Dual-path laser interferometer, grating measurement method, and optical detection system

Abstract

The application discloses a double-path laser interferometer, a grating measurement method and an optical detection system, and relates to the technical field of optical detection. The double-path laser interferometer comprises a laser light source for providing a laser beam, a light splitting module for splitting the laser beam into a first light beam and a second light beam, a first light path module, a second light path module and an imaging acquisition module. The first light path module is used for making the first light beam incident to a measured grating and receiving first diffraction light emitted by the measured grating to form a first interference diagram. The second light path module is used for making the second light beam incident to the measured grating and receiving second diffraction light emitted by the measured grating to form a second interference diagram. The imaging acquisition module is arranged on the light emitting side of the first light path module and the second light path module and is used for determining the measurement result of the measured grating according to the first interference diagram and the second interference diagram. Therefore, the measurement efficiency of grating uniformity is improved without sacrificing the measurement accuracy.

Description

Technical Field

[0001] This application relates to the field of optical inspection technology, and in particular to a dual-channel laser interferometer, a grating measurement method, and an optical inspection system. Background Technology

[0002] With the continuous development of optical inspection technology, users have put forward higher requirements for the measurement accuracy and efficiency of grating uniformity.

[0003] Currently, most methods for measuring grating uniformity in the industry employ a manual measurement architecture based on a single-channel laser interferometer. This requires sequentially acquiring two interferograms of the grating structure under test along the symmetrical direction to detect its uniformity. However, this manual measurement architecture based on a single-channel laser interferometer has significant technical drawbacks. During the acquisition of the two interferograms along the symmetrical direction, the relative pose between the single-channel laser interferometer and the grating under test needs to be repeatedly adjusted based on human experience. This not only results in a long measurement cycle for grating uniformity but also easily introduces human alignment errors, reducing the measurement accuracy of grating uniformity.

[0004] Therefore, improving the measurement efficiency of grating uniformity without sacrificing the measurement accuracy of grating uniformity is a pressing technical problem that needs to be solved. Summary of the Invention

[0005] The main objective of this application is to provide a dual-channel laser interferometer, a grating measurement method, and an optical detection system, which aims to improve the measurement efficiency of grating uniformity without sacrificing the measurement accuracy of grating uniformity.

[0006] To achieve the above objectives, this application proposes a dual-channel laser interferometer, which includes:

[0007] A laser source, wherein the laser source is configured to provide a laser beam;

[0008] A beam splitter module is configured to split the laser beam into a first beam and a second beam.

[0009] The first optical path module is configured to incident the first light beam onto the grating under test and receive the first diffracted light emitted through the grating under test to form a first interference pattern.

[0010] The second optical path module is symmetrically arranged with the first optical path module. The second optical path module is configured to incident the second beam onto the grating under test and receive the second diffracted light emitted through the grating under test to form a second interference pattern.

[0011] An imaging acquisition module is provided, which is located on the light-emitting side of the first optical path module and the light-emitting side of the second optical path module. 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.

[0012] In one embodiment, the beam splitting module includes at least:

[0013] A first optical element is disposed on the light-emitting side of the laser source. The first optical element is configured to split the laser beam into a transmitted first beam and a reflected second beam, and to project the second beam onto the second optical path module.

[0014] A reflective optical element is disposed on the side of the first optical element that transmits the first light beam. The reflective optical element is configured to receive the first light beam transmitted by the first optical element and reflect the first light beam to the first optical path module.

[0015] In one embodiment, the first optical path module includes:

[0016] A second optical element is disposed facing the side of the reflecting optical element that reflects the first light beam.

[0017] A first reference optical mirror is disposed between the second optical element and the grating under test.

[0018] In one embodiment, the first optical path module is configured to project the first light beam reflected by the reflecting optical element through the second optical element onto the grating under test via the first reference optical mirror. When the first diffracted light of the grating under test based on the first light beam is projected onto the second optical element via the first reference optical mirror, the reflected light formed by the first light beam on the first reference optical mirror is synchronously projected onto the second optical element as the first reference light, so that the second optical element can form the first interference pattern based on the first diffracted light and the first reference light.

[0019] In one embodiment, the second optical path module includes a third optical element and a second reference optical mirror, the second reference optical mirror being disposed between the third optical element and the grating under test, and the third optical element being disposed on the side of the first optical element that reflects the second light beam.

[0020] In one embodiment, the second optical path module is configured to project the second light beam reflected by the first optical element through the third optical element onto the grating under test via the second reference optical mirror. When the second diffracted light of the grating under test based on the first light beam is projected onto the third optical element via the second reference optical mirror, the reflected light formed on the second reference optical mirror by the second light beam is synchronously projected onto the third optical element as the second reference light, so that the third optical element can form the second interference pattern based on the second diffracted light and the second reference light.

[0021] Furthermore, this application also provides a grating measurement method, which is applied to the dual-channel laser interferometer described above, and the grating measurement method includes:

[0022] The laser beam provided by the laser source is split into a first beam and a second beam using a beam splitting module;

[0023] After the first optical path module and the second optical path module respectively incident the first beam and the second beam onto the grating under test, the first optical path module is enabled to form a first interference pattern based on the first diffracted light of the grating under test based on the first beam, and the second optical path module is simultaneously enabled to form a second interference pattern based on the second diffracted light of the grating under test based on the second beam.

[0024] After the imaging acquisition module receives the first interferogram and the second interferogram, it determines the measurement result of the grating under test based on the first interferogram and the second interferogram.

[0025] 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:

[0026] 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.

[0027] 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.

[0028] 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.

[0029] In one embodiment, the step of determining the measurement result of the grating under test based on the uniformity threshold includes:

[0030] Detect whether the uniformity threshold exceeds a preset uniformity reference threshold;

[0031] 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.

[0032] If the uniformity threshold exceeds the uniformity reference threshold, then the measurement result of the grating under test is determined to be qualified.

[0033] In addition, to achieve the above objectives, this application also proposes an optical inspection system, which includes the dual-channel 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 grating measurement method described above.

[0034] The dual-path laser interferometer described in this application significantly improves the measurement efficiency of grating uniformity without sacrificing measurement accuracy. Specifically, the dual-path laser interferometer integrates a laser source, a beam splitting module, a first optical path module, a second optical path module, and an imaging acquisition module. After the laser beam provided by the laser source is split into a first beam and a second beam by the beam splitting module, the symmetrically arranged optical path modules and the second optical path module respectively incident the two measurement beams (i.e., the first beam and the second beam) onto the grating under test at opposite Littrow angles. At this time, while the first optical path module forms a first interferogram based on the first diffracted light of the grating under test based on the first beam, the second optical path module is simultaneously enabled to form a second interferogram based on the second diffracted light of the grating under test based on the second beam. This effectively avoids the low measurement efficiency caused by repeated manual adjustments of the pose in traditional single-path laser interferometers, and also eliminates the degradation of measurement accuracy caused by human alignment errors. Subsequently, the first and second interferograms are synchronously acquired by the imaging acquisition modules located on the light-emitting sides of the first and second optical path modules, and the measurement results of the grating under test can be accurately obtained based on the first and second interferograms. Thus, high-precision grating uniformity detection can be completed without moving the grating under test, significantly improving the measurement efficiency of grating uniformity. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the architecture of the dual-channel laser interferometer involved in this application;

[0036] Figure 2 This is a schematic diagram of the structure involved in the dual-channel laser interferometer of this application;

[0037] Figure 3This is a flowchart illustrating the second embodiment of the grating measurement method described in this application;

[0038] Figure 4 This is a schematic diagram of the measurement result judgment process involved in the grating measurement method of this application;

[0039] Figure 5 This is a schematic diagram of the hardware operating environment involved in the device in this application.

[0040] Explanation of icon numbers:

[0041] 10. Laser source; 20. Beam splitting module; 30. First optical path module; 40. Second optical path module; 50. Imaging acquisition module; 21. First optical element; 22. Reflective optical element; 31. Second optical element; 32. First reference optical mirror; 41. Third optical element; 42. Second reference optical mirror.

[0042] 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

[0043] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0044] 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.

[0045] With the continuous development of optical inspection technology, users have put forward higher requirements for the measurement accuracy and efficiency of grating uniformity.

[0046] Currently, most methods for measuring grating uniformity in the industry employ a manual measurement architecture based on a single-channel laser interferometer. This requires sequentially acquiring two interferograms of the grating structure under test along the symmetrical direction to detect its uniformity. However, this manual measurement architecture based on a single-channel laser interferometer has significant technical drawbacks. During the acquisition of the two interferograms along the symmetrical direction, the relative pose between the single-channel laser interferometer and the grating under test needs to be repeatedly adjusted based on human experience. This not only results in a long measurement cycle for grating uniformity but also easily introduces human alignment errors, reducing the measurement accuracy of grating uniformity.

[0047] Therefore, improving the measurement efficiency of grating uniformity without sacrificing the measurement accuracy of grating uniformity is a pressing technical problem that needs to be solved.

[0048] Therefore, based on the technical shortcomings of single-channel laser interferometers that rely on manual experience for measurement, this application proposes a dual-channel laser interferometer. The solution of this application embodiment is as follows: The dual-channel laser interferometer provided in this application integrates a laser source, a beam splitting module, a first optical path module, a second optical path module, and an imaging acquisition module. After the laser beam provided by the laser source is split into a first beam and a second beam by the beam splitting module, the two measurement beams (i.e., the first beam and the second beam) are incident on the grating under test at opposite Littrow angles by the symmetrically arranged optical path modules and the second optical path module, respectively. At this time, while the first optical path module forms a first interferogram based on the first diffracted light of the grating under test based on the first beam, the second optical path module is simultaneously enabled to form a second interferogram based on the second diffracted light of the grating under test based on the second beam. This effectively avoids the low measurement efficiency caused by repeated manual adjustments of the pose in traditional single-path laser interferometers, and also eliminates the degradation of measurement accuracy caused by human alignment errors. Subsequently, the first and second interferograms are synchronously acquired by the imaging acquisition modules located on the light-emitting sides of the first and second optical path modules, and the measurement results of the grating under test can be accurately obtained based on the first and second interferograms. Thus, high-precision grating uniformity detection can be completed without moving the grating under test, significantly improving the measurement efficiency of grating uniformity.

[0049] Based on this, the embodiments of this application provide a dual-path laser interferometer, referring to... Figure 1 , Figure 1 This is a schematic diagram of the architecture of the dual-channel laser interferometer involved in this application.

[0050] Laser source 10, which is configured to provide a laser beam.

[0051] In this embodiment, the laser source 10 can be a gas laser or a solid-state single-frequency laser, which can provide a highly coherent laser beam for grating uniformity measurement.

[0052] Beam splitting module 20, which is configured to split the laser beam into a first beam and a second beam.

[0053] In this embodiment, the beam splitting module 20 splits the laser beam into a first beam and a second beam, forming a parallel dual-path interference optical path, thereby constructing two parallel and independent interference measurement channels on the physical optical path.

[0054] It should be noted that the beam splitting module 20 may include a first optical element 21 and a reflective optical element 22.

[0055] In a specific embodiment, the surface of the first optical element 21 is coated with a dielectric thin film optimized for the laser operating wavelength. By precisely controlling the ratio of reflectivity to transmittance of the dielectric thin film (e.g., using a 50:50 splitting ratio), the collimated laser beam provided by the laser source 10 can be reliably and predictably split into a first beam and a second beam with equal light intensity. Next, the first beam transmitted through the first optical element 21 is projected onto the planar emission mirror, and the first beam is projected onto the first optical path module 30 through the reflection function of the reflecting optical element 22. The second beam formed by reflection enters the second optical path module 40, which is symmetrically arranged with the first optical path module 30, through the reflection of the first optical element 21, thereby constructing two spatially separated, optically independent and strictly symmetrical parallel interferometric measurement optical paths.

[0056] The first optical path module 30 is configured to incident the first light beam onto the grating under test and receive the first diffracted light emitted through the grating under test to form a first interference pattern.

[0057] In this embodiment, the first optical path module 30 receives the first beam transmitted from the beam splitter module 20 and guides the first beam to be incident on the grating under test at the Littrow angle. It also receives the first-order diffracted light (i.e., the first diffracted light) returned by the grating under test based on the incident path of the first beam, so that the first diffracted light interferes with the reference light (i.e., the first reference light) inside the first optical path module 30 to form a high-quality first interferogram.

[0058] The second optical path module 40 is symmetrically arranged with the first optical path module 30. The second optical path module 40 is configured to incident the second light beam onto the grating under test and receive the second diffracted light emitted through the grating under test to form a second interference pattern.

[0059] In this embodiment, the second optical path module 40, symmetrically arranged with the first optical path module 30, synchronously receives the second beam reflected from the beam splitting module 20 and guides the second beam to be incident on the grating under test at Littrow angles of opposite direction and equal magnitude. At the same time, it receives the first-order diffracted light (i.e., the second diffracted light) returned by the grating under test based on the incident path of the second beam, so that the second diffracted light interferes with the reference light (i.e., the second reference light) inside the second optical path module 40, thereby forming a high-quality second interferogram. That is, through the dual-path synchronous interferometry measurement structure composed of the symmetrically arranged first optical path module 30 and second optical path module 40, two first interferograms and second interferograms that are completely synchronized in the time domain and strictly symmetrical in the spatial domain can be obtained at one time without relying on manual movement or adjustment of the grating under test.

[0060] An imaging acquisition module 50 is provided, which is disposed on the light-emitting side of the first optical path module 30 and the light-emitting side of the second optical path module 40. The imaging acquisition module 50 is configured to 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 50 is respectively disposed on the light-emitting side of the first optical path module 30 and the second optical path module 40. It is used to synchronously receive and acquire the first interferogram formed by the first optical path module 30 and the second interferogram formed by the second optical path module 40, and to measure the grating uniformity of the first interferogram and the second interferogram. Thus, the measurement result of the grating under test can be accurately obtained. Therefore, high-precision grating uniformity detection can be completed without moving the grating under test, which significantly improves the measurement efficiency of grating uniformity.

[0062] It should be noted that the imaging acquisition module 50 can be a camera or an image acquisition sensor, etc.

[0063] Furthermore, in some other feasible embodiments, the beam splitting module 20 includes at least: a first optical element 21, which is disposed on the light-emitting side of the laser source 10, and is configured to split the laser beam into a transmitted first beam and a reflected second beam, and project the second beam onto the second optical path module 40; and a reflective optical element 22, which is disposed toward the side of the first optical element 21 that transmits the first beam, and is configured to receive the first beam transmitted by the first optical element 21 and reflect the first beam to the first optical path module 30.

[0064] In this embodiment, refer to Figure 2 The beam splitting module 20 provided in this application integrates a first optical element 21 and a reflective optical element 22. The first optical element 21 splits the incident laser beam into a transmitted first beam and a reflected second beam. When the reflected second beam is guided into the second optical path module 40 through the first optical element 21, the first beam is simultaneously guided into the first optical path module 30 by the reflective optical element 22 disposed on the transmitted optical path of the first optical element 21. This allows the first beam and the second beam to be synchronously and symmetrically incident on the Littrow angle position of the grating under test, thereby acquiring two interferograms (i.e., the first interferogram and the second interferogram) in one measurement. This completely eliminates the dependence on repeated adjustments of the grating pose by human experience, which not only greatly improves the measurement efficiency but also reduces the random errors introduced by manual operation, ensuring the consistency of the measurement process and the reliability of the results.

[0065] It should be noted that the first optical element 21 can be a partial reflector, and the beam splitting ratio of the partial reflector can be 50:50. This beam splitting ratio refers to the ratio between the reflectivity and transmittance of the dielectric thin film of the partial reflector. The reflective optical element 22 can be a plane reflector.

[0066] Furthermore, in some feasible embodiments, the first optical path module 30 includes: a second optical element 31, which is disposed on the side of the reflecting optical element 22 that reflects the first light beam; and a first reference optical mirror 32, which is disposed between the second optical element 31 and the grating under test.

[0067] Furthermore, in some other feasible embodiments, the first optical path module 30 is configured to project the first light beam reflected by the reflecting optical element 22 onto the grating under test via the first reference optical mirror 32 through the second optical element 31. When the first diffracted light of the grating under test based on the first light beam is projected onto the second optical element 31 via the first reference optical mirror 32, the reflected light formed on the first reference optical mirror 32 by the first light beam is synchronously projected onto the second optical element 31 as the first reference light, so that the second optical element 31 can form the first interference pattern based on the first diffracted light and the first reference light.

[0068] In this embodiment, refer to Figure 2The first optical path module 30 of this application includes a second optical element 31 and a first reference optical mirror 32. The second optical element 31 is arranged parallel to the side of the reflecting optical element 22 that reflects the first beam, and the first reference optical mirror 32 is disposed between the second optical element 31 and the grating under test. Thus, the first beam reflected from the reflecting optical element 22 can be projected onto the grating under test through the first reference optical mirror 32 via the second optical element 31. When the first beam diffracts at the grating under test and the resulting first diffracted light returns to the second optical element 31 along the original path through the first reference optical mirror 32, the reflected light formed on the surface of the first reference optical mirror 32 will serve as the first reference light and be simultaneously projected onto the second optical element 31. At this time, the second optical element 31 receives the first diffracted light and the first reference light. The reference light is used to cause the first diffracted light to interfere with the first reference light, ultimately forming the first interferogram. This ensures that the first light path reflected by the reflective optical element 22 can complete the entire process of illumination, diffraction, reference, and interference in the first light path module 30. Combined with the symmetrically arranged second light path module 40, the acquisition of two interferograms can be achieved simultaneously in one measurement without relying on manual adjustment of the grating posture. This completely eliminates the dependence on repeated adjustments based on human experience, which not only greatly improves the efficiency of grating uniformity measurement but also significantly reduces random errors introduced by human operation, ensuring high consistency of the measurement process and reliability of the results.

[0069] It should be noted that the second optical element 31 can be a partial reflector, and the beam splitting ratio of the partial reflector can be customized according to the application requirements, for example, the beam splitting ratio is 50:50; the first reference optical mirror 32 can be a reference mirror.

[0070] Furthermore, in some feasible embodiments, the second optical path module 40 includes a third optical element 41 and a second reference optical mirror 42, the second reference optical mirror 42 being disposed between the third optical element 41 and the grating under test, and the third optical element 41 being disposed toward the side of the first optical element 21 that reflects the second light beam.

[0071] Furthermore, in some other feasible embodiments, the second optical path module 40 is configured to project the second beam reflected by the first optical element 21 onto the grating under test via the second reference optical mirror 42 through the third optical element 41. When the second diffracted light of the grating under test based on the first beam is projected onto the third optical element 41 via the second reference optical mirror 42, the reflected light formed on the second reference optical mirror 42 by the second beam is synchronously projected onto the third optical element 41 as the second reference light, so that the third optical element 41 can form the second interference pattern based on the second diffracted light and the second reference light.

[0072] In this embodiment, refer to Figure 2 The second optical path module 40 provided in this application includes a third optical element 41 and a second reference optical mirror 42. The third optical element 41 is positioned facing the side of the first optical element 21 that reflects the second beam, and the second reference optical mirror 42 is further positioned between the third optical element 41 and the grating under test. This allows the second beam reflected from the first optical element 21 to be projected onto the grating under test via the second reference optical mirror 42 through the third optical element 41. When the second beam diffracts at the grating under test, and the resulting second diffracted light returns to the third optical element 41 along the original path via the second reference optical mirror 42, the reflected light formed on the surface of the second reference optical mirror 42 serves as the second reference light and is simultaneously projected onto the third optical element 41. The third optical element 41 receives the second diffracted light and the second reference light, causing them to interfere and ultimately forming a second interference pattern. The second optical path module 40 and the first optical path module 30 provided in this application are structurally completely symmetrical, enabling the second beam to simultaneously complete the entire process of illumination, diffraction, reference, and interference in another independent interferometric measurement optical path. The first and second interferograms from two symmetrical optical paths can be obtained simultaneously with a single measurement without any manual adjustment, which significantly improves the efficiency and consistency of grating uniformity measurement, while effectively avoiding random errors introduced by human operation.

[0073] It should be noted that the third optical element 41 can be a partial reflector, and the beam splitting ratio of the partial reflector can be customized according to the application requirements, for example, the beam splitting ratio is 50:50; the second reference optical mirror 42 can be a reference mirror.

[0074] In another embodiment, Figure 2 (in) () indicates the Littrow angle. Figure 3 The first optical element 21, the second optical element 31, the third optical element 41, the first reference optical mirror 32, the second reference optical mirror 42, and the reflecting optical element 22 can be adjusted according to the adjustment of the Littrow angle of the grating being measured.

[0075] In summary, the dual-path laser interferometer configured in this application significantly improves the measurement efficiency of grating uniformity without sacrificing measurement accuracy. Specifically, the dual-path laser interferometer configured in this application integrates a laser source 10, a beam splitting module 20, a first optical path module 30, a second optical path module 40, and an imaging acquisition module 50. After the laser beam provided by the laser source 10 is split into a first beam and a second beam by the beam splitting module 20, the symmetrically arranged optical path modules 30 and 40 respectively incident the two measurement beams (i.e., the first beam and the second beam) onto the grating under test at opposite Littrow angles. At this time, when the first optical path module 30 forms a first interferogram based on the first diffracted light of the grating under test based on the first beam, the second optical path module 40 is simultaneously enabled to form a second interferogram based on the second diffracted light of the grating under test based on the second beam. This effectively avoids the low measurement efficiency caused by repeated manual adjustment of the pose in traditional single-path laser interferometers, and also eliminates the degradation of measurement accuracy caused by human alignment errors. Subsequently, the first and second interferograms are synchronously acquired by the imaging acquisition modules 50 located on the light-emitting sides of the first and second optical path modules 30 and 40, respectively. Based on the first and second interferograms, the measurement results of the grating under test can be accurately obtained. Thus, high-precision grating uniformity detection can be completed without moving the grating under test, significantly improving the measurement efficiency of grating uniformity.

[0076] Furthermore, based on the first embodiment of this application described above, referring to... Figure 3 This application presents a second embodiment of the grating measurement method applied to a dual-channel 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 dual-channel laser interferometer as an example to illustrate this embodiment and the subsequent embodiments.

[0077] The grating measurement method provided in this application includes steps S10 to S30.

[0078] Step S10: The laser beam provided by the laser source is split into a first beam and a second beam by the beam splitting module.

[0079] In this embodiment, the beam splitting module divides the laser beam into a first beam and a second beam, forming a parallel dual-path interference optical path, thereby constructing two parallel and independent interference measurement channels on the physical optical path.

[0080] Step S20: After the first optical path module and the second optical path module respectively incident the first beam and the second beam onto the grating under test, the first optical path module is enabled to form a first interference pattern based on the first diffracted light of the grating under test based on the first beam, and the second optical path module is simultaneously enabled to form a second interference pattern based on the second diffracted light of the grating under test based on the second beam.

[0081] In this embodiment, the first optical path module receives the first beam transmitted from the beam splitter module and guides the first beam to be incident on the grating under test at the Littrow angle of the grating under test. It also receives the first-order diffracted light (i.e., the first diffracted light) returned by the grating under test based on the incident path of the first beam, so that the first diffracted light interferes with the reference light (i.e., the first reference light) inside the first optical path module to form a high-quality first interferogram. At this time, the second optical path module, symmetrically arranged with the first optical path module, synchronously receives the second beam reflected from the beam splitter module and guides the second beam to be incident on the grating under test at a Littrow angle with opposite directions and equal magnitude. At the same time, it receives the first-order diffracted light (i.e., the second diffracted light) returned by the grating under test based on the incident path of the second beam, so that the second diffracted light interferes with the reference light (i.e., the second reference light) inside the second optical path module, thereby forming a high-quality second interferogram. That is, this application uses a dual-path synchronous interferometry measurement structure composed of a symmetrically arranged first optical path module and a second optical path module to obtain two first interferograms and second interferograms that are completely synchronized in the time domain and strictly symmetrical in the spatial domain at the same time without relying on manual movement or adjustment of the grating under test.

[0082] Step S30: After the imaging acquisition module receives the first interferogram and the second interferogram, it determines the measurement result of the grating under test based on the first interferogram and the second interferogram.

[0083] In this embodiment, the imaging acquisition module 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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. After performing multiplication, the cumulative periodic error of the actual grating under test relative to the ideal grating is obtained; next, the cumulative periodic error function 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 Subsequently, the lateral position coordinates of all gratings were determined. The total number of coordinate measurements, and count all those that satisfy the condition. Conditional grating lateral position coordinates The system calculates the percentage of coordinates obtained from the statistical analysis to the total number of coordinate measurements, thus obtaining the uniformity threshold of the grating under test. Finally, by comparing the uniformity threshold with the preset uniformity reference threshold, the measurement result of whether the uniformity of the grating under test is qualified can be accurately obtained. This realizes the transformation of complex interferogram information into an objective and quantitative qualification judgment, significantly improving the efficiency and reliability of grating uniformity measurement.

[0092] It should be noted 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.

[0093] Local periodic error The expression for the calculation algorithm is as follows:

[0094] ;

[0095] ;

[0096] 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.

[0097] Furthermore, in some feasible embodiments, reference is made to Figure 4 The above step S303: determining the measurement result of the grating under test based on the uniformity threshold may further include steps S3031 to S3033:

[0098] Step S3031: Detect whether the uniformity threshold exceeds a preset uniformity reference threshold;

[0099] 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.

[0100] 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.

[0101] Step S3032: If the uniformity threshold does not exceed the uniformity reference threshold, then the measurement result of the grating under test is determined to be unqualified.

[0102] 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.

[0103] Step S3033: If the uniformity threshold exceeds the uniformity reference threshold, then the measurement result of the grating under test is determined to be qualified.

[0104] 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.

[0105] 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 perform the grating measurement method in Embodiment 1 above.

[0106] The following is for reference. Figure 5 It shows a schematic diagram of the structure of an optical detection system suitable for implementing the embodiments of this application. Figure 5 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.

[0107] like Figure 5As 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.

[0108] 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.

[0109] The optical inspection system provided in this application employs the grating measurement method described in the above embodiments, which solves the technical problem of improving the measurement efficiency of grating uniformity without sacrificing the measurement accuracy of grating uniformity. Compared with the prior art, the beneficial effects of the optical inspection system provided in this application are the same as those of the dual-path 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.

[0110] 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.

[0111] 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.

[0112] This application provides a medium having computer-readable program instructions (i.e., a computer program) stored thereon, which are used to perform the grating measurement method described in the above embodiments.

[0113] 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.

[0114] The aforementioned medium may be included in the optical inspection system, or it may exist independently without being assembled into the optical inspection system.

[0115] The aforementioned medium carries one or more programs, which, when executed by the optical inspection system, cause the optical inspection system to perform the following grating measurement operations:

[0116] The laser beam provided by the laser source is split into a first beam and a second beam using a beam splitting module;

[0117] After the first optical path module and the second optical path module respectively incident the first beam and the second beam onto the grating under test, the first optical path module is enabled to form a first interference pattern based on the first diffracted light of the grating under test based on the first beam, and the second optical path module is simultaneously enabled to form a second interference pattern based on the second diffracted light of the grating under test based on the second beam.

[0118] After the imaging acquisition module receives the first interferogram and the second interferogram, it determines the measurement result of the grating under test based on the first interferogram and the second interferogram.

[0119] 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).

[0120] 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.

[0121] 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.

[0122] The computer storage medium provided in this application stores computer-readable program instructions (i.e., a computer program) for executing the aforementioned dual-channel laser interferometer. This addresses the technical problem of improving the measurement efficiency of grating uniformity without sacrificing the measurement accuracy of grating uniformity. Compared to the prior art, the beneficial effects of the computer storage medium provided in this application are the same as those of the dual-channel laser interferometer provided in the above embodiments, and will not be elaborated upon here.

[0123] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the grating measurement method described above.

[0124] The computer program product provided in this application can solve the technical problem of how to improve the measurement efficiency of grating uniformity without sacrificing the measurement accuracy of grating uniformity. Compared with the prior art, the beneficial effects of the computer program product provided in this application are the same as the beneficial effects of the grating measurement method provided in the above embodiments, and will not be repeated here.

[0125] 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 two-path laser interferometer, characterized in that, The double-path laser interferometer comprises: a laser light source configured to provide a laser beam; a light splitting module configured to split the laser beam into a first beam and a second beam; a first optical path module configured to cause the first beam to be incident on a measured grating and receive first diffraction light emitted by the measured grating to form a first interference pattern; a second optical path module symmetrically arranged with the first optical path module, the second optical path module being configured to cause the second beam to be incident on the measured grating and receive second diffraction light emitted by the measured grating to form a second interference pattern; wherein the first optical path module and the second optical path module are configured to operate synchronously, the measured grating does not need to move, and the first beam and the second beam are simultaneously incident on the measured grating at Littrow angles in opposite directions to generate the first interference pattern and the second interference pattern which are completely synchronized in time domain and strictly symmetrical in space domain; an imaging and collecting module arranged on the light exit side of the first optical path module and the light exit side of the second optical path module, the imaging and collecting module being configured to determine a measurement result of the measured grating based on the first interference pattern and the second interference pattern; the imaging and collecting module is configured to subtract a first transverse axis phase distribution function of the first interference pattern from a second transverse axis phase distribution function of the second interference pattern, multiply the result by a nominal period of the measured grating to obtain a period error accumulation of an actual grating of the measured grating relative to an ideal grating, calculate a first derivative of the period error accumulation with respect to each grating transverse position coordinate to obtain a local period error of the measured grating at each grating transverse position coordinate, count a coordinate number of all grating transverse position coordinates within an ideal error interval, determine a percentage between the coordinate number and a total coordinate measurement number of all grating transverse position coordinates as a uniformity threshold of the measured grating, compare the uniformity threshold with a preset uniformity reference threshold to obtain a measurement result of whether the uniformity of the measured grating is qualified.

2. The dual-path laser interferometer of claim 1, wherein, The light splitting module at least comprises: a first optical element arranged on a light emitting side of the laser light source, the first optical element being configured to split the laser beam into the first beam transmitted and the second beam reflected, and project the second beam to the second optical path module; a reflective optical element arranged on a side of the first optical element through which the first beam is transmitted, the reflective optical element being configured to receive the first beam transmitted by the first optical element and reflect the first beam to the first optical path module.

3. The dual-path laser interferometer of claim 2, wherein, The first optical path module comprises: a second optical element arranged on a side of the reflective optical element through which the first beam is reflected, a first reference optical mirror arranged between the second optical element and the measured grating.

4. The dual-path laser interferometer of claim 3, wherein, The first optical path module is configured to project the first light beam reflected by the reflective optical element to the measured grating via the first reference optical mirror through the second optical element, and when the first diffracted light diffracted by the first light beam based on the measured grating is projected to the second optical element via the first reference optical mirror, the first optical path module is configured to project the reflected light formed on the first reference optical mirror by the first light beam as the first reference light to the second optical element synchronously, so that the second optical element forms the first interference pattern based on the first diffracted light and the first reference light.

5. The dual-path laser interferometer of claim 2, wherein, The second optical path module comprises a third optical element and a second reference optical mirror, and the second reference optical mirror is arranged between the third optical element and the measured grating, and the third optical element is arranged on the side of the first optical element reflecting the second light beam.

6. The dual-path laser interferometer of claim 5, wherein, The second optical path module is configured to project the second light beam reflected by the first optical element to the measured grating via the second reference optical mirror through the third optical element, and when the second diffracted light diffracted by the first light beam based on the measured grating is projected to the third optical element via the second reference optical mirror, the second optical path module is configured to project the reflected light formed on the second reference optical mirror by the second light beam as the second reference light to the third optical element synchronously, so that the third optical element forms the second interference pattern based on the second diffracted light and the second reference light.

7. A grating measurement method, characterized by, The grating measurement method is applied to the dual-path laser interferometer of any one of claims 1 to 6, and the grating measurement method comprises: The light beam provided by the laser light source is divided into a first light beam and a second light beam by a light splitting module; After the first light beam and the second light beam are respectively incident on the measured grating by the first optical path module and the second optical path module, the first optical path module is enabled to form a first interference pattern based on the first diffracted light diffracted by the measured grating based on the first light beam, and the second optical path module is simultaneously enabled to form a second interference pattern based on the second diffracted light diffracted by the measured grating based on the second light beam; wherein the first optical path module and the second optical path module are configured to work synchronously, so that the first light beam and the second light beam are simultaneously incident on the measured grating at opposite Littrow angles to synchronously generate the first interference pattern and the second interference pattern; After the imaging acquisition module receives the first interference pattern and the second interference pattern, the measurement result of the measured grating is determined based on the first interference pattern and the second interference pattern. The step of determining the measurement result of the measured grating based on the first interference pattern and the second interference pattern comprises: The period error accumulation is determined according to a first lateral axis phase distribution function of the first interference pattern, a second lateral axis phase distribution function of the second interference pattern, and a nominal period of the measured grating, and a first derivative of the period error accumulation with respect to each grating lateral position coordinate is calculated to obtain a local period error of the measured grating at each grating lateral position coordinate, a coordinate number of all grating lateral position coordinates within an ideal error interval is counted, and a percentage between the coordinate number and a total measurement number of all grating lateral position coordinates is determined as a uniformity threshold of the measured grating, and a measurement result of the measured grating is obtained by comparing the uniformity threshold with a preset uniformity reference threshold.

8. The grating measurement method of claim 7, wherein, The step of determining the measurement result of the measured grating according to the first interference pattern and the second interference pattern comprises: a two-dimensional image coordinate system is constructed with an image width of the first interference pattern and the second interference pattern as a horizontal axis and an image height of the first interference pattern and the second interference pattern as a vertical axis; a first lateral axis phase distribution function of the first interference pattern in a horizontal axis direction and a second lateral axis phase distribution function of the second interference pattern in the horizontal axis direction are determined based on the two-dimensional image coordinate system; the uniformity threshold of the measured grating is determined according to the first lateral axis phase distribution function and the second lateral axis phase distribution function, and the measurement result of the measured grating is determined according to the uniformity threshold.

9. The grating measurement method of claim 8, wherein, The step of determining the measurement result of the measured grating according to the uniformity threshold comprises: detecting whether the uniformity threshold exceeds a preset uniformity reference threshold; if the uniformity threshold does not exceed the uniformity reference threshold, determining that the measurement result of the measured grating is that the measured grating is unqualified; if the uniformity threshold exceeds the uniformity reference threshold, determining that the measurement result of the measured grating is that the measured grating is qualified.

10. An optical detection system, characterized in that The optical detection system comprises the dual-path laser interferometer according to any one of claims 1 to 6. Alternatively, a memory, a processor, and a computer program stored in the memory and executable on the processor, when the computer program is executed by the processor, implement the steps of the grating measurement method according to any one of claims 7 to 9.

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