An optical auxiliary positioning system, method and control terminal for electron beam scanning imaging equipment

Abstract

This invention discloses an optical auxiliary positioning system for an electron beam scanning imaging device. Located between the electron optical system and the optical camera, it includes an optical structure that shortens the offset between the electron beam scanning area and the optical detection area. The optical structure comprises a focusing module, a lens module, and a base module. Light generated by the light source is absorbed and reflected by the base module before illuminating the wafer. The wafer generates imaging light carrying texture information, which, after being reflected twice by the lens module and the base module, enters the optical camera for imaging. The system allows for rapid and accurate adjustment of the focal length to adapt to the surface morphology of wafers with different thicknesses, ensuring stable detection performance of the electron beam scanning imaging device under complex process conditions.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor testing equipment technology, and more specifically, relates to an optical auxiliary positioning system, method and control terminal for electron beam scanning imaging equipment. Background Technology

[0002] Electron beam scanning imaging equipment is the main equipment used for measuring critical dimensions and detecting defects in integrated circuits during the semiconductor chip manufacturing process. The optical-assisted positioning system, through the synergistic effect of high-precision optical guidance and electron beam, significantly improves imaging efficiency and positioning accuracy, and is an indispensable part of it.

[0003] Currently, electron beam scanning imaging equipment used for wafer inspection generally uses coaxial fixed focal length or object plane focusing optical lenses as optical auxiliary positioning systems.

[0004] Traditional optical-assisted positioning systems typically employ a coaxial design, such as... Figure 1 As shown, the optical path is parallel to the electron beam direction. This design results in a significant offset between the installation position and the electron beam center, which can easily accumulate motion errors during assisted positioning, affecting the electron beam imaging accuracy and the efficiency of assisted positioning. Furthermore, when using a fixed-focus optical system for quantitative inspection of wafers with significant variations in thickness and warpage, the optical system is prone to defocusing. This type of application is common in third-generation semiconductor wafers.

[0005] The object plane focusing design requires adjusting the position of the entire optical system according to the change in wafer height, which places higher demands on assembly and control precision and increases systemic risk. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an optical auxiliary positioning system, method, and control terminal for electron beam scanning imaging equipment.

[0007] To achieve the aforementioned objective, the technical solution adopted by the present invention includes: an optical auxiliary positioning system for an electron beam scanning imaging device, which is set between the electron optical system and the optical camera, including an optical component structure that shortens the offset between the electron beam scanning area and the optical detection area. The optical component structure includes a focusing module, a lens barrel module, and a base module. The light generated by the light source is absorbed and reflected by the base module and then illuminates the wafer. The wafer generates imaging light carrying texture information, which is reflected twice by the lens barrel module and the base module and then enters the optical camera to form an image.

[0008] Furthermore, the focusing module includes a coaxially mounted centering ring, a focusing ring, a focusing base, a focusing ring, and a focusing plate. One end of the centering ring is connected to the optical camera, and the other end is connected to the focusing ring. One end of the focusing base is located inside the focusing ring and can move axially. The focusing ring is installed outside the focusing ring and can rotate around the axis of the focusing ring for focusing, while also moving axially in coordination with it. The focusing ring is fixed to the base module. The focusing ring is mounted on the base module via the focusing plate.

[0009] Furthermore, the other end of the centering ring mates with the conical surface of the focusing ring to form a centering and fastening structure; the inner wall of the focusing ring has symmetrical guide grooves that mate with the guide key on the outer wall of the focusing base; the outer wall of the focusing ring is designed with threads that mate with the focusing ring to form a focusing motion mechanism; the outer wall of the focusing base mates with the focusing ring to form an axial motion mechanism and is fixed to the base module by bolts; the focusing pressure plate mates with the focusing ring to form an elastic clamping mechanism, and the focusing pressure plate is fixed to the base module by bolts.

[0010] Furthermore, the lens module includes a reflector, a condenser lens group, and an imaging lens group. The focusing module axis is parallel to the electron beam axis and forms a 90-degree angle with the optical axis of the condenser lens group.

[0011] Furthermore, the base module includes a light-absorbing plate, a beam splitter, and a light source. Both the reflector and the beam splitter are installed at a 45-degree angle to the optical axis of the condenser lens assembly and at a 45-degree angle to the axis of the focusing module.

[0012] In this invention, as Figure 4 As shown, the light generated by the light source is split into transmitted light and reflected light after passing through a beam splitter. The reflected light is absorbed by the light-absorbing plate, while the transmitted light is totally reflected by a reflector and then illuminates the wafer. The wafer generates imaging light carrying texture information, which is reflected twice by the reflector and beam splitter, and then imaged on the optical sensor.

[0013] Furthermore, the reflector surface has an aluminum metal coating with a flat reflectivity curve and a wide bandwidth (visible to near-infrared band), which is less affected by the incident angle. The reflectivity is significantly improved through a dielectric film enhancement process, reaching up to 99%, and a silicon oxide protective layer is applied to improve its durability. The substrate of the beam splitter is high-quality BK7 glass with multilayer dielectric film deposition, reducing optical path difference and energy loss. The dielectric multilayer film has almost no absorption, resulting in extremely low light loss (T:R=50:50). The light-absorbing plate is light-absorbing foam, which is a micro-foamed polyurethane material with a fine porous structure on the surface. The hemispherical reflectivity can be less than 1%, exhibiting excellent light absorption performance.

[0014] An optical-assisted positioning method for an electron beam scanning imaging device, comprising the following steps: A1. Turn on the autofocus function, first perform a global focus search, and then perform average interpolation based on the maximum focus range f of the autofocus module to obtain five focus positions: 0, f / 4, f / 2, 3f / 4, f. A2. Perform drive focusing, camera image capture, and sharpness data calculation for each of the five focal length positions, and add the sharpness data to the fitting database for storage. A3. Based on the obtained sharpness data, model and perform fitting calculations to obtain the optimal focal length position f_max; A4. Drive the focus to f_max focal length position, and perform camera image capture and sharpness calculation to obtain sharpness_max; A5. Determine whether sharpness_max is greater than the set standard sharpness threshold s_standard. If it is, the optimal focal length has been obtained, and autofocus ends. A6. If the judgment is negative, query the two points adjacent to f_max in the original fitted database focal length position, calculate the difference f_max_right - f_max_left, and perform average interpolation within the range of the difference to obtain three new focal length positions. A7. Perform focus adjustment, camera image capture, and sharpness data calculation for the three focal length positions respectively, and add the sharpness data to the fitting database for storage. Repeat the process from A3 to A7 again.

[0015] This invention integrates a small-volume, high-precision zoom lens module, a drive control module, and an autofocus algorithm module, which can quickly and accurately adjust the focal length to adapt to the surface morphology of wafers of different thicknesses, ensuring the stable detection performance of electron beam scanning imaging equipment under complex process conditions.

[0016] Furthermore, the sharpness data calculation employs at least one of the following: gradient function algorithm, grayscale value statistical characteristic analysis, frequency domain analysis, and histogram analysis. The gradient function algorithm is preferred for sharpness data calculation because it is sensitive to edge information, has high computational efficiency, and is well-correlated with subjective evaluation. The fitting calculation employs at least one of the following: Gaussian mixture model, multinomial model, multivariate linear model, and nonlinear model. The Gaussian mixture model is preferred for fitting calculation because it is a probability-based generative model with powerful expressive capabilities and can approximate arbitrarily complex continuous distributions.

[0017] Furthermore, the autofocus mechanism is driven by an S-curve acceleration and deceleration control algorithm to smooth the target value. In order to reduce the damping vibration of the mechanism and improve the control efficiency during each focus drive, an S-curve acceleration and deceleration control algorithm with lower complexity and higher accuracy is used to smooth the target value before driving the autofocus mechanism.

[0018] A control terminal includes a mobile terminal and a controller. The controller includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps of an optically assisted positioning method for an electron beam scanning imaging device.

[0019] Compared with the prior art, the advantages of the present invention include: (1) The present invention provides an optical auxiliary positioning system, method and control terminal for an electron beam scanning imaging device. The optical auxiliary positioning system adopts a non-coaxial small volume lens and innovatively uses a dual reflection optical path structure. This design makes the entire system structure compact, significantly shortens the offset distance between the electron beam scanning area and the optical detection area, thereby effectively reducing the impact of motion error accumulation during the auxiliary positioning process and greatly improving the execution efficiency of the auxiliary positioning process; (2) The present invention provides an optical auxiliary positioning system, method, and control terminal for an electron beam scanning imaging device. The high-precision zoom lens adopts an image plane zoom design, which, compared with the traditional object plane focusing design, reduces image plane shift or aberration accumulation caused by mechanical structure precision limitations in the optical path, thereby improving imaging stability and resolution. While maintaining high resolution, it reduces the demand for high-precision lens groups, resulting in cost advantages. Combined with the drive control module, automatic focusing control is performed, reducing manual intervention. For situations with large differences in wafer thickness, it significantly improves production efficiency and positioning consistency. (3) The present invention provides an optical auxiliary positioning system, method, and control terminal for electron beam scanning imaging equipment. In the system's autofocus control scheme, an innovative S-curve algorithm is used for smooth control. The autofocus control first employs a gradient function algorithm with high computational efficiency to calculate image sharpness, followed by fitting calculations using a Gaussian mixture model to quickly locate the optimal focal length. After accurately obtaining the target focal length, the system uses an S-curve acceleration / deceleration algorithm to smoothly output the control quantity, ensuring the flexibility and stability of the motion. The S-curve acceleration / deceleration algorithm has a smooth velocity curve and a continuous acceleration curve, effectively reducing system shock and oscillation. Furthermore, the algorithm has low complexity and high execution efficiency, significantly improving the execution efficiency of autofocus control. In summary, the combination of these algorithms enables the system to quickly adapt to different working distances, target sizes, or environmental changes, maintaining optimal performance. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application 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 only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of existing technology; Figure 2 This is a schematic diagram of the optical components of an optical auxiliary positioning system for an electron beam scanning imaging device according to the present invention; Figure 3 This is an optical path transmission diagram of an optical component in an optical auxiliary positioning system for an electron beam scanning imaging device according to the present invention; Figure 4 This is a focusing flowchart of an optical auxiliary positioning method for an electron beam scanning imaging device according to the present invention; Figure 5 This is a schematic diagram of the S-curve function in this invention; Figure 6 This is a graph showing the focus control response in this invention. Figure 7 This is a top view of the optical component structure of an optical auxiliary positioning system for an electron beam scanning imaging device according to the present invention.

[0022] Figure label: 100. Lens barrel module; 101. Base module; 102. Focusing module; 103. Electro-optical system; 104. Optical camera; 200. Centering ring; 201. Focusing ring; 202. Focusing base; 203. Focusing ring; 204. Focusing pressure plate; 205. Reflector; 206. Condenser lens group; 207. Imaging lens group; 208. Absorber plate; 209. Beam splitter; 210. Light source; 300. Wafer; 301. Transmitted light; 302. Reflected light; 303. Imaging light; 304. Optical sensor. Detailed Implementation

[0023] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution, its implementation process, and principles will be further explained below with reference to the accompanying drawings and specific implementation examples in the embodiments of this application.

[0024] It should be noted that the embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, the present invention covers any substitutions, modifications, equivalent methods and solutions made on the spirit, principles and scope of the present invention as defined by the claims. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In the description of this application, the terms "first," "second," "third," and similar words do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "a" or "one," and similar words, do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including," and similar words, mean that the elements or objects preceding "comprising" or "including" encompass the elements or objects listed following "comprising" or "including," and their equivalents, but do not exclude other elements or objects. The terms "connected" or "linked," and similar words, are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0026] In the description of this application, the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used solely for the convenience of describing this application and for simplification, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, when using positional terms such as "both sides," "outer side," and "upper and lower," it should be understood that they are used only for ease of understanding and description, taking into account that the structure may be oriented to other positions.

[0027] In the description of this application, unless otherwise expressly specified and limited, the technical or scientific terms used shall have the ordinary meaning understood by a person with ordinary skills in the art to which this application pertains. Terms such as “installation,” “connection,” and “joining” shall be interpreted broadly, for example, as fixed connection, detachable connection, mating connection, or integral connection. For a person skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0028] The present invention aims to introduce and explain the structural composition and the cooperation relationship between the components of an optical auxiliary positioning system, method and control terminal for an electron beam scanning imaging device. Unless otherwise specified, the dimensions, materials and manufacturing processes of the components in the optical auxiliary positioning system, method and control terminal suitable for an electron beam scanning imaging device in the present invention can be selected according to specific circumstances, and no special limitations or explanations are made here.

[0029] Furthermore, to provide the public with a better understanding of the present invention, certain specific details are described in detail in the following description of the invention. However, those skilled in the art will fully understand the invention even without these detailed descriptions.

[0030] Example 1 Please see Figures 1-7 An optical auxiliary positioning system for an electron beam scanning imaging device is provided between an electron optical system and an optical camera. The system includes an optical component structure that shortens the offset between the electron beam scanning area and the optical detection area. The optical component structure includes a focusing module 102, a lens barrel module 100, and a base module 101. Light generated by a light source 210 is absorbed and reflected by the base module 101 and then illuminates a wafer 300. The wafer 300 generates imaging light carrying texture information. After being reflected twice by the lens barrel module 100 and the base module 101, the light enters the optical camera for imaging. The focusing module 102 is used for focusing to adapt to different imaging requirements.

[0031] The focusing module 102 includes a coaxially mounted centering ring 200, a focusing ring 201, a focusing base 202, a focusing ring 203, and a focusing pressure plate 204. One end of the centering ring 200 is connected to the optical camera, and the other end mates with the conical surface of the focusing ring 201 to form a centering and fastening structure. The inner wall of the focusing ring 201 has symmetrical guide grooves that mate with guide keys on the outer wall of the focusing base 202. One end of the focusing base 202 is located inside the focusing ring 201 and can move axially. The outer wall of the focusing ring 201 is designed with threads that mate with the focusing ring 203 to form a focusing motion mechanism. The outer wall of the base 202 cooperates with the focusing ring 201 to form an axial movement mechanism and is fixed to the base module 101 by bolts; the focusing ring 203 is installed outside the focusing ring 201 and can rotate around the axis of the focusing ring 201 for focusing, while cooperating with it for axial movement; the focusing ring 201 is fixed on the base module 101; the focusing ring 203 is installed on the base module 101 through the focusing pressure plate 204, the focusing pressure plate 204 cooperates with the focusing ring 203 to form an elastic pressing mechanism, and the focusing pressure plate 204 is fixed to the base module 101 by bolts to ensure focusing stability.

[0032] The lens module 100 includes a reflector 205, a condenser lens group 206, and an imaging lens group 207. The axis of the focusing module 102 is parallel to the axis of the electron beam and perpendicular to the optical axis of the condenser lens group 206 at a 90-degree angle.

[0033] The base module 101 includes a light-absorbing plate 208, a beam splitter 209, and a light source 210. The reflector 205 and the beam splitter 209 are both installed at a 45-degree angle to the optical axis of the condenser lens group 206 and at a 45-degree angle to the axis of the focusing module 102.

[0034] In this invention, as Figure 4 As shown, the light generated by the light source 210 is split into two parts, transmitted light 301 and reflected light 302, after passing through the beam splitter 209. The reflected light 302 is absorbed by the light-absorbing plate 208, while the transmitted light 301 illuminates the wafer 300 after total internal reflection by the reflector 205. The wafer 300 generates imaging light 303 carrying texture information, which is reflected twice by the reflector 205 and the beam splitter 209, and then imaged on the optical sensor 304.

[0035] The reflector 205 has an aluminum metal coating with a flat reflectivity curve and a wide bandwidth (visible to near-infrared band), which is less affected by the incident angle. The reflectivity is significantly improved through a dielectric film enhancement process, reaching up to 99%, and a silicon oxide protective layer is applied to improve its durability. The substrate of the beam splitter 209 is high-quality BK7 glass with multilayer dielectric film deposition, which reduces optical path difference and energy loss. The dielectric multilayer film has almost no absorption, resulting in extremely low light loss (T:R=50:50). The light-absorbing plate 208 is light-absorbing foam, which is a micro-foamed polyurethane material with a fine porous structure on the surface. The hemispherical reflectivity can be less than 1%, and the light absorption performance is excellent.

[0036] An optical-assisted positioning method for an electron beam scanning imaging device, comprising the following steps: A1. Turn on the autofocus function, first perform a global focus search, and then perform average interpolation based on the maximum focus range f of the autofocus module to obtain five focus positions: 0, f / 4, f / 2, 3f / 4, f. A2. Perform drive focusing, camera image capture, and sharpness data calculation for each of the five focal length positions, and add the sharpness data to the fitting database for storage. A3. Based on the obtained sharpness data, model and perform fitting calculations to obtain the optimal focal length position f_max; A4. Drive the focus to f_max focal length position, and perform camera image capture and sharpness calculation to obtain sharpness_max; A5. Determine whether sharpness_max is greater than the set standard sharpness threshold s_standard. If it is, the optimal focal length has been obtained, and autofocus ends. A6. If the judgment is negative, query the two points adjacent to f_max in the original fitted database focal length position, calculate the difference f_max_right - f_max_left, and perform average interpolation within the range of the difference to obtain three new focal length positions. A7. Perform focus adjustment, camera image capture, and sharpness data calculation for the three focal length positions respectively, and add the sharpness data to the fitting database for storage. Repeat the process from A3 to A7 again.

[0037] Sharpness data calculation employs at least one of the following: gradient function algorithm, grayscale value statistical characteristic analysis, frequency domain analysis, and histogram analysis. The gradient function algorithm is preferred for sharpness data calculation because it is sensitive to edge information, has high computational efficiency, and is well-correlated with subjective evaluation. Fitting calculation employs at least one of the following: Gaussian mixture model, multinomial model, multivariate linear model, and nonlinear model. The Gaussian mixture model is preferred for fitting calculation because it is a probability-based generative model with powerful expressive capabilities and can approximate arbitrarily complex continuous distributions.

[0038] The autofocus mechanism is driven by an S-curve acceleration / deceleration control algorithm, which smooths the target value before driving it. To reduce damping vibration and improve control efficiency during each focus adjustment, a less complex and more precise S-curve acceleration / deceleration control algorithm is used to smooth the target value before driving the autofocus mechanism. Figure 5 As shown, the S-curve acceleration / deceleration control algorithm is based on the Sigmoid function and is mainly divided into seven parts: acceleration control segment, uniform acceleration control segment, deceleration control segment, uniform speed control segment, acceleration / deceleration control segment, uniform deceleration control segment, and deceleration control segment. The algorithm controls the drive mechanism in seven parts. The speed control curve is smooth and the acceleration control curve is continuous, which can achieve better flexibility, reduce system oscillation caused by input impact, and improve control efficiency.

[0039] like Figure 6 As shown in the diagram, the green line represents the S-curve algorithm smoothing control focus response curve, and the yellow line represents the direct drive focus response curve. t1 and t5 are the response times for focusing 0.1mm and 0.5mm, respectively, with t1_s / t1≈0.56 and t5_s / t5≈0.43. The response curves demonstrate that the S-curve algorithm smoothing focus control is more stable during small focus adjustments and achieves faster and more stable focusing during large focus adjustments, significantly improving focusing efficiency.

[0040] A control terminal includes a mobile terminal and a controller. The controller includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps of an optically assisted positioning method for an electron beam scanning imaging device.

[0041] It is understandable that, through this method, the present invention system, with its small and compact dual-reflection optical path design, significantly shortens the offset distance between the electron beam scanning area and the optical detection area, thereby improving the efficiency and accuracy of the auxiliary positioning process. The modular design, consisting of a lens barrel module, a base module, a focusing module, and a control module, improves debugging and optimization efficiency and reduces costs. The control module adopts a compatible design, providing multiple implementation schemes to meet various cost and performance requirements.

[0042] The system's image plane zoom design reduces image plane shift or aberration accumulation caused by mechanical structure precision limitations in the optical path, improving imaging stability and resolution. Combined with the drive control module, it achieves high-precision and high-stability autofocus, significantly improving adaptability to wafers of different heights and enhancing the accuracy and efficiency of the auxiliary positioning process. The design of the autofocus scheme for the optical-assisted positioning system combines a sharpness algorithm based on gradient algorithm with fitting calculation based on Gaussian mixture model to accurately and efficiently output the target focal length. When driving the target focal length, an S-curve smoothing control algorithm is used to reduce system oscillation caused by input shock and significantly improve the control efficiency of autofocus.

[0043] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It should not be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. An optical auxiliary positioning system for an electron beam scanning imaging device, characterized by: The optical structure includes an optical component structure that shortens the bias between the electron beam scanning area and the optical detection area. The optical component structure includes a focusing module, a lens module, and a base module. The light generated by the light source is absorbed and reflected by the base module and then illuminates the wafer. The wafer generates imaging light carrying texture information. After being reflected twice by the lens module and the base module, the light enters the optical camera to form an image.

2. An optical auxiliary positioning system for an electron beam scanning imaging apparatus according to claim 1, characterized in that: The focusing module includes a coaxially mounted centering ring, a focusing ring, a focusing base, a focusing ring, and a focusing pressure plate. One end of the centering ring is connected to the optical camera, and the other end is connected to the focusing ring. One end of the focusing base is located inside the focusing ring and can move axially; the focusing ring is installed outside the focusing ring and can rotate around the axis of the focusing ring for focusing, while cooperating with it to move axially; the focusing ring is fixed on the base module; the focusing ring is installed on the base module through a focusing pressure plate.

3. An optical auxiliary positioning system for an electron beam scanning imaging apparatus according to claim 2, characterized in that: The other end of the centering ring mates with the conical surface of the focusing ring to form a centering and fastening structure; the inner wall of the focusing ring has symmetrical guide grooves that mate with the guide key on the outer wall of the focusing base; the outer wall of the focusing ring is designed with threads that mate with the focusing ring to form a focusing motion mechanism; the outer wall of the focusing base mates with the focusing ring to form an axial motion mechanism and is fixed to the base module by bolts; the focusing pressure plate mates with the focusing ring to form an elastic clamping mechanism and is fixed to the base module by bolts.

4. An optical auxiliary positioning system for an electron beam scanning imaging apparatus according to claim 3, characterized in that: The lens module includes a reflector, a condenser lens group, and an imaging lens group. The axis of the focusing module is parallel to the electron beam axis and perpendicular to the optical axis of the condenser lens group.

5. An optical auxiliary positioning system for an electron beam scanning imaging apparatus according to claim 4, characterized in that: The base module includes a light-absorbing plate, a beam splitter, and a light source. The reflector and beam splitter are both installed at an angle to the optical axis of the condenser lens group and at an angle to the axis of the focusing module.

6. An optical auxiliary positioning system for an electron beam scanning imaging apparatus according to claim 5, characterized in that: The reflector surface has an aluminum metal coating; the substrate of the beam splitter is high-quality BK glass with multilayer dielectric thin film deposition; the light-absorbing plate is light-absorbing foam.

7. An optical assisted positioning method for an electron beam scanning imaging device, using the method of the system according to any one of claims 1-6, characterized in that: Includes the following steps: A1. Turn on the autofocus function, first perform a global focus search, and then perform average interpolation based on the maximum focus range f of the autofocus module to obtain five focus positions: 0, f / 4, f / 2, 3f / 4, f. A2. Perform drive focusing, camera image capture, and sharpness data calculation for each of the five focal length positions, and add the sharpness data to the fitting database for storage. A3. Based on the obtained sharpness data, model and perform fitting calculations to obtain the optimal focal length position f_max; A4. Drive the focus to f_max focal length position, and perform camera image capture and sharpness calculation to obtain sharpness_max; A5. Determine whether sharpness_max is greater than the set standard sharpness threshold s_standard. If it is, the optimal focal length has been obtained, and autofocus ends. A6. If the judgment is negative, query the two points adjacent to f_max in the original fitted database focal length position, calculate the difference f_max_right - f_max_left, and perform average interpolation within the range of the difference to obtain three new focal length positions. A7. Perform focus adjustment, camera image capture, and sharpness data calculation for the three focal length positions respectively, and add the sharpness data to the fitting database for storage. Repeat A3 to A7 again.

8. The method of claim 7, wherein: The sharpness data calculation employs at least one of the following: gradient function algorithm, grayscale value statistical characteristic analysis, frequency domain analysis, and histogram analysis; the fitting calculation employs at least one of the following: Gaussian mixture model, polynomial model, multivariate linear model, and nonlinear model.

9. The method of claim 7, wherein: The focusing drive uses an S-curve acceleration / deceleration control algorithm to smooth the target value before driving the autofocus mechanism.

10. A control terminal comprising a mobile terminal and a controller, characterized by: The controller includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the method as described in any one of claims 7-9.

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