WO2022052292A1 - 外差光栅测量装置及测量方法 - Google Patents

外差光栅测量装置及测量方法 Download PDF

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Publication number
WO2022052292A1
WO2022052292A1 PCT/CN2020/128528 CN2020128528W WO2022052292A1 WO 2022052292 A1 WO2022052292 A1 WO 2022052292A1 CN 2020128528 W CN2020128528 W CN 2020128528W WO 2022052292 A1 WO2022052292 A1 WO 2022052292A1
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Prior art keywords
order diffracted
diffracted light
polarized light
light
dimension
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PCT/CN2020/128528
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English (en)
French (fr)
Inventor
李文昊
刘兆武
王玮
吉日嘎兰图
姚雪峰
于宏柱
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中国科学院长春光学精密机械与物理研究所
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Priority claimed from CN202010953635.9A external-priority patent/CN112097649B/zh
Priority claimed from CN202010953637.8A external-priority patent/CN112097650B/zh
Priority claimed from CN202010953595.8A external-priority patent/CN112097647B/zh
Priority claimed from CN202010953663.0A external-priority patent/CN112097651B/zh
Application filed by 中国科学院长春光学精密机械与物理研究所 filed Critical 中国科学院长春光学精密机械与物理研究所
Priority to DE112020005233.8T priority Critical patent/DE112020005233T5/de
Publication of WO2022052292A1 publication Critical patent/WO2022052292A1/zh
Priority to US17/710,967 priority patent/US11860057B2/en
Priority to US17/711,006 priority patent/US20220228890A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/36—Forming the light into pulses
    • G01D5/38—Forming the light into pulses by diffraction gratings

Definitions

  • the invention relates to the technical field of precise displacement measurement, in particular to a heterodyne grating measurement device and a measurement method for realizing 4-fold optical subdivision based on single diffraction.
  • the grating displacement measurement system uses the grating as the measuring ruler and the grating pitch as the measurement benchmark. Compared with the laser measurement technology, the grating measurement is less sensitive to environmental changes, and the beam incident on the grating will cover many grooves, which can play a role in the measurement of the grating. average effect.
  • the structure of the reading head in the grating displacement measurement system is simple and compact, the distance between the grating and the reading head is very small, and does not increase with the increase of the distance to be measured, which can greatly reduce the influence of the environment on the measurement accuracy of the system and the measurement cost. With the improvement of the grating manufacturing level, the measurement accuracy and measurement resolution of the grating displacement measurement system are gradually improved, and the application range is also wider and wider.
  • the measurement resolution of the grating displacement measurement technology is directly related to the period of the grating.
  • the displacement measurement technology based on the principle of diffracted light interference adopts the diffraction grating with high scribe line density to achieve high-resolution and high-precision displacement measurement.
  • Optical subdivision and electronic Subdivision is the main way to further improve the measurement resolution. Compared with electronic subdivision, optical subdivision has higher reliability.
  • the traditional grating displacement measurement system uses single diffraction to achieve 2x optical subdivision. In order to further improve the optical subdivision, the existing technology mostly uses the second diffraction principle to achieve 4x optical subdivision or multiple diffraction to achieve higher multiples of optical subdivision.
  • both the second diffraction and the multiple diffraction will make the optical structure of the measurement system more complicated, and the multiple diffraction uses the diffracted light at different positions of the grating, the surface accuracy of the grating and the attitude error between the grating and the reading head will be It has a great influence on the measurement accuracy.
  • the present invention aims to overcome the defects existing in the prior art, and adopts the following technical solutions:
  • the invention provides a heterodyne one-dimensional grating measurement device, comprising a light source, the light source is used to generate two overlapping linearly polarized lights with orthogonal polarizations and a fixed frequency difference, which are a first polarized light with a frequency f A and a frequency is the second polarized light of f B , the first polarized light is S polarized light, and the second polarized light is P polarized light; it is characterized in that, it also includes a reading head, a photoelectric receiving module and a signal processing system; wherein, the reading head is used for receiving the first polarized light and the second polarized light, and respectively incident on the surface of the moving one-dimensional measurement grating to generate +1-order diffracted light and -1-order diffracted light respectively including the first polarized light component and the second polarized light component, The +1-order diffracted light and the -1-order diffracted light are respectively incident on the photoelectric receiving module through the reading head
  • the reading head includes a reflecting mirror, a polarizing beam splitter prism, a first 1/4 wave plate, a second 1/4 wave plate, a compensating mirror coated with a reflective film, a gyroscopic prism and a turning element; wherein, the reflecting mirror is arranged on the The outgoing light path of the light source is used to vertically reflect the first polarized light and the second polarized light to the surface of the one-dimensional measurement grating to generate +1-order diffracted light and -1-order diffracted light; the turning element is arranged on the one-dimensional measurement grating.
  • the polarizing beam splitting prism is set at On the transmission light path of the turning element, it is used to reflect the first polarized light components of the +1st-order diffracted light and the -1st-order diffracted light to the first 1/4 wave plate respectively, and to reflect the +1st-order diffracted light and the -1st-order diffracted light to the first 1/4 wave plate.
  • the second polarized light components of the light are respectively transmitted to the second 1/4 wave plate;
  • the first 1/4 wave plate is arranged on the reflected light path of the polarized beam splitter prism, which is used to separate the +1st-order diffracted light and the -1st-order diffracted light
  • the first polarized light components of respectively, become left-handed polarized light and are incident on the gyroscopic prism;
  • the gyroscopic prism is arranged on the transmission light path of the first 1/4 wave plate, and is used to detect the first order diffracted light of the +1st order and the -1st order diffracted light.
  • a polarized light component is reflected twice, so that the first polarized light components of the +1-order diffracted light and the -1-order diffracted light are transformed into P-polarized light through the first 1/4 wave plate and then incident on the polarization beam splitter prism;
  • Two 1/4 wave plates are arranged on the transmission light path of the polarizing beam splitter prism, and are used to convert the second polarized light components of the +1st-order diffracted light and the -1st-order diffracted light into right-handed polarized light respectively and incident on the compensation mirror;
  • the compensation mirror is arranged on the transmission light path of the second 1/4 wave plate, and is used to reflect the second polarized light components of the +1st-order diffracted light and the -1st-order diffracted light, so that the +1st-order diffracted light and the -1st-order diffracted light are diffracted.
  • the second polarized light component of the light is converted into S-polarized light by the second 1/4 wave plate and then incident on the polarizing beam splitter prism;
  • the first polarized light component of the first-order diffracted light is transmitted to the photoelectric receiving module, and the second polarized light components of the +1-order diffracted light and the -1st-order diffracted light, which become S-polarized light, are reflected to the photoelectric receiving module.
  • the photoelectric receiving module includes a first receiver and a second receiver; wherein the first receiver is used to receive the second polarized light component of the -1st order diffracted light and the first polarized light component of the +1st order diffracted light, and The beat frequency signal with frequency f B -f A is generated and transmitted to the signal processing system; the second receiver is used to receive the first polarized light component of the -1st order diffracted light and the second polarized light component of the +1st order diffracted light, and A beat signal with frequency f B -f A is generated and transmitted to the signal processing system.
  • the -1st order diffracted light has a negative frequency shift of - ⁇ f
  • the +1st order diffracted light has a positive frequency shift of + ⁇ f
  • the beat frequency signal output by the first receiver The frequency of the second receiver becomes f B -f A -2 ⁇ f
  • the frequency of the beat signal output by the second receiver becomes f B -f A +2 ⁇ f.
  • the thickness of the compensating mirror is equal to 1/2 of the length of the rotary prism, and is used to compensate the transmission optical path of the second polarized light components of the +1st-order diffracted light and the -1st-order diffracted light, so that the +1st-order diffracted light and the -1st-order diffracted light and
  • the transmission optical path of the second polarized light component of the first-order diffracted light is equal to the transmission optical path of the first polarized light component of the +1-order diffracted light and the ⁇ 1-order diffracted light.
  • the reading head further comprises a first right-angle prism and a second right-angle prism respectively arranged on the diffraction light path of the one-dimensional measurement grating, and the first right-angle prism and the second right-angle prism measure the +1-order diffracted light and the -1-order diffracted light respectively. After two reflections, they are incident on the surface of the one-dimensional measurement grating again at the diffraction exit angle, and two new diffracted beams are incident vertically on the polarizing beam splitter prism.
  • the reading head includes a polarization beam splitter prism, a first 1/4 wave plate, a second 1/4 wave plate coated with a reflective film, and a gyroscopic prism; wherein, the polarization beam splitter prism is arranged on the outgoing light path of the light source, and uses To receive the first polarized light and the second polarized light, transmit the second polarized light to the first 1/4 wave plate, and reflect the first polarized light to the second 1/4 wave plate; the first 1/4 wave plate is set On the transmitted light path of the polarized beam splitter prism, it is used to convert the second polarized light into right-handed polarized light and incident on the gyroscopic prism; The polarized light is retroreflected, so that the second polarized light passes through the first 1/4 wave plate to become S-polarized light and then returns to the polarization beam splitter prism; the second 1/4 wave plate is arranged on the reflected light path of the polarization beam splitter prism, It is used to turn the first
  • the reading head further comprises a turning element and a third 1/4 wave plate; wherein, the turning element is arranged on the diffraction light path of the one-dimensional measurement grating, and is used for turning the -1st order diffracted light and the +1st order diffracted light, Make the -1st-order diffracted light and the +1st-order diffracted light parallel to each other and vertically incident on the third 1/4 wave plate; and the first polarized light component of the -1st-order diffracted light becomes S-polarized light, which is vertically incident on the polarization beam splitter prism, and the second polarized light component of the +1st-order diffracted light and the -1st-order diffracted light becomes P-polarized light , perpendicularly incident on the polarization beam splitter prism; the polarization beam splitter prism is used to reflect the first polarized light components of the +1st-order diffracted light and the -1st-order diff
  • the photoelectric receiving module includes a first receiver and a second receiver; wherein the first receiver is used to receive the first polarized light component of the +1st order diffracted light and the second polarized light component of the ⁇ 1st order diffracted light, and A beat frequency signal with frequency f B -f A is generated and transmitted to the signal processing system; the second receiver is used to receive the first polarized light component in the -1st order diffracted light and the second polarized light component in the +1st order diffracted light , and generate a beat frequency signal with frequency f B -f A , which is transmitted to the signal processing system.
  • the first receiver is used to receive the first polarized light component of the +1st order diffracted light and the second polarized light component of the ⁇ 1st order diffracted light, and A beat frequency signal with frequency f B -f A is generated and transmitted to the signal processing system
  • the second receiver is used to receive the first polarized light component in the -1st
  • the -1st order diffracted light has a negative frequency shift of - ⁇ f
  • the +1st order diffracted light has a positive frequency shift of + ⁇ f
  • the beat frequency signal output by the first receiver The frequency of the second receiver becomes f B -f A -2 ⁇ f
  • the frequency of the beat signal output by the second receiver becomes f B -f A +2 ⁇ f.
  • the transmission optical paths of the first polarized light component of the -1st-order diffracted light and the second polarized light component of the -1st-order diffracted light are equal, and the first polarized light component of the +1st-order diffracted light and the +1st-order diffracted light
  • the transmission optical paths of the second polarized light components are equal.
  • the reading head further comprises a first right-angle prism and a second right-angle prism respectively arranged on the diffraction light path of the one-dimensional measurement grating, and the first right-angle prism and the second right-angle prism measure the +1-order diffracted light and the -1-order diffracted light respectively. After two reflections, they are incident on the surface of the one-dimensional measurement grating again at the diffraction exit angle, and two new diffracted beams are incident vertically on the polarizing beam splitter prism.
  • the present invention also provides a heterodyne one-dimensional grating measurement method, comprising the following steps:
  • the first polarized light and the second polarized light respectively enter the reading head, and after the reading head is turned, they are respectively incident on the surface of the one-dimensional measurement grating to generate +1 order diffracted light including the first polarized light component and the second polarized light component respectively And -1st-order diffracted light, +1st-order diffracted light and -1st-order diffracted light respectively enter the photoelectric receiving module through the reading head;
  • step S2 specifically includes the following steps:
  • the first polarized light components of the +1st-order diffracted light and the -1st-order diffracted light are respectively changed into left-handed polarized light through the first 1/4 wave plate and incident to the rotary prism of the reading head, and then the +1 The first polarized light components of the first-order diffracted light and the -1-order diffracted light are reflected twice respectively, so that the first polarized light components of the +1-order diffracted light and the -1-order diffracted light become P through the first 1/4 wave plate
  • the polarized light is incident on the polarizing beam splitter prism; and the second polarized light components of the +1st-order diffracted light and the -1st-order diffracted light are respectively changed into right-handed polarized light and incident on the reading head through the second 1/4 wave plate.
  • the compensation mirror is used to reflect the second polarized light components of the +1-order diffracted light and the -1-order diffracted light through the compensation mirror, so that the second polarized light components of the +1-order diffracted light and the -1-order diffracted light pass through the second 1-order diffracted light.
  • the /4 wave plate becomes S polarized light and then enters the polarizing beam splitter prism;
  • the thickness of the compensating mirror is equal to 1/2 of the length of the rotary prism, and is used to compensate the transmission optical path of the second polarized light components of the +1st-order diffracted light and the -1st-order diffracted light, so that the +1st-order diffracted light and the -1st-order diffracted light and
  • the transmission optical path of the second polarized light component of the first-order diffracted light is equal to the transmission optical path of the first polarized light component of the +1-order diffracted light and the ⁇ 1-order diffracted light.
  • step S2 specifically includes the following steps:
  • the first polarized light and the second polarized light are incident on the polarizing beam splitter prism of the reading head, the second polarized light is transmitted to the first 1/4 wave plate of the reading head through the polarizing beam splitting prism, and the first polarized light Reflected to the second 1/4 wave plate of the readhead;
  • the second polarized light is changed into right-handed polarized light through the first 1/4 wave plate and incident on the gyratory prism, and the second polarized light is retroreflected through the gyratory prism, so that the second polarized light passes through the first 1/4 wave plate.
  • the 4-wave plate becomes S-polarized light and then returns to the polarizing beam splitter prism; and the first polarized light is changed into left-handed polarized light through the second 1/4-wave plate, which is reflected by the reflective film and then goes through the second 1/4-wave plate to change again. It is P polarized light and returns to the polarizing beam splitter prism;
  • the -1st-order diffracted light and the +1st-order diffracted light are turned by the turning element of the reading head, so that the -1st-order diffracted light and the +1st-order diffracted light are parallel to each other and vertically incident on the third 1/4 of the reading head wave plate;
  • the first polarized light components of the +1st-order diffracted light and the -1st-order diffracted light are converted into S-polarized light through the third 1/4 wave plate, and incident to the polarization beam splitter prism vertically, and the +1st-order diffracted light is converted into S-polarized light. and the second polarized light component of the -1st-order diffracted light becomes P-polarized light, which is vertically incident on the polarizing beam splitter prism;
  • the first 1/4 wave plate is used to convert the first polarized light components of the +1st-order diffracted light and the -1st-order diffracted light into left-handed polarized light and incident on the gyroscopic prism, and the +1st-order diffracted light is diffracted by the gyroscopic prism
  • the light and the first polarized light component of the -1st-order diffracted light are reflected twice and returned to the first 1/4 wave plate to become P-polarized light, then incident on the polarization beam splitter prism again, and transmitted to the photoelectric receiver through the polarization beam splitter prism.
  • the second polarized light components of the +1st-order diffracted light and the -1st-order diffracted light are changed into right-handed polarized light through the second 1/4 wave plate, and are reflected by the reflective film and pass through the second 1/4 wave plate again After it becomes S-polarized light, it is incident on the polarization beam splitter prism, and reflected to the photoelectric receiving module by the polarization beam splitter prism.
  • the transmission optical paths of the first polarized light component of the -1st-order diffracted light and the second polarized light component of the -1st-order diffracted light are equal, and the first polarized light component of the +1st-order diffracted light and the +1st-order diffracted light
  • the transmission optical paths of the second polarized light components are equal.
  • the photoelectric receiving module includes a first receiver and a second receiver; wherein the second polarized light component of the -1st order diffracted light and the first polarized light component of the +1st order diffracted light are received by the first receiver, and A beat frequency signal with a frequency of f B -f A is generated and transmitted to the signal processing system; the first polarized light component of the -1st order diffracted light and the second polarized light component of the +1st order diffracted light are received by the second receiver, and A beat signal with frequency f B -f A is generated and transmitted to the signal processing system.
  • the -1st order diffracted light has a negative frequency shift of - ⁇ f
  • the +1st order diffracted light has a positive frequency shift of + ⁇ f
  • the beat frequency signal output by the first receiver The frequency of the second receiver becomes f B -f A -2 ⁇ f
  • the frequency of the beat signal output by the second receiver becomes f B -f A +2 ⁇ f.
  • the +1-order diffracted light and the ⁇ 1-order diffracted light generated by the diffraction of the one-dimensional measurement grating are respectively incident on the first right-angle prism and the second right-angle prism, and the +1-order diffracted light is respectively detected by the first right-angle prism and the second right-angle prism.
  • the diffracted light and the -1st-order diffracted light are reflected twice, and are incident on the surface of the one-dimensional measurement grating again at the diffracted exit angle, and the two new diffracted lights are vertically incident on the polarizing beam splitter prism.
  • the invention provides a heterodyne two-dimensional grating measurement device, comprising a light source, the light source is used to generate two overlapping linearly polarized lights with orthogonal polarizations and a fixed frequency difference, the first polarized light and the second polarized light respectively; It is characterized in that it also includes a reading head, a photoelectric receiving module and a signal processing system; wherein, the reading head is used to receive the first polarized light and the second polarized light, and respectively incident on the surface of the moving two-dimensional measurement grating to generate the first dimension ⁇ The first-order diffracted light and the second-dimension ⁇ 1-order diffracted light, the first-dimension ⁇ 1-order diffracted light and the second-dimension ⁇ 1-order diffracted light respectively enter the photoelectric receiving module through the reading head; The one-dimensional ⁇ 1st-order diffracted light and the second-dimension ⁇ 1st-order diffracted light generate corresponding beat frequency signals, which are sent to the signal processing system
  • the first polarized light is S-polarized light with a frequency of f A
  • the second polarized light is P-polarized light with a frequency of f B
  • the second 1/4 wave plate, the third 1/4 wave plate, the gyroscopic prism and the turning element of the reflective film wherein, the polarizing beam splitter prism is used to receive the first polarized light and the second polarized light, and transmit the second polarized light
  • the first polarized light is reflected to the second 1/4 wave plate
  • the first 1/4 wave plate is arranged on the transmitted light path of the polarizing beam splitter prism to convert the second polarized light into
  • the right-handed polarized light is incident on the gyroscopic prism
  • the gyroscopic prism is arranged on the transmitted light path of the first 1/4 wave plate to retroreflect the second polarized light.
  • the second 1/4 wave plate is set on the reflected light path of the polarization beam splitter prism, which is used to convert the first polarized light into left-handed polarized light for reflection, and then passes through the first polarization beam again.
  • the 2 1/4 wave plate After the 2 1/4 wave plate becomes P polarized light, it returns to the polarizing beam splitting prism; the polarizing beam splitting prism is also used to transmit the first polarized light, reflect the second polarized light, and combine the first polarized light with the second polarized light
  • the beam is incident on the third 1/4 wave plate; the third 1/4 wave plate is arranged on the optical path of the polarizing beam splitter prism to transmit the first polarized light, which is used to convert the first polarized light into right-handed polarized light and then vertically Incident to the surface of the two-dimensional measurement grating, the second polarized light is changed to left-handed polarized light and then vertically incident on the surface of the two-dimensional measurement grating, the first polarized light and the second polarized light are diffracted to generate the first dimension ⁇ 1st order diffracted light respectively and the second dimension ⁇ 1st order diffracted light.
  • the ⁇ 1st-order diffracted light in the first dimension includes the first-dimension-1st-order diffracted light and the first-dimension+1st-order diffracted light
  • the second-dimension ⁇ 1st-order diffracted light includes the second-dimension-1st-order diffracted light and the second dimension Dimension + 1st order diffracted light
  • the first dimension -1st order diffracted light, the first dimension +1st order diffracted light, the second dimension -1st order diffracted light, and the second dimension +1st order diffracted light respectively contain the first polarized light component and the second polarized light component.
  • the reading head further includes a turning element arranged on the diffraction light path of the two-dimensional measurement grating, which is used for the first dimension -1st order diffracted light, the first dimension +1st order diffracted light, the second dimension -1st order diffracted light, The second dimension+1st-order diffracted light is turned, so that the first-dimension-1st-order diffracted light, the first-dimension+1st-order diffracted light, the second-dimension-1st-order diffracted light, and the second-dimension+1st-order diffracted light are parallel to each other.
  • the third 1/4 wave plate is vertically incident on the third 1/4 wave plate;
  • the first polarized light component in the dimension+1st order diffracted light becomes S polarized light and is vertically incident on the polarized beam splitter prism, and the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension
  • the second polarized light component in the -1st-order diffracted light and the +1st-order diffracted light in the second dimension becomes P-polarized light and is vertically incident on the polarizing beam splitter prism;
  • the polarizing beam splitter prism is used to convert the -1st-order diffracted light in the first dimension , the first dimension +1st order diffracted light, the second dimension -1st order diffracted light, and the first polarized light component in the second dimension +1st order diffracted light are reflected to the first 1/4 wave plate, and the first dimension - The second polarized light component in the first-order diffr
  • the photoelectric receiving module includes a first receiver, a second receiver, a third receiver and a fourth receiver; wherein the first receiver is used to receive the first polarized light component in the +1st-order diffracted light in the first dimension and the second polarized light component in the first dimension-1st order diffracted light, and generate a beat frequency signal with a frequency of f B -f A , which is sent to the signal processing system; the second receiver is used to receive the first dimension-1st order diffraction The first polarized light component in the light and the second polarized light component in the first dimension + 1st-order diffracted light, and generate a beat frequency signal with a frequency of f B -f A , and send it to the signal processing system; the third receiver is used for Receive the first polarized light component in the +1st order diffracted light in the second dimension and the second polarized light component in the second dimension -1st order diffracted light, generate a beat frequency signal with a frequency
  • the first polarized light component and the second polarized light component respectively received by the first receiver, the second receiver, the third receiver and the fourth receiver respectively pass through the gyratory prism twice, which are transmitted in the reading head.
  • the optical path is equal.
  • the two-dimensional measurement grating moves along the grating vector direction of the first dimension
  • the -1st-order diffracted light in the first dimension has a negative frequency shift - ⁇ f
  • the +1st-order diffracted light in the first dimension has a positive frequency shift + ⁇ f
  • the frequency of the beat signal output by the first receiver becomes f B -f A -2 ⁇ f
  • the frequency of the beat signal output by the second receiver becomes f B -f A +2 ⁇ f
  • the two-dimensional measurement grating is along the second
  • the second dimension -1st order diffracted light has a negative frequency shift - ⁇ f
  • the second dimension +1st order diffracted light has a positive frequency shift + ⁇ f
  • the frequency of the beat frequency signal output by the third receiver becomes f B -f A -2 ⁇ f
  • the frequency of the beat signal output by the fourth receiver becomes f B -f A +2 ⁇ f.
  • the signal processing system is used to perform differential calculation on the beat frequency signal output by the first receiver and the beat frequency signal output by the second receiver, so as to realize the single diffraction 4 times optical subdivision of the first dimension of the two-dimensional measurement grating
  • differential calculation is performed between the beat frequency signal output by the third receiver and the beat frequency signal output by the fourth receiver, so as to realize the displacement measurement of single diffraction 4 times optical subdivision of the second dimension of the two-dimensional measurement grating.
  • the present invention also provides a heterodyne two-dimensional grating measurement method, comprising the following steps:
  • the first polarized light and the second polarized light respectively enter the reading head, and after reflection and transmission by the reading head, respectively enter the surface of the moving two-dimensional measurement grating to generate the first dimension ⁇ 1 order diffracted light and the second dimension ⁇ 1 order Diffracted light, the first-dimension ⁇ 1st-order diffracted light and the second-dimension ⁇ 1st-order diffracted light respectively enter the photoelectric receiving module through the reading head;
  • the photoelectric receiving module generates corresponding beat frequency signals according to the ⁇ 1st order diffracted light of the first dimension and the ⁇ 1st order diffracted light of the second dimension respectively, and sends them to the signal processing system;
  • the signal processing system respectively performs differential calculation on the beat frequency signals generated by the ⁇ 1st order diffracted light in the first dimension and performs differential calculation on the beat frequency signals generated by the ⁇ 1st order diffracted light in the second dimension, so as to realize the first dimension of the two-dimensional measurement grating and displacement measurements of single diffraction 4x optical subdivisions in the second dimension.
  • step S2 specifically includes the following steps:
  • the first polarized light is reflected to the second 1/4 wave plate by the polarizing beam splitter, and after the first polarized light is changed into left-handed polarized light, the reflection is performed again after the second 1/4 wave plate becomes P-polarized light, Back to the polarizing beam splitting prism; and, the second polarized light is transmitted to the first 1/4 wave plate through the polarizing beam splitting prism, and is incident on the gyroscopic prism after the second polarized light is changed to right-handed polarized light, and the second polarized light is polarized by the gyroscopic prism. The light is retroreflected, and when the second polarized light passes through the first 1/4 wave plate to become S-polarized light again, it returns to the polarizing beam splitter prism;
  • the polarizing beam splitting prism transmits the first polarized light and reflects the second polarized light, so that the first polarized light and the second polarized light are combined into a third 1/4 wave plate, and the third 1/4 wave plate will
  • the first polarized light is transformed into right-handed polarized light and then vertically incident on the surface of the two-dimensional measurement grating
  • the second polarized light is transformed into left-handed polarized light and then vertically incident on the surface of the two-dimensional measurement grating.
  • the polarized light is diffracted to generate the first-dimension ⁇ 1st-order diffracted light and the second-dimension ⁇ 1st-order diffracted light, respectively.
  • the ⁇ 1st-order diffracted light in the first dimension includes the first-dimension-1st-order diffracted light and the first-dimension+1st-order diffracted light
  • the second-dimension ⁇ 1st-order diffracted light includes the second-dimension-1st-order diffracted light and the second dimension Dimension + 1st order diffracted light
  • the first dimension -1st order diffracted light, the first dimension +1st order diffracted light, the second dimension -1st order diffracted light, and the second dimension +1st order diffracted light respectively contain the first polarized light component and the second polarized light component.
  • step S202 the following steps are further included:
  • the third 1/4 wave plate converts the first polarization in the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light
  • the light component becomes S-polarized light, it is vertically incident on the polarizing beam splitter prism, and the first dimension -1st order diffracted light, the first dimension +1st order diffracted light, the second dimension -1st order diffracted light, the second dimension +1st order diffracted light
  • the second polarized light component in the diffracted light becomes P-polarized light and then vertically incident on the polarization beam splitter prism;
  • the polarization beam splitter prism reflects the first polarized light component in the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light to the first 1/4 wave plate, and the second dimension of the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light
  • the polarized light component is transmitted to the second 1/4 wave plate;
  • the second 1/4 wave plate polarizes the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light
  • the light component becomes right-handed polarized light, it is reflected, and then passes through the second 1/4 wave plate to become S-polarized light, then enters the polarization beam splitter prism, and is reflected to the photoelectric receiving module through the polarization beam splitter prism, and the first 1
  • the /4 wave plate changes the first polarized light component in the first dimension -1st order diffracted light, the first dimension +1st order diffracted light, the second dimension -1st order diffracted light, and the second dimension +1st order diffracted light into left-handed
  • the polarized light is incident on the gyroscopic prism again, and the gyroscopic prism is respectively responsible for the diffracted light of the first dimension +1st order, the first dimension
  • the photoelectric receiving module includes a first receiver, a second receiver, a third receiver and a fourth receiver; wherein the first receiver is used to receive the first polarized light component in the +1st-order diffracted light in the first dimension and the second polarized light component in the first dimension-1st order diffracted light, and generate a beat frequency signal with a frequency of f B -f A , which is sent to the signal processing system; the second receiver is used to receive the first dimension-1st order diffraction The first polarized light component in the light and the second polarized light component in the first dimension + 1st-order diffracted light, and generate a beat frequency signal with a frequency of f B -f A , and send it to the signal processing system; the third receiver is used for Receive the first polarized light component in the +1st order diffracted light in the second dimension and the second polarized light component in the second dimension -1st order diffracted light, generate a beat frequency signal with a frequency
  • the first polarized light component and the second polarized light component respectively received by the first receiver, the second receiver, the third receiver and the fourth receiver respectively pass through the gyratory prism twice, which are transmitted in the reading head.
  • the optical path is equal.
  • the two-dimensional measurement grating moves along the grating vector direction of the first dimension
  • the -1st-order diffracted light in the first dimension has a negative frequency shift - ⁇ f
  • the +1st-order diffracted light in the first dimension has a positive frequency shift + ⁇ f
  • the frequency of the beat signal output by the first receiver becomes f B -f A -2 ⁇ f
  • the frequency of the beat signal output by the second receiver becomes f B -f A +2 ⁇ f
  • the two-dimensional measurement grating is along the second
  • the second dimension -1st order diffracted light has a negative frequency shift - ⁇ f
  • the second dimension +1st order diffracted light has a positive frequency shift + ⁇ f
  • the frequency of the beat frequency signal output by the third receiver becomes f B -f A -2 ⁇ f
  • the frequency of the beat signal output by the fourth receiver becomes f B -f A +2 ⁇ f.
  • the signal processing system performs differential calculation on the beat frequency signal output by the first receiver and the beat frequency signal output by the second receiver, so as to realize the displacement measurement of the single diffraction 4 times optical subdivision of the first dimension of the two-dimensional measurement grating , performing differential calculation on the beat frequency signal output by the third receiver and the beat frequency signal output by the fourth receiver, so as to realize the displacement measurement of single diffraction 4 times optical subdivision of the second dimension of the two-dimensional measurement grating.
  • the present invention can realize 4 times optical subdivision through the first diffraction of the one-dimensional measurement grating or the surface of the two-dimensional measurement grating, effectively avoiding the influence of the grating surface shape accuracy and the grating attitude error on the measurement accuracy, and It has the advantages of simple structure, small size, light weight, easy installation, convenient application, etc. At the same time, it can also combine the method of second diffraction or multiple diffraction to achieve higher multiples of optical subdivision.
  • FIG. 1 is a schematic structural diagram of a heterodyne one-dimensional grating measurement device according to Embodiment 1 of the present invention.
  • FIG. 2 is a schematic diagram of the principle of a heterodyne one-dimensional grating measurement device according to Embodiment 1 of the present invention
  • FIG. 3 is a schematic diagram of a generation principle of a first beat signal according to Embodiment 1 of the present invention.
  • FIG. 4 is a schematic diagram of a generation principle of a second beat signal according to Embodiment 1 of the present invention.
  • FIG. 5 is a schematic diagram of the principle of realizing 8-fold optical subdivision in combination with secondary diffraction according to Embodiment 1 of the present invention.
  • FIG. 6 is a schematic flowchart of a method for measuring a heterodyne one-dimensional grating according to Embodiment 2 of the present invention.
  • FIG. 7 is a schematic diagram of the principle of a heterodyne one-dimensional grating measurement device according to Embodiment 3 of the present invention.
  • FIG. 8 is a schematic diagram of a generation principle of a first beat signal according to Embodiment 3 of the present invention.
  • FIG. 9 is a schematic diagram of a generation principle of a second beat signal according to Embodiment 3 of the present invention.
  • FIG. 10 is a schematic flowchart of a method for measuring a heterodyne one-dimensional grating according to Embodiment 4 of the present invention.
  • FIG. 11 is a schematic diagram of the principle of realizing 4 times optical subdivision by single diffraction of the heterodyne two-dimensional grating measuring device according to the fifth embodiment of the present invention.
  • FIG. 12 is a schematic diagram of the optical path transmission principle before beam diffraction according to Embodiment 5 of the present invention.
  • FIG. 13 is a schematic diagram of a generation principle of a first-dimension first beat frequency signal according to Embodiment 5 of the present invention.
  • FIG. 14 is a schematic diagram of the generation principle of the second beat signal in the first dimension according to Embodiment 5 of the present invention.
  • FIG. 15 is a schematic diagram of the generation principle of the second-dimension first beat signal according to Embodiment 5 of the present invention.
  • FIG. 16 is a schematic diagram of a generation principle of a second-dimension second beat signal according to Embodiment 5 of the present invention.
  • FIG. 17 is a schematic flowchart of a method for measuring displacement of a heterodyne two-dimensional grating according to Embodiment 6 of the present invention.
  • the reference signs of the first embodiment include: light source 1, reading head 2, mirror 201, polarizing beam splitter prism 202, first 1/4 wave plate 203, second 1/4 wave plate 204, gyroscopic prism 205, turning element 206 , compensating mirror 207 , first right angle prism 208 , second right angle prism 209 , first receiver 301 , second receiver 302 , signal processing system 4 , measurement grating 5 .
  • the reference signs of the third embodiment include: light source 1', reading head 2', polarizing beam splitter prism 201', first 1/4 wave plate 202', second 1/4 wave plate 203', third 1/4 wave plate Wave plate 204', gyroscopic prism 205', turning element 206', first right angle prism 207', second right angle prism 208', first receiver 301', second receiver 302', signal processing system 4', measurement Grating 5 ⁇ .
  • the reference signs of the fifth embodiment include: light source 1, polarizing beam splitter prism 201, first 1/4 wave plate 202, second 1/4 wave plate 203, third 1/4 wave plate 204, gyroscopic prism 205, turning element 206 , a first receiver 301 , a second receiver 302 , a third receiver 303 , a fourth receiver 304 , a signal processing system 4 , and a two-dimensional measurement grating 5 .
  • the heterodyne grating measuring device fixes the measuring grating on the measured object as a ruler for displacement measurement.
  • the displacement measurement of the measuring grating realizes the measurement of the measured object Displacement measurement.
  • the heterodyne one-dimensional grating measuring device has a special structural design for the reading head, so that two beams of polarized light with a fixed frequency difference emitted by the light source can be realized by one diffraction when they are incident on the surface of the measuring grating through the reading head.
  • optical subdivision can avoid the influence of grating surface shape accuracy and grating attitude error on measurement accuracy, and the reading head in the present invention has a simple structure, small volume and light weight, which can simplify the complexity of the optical structure in the measurement system.
  • the present invention can also combine second diffraction or more diffractions to achieve better multiples of optical subdivision.
  • the measuring grating can be a one-dimensional measuring grating or a two-dimensional measuring grating, corresponding to a one-dimensional measuring grating
  • the heterodyne grating measuring device is a heterodyne one-dimensional grating measuring device, corresponding to a two-dimensional measuring grating, a heterodyne grating measuring device It is a heterodyne two-dimensional grating measuring device.
  • heterodyne grating measuring device provided by the present invention will be described below by taking the realization of 4x optical subdivision by first diffraction as an example in conjunction with the accompanying drawings.
  • the heterodyne one-dimensional grating measurement device includes: a light source 1, a reading head 2, a photoelectric receiving module and a signal processing system 4; wherein, the light source 1 is used to generate two Linearly polarized light with overlapping beams, orthogonal polarizations and a fixed frequency difference is used as the measurement beam, which are the first polarized light and the second polarized light respectively, the first polarized light is S polarized light, the frequency is f A , and the second polarized light is P-polarized light, the frequency is f B , the light source 1 can be a dual-frequency laser 1 or two lasers with a fixed frequency difference; the reading head is used to inject the two beams of polarized light into the surface of the moving one-dimensional measurement grating 5, After the two beams of polarized light are diffracted by the surface of the one-dimensional measurement grating 5, the +1-order diffracted light and
  • the +1-order diffracted light and the -1-order diffracted light both include the first polarization.
  • the light component and the second polarized light component, the first polarized light component and the second polarized light component of the +1-order diffracted light, and the first polarized light component and the second polarized light component of the -1-order diffracted light are respectively incident on the reading head.
  • Photoelectric receiving module is a photoelectric receiving module.
  • the reading head 2 includes a reflecting mirror 201, a polarizing beam splitter prism 202, a first 1/4 wave plate 203, a second 1/4 wave plate 204, a gyroscopic prism 205, a turning element 206 and a compensating mirror 207 coated with a reflective film.
  • the mirror 201 is arranged on the outgoing light path of the light source 1, the turning element 206 is arranged on the diffraction light path of the one-dimensional measurement grating 5, the polarization beam splitting prism 202 is arranged on the transmission light path of the turning element 206, and the first 1/4 wave plate 203 set on the reflected light path of the polarization beam splitter prism 202, the second 1/4 wave plate 204 is set on the transmitted light path of the polarization beam splitter prism 202, and the gyroscopic prism 205 is set on the transmitted light path of the first 1/4 wave plate 204,
  • the compensation mirror 207 is arranged on the transmission light path of the second 1/4 wave plate 204 .
  • the mirror 201 vertically reflects the first polarized light and the second polarized light to the surface of the one-dimensional measurement grating 5, and the +1-order diffracted light and the -1-order diffracted light generated after diffraction are turned by the turning element 206 and are parallel to each other and incident vertically.
  • the polarization beam splitter prism 202 reflects the first polarized light component of the +1st order diffracted light and the first polarized light component of the ⁇ 1st order diffracted light to the first quarter wave plate 203, and the + The second polarized light component of the 1st-order diffracted light and the second polarized light component of the -1st-order diffracted light are transmitted to the second quarter wave plate 204 .
  • the first 1/4 wave plate 203 converts the first polarized light components of the +1st-order diffracted light and the -1st-order diffracted light into left-handed polarized light respectively and is incident on the gyroscopic prism 205; A polarized light component and the first polarized light component of the -1st-order diffracted light are reflected twice respectively, so that the first polarized light component of the +1st-order diffracted light and the first polarized light component of the -1st-order diffracted light pass through the first
  • the 1/4 wave plate 203 becomes P-polarized light, which is incident on the polarization beam splitter prism 202 again, and the polarization beam splitter prism 202 transmits the first polarized light component of the +1-order diffracted light that becomes the P-polarized light to the first receiver 301 , and transmit the first polarized light component of the -1st order diffracted light that becomes P polarized light to the second receiver 302
  • the second 1/4 wave plate 204 converts the second polarized light component of the +1st-order diffracted light and the second polarized light component of the -1st-order diffracted light into right-handed polarized light respectively and incident to the compensation mirror 207; +1st-order diffraction
  • the second polarized light component of the light and the second polarized light component of the -1st order diffracted light are reflected by the compensation mirror 207 and return to the second 1/4 wave plate 204 again, so that the second polarized light component of the +1st order diffracted light and -
  • the second polarized light component of the first-order diffracted light becomes S-polarized light, and is incident on the polarization beam splitter prism 202 again, and the polarization beam splitter prism 202 reflects the second polarized light component of the +1-order diffracted light that becomes S-polarized light to the second receiver 302 and reflect the second polarized light component of the -1st order diff
  • the second polarized light component of the +1st-order diffracted light and the second polarized light component of the -1st-order diffracted light pass through the gyratory prism 205, the second polarized light component of the +1st-order diffracted light and the second polarized light component of the -1st-order diffracted light
  • the polarized light component does not pass through the gyroscopic prism 205, resulting in the transmission optical path of the first polarized light component and the second polarized light component of the +1 order diffracted light and the difference between the first polarized light component and the second polarized light component of the ⁇ 1 order diffracted light.
  • the transmission optical paths are different, so the compensation mirror 207 compensates the transmission optical paths of the second polarized light component of the +1st-order diffracted light and the second polarized light component of the -1st-order diffracted light.
  • the thickness of the compensation mirror 207 is equal to 1/2 of the length of the rotary prism 205, so that the second polarized light component of the +1st-order diffracted light is incident on the second receiving light after passing through the compensation mirror 207 twice.
  • the transmission optical path of the receiver 302 is equal to the transmission optical path of the first polarized light component of the +1st-order diffracted light incident on the first receiver 301 after passing through the gyroscopic prism 205, so that the second polarized light component of the -1st-order diffracted light is between the two.
  • the transmission optical path of the first receiver 301 is equal to the transmission optical path of the first polarized light component of the -1st-order diffracted light, which is incident to the second receiver 302 after passing through the gyroscopic prism 205. Compensation of the transmission optical path of the second polarized light component of the 1st-order diffracted light and the second polarized light component of the -1st-order diffracted light.
  • the first one ensure that the path difference of the measuring beam entering the first receiver 301 and the second receiver 302 is a constant value.
  • the second one When the ambient temperature of the measurement optical system changes with the heterodyne grating displacement, the optical path difference of the measurement beam changes in the same way, which is not affected by the thermal expansion and contraction of the optical elements of the reading head, and will not introduce measurement errors.
  • the photoelectric receiving module includes a first receiver 301 and a second receiver 302.
  • the first receiver 301 is used to receive the second polarized light component of the -1st-order diffracted light and the first polarized light component of the +1st-order diffracted light.
  • the first receiver 301 converts the first beat signal to It is transmitted to the signal processing system 4; the second receiver 302 is used to receive the first polarized light component of the -1st-order diffracted light and the second polarized light component of the +1st-order diffracted light, and the first polarized light of the -1st-order diffracted light After the component interferes with the second polarized light component of the +1st-order diffracted light to form a second beat signal with a frequency of f B ⁇ f A , the second receiver 302 transmits the second beat signal to the signal processing system 4 .
  • the one-dimensional measurement grating 5 moves along the grating vector direction, due to the Doppler frequency shift effect of the grating, the -1st order diffracted light undergoes a negative frequency shift - ⁇ f, and the +1st order diffracted light undergoes a positive frequency shift + ⁇ f, so the first receiving The frequency of the first beat signal output by the receiver 201 becomes f B -f A -2 ⁇ f, and the frequency of the second beat signal output by the second receiver 302 becomes f B -f A +2 ⁇ f.
  • the signal processing system 4 is configured to receive the first beat signal and the second beat signal sent by the first receiver 301 and the second receiver 302, and perform differential calculation on the first beat signal and the second beat signal to achieve One-dimensional measurement grating 5 displacement measurement of 4x optical subdivision by single diffraction. Since the difference calculation is in the prior art, it is not repeated here.
  • the reading head further includes a first right angle prism 208 and a second right angle prism 209.
  • the first right angle prism 208 and the second right angle prism 209 are respectively arranged on the diffraction light path of the one-dimensional measurement grating 5.
  • the diffracted light and the -1st-order diffracted light are reflected twice, and are incident on the surface of the one-dimensional measurement grating 5 again at the diffracted exit angle to achieve two-dimensional diffraction, resulting in two new diffracted lights.
  • the surface of the measurement grating 5 emerges vertically and is vertically incident on the polarizing beam splitter prism 202 .
  • the optical subdivision multiple is doubled, thereby improving the measurement resolution.
  • the first embodiment shows the structure of a heterodyne one-dimensional grating measurement device, which corresponds to the heterodyne one-dimensional grating measurement device of the first embodiment, and the second embodiment provides a heterodyne one-dimensional grating using the first embodiment.
  • a method for measuring grating displacement by a measuring device is a method for measuring grating displacement by a measuring device.
  • FIG. 6 shows the flow of the heterodyne one-dimensional grating measurement method according to the second embodiment of the present invention.
  • the method for measuring a heterodyne one-dimensional grating according to the second embodiment of the present invention includes the following steps:
  • the first polarized light and the second polarized light respectively enter the reading head, and after the reading head is turned, they are respectively incident on the surface of the one-dimensional measurement grating to generate +1 order diffracted light including the first polarized light component and the second polarized light component respectively And -1st-order diffracted light, +1st-order diffracted light and -1st-order diffracted light are respectively incident on the photoelectric receiving module through the reading head.
  • Step S2 specifically includes the following steps:
  • the first polarized light and the second polarized light are vertically reflected to the surface of the one-dimensional measurement grating by the reflection mirror of the reading head, so as to generate +1-order diffracted light and -1-order diffracted light.
  • the +1st-order diffracted light and the -1st-order diffracted light are turned by the turning element of the reading head, so that the +1st-order diffracted light and the -1st-order diffracted light are parallel to each other and vertically incident on the polarization beam splitting prism of the reading head.
  • the first polarized light components of the +1st-order diffracted light and the -1st-order diffracted light are respectively changed into left-handed polarized light through the first 1/4 wave plate and incident to the rotary prism of the reading head, and then the +1 The first polarized light components of the first-order diffracted light and the -1-order diffracted light are reflected twice respectively, so that the first polarized light components of the +1-order diffracted light and the -1-order diffracted light become P through the first 1/4 wave plate
  • the polarized light is incident on the polarizing beam splitter prism; and the second polarized light components of the +1st-order diffracted light and the -1st-order diffracted light are respectively changed into right-handed polarized light and incident on the reading head through the second 1/4 wave plate.
  • the compensation mirror is used to reflect the second polarized light components of the +1-order diffracted light and the -1-order diffracted light through the compensation mirror, so that the second polarized light components of the +1-order diffracted light and the -1-order diffracted light pass through the second 1-order diffracted light.
  • the /4 wave plate becomes S-polarized light and then enters the polarization beam splitter prism.
  • the thickness of the compensating mirror is equal to 1/2 of the length of the rotary prism, which is used to compensate the transmission optical path of the second polarized light components of the +1st-order diffracted light and the -1st-order diffracted light, so that the +1st-order diffracted light and the -1st-order diffracted light are
  • the transmission optical path of the second polarized light component is equal to the transmission optical path of the first polarized light component of the +1st-order diffracted light and the -1st-order diffracted light.
  • the photoelectric receiving module receives the +1-order diffracted light and the -1-order diffracted light; wherein, the interference formation frequency of the second polarized light component of the -1-order diffracted light and the first polarized light component of the +1-order diffracted light is f B ⁇
  • the first polarized light component of the -1st order diffracted light interferes with the second polarized light component of the +1st order diffracted light to form a beat frequency signal with a frequency of f B -f A.
  • the photoelectric receiving module includes a first receiver and a second receiver.
  • the second polarized light component of the -1st order diffracted light and the first polarized light component of the +1st order diffracted light are received by the first receiver.
  • the interference generation frequency of the two is The first beat frequency signal of f B -f A is transmitted to the signal processing system; the first polarized light component of the -1st order diffracted light and the second polarized light component of the +1st order diffracted light are received by the second receiver, both of which are The interference generates a second beat signal of frequency f B - f A , which is transmitted to the signal processing system.
  • the -1st order diffracted light undergoes a negative frequency shift of - ⁇ f
  • the +1st order diffracted light undergoes a positive frequency shift + ⁇ f
  • the first beat frequency signal output by the first receiver has a negative frequency shift of - ⁇ f.
  • the frequency becomes f B -f A -2 ⁇ f
  • the frequency of the second beat signal output by the second receiver becomes f B -f A +2 ⁇ f.
  • the signal processing system respectively performs differential calculation on the two beat frequency signals, so as to realize the displacement measurement of the one-dimensional measurement grating single diffraction 4 times optical subdivision.
  • the signal processing system performs differential calculation on the first beat frequency signal output by the first receiver and the second beat frequency signal output by the second receiver, so as to realize the displacement measurement of the one-dimensional measurement grating single diffraction 4 times optical subdivision. Since the difference calculation is in the prior art, it is not repeated here.
  • the +1st-order diffracted light and the -1st-order diffracted light generated by the diffraction of the one-dimensional measurement grating can be incident on the first right-angle prism and the second right-angle prism, respectively.
  • the +1st-order diffracted light and the -1st-order diffracted light are reflected twice by the two right-angle prisms respectively, and then incident on the surface of the one-dimensional measurement grating again at the diffraction exit angle, and the two new diffracted lights are vertically incident on the polarizing beam splitter prism.
  • the optical subdivision multiple is doubled, thereby improving the measurement resolution.
  • the heterodyne one-dimensional grating measurement device includes: a light source 1', a reading head 2', a photoelectric receiving module and a signal processing system 4'; wherein, the light source 1' It is used to generate two overlapping linearly polarized lights with orthogonal polarizations and a fixed frequency difference as measurement beams, which are the first polarized light and the second polarized light respectively, the first polarized light is S polarized light, the frequency is f A , the The two-polarized light is P-polarized light, the frequency is f B , the light source 1' can be a dual-frequency laser or two lasers with a fixed frequency difference; the reading head is used to inject the two beams of polarized light into the moving one-dimensional measurement grating 5, after the two beams of polarized light are diffracted by the surface of the one-dimensional measurement grating 5, the +1-order diffracted light and the
  • the +1-order diffracted light and the -1-order diffracted light are both. Including the first polarized light component and the second polarized light component, the first polarized light component and the second polarized light component of the +1-order diffracted light, and the first polarized light component and the second polarized light component of the -1-order diffracted light are respectively processed.
  • the reading head is incident on the photoelectric receiving module.
  • the reading head 2' includes a polarization beam splitter prism 201', a first quarter wave plate 202', a second quarter wave plate 203' coated with a reflective film, a third quarter wave plate 204', and a gyroscopic prism 205 ⁇ and the turning element 206', the polarization beam splitting prism 201' is arranged on the outgoing light path of the light source 1', the turning element 206' is arranged on the diffracted light path of the one-dimensional measuring grating 5, and the first 1/4 wave plate 202' is arranged On the reflected light path of the polarizing beam splitting prism 201', the second 1/4 wave plate 203' is arranged on the transmitted light path of the polarizing beam splitting prism 201', and the third 1/4 wave plate 204' is arranged on the turning element 206'. On the transmitted light path, the rotary prism 205' is arranged on the transmitted light path of the first quarter wave plate 202'.
  • the polarizing beam splitter prism 201' receives the first polarized light and the second polarized light, transmits the second polarized light to the first quarter wave plate 202', and reflects the first polarized light to the second quarter wave plate 203' , the first 1/4 wave plate 202' changes the second polarized light into right-handed polarized light and is incident on the gyroscopic prism 205', the gyroscopic prism 205' retroreflects the second polarized light, so that the second polarized light passes through the first
  • the 1/4 wave plate 202' becomes S-polarized light and then returns to the polarizing beam splitter prism 201', and the second 1/4 wave plate 203' is set to change the first polarized light into left-handed polarized light, which is reflected by the reflective film and passes through the first polarized light again.
  • the second 1/4 wave plate 203' becomes the P-polarized light and then returns to the polarization beam splitter prism 203'.
  • the polarization beam splitter prism 201' transmits the first polarized light that becomes the P-polarized light, and transmits the first polarized light that becomes the S-polarized light.
  • the second polarized light is reflected, so that the first polarized light and the second polarized light are combined and incident on the surface of the one-dimensional measurement grating 5, and the diffraction produces -1-order diffracted light and +1-order diffracted light.
  • the first-order diffracted light and the +1-order diffracted light are turned, so that the -1-order diffracted light and the +1-order diffracted light are parallel to each other and are vertically incident on the third 1/4 wave plate 204 ⁇ , and the third 1/4 wave plate 204 ⁇ will
  • the first polarized light components of the +1st-order diffracted light and the -1st-order diffracted light become S-polarized light, which is vertically incident on the polarization beam splitter prism 201'
  • the second polarized light components of the +1st-order diffracted light and the -1st-order diffracted light are
  • the light component becomes P-polarized light, which is vertically incident on the polarization beam splitter prism 201'
  • the polarization beam splitter prism 201' reflects the first polarized light components of the +1st-order diffracted light and the -1st-order diffracted light to the first 1/4 wave plate 202', and transmits
  • the polarizing beam splitting prism 201' is reflected to the photoelectric receiving module through the polarizing beam splitting prism 201'.
  • the second polarized light component of the diffracted light has the same transmission optical path in the reading head, which plays two roles:
  • the optical path difference of the measuring beam changes uniformly, which is not affected by the thermal expansion and contraction of the optical elements of the reading head, and will not introduce measurement errors.
  • the photoelectric receiving module includes a first receiver 301' and a second receiver 302', and the first receiver 301' is used to receive the second polarized light component of the -1st order diffracted light and the first polarized light component of the +1st order diffracted light , after the second polarized light component of the -1st-order diffracted light interferes with the first polarized light component of the +1st-order diffracted light to form a first beat frequency signal with a frequency of fB - fA, the first receiver 301' will A beat frequency signal is transmitted to the signal processing system 4'; the second receiver 302' is used to receive the first polarized light component of the -1st-order diffracted light and the second polarized light component of the +1st-order diffracted light, and diffracted at the -1st-order After the first polarized light component of the light interferes with the second polarized light component of the +1st-order diffracted light to form
  • the one-dimensional measurement grating 5 moves along the grating vector direction, due to the Doppler frequency shift effect of the grating, the -1st order diffracted light undergoes a negative frequency shift - ⁇ f, and the +1st order diffracted light undergoes a positive frequency shift + ⁇ f, so the first receiving The frequency of the first beat signal output by the receiver 201' becomes f B -f A -2 ⁇ f, and the frequency of the second beat signal output by the second receiver 302' becomes f B -f A +2 ⁇ f.
  • the signal processing system 4' is used to receive the beat signal sent by the first receiver 301' and the second receiver 302', and perform differential calculation on the two beat signals, so as to realize the one-dimensional measurement grating 5' single diffraction 4 times Displacement measurement for optical subdivisions. Since the difference calculation is in the prior art, it is not repeated here.
  • the third embodiment shows the structure of another heterodyne one-dimensional grating measuring device, which corresponds to the heterodyne one-dimensional grating measuring device in the third embodiment, and the fourth embodiment provides a heterodyne one-dimensional grating measuring device using the third embodiment.
  • FIG. 10 shows a flow of a method for measuring a heterodyne one-dimensional grating according to Embodiment 4 of the present invention.
  • the method for measuring a heterodyne one-dimensional grating according to Embodiment 4 of the present invention includes the following steps:
  • the first polarized light and the second polarized light respectively enter the reading head, and after the reading head is turned, they are respectively incident on the surface of the one-dimensional measurement grating to generate +1 order diffracted light including the first polarized light component and the second polarized light component respectively And -1st-order diffracted light, +1st-order diffracted light and -1st-order diffracted light are respectively incident on the photoelectric receiving module through the reading head.
  • Step S2 specifically includes the following steps:
  • the first polarized light and the second polarized light are incident on the polarizing beam splitter prism of the reading head, the second polarized light is transmitted to the first 1/4 wave plate of the reading head through the polarizing beam splitting prism, and the first polarized light Reflected to the second 1/4 wave plate of the readhead;
  • the second polarized light is changed into right-handed polarized light through the first 1/4 wave plate and incident on the gyratory prism, and the second polarized light is retroreflected through the gyratory prism, so that the second polarized light passes through the first 1/4 wave plate.
  • the 4-wave plate becomes S-polarized light and then returns to the polarizing beam splitter prism; and the first polarized light is changed into left-handed polarized light through the second 1/4-wave plate, which is reflected by the reflective film and then goes through the second 1/4-wave plate to change again. It is P polarized light and returns to the polarizing beam splitter prism;
  • the -1st-order diffracted light and the +1st-order diffracted light are turned by the turning element of the reading head, so that the -1st-order diffracted light and the +1st-order diffracted light are parallel to each other and vertically incident on the third 1/4 of the reading head wave plate;
  • the first polarized light components of the +1st-order diffracted light and the -1st-order diffracted light are converted into S-polarized light through the third 1/4 wave plate, and incident to the polarization beam splitter prism vertically, and the +1st-order diffracted light is converted into S-polarized light. and the second polarized light component of the -1st-order diffracted light becomes P-polarized light, which is vertically incident on the polarizing beam splitter prism;
  • the first 1/4 wave plate is used to convert the first polarized light components of the +1st-order diffracted light and the -1st-order diffracted light into left-handed polarized light and incident on the gyroscopic prism, and the +1st-order diffracted light is diffracted by the gyroscopic prism
  • the light and the first polarized light component of the -1st-order diffracted light are reflected twice and returned to the first 1/4 wave plate to become P-polarized light, then incident on the polarization beam splitter prism again, and transmitted to the photoelectric receiver through the polarization beam splitter prism.
  • the second polarized light components of the +1st-order diffracted light and the -1st-order diffracted light are changed into right-handed polarized light through the second 1/4 wave plate, and are reflected by the reflective film and pass through the second 1/4 wave plate again After it becomes S-polarized light, it is incident on the polarization beam splitter prism, and reflected to the photoelectric receiving module by the polarization beam splitter prism.
  • the transmission optical path of the first polarized light component of the -1st-order diffracted light and the second polarized light component of the -1st-order diffracted light in the reading head are equal, and the first polarized light component of the +1st-order diffracted light is the same as the +1st-order diffracted light.
  • the effect of the equal transmission optical path of the second polarized light component of the diffracted light in the reading head is reflected in the following two aspects:
  • the first aspect ensure that the path difference when the measuring beam enters the photoelectric receiving module is a fixed value.
  • the second aspect when the ambient temperature of the heterodyne one-dimensional grating measuring device changes, the optical path difference of the measuring beam changes uniformly, which is not affected by the thermal expansion and contraction of the optical element of the reading head, and will not introduce measurement errors.
  • the photoelectric receiving module receives the +1-order diffracted light and the -1-order diffracted light; wherein, the interference formation frequency of the second polarized light component of the -1-order diffracted light and the first polarized light component of the +1-order diffracted light is f B ⁇
  • the first polarized light component of the -1st order diffracted light interferes with the second polarized light component of the +1st order diffracted light to form a beat frequency signal with a frequency of f B -f A.
  • the photoelectric receiving module includes a first receiver and a second receiver; wherein, the second polarized light component of the -1st order diffracted light and the first polarized light component of the +1st order diffracted light are received by the first receiver, and the generated frequency is The beat frequency signal of f B -f A is transmitted to the signal processing system; the first polarized light component of the -1st order diffracted light and the second polarized light component of the +1st order diffracted light are received by the second receiver, and the generated frequency is The beat frequency signal of f B -f A is transmitted to the signal processing system.
  • the one-dimensional measurement grating moves along the grating vector direction
  • the -1st order diffracted light undergoes a negative frequency shift - ⁇ f
  • the +1st order diffracted light undergoes a positive frequency shift + ⁇ f
  • the frequency of the beat signal output by the first receiver changes.
  • f B -f A -2 ⁇ f the frequency of the beat signal output by the second receiver becomes f B -f A +2 ⁇ f.
  • the +1st-order diffracted light and the -1st-order diffracted light generated by the diffraction of the one-dimensional measurement grating can be incident on the first right-angle prism and the second right-angle prism, respectively.
  • the +1st-order diffracted light and the -1st-order diffracted light are reflected twice by the two right-angle prisms respectively, and then incident on the surface of the one-dimensional measurement grating again at the diffraction exit angle, and the two new diffracted lights are vertically incident on the polarizing beam splitter prism.
  • the optical subdivision multiple is doubled, thereby improving the measurement resolution.
  • the signal processing system respectively performs differential calculation on the two beat frequency signals, so as to realize the displacement measurement of the one-dimensional measurement grating single diffraction 4 times optical subdivision.
  • the signal processing system performs differential calculation on the first beat frequency signal output by the first receiver and the second beat frequency signal output by the second receiver, so as to realize the displacement measurement of the one-dimensional measurement grating single diffraction 4 times optical subdivision. Since the difference calculation is in the prior art, it is not repeated here.
  • FIG. 11 shows the structure of a heterodyne two-dimensional grating measurement device according to Embodiment 5 of the present invention.
  • the heterodyne two-dimensional grating measurement device includes: a light source 1, a reading head, a photoelectric receiving module, and a signal processing system 4; wherein, the light source 1 is used to generate two overlapping beams, polarization Orthogonal linearly polarized light with a fixed frequency difference, respectively the first polarized light and the second polarized light, the first polarized light is S-polarized light, the frequency is f A , the second polarized light is P-polarized light, the frequency is f B , the light source 1 can be a dual-frequency laser 1 or two lasers with a fixed frequency difference; the reading head is used to inject two linearly polarized lights into the surface of the moving two-dimensional measuring grating 5, and the two linearly polarized lights are After the surface of the two-dimensional measurement grating 5 is diffracted, the ⁇ 1st-order diffracted light of the first dimension and the ⁇ 1st-
  • the photoelectric receiving module is used to receive the ⁇ 1st-order diffracted light in the first dimension and the ⁇ 1st-order diffracted light in the second dimension, and generate four-channel beat frequency signals to achieve 4x optical Subdivided, the photoelectric receiving module includes a first receiver 301, a second receiver 302, a third receiver 303 and a fourth receiver 304, the first receiver 301 and the second receiver 302 are used to receive the first dimension ⁇ 1
  • the third and fourth receivers 303 and 304 are used to receive the ⁇ 1st-order diffracted light in the second dimension, generate two beat signals and send them to the signal processing system.
  • the signal processing system 4 is used to receive the beat signal sent by the first receiver 301, the second receiver 302, the third receiver 303 and the fourth receiver 304, and to receive the first receiver 301 and the second receiver 301 and the second receiver 304.
  • the beat frequency signal sent by the receiver 302 is subjected to differential calculation to realize the displacement measurement of the single diffraction 4 times optical subdivision of the first dimension of the two-dimensional measurement grating 5, and the beat frequency signal sent by the third receiver 303 and the fourth receiver 304 is measured.
  • the differential calculation is performed to realize the displacement measurement of the single diffraction 4 times optical subdivision of the second dimension of the two-dimensional measurement grating 5 .
  • the reading head includes a polarization beam splitter prism 201, a first 1/4 wave plate 202, a second 1/4 wave plate 203, a third 1/4 wave plate 204, a gyroscopic prism 205 and a turning element 206; wherein, the polarization beam splitter prism 201 uses Reflect the S-polarized light and transmit the P-polarized light; the first 1/4 wave plate 202 is arranged on the transmission light path of the polarizing beam splitting prism 201, and the second 1/4 wave plate 203 is arranged on the reflected light of the polarizing beam splitting prism 201 On the way, the surface of the second 1/4 wave plate 203 is coated with a reflective film to realize the reflection of the laser; The beam splitting prism 201 is on the transmission light path in the other direction; the rotary prism 205 is arranged on the transmission light path of the first 1/4 wave plate 202 to realize the rotation of the laser light; the turning element 206 is arranged on the diffraction light path of the two-dimensional measurement grating 5, Used
  • FIG. 12 shows the principle of optical path transmission before beam diffraction according to Embodiment 5 of the present invention.
  • the optical transmission path is as follows: the first polarized light emitted by the light source 1 is incident on the polarizing beam splitting prism 201 , and the first polarized light The polarized light is reflected by the polarizing beam splitting prism 201 to the second 1/4 wave plate 203 to become left-handed polarized light, and the first polarized light is reflected back to the second 1 through the reflective film plated on the second 1/4 wave plate 203 /4 wave plate 203 , the second 1/4 wave plate 203 changes the first polarized light into P polarized light and returns to the polarizing beam splitting prism 201 .
  • the second polarized light emitted by the light source 1 is incident on the polarizing beam splitter prism 201 , and the second polarized light is transmitted through the polarizing beam splitting prism 201 to the first 1/4 wave plate 202 to become right-handed polarized light and then enters the gyroscopic prism 205 , and the gyroscopic prism 205
  • the second polarized light is retroreflected to the first 1/4 wave plate 202 , and the first 1/4 wave plate 202 changes the second polarized light to S-polarized light and returns to the polarization beam splitting prism 201 .
  • the polarizing beam splitter prism 201 transmits the first polarized light (P polarized light) and reflects the second polarized light (S polarized light), so that the first polarized light and the second polarized light are combined and incident on the third 1/4 wave Plate 204, the third 1/4 wave plate 204 changes the first polarized light into right-handed polarized light and then is incident on the surface of the two-dimensional measurement grating 5, and changes the second polarized light into left-handed polarized light and is incident on the two-dimensional measurement grating 5 surface.
  • the first polarized light is diffracted by the two-dimensional measurement grating 5 to generate the first-dimension -1-order diffracted light and the first-dimension +1-order diffracted light
  • the second polarized light is diffracted by the two-dimensional measurement grating 5 to generate the second dimension -1-order diffracted light Diffracted light and second dimension +1st order diffracted light.
  • the first dimension and the second dimension are dimension divisions according to the direction of the lines of the two-dimensional measurement grating, that is, two directions of the lines of the surface of the two-dimensional measurement grating.
  • the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light all contain a first polarized light component and a second polarized light component.
  • the first polarized light component in the +1st order diffracted light in the first dimension and the second polarized light component in the first dimension -1st order diffracted light generate a first dimension first beat signal.
  • the first polarized light component in the first dimension -1st order diffracted light and the second polarized light component in the first dimension +1st order diffracted light generate a first dimension second beat frequency signal.
  • the first polarized light component in the +1st-order diffracted light in the second dimension and the second polarized light component in the -1st-order diffracted light in the second dimension generate a second-dimension first beat signal.
  • the first polarized light component in the second dimension -1st order diffracted light and the second polarized light component in the second dimension +1st order diffracted light generate a second dimension second beat signal.
  • FIG. 13-16 show the first-dimension first beat signal, the first-dimension second-beat signal, the second-dimension first-beat signal, and the second-dimension second-beat signal according to Embodiment 5 of the present invention the principle of production.
  • the turning element 206 As shown in FIG. 13 to FIG. 16 , after the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light are turned by the turning element 206 , which are parallel to each other and are perpendicular to the third 1/4 wave plate 204 .
  • the third quarter wave plate 204 converts the first polarized light among the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light
  • the component becomes S-polarized light, which is vertically incident on the polarized beam splitter prism 2, and the first dimension -1st order diffracted light, the first dimension +1st order diffracted light, the second dimension -1st order diffracted light, the second dimension +1
  • the second polarized light component of the first-order diffracted light becomes P-polarized light, and is vertically incident on the polarization beam splitting prism 201 .
  • the polarizing beam splitter prism 201 reflects the first polarized light component in the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light to the polarized light.
  • the polarized light component is transmitted to the second 1/4 wave plate 203 .
  • the second quarter wave plate 203 converts the second polarized light among the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light After the component becomes right-handed polarized light, it is reflected by the reflective film, and then becomes S-polarized light through the second 1/4 wave plate 203 again, and then enters the polarization beam splitter prism 201, and is reflected by the polarization beam splitter prism 201.
  • the receiver 301 , the second receiver 302 , the third receiver 303 , and the fourth receiver 304 are examples of the second quarter wave plate 203 .
  • the first 1/4 wave plate converts the first polarized light component in the first dimension -1st order diffracted light, the first dimension +1st order diffracted light, the second dimension -1st order diffracted light, and the second dimension +1st order diffracted light It becomes left-handed polarized light and is incident on the gyroscopic prism 205 again, and the gyroscopic prism 205 reflects twice the first polarized light component in the first dimension + 1st order diffracted light along the first dimension - the first polarization in the first order diffracted light The incident light path of the light component exits back to the first quarter wave plate 202, and the first polarized light component in the -1st order diffracted light in the first dimension is reflected twice along the first dimension +1st order diffracted light.
  • the incident light path of the polarized light component exits back to the first quarter wave plate 202, and the first polarized light component in the second dimension +1st order diffracted light is reflected twice along the second dimension -1st order diffracted light.
  • the incident light path of the first polarized light component exits back to the first quarter wave plate 202, and the first polarized light component in the second dimension -1st order diffracted light is reflected twice along the second dimension +1st order diffracted light.
  • the incident light path of the first polarized light component exits back to the first quarter wave plate 202; the first dimension -1st order diffracted light, the first dimension +1st order diffracted light, the second dimension -1st order diffracted light, the The first polarized light component in the two-dimensional +1st-order diffracted light passes through the first 1/4 wave plate 201 again to become P-polarized light, and then enters the polarization beam splitter prism 201 again.
  • first polarized light component and the second polarized light component received by the first receiver 301, the second receiver 302, the third receiver 303, and the fourth receiver 304 respectively pass through the gyratory prism 205 twice, respectively, It transmits the same optical path in the readhead and serves two functions:
  • the first aspect ensure that the path difference when the measurement signal enters the first receiver 301 , the second receiver 302 , the third receiver 303 , and the fourth receiver 304 is a constant value.
  • the optical path difference of the measuring beam changes uniformly, which is not affected by the thermal expansion and contraction of the optical element of the reading head, and will not introduce measurement errors.
  • the first receiver 301 is configured to receive the first polarized light component in the +1st order diffracted light in the first dimension and the second polarized light component in the first dimension ⁇ 1st order diffracted light, and generate a frequency of (fB ⁇ fA ) ) of the first dimension and the first beat frequency signal, which is transmitted to the signal processing system 4 .
  • the second receiver 302 is configured to receive the first polarized light component in the -1st order diffracted light in the first dimension and the second polarized light component in the +1st order diffracted light in the first dimension, and generate a frequency of (f B -f A ) and the second beat frequency signal of the first dimension is transmitted to the signal processing system 4 .
  • the third receiver 303 is configured to receive the first polarized light component in the +1st order diffracted light in the second dimension and the second polarized light component in the second dimension ⁇ 1st order diffracted light, and generate a frequency of (f B ⁇ f A ) of the second dimension of the first beat frequency signal, which is transmitted to the signal processing system 4 .
  • the fourth receiver 304 is used to receive the first polarized light component in the second dimension-1st order diffracted light and the second polarized light component in the second dimension+1st order diffracted light, and the generation frequency is (f B -f A ) and the second beat frequency signal of the second dimension is transmitted to the signal processing system 4 .
  • the two-dimensional measurement grating 5 moves along the grating vector direction of the first dimension, due to the Doppler frequency shift effect of the grating, the -1st order diffracted light in the first dimension has a negative frequency shift - ⁇ f, and the +1st order diffracted light in the first dimension has a positive frequency shift Frequency shift + ⁇ f, the frequency of the first-dimension first beat signal output by the first receiver 201 becomes (f B -f A -2 ⁇ f), and the frequency of the first-dimension second beat signal output by the second receiver 302 changes is (f B - f A + 2 ⁇ f).
  • the two-dimensional measurement grating 5 moves along the grating vector direction of the second dimension, due to the Doppler frequency shift effect of the grating, the -1st order diffracted light in the second dimension has a negative frequency shift - ⁇ f, and the +1st order diffracted light in the second dimension has a positive frequency shift Frequency shift + ⁇ f, the frequency of the second-dimensional first beat signal output by the third receiver 303 becomes (f B -f A -2 ⁇ f), and the frequency of the second-dimensional second beat signal output by the fourth receiver 304 changes is (f B - f A + 2 ⁇ f).
  • the signal processing system 4 is used to perform a differential calculation on the first-dimension first beat signal output by the first receiver 301 and the first-dimension second beat signal output by the second receiver 302 to realize the first-dimension single diffraction 4
  • the fifth embodiment shows the structure of a heterodyne two-dimensional grating measuring device, which corresponds to the heterodyne two-dimensional grating measuring device in the fifth embodiment.
  • the sixth embodiment provides a heterodyne two-dimensional grating using the fifth embodiment. A method for measuring grating displacement by a measuring device.
  • FIG. 17 shows a flow of a method for measuring a heterodyne two-dimensional grating according to Embodiment 6 of the present invention.
  • the method for measuring a heterodyne two-dimensional grating includes the following steps:
  • the light source can be a dual-frequency laser 1 or two lasers with a fixed frequency difference, and two lasers with a fixed frequency difference, which are the first polarized light and the second polarized light, the first polarized light is S polarized light, and the frequency is f A , the second polarized light is P-polarized light, and the frequency is f B .
  • the first polarized light and the second polarized light enter the reading head respectively, and after being reflected and transmitted by the reading head, they are respectively incident on the surface of the two-dimensional measurement grating to generate the first-dimension ⁇ 1-order diffracted light and the second-dimension ⁇ 1-order diffracted light , the ⁇ 1st-order diffracted light of the first dimension and the ⁇ 1st-order diffracted light of the second dimension are respectively incident on the photoelectric receiving module through the reading head.
  • Step S2 specifically includes the following steps:
  • the first polarized light is reflected to the second 1/4 wave plate by the polarizing beam splitter, and after the first polarized light is changed into left-handed polarized light, the reflection is performed again after the second 1/4 wave plate becomes P-polarized light, Back to the polarizing beam splitting prism; and, the second polarized light is transmitted to the first 1/4 wave plate through the polarizing beam splitting prism, and is incident on the gyroscopic prism after the second polarized light is changed to right-handed polarized light, and the second polarized light is polarized by the gyroscopic prism.
  • the light is retroreflected, and when the second polarized light passes through the first 1/4 wave plate again to become S-polarized light, it returns to the polarizing beam splitter prism.
  • the polarizing beam splitting prism transmits the first polarized light and reflects the second polarized light, so that the first polarized light and the second polarized light are combined into a third 1/4 wave plate, and the third 1/4 wave plate will
  • the first polarized light is transformed into right-handed polarized light and then vertically incident on the surface of the two-dimensional measurement grating
  • the second polarized light is transformed into left-handed polarized light and then vertically incident on the surface of the two-dimensional measurement grating.
  • the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light respectively contain a first polarized light component and a second polarized light component.
  • the third 1/4 wave plate converts the first polarization in the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light
  • the light component becomes S-polarized light, it is vertically incident on the polarizing beam splitter prism, and the first dimension -1st order diffracted light, the first dimension +1st order diffracted light, the second dimension -1st order diffracted light, the second dimension +1st order diffracted light
  • the second polarized light component in the diffracted light becomes P-polarized light and then vertically enters the polarizing beam splitter prism.
  • the polarization beam splitter prism reflects the first polarized light component in the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light to the first 1/4 wave plate, and the second dimension of the -1st order diffracted light, the first dimension +1st order diffracted light, the second dimension -1st order diffracted light, and the second dimension +1st order diffracted light
  • the polarized light component is transmitted to the second 1/4 wave plate.
  • the second 1/4 wave plate polarizes the first dimension-1st order diffracted light, the first dimension+1st order diffracted light, the second dimension-1st order diffracted light, and the second dimension+1st order diffracted light
  • the light component becomes right-handed polarized light, it is reflected, and then passes through the second 1/4 wave plate to become S-polarized light, then enters the polarization beam splitter prism, and is reflected to the photoelectric receiving module through the polarization beam splitter prism, and the first 1
  • the /4 wave plate changes the first polarized light component in the first dimension -1st order diffracted light, the first dimension +1st order diffracted light, the second dimension -1st order diffracted light, and the second dimension +1st order diffracted light into left-handed
  • the polarized light is incident on the gyroscopic prism again, and the gyroscopic prism is respectively responsible for the diffracted light of the first dimension +1st order, the first dimension
  • the photoelectric receiving module generates corresponding beat frequency signals according to the ⁇ 1st-order diffracted light of the first dimension and the ⁇ 1st-order diffracted light of the second dimension, and sends them to the signal processing system.
  • the photoelectric receiving module includes a first receiver, a second receiver, a third receiver and a fourth receiver; wherein, the first receiver is used for receiving the first polarized light component and the first polarized light component in the +1st order diffracted light in the first dimension The second polarized light component in the diffracted light of the dimension-1st order, and generates a first-dimension first beat frequency signal with a frequency of (f B -f A ), and sends it to the signal processing system; the second receiver is used for receiving the first dimension The first polarized light component in the -1st-order diffracted light and the second polarized light component in the +1st-order diffracted light in the first dimension, and a first-dimension second beat signal with a frequency of (f B -f A ) is generated, Send to the signal processing system; the third receiver is used to receive the first polarized light component in the second dimension +1st order diffracted light and the second polarized light component in the second dimension -1st order
  • the -1st-order diffracted light in the first dimension has a negative frequency shift - ⁇ f
  • the +1st-order diffracted light in the first dimension has a positive frequency shift + ⁇ f
  • the first receiving The frequency of the first-dimension first beat signal output by the receiver becomes f B -f A -2 ⁇ f
  • the frequency of the first-dimension second beat signal output by the second receiver becomes f B -f A +2 ⁇ f
  • the third receiver The frequency of the output second-dimensional first beat signal becomes f B -f A -2 ⁇ f
  • the frequency of the second-dimensional second beat signal output by the fourth receiver becomes f B
  • the signal processing system respectively performs differential calculation on the beat frequency signals generated by the ⁇ 1st order diffracted light in the first dimension and performs differential calculation on the beat frequency signals generated by the ⁇ 1st order diffracted light in the second dimension, so as to realize the first dimension of the two-dimensional measurement grating and displacement measurements of single diffraction 4x optical subdivisions in the second dimension.
  • the signal processing system performs differential calculation on the first-dimension first beat frequency signal output by the first receiver and the first-dimension second beat frequency signal output by the second receiver, so as to realize the first dimension of the two-dimensional measurement grating.
  • the displacement measurement of the single diffraction 4 times optical subdivision, the difference calculation is performed on the second-dimensional first beat signal output by the third receiver and the second-dimensional second beat signal output by the fourth receiver to achieve a two-dimensional Displacement measurement of single diffraction 4x optical subdivision in the second dimension of the grating.

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Abstract

一种外差一维光栅测量装置，包括光源（1）、读数头（2）、光电接收模块和信号处理系统（4），光源（1）用于产生两束重合、偏振正交且具有固定频差的偏振光；读数头（2）用于接收两束偏振光，并分别入射到移动的测量光栅（5）的表面生成分别包括第一偏振光分量与第二偏振光分量的+1级衍射光和-1级衍射光，+1级衍射光和-1级衍射光分别经读数头（2）入射到光电接收模块；光电接收模块用于接收+1级衍射光的第一偏振光分量和第二偏振光分量及-1级衍射光的第一偏振光分量和第二偏振光分量形成两路拍频信号；信号处理系统（4）用于对两路拍频信号进行差分计算，实现测量光栅单次衍射4倍光学细分的位移测量。可以避免光栅面形精度和光栅姿态误差对测量精度的影响。还提供了一种外差一维光栅测量方法，一种外差二维光栅测量装置以及一种外差二维光栅测量方法。

Description

外差光栅测量装置及测量方法
本申请要求于2020年9月11日提交至中国专利局、申请号为202010953637.8、发明名称为“外差光栅位移测量方法”,申请号为202010953635.9、发明名称为“外差光栅位移测量光学系统”,申请号为202010953595.8、发明名称为“外差光栅位移测量装置”,申请号为202010953663.0、发明名称为“外差二维光栅位移测量系统及测量方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及精密位移测量技术领域，特别涉及一种基于单次衍射实现4倍光学细分的外差光栅测量装置及测量方法。
背景技术
光栅位移测量系统以光栅作为量尺，以光栅的栅距为测量基准，相比于激光测量技术，光栅测量对环境变化的敏感度低，而且光束入射到光栅上会覆盖很多刻槽，起到平均的作用。光栅位移测量系统中读数头的结构简单紧凑，光栅和读数头之间的距离很小，并且不会随着待测距离的增加而增加，可以大幅度地降低环境对系统测量精度的影响和测量成本。随着光栅制造水平的提高，光栅位移测量系统的测量精度和测量分辨力也逐渐提高，应用范围也越来越广。
光栅位移测量技术的测量分辨力与光栅的周期直接相关，基于衍射光干涉原理的位移测量技术，采用高刻线密度的衍射光栅实现高分辨力、高精度的位移测量，光学细分和电子细分是进一步提高测量分辨力的主要途径，相比于电子细分，光学细分有更高的可靠性。传统光栅位移测量系统采用单次衍射实现2倍光学细分，为进一步提高光学细分，现有技术多采用二次衍射原理实现4倍光学细分或多次衍射实现更高倍数的光学细分，但是无论是二次衍射还是多次衍射都会使测量系统的光学结构变得更加复杂，并且多次衍射利用光栅不同位置的衍射光，光栅面形精度及光栅与读数头之间的姿态误 差会对测量精度造成很大的影响。
发明内容
本发明旨在克服现有技术存在的缺陷，采用以下技术方案：
本发明提供一种外差一维光栅测量装置，包括光源，光源用于产生两束重合、偏振正交且具有固定频差的线偏振光，分别为频率为f A的第一偏振光和频率为f B的第二偏振光，第一偏振光为S偏振光，第二偏振光为P偏振光；其特征在于，还包括读数头、光电接收模块和信号处理系统；其中，读数头用于接收第一偏振光和第二偏振光，并分别入射到移动的一维测量光栅的表面产生分别包括第一偏振光分量与第二偏振光分量的+1级衍射光和-1级衍射光，+1级衍射光和-1级衍射光分别经读数头入射到光电接收模块；光电接收模块用于接收+1级衍射光和-1级衍射光形成两路拍频信号；其中，一路为-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量干涉形成频率为f B-f A的拍频信号，另一路为-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量干涉形成频率为f B-f A的拍频信号；信号处理系统用于对两路拍频信号进行差分计算，实现一维测量光栅单次衍射4倍光学细分的位移测量。
优选地，读数头包括反射镜、偏振分束棱镜、第一1/4波片、第二1/4波片、镀有反射膜的补偿镜、回转棱镜和转折元件；其中，反射镜设置在光源的出射光路上，用于将第一偏振光和第二偏振光垂直反射至一维测量光栅的表面，产生+1级衍射光和-1级衍射光；转折元件设置在一维测量光栅的衍射光路上，用于对+1级衍射光和-1级衍射光进行转折，使+1级衍射光和-1级衍射光相互平行并垂直入射至偏振分束棱镜；偏振分束棱镜设置在转折元件的透射光路上，用于将+1级衍射光和-1级衍射光的第一偏振光分量分别反射至第一1/4波片，以及将+1级衍射光和-1级衍射光的第二偏振光分量分别透射至第二1/4波片；第一1/4波片设置在偏振分束棱镜的反射光路上，用于将+1级衍射光和-1级衍射光的第一偏振光分量分别变为左旋偏振光并入射至回转棱镜；回转棱镜设置在第一1/4波片的透射光路上，用于对+1级衍射光和-1级衍射光的第一偏振光分量分别进行两次反射，使+1级衍射光和-1级衍射光的第一偏振光分量经过第一1/4波片变为P偏振光后入射至偏振分束棱镜；第二1/4波片设置在偏振分束棱镜的透射光路上，用于将+1级衍射光和-1级衍射光的第二偏振光分量分别变为 右旋偏振光并入射至补偿镜；补偿镜设置在第二1/4波片的透射光路上，用于对+1级衍射光和-1级衍射光的第二偏振光分量进行反射，使+1级衍射光和-1级衍射光的第二偏振光分量经第二1/4波片变为S偏振光后入射至偏振分束棱镜；偏振分束棱镜还用于将变为P偏振光的+1级衍射光和-1级衍射光的第一偏振光分量透射至光电接收模块，以及将变为S偏振光的+1级衍射光和-1级衍射光的第二偏振光分量反射至光电接收模块。
优选地，光电接收模块包括第一接收器和第二接收器；其中，第一接收器用于接收-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量，并生成频率为f B-f A的拍频信号，传输到信号处理系统；第二接收器用于接收-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量，并生成频率为f B-f A的拍频信号，传输到信号处理系统。
优选地，当一维测量光栅沿光栅矢量方向移动时，-1级衍射光发生负向频移-Δf，+1级衍射光发生正向频移+Δf，第一接收器输出的拍频信号的频率变为f B-f A-2Δf，第二接收器输出的拍频信号的频率变为f B-f A+2Δf。
优选地，补偿镜的厚度等于回转棱镜的1/2长度，用于补偿+1级衍射光和-1级衍射光的第二偏振光分量的传输光程，使+1级衍射光和-1级衍射光的第二偏振光分量的传输光程与+1级衍射光和-1级衍射光的第一偏振光分量的传输光程相等。
优选地，读数头还包括分别设置一维测量光栅衍射光路上的第一直角棱镜和第二直角棱镜，第一直角棱镜和第二直角棱镜分别对+1级衍射光和-1级衍射光进行两次反射，以衍射出射角度再次入射到一维测量光栅的表面，两束新的衍射光垂直入射到偏振分束棱镜。
优选地，读数头包括偏振分束棱镜、第一1/4波片、镀有反射膜的第二1/4波片和回转棱镜；其中，偏振分束棱镜设置在光源的出射光路上，用于接收第一偏振光和第二偏振光，将第二偏振光透射至第一1/4波片，将第一偏振光反射至第二1/4波片；第一1/4波片设置在偏振分束棱镜的透射光路上，用于将第二偏振光变为右旋偏振光并入射到回转棱镜；回转棱镜设置在第一1/4波片的透射光路上，用于对第二偏振光进行回射，使第二偏振光经过第一1/4波片变为S偏振光后回到偏振分束棱镜；第二1/4波片设置在偏振分束棱镜的反射光路上，用于将第一偏振光变为左旋偏振光，经反射膜反射再次经过第二1/4波片变为P 偏振光后回到偏振分束棱镜；偏振分束棱镜还用于对变为P偏振光的第一偏振光进行透射，对变为S偏振光的第二偏振光进行反射，使第一偏振光与第二偏振光合束后入射至一维测量光栅的表面，衍射产生-1级衍射光和+1级衍射光。
优选地，读数头还包括转折元件和第三1/4波片；其中，转折元件设置在一维测量光栅的衍射光路上，用于对-1级衍射光和+1级衍射光进行转折，使-1级衍射光和+1级衍射光相互平行并垂直入射至第三1/4波片；第三1/4波片设置在转折元件的透射光路上，用于将+1级衍射光和-1级衍射光的第一偏振光分量变为S偏振光，垂直入射到偏振分束棱镜，以及将+1级衍射光和-1级衍射光的第二偏振光分量变为P偏振光，垂直入射到偏振分束棱镜；偏振分束棱镜用于将+1级衍射光和-1级衍射光的第一偏振光分量反射至第一1/4波片，以及将+1级衍射光和-1级衍射光的第二偏振光分量透射至第二1/4波片；第一1/4波片用于将+1级衍射光和-1级衍射光的第一偏振光分量变为左旋偏振光并入射到回转棱镜；回转棱镜用于对+1级衍射光和-1级衍射光的第一偏振光分量进行两次反射回到第一1/4波片变为P偏振光后，再次入射至偏振分束棱镜，经偏振分束棱镜透射至光电接收模块；第二1/4波片用于将+1级衍射光和-1级衍射光的第二偏振光分量变为右旋偏振光，并经反射膜反射再次经过第二1/4波片变为S偏振光后入射至偏振分束棱镜，经偏振分束棱镜反射至光电接收模块。
优选地，光电接收模块包括第一接收器和第二接收器；其中，第一接收器用于接收+1级衍射光的第一偏振光分量和-1级衍射光的第二偏振光分量，并生成频率为f B-f A的拍频信号，传输到信号处理系统；第二接收器用于接收-1级衍射光中的第一偏振光分量和+1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，传输到信号处理系统。
优选地，当一维测量光栅沿光栅矢量方向移动时，-1级衍射光发生负向频移-Δf，+1级衍射光发生正向频移+Δf，第一接收器输出的拍频信号的频率变为f B-f A-2Δf，第二接收器输出的拍频信号的频率变为f B-f A+2Δf。
优选地，-1级衍射光的第一偏振光分量与-1级衍射光的第二偏振光分量的传输光程相等，+1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量的传输光程相等。
优选地，读数头还包括分别设置一维测量光栅衍射光路上的第一直角棱镜和第二直角棱镜，第一直角棱镜和第二直角棱镜分别对+1级衍射光和-1级衍射 光进行两次反射，以衍射出射角度再次入射到一维测量光栅的表面，两束新的衍射光垂直入射到偏振分束棱镜。
本发明还提供一种外差一维光栅测量方法，包括如下步骤：
S1、通过光源产生两束重合、偏振正交且具有固定频差的线偏振光，分别为频率为f A的第一偏振光和频率为f B的第二偏振光，第一偏振光为S偏振光，第二偏振光为P偏振光；
S2、第一偏振光和第二偏振光分别进入读数头，经读数头转折后分别入射到一维测量光栅的表面产生分别包括第一偏振光分量与第二偏振光分量的+1级衍射光和-1级衍射光，+1级衍射光和-1级衍射光再经读数头分别入射到光电接收模块；
S3、通过光电接收模块接收+1级衍射光和-1级衍射光；其中，-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量干涉形成频率为f B-f A的拍频信号，-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量干涉形成频率为f B-f A的拍频信号；
S4、通过信号处理系统分别对两路拍频信号进行差分计算，实现一维测量光栅单次衍射4倍光学细分的位移测量。
优选地，步骤S2具体包括如下步骤：
S201、通过读数头的反射镜将第一偏振光和第二偏振光垂直反射至一维测量光栅的表面，产生+1级衍射光和-1级衍射光；
S202、通过读数头的转折元件对+1级衍射光和-1级衍射光进行转折，使+1级衍射光和-1级衍射光相互平行并垂直入射至读数头的偏振分束棱镜；
S203、通过偏振分束棱镜将+1级衍射光和-1级衍射光的第一偏振光分量分别反射至读数头的第一1/4波片，以及将+1级衍射光和-1级衍射光的第二偏振光分量分别透射至读数头的第二1/4波片；
S204、通过第一1/4波片将+1级衍射光和-1级衍射光的第一偏振光分量分别变为左旋偏振光并入射至读数头的回转棱镜，再通过回转棱镜对+1级衍射光和-1级衍射光的第一偏振光分量分别进行两次反射，使+1级衍射光和-1级衍射光的第一偏振光分量经第一1/4波片变为P偏振光后入射至偏振分束棱镜；以及通过第二1/4波片将+1级衍射光和-1级衍射光的第二偏振光分量分别变为右旋偏振光并入射至读数头的补偿镜，再通过补偿镜对+1级衍射光和-1级衍射光的 第二偏振光分量进行反射，使+1级衍射光和-1级衍射光的第二偏振光分量经第二1/4波片变为S偏振光后入射至偏振分束棱镜；
S205、通过偏振分束棱镜将变为P偏振光的+1级衍射光和-1级衍射光的第一偏振光分量透射至光电接收模块，以及将变为S偏振光的+1级衍射光和-1级衍射光的第二偏振光分量反射至光电接收模块。
优选地，补偿镜的厚度等于回转棱镜的1/2长度，用于补偿+1级衍射光和-1级衍射光的第二偏振光分量的传输光程，使+1级衍射光和-1级衍射光的第二偏振光分量的传输光程与+1级衍射光和-1级衍射光的第一偏振光分量的传输光程相等。
优选地，步骤S2具体包括如下步骤：
S201`、第一偏振光和第二偏振光入射至读数头的偏振分束棱镜，通过偏振分束棱镜将第二偏振光透射至读数头的第一1/4波片，将第一偏振光反射至读数头的第二1/4波片；
S202`、通过第一1/4波片将第二偏振光变为右旋偏振光并入射到回转棱镜，通过回转棱镜对第二偏振光进行回射，使第二偏振光经过第一1/4波片变为S偏振光后回到偏振分束棱镜；以及通过第二1/4波片将第一偏振光变为左旋偏振光，经反射膜反射再次经过第二1/4波片变为P偏振光后回到偏振分束棱镜；
S203`、通过偏振分束棱镜对变为P偏振光的第一偏振光进行透射，对变为S偏振光的第二偏振光进行反射，使第一偏振光与第二偏振光合束后入射至一维测量光栅的表面，衍射产生-1级衍射光和+1级衍射光；
S204`、通过读数头的转折元件对-1级衍射光和+1级衍射光进行转折，使-1级衍射光和+1级衍射光相互平行并垂直入射至读数头的第三1/4波片；
S205`、通过第三1/4波片将+1级衍射光和-1级衍射光的第一偏振光分量变为S偏振光，垂直入射到偏振分束棱镜，以及将+1级衍射光和-1级衍射光的第二偏振光分量变为P偏振光，垂直入射到偏振分束棱镜；
S206`、通过偏振分束棱镜将+1级衍射光和-1级衍射光的第一偏振光分量反射至第一1/4波片，以及将+1级衍射光和-1级衍射光的第二偏振光分量透射至第二1/4波片；
S207`、通过第一1/4波片用于将+1级衍射光和-1级衍射光的第一偏振光分量变为左旋偏振光并入射到回转棱镜，经回转棱镜对+1级衍射光和-1级衍射光 的第一偏振光分量进行两次反射回到第一1/4波片变为P偏振光后，再次入射至偏振分束棱镜，经偏振分束棱镜透射至光电接收模块；以及通过第二1/4波片将+1级衍射光和-1级衍射光的第二偏振光分量变为右旋偏振光，并经反射膜反射再次经过第二1/4波片变为S偏振光后入射至偏振分束棱镜，经偏振分束棱镜反射至光电接收模块。
优选地，-1级衍射光的第一偏振光分量与-1级衍射光的第二偏振光分量的传输光程相等，+1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量的传输光程相等。
优选地，光电接收模块包括第一接收器和第二接收器；其中，通过第一接收器接收-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量，并生成频率为f B-f A的拍频信号，传输到信号处理系统；通过第二接收器接收-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量，并生成频率为f B-f A的拍频信号，传输到信号处理系统。
优选地，当一维测量光栅沿光栅矢量方向移动时，-1级衍射光发生负向频移-Δf，+1级衍射光发生正向频移+Δf，第一接收器输出的拍频信号的频率变为f B-f A-2Δf，第二接收器输出的拍频信号的频率变为f B-f A+2Δf。
优选地，经一维测量光栅衍射产生的+1级衍射光和-1级衍射光分别入射至第一直角棱镜和第二直角棱镜，通过第一直角棱镜和第二直角棱镜分别对+1级衍射光和-1级衍射光进行两次反射，以衍射出射角度再次入射到一维测量光栅的表面，两束新的衍射光垂直入射到偏振分束棱镜。
本发明提供一种外差二维光栅测量装置，包括光源，光源用于产生两束重合、偏振正交且具有固定频差的线偏振光，分别为第一偏振光和第二偏振光；其特征在于，还包括读数头、光电接收模块和信号处理系统；其中，读数头用于接收第一偏振光和第二偏振光，并分别入射到移动的二维测量光栅的表面生成第一维度±1级衍射光和第二维度±1级衍射光，第一维度±1级衍射光和第二维度±1级衍射光再经读数头分别入射到光电接收模块；光电接收模块用于分别根据第一维度±1级衍射光和第二维度±1级衍射光生成对应的拍频信号，发送至信号处理系统；信号处理系统用于对第一维度±1级衍射光生成的拍频信号进行差分计算和对第二维度±1级衍射光的拍频信号进行差分计算，实现二维测量光栅第一维度和第二维度的单次衍射4倍光学细分的位移测量。
优选地，第一偏振光是频率为f A的S偏振光，第二偏振光为频率为f B的P偏振光；以及，读数头包括偏振分光棱镜、第一1/4波片、镀有反射膜的第二1/4波片、第三1/4波片、回转棱镜和转折元件；其中，偏振分光棱镜用于接收第一偏振光和第二偏振光，并将第二偏振光透射到第一1/4波片，将第一偏振光反射到第二1/4波片；第一1/4波片设置在偏振分光棱镜的透射光路上，用于将第二偏振光变为右旋偏振光后入射到回转棱镜；回转棱镜设置在第一1/4波片的透射光路上，用于对第二偏振光进行回射，当第二偏振光再次经过第一1/4波片变为S偏振光后，回到偏振分光棱镜；第二1/4波片设置在偏振分光棱镜的反射光路上，用于将第一偏振光变为左旋偏振光后进行反射，再次经过第二1/4波片变为P偏振光后，回到偏振分光棱镜；偏振分光棱镜还用于对第一偏振光进行透射，对第二偏振光反射，使第一偏振光与第二偏振光合束后入射到第三1/4波片；第三1/4波片设置在偏振分光棱镜对第一偏振光进行透射的光路上，用于将第一偏振光变为右旋偏振光后垂直入射到二维测量光栅的表面，将第二偏振光变为左旋偏振光后垂直入射到二维测量光栅的表面，第一偏振光与第二偏振光分别衍射生成第一维度±1级衍射光和第二维度±1级衍射光。
优选地，第一维度±1级衍射光包括第一维度-1级衍射光和第一维度+1级衍射光，第二维度±1级衍射光包括第二维度-1级衍射光和第二维度+1级衍射光，第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光分别包含第一偏振光分量和第二偏振光分量。
优选地，读数头还包括设置在二维测量光栅衍射光路上的转折元件，用于对第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光进行转折，使第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光相互平行并垂直入射到第三1/4波片；第三1/4波片用于将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量变为S偏振光并垂直入射到偏振分束棱镜，以及将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量变为P偏振光并垂直入射到偏振分束棱镜；偏振分束棱镜用于将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量反射到第一1/4波片，以及将第一维度-1级衍射光、第一维度 +1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量透射到第二1/4波片；第一1/4波片用于将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量变为左旋偏振光并再次入射到回转棱镜；回转棱镜用于分别对第一维度+1级衍射光、第一维度-1级衍射光、第二维度-1级衍射光和第二维度+1级衍射光中的第一偏振光分量进行两次反射出射到第一1/4波片，在变为P偏振光后再次入射到偏振分束棱镜，经偏振分束棱镜透射到光电接收模块；第二1/4波片用于将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量变为右旋偏振光后进行反射，再次经过第二1/4波片变为S偏振光后入射到偏振分束棱镜，经偏振分束棱镜分别反射到光电接收模块。
优选地，光电接收模块包括第一接收器、第二接收器、第三接收器和第四接收器；其中，第一接收器用于接收第一维度+1级衍射光中的第一偏振光分量和第一维度-1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至信号处理系统；第二接收器用于接收第一维度-1级衍射光中的第一偏振光分量和第一维度+1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至信号处理系统；第三接收器用于接收第二维度+1级衍射光中的第一偏振光分量和第二维度-1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至信号处理系统；第四接收器用于接收第二维度-1级衍射光中的第一偏振光分量和第二维度+1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至信号处理系统。
优选地，第一接收器、第二接收器、第三接收器和第四接收器各自接收的第一偏振光分量和第二偏振光分量分别两次经过回转棱镜，其在读数头中传输的光程相等。
优选地，当二维测量光栅沿第一维度光栅矢量方向移动时，第一维度-1级衍射光发生负向频移-Δf，第一维度+1级衍射光发生正向频移+Δf，第一接收器输出的拍频信号的频率变为f B-f A-2Δf，第二接收器输出的拍频信号的频率变为f B-f A+2Δf；当二维测量光栅沿第二维度光栅矢量方向移动时，第二维度-1级衍射光发生负向频移-Δf，第二维度+1级衍射光发生正向频移+Δf，第三接收器输出的拍频信号的频率变为f B-f A-2Δf，第四接收器输出的拍频信号的频率变为f B-f A+2Δf。
优选地，信号处理系统用于对第一接收器输出的拍频信号和第二接收器输出的拍频信号进行差分计算，实现二维测量光栅第一维度的单次衍射4倍光学细分的位移测量，对第三接收器输出的拍频信号和第四接收器输出的拍频信号进行差分计算，实现二维测量光栅第二维度的单次衍射4倍光学细分的位移测量。
本发明还提供一种外差二维光栅测量方法，包括如下步骤：
S1、通过光源产生两束重合、偏振正交且具有固定频差的线偏振光，分别为频率为f A的第一偏振光和频率为f B的第二偏振光，第一偏振光为S偏振光，第二偏振光为P偏振光；
S2、第一偏振光和第二偏振光分别进入读数头，经读数头反射与透射后分别入射到移动的二维测量光栅的表面生成第一维度±1级衍射光和第二维度±1级衍射光，第一维度±1级衍射光和第二维度±1级衍射光再经读数头分别入射到光电接收模块；
S3、光电接收模块分别根据第一维度±1级衍射光和第二维度±1级衍射光生成对应的拍频信号，发送至信号处理系统；
S4、信号处理系统分别对第一维度±1级衍射光生成的拍频信号进行差分计算及对第二维度±1级衍射光生成的拍频信号进行差分计算，实现二维测量光栅第一维度和第二维度的单次衍射4倍光学细分的位移测量。
优选地，步骤S2具体包括如下步骤：
S201、第一偏振光经偏振分光棱镜反射到第二1/4波片，在将第一偏振光变为左旋偏振光后进行反射再次经过第二1/4波片变为P偏振光后，回到偏振分光棱镜；以及，第二偏振光经偏振分光棱镜透射到第一1/4波片，在将第二偏振光变为右旋偏振光后入射到回转棱镜，回转棱镜对第二偏振光进行回射，当第二偏振光再次经过第一1/4波片变为S偏振光后，回到偏振分光棱镜；
S202、偏振分光棱镜对第一偏振光进行透射，对第二偏振光反射，使第一偏振光与第二偏振光合束后入射到第三1/4波片，第三1/4波片将第一偏振光变为右旋偏振光后垂直入射到二维测量光栅的表面，及将第二偏振光变为左旋偏振光后垂直入射到二维测量光栅的表面，第一偏振光与第二偏振光分别衍射生成第一维度±1级衍射光和第二维度±1级衍射光。
优选地，第一维度±1级衍射光包括第一维度-1级衍射光和第一维度+1级衍 射光，第二维度±1级衍射光包括第二维度-1级衍射光和第二维度+1级衍射光，第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光分别包含第一偏振光分量和第二偏振光分量。
优选地，在步骤S202之后还包括如下步骤：
S203、第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光经转折元件转折后，相互平行并垂直入射到第三1/4波片；
S204、第三1/4波片将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量变为S偏振光后垂直入射到偏振分束棱镜，以及第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量变为P偏振光后垂直入射到偏振分束棱镜；
S205、偏振分束棱镜将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量反射到第一1/4波片，以及将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量透射到第二1/4波片；
S206、第二1/4波片将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量变为右旋偏振光后进行反射，再次经过第二1/4波片变为S偏振光后入射到偏振分束棱镜，经偏振分束棱镜分别反射到光电接收模块，以及第一1/4波片将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量变为左旋偏振光并再次入射到回转棱镜，回转棱镜分别对第一维度+1级衍射光、第一维度-1级衍射光、第二维度-1级衍射光和第二维度+1级衍射光中的第一偏振光分量进行两次反射出射到第一1/4波片，在变为P偏振光后再次入射到偏振分束棱镜，经偏振分束棱镜透射到光电接收模块。
优选地，光电接收模块包括第一接收器、第二接收器、第三接收器和第四接收器；其中，第一接收器用于接收第一维度+1级衍射光中的第一偏振光分量和第一维度-1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至信号处理系统；第二接收器用于接收第一维度-1级衍射光中的第一偏振光分量和第一维度+1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频 信号，发送至信号处理系统；第三接收器用于接收第二维度+1级衍射光中的第一偏振光分量和第二维度-1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至信号处理系统；第四接收器用于接收第二维度-1级衍射光中的第一偏振光分量和第二维度+1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至信号处理系统。
优选地，第一接收器、第二接收器、第三接收器和第四接收器各自接收的第一偏振光分量和第二偏振光分量分别两次经过回转棱镜，其在读数头中传输的光程相等。
优选地，当二维测量光栅沿第一维度光栅矢量方向移动时，第一维度-1级衍射光发生负向频移-Δf，第一维度+1级衍射光发生正向频移+Δf，第一接收器输出的拍频信号的频率变为f B-f A-2Δf，第二接收器输出的拍频信号的频率变为f B-f A+2Δf；当二维测量光栅沿第二维度光栅矢量方向移动时，第二维度-1级衍射光发生负向频移-Δf，第二维度+1级衍射光发生正向频移+Δf，第三接收器输出的拍频信号的频率变为f B-f A-2Δf，第四接收器输出的拍频信号的频率变为f B-f A+2Δf。
优选地，信号处理系统对第一接收器输出的拍频信号和第二接收器输出的拍频信号进行差分计算，实现二维测量光栅第一维度的单次衍射4倍光学细分的位移测量，对第三接收器输出的拍频信号和第四接收器输出的拍频信号进行差分计算，实现二维测量光栅第二维度的单次衍射4倍光学细分的位移测量。
与现有技术相比，本发明通过在一维测量光栅或二维测量光栅表面的一次衍射就可以实现4倍光学细分，有效避免光栅面形精度和光栅姿态误差对测量精度的影响，并且具有结构简洁、体积小、质量轻、易于安装、方便应用等优点，同时也可以结合二次衍射或多次衍射的方法实现更高倍数的光学细分。
附图说明
图1是根据本发明实施例一的外差一维光栅测量装置的结构示意图；
图2是根据本发明实施例一的外差一维光栅测量装置的原理示意图；
图3是根据本发明实施例一的第一拍频信号的产生原理示意图；
图4是根据本发明实施例一的第二拍频信号的产生原理示意图；
图5是根据本发明实施例一结合二次衍射实现8倍光学细分的原理示意图；
图6是根据本发明实施例二的外差一维光栅测量方法的流程示意图；
图7是根据本发明实施例三的外差一维光栅测量装置的原理示意图；
图8是根据本发明实施例三的第一拍频信号的产生原理示意图；
图9是根据本发明实施例三的第二拍频信号的产生原理示意图；
图10是根据本发明实施例四的外差一维光栅测量方法的流程示意图；
图11是根据本发明实施例五的外差二维光栅测量装置单次衍射实现4倍光学细分的原理示意图；
图12是根据本发明实施例五的光束衍射前光路传输原理的示意图；
图13是根据本发明实施例五的第一维度第一拍频信号的产生原理示意图；
图14是根据本发明实施例五的第一维度第二拍频信号的产生原理示意图；
图15是根据本发明实施例五的第二维度第一拍频信号的产生原理示意图；
图16是根据本发明实施例五的第二维度第二拍频信号的产生原理示意图；
图17是根据本发明实施例六的外差二维光栅位移测量方法的流程示意图。
实施例一的附图标记包括：光源1、读数头2、反射镜201、偏振分束棱镜202、第一1/4波片203、第二1/4波片204、回转棱镜205、转折元件206、补偿镜207、第一直角棱镜208、第二直角棱镜209、第一接收器301、第二接收器302、信号处理系统4、测量光栅5。
实施例三的附图标记包括：光源1`、读数头2`、偏振分束棱镜201`、第一1/4波片202`、第二1/4波片203`、第三1/4波片204`、回转棱镜205`、转折元件206`、第一直角棱镜207`、第二直角棱镜208`，第一接收器301`、第二接收器302`、信号处理系统4`、测量光栅5`。
实施例五的附图标记包括：光源1、偏振分光棱镜201、第一1/4波片202、第二1/4波片203、第三1/4波片204、回转棱镜205、转折元件206、第一接收器301、第二接收器302、第三接收器303、第四接收器304、信号处理系统4、二维测量光栅5。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及具体实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅用以解释本发明，而不构成对本发明的限制。
本发明提供的外差光栅测量装置，是将测量光栅固定在被测物体上，作为位移测量的标尺，在测量光栅随被测物体移动时，通过对测量光栅的位移测量实现对被测物体的位移测量。
为了解决现有技术中通过2次衍射或更多次衍射实现4倍或更高倍数的光学细分，会导致测量系统的光学结构变得更加复杂，并且多次衍射利用光栅不同位置的衍射光，光栅面形精度和光栅姿态误差会对测量精度造成很大影响的问题。本发明提供的外差一维光栅测量装置，对读数头进行特殊的结构设计，使光源发出的固定频差的两束偏振光在通过读数头入射到测量光栅表面时，发生一次衍射就可以实现4倍光学细分，可以避免光栅面形精度和光栅姿态误差对测量精度的影响，并且本发明中读数头的结构简洁、体积小、质量轻，可以简化测量系统中光学结构的复杂度。本发明也可以结合二次衍射或更多次衍射实现更好倍数的光学细分。
测量光栅光栅可以为一维测量光栅光栅或二维测量光栅光栅，对应于一维测量光栅，外差光栅测量装置为外差一维光栅测量装置，对应于二维测量光栅，外差光栅测量装置为外差二维光栅测量装置。
下面以一次衍射实现4倍光学细分为例结合附图对本发明提供的外差光栅测量装置进行展开说明。
实施例一
如图1-图4所示，本发明实施例一提供的外差一维光栅测量装置，包括：光源1、读数头2、光电接收模块和信号处理系统4；其中，光源1用于产生两束重合、偏振正交且具有固定频差的线偏振光作为测量光束，分别为第一偏振光和第二偏振光，第一偏振光为S偏振光，频率为f A，第二偏振光为P偏振光，频率为f B，光源1可以为一台双频激光器1或两台发出固定频差的激光器；读数头用于将两束偏振光入射到移动的一维测量光栅5的表面，两束偏振光在经一维测量光栅5的表面发生衍射后，产生携带测量信息的+1级衍射光和-1级衍射光，+1级衍射光和-1级衍射光均包括第一偏振光分量和第二偏振光分量，+1级衍射光的第一偏振光分量和第二偏振光分量、-1级衍射光的第一偏振光分量和第二偏振光分量分别经读数头入射到光电接收模块。
读数头2包括反射镜201、偏振分束棱镜202、第一1/4波片203、第二1/4波片204、回转棱镜205、转折元件206和镀有反射膜的补偿镜207，反射镜 201设置在光源1的出射光路上，转折元件206设置在在一维测量光栅5的衍射光路上，偏振分束棱镜202设置在转折元件206的透射光路上，第一1/4波片203设置在偏振分束棱镜202的反射光路上，第二1/4波片204设置在偏振分束棱镜202的透射光路上，回转棱镜205设置在第一1/4波片204的透射光路上，补偿镜207设置在第二1/4波片204的透射光路上。
反射镜201将第一偏振光和第二偏振光垂直反射至一维测量光栅5的表面，衍射后产生的+1级衍射光和-1级衍射光经转折元件206转折后相互平行并垂直入射至偏振分束棱镜202；偏振分束棱镜202将+1级衍射光的第一偏振光分量和-1级衍射光的第一偏振光分量反射至第一1/4波片203，以及将+1级衍射光的第二偏振光分量和-1级衍射光的第二偏振光分量透射至第二1/4波片204。
第一1/4波片203将+1级衍射光和-1级衍射光的第一偏振光分量分别变为左旋偏振光并入射至回转棱镜205；回转棱镜205对+1级衍射光的第一偏振光分量和-1级衍射光的第一偏振光分量分别进行两次反射，使+1级衍射光的第一偏振光分量和-1级衍射光的第一偏振光分量再次经过第一1/4波片203变为P偏振光，再次入射至偏振分束棱镜202，偏振分束棱镜202将变为P偏振光的+1级衍射光的第一偏振光分量透射至第一接收器301，以及将变为P偏振光的-1级衍射光的第一偏振光分量透射至第二接收器302。
第二1/4波片204将+1级衍射光的第二偏振光分量和-1级衍射光的第二偏振光分量分别变为右旋偏振光并入射至补偿镜207；+1级衍射光的第二偏振光分量和-1级衍射光的第二偏振光分量经补偿镜207反射再次回到第二1/4波片204，使+1级衍射光的第二偏振光分量和-1级衍射光的第二偏振光分量变为S偏振光，并再次入射至偏振分束棱镜202，偏振分束棱镜202将变为S偏振光的+1级衍射光的第二偏振光分量反射至第二接收器302，以及将-1级衍射光的第二偏振光分量反射至第一接收器301。
由于+1级衍射光的第一偏振光分量和-1级衍射光的第一偏振光分量经过回转棱镜205，而+1级衍射光的第二偏振光分量和-1级衍射光的第二偏振光分量未经过回转棱镜205，导致+1级衍射光的第一偏振光分量与第二偏振光分量的传输光程及-1级衍射光的第一偏振光分量与第二偏振光分量的传输光程不同，因此通过补偿镜207对+1级衍射光的第二偏振光分量和-1级衍射光的第二偏振光分量的传输光程进行补偿。
在本发明的一个具体实施例中，补偿镜207的厚度等于回转棱镜205的1/2长度，使+1级衍射光的第二偏振光分量在两次经过补偿镜207后入射到第二接收器302的传输光程与+1级衍射光的第一偏振光分量经回转棱镜205后入射到第一接收器301的传输光程相等，使-1级衍射光的第二偏振光分量在两次经过补偿镜207后入射到第一接收器301的传输光程与-1级衍射光的第一偏振光分量经回转棱镜205后入射到第二接收器302的传输光程相等，实现对+1级衍射光的第二偏振光分量和-1级衍射光的第二偏振光分量的传输光程的补偿。
补偿传输光程的目的有两个：
第一个：保证测量光束进入第一接收器301、第二接收器302时光程差为定值。
第二个：当外差光栅位移测量光学系统的环境温度变化时，使测量光束的光程差变化一致，不受读数头的光学元件热胀冷缩的影响，不会引入测量误差。
光电接收模块包括第一接收器301和第二接收器302，第一接收器301用于接收-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量，在-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量干涉形成频率为f B-f A的第一拍频信号后，第一接收器301将第一拍频信号传输至信号处理系统4；第二接收器302用于接收-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量，在-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量干涉形成频率为f B-f A的第二拍频信号后，第二接收器302将第二拍频信号传输至信号处理系统4。
当一维测量光栅5沿光栅矢量方向运动时，由于光栅Doppler频移效应，-1级衍射光发生负向频移-Δf，+1级衍射光发生正向频移+Δf，因此第一接收器201输出的第一拍频信号频率变为f B-f A-2Δf，第二接收器302输出的第二拍频信号频率变为f B-f A+2Δf。
信号处理系统4用于接收第一接收器301和第二接收器302发送的第一拍频信号和第二拍频信号，并对第一拍频信号和第二拍频信号进行差分计算，实现一维测量光栅5单次衍射4倍光学细分的位移测量。由于差分计算为现有技术，故在此不再赘述。
本发明还可以结合二次衍射实现8倍光学细分。如图5所示，读数头还包括第一直角棱镜208和第二直角棱镜209，第一直角棱镜208和第二直角棱镜 209分别设置在一维测量光栅5的衍射光路上，对+1级衍射光和-1级衍射光进行两次反射，并以衍射出射角度再次入射到一维测量光栅5的表面实现二次衍射，产生两束新的衍射光，两束新的衍射光从一维测量光栅5的表面垂直出射，并垂直入射到偏振分束棱镜202。通过对+1级衍射光和-1级衍射光的二次衍射，使得光学细分倍数的翻倍，从而提高测量分辨力。
实施例二
实施例一示出了一种外差一维光栅测量装置的结构，与实施例一的外差一维光栅测量装置相对应，实施例二提供了一种利用实施例一的外差一维光栅测量装置进行光栅位移测量的方法。
图6示出了根据本发明实施例二的外差一维光栅测量方法的流程。
如图6所示，本发明实施例二的外差一维光栅测量方法，包括如下步骤：
S1、通过光源产生两束重合、偏振正交且具有固定频差的线偏振光，分别是频率为f A的第一偏振光和频率为f B的第二偏振光，第一偏振光为S偏振光，第二偏振光为P偏振光。
S2、第一偏振光和第二偏振光分别进入读数头，经读数头转折后分别入射到一维测量光栅的表面产生分别包括第一偏振光分量与第二偏振光分量的+1级衍射光和-1级衍射光，+1级衍射光和-1级衍射光再经读数头分别入射到光电接收模块。
步骤S2具体包括如下步骤：
S201、通过读数头的反射镜将第一偏振光和第二偏振光垂直反射至一维测量光栅的表面，产生+1级衍射光和-1级衍射光。
S202、通过读数头的转折元件对+1级衍射光和-1级衍射光进行转折，使+1级衍射光和-1级衍射光相互平行并垂直入射至读数头的偏振分束棱镜。
S203、通过偏振分束棱镜将+1级衍射光和-1级衍射光的第一偏振光分量分别反射至读数头的第一1/4波片，以及将+1级衍射光和-1级衍射光的第二偏振光分量分别透射至读数头的第二1/4波片。
S204、通过第一1/4波片将+1级衍射光和-1级衍射光的第一偏振光分量分别变为左旋偏振光并入射至读数头的回转棱镜，再通过回转棱镜对+1级衍射光和-1级衍射光的第一偏振光分量分别进行两次反射，使+1级衍射光和-1级衍射光的第一偏振光分量经第一1/4波片变为P偏振光后入射至偏振分束棱镜；以及 通过第二1/4波片将+1级衍射光和-1级衍射光的第二偏振光分量分别变为右旋偏振光并入射至读数头的补偿镜，再通过补偿镜对+1级衍射光和-1级衍射光的第二偏振光分量进行反射，使+1级衍射光和-1级衍射光的第二偏振光分量经第二1/4波片变为S偏振光后入射至偏振分束棱镜。
补偿镜的厚度等于回转棱镜的1/2长度，用于补偿+1级衍射光和-1级衍射光的第二偏振光分量的传输光程，使+1级衍射光和-1级衍射光的第二偏振光分量的传输光程与+1级衍射光和-1级衍射光的第一偏振光分量的传输光程相等。
S205、通过偏振分束棱镜将变为P偏振光的+1级衍射光和-1级衍射光的第一偏振光分量透射至光电接收模块，以及将变为S偏振光的+1级衍射光和-1级衍射光的第二偏振光分量反射至光电接收模块。
S3、光电接收模块接收+1级衍射光和-1级衍射光；其中，-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量干涉形成频率为f B-f A的拍频信号，-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量干涉形成频率为f B-f A的拍频信号。
光电接收模块包括第一接收器和第二接收器，通过第一接收器接收-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量，两者干涉生成频率为f B-f A的第一拍频信号，传输到信号处理系统；通过第二接收器接收-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量，两者干涉生成频率为f B-f A的第二拍频信号，传输到信号处理系统。
当一维测量光栅沿光栅矢量方向移动时，-1级衍射光发生负向频移-Δf，+1级衍射光发生正向频移+Δf，第一接收器输出的第一拍频信号的频率变为f B-f A-2Δf，第二接收器输出的第二拍频信号的频率变为f B-f A+2Δf。
S4、信号处理系统分别对两路拍频信号进行差分计算，实现一维测量光栅单次衍射4倍光学细分的位移测量。
信号处理系统对第一接收器输出的第一拍频信号及第二接收器输出的第二拍频信号进行差分计算，实现一维测量光栅单次衍射4倍光学细分的位移测量。由于差分计算为现有技术，故在此不再赘述。
为了实现更高倍数的光学细分，可以将一维测量光栅衍射产生的+1级衍射光和-1级衍射光分别入射至第一直角棱镜和第二直角棱镜，通过第一直角棱镜和第二直角棱镜分别对+1级衍射光和-1级衍射光进行两次反射，以衍射出射角 度再次入射到一维测量光栅的表面，两束新的衍射光垂直入射到偏振分束棱镜。通过对+1级衍射光和-1级衍射光的二次衍射，使得光学细分倍数的翻倍，从而提高测量分辨力。
实施例三
如图7-图9所示，本发明实施例三提供的外差一维光栅测量装置，包括：光源1`、读数头2`、光电接收模块和信号处理系统4`；其中，光源1`用于产生两束重合、偏振正交且具有固定频差的线偏振光作为测量光束，分别为第一偏振光和第二偏振光，第一偏振光为S偏振光，频率为f A，第二偏振光为P偏振光，频率为f B，光源1`可以为一台双频激光器或两台发出固定频差的激光器；读数头用于将两束偏振光入射到移动的一维测量光栅5的表面，两束偏振光在经一维测量光栅5的表面发生衍射后，产生携带测量信息的+1级衍射光和-1级衍射光，+1级衍射光和-1级衍射光均包括第一偏振光分量和第二偏振光分量，+1级衍射光的第一偏振光分量和第二偏振光分量、-1级衍射光的第一偏振光分量和第二偏振光分量分别经读数头入射到光电接收模块。
读数头2`包括偏振分束棱镜201`、第一1/4波片202`、镀有反射膜的第二1/4波片203`、第三1/4波片204`、回转棱镜205`和转折元件206`，偏振分束棱镜201`设置在光源1`的出射光路上，转折元件206`设置在在一维测量光栅5的衍射光路上，第一1/4波片202`设置在偏振分束棱镜201`的反射光路上，第二1/4波片203`设置在偏振分束棱镜201`的透射光路上，第三1/4波片204`设置在转折元件206`的透射光路上，回转棱镜205`设置在第一1/4波片202`的透射光路上。
偏振分束棱镜201`接收第一偏振光和第二偏振光，将第二偏振光透射至第一1/4波片202`，将第一偏振光反射至第二1/4波片203`，第一1/4波片202`将第二偏振光变为右旋偏振光并入射到回转棱镜205`，回转棱镜205`对第二偏振光进行回射，使第二偏振光经过第一1/4波片202`变为S偏振光后回到偏振分束棱镜201`，第二1/4波片203`设将第一偏振光变为左旋偏振光，经反射膜反射再次经过第二1/4波片203`变为P偏振光后回到偏振分束棱镜203`，偏振分束棱镜201`对变为P偏振光的第一偏振光进行透射，对变为S偏振光的第二偏振光进行反射，使第一偏振光与第二偏振光合束后入射至一维测量光栅5的表面，衍射产生-1级衍射光和+1级衍射光，转折元件206`对-1级衍射光和+1级衍射光 进行转折，使-1级衍射光和+1级衍射光相互平行并垂直入射至第三1/4波片204`，第三1/4波片204`将+1级衍射光和-1级衍射光的第一偏振光分量变为S偏振光，垂直入射到偏振分束棱镜201`，以及将+1级衍射光和-1级衍射光的第二偏振光分量变为P偏振光，垂直入射到偏振分束棱镜201`，偏振分束棱镜201`将+1级衍射光和-1级衍射光的第一偏振光分量反射至第一1/4波片202`，以及将+1级衍射光和-1级衍射光的第二偏振光分量透射至第二1/4波片203`，第一1/4波片202`将+1级衍射光和-1级衍射光的第一偏振光分量变为左旋偏振光并入射到回转棱镜205`，回转棱镜205`对+1级衍射光和-1级衍射光的第一偏振光分量进行两次反射回到第一1/4波片202`变为P偏振光后，再次入射至偏振分束棱镜201`，经偏振分束棱镜201`透射至光电接收模块，第二1/4波片203`将+1级衍射光和-1级衍射光的第二偏振光分量变为右旋偏振光，并经反射膜反射再次经过第二1/4波片203`变为S偏振光后入射至偏振分束棱镜201`，经偏振分束棱镜201`反射至光电接收模块。
由于-1级衍射光的第一偏振光分量与-1级衍射光的第二偏振光分量及+1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量均两次经过回转棱镜205`。因此，-1级衍射光的第一偏振光分量与-1级衍射光的第二偏振光分量在读数头中的传输光程相等，+1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量在读数头中的传输光程相等，起到两方面作用：
一方面：保证测量光束进入光电接收模块时光程差为定值。
另一方面：当外差一维光栅测量装置的环境温度变化时，使测量光束的光程差变化一致，不受读数头的光学元件热胀冷缩的影响，不会引入测量误差。
光电接收模块包括第一接收器301`和第二接收器302`，第一接收器301`用于接收-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量，在-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量干涉形成频率为f B-f A的第一拍频信号后，第一接收器301`将第一拍频信号传输至信号处理系统4`；第二接收器302`用于接收-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量，在-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量干涉形成频率为f B-f A的第二拍频信号后，第二接收器302`将第二拍频信号传输至信号处理系统4`。
当一维测量光栅5沿光栅矢量方向运动时，由于光栅Doppler频移效应，-1 级衍射光发生负向频移-Δf，+1级衍射光发生正向频移+Δf，因此第一接收器201`输出的第一拍频信号频率变为f B-f A-2Δf，第二接收器302`输出的第二拍频信号频率变为f B-f A+2Δf。
信号处理系统4`用于接收第一接收器301`和第二接收器302`发送的拍频信号，并对两路拍频信号进行差分计算，实现一维测量光栅5`单次衍射4倍光学细分的位移测量。由于差分计算为现有技术，故在此不再赘述。
实施例四
实施例三示出了另一种外差一维光栅测量装置的结构，与实施例三的外差一维光栅测量装置相对应，实施例四提供了一种利用实施例三的外差一维光栅测量装置进行光栅位移测量的方法。
图10示出了根据本发明实施例四的外差一维光栅测量方法的流程。
如图10所示，本发明实施例四的外差一维光栅测量方法，包括如下步骤：
S1、通过光源产生两束重合、偏振正交且具有固定频差的线偏振光，分别是频率为f A的第一偏振光和频率为f B的第二偏振光，第一偏振光为S偏振光，第二偏振光为P偏振光。
S2、第一偏振光和第二偏振光分别进入读数头，经读数头转折后分别入射到一维测量光栅的表面产生分别包括第一偏振光分量与第二偏振光分量的+1级衍射光和-1级衍射光，+1级衍射光和-1级衍射光再经读数头分别入射到光电接收模块。
步骤S2具体包括如下步骤：
S201`、第一偏振光和第二偏振光入射至读数头的偏振分束棱镜，通过偏振分束棱镜将第二偏振光透射至读数头的第一1/4波片，将第一偏振光反射至读数头的第二1/4波片；
S202`、通过第一1/4波片将第二偏振光变为右旋偏振光并入射到回转棱镜，通过回转棱镜对第二偏振光进行回射，使第二偏振光经过第一1/4波片变为S偏振光后回到偏振分束棱镜；以及通过第二1/4波片将第一偏振光变为左旋偏振光，经反射膜反射再次经过第二1/4波片变为P偏振光后回到偏振分束棱镜；
S203`、通过偏振分束棱镜对变为P偏振光的第一偏振光进行透射，对变为S偏振光的第二偏振光进行反射，使第一偏振光与第二偏振光合束后入射至一维测量光栅的表面，衍射产生-1级衍射光和+1级衍射光；
S204`、通过读数头的转折元件对-1级衍射光和+1级衍射光进行转折，使-1级衍射光和+1级衍射光相互平行并垂直入射至读数头的第三1/4波片；
S205`、通过第三1/4波片将+1级衍射光和-1级衍射光的第一偏振光分量变为S偏振光，垂直入射到偏振分束棱镜，以及将+1级衍射光和-1级衍射光的第二偏振光分量变为P偏振光，垂直入射到偏振分束棱镜；
S206`、通过偏振分束棱镜将+1级衍射光和-1级衍射光的第一偏振光分量反射至第一1/4波片，以及将+1级衍射光和-1级衍射光的第二偏振光分量透射至第二1/4波片；
S207`、通过第一1/4波片用于将+1级衍射光和-1级衍射光的第一偏振光分量变为左旋偏振光并入射到回转棱镜，经回转棱镜对+1级衍射光和-1级衍射光的第一偏振光分量进行两次反射回到第一1/4波片变为P偏振光后，再次入射至偏振分束棱镜，经偏振分束棱镜透射至光电接收模块；以及通过第二1/4波片将+1级衍射光和-1级衍射光的第二偏振光分量变为右旋偏振光，并经反射膜反射再次经过第二1/4波片变为S偏振光后入射至偏振分束棱镜，经偏振分束棱镜反射至光电接收模块。
由于-1级衍射光的第一偏振光分量与-1级衍射光的第二偏振光分量及+1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量均两次经过回转棱镜205`。因此，-1级衍射光的第一偏振光分量与-1级衍射光的第二偏振光分量在读数头中的传输光程相等，+1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量在读数头中的传输光程相等的作用体现在如下两方面：
第一方面：保证测量光束进入光电接收模块时光程差为定值。
第二方面：当外差一维光栅测量装置的环境温度变化时，使测量光束的光程差变化一致，不受读数头的光学元件热胀冷缩的影响，不会引入测量误差。
S3、光电接收模块接收+1级衍射光和-1级衍射光；其中，-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量干涉形成频率为f B-f A的拍频信号，-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量干涉形成频率为f B-f A的拍频信号。
光电接收模块包括第一接收器和第二接收器；其中，通过第一接收器接收-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量，并生成频率为f B-f A的拍频信号，传输到信号处理系统；通过第二接收器接收-1级衍射光的第 一偏振光分量与+1级衍射光的第二偏振光分量，并生成频率为f B-f A的拍频信号，传输到信号处理系统。
当一维测量光栅沿光栅矢量方向移动时，-1级衍射光发生负向频移-Δf，+1级衍射光发生正向频移+Δf，第一接收器输出的拍频信号的频率变为f B-f A-2Δf，第二接收器输出的拍频信号的频率变为f B-f A+2Δf。
为了实现更高倍数的光学细分，可以将一维测量光栅衍射产生的+1级衍射光和-1级衍射光分别入射至第一直角棱镜和第二直角棱镜，通过第一直角棱镜和第二直角棱镜分别对+1级衍射光和-1级衍射光进行两次反射，以衍射出射角度再次入射到一维测量光栅的表面，两束新的衍射光垂直入射到偏振分束棱镜。通过对+1级衍射光和-1级衍射光的二次衍射，使得光学细分倍数的翻倍，从而提高测量分辨力。
S4、信号处理系统分别对两路拍频信号进行差分计算，实现一维测量光栅单次衍射4倍光学细分的位移测量。
信号处理系统对第一接收器输出的第一拍频信号及第二接收器输出的第二拍频信号进行差分计算，实现一维测量光栅单次衍射4倍光学细分的位移测量。由于差分计算为现有技术，故在此不再赘述。
实施例五
图11示出了根据本发明实施例五的外差二维光栅测量装置的结构。
如图11所示，本发明实施例五提供的外差二维光栅测量装置，包括：光源1、读数头、光电接收模块和信号处理系统4；其中，光源1用于产生两束重合、偏振正交且具有固定频差的线偏振光，分别为第一偏振光和第二偏振光，第一偏振光为S偏振光，频率为f A，第二偏振光为P偏振光，频率为f B，光源1可以为一台双频激光器1或两台发出固定频差的激光器；读数头用于将两束线偏振光入射到移动的二维测量光栅5的表面，两束线偏振光在经二维测量光栅5的表面发生衍射后，产生第一维度±1级衍射光和第二维度±1级衍射光，第一维度±1级衍射光和第二维度±1级衍射光再入射到读数头，最后从读数头射出入射到光电接收模块；光电接收模块用于接收第一维度±1级衍射光和第二维度±1级衍射光，生成四路拍频信号，实现4倍光学细分，光电接收模块包括第一接收器301、第二接收器302、第三接收器303和第四接收器304，第一接收器301和第二接收器302用于接收第一维度±1级衍射光，生成两路拍频信号 发送至信号处理系统4，第三接收器303和第四接收器304用于接收第二维度±1级衍射光，生成两路拍频信号发送至信号处理系统4；信号处理系统4用于接收第一接收器301、第二接收器302、第三接收器303和第四接收器304发送的拍频信号，并对第一接收器301与第二接收器302发送的拍频信号进行差分计算实现二维测量光栅5第一维度的单次衍射4倍光学细分的位移测量，以及对第三接收器303和第四接收器304发送的拍频信号进行差分计算实现二维测量光栅5第二维度的单次衍射4倍光学细分的位移测量。
读数头包括偏振分光棱镜201、第一1/4波片202、第二1/4波片203、第三1/4波片204、回转棱镜205和转折元件206；其中，偏振分光棱镜201用于S偏振光进行反射，对P偏振光进行透射；第一1/4波片202设置在偏振分光棱镜201的透射光路上，第二1/4波片203设置在偏振分光棱镜201的反射光路上，在第二1/4波片203的表面镀有反射膜，用于实现激光的反射；第三1/4波片204设置在第二1/4波片203的对立面，即设置在偏振分光棱镜201另一方向的透射光路上；回转棱镜205设置在第一1/4波片202的透射光路上，实现对激光的回转；转折元件206设置在二维测量光栅5的衍射光路上，用于对激光进行转折。
图12示出了根据本发明实施例五的光束衍射前光路传输原理。
如图12所示，在第一偏振光与第二偏振光入射到二维测量光栅5发生衍射之前，其光路传输路径为：光源1发出的第一偏振光入射到偏振分光棱镜201，第一偏振光经偏振分光棱镜201反射至第二1/4波片203变为左旋偏振光，并通过在第二1/4波片203上镀制的反射膜将第一偏振光反射回第二1/4波片203，第二1/4波片203将第一偏振光变为P偏振光并回到偏振分光棱镜201。光源1发出的第二偏振光入射到偏振分光棱镜201，第二偏振光经偏振分光棱镜201透射至第一1/4波片202变为右旋偏振光后入射至回转棱镜205，回转棱镜205将第二偏振光回射到第一1/4波片202，第一1/4波片202将第二偏振光变为S偏振光并回到偏振分光棱镜201。偏振分光棱镜201对第一偏振光(P偏振光)进行透射，对第二偏振光进行反射(S偏振光)，使第一偏振光与第二偏振光合束后入射至第三1/4波片204，第三1/4波片204将第一偏振光变为右旋偏振光后入射到二维测量光栅5的表面，以及将第二偏振光变为左旋偏振光入射到二维测量光栅5的表面。
第一偏振光经二维测量光栅5衍射后生成第一维度-1级衍射光和第一维度+1级衍射光，第二偏振光经二维测量光栅5衍射后生成第二维度-1级衍射光和第二维度+1级衍射光。
第一维度和第二维度是按照二维测量光栅的刻线方向进行的维度划分，也就是指二维测量光栅表面刻线的两个方向。
第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光均包含第一偏振光分量和第二偏振光分量。
第一维度+1级衍射光中的第一偏振光分量与第一维度-1级衍射光中的第二偏振光分量生成第一维度第一拍频信号。
第一维度-1级衍射光中的第一偏振光分量与第一维度+1级衍射光中的第二偏振光分量生成第一维度第二拍频信号。
第二维度+1级衍射光中的第一偏振光分量与第二维度-1级衍射光中的第二偏振光分量生成第二维度第一拍频信号。
第二维度-1级衍射光中的第一偏振光分量与第二维度+1级衍射光中的第二偏振光分量生成第二维度第二拍频信号。
图13-图16示出了根据本发明实施例五的第一维度第一拍频信号、第一维度第二拍频信号、第二维度第一拍频信号、第二维度第二拍频信号的产生原理。
如图13-图16所示，第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光经转折元件206转折后，相互平行并垂直入射至第三1/4波片204。
第三1/4波片204将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量变为S偏振光，垂直入射到偏振分束棱镜2，以及将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量变为P偏振光，并垂直入射到偏振分束棱镜201。
偏振分束棱镜201将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量反射到第一1/4波片202，以及将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量透射到第二1/4波片203。
第二1/4波片203将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量变为右旋偏振光后通过反射膜进行反射，再次经过第二1/4波片203变为S偏振光后入射到偏振分束棱镜201，经偏振分束棱镜201反射分别入射到第一接收器301、第二接收器302、第三接收器303、第四接收器304中。
第一1/4波片将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量变为左旋偏振光并再次入射到回转棱镜205，回转棱镜205对第一维度+1级衍射光中的第一偏振光分量进行两次反射沿第一维度-1级衍射光中的第一偏振光分量的入射光路出射回到第一1/4波片202中，对第一维度-1级衍射光中的第一偏振光分量两次反射沿第一维度+1级衍射光中的第一偏振光分量的入射光路出射回到第一1/4波片202中，对第二维度+1级衍射光中的第一偏振光分量进行两次反射沿第二维度-1级衍射光中的第一偏振光分量的入射光路出射回到第一1/4波片202中，对第二维度-1级衍射光中的第一偏振光分量两次反射沿第二维度+1级衍射光中的第一偏振光分量的入射光路出射回到第一1/4波片202中；第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量再次经过第一1/4波片201变为P偏振光，再次入射到偏振分束棱镜201，经偏振分束棱镜201透射分别入射到第二接收器302、第一接收器301、第四接收器304和第三接收器303中。
需要说明的是，第一接收器301、第二接收器302、第三接收器303、第四接收器304各自接收的第一偏振光分量和第二偏振光分量分别两次经过回转棱镜205，其在读数头中传输的光程相等，起到两方面作用：
第一方面：保证测量信号进入第一接收器301、第二接收器302、第三接收器303、第四接收器304时光程差为定值。
第二方面：
当外差二维光栅测量装置的环境温度变化时，使测量光束的光程差变化一致，不受读数头的光学元件热胀冷缩的影响，不会引入测量误差。
第一接收器301用于接收第一维度+1级衍射光中的第一偏振光分量和第一维度-1级衍射光中的第二偏振光分量，并生成频率为(f B-f A)的第一维度第一拍频信号，传输到信号处理系统4中。
第二接收器302用于接收第一维度-1级衍射光中的第一偏振光分量和第一维度+1级衍射光中的第二偏振光分量，并生成频率为(f B-f A)的第一维度第二拍频信号，传输到信号处理系统4中。
第三接收器303用于接收第二维度+1级衍射光中的第一偏振光分量和第二维度-1级衍射光中的第二偏振光分量，并生成频率为(f B-f A)的第二维度第一拍频信号，传输到信号处理系统4中。
第四接收器304用于接收第二维度-1级衍射光中的第一偏振光分量和第二维度+1级衍射光中的第二偏振光分量，并生成频率为(f B-f A)的第二维度第二拍频信号，传输到信号处理系统4中。
当二维测量光栅5沿第一维度光栅矢量方向运动时，由于光栅Doppler频移效应，第一维度-1级衍射光发生负向频移-Δf，第一维度+1级衍射光发生正向频移+Δf，第一接收器201输出的第一维度第一拍频信号频率变为(f B-f A-2Δf)，第二接收器302输出的第一维度第二拍频信号频率变为(f B-f A+2Δf)。
当二维测量光栅5沿第二维度光栅矢量方向运动时，由于光栅Doppler频移效应，第二维度-1级衍射光发生负向频移-Δf，第二维度+1级衍射光发生正向频移+Δf，第三接收器303输出的第二维度第一拍频信号频率变为(f B-f A-2Δf)，第四接收器304输出的第二维度第二拍频信号频率变为(f B-f A+2Δf)。
信号处理系统4用于对第一接收器301输出的第一维度第一拍频信号和第二接收器302输出的第一维度第二拍频信号进行差分计算，实现第一维度单次衍射4倍光学细分的外差光栅位移测量，以及对第三接收器303输出的第二维度第一拍频信号和第四接收器304输出的第二维度第二拍频信号进行差分计算，实现第二维度单次衍射4倍光学细分的外差光栅位移测量。
实施例六
实施例五示出了一种外差二维光栅测量装置的结构，与实施例五的外差二维光栅测量装置相对应，实施例六提供了一种利用实施例五的外差二维光栅测量装置进行光栅位移测量的方法。
图17示出了根据本发明实施例六的外差二维光栅测量方法的流程。
如图17所示，本发明实施例提供的外差二维光栅测量方法，包括如下步骤：
S1、通过光源产生两束重合、偏振正交且具有固定频差的线偏振光，分别为S偏振态的第一偏振光和P偏振态的第二偏振光。
光源可以为一台双频激光器1或两台发出固定频差的激光器，发出两束 固定频差的激光，分别为第一偏振光和第二偏振光，第一偏振光为S偏振光，频率为f A，第二偏振光为P偏振光，频率为f B。
S2、第一偏振光和第二偏振光分别进入读数头，经读数头反射与透射后分别入射到二维测量光栅的表面生成第一维度±1级衍射光和第二维度±1级衍射光，第一维度±1级衍射光和第二维度±1级衍射光再经读数头分别入射到光电接收模块。
步骤S2具体包括如下步骤：
S201、第一偏振光经偏振分光棱镜反射到第二1/4波片，在将第一偏振光变为左旋偏振光后进行反射再次经过第二1/4波片变为P偏振光后，回到偏振分光棱镜；以及，第二偏振光经偏振分光棱镜透射到第一1/4波片，在将第二偏振光变为右旋偏振光后入射到回转棱镜，回转棱镜对第二偏振光进行回射，当第二偏振光再次经过第一1/4波片变为S偏振光后，回到偏振分光棱镜。
S202、偏振分光棱镜对第一偏振光进行透射，对第二偏振光反射，使第一偏振光与第二偏振光合束后入射到第三1/4波片，第三1/4波片将第一偏振光变为右旋偏振光后垂直入射到二维测量光栅的表面，及将第二偏振光变为左旋偏振光后垂直入射到二维测量光栅的表面，第一偏振光衍射生成第一维度-1级衍射光和第一维度+1级衍射光，第二偏振光衍射生成第二维度-1级衍射光和第二维度+1级衍射光。
第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光分别包含第一偏振光分量和第二偏振光分量。
S203、第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光经转折元件转折后，相互平行并垂直入射到第三1/4波片。
S204、第三1/4波片将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量变为S偏振光后垂直入射到偏振分束棱镜，以及第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量变为P偏振光后垂直入射到偏振分束棱镜。
S205、偏振分束棱镜将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量反射到第一1/4波片，以及将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1 级衍射光、第二维度+1级衍射光中的第二偏振光分量透射到第二1/4波片。
S206、第二1/4波片将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量变为右旋偏振光后进行反射，再次经过第二1/4波片变为S偏振光后入射到偏振分束棱镜，经偏振分束棱镜分别反射到光电接收模块，以及第一1/4波片将第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第一偏振光分量变为左旋偏振光并再次入射到回转棱镜，回转棱镜分别对第一维度+1级衍射光、第一维度-1级衍射光、第二维度-1级衍射光和第二维度+1级衍射光中的第一偏振光分量进行两次反射出射到第一1/4波片，在变为P偏振光后再次入射到偏振分束棱镜，经偏振分束棱镜透射到光电接收模块。
S3、光电接收模块分别根据第一维度±1级衍射光和第二维度±1级衍射光生成对应的拍频信号，发送至信号处理系统。
光电接收模块包括第一接收器、第二接收器、第三接收器和第四接收器；其中，第一接收器用于接收第一维度+1级衍射光中的第一偏振光分量和第一维度-1级衍射光中的第二偏振光分量，并生成频率为(f B-f A)的第一维度第一拍频信号，发送至信号处理系统；第二接收器用于接收第一维度-1级衍射光中的第一偏振光分量和第一维度+1级衍射光中的第二偏振光分量，并生成频率为(f B-f A)的第一维度第二拍频信号，发送至信号处理系统；第三接收器用于接收第二维度+1级衍射光中的第一偏振光分量和第二维度-1级衍射光中的第二偏振光分量，并生成频率为(f B-f A)的第二维度第一拍频信号，发送至信号处理系统；第四接收器用于接收第二维度-1级衍射光中的第一偏振光分量和第二维度+1级衍射光中的第二偏振光分量，并生成频率为(f B-f A)的第二维度第二拍频信号，发送至信号处理系统。
当二维测量光栅沿第一维度光栅矢量方向移动时，第一维度-1级衍射光发生负向频移-Δf，第一维度+1级衍射光发生正向频移+Δf，第一接收器输出的第一维度第一拍频信号的频率变为f B-f A-2Δf，第二接收器输出的第一维度第二拍频信号的频率变为f B-f A+2Δf；当二维测量光栅沿第二维度光栅矢量方向移动时，第二维度-1级衍射光发生负向频移-Δf，第二维度+1级衍射光发生正向频移+Δf，第三接收器输出的第二维度第一拍频信号的频率变为f B-f A-2Δf，第四接收器输出 的第二维度第二拍频信号的频率变为f B-f A+2Δf。
S4、信号处理系统分别对第一维度±1级衍射光生成的拍频信号进行差分计算及对第二维度±1级衍射光生成的拍频信号进行差分计算，实现二维测量光栅第一维度和第二维度的单次衍射4倍光学细分的位移测量。
更为具体地，信号处理系统对第一接收器输出的第一维度第一拍频信号和第二接收器输出的第一维度第二拍频信号进行差分计算，实现二维测量光栅第一维度的单次衍射4倍光学细分的位移测量，对第三接收器输出的第二维度第一拍频信号和第四接收器输出的第二维度第二拍频信号进行差分计算，实现二维测量光栅第二维度的单次衍射4倍光学细分的位移测量。
在本说明书的描述中，参考术语“一个实施例”、“一些实施例”、“示例”、“具体示例”、或“一些示例”等的描述意指结合该实施例或示例描述的具体特征、结构、材料或者特点包含于本发明的至少一个实施例或示例中。在本说明书中，对上述术语的示意性表述不必须针对的是相同的实施例或示例。而且，描述的具体特征、结构、材料或者特点可以在任一个或多个实施例或示例中以合适的方式结合。此外，在不相互矛盾的情况下，本领域的技术人员可以将本说明书中描述的不同实施例或示例以及不同实施例或示例的特征进行结合和组合。
尽管上面已经示出和描述了本发明的实施例，可以理解的是，上述实施例是示例性的，不能理解为对本发明的限制，本领域的普通技术人员在本发明的范围内可以对上述实施例进行变化、修改、替换和变型。
以上本发明的具体实施方式，并不构成对本发明保护范围的限定。任何根据本发明的技术构思所作出的各种其他相应的改变与变形，均应包含在本发明权利要求的保护范围内。

Claims (36)

  1. 一种外差一维光栅测量装置，包括光源，所述光源用于产生两束重合、偏振正交且具有固定频差的线偏振光，分别为频率为f A的第一偏振光和频率为f B的第二偏振光，所述第一偏振光为S偏振光，所述第二偏振光为P偏振光；其特征在于，还包括读数头、光电接收模块和信号处理系统；其中，
    所述读数头用于接收所述第一偏振光和所述第二偏振光，并分别入射到移动的一维测量光栅的表面产生分别包括第一偏振光分量与第二偏振光分量的+1级衍射光和-1级衍射光，所述+1级衍射光和所述-1级衍射光分别经所述读数头入射到所述光电接收模块；
    所述光电接收模块用于接收所述+1级衍射光和所述-1级衍射光形成两路拍频信号；其中，一路为-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量干涉形成频率为f B-f A的拍频信号，另一路为-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量干涉形成频率为f B-f A的拍频信号；
    所述信号处理系统用于对两路拍频信号进行差分计算，实现所述一维测量光栅单次衍射4倍光学细分的位移测量。
  2. 如权利要求1所述的外差一维光栅测量装置，其特征在于，所述读数头包括反射镜、偏振分束棱镜、第一1/4波片、第二1/4波片、镀有反射膜的补偿镜、回转棱镜和转折元件；其中，
    所述反射镜设置在所述光源的出射光路上，用于将所述第一偏振光和所述第二偏振光垂直反射至所述一维测量光栅的表面，产生+1级衍射光和-1级衍射光；
    所述转折元件设置在所述一维测量光栅的衍射光路上，用于对所述+1级衍射光和所述-1级衍射光进行转折，使所述+1级衍射光和所述-1级衍射光相互平行并垂直入射至所述偏振分束棱镜；
    所述偏振分束棱镜设置在所述转折元件的透射光路上，用于将所述+1级衍射光和所述-1级衍射光的第一偏振光分量分别反射至所述第一1/4波片，以及将所述+1级衍射光和所述-1级衍射光的第二偏振光分量分别透射至所述第二1/4波片；
    所述第一1/4波片设置在所述偏振分束棱镜的反射光路上，用于将所述+1 级衍射光和所述-1级衍射光的第一偏振光分量分别变为左旋偏振光并入射至所述回转棱镜；
    所述回转棱镜设置在所述第一1/4波片的透射光路上，用于对所述+1级衍射光和所述-1级衍射光的第一偏振光分量分别进行两次反射，使所述+1级衍射光和所述-1级衍射光的第一偏振光分量经过所述第一1/4波片变为P偏振光后入射至所述偏振分束棱镜；
    所述第二1/4波片设置在所述偏振分束棱镜的透射光路上，用于将所述+1级衍射光和所述-1级衍射光的第二偏振光分量分别变为右旋偏振光并入射至所述补偿镜；
    所述补偿镜设置在所述第二1/4波片的透射光路上，用于对所述+1级衍射光和所述-1级衍射光的第二偏振光分量进行反射，使所述+1级衍射光和所述-1级衍射光的第二偏振光分量经所述第二1/4波片变为S偏振光后入射至所述偏振分束棱镜；
    所述偏振分束棱镜还用于将变为P偏振光的所述+1级衍射光和所述-1级衍射光的第一偏振光分量透射至所述光电接收模块，以及将变为S偏振光的所述+1级衍射光和所述-1级衍射光的第二偏振光分量反射至所述光电接收模块。
  3. 如权利要求2所述的外差一维光栅测量装置，其特征在于，所述光电接收模块包括第一接收器和第二接收器；其中，所述第一接收器用于接收所述-1级衍射光的第二偏振光分量与所述+1级衍射光的第一偏振光分量，并生成频率为f B-f A的拍频信号，传输到所述信号处理系统；所述第二接收器用于接收所述-1级衍射光的第一偏振光分量与所述+1级衍射光的第二偏振光分量，并生成频率为f B-f A的拍频信号，传输到所述信号处理系统。
  4. 如权利要求3所述的外差一维光栅测量装置，其特征在于，当所述一维测量光栅沿光栅矢量方向移动时，所述-1级衍射光发生负向频移-Δf，所述+1级衍射光发生正向频移+Δf，所述第一接收器输出的拍频信号的频率变为f B-f A-2Δf，所述第二接收器输出的拍频信号的频率变为f B-f A+2Δf。
  5. 如权利要求2所述的外差一维光栅测量装置，其特征在于，所述补偿镜的厚度等于所述回转棱镜的1/2长度，用于补偿所述+1级衍射光和所述-1级衍射光的第二偏振光分量的传输光程，使所述+1级衍射光和所述-1级衍射光的第二偏振光分量的传输光程与+1级衍射光和所述-1级衍射光的第一偏振光分量 的传输光程相等。
  6. 如权利要求2所述的外差一维光栅测量装置，其特征在于，所述读数头还包括分别设置所述一维测量光栅衍射光路上的第一直角棱镜和第二直角棱镜，所述第一直角棱镜和所述第二直角棱镜分别对+1级衍射光和-1级衍射光进行两次反射，以衍射出射角度再次入射到所述一维测量光栅的表面，两束新的衍射光垂直入射到所述偏振分束棱镜。
  7. 如权利要求1所述的外差一维光栅测量装置，其特征在于，所述读数头包括偏振分束棱镜、第一1/4波片、镀有反射膜的第二1/4波片和回转棱镜；其中，
    所述偏振分束棱镜设置在所述光源的出射光路上，用于接收所述第一偏振光和所述第二偏振光，将所述第二偏振光透射至所述第一1/4波片，将所述第一偏振光反射至所述第二1/4波片；
    所述第一1/4波片设置在所述偏振分束棱镜的透射光路上，用于将所述第二偏振光变为右旋偏振光并入射到所述回转棱镜；
    所述回转棱镜设置在所述第一1/4波片的透射光路上，用于对所述第二偏振光进行回射，使所述第二偏振光经过所述第一1/4波片变为S偏振光后回到所述偏振分束棱镜；
    所述第二1/4波片设置在所述偏振分束棱镜的反射光路上，用于将所述第一偏振光变为左旋偏振光，经所述反射膜反射再次经过所述第二1/4波片变为P偏振光后回到所述偏振分束棱镜；
    所述偏振分束棱镜还用于对变为P偏振光的第一偏振光进行透射，对变为S偏振光的第二偏振光进行反射，使所述第一偏振光与所述第二偏振光合束后入射至所述一维测量光栅的表面，衍射产生-1级衍射光和+1级衍射光。
  8. 如权利要求7所述的外差一维光栅测量装置，其特征在于，所述读数头还包括转折元件和第三1/4波片；其中，
    所述转折元件设置在所述一维测量光栅的衍射光路上，用于对所述-1级衍射光和所述+1级衍射光进行转折，使所述-1级衍射光和所述+1级衍射光相互平行并垂直入射至所述第三1/4波片；
    所述第三1/4波片设置在所述转折元件的透射光路上，用于将所述+1级衍射光和所述-1级衍射光的第一偏振光分量变为S偏振光，垂直入射到所述偏振 分束棱镜，以及将所述+1级衍射光和所述-1级衍射光的第二偏振光分量变为P偏振光，垂直入射到所述偏振分束棱镜；
    所述偏振分束棱镜用于将所述+1级衍射光和所述-1级衍射光的第一偏振光分量反射至所述第一1/4波片，以及将所述+1级衍射光和所述-1级衍射光的第二偏振光分量透射至所述第二1/4波片；
    所述第一1/4波片用于将所述+1级衍射光和所述-1级衍射光的第一偏振光分量变为左旋偏振光并入射到所述回转棱镜；
    所述回转棱镜用于对所述+1级衍射光和-1级衍射光的第一偏振光分量进行两次反射回到所述第一1/4波片变为P偏振光后，再次入射至所述偏振分束棱镜，经所述偏振分束棱镜透射至所述光电接收模块；
    所述第二1/4波片用于将所述+1级衍射光和所述-1级衍射光的第二偏振光分量变为右旋偏振光，并经所述反射膜反射再次经过所述第二1/4波片变为S偏振光后入射至所述偏振分束棱镜，经所述偏振分束棱镜反射至所述光电接收模块。
  9. 如权利要求8所述的外差一维光栅测量装置，其特征在于，所述光电接收模块包括第一接收器和第二接收器；其中，所述第一接收器用于接收所述+1级衍射光的第一偏振光分量和所述-1级衍射光的第二偏振光分量，并生成频率为f B-f A的拍频信号，传输到所述信号处理系统；所述第二接收器用于接收所述-1级衍射光中的第一偏振光分量和所述+1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，传输到所述信号处理系统。
  10. 如权利要求9所述的外差光栅位移测量装置，其特征在于，当所述一维测量光栅沿光栅矢量方向移动时，所述-1级衍射光发生负向频移-Δf，所述+1级衍射光发生正向频移+Δf，所述第一接收器输出的拍频信号的频率变为f B-f A-2Δf，所述第二接收器输出的拍频信号的频率变为f B-f A+2Δf。
  11. 如权利要求7所述的外差一维光栅测量装置，其特征在于，所述-1级衍射光的第一偏振光分量与所述-1级衍射光的第二偏振光分量的传输光程相等，所述+1级衍射光的第一偏振光分量与所述+1级衍射光的第二偏振光分量的传输光程相等。
  12. 如权利要求7所述的外差一维光栅测量装置，其特征在于，所述读数头还包括分别设置所述一维测量光栅衍射光路上的第一直角棱镜和第二直角 棱镜，所述第一直角棱镜和所述第二直角棱镜分别对+1级衍射光和-1级衍射光进行两次反射，以衍射出射角度再次入射到所述一维测量光栅的表面，两束新的衍射光垂直入射到所述偏振分束棱镜。
  13. 一种外差一维光栅测量方法，其特征在于，包括如下步骤：
    S1、通过光源产生两束重合、偏振正交且具有固定频差的线偏振光，分别为频率为f A的第一偏振光和频率为f B的第二偏振光，所述第一偏振光为S偏振光，所述第二偏振光为P偏振光；
    S2、所述第一偏振光和第二偏振光分别进入读数头，经所述读数头转折后分别入射到一维测量光栅的表面产生分别包括第一偏振光分量与第二偏振光分量的+1级衍射光和-1级衍射光，+1级衍射光和-1级衍射光再经所述读数头分别入射到光电接收模块；
    S3、通过所述光电接收模块接收所述+1级衍射光和所述-1级衍射光；其中，-1级衍射光的第二偏振光分量与+1级衍射光的第一偏振光分量干涉形成频率为f B-f A的拍频信号，-1级衍射光的第一偏振光分量与+1级衍射光的第二偏振光分量干涉形成频率为f B-f A的拍频信号；
    S4、通过所述信号处理系统分别对两路拍频信号进行差分计算，实现所述一维测量光栅单次衍射4倍光学细分的位移测量。
  14. 如权利要求13所述的外差一维光栅测量方法，其特征在于，步骤S2具体包括如下步骤：
    S201、通过所述读数头的反射镜将所述第一偏振光和所述第二偏振光垂直反射至所述一维测量光栅的表面，产生+1级衍射光和-1级衍射光；
    S202、通过所述读数头的转折元件对所述+1级衍射光和所述-1级衍射光进行转折，使所述+1级衍射光和所述-1级衍射光相互平行并垂直入射至所述读数头的偏振分束棱镜；
    S203、通过所述偏振分束棱镜将所述+1级衍射光和所述-1级衍射光的第一偏振光分量分别反射至所述读数头的第一1/4波片，以及将所述+1级衍射光和所述-1级衍射光的第二偏振光分量分别透射至所述读数头的第二1/4波片；
    S204、通过所述第一1/4波片将所述+1级衍射光和所述-1级衍射光的第一偏振光分量分别变为左旋偏振光并入射至所述读数头的回转棱镜，再通过所述回转棱镜对所述+1级衍射光和所述-1级衍射光的第一偏振光分量分别进行两次 反射，使所述+1级衍射光和所述-1级衍射光的第一偏振光分量经所述第一1/4波片变为P偏振光后入射至所述偏振分束棱镜；以及通过所述第二1/4波片将所述+1级衍射光和所述-1级衍射光的第二偏振光分量分别变为右旋偏振光并入射至所述读数头的补偿镜，再通过所述补偿镜对所述+1级衍射光和所述-1级衍射光的第二偏振光分量进行反射，使所述+1级衍射光和所述-1级衍射光的第二偏振光分量经所述第二1/4波片变为S偏振光后入射至所述偏振分束棱镜；
    S205、通过所述偏振分束棱镜将变为P偏振光的所述+1级衍射光和所述-1级衍射光的第一偏振光分量透射至所述光电接收模块，以及将变为S偏振光的所述+1级衍射光和所述-1级衍射光的第二偏振光分量反射至所述光电接收模块。
  15. 如权利要求14所述的外差一维光栅测量方法，其特征在于，所述补偿镜的厚度等于所述回转棱镜的1/2长度，用于补偿所述+1级衍射光和所述-1级衍射光的第二偏振光分量的传输光程，使所述+1级衍射光和所述-1级衍射光的第二偏振光分量的传输光程与+1级衍射光和所述-1级衍射光的第一偏振光分量的传输光程相等。
  16. 如权利要求13所述的外差一维光栅测量方法，其特征在于，步骤S2具体包括如下步骤：
    S201`、所述第一偏振光和所述第二偏振光入射至所述读数头的偏振分束棱镜，通过所述偏振分束棱镜将所述第二偏振光透射至所述读数头的第一1/4波片，将所述第一偏振光反射至所述读数头的第二1/4波片；
    S202`、通过所述第一1/4波片将所述第二偏振光变为右旋偏振光并入射到所述回转棱镜，通过回转棱镜对所述第二偏振光进行回射，使所述第二偏振光经过所述第一1/4波片变为S偏振光后回到所述偏振分束棱镜；以及通过所述第二1/4波片将所述第一偏振光变为左旋偏振光，经所述反射膜反射再次经过所述第二1/4波片变为P偏振光后回到所述偏振分束棱镜；
    S203`、通过所述偏振分束棱镜对变为P偏振光的第一偏振光进行透射，对变为S偏振光的第二偏振光进行反射，使所述第一偏振光与所述第二偏振光合束后入射至所述一维测量光栅的表面，衍射产生-1级衍射光和+1级衍射光；
    S204`、通过所述读数头的转折元件对所述-1级衍射光和所述+1级衍射光进行转折，使所述-1级衍射光和所述+1级衍射光相互平行并垂直入射至所述读数 头的第三1/4波片；
    S205`、通过所述第三1/4波片将所述+1级衍射光和所述-1级衍射光的第一偏振光分量变为S偏振光，垂直入射到所述偏振分束棱镜，以及将所述+1级衍射光和所述-1级衍射光的第二偏振光分量变为P偏振光，垂直入射到所述偏振分束棱镜；
    S206`、通过所述偏振分束棱镜将所述+1级衍射光和所述-1级衍射光的第一偏振光分量反射至所述第一1/4波片，以及将所述+1级衍射光和所述-1级衍射光的第二偏振光分量透射至所述第二1/4波片；
    S207`、通过所述第一1/4波片用于将所述+1级衍射光和所述-1级衍射光的第一偏振光分量变为左旋偏振光并入射到所述回转棱镜，经所述回转棱镜对所述+1级衍射光和-1级衍射光的第一偏振光分量进行两次反射回到所述第一1/4波片变为P偏振光后，再次入射至所述偏振分束棱镜，经所述偏振分束棱镜透射至所述光电接收模块；以及通过所述第二1/4波片将所述+1级衍射光和所述-1级衍射光的第二偏振光分量变为右旋偏振光，并经所述反射膜反射再次经过所述第二1/4波片变为S偏振光后入射至所述偏振分束棱镜，经所述偏振分束棱镜反射至所述光电接收模块。
  17. 如权利要求16所述的外差一维光栅测量方法，其特征在于，所述-1级衍射光的第一偏振光分量与所述-1级衍射光的第二偏振光分量的传输光程相等，所述+1级衍射光的第一偏振光分量与所述+1级衍射光的第二偏振光分量的传输光程相等。
  18. 如权利要求14或16所述的外差一维光栅测量方法，其特征在于，所述光电接收模块包括第一接收器和第二接收器；其中，通过所述第一接收器接收所述-1级衍射光的第二偏振光分量与所述+1级衍射光的第一偏振光分量，并生成频率为f B-f A的拍频信号，传输到所述信号处理系统；通过所述第二接收器接收所述-1级衍射光的第一偏振光分量与所述+1级衍射光的第二偏振光分量，并生成频率为f B-f A的拍频信号，传输到所述信号处理系统。
  19. 如权利要求18所述的外差一维光栅测量方法，其特征在于，当所述一维测量光栅沿光栅矢量方向移动时，所述-1级衍射光发生负向频移-Δf，所述+1级衍射光发生正向频移+Δf，所述第一接收器输出的拍频信号的频率变为f B-f A-2Δf，所述第二接收器输出的拍频信号的频率变为f B-f A+2Δf。
  20. 如权利要求14或16所述的外差一维光栅测量方法，其特征在于， 经所述一维测量光栅衍射产生的+1级衍射光和-1级衍射光分别入射至第一直角棱镜和第二直角棱镜，通过所述第一直角棱镜和所述第二直角棱镜分别对+1级衍射光和-1级衍射光进行两次反射，以衍射出射角度再次入射到所述一维测量光栅的表面，两束新的衍射光垂直入射到所述偏振分束棱镜。
  21. 一种外差二维光栅测量装置，包括光源，所述光源用于产生两束重合、偏振正交且具有固定频差的线偏振光，分别为第一偏振光和第二偏振光；其特征在于，还包括读数头、光电接收模块和信号处理系统；其中，
    所述读数头用于接收所述第一偏振光和所述第二偏振光，并分别入射到移动的二维测量光栅的表面生成第一维度±1级衍射光和第二维度±1级衍射光，第一维度±1级衍射光和第二维度±1级衍射光再经所述读数头分别入射到所述光电接收模块；
    所述光电接收模块用于分别根据所述第一维度±1级衍射光和所述第二维度±1级衍射光生成对应的拍频信号，发送至所述信号处理系统；
    所述信号处理系统用于对所述第一维度±1级衍射光生成的拍频信号进行差分计算和对所述第二维度±1级衍射光的拍频信号进行差分计算，实现所述二维测量光栅第一维度和第二维度的单次衍射4倍光学细分的位移测量。
  22. 如权利要求21所述的外差二维光栅测量装置，其特征在于，所述第一偏振光是频率为f A的S偏振光，所述第二偏振光为频率为f B的P偏振光；以及，所述读数头包括偏振分光棱镜、第一1/4波片、镀有反射膜的第二1/4波片、第三1/4波片、回转棱镜和转折元件；其中，
    所述偏振分光棱镜用于接收所述第一偏振光和所述第二偏振光，并将所述第二偏振光透射到所述第一1/4波片，将所述第一偏振光反射到所述第二1/4波片；
    所述第一1/4波片设置在所述偏振分光棱镜的透射光路上，用于将所述第二偏振光变为右旋偏振光后入射到所述回转棱镜；
    所述回转棱镜设置在所述第一1/4波片的透射光路上，用于对所述第二偏振光进行回射，当所述第二偏振光再次经过所述第一1/4波片变为S偏振光后，回到所述偏振分光棱镜；
    所述第二1/4波片设置在所述偏振分光棱镜的反射光路上，用于将所述第一偏振光变为左旋偏振光后进行反射，再次经过所述第二1/4波片变为P偏振光后， 回到所述偏振分光棱镜；
    所述偏振分光棱镜还用于对所述第一偏振光进行透射，对所述第二偏振光反射，使所述第一偏振光与所述第二偏振光合束后入射到所述第三1/4波片；
    所述第三1/4波片设置在所述偏振分光棱镜对所述第一偏振光进行透射的光路上，用于将所述第一偏振光变为右旋偏振光后垂直入射到所述二维测量光栅的表面，将所述第二偏振光变为左旋偏振光后垂直入射到所述二维测量光栅的表面，所述第一偏振光与所述第二偏振光分别衍射生成所述第一维度±1级衍射光和所述第二维度±1级衍射光。
  23. 如权利要求22所述的外差二维光栅测量装置，其特征在于，所述第一维度±1级衍射光包括第一维度-1级衍射光和第一维度+1级衍射光，所述第二维度±1级衍射光包括第二维度-1级衍射光和第二维度+1级衍射光，所述第一维度-1级衍射光、所述第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光分别包含所述第一偏振光分量和所述第二偏振光分量。
  24. 如权利要求23所述的外差二维光栅测量装置，其特征在于，所述读数头还包括设置在所述二维测量光栅衍射光路上的转折元件，用于对所述第一维度-1级衍射光、所述第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光进行转折，使所述第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光相互平行并垂直入射到所述第三1/4波片；
    所述第三1/4波片用于将所述第一维度-1级衍射光、所述第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光中的第一偏振光分量变为S偏振光并垂直入射到所述偏振分束棱镜，以及将所述第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量变为P偏振光并垂直入射到所述偏振分束棱镜；
    所述偏振分束棱镜用于将所述第一维度-1级衍射光、所述第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光中的第一偏振光分量反射到所述第一1/4波片，以及将所述第一维度-1级衍射光、所述第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光中的第二偏振光分量透射到所述第二1/4波片；
    所述第一1/4波片用于将所述第一维度-1级衍射光、所述第一维度+1级 衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光中的第一偏振光分量变为左旋偏振光并再次入射到所述回转棱镜；
    所述回转棱镜用于分别对所述第一维度+1级衍射光、所述第一维度-1级衍射光、所述第二维度-1级衍射光和所述第二维度+1级衍射光中的第一偏振光分量进行两次反射出射到所述第一1/4波片，在变为P偏振光后再次入射到所述偏振分束棱镜，经所述偏振分束棱镜透射到所述光电接收模块；
    所述第二1/4波片用于将所述第一维度-1级衍射光、所述第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光中的第二偏振光分量变为右旋偏振光后进行反射，再次经过所述第二1/4波片变为S偏振光后入射到所述偏振分束棱镜，经所述偏振分束棱镜分别反射到所述光电接收模块。
  25. 如权利要求24所述的外差二维光栅测量装置，其特征在于，所述光电接收模块包括第一接收器、第二接收器、第三接收器和第四接收器；其中，
    所述第一接收器用于接收所述第一维度+1级衍射光中的第一偏振光分量和所述第一维度-1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至所述信号处理系统；
    所述第二接收器用于接收所述第一维度-1级衍射光中的第一偏振光分量和所述第一维度+1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至所述信号处理系统；
    所述第三接收器用于接收所述第二维度+1级衍射光中的第一偏振光分量和所述第二维度-1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至所述信号处理系统；
    所述第四接收器用于接收所述第二维度-1级衍射光中的第一偏振光分量和所述第二维度+1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至所述信号处理系统。
  26. 如权利要求25所述的外差二维光栅测量装置，其特征在于，所述第一接收器、所述第二接收器、所述第三接收器和所述第四接收器各自接收的第一偏振光分量和第二偏振光分量分别两次经过所述回转棱镜，其在所述读数头中传输的光程相等。
  27. 如权利要求25所述的外差二维光栅测量装置，其特征在于，当所述 二维测量光栅沿第一维度光栅矢量方向移动时，所述第一维度-1级衍射光发生负向频移-Δf，所述第一维度+1级衍射光发生正向频移+Δf，所述第一接收器输出的拍频信号的频率变为f B-f A-2Δf，所述第二接收器输出的拍频信号的频率变为f B-f A+2Δf；
    当所述二维测量光栅沿第二维度光栅矢量方向移动时，所述第二维度-1级衍射光发生负向频移-Δf，所述第二维度+1级衍射光发生正向频移+Δf，所述第三接收器输出的拍频信号的频率变为f B-f A-2Δf，所述第四接收器输出的拍频信号的频率变为f B-f A+2Δf。
  28. 如权利要求27所述的外差二维光栅测量装置，其特征在于，所述信号处理系统用于对所述第一接收器输出的拍频信号和所述第二接收器输出的拍频信号进行差分计算，实现所述二维测量光栅第一维度的单次衍射4倍光学细分的位移测量，对所述第三接收器输出的拍频信号和所述第四接收器输出的拍频信号进行差分计算，实现所述二维测量光栅第二维度的单次衍射4倍光学细分的位移测量。
  29. 一种外差二维光栅测量方法，其特征在于，包括如下步骤：
    S1、通过光源产生两束重合、偏振正交且具有固定频差的线偏振光，分别为频率为f A的第一偏振光和频率为f B的第二偏振光，所述第一偏振光为S偏振光，所述第二偏振光为P偏振光；
    S2、所述第一偏振光和第二偏振光分别进入读数头，经所述读数头反射与透射后分别入射到移动的二维测量光栅的表面生成第一维度±1级衍射光和第二维度±1级衍射光，第一维度±1级衍射光和第二维度±1级衍射光再经所述读数头分别入射到光电接收模块；
    S3、所述光电接收模块分别根据所述第一维度±1级衍射光和所述第二维度±1级衍射光生成对应的拍频信号，发送至信号处理系统；
    S4、所述信号处理系统分别对所述第一维度±1级衍射光生成的拍频信号进行差分计算及对所述第二维度±1级衍射光生成的拍频信号进行差分计算，实现所述二维测量光栅第一维度和第二维度的单次衍射4倍光学细分的位移测量。
  30. 如权利要求29所述的外差二维光栅测量方法，其特征在于，所述步骤S2具体包括如下步骤：
    S201、所述第一偏振光经所述偏振分光棱镜反射到所述第二1/4波片，在将所述第一偏振光变为左旋偏振光后进行反射再次经过所述第二1/4波片变为P偏振光后，回到所述偏振分光棱镜；以及，所述第二偏振光经所述偏振分光棱镜透射到所述第一1/4波片，在将所述第二偏振光变为右旋偏振光后入射到所述回转棱镜，所述回转棱镜对所述第二偏振光进行回射，当所述第二偏振光再次经过所述第一1/4波片变为S偏振光后，回到所述偏振分光棱镜；
    S202、所述偏振分光棱镜对所述第一偏振光进行透射，对所述第二偏振光反射，使所述第一偏振光与所述第二偏振光合束后入射到第三1/4波片，所述第三1/4波片将所述第一偏振光变为右旋偏振光后垂直入射到所述二维测量光栅的表面，及将第二偏振光变为左旋偏振光后垂直入射到所述二维测量光栅的表面，所述第一偏振光与所述第二偏振光分别衍射生成所述第一维度±1级衍射光和所述第二维度±1级衍射光。
  31. 如权利要求30所述的外差二维光栅测量方法，其特征在于，所述第一维度±1级衍射光包括第一维度-1级衍射光和第一维度+1级衍射光，所述第二维度±1级衍射光包括第二维度-1级衍射光和第二维度+1级衍射光，所述第一维度-1级衍射光、所述第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光分别包含所述第一偏振光分量和所述第二偏振光分量。
  32. 如权利要求31所述的外差二维光栅测量方法，其特征在于，在步骤S202之后还包括如下步骤：
    S203、所述第一维度-1级衍射光、所述第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光经转折元件转折后，相互平行并垂直入射到第三1/4波片；
    S204、所述第三1/4波片将所述第一维度-1级衍射光、所述第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光中的第一偏振光分量变为S偏振光后垂直入射到所述偏振分束棱镜，以及所述第一维度-1级衍射光、第一维度+1级衍射光、第二维度-1级衍射光、第二维度+1级衍射光中的第二偏振光分量变为P偏振光后垂直入射到所述偏振分束棱镜；
    S205、所述偏振分束棱镜将所述第一维度-1级衍射光、所述第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光中的第一偏振光分量反射到所述第一1/4波片，以及将所述第一维度-1级衍射光、所述 第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光中的第二偏振光分量透射到所述第二1/4波片；
    S206、所述第二1/4波片将所述第一维度-1级衍射光、所述第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光中的第二偏振光分量变为右旋偏振光后进行反射，再次经过所述第二1/4波片变为S偏振光后入射到所述偏振分束棱镜，经所述偏振分束棱镜分别反射到所述光电接收模块，以及所述第一1/4波片将所述第一维度-1级衍射光、所述第一维度+1级衍射光、所述第二维度-1级衍射光、所述第二维度+1级衍射光中的第一偏振光分量变为左旋偏振光并再次入射到所述回转棱镜，所述回转棱镜分别对所述第一维度+1级衍射光、所述第一维度-1级衍射光、所述第二维度-1级衍射光和所述第二维度+1级衍射光中的第一偏振光分量进行两次反射出射到所述第一1/4波片，在变为P偏振光后再次入射到所述偏振分束棱镜，经所述偏振分束棱镜透射到所述光电接收模块。
  33. 如权利要求32所述的外差二维光栅测量方法，其特征在于，所述光电接收模块包括第一接收器、第二接收器、第三接收器和第四接收器；其中，
    所述第一接收器用于接收所述第一维度+1级衍射光中的第一偏振光分量和所述第一维度-1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至所述信号处理系统；
    所述第二接收器用于接收所述第一维度-1级衍射光中的第一偏振光分量和所述第一维度+1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至所述信号处理系统；
    所述第三接收器用于接收所述第二维度+1级衍射光中的第一偏振光分量和所述第二维度-1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至所述信号处理系统；
    所述第四接收器用于接收所述第二维度-1级衍射光中的第一偏振光分量和所述第二维度+1级衍射光中的第二偏振光分量，并生成频率为f B-f A的拍频信号，发送至所述信号处理系统。
  34. 如权利要求33所述的外差二维光栅测量方法，其特征在于，所述第一接收器、所述第二接收器、所述第三接收器和所述第四接收器各自接收的第一偏振光分量和第二偏振光分量分别两次经过所述回转棱镜，其在所述读数头 中传输的光程相等。
  35. 如权利要求33所述的外差二维光栅测量方法，其特征在于，当所述二维测量光栅沿第一维度光栅矢量方向移动时，所述第一维度-1级衍射光发生负向频移-Δf，所述第一维度+1级衍射光发生正向频移+Δf，所述第一接收器输出的拍频信号的频率变为f B-f A-2Δf，所述第二接收器输出的拍频信号的频率变为f B-f A+2Δf；
    当所述二维测量光栅沿第二维度光栅矢量方向移动时，所述第二维度-1级衍射光发生负向频移-Δf，所述第二维度+1级衍射光发生正向频移+Δf，所述第三接收器输出的拍频信号的频率变为f B-f A-2Δf，所述第四接收器输出的拍频信号的频率变为f B-f A+2Δf。
  36. 如权利要求35所述的外差二维光栅测量方法，其特征在于，所述信号处理系统对所述第一接收器输出的拍频信号和所述第二接收器输出的拍频信号进行差分计算，实现所述二维测量光栅第一维度的单次衍射4倍光学细分的位移测量，对所述第三接收器输出的拍频信号和所述第四接收器输出的拍频信号进行差分计算，实现所述二维测量光栅第二维度的单次衍射4倍光学细分的位移测量。
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115276817A (zh) * 2022-07-20 2022-11-01 陕西师范大学 一种基于矢量涡旋光双维度多模式的通信方法及系统

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102353327A (zh) * 2011-06-27 2012-02-15 中国人民解放军国防科学技术大学 双频激光光栅干涉测量方法及测量系统
CN102944176A (zh) * 2012-11-09 2013-02-27 清华大学 一种外差光栅干涉仪位移测量系统
CN103604375A (zh) * 2013-11-19 2014-02-26 哈尔滨工业大学 抗光学混叠的双频激光光栅干涉二维测量方法及系统
CN103759656A (zh) * 2014-01-23 2014-04-30 清华大学 一种二自由度外差光栅干涉仪位移测量系统
US9030661B1 (en) * 2013-03-15 2015-05-12 Kla-Tencor Corporation Alignment measurement system
CN104634254A (zh) * 2015-03-06 2015-05-20 中国科学院光电技术研究所 一种基于外差干涉和二次衍射效应的光栅位移测量系统

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102353327A (zh) * 2011-06-27 2012-02-15 中国人民解放军国防科学技术大学 双频激光光栅干涉测量方法及测量系统
CN102944176A (zh) * 2012-11-09 2013-02-27 清华大学 一种外差光栅干涉仪位移测量系统
US9030661B1 (en) * 2013-03-15 2015-05-12 Kla-Tencor Corporation Alignment measurement system
CN103604375A (zh) * 2013-11-19 2014-02-26 哈尔滨工业大学 抗光学混叠的双频激光光栅干涉二维测量方法及系统
CN103759656A (zh) * 2014-01-23 2014-04-30 清华大学 一种二自由度外差光栅干涉仪位移测量系统
CN104634254A (zh) * 2015-03-06 2015-05-20 中国科学院光电技术研究所 一种基于外差干涉和二次衍射效应的光栅位移测量系统

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115276817A (zh) * 2022-07-20 2022-11-01 陕西师范大学 一种基于矢量涡旋光双维度多模式的通信方法及系统
CN115276817B (zh) * 2022-07-20 2024-01-16 陕西师范大学 一种基于矢量涡旋光双维度多模式的通信方法及系统

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