Heterodyne laser interference measuring device based on phase decoupling and multiple frequency multiplication

Abstract

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

Description

Technical Field

[0001] The present application relates to the technical field of optical equipment, and in particular to a heterodyne laser interferometry measurement device based on phase decoupling and multiple frequency doubling. Background Art

[0002] With the rapid development of the semiconductor manufacturing industry, the development needs of various subsystem equipment of lithography machines that comply with Extreme Ultraviolet Lithography (EUV) or Deep Ultraviolet Lithography (DUV) technology, as well as equipment detection and positioning, require laser interferometer displacement measurement accuracy of sub-nanometer level.

[0003] Currently, when performing laser interferometry displacement measurement, the existing 4x optical subdivision mirror group with equal optical path length, as well as the existing 8x optical subdivision mirror group and 12x optical subdivision mirror group with equal optical path length, all use the multiple frequency doubling principle of Doppler frequency shift technology to perform ultra-precision displacement measurement.

[0004] However, existing measurement devices are limited by the spatial positioning vibration of the translation stage, the influence of noise in signal processing, the influence of fluctuation in signal transmission, etc., which all affect the improvement of displacement measurement accuracy. Summary of the Invention

[0005] The present application aims to at least solve the technical problems existing in the prior art. To this end, in a first aspect, the present application proposes a heterodyne laser interferometer 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 optic coupler, a second fiber optic coupler, a data acquisition module, and a host computer. The displacement measuring substrate comprises a first plane reflector, a linear displacement platform, and a second plane reflector. The linear displacement platform is arranged in the middle position between the forward displacement measuring device and the reverse displacement measuring device. The first plane reflector and the second plane reflector are arranged on both sides of the linear displacement platform and move synchronously with the linear displacement platform. The dual-frequency laser is used to generate a beam of orthogonal linearly polarized light. The linearly polarized light is split according to energy by a beam splitter prism into reflected light and transmitted light. The reflected light is incident on the second fiber coupler, and the transmitted light is incident on the forward displacement measurement device for polarization splitting, into 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 measurement device and the displacement measurement substrate and then incident on the first optical 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 optical fiber coupler; The first fiber optic coupler and the second fiber optic coupler transmit the interference displacement measurement signal to the data acquisition module, which is then transmitted to the host computer after data processing to obtain real-time displacement measurement information.

[0006] In a possible implementation, the forward displacement measuring device includes a first polarization beam splitter prism, a first quarter-wave plate, a first right-angle reflecting prism, a second right-angle reflecting prism, and a first oblique reflecting mirror.

[0007] In a possible implementation, the P-polarized light is processed by the forward displacement measurement device and the displacement measurement substrate and then incident on the first optical fiber coupler, including: The P-polarized light is transmitted through the first quarter-wave plate, incident on the first plane reflector, returns along the original path, is transmitted through the first quarter-wave plate, reflected by the first polarization splitting prism, internally reflected twice by the first right-angle reflecting prism and reflected by the first polarization splitting prism, transmitted through the first quarter-wave plate, incident on the first plane reflector, returns along the original path, transmitted through the first quarter-wave plate, transmitted through the first polarization splitting prism, internally reflected twice by the second right-angle reflecting prism and transmitted through the first polarization splitting prism, and then the above steps are repeated, and then the light is transmitted through the first quarter-wave plate, incident on the first plane reflector, returns along the original path, transmitted through the first quarter-wave plate, internally reflected twice by the first right-angle reflecting prism and reflected by the first polarization splitting prism, transmitted through the first quarter-wave plate, incident on the first plane reflector, returns along the original path, transmitted through the first quarter-wave plate, transmitted through the first polarization splitting prism, and incident on the first fiber coupler.

[0008] In a possible implementation, the reverse displacement measuring device includes a second oblique reflector, a second polarization beam splitter, a second quarter-wave plate, a third plane reflector, a third quarter-wave plate, and a third right-angle reflector.

[0009] In one possible embodiment, the forward displacement measurement device includes a first polarization beam splitter, a first quarter-wave plate, a first right-angle reflection prism, a second right-angle reflection prism, and a first bevel reflector. S-polarized light is processed by the forward displacement measurement device, the displacement measurement substrate, and the reverse displacement measurement device, and then incident on a first fiber coupler, including: The S-polarized light is obliquely reflected twice by the first oblique reflector and the second oblique reflector, reflected by the second polarization splitting prism, transmitted through the second quarter-wave plate, incident on the third plane reflector, returns along the original path, is transmitted through the second quarter-wave plate, transmitted through the second polarization splitting prism, transmitted through the third quarter-wave plate, incident on the second plane reflector, returns along the original path, is transmitted through the third quarter-wave plate, reflected by the second polarization splitting prism, is internally reflected twice by the third right-angle reflector prism and reflected by the second polarization splitting prism, is transmitted through the third quarter-wave plate, incident on the second plane reflector, returns along the original path, is transmitted through the third quarter-wave plate, transmitted through the second polarization splitting prism, is transmitted through the second quarter-wave plate, incident on the third plane reflector, returns along the original path, is transmitted through the second quarter-wave plate, reflected by the second polarization splitting prism, and then repeats the steps of the preset reflection and transmission process, then is obliquely reflected twice by the second oblique reflector and the first oblique reflector, reflected by the first polarization splitting prism, and incident on the first fiber coupler.

[0010] In a possible embodiment, the preset reflection and transmission process is: two oblique reflections by the second oblique reflector and the first oblique reflector, reflection by the first polarization splitting prism and two internal reflections by the second right-angle reflector, reflection by the first polarization splitting prism, two oblique reflections by the first oblique reflector and the second oblique reflector, reflection by the second polarization splitting prism, transmission through the second quarter-wave plate, incident on the third plane reflector, return along the original path, transmission through the second quarter-wave plate, transmission through the second polarization splitting prism, transmission through the third quarter-wave plate, incident on the second plane reflector, return along the original path, transmission through the third quarter-wave plate, reflection by the second polarization splitting prism, two internal reflections by the third right-angle reflector and reflection by the second polarization splitting prism, transmission through the third quarter-wave plate, incident on the second plane reflector, return along the original path, transmission through the third quarter-wave plate, transmission through the second polarization splitting prism, transmission through the second quarter-wave plate, incident on the third plane reflector, return along the original path, transmission through the second quarter-wave plate, and reflection by the second polarization splitting prism.

[0011] In one possible implementation, the Doppler frequency shift signal of the forward displacement measuring device is expressed as , the Doppler frequency shift signal of the negative displacement measurement device is expressed as , the Doppler frequency shift signal of the second fiber coupler is expressed as f1-f2, and the interference signal of the first fiber coupler is expressed as ; Wherein, f1 represents the first frequency, f2 represents the second frequency, Indicates the Doppler shift.

[0012] In a second aspect, the present application provides a heterodyne laser interferometry method based on phase decoupling and multiple frequency doubling, which is applied to the heterodyne laser interferometry device based on phase decoupling and multiple frequency doubling provided in the first aspect above. The device includes: a dual-frequency laser, a beam splitter, 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 reflector, a linear displacement platform, and a second plane reflector. The linear displacement platform is arranged at a position between the forward displacement measuring device and the reverse displacement measuring device. The first plane reflector and the second plane reflector are arranged on both sides of the linear displacement platform and move synchronously with the linear displacement platform. The method is characterized in that the method includes: The dual-frequency laser is used to generate a beam of orthogonal linearly polarized light. The linearly polarized light is split according to energy by a beam splitter prism into reflected light and transmitted light. The reflected light is incident on the second fiber coupler, and the transmitted light is incident on the forward displacement measurement device for polarization splitting, into 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 measurement device and the displacement measurement substrate and then incident on the first optical 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 optical fiber coupler; The first fiber optic coupler and the second fiber optic coupler transmit the interference displacement measurement signal to the data acquisition module, which is then transmitted to the host computer after data processing to obtain real-time displacement measurement information.

[0013] The technical solutions provided in the embodiments of the present application can achieve at least the following beneficial effects: An embodiment of the present 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, 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 arranged in 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 arranged on both sides of the linear displacement platform and move synchronously with the linear displacement platform. Among them, the dual-frequency laser is used to generate a beam of orthogonal linearly polarized light, which is split according to energy by a beam splitter prism into reflected light and transmitted light; the reflected light is incident on the second fiber coupler, and the transmitted light is incident on the forward displacement measurement device for polarization splitting, and is divided into 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 measurement device and the displacement measurement substrate respectively, and then is incident on the first fiber coupler; the S-polarized light is processed by the forward displacement measurement device, the displacement measurement substrate, and the reverse displacement measurement device respectively, and then is incident on the first fiber coupler; the first fiber coupler and the second fiber coupler transmit the interference displacement measurement signal to the data acquisition module, which is transmitted to the host computer after data processing to obtain real-time displacement measurement information. This solution improves measurement accuracy by utilizing phase decoupling and multiple frequency doubling technology. Multiple frequency doubling provides multiple laser displacement information in the state of multiple round-trip measurement, and phase decoupling provides forward and reverse measurement in the state of real-time measurement to reduce the influence of positioning fluctuation error and environmental disturbance error of the displacement stage. In addition, in the state of phase decoupling, the measurement accuracy is transformed from the original 6 times Doppler frequency shift to 12 times Doppler frequency shift, further improving the measurement accuracy. In addition, by utilizing the multi-point incidence of a single light beam and the positioning of the same position on the left and right sides of a single light beam, 6 linear light spots are incident on both the front and rear surfaces simultaneously. , it can simultaneously detect the spatial positioning accuracy of the measurement reference mirror on the displacement table in real time on the left and right sides, avoid the beam offset of the plane mirror during linear displacement, and when the displacement table is in operation, the front and rear plane mirrors operate synchronously, and the displacement measurement information can be accurately fed back to the displacement table for precise control of the positioning accuracy of the displacement table; at the same time, using the positive and negative dimensions, the synchronously acquired signals also include the vibration information of the displacement table and the disturbance information of the environment. Therefore, in the phase decoupling state, the error information can be reduced within the system according to the real-time information to ensure the overall stability of its displacement measurement device. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of a heterodyne laser interferometry measurement device based on phase decoupling and multiple frequency doubling provided in an embodiment of the present application; Figure 2A schematic diagram of an ultra-low thermal expansion coefficient measurement device based on a dual-frequency laser provided in an embodiment of the present application.

[0015] Description of reference numerals: 1-dual-frequency laser; 2-beam splitter; 3-forward displacement measuring device; 301-first polarization beam splitter; 302-first quarter-wave plate; 303-first right-angle reflecting prism; 304-second right-angle reflecting prism; 305-first bevel reflecting mirror; 4-displacement measuring substrate; 401-first plane reflecting mirror; 402-linear displacement platform; 403-second plane reflecting mirror; 5-reverse displacement measuring device; 501-second bevel reflecting mirror; 502-second polarization beam splitter; 503-second quarter-wave plate; 504-third plane reflecting mirror; 505-third quarter-wave plate; 506-third right-angle reflecting prism; 6-first fiber coupler; 7-second fiber coupler; 8-digital acquisition module; 9-host computer. DETAILED DESCRIPTION

[0016] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0017] With the rapid development of the semiconductor manufacturing industry, the development needs of various subsystem equipment and equipment detection and positioning that meet EUV / DUV lithography machines, precision control and accurate positioning of high-end CNC machine tools for fine processing and ultra-precision detection equipment require laser interferometer displacement measurement accuracy of sub-nanometer level.

[0018] The basic principles of displacement measurement are homodyne and heterodyne laser interferometry, which include the existing 4x optical interpolation laser mirror group with common optical path, the multi-axis interferometry mirror group formed by compact wavelength compensator and cross-line table, and a set of spatially separated 4x optical interpolation laser mirror groups.

[0019] At present, for the 4x optical subdivision mirror group with equal optical path and common optical path, as well as the existing designed 8x optical subdivision mirror group and 12x optical subdivision mirror group with equal optical path and common optical path, ultra-precision displacement measurement is performed using the multiple frequency doubling principle of Doppler frequency shift technology; secondly, for the phase decoupling 8x optical subdivision structure of the second-order diffraction light of the two-dimensional grating, as well as the existing phase decoupling 4x optical subdivision structure of the first-order diffraction light based on the two-dimensional grating, both use the multiple subdivision measurement structure with opposite phase decoupling of the Doppler frequency shift signal to reduce measurement error and improve measurement accuracy.

[0020] However, the main deficiencies of the existing technology are: first, the displacement measurement based on laser cannot reduce the measurement error in real time while ensuring multiple Doppler frequency shifts; second, it is limited by the spatial positioning vibration of the displacement stage, the noise influence in signal processing, the fluctuation influence in signal transmission, etc., which will affect the improvement of displacement measurement accuracy; third, error compensation still stays at the real-time measurement error signal to form a feedback data set to compensate the measurement, which affects the accuracy and timeliness of the system and has limited compensation capabilities; fourth, phase decoupling technology and multiple frequency doubling technology are not used in laser interferometry measurement to perform higher-precision displacement measurement, and the exploration of measurement limits is insufficient.

[0021] Based on this, the present application proposes a heterodyne laser interferometer measurement device based on phase decoupling and multiple frequency doubling. This solution improves the measurement accuracy by utilizing two aspects of phase decoupling and multiple frequency doubling technology. Multiple frequency doubling provides multiple laser displacement information in the state of multiple round-trip measurement, and phase decoupling provides forward measurement and reverse measurement in the state of real-time measurement, so as to weaken the influence of positioning fluctuation error and environmental disturbance error of the displacement stage; in addition, in the state of phase decoupling, the measurement accuracy is changed from the original 6 times Doppler frequency shift to 12 times Doppler frequency shift, which further improves the measurement accuracy; and, by utilizing the multi-point incidence of a single light beam and the positioning of the same position on the left and right sides of a single light beam, in the front The two rear surfaces are synchronously incident with six light spots in a linear state, which can simultaneously detect the spatial positioning accuracy of the measurement reference mirror on the displacement table in real time on both the left and right sides, avoiding beam offset of the plane mirror during linear displacement. When the displacement table is in operation, the front and rear plane mirrors operate synchronously, and the displacement measurement information can be accurately fed back to the displacement table for precise control of the positioning accuracy of the displacement table. At the same time, using the positive and negative dimensions, the synchronously acquired signals also include the vibration information of the displacement table 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 its displacement measurement device.

[0022] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. Unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by a person of ordinary skill in the art to which this application belongs. The singular forms "a," "the," and "the" used in this specification and the 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" 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," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of the embodiments of this application and to simplify the description. They do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the embodiments of this application.

[0023] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the embodiments of the present application, the meaning of "plurality" is at least two, for example, two, three, etc., unless otherwise clearly specified.

[0024] In the embodiments of the present application, unless otherwise specified or limited, the terms "installed," "connected," "connected," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections, electrical connections; direct connections, or indirect connections through an intermediate medium; internal connections between two components, or interactions between two components, unless otherwise specified. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0025] In the embodiments of the present application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0026] It should be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in the embodiments of the present application are for illustrative purposes only and do not represent the only implementation method.

[0027] The following is combined with Figure 1-2 An exemplary description is given of a heterodyne laser interferometry measurement device based on phase decoupling and multiple frequency doubling according to an embodiment of the present application.

[0028] like Figure 1 As shown, Figure 1 A schematic diagram of a heterodyne laser interferometry device based on phase decoupling and multiple frequency doubling provided in an embodiment of the present application. The device comprises: a dual-frequency laser 1, a beam splitter prism 2, a forward displacement measurement device 3, a displacement measurement substrate 4, a reverse displacement measurement device 5, a first fiber coupler 6, a second fiber coupler 7, a data acquisition module 8, and a host computer 9. The displacement measurement substrate 4 comprises a first plane mirror 401, a linear displacement platform 402, and a second plane mirror 403. The linear displacement platform 402 is disposed between the forward displacement measurement device 3 and the reverse displacement measurement device 5. The first plane mirror 401 and the second plane mirror 403 are disposed on either side of the linear displacement platform 402 and move synchronously with the linear displacement platform 402.

[0029] The dual-frequency laser 1 is used to generate a beam of orthogonal linearly polarized light with a laser wavelength of 632.8 nm and frequencies of first frequency f1 and second frequency f2. The linearly polarized light is first split according to energy by a beam splitter prism 2 and then divided into reflected light and transmitted light. The reflected light is incident on the second fiber coupler 7, and the transmitted light is incident on the forward displacement measurement device 3 for polarization splitting, into 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 measurement device 3 and the displacement measurement substrate 4, respectively, before being incident on the first fiber coupler 6. The S-polarized light is processed by the forward displacement measurement device 3, the displacement measurement substrate 4, and the reverse displacement measurement device 5, respectively, before being incident on the first fiber coupler 6. The first fiber coupler 6 and the second fiber coupler 7 transmit the interference displacement measurement signal to the data acquisition module 8, which is then transmitted to the host computer 9 after data processing to obtain real-time displacement measurement information.

[0030] In some optional embodiments, please continue to refer to Figure 1 The forward displacement measuring device 3 includes a first polarization beam splitter prism 301 , a first quarter-wave plate 302 , a first right-angle reflecting prism 303 , a second right-angle reflecting prism 304 , and a first bevel reflecting mirror 305 .

[0031] Thus, the P-polarized light is processed by the forward displacement measuring device 3 and the displacement measuring substrate 4, and then incident on the first optical fiber coupler 6, including: the P-polarized light is transmitted through the first quarter-wave plate 302, incident on the first plane reflector 401, returns along the original path, is transmitted through the first quarter-wave plate 302, is reflected by the first polarization splitting prism 301, is internally reflected twice by the first right-angle reflecting prism 303 and reflected by the first polarization splitting prism 301, is transmitted through the first quarter-wave plate 302, is incident on the first plane reflector 401, returns along the original path, is transmitted through the first quarter-wave plate 302, is reflected by the first polarization splitting prism 302, and is incident on the first plane reflector 401. The light is transmitted through the mirror 301, reflected twice internally by the second right-angle reflecting prism 304 and transmitted through the first polarization splitting prism 301, and then the above steps are repeated. The light is then transmitted through the first quarter-wave plate 302 and incident on the first plane reflecting mirror 401. The light returns along the original path, is transmitted through the first quarter-wave plate 302, is internally reflected twice by the first right-angle reflecting prism 303 and reflected by the first polarization splitting prism 301, is transmitted through the first quarter-wave plate 302, is incident on the first plane reflecting mirror 401, returns along the original path, is transmitted through the first quarter-wave plate 302, is transmitted through the first polarization splitting prism 301, and is incident on the first fiber coupler 6.

[0032] Specifically, the P polarized light is transmitted through the first quarter wave plate 302 to change its polarization state, from horizontal linear polarized light to circular polarized light, incident on the first plane reflector 401, and returns along the original path. The polarization state is changed through the first quarter wave plate 302 to change its polarization state, from circular polarized light to vertical linear polarized light, reflected by the first polarization splitter prism 301, and reflected twice by the first right-angle reflection prism 303 and the first polarization splitter prism 301. The polarization state is changed through the first quarter wave plate 302 to change its polarization state, from vertical linear polarized light to circular polarized light, incident on the first plane reflector 401, and returns along the original path. The quarter wave plate 302 changes the polarization state from circularly polarized light to horizontally polarized light, passes through the first polarization splitter prism 301, is internally reflected twice by the second right-angle reflection prism 304 and passes through the first polarization splitter prism 301, passes through the first quarter wave plate 302 and changes the polarization state from horizontally polarized light to circularly polarized light, enters the first plane reflector 401, returns along the original path, passes through the first quarter wave plate 302 and changes the polarization state from circularly polarized light to vertically polarized light, is reflected by the first polarization splitter prism 301, is internally reflected twice by the first right-angle reflection prism 303 and passes through the first polarization splitter prism 301. The light is reflected by the first polarization beam splitter prism 301, transmitted through the first quarter wave plate 302 to change the polarization state, and converted from vertical linear polarized light to circular polarized light, and then enters the first plane reflector 401, and then returns along the original path, and transmitted through the first quarter wave plate 302 to change the polarization state, and converted from circular polarized light to horizontal linear polarized light, and then enters the first polarization beam splitter prism 301, and then passes through the second right-angle reflector 304 for two internal reflections and the first polarization beam splitter prism 301, and then passes through the first quarter wave plate 300 to change the polarization state, and converted from horizontal linear polarized light to circular polarized light, and then enters the first plane reflector 401, and then returns along the original path. The light returns, passes through the first quarter-wave plate 302 to change its polarization state, and is converted from circularly polarized light to vertically polarized light. The light is then reflected by the first polarization splitter prism 301. After two internal reflections from the first right-angle reflection prism 303 and the reflection from the first polarization splitter prism 301, the light is passed through the first quarter-wave plate 302 to change its polarization state, and is converted from vertically polarized light to circularly polarized light. The light is incident on the first plane reflector 401, and returns along the original path. The light is passed through the first quarter-wave plate 302 to change its polarization state, and is converted from circularly polarized light to horizontally polarized light. The light is then passed through the first polarization splitter prism 301 and is incident on the first fiber coupler 6.

[0033] In some other optional embodiments, the reverse displacement measuring device 5 includes a second bevel reflector 501, a second polarization beam splitter prism 502, a second quarter-wave plate 503, a third plane reflector 504, a third quarter-wave plate 505, and a third right-angle reflective prism 506. The forward displacement measuring device 3 includes a first polarization beam splitter prism 301, a first quarter-wave plate 302, a first right-angle reflective prism 303, a second right-angle reflective prism 304, and a first bevel reflector 305.

[0034] Based on this, the S-polarized light is processed by the forward displacement measuring device 3, the displacement measuring substrate, and the reverse displacement measuring device 5, and then incident on the first fiber coupler 6, including: the S-polarized light is obliquely reflected twice by the first oblique reflector 305 and the second oblique reflector 501, reflected by the second polarization beam splitter prism 502, transmitted by the second quarter-wave plate 503, incident on the third plane reflector 504, returns along the original path, is transmitted by the second quarter-wave plate 503, is transmitted by the second polarization beam splitter prism 502, is transmitted by the third quarter-wave plate 505, is incident on the second plane reflector 403, returns along the original path, is transmitted by the third quarter-wave plate 505, and is reflected by the second polarization beam splitter prism 502. After two internal reflections from the third right-angle reflecting prism 506 and reflection from the second polarization beam splitting prism 502, the optical fiber is transmitted through the third quarter-wave plate 505 and incident on the second plane reflecting mirror 403. The optical fiber returns to the original path, is transmitted through the third quarter-wave plate 505, is transmitted through the second polarization beam splitting prism 502, is transmitted through the second quarter-wave plate 503, is incident on the third plane reflecting mirror 504, returns to the original path, is transmitted through the second quarter-wave plate 503, is reflected from the second polarization beam splitting prism 502, and then repeats the steps of the preset reflection and transmission process. The optical fiber is then obliquely reflected twice by the second bevel reflecting mirror 501 and the first bevel reflecting mirror 305, is reflected by the first polarization beam splitting prism 301, and is incident on the first fiber coupler.

[0035] The preset reflection and transmission process is as follows: two oblique reflections by the second oblique reflector 501 and the first oblique reflector 305, two internal reflections by the first polarization beam splitter prism 301 and the second right-angle reflector 304, reflection by the first polarization beam splitter prism 301, two oblique reflections by the first oblique reflector 305 and the second oblique reflector 501, reflection by the second polarization beam splitter prism 502, transmission by the second quarter-wave plate 503, incident on the third plane reflector 504, returning along the original path, transmission by the second quarter-wave plate 503, transmission by the second polarization beam splitter prism 502, and transmission by the third quarter-wave plate 505. The light is transmitted through the third quarter-wave plate 505, incident on the second plane reflector 403, returned along the original path, transmitted through the third quarter-wave plate 505, reflected by the second polarization splitter prism 502, internally reflected twice by the third right-angle reflective prism 506 and reflected by the second polarization splitter prism 502, transmitted through the third quarter-wave plate 505, incident on the second plane reflector 403, returned along the original path, transmitted through the third quarter-wave plate 505, transmitted through the second polarization splitter prism 502, transmitted through the second quarter-wave plate 503, incident on the third plane reflector 504, returned along the original path, transmitted through the second quarter-wave plate 503, and reflected by the second polarization splitter prism 502.

[0036] Specifically, the S-polarized light is reflected twice by the first bevel mirror 305 and the second bevel mirror 501, reflected by the second polarization splitting prism 502, transmitted through the second quarter-wave plate 503 to change the polarization state, and converted from vertical linear polarized light to circular polarized light, and then enters the third plane reflector 504, returns along the original path, and then passes through the second quarter-wave plate 503 to change the polarization state, and converts the circular polarized light to horizontal linear polarized light, and then enters the second polarization splitting prism 502, and then passes through the third quarter-wave plate 505 to change the polarization state, and converts the horizontal linear polarized light to circular polarized light, and then enters the second plane reflector 403, returns along the original path, and then passes through the third quarter-wave plate 505 to change the polarization state, and converts the circular polarized light to vertical linear polarized light. After being reflected by the second polarization splitter prism 502, it is internally reflected twice by the third right-angle reflecting prism 506 and reflected by the second polarization splitter prism 502, and then transmitted through the third quarter-wave plate 505 to change the polarization state, from vertical linear polarization light to circular polarization light, and then incident on the second plane reflector 403, and then returns along the same route, and then transmitted through the third quarter-wave plate 505 to change the polarization state, from circular polarization light to horizontal linear polarization light, and then transmitted through the second polarization splitter prism 502, and then transmitted through the second quarter-wave plate 503 to change the polarization state, from horizontal linear polarization light to circular polarization light, and then incident on the third plane reflector 504, and then returns along the same route, and then transmitted through the second quarter-wave plate 503 to change the polarization state, from circular polarization light to vertical linear polarization light, and then passes through the second polarization splitter prism 504. The light is reflected by the prism 502, and is reflected twice by the second bevel reflector 501 and the first bevel reflector 305, and is reflected by the first polarization beam splitter prism 301 and internally reflected twice by the second right-angle reflector 304, and is reflected by the first polarization beam splitter prism 301, and is reflected twice by the first bevel reflector 305 and the second bevel reflector 501, and is reflected by the second polarization beam splitter prism 502, and is transmitted through the second quarter-wave plate 503 to change the polarization state, from vertical linear polarization light to circular polarization light, and is incident on the third plane reflector 504, and returns along the original path, and is transmitted through the second quarter-wave plate 503 to change the polarization state, from circular polarization light to horizontal linear polarization light, and is transmitted through the second polarization beam splitter prism 502, and is transmitted through the third quarter-wave plate 505. The polarization state is changed from horizontal linear polarized light to circular polarized light, and the light is incident on the second plane reflector 403, returns along the original path, and is transmitted through the third quarter wave plate 505 to change the polarization state, and is converted from circular polarized light to vertical linear polarized light. The light is reflected by the second polarization splitting prism 502, and is internally reflected twice by the third right-angle reflecting prism 506 and reflected by the second polarization splitting prism 502, and is transmitted through the third quarter wave plate 505 to change the polarization state, and is converted from vertical linear polarized light to circular polarized light. The light is incident on the second plane reflector 403, returns along the original path, and is transmitted through the third quarter wave plate 505 to change the polarization state, and is converted from circular polarized light to horizontal linear polarized light. The light is transmitted through the second polarization splitting prism 502, and is transmitted through the second quarter wave plate 503 to change the polarization state.The horizontal linear polarized light is converted into circular polarized light, incident on the third plane reflector 504, returns along the original path, is transmitted through the second quarter wave plate 503 to change the polarization state, and is converted from circular polarized light into vertical linear polarized light, is reflected by the second polarization splitting prism 502, is reflected twice by the second bevel reflector 501 and the first bevel reflector 305, is reflected by the first polarization splitting prism 301 and is internally reflected twice by the second right-angle reflector 304, is reflected by the first polarization splitting prism 301, is reflected by the first bevel reflector 305 and the second bevel reflector The light is reflected twice by the oblique surface of the reflector 501, reflected by the second polarization splitter prism 502, transmitted through the second quarter-wave plate 503 to change the polarization state, from vertical linear polarization light to circular polarization light, and incident on the third plane reflector 504. It returns along the original path, transmitted through the second quarter-wave plate 503 to change the polarization state, from circular polarization light to horizontal linear polarization light, transmitted through the second polarization splitter prism 502, transmitted through the third quarter-wave plate 505 to change the polarization state, from horizontal linear polarization light to circular polarization light, and incident on the second plane reflector. 403, returns to the original path, transmits through the third quarter wave plate 505 to change the polarization state, and changes from circular polarized light to vertical linear polarized light, is reflected by the second polarization splitter prism 502, is internally reflected twice by the third right-angle reflecting prism 506 and reflected by the second polarization splitter prism 502, transmits through the third quarter wave plate 505 to change the polarization state, and changes from vertical linear polarized light to circular polarized light, is incident on the second plane reflector 403, returns to the original path, transmits through the third quarter wave plate 505 to change the polarization state, and changes from circular polarized light to horizontal linear polarized light. The polarized light is transmitted through the second polarization beam splitter prism 502, and then through the second quarter-wave plate 503, where its polarization state is changed from horizontally polarized light to circularly polarized light. The light then enters the third plane reflector 504, returns along the original path, and then through the second quarter-wave plate 503, where its polarization state is changed from circularly polarized light to vertically polarized light. The light then reflects from the second polarization beam splitter prism 502, undergoes two oblique reflections from the second bevel reflector 501 and the first bevel reflector 305, and finally enters the first fiber coupler 6.

[0037] Finally, the first fiber coupler 6 and the second fiber coupler 7 transmit the interferometric displacement measurement signal to a data acquisition module 8. After data processing, the signal is transmitted to a host computer 9 to obtain real-time displacement measurement information. Optionally, the data processing process may include, but is not limited to, photoelectric conversion and low-pass filtering. Alternatively, the data acquisition module 9 may be a data acquisition card.

[0038] In addition, the linear displacement platform 402 is located in the middle position between 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, the forward displacement information and the reverse displacement information are obtained synchronously, and the real-time displacement measurement value is obtained by subtracting the forward displacement information from the reverse displacement information.

[0039] The Doppler frequency shift signal of the above forward displacement measurement device is expressed as , the Doppler frequency shift signal of the negative displacement measurement device is expressed as , the Doppler frequency shift signal of the second fiber coupler is expressed as f1-f2, and the interference signal of the first fiber coupler is expressed as ; Wherein, f1 represents the first frequency, f2 represents the second frequency, Indicates the Doppler shift.

[0040] Thus, the phase change is related to the measured displacement The relationship between can be expressed as: ,in, represents the phase change, represents the measured displacement, Indicates the laser wavelength generated by the dual-frequency laser, Indicates the Doppler shift.

[0041] In addition, the present invention also provides an ultra-low thermal expansion coefficient measurement device based on dual-frequency laser, such as Figure 2 As shown, Figure 2 Schematic diagram of an ultra-low thermal expansion coefficient measuring device based on a dual-frequency laser provided in an embodiment of the present application, the principle and Figure 1 Completely consistent, ultra-low thermal expansion material 404 heats up under the control of vacuum temperature control 405. As it heats up, ultra-low thermal expansion material 404 deforms. By detecting the magnitude of the deformation in response to the reflected light, the expansion coefficient of the ultra-low thermal expansion material can be determined in real time. Thermal expansion material 404 is located between first plane reflector 401 and second plane reflector 403. Thermal expansion material 404 can be coated on both sides, or a higher thermal expansion material substrate can be used.

[0042] An embodiment of the present 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, a forward displacement measurement device, a displacement measurement substrate, a reverse displacement measurement device, a first fiber optic coupler, a second fiber optic coupler, a data acquisition module, and a host computer. The displacement measurement substrate includes a first plane mirror, a linear displacement platform, and a second plane mirror. The linear displacement platform is arranged in the middle position between the forward displacement measurement device and the reverse displacement measurement device. The first plane mirror and the second plane mirror are arranged on both sides of the linear displacement platform and move synchronously with the linear displacement platform. Among them, the dual-frequency laser is used to generate a beam of orthogonal linearly polarized light, which is split according to energy by a beam splitter prism into reflected light and transmitted light; the reflected light is incident on the second fiber coupler, and the transmitted light is incident on the forward displacement measurement device for polarization splitting, and is divided into 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 measurement device and the displacement measurement substrate respectively, and then is incident on the first fiber coupler; the S-polarized light is processed by the forward displacement measurement device, the displacement measurement substrate, and the reverse displacement measurement device respectively, and then is incident on the first fiber coupler; the first fiber coupler and the second fiber coupler transmit the interference displacement measurement signal to the data acquisition module, which is transmitted to the host computer after data processing to obtain real-time displacement measurement information. This solution improves measurement accuracy by utilizing phase decoupling and multiple frequency doubling technology. Multiple frequency doubling provides multiple laser displacement information in the state of multiple round-trip measurement, and phase decoupling provides forward and reverse measurement in the state of real-time measurement to reduce the influence of positioning fluctuation error and environmental disturbance error of the displacement stage. In addition, in the state of phase decoupling, the measurement accuracy is transformed from the original 6 times Doppler frequency shift to 12 times Doppler frequency shift, further improving the measurement accuracy. In addition, by utilizing the multi-point incidence of a single light beam and the positioning of the same position on the left and right sides of a single light beam, 6 linear light spots are incident on both the front and rear surfaces simultaneously. , it can simultaneously detect the spatial positioning accuracy of the measurement reference mirror on the displacement table in real time on the left and right sides, avoid the beam offset of the plane mirror during linear displacement, and when the displacement table is in operation, the front and rear plane mirrors operate synchronously, and the displacement measurement information can be accurately fed back to the displacement table for precise control of the positioning accuracy of the displacement table; at the same time, using the positive and negative dimensions, the synchronously acquired signals also include the vibration information of the displacement table and the disturbance information of the environment. Therefore, in the phase decoupling state, the error information can be reduced within the system according to the real-time information to ensure the overall stability of its displacement measurement device.

[0043] In addition, an embodiment of the present application further provides a heterodyne laser interferometry method based on phase decoupling and multiple frequency doubling. The 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, 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 reflector, a linear displacement platform, and a second plane reflector. The linear displacement platform is arranged in the middle position between the forward displacement measuring device and the reverse displacement measuring device. The first plane reflector and the second plane reflector are arranged on both sides of the linear displacement platform and move synchronously with the linear displacement platform. The method includes: The dual-frequency laser is used to generate a beam of orthogonal linearly polarized light. The linearly polarized light is split according to energy by a beam splitter prism into reflected light and transmitted light. The reflected light is incident on the second fiber coupler, and the transmitted light is incident on the forward displacement measurement device for polarization splitting, into 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 measurement device and the displacement measurement substrate and then incident on the first optical 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 optical fiber coupler; The first fiber optic coupler and the second fiber optic coupler transmit the interference displacement measurement signal to the data acquisition module, which is then transmitted to the host computer after data processing to obtain real-time displacement measurement information.

[0044] The implementation process and beneficial effects of the above-mentioned 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.

[0045] It is easy to understand that those skilled in the art can combine, split, reorganize, etc. the embodiments of the present application based on the several embodiments provided in the present application to obtain other embodiments, and these embodiments do not exceed the scope of protection of the present application.

[0046] The above specific implementation methods further explain in detail the purpose, technical solutions and beneficial effects of the embodiments of the present application. It should be understood that the above are only specific implementation methods of the embodiments of the present application and are not intended to limit the scope of protection of the embodiments of the present application. Any modifications, equivalent replacements, improvements, etc. made on the basis of the technical solutions of the embodiments of the present application should be included in the scope of protection of the embodiments of the present application.

Claims

1. A heterodyne laser interferometry device based on phase decoupling and multiple frequency doubling, characterized in that: include: A dual-frequency laser, a beam splitter, 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 reflector, a linear displacement platform, and a second plane reflector. The linear displacement platform is disposed between the forward displacement measuring device and the reverse displacement measuring device. The first plane reflector and the second plane reflector are disposed on both sides of the linear displacement platform and move synchronously with the linear displacement platform. The dual-frequency laser is used to generate a beam of orthogonal linearly polarized light, which is split according to energy by the beam splitter prism into reflected light and transmitted light; the reflected light is incident on the second fiber coupler, and the transmitted light is incident on the forward displacement measurement device for polarization splitting, into 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 respectively and then incident on the first optical fiber coupler; The S-polarized light is respectively processed by the forward displacement measuring device, the displacement measuring substrate, and the reverse displacement measuring device, and then incident on the first optical fiber coupler; The first optical fiber coupler and the second optical fiber coupler transmit interference displacement measurement signals to the data acquisition module, which are then transmitted to the host computer after data processing to obtain real-time displacement measurement information.

2. The device according to claim 1, characterized in that The forward displacement measuring device includes a first polarization beam splitter prism, a first quarter-wave plate, a first right-angle reflecting prism, a second right-angle reflecting prism, and a first oblique reflecting mirror.

3. The device according to claim 2, characterized in that The P-polarized light is processed by the forward displacement measuring device and the displacement measuring substrate and then incident on the first optical fiber coupler, including: The P-polarized light is transmitted through the first quarter-wave plate, incident on the first plane reflector, returns along the original path, is transmitted through the first quarter-wave plate, is reflected through the first polarization beam splitter prism, is internally reflected twice by the first right-angle reflection prism and reflected by the first polarization beam splitter prism, is transmitted through the first quarter-wave plate, is incident on the first plane reflector, returns along the original path, is transmitted through the first quarter-wave plate, is transmitted through the first polarization beam splitter prism, is internally reflected twice by the second right-angle reflection prism and is transmitted through the first polarization beam splitter prism, and then the above steps are repeated, the light is transmitted through the first quarter-wave plate again, is incident on the first plane reflector, returns along the original path, is transmitted through the first quarter-wave plate, is internally reflected twice by the first right-angle reflection prism and reflected by the first polarization beam splitter prism, is transmitted through the first quarter-wave plate, is incident on the first plane reflector, returns along the original path, is transmitted through the first quarter-wave plate, is internally reflected twice by the first right-angle reflection prism and reflected by the first polarization beam splitter prism, is transmitted through the first quarter-wave plate, is incident on the first plane reflector, returns along the original path, is transmitted through the first quarter-wave plate, is transmitted through the first polarization beam splitter prism, and is incident on the first fiber coupler.

4. The device according to any one of claims 1 to 3, characterized in that The reverse displacement measuring device includes a second oblique reflecting mirror, a second polarization beam splitting prism, a second quarter-wave plate, a third plane reflecting mirror, a third quarter-wave plate, and a third right-angle reflecting prism.

5. The device according to claim 4, characterized in that The forward displacement measuring device includes a first polarization beam splitter, a first quarter-wave plate, a first right-angle reflecting prism, a second right-angle reflecting prism, and a first bevel 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 optical fiber coupler, including: The S-polarized light is obliquely reflected twice by the first oblique reflector and the second oblique reflector, reflected by the second polarization beam splitter prism, transmitted by the second quarter-wave plate, incident on the third plane reflector, returns along the original path, is transmitted by the second quarter-wave plate, is transmitted by the second polarization beam splitter prism, is transmitted by the third quarter-wave plate, is incident on the second plane reflector, returns along the original path, is transmitted by the third quarter-wave plate, is reflected by the second polarization beam splitter prism, is internally reflected twice by the third right-angle reflector and reflected by the second polarization beam splitter prism, is transmitted by the third quarter-wave plate, is incident on the second plane reflector, returns along the original path, is transmitted by the third quarter-wave plate, is transmitted by the second polarization beam splitter prism, is transmitted by the second quarter-wave plate, is incident on the third plane reflector, returns along the original path, is transmitted by the third quarter-wave plate, is transmitted by the second polarization beam splitter prism, is transmitted by the second quarter-wave plate, is incident on the third plane reflector, returns along the original path, is transmitted by the second quarter-wave plate, is reflected by the second polarization beam splitter prism, and then the preset reflection and transmission process is repeated. The light is then obliquely reflected twice by the second oblique reflector and the first oblique reflector, is reflected by the first polarization beam splitter prism, and is incident on the first fiber coupler.

6. The device according to claim 5, characterized in that The preset reflection and transmission process is: oblique reflection twice by the second oblique reflecting mirror and the first oblique reflecting mirror, reflection by the first polarization beam splitting prism and internal reflection twice by the second right-angle reflecting prism, reflection by the first polarization beam splitting prism, oblique reflection twice by the first oblique reflecting mirror and the second oblique reflecting mirror, reflection by the second polarization beam splitting prism, transmission through the second quarter-wave plate, incident on the third plane reflecting mirror, return along the original path, transmission through the second quarter-wave plate, transmission through the second polarization beam splitting prism, transmission through the third quarter-wave plate, incident on the second plane reflecting mirror, return along the original path, transmission through the third quarter-wave plate, reflection by the second polarization beam splitting prism, internal reflection twice by the third right-angle reflecting prism and reflection by the second polarization beam splitting prism, transmission through the third quarter-wave plate, incident on the second plane reflecting mirror, return along the original path, transmission through the third quarter-wave plate, transmission through the second polarization beam splitting prism, transmission through the second quarter-wave plate, incident on the third plane reflecting mirror, return along the original path, transmission through the second quarter-wave plate, and reflection by the second polarization beam splitting prism.

7. The device according to any one of claims 1 to 3, characterized in that The Doppler frequency shift signal of the forward 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 expressed as f1-f2, and the interference signal of the first fiber coupler is expressed as ; wherein f1 represents the first frequency, f2 represents the second frequency, Indicates the Doppler shift.

8. A heterodyne laser interferometry measurement method based on phase decoupling and multiple frequency doubling, applied to the heterodyne laser interferometry measurement device based on phase decoupling and multiple frequency doubling according to any one of claims 1 to 7, the device comprising a dual-frequency laser, a beam splitter, 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 reflector, a linear displacement platform, and a second plane reflector, the linear displacement platform being disposed between the forward displacement measuring device and the reverse displacement measuring device, the first plane reflector and the second plane reflector being disposed on either side of the linear displacement platform and moving synchronously with the linear displacement platform, characterized in that: The method comprises: The dual-frequency laser is used to generate a beam of orthogonal linearly polarized light, which is split according to energy by the beam splitter prism into reflected light and transmitted light; the reflected light is incident on the second fiber coupler, and the transmitted light is incident on the forward displacement measurement device for polarization splitting, into 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 respectively and then incident on the first optical fiber coupler; The S-polarized light is respectively processed by the forward displacement measuring device, the displacement measuring substrate, and the reverse displacement measuring device, and then incident on the first optical fiber coupler; The first optical fiber coupler and the second optical fiber coupler transmit interference displacement measurement signals to the data acquisition module, which are then transmitted to the host computer after data processing to obtain real-time displacement measurement information.

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