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

Abstract

The invention 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, the light splitting module is used for splitting the laser beam into a first light beam and a second light beam, and the first light path module is used for enabling the first light beam to enter a measured grating and receiving first diffraction light emitted by the measured grating to form a first interferogram; the second light path module is used for enabling the second light beam to enter the measured grating and receiving second diffraction light emitted by the measured grating to form a second interferogram; the imaging acquisition modules are arranged on the light emitting sides of the first light path module and the second light path module respectively, and the imaging acquisition modules are set to determine the measurement result of the measured grating according to the first interference pattern and the second interference pattern, so that the measurement efficiency of the uniformity of the grating is improved on the premise that the measurement precision is not sacrificed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical detection, in particular to a dual-path laser interferometer, a grating measurement method and an optical detection system. BACKGROUND

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

[0003] At present, the measurement method of grating uniformity in the industry mostly adopts a manual measurement architecture based on a single-path laser interferometer, which needs to collect two interference patterns of the measured grating structure in the symmetric direction in sequence to detect the uniformity of the measured grating structure. However, this manual measurement architecture based on a single-path laser interferometer has great technical defects. In the process of collecting two interference patterns in the symmetric direction, the relative pose between the single-path laser interferometer and the measured grating needs to be adjusted repeatedly according to manual experience, which not only leads to a long time-consuming period of grating uniformity measurement, but also easily introduces artificial alignment errors to reduce the measurement accuracy of grating uniformity.

[0004] Therefore, without sacrificing the measurement accuracy of grating uniformity, how to improve the measurement efficiency of grating uniformity is a technical problem to be solved at present. SUMMARY

[0005] The main purpose of the present application is to provide a dual-path 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-mentioned purpose, the present application provides a dual-path laser interferometer, which 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 diffracted 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 diffracted light emitted by the measured grating to form a second interference pattern; 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 the measurement result of the measured grating according to the first interference pattern and the second interference pattern.

[0007] In an embodiment, the light splitting module comprises at least: a first optical element disposed at a light emitting side of the laser light source, the first optical element being configured to split the laser light beam into the first light beam transmitted and the second light beam reflected, and to project the second light beam to the second optical path module; a reflective optical element disposed at a side of the first optical element where the first light beam is transmitted, the reflective optical element being configured to receive the first light beam transmitted by the first optical element and to reflect the first light beam to the first optical path module.

[0008] In an embodiment, the first optical path module comprises: a second optical element disposed at a side of the reflective optical element where the first light beam is reflected, a first reference optical mirror disposed between the second optical element and the measured grating.

[0009] In an embodiment, 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 to project a reflected light formed on the first reference optical mirror by the first light beam as a first reference light to the second optical element synchronously when the first diffracted light based on the first light beam diffracted by the measured grating is projected to the second optical element via the first reference optical mirror, so as to form the first interference pattern by the second optical element based on the first diffracted light and the first reference light.

[0010] In an embodiment, the second optical path module comprises a third optical element and a second reference optical mirror disposed between the third optical element and the measured grating, the third optical element being disposed at a side of the first optical element where the second light beam is reflected.

[0011] In an embodiment, 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 to project a reflected light formed on the second reference optical mirror by the second light beam as a second reference light to the third optical element synchronously when the second diffracted light based on the first light beam diffracted by the measured grating is projected to the third optical element via the second reference optical mirror, so as to form the second interference pattern by the third optical element based on the second diffracted light and the second reference light.

[0012] Further, the application also provides a grating measurement method, which is applied to the dual-channel laser interferometer described above, and the grating measurement method comprises the following steps of: splitting a laser beam provided by a laser source 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 to a measured grating by a first optical path module and a second optical path module, enabling the first optical path module to form a first interference pattern based on first diffracted light diffracted by the measured grating based on the first light beam, and synchronously enabling the second optical path module to form a second interference pattern based on second diffracted light diffracted by the measured grating based on the second light beam; after the first interference pattern and the second interference pattern are received by an imaging acquisition module, determining a measurement result of the measured grating based on the first interference pattern and the second interference pattern.

[0013] In an embodiment, the step of determining the measurement result of the measured grating based on the first interference pattern and the second interference pattern comprises the following steps of: constructing a two-dimensional image coordinate system 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; determining a first horizontal axis phase distribution function of the first interference pattern in a horizontal axis direction and a second horizontal axis phase distribution function of the second interference pattern in the horizontal axis direction based on the two-dimensional image coordinate system; determining a uniformity threshold of the measured grating based on the first horizontal axis phase distribution function and the second horizontal axis phase distribution function, and determining the measurement result of the measured grating based on the uniformity threshold.

[0014] In an embodiment, the step of determining the measurement result of the measured grating based on the uniformity threshold comprises the following steps of: 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.

[0015] Further, in order to achieve the above-mentioned purpose, the application also provides an optical detection system, which comprises 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 is executed by the processor to implement the steps of the grating measurement method described above.

[0016] The double-path laser interferometer provided by the application significantly improves the measurement efficiency of grating uniformity without sacrificing measurement accuracy. Specifically, the double-path laser interferometer provided by the application is integrated with a laser light source, a light splitting module, a first light path module, a second light path module, and an imaging acquisition module. After the light splitting module splits the laser beam provided by the laser light source into a first light beam and a second light beam, the symmetrically arranged first light path module and second light path module respectively cause the two measurement lights (i.e., the first light beam and the second light beam) to be incident on the measured grating at opposite Littrow angles. At this time, while the first light path module forms a first interference pattern based on the first diffraction light diffracted by the measured grating based on the first light beam, the second light path module is simultaneously enabled to form a second interference pattern based on the second diffraction light diffracted by the measured grating based on the second light beam, effectively avoiding the low measurement efficiency phenomenon caused by repeated manual adjustment of the position and posture of the traditional single-path laser interferometer, and eliminating the measurement accuracy degradation caused by the introduction of human alignment errors. Subsequently, the first interference pattern and the second interference pattern are synchronously acquired by the imaging acquisition modules arranged at the light exit sides of the first light path module and the second light path module, respectively, and the measurement result of the measured grating can be accurately obtained based on the first interference pattern and the second interference pattern, thereby completing high-precision grating uniformity detection without moving the measured grating, and significantly improving the measurement efficiency of grating uniformity. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The figure is a schematic diagram of the architecture of the double-path laser interferometer involved in the application. Figure 2 The figure is a schematic diagram of the structure of the double-path laser interferometer involved in the application. Figure 3 The figure is a flowchart of the second embodiment of the grating measurement method involved in the application. Figure 4 The figure is a flowchart of the measurement result judgment of the grating measurement method involved in the application. Figure 5 The figure is a schematic diagram of the device structure of the hardware running environment of the device involved in the application.

[0018] Explanation of the reference numerals: 10, laser light source; 20, light splitting module; 30, first light path module; 40, second light path module; 50, imaging acquisition module; 21, first optical element; 22, reflecting optical element; 31, second optical element; 32, first reference optical mirror; 41, third optical element; 42, second reference optical mirror.

[0019] The implementation, functional features, and advantages of the application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0020] It should be understood that the specific embodiments described herein are merely exemplary and do not limit the application.

[0021] In order to better understand the technical solutions of the present application, the following will be described in detail in conjunction with the drawings and specific embodiments.

[0022] With the continuous development of optical detection technology, users have higher requirements for the measurement accuracy and efficiency of grating uniformity.

[0023] At present, the measurement method of grating uniformity in the industry mostly adopts a manual measurement architecture based on a single laser interferometer, which needs to sequentially collect two interference patterns of the measured grating structure in the symmetric direction to detect the uniformity of the measured grating structure. However, this manual measurement architecture based on a single laser interferometer has great technical defects. In the process of collecting two interference patterns in the symmetric direction, the relative pose between the single laser interferometer and the measured grating needs to be repeatedly adjusted according to manual experience, which not only leads to a long time-consuming period of grating uniformity measurement, but also easily introduces artificial alignment errors to reduce the measurement accuracy of grating uniformity.

[0024] Therefore, without sacrificing the measurement accuracy of grating uniformity, how to improve the measurement efficiency of grating uniformity is a technical problem to be solved at present.

[0025] Therefore, based on the technical defects of the single laser interferometer relying on manual experience for measurement, the dual laser interferometer of the present application is proposed. The solution of the embodiments of the present application is that the dual laser interferometer provided by the present application is integrated with a laser light source, a light splitting module, a first optical path module, a second optical path module, and an imaging and collecting module. After the light splitting module splits the laser beam provided by the laser light source into a first beam and a second beam, the symmetrically arranged first optical path module and second optical path module respectively cause the two measurement lights (i.e. the first beam and the second beam) to be incident on the measured grating at opposite Littrow angles. At this time, when the first optical path module forms a first interference pattern based on the first diffracted light of the measured grating based on the first beam, the second optical path module is simultaneously enabled to form a second interference pattern based on the second diffracted light of the measured grating based on the second beam, effectively avoiding the low measurement efficiency phenomenon caused by the repeated adjustment of the pose of the traditional single laser interferometer by the human, and eliminating the measurement accuracy degradation caused by the introduction of artificial alignment errors. Subsequently, the first interference pattern and the second interference pattern are synchronously acquired by the imaging and collecting modules arranged at the light exit sides of the first optical path module and the second optical path module respectively, and the measurement result of the measured grating can be accurately obtained based on the first interference pattern and the second interference pattern, so that high-precision grating uniformity detection is completed without moving the measured grating, and the measurement efficiency of grating uniformity is significantly improved.

[0026] Based on this, the embodiment of the present application provides a double-path laser interferometer, referring to Figure 1 , Figure 1 The schematic diagram of the architecture related to the double-path laser interferometer of the present application.

[0027] A laser light source 10 is arranged to provide a laser light beam.

[0028] In the embodiment, the laser light source 10 can be a gas laser or a solid-state single-frequency laser, which can provide a laser light beam with high coherence for grating uniformity measurement.

[0029] A light splitting module 20 is arranged to split the laser light beam into a first light beam and a second light beam.

[0030] In the embodiment, the light splitting module 20 splits the laser light beam into the first light beam and the second light beam, forming double-path interference light paths working in parallel, so as to construct two parallel and independent interference measurement channels on the physical light path.

[0031] It should be noted that the light splitting module 20 can include a first optical element 21 and a reflecting optical element 22.

[0032] In a specific embodiment, the surface of the first optical element 21 is coated with a dielectric film optimized for the working wavelength of the laser, and by accurately controlling the reflectivity and transmissivity ratio (for example, using a 50:50 splitting ratio) of the dielectric film, the collimated laser light beam provided by the laser light source 10 can be reliably and predictably split into the first light beam and the second light beam with balanced light intensity; then, the first light beam transmitted through the first optical element 21 is projected to a plane mirror, and the first light beam is projected to the first light path module 30 through the reflecting function of the reflecting optical element 22; while the second light beam formed by reflection enters the second light path module 40 symmetrically arranged with the first light path module 30 through the reflection of the first optical element 21, so as to construct two parallel interference measurement light paths which are spatially separated, have independent optical paths and are strictly symmetrical.

[0033] The first light path module 30 is arranged to cause the first light beam to be incident to a measured grating and receive first diffraction light emitted by the measured grating to form a first interference pattern.

[0034] In the embodiment, the first light path module 30 receives the first light beam transmitted from the light splitting module 20, and guides the first light beam to be incident to the measured grating at the Littrow angle of the measured grating, and receives the first-order diffraction light (i.e., the first diffraction light) returned by the measured grating based on the incident path of the first light beam, so that the first diffraction light interferes with the reference light (i.e., the first reference light) inside the first light path module 30 to form a high-quality first interference pattern.

[0035] A second optical path module 40 is symmetrically arranged with the first optical path module 30, and is configured to make the second light beam incident to the measured grating and receive second diffraction light emitted by the measured grating to form a second interference pattern.

[0036] In the embodiment, the second optical path module 40 symmetrically arranged with the first optical path module 30 synchronously receives the second light beam reflected from the light module 20, and guides the second light beam to be incident to the measured grating at a Littrow angle in a direction opposite to and equal in size to the first light beam, and receives first-order diffraction light (i.e., second diffraction light) returned by the measured grating based on the incident path of the second light beam, so that the second diffraction light interferes with reference light (i.e., second reference light) inside the second optical path module 40, thereby forming a high-quality second interference pattern. That is, the double-path synchronous interference measurement structure composed of the symmetrically arranged first optical path module 30 and the second optical path module 40 can obtain two first interference patterns and second interference patterns which are completely synchronous in time domain and strictly symmetrical in space domain at one time without relying on manual movement or adjustment of the measured grating.

[0037] An imaging acquisition module 50 is arranged on the light exit side of the first optical path module 30 and the light exit side of the second optical path module 40, and is configured to determine the measurement result of the measured grating according to the first interference pattern and the second interference pattern.

[0038] In the embodiment, the imaging acquisition module 50 is arranged on the light exit side of the first optical path module 30 and the second optical path module 40, respectively, for synchronously receiving and acquiring the first interference pattern formed by the first optical path module 30 and the second interference pattern formed by the second optical path module 40, and performing grating uniformity measurement on the first interference pattern and the second interference pattern, so that the measurement result of the measured grating can be accurately obtained, and high-precision grating uniformity detection can be completed without moving the measured grating, thereby significantly improving the measurement efficiency of grating uniformity.

[0039] It should be noted that the imaging acquisition module 50 can be a camera or an image acquisition sensor, etc.

[0040] Further, in some possible embodiments, the light splitting module 20 comprises at least: a first optical element 21 arranged on the light emitting side of the laser light source 10, the first optical element 21 being arranged to split the laser light beam into the first light beam transmitted and the second light beam reflected, and to project the second light beam to the second light path module 40; and a reflective optical element 22 arranged on the side of the first optical element 21 transmitting the first light beam, the reflective optical element 22 being arranged to receive the first light beam transmitted by the first optical element 21 and to reflect the first light beam to the first light path module 30.

[0041] In the present embodiment, with reference to Figure 2 , the light splitting module 20 is integrated with the first optical element 21 and the reflective optical element 22, the first optical element 21 splits the incident laser light beam into the first light beam transmitted and the second light beam reflected, and when the second light beam reflected is guided to the second light path module 40 through the first optical element 21, the first light beam is guided to the first light path module 30 by means of the reflective optical element 22 arranged on the light transmission path of the first optical element 21, so that the first light beam and the second light beam can be symmetrically incident to the Littrow angle position of the measured grating at the same time, thereby obtaining two interference patterns (i.e., the first interference pattern and the second interference pattern) at the same time in one measurement, completely eliminating the dependence on manual experience to repeatedly adjust the grating position, greatly improving the measurement efficiency, and reducing the random error introduced by manual operation, ensuring the consistency of the measurement process and the reliability of the results.

[0042] It should be noted that the first optical element 21 can be a partial mirror, and the splitting ratio of the partial mirror can be 50:50, which refers to the ratio between the reflectivity and the transmissivity of the medium film of the partial mirror. The reflective optical element 22 can be a plane mirror.

[0043] Further, in some possible embodiments, the first light path module 30 comprises: a second optical element 31 arranged on the side of the reflective optical element 22 reflecting the first light beam; and a first reference optical mirror 32 arranged between the second optical element 31 and the measured grating.

[0044] Further, in some possible embodiments, the first optical path module 30 is configured to project the first light beam reflected by the reflective optical element 22 to the measured grating via the first reference optical mirror 32 through the second optical element 31, and when the first diffraction light generated by the diffraction of the first light beam at the measured grating returns to the second optical element 31 along the original path via the first reference optical mirror 32, the reflected light formed by the first light beam on the surface of the first reference optical mirror 32 is synchronously projected to the second optical element 31 as the first reference light, so that the second optical element 31 receives the first diffraction light and the first reference light and makes the first diffraction light interfere with the first reference light to form the first interference pattern.

[0045] In the embodiment, the first optical path module 30 is configured to project the first light beam reflected by the reflective optical element 22 to the measured grating via the first reference optical mirror 32 through the second optical element 31, and when the first diffraction light generated by the diffraction of the first light beam at the measured grating returns to the second optical element 31 along the original path via the first reference optical mirror 32, the reflected light formed by the first light beam on the surface of the first reference optical mirror 32 is synchronously projected to the second optical element 31 as the first reference light, so that the second optical element 31 receives the first diffraction light and the first reference light and makes the first diffraction light interfere with the first reference light to form the first interference pattern. Figure 2 In the embodiment, the first optical path module 30 is configured to project the first light beam reflected by the reflective optical element 22 to the measured grating via the first reference optical mirror 32 through the second optical element 31, and when the first diffraction light generated by the diffraction of the first light beam at the measured grating returns to the second optical element 31 along the original path via the first reference optical mirror 32, the reflected light formed by the first light beam on the surface of the first reference optical mirror 32 is synchronously projected to the second optical element 31 as the first reference light, so that the second optical element 31 receives the first diffraction light and the first reference light and makes the first diffraction light interfere with the first reference light to form the first interference pattern.

[0046] It should be noted that the second optical element 31 can be a partial mirror, and the light splitting ratio of the partial mirror can be customized according to application requirements, for example, the light splitting ratio is 50:50; and the first reference optical mirror 32 can be a reference mirror.

[0047] Further, in some possible embodiments, the second optical path module 40 comprises a third optical element 41 and a second reference optical mirror 42, the second reference optical mirror 42 is arranged between the third optical element 41 and the measured grating, and the third optical element 41 is arranged to reflect the second light beam toward the first optical element 21.

[0048] Further, in some possible embodiments, the second optical path module 40 comprises a third optical element 41 and a second reference optical mirror 42, the second reference optical mirror 42 is arranged between the third optical element 41 and the measured grating, and the third optical element 41 is arranged to reflect the second light beam toward the first optical element 21.

[0049] In the present embodiment, referring to Figure 2 , the second optical path module 40 comprises a third optical element 41 and a second reference optical mirror 42. The third optical element 41 is arranged to reflect the second light beam toward the first optical element 21, and the second reference optical mirror 42 is further arranged between the third optical element 41 and the measured grating, so that the second light beam reflected by the first optical element 21 can be projected to the measured grating via the second reference optical mirror 42 through the third optical element 41. When the second light beam is diffracted at the measured grating and the generated 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 by the second light beam on the surface of the second reference optical mirror 42 will be synchronously projected to the third optical element 41 as the second reference light. The third optical element 41 receives the second diffracted light and the second reference light, and makes the second diffracted light and the second reference light interfere with each other to form a second interference pattern. The second optical path module 40 is completely symmetrical to the first optical path module 30 in structure, so that the second light beam can complete the whole process of illumination, diffraction, reference and interference synchronously in another independent interference measurement optical path. The first interference pattern and the second interference pattern from the two symmetrical optical paths can be synchronously obtained by one measurement without any manual adjustment, which significantly improves the efficiency and consistency of the grating uniformity measurement and effectively avoids random errors introduced by manual operation.

[0050] It should be noted that the third optical element 41 can be a partial mirror, and the splitting ratio of the partial mirror can be customized according to application requirements, for example, the splitting ratio is 50:50. The second reference optical mirror 42 can be a reference mirror.

[0051] In another embodiment, Figure 2 represents the Littrow angle, represents 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 in the above embodiment can be adjusted according to the adjustment of the measured grating Littrow angle.

[0052] In summary, the double-path laser interferometer provided by the application can significantly improve the measurement efficiency of grating uniformity without sacrificing measurement accuracy. Specifically, the double-path laser interferometer provided by the application is integrated with a laser light source 10, a light splitting module 20, a first optical path module 30, a second optical path module 40 and an imaging acquisition module 50. After the light splitting module 20 splits the laser beam provided by the laser light source 10 into a first beam and a second beam, the symmetrically arranged first optical path module 30 and second optical path module 40 respectively cause the two measurement lights (i.e. the first beam and the second beam) to be incident on the measured grating at opposite Littrow angles. At this time, while the first optical path module 30 forms a first interference pattern based on the first diffraction light diffracted by the measured grating based on the first beam, the second optical path module 40 is simultaneously enabled to form a second interference pattern based on the second diffraction light diffracted by the measured grating based on the second beam, effectively avoiding the low measurement efficiency caused by repeated manual adjustment of the position and posture of the traditional single-path laser interferometer, and eliminating the measurement accuracy degradation caused by the introduction of human alignment errors. Then, the first interference pattern and the second interference pattern are synchronously acquired by the imaging acquisition modules 50 arranged at the light exit sides of the first optical path module 30 and the second optical path module 40 respectively, and the measurement result of the measured grating can be accurately obtained based on the first interference pattern and the second interference pattern, thereby completing high-precision grating uniformity detection without moving the measured grating, and significantly improving the measurement efficiency of grating uniformity.

[0053] Further, based on the first embodiment of the application described above, referring to Figure 3 , a second embodiment of the grating measurement method applied to the double-path laser interferometer is proposed. It should be noted that the execution subject of the present embodiment can be a computing service device with data processing, network communication and program running functions, such as a tablet computer, a personal computer, a mobile phone, etc., or a device capable of realizing the above functions, an optical detection system, etc. The following takes an optical detection system integrated with a double-path laser interferometer as an example to describe the present embodiment and the following embodiments.

[0054] The grating measurement method provided by the application includes steps S10 to S30.

[0055] Step S10: Split the laser beam provided by the laser light source into a first beam and a second beam by the light splitting module.

[0056] In the embodiment, the light splitting module splits the laser beam into the first light beam and the second light beam, forms a double-path interference light path working in parallel, and thus constructs two parallel and independent interference measurement channels on the physical light path.

[0057] Step S20: after the first light path module and the second light path module respectively cause the first light beam and the second light beam to be incident on the measured grating, the first light path module is enabled to form a first interference pattern based on first diffraction light diffracted by the measured grating based on the first light beam, and the second light path module is simultaneously enabled to form a second interference pattern based on second diffraction light diffracted by the measured grating based on the second light beam.

[0058] In the embodiment, the first light path module receives the first light beam transmitted from the light splitting module, guides the first light beam to be incident on the measured grating at a Littrow angle of the measured grating, receives first-order diffraction light (i.e., first diffraction light) returned by the measured grating based on an incident path of the first light beam, causes the first diffraction light to interfere with reference light (i.e., first reference light) inside the first light path module, and forms a high-quality first interference pattern. At this time, the second light path module symmetrically arranged with the first light path module simultaneously receives the second light beam reflected from the light splitting module, guides the second light beam to be incident on the measured grating at a Littrow angle opposite in direction and equal in size, receives first-order diffraction light (i.e., second diffraction light) returned by the measured grating based on an incident path of the second light beam, causes the second diffraction light to interfere with reference light (i.e., second reference light) inside the second light path module, and forms a high-quality second interference pattern. That is, the present application forms a double-path synchronous interference measurement structure by symmetrically arranging the first light path module and the second light path module, so that two first interference patterns and second interference patterns completely synchronous in time domain and strictly symmetrical in space domain can be obtained at one time without relying on manual movement or adjustment of the measured grating.

[0059] Step S30: after the imaging acquisition module receives the first interference pattern and the second interference pattern, determines a measurement result of the measured grating based on the first interference pattern and the second interference pattern.

[0060] In the embodiment, the imaging acquisition module is arranged at an out-light side of the first light path module and the second light path module, is used to synchronously receive and acquire the first interference pattern formed by the first light path module and the second interference pattern formed by the second light path module, and performs grating uniformity measurement on the first interference pattern and the second interference pattern, so that the measurement result of the measured grating can be accurately obtained, high-precision grating uniformity detection can be completed without moving the measured grating, and the measurement efficiency of the grating uniformity is significantly improved.

[0061] Further, in some possible embodiments, the step S30 of determining the measurement result of the measured grating according to the first interference pattern and the second interference pattern can further include steps S301-S303.

[0062] The step S301 includes: constructing a two-dimensional image coordinate system with the image width of the first interference pattern and the second interference pattern as the horizontal axis and the image height of the first interference pattern and the second interference pattern as the vertical axis.

[0063] In this embodiment, the two-dimensional image coordinate system is constructed with the image width of the first interference pattern and the second interference pattern as the horizontal axis and the image height of the first interference pattern and the second interference pattern as the vertical axis, so that the first interference pattern and the second interference pattern can be pixel-level spatially registered.

[0064] The step S302 includes: determining a first horizontal-axis phase distribution function of the first interference pattern and a second horizontal-axis phase distribution function of the second interference pattern in the horizontal-axis direction based on the two-dimensional image coordinate system.

[0065] In this embodiment, the first interference pattern and the second interference pattern are respectively phase demodulated in the two-dimensional image coordinate system to extract the phase distribution of the first interference pattern and the second interference pattern in the horizontal-axis direction (usually corresponding to the direction of the grating lines), so that the first horizontal-axis phase distribution function of the first interference pattern and the second horizontal-axis phase distribution function of the second interference pattern can be accurately obtained.

[0066] It should be noted that the first horizontal-axis phase distribution function can be a phase distribution function varying with the grating horizontal position coordinate x extracted from the first interference pattern, and the second horizontal-axis phase distribution function can be a phase distribution function varying with the grating horizontal position coordinate x extracted from the second interference pattern.

[0067] The step S303 includes: determining a uniformity threshold of the measured grating according to the first horizontal-axis phase distribution function and the second horizontal-axis phase distribution function, and determining the measurement result of the measured grating according to the uniformity threshold.

[0068] In this embodiment, the first horizontal-axis phase distribution function is subtracted from the second horizontal-axis phase distribution function to obtain the product of the nominal period of the measured grating , so as to obtain the period error accumulation of the actual grating of the measured grating relative to the ideal grating; then, the accumulated period error function is calculated about each grating horizontal position coordinate ​​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.

[0069] 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.

[0070] Local periodic error 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.

[0071] 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: Step S3031: Detect whether the uniformity threshold exceeds a preset uniformity reference threshold; In the embodiment, by automatically comparing the calculated uniformity threshold value with the preset uniformity reference threshold value, an objective and unified judgment criterion is established, the subjectivity and inconsistency introduced by relying on manual experience to interpret the interference pattern in the traditional detection are completely eliminated, the measurement result has the standardized characteristics of repeatability and verifiability, and a reliable data decision basis is laid for subsequent automatic judgment.

[0072] It should be noted that the preset uniformity reference threshold value can be customized according to application requirements, and the present application does not make any limitation here.

[0073] Step S3032: If the uniformity threshold value does not exceed the uniformity reference threshold value, it is determined that the measurement result of the measured grating is that the measured grating is unqualified. In the embodiment, when it is detected that the uniformity threshold value does not exceed the preset reference threshold value, it is automatically determined that the measurement result of the measured grating is that the measured grating is unqualified, the fast and accurate screening of substandard grating products is realized, the defective gratings are prevented from flowing into the subsequent process link, the real-time closed-loop quality interception mechanism is realized, the decision can be made without manual intervention, and the response speed and overall quality control efficiency of the detection process are significantly improved.

[0074] Step S3033: If the uniformity threshold value exceeds the uniformity reference threshold value, it is determined that the measurement result of the measured grating is that the measured grating is qualified.

[0075] In the embodiment, if the uniformity threshold value exceeds the preset uniformity reference threshold value, it is automatically determined that the measurement result of the measured grating is that the measured grating is qualified, so that the uncertainty of human judgment is eliminated, and the accuracy of grating uniformity measurement is ensured.

[0076] The present application provides an optical detection system, which comprises at least one processor and a memory in communication connection with the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the grating measurement method in the above-mentioned embodiment one.

[0077] Reference will be made to the accompanying drawings Figure 5 which shows a structural schematic diagram of an optical detection system suitable for being used to implement the embodiments of the present application. Figure 5 The optical detection system shown is only an example, and should not bring any limitation to the functions and use range of the embodiments of the present application.

[0078] As Figure 5As shown, the optical detection system can include a processing device 1001 (e.g., a central processing unit, a graphics processing unit, etc.) that can perform various appropriate actions and processes according to programs stored in a read-only memory (ROM) 1002 or programs loaded from a storage device 1003 into a random access memory (RAM) 1004. Various programs and data required for operation of the optical detection system are also stored in the RAM 1004. The processing device 1001, the ROM 1002, and the RAM 1004 are connected to each other by a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Generally, the following systems can be connected to the I / O interface 1006: input devices 1007 including, for example, a touch screen, a touch pad, a keyboard, a mouse, an image sensor, a microphone, an accelerometer, a gyroscope, etc.; output devices 1008 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; the storage device 1003 including, for example, a magnetic tape, a hard disk, etc.; and a communication device 1009. The communication device 1009 can allow the optical detection system to communicate wirelessly or by wire with other devices to exchange data. Although the optical detection system is shown as having various devices, it should be understood that all of the shown devices are not required to be implemented or possessed. More or fewer devices can alternatively be implemented or possessed.

[0079] In particular, the processes described above with reference to the flowcharts can be implemented as a computer software program according to embodiments of the present disclosure. For example, embodiments of the present disclosure 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 by a communication device, or installed from the storage device 1003, or installed from the ROM 1002. When the computer program is executed by the processing device 1001, the above-mentioned functions defined in the methods of embodiments of the present disclosure are performed.

[0080] The optical detection system provided by the present disclosure adopts the grating measurement method in the above embodiments, which 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 optical detection system provided by the present disclosure has the same beneficial effects as the dual-channel laser interferometer provided by the above embodiments, and other technical features in the optical detection system are the same as the features disclosed in the previous embodiment method, which will not be repeated here.

[0081] It should be understood that various aspects of the disclosure can be implemented in 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 one or more embodiments or examples in a suitable manner.

[0082] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0083] The present application provides a medium having computer readable program instructions (i.e. computer programs) stored thereon, the computer readable program instructions being used to perform the grating measurement method in the above embodiments.

[0084] The computer storage medium provided by the present application may, for example, be a U disk, but is not limited to an electric, magnetic, optical, electromagnetic, infrared, or semiconductor system, system or device, or any combination thereof. More specific examples of the medium can include, but are not limited to, an electric connection with one or more conductive wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present embodiment, the medium can be any tangible medium containing or storing a program, which can be used by or in combination with an instruction execution system, system or device. The program code contained on the medium can be transmitted by any suitable medium, including but not limited to an electric wire, an optical cable, an RF (Radio Frequency: radio frequency), etc., or any suitable combination thereof.

[0085] The above medium can be contained in the optical detection system; or can exist separately without being assembled into the optical detection system.

[0086] The above medium carries one or more programs, which, when executed by the optical detection system, cause the optical detection system to perform the following grating measurement operations: The laser beam provided by the laser light source is divided into a first light beam and a second light beam by the light splitting module; After the first light path module and the second light path module respectively make the first light beam and the second light beam incident to the measured grating, the first light path module is enabled to form a first interference figure based on first diffracted light diffracted by the measured grating based on the first light beam, and the second light path module is simultaneously enabled to form a second interference figure based on second diffracted light diffracted by the measured grating based on the second light beam; After the imaging acquisition module receives the first interference figure and the second interference figure, a measurement result of the measured grating is determined based on the first interference figure and the second interference figure.

[0087] Computer program code for carrying out operations of the present application can be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0088] The computer program instructions can also be loaded onto a computer or other programmable information processing apparatus to cause a series of operations to be performed on the computer or other programmable information processing apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable information processing apparatus implement the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0089] The modules described in the embodiments of the present application can be implemented in the form of software or in the form of hardware. In some cases, the name of the module does not constitute a limitation on the module itself.

[0090] The computer storage medium provided in the present application stores computer readable program instructions (i.e., computer programs) for executing the above-mentioned dual-channel laser interferometer, and can solve the technical problem of how to improve the measurement efficiency of the uniformity of the grating without sacrificing the measurement accuracy of the uniformity of the grating. Compared with the prior art, the computer storage medium provided in the present application has the same beneficial effects as the dual-channel laser interferometer provided in the above-mentioned embodiments, and will not be described here.

[0091] The present application also provides a computer program product comprising a computer program, which, when executed by a processor, implements the steps of the grating measurement method as described above.

[0092] The computer program product provided in the present application can solve the technical problem of how to improve the measurement efficiency of the uniformity of the grating without sacrificing the measurement accuracy of the uniformity of the grating. Compared with the prior art, the computer program product provided in the present application has the same beneficial effects as the grating measurement method provided in the above-mentioned embodiments, and will not be described here.

[0093] The above is only some embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation made by using the content of the present application specification and drawings, or direct / indirect application in other related technical fields is included in the patent protection scope of the present 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; an imaging acquisition module arranged on an outgoing light side of the first optical path module and an outgoing light side of the second optical path module, the imaging acquisition module being configured to determine a measurement result of the measured grating based on the first interference pattern and the second interference pattern.

2. The dual-path laser interferometer of claim 1, wherein, The light splitting module comprises at least: 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 beam reflected by the reflective optical element to the measured grating through the second optical element and the first reference optical mirror, and when the first diffraction light diffracted by the measured grating based on the first beam is projected to the second optical element through the first reference optical mirror, the reflective light formed by the first beam on the first reference optical mirror is synchronously projected to the second optical element as first reference light, so that the second optical element forms the first interference pattern based on the first diffraction 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 arranged between the third optical element and the measured grating, and the third optical element is arranged on a side of the first optical element through which the second beam is reflected.

6. The dual-path laser interferometer of claim 5, wherein, The second light path module is configured to project the second 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 measured grating based on the first beam is projected to the third optical element via the second reference optical mirror, the second light path module is configured to project the reflected light formed on the second reference optical mirror by the second beam as a 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 according to any one of claims 1 to 6, and the grating measurement method comprises: a light splitting module configured to split a laser beam provided by a laser source into a first beam and a second beam; a first light path module and a second light path module configured to respectively cause the first beam and the second beam to be incident on a measured grating; the first light path module is enabled to form a first interference pattern based on first diffracted light diffracted by the measured grating based on the first beam, and the second light path module is synchronously enabled to form a second interference pattern based on second diffracted light diffracted by the measured grating based on the second beam; 8. The grating measurement method of claim 7, wherein, an imaging acquisition module configured to receive the first interference pattern and the second interference pattern, and determine a measurement result of the measured grating 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: constructing a two-dimensional image coordinate system 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; determining a first horizontal axis phase distribution function of the first interference pattern in a horizontal axis direction and a second horizontal axis phase distribution function of the second interference pattern in the horizontal axis direction based on the two-dimensional image coordinate system; 9. The grating measurement method of claim 8, wherein, determining a uniformity threshold of the measured grating based on the first horizontal axis phase distribution function and the second horizontal axis phase distribution function, and determining the measurement result of the measured grating based on the uniformity threshold. The step of determining the measurement result of the measured grating based on 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; 10. An optical detection system, characterized in that 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. 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, wherein the computer program is executed by the processor to implement the steps of the grating measurement method according to any one of claims 7 to 9.

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