An interferometric displacement measuring device based on a Sagnac configuration

Abstract

The application discloses an interference displacement measuring device based on Sagnac structure, solves the problem that the displacement measurement error of a right-angle prism is relatively large in the prior art, and the displacement measurement of the right-angle prism and a plane mirror cannot be simultaneously applied, the right-angle prism is used instead of the plane mirror, the influence of the original reflection of multi-order virtual reflection light is avoided, in the case of obtaining four times of optical subdivision, compared with a laser interferometer available on the market and reported in the literature, the application uses a to-be-measured right-angle prism to form a Sagnac structure, and uses a phase decoupling form formed by a measurement structure and a reference structure, so that the measurement error of the to-be-measured right-angle prism in phase shift is reduced by using the measurement reference of the to-be-measured right-angle prism, the periodic nonlinear error of the measurement system is reduced, the measurement error of the to-be-measured right-angle prism in phase shift is weakened by using the phase coupling of the reference and the measurement, and the displacement measurement precision is improved.

Description

Technical Field

[0001] This invention relates to displacement measuring devices, and more specifically to an interferometric displacement measuring device based on a Sagnac structure. Background Technology

[0002] In high-precision step displacement measurement, heterodyne laser interferometry (LIFT) devices often introduce multi-level nonlinear errors with progressively varying degrees of nonlinearity due to periodic nonlinearity, resulting in significant stray light in nanometer-scale step measurements. Numerous studies have shown that periodic nonlinearity mainly comprises two parts: one is the periodic nonlinearity introduced by the laser cross-aliasing of the dual-frequency laser itself; the other is the periodic nonlinearity of the multi-order virtual reflection beams generated by the optical interfaces of the optical elements within the measurement structure. Using a right-angle prism as the measurement substrate instead of a plane mirror can significantly reduce the impact of nonlinearity errors.

[0003] In the current development of lithography machines, reducing the overlay error between the mask stage and the workpiece stage to achieve a silicon wafer circuit linewidth of 1nm requires a displacement measurement accuracy of 1nm or even sub-picometer. However, existing technologies still have relatively large displacement measurement errors for right-angle prisms and cannot be applied to the displacement measurement of both plane mirrors and right-angle prisms simultaneously. Summary of the Invention

[0004] The purpose of this invention is to provide an interferometric displacement measurement device based on the Sagnac structure, in order to solve the technical problems of large displacement measurement errors of right-angle prisms in existing technologies, and the inability to simultaneously apply it to the displacement measurement of plane mirrors and right-angle prisms.

[0005] This invention uses a right-angle prism instead of a plane mirror to avoid the influence of the original path reflection of multi-order virtual reflection light, thereby improving the measurement accuracy while obtaining four times the optical subdivision.

[0006] To achieve the above objectives and complete the above inventive concept, the present invention adopts the following technical solution:

[0007] An interferometric displacement measurement device based on the Sagnac structure is used to measure the displacement of a right-angle prism and a plane mirror under test. Its special feature is that it includes a dual-frequency laser, a first polarizing beam splitter, a mirror, and a first fiber coupler.

[0008] The first polarizing beam splitter includes four sides, wherein the first side is opposite to the third side, and the second side is opposite to the fourth side;

[0009] The first side is sequentially provided with the dual-frequency laser and the first fiber coupler along the length direction of the side, the dual-frequency laser is used for emitting measurement light and reference light to the first polarization beam splitter prism; and the first fiber coupler is used for receiving the measurement light and the reference light after participating in measurement, obtaining corresponding Doppler shift information, and realizing displacement measurement.

[0010] The second side is provided with the mirror, the mirror is used for reflecting light emitted from the first polarization beam splitter prism to the to-be-measured right-angle prism;

[0011] The third side is used for providing the to-be-measured right-angle prism, one part of the bottom side of the to-be-measured right-angle prism is opposite to the third side, and the other part corresponds to the mirror, and is used for receiving light reflected by the mirror and reflecting the light to the first polarization beam splitter prism;

[0012] The fourth side is used for providing the to-be-measured plane mirror, the to-be-measured plane mirror can reflect light emitted from the first polarization beam splitter prism back to the first polarization beam splitter prism.

[0013] Further, the first quarter-wave plate, the second quarter-wave plate and the third quarter-wave plate are further included;

[0014] The first quarter-wave plate is arranged on an optical path between the to-be-measured plane mirror and the first polarization beam splitter prism;

[0015] The second quarter-wave plate is arranged on a part of an optical path between the first polarization beam splitter prism and the to-be-measured right-angle prism, and the part of the optical path corresponds to the first fiber coupler;

[0016] The third quarter-wave plate is arranged on a part of an optical path between the first polarization beam splitter prism and the first mirror, and the part of the optical path is close to the to-be-measured right-angle prism.

[0017] Further, the first fiber coupler and the second quarter-wave plate are arranged close to the fourth side of the first polarization beam splitter prism;

[0018] The dual-frequency laser is arranged close to the second side of the first polarization beam splitter prism.

[0019] Further, the polarization angles of the first quarter-wave plate, the second quarter-wave plate and the third quarter-wave plate are all 45°.

[0020] Further, the second polarization beam splitter prism and the beam splitter prism are further included;

[0021] The second polarization beam splitter prism is arranged on an optical path between the dual-frequency laser and the first polarization beam splitter prism, and a beam splitting surface of the second polarization beam splitter prism is perpendicular to a beam splitting surface of the first polarization beam splitter prism;

[0022] The light splitting prism is arranged on the light path between the first fiber coupler and the first polarization light splitting prism; the light splitting surface of the light splitting prism is parallel to the light splitting surface of the first polarization light splitting prism.

[0023] Further, the light splitting prism, the second polarization light splitting prism and the second fiber coupler are further included;

[0024] The light splitting prism is arranged on the light path between the double-frequency laser and the first polarization light splitting prism; the light splitting surface of the light splitting prism is perpendicular to the light splitting surface of the first polarization light splitting prism;

[0025] The second polarization light splitting prism is arranged on the light path between the first fiber coupler and the first polarization light splitting prism; the light splitting surface of the second polarization light splitting prism is parallel to the light splitting surface of the first polarization light splitting prism;

[0026] The second fiber coupler is arranged on the side of the second polarization light splitting prism close to the second side of the first polarization light splitting prism and away from the light splitting prism, so that the first fiber coupler receives part of the measurement light and the reference light after participating in the measurement to realize the coarse displacement measurement, and the second fiber coupler receives another part of the measurement light and the reference light after participating in the measurement to realize the fine displacement measurement.

[0027] An interference displacement measurement method based on a Sagnac structure, which adopts the interference displacement measurement device based on the Sagnac structure, and is characterized in that the method comprises displacement measurement of a to-be-measured right-angle prism and displacement measurement of a to-be-measured plane mirror;

[0028] The displacement measurement of the to-be-measured right-angle prism comprises the following steps:

[0029] Step A1, the to-be-measured plane mirror is fixed, the double-frequency laser emits measurement light with a frequency of f1 and reference light with a frequency of f2;

[0030] Step A2, the measurement light and the reference light enter the first fiber coupler after being affected by corresponding optical devices;

[0031] Step A3, the first fiber coupler obtains a Doppler frequency shift amount;

[0032] Step A4, the displacement amount of the to-be-measured right-angle prism is calculated through the Doppler frequency shift amount obtained in step A3, and the displacement measurement of the to-be-measured right-angle prism is completed;

[0033] The displacement measurement of the to-be-measured plane mirror comprises the following steps:

[0034] Step B1, the to-be-measured right-angle prism is fixed, the double-frequency laser emits measurement light with a frequency of f1 and reference light with a frequency of f2;

[0035] Step B2, the measurement light and the reference light enter the first fiber coupler after being affected by the corresponding optical devices respectively;

[0036] Step B3, the first fiber coupler receives the affected measurement light and reference light, and obtains the Doppler frequency shift amount;

[0037] Step B4, the displacement amount of the to-be-measured plane mirror is calculated by the Doppler frequency shift amount obtained in step B3, and the displacement measurement of the to-be-measured plane mirror is completed.

[0038] Further, step A2 is specifically that the measurement light with the frequency f1 is transmitted by the first polarization beam splitter prism into horizontal linearly polarized light, and then is reflected twice by the to-be-measured right-angle prism, reflected by the mirror, transmitted by the first polarization beam splitter prism, transmitted by the first quarter-wave plate, and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then is reflected by the to-be-measured plane mirror, transmitted by the first quarter-wave plate, and the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light, and then is reflected by the first polarization beam splitter prism, transmitted by the second quarter-wave plate, and the polarization state changes from vertical linearly polarized light to right-handed elliptical polarized light, and then is reflected twice by the to-be-measured right-angle prism, reflected by the mirror, transmitted by the third quarter-wave plate, and the polarization state changes from right-handed elliptical polarized light to horizontal linearly polarized light, and then is transmitted by the first polarization beam splitter prism and the first quarter-wave plate, and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then is reflected by the to-be-measured plane mirror and the first quarter-wave plate, and the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light, and then is reflected by the first polarization beam splitter prism, reflected twice by the to-be-measured right-angle prism, reflected by the mirror, and reflected by the first polarization beam splitter prism, and finally enters the first fiber coupler;

[0039] The reference light with the frequency f2 is reflected by the first polarization beam splitter prism into vertical linearly polarized light, and then is transmitted by the third quarter-wave plate, and the polarization state changes from vertical linearly polarized light to left-handed elliptical polarized light, and then is reflected by the mirror, reflected twice by the to-be-measured right-angle prism, transmitted by the second quarter-wave plate, and the polarization state changes from left-handed elliptical polarized light to horizontal linearly polarized light, and then is transmitted by the first polarization beam splitter prism, and finally enters the first fiber coupler;

[0040] Step A3 is specifically that the first fiber coupler obtains the Doppler frequency shift amount Δf1;

[0041] Step A4 is specifically that the displacement amount S1 of the to-be-measured right-angle prism is calculated by the Doppler frequency shift amount Δf1 obtained in step A3:

[0042]

[0043] Wherein, c is the speed of light, is the total phase delay amount of the laser round trip measurement;

[0044] complete the displacement measurement of the tested right-angle prism;

[0045] Specifically, the measurement light with the frequency of f1 is transmitted by the first polarization beam splitter prism into horizontal linearly polarized light, and then is reflected twice by the tested right-angle prism, reflected by the mirror, transmitted by the first polarization beam splitter prism, and transmitted by the first quarter-wave plate, so that the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light; then the left-handed elliptical polarized light is reflected by the tested plane mirror, transmitted by the first quarter-wave plate, so that the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light; then the vertical linearly polarized light is reflected by the first polarization beam splitter prism, transmitted by the second quarter-wave plate, so that the polarization state changes from vertical linearly polarized light to right-handed elliptical polarized light; then the right-handed elliptical polarized light is reflected by the mirror, reflected twice by the tested right-angle prism, and transmitted by the third quarter-wave plate, so that the polarization state changes from right-handed elliptical polarized light to horizontal linearly polarized light; then the horizontal linearly polarized light is transmitted by the first polarization beam splitter prism, transmitted by the first quarter-wave plate, so that the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light; then the left-handed elliptical polarized light is reflected by the tested plane mirror, transmitted by the first quarter-wave plate, so that the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light; then the vertical linearly polarized light is reflected by the first polarization beam splitter prism, reflected twice by the tested right-angle prism, reflected by the mirror, and reflected by the first polarization beam splitter prism, and finally is incident on the first fiber coupler;

[0046] Specifically, the reference light with the frequency of f2 is reflected by the first polarization beam splitter prism into vertical linearly polarized light, and then is transmitted by the third quarter-wave plate, so that the polarization state changes from vertical linearly polarized light to left-handed elliptical polarized light; then the left-handed elliptical polarized light is reflected by the mirror, reflected twice by the tested right-angle prism, and transmitted by the second quarter-wave plate, so that the polarization state changes from left-handed elliptical polarized light to horizontal linearly polarized light; then the horizontal linearly polarized light is transmitted by the first polarization beam splitter prism, and finally is incident on the first fiber coupler;

[0047] Specifically, the first fiber coupler receives the affected measurement light and reference light, and obtains the Doppler frequency shift amount Δf2;

[0048] Specifically, the Doppler frequency shift amount Δf2 obtained in step B3 is used to calculate the displacement amount S2 of the tested plane mirror:

[0049]

[0050] complete the displacement measurement of the tested plane mirror.

[0051] Further, the step A2 is specifically that the measuring light with the frequency f1 is transmitted by the second polarizing beam splitter prism into horizontal linearly polarized light, and then is transmitted by the first polarizing beam splitter prism, reflected twice by the to-be-measured right-angle prism, reflected by the mirror, transmitted by the first polarizing beam splitter prism, transmitted by the first quarter-wave plate, and the polarization state changes from horizontal linearly polarized light to left-handed elliptically polarized light, and then is reflected by the to-be-measured plane mirror, transmitted by the first quarter-wave plate, and the polarization state changes from left-handed elliptically polarized light to vertical linearly polarized light, and then is reflected by the first polarizing beam splitter prism, transmitted by the second quarter-wave plate, and the polarization state changes from vertical linearly polarized light to right-handed elliptically polarized light, and then is reflected twice by the to-be-measured right-angle prism, reflected by the mirror, transmitted by the third quarter-wave plate, and the polarization state changes from right-handed elliptically polarized light to horizontal linearly polarized light, and then is transmitted by the first polarizing beam splitter prism, transmitted by the first quarter-wave plate, and the polarization state changes from horizontal linearly polarized light to left-handed elliptically polarized light, and then is reflected by the to-be-measured plane mirror, transmitted by the first quarter-wave plate, and the polarization state changes from left-handed elliptically polarized light to vertical linearly polarized light, and then is reflected by the first polarizing beam splitter prism, reflected twice by the to-be-measured right-angle prism, reflected by the mirror, transmitted by the first polarizing beam splitter prism, and then is transmitted by the beam splitter prism, and finally is incident on the first fiber coupler;

[0052] The reference light with the frequency f2 is reflected by the second polarizing beam splitter prism into vertical linearly polarized light, and then is reflected by the beam splitter prism, and finally is incident on the first fiber coupler;

[0053] The step A3 is specifically that the first fiber coupler obtains the Doppler frequency shift amount Δf1;

[0054] The step A4 is specifically that the Doppler frequency shift amount Δf1 obtained by the step A3 is used to calculate the displacement amount S1 of the to-be-measured right-angle prism:

[0055]

[0056] The displacement measurement of the to-be-measured right-angle prism is completed;

[0057] The step B2 is specifically that the measuring light with the frequency of f1 is transmitted by the second polarizing beam splitter prism into horizontal linearly polarized light, and then is transmitted by the first polarizing beam splitter prism, reflected twice by the right-angle prism to be measured, reflected by the mirror, transmitted by the first polarizing beam splitter prism, transmitted by the first quarter-wave plate, and the polarization state changes from horizontal linearly polarized light into left-handed elliptical polarized light, and then is reflected by the plane mirror to be measured, transmitted by the first quarter-wave plate, and the polarization state changes from left-handed elliptical polarized light into vertical linearly polarized light, and then is reflected by the first polarizing beam splitter prism, transmitted by the second quarter-wave plate, and the polarization state changes from vertical linearly polarized light into right-handed elliptical polarized light, and then is reflected by the right-angle prism to be measured twice, reflected by the mirror, transmitted by the third quarter-wave plate, and the polarization state changes from right-handed elliptical polarized light into horizontal linearly polarized light, and then is transmitted by the first polarizing beam splitter prism, transmitted by the first quarter-wave plate, and the polarization state changes from horizontal linearly polarized light into left-handed elliptical polarized light, and then is reflected by the plane mirror to be measured, transmitted by the first quarter-wave plate, and the polarization state changes from left-handed elliptical polarized light into vertical linearly polarized light, and then is reflected by the first polarizing beam splitter prism, reflected twice by the right-angle prism to be measured, reflected by the mirror, transmitted by the first polarizing beam splitter prism, and finally is incident on the first fiber coupler;

[0058] The reference light with the frequency of f2 is reflected by the second polarizing beam splitter prism into vertical linearly polarized light, and then is reflected by the beam splitter prism, and finally is incident on the first fiber coupler;

[0059] The step B3 is specifically that the first fiber coupler receives the affected measuring light and reference light, and obtains the Doppler frequency shift amount Δf2;

[0060] The step B4 is specifically that the Doppler frequency shift amount Δf2 obtained by the step B3 is used to calculate the displacement amount S2 of the plane mirror to be measured:

[0061]

[0062] The displacement measurement of the plane mirror to be measured is completed.

[0063] Further, the step A2 is specifically that the measuring light and the reference light enter the beam splitter prism together, and are spectrally split by the beam splitter prism to form reflected light and transmitted light;

[0064] The reflected light is transmitted by the second polarizing beam splitter prism to form horizontal linearly polarized light a1 with the frequency of f1, and reflected to form vertical linearly polarized light a2 with the frequency of f2;

[0065] The horizontal linearly polarized light a1 is incident on the second fiber coupler;

[0066] The vertical linearly polarized light a2 is incident on the first fiber coupler;

[0067] The transmitted light is transmitted by the first polarization beam splitter prism to form horizontal linearly polarized light b1 with a frequency f1, and reflected to form vertical polarized light b2 with a frequency f2;

[0068] The horizontal linearly polarized light b1 is reflected twice by the to-be-measured right-angle prism, reflected by the mirror, transmitted by the first polarization beam splitter prism, and transmitted by the first quarter-wave plate, and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then reflected by the to-be-measured plane mirror, transmitted by the first quarter-wave plate, and the polarization state changes from left-handed elliptical polarized light to vertical polarized light, and then reflected by the first polarization beam splitter prism, transmitted by the second quarter-wave plate, and the polarization state changes from vertical polarized light to right-handed elliptical polarized light, and then reflected twice by the to-be-measured right-angle prism, reflected by the mirror, and transmitted by the third quarter-wave plate, and the polarization state changes from right-handed elliptical polarized light to horizontal linearly polarized light, and then transmitted by the first polarization beam splitter prism and the first quarter-wave plate, and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then reflected by the to-be-measured plane mirror and the first quarter-wave plate, and the polarization state changes from left-handed elliptical polarized light to vertical polarized light, and then reflected by the first polarization beam splitter prism, reflected twice by the to-be-measured right-angle prism, reflected by the mirror, reflected by the first polarization beam splitter prism, and reflected by the second polarization beam splitter prism, and finally incident on the second fiber coupler;

[0069] The vertical polarized light b2 is transmitted by the third quarter-wave plate, and the polarization state changes from vertical polarized light to left-handed elliptical polarized light, and then reflected by the mirror, reflected twice by the to-be-measured right-angle prism, and transmitted by the second quarter-wave plate, and the polarization state changes from left-handed elliptical polarized light to horizontal linearly polarized light, and then transmitted by the first polarization beam splitter prism and the second polarization beam splitter prism, and finally incident on the first fiber coupler;

[0070] Step A3 is specifically that the first fiber coupler simultaneously receives two beams of orthogonal linearly polarized light, and obtains a Doppler frequency shift amount Δf1 of an interference signal after phase decoupling of the two beams of orthogonal linearly polarized light;

[0071] The second fiber coupler simultaneously receives two beams of orthogonal linearly polarized light, and obtains a Doppler frequency shift amount 3Δf1 of an interference signal after phase decoupling of the two beams of orthogonal linearly polarized light;

[0072] Step A4 is specifically that the displacement amount S1 of the to-be-measured right-angle prism is calculated according to the Doppler frequency shift amounts Δf1 and 3Δf1 obtained in step A3:

[0073] When the phase coupling is subtracted, the total phase delay is phase 1, and then

[0074] When the phase coupling is added, the total phase delay is phase 2, and then

[0075] The displacement measurement of the to-be-measured right-angle prism is completed;

[0076] Specifically, the measurement light and the reference light enter the beam splitter prism together, and the beam splitter prism performs energy splitting on the measurement light and the reference light to form reflected light and transmitted light;

[0077] The reflected light is transmitted through the second polarization beam splitter prism to form horizontal linearly polarized light a1 with a frequency f1, and is reflected to form vertical linearly polarized light a2 with a frequency f2;

[0078] The horizontal linearly polarized light a1 is incident on the second optical fiber coupler;

[0079] The vertical linearly polarized light a2 is incident on the first optical fiber coupler;

[0080] The transmitted light is transmitted through the first polarization beam splitter prism to form horizontal linearly polarized light b1 with a frequency f1, and is reflected to form vertical linearly polarized light b2 with a frequency f2;

[0081] The horizontal linearly polarized light b1 is sequentially reflected twice by the to-be-measured right-angle prism, reflected by the mirror, transmitted by the first polarization beam splitter prism, and transmitted by the first quarter-wave plate, and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then is sequentially reflected by the to-be-measured plane mirror, transmitted by the first quarter-wave plate, and the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light, and then is sequentially reflected by the first polarization beam splitter prism, transmitted by the second quarter-wave plate, and the polarization state changes from vertical linearly polarized light to right-handed elliptical polarized light, and then is sequentially reflected twice by the to-be-measured right-angle prism, reflected by the mirror, transmitted by the third quarter-wave plate, and the polarization state changes from right-handed elliptical polarized light to horizontal linearly polarized light, and then is sequentially transmitted by the first polarization beam splitter prism and the first quarter-wave plate, and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then is sequentially reflected by the to-be-measured plane mirror and the first quarter-wave plate, and the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light, and then is sequentially reflected by the first polarization beam splitter prism, reflected twice by the to-be-measured right-angle prism, reflected by the mirror, reflected by the first polarization beam splitter prism, and reflected by the second polarization beam splitter prism, and finally is incident on the second optical fiber coupler;

[0082] The vertical linearly polarized light b2 is transmitted through the third quarter-wave plate, and the polarization state changes from vertical linearly polarized light to left-handed elliptical polarized light, and then is sequentially reflected by the mirror, reflected twice by the to-be-measured right-angle prism, and transmitted by the second quarter-wave plate, and the polarization state changes from left-handed elliptical polarized light to horizontal linearly polarized light, and then is sequentially transmitted by the first polarization beam splitter prism and the second polarization beam splitter prism, and finally is incident on the first optical fiber coupler;

[0083] Specifically, the first optical fiber coupler simultaneously receives two beams of orthogonal linearly polarized light, and obtains a Doppler frequency shift amount 0 of interference signals after phase decoupling of the two beams of orthogonal linearly polarized light;

[0084] The second fiber coupler receives two beams of orthogonal linearly polarized light simultaneously, and obtains a Doppler frequency shift of 2Delta f2 of the interference signal after phase decoupling of the two beams of orthogonal linearly polarized light;

[0085] Step B4 is specifically that, based on the Doppler frequency shifts of 0 and 2Delta f2 obtained in step B3, the displacement S2 of the plane mirror to be measured is calculated by phase decoupling:

[0086]

[0087] The displacement measurement of the plane mirror to be measured is completed.

[0088] The beneficial effects of the present application are:

[0089] 1. Compared with the laser interferometer available on the market and reported in the literature, the present application uses a to-be-measured right-angle prism to form a Sagnac structure, and uses the phase decoupling formed by the measurement structure and the reference structure, so as to not only reduce the periodic nonlinear error of the measurement system by using the measurement reference of the to-be-measured right-angle prism, but also weaken the measurement error in the phase shift of the to-be-measured right-angle prism by using the phase coupling of the reference and the measurement, thereby improving the displacement measurement precision.

[0090] 2. The to-be-measured right-angle prism in the present application serves as a measurement reference, can realize 4 times of optical subdivision, and also separates the double-frequency laser of the double-frequency laser twice by using a polarization beam splitter prism, thereby further improving the displacement measurement precision.

[0091] 3. The present application can perform two-dimensional synchronous measurement, one of which is displacement measurement based on a plane mirror, and the other of which is displacement measurement based on a to-be-measured right-angle prism, and in actual engineering application, can be applied to plane machining of a numerical control machine tool, workpiece table and displacement table surface control. BRIEF DESCRIPTION OF DRAWINGS

[0092] Figure 1 is a structural schematic diagram of a first embodiment of an interference displacement measurement device based on a Sagnac structure according to the present application;

[0093] Figure 2 is a structural schematic diagram in a second embodiment of an interference displacement measurement device based on a Sagnac structure according to the present application;

[0094] Figure 3 is a structural schematic diagram of a third embodiment of an interference displacement measurement device based on a Sagnac structure according to the present application.

[0095] REFERENCE NUMERALS:

[0096] 1-Dual-frequency laser, 201-First polarizing beam splitter, 202-Second polarizing beam splitter, 3-Right-angle prism under test, 401-Reflector, 402-Plane reflector under test, 501-First quarter-wave plate, 502-Second quarter-wave plate, 503-Third quarter-wave plate, 601-First fiber coupler, 602-Second fiber coupler, 7-Beam splitter. Detailed Implementation

[0097] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0098] Example 1:

[0099] An interferometric displacement measurement device based on the Sagnac structure is used for measuring the right-angle prism 3 and the plane mirror 402 to be measured, such as... Figure 1 As shown, the displacement measuring device includes a dual-frequency laser 1, a first polarizing beam splitter 201, a reflector 401, a first fiber coupler 601, a first quarter-wave plate 501, a second quarter-wave plate 502, and a third quarter-wave plate 503.

[0100] The first polarization beam splitter prism 201 comprises four sides, wherein the first side is opposite to the third side, and the second side is opposite to the fourth side; the first side is sequentially provided with the double-frequency laser 1 and the first fiber coupler 601 along the length direction of the side, the double-frequency laser 1 is used for emitting the measurement light and the reference light out of the first polarization beam splitter prism 201; the first fiber coupler 601 is used for receiving the measurement light and the reference light after participating in the measurement, obtaining the corresponding Doppler frequency shift information, and realizing the displacement measurement; the second side is provided with the mirror 401, the mirror 401 is used for reflecting the light emitted from the first polarization beam splitter prism 201 to the to-be-measured right-angle prism 3; the third side is used for setting the to-be-measured right-angle prism 3, one part of the bottom side of the to-be-measured right-angle prism 3 is opposite to the third side, and the other part corresponds to the mirror 401, and is used for receiving the light reflected by the mirror 401 and reflecting the light to the first polarization beam splitter prism 201; the fourth side is used for setting the to-be-measured plane mirror 402, the to-be-measured plane mirror 402 can reflect the light emitted from the first polarization beam splitter prism 201 back to the first polarization beam splitter prism 201. The first quarter-wave plate 501 is arranged on the light path between the to-be-measured plane mirror 402 and the first polarization beam splitter prism 201; the second quarter-wave plate 502 is arranged on the part of the light path between the first polarization beam splitter prism 201 and the to-be-measured right-angle prism 3, and the part of the light path corresponds to the first fiber coupler 601; the third quarter-wave plate 503 is arranged on the part of the light path between the first polarization beam splitter prism 201 and the first mirror 401, and the part of the light path is close to the to-be-measured right-angle prism 3. The polarization angles of the first quarter-wave plate 501, the second quarter-wave plate 502 and the third quarter-wave plate 503 are all 45°. The first fiber coupler 601 and the second quarter-wave plate 502 are arranged close to the fourth side of the first polarization beam splitter prism 201; the double-frequency laser 1 is arranged close to the second side of the first polarization beam splitter prism 201.

[0101] The displacement measurement device of the embodiment one is used for measuring the displacement of the to-be-measured right-angle prism 3, and the steps include:

[0102] In step A1, the to-be-measured plane mirror 402 is fixed, the double-frequency laser 1 emits the measurement light with the frequency f1 and the reference light with the frequency f2;

[0103] Step A2, the measuring light with frequency f1 is transmitted by the first polarizing beam splitter 201 into horizontal linearly polarized light, and then is reflected twice by the to-be-measured right-angle prism 3, reflected by the mirror 401, transmitted by the first polarizing beam splitter 201, transmitted by the first quarter-wave plate 501, and the polarization state changes from horizontal linearly polarized light to left-handed elliptically polarized light, and then is reflected by the to-be-measured plane mirror 402, transmitted by the first quarter-wave plate 501, and the polarization state changes from left-handed elliptically polarized light to vertical linearly polarized light, and then is reflected by the first polarizing beam splitter 201, transmitted by the second quarter-wave plate 502, and the polarization state changes from vertical linearly polarized light to right-handed elliptically polarized light, and then is reflected twice by the to-be-measured right-angle prism 3, reflected by the mirror 401, transmitted by the third quarter-wave plate 503, and the polarization state changes from right-handed elliptically polarized light to horizontal linearly polarized light, and then is transmitted by the first polarizing beam splitter 201, transmitted by the first quarter-wave plate 501, and the polarization state changes from horizontal linearly polarized light to left-handed elliptically polarized light, and then is reflected by the to-be-measured plane mirror 402, transmitted by the first quarter-wave plate 501, and the polarization state changes from left-handed elliptically polarized light to vertical linearly polarized light, and then is reflected by the first polarizing beam splitter 201, reflected twice by the to-be-measured right-angle prism 3, reflected by the mirror 401, and reflected by the first polarizing beam splitter 201, and finally is incident on the first fiber coupler 601;

[0104] The reference light with frequency f2 is reflected by the first polarizing beam splitter 201 into vertical linearly polarized light, and then is transmitted by the third quarter-wave plate 503, and the polarization state changes from vertical linearly polarized light to left-handed elliptically polarized light, and then is reflected by the mirror 401, reflected twice by the to-be-measured right-angle prism 3, transmitted by the second quarter-wave plate 502, and the polarization state changes from left-handed elliptically polarized light to horizontal linearly polarized light, and then is transmitted by the first polarizing beam splitter 201, and finally is incident on the first fiber coupler 601;

[0105] Step A3, the first fiber coupler 601 obtains the Doppler frequency shift amount Δf1;

[0106] Step A4, the Doppler frequency shift information of the measuring light is recorded as f1-3Δf1, the Doppler frequency shift information of the reference light is recorded as f2-Δf1, and the Doppler frequency shift information of the interference signal when the measuring light and the reference light interfere is recorded as f1-f2-2Δf1;

[0107] According to the Doppler frequency shift information f1-3Δf1, f2-Δf1, f1-f2-2Δf1 and the laser itself reference frequency information f1-f2, the displacement amount S1 of the to-be-measured right-angle prism 3 is calculated:

[0108]

[0109] Wherein, c is the speed of light, is the total phase delay amount of the laser round trip measurement;

[0110] The displacement measurement of the tested right-angle prism 3 is completed;

[0111] The displacement measurement of the tested planar mirror 402 is performed by using the displacement measurement device of the embodiment one, and the steps include:

[0112] Step B1, the tested right-angle prism 3 is fixed, the measurement light with the frequency of f1 and the reference light with the frequency of f2 are emitted by the dual-frequency laser 1;

[0113] Step B2, the measurement light with the frequency of f1 is transmitted by the first polarization beam splitter 201 to become horizontal linearly polarized light, and then is reflected by the tested right-angle prism 3 twice, the mirror 401, transmitted by the first polarization beam splitter 201, transmitted by the first quarter-wave plate 501, and the polarization state is changed from horizontal linearly polarized light to left-handed elliptical polarized light, and then is reflected by the tested planar mirror 402, transmitted by the first quarter-wave plate 501, and the polarization state is changed from left-handed elliptical polarized light to vertical linearly polarized light, and then is reflected by the first polarization beam splitter 201, transmitted by the second quarter-wave plate 502, and the polarization state is changed from vertical linearly polarized light to right-handed elliptical polarized light, and then is reflected by the mirror 401, transmitted by the third quarter-wave plate 503, and the polarization state is changed from right-handed elliptical polarized light to horizontal linearly polarized light, and then is transmitted by the first polarization beam splitter 201, transmitted by the first quarter-wave plate 501, and the polarization state is changed from horizontal linearly polarized light to left-handed elliptical polarized light, and then is reflected by the tested planar mirror 402, transmitted by the first quarter-wave plate 501, and the polarization state is changed from left-handed elliptical polarized light to vertical linearly polarized light, and then is reflected by the first polarization beam splitter 201, reflected by the tested right-angle prism 3 twice, reflected by the mirror 401, and reflected by the first polarization beam splitter 201, and finally is incident on the first fiber coupler 601;

[0114] The reference light with the frequency of f2 is reflected by the first polarization beam splitter 201 to become vertical linearly polarized light, and then is transmitted by the third quarter-wave plate 503, and the polarization state is changed from vertical linearly polarized light to left-handed elliptical polarized light, and then is reflected by the mirror 401, reflected by the tested right-angle prism 3 twice, transmitted by the second quarter-wave plate 502, and the polarization state is changed from left-handed elliptical polarized light to horizontal linearly polarized light, and then is transmitted by the first polarization beam splitter 201, and finally is incident on the first fiber coupler 601;

[0115] Step B3, the first fiber coupler 601 receives the measurement light and the reference light after being acted, and obtains the Doppler frequency shift amount Δf;

[0116] Step B4, record the Doppler shift information of the measurement light as f1-2Δf2; record the Doppler shift information of the reference light as f2; record the Doppler shift information of the interference signal of the measurement light and the reference light as f1-f2-2Δf2;

[0117] According to the Doppler shift information f1-2Δf2, f2, f1-f2-2Δf2 and the laser self reference frequency information f1-f2, the displacement S2 of the plane mirror 402 to be measured is calculated:

[0118]

[0119] The displacement measurement of the plane mirror 402 to be measured is completed.

[0120] Embodiment two:

[0121] As shown in Figure 2 the displacement measurement device of the embodiment is basically the same as that of the first embodiment, except that the displacement measurement device of the embodiment further comprises a second polarization beam splitter 202 and a beam splitter 7; the second polarization beam splitter 202 is arranged on the light path between the dual-frequency laser 1 and the first polarization beam splitter 201; the beam splitting surface of the second polarization beam splitter 202 is perpendicular to the beam splitting surface of the first polarization beam splitter 201; the beam splitter 7 is arranged on the light path between the first fiber coupler 601 and the first polarization beam splitter 201; the beam splitting surface of the beam splitter 7 is parallel to the beam splitting surface of the first polarization beam splitter 201.

[0122] The displacement measurement of the plane mirror 402 to be measured is completed.

[0123] Step A1, the plane mirror 402 to be measured is fixed, the dual-frequency laser 1 emits measurement light with a frequency of f1 and reference light with a frequency of f2;

[0124] Step A2, the measuring light with frequency f1 is transmitted by the second polarizing beam splitter 202 into horizontal linearly polarized light, then transmitted by the first polarizing beam splitter 201, reflected twice by the measured right-angle prism 3, reflected by the mirror 401, transmitted by the first polarizing beam splitter 201, transmitted by the first quarter-wave plate 501, and the polarization state changes from horizontal linearly polarized light into left-handed elliptically polarized light, then reflected by the measured plane mirror 402, transmitted by the first quarter-wave plate 501, and the polarization state changes from left-handed elliptically polarized light into vertical linearly polarized light, then reflected by the first polarizing beam splitter 201, transmitted by the second quarter-wave plate 502, and the polarization state changes from vertical linearly polarized light into right-handed elliptically polarized light, then transmitted by the third quarter-wave plate 503, reflected twice by the measured right-angle prism 3, reflected by the mirror 401, transmitted by the first polarizing beam splitter 201, transmitted by the first quarter-wave plate 501, and the polarization state changes from right-handed elliptically polarized light into horizontal linearly polarized light, then transmitted by the first polarizing beam splitter 201, transmitted by the first quarter-wave plate 501, and the polarization state changes from horizontal linearly polarized light into left-handed elliptically polarized light, then reflected by the measured plane mirror 402, transmitted by the first quarter-wave plate 501, and the polarization state changes from left-handed elliptically polarized light into vertical linearly polarized light, then reflected by the first polarizing beam splitter 201, reflected twice by the measured right-angle prism 3, reflected by the mirror 401, transmitted by the first polarizing beam splitter 201, and finally transmitted by the beam splitter 7 and incident into the first fiber coupler 601;

[0125] The reference light with frequency f2 is reflected by the second polarizing beam splitter 202 into vertical linearly polarized light, then reflected by the beam splitter 7, and finally incident into the first fiber coupler 601;

[0126] Step A3, the first fiber coupler 601 obtains the Doppler frequency shift amount Δf1;

[0127] Step A4, the Doppler frequency shift information of the measuring light is recorded as f1-3Δf1, the Doppler frequency shift information of the reference light is recorded as f2, and the Doppler frequency shift information of the interference signal when the measuring light and the reference light interfere is recorded as f1-f2-3Δf1;

[0128] According to the Doppler frequency shift information f1-3Δf1, f2, f1-f2-3Δf1 and the laser reference frequency information f1-f2, the displacement amount S1 of the measured right-angle prism 3 is calculated:

[0129]

[0130] The displacement measurement of the measured right-angle prism 3 is completed;

[0131] The displacement measurement of the measured plane mirror 402 is performed by using the displacement measurement device of the second embodiment, which specifically includes the following steps:

[0132] Step B1, the measured right-angle prism 3 is fixed, the measuring light with frequency f1 and the reference light with frequency f2 from the dual-frequency laser 1 are used;

[0133] Step B2, the measuring light with frequency f1 is transmitted by the second polarization beam splitter 202 to become horizontal linearly polarized light, and then is transmitted by the first polarization beam splitter 201, reflected by the measured right-angle prism 3 twice, reflected by the mirror 401, transmitted by the first polarization beam splitter 201, transmitted by the first quarter-wave plate 501, and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then is reflected by the measured plane mirror 402, transmitted by the first quarter-wave plate 501, and the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light, and then is reflected by the first polarization beam splitter 201, transmitted by the second quarter-wave plate 502, and the polarization state changes from vertical linearly polarized light to right-handed elliptical polarized light, and then is reflected by the measured right-angle prism 3 twice, reflected by the mirror 401, transmitted by the third quarter-wave plate 503, and the polarization state changes from right-handed elliptical polarized light to horizontal linearly polarized light, and then is transmitted by the first polarization beam splitter 201, transmitted by the first quarter-wave plate 501, and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then is reflected by the measured plane mirror 402, transmitted by the first quarter-wave plate 501, and the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light, and then is reflected by the first polarization beam splitter 201, reflected by the measured right-angle prism 3 twice, reflected by the mirror 401, transmitted by the first polarization beam splitter 201, and then is transmitted by the beam splitter 7, and finally is incident on the first fiber coupler 601;

[0134] The reference light with frequency f2 is reflected by the second polarization beam splitter 202 to become vertical linearly polarized light, and then is reflected by the beam splitter 7, and finally is incident on the first fiber coupler 601;

[0135] Step B3, the first fiber coupler 601 receives the affected measuring light and reference light, and obtains the Doppler frequency shift amount Δf2;

[0136] Step B4, the Doppler frequency shift information of the measuring light is recorded as f1-2Δf2, the Doppler frequency shift information of the reference light is recorded as f2, and the Doppler frequency shift information of the interference signal when the measuring light and the reference light interfere is recorded as f1-f2-2Δf2;

[0137] According to the Doppler frequency shift information f1-2Δf2, f2, f1-f2-2Δf2 and the laser itself reference frequency information f1-f2, the displacement amount S2 of the measured plane mirror 402 is calculated:

[0138]

[0139] The displacement measurement of the measured plane mirror 402 is completed.

[0140] Example 3:

[0141] like Figure 3 As shown, the displacement measuring device in this embodiment is basically the same as the displacement measuring device in Embodiment 1. The difference is that the displacement measuring device in this embodiment also includes a beam splitter 7, a second polarizing beam splitter 202, and a second fiber coupler 602. The beam splitter 7 is disposed in the optical path between the dual-frequency laser 1 and the first polarizing beam splitter 201. The beam splitting surface of the beam splitter 7 is perpendicular to the beam splitting surface of the first polarizing beam splitter 201. The second polarizing beam splitter 202 is disposed in the optical path between the first fiber coupler 601 and the first polarizing beam splitter 201. The beam splitting surface of the second polarizing beam splitter 202 is parallel to the beam splitting surface of the first polarizing beam splitter 201. The second fiber coupler 602 is disposed on the side of the second polarizing beam splitter 202 near the second side of the first polarizing beam splitter 201, so that the first fiber coupler 601 receives part of the measurement light and reference light after participating in the measurement, realizing coarse displacement measurement, and the second fiber coupler 602 receives another part of the measurement light and reference light after participating in the measurement, realizing fine displacement measurement.

[0142] The displacement measurement of the right-angle prism 3 under test using the displacement measuring device of this embodiment includes the following steps:

[0143] Step A1: The plane mirror 402 under test is fixed in place, and the dual-frequency laser 1 outputs a measurement light with a frequency of f1 and a reference light with a frequency of f2.

[0144] Step A2: The measuring light and the reference light enter the beam splitter 7 together, and are split according to energy by the beam splitter 7 to form reflected light and transmitted light;

[0145] The reflected light is transmitted through the second polarizing beam splitter 202 to form horizontally linearly polarized light a1 with frequency f1, and reflected to form vertically linearly polarized light a2 with frequency f2.

[0146] Horizontally linearly polarized light a1 is incident on the second fiber coupler 602;

[0147] Vertically linearly polarized light a2 is incident on the first fiber coupler 601;

[0148] The transmitted light is transmitted through the first polarizing beam splitter 201 to form horizontally polarized light b1 with frequency f1, and reflected to form vertically polarized light b2 with frequency f2.

[0149] The horizontal linearly polarized light b1 is reflected by the two reflections of the to-be-measured right-angle prism 3, reflected by the mirror 401, transmitted by the first polarization beam-splitting prism 201, transmitted by the first quarter-wave plate 501, and the polarization state changes from horizontal linear polarization to left-handed elliptical polarization. Then, the left-handed elliptical polarization is reflected by the to-be-measured plane mirror 402, transmitted by the first quarter-wave plate 501, and the polarization state changes from left-handed elliptical polarization to vertical polarization. Then, the vertical polarization is reflected by the first polarization beam-splitting prism 201, transmitted by the second quarter-wave plate 502, and the polarization state changes from vertical polarization to right-handed elliptical polarization. Then, the right-handed elliptical polarization is reflected by the two reflections of the to-be-measured right-angle prism 3, reflected by the mirror 401, transmitted by the third quarter-wave plate 503, and the polarization state changes from right-handed elliptical polarization to horizontal linear polarization. Then, the horizontal linear polarization is transmitted by the first polarization beam-splitting prism 201 and the first quarter-wave plate 501, and the polarization state changes from horizontal linear polarization to left-handed elliptical polarization. Then, the left-handed elliptical polarization is reflected by the to-be-measured plane mirror 402 and transmitted by the first quarter-wave plate 501, and the polarization state changes from left-handed elliptical polarization to vertical polarization. Then, the vertical polarization is reflected by the first polarization beam-splitting prism 201, reflected by the two reflections of the to-be-measured right-angle prism 3, reflected by the mirror 401, reflected by the first polarization beam-splitting prism 201, reflected by the second polarization beam-splitting prism 202, and finally incident on the second fiber coupler 602.

[0150] The vertical polarization b2 is transmitted by the third quarter-wave plate 503, and the polarization state changes from vertical polarization to left-handed elliptical polarization. Then, the left-handed elliptical polarization is reflected by the mirror 401, reflected by the two reflections of the to-be-measured right-angle prism 3, transmitted by the second quarter-wave plate 502, and the polarization state changes from left-handed elliptical polarization to horizontal linear polarization. Then, the horizontal linear polarization is transmitted by the first polarization beam-splitting prism 201 and the second polarization beam-splitting prism 202, and finally incident on the first fiber coupler 601.

[0151] In step A3, the first fiber coupler 601 receives two beams of orthogonal linearly polarized light at the same time. The Doppler frequency shift information of the reference light is f2, the Doppler frequency shift information of the measurement light is f2-Δf1, and the Doppler frequency shift information of the interference signal when the measurement light and the reference light interfere is Δf1.

[0152] In step A3, the first fiber coupler 601 receives two beams of orthogonal linearly polarized light at the same time. The Doppler frequency shift information of the reference light is f2, the Doppler frequency shift information of the measurement light is f2-Δf1, and the Doppler frequency shift information of the interference signal when the measurement light and the reference light interfere is Δf1.

[0153] In step A4, by phase decoupling, when the interference signal of the first fiber coupler 601 and the interference signal of the second fiber coupler 602 are added, the Doppler frequency shift amount is 4Δf1, and when they are subtracted, the Doppler frequency shift amount is 2Δf1. Then, the displacement amount S1 of the to-be-measured right-angle prism 3 is calculated.

[0154] When the phase coupling is subtracted, the total phase delay is phase 1, then

[0155] When the phase coupling is added, the total phase delay is phase 2, then

[0156] The displacement measurement device of the third embodiment is used to measure the displacement of the to-be-measured plane mirror 402, and the specific steps include the following steps:

[0157] Step B1, the to-be-measured right-angle prism 3 is fixed, the measurement light with a frequency of f1 and the reference light with a frequency of f2 are generated by the dual-frequency laser 1;

[0158] Step B2 is specifically that the measurement light and the reference light enter the beam splitter prism 7 together, and the beam splitter prism 7 performs energy splitting on the measurement light and the reference light to form reflected light and transmitted light;

[0159] The reflected light is transmitted by the second polarization beam splitter 202 to form horizontal linearly polarized light a1 with a frequency of f1, and reflected to form vertical linearly polarized light a2 with a frequency of f2;

[0160] The horizontal linearly polarized light a1 is incident on the second fiber coupler 602;

[0161] The vertical linearly polarized light a2 is incident on the first fiber coupler 601;

[0162] The transmitted light is transmitted by the first polarization beam splitter 201 to form horizontal linearly polarized light b1 with a frequency of f1, and reflected to form vertical linearly polarized light b2 with a frequency of f2;

[0163] Horizontally linearly polarized light b1 is sequentially reflected twice by the right-angle prism 3 under test, reflected by mirror 401, transmitted by the first polarizing beam splitter 201, and transmitted by the first quarter-wave plate 501, changing its polarization state from horizontally polarized to left-handed elliptically polarized. It is then sequentially reflected by the plane mirror 402 under test and transmitted by the first quarter-wave plate 501, changing its polarization state from left-handed elliptically polarized to vertically polarized. It is then sequentially reflected by the first polarizing beam splitter 201 and transmitted by the second quarter-wave plate 502, changing its polarization state from vertically polarized to right-handed elliptically polarized. Finally, it is sequentially reflected twice by the right-angle prism 3 under test, reflected by mirror 401, and transmitted by the third quarter-wave plate 501. The light is transmitted through a wave plate 503, changing its polarization state from right-handed elliptically polarized light to horizontally polarized light. Then, it is transmitted through the first polarizing beam splitter 201 and the first quarter-wave plate 501, changing its polarization state from horizontally polarized light to left-handed elliptically polarized light. Then, it is reflected by the plane mirror 402 under test and transmitted through the first quarter-wave plate 501, changing its polarization state from left-handed elliptically polarized light to vertically polarized light. Then, it is reflected by the first polarizing beam splitter 201, reflected twice by the right-angle prism 3 under test, reflected by the mirror 401, reflected by the first polarizing beam splitter 201, reflected by the second polarizing beam splitter 202, and finally incident on the second fiber coupler 602.

[0164] Vertically polarized light b2 is transmitted through the third quarter-wave plate 503, changing its polarization state from vertically polarized light to left-handed elliptically polarized light. Then, it is reflected by the mirror 401, reflected twice by the right-angle prism 3 to be tested, and transmitted through the second quarter-wave plate 502, changing its polarization state from left-handed elliptically polarized light to horizontally polarized light. Finally, it is transmitted through the first polarizing beam splitter 201 and the second polarizing beam splitter 202, and finally incident on the first fiber coupler 601.

[0165] Step B3: The first fiber coupler 601 simultaneously receives two beams of orthogonally linearly polarized light and obtains the interference signal after phase decoupling of the two beams of orthogonally linearly polarized light; the Doppler frequency shift information of the reference light is recorded as f2; the Doppler frequency shift information of the measurement light is recorded as f2; the Doppler frequency shift information of the interference signal when the measurement light and the reference light interfere is recorded as 0.

[0166] The second fiber coupler 602 simultaneously receives two beams of orthogonally linearly polarized light. The Doppler frequency shift information of the reference light is denoted as f1; the Doppler frequency shift information of the measurement light is denoted as f1-2Δf2; and the Doppler frequency shift information of the interference signal when the measurement light and the reference light interfere is denoted as 2Δf2.

[0167] Step B4: Based on the Doppler frequency shift 0 and 2Δf2, calculate the displacement S2 of the plane mirror 402 under test through phase decoupling:

[0168]

[0169] The displacement measurement of the plane mirror 402 under test is completed.

[0170] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited thereto, any change or replacement within the technical range disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An interferometric displacement measuring device based on a Sagnac structure, used to measure the displacement of a right-angle prism (3) and a plane mirror (402) under test, characterized in that: The application relates to a dual-frequency laser displacement measurement device, which comprises a dual-frequency laser (1), a first polarization beam splitter prism (201), a mirror (401) and a first fiber coupler (601). The first polarization beam splitter prism (201) comprises four sides, wherein a first side is opposite to a third side, and a second side is opposite to a fourth side. The dual-frequency laser (1) and the first fiber coupler (601) are arranged on the first side along the length direction of the side, the dual-frequency laser (1) is used for emitting measuring light and reference light to the first polarization beam splitter prism (201), and the first fiber coupler (601) is used for receiving the measuring light and the reference light after participating in measurement, obtaining corresponding Doppler frequency shift information and realizing displacement measurement. The mirror (401) is arranged on the second side and is used for reflecting light emitted from the first polarization beam splitter prism (201) to a to-be-measured right-angle prism (3). The third side is used for arranging the to-be-measured right-angle prism (3), one part of a bottom side of the to-be-measured right-angle prism (3) is opposite to the third side, and the other part corresponds to the mirror (401), is used for receiving light reflected by the mirror (401) and reflecting the light to the first polarization beam splitter prism (201). The fourth side is used for arranging a to-be-measured plane mirror (402), and the to-be-measured plane mirror (402) can reflect light emitted from the first polarization beam splitter prism (201) back to the first polarization beam splitter prism (201).

2. An interferometric displacement measurement apparatus based on a Sagnac structure according to claim 1, characterized in that: The first quarter-wave plate (501), the second quarter-wave plate (502) and the third quarter-wave plate (503) are further included. The first quarter-wave plate (501) is arranged on a light path between the to-be-measured plane mirror (402) and the first polarization beam splitter prism (201). The second quarter-wave plate (502) is arranged on a part of a light path between the first polarization beam splitter prism (201) and the to-be-measured right-angle prism (3), and the part of the light path corresponds to the first fiber coupler (601). The third quarter-wave plate (503) is arranged on a part of a light path between the first polarization beam splitter prism (201) and the first mirror (401), and the part of the light path is close to the to-be-measured right-angle prism (3).

3. An interferometric displacement measurement apparatus based on a Sagnac structure according to claim 2, characterised in that: The first fiber coupler (601) and the second quarter-wave plate (502) are arranged close to the fourth side of the first polarization beam splitter prism (201). The dual-frequency laser (1) is arranged close to the second side of the first polarization beam splitter prism (201).

4. An interferometric displacement measurement apparatus based on a Sagnac structure according to claim 2 or 3, characterised in that: The polarization angles of the first quarter-wave plate (501), the second quarter-wave plate (502) and the third quarter-wave plate (503) are all 45 degrees.

5. An interferometric displacement measurement apparatus based on a Sagnac structure according to claim 4, characterised in that: The second polarization beam splitter prism (202) and a beam splitter prism (7) are further included. The second polarization beam splitter prism (202) is arranged on a light path between the dual-frequency laser (1) and the first polarization beam splitter prism (201), and a beam splitting surface of the second polarization beam splitter prism (202) is perpendicular to a beam splitting surface of the first polarization beam splitter prism (201). The light splitting prism (7) is arranged on the light path between the first fiber coupler (601) and the first polarization light splitting prism (201); the light splitting surface of the light splitting prism (7) is parallel to the light splitting surface of the first polarization light splitting prism (201).

6. The Sagnac structure based interferometric displacement measuring device according to claim 4, characterized in that: Further comprising a light splitting prism (7), a second polarization light splitting prism (202) and a second fiber coupler (602); The light splitting prism (7) is arranged on the light path between the dual-frequency laser (1) and the first polarization light splitting prism (201); the light splitting surface of the light splitting prism (7) is perpendicular to the light splitting surface of the first polarization light splitting prism (201); The second polarization light splitting prism (202) is arranged on the light path between the first fiber coupler (601) and the first polarization light splitting prism (201); the light splitting surface of the second polarization light splitting prism (202) is parallel to the light splitting surface of the first polarization light splitting prism (201); The second fiber coupler (602) is arranged on the side of the second polarization light splitting prism (202) close to the second side of the first polarization light splitting prism (201) and away from the light splitting prism (7), so that the first fiber coupler (601) receives part of the measurement light and reference light after participating in the measurement to realize coarse displacement measurement, and the second fiber coupler (602) receives another part of the measurement light and reference light after participating in the measurement to realize fine displacement measurement.

7. A method for measuring displacement of interference based on Sagnac structure, using the apparatus for measuring displacement of interference based on Sagnac structure according to claim 1, characterized in that, The displacement measurement of the measured right-angle prism (3) and the displacement measurement of the measured plane mirror (402) are included. The displacement measurement of the measured right-angle prism (3) includes the following steps: Step A1, the measured plane mirror (402) is fixed, the dual-frequency laser (1) emits measurement light with a frequency of f1 and reference light with a frequency of f2; Step A2, the measurement light and the reference light enter the first fiber coupler (601) after being affected by the corresponding optical devices; Step A3, the first fiber coupler (601) obtains the Doppler frequency shift amount; Step A4, the displacement amount of the measured right-angle prism (3) is calculated by the Doppler frequency shift amount obtained in step A3, and the displacement measurement of the measured right-angle prism (3) is completed; The displacement measurement of the measured plane mirror (402) includes the following steps: Step B1, the measured right-angle prism (3) is fixed, the dual-frequency laser (1) emits measurement light with a frequency of f1 and reference light with a frequency of f2; Step B2, the measurement light and the reference light enter the first fiber coupler (601) after being affected by the corresponding optical devices; Step B3, the first fiber coupler (601) receives the affected measurement light and reference light to obtain the Doppler frequency shift amount; Step B4, the displacement amount of the measured plane mirror (402) is calculated by the Doppler frequency shift amount obtained in step B3, and the displacement measurement of the measured plane mirror (402) is completed.

8. The Sagnac structure-based interference displacement measurement method according to claim 7, characterized in that: Step A2 is specifically that the measuring light with the frequency of f1 is transmitted by the first polarizing beam splitter prism (201) into horizontal linearly polarized light, and then is reflected by the two reflections of the to-be-measured right-angle prism (3), reflected by the mirror (401), transmitted by the first polarizing beam splitter prism (201), transmitted by the first quarter-wave plate (501), and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then is reflected by the to-be-measured plane mirror (402), transmitted by the first quarter-wave plate (501), and the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light, and then is reflected by the first polarizing beam splitter prism (201), transmitted by the second quarter-wave plate (502), and the polarization state changes from vertical linearly polarized light to right-handed elliptical polarized light, and then is reflected by the mirror (401) and the two reflections of the to-be-measured right-angle prism (3), transmitted by the third quarter-wave plate (503), and the polarization state changes from right-handed elliptical polarized light to horizontal linearly polarized light, and then is transmitted by the first polarizing beam splitter prism (201) and the first quarter-wave plate (501), and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then is reflected by the to-be-measured plane mirror (402) and the first quarter-wave plate (501), and the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light, and then is reflected by the first polarizing beam splitter prism (201), the two reflections of the to-be-measured right-angle prism (3), the mirror (401), and the first polarizing beam splitter prism (201), and finally is incident on the first fiber coupler (601); the reference light with the frequency of f2 is reflected by the first polarizing beam splitter prism (201) into vertical linearly polarized light, and then is transmitted by the third quarter-wave plate (503), and the polarization state changes from vertical linearly polarized light to left-handed elliptical polarized light, and then is reflected by the mirror (401) and the two reflections of the to-be-measured right-angle prism (3), and is transmitted by the second quarter-wave plate (502), and the polarization state changes from left-handed elliptical polarized light to horizontal linearly polarized light, and then is transmitted by the first polarizing beam splitter prism (201), and finally is incident on the first fiber coupler (601); Step A3 is specifically that the first fiber coupler (601) obtains the Doppler frequency shift amount Δf1; Step A4 is specifically that the Doppler frequency shift amount Δf1 obtained in step A3 is used to calculate the displacement amount S1 of the to-be-measured right-angle prism (3): where c is the speed of light, is the total phase delay of the laser round trip measurement; the displacement measurement of the to-be-measured right-angle prism (3) is completed; Step B2 is specifically that the measuring light with the frequency of f1 is transmitted by the first polarization beam splitter prism (201) into horizontal linearly polarized light, and then is reflected by the two reflections of the to-be-measured right-angle prism (3), reflected by the mirror (401), transmitted by the first polarization beam splitter prism (201), transmitted by the first quarter-wave plate (501), and the polarization state changes from horizontal linearly polarized light to left-handed elliptically polarized light, and then is reflected by the to-be-measured plane mirror (402), transmitted by the first quarter-wave plate (501), and the polarization state changes from left-handed elliptically polarized light to vertical linearly polarized light, and then is reflected by the first polarization beam splitter prism (201), transmitted by the second quarter-wave plate (502), and the polarization state changes from vertical linearly polarized light to right-handed elliptically polarized light, and then is reflected by the mirror (401) and the two reflections of the to-be-measured right-angle prism (3), transmitted by the third quarter-wave plate (503), and the polarization state changes from right-handed elliptically polarized light to horizontal linearly polarized light, and then is transmitted by the first polarization beam splitter prism (201) and the first quarter-wave plate (501), and the polarization state changes from horizontal linearly polarized light to left-handed elliptically polarized light, and then is reflected by the to-be-measured plane mirror (402) and the first quarter-wave plate (501), and the polarization state changes from left-handed elliptically polarized light to vertical linearly polarized light, and then is reflected by the first polarization beam splitter prism (201), the two reflections of the to-be-measured right-angle prism (3), the mirror (401), and the first polarization beam splitter prism (201), and finally is incident on the first fiber coupler (601); the reference light with the frequency of f2 is reflected by the first polarization beam splitter prism (201) into vertical linearly polarized light, and then is transmitted by the third quarter-wave plate (503), and the polarization state changes from vertical linearly polarized light to left-handed elliptically polarized light, and then is reflected by the mirror (401) and the two reflections of the to-be-measured right-angle prism (3), and is transmitted by the second quarter-wave plate (502), and the polarization state changes from left-handed elliptically polarized light to horizontal linearly polarized light, and then is transmitted by the first polarization beam splitter prism (201), and finally is incident on the first fiber coupler (601); Step B3 is specifically that the first fiber coupler (601) receives the affected measuring light and reference light, and obtains the Doppler frequency shift amount Δf2; Step B4 is specifically that the displacement amount S2 of the to-be-measured plane mirror (402) is calculated by the Doppler frequency shift amount Δf2 obtained in step B3: The displacement measurement of the to-be-measured plane mirror (402) is completed.

9. The Sagnac structure-based interference displacement measurement method according to claim 7, characterized in that: Step A2 is specifically that the measuring light with the frequency of f1 is transmitted by the second polarizing beam splitter prism (202) into horizontal linearly polarized light, and then is transmitted by the first polarizing beam splitter prism (201), reflected by the mirror (401), transmitted by the first polarizing beam splitter prism (201), transmitted by the first quarter-wave plate (501), and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then is reflected by the measured plane mirror (402), transmitted by the first quarter-wave plate (501), and the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light, and then is reflected by the first polarizing beam splitter prism (201), transmitted by the second quarter-wave plate (502), and the polarization state changes from vertical linearly polarized light to right-handed elliptical polarized light, and then is reflected by the measured right-angle prism (3) twice, reflected by the mirror (401), transmitted by the third quarter-wave plate (503), and the polarization state changes from right-handed elliptical polarized light to horizontal linearly polarized light, and then is transmitted by the first polarizing beam splitter prism (201), transmitted by the first quarter-wave plate (501), and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then is reflected by the measured plane mirror (402), transmitted by the first quarter-wave plate (501), and the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light, and then is reflected by the first polarizing beam splitter prism (201), reflected by the measured right-angle prism (3) twice, reflected by the mirror (401), transmitted by the first polarizing beam splitter prism (201), reflected by the beam splitter prism (7), and finally is incident on the first fiber coupler (601); the reference light with the frequency of f2 is reflected by the second polarizing beam splitter prism (202) into vertical linearly polarized light, and then is reflected by the beam splitter prism (7), and finally is incident on the first fiber coupler (601); Step A3 is specifically that the first fiber coupler (601) obtains the Doppler frequency shift amount Δf1; Step A4 is specifically that the displacement amount S1 of the measured right-angle prism (3) is calculated by the Doppler frequency shift amount Δf1 obtained in step A3: the displacement measurement of the measured right-angle prism (3) is completed; Step B2 is specifically that the measuring light with the frequency of f1 is transmitted by the second polarization beam splitter prism (202) into horizontal linearly polarized light, and then is transmitted by the first polarization beam splitter prism (201) in turn, reflected twice by the to-be-measured right-angle prism (3), reflected by the mirror (401), transmitted by the first polarization beam splitter prism (201) in turn, transmitted by the first quarter-wave plate (501), and the polarization state changes from horizontal linearly polarized light into left-handed elliptical polarized light, and then is reflected by the to-be-measured plane mirror (402) in turn, transmitted by the first quarter-wave plate (501) in turn, and the polarization state changes from left-handed elliptical polarized light into vertical linearly polarized light, and then is reflected by the first polarization beam splitter prism (201) in turn, transmitted by the second quarter-wave plate (502) in turn, and the polarization state changes from vertical linearly polarized light into right-handed elliptical polarized light, and then is reflected twice by the to-be-measured right-angle prism (3), reflected by the mirror (401), transmitted by the third quarter-wave plate (503), and the polarization state changes from right-handed elliptical polarized light into horizontal linearly polarized light, and then is transmitted by the first polarization beam splitter prism (201) in turn, transmitted by the first quarter-wave plate (501) in turn, and the polarization state changes from horizontal linearly polarized light into left-handed elliptical polarized light, and then is reflected by the to-be-measured plane mirror (402) in turn, transmitted by the first quarter-wave plate (501) in turn, and the polarization state changes from left-handed elliptical polarized light into vertical linearly polarized light, and then is reflected by the first polarization beam splitter prism (201) in turn, reflected twice by the to-be-measured right-angle prism (3), reflected by the mirror (401), transmitted by the first polarization beam splitter prism (201) in turn, and transmitted by the beam splitter prism (7) in turn, and finally is incident on the first fiber coupler (601); The reference light with the frequency of f2 is reflected by the second polarization beam splitter prism (202) into vertical linearly polarized light, and then is reflected by the beam splitter prism (7), and finally is incident on the first fiber coupler (601); Step B3 is specifically that the first fiber coupler (601) receives the affected measuring light and reference light, and obtains the Doppler frequency shift amount Δf2; Step B4 is specifically that the Doppler frequency shift amount Δf2 obtained through step B3 is used to calculate the displacement amount S2 of the to-be-measured plane mirror (402): The displacement measurement of the to-be-measured plane mirror (402) is completed.

10. The Sagnac structure-based interference displacement measurement method according to claim 7, characterized in that: Step A2 is specifically that the measuring light and the reference light enter the beam splitter prism (7) together, and are spectrally split by the beam splitter prism (7) to form reflected light and transmitted light; The reflected light is transmitted by the second polarization beam splitter prism (202) to form horizontal linearly polarized light a1 with the frequency of f1, and is reflected to form vertical linearly polarized light a2 with the frequency of f2; The horizontal linearly polarized light a1 is incident on the second fiber coupler (602); The vertical linearly polarized light a2 is incident on the first fiber coupler (601); The transmitted light is transmitted by the first polarization beam splitter prism (201) to form horizontal linearly polarized light b1 with the frequency of f1, and is reflected to form vertical linearly polarized light b2 with the frequency of f2; The horizontal linearly polarized light b1 is reflected by the two reflections of the to-be-measured right-angle prism (3), reflected by the mirror (401), transmitted by the first polarization beam-splitting prism (201), and transmitted by the first quarter-wave plate (501) in sequence, and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light; then the left-handed elliptical polarized light is reflected by the to-be-measured plane mirror (402), transmitted by the first quarter-wave plate (501) in sequence, and the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light; then the vertical linearly polarized light is reflected by the first polarization beam-splitting prism (201), transmitted by the second quarter-wave plate (502) in sequence, and the polarization state changes from vertical linearly polarized light to right-handed elliptical polarized light; then the right-handed elliptical polarized light is reflected by the two reflections of the to-be-measured right-angle prism (3), reflected by the mirror (401), and transmitted by the third quarter-wave plate (503) in sequence, and the polarization state changes from right-handed elliptical polarized light to horizontal linearly polarized light; then the horizontal linearly polarized light is transmitted by the first polarization beam-splitting prism (201) and the first quarter-wave plate (501) in sequence, and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light; then the left-handed elliptical polarized light is reflected by the to-be-measured plane mirror (402) and the first quarter-wave plate (501) in sequence, and the polarization state changes from left-handed elliptical polarized light to vertical linearly polarized light; then the vertical linearly polarized light is reflected by the first polarization beam-splitting prism (201), reflected by the two reflections of the to-be-measured right-angle prism (3), reflected by the mirror (401), reflected by the first polarization beam-splitting prism (201), and reflected by the second polarization beam-splitting prism (202) in sequence, and finally enters the second optical fiber coupler (602); The vertical linearly polarized light b2 is transmitted by the third quarter-wave plate (503), and the polarization state changes from vertical linearly polarized light to left-handed elliptical polarized light; then the left-handed elliptical polarized light is reflected by the mirror (401), reflected by the two reflections of the to-be-measured right-angle prism (3), and transmitted by the second quarter-wave plate (502) in sequence, and the polarization state changes from left-handed elliptical polarized light to horizontal linearly polarized light; then the horizontal linearly polarized light is transmitted by the first polarization beam-splitting prism (201) and the second polarization beam-splitting prism (202) in sequence, and finally enters the first optical fiber coupler (601); Step A3 is specifically that the first optical fiber coupler (601) simultaneously receives two beams of orthogonal linearly polarized light, and obtains the Doppler frequency shift amount Δf1 of the interference signal after phase decoupling of the two beams of orthogonal linearly polarized light; The second optical fiber coupler (602) simultaneously receives two beams of orthogonal linearly polarized light, and obtains the Doppler frequency shift amount 3Δf1 of the interference signal after phase decoupling of the two beams of orthogonal linearly polarized light; Step A4 is specifically that the displacement amount S1 of the to-be-measured right-angle prism (3) is calculated through the Doppler frequency shift amounts Δf1 and 3Δf1 obtained in step A3: When the phase-coupled subtraction is performed, the total phase delay is phase 1, then When the phase-coupled addition is performed, the total phase delay is phase 2, then The displacement measurement of the to-be-measured right-angle prism (3) is completed; Step B2 is specifically that the measurement light and the reference light enter the beam-splitting prism (7) together, and the beam-splitting prism (7) performs energy beam-splitting to form reflected light and transmitted light; The reflected light is transmitted by the second polarization beam-splitting prism (202) to form horizontal linearly polarized light a1 with a frequency f1, and reflected to form vertical linearly polarized light a2 with a frequency f2; The horizontal linearly polarized light a1 enters the second optical fiber coupler (602); The vertical linearly polarized light a2 enters the first optical fiber coupler (601); The transmitted light is transmitted by the first polarization beam splitter prism (201) to form horizontal linearly polarized light b1 with a frequency of f1, and reflected to form vertical polarized light b2 with a frequency of f2; The horizontal linearly polarized light b1 is reflected by the two reflections of the to-be-measured right-angle prism (3) in turn, reflected by the mirror (401), transmitted by the first polarization beam splitter prism (201), and transmitted by the first quarter-wave plate (501), and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then reflected by the to-be-measured plane mirror (402) in turn, transmitted by the first quarter-wave plate (501), and the polarization state changes from left-handed elliptical polarized light to vertical polarized light, and then transmitted by the first polarization beam splitter prism (201) in turn, transmitted by the second quarter-wave plate (502), and the polarization state changes from vertical polarized light to right-handed elliptical polarized light, and then reflected by the to-be-measured right-angle prism (3) in turn, reflected by the mirror (401), and transmitted by the third quarter-wave plate (503), and the polarization state changes from right-handed elliptical polarized light to horizontal linearly polarized light, and then transmitted by the first polarization beam splitter prism (201) in turn, transmitted by the first quarter-wave plate (501), and the polarization state changes from horizontal linearly polarized light to left-handed elliptical polarized light, and then reflected by the to-be-measured plane mirror (402) in turn, transmitted by the first quarter-wave plate (501), and the polarization state changes from left-handed elliptical polarized light to vertical polarized light, and then reflected by the first polarization beam splitter prism (201) in turn, reflected by the to-be-measured right-angle prism (3) twice, reflected by the mirror (401), reflected by the first polarization beam splitter prism (201), and reflected by the second polarization beam splitter prism (202), and finally incident on the second fiber coupler (602); The vertical polarized light b2 is transmitted by the third quarter-wave plate (503), and the polarization state changes from vertical polarized light to left-handed elliptical polarized light, and then reflected by the mirror (401) in turn, reflected by the to-be-measured right-angle prism (3) twice, transmitted by the second quarter-wave plate (502), and the polarization state changes from left-handed elliptical polarized light to horizontal linearly polarized light, and then transmitted by the first polarization beam splitter prism (201) in turn, transmitted by the second polarization beam splitter prism (202), and finally incident on the first fiber coupler (601); Step B3 is specifically that the first fiber coupler (601) simultaneously receives two beams of orthogonal linearly polarized light, and obtains a Doppler frequency shift amount 0 of an interference signal after phase decoupling of the two beams of orthogonal linearly polarized light; The second fiber coupler (602) simultaneously receives two beams of orthogonal linearly polarized light, and obtains a Doppler frequency shift amount 2Δf2 of an interference signal after phase decoupling of the two beams of orthogonal linearly polarized light; Step B4 is specifically that based on the Doppler frequency shift amounts 0 and 2Δf2 obtained in step B3, the displacement amount S2 of the to-be-measured plane mirror (402) is calculated through phase decoupling: The displacement measurement of the to-be-measured plane mirror (402) is completed.

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