CN116007503A - Interference displacement measuring device based on polarization beam splitting grating - Google Patents
Interference displacement measuring device based on polarization beam splitting grating Download PDFInfo
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- CN116007503A CN116007503A CN202211314696.6A CN202211314696A CN116007503A CN 116007503 A CN116007503 A CN 116007503A CN 202211314696 A CN202211314696 A CN 202211314696A CN 116007503 A CN116007503 A CN 116007503A
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Abstract
The invention discloses an interference displacement measuring device based on a polarization beam splitting grating, which comprises a light source assembly, a light path assembly, a photoelectric receiving module and a signal processing module; the light source component is used for generating a measuring beam; the light path component comprises a first reflecting prism, a reflecting grating, a second reflecting prism, a third reflecting prism and a polarization beam splitting grating; the light source component emits measuring light beams to the first reflecting prism, the first reflecting prism is used for reflecting the measuring light beams to the reflecting grating, the reflecting grating divides the measuring light beams into first diffracted light and second diffracted light, the first diffracted light and the second diffracted light are respectively reflected to the second reflecting prism and the third reflecting prism, and the second reflecting prism and the third reflecting prism are used for adjusting the first diffracted light and the second diffracted light and then making the first diffracted light and the second diffracted light incident on the polarization beam splitting grating; the photoelectric receiving module is in telecommunication connection with the signal processing module, and the signal processing module is used for carrying out differential calculation on the first beat frequency signal and the second beat frequency signal to calculate displacement.
Description
Technical Field
The invention relates to the technical field of grating interferometers, in particular to an interference displacement measuring device based on a polarization beam splitting grating.
Background
With the development of high-end manufacturing industry, the precision requirement on precision measurement is also higher and higher. In the field of high-precision measurement, two measurement systems exist at present, one is that a laser displacement measurement system takes laser wavelength as a measurement reference, the laser wavelength is easily influenced by air refractive index change, and even in a working environment with very good temperature, humidity and air flow pressure control due to air flow caused by rapid movement of a workpiece table, the laser wavelength is easily influenced by air refractive index change, so that the further improvement of positioning precision is influenced. The grating displacement measurement system takes grating pitch as a measurement reference, can greatly reduce errors caused by air refractive index, has measurement accuracy from micron level to nano level and even sub-nano level, and provides effective technical support for development of ultra-precise processing technology. The core element of the grating displacement measurement system is a grating, and the grating displacement measurement system uses the grating pitch as a reference, has compact structure, symmetrical light path, short light path and low sensitivity to external environment, and can be applied to multidimensional precise displacement measurement. In principle, grating displacement measurement systems can be divided into homodyne grating interferometric displacement measurement systems and heterodyne grating interferometric displacement measurement systems. The homodyne grating interference displacement measuring system uses a light splitting device to split a light source into reference light and measuring light, and then the two light beams are overlapped through different paths to form an interference signal which can be measured. Because the carrier frequencies of the light to be measured and the reference light are the same, the obtained interference light field can eliminate the influence caused by the frequency noise of the electromagnetic wave. Heterodyne grating interferometry is a method of measuring optical phase changes. The heterodyne grating interference displacement measurement is to superimpose two light beams with slight frequency difference, the interference signal formed is beat frequency changing along with time and phase, when displacement measurement is carried out, the change information of displacement is recorded in the phase of beat frequency signal, and the required phase change can be demodulated by corresponding demodulation technology.
The conventional heterodyne grating displacement measurement system divides an incident unpolarized light beam into two orthogonal polarized light beams through a polarization beam splitter, so that a stable interference signal is obtained. However, the polarizing beam splitter is made of natural birefringent crystal, which is large and heavy, or multilayer dielectric film, which is expensive to manufacture, and it is difficult to meet the requirements of the optical system.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides an interference displacement measuring device based on a polarization beam splitting grating, and solves the problems of large volume and high cost of the interference device in the prior art.
The technical scheme of the invention is as follows: an interference displacement measuring device based on polarization beam splitting grating comprises a light source component, a light path component, a photoelectric receiving module and a signal processing module;
the light source component is used for generating two polarized light beams which are overlapped, have orthogonal polarization and have fixed frequency difference to serve as measuring light beams;
the light path component comprises a first reflecting prism, a reflecting grating, a second reflecting prism, a third reflecting prism and a polarization beam splitting grating;
the light source assembly emits measuring light beams to the first reflecting prism, the first reflecting prism is arranged on an emergent light path of the light source assembly and is used for reflecting the measuring light beams to the reflecting grating, the reflecting grating divides the measuring light beams into first diffracted light and second diffracted light, the second reflecting prism and the third reflecting prism are arranged on a reflecting light path of the reflecting grating, the first diffracted light and the second diffracted light are respectively reflected to the second reflecting prism and the third reflecting prism, and the second reflecting prism and the third reflecting prism are used for adjusting the first diffracted light and the second diffracted light and then making the first diffracted light and the second diffracted light enter the polarization beam splitting grating;
the first diffracted light is incident on the polarization beam splitting grating to generate a first S light component and a first P light component, and the second diffracted light is incident on the polarization beam splitting grating to generate a second S light component and a second P light component;
the reflection type grating is arranged on the surface of a moving object, and the moving object is used for driving the reflection type grating to move along the grating vector direction Y;
the photoelectric receiving module is in telecommunication connection with the signal processing module and comprises a first photoelectric detector and a second photoelectric detector, the first photoelectric receiver is used for receiving the first P light component and the second S light component and generating a first beat signal, and the second photoelectric receiver is used for receiving the second P light component and the first S light component and generating a second beat signal; the signal processing module is used for carrying out differential calculation on the first beat frequency signal and the second beat frequency signal, and calculating displacement.
Further, the first diffracted light is-1 order, and the second diffracted light is +1 order.
Further, the transmission optical path length of the first P-light component is equal to the transmission optical path length of the second S-light component, and the transmission optical path length of the second P-light component is equal to the transmission optical path length of the first S-light component.
Further, the polarization beam splitting grating adopts a transmission type polarization beam splitting grating structure.
Further, the second reflecting prism and the third reflecting prism are used for adjusting the first diffracted light and the second diffracted light and then making the first diffracted light and the second diffracted light incident on the polarization beam splitting grating at a Li Teluo angle.
Further, the measuring beam comprises a first polarized light and a second polarized light, wherein the first polarized light is P polarized light, and the frequency is f A The second polarized light is S polarized light with the frequency f B The first polarized light and the second polarized light are reflected by the first reflecting prism to form first diffracted light and second diffracted light.
Further, the second reflecting prism is opposite to the third reflecting prism and is arranged in parallel, the reflecting grating is opposite to the polarization beam splitting grating and is arranged in parallel, the first reflecting prism is located between the second reflecting prism and the third reflecting prism, the second reflecting prism and the third reflecting prism are respectively located at two sides of the reflecting grating and the polarization beam splitting grating, meanwhile, the first reflecting prism is located between the reflecting grating and the polarization beam splitting grating, and the first reflecting prism is obliquely arranged to enable the light source assembly to send out measuring light beams to reflect to the reflecting grating.
Further, the included angle between the first reflecting prism and the reflecting grating is an acute angle, and the first reflecting prism is used for making the measuring light beam vertically incident to the reflecting grating.
The working principle of the interference displacement measuring device based on the polarization beam splitting grating is as follows:
the light source component is used for generating two polarized light beams which are coincident, have orthogonal polarization and have fixed frequency difference as measuring light beams, the measuring light beams comprise first polarized light and second polarized light, the first polarized light is P polarized light, and the frequency is f A The second polarized light is S polarized light with the frequency f B The first polarized light and the second polarized light are reflected by the first reflecting prism to form first diffracted light and second diffracted light, the first diffracted light is incident on the polarization beam splitting grating to generate a first S light component and a first P light component, the second diffracted light is incident on the polarization beam splitting grating to generate a second S light component and a second P light component, and the first photoelectric receiver is used for receiving the first P light component and the second S light component and generating a frequency f A -f B A second photoelectric receiver for receiving the second P light component and the first S light component and generating a first beat signal with frequency f A -f B The first beat signal and the second beat signal are respectively transmitted to the signal processing module; when the reflective grating moves along the direction of the grating vector, the first diffracted light is negatively shifted by- Δf and the second diffracted light is positively shifted by +Δf due to the Doppler shift effect of the grating, so that the first beat signal output by the first photoelectric receiver becomes f A -f B -2Δf, the second beat signal output by the second photo receiver becomes f A -f B And the signal processing module carries out differential calculation on the first beat frequency signal and the second beat frequency signal to realize displacement measurement of measuring 4 times of optical subdivision of single diffraction of the reflection type grating.
Compared with the prior art, the invention has the following beneficial effects:
the invention adopts two gratings, one of which is a reflective grating and the other is a transmission polarization beam splitting grating, the two gratings are simple in structure and easy to manufacture in large scale, are both high diffraction efficiency grating structures, and can realize displacement measurement of 4 times of optical subdivision by measuring single diffraction of the gratings. Moreover, the grating arrangement configuration adopted by the invention greatly improves the anti-interference capability and integration degree of the displacement measurement system, reduces the influence of environmental factors on the measurement system, has strong anti-interference capability, reduces errors in the measurement process, and improves the resolution of the measurement system.
Drawings
FIG. 1 is a schematic diagram of an interferometric displacement measuring device based on polarization beam splitter gratings according to the present invention.
Fig. 2 is a schematic diagram of a transmissive polarization beam splitter grating.
The light source module 1, a measuring beam 11, a first reflecting prism 2, a reflecting grating 3, a second reflecting prism 4, a third reflecting prism 5, a polarization beam splitting grating 6, a first photodetector 7, a second photodetector 8, a first diffracted light 9, a first S light component 91, a first P light component 92, a second diffracted light 10, a second S light component 101, a second P light component 102, and a signal processing module 100.
Detailed Description
The present invention will be described in further detail with reference to examples, but embodiments of the present invention are not limited thereto.
Examples
In order to solve the problems that in the prior art, optical subdivision of 4 times or more is realized through 2 times of diffraction or more, the optical structure of a measurement system becomes more complex, the diffraction light at different positions of a grating is utilized through multiple times of diffraction, and the surface shape precision of the grating and the attitude error between the grating and a reading head can greatly influence the measurement precision.
The embodiment provides an interference displacement measuring device based on a polarization beam splitting grating, so that when two beams of polarized light with fixed frequency difference emitted by a light source component are incident on the surface of a measuring grating through a light path component, 4 times of optical subdivision can be realized by primary diffraction, the influence on the measuring precision caused by the surface shape precision of the grating and the attitude error between the light path components can be avoided, and the light path component has a simple structure, a small volume and light weight, and the complexity of an optical structure in a measuring system can be simplified.
The embodiment provides an interference displacement measuring device based on a polarization beam splitting grating, which comprises a light source assembly 1, a light path assembly, a photoelectric receiving module and a signal processing module 100.
The light source assembly is used for generating two polarized light beams 11 which are coincident, have orthogonal polarization and have fixed frequency difference. Wherein the measuring beam comprises a first polarized light and a second polarized light, the first polarized light is P polarized light, and the frequency is f A The second polarized light is S polarized light with the frequency f B 。
In one embodiment, the light source assembly employs a red laser light source.
As shown in fig. 1, the optical path assembly includes a first reflecting prism 2, a reflecting grating 3, a second reflecting prism 4, a third reflecting prism 5, and a polarization beam splitter grating 6.
The light source component 1 emits measuring light beams to the first reflecting prism 2, the first reflecting prism 2 is arranged on an emergent light path of the light source component 1, the first reflecting prism 2 is used for reflecting the measuring light beams to the reflecting grating 3, the reflecting grating divides the measuring light beams into first diffracted light 9 and second diffracted light 10, the second reflecting prism and the third reflecting prism are arranged on a reflecting light path of the reflecting grating, the first diffracted light and the second diffracted light are respectively reflected to the second reflecting prism and the third reflecting prism, and the second reflecting prism and the third reflecting prism are used for adjusting the first diffracted light and the second diffracted light and then making the first diffracted light and the second diffracted light incident on the polarization beam splitting grating.
In one embodiment, the second reflecting prism and the third reflecting prism are opposite and parallel, the reflecting grating and the polarization beam splitting grating are opposite and parallel, the first reflecting prism is located between the second reflecting prism and the third reflecting prism, the second reflecting prism and the third reflecting prism are located at two sides of the reflecting grating and the polarization beam splitting grating respectively, meanwhile, the first reflecting prism is located between the reflecting grating and the polarization beam splitting grating, the first reflecting prism is obliquely arranged to enable the light source assembly to send out the measuring beam to reflect to the reflecting grating, an included angle between the first reflecting prism and the reflecting grating is an acute angle, and the first reflecting prism is used for enabling the measuring beam to vertically enter the reflecting grating.
In one embodiment, the first diffracted light is-1 order and the second diffracted light is +1 order.
In one embodiment, the second reflecting prism and the third reflecting prism are configured to adjust the first diffracted light and the second diffracted light to be incident on the polarization beam splitter grating at Li Teluo.
The first diffracted light is incident on the polarization beam splitter grating to produce a first S light component 91 and a first P light component 92, and the second diffracted light is incident on the polarization beam splitter grating to produce a second S light component 101 and a second P light component 102.
In one embodiment, the transmission optical path of the first P-light component is equal to the transmission optical path of the second S-light component, and the transmission optical path of the second P-light component is equal to the transmission optical path of the first S-light component.
The photoelectric receiving module is in telecommunication connection with the signal processing module 100, and comprises a first photoelectric detector 7 and a second photoelectric detector 8, wherein the first photoelectric receiver is used for receiving a first P light component and a second S light component and generating a first beat signal, and the second photoelectric receiver is used for receiving a second P light component and a first S light component and generating a second beat signal; the signal processing module is used for carrying out differential calculation on the first beat frequency signal and the second beat frequency signal, and calculating displacement.
In one embodiment, the polarization beam splitter grating employs a transmissive polarization beam splitter grating structure. Fig. 2 shows a schematic diagram of a transmissive polarization beam splitter grating, taking first diffracted light as an example, the first diffracted light is incident on the polarization beam splitter grating at Li Teluo, the energy of the generated first S light component is concentrated in the 0 order, and the energy of the first P light component is concentrated in the-1 order.
In one embodiment, the reflective grating is disposed on a surface of a moving object, and the moving object is configured to drive the reflective grating to move along the grating vector direction Y. The grating is taken as a periodic structure, and the direction of the grating vector is understood herein to be the direction of the period extension of the grating.
The working principle of the interference displacement measuring device based on the polarization beam splitting grating is as follows:
the light source component is used for generating two polarized light beams which are coincident, have orthogonal polarization and have fixed frequency difference as measuring light beams, the measuring light beams comprise first polarized light and second polarized light, the first polarized light is P polarized light, and the frequency is f A The second polarized light is S polarized light with the frequency f B The first polarized light and the second polarized light are reflected by the first reflecting prism to form first diffracted light and second diffracted light, the first diffracted light is incident on the polarization beam splitting grating to generate a first S light component and a first P light component, the second diffracted light is incident on the polarization beam splitting grating to generate a second S light component and a second P light component, and the first photoelectric receiver is used for receiving the first P light component and the second S light component and generating a frequency f A -f B A second photoelectric receiver for receiving the second P light component and the first S light component and generating a first beat signal with frequency f A -f B The first beat signal and the second beat signal are respectively transmitted to the signal processing module; when the reflective grating moves along the direction of the grating vector, the first diffracted light is negatively shifted by- Δf and the second diffracted light is positively shifted by +Δf due to the Doppler shift effect of the grating, so that the first beat signal output by the first photoelectric receiver becomes f A -f B -2Δf, the second beat signal output by the second photo receiver becomes f A -f B And the signal processing module carries out differential calculation on the first beat frequency signal and the second beat frequency signal to realize displacement measurement of measuring 4 times of optical subdivision of single diffraction of the reflection type grating.
As described above, the present invention can be better realized, and the above-described embodiments are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention; all equivalent changes and modifications are intended to be covered by the scope of the appended claims.
Claims (8)
1. The interference displacement measuring device based on the polarization beam splitting grating is characterized by comprising a light source assembly, a light path assembly, a photoelectric receiving module and a signal processing module;
the light source component is used for generating two polarized light beams which are overlapped, have orthogonal polarization and have fixed frequency difference to serve as measuring light beams;
the light path component comprises a first reflecting prism, a reflecting grating, a second reflecting prism, a third reflecting prism and a polarization beam splitting grating;
the light source assembly emits measuring light beams to the first reflecting prism, the first reflecting prism is arranged on an emergent light path of the light source assembly and is used for reflecting the measuring light beams to the reflecting grating, the reflecting grating divides the measuring light beams into first diffracted light and second diffracted light, the second reflecting prism and the third reflecting prism are arranged on a reflecting light path of the reflecting grating, the first diffracted light and the second diffracted light are respectively reflected to the second reflecting prism and the third reflecting prism, and the second reflecting prism and the third reflecting prism are used for adjusting the first diffracted light and the second diffracted light and then making the first diffracted light and the second diffracted light enter the polarization beam splitting grating;
the first diffracted light is incident on the polarization beam splitting grating to generate a first S light component and a first P light component, and the second diffracted light is incident on the polarization beam splitting grating to generate a second S light component and a second P light component;
the reflection type grating is arranged on the surface of a moving object, and the moving object is used for driving the reflection type grating to move along the grating vector direction Y;
the photoelectric receiving module is in telecommunication connection with the signal processing module and comprises a first photoelectric detector and a second photoelectric detector, the first photoelectric receiver is used for receiving the first P light component and the second S light component and generating a first beat signal, and the second photoelectric receiver is used for receiving the second P light component and the first S light component and generating a second beat signal; the signal processing module is used for carrying out differential calculation on the first beat frequency signal and the second beat frequency signal, and calculating displacement.
2. The polarization beam splitter grating-based interferometric displacement measuring device of claim 1, wherein the first diffracted light is-1 order and the second diffracted light is +1 order.
3. The polarization beam splitter grating-based interferometric displacement measurement device of claim 1, wherein the first P-light component and the second S-light component have equal transmission optical paths and the second P-light component and the first S-light component have equal transmission optical paths.
4. The device for measuring the interference displacement based on the polarization beam splitter grating according to claim 1, wherein the polarization beam splitter grating adopts a transmission type polarization beam splitter grating structure.
5. The device of claim 1, wherein the second and third reflecting prisms are configured to adjust the first and second diffracted lights to be incident on the polarization beam splitter grating at Li Teluo.
6. The device of claim 1, wherein the measuring beam comprises a first polarized light and a second polarized light, the first polarized light is P polarized light, and the frequency is f A The second polarized light is S polarized light with the frequency f B The first polarized light and the second polarized light are reflected by the first reflecting prism to form first diffracted light and second diffracted light.
7. The device for measuring the interference displacement based on the polarization beam splitter grating according to claim 1, wherein the second reflecting prism and the third reflecting prism are arranged oppositely and in parallel, the reflecting grating and the polarization beam splitter grating are arranged oppositely and in parallel, the first reflecting prism is positioned between the second reflecting prism and the third reflecting prism, the second reflecting prism and the third reflecting prism are respectively positioned at two sides of the reflecting grating and the polarization beam splitter grating, and meanwhile, the first reflecting prism is positioned between the reflecting grating and the polarization beam splitter grating, and the first reflecting prism is obliquely arranged so that the light source component emits the measuring light beam to reflect to the reflecting grating.
8. The device of claim 7, wherein an included angle between the first reflecting prism and the reflective grating is an acute angle, and the first reflecting prism is configured to make the measuring beam vertically incident on the reflective grating.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117367291A (en) * | 2023-12-08 | 2024-01-09 | 中国科学院长春光学精密机械与物理研究所 | Bidirectional Littrow two-degree-of-freedom grating interferometry device based on double gratings |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117367291A (en) * | 2023-12-08 | 2024-01-09 | 中国科学院长春光学精密机械与物理研究所 | Bidirectional Littrow two-degree-of-freedom grating interferometry device based on double gratings |
| CN117367291B (en) * | 2023-12-08 | 2024-02-13 | 中国科学院长春光学精密机械与物理研究所 | Bidirectional Littrow two-degree-of-freedom grating interferometry device based on double gratings |
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