A bidirectional second-order diffraction homodyne grating interferometer measuring device

Abstract

The application relates to the technical field of grating measurement, and discloses a bidirectional second-order diffraction homodyne grating interference measurement device which comprises a light source, a beam splitter grating, a scale grating, a measurement grating, a corner cube prism group, a photoelectric detector group and a data processing device; after the light emitted by the light source passes through the beam splitter grating, +1 order transmission diffraction light and -1 order transmission diffraction light are formed. The +1 order transmission diffraction light and the -1 order transmission diffraction light pass through the scale grating, the measurement grating and the corner cube prism group to form multiple paths of diffraction light which enters the photoelectric detector group to form interference signals, and the data processing device calculates the displacement of a target piece to be measured based on the interference output signals of the photoelectric detector group. The application utilizes the back reflection characteristic of the corner cube prism, constructs second-order diffraction in a measurement path, and realizes four times of optical subdivision measurement of two degrees of freedom.

Description

Technical Field

[0001] This application relates to the field of grating measurement technology, and more specifically to a bidirectional secondary diffraction zero-difference grating interferometric measurement device. Background Technology

[0002] In the fields of precision manufacturing and semiconductor equipment, displacement measurement systems must simultaneously meet stringent requirements such as sub-nanometer resolution, high dynamic response, and simultaneous detection of multiple degrees of freedom. Traditional laser interferometers rely on long-arm reference optical paths, making them extremely sensitive to environmental temperature, air pressure fluctuations, and mechanical vibrations. Furthermore, single-beam measurements struggle to directly decouple multi-degree-of-freedom motion. While capacitive or eddy current sensors can achieve non-contact measurement, they have limitations in multi-degree-of-freedom integration and balancing range and resolution. Against this backdrop, grating interferometric displacement measurement technology, which uses physical grating pitch as the measurement reference, exhibits significant environmental robustness advantages due to its short optical path and independence from long-arm lasers. Its interference signal is determined solely by the local optical path difference between grating diffraction orders, significantly suppressing the impact of environmental disturbances on measurement accuracy.

[0003] In servo positioning of wafer stages, 2D scanning platforms, and ultra-precision machine tools, the motion stage exhibits in-plane displacement along the grating vector direction, as well as out-of-plane motion caused by uneven guide rails, load deformation, or thermal drift. If only in-plane displacement is monitored while ignoring the out-of-plane component, out-of-plane fluctuations will introduce cosine and Abbe errors, directly limiting positioning accuracy. A grating zero-difference two-DOF interferometer simultaneously acquires two sets of orthogonal diffraction signals through a single optical path. Utilizing the inherent anti-vibration phase characteristics of zero-difference interferometry and a symmetrical optical path design, it can simultaneously decouple one degree of freedom in-plane displacement from one degree of freedom out-of-plane displacement, with no inherent measurement blind zone across the entire range. Compared to heterodyne schemes, the zero-difference optical system is more compact, requires no acousto-optic frequency shifting devices, and is easier to integrate into vacuum and confined space environments, while maintaining high response bandwidth to meet nanometer-level dynamic tracking requirements.

[0004] Traditional zero-difference grating interferometers utilize the self-interference of a single-frequency laser with the diffraction order of the grating to form a measurement signal. While offering advantages such as a simple optical path and strong resistance to environmental disturbances, their structural design typically revolves around single-degree-of-freedom displacement measurement. With only a single readhead or insufficient decoupling of the symmetrical diffraction optical path, the zero-difference interference signal is only sensitive to in-plane lateral displacement of the grating. The out-of-plane gap fluctuation between the grating and the readhead is suppressed as a common mode or directly introduced into nonlinear errors, making it impossible to synchronously extract independent out-of-plane displacement information from the interference phase. Therefore, conventional zero-difference schemes struggle to simultaneously achieve real-time, independent measurement of one degree-of-freedom in-plane displacement and one degree-of-freedom out-of-plane displacement within a single optical architecture, limiting their application in scenarios requiring multi-degree-of-freedom linkage, such as wafer stage focusing compensation and scanning platform flatness monitoring.

[0005] To achieve synchronous decoupling of in-plane and out-of-plane displacements, heterodyne Littrow grating interferometers utilize dual-frequency lasers and the Littrow self-collimating diffraction principle. By measuring the beat frequency phase change formed by the interference of positive and negative diffraction orders and reference light, the in-plane and out-of-plane displacement components of the grating can be effectively separated. However, this approach places stringent requirements on the light source system: the dual-frequency laser must possess high frequency stability, strictly orthogonal polarization states, and compact spatial beam combining capabilities. This typically relies on discrete Zeeman dual-frequency lasers or acousto-optic frequency shifting modules, supplemented by complex fiber coupling and polarization management units. This results in a large light source volume and complex optical path calibration for heterodyne Littrow systems, making it difficult to achieve monolithic integration or miniaturized packaging with the readhead. Especially in confined vacuum environments such as inside a wafer fab, the separate layout of the light source not only increases the system footprint and thermal load but also introduces polarization state degradation and phase delay drift due to long-distance fiber transmission, directly affecting measurement repeatability and long-term stability. Summary of the Invention

[0006] To address the above problems, this application proposes a bidirectional secondary diffraction zero-difference grating interferometry device. Based on a dual-grating group and configuration, the zero-difference grating interferometry device is designed. This invention not only possesses the advantage of good light source integration but also enables 4x optical subdivision two-degree-of-freedom displacement measurement. The specific scheme is as follows: According to a specific embodiment of this application, this application provides a bidirectional secondary diffraction zero-difference grating interferometry measurement device, comprising: Light source, beam splitter grating, scale grating, measuring grating, cornerstone prism assembly, photodetector assembly, and data processing device; The light emitted from the light source forms +1st order transmission diffraction light and -1st order transmission diffraction light after passing through the beam splitter grating. The +1st order transmission diffraction light passes through the scale grating to obtain a first 0th order transmission diffraction light and a second +1st order transmission diffraction light; the first 0th order transmission diffraction light passes through the measurement grating and the cornerstone prism group and returns to the scale grating to generate a first multi-order transmission diffraction light, which then enters the photodetector group; the second +1st order transmission diffraction light passes through the measurement grating and the cornerstone prism group and returns to the scale grating to generate a second multi-order transmission diffraction light, which then enters the photodetector group. The -1st order transmission diffraction light passes through the scale grating to obtain the third 0th order transmission diffraction light and the fourth -1st order transmission diffraction light; the third 0th order transmission diffraction light passes through the measurement grating and the cornerstone prism group and returns to the scale grating to generate third multi-order transmission diffraction light, which then enters the photodetector group; the fourth -1st order transmission diffraction light passes through the measurement grating and the cornerstone prism group and returns to the scale grating to generate fourth multi-order transmission diffraction light, which then enters the photodetector group. The first multi-level transmission diffraction light, the second multi-level transmission diffraction light, the third multi-level transmission diffraction light, and the fourth multi-level transmission diffraction light interfere with each other in the photodetector group to form an interference output signal; The data processing device is connected to the photodetector group and is used to calculate the displacement of the target component under test based on the interference output signal of the photodetector group.

[0007] In some embodiments, the photodetector group includes a first photodetector, a second photodetector, a third photodetector, a fourth photodetector, a fifth photodetector, and a sixth photodetector; The first multi-level transmission diffraction light enters the third photodetector, the second photodetector, and the first photodetector, respectively; the second multi-level transmission diffraction light enters the fifth photodetector, the sixth photodetector, and the fourth photodetector, respectively; The third multi-level transmission diffraction light enters the fourth, fifth, and sixth photodetectors respectively and interferes with the second multi-level transmission diffraction light; the fourth multi-level transmission diffraction light enters the second, first, and third photodetectors respectively and interferes with the first multi-level transmission diffraction light.

[0008] In some embodiments, the first multi-level transmission diffraction light includes a first 0th-order sub-transmission diffraction light, a first +1st-order sub-transmission diffraction light, and a first +2nd-order sub-transmission diffraction light, and the first 0th-order sub-transmission diffraction light, the first +1st-order sub-transmission diffraction light, and the first +2nd-order sub-transmission diffraction light enter the third photodetector, the second photodetector, and the first photodetector, respectively. The second multi-level transmission diffraction light includes a second 0th-order sub-transmission diffraction light, a second -1st-order sub-transmission diffraction light, and a second +1st-order sub-transmission diffraction light. The second 0th-order sub-transmission diffraction light, the second -1st-order sub-transmission diffraction light, and the second +1st-order sub-transmission diffraction light enter the fifth photodetector, the sixth photodetector, and the fourth photodetector, respectively. The third multi-level transmission diffraction light includes the third 0th-order sub-transmission diffraction light, the third-1st-order sub-transmission diffraction light, and the third-2nd-order sub-transmission diffraction light, which enter the fourth, fifth, and sixth photodetectors, respectively. The fourth multi-level transmission diffraction light includes the fourth 0th-order sub-transmission diffraction light, the fourth+1st-order sub-transmission diffraction light, and the fourth-1st-order sub-transmission diffraction light, which enter the second photodetector, the first photodetector, and the third photodetector, respectively.

[0009] In some embodiments, the cornerstone prism group includes a first cornerstone prism, the first 0th order transmitted diffracted light passes through the measurement grating to generate a first reflected diffracted light, the first reflected diffracted light is reflected by the first cornerstone prism to the measurement grating to generate a second reflected diffracted light, and the second reflected diffracted light passes through the scale grating to generate a first 0th order sub-transmitted diffracted light, a first +1st order sub-transmitted diffracted light, and a first +2nd order sub-transmitted diffracted light.

[0010] In some embodiments, the cornerstone prism group includes a second cornerstone prism, the second+1st order transmitted diffracted light passes through the measurement grating to generate a third reflected diffracted light, the third reflected diffracted light is reflected by the second cornerstone prism to the measurement grating to generate a fourth reflected diffracted light, and the fourth reflected diffracted light passes through the scale grating to generate a second 0th order sub-transmitted diffracted light, a second--1st order sub-transmitted diffracted light, and a second+1st order sub-transmitted diffracted light.

[0011] In some embodiments, the third 0th order transmission diffraction light passes through the measurement grating to generate a fifth reflection diffraction light, the fifth reflection diffraction light is reflected by the second corner bevel prism to the measurement grating to generate a sixth reflection diffraction light, and the sixth reflection diffraction light passes through the scale grating to generate a third 0th order sub-transmission diffraction light, a third-1st order sub-transmission diffraction light, and a third-2nd order sub-transmission diffraction light.

[0012] In some embodiments, the cornerstone prism group includes a third cornerstone prism, the fourth-1st order transmitted diffracted light passes through the measurement grating to generate a seventh reflected diffracted light, the seventh reflected diffracted light is reflected by the third cornerstone prism to the measurement grating to generate an eighth reflected diffracted light, and the eighth reflected diffracted light passes through the scale grating to generate a fourth 0th order sub-transmitted diffracted light, a fourth+1st order sub-transmitted diffracted light, and a fourth-1st order sub-transmitted diffracted light.

[0013] In some embodiments, the photodetector group includes a first photodetector, a second photodetector, a third photodetector, a fourth photodetector, a fifth photodetector, and a sixth photodetector; The first multi-level transmission diffraction light enters the third photodetector, the second photodetector, and the first photodetector, respectively; the second multi-level transmission diffraction light enters the third photodetector, the second photodetector, and the first photodetector, respectively, and interferes with the first multi-level transmission diffraction light; The third multi-level transmission diffraction light enters the fourth, fifth, and sixth photodetectors respectively; the fourth multi-level transmission diffraction light interferes with the third multi-level transmission diffraction light by entering the fourth, fifth, and sixth photodetectors respectively.

[0014] In some embodiments, the cornerstone prism group includes a first cornerstone prism. The first 0th-order transmitted diffracted light passes through the measurement grating to generate a first reflected diffracted light. The first reflected diffracted light is reflected by the first cornerstone prism to the measurement grating to generate a second reflected diffracted light. The second reflected diffracted light passes through the scale grating to generate a first 0th-order sub-transmitted diffracted light, a first +1st-order sub-transmitted diffracted light, and a first +2nd-order sub-transmitted diffracted light. The first 0th-order sub-transmitted diffracted light, the first +1st-order sub-transmitted diffracted light, and the first +2nd-order sub-transmitted diffracted light enter the third photodetector, the second photodetector, and the first photodetector, respectively. The second +1 order transmission diffraction light passes through the measurement grating to generate a third reflection diffraction light. The third reflection diffraction light is reflected by the first corner bevel prism to the measurement grating to generate a fourth reflection diffraction light. The fourth reflection diffraction light passes through the scale grating to generate a second 0th order sub-transmission diffraction light, a second -1st order sub-transmission diffraction light, and a second +1st order sub-transmission diffraction light. The second 0th order sub-transmission diffraction light, the second -1st order sub-transmission diffraction light, and the second +1st order sub-transmission diffraction light enter the second photodetector, the first photodetector, and the third photodetector, respectively.

[0015] In some embodiments, the cornerstone prism group includes a second cornerstone prism; the third 0th-order transmitted diffracted light passes through the measurement grating to generate a fifth reflected diffracted light; the fifth reflected diffracted light is reflected by the second cornerstone prism to the measurement grating to generate a sixth reflected diffracted light; the sixth reflected diffracted light passes through the scale grating to generate a third 0th-order sub-transmitted diffracted light, a third-1st-order sub-transmitted diffracted light, and a third-2nd-order sub-transmitted diffracted light; the third 0th-order sub-transmitted diffracted light, the third-1st-order sub-transmitted diffracted light, and the third-2nd-order sub-transmitted diffracted light enter the fourth photodetector, the fifth photodetector, and the sixth photodetector, respectively. The fourth-1st order transmission diffraction light passes through the measurement grating to generate a seventh reflection diffraction light. The seventh reflection diffraction light is reflected by the second corner bevel prism to the measurement grating to generate an eighth reflection diffraction light. The eighth reflection diffraction light passes through the scale grating to generate a fourth 0th order sub-transmission diffraction light, a fourth+1st order sub-transmission diffraction light, and a fourth-1st order sub-transmission diffraction light. The fourth 0th order sub-transmission diffraction light, the fourth+1st order sub-transmission diffraction light, and the fourth-1st order sub-transmission diffraction light enter the fifth photodetector, the sixth photodetector, and the fourth photodetector, respectively.

[0016] Compared with the prior art, the above-described solutions of this application have at least the following beneficial effects: This application proposes a bidirectional secondary diffraction zero-difference grating interferometric measurement device. Through a dual-grating structure, a combination of a transmission scale grating and a measurement grating forms two sets of stable interference signals totaling six paths, enabling the calculation of the two-degree-of-freedom displacement of the measurement grating in both in-plane and out-of-plane directions. Furthermore, by utilizing the retroreflection characteristics of a cornerstone prism, secondary diffraction is constructed along the measurement path, achieving four-fold optical subdivision measurement. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 This is a schematic diagram of the structure of the bidirectional secondary diffraction zero-difference grating interferometry device provided in the embodiments of this application.

[0018] Figure 2 This is a schematic diagram of the structure of a bidirectional secondary diffraction zero-difference grating interferometry device provided in another embodiment of this application.

[0019] Figure descriptions: 1. Light source; 2. Beam splitter grating; 3. Scale grating; 4. Measuring grating; 20. Cornerstone prism group; 5. First cornerstone prism; 6. Second cornerstone prism; 7. Third cornerstone prism; 8. First photodetector; 9. Second photodetector; 10. Third photodetector; 11. Fourth photodetector; 12. Fifth photodetector; 13. Sixth photodetector; 30. Photodetector group; 40. Data processing device. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or device. Without further limitation, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the product or device that includes that element.

[0022] The embodiments of this application are described in detail below with reference to the accompanying drawings.

[0023] According to the specific implementation of this application, such as Figure 1 As shown, this application provides a bidirectional secondary diffraction zero-difference grating interferometric measurement device, including a light source 1, a beam splitter grating 2, a scale grating 3, a measurement grating 4, a cornerstone prism group 20, a photodetector group 30, and a data processing device 40. In this design, light source 1 is a zero-difference single-frequency light source, such as an infrared laser with a wavelength of 1064 nm, or it can be a zero-difference single-frequency light source of other wavelengths. The beam splitter grating 2 and the scale grating 3 are transmission gratings, with a grating pitch of, for example, 2 micrometers, or other grating pitches, which are not limited thereto. The light emitted from light source 1, after passing through the beam splitter grating 2, forms +1st order transmission diffraction light and -1st order transmission diffraction light.

[0024] In some embodiments, the scale grating 3 and the measuring grating 4 have the same grating pitch. For example, both have a grating pitch of 2 micrometers. This improves the compactness of the system structure and enhances the measurement performance of the system.

[0025] The +1st order transmission diffraction light passes through the scale grating 3 to obtain a first 0th order transmission diffraction light and a second +1st order transmission diffraction light; the first 0th order transmission diffraction light passes through the measurement grating 4 and the cornerstone prism group 20 and returns to the scale grating 3 to generate a first multi-order transmission diffraction light, which then enters the photodetector group 30; the second +1st order transmission diffraction light passes through the measurement grating 4 and the cornerstone prism group 20 and returns to the scale grating 3 to generate a second multi-order transmission diffraction light, which then enters the photodetector group 30. The -1st order transmission diffraction light passes through the scale grating 3 to obtain the third 0th order transmission diffraction light and the fourth -1st order transmission diffraction light; the third 0th order transmission diffraction light passes through the measurement grating 4 and the cornerstone prism group 20 and returns to the scale grating 3 to generate the third multi-order transmission diffraction light, which then enters the photodetector group 30; the fourth -1st order transmission diffraction light passes through the measurement grating 4 and the cornerstone prism group 20 and returns to the scale grating 3 to generate the fourth multi-order transmission diffraction light, which then enters the photodetector group 30. The first multi-level transmission diffraction light, the second multi-level transmission diffraction light, the third multi-level transmission diffraction light, and the fourth multi-level transmission diffraction light interfere with each other in the photodetector group 30 to form an interference output signal; The data processing device 40 is connected to the photodetector group 30 and is used to calculate the displacement of the target component under test based on the interference output signal of the photodetector group 30.

[0026] Furthermore, the photodetector group 30 includes a first photodetector 8, a second photodetector 9, a third photodetector 10, a fourth photodetector 11, a fifth photodetector 12, and a sixth photodetector 13; The first multi-level transmission diffraction light enters the third photodetector 10, the second photodetector 9, and the first photodetector 8, respectively; the second multi-level transmission diffraction light enters the fifth photodetector 12, the sixth photodetector 13, and the fourth photodetector 11, respectively. The third multi-level transmission diffraction light enters the fourth photodetector 11, the fifth photodetector 12, and the sixth photodetector 13 respectively and interferes with the second multi-level transmission diffraction light; the fourth multi-level transmission diffraction light enters the second photodetector 9, the first photodetector 8, and the third photodetector 10 respectively and interferes with the first multi-level transmission diffraction light.

[0027] Furthermore, the first multi-level transmission diffraction light includes a first 0th-order sub-transmission diffraction light, a first +1st-order sub-transmission diffraction light, and a first +2nd-order sub-transmission diffraction light, which respectively enter the third photodetector 10, the second photodetector 9, and the first photodetector 8. The second multi-level transmission diffraction light includes the second 0th-order sub-transmission diffraction light, the second -1st-order sub-transmission diffraction light, and the second +1st-order sub-transmission diffraction light. The second 0th-order sub-transmission diffraction light, the second -1st-order sub-transmission diffraction light, and the second +1st-order sub-transmission diffraction light enter the fifth photodetector 12, the sixth photodetector 13, and the fourth photodetector 11, respectively. The third multi-level transmission diffraction light includes the third 0th-order sub-transmission diffraction light, the third-1st-order sub-transmission diffraction light, and the third-2nd-order sub-transmission diffraction light. The third 0th-order sub-transmission diffraction light, the third-1st-order sub-transmission diffraction light, and the third-2nd-order sub-transmission diffraction light enter the fourth photodetector 11, the fifth photodetector 12, and the sixth photodetector 13, respectively. The fourth multi-level transmission diffraction light includes the fourth 0th-order sub-transmission diffraction light, the fourth +1st-order sub-transmission diffraction light, and the fourth -1st-order sub-transmission diffraction light. The fourth 0th-order sub-transmission diffraction light, the fourth +1st-order sub-transmission diffraction light, and the fourth -1st-order sub-transmission diffraction light enter the second photodetector 9, the first photodetector 8, and the third photodetector 10, respectively.

[0028] In some embodiments, the cornerstone prism group 20 includes a first cornerstone prism 5, the first 0th order transmitted diffracted light passes through the measurement grating 4 to generate a first reflected diffracted light, the first reflected diffracted light is reflected by the first cornerstone prism 5 to the measurement grating 4 to generate a second reflected diffracted light, and the second reflected diffracted light passes through the scale grating 3 to generate a first 0th order sub-transmitted diffracted light, a first +1st order sub-transmitted diffracted light, and a first +2nd order sub-transmitted diffracted light.

[0029] In some embodiments, the cornerstone prism group 20 includes a second cornerstone prism 6, the second +1st order transmitted diffracted light passes through the measurement grating 4 to generate a third reflected diffracted light, the third reflected diffracted light is reflected by the second cornerstone prism 6 to the measurement grating 4 to generate a fourth reflected diffracted light, the fourth reflected diffracted light passes through the scale grating 3 to generate a second 0th order sub-transmitted diffracted light, a second -1st order sub-transmitted diffracted light and a second +1st order sub-transmitted diffracted light.

[0030] Furthermore, the third 0th order transmission diffraction light passes through the measurement grating 4 to generate a fifth reflection diffraction light, the fifth reflection diffraction light is reflected by the second corner bevel prism 6 to the measurement grating 4 to generate a sixth reflection diffraction light, and the sixth reflection diffraction light passes through the scale grating 3 to generate a third 0th order sub-transmission diffraction light, a third-1st order sub-transmission diffraction light, and a third-2nd order sub-transmission diffraction light.

[0031] In some embodiments, the cornerstone prism group 20 includes a third cornerstone prism 7, the fourth-1st order transmitted diffracted light passes through the measurement grating 4 to generate a seventh reflected diffracted light, the seventh reflected diffracted light is reflected by the third cornerstone prism 7 to the measurement grating 4 to generate an eighth reflected diffracted light, and the eighth reflected diffracted light passes through the scale grating 3 to generate a fourth 0th order sub-transmitted diffracted light, a fourth+1st order sub-transmitted diffracted light, and a fourth-1st order sub-transmitted diffracted light.

[0032] As can be seen, this application, through the measurement configuration of the dual-grating structure, utilizes the combination of the transmission scale grating 3 and the measurement grating 4 to form two sets of stable interference signals totaling six paths, which can be used to calculate the two-degree-of-freedom displacement of the measurement grating in the in-plane and out-of-plane directions. Furthermore, by utilizing the retroreflection characteristics of the first corner prism 5, the second corner prism 6, and the third corner prism 7, secondary diffraction is constructed along the measurement path, achieving four-fold optical subdivision measurement.

[0033] According to another specific embodiment of this application, such as Figure 2 As shown, this application provides a bidirectional secondary diffraction zero-difference grating interferometric measurement device, including a light source 1, a beam splitter grating 2, a scale grating 3, a measurement grating 4, a cornerstone prism group 20, a photodetector group 30, and a data processing device 40; the same structure has the same function and effect, and will not be described again here, please refer to the foregoing embodiments.

[0034] The light emitted from the light source 1 is divided into +1st order transmission diffraction light and -1st order transmission diffraction light after passing through the beam splitter grating 2.

[0035] The +1st order transmission diffraction light passes through the scale grating 3 to obtain a first 0th order transmission diffraction light and a second +1st order transmission diffraction light; the first 0th order transmission diffraction light passes through the measurement grating 4 and the cornerstone prism group 20 and returns to the scale grating 3 to generate a first multi-order transmission diffraction light, which then enters the photodetector group 30; the second +1st order transmission diffraction light passes through the measurement grating 4 and the cornerstone prism group 20 and returns to the scale grating 3 to generate a second multi-order transmission diffraction light, which then enters the photodetector group 30. The -1st order transmission diffraction light passes through the scale grating 3 to obtain the third 0th order transmission diffraction light and the fourth -1st order transmission diffraction light; the third 0th order transmission diffraction light passes through the measurement grating 4 and the cornerstone prism group 20 and returns to the scale grating 3 to generate the third multi-order transmission diffraction light, which then enters the photodetector group 30; the fourth -1st order transmission diffraction light passes through the measurement grating 4 and the cornerstone prism group 20 and returns to the scale grating 3 to generate the fourth multi-order transmission diffraction light, which then enters the photodetector group 30. The first multi-level transmission diffraction light, the second multi-level transmission diffraction light, the third multi-level transmission diffraction light, and the fourth multi-level transmission diffraction light interfere with each other in the photodetector group 30 to form an interference output signal; The data processing device 40 is connected to the photodetector group 30 and is used to calculate the displacement of the target component under test based on the interference output signal of the photodetector group 30.

[0036] Furthermore, the photodetector group 30 includes a first photodetector 8, a second photodetector 9, a third photodetector 10, a fourth photodetector 11, a fifth photodetector 12, and a sixth photodetector 13; The first multi-level transmission diffraction light enters the third photodetector 10, the second photodetector 9, and the first photodetector 8, respectively; the second multi-level transmission diffraction light enters the third photodetector 10, the second photodetector 9, and the first photodetector 8, respectively, and interferes with the first multi-level transmission diffraction light; The third multi-level transmission diffraction light enters the fourth photodetector 11, the fifth photodetector 12, and the sixth photodetector 13 respectively; the fourth multi-level transmission diffraction light interferes with the third multi-level transmission diffraction light by entering the fourth photodetector 11, the fifth photodetector 12, and the sixth photodetector 13 respectively.

[0037] In some embodiments, the cornerstone prism group 20 includes a first cornerstone prism 5. The first 0th-order transmitted diffracted light passes through the measurement grating 4 to generate a first reflected diffracted light. The first reflected diffracted light is reflected by the first cornerstone prism 5 to the measurement grating 4 to generate a second reflected diffracted light. The second reflected diffracted light passes through the scale grating 3 to generate a first 0th-order sub-transmitted diffracted light, a first +1st-order sub-transmitted diffracted light, and a first +2nd-order sub-transmitted diffracted light. The first 0th-order sub-transmitted diffracted light, the first +1st-order sub-transmitted diffracted light, and the first +2nd-order sub-transmitted diffracted light enter the third photodetector 10, the second photodetector 9, and the first photodetector 8, respectively. The second +1 order transmission diffraction light passes through the measurement grating 4 to generate a third reflection diffraction light. The third reflection diffraction light is reflected by the first corner bevel prism 5 back to the measurement grating 4 to generate a fourth reflection diffraction light. The fourth reflection diffraction light passes through the scale grating 3 to generate a second 0th order sub-transmission diffraction light, a second -1st order sub-transmission diffraction light, and a second +1st order sub-transmission diffraction light. The second 0th order sub-transmission diffraction light, the second -1st order sub-transmission diffraction light, and the second +1st order sub-transmission diffraction light enter the second photodetector 9, the first photodetector 8, and the third photodetector 10, respectively.

[0038] In some embodiments, the cornerstone prism group 20 includes a second cornerstone prism 6. The third 0th-order transmitted diffracted light passes through the measurement grating 4 to generate a fifth reflected diffracted light. The fifth reflected diffracted light is reflected by the second cornerstone prism 6 to the measurement grating 4 to generate a sixth reflected diffracted light. The sixth reflected diffracted light passes through the scale grating 3 to generate a third 0th-order sub-transmitted diffracted light, a third-1st-order sub-transmitted diffracted light, and a third-2nd-order sub-transmitted diffracted light. The third 0th-order sub-transmitted diffracted light, the third-1st-order sub-transmitted diffracted light, and the third-2nd-order sub-transmitted diffracted light enter the fourth photodetector 11, the fifth photodetector 12, and the sixth photodetector 13, respectively. The fourth-1st order transmitted diffracted light passes through the measurement grating 4 to generate a seventh reflected diffracted light. The seventh reflected diffracted light is reflected by the second corner bevel prism 6 back to the measurement grating 4 to generate an eighth reflected diffracted light. The eighth reflected diffracted light passes through the scale grating 3 to generate a fourth 0th order sub-transmitted diffracted light, a fourth+1st order sub-transmitted diffracted light, and a fourth-1st order sub-transmitted diffracted light. The fourth 0th order sub-transmitted diffracted light, the fourth+1st order sub-transmitted diffracted light, and the fourth-1st order sub-transmitted diffracted light enter the fifth photodetector 12, the sixth photodetector 13, and the fourth photodetector 11, respectively.

[0039] This application utilizes a combination of a transmission scale grating 3 and a measurement grating 4 to form two sets of stable interference signals totaling six channels, which can be used to calculate the two-degree-of-freedom displacement of the measurement grating in the in-plane and out-of-plane directions. Furthermore, by leveraging the retroreflection characteristics of the simplified optical path structure of the first and second corner pyramid prisms 5 and 6, secondary diffraction is constructed along the measurement path, achieving four-fold optical subdivision measurement. The movement of the measurement grating 4 causes a phase change of one period π in the diffracted light, and the phase change period obtained by the detector analysis is 4π. This demonstrates that the influence of motion on the phase of the measurement interference signal is amplified through the system's optical structure design, thereby improving measurement accuracy.

[0040] In some embodiments, the calculation process of the data processing device 40 is as follows: The output signals of the first photodetector 8, the second photodetector 9, and the third photodetector 10 are as follows:

[0041] in, This represents the phase change caused by displacement in the X direction. This represents the phase change caused by displacement in the Z direction. Φ1, Φ2, and Φ3 represent fixed phase shifts. I1, I2, and I3 together constitute a three-step phase shift. The three electrical signals can be processed together to obtain the phase shift. The value.

[0042] The output signals of the fourth photodetector 11, the fifth photodetector 12, and the sixth photodetector 13 are as follows:

[0043] Among them, I4, I5, and I6 together constitute a three-step phase shift, and the three electrical signals can be processed together to obtain... The value.

[0044] Furthermore, the displacement of the target component under two degrees of freedom is calculated, including: Based on equations (1) and (2), by combining... and Phase changes in the X direction were obtained respectively. Phase change in the Z direction ; Based on X-direction phase change Phase change in the Z direction Calculate the displacement in the X direction S x and Z-direction displacement S z ; in, , , d This indicates the grating pitch.

[0045] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0046] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A bidirectional second-order diffraction zero-difference grating interferometric measurement device, characterized in that, include: The light source (1), the beam splitter grating (2), the scale grating (3), the measuring grating (4), the corner cube prism group (20), the photodetector group (30), and the data processing device (40); The light emitted from the light source (1) forms +1 order transmission diffraction light and -1 order transmission diffraction light after passing through the beam splitter (2); The +1 order transmission diffraction light passes through the scale grating (3) to obtain the first 0th order transmission diffraction light and the second +1 order transmission diffraction light; the first 0th order transmission diffraction light passes through the measurement grating (4) and the cornerstone prism group (20) and returns to the scale grating (3) to generate the first multi-order transmission diffraction light, which then enters the photodetector group (30); the second +1 order transmission diffraction light passes through the measurement grating (4) and the cornerstone prism group (20) and returns to the scale grating (3) to generate the second multi-order transmission diffraction light, which then enters the photodetector group (30). The -1st order transmission diffraction light passes through the scale grating (3) to obtain the third 0th order transmission diffraction light and the fourth -1st order transmission diffraction light; the third 0th order transmission diffraction light passes through the measurement grating (4) and the cornerstone prism group (20) and returns to the scale grating (3) to generate the third multi-order transmission diffraction light, which then enters the photodetector group (30); the fourth -1st order transmission diffraction light passes through the measurement grating (4) and the cornerstone prism group (20) and returns to the scale grating (3) to generate the fourth multi-order transmission diffraction light, which then enters the photodetector group (30). The first multi-level transmission diffraction light, the second multi-level transmission diffraction light, the third multi-level transmission diffraction light, and the fourth multi-level transmission diffraction light interfere with each other in the photodetector group (30) to form an interference output signal; The data processing device (40) is connected to the photodetector group (30) and is used to calculate the displacement of the target component under test based on the interference output signal of the photodetector group (30).

2. The bidirectional second-order diffraction zero-difference grating interferometry device according to claim 1, characterized in that, The photodetector group (30) includes a first photodetector (8), a second photodetector (9), a third photodetector (10), a fourth photodetector (11), a fifth photodetector (12), and a sixth photodetector (13); The first multi-level transmission diffraction light enters the third photodetector (10), the second photodetector (9), and the first photodetector (8), respectively; the second multi-level transmission diffraction light enters the fifth photodetector (12), the sixth photodetector (13), and the fourth photodetector (11), respectively; The third multi-level transmission diffraction light enters the fourth photodetector (11), the fifth photodetector (12), and the sixth photodetector (13) respectively and interferes with the second multi-level transmission diffraction light; the fourth multi-level transmission diffraction light enters the second photodetector (9), the first photodetector (8), and the third photodetector (10) respectively and interferes with the first multi-level transmission diffraction light.

3. The bidirectional secondary diffraction zero-difference grating interferometry measuring device according to claim 2, characterized in that, The first multi-level transmission diffraction light includes a first 0th-order sub-transmission diffraction light, a first +1st-order sub-transmission diffraction light, and a first +2nd-order sub-transmission diffraction light. The first 0th-order sub-transmission diffraction light, the first +1st-order sub-transmission diffraction light, and the first +2nd-order sub-transmission diffraction light enter the third photodetector (10), the second photodetector (9), and the first photodetector (8), respectively. The second multi-level transmission diffraction light includes the second 0th-order sub-transmission diffraction light, the second -1st-order sub-transmission diffraction light, and the second +1st-order sub-transmission diffraction light. The second 0th-order sub-transmission diffraction light, the second -1st-order sub-transmission diffraction light, and the second +1st-order sub-transmission diffraction light enter the fifth photodetector (12), the sixth photodetector (13), and the fourth photodetector (11), respectively. The third multi-level transmission diffraction light includes the third 0th-order sub-transmission diffraction light, the third-1st-order sub-transmission diffraction light, and the third-2nd-order sub-transmission diffraction light. The third 0th-order sub-transmission diffraction light, the third-1st-order sub-transmission diffraction light, and the third-2nd-order sub-transmission diffraction light enter the fourth photodetector (11), the fifth photodetector (12), and the sixth photodetector (13), respectively. The fourth multi-level transmission diffraction light includes the fourth 0th-order sub-transmission diffraction light, the fourth +1st-order sub-transmission diffraction light, and the fourth -1st-order sub-transmission diffraction light. The fourth 0th-order sub-transmission diffraction light, the fourth +1st-order sub-transmission diffraction light, and the fourth -1st-order sub-transmission diffraction light enter the second photodetector (9), the first photodetector (8), and the third photodetector (10), respectively.

4. The bidirectional second-order diffraction zero-difference grating interferometry measuring device according to claim 3, characterized in that, The cornerstone prism group (20) includes a first cornerstone prism (5). The first 0th order transmitted diffracted light passes through the measurement grating (4) to generate a first reflected diffracted light. The first reflected diffracted light is reflected by the first cornerstone prism (5) to the measurement grating (4) to generate a second reflected diffracted light. The second reflected diffracted light passes through the scale grating (3) to generate a first 0th order sub-transmitted diffracted light, a first +1st order sub-transmitted diffracted light, and a first +2nd order sub-transmitted diffracted light.

5. The bidirectional second-order diffraction zero-difference grating interferometry device according to claim 3, characterized in that, The cornerstone prism group (20) includes a second cornerstone prism (6). The second +1 order transmitted diffracted light passes through the measurement grating (4) to generate a third reflected diffracted light. The third reflected diffracted light is reflected by the second cornerstone prism (6) to the measurement grating (4) to generate a fourth reflected diffracted light. The fourth reflected diffracted light passes through the scale grating (3) to generate a second 0th order sub-transmitted diffracted light, a second -1st order sub-transmitted diffracted light, and a second +1st order sub-transmitted diffracted light.

6. The bidirectional second-order diffraction zero-difference grating interferometry device according to claim 5, characterized in that, The third 0th order transmission diffraction light is reflected by the measurement grating (4) to generate the fifth reflection diffraction light. The fifth reflection diffraction light is reflected by the second corner prism (6) to the measurement grating (4) to generate the sixth reflection diffraction light. The sixth reflection diffraction light is reflected by the scale grating (3) to generate the third 0th order sub-transmission diffraction light, the third-1st order sub-transmission diffraction light and the third-2nd order sub-transmission diffraction light.

7. The bidirectional second-order diffraction zero-difference grating interferometry device according to claim 3, characterized in that, The cornerstone prism group (20) includes a third cornerstone prism (7). The fourth-1st order transmitted diffracted light is reflected by the measuring grating (4) to generate a seventh reflected diffracted light. The seventh reflected diffracted light is reflected by the third cornerstone prism (7) to the measuring grating (4) to generate an eighth reflected diffracted light. The eighth reflected diffracted light is reflected by the scale grating (3) to generate a fourth 0th order sub-transmitted diffracted light, a fourth+1st order sub-transmitted diffracted light, and a fourth-1st order sub-transmitted diffracted light.

8. The bidirectional second-order diffraction zero-difference grating interferometry device according to claim 1, characterized in that, The photodetector group (30) includes a first photodetector (8), a second photodetector (9), a third photodetector (10), a fourth photodetector (11), a fifth photodetector (12), and a sixth photodetector (13); The first multi-level transmission diffraction light enters the third photodetector (10), the second photodetector (9), and the first photodetector (8), respectively; the second multi-level transmission diffraction light enters the third photodetector (10), the second photodetector (9), and the first photodetector (8), respectively, and interferes with the first multi-level transmission diffraction light; The third multi-level transmission diffraction light enters the fourth photodetector (11), the fifth photodetector (12), and the sixth photodetector (13), respectively; the fourth multi-level transmission diffraction light enters the fourth photodetector (11), the fifth photodetector (12), and the sixth photodetector (13) and interferes with the third multi-level transmission diffraction light.

9. The bidirectional second-order diffraction zero-difference grating interferometry device according to claim 8, characterized in that, The cornerstone prism group (20) includes a first cornerstone prism (5). The first 0th order transmitted diffracted light passes through the measurement grating (4) to generate a first reflected diffracted light. The first reflected diffracted light is reflected by the first cornerstone prism (5) to the measurement grating (4) to generate a second reflected diffracted light. The second reflected diffracted light passes through the scale grating (3) to generate a first 0th order sub-transmitted diffracted light, a first +1st order sub-transmitted diffracted light, and a first +2nd order sub-transmitted diffracted light. The first 0th order sub-transmitted diffracted light, the first +1st order sub-transmitted diffracted light, and the first +2nd order sub-transmitted diffracted light enter the third photodetector (10), the second photodetector (9), and the first photodetector (8), respectively. The second +1 order transmission diffraction light passes through the measurement grating (4) to generate a third reflection diffraction light. The third reflection diffraction light is reflected by the first corner bevel prism (5) back to the measurement grating (4) to generate a fourth reflection diffraction light. The fourth reflection diffraction light passes through the scale grating (3) to generate a second 0th order sub-transmission diffraction light, a second -1st order sub-transmission diffraction light, and a second +1st order sub-transmission diffraction light. The second 0th order sub-transmission diffraction light, the second -1st order sub-transmission diffraction light, and the second +1st order sub-transmission diffraction light enter the second photodetector (9), the first photodetector (8), and the third photodetector (10), respectively.

10. The bidirectional secondary diffraction null-difference grating interferometry device according to claim 8, characterized in that, The cornerstone prism group (20) includes a second cornerstone prism (6). The third 0th order transmitted diffracted light passes through the measurement grating (4) to generate a fifth reflected diffracted light. The fifth reflected diffracted light is reflected by the second cornerstone prism (6) to the measurement grating (4) to generate a sixth reflected diffracted light. The sixth reflected diffracted light passes through the scale grating (3) to generate a third 0th order sub-transmitted diffracted light, a third-1st order sub-transmitted diffracted light, and a third-2nd order sub-transmitted diffracted light. The third 0th order sub-transmitted diffracted light, the third-1st order sub-transmitted diffracted light, and the third-2nd order sub-transmitted diffracted light enter the fourth photodetector (11), the fifth photodetector (12), and the sixth photodetector (13), respectively. The fourth-1st order transmission diffraction light is reflected by the measurement grating (4) to generate the seventh reflection diffraction light. The seventh reflection diffraction light is reflected by the second corner bevel prism (6) to the measurement grating (4) to generate the eighth reflection diffraction light. The eighth reflection diffraction light is reflected by the scale grating (3) to generate the fourth 0th order sub-transmission diffraction light, the fourth+1st order sub-transmission diffraction light and the fourth-1st order sub-transmission diffraction light. The fourth 0th order sub-transmission diffraction light, the fourth+1st order sub-transmission diffraction light and the fourth-1st order sub-transmission diffraction light enter the fifth photodetector (12), the sixth photodetector (13) and the fourth photodetector (11) respectively.

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