically obtained average jitter offset is greater than the standard deviation of the real-time jitter offset.

[0058] In step S140 , the position of the laser target is adjusted according to the average jitter offset, thereby performing feedback and pre-compensation on the offset of the X-ray source 1 within the specified time Δt.

[0059] In step S150 , the corresponding result generated by the X-ray source 1 is corrected through data post-processing based on the collected real-time jitter offset.

[0060] The real-time jitter offset of the X-ray source 1 is obtained by real-time acquisition of the position difference of the X-ray source 1 relative to its initial position origin. For lateral source position jitter of the laser plasma accelerator-driven X-ray source 1, the average jitter offset within a specified time period Δt is calculated based on the measured real-time jitter offset data. The position of the laser target is initially adjusted based on the average jitter offset to eliminate the impact of the average jitter offset. Through data post-processing, the corresponding data generated by the X-ray source 1 during actual application is further corrected for source position jitter based on the real-time jitter offset data to correct for the impact of high-frequency jitter of the real-time jitter offset on the results. For example, when the laser plasma accelerator-driven X-ray source 1 is used in imaging applications, the image to be imaged can be subjected to corresponding translation processing to compensate for and mitigate the impact of position jitter and offset of the X-ray source 1 on the image. Alternatively, the laser plasma accelerator-driven X-ray source 1 can be used in spectroscopy.

[0061] By adjusting the position of the laser target and working together with data post-processing methods, the high-frequency jitter of the average jitter offset and real-time jitter offset generated during the application process are compensated and corrected respectively, thereby reducing and eliminating the impact of jitter and offset on the results and effects during actual application, and improving the precision and accuracy of the results obtained.

[0062] refer to Figure 1 and Figure 2 As an optional implementation, the method for measuring and compensating for the drift and jitter of the position of the X-ray source 1 provided in the present application also includes step S160.

[0063] In step S160 , the positioning sample 2 is placed between the X-ray detector 3 and the X-ray light source 1 , the plane of the X-ray detector 3 is perpendicular to the transmission direction of the X-ray light source 1 , and the X-ray light source 1 projects the positioning sample 2 onto the X-ray detector 3 for imaging.

[0064] like Figure 2 As shown, the positioning sample 2 is placed between the X-ray detector 3 and the X-ray light source 1, the distance between the positioning sample 2 and the X-ray light source 1 along the longitudinal direction is l, and the distance between the positioning sample 2 and the X-ray detector 3 along the longitudinal direction is L.

[0065] Among them, the horizontal placement position of the positioning sample 2 should follow the principle of being close to the transmission center of the X-ray source 1 without blocking the X-ray source 1 and affecting the actual application results, so as to enable the positioning sample 2 to obtain an imaging result with a better signal-to-noise ratio.

[0066] refer to Figure 1 and Figure 2 As an optional implementation, step S110 includes collecting initial position information of the projection of the positioning sample 2 formed by the X-ray light source 1 transmitting the positioning sample 2 in the initial stage through the X-ray detector 3, thereby obtaining the initial position origin of the X-ray light source 1.

[0067] refer to Figure 2 and Figure 3 As an optional implementation, step S120 includes sub-steps S121-S122.

[0068] In sub-step S121 , the X-ray detector 3 collects offset position information of the positioning sample projection formed by transmitting the positioning sample 2 after the position of the X-ray light source 1 is offset and shaken.

[0069] When the lateral source position of the X-ray source 1 is offset and jittered, the X-ray detector 3 collects the offset position information of the positioning sample projection formed by the positioning sample 2 with a fixed transmission position of the X-ray source 1. The position difference between the offset position of the positioning sample projection and the initial position origin is the change Δa of the characteristic position of the positioning sample 2.

[0070] In sub-step S122 , the actual real-time jitter offset of the X-ray source 1 is calculated based on the offset position information.

[0071] The real-time jitter offset Δd of the lateral source position of the X-ray source 1 can be obtained by inversely deducing Δa in combination with the distance l and the distance L of the positioning sample 2 relative to the X-ray source 1 and the X-ray detector 3 .

[0072] refer to Figure 1 and Figure 2 As an optional implementation, step S122 includes calculating the lateral source position offset Δd of the X-ray source 1 using the following formula.

[0073] Δd=(-Δa×l) / L

[0074] Among them, Δa is the position change of the current position of the projection imaging result of the positioning sample 2 relative to the initial position origin of the projection imaging result, l is the distance from the X-ray light source 1 to the positioning sample 2 along the longitudinal direction, and L is the distance from the positioning sample 2 to the X-ray detector plane along the longitudinal direction.

[0075] As an optional implementation, in sub-step S122, Δa is made larger than the effective width of the imaging plane point spread function under the imaging magnification ratio, and the imaging magnification ratio M=(L+l) / l.

[0076] refer to Figure 2 and Figure 4As an optional implementation, step S130 includes sub-steps S131-S132.

[0077] In sub-step S131 , a plurality of consecutive designated times Δt are set within the application time.

[0078] In sub-step S132, the average jitter offset over multiple specified time periods Δt is measured and calculated, and a temporal trend curve of the offset of the X-ray source 1 is obtained based on the average jitter offset over multiple specified time periods Δt. The temporal trend curve of the lateral source position of the X-ray source 1 obtained by measuring and calculating the average jitter offset of the lateral source position of the X-ray source 1 over a series of multiple specified time periods Δt is used to predict drift and implement pre-compensation.

[0079] refer to Figure 1 and Figure 2 As an optional implementation, step S140 includes using an electric optical adjustment frame to move the position of the laser target by an average jitter offset and in a direction opposite to the average jitter offset direction of the X-ray source 1 to achieve pre-compensation.

[0080] When a series of average jitter offsets within a plurality of consecutive specified time periods Δt are measured and calculated, steps S130 and S140 are executed in a loop, so that the electric optical adjustment frame adjusts the lateral position of the laser target in advance along the compensation direction according to the trend curve of the offset of the X-ray source 1 changing with time, thereby achieving pre-compensation and feedback.

[0081] refer to Figure 1 、 Figure 5 and Figure 6 As an optional implementation, the method for measuring and compensating for the drift and jitter of the position of the X-ray source 1 provided in the present application also includes step S170.

[0082] In step S170 , the positioning piece projection of the positioning piece 2 is decomposed along any two mutually perpendicular directions in the projection plane, so that the positioning piece projection of the positioning piece 2 has a two-dimensional property, thereby reducing the difficulty of extracting position information.

[0083] As an optional embodiment, the positioning sample 2 includes: Figure 5 The thin sheet sample with vertical hard edge structure shown, the round thin sheet sample or the Figure 6 Spherical specimen shown.

[0084] For example, when the positioning sample 2 is a thin sheet with vertical hard edges, the real-time jitter offset of the X-ray source 1 in the horizontal direction can be obtained by analyzing the position changes of the two vertical hard edges. When the positioning sample 2 is a circular thin sheet or spherical sample, the real-time jitter offset of the X-ray source 1 in the horizontal direction can be obtained by analyzing the position changes of the center of the circle or sphere.

[0085] like Figure 7 and Figure 8 As shown, the method of the present application was applied to an imaging experiment based on an all-optical inverse Compton scattering X-ray source 1 driven by a laser plasma accelerator. The energy of the main laser beam pulse used in the experiment to hit the target was approximately 0.35J (Joules), the pulse width was approximately 25fs (femtoseconds), and the full width at half maximum of the focal diameter was approximately 13μm (micrometers); the pulse energy of the collision laser beam was approximately 0.15J (Joules), the pulse width was approximately 25fs (femtoseconds), and the full width at half maximum of the focal diameter was approximately 7μm (micrometers). The plasma source was generated by a De Laval-type supersonic nozzle with an outlet diameter of 2mm (millimeters). This imaging application experiment projected images of a 100μm (micrometer) thick stainless steel sheet using a flat-panel detector with a pixel size of 50μm (micrometers), and the imaging magnification ratio of the projection imaging was approximately 2.5. During the imaging application process, a spherical positioning sample was simultaneously imaged to measure the lateral source position offset of the X-ray source 1. The imaging magnification ratio of the spherical positioning sample was approximately 2.8.

[0086] Figure 7 : The modulation transfer function (MTF) of the original image of the stainless steel sheet and the image edge obtained without using the method described in this application. As can be seen from the figure, based on the spatial frequency corresponding to MTF = 0.1, the image resolution of the original image of the stainless steel sheet obtained without using the method described in this application is approximately 75 μm (micrometers).

[0087] Figure 8 The following figure shows a transmission image of a stainless steel sheet obtained using the method of the present invention, along with the MTF (Modulation Transfer Function) at the image edge. For an MTF of 0.1, the resolution corresponding to the spatial frequency is approximately 27 μm. This demonstrates that the method of the present invention effectively compensates for the degradation in image resolution caused by lateral source position jitter of the X-ray source 1.

[0088] It should be noted that the resolution in this application refers to the smallest size that can be measured by the entire system. The smaller the resolution value, the clearer and better the image resolution.

[0089] The embodiments of the present application are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only intended to help understand the method and core ideas of the present application. At the same time, changes or modifications made by those skilled in the art based on the ideas of the present application, the specific implementation methods, and the scope of application of the present application, all fall within the scope of protection of the present application. In summary, the contents of this specification should not be construed as limiting the present application.

Claims

1. A method for measuring and compensating for the drift and jitter of the X-ray source position, characterized in that: include: Collect the initial position origin of the X-ray source driven by the laser plasma accelerator; Synchronously collecting the real-time jitter offset of the X-ray source within the application time; Setting a specified time within the application time, counting the real-time jitter offset within the specified time, and calculating the average jitter offset within the specified time; Adjusting the position of the laser target according to the average jitter offset, thereby providing feedback and pre-compensating for the offset of the X-ray source within the specified time; According to the real-time jitter offset collected, the corresponding result generated by the X-ray source is corrected through data post-processing.

2. The method according to claim 1, characterized in that Also includes: The positioning sample is placed between the X-ray detector and the X-ray light source, the plane of the X-ray detector is perpendicular to the transmission direction of the X-ray light source, and the X-ray light source projects an image of the positioning sample onto the X-ray detector.

3. The method according to claim 2, characterized in that The initial position origin of the X-ray source driven by the laser plasma accelerator is collected as follows: The X-ray detector collects initial position information of the positioning sample projection formed by the X-ray light source transmitting through the positioning sample in the initial stage, thereby obtaining the initial position origin of the X-ray light source.

4. The method according to claim 2, characterized in that The real-time jitter offset of the X-ray source collected synchronously during the application time includes: The X-ray detector collects offset position information of the positioning sample projection formed by transmitting the positioning sample after the X-ray light source position is offset and jittered; The actual real-time jitter offset of the X-ray source is calculated based on the offset position information.

5. The method according to claim 4, characterized in that Calculating the actual real-time jitter offset of the X-ray source according to the offset position information includes: The position offset Δd of the X-ray source is calculated by the following formula: Δd=(-Δa×l) / L Among them, Δa is the position change of the current position of the projection imaging result of the positioning sample relative to the initial position origin of the projection imaging result, l is the distance from the position of the X-ray light source to the positioning sample along the longitudinal direction, and L is the distance from the positioning sample to the X-ray detector plane along the longitudinal direction.

6. The method according to claim 5, characterized in that In the step of calculating the actual real-time jitter offset of the X-ray source according to the offset position information, Δa is made larger than the effective width of the imaging surface point spread function under the imaging magnification ratio, wherein the imaging magnification ratio M=(L+l) / l.

7. The method according to claim 1, characterized in that Setting a specified time within the application time, counting the real-time jitter offset within the specified time, and calculating the average jitter offset within the specified time includes: Setting a plurality of consecutive designated times within the application time; The average jitter offsets within the multiple specified times are measured and calculated, and a trend curve of the offset of the X-ray source changing with time is obtained through the average jitter offsets within the multiple specified times.

8. The method according to claim 1, characterized in that Adjusting the position of the laser target according to the average jitter offset, thereby providing feedback and pre-compensating for the offset of the X-ray source within the specified time, includes: The position of the laser target is moved by using an electric optical adjustment frame according to the average jitter offset and in a direction opposite to the average jitter offset direction of the X-ray source to achieve pre-compensation.

9. The method according to claim 2, characterized in that Also includes: The positioning sample projection of the positioning sample is decomposed along any two mutually perpendicular directions in the projection plane, so that the positioning sample projection of the positioning sample has a two-dimensional property, thereby reducing the difficulty of extracting position information.

10. The method according to claim 2, characterized in that The positioning sample includes a thin sheet sample with a vertical hard edge structure, a circular thin sheet sample or a spherical sample.

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