Sample piece pre-alignment method and system for angle resolution polarization scattering measurement

Abstract

The invention belongs to the technical field of optical measurement, and particularly discloses a sample piece pre-alignment method and system for angle resolution polarization scattering measurement. According to the invention, the method does not depend on a conventional focusing imaging method, but directly analyzes the diffraction image in the defocus state, specifically, when the sample piece is in the defocus state, the zero-order light is separated from the positive and negative first-order diffraction light, and the form and position of the diffraction light spot are easy to detect, thereby obtaining more accurate diffraction characteristic information. The method is characterized in that the traditional limitation of focusing imaging is broken through by analyzing the out-of-focus diffraction image, and the flexibility and precision of measurement are improved. The method can effectively improve the sample piece alignment precision in nanostructure angle resolution polarization scattering measurement. Under different experiment conditions, through automatic image analysis and azimuth angle calculation, the system can adjust the position of a sample piece in real time, manual errors can be effectively reduced, the experiment efficiency is improved, and the accuracy of angle resolution polarization scattering measurement is ensured.

Description

Technical Field

[0001] This application belongs to the field of optical measurement technology, and more specifically, relates to a sample pre-alignment method and system for angle-resolved polarization scattering measurement. Background Art

[0002] With the rapid development of nanotechnology, optical characterization techniques of nanostructures have become one of the core tools in modern materials science and nano-optics. Angle-resolution polarization scatterometry (ARPS), as a commonly used optical characterization method for nanostructures, analyzes the surface and structural characteristics of a sample by measuring the scattering signals at different incident light angles. This method has been widely applied in the fields of optical property research of nanomaterials, surface plasmon detection, photocatalysis research, etc. However, the accurate alignment of the azimuth angle of the sample is a key factor to ensure the accuracy of experimental results in these precise measurements.

[0003] In traditional optical experiments, the accuracy of the azimuth angle of the sample directly determines the measurement accuracy of optical properties. Especially in high-precision nano-optical experiments, a small azimuth angle deviation of the sample will significantly affect the intensity and orientation of the scattering signal, thereby affecting the reliability of the measurement results. To ensure measurement accuracy, nanostructure samples need to be precisely aligned with the detection system. However, traditional nanostructure sample alignment methods usually rely on manual operation, and the experimenter needs to manually adjust the azimuth angle and position of the sample. This manual operation is not only inefficient but also prone to large errors. Especially in the application of nanostructure optical measurement, a small azimuth angle deviation may lead to significant measurement errors.

[0004] Although existing alignment technologies use high-precision devices such as electric rotary tables and real-time monitoring systems, most rely on mechanical control and can only achieve rough sample alignment, making it difficult to meet the extremely high precision requirements of nano-optical experiments. Although existing alignment devices can adjust the azimuth angle of the sample, most lack the ability to process images in the defocused state. More importantly, existing technologies are usually not combined with diffraction spot analysis and lack an efficient calculation method to real-time monitor the small azimuth angle deviation of the sample and perform automatic adjustment. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of this application is to provide a sample pre-alignment method and system for angle-resolved polarization scattering measurement, aiming to solve the limitations of traditional alignment methods and the problems of low measurement accuracy and low experimental efficiency caused by manual errors.

[0006] The first aspect of the present application relates to a method for pre-aligning a sample in angular-resolved polarization scattering measurement, including: S1. Obtaining a diffraction image of a rectangular grating sample in a defocused state; S2. After preprocessing the diffraction image, detecting the zero-order light, the positive first-order diffracted light, and the negative first-order diffracted light using geometric features; S3. Respectively extracting the centroids of the zero-order light, the positive first-order diffracted light, and the negative first-order diffracted light, constructing a first vector from the centroid of the zero-order light to the centroid of the positive first-order diffracted light, and a second vector from the centroid of the zero-order light to the centroid of the negative first-order diffracted light; S4. Respectively calculating the angles between the first vector and the second vector and the horizontal direction, taking the average value of the two angles as the actual azimuth angle, and calculating the difference between the actual azimuth angle and the preset azimuth angle as the azimuth deviation, where the azimuth deviation is used to guide the rotation displacement stage to perform rotational adjustment until the sample is completely aligned with the preset azimuth angle.

[0007] Preferably, the resolution of the diffraction image is above 2000x2000 pixels to ensure the clarity of the diffraction light spots.

[0008] Preferably, in step S2, the preprocessing is to perform a binarization operation on the diffraction image.

[0009] Preferably, in step S2, a threshold determination method or a geometric feature rule method is used to detect the zero-order light, the positive first-order diffracted light, and the negative first-order diffracted light.

[0010] Preferably, in step S3, a region labeling method is used to perform connected region labeling, and the coordinates are extracted by calculating the centroid of each connected region.

[0011] Preferably, in step S4, according to the difference in centroid coordinates, the arctangent function is used to calculate the angle:

[0012] where , are respectively the deviations of the zero-order light and the positive first-order diffracted light in the horizontal and vertical directions.

[0013] The second aspect of the present application relates to a sample pre-alignment system for angular-resolved polarization scattering measurement, including: at least one memory for storing a computer program; at least one processor for executing the program stored in the memory, and when the program stored in the memory is executed, the processor is used to execute the alignment method as described in the first aspect.

[0014] It can be understood that the beneficial effects of the above second aspect can be referred to the relevant descriptions in the above first aspect and will not be elaborated here.

[0015] Generally speaking, compared with the prior art through the above technical solutions conceived by the present application, the following beneficial effects are achieved: The present application provides a method for pre-aligning a sample in angular resolved polarization scattering measurement. The present application does not rely on traditional focusing imaging methods, but directly analyzes the diffraction image in the defocus state. Specifically, when the sample is in the defocus state, the zero-order light and the positive and negative first-order diffracted lights are separated, and the morphology and position of their diffraction spots are easily detected, so as to obtain more accurate diffraction feature information. The innovation of this method lies in that by analyzing the defocus diffraction image, it breaks through the traditional limitations of focusing imaging and improves the flexibility and accuracy of measurement. It can effectively improve the sample alignment accuracy in angular resolved polarization scattering measurement of nanostructures. Under different experimental conditions, through automated image analysis and azimuth angle calculation, the system can adjust the sample position in real time, effectively reduce human errors, improve experimental efficiency, and ensure the accuracy of angular resolved polarization scattering measurement. Brief Description of the Drawings

[0016] Figure 1 is a flowchart of a method for pre-aligning a sample in angular resolved polarization scattering measurement provided by an embodiment of the present application.

[0017] Figure 2 is a schematic diagram of a sample pre-alignment device provided by an embodiment of the present application.

[0018] Figure 3 is a diagram of image processing, azimuth angle calculation and fitting results provided by an embodiment of the present application.

[0019] In all the drawings, the same reference numerals are used to represent the same elements or structures, where: 10 is a sample stage, 20 is a rectangular grating sample, 30 is a microscope objective, 40 is an image detector, 50 is a data processing module, 60 is a rotational displacement stage control system, and 70 is a rotational displacement stage. Detailed Embodiments

[0020] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] The term "and / or" in the present application is a relationship description of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. The symbol " / " in the present application represents an "or" relationship between associated objects. For example, A / B represents A or B.

[0022] In the description of the specification and claims of this application, terms such as "first" and "second" are used to distinguish different objects, rather than to describe a specific order of the objects. For example, the first response message and the second response message are used to distinguish different response messages, rather than to describe a specific order of the response messages.

[0023] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0024] In the description of the embodiments of this application, unless otherwise specified, the meaning of "a plurality of" refers to two or more. For example, a plurality of processing units refers to two or more processing units, etc.; a plurality of elements refers to two or more elements, etc.

[0025] The embodiments of this application will be described below with reference to the accompanying drawings in the embodiments of this application.

[0026] As Figure 1 shown, this application provides a method for pre-aligning a sample in angular-resolved polarization scattering measurement, including: S1. Obtain a diffraction image of a rectangular grating sample in a defocused state.

[0027] The image acquisition device needs to have a high enough resolution and light sensitivity to accurately capture the subtle changes in the diffraction pattern of the sample for subsequent accurate image processing and angle calculation. In this embodiment, a CCD is used as the image acquisition device.

[0028] First, as Figure 2 shown, place the rectangular grating sample 20 on the sample stage 10, raise the sample stage 10 so that it approaches the microscope objective 30 and is in a slightly defocused state. At this time, clear zero-order light and positive and negative first-order diffraction lights can be observed on the CCD camera 40, as Figure 3 shown in (a) of. Use the CCD camera 40 to acquire the diffraction image of the sample at this azimuth angle. The diffraction image includes zero-order light and positive and negative first-order diffraction lights.

[0029] The quality of the image is crucial for subsequent spot recognition and azimuth angle calculation. The resolution of each image should be high enough to ensure clear display of the spots, usually required to be above 2000x2000 pixels.

[0030] S2. After preprocessing the diffraction image, use geometric features to detect the zero-order light, positive first-order diffraction light, and negative first-order diffraction light.

[0031] The image captured by the CCD camera 40 is transmitted to the data processing module 50 to perform a series of preprocessing on the captured image, so as to extract diffraction light spots and accurately identify the zero-order light and the positive and negative first-order diffraction lights.

[0032] Preferably, in step S2, the preprocessing is to perform a binarization operation on the diffraction image, and may also include noise filtering and image enhancement.

[0033] The zero-order light usually appears circular or nearly circular, and the ratio of its major axis to minor axis is close to 1; the positive and negative first-order diffraction lights appear elliptical, and the ratio of their major axis to minor axis is greater than 1. Based on this characteristic, an image analysis algorithm is used to accurately extract the centroid coordinates of the diffraction light spots, providing high-precision data input for subsequent azimuth calculation.

[0034] Preferably, in step S2, a threshold determination method or a geometric feature rule method is used to detect the zero-order light, the positive first-order diffraction light, and the negative first-order diffraction light.

[0035] The threshold determination method is to classify by setting a threshold for the ratio of the major axis to minor axis. For example, the light spots with a ratio of the major axis to minor axis close to 1 are classified as zero-order light, and the light spots with a ratio greater than 1 are classified as first-order diffraction light.

[0036] The geometric feature rule method is to set rules to judge the type of light spots according to the geometric features of the light spots (such as the ratio of the major axis to minor axis, area, shape, etc.). The zero-order light is usually close to circular, and the first-order diffraction light is elliptical.

[0037] S3. Respectively extract the centroids of the zero-order light, the positive first-order diffraction light, and the negative first-order diffraction light, and construct a first vector from the centroid of the zero-order light to the centroid of the positive first-order diffraction light and a second vector from the centroid of the zero-order light to the centroid of the negative first-order diffraction light.

[0038] Preferably, in step S3, the region labeling method is used for connected region labeling, and the coordinates are extracted by calculating the centroid of each connected region.

[0039] S4. Respectively calculate the angles between the first vector, the second vector and the horizontal direction, take the average value of the two angles as the actual azimuth, and calculate the difference between the actual azimuth and the preset azimuth as the azimuth deviation. The azimuth deviation is used to guide the rotation stage to perform rotation adjustment until the sample is completely aligned with the preset azimuth.

[0040] Preferably, in step S4, assuming that the centroid coordinates of the zero-order light are , and the centroid coordinates of the positive first-order diffraction light are , according to the difference of the centroid coordinates, the arctangent function is used to calculate the angle:

[0041] Where , They are the deviations of the zero-order light and the positive first-order diffracted light in the horizontal and vertical directions respectively.

[0042] Calculate the angles between the first vector and the second vector and the horizontal direction respectively, and take the average value of the two angles as the actual azimuth angle. .

[0043] Azimuth deviation The calculation formula is:

[0044] Wherein, represents the preset azimuth angle.

[0045] This azimuth deviation value is the basis for adjusting the rotary displacement stage, as shown in (b) of Figure 3 .

[0046] The control system 60 of the rotary displacement stage receives the azimuth deviation , and drives the rotary displacement stage to make precise adjustments until the sample is completely aligned with the preset azimuth angle. This method can effectively avoid manual alignment errors and has a high degree of automation, making the entire experimental process more efficient and reliable.

[0047] The second aspect of the present application relates to a sample pre-alignment system for angular-resolved polarization scattering measurement, including: at least one memory for storing a computer program; at least one processor for executing the program stored in the memory, and when the program stored in the memory is executed, the processor is used to execute the alignment method as described in the first aspect.

[0048] It can be understood that the detailed function implementation of the above-mentioned various units / modules can be referred to the introduction in the foregoing method embodiments, and will not be elaborated herein.

[0049] It should be understood that the above-mentioned device is used to execute the method in the above-mentioned embodiments. For the corresponding program modules in the device, their implementation principles and technical effects are similar to those described in the above method. The working process of the device can refer to the corresponding process in the above method, and will not be elaborated herein.

[0050] Based on the method in the above-mentioned embodiments, the embodiments of the present application provide an electronic device, which may include: a processor (Processor), a communication interface (Communications Interface), a memory (Memory), and a communication bus. Among them, the processor, the communication interface, and the memory communicate with each other through the communication bus. The processor can call the logical instructions in the memory to execute the method in the above-mentioned embodiments.

[0051] In addition, when the logical instructions in the above-mentioned memory are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of this application.

[0052] Based on the method in the above-mentioned embodiments, an embodiment of this application provides a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer program runs on a processor, it causes the processor to execute the method in the above-mentioned embodiments.

[0053] Based on the method in the above-mentioned embodiments, an embodiment of this application provides a computer program product. When the computer program product runs on a processor, it causes the processor to execute the method in the above-mentioned embodiments.

[0054] It can be understood that the processor in the embodiments of this application may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0055] The method steps in the embodiments of this application can be implemented in a hardware manner or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, and the software modules can be stored in a random access memory (RAM), flash memory, read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), registers, hard disks, removable hard disks, CD-ROMs, or any other form of storage medium well-known in the art. An exemplary storage medium is coupled to the processor, enabling the processor to read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an ASIC.

[0056] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions described in the embodiments of this application are generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center in a wired manner (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or a wireless manner (such as infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that the computer can access or a data storage device such as a server or data center that includes one or more integrated available media. The available medium can be a magnetic medium (such as a floppy disk, hard disk, magnetic tape), an optical medium (such as a DVD), or a semiconductor medium (such as a solid state disk (SSD)).

[0057] It can be understood that the various numerical numbers involved in the embodiments of this application are only for the convenience of description and are not used to limit the scope of the embodiments of this application.

[0058] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A sample pre-alignment method for angle-resolved polarization scattering measurement, characterized in that: include: S1. Obtaining a diffraction image of a rectangular grating sample in a defocused state; S2. After preprocessing the diffraction image, the zero-order light, the positive first-order diffraction light and the negative first-order diffraction light are detected using geometric features; S3. extract the centroids of the zero-order light, the positive first-order diffracted light, and the negative first-order diffracted light respectively, and construct a first vector from the centroid of the zero-order light to the centroid of the positive first-order diffracted light, and a second vector from the centroid of the zero-order light to the centroid of the negative first-order diffracted light; S4. Calculate the angles between the first vector, the second vector and the horizontal direction respectively, take the average of the two angles as the actual azimuth, calculate the difference between the actual azimuth and the preset azimuth as the azimuth deviation, and the azimuth deviation is used to guide the rotational adjustment of the rotational translation stage until the sample is completely aligned with the preset azimuth.

2. The alignment method according to claim 1, characterized in that: The resolution of the diffraction image is above 2000x2000 pixels to ensure the clarity of the diffraction light spots.

3. The alignment method according to claim 1, characterized in that: In step S2, the preprocessing is to perform a binarization operation on the diffraction image.

4. The alignment method according to claim 1, characterized in that: In step S2, a threshold determination method or a geometric feature rule method is used to detect zero-order light, positive first-order diffraction light, and negative first-order diffraction light.

5. The alignment method according to claim 1, characterized in that: In step S3, the connected regions are marked using a region marking method, and the coordinates of each connected region are extracted by calculating the centroid of each connected region.

6. The alignment method according to claim 1, characterized in that: In step S4, the inverse tangent function is used according to the difference in the centroid coordinates Calculate the angle: in, , are the deviations of the zero-order light and the positive first-order diffracted light in the horizontal and vertical directions respectively.

7. A sample pre-alignment system for angle-resolved polarization scattering measurement, characterized in that: include: at least one memory for storing a computer program; At least one processor is used to execute the program stored in the memory. When the program stored in the memory is executed, the processor is used to execute the alignment method according to any one of claims 1 to 6.

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