Laser interferometer and measurement method thereof, optical detection system and storage medium

Abstract

The invention discloses a laser interferometer and a measurement method thereof, an optical detection system and a storage medium, and relates to the technical field of optical detection.In the laser interferometer, a first optical measurement element projects first measurement light to a measured grating according to a preset first incident direction angle; receiving a first interference pattern formed by diffracting the first measuring light through the measured grating; a second optical measuring element arranged symmetrically with the first optical measuring element projects second measuring light to the measured grating according to a second incident direction angle symmetrical with the first incident direction angle, and receives a second interference pattern formed by diffracting the second measuring light through the measured grating; and the imaging acquisition module is used for determining a measurement result of the measured grating according to the first interferogram and the second interferogram, so that the rapid measurement of the period uniformity of the large-size grating is realized on the premise of not sacrificing the measurement precision and non-destructiveness, and the detection requirements in industrial mass production are met.

Description

Technical Field

[0001] This application relates to the field of optical detection technology, and in particular to a laser interferometer and its measurement method, optical detection system and storage medium. Background Technology

[0002] As the industrial application of micro-nano optical components in consumer-grade AR (Augmented Reality) / XR (Extended Reality) and other fields continues to deepen, users have put forward higher requirements for the measurement accuracy, measurement efficiency and mass production applicability of micro-nano structures such as gratings in terms of periodic uniformity.

[0003] Currently, the industry primarily relies on optical microscopy, electron microscopy, and atomic force microscopy to measure the uniformity of grating periods. However, all of these methods have significant technical limitations. Optical microscopy can only perform qualitative observations and cannot achieve quantitative measurements; electron microscopy is a destructive method, requiring sample preparation and easily damaging the grating structure, affecting the accuracy of the measurement; while atomic force microscopy can perform quantitative measurements, it is extremely slow and only suitable for small-field-of-view inspections during the process development stage. In other words, none of these methods can achieve rapid, non-destructive, and quantitative measurements of large-size (e.g., cm²-scale) grating samples, failing to meet the real-time monitoring and quality inspection requirements of mass production.

[0004] Therefore, how to achieve rapid measurement of the periodic uniformity of large-size gratings without sacrificing measurement accuracy and non-destructiveness, so as to meet the detection requirements in industrial mass production, is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The main objective of this application is to provide a laser interferometer and its measurement method, optical detection system and storage medium, which aim to achieve rapid measurement of the periodic uniformity of large-size gratings without sacrificing measurement accuracy and non-destructiveness, so as to meet the detection requirements in industrial mass production.

[0006] To achieve the above objectives, this application proposes a laser interferometer, which includes: A first optical measuring element is configured to project a first measuring light onto the grating under test at a preset first incident direction angle, and to receive a first interference pattern formed by the diffraction of the first measuring light through the grating under test. A second optical measuring element is arranged symmetrically with the first optical measuring element. The second optical measuring element is configured to project a second measuring light onto the grating under test at a second incident direction angle symmetrical to the first incident direction angle, and to receive a second interference pattern formed by the diffraction of the second measuring light through the grating under test. An imaging acquisition module is provided, which is located on the imaging side of the first optical measuring element and the imaging side of the second optical measuring element. The imaging acquisition module is configured to determine the measurement result of the grating under test based on the first interferogram and the second interferogram.

[0007] In one embodiment, the first optical measuring element and the second optical measuring element are the same optical measuring structure, and the optical measuring structure is disposed on the grating period side of the grating under test; The optical measurement structure includes a laser source, a reflective optical element, and a reference optical element. The reflective optical element is disposed between the laser source and the reference optical element. The imaging side of the reflective optical element is disposed facing the imaging acquisition module, and the reference optical element is disposed close to the grating period side.

[0008] In one embodiment, the first incident direction angle is the Littoral angle corresponding to the +1 diffraction order of the grating under test, and the second incident direction angle is the Littoral angle corresponding to the -1 diffraction order of the grating under test.

[0009] In one embodiment, the imaging acquisition module includes: A first image acquisition unit is disposed on the imaging side of the first optical measurement element, and the first image acquisition unit is configured to acquire the first interferogram. The second image acquisition unit is disposed on the imaging side of the second optical measurement element, and the second image acquisition unit is configured to acquire the second interferogram; The processing unit is electrically connected to the first image acquisition unit and the second image acquisition unit, respectively, and is configured to determine the measurement result of the grating under test based on the first interferogram and the second interferogram.

[0010] Furthermore, this application also provides a measurement method for a laser interferometer, wherein the measurement method is applied to the laser interferometer described above, and the measurement method includes: After the first optical measuring element projects the first measuring light onto the grating under test at a preset first incident direction angle, a first interference pattern is obtained by diffracting the first measuring light through the grating under test. After the second optical measuring element projects a second measuring light onto the grating under test at a second incident direction angle symmetrical to the first incident direction angle, a second interference pattern is obtained by diffracting the second measuring light through the grating under test. The measurement results of the grating under test are determined based on the first interferogram and the second interferogram.

[0011] In one embodiment, the step of determining the measurement result of the grating under test based on the first interferogram and the second interferogram includes: A two-dimensional image coordinate system is constructed with the image widths of the first and second interferograms as the horizontal axis and the image heights of the first and second interferograms as the vertical axis. Based on the two-dimensional image coordinate system, the first horizontal axis phase distribution function of the first interferogram in the horizontal axis direction and the second horizontal axis phase distribution function of the second interferogram in the horizontal axis direction are determined respectively. The uniformity threshold of the grating under test is determined based on the first horizontal axis phase distribution function and the second horizontal axis phase distribution function, and the measurement result of the grating under test is determined based on the uniformity threshold.

[0012] In one embodiment, the step of determining the uniformity threshold of the grating under test based on the first horizontal axis phase distribution function and the second horizontal axis phase distribution function includes: Based on the first horizontal axis phase distribution function and the second horizontal axis phase distribution function, the cumulative periodic error of the grating under test along the grating periodic arrangement direction is determined; Based on the cumulative periodic error, perform differential processing to obtain all local periodic errors of the grating under test along the periodic arrangement direction of the grating, and count the number of local periodic errors that meet the preset error conditions among all the local periodic errors. The uniformity threshold of the grating under test is obtained based on the number of local periodic errors that meet the preset error conditions and the total number of all local periodic errors.

[0013] In one embodiment, the step of determining the measurement result of the grating under test based on the uniformity threshold includes: Detect whether the uniformity threshold exceeds a preset uniformity reference threshold; If the uniformity threshold does not exceed the uniformity reference threshold, then the measurement result of the grating under test is determined to be that the grating under test is unqualified. If the uniformity threshold exceeds the uniformity reference threshold, then the measurement result is determined to be a qualified grating under test. In addition, to achieve the above objectives, this application also proposes an optical detection system, which includes the laser interferometer described above; or, a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the steps of the measurement method of the laser interferometer as described above.

[0014] In addition, to achieve the above objectives, this application also proposes a computer storage medium storing a computer program that, when executed by a processor, implements the steps of the measurement method of the laser interferometer as described above.

[0015] The laser interferometer provided in this application enables rapid and quantitative measurement of the periodic uniformity of large-size gratings without sacrificing measurement accuracy and non-destructiveness, significantly improving the detection efficiency and applicability in the mass production process of gratings. Specifically, a first and second optical measuring element are symmetrically arranged to project a first measuring light and a second measuring light onto the grating under test at symmetrical first and second incident angles, respectively. Next, the first and second optical measuring elements receive the first and second measuring lights diffracted by the grating under test, forming a first interferogram and a second interferogram, respectively. This effectively avoids the problems of traditional optical microscopes, which can only perform qualitative observations and cannot achieve quantitative measurements, as well as the destructive, slow, or limited field-of-view issues of electron microscopes and atomic force microscopes. Subsequently, through imaging acquisition modules located on the imaging side of the first and second optical measuring elements, respectively, the measurement result of the grating under test is determined based on the acquired first and second interferograms. This overcomes the shortcomings of traditional measurement methods, which suffer from low measurement efficiency and limited applicability due to the inability to simultaneously acquire and integrate multi-angle diffraction information. Thus, while maintaining non-destructiveness and high precision, it supports rapid and quantitative measurement of large-size grating samples, significantly improving real-time monitoring and quality inspection capabilities in mass production scenarios and meeting the high-efficiency testing requirements in industrial applications. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the architecture of the laser interferometer involved in this application; Figure 2 This is a schematic diagram of the structure involved in the laser interferometer of this application; Figure 3 This is a two-dimensional phase distribution diagram related to the embodiments of this application; Figure 4 This is a diagram showing the net phase difference distribution involved in the embodiments of this application; Figure 5 This is a local periodic error distribution diagram involving the embodiments of this application; Figure 6 This is a flowchart illustrating the second embodiment of the measurement method of the laser interferometer in this application; Figure 7 This is a schematic diagram of the hardware operating environment involved in the device in this application.

[0017] Explanation of icon numbers: 10. First optical measuring element; 20. Second optical measuring element; 30. Imaging acquisition module; 100. Laser source; 200. Reflective optical element; 300. Reference optical element; 31. First image acquisition unit; 32. Second image acquisition unit; 33. Processing unit.

[0018] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0020] To better understand the technical solution of this application, a detailed description will be provided below in conjunction with the accompanying drawings and specific implementation methods.

[0021] Micro- and nano-optical components, such as diffraction gratings and superlenses, are being industrialized. In particular, waveguide components based on diffraction gratings have been applied to many consumer-grade AR (Augmented Reality) and XR (Extended Reality) products.

[0022] Measurement methods for micro / nano optical components typically include OM (Optical Microscope), SEM (Scanning Electron Microscope), and AFM (Atomic Force Microscope). OM cannot quantitatively represent the characteristics of micro / nano components and usually uses dark-field mode to qualitatively observe the uniformity of the fabrication. SEM is destructive, requiring sample preparation methods such as slicing and gold powder sputtering, and the photoresist structure undergoes structural changes under electron bombardment, making it difficult to guarantee measurement accuracy. AFM has an extremely slow testing speed and can only be used to develop process parameters. SEM and AFM are generally only used for quantitative measurements in very small fields of view (µm). 2 Micro- and nano-structures (at the micro- and nano-scale) cannot be measured in a single imaging session if they are relatively large (cm). 2 The macroscopic region (at the level of nanometers). Clearly, the three conventional measurement methods mentioned above are difficult to use for mass production monitoring. There is an urgent need to develop non-destructive, rapid, and quantitative measurement methods for micro / nano components to meet the measurement requirements of mass production.

[0023] Therefore, based on the technical shortcomings of the above three methods for measuring micro-nano components, the laser interferometer of this application is proposed. The solution of this application embodiment is as follows: A first optical measuring element and a second optical measuring element are symmetrically arranged to project a first measuring light and a second measuring light onto the grating under test at symmetrical first and second incident angles, respectively. Next, the first and second optical measuring elements receive the first and second measuring lights diffracted by the grating under test, respectively, forming a first interferogram and a second interferogram. This effectively avoids the problems of traditional optical microscopes, which can only perform qualitative observations and cannot achieve quantitative measurements, as well as the destructive, slow, or limited field-of-view problems of electron microscopes and atomic force microscopes. Subsequently, through imaging acquisition modules located on the imaging side of the first and second optical measuring elements, respectively, the measurement result of the grating under test is determined based on the acquired first and second interferograms. This overcomes the shortcomings of traditional measurement methods, which suffer from low measurement efficiency and limited applicable scale due to the inability to simultaneously acquire and integrate multi-angle diffraction information. Thus, while maintaining non-destructiveness and high precision, it supports rapid and quantitative measurement of large-size grating samples, significantly improving real-time monitoring and quality inspection capabilities in mass production scenarios and meeting the high-efficiency detection requirements in industrial applications.

[0024] Based on this, the embodiments of this application provide a laser interferometer, referring to... Figure 1 , Figure 1 This is a schematic diagram of the architecture of the laser interferometer involved in this application. The laser interferometer includes: A first optical measuring element 10 is configured to project a first measuring light onto the grating under test at a preset first incident direction angle, and to receive a first interference pattern formed by the diffraction of the first measuring light through the grating under test.

[0025] In this embodiment, refer to Figure 1 The first optical measuring element 10 projects a first measuring light onto the grating under test at a preset first incident angle, and receives the first-order diffracted light of the first measuring light that returns along the same path after being diffracted by the grating under test. Subsequently, the first-order diffracted light and the first reference light inside the first optical measuring element 10 form a first interference pattern on the imaging side of the first optical measuring element 10. This enables rapid, non-contact, full-field acquisition of the phase information of the grating under test in a specific direction (usually the Littrow angle).

[0026] It should be noted that the preset first incident direction angle usually refers to the Littrow angle, that is, a specific incident angle that satisfies the Littrow configuration. This first incident direction angle can be determined based on the grating equation of the grating under test, or it can be customized according to application requirements; this application does not impose any restrictions here. The grating equation based on the grating under test is as follows: ...Formula (1) in, Indicates the nominal period of the grating being measured; Indicates the first incident direction angle; Indicates the diffraction angle; For diffraction orders, =1; This refers to the laser wavelength used in the laser interferometer.

[0027] In the Littrow configuration, the first-order diffracted light returns along the original path, i.e., the diffraction angle... Angle with first incident direction They are equal in size. Therefore, substituting the condition... The simplified equation based on formula (1) is obtained. This allows for the accurate calculation of the first incident direction angle. .

[0028] The first interferogram includes the periodic distribution information of the grating under test and the geometric contribution of the substrate surface.

[0029] The second optical measuring element 20 is symmetrically arranged with the first optical measuring element 10. The second optical measuring element 20 is configured to project a second measuring light onto the grating under test at a second incident direction angle symmetrical to the first incident direction angle, and to receive a second interference pattern formed by the diffraction of the second measuring light through the grating under test.

[0030] In this embodiment, refer to Figure 1 The second optical measuring element 20 is strictly symmetrical to the first optical measuring element 10 about the normal of the grating under test in terms of spatial optical path arrangement. The second optical measuring element 20 projects a second measuring light onto the same grating under test according to a second incident direction angle symmetrical to the first incident direction angle, and receives the corresponding first-order diffracted light returning along the original path to form a second interferogram.

[0031] It should be noted that in this application, the second optical measuring element 20 and the first optical measuring element 10 are symmetrically arranged, so that the second measuring light and the first measuring light are incident on the same grating under test at an angle of equal size and opposite direction, which lays the physical basis for the subsequent differential measurement to eliminate common mode error.

[0032] The second interferogram also includes the periodic distribution information of the grating under test and the geometric contribution of the substrate surface.

[0033] An imaging acquisition module 30 is provided on the imaging side of the first optical measuring element 10 and the imaging side of the second optical measuring element 20. The imaging acquisition module 30 is configured to determine the measurement result of the grating under test based on the first interferogram and the second interferogram.

[0034] In this embodiment, refer to Figure 1 The imaging acquisition module 30 is respectively disposed on the imaging side of the first optical measuring element 10 and the second optical measuring element 20. The imaging acquisition module 30 is responsible for synchronously or according to a preset image acquisition sequence to acquire the first interferogram and the second interferogram. Next, the first interferogram and the second interferogram are image registered to ensure strict correspondence between the first interferogram and the second interferogram in spatial pixel positions, thereby laying the foundation for subsequent accurate differential calculation. After the image registration is completed, the corresponding first horizontal axis phase distribution function and second horizontal axis phase are extracted from the first interferogram and the second interferogram respectively by calling the phase demodulation algorithm set inside the imaging acquisition module 30. The phase distribution function is then used. Next, the difference between the first horizontal axis phase distribution function and the second horizontal axis phase distribution function is processed to automatically cancel the common-mode error introduced by the substrate surface shape of the grating under test, thereby extracting the phase difference information that purely reflects the periodic distribution of the grating under test. Subsequently, by performing spatial differentiation on this phase difference information, a two-dimensional distribution map of the local periodic error in nanometers / period can be directly obtained. Then, based on the two-dimensional distribution map of the local periodic error, the measurement results of the grating under test can be accurately obtained, realizing a rapid and quantitative evaluation of the periodic uniformity of large-size gratings (centimeter level) across the entire field of view, providing a direct basis for process monitoring and product quality grading.

[0035] It should be noted that the preset image acquisition order can be understood as being customized based on application requirements. The image acquisition order can be to acquire the first interferogram first and then the second interferogram, or it can be to acquire the second interferogram first and then the first interferogram. This application does not impose any restrictions here.

[0036] Furthermore, in some other feasible embodiments, reference is made to... Figure 2The first optical measurement element 10 and the second optical measurement element 20 are the same optical measurement structure, which is disposed on the grating period side of the grating under test. The optical measurement structure includes a laser source 100, a reflective optical element 200 and a reference optical element 300. The reflective optical element 200 is disposed between the laser source 100 and the reference optical element 300. The imaging side of the reflective optical element 200 is disposed on the side facing the imaging acquisition module 30, and the reference optical element 300 is disposed close to the grating period side.

[0037] In this embodiment, by adjusting the position of the reflective optical element 200, the measurement light provided by the laser source 100 is incident at a Littrow angle and passes through the reference optical element 300 to be projected onto the grating period side of the grating under test. At this time, the reflected light formed by the measurement light on the reference optical element 300 is projected onto the reflective optical element 200 as a reference light. Next, the diffracted light formed by the diffraction of the measurement light through the grating under test returns to the reflective optical element 200 along the original path. The diffracted light interferes with the reference light to form an interference phase diagram.

[0038] It should be noted that the laser source 100 can be a gas laser or a solid-state single-frequency laser, which can provide a highly coherent laser beam for grating uniformity measurement.

[0039] The reference optical element 300 can be a reference mirror. The reflecting optical element 200 can be a partial reflecting mirror, which can split the measurement light into two paths. One path is reflected as a reference light onto the reflecting optical element 200, and the other path passes through the partial reflecting mirror and is directed onto the grating under test. In addition, the ratio of the two paths can be customized according to the application requirements, for example, the ratio can be 50:50.

[0040] When the optical measurement structure is the first optical measurement element 10, the measurement ray is the first measurement ray, the reference ray is the first reference ray, the diffracted ray is the first diffracted ray, and the interference phase diagram is the first interference diagram; when the optical measurement structure is the second optical measurement element 20, the measurement ray is the second measurement ray, the reference ray is the second reference ray, the diffracted ray is the second diffracted ray, and the interference phase diagram is the second interference diagram.

[0041] Furthermore, in some feasible embodiments, the first incident direction angle is the Littoral angle corresponding to the +1 diffraction order of the grating under test, and the second incident direction angle is the Littoral angle corresponding to the -1 diffraction order of the grating under test.

[0042] In this embodiment, the first incident direction angle is the Littrow angle corresponding to the +1 diffraction order of the grating under test, and the second incident direction angle is the Littrow angle corresponding to the -1 diffraction order of the grating under test. Specifically, the Littrow angles of the ±1 diffraction order can be understood as two specific incident angles of equal magnitude but opposite directions when the Littrow condition (diffracted rays return along the original path) is satisfied. These two specific incident angles are symmetrically distributed in... Figure 2 The dashed lines shown represent the two sides of the grating normal.

[0043] Furthermore, in some other feasible embodiments, the imaging acquisition module 30 includes: a first image acquisition unit 31, which is disposed on the imaging side of the first optical measuring element 10 and is configured to acquire the first interferogram; a second image acquisition unit 32, which is disposed on the imaging side of the second optical measuring element 20 and is configured to acquire the second interferogram; and a processing unit 33, which is electrically connected to the first image acquisition unit 31 and the second image acquisition unit 32 respectively, and is configured to determine the measurement result of the grating under test based on the first interferogram and the second interferogram.

[0044] In this embodiment, refer to Figure 2The first image acquisition unit 31 is disposed on the imaging side of the first optical measurement element 10. The first image acquisition unit 31 acquires the first interferogram formed by the interaction between the first measurement light and the grating under test. The second image acquisition unit 32, symmetrically disposed on the imaging side of the second optical measurement element 20, acquires the second interferogram formed by the interaction between the second measurement light and the grating under test. Next, through the electrical connection between the processing unit 33 and the first image acquisition unit 31 and the second image acquisition unit 32, the processing unit 33, upon receiving the first and second interferograms respectively from the first and second image acquisition units 31 and 32, performs image registration on the first and second interferograms, ensuring a strict correspondence between the first and second interferograms in spatial pixel positions, thus laying the foundation for subsequent accurate differential calculations. The process begins with establishing a foundation. After image registration, the phase demodulation algorithm within the imaging acquisition module 30 is invoked to extract the corresponding first horizontal axis phase distribution function and second horizontal axis phase distribution function from the first and second interferograms, respectively. Next, the difference between the first and second horizontal axis phase distribution functions is calculated to automatically cancel the common-mode error introduced by the substrate surface shape of the grating under test, thereby extracting the phase difference information that purely reflects the periodic distribution of the grating under test. Subsequently, by performing spatial differentiation on this phase difference information, a two-dimensional distribution map of the local periodic error in nanometers per period can be directly obtained. Based on this two-dimensional distribution map of the local periodic error, the measurement results of the grating under test can be accurately obtained, enabling rapid and quantitative evaluation of the periodic uniformity across the entire field of view of large-size gratings (centimeter level), providing a direct basis for process monitoring and product quality grading.

[0045] It should be noted that the first image acquisition unit 31 and the second image acquisition unit 32 can be cameras, cameras, and image sensors, etc.

[0046] In a specific embodiment, after receiving the first interferogram and the second interferogram sent by the first image acquisition unit 31 and the second image acquisition unit 32 respectively, the processing unit 33 performs phase demodulation on the first interferogram and the second interferogram respectively to obtain... Figure 3 The first two-dimensional phase distribution diagram shown in (a) and Figure 3 The second two-dimensional phase distribution map is shown in (b) in the figure; next, the first two-dimensional phase distribution map and the second two-dimensional phase distribution map are precisely image registered to achieve pixel-level spatial alignment; then, the registered first two-dimensional phase distribution map and the second two-dimensional phase distribution map are subtracted to obtain Figure 4The net phase difference distribution map shown has eliminated the common-mode error of the substrate surface. This map represents the cumulative periodic error of the actual grating relative to the ideal grating at any position in the two-dimensional plane, providing a direct basis for further extraction of local periodic uniformity. Subsequently, the spatial derivative of this cumulative periodic error is obtained along the grating scribe line direction (i.e., the horizontal axis direction) of the grating under test. Figure 5 The local periodic error distribution diagram shown is in nanometers / period, thus enabling full-field quantitative characterization of the grating periodic uniformity.

[0047] It should be noted that the phase information of the first two-dimensional phase distribution map can be represented by the first horizontal axis phase distribution function; the phase information of the second two-dimensional phase distribution map can be represented by the second horizontal axis phase distribution function; the local periodic error distribution map includes several local periodic errors, which can be the error of the grating period corresponding to each horizontal axis coordinate relative to the ideal optical period.

[0048] In summary, the laser interferometer provided in this application achieves rapid and quantitative measurement of the periodic uniformity of large-size gratings without sacrificing measurement accuracy and non-destructiveness, significantly improving the detection efficiency and applicability in the mass production process of gratings. Specifically, a first measurement light and a second measurement light are projected onto the grating under test through symmetrically arranged first optical measurement element 10 and second optical measurement element 20 at symmetrical first and second incident angles, respectively; then, the first optical measurement element 10 and the second optical measurement element 20 respectively receive the first and second measurement lights diffracted by the grating under test to form a first interferogram and a second interferogram, effectively avoiding the problems of traditional optical microscopes that can only perform qualitative observations and cannot achieve quantitative measurements, as well as the destructive, slow, or field-of-view limitations of electron microscopes and atomic force microscopes; with Subsequently, the imaging acquisition module 30, which is located on the imaging side of the first optical measuring element 10 and the imaging side of the second optical measuring element 20, determines the measurement result of the grating under test based on the acquired first and second interferograms. This overcomes the shortcomings of traditional measurement methods, which are characterized by low measurement efficiency and limited applicable scale due to the inability to simultaneously acquire and integrate multi-angle diffraction information. As a result, it enables rapid and quantitative measurement of large-size grating samples while maintaining non-destructiveness and high precision, significantly improving real-time monitoring and quality inspection capabilities in mass production scenarios and meeting the high-efficiency detection requirements in industrial applications.

[0049] Furthermore, based on the first embodiment of this application described above, referring to... Figure 6This application presents a second embodiment of the measurement method for a laser interferometer. It should be noted that the executing entity of this embodiment can be a computing service device with data processing, network communication, and program execution functions, such as a tablet computer, personal computer, or mobile phone, or a device or optical inspection system capable of performing the aforementioned functions. The following description uses an optical inspection system integrating a laser interferometer as an example to illustrate this embodiment and the subsequent embodiments.

[0050] The measurement method of the laser interferometer set in this application includes steps S10 to S30.

[0051] Step S10: After the first optical measuring element 10 projects the first measuring light onto the grating under test at a preset first incident direction angle, a first interference pattern is obtained formed by the diffraction of the first measuring light through the grating under test.

[0052] In this embodiment, refer to Figure 1 The first optical measuring element 10 projects a first measuring light onto the grating under test at a preset first incident angle, and receives the first-order diffracted light of the first measuring light that returns along the same path after being diffracted by the grating under test. Subsequently, the first-order diffracted light and the first reference light inside the first optical measuring element 10 form a first interference pattern on the imaging side of the first optical measuring element 10. This enables rapid, non-contact, full-field acquisition of the phase information of the grating under test in a specific direction (usually the Littrow angle).

[0053] It should be noted that the preset first incident direction angle usually refers to the Littrow angle, that is, a specific incident angle that satisfies the Littrow configuration. This first incident direction angle can be determined based on the grating equation of the grating under test, or it can be customized according to application requirements; this application does not impose any restrictions here. The grating equation based on the grating under test is as follows: ...Formula (1) in, Indicates the nominal period of the grating being measured; Indicates the first incident direction angle; Indicates the diffraction angle; For diffraction orders, =1; This refers to the laser wavelength used in the laser interferometer.

[0054] In the Littrow configuration, the first-order diffracted light returns along the original path, i.e., the diffraction angle... Angle with first incident direction They are equal in size. Therefore, substituting the condition... The simplified equation based on formula (1) is obtained. This allows for the accurate calculation of the first incident direction angle. .

[0055] The first interferogram includes the periodic distribution information of the grating under test and the geometric contribution of the substrate surface.

[0056] Step S20: After the second optical measuring element 20 projects the second measuring light onto the grating under test at a second incident direction angle symmetrical to the first incident direction angle, a second interference pattern is obtained by diffracting the second measuring light through the grating under test.

[0057] In this embodiment, refer to Figure 1 The second optical measuring element 20 is strictly symmetrical to the first optical measuring element 10 about the normal of the grating under test in terms of spatial optical path arrangement. The second optical measuring element 20 projects a second measuring light onto the same grating under test according to a second incident direction angle symmetrical to the first incident direction angle, and receives the corresponding first-order diffracted light returning along the original path to form a second interferogram.

[0058] It should be noted that in this application, the second optical measuring element 20 and the first optical measuring element 10 are symmetrically arranged, so that the second measuring light and the first measuring light are incident on the same grating under test at an angle of equal size and opposite direction, which lays the physical basis for the subsequent differential measurement to eliminate common mode error.

[0059] The second interferogram also includes the periodic distribution information of the grating under test and the geometric contribution of the substrate surface.

[0060] Step S30: Determine the measurement result of the grating under test based on the first interferogram and the second interferogram.

[0061] In this embodiment, the imaging acquisition module 30 is respectively disposed on the light-emitting side of the first optical path module and the second optical path module. It is used to synchronously receive and acquire the first interferogram formed by the first optical path module and the second interferogram formed by the second optical path module, and to measure the grating uniformity of the first interferogram and the second interferogram. This allows for accurate measurement results of the grating under test, thus enabling high-precision grating uniformity detection without moving the grating under test, significantly improving the measurement efficiency of grating uniformity.

[0062] In this embodiment, refer to Figure 1The imaging acquisition module 30 is respectively disposed on the imaging side of the first optical measuring element 10 and the second optical measuring element 20. The imaging acquisition module 30 is responsible for synchronously or according to a preset image acquisition sequence to acquire the first interferogram and the second interferogram. Next, the first interferogram and the second interferogram are image registered to ensure strict correspondence between the first interferogram and the second interferogram in spatial pixel positions, thereby laying the foundation for subsequent accurate differential calculation. After the image registration is completed, the corresponding first horizontal axis phase distribution function and second horizontal axis phase are extracted from the first interferogram and the second interferogram respectively by calling the phase demodulation algorithm set inside the imaging acquisition module 30. The phase distribution function is then used. Next, the difference between the first horizontal axis phase distribution function and the second horizontal axis phase distribution function is processed to automatically cancel the common-mode error introduced by the substrate surface shape of the grating under test, thereby extracting the phase difference information that purely reflects the periodic distribution of the grating under test. Subsequently, by performing spatial differentiation on this phase difference information, a two-dimensional distribution map of the local periodic error in nanometers / period can be directly obtained. Then, based on the two-dimensional distribution map of the local periodic error, the measurement results of the grating under test can be accurately obtained, realizing a rapid and quantitative evaluation of the periodic uniformity of large-size gratings (centimeter level) across the entire field of view, providing a direct basis for process monitoring and product quality grading.

[0063] It should be noted that the preset image acquisition order can be understood as being customized based on application requirements. The image acquisition order can be to acquire the first interferogram first and then the second interferogram, or it can be to acquire the second interferogram first and then the first interferogram. This application does not impose any restrictions here.

[0064] Furthermore, in some other feasible embodiments, step S30: determining the measurement result of the grating under test based on the first interferogram and the second interferogram may also include steps S301 to S303.

[0065] Step S301: Construct a two-dimensional image coordinate system with the image widths of the first and second interferograms as the horizontal axis and the image heights of the first and second interferograms as the vertical axis.

[0066] In this embodiment, the image widths of the first and second interferograms are used as the horizontal axis, and the image heights of the first and second interferograms are used as the vertical axis, thereby constructing a unified two-dimensional image coordinate system for pixel-level spatial registration of the first and second interferograms.

[0067] Step S302: Based on the two-dimensional image coordinate system, determine the first horizontal axis phase distribution function of the first interferogram in the horizontal axis direction and the second horizontal axis phase distribution function of the second interferogram in the horizontal axis direction.

[0068] In this embodiment, in a two-dimensional image coordinate system, phase demodulation processing is performed on the first interferogram and the second interferogram respectively, and the phase distribution of the first interferogram and the second interferogram in the horizontal axis direction (usually corresponding to the grating line direction) is extracted, so that the first horizontal axis phase distribution function of the first interferogram and the second horizontal axis phase distribution function of the second interferogram can be accurately obtained.

[0069] It should be noted that the first horizontal axis phase distribution function can be the horizontal position coordinates of the grating extracted from the first interferogram. The changing phase distribution function, the second horizontal axis phase distribution function can be the lateral position coordinates of the grating extracted from the second interferogram. The changing phase distribution function.

[0070] Step S303: Determine the uniformity threshold of the grating under test based on the first horizontal axis phase distribution function and the second horizontal axis phase distribution function, and determine the measurement result of the grating under test based on the uniformity threshold.

[0071] In this embodiment, based on the first horizontal axis phase distribution function and the second horizontal axis phase distribution function, the cumulative periodic error of the grating under test along the grating scribe line direction (i.e., the horizontal axis direction) can be accurately calculated, thereby reflecting the overall distribution trend and accumulation degree of the grating periodic error. Next, by differentiating the cumulative periodic error, the horizontal position coordinates of each grating on the grating under test are obtained. The local periodic error is transformed from macroscopic cumulative quantity to microscopic local characteristics. Finally, by counting the number of local periodic errors that meet the preset error conditions among all local periodic errors and comparing it with the total number of all local periodic errors, the uniformity threshold that can quantify the overall uniformity level of the grating under test is finally calculated.

[0072] It should be noted that the preset error condition can be understood as the condition that the local periodic error is within a preset ideal error range, which can be represented by […]. ] indicates that, This represents the lower limit of the error corresponding to the ideal error range. This represents the upper limit of the error corresponding to the ideal error range, and as well as The value can be customized according to application requirements, and this application does not impose any restrictions here.

[0073] Furthermore, in some other feasible embodiments, the above step S303: determining the uniformity threshold of the grating under test based on the first horizontal axis phase distribution function and the second horizontal axis phase distribution function may also include steps S3031 to S3033.

[0074] Step S3031: Based on the first horizontal axis phase distribution function and the second horizontal axis phase distribution function, determine the cumulative periodic error of the grating under test arranged along the horizontal axis direction.

[0075] In this embodiment, the first horizontal axis phase distribution function is... Phase distribution function with the second horizontal axis After subtraction, it is compared with the nominal period of the grating being measured. By performing a product process, the cumulative periodic error of the actual grating relative to the ideal grating is obtained, which can reflect the distribution trend and accumulation degree of the grating periodic error as a whole.

[0076] Step S3032: Perform differentiation processing based on the cumulative periodic error to obtain all local periodic errors of the grating under test, and count the number of local periodic errors that meet the preset error conditions among all the local periodic errors.

[0077] In this embodiment, the cumulative periodic error is calculated. Regarding the lateral position coordinates of each grating The first derivative is used to obtain the coordinates of the transverse position of the grating under test in each grating. Local periodic error at the location This process transforms macroscopic cumulative quantities into microscopic local characteristics. Subsequently, it detects whether each local periodic error is within a preset ideal error range and counts the number of local periodic errors within this ideal error range, thus obtaining the number of local periodic errors that meet the preset error conditions.

[0078] It should be noted that local periodic errors The expression for the calculation algorithm is as follows: ; ; in, Indicates the lateral position coordinates of the grating; This represents the cumulative periodic error of the actual grating relative to the ideal grating. Represents the phase distribution function of the first horizontal axis; This represents the phase distribution function along the second horizontal axis; Indicates the nominal period of the grating being measured; This represents the local periodic error, which can be understood as the lateral position coordinate of the grating under test. The error of the grating period at a given location relative to the ideal optical period.

[0079] Step S3033: Based on the number of local periodic errors that satisfy the preset error conditions and the total number of all local periodic errors, obtain the uniformity threshold of the grating under test.

[0080] In this embodiment, the ratio between the number of local periodic errors that meet the preset error conditions and the total number of all local periodic errors is calculated, and the percentage of this ratio is used as a uniformity threshold that can quantify the overall uniformity level of the grating under test. Finally, the uniformity threshold is compared with a preset uniformity reference threshold, which can accurately obtain the measurement result of whether the uniformity of the grating under test is qualified. This realizes the transformation of complex interferogram information into an objective and quantitative qualification judgment, which significantly improves the efficiency and reliability of grating uniformity measurement.

[0081] Furthermore, in some feasible embodiments, step S303 above: determining the measurement result of the grating under test based on the uniformity threshold, may further include steps A10 to A30: Step A10: Detect whether the uniformity threshold exceeds a preset uniformity reference threshold; In this embodiment, by automatically comparing the calculated uniformity threshold with the preset uniformity reference threshold, an objective and unified judgment benchmark is established, which completely eliminates the subjectivity and inconsistency introduced by relying on human experience to interpret the interferogram in traditional detection. This makes the measurement results have the standardized characteristics of being repeatable and verifiable, laying a reliable data decision-making foundation for subsequent automated judgment.

[0082] It should be noted that the preset uniformity reference threshold can be customized according to application requirements, and this application does not impose any restrictions on it.

[0083] Step A20: If the uniformity threshold does not exceed the uniformity reference threshold, then the measurement result of the grating under test is determined to be that the grating under test is unqualified; In this embodiment, when the uniformity threshold is detected to be less than the preset reference threshold, the measurement result of the grating under test is automatically determined to be unqualified. This enables rapid and accurate screening of substandard grating products, avoids defective gratings from flowing into subsequent process steps, and realizes a real-time closed-loop quality interception mechanism. Decisions can be made without manual intervention, significantly improving the response speed of the detection process and the overall quality control efficiency.

[0084] Step A30: If the uniformity threshold exceeds the uniformity reference threshold, then the measurement result is determined to be a qualified grating under test.

[0085] In this embodiment, if the uniformity threshold exceeds the preset uniformity reference threshold, the measurement result of the grating under test is automatically determined to be qualified, thereby eliminating the uncertainty of human judgment and ensuring the accuracy of grating uniformity measurement.

[0086] This application provides an optical inspection system, which includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, which are executed by the at least one processor to enable the at least one processor to execute the laser interferometer in the first embodiment described above.

[0087] The following is for reference. Figure 7 It shows a schematic diagram of the structure of an optical detection system suitable for implementing the embodiments of this application. Figure 7 The optical inspection system shown is merely an example and should not be construed as limiting the functionality and scope of the embodiments of this application.

[0088] like Figure 7 As shown, the optical inspection system may include a processing device 1001 (e.g., a central processing unit, a graphics processing unit, etc.), which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 1002 or a program loaded from a storage device 1003 into a random access memory (RAM) 1004. The RAM 1004 also stores various programs and data required for the operation of the optical inspection system. The processing device 1001, ROM 1002, and RAM 1004 are interconnected via a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Typically, the following systems can be connected to the I / O interface 1006: input devices 1007 including, for example, a touchscreen, touchpad, keyboard, mouse, image sensor, microphone, accelerometer, gyroscope, etc.; output devices 1008 including, for example, a liquid crystal display (LCD), speaker, vibrator, etc.; storage devices 1003 including, for example, magnetic tape, hard disk, etc.; and communication devices 1009. Communication device 1009 allows the optical inspection system to communicate wirelessly or wiredly with other devices to exchange data. Although an optical inspection system with various devices is shown in the figure, it should be understood that it is not required to implement or possess all of the devices shown. More or fewer devices may be implemented alternatively.

[0089] Specifically, according to the embodiments disclosed in this application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments disclosed in this application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via a communication device, or installed from storage device 1003, or installed from ROM 1002. When the computer program is executed by processing device 1001, it performs the functions defined in the methods of the embodiments disclosed in this application.

[0090] The optical inspection system provided in this application employs the measurement method of the laser interferometer in the above embodiments, which can solve the technical problem of how to improve the measurement efficiency of grating uniformity without sacrificing measurement accuracy and non-destructiveness. Compared with the prior art, the beneficial effects of the optical inspection system provided in this application are the same as those of the laser interferometer provided in the above embodiments, and other technical features of this optical inspection system are the same as those disclosed in the method of the previous embodiment, and will not be repeated here.

[0091] It should be understood that the various parts disclosed in this application can be implemented using hardware, software, firmware, or a combination thereof. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0092] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0093] This application provides a medium having computer-readable program instructions (i.e., a computer program) stored thereon, which are used to perform the measurement method of the laser interferometer in the above embodiments.

[0094] The computer storage medium provided in this application may be, for example, a USB flash drive, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or any combination thereof. More specific examples of the medium may include, but are not limited to: electrical connections with one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this embodiment, the medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, system, or device. The program code contained on the medium may be transmitted using any suitable medium, including but not limited to: wires, optical cables, RF (Radio Frequency), etc., or any suitable combination thereof.

[0095] The aforementioned medium may be included in the optical inspection system, or it may exist independently without being assembled into the optical inspection system.

[0096] The aforementioned medium carries one or more programs, which, when executed by the optical detection system, cause the optical detection system to perform the following measurement operations of the laser interferometer: After the first optical measuring element projects the first measuring light onto the grating under test at a preset first incident direction angle, a first interference pattern is obtained by diffracting the first measuring light through the grating under test. After the second optical measuring element projects a second measuring light onto the grating under test at a second incident direction angle symmetrical to the first incident direction angle, a second interference pattern is obtained by diffracting the second measuring light through the grating under test. The measurement results of the grating under test are determined based on the first interferogram and the second interferogram.

[0097] Computer program code for performing the operations of this application can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a Local Area Network (LAN) or a Wide Area Network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0098] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0099] The modules described in the embodiments of this application can be implemented in software or hardware. The names of the modules do not necessarily limit the functionality of the unit itself.

[0100] The computer storage medium provided in this application stores computer-readable program instructions (i.e., computer programs) for executing the aforementioned laser interferometer. This addresses the technical problem of improving the measurement efficiency of grating uniformity without sacrificing measurement accuracy or non-destructiveness. Compared to the prior art, the beneficial effects of the computer storage medium provided in this application are the same as those of the laser interferometer provided in the above embodiments, and will not be elaborated upon here.

[0101] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the measurement method of the laser interferometer as described above.

[0102] The computer program product provided in this application can solve the technical problem of improving the measurement efficiency of grating uniformity without sacrificing measurement accuracy and non-destructiveness. Compared with the prior art, the beneficial effects of the computer program product provided in this application are the same as those of the measurement method of the laser interferometer provided in the above embodiments, and will not be repeated here.

[0103] The above are only some embodiments of this application and do not limit the patent scope of this application. All equivalent structural transformations made under the technical concept of this application and using the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included in the patent protection scope of this application.

Claims

1. A laser interferometer, characterized in that, The laser interferometer includes: A first optical measuring element is configured to project a first measuring light onto the grating under test at a preset first incident direction angle, and to receive a first interference pattern formed by the diffraction of the first measuring light through the grating under test. A second optical measuring element is arranged symmetrically with the first optical measuring element. The second optical measuring element is configured to project a second measuring light onto the grating under test at a second incident direction angle symmetrical to the first incident direction angle, and to receive a second interference pattern formed by the diffraction of the second measuring light through the grating under test. An imaging acquisition module is provided, which is located on the imaging side of the first optical measuring element and the imaging side of the second optical measuring element. The imaging acquisition module is configured to determine the measurement result of the grating under test based on the first interferogram and the second interferogram.

2. The laser interferometer as described in claim 1, characterized in that, The first optical measuring element and the second optical measuring element are the same optical measuring structure, and the optical measuring structure is disposed on the grating period side of the grating under test; The optical measurement structure includes a laser source, a reflective optical element, and a reference optical element. The reflective optical element is disposed between the laser source and the reference optical element. The imaging side of the reflective optical element is disposed facing the imaging acquisition module, and the reference optical element is disposed close to the grating period side.

3. The laser interferometer as described in claim 1, characterized in that, The first incident direction angle is the Littoral angle of the +1 diffraction order of the grating under test, and the second incident direction angle is the Littoral angle of the -1 diffraction order of the grating under test.

4. The laser interferometer as described in claim 1, characterized in that, The imaging acquisition module includes: A first image acquisition unit is disposed on the imaging side of the first optical measurement element, and the first image acquisition unit is configured to acquire the first interferogram. The second image acquisition unit is disposed on the imaging side of the second optical measurement element, and the second image acquisition unit is configured to acquire the second interferogram; The processing unit is electrically connected to the first image acquisition unit and the second image acquisition unit, respectively, and is configured to determine the measurement result of the grating under test based on the first interferogram and the second interferogram.

5. A measurement method using a laser interferometer, characterized in that, The measurement method of the laser interferometer is applied to the laser interferometer according to any one of claims 1 to 4, and the measurement method of the laser interferometer includes: After the first optical measuring element projects the first measuring light onto the grating under test at a preset first incident direction angle, a first interference pattern is obtained by diffracting the first measuring light through the grating under test. After the second optical measuring element projects a second measuring light onto the grating under test at a second incident direction angle symmetrical to the first incident direction angle, a second interference pattern is obtained by diffracting the second measuring light through the grating under test. The measurement results of the grating under test are determined based on the first interferogram and the second interferogram.

6. The measurement method of the laser interferometer as described in claim 5, characterized in that, The step of determining the measurement result of the grating under test based on the first interferogram and the second interferogram includes: A two-dimensional image coordinate system is constructed with the image widths of the first and second interferograms as the horizontal axis and the image heights of the first and second interferograms as the vertical axis. Based on the two-dimensional image coordinate system, the first horizontal axis phase distribution function of the first interferogram in the horizontal axis direction and the second horizontal axis phase distribution function of the second interferogram in the horizontal axis direction are determined respectively. The uniformity threshold of the grating under test is determined based on the first horizontal axis phase distribution function and the second horizontal axis phase distribution function, and the measurement result of the grating under test is determined based on the uniformity threshold.

7. The measurement method of the laser interferometer as described in claim 6, characterized in that, The step of determining the uniformity threshold of the grating under test based on the first horizontal axis phase distribution function and the second horizontal axis phase distribution function includes: Based on the first horizontal axis phase distribution function and the second horizontal axis phase distribution function, the cumulative periodic error of the grating under test arranged along the horizontal axis direction is determined; Based on the cumulative periodic error, perform differential processing to obtain all local periodic errors of the grating under test, and count the number of local periodic errors that meet the preset error conditions among all the local periodic errors. The uniformity threshold of the grating under test is obtained based on the number of local periodic errors that meet the preset error conditions and the total number of all local periodic errors.

8. The measurement method of the laser interferometer as described in claim 6, characterized in that, The step of determining the measurement result of the grating under test based on the uniformity threshold includes: Detect whether the uniformity threshold exceeds a preset uniformity reference threshold; If the uniformity threshold does not exceed the uniformity reference threshold, then the measurement result of the grating under test is determined to be that the grating under test is unqualified. If the uniformity threshold exceeds the uniformity reference threshold, then the measurement result is determined to be a qualified grating under test.

9. An optical detection system, characterized in that, The optical detection system includes the laser interferometer as described in any one of claims 1 to 4; Alternatively, a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the steps of the measurement method of the laser interferometer as described in any one of claims 5 to 8.

10. A computer storage medium, characterized in that, The computer storage medium stores a computer program, which, when executed by a processor, implements the steps of the measurement method of the laser interferometer as described in any one of claims 5 to 8.

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