A heterodyne laser interferometer measuring device based on phase decoupling and multiple frequency multiplication

Abstract

The application provides a heterodyne laser interference measurement device based on phase decoupling and multiple frequency multiplication, which improves measurement accuracy by using two aspects of phase decoupling and multiple frequency multiplication technology, wherein the multiple frequency multiplication provides multiple times of laser displacement information in the multiple round trip measurement state, and the phase decoupling provides forward measurement and reverse measurement in the real-time measurement state, so as to weaken the influence of positioning fluctuation error and environmental disturbance error of the displacement table; in addition, in the phase decoupling state, the measurement accuracy is changed from 6 times of Doppler frequency shift to 12 times of Doppler frequency shift, and the measurement accuracy is further improved.

Description

Technical Field

[0001] This application relates to the field of optical equipment technology, and in particular to a heterodyne laser interferometry device based on phase decoupling and multiple frequency doubling. Background Technology

[0002] With the rapid development of the semiconductor manufacturing industry, the development needs of various subsystems of lithography machines that meet the requirements of extreme ultraviolet lithography (EUV) or deep ultraviolet lithography (DUV) technologies, as well as equipment testing and positioning, require laser interferometer displacement measurement accuracy at the sub-nanometer level.

[0003] Currently, when performing laser interferometric displacement measurement, the existing 4x optical subdivision mirror group with equal optical path and common optical path, as well as the existing 8x and 12x optical subdivision mirror groups with equal optical path and common optical path, all utilize the multiple frequency doubling principle of Doppler frequency shift technology for ultra-precision displacement measurement.

[0004] However, existing measuring devices are limited by spatial positioning vibrations of the displacement stage, noise in signal processing, and fluctuations in signal transmission, all of which affect the improvement of displacement measurement accuracy. Summary of the Invention

[0005] This application aims to at least solve the technical problems existing in the prior art. To this end, the first aspect of this application proposes a heterodyne laser interferometry measurement device based on phase decoupling and multiple frequency doubling, comprising: a dual-frequency laser, a beam splitter prism, a forward displacement measuring device, a displacement measuring substrate, a reverse displacement measuring device, a first fiber coupler, a second fiber coupler, a data acquisition module, and a host computer. The displacement measuring substrate includes a first plane mirror, a linear displacement platform, and a second plane mirror. The linear displacement platform is positioned between the forward and reverse displacement measuring devices. The first and second plane mirrors are positioned on either side of the linear displacement platform and move synchronously with it.

[0006] The dual-frequency laser is used to generate a beam of orthogonally linearly polarized light. The linearly polarized light is split into reflected light and transmitted light according to energy after passing through a beam splitter. The reflected light is incident on the second fiber coupler, and the transmitted light is incident on the forward displacement measuring device for polarization splitting, which splits into P-polarized light of the first frequency and S-polarized light of the second frequency.

[0007] P-polarized light is processed by the forward displacement measuring device and the displacement measuring substrate before being incident on the first fiber coupler.

[0008] S-polarized light is processed by the forward displacement measuring device, the displacement measuring substrate, and the reverse displacement measuring device before being incident on the first fiber coupler.

[0009] The first and second fiber optic couplers transmit the interferometric displacement measurement signal to the data acquisition module. After data processing, the signal is transmitted to the host computer to obtain real-time displacement measurement information.

[0010] In one possible implementation, the forward displacement measuring device includes a first polarizing beam splitter, a first quarter-wave plate, a first right-angle reflecting prism, a second right-angle reflecting prism, and a first inclined plane reflecting mirror.

[0011] In one possible implementation, the P-polarized light, after being processed by a forward displacement measuring device and a displacement measuring substrate, is incident on a first fiber coupler, including:

[0012] P-polarized light is transmitted through the first quarter-wave plate, incident on the first plane mirror, returns along the same path, is transmitted through the first quarter-wave plate, reflected by the first polarizing beam splitter, undergoes two internal reflections by the first right-angle reflecting prism and another reflection by the first polarizing beam splitter, is transmitted through the first quarter-wave plate, incident on the first plane mirror, returns along the same path, is transmitted through the first quarter-wave plate, is transmitted through the first polarizing beam splitter, undergoes two internal reflections by the second right-angle reflecting prism and another transmission by the first polarizing beam splitter, repeats the above steps, is transmitted through the first quarter-wave plate again, incident on the first plane mirror, returns along the same path, is transmitted through the first quarter-wave plate, undergoes two internal reflections by the first right-angle reflecting prism and another reflection by the first polarizing beam splitter, is transmitted through the first quarter-wave plate, incident on the first plane mirror, returns along the same path, is transmitted through the first quarter-wave plate, is transmitted through the first polarizing beam splitter, and finally incident on the first fiber coupler.

[0013] In one possible implementation, the reverse displacement measuring device includes a second inclined plane mirror, a second polarizing beam splitter, a second quarter-wave plate, a third plane mirror, a third quarter-wave plate, and a third right-angle reflecting prism.

[0014] In one possible implementation, the forward displacement measuring device includes a first polarizing beam splitter, a first quarter-wave plate, a first right-angle reflecting prism, a second right-angle reflecting prism, and a first inclined plane reflecting mirror. S-polarized light, after being processed by the forward displacement measuring device, the displacement measuring substrate, and the reverse displacement measuring device, is incident on the first fiber optic coupler, comprising:

[0015] S-polarized light undergoes two inclined plane reflections by the first and second inclined plane mirrors, is reflected by the second polarizing beam splitter, transmitted through the second quarter-wave plate, and incident on the third plane mirror. It then returns along the same path, is transmitted through the second quarter-wave plate, again through the second polarizing beam splitter, and through the third quarter-wave plate, before being incident on the second plane mirror again. It returns along the same path, is transmitted through the third quarter-wave plate, is reflected by the second polarizing beam splitter, undergoes two internal reflections by the third right-angle mirror, is reflected by the second polarizing beam splitter, is transmitted through the third quarter-wave plate, and incident on the second plane mirror again. It returns along the same path, is transmitted through the third quarter-wave plate, is transmitted through the second polarizing beam splitter, and then incident on the third plane mirror again. It returns along the same path, is transmitted through the second quarter-wave plate, and after being reflected by the second polarizing beam splitter, repeats the preset reflection and transmission process. Finally, it undergoes two more inclined plane reflections by the second and first inclined plane mirrors, is reflected by the first polarizing beam splitter, and incident on the first fiber coupler.

[0016] In one possible implementation, the preset reflection and transmission process is as follows: after two inclined plane reflections by the second inclined plane mirror and the first inclined plane mirror, after two internal reflections by the first polarizing beam splitter prism and the second right-angle reflecting prism, after two inclined plane reflections by the first polarizing beam splitter prism, the first inclined plane mirror, and the second inclined plane mirror, after reflection by the second polarizing beam splitter prism, after transmission through the second quarter-wave plate, it enters the third plane mirror, returns along the same path, is transmitted through the second quarter-wave plate, is transmitted through the second polarizing beam splitter prism, is transmitted through the third quarter-wave plate, enters the second plane mirror, returns along the same path, is transmitted through the third quarter-wave plate, is reflected by the second polarizing beam splitter prism, after two internal reflections by the third right-angle reflecting prism and the second polarizing beam splitter prism, is transmitted through the third quarter-wave plate, enters the second plane mirror, returns along the same path, is transmitted through the third quarter-wave plate, is transmitted through the second polarizing beam splitter prism, is transmitted through the second quarter-wave plate, enters the third plane mirror, returns along the same path, is transmitted through the second quarter-wave plate, and is reflected by the second polarizing beam splitter prism.

[0017] In one possible implementation, the Doppler frequency shift signal of the forward displacement measuring device is represented as: The Doppler frequency shift signal of the negative displacement measuring device is expressed as The Doppler frequency shift signal of the second fiber coupler is represented as f1-f2, and the interference signal of the first fiber coupler is represented as... Where f1 represents the first frequency and f2 represents the second frequency. This indicates Doppler frequency shift.

[0018] The second aspect of this application proposes a heterodyne laser interferometry method based on phase decoupling and multiple frequency doubling, applied to the heterodyne laser interferometry device based on phase decoupling and multiple frequency doubling given in the first aspect. The device includes: a dual-frequency laser, a beam splitter prism, a forward displacement measuring device, a displacement measuring substrate, a reverse displacement measuring device, a first fiber coupler, a second fiber coupler, a data acquisition module, and a host computer. The displacement measuring substrate includes a first plane mirror, a linear displacement platform, and a second plane mirror. The linear displacement platform is positioned between the forward and reverse displacement measuring devices. The first and second plane mirrors are positioned on either side of the linear displacement platform and move synchronously with it. The method comprises:

[0019] The dual-frequency laser is used to generate a beam of orthogonally linearly polarized light. The linearly polarized light is split into reflected light and transmitted light according to energy after passing through a beam splitter. The reflected light is incident on the second fiber coupler, and the transmitted light is incident on the forward displacement measuring device for polarization splitting, which splits into P-polarized light of the first frequency and S-polarized light of the second frequency.

[0020] P-polarized light is processed by the forward displacement measuring device and the displacement measuring substrate before being incident on the first fiber coupler.

[0021] S-polarized light is processed by the forward displacement measuring device, the displacement measuring substrate, and the reverse displacement measuring device before being incident on the first fiber coupler.

[0022] The first and second fiber optic couplers transmit the interferometric displacement measurement signal to the data acquisition module. After data processing, the signal is transmitted to the host computer to obtain real-time displacement measurement information.

[0023] The technical solution provided in this application can achieve at least the following beneficial effects:

[0024] The heterodyne laser interferometry measurement device based on phase decoupling and multiple frequency doubling provided in this application includes a dual-frequency laser, a beam splitter prism, a forward displacement measuring device, a displacement measuring substrate, a reverse displacement measuring device, a first fiber coupler, a second fiber coupler, a data acquisition module, and a host computer. The displacement measuring substrate includes a first plane mirror, a linear displacement platform, and a second plane mirror. The linear displacement platform is located at the middle position of the forward displacement measuring device and the reverse displacement measuring device. The first plane mirror and the second plane mirror are located on both sides of the linear displacement platform and move synchronously with the linear displacement platform. The dual-frequency laser generates an orthogonally linearly polarized beam. This beam is split into reflected and transmitted light by a beam splitter according to energy. The reflected light is incident on a second fiber coupler, while the transmitted light is incident on a forward displacement measuring device for polarization splitting, resulting in P-polarized light of the first frequency and S-polarized light of the second frequency. The P-polarized light is processed by the forward displacement measuring device and the displacement measuring substrate before being incident on a first fiber coupler. The S-polarized light is processed by the forward displacement measuring device, the displacement measuring substrate, and the reverse displacement measuring device before being incident on a first fiber coupler. The first and second fiber couplers transmit the interference displacement measurement signal to a data acquisition module, which processes the data and transmits it to a host computer to obtain real-time displacement measurement information. This scheme improves measurement accuracy by utilizing phase decoupling and multiple frequency doubling techniques. Multiple frequency doubling provides multiple times the laser displacement information under multiple round trip measurement conditions, while phase decoupling provides forward and reverse measurements under real-time measurement conditions, thus mitigating the impact of positioning fluctuation errors of the displacement stage and environmental disturbance errors. Furthermore, under phase decoupling, the measurement accuracy is increased from 6 times the Doppler frequency shift to 12 times the Doppler frequency shift, further improving measurement accuracy. Additionally, by utilizing multi-point incident beams and positioning the single beam at the same location on both sides, six beam points are simultaneously incident linearly on both the front and rear surfaces. It can simultaneously detect and measure the spatial positioning accuracy of the reference mirror on the displacement stage in real time on both the left and right sides, avoiding beam deviation of the plane mirror during linear displacement. In the operation of the displacement stage, the front and rear plane mirrors operate synchronously, and the displacement measurement information can be accurately fed back to the displacement stage for precise control of the positioning accuracy of the displacement stage. At the same time, the signals acquired synchronously in both positive and negative dimensions contain the flutter information of the displacement stage and the disturbance information of the environment. Therefore, in the phase decoupling state, the error information can be reduced within the system based on real-time information to ensure the overall stability of the displacement measurement device. Attached Figure Description

[0025] Figure 1 A schematic diagram of a heterodyne laser interferometry device based on phase decoupling and multiple frequency doubling provided in this application embodiment;

[0026] Figure 2 This is a schematic diagram of an ultra-low thermal expansion coefficient measuring device based on dual-frequency laser, provided as an embodiment of this application.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1-Dual-frequency laser; 2-Beam splitter prism; 3-Forward displacement measurement device; 301-First polarizing beam splitter prism; 302-First quarter-wave plate; 303-First right-angle reflecting prism; 304-Second right-angle reflecting prism; 305-First inclined plane reflecting mirror; 4-Displacement measurement substrate; 401-First plane reflecting mirror; 402-Linear displacement platform; 403-Second plane reflecting mirror; 5-Reverse displacement measurement device; 501-Second inclined plane reflecting mirror; 502-Second polarizing beam splitter prism; 503-Second quarter-wave plate; 504-Third plane reflecting mirror; 505-Third quarter-wave plate; 506-Third right-angle reflecting prism; 6-First fiber optic coupler; 7-Second fiber optic coupler; 8-Digital acquisition module; 9-Host computer. Detailed Implementation

[0029] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0030] With the rapid development of the semiconductor manufacturing industry, the demand for equipment and equipment testing and positioning for various subsystems of EUV / DUV lithography machines, precision control and accurate positioning of high-end CNC machine tools for fine processing, and ultra-precision testing equipment requires laser interferometer displacement measurement accuracy at the sub-nanometer level.

[0031] The fundamental principles in displacement measurement are zero-difference and heterodyne laser interferometric displacement measurement, including the existing 4x optical subdivision laser mirror group with common optical path, the multi-axis interferometric measurement mirror group formed by using a compact wavelength compensator and a cross-shaped scribe stage, and a spatially separated 4x optical subdivision laser mirror group.

[0032] Currently, for 4x optical subdivision mirror groups with equal optical path and common optical path, as well as existing 8x and 12x optical subdivision mirror groups with equal optical path and common optical path, all utilize the multiple frequency doubling principle of Doppler frequency shift technology for ultra-precision displacement measurement. Secondly, for the phase decoupling 8x optical subdivision structure of second-order diffraction light of two-dimensional gratings, as well as the existing phase decoupling 4x optical subdivision structure of first-order diffraction light based on two-dimensional gratings, all utilize multiple subdivision measurement structures that use the opposite Doppler frequency shift signals for phase decoupling to reduce measurement errors and improve measurement accuracy.

[0033] However, the main shortcomings of existing technologies are as follows: First, while laser-based displacement measurement ensures multiple Doppler frequency shifts, it cannot reduce measurement errors in real time. Second, limitations such as spatial positioning vibrations of the displacement stage, noise in signal processing, and fluctuations in signal transmission all affect the improvement of displacement measurement accuracy. Third, error compensation still relies on forming a feedback dataset from real-time measurement error signals to compensate for the measurement, which affects both the accuracy and timeliness of the system, and has limited compensation capabilities. Fourth, laser interferometry does not utilize phase decoupling technology and multiple frequency doubling technology for higher-precision displacement measurement, and the exploration of measurement limits is insufficient.

[0034] Based on this, this application proposes a heterodyne laser interferometry measurement device based on phase decoupling and multiple frequency doubling. This scheme improves measurement accuracy by utilizing phase decoupling and multiple frequency doubling techniques. Multiple frequency doubling provides multiple times the laser displacement information under multiple round trip measurement conditions, while phase decoupling provides forward and reverse measurements under real-time measurement conditions, thus reducing the influence of positioning fluctuation errors of the displacement stage and environmental disturbance errors. Furthermore, under phase decoupling, the measurement accuracy is increased from 6 times the Doppler frequency shift to 12 times the Doppler frequency shift, further improving measurement accuracy. Moreover, by utilizing multi-point incident illumination of a single beam and positioning at the same position on both sides of the single beam, the measurement accuracy is improved. Both surfaces are simultaneously incident with six light spots in a linear state, allowing for real-time detection and measurement of the spatial positioning accuracy of the reference mirror on the displacement stage from both sides. This avoids beam offset during linear displacement of the plane mirror. Furthermore, with the two plane mirrors operating synchronously during displacement stage operation, displacement measurement information can be accurately fed back to the displacement stage for precise control of its positioning accuracy. Simultaneously, the signals acquired synchronously from both positive and negative dimensions include displacement stage flutter information and environmental disturbance information. Therefore, in a phase-decoupled state, error information can be reduced within the system based on real-time information, ensuring the overall stability of the displacement measurement device.

[0035] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the application. Unless otherwise defined, the technical or scientific terms used in this application should be understood in their ordinary sense by one of ordinary skill in the art to which this application pertains. The singular forms “a,” “described,” and “the” used in this application specification and appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more associated listed items. In the description of the embodiments of this application, it should be understood that the terms “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” “circumferential,” etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the embodiments of this application.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of embodiments of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0037] In the embodiments of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0038] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0039] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in the embodiments of this application are for illustrative purposes only and do not represent the only implementation.

[0040] The following is in conjunction with the appendix Figure 1-2 The heterodyne laser interferometry apparatus based on phase decoupling and multiple frequency doubling of embodiments of this application will be described by way of example.

[0041] like Figure 1 As shown, Figure 1 This is a schematic diagram of a heterodyne laser interferometry measurement device based on phase decoupling and multiple frequency doubling, provided in an embodiment of this application. The device includes: a dual-frequency laser 1, a beam splitter prism 2, a forward displacement measuring device 3, a displacement measuring substrate 4, a reverse displacement measuring device 5, a first fiber coupler 6, a second fiber coupler 7, a data acquisition module 8, and a host computer 9. The displacement measuring substrate 4 includes a first plane mirror 401, a linear displacement platform 402, and a second plane mirror 403. The linear displacement platform 402 is located between the forward displacement measuring device 3 and the reverse displacement measuring device 5. The first plane mirror 401 and the second plane mirror 403 are located on both sides of the linear displacement platform 402 and move synchronously with the linear displacement platform 402.

[0042] The dual-frequency laser 1 generates a beam of orthogonally linearly polarized light with a wavelength of 632.8 nm and frequencies of f1 and f2. After being split by a beam splitter prism 2 according to energy, the linearly polarized light is divided into reflected and transmitted light. The reflected light is incident on a second fiber coupler 7, and the transmitted light is incident on a forward displacement measuring device 3 for polarization splitting, resulting in P-polarized light of the first frequency and S-polarized light of the second frequency. The P-polarized light is processed by the forward displacement measuring device 3 and the displacement measuring substrate 4 before being incident on a first fiber coupler 6. The S-polarized light is processed by the forward displacement measuring device 3, the displacement measuring substrate 4, and the reverse displacement measuring device 5 before being incident on a first fiber coupler 6. The first fiber coupler 6 and the second fiber coupler 7 transmit the interference displacement measurement signal to a data acquisition module 8, which, after data processing, transmits it to a host computer 9 to obtain real-time displacement measurement information.

[0043] In some alternative embodiments, please continue to refer to Figure 1 The forward displacement measuring device 3 includes a first polarizing beam splitter 301, a first quarter-wave plate 302, a first right-angle reflecting prism 303, a second right-angle reflecting prism 304, and a first inclined plane reflecting mirror 305.

[0044] Thus, after being processed by the forward displacement measuring device 3 and the displacement measuring substrate 4, the P-polarized light is incident on the first fiber coupler 6. This process includes: the P-polarized light is transmitted through the first quarter-wave plate 302, incident on the first plane mirror 401, returns along the same path, is transmitted through the first quarter-wave plate 302, reflected by the first polarizing beam splitter 301, undergoes two internal reflections by the first right-angle reflecting prism 303 and reflection by the first polarizing beam splitter 301, is transmitted through the first quarter-wave plate 302, incident on the first plane mirror 401, returns along the same path, is transmitted through the first quarter-wave plate 302, and then... The light is transmitted through mirror 301, and after two internal reflections by the second right-angle reflecting prism 304 and transmission through the first polarizing beam splitter 301, the above steps are repeated. Then, it is transmitted through the first quarter-wave plate 302 and enters the first plane reflecting mirror 401. It returns along the same path, is transmitted through the first quarter-wave plate 302, undergoes two internal reflections by the first right-angle reflecting prism 303 and reflection by the first polarizing beam splitter 301, is transmitted through the first quarter-wave plate 302, enters the first plane reflecting mirror 401, returns along the same path, is transmitted through the first quarter-wave plate 302, is transmitted through the first polarizing beam splitter 301, and enters the first fiber coupler 6.

[0045] Specifically, P-polarized light is transmitted through the first quarter-wave plate 302, changing its polarization state from horizontally linearly polarized light to circularly polarized light. It then enters the first plane mirror 401, returns along the same path, is transmitted through the first quarter-wave plate 302 again, changing its polarization state from circularly polarized light to vertically linearly polarized light. It is then reflected by the first polarizing beam splitter 301, undergoes two internal reflections by the first right-angle reflecting prism 303 and another reflection by the first polarizing beam splitter prism 301, is transmitted through the first quarter-wave plate 302 again, changing its polarization state from vertically linearly polarized light to circularly polarized light. It then enters the first plane mirror 401, returns along the same path, and enters the first... The quarter-wave plate 302 transmits light, changing its polarization state from circularly polarized to horizontally linearly polarized. This light is then transmitted through the first polarizing beam splitter 301, undergoes two internal reflections by the second right-angle reflecting prism 304, and is transmitted through the first polarizing beam splitter 301 again. The polarization state is then changed again by the first quarter-wave plate 302, changing it from horizontally linearly polarized to circularly polarized. This light then enters the first plane mirror 401, returns along the same path, and is transmitted through the first quarter-wave plate 302 again, changing its polarization state from circularly polarized to vertically linearly polarized. This light is then reflected by the first polarizing beam splitter prism 301, undergoes two internal reflections by the first right-angle reflecting prism 303, and... Reflected by the first polarizing beam splitter prism 301, the light undergoes a polarization change after transmission through the first quarter-wave plate 302, transforming from vertically linearly polarized light to circularly polarized light. It then enters the first plane mirror 401, returns along the same path, and is again transmitted through the first quarter-wave plate 302, changing its polarization from circularly polarized to horizontally linearly polarized light. After transmission through the first polarizing beam splitter prism 301, it undergoes two internal reflections by the second right-angle reflecting prism 304 and transmission through the first polarizing beam splitter prism 301, again undergoing a polarization change after transmission through the first quarter-wave plate 302, transforming from horizontally linearly polarized light to circularly polarized light. It then enters the first plane mirror 401 and returns along the same path. Returning, the light undergoes a polarization change after transmission through the first quarter-wave plate 302, transforming from circularly polarized light to vertically linearly polarized light. It is then reflected by the first polarizing beam splitter 301, undergoes two internal reflections by the first right-angle reflecting prism 303 and another reflection by the first polarizing beam splitter 301, and is again transmitted through the first quarter-wave plate 302, changing its polarization from vertically linearly polarized light to circularly polarized light. This light then enters the first plane mirror 401, returns along the same path, undergoes another polarization change after transmission through the first quarter-wave plate 302, transforming from circularly polarized light to horizontally linearly polarized light, and is transmitted through the first polarizing beam splitter 301 before entering the first fiber coupler 6.

[0046] In some alternative embodiments, the reverse displacement measuring device 5 includes a second inclined plane mirror 501, a second polarizing beam splitter 502, a second quarter-wave plate 503, a third plane mirror 504, a third quarter-wave plate 505, and a third right-angle reflecting prism 506. The forward displacement measuring device 3 includes a first polarizing beam splitter 301, a first quarter-wave plate 302, a first right-angle reflecting prism 303, a second right-angle reflecting prism 304, and a first inclined plane mirror 305.

[0047] Based on this, the S-polarized light, after being processed by the forward displacement measuring device 3, the displacement measuring substrate, and the reverse displacement measuring device 5, is incident on the first fiber coupler 6. This process includes: the S-polarized light undergoing two inclined plane reflections (one by the first inclined plane mirror 305 and the other by the second inclined plane mirror 501), being reflected by the second polarizing beam splitter 502, transmitted through the second quarter-wave plate 503, incident on the third plane mirror 504, returning along the same path, being transmitted through the second quarter-wave plate 503, then through the second polarizing beam splitter 502, and finally through the third quarter-wave plate 505, incident on the second plane mirror 403, returning along the same path, being transmitted through the third quarter-wave plate 505, and then being reflected by the second polarizing beam splitter 502. After two internal reflections by the third right-angle reflecting prism 506 and the second reflection by the second polarizing beam splitter prism 502, the light is transmitted through the third quarter-wave plate 505 and enters the second plane reflecting mirror 403. It returns along the same path, is transmitted through the third quarter-wave plate 505, the second polarizing beam splitter prism 502, and the second quarter-wave plate 503, and enters the third plane reflecting mirror 504. It returns along the same path, is transmitted through the second quarter-wave plate 503, and is reflected by the second polarizing beam splitter prism 502. The preset reflection and transmission process is repeated. After two oblique reflections by the second oblique reflecting mirror 501 and the first oblique reflecting mirror 305, the light is reflected by the first polarizing beam splitter prism 301 and enters the first fiber coupler.

[0048] The preset reflection and transmission process is as follows: After two inclined plane reflections by the second inclined mirror 501 and the first inclined mirror 305, followed by two internal reflections by the first polarizing beam splitter prism 301 and the second right-angle reflecting prism 304, then two more inclined plane reflections by the first polarizing beam splitter prism 301, the first inclined mirror 305, and the second inclined mirror 501, followed by reflection by the second polarizing beam splitter prism 502, transmission through the second quarter-wave plate 503, incident on the third plane mirror 504, returning along the same path, transmission through the second quarter-wave plate 503, transmission through the second polarizing beam splitter prism 502, and transmission through the third quarter-wave plate 505. The light is transmitted through the second plane mirror 403, returns along the same path, is transmitted through the third quarter-wave plate 505, reflected by the second polarizing beam splitter 502, undergoes two internal reflections by the third right-angle reflecting prism 506 and the second polarizing beam splitter 502, is transmitted through the third quarter-wave plate 505, is transmitted through the second plane mirror 403, returns along the same path, is transmitted through the third quarter-wave plate 505, is transmitted through the second polarizing beam splitter 502, is transmitted through the second quarter-wave plate 503, is transmitted through the third plane mirror 504, returns along the same path, is transmitted through the second quarter-wave plate 503, and is reflected by the second polarizing beam splitter 502.

[0049] Specifically, S-polarized light undergoes two inclined plane reflections (305 and 501), then is reflected by the second polarizing beam splitter prism 502, and transmitted through the second quarter-wave plate 503, changing its polarization state from vertically linearly polarized light to circularly polarized light. It then enters the third plane mirror 504, returns along the same path, and is again transmitted through the second quarter-wave plate 503, changing its polarization state from circularly polarized light to horizontally linearly polarized light. It is then transmitted through the second polarizing beam splitter prism 502, and again through the third quarter-wave plate 505, changing its polarization state from horizontally linearly polarized light to circularly polarized light. Finally, it enters the second plane mirror 403, returns along the same path, and is again transmitted through the third quarter-wave plate 505, changing its polarization state from circularly polarized light to vertically linearly polarized light. After reflection by the second polarizing beam splitter prism 502, and then by two internal reflections by the third right-angle reflecting prism 506 and the second polarizing beam splitter prism 502, the light is transmitted through the third quarter-wave plate 505, changing its polarization state from vertically linearly polarized light to circularly polarized light. It then enters the second plane mirror 403, returns along the same path, and is transmitted through the third quarter-wave plate 505 again, changing its polarization state from circularly polarized light to horizontally linearly polarized light. It is then transmitted through the second polarizing beam splitter prism 502, and then by the second quarter-wave plate 503, changing its polarization state from horizontally linearly polarized light to circularly polarized light. It enters the third plane mirror 504, returns along the same path, and is transmitted through the second quarter-wave plate 503 again, changing its polarization state from circularly polarized light to vertically linearly polarized light. Finally, it enters the second polarizing beam splitter prism 404... The light is reflected by prism 502, then reflected twice by the second inclined mirror 501 and the first inclined mirror 305, then reflected twice internally by the first polarizing beam splitter prism 301 and the second right-angle reflecting prism 304, then reflected twice more by the first polarizing beam splitter prism 301, the first inclined mirror 305 and the second inclined mirror 501, then reflected by the second polarizing beam splitter prism 502, and transmitted through the second quarter-wave plate 503, changing its polarization state from vertically linearly polarized light to circularly polarized light. It then enters the third plane mirror 504, returns along the same path, is transmitted through the second quarter-wave plate 503, changing its polarization state from circularly polarized light to horizontally linearly polarized light, and is transmitted through the second polarizing beam splitter prism 502 and the third quarter-wave plate 505. The polarization state is changed from horizontally linearly polarized light to circularly polarized light. This light is incident on the second plane mirror 403, returns along the same path, and is transmitted through the third quarter-wave plate 505, where its polarization state is changed again from circularly polarized to vertically linearly polarized light. It is then reflected by the second polarizing beam splitter 502, undergoes two internal reflections by the third right-angle reflecting prism 506 and the second polarizing beam splitter 502, and is transmitted through the third quarter-wave plate 505, where its polarization state is changed again from vertically linearly polarized to circularly polarized light. This light is then incident on the second plane mirror 403, returns along the same path, and is transmitted through the third quarter-wave plate 505, where its polarization state is changed again from circularly polarized to horizontally linearly polarized light. Finally, it is transmitted through the second polarizing beam splitter prism 502 and the second quarter-wave plate 503, where its polarization state is changed again.The horizontally linearly polarized light is transformed into circularly polarized light, incident on the third plane mirror 504, and returns along the same path. It is then transmitted through the second quarter-wave plate 503, changing its polarization state from circularly polarized to vertically linearly polarized light. After reflection by the second polarizing beam splitter 502, it undergoes two oblique reflections by the second oblique mirror 501 and the first oblique mirror 305, two internal reflections by the first polarizing beam splitter 501 and the second right-angle reflecting prism (304), and finally reflections by the first polarizing beam splitter 501, the first oblique mirror 305, and the second oblique mirror 504. The light is reflected twice by the inclined plane of the mirror 501, reflected by the second polarizing beam splitter 502, and transmitted through the second quarter-wave plate 503, changing its polarization state from vertically linearly polarized light to circularly polarized light. It then enters the third plane mirror 504, returns along the same path, is transmitted through the second quarter-wave plate 503, changing its polarization state from circularly polarized light to horizontally linearly polarized light, is transmitted through the second polarizing beam splitter 502, and transmitted through the third quarter-wave plate 505, changing its polarization state from horizontally linearly polarized light to circularly polarized light. Finally, it enters the second plane mirror. 403. Returning along the original path, the light is transmitted through the third quarter-wave plate 505, changing its polarization state from circularly polarized to vertically linearly polarized. It is then reflected by the second polarizing beam splitter 502, undergoes two internal reflections by the third right-angle reflecting prism 506 and the second polarizing beam splitter 502, and is transmitted through the third quarter-wave plate 505 again, changing its polarization state from vertically linearly polarized to circularly polarized. This light then enters the second plane mirror 403, returns along the original path, and is transmitted through the third quarter-wave plate 505 again, changing its polarization state from circularly polarized to horizontally linearly polarized. The light beam, after being transmitted through the second polarizing beam splitter 502 and then through the second quarter-wave plate 503, changes its polarization state from horizontally linearly polarized light to circularly polarized light. It then enters the third plane mirror 504, returns along the same path, and is again transmitted through the second quarter-wave plate 503, changing its polarization state from circularly polarized light to vertically linearly polarized light. After being reflected by the second polarizing beam splitter 502, and then through two inclined plane reflections by the second inclined mirror 501 and the first inclined mirror 305, it is reflected by the first polarizing beam splitter 301 and enters the first fiber coupler 6.

[0050] Finally, the first fiber optic coupler 6 and the second fiber optic coupler 7 transmit the interferometric displacement measurement signal to the data acquisition module 8. After data processing, the signal is transmitted to the host computer 9 to obtain real-time displacement measurement information. Optionally, the data processing may include, but is not limited to, photoelectric conversion and low-pass filtering. Optionally, the data acquisition module 9 can be a data acquisition card.

[0051] In addition, the linear displacement platform 402 is located in the middle of the forward displacement measuring device 3 and the reverse displacement measuring device 5. When the linear displacement platform 402 moves linearly in the horizontal direction, it simultaneously acquires forward displacement information and reverse displacement information. By subtracting the forward displacement information from the reverse displacement information, the real-time displacement measurement value is obtained.

[0052] The Doppler frequency shift signal of the above-mentioned positive displacement measuring device is expressed as: The Doppler frequency shift signal of the negative displacement measuring device is expressed as The Doppler frequency shift signal of the second fiber coupler is represented as f1-f2, and the interference signal of the first fiber coupler is represented as... Where f1 represents the first frequency and f2 represents the second frequency. This indicates Doppler frequency shift.

[0053] Therefore, the phase change is related to the measured displacement. The relationship between them can be represented as: ,in, Indicates phase change, Indicates the measured displacement. This indicates the wavelength of the laser produced by the dual-frequency laser. This indicates Doppler frequency shift.

[0054] In addition, embodiments of this application also provide a device for measuring the ultra-low coefficient of thermal expansion based on dual-frequency laser, such as... Figure 2 As shown, Figure 2 This application provides a schematic diagram of an ultra-low thermal expansion coefficient measuring device based on dual-frequency laser, illustrating the principle and... Figure 1 Completely identical, the ultra-low thermal expansion material 404 is heated under the control of the vacuum temperature control 405. During the heating process, the ultra-low thermal expansion material 404 will deform accordingly. By detecting the magnitude of the deformation of the reflected light, the expansion coefficient of the ultra-low thermal expansion material can be obtained in real time. The thermal expansion material 404 is located between the first plane mirror 401 and the second plane mirror 403. It can be double-sided coated with thermal expansion material 404, or a higher thermal expansion material substrate can be used.

[0055] This application provides a heterodyne laser interferometry measurement device based on phase decoupling and multiple frequency doubling. The device includes a dual-frequency laser, a beam splitter prism, a forward displacement measuring device, a displacement measuring substrate, a reverse displacement measuring device, a first fiber coupler, a second fiber coupler, a data acquisition module, and a host computer. The displacement measuring substrate includes a first plane mirror, a linear displacement platform, and a second plane mirror. The linear displacement platform is located at the middle position of the forward displacement measuring device and the reverse displacement measuring device. The first plane mirror and the second plane mirror are located on both sides of the linear displacement platform and move synchronously with the linear displacement platform. The dual-frequency laser generates an orthogonally linearly polarized beam. This beam is split into reflected and transmitted light by a beam splitter according to energy. The reflected light is incident on a second fiber coupler, while the transmitted light is incident on a forward displacement measuring device for polarization splitting, resulting in P-polarized light of the first frequency and S-polarized light of the second frequency. The P-polarized light is processed by the forward displacement measuring device and the displacement measuring substrate before being incident on a first fiber coupler. The S-polarized light is processed by the forward displacement measuring device, the displacement measuring substrate, and the reverse displacement measuring device before being incident on a first fiber coupler. The first and second fiber couplers transmit the interference displacement measurement signal to a data acquisition module, which processes the data and transmits it to a host computer to obtain real-time displacement measurement information. This scheme improves measurement accuracy by utilizing phase decoupling and multiple frequency doubling techniques. Multiple frequency doubling provides multiple times the laser displacement information under multiple round trip measurement conditions, while phase decoupling provides forward and reverse measurements under real-time measurement conditions, thus mitigating the impact of positioning fluctuation errors of the displacement stage and environmental disturbance errors. Furthermore, under phase decoupling, the measurement accuracy is increased from 6 times the Doppler frequency shift to 12 times the Doppler frequency shift, further improving measurement accuracy. Additionally, by utilizing multi-point incident beams and positioning the single beam at the same location on both sides, six beam points are simultaneously incident linearly on both the front and rear surfaces. It can simultaneously detect and measure the spatial positioning accuracy of the reference mirror on the displacement stage in real time on both the left and right sides, avoiding beam deviation of the plane mirror during linear displacement. In the operation of the displacement stage, the front and rear plane mirrors operate synchronously, and the displacement measurement information can be accurately fed back to the displacement stage for precise control of the positioning accuracy of the displacement stage. At the same time, the signals acquired synchronously in both positive and negative dimensions contain the flutter information of the displacement stage and the disturbance information of the environment. Therefore, in the phase decoupling state, the error information can be reduced within the system based on real-time information to ensure the overall stability of the displacement measurement device.

[0056] In addition, this application embodiment also provides a heterodyne laser interferometry method based on phase decoupling and multiple frequency doubling. This heterodyne laser interferometry method based on phase decoupling and multiple frequency doubling is applied to the heterodyne laser interferometry device based on phase decoupling and multiple frequency doubling provided in any of the above embodiments. The device includes a dual-frequency laser, a beam splitter prism, a forward displacement measuring device, a displacement measuring substrate, a reverse displacement measuring device, a first fiber coupler, a second fiber coupler, a data acquisition module, and a host computer. The displacement measuring substrate includes a first plane mirror, a linear displacement platform, and a second plane mirror. The linear displacement platform is located at the middle position of the forward displacement measuring device and the reverse displacement measuring device. The first plane mirror and the second plane mirror are located on both sides of the linear displacement platform and move synchronously with the linear displacement platform. The method includes:

[0057] The dual-frequency laser is used to generate a beam of orthogonally linearly polarized light. The linearly polarized light is split into reflected light and transmitted light according to energy after passing through a beam splitter. The reflected light is incident on the second fiber coupler, and the transmitted light is incident on the forward displacement measuring device for polarization splitting, which splits into P-polarized light of the first frequency and S-polarized light of the second frequency.

[0058] P-polarized light is processed by the forward displacement measuring device and the displacement measuring substrate before being incident on the first fiber coupler.

[0059] S-polarized light is processed by the forward displacement measuring device, the displacement measuring substrate, and the reverse displacement measuring device before being incident on the first fiber coupler.

[0060] The first and second fiber optic couplers transmit the interferometric displacement measurement signal to the data acquisition module. After data processing, the signal is transmitted to the host computer to obtain real-time displacement measurement information.

[0061] The implementation process and beneficial effects of the heterodyne laser interferometry measurement method based on phase decoupling and multiple frequency doubling are the same as those of the above-mentioned device, and will not be repeated here.

[0062] It is readily understood that, based on the several embodiments provided in this application, those skilled in the art can combine, split, or reorganize the embodiments of this application to obtain other embodiments, none of which exceed the protection scope of this application.

[0063] The above detailed embodiments further illustrate the purpose, technical solution, and beneficial effects of the embodiments of this application. It should be understood that the above are merely specific embodiments of the embodiments of this application and are not intended to limit the protection scope of the embodiments of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solutions of the embodiments of this application should be included within the protection scope of the embodiments of this application.

Claims

1. A heterodyne laser interferometry measurement device based on phase decoupling and multiple frequency doubling, characterized in that, include: The system comprises a dual-frequency laser, a beam splitter, a forward displacement measuring device, a displacement measuring substrate, a reverse displacement measuring device, a first fiber optic coupler, a second fiber optic coupler, a data acquisition module, and a host computer. The displacement measuring substrate includes a first plane mirror, a linear displacement platform, and a second plane mirror. The linear displacement platform is positioned between the forward and reverse displacement measuring devices. The first and second plane mirrors are located on either side of the linear displacement platform and move synchronously with it. The forward displacement measuring device includes a first polarizing beam splitter, a first quarter-wave plate, a first right-angle reflecting prism, a second right-angle reflecting prism, and a first inclined plane mirror. The reverse displacement measuring device includes a second inclined plane mirror, a second polarizing beam splitter, a second quarter-wave plate, a third plane mirror, a third quarter-wave plate, and a third right-angle reflecting prism. The dual-frequency laser is used to generate a beam of orthogonally linearly polarized light. The linearly polarized light is split into reflected light and transmitted light according to energy by the beam splitter. The reflected light is incident on the second fiber coupler, and the transmitted light is incident on the forward displacement measuring device for polarization splitting, which splits it into P-polarized light of the first frequency and S-polarized light of the second frequency. The P-polarized light is processed by the positive displacement measuring device and the displacement measuring substrate, and then incident on the first fiber coupler. The S-polarized light is processed by the forward displacement measuring device, the displacement measuring substrate, and the reverse displacement measuring device, and then incident on the first fiber coupler. The first and second fiber optic couplers transmit the interference displacement measurement signal to the data acquisition module, and after data processing, it is transmitted to the host computer to obtain real-time displacement measurement information.

2. The apparatus according to claim 1, characterized in that, The P-polarized light, after being processed by the forward displacement measuring device and the displacement measuring substrate, is incident on the first fiber coupler, including: The P-polarized light is transmitted through the first quarter-wave plate, incident on the first plane mirror, returns along the same path, is transmitted through the first quarter-wave plate, reflected by the first polarizing beam splitter, undergoes two internal reflections by the first right-angle reflecting prism and another reflection by the first polarizing beam splitter, is transmitted through the first quarter-wave plate, incident on the first plane mirror, returns along the same path, is transmitted through the first quarter-wave plate, is transmitted through the first polarizing beam splitter, undergoes two internal reflections by the second right-angle reflecting prism and another transmission by the first polarizing beam splitter, repeats the above steps, is transmitted through the first quarter-wave plate again, incident on the first plane mirror, returns along the same path, is transmitted through the first quarter-wave plate, undergoes two internal reflections by the first right-angle reflecting prism and another reflection by the first polarizing beam splitter, is transmitted through the first quarter-wave plate, incident on the first plane mirror, returns along the same path, is transmitted through the first quarter-wave plate, is transmitted through the first polarizing beam splitter, and finally incident on the first fiber coupler.

3. The apparatus according to claim 1, characterized in that, The forward displacement measuring device includes a first polarizing beam splitter, a first quarter-wave plate, a first right-angle reflecting prism, a second right-angle reflecting prism, and a first inclined plane reflecting mirror. The S-polarized light is processed by the forward displacement measuring device, the displacement measuring substrate, and the reverse displacement measuring device, and then incident on the first fiber coupler, including: The S-polarized light undergoes two oblique reflections by the first and second oblique mirrors, is reflected by the second polarizing beam splitter, transmitted through the second quarter-wave plate, and enters the third plane mirror. It then returns along the same path, is transmitted through the second quarter-wave plate, again through the second polarizing beam splitter, and then through the third quarter-wave plate. It then returns along the same path, is transmitted through the third quarter-wave plate, is reflected by the second polarizing beam splitter, undergoes two internal reflections by the third right-angle prism and another reflection by the second polarizing beam splitter, is transmitted through the third quarter-wave plate, and enters the second plane mirror. It then returns along the same path, is transmitted through the third quarter-wave plate, again through the second polarizing beam splitter, and enters the third plane mirror. It then returns along the same path, is transmitted through the second quarter-wave plate, and then through the second quarter-wave plate. After being reflected by the second polarizing beam splitter, the preset reflection and transmission process is repeated. Finally, after two oblique reflections by the second and first oblique mirrors, and after being reflected by the first polarizing beam splitter, it enters the first fiber coupler.

4. The apparatus according to claim 3, characterized in that, The preset reflection and transmission process is as follows: after two oblique reflections by the second oblique mirror and the first oblique mirror, after two internal reflections by the first polarizing beam splitter and the second right-angle reflecting prism, after two oblique reflections by the first polarizing beam splitter, the first oblique mirror, and the second oblique mirror, after reflection by the second polarizing beam splitter, after transmission through the second quarter-wave plate, it enters the third plane mirror, returns along the same path, is transmitted through the second quarter-wave plate, is transmitted through the second polarizing beam splitter, is transmitted through the third quarter-wave plate, enters the second plane mirror, returns along the same path, is transmitted through the third quarter-wave plate, is reflected by the second polarizing beam splitter, after two internal reflections by the third right-angle reflecting prism and the second polarizing beam splitter, is transmitted through the third quarter-wave plate, enters the second plane mirror, returns along the same path, is transmitted through the third quarter-wave plate, is transmitted through the second polarizing beam splitter, is transmitted through the second quarter-wave plate, enters the third plane mirror, returns along the same path, is transmitted through the second quarter-wave plate, and is reflected by the second polarizing beam splitter.

5. The apparatus according to claim 1, characterized in that, The Doppler frequency shift signal of the positive displacement measuring device is expressed as: The Doppler frequency shift signal of the reverse displacement measuring device is expressed as: The Doppler frequency shift signal of the second fiber coupler is represented as f1-f2, and the interference signal of the first fiber coupler is represented as... Where f1 represents the first frequency and f2 represents the second frequency. This indicates Doppler frequency shift.

6. A heterodyne laser interferometry method based on phase decoupling and multiple frequency doubling, applied to the heterodyne laser interferometry device based on phase decoupling and multiple frequency doubling as described in any one of claims 1-5, the device comprising a dual-frequency laser, a beam splitter prism, a forward displacement measuring device, a displacement measuring substrate, a reverse displacement measuring device, a first fiber coupler, a second fiber coupler, a data acquisition module, and a host computer; the displacement measuring substrate comprising a first plane mirror, a linear displacement platform, and a second plane mirror; the linear displacement platform being disposed at the midpoint between the forward displacement measuring device and the reverse displacement measuring device; the first plane mirror and the second plane mirror being disposed on both sides of the linear displacement platform and moving synchronously with the linear displacement platform; the forward displacement measuring device comprising a first polarizing beam splitter prism, a first quarter-wave plate, a first right-angle reflecting prism, a second right-angle reflecting prism, and a first inclined plane mirror; the reverse displacement measuring device comprising a second inclined plane mirror, a second polarizing beam splitter prism, a second quarter-wave plate, a third plane mirror, a third quarter-wave plate, and a third right-angle reflecting prism, characterized in that... The method includes: The dual-frequency laser is used to generate a beam of orthogonally linearly polarized light. The linearly polarized light is split into reflected light and transmitted light according to energy by the beam splitter. The reflected light is incident on the second fiber coupler, and the transmitted light is incident on the forward displacement measuring device for polarization splitting, which splits it into P-polarized light of the first frequency and S-polarized light of the second frequency. The P-polarized light is processed by the positive displacement measuring device and the displacement measuring substrate, and then incident on the first fiber coupler. The S-polarized light is processed by the forward displacement measuring device, the displacement measuring substrate, and the reverse displacement measuring device, and then incident on the first fiber coupler. The first and second fiber optic couplers transmit the interference displacement measurement signal to the data acquisition module, and after data processing, it is transmitted to the host computer to obtain real-time displacement measurement information.

Images