Interference fringe period determination method and device and electronic equipment

Abstract

The invention discloses an interference fringe period determination method and apparatus, and an electronic device. The method comprises the steps of obtaining an interference image obtained by performing transverse scanning on a standard sample piece by a transverse scanning interference measurement system; gradient energy of the interference image in different directions is calculated, and the direction where the maximum gradient energy is located is determined as the interference fringe direction of the transverse scanning interference measurement system; performing region division on the interference image along a direction perpendicular to the interference fringes to obtain a plurality of sub-regions; determining a spectrum distribution diagram of the interference image according to the gray data of the plurality of sub-regions; acquiring a peak position of the spectrum distribution diagram, and determining an interference fringe period of the transverse scanning interference measurement system according to the peak position; the direction of the maximum gradient energy value is determined as the interference fringe direction of the transverse scanning interference measurement system, so that the reliability of region division of the interference image is ensured; the interference fringe period is determined according to the peak value position, so that the interference fringe period is automatically, accurately and quickly determined.

Description

Technical Field

[0001] This invention relates to the field of precision optical measurement technology, specifically to a method, apparatus, and electronic device for determining the period of interference fringes. Background Technology

[0002] In recent years, micro- and nano-scale three-dimensional topography measurement has played a crucial role in fields such as semiconductors and biomedicine. Lateral scanning interferometry uses a tilted reference mirror to acquire images of a moving sample at regular intervals. A large field of view and phase shift acquisition can be completed in a single scan, enabling continuous phase imaging of moving samples. This technique features a large field of view, high speed, non-contact operation, and high resolution. During measurement, the lateral movement of the sample generates a longitudinal phase change, which can be demodulated using spatiotemporal signal conversion and the phase shift method. Generally, the phase shift method requires a longitudinal phase shift of π / 2 between adjacent interferograms. If the phase shift is too small, it introduces significant noise; if it is too large, it leads to signal loss and distortion, and may even cause algorithm failure. To ensure the phase shift between adjacent interferograms is optimal, the interference fringe period needs to be calibrated to control the lateral movement.

[0003] However, due to unavoidable external system factors such as instrument noise and unstable light source in the transverse scanning interferometry system, problems such as decreased contrast and low signal-to-noise ratio occur in the interferogram used for interferometric fringe period calibration. Since the quality of the interferogram is directly related to the reliability of the interferometric fringe period, the reliability of the interferometric fringe period is low due to the influence of external systems on the transverse scanning interferometry system. Furthermore, since the transverse scanning interferometry system is in a dynamically changing environment, it is also necessary to dynamically acquire and correct the interferometric fringe period in order to reduce measurement deviation and improve the quality of measurement data.

[0004] Therefore, in the process of performing transverse scanning interferometry, existing technologies require the rapid and accurate determination of the interference fringe period of the transverse scanning interferometry system. Summary of the Invention

[0005] This invention provides a method, apparatus, and electronic device for determining the fringe period of an interference system, which aims to quickly and accurately determine the fringe period of a transverse scanning interference system.

[0006] To address the aforementioned technical problems, the embodiments of the present invention provide the following technical solutions: A method for determining the period of interference fringes, comprising: Acquire the interferometric image obtained by the transverse scanning interferometry system performing a transverse scan on a standard sample; Calculate the gradient energy of the interferometric image in different directions, and determine the direction where the maximum gradient energy is located as the direction of the interference fringes of the transverse scanning interferometry system; The interference image is divided into multiple sub-regions along the direction perpendicular to the interference fringes; The spectral distribution of the interference image is determined based on the grayscale data of the multiple sub-regions; The peak position of the spectrum distribution is obtained, and the interference fringe period of the transverse scanning interferometry system is determined based on the peak position.

[0007] Optionally, determining the spectral distribution map of the interferometric image based on the grayscale data of the plurality of sub-regions includes: Calculate the mean gray value of each sub-region, and determine the one-dimensional gray value signal of the interference image along the direction of the interference fringes based on the mean gray value; The DC component of the one-dimensional grayscale signal is removed and a discrete Fourier transform is performed to obtain the spectral distribution of the interference image.

[0008] Optionally, obtaining the peak position of the spectral distribution map and determining the interference fringe period of the transverse scanning interferometry system based on the peak position includes: Obtain the initial peak position of the spectrum distribution map; Interpolation and fitting are performed on the neighborhood of the initial peak position to obtain a continuous spectral distribution map of the peak neighborhood, and the peak position is determined based on the continuous spectral distribution map of the peak neighborhood. Obtain the sampling interval and length of the one-dimensional grayscale signal; The frequency corresponding to the peak position is determined based on the peak position, the sampling interval, and the length. The period of the interference fringes is determined based on the frequency of the peak position.

[0009] Optionally, the process of dividing the interference image into multiple sub-regions along a direction perpendicular to the interference fringes includes: Obtain the target region of the interference image; Using the direction perpendicular to the interference fringes as the cutting direction, the target area is uniformly divided into multiple narrow sub-regions along the cutting direction; In this configuration, the long side of each sub-region is perpendicular to the direction of the interference fringes.

[0010] Optionally, calculating the gradient energy of the interferometric image in different directions includes: The interference image is subjected to contrast enhancement and filtering processing to obtain the grayscale data of the interference image; The gradient energy of the interferometric image in different directions is calculated based on the gradient of the grayscale data in different directions.

[0011] Optionally, the step of performing contrast enhancement and filtering processing on the interference image to obtain grayscale data of the interference image includes: Based on the image features of the interference image, the interference image is adaptively divided into multiple interference image regions; Contrast-limited histogram equalization is performed on each interference image region to obtain a grayscale transformation function that includes detailed contrast features; The grayscale data of the interference image is obtained by fusing the grayscale transformation function of adjacent interference image regions through bilinear interpolation.

[0012] Optionally, the contrast enhancement processing of the interference image includes: The interference image is denoised by wavelet transform to obtain the denoised interference image; High-frequency noise in the denoised interference image is suppressed by a soft thresholding function to obtain an interference image with enhanced contrast.

[0013] Optionally, determining the spectral distribution of the interferometric image based on the grayscale data of the plurality of sub-regions further includes: When the spectrum distribution map has sidelobe interference, a Hanning window is applied to the spectrum distribution map to obtain a smooth spectrum distribution map.

[0014] An interference fringe period determination device, comprising: The interferometric image acquisition module is used to acquire the interferometric image obtained by the transverse scanning interferometry system scanning the standard sample in the transverse direction. The interference fringe direction determination module is used to calculate the gradient energy of the interference image in different directions and determine the direction where the maximum gradient energy is located as the interference fringe direction of the transverse scanning interferometry system. The region division module is used to divide the interference image into multiple sub-regions along the direction perpendicular to the interference fringes. A spectrum distribution determination module is used to determine the spectrum distribution map of the interference image based on the grayscale data of the multiple sub-regions; The interference fringe period determination module is used to obtain the peak position of the spectrum distribution map and determine the interference fringe period of the transverse scanning interferometry system based on the peak position.

[0015] An electronic device includes a memory and a processor, the memory storing a computer program that, when executed by the processor, causes the processor to perform the following steps: Acquire the interferometric image obtained by the transverse scanning interferometry system performing a transverse scan on a standard sample; Calculate the gradient energy of the interferometric image in different directions, and determine the direction where the maximum gradient energy is located as the direction of the interference fringes of the transverse scanning interferometry system; The interference image is divided into multiple sub-regions along the direction perpendicular to the interference fringes; The spectral distribution of the interference image is determined based on the grayscale data of the multiple sub-regions; The peak position of the spectrum distribution is obtained, and the interference fringe period of the transverse scanning interferometry system is determined based on the peak position.

[0016] In this embodiment of the invention, the gradient energy of the interferometric image in different directions is calculated. Since the gradient energy reflects the drastic change in image grayscale, the direction where the maximum gradient energy is located is determined as the direction of the interference fringes of the transverse scanning interferometry system to ensure the reliability of the region division of the interferometric image. The interferometric image is divided into regions along the direction perpendicular to the interference fringes, and the spectral distribution map of the interferometric image is determined based on the grayscale data of multiple sub-regions. The period of the interference fringes of the transverse scanning interferometry system is determined based on the peak position. Since the grayscale data reflects the light intensity information of the interferometric image at different positions, the grayscale information in the spatial domain is converted to the frequency domain to obtain the spectral distribution map of the interferometric image, thereby realizing the automated and accurate determination of the period of the interference fringes of the transverse scanning interferometry system. In addition, since the process of determining the period of the interference fringes of the transverse scanning interferometry system only involves the calculation of the gradient energy of the interferometric image and the grayscale spectrum conversion, the period of the interference fringes can be obtained quickly. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of a scenario of an embodiment of the interference fringe period determination system provided in this invention. Figure 2 This is a schematic diagram of another embodiment of the interference fringe period determination system provided in this invention. Figure 3 This is a flowchart illustrating an embodiment of the interference fringe period determination method provided by the present invention. Figure 4 This is a schematic diagram of the result of the first embodiment of the interference image provided in this invention; Figure 5This is a schematic diagram of the result of the second embodiment of the interference image provided in the present invention; Figure 6 This is a schematic diagram showing the result of an embodiment of a one-dimensional grayscale signal provided by the present invention; Figure 7 The spectrum distribution provided in the embodiments of the present invention Figure 1 A schematic diagram illustrating the results of the embodiment; Figure 8 This is a schematic flowchart of an embodiment of the automatic calibration of the fringe period of a transverse scanning interferometry system provided by the present invention. Figure 9 This is a schematic diagram of an embodiment of the interference fringe period determination device provided in this invention. Figure 10 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 are within the scope of protection of the present invention.

[0020] In the following description, specific embodiments of the invention will be illustrated with reference to steps and symbols performed by one or more computers, unless otherwise stated. Therefore, these steps and operations will be referred to several times as being performed by a computer, and computer execution as referred to herein includes operations by a computer processing unit representing electronic signals of data in a structured format. This operation transforms the data or maintains it at a location in the computer's memory system, which can be reconfigured or otherwise alter the operation of the computer in a manner well known to those skilled in the art. The data structure maintained by the data is the physical location of the memory, which has specific characteristics defined by the data format. However, the principles of the invention described above are not intended to be limiting, and those skilled in the art will understand that many of the steps and operations described below can also be implemented in hardware.

[0021] The terms "module" or "unit" as used herein can be considered as software objects executing on the computing system. The different components, modules, engines, and services described herein can be considered as implementation objects on the computing system. The apparatus and methods described herein are preferably implemented in software, but can also be implemented in hardware, both of which are within the scope of this invention.

[0022] This invention provides a method, apparatus, and electronic device for determining the period of interference fringes.

[0023] Please see Figure 1 , Figure 1 This is a schematic diagram of a scenario from an embodiment of the interference fringe period determination system provided by the present invention. The interference fringe period determination system may include a client 100 and a server 200, which are connected via a network. The server 200 integrates an interference fringe period determination device. The server 200 may be a work platform server (i.e., a server loaded with a work platform), such as... Figure 1 In this embodiment of the invention, the server 200 is mainly used to acquire the interference image obtained by the transverse scanning interferometry system through transverse scanning of a standard sample; calculate the gradient energy of the interference image in different directions, and determine the direction where the maximum gradient energy is located as the direction of the interference fringes of the transverse scanning interferometry system; divide the interference image into regions along the direction perpendicular to the interference fringes to obtain multiple sub-regions; determine the spectral distribution map of the interference image based on the grayscale data of the multiple sub-regions; obtain the peak position of the spectral distribution map, and determine the period of the interference fringes of the transverse scanning interferometry system based on the peak position.

[0024] In this embodiment of the invention, the server 200 can be a standalone server, a server network, or a server cluster. For example, the server 200 described in this embodiment includes, but is not limited to, a computer, a network host, a single network server, a set of multiple network servers, or a cloud server composed of multiple servers. The cloud server is composed of a large number of computers or network servers based on cloud computing. In this embodiment of the invention, communication between the server and the client can be achieved through any communication method, including but not limited to, mobile communication based on the 3rd Generation Partnership Project (3GPP), Long Term Evolution (LTE), and Worldwide Interoperability for Microwave Access (WiMAX), or computer network communication based on the TCP / IP Protocol Suite (TCP / IP) and User Datagram Protocol (UDP).

[0025] It is understood that the client 100 used in this embodiment of the invention can be understood as a client device. A client device includes both receiving and transmitting hardware, that is, a device with receiving and transmitting hardware capable of performing bidirectional communication on a bidirectional communication link. Such a client device may include cellular or other communication devices, having a single-line display, a multi-line display, or a cellular or other communication device without a multi-line display. Specifically, the client 100 may be a desktop terminal or a mobile terminal, specifically a mobile phone, tablet computer, laptop computer, etc.

[0026] Those skilled in the art will understand that Figure 1 The application environment shown is merely one application scenario of the solution in this application and does not constitute a limitation on the application scenario of the solution in this application. Other application environments may include those that are more specific to this application. Figure 1 The number of servers shown, or the server network connectivity relationships, for example... Figure 1 Only one server and two clients are shown in the diagram. It is understood that the interference fringe period determination system may also include one or more other servers, and / or one or more clients connected to the server network, which is not limited here.

[0027] In some embodiments of the present invention, the working platform may be an enterprise office platform, such as WeChat for Business. Taking server 200 as an example, it may further include an enterprise office platform contact server, an enterprise office platform configuration management server, and a web management server. Enterprise users or developers can access the web management server using a web browser terminal to configure the field configuration information on the enterprise office platform configuration management server, and set and store the enterprise user information of enterprise employees of the enterprise office platform on the enterprise office platform contact server.

[0028] In addition, such as Figure 2 As shown, Figure 2 This is a schematic diagram of another embodiment of the interference fringe period determination system provided in this invention. The interference fringe period determination system may further include a storage terminal 300 for storing data, such as a storage object database. The object database stores object data, which may include application templates (such as approval templates, attendance templates, and other application templates), file data (such as Word files, Excel files, or PPT files in various formats), image data (such as images in various formats such as jpg, png, and bmp), and other types of data. Correspondingly, the object database may also be divided into multiple types of data, such as an application database, a file database, or an image database.

[0029] It should be noted that, Figure 1-2The schematic diagram of the interference fringe period determination system shown is merely an example. The interference fringe period determination system and scenario described in the embodiments of the present invention are for the purpose of more clearly illustrating the technical solutions of the embodiments of the present invention, and do not constitute a limitation on the technical solutions provided by the embodiments of the present invention. As those skilled in the art will know, with the evolution of the interference fringe period determination system and the emergence of new business scenarios, the technical solutions provided by the embodiments of the present invention are also applicable to similar technical problems.

[0030] The following detailed description is based on specific embodiments.

[0031] In this embodiment, the description will be from the perspective of the interference fringe period determination device, which can be integrated into the server 200.

[0032] This invention provides a method for determining the period of interference fringes. Please refer to [link / reference]. Figure 3 , Figure 3 A flowchart illustrating an embodiment of the interference fringe period determination method provided by this invention includes: S301: Acquire the interferometric image obtained by the transverse scanning interferometry system performing a transverse scan on a standard sample; In one specific embodiment, the transverse scanning interferometry system is a precision optical measurement device. Its core principle is to generate interference signals through the relative displacement of a tilted reference mirror and a moving sample, thereby achieving large-scale three-dimensional topographic measurement. The system generates longitudinal phase changes by moving the sample laterally, and demodulates the phase information using spatiotemporal signal conversion and phase-shifting methods. The system employs a tilted reference mirror structure, enabling large-field-of-view scanning and phase-shifting acquisition in a single scan, supporting continuous phase imaging of moving samples. Its key components include a displacement stage (for controlling the lateral movement of the sample), a high-precision camera (for acquiring interferometric images), and an optical reference mirror system.

[0033] A standard sample refers to a planar sample (such as an optical flat plate or polished silicon wafer) with no obvious changes in surface structure. Its surface roughness must meet the optical flatness requirements of λ / 10 (λ is the wavelength of the light source). Such a sample serves as a reference standard and can generate stable and uniform interference fringes.

[0034] Lateral scanning is a precision optical measurement technique whose core principle is to acquire phase information by combining lateral movement of the sample with tilting of a reference mirror. Specifically, lateral scanning interferometry utilizes a combination of tilted reference mirror and lateral movement of the sample to complete a large field-of-view measurement in a single scan. Continuous interferometric image acquisition is achieved by moving the sample stage, and phase information is demodulated using spatiotemporal signal conversion and phase-shifting methods.

[0035] An interferometric image is a two-dimensional grayscale image with alternating bright and dark fringes formed by the coherent superposition of two light waves (reference light and measurement light) in interferometric measurement technology.

[0036] S302: Calculate the gradient energy of the interferometric image in different directions, and determine the direction of the maximum gradient energy as the direction of the interference fringes of the transverse scanning interferometry system; In one specific embodiment, gradient energy is used to describe how quickly energy changes with spatial location in a system or field. It is represented by a gradient vector, whose direction points to the direction of the fastest energy change, and whose magnitude represents the rate of energy change in that direction.

[0037] Interference fringes are alternating bright and dark fringes formed when two or more light waves meet and overlap. They are a manifestation of interference phenomena, and their distribution is closely related to the optical path difference and the properties of the medium.

[0038] The direction of interference fringes is an important observational feature in interference phenomena, and its directionality depends on the specific experimental setup. In this embodiment, the direction of interference fringes serves as the fundamental directional reference for subsequent signal processing. By extracting an analysis region perpendicular to the fringe direction, this orthogonality ensures that the analysis region can completely capture the periodic characteristics of the fringes, avoiding signal distortion caused by oblique truncation.

[0039] S303: Divide the interference image into regions along the direction perpendicular to the interference fringes to obtain multiple sub-regions; It should be noted that since interference fringes reflect important information such as phase changes during the measurement process, dividing the region along the direction perpendicular to the interference fringes makes the distribution of key information such as phase in the divided sub-regions more regular. When determining the spectral distribution map and finally determining the interference fringe period based on the grayscale data of the sub-regions, it is possible to better extract key parameters from the information carried by the interference fringes, which is conducive to the accurate analysis and processing of interference images and is closely related to the physical process and inherent laws of interferometry.

[0040] Therefore, by dividing the interference image into regions along the direction perpendicular to the interference fringes, the periodicity and phase information of the interference fringes can be precisely analyzed in a targeted manner, ensuring data consistency within each sub-region and thus improving overall measurement accuracy and data processing efficiency. This partitioning strategy not only optimizes the information extraction process but also enhances the system's ability to resolve complex interference patterns, laying a solid foundation for subsequent high-precision measurements and applications.

[0041] S304: Determine the spectral distribution of the interference image based on the grayscale data of multiple sub-regions; In one specific embodiment, grayscale data refers to the brightness value of each pixel in the interference image, which is the core input parameter for image processing and analysis.

[0042] A spectral distribution map is a visual representation of an interferometric image whose spatial domain information is converted into the frequency domain through Fourier transform.

[0043] S305: Obtain the peak position of the spectrum distribution and determine the interference fringe period of the transverse scanning interferometry system based on the peak position.

[0044] In one specific embodiment, the peak position refers to the frequency point where the energy is most concentrated in the spectral distribution diagram, and its physical meaning corresponds to the fundamental frequency component of the interference fringes.

[0045] The period of interference fringes refers to the spatial distance between adjacent bright or dark fringes, and this period parameter directly affects the accuracy of phase shift.

[0046] In this embodiment of the invention, the gradient energy of the interferometric image in different directions is calculated. Since the gradient energy reflects the drastic change in image grayscale, the direction where the maximum gradient energy is located is determined as the direction of the interference fringe of the transverse scanning interferometry system, thus ensuring the reliability of region division of the interferometric image based on the direction of the interference fringe. The interferometric image is divided into regions along the direction perpendicular to the direction of the interference fringe, and the spectral distribution map of the interferometric image is determined based on the grayscale data of multiple sub-regions. The period of the interference fringe of the transverse scanning interferometry system is determined based on the peak position. Since the grayscale data reflects the light intensity information of the interferometric image at different positions, the grayscale information in the spatial domain is converted to the frequency domain to obtain the spectral distribution map of the interferometric image, thereby realizing the automated and accurate determination of the period of the interference fringe of the transverse scanning interferometry system. In addition, since the process of determining the period of the interference fringe of the transverse scanning interferometry system only involves the calculation of the gradient energy of the interferometric image and the grayscale spectrum conversion, the period of the interference fringe can be obtained quickly.

[0047] In one specific embodiment, in S301, when acquiring the interferometric image of the standard sample in the transverse scanning interferometry system (PSI or VSI mode), in order to avoid differences in the quality of the interferometric image due to environmental differences (such as fringe distortion or increased noise), and to ensure the consistency of the physical conditions between the calibration data of the transverse scanning interferometry system and the actual measurement data, it is necessary to ensure that the working environment of the transverse scanning standard sample is completely consistent with the working environment of the transverse scanning interferometry system in actual operation.

[0048] In one specific embodiment, in S302, in order to determine the direction of the interference fringes of the transverse scanning interferometry system, the direction of the interference fringes is automatically identified by the gradient energy of the interference image in different directions.

[0049] The steps for calculating the gradient energy of the interferometric image in different directions include: performing contrast enhancement and filtering processing on the pixels of the interferometric image to obtain grayscale data of the interferometric image; and calculating the gradient energy of the interferometric image in different directions based on the gradient of the grayscale data in different directions.

[0050] In one specific embodiment, the interference image is subjected to contrast enhancement and filtering processing to obtain grayscale data of the interference image. Specifically, this includes: adaptively dividing the interference image into multiple interference image regions based on its image features; performing contrast-limited histogram equalization on each interference image region to obtain a grayscale transformation function containing detail contrast features; and fusing the grayscale transformation functions of adjacent interference image regions through bilinear interpolation to obtain grayscale data of the interference image.

[0051] It should be noted that in the process of adaptively dividing an interferometric image into regions based on its image characteristics, the size, shape, and number of regions can be determined based on the required data processing precision. For example, when the data processing precision requirement is high, the interferometric image is divided into finer regions, resulting in a larger number of regions. Furthermore, the shape of the regions can be adjusted as needed; they can be regular squares, circles, or even irregularly divided based on the characteristics of the interferometric image itself. No specific limitations are imposed here; the choice is based on meeting actual requirements. On the other hand, the size, shape, and number of regions can also be determined based on different image characteristics. For example, if certain parts of the image are rich in detail, the division may be finer; if the overall features are relatively uniform, the divided regions can be relatively larger.

[0052] In another specific embodiment, the contrast enhancement processing of the interference image may further include: performing wavelet transform denoising on the interference image to obtain a denoised interference image; and suppressing high-frequency noise in the denoised interference image through a soft threshold function to obtain a contrast-enhanced interference image.

[0053] Wavelet transform decomposes an image into different frequencies and directions, effectively separating useful interference fringe signals (typically in the low to mid-frequency domain) from high-frequency noise (such as speckle noise, detector noise, etc.). By filtering out or significantly attenuating the noise-contributing portions of the high-frequency subband coefficients, the random noise level of the denoised image is effectively suppressed.

[0054] The soft threshold function shrinks coefficients above the threshold instead of setting them to zero, further smoothing residual high-frequency noise and effectively reducing "ringing" or artifact effects (especially near the edges of stripes). It further suppresses high-frequency noise on the basis of denoising.

[0055] Please see Figure 4 , Figure 4 This is a schematic diagram of the result of the first embodiment of the interference image provided in this invention. The interference image is directly acquired and has not undergone contrast enhancement or filtering.

[0056] Please see Figure 5 , Figure 5 This is a schematic diagram of the result of the second embodiment of the interference image provided in this invention. The grayscale data of the interference image is obtained by performing contrast enhancement and filtering processing on the pixels of the interference image. This is to intuitively demonstrate the difference between the two images. Figure 4 The difference, Figure 5 It is still a complete interference image.

[0057] In this embodiment, by significantly reducing background noise and specifically suppressing noise near the edges of the stripes (including high-frequency components) (soft thresholding), the effective interference signal (i.e., stripes) becomes more prominent relative to the background, significantly improving the quality and interpretability of the interference image.

[0058] Histogram equalization refers to a method that enhances image contrast by redistributing pixel values ​​to make the gray-level distribution of an image more uniform. Contrast limiting, on the other hand, refers to a method that limits the excessive enhancement of gray levels during histogram equalization to avoid localized overexposure or underexposure, making the enhancement effect more in line with actual needs and better preserving image details.

[0059] In this embodiment, by performing contrast-limited histogram equalization on each interference image region, targeted contrast adjustment can be made for the local features of different regions, taking into account the detail display of different parts of the image, and obtaining a grayscale transformation function containing detailed contrast features for each interference image region.

[0060] Bilinear interpolation calculates the target pixel value by linear weighting when the gray values ​​of four adjacent points are known (obtained from the gray-level transformation function of adjacent regions). This smoothly transitions the gray-level changes between different regions, avoids the block effect caused by region division, and makes the enhanced image have a better overall visual effect, maintaining the continuity and naturalness of the image.

[0061] In this embodiment, by fusing the grayscale transformation functions of adjacent interference image regions, the information of adjacent regions is fully utilized, the relationship between local and global factors is comprehensively considered, the contrast enhancement effect is further optimized, and the rationality and coherence of the grayscale data of the interference image are improved.

[0062] Among them, for pixels ( x , y Grayscale values ​​after contrast enhancement Represented as:

[0063]

[0064] The grayscale values ​​of the pixels in the input interference image, ( x i , y i ) is the distance to the target pixel ( x , y The centers of the four nearest rectangular regions, d x , d y The dimensions of the rectangular area are... G(x , y) For target pixels (x , y) Grayscale values ​​after contrast enhancement w ij These are weighting coefficients. express.

[0065] Obtain the grayscale data of the interference image Then, by solving for the gradients in different directions of the image and calculating the sum of squares of the gradient magnitudes, the gradient energy of the interferometric image in different directions is obtained. :

[0066]

[0067] in, G s For along the direction s The gradient.

[0068] In this embodiment, the direction corresponding to the maximum energy is located by calculating the sum of squares of the gradient magnitudes of the fringes in different directions. Since this method is sensitive to the response of the fringes edges, it can effectively avoid noise interference and achieve sub-pixel level direction recognition accuracy. In addition, in the process of determining the direction of the interference fringes, all steps of image preprocessing, gradient calculation, energy calculation and direction determination do not require manual intervention, and the process is fully automated.

[0069] Furthermore, for non-uniform illumination in the interference image (such as vignetting at the edges and bright spots at the center), histogram equalization is performed in partitions to avoid overexposure / underexposure caused by global processing; weak fringe areas (such as low-contrast areas) are enhanced in partitions while preserving high-frequency details (such as fringe edge sharpness); and block artifacts are avoided by smoothly transitioning the grayscale transformation functions of adjacent partitions, ensuring global grayscale consistency. In summary, through adaptive image enhancement and directional gradient analysis, high-quality grayscale data is obtained, separating the fringes from the background and significantly improving the accuracy and robustness of interference fringe direction recognition.

[0070] In one specific embodiment, in S303, after determining the direction of the interference fringes, the interference image is divided into regions along the direction perpendicular to the interference fringes to obtain multiple sub-regions. Specifically, this includes: acquiring the target region of the interference image; dividing the target region into multiple elongated sub-regions along the cutting direction perpendicular to the direction of the interference fringes; wherein the long side of each sub-region is perpendicular to the direction of the interference fringes.

[0071] It should be noted that, generally, multiple narrow sub-regions are grouped into a single column, meaning that there is only one column of sub-regions within the target area.

[0072] In this embodiment, since any part of the interferometric image exhibits the same characteristics, by selectively filtering out target regions in the interferometric image, the complexity of the data can be reduced, and the reliability of the analysis results can be guaranteed. Furthermore, by forcing the long side of the sub-region to be perpendicular to the fringe direction, it is ensured that the fringes in each sub-region are arranged in a single direction (usually parallel to the short side), avoiding local period calculation deviations caused by fringe tilting or bending, and providing standardized input with consistent direction for subsequent frequency domain analysis such as Fourier transform.

[0073] In one specific embodiment, in S304, in order to determine the spectral distribution map of the interference image based on the grayscale data of multiple sub-regions, specifically: the grayscale mean of each sub-region is calculated, and the one-dimensional grayscale signal of the interference image along the direction of the interference fringes is determined based on the grayscale mean; the DC component is removed and the discrete Fourier transform is performed on the one-dimensional grayscale signal to obtain the spectral distribution map of the interference image.

[0074] It should be noted that the spectrum distribution diagram is a graph obtained by performing a Fourier transform on the grayscale signal of the interference fringes. Its horizontal axis represents the spatial frequency, and the vertical axis represents the intensity or amplitude of the corresponding frequency component.

[0075] In this embodiment, firstly, a two-dimensional interference image is divided into multiple sub-regions along the direction parallel to the interference fringes. The average gray value (gray mean) of each sub-region is calculated. Then, these gray mean values ​​are arranged in order according to the corresponding sub-region positions, forming a gray value variation curve along the direction of the interference fringes (usually perpendicular to the fringe gradient direction). That is, the one-dimensional gray signal of the interference image along the direction of the interference fringes reflects the spatial variation of the brightness (corresponding to light intensity) of the interference image along the direction of the interference fringes. Please refer to [link to previous document]. Figure 6 , Figure 6 This is a schematic diagram of the result of an embodiment of a one-dimensional grayscale signal provided by the present invention. Obviously, the one-dimensional grayscale signal can intuitively show the relationship between the pixel position and the grayscale value of the interference image.

[0076] Since the acquired interference signal typically contains a constant background brightness (DC component), it is superimposed on the AC signal reflecting actual physical changes. By removing the DC component from the one-dimensional grayscale signal, the components of the spectrum obtained after Fourier transform that are concentrated near zero frequency are eliminated or greatly reduced, thus more clearly highlighting the useful frequency components characterizing the fringe changes. A common method for DC component removal is to subtract the average value of the entire one-dimensional grayscale signal.

[0077] Then, after obtaining the one-dimensional grayscale signal along the direction of the interference fringes in the interference image, since one-dimensional grayscale signals are not convenient for data analysis, it is necessary to convert the time-domain data into frequency-domain data through discrete Fourier transform in order to obtain the spectral distribution map of the interference image. Specifically, a one-dimensional signal is selected... f(n) length N ≥512 is used to ensure spectral resolution; when removing the DC component, mean subtraction is used to avoid high-frequency signal distortion, resulting in the spectral distribution map of the interferometric image. Represented as:

[0078] in, N This represents the total number of sample points; n For discrete time indexes, n = 0, 1, 2, ..., N-1; Expressing the request The arithmetic mean, j The imaginary unit, k For discrete frequency indexes, k = 0, 1, 2, ..., N -1.

[0079] Furthermore, since the spectral distribution is symmetrical, in order to simplify the data processing, we take... |F(k) |The first or second half of the amplitude is used as the amplitude signal of the first-level spectrum. |F 1 (k)| Please see Figure 7 , Figure 7 The spectrum distribution provided in the embodiments of the present invention Figure 1 A schematic diagram of the results of the embodiment. Figure 7 The diagram visually illustrates the correspondence between spatial frequency and amplitude in an interference image. In Fourier spectrum analysis, pixel position is positively correlated with spatial frequency. Therefore, the peak position can be directly determined based on the spectrum distribution diagram.

[0080] Furthermore, when sidelobe interference exists in the spectral distribution map, a Hanning window is applied to the spectral distribution map to obtain a smoother spectral distribution map.

[0081] In one specific embodiment, sidelobe interference is a common phenomenon in Fourier transform spectrum analysis, specifically referring to the unwanted energy distribution that appears around the main peak in the signal spectrum. The sidelobe energy may mask the true peak value, causing frequency identification deviation.

[0082] By applying a Hanning window to the spectral distribution map, signal edges can be smoothed to reduce spectral leakage. After effectively suppressing sidelobe interference, the main lobe width can be increased to 1.5 times that of a rectangular window, while the sidelobe peak value is reduced to below -32dB of the main lobe, significantly improving peak detection accuracy.

[0083] In one specific embodiment, in S305, after obtaining the spectral distribution map, it is also necessary to obtain the peak position of the spectral distribution map in order to determine the interference fringe period of the transverse scanning interferometry system based on the peak position. Specifically: the initial peak position of the spectral distribution map is obtained; interpolation and fitting processing is performed on the neighborhood of the initial peak position to obtain a spectral distribution map with continuous peak neighborhood, and the peak position is determined based on the spectral distribution map with continuous peak neighborhood; the sampling interval and length of the one-dimensional grayscale signal are obtained; the frequency corresponding to the peak position is determined based on the peak position, sampling interval and length; and the interference fringe period is determined based on the frequency of the peak position.

[0084] Find the amplitude signal of the first-order spectrum | F 1( k After the peak position, in order to have more detailed and dense points when drawing the limited discrete spectrum distribution map, and finally obtain a smoother and more detailed visualization effect (enhanced visual "continuity"), it is necessary to interpolate and fit the neighborhood of the initial peak position to obtain a continuous spectrum distribution map of the peak neighborhood, so as to observe the peak position and its frequency more accurately.

[0085] Determining the peak position x m Then, based on the sampling interval of the one-dimensional grayscale signal ds and the length of the one-dimensional grayscale signal N Determine the frequency corresponding to the peak position f m The formula is:

[0086] Furthermore, the frequency corresponding to the peak position is negatively correlated with the number of pixels the interference fringe period occupies on the sensor. Specifically, the formula for calculating the fringe period T measured or calculated by the transverse scanning interferometry system is as follows:

[0087] Based on the pixel physical size and the magnification of the transverse scanning interferometry system, the above fringe period... T By performing a physical scale conversion, the true interference fringe period can be obtained. T' The calculation formula is:

[0088] in, M The magnification of the transverse scanning interferometry system. w This refers to the pixel size in a transverse scanning interferometry system.

[0089] In this embodiment, by performing data conversion on the grayscale signal of the transverse scanning interferometry system, pixel-level fringe periods can be obtained since the peak position is usually at the sub-pixel level with high precision. By performing physical scale conversion on the pixel-level fringe periods, the detection accuracy of the interference fringe periods of the transverse scanning interferometry system is greatly improved.

[0090] Furthermore, for automated calibration of the fringe period of the transverse scanning interferometry system, please refer to [link to relevant documentation]. Figure 8 , Figure 8 This is a flowchart illustrating an embodiment of the automatic calibration of the fringe period of a transverse scanning interferometry system provided by the present invention. In the transverse scanning interferometry system, a planar sample is fixedly installed on a displacement stage by vacuum adsorption to avoid vibration causing fringe shift and thus affecting the accuracy of the calculation results. Then, the detection interference image of the transverse scanning interferometry system is processed by the above-mentioned interference fringe period determination method to calculate the corresponding interference fringe period and transmit it to the displacement stage and camera, thereby realizing the automatic calibration of the fringe period of the transverse scanning interferometry system.

[0091] To facilitate better implementation of the interference fringe period determination method provided in the embodiments of the present invention, the present invention also provides an apparatus based on the above-described interference fringe period determination method. The meanings of the terms used are the same as in the above-described interference fringe period determination method, and specific implementation details can be found in the descriptions in the method embodiments.

[0092] Please see Figure 9 , Figure 9 This is a schematic diagram of an embodiment of the interference fringe period determination device provided in this invention. The interference fringe period determination device 900 may include: Interference image acquisition module 901 is used to acquire the interference image obtained by the transverse scanning interferometry system scanning the standard sample in the transverse direction. The interference fringe direction determination module 902 is used to calculate the gradient energy of the interference image in different directions and determine the direction where the maximum gradient energy is located as the interference fringe direction of the transverse scanning interferometry system. The region division module 903 is used to divide the interference image into regions along the direction perpendicular to the interference fringes, thereby obtaining multiple sub-regions; The spectrum distribution determination module 904 is used to determine the spectrum distribution of the interference image based on the grayscale data of multiple sub-regions; The interference fringe period determination module 905 is used to obtain the peak position of the spectrum distribution map and determine the interference fringe period of the transverse scanning interferometry system based on the peak position.

[0093] This invention also provides an electronic device, such as... Figure 10 As shown, Figure 10 This is a schematic diagram of the structure of an electronic device according to an embodiment of the present invention, specifically: The electronic device may include components such as a processor 1001 with one or more processing cores, a memory 1002 with one or more computer-readable storage media, a power supply 1003, and an input unit 1004. Those skilled in the art will understand that... Figure 10 The electronic device structure shown does not constitute a limitation on the electronic device and may include more or fewer components than shown, or combine certain components, or have different component arrangements. Wherein: The processor 1001 is the control center of the electronic device. It connects various parts of the electronic device via various interfaces and lines. By running or executing software programs and / or modules stored in the memory 1002, and by calling data stored in the memory 1002, it performs various functions and processes data, thereby providing overall monitoring of the electronic device. Optionally, the processor 1001 may include one or more processing cores; preferably, the processor 1001 may integrate an application processor and a modem processor. The application processor mainly handles the operation of the storage medium, user interface, and application programs, while the modem processor mainly handles wireless communication. It is understood that the modem processor may not be integrated into the processor 1001.

[0094] The memory 1002 can be used to store software programs and modules. The processor 1001 executes various functional applications and data processing by running the software programs and modules stored in the memory 1002. The memory 1002 may mainly include a program storage area and a data storage area. The program storage area may store applications required for operating the storage medium and at least one function (such as sound playback function, image playback function, etc.); the data storage area may store data created according to the use of the electronic device. In addition, the memory 1002 may include high-speed random access memory and may also include non-volatile memory, such as at least one disk storage device, flash memory device, or other volatile solid-state storage device. Accordingly, the memory 1002 may also include a memory controller to provide the processor 1001 with access to the memory 1002.

[0095] The electronic device also includes a power supply 1003 that supplies power to various components. Preferably, the power supply 1003 can be logically connected to the processor 1001 through a power management storage medium, thereby enabling functions such as charging, discharging, and power consumption management through the power management storage medium. The power supply 1003 may also include one or more DC or AC power supplies, recharge storage media, power fault detection circuits, power converters or inverters, power status indicators, and other arbitrary components.

[0096] The electronic device may also include an input unit 1004, which can be used to receive input digital or character information, and generate keyboard, mouse, joystick, optical or trackball signal inputs related to user settings and function control.

[0097] Although not shown, the electronic device may also include a display unit, etc., which will not be described in detail here. Specifically, in this embodiment, the processor 1001 in the electronic device loads the executable files corresponding to the processes of one or more applications into the memory 1002 according to the following instructions, and the processor 1001 runs the applications stored in the memory 1002 to realize various functions, as follows: The process involves acquiring an interference image obtained by transverse scanning of a standard sample using a transverse scanning interferometry system; calculating the gradient energy of the interference image in different directions and determining the direction of the maximum gradient energy as the direction of the interference fringes of the transverse scanning interferometry system; dividing the interference image into multiple sub-regions along the direction perpendicular to the interference fringes; determining the spectral distribution of the interference image based on the grayscale data of the multiple sub-regions; obtaining the peak position of the spectral distribution and determining the period of the interference fringes of the transverse scanning interferometry system based on the peak position.

[0098] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be performed by instructions, or by instructions controlling related hardware. These instructions can be stored in a computer-readable storage medium and loaded and executed by a processor.

[0099] Therefore, embodiments of the present invention provide a computer-readable storage medium storing a computer program thereon, the computer program being loaded by a processor to execute the steps in any of the interference fringe period determination methods provided in the embodiments of the present invention. For example, the computer program, when loaded by a processor, can execute the following steps: The process involves acquiring an interference image obtained by transverse scanning of a standard sample using a transverse scanning interferometry system; calculating the gradient energy of the interference image in different directions and determining the direction of the maximum gradient energy as the direction of the interference fringes of the transverse scanning interferometry system; dividing the interference image into multiple sub-regions along the direction perpendicular to the interference fringes; determining the spectral distribution of the interference image based on the grayscale data of the multiple sub-regions; obtaining the peak position of the spectral distribution and determining the period of the interference fringes of the transverse scanning interferometry system based on the peak position.

[0100] For details on the implementation of each of the above operations, please refer to the previous examples, which will not be repeated here.

[0101] The computer-readable storage medium may include: read-only memory (ROM), random access memory (RAM), disk or optical disk, etc.

[0102] Since the computer program stored in the computer-readable storage medium can execute the steps in any of the interference fringe period determination methods provided in the embodiments of the present invention, the beneficial effects that any of the interference fringe period determination methods provided in the embodiments of the present invention can achieve can be realized, as detailed in the preceding embodiments, and will not be repeated here.

[0103] The foregoing has provided a detailed description of the interference fringe period determination method, apparatus, and electronic device provided by the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for determining the period of interference fringes, characterized in that, include: Acquire the interferometric image obtained by the transverse scanning interferometry system performing a transverse scan on a standard sample; Calculate the gradient energy of the interferometric image in different directions, and determine the direction where the maximum gradient energy is located as the direction of the interference fringes of the transverse scanning interferometry system; The interference image is divided into multiple sub-regions along the direction perpendicular to the interference fringes; The spectral distribution of the interference image is determined based on the grayscale data of the multiple sub-regions; The peak position of the spectrum distribution is obtained, and the interference fringe period of the transverse scanning interferometry system is determined based on the peak position.

2. The method for determining the period of interference fringes according to claim 1, characterized in that, Determining the spectral distribution map of the interference image based on the grayscale data of the multiple sub-regions includes: Calculate the mean gray value of each sub-region, and determine the one-dimensional gray value signal of the interference image along the direction of the interference fringes based on the mean gray value; The DC component of the one-dimensional grayscale signal is removed and a discrete Fourier transform is performed to obtain the spectral distribution of the interference image.

3. The method for determining the period of interference fringes according to claim 2, characterized in that, The step of obtaining the peak position of the spectral distribution map and determining the interference fringe period of the transverse scanning interferometry system based on the peak position includes: Obtain the initial peak position of the spectrum distribution map; Interpolation and fitting are performed on the neighborhood of the initial peak position to obtain a continuous spectral distribution map of the peak neighborhood, and the peak position is determined based on the continuous spectral distribution map of the peak neighborhood. Obtain the sampling interval and length of the one-dimensional grayscale signal; The frequency corresponding to the peak position is determined based on the peak position, the sampling interval, and the length. The period of the interference fringes is determined based on the frequency of the peak position.

4. The method for determining the period of interference fringes according to claim 1, characterized in that, The interference image is divided into regions along a direction perpendicular to the interference fringes to obtain multiple sub-regions, including: Obtain the target region of the interference image; Using the direction perpendicular to the interference fringes as the cutting direction, the target area is uniformly divided into multiple narrow sub-regions along the cutting direction; In this configuration, the long side of each sub-region is perpendicular to the direction of the interference fringes.

5. The method for determining the period of interference fringes according to claim 1, characterized in that, The calculation of the gradient energy of the interferometric image in different directions includes: The interference image is subjected to contrast enhancement and filtering processing to obtain the grayscale data of the interference image; The gradient energy of the interferometric image in different directions is calculated based on the gradient of the grayscale data in different directions.

6. The method for determining the period of interference fringes according to claim 5, characterized in that, The step of performing contrast enhancement and filtering processing on the interference image to obtain grayscale data of the interference image includes: Based on the image features of the interference image, the interference image is adaptively divided into multiple interference image regions; Contrast-limited histogram equalization is performed on each interference image region to obtain a grayscale transformation function that includes detailed contrast features; The grayscale data of the interference image is obtained by fusing the grayscale transformation function of adjacent interference image regions through bilinear interpolation.

7. The method for determining the period of interference fringes according to claim 5, characterized in that, The contrast enhancement processing of the interference image includes: The interference image is denoised by wavelet transform to obtain the denoised interference image; High-frequency noise in the denoised interference image is suppressed by a soft thresholding function to obtain an interference image with enhanced contrast.

8. The method for determining the period of interference fringes according to claim 1, characterized in that, Determining the spectral distribution map of the interference image based on the grayscale data of the multiple sub-regions further includes: When the spectrum distribution map has sidelobe interference, a Hanning window is applied to the spectrum distribution map to obtain a smooth spectrum distribution map.

9. A device for determining the period of interference fringes, characterized in that, include: The interferometric image acquisition module is used to acquire the interferometric image obtained by the transverse scanning interferometry system scanning the standard sample in the transverse direction. The interference fringe direction determination module is used to calculate the gradient energy of the interference image in different directions and determine the direction where the maximum gradient energy is located as the interference fringe direction of the transverse scanning interferometry system. The region division module is used to divide the interference image into multiple sub-regions along the direction perpendicular to the interference fringes. A spectrum distribution determination module is used to determine the spectrum distribution map of the interference image based on the grayscale data of the multiple sub-regions; The interference fringe period determination module is used to obtain the peak position of the spectrum distribution map and determine the interference fringe period of the transverse scanning interferometry system based on the peak position.

10. An electronic device, characterized in that, It includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor causes the processor to perform the following steps: Acquire the interferometric image obtained by the transverse scanning interferometry system performing a transverse scan on a standard sample; Calculate the gradient energy of the interferometric image in different directions, and determine the direction where the maximum gradient energy is located as the direction of the interference fringes of the transverse scanning interferometry system; The interference image is divided into multiple sub-regions along the direction perpendicular to the interference fringes; The spectral distribution of the interference image is determined based on the grayscale data of the multiple sub-regions; The peak position of the spectrum distribution is obtained, and the interference fringe period of the transverse scanning interferometry system is determined based on the peak position.

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