Method for automatic centering of an electron beam spot

Abstract

This invention provides an automatic electron beam spot centering method, belonging to the field of electron beam spot control technology in electron microscopy. The method involves extracting the foreground of the electron beam spot from an electron beam spot image; constructing a coordinate system with the length corresponding to one pixel in the electron beam spot image as the unit length and the target reference center as the origin, and determining the centroid coordinates of the foreground of the electron beam spot; calculating the Euclidean distance between the centroid of the foreground of the electron beam spot and the origin; if the Euclidean distance is greater than a preset tolerance, performing the following adjustment steps: S1, acquiring the current value of the current deflection coil and calculating the current adjustment amount of the deflection coil; S2, adding the adjustment amount to the current value of the current deflection coil; S3, determining whether the adjusted Euclidean distance is less than or equal to the preset tolerance; if not, repeating S1 to S3 until the Euclidean distance meets the preset tolerance requirement. By gradually adjusting the current value of the deflection coil, the centroid of the foreground of the electron beam spot gradually approaches the target reference center, achieving automatic electron beam spot centering.

Description

Technical Field

[0001] This invention relates to the field of electron beam spot control technology in electron microscopes, and in particular to an automatic electron beam spot centering method. Background Technology

[0002] An electron microscope is a high-resolution microscopic imaging instrument that uses an electron beam as a probe source. Its imaging resolution can reach the nanometer or even atomic level, and it has wide applications in materials science, biomedicine, and nanotechnology. Precise alignment of the electron beam spot is crucial for ensuring image quality. The electron beam spot must be accurately aligned with the reference center of the field of view or the observation camera to ensure image clarity and measurement accuracy. This process places stringent requirements on the instrument's stability and operational precision.

[0003] Currently, electron beam spot alignment is mainly achieved through manual adjustment. This manual adjustment method relies heavily on the operator's experience and judgment, resulting in low efficiency, poor repeatability, and difficulty in standardization. This severely restricts the application of electron microscopy in high-precision imaging and also fails to meet the urgent need for automated, high-precision nanoscale imaging in unmanned AI laboratories. Summary of the Invention

[0004] In view of this, the present invention provides an automatic centering method for electron beam spots, which extracts the electron beam spot foreground from the electron beam spot image, and adjusts the current value of the corresponding deflection coil to make the centroid of the electron beam spot foreground gradually approach the target reference center, thereby achieving automatic centering of the electron beam spot.

[0005] Therefore, the present invention provides the following technical solution:

[0006] An automatic electron beam spot alignment method, comprising:

[0007] Use a detector to acquire electron beam spot images;

[0008] Extract the electron beam spot foreground from the electron beam spot image;

[0009] A coordinate system is constructed with the length corresponding to one pixel in the electron beam spot image as the unit length and the target reference center as the origin, and the centroid coordinates of the foreground of the electron beam spot are determined.

[0010] Calculate the Euclidean distance between the centroid of the electron beam spot foreground and the origin;

[0011] When the Euclidean distance is less than or equal to the preset tolerance, it is determined that the electron beam spot has been aligned and the adjustment ends;

[0012] When the Euclidean distance is greater than the preset tolerance, perform the following adjustment steps:

[0013] S1. Collect the current value of the current deflection coil and calculate the current adjustment amount of the deflection coil;

[0014] S2. Add the adjustment amount to the current deflection coil current value;

[0015] S3. Determine whether the adjusted Euclidean distance is less than or equal to the preset tolerance;

[0016] If not, repeat S1 to S3 until the Euclidean distance meets the preset tolerance requirements.

[0017] Further, extracting the electron beam spot foreground from the electron beam spot image includes:

[0018] The image is binarized based on a preset threshold, and the portion above the preset threshold is used as the electron beam spot foreground.

[0019] Furthermore, the target reference center includes:

[0020] The center of the electronic detection camera's field of view.

[0021] Furthermore, the preset tolerance includes:

[0022] The length corresponding to one pixel in an electron beam spot image.

[0023] Furthermore, the acquisition of the current value of the current deflection coil includes:

[0024] Collect the current values ​​of the first deflection coil and the second deflection coil;

[0025] The first deflection line is perpendicular to the second deflection coil.

[0026] Furthermore, the deflection coil current adjustment amount includes:

[0027]

[0028]

[0029]

[0030]

[0031] in, The displacement vector corresponding to the shift of the electron beam spot centroid by increasing the current value of the first deflection coil by 1 unit; The displacement vector corresponding to the movement of the electron beam spot centroid by increasing the current value of the second deflection coil by 1 unit; Using the target reference center coordinates, The coordinates of the centroid of the electron beam spot foreground are given. This is the adjustment amount of the first deflection coil current value. This is the adjustment amount for the current value of the second deflection coil.

[0032] Advantages and positive effects of the present invention:

[0033] This method extracts the electron beam spot foreground from the electron beam spot image and obtains the centroid of the electron beam spot foreground. With the target reference center as the origin and the length corresponding to 1 pixel in the electron beam spot image as the unit length, a coordinate system is constructed to determine the position of the electron beam spot relative to the target reference center. This enables the quantization of the offset of the electron beam spot relative to the target reference center using Euclidean distance.

[0034] This method improves the centering accuracy by determining whether the electron beam spot is centered by setting a preset tolerance; and it determines the correspondence between the deflection coil current value and the electron beam spot adjustment amount, and then gradually adjusts the current value of the deflection coil to make the centroid of the electron beam spot foreground gradually approach the target reference center, and finally realizes the automatic centering of the electron beam spot.

[0035] This method eliminates the need for complex inversion techniques to locate the actual electron beam center. Only accurate identification of the foreground of the electron beam in the current field of view is required. After one or more automatic adjustments to the electromagnetic deflection coil current, the electron beam position deviation can be quickly converged to a preset tolerance range, ensuring image quality for subsequent high-precision imaging operations under the electron microscope. This also solves the problem of electron beam misalignment caused by insufficient symmetry of the electromagnetic lens or partial obstruction of the electron beam by the aperture, which is common in routine electron microscope operations. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of the automatic centering method for the electron beam spot in the embodiment.

[0038] Figure 2 This is an electron beam spot image from an embodiment.

[0039] Figure 3 This is the electron beam spot foreground image obtained after processing the electron beam spot image in the embodiment.

[0040] Figure 4 This is the electron beam spot image after centering in the embodiment. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0042] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0043] An automatic electron beam spot alignment method includes the following steps:

[0044] S1. Use a detector to acquire observational data to characterize the position of the electron beam spot.

[0045] Preferably, the detector is an electronic detection camera, and the observation data is the captured electron beam spot image.

[0046] S2. Process the observation data and extract the electron beam spot foreground.

[0047] Preferably, the image is binarized based on a preset threshold, and the portion above the preset threshold is used as the electron beam spot foreground; denoising and morphological processing can also be combined to achieve image denoising.

[0048] S3. Determine the centroid coordinates of the electron beam spot foreground.

[0049] A coordinate system is constructed with the length corresponding to one pixel in the electron beam spot image as the unit length and the target reference center as the origin; the centroid coordinates of the electron beam spot foreground are defined as follows: .

[0050] Preferably, the target reference center is the center of the electronic detection camera's field of view.

[0051] S4. Calculate the Euclidean distance between the centroid of the electron beam foreground and the target reference center:

[0052]

[0053] S5. Based on the relationship between the Euclidean distance between the centroid of the electron beam spot and the target reference center and the preset tolerance, determine whether the electron beam spot is centered:

[0054] If the Euclidean distance between the centroid of the electron beam spot foreground and the target reference center is less than or equal to the preset tolerance, then it is determined that the centering is complete.

[0055] If the Euclidean distance between the centroid of the electron beam spot and the target reference center is greater than the preset tolerance, it is determined that the electron beam spot is misaligned, and the electron beam spot is aligned by adjusting the coil current value.

[0056] Preferably, the preset tolerance is the length corresponding to one pixel in the image of the electron beam spot.

[0057] S6. When the Euclidean distance is greater than the preset tolerance, perform the following adjustment steps:

[0058] 1) Collect the current value of the current deflection coil and calculate the current adjustment amount of the deflection coil;

[0059] 2) Add the adjustment amount to the current deflection coil current value;

[0060] 3) Determine whether the adjusted Euclidean distance is less than or equal to the preset tolerance;

[0061] If not, repeat steps 1) to 3) until the Euclidean distance meets the preset tolerance requirements.

[0062] 1) Collect current deflection coil current data and calculate deflection coil current adjustment: Collect the current values ​​of the first and second deflection coils, with the first deflection coil perpendicular to the second deflection coil. The current value of the first deflection coil is... The current value of the second deflection coil is .

[0063] Preferably, the deflection coil current data is obtained directly using an electron microscope.

[0064] Calculate the deflection coil current adjustment:

[0065]

[0066]

[0067]

[0068]

[0069] in, The displacement vector corresponding to the shift of the electron beam spot centroid by increasing the current value of the first deflection coil by 1 unit; The displacement vector corresponding to the movement of the electron beam spot centroid by increasing the current value of the second deflection coil by 1 unit; Using the target reference center coordinates, The coordinates of the centroid of the electron beam spot foreground are given. This is the adjustment amount of the first deflection coil current value. This is the adjustment amount for the current value of the second deflection coil.

[0070] 2) Add the adjustment amount to the current deflection coil current value:

[0071]

[0072]

[0073] in, Set the current value for the first deflection coil. Set the current value for the second deflection coil; and Take the integer part.

[0074] 3) Determine whether the adjusted Euclidean distance is less than or equal to the preset tolerance; if not, repeat steps 1) to 3) until the Euclidean distance meets the preset tolerance requirement.

[0075] Example

[0076] Combination Figure 1 An automatic electron beam spot alignment method includes the following steps:

[0077] S1. Use an electron detector camera to acquire electron beam spot images with a resolution of 1024×1024, such as... Figure 2 As shown.

[0078] S2, Extraction Figure 2 The electron beam spot foreground in the image, and the results are as follows: Figure 3 As shown.

[0079] S3, the target reference center coordinates are (0, 0), and the centroid coordinates of the electron beam spot foreground are (-15.75, 85.93).

[0080] S4. The Euclidean distance between the centroid of the electron beam spot foreground and the target reference center is 87.36, with a preset tolerance of 1; therefore, it is determined that the electron beam spot is not aligned.

[0081] S5. Obtain the current data of the deflection coil. This result is directly provided by the electron microscope:

[0082] The current value of the first deflection coil The value is 100405, which is the current value of the second deflection coil. It is 156009;

[0083] The electron microscope has a magnification of 10k. ; ; ; Then the current setting value and ;

[0084] S6. After adjusting the deflection coil current to the set value, use an electron detection camera to acquire an electron beam spot image, as shown below. Figure 4 As shown.

[0085] S8, Extract Figure 4 The foreground electron beam spot in the image is used to obtain the centroid coordinates (0.05, 0.09).

[0086] If the Euclidean distance between the centroid of the electron beam foreground and the target reference center is 0.10, which is less than the preset tolerance of 1, then the electron beam is considered to be aligned and the adjustment ends.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An automatic electron beam spot alignment method, characterized in that, include: Use a detector to acquire electron beam spot images; Extract the electron beam spot foreground from the electron beam spot image; A coordinate system is constructed with the length corresponding to one pixel in the electron beam spot image as the unit length and the target reference center as the origin, and the centroid coordinates of the foreground of the electron beam spot are determined. Calculate the Euclidean distance between the centroid of the electron beam spot foreground and the origin; When the Euclidean distance is less than or equal to the preset tolerance, it is determined that the electron beam spot has been aligned and the adjustment ends; When the Euclidean distance is greater than the preset tolerance, perform the following adjustment steps: S1. Collect the current value of the current deflection coil and calculate the current adjustment amount of the deflection coil; S2. Add the adjustment amount to the current deflection coil current value; S3. Determine whether the adjusted Euclidean distance is less than or equal to the preset tolerance; If not, repeat S1 to S3 until the Euclidean distance meets the preset tolerance requirements; The acquisition of the current value of the current deflection coil includes: Collect the current values ​​of the first deflection coil and the second deflection coil; the first deflection line is perpendicular to the second deflection coil. The deflection coil current adjustment includes: in, The displacement vector corresponding to the shift of the electron beam spot centroid by increasing the current value of the first deflection coil by 1 unit; The displacement vector corresponding to the movement of the electron beam spot centroid by increasing the current value of the second deflection coil by 1 unit; Using the target reference center coordinates, The coordinates of the centroid of the electron beam spot foreground are given. This is the adjustment amount of the first deflection coil current value. This is the adjustment amount for the current value of the second deflection coil.

2. The method according to claim 1, characterized in that, Extracting the electron beam spot foreground from the electron beam spot image includes: The image is binarized based on a preset threshold, and the portion above the preset threshold is used as the electron beam spot foreground.

3. The method according to claim 1, characterized in that, The target reference center includes: The center of the electronic detection camera's field of view.

4. The method according to claim 1, characterized in that, The preset tolerance includes: The length corresponding to one pixel in an electron beam spot image.

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