CN112484646B - Homodyne one-dimensional grating displacement measuring device - Google Patents
Homodyne one-dimensional grating displacement measuring device Download PDFInfo
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- CN112484646B CN112484646B CN202011287432.7A CN202011287432A CN112484646B CN 112484646 B CN112484646 B CN 112484646B CN 202011287432 A CN202011287432 A CN 202011287432A CN 112484646 B CN112484646 B CN 112484646B
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
- G01B11/27—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes
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Abstract
The invention provides a homodyne one-dimensional grating displacement measuring device which comprises a single-frequency laser, a polarization beam splitter prism, a plane mirror group, 1/4 wave plates, two signal receiving units and a signal processing system, wherein the single-frequency laser is used for sending a beam of linearly polarized light with fixed frequency to be incident to the polarization beam splitter prism for splitting, one beam of linearly polarized light is reflected to the plane mirror group, is vertically incident to a diffraction grating through a 1/4 wave plate, is diffracted to generate diffracted light through the diffraction grating, and is incident to the beam splitter prism through the plane mirror group, a 1/4 wave plate and the polarization beam splitter prism; the other beam of the light beam is symmetrical to the other beam of the light beam to generate diffracted light, and the two beams of the diffracted light interfere to form interference light which enters the two signal receiving units respectively after being split by the beam splitter prism. The invention can realize the large-stroke straightness measurement and the displacement measurement of single-time diffraction four-time subdivision, and can realize the displacement measurement of eight-time subdivision by adopting a right-angle prism or a pyramid prism.
Description
Technical Field
The invention relates to the technical field of ultra-precise displacement measurement, in particular to a homodyne one-dimensional grating displacement measuring device which can realize 4-time optical subdivision based on single diffraction and can also form the traditional four-step phase-shift structure measurement.
Background
The grating displacement measurement system is widely applied to the fields of aerospace, semiconductor processing and manufacturing, ultra-precision processing and the like, and along with the rapid development of industrial technology, the requirements on the aspects of measurement dimension, measurement speed, measurement precision, measurement range and the like of the ultra-precision displacement measurement technology are higher and higher. The grating displacement measuring system takes the grating pitch of the grating as a measuring reference, eliminates the error influence caused by the change of the laser wavelength, has low requirement on the environment, low cost and simple structure, and is particularly suitable for ultra-precise instruments and high-end experimental equipment.
At present, with the improvement of the high-scribing-precision grating manufacturing technology and the improvement of the grating splicing technology, the grating displacement measurement is developed towards higher measurement precision and wider measurement dimension, wherein the multi-dimensional measurement is realized by adding one more measurement signal at most. In order to achieve higher-precision measurement, not only a multi-path measurement mode can be adopted, but also high-power subdivision measurement can be realized by adopting different turning devices to perform multiple diffraction, wherein a right-angle prism, a pyramid prism and the like are mostly adopted.
The traditional four-step phase shift structure is adopted in home and abroad zero-difference grating displacement measurement systems, one is used as a reference grating, the other is used as a measurement grating, diffraction light generated by the reference grating and diffraction light generated by the measurement grating are interfered at a polarization beam splitter prism, the cost is reduced, the volume of the grating measurement system is increased, and the measurement precision is limited.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a dual-channel grating displacement measuring device taking the same diffraction grating as a reference, wherein two beams of light are used as measuring light, and the two beams of light are vertically incident to the diffraction grating in parallel at a spatial position, so that quadruple optical subdivision of single diffraction can be realized, and also octave optical subdivision can be realized; in the aspect of measurement, long-stroke measurement is realized, and meanwhile, the accuracy of small-range measurement is also ensured.
Specifically, the homodyne one-dimensional grating displacement measuring device provided by the invention adopts the following technical scheme:
the homodyne one-dimensional grating displacement measuring device comprises: the single-frequency laser device comprises a single-frequency laser device, a first polarization beam splitter prism, a first plane reflector, a second plane reflector, a third plane reflector, a fourth plane reflector, a fifth plane reflector, a sixth plane reflector, a first 1/4 wave plate, a first signal receiving unit, a second signal receiving unit and a signal processing system, wherein the first polarization beam splitter prism is arranged in the emergent direction of the single-frequency laser device, the first plane reflector and the fourth plane reflector are symmetrically arranged in the reflecting direction and the transmitting direction of the first polarization beam splitter prism, a first 1/4 wave plate is arranged in the reflecting direction of the first plane reflector and the fourth plane reflector, and the first signal receiving unit and the second signal receiving unit are symmetrically arranged in the reflecting direction and the transmitting direction of the beam splitter prism; the single-frequency laser emits a beam of linearly polarized light with fixed frequency f to enter a first polarization splitting prism for splitting, one beam of linearly polarized light is reflected to a first plane reflector, is vertically reflected to a first 1/4 wave plate through the first plane reflector, is vertically incident to a diffraction grating, is diffracted by the diffraction grating to generate first diffracted light comprising +/-1-order diffracted light, is vertically reflected to a first 1/4 wave plate through a second plane reflector and a third plane reflector respectively, is reflected to the first polarization splitting prism through the first plane reflector, and is transmitted to the splitting prism; the other beam is transmitted to the fourth plane mirror, is vertically reflected to the first 1/4 wave plate by the fourth plane mirror, is vertically incident to the diffraction grating, is diffracted by the diffraction grating to generate second diffraction light comprising +/-1-order diffraction light, is vertically reflected to the first 1/4 wave plate by the fifth plane mirror and the sixth plane mirror respectively, is reflected to the first polarization beam splitter prism by the second plane mirror and is reflected to the beam splitter prism; the +1 st order diffraction light of the first diffraction light and the-1 st order diffraction light of the second diffraction light are interfered to form first interference light, the first interference light is divided into two beams through a beam splitter prism, one beam is reflected to enter a first signal receiving unit, and the other beam is transmitted to enter a second signal receiving unit; the-1 st order diffraction light of the first diffraction light interferes with the +1 st order diffraction light of the second diffraction light to form second interference light, the second interference light is divided into two beams by the light splitting prism, one beam is reflected to enter the first signal receiving unit, and the other beam is transmitted to enter the second signal receiving unit; the signal processing system is used for carrying out differential processing on interference signals received by the first signal receiving unit and the second signal receiving unit, and displacement measurement of single-diffraction quadruple optical subdivision of the diffraction grating is achieved.
Preferably, the first signal receiving unit comprises an 1/2 wave plate, a second polarization splitting prism, a first photodetector, a second photodetector, a third photodetector and a fourth photodetector; after being split by the second polarization splitting prism, the first interference light and the second interference light which enter the 1/2 wave plate respectively enter the first photodetector, the second photodetector, the third photodetector and the fourth photodetector.
Preferably, the second signal receiving unit includes a second 1/4 wave plate, a third polarization splitting prism, a fifth photodetector, a sixth photodetector, a seventh photodetector, and an eighth photodetector; after being split by the third polarization splitting prism, the first interference light and the second interference light which enter the second 1/4 wave plate respectively enter the fifth photodetector, the sixth photodetector, the seventh photodetector and the eighth photodetector.
Preferably, the 1/2 wave plate makes the first interference light and the second interference light distributed at 90 ° and pass through the second polarization splitting prism to form a four-step phase shift structure, which is 0 ° and 180 °, respectively.
Preferably, the second 1/4 wave plate makes the first interference light and the second interference light form 45 ° elliptical or circular distribution, and forms a four-step phase shift structure through the third polarization beam splitter prism, which is 90 ° and-90 °, respectively.
Preferably, when the diffraction grating is moved, the amount of frequency shift between +1 st order diffracted light of the first diffracted light and-1 st order diffracted light of the second diffracted light is 2 Δ f, and the amount of frequency shift between-1 st order diffracted light of the first diffracted light and +1 st order diffracted light of the second diffracted light is-2 Δ f.
Preferably, the first interference light forms an interference signal with a frequency shift of 2 Δ f as a fixed frequency, and the second interference light forms an interference signal with a frequency shift of-2 Δ f as a fixed frequency.
Preferably, the second plane mirror and the fourth plane mirror are replaced by a right-angle prism or a pyramid prism, and diffracted light generated by the diffraction grating is diffracted twice through the right-angle prism or the pyramid prism respectively, so that eight-fold optical subdivision is realized.
Preferably, the diffraction grating is replaced by a reference grating and a measurement grating, the linearly polarized light reflected by the first plane mirror is incident to the reference grating, and the linearly polarized light reflected by the second plane mirror is incident to the measurement grating.
Compared with the prior art, the invention can realize the measurement of the straightness of the large stroke, wherein the displacement measurement along the movement direction of the grating adopts the interference measurement of plus or minus 1-order diffraction light, and the displacement measurement of single-diffraction quadruple optical subdivision can be realized; while satisfying the measuring scheme, the diffraction grating can be separated into a fixed structure, one is a measuring grating and the other is a reference grating, and the displacement measurement of the single-diffraction quadruple optical subdivision can also be realized; and the displacement measurement of eight-time optical subdivision can be realized by adopting a right-angle prism or a pyramid prism.
Drawings
FIG. 1 is a schematic diagram of a homodyne one-dimensional grating displacement measurement device according to one embodiment of the present invention;
FIG. 2 is a schematic diagram of the optical path for generating a first interference signal according to one embodiment of the present invention;
FIG. 3 is a schematic diagram of the optical path for generating a second interference signal according to one embodiment of the present invention;
FIG. 4 is a schematic diagram of the principle of a split homodyne one-dimensional grating displacement measurement according to one embodiment of the present invention;
fig. 5 is a schematic diagram of the principle of implementing eight-fold optical subdivision according to one embodiment of the present invention.
Wherein the reference numerals include: the single-frequency laser device comprises a single-frequency laser 1, a first polarization beam splitter prism 2, a first plane mirror 301, a second plane mirror 302, a third plane mirror 303, a fourth plane mirror 304, a fifth plane mirror 305, a sixth plane mirror 306, a first 1/4 wave plate 4, a beam splitter prism 5, a first signal receiving unit 6, a 1/2 wave plate 601, a second polarization beam splitter prism 602, a first photodetector 603, a second photodetector 604, a third photodetector 605, a fourth photodetector 606, a second signal receiving unit 7, a second 1/4 wave plate 701, a third polarization beam splitter prism 702, a fifth photodetector 703, a sixth photodetector 704, a seventh photodetector 705, an eighth photodetector 706, a diffraction grating 801, a measurement grating 802, a reference grating 803 and a right-angle prism 9.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention.
Fig. 1 shows the principle of a homodyne one-dimensional grating displacement measurement device according to an embodiment of the present invention.
As shown in fig. 1, a homodyne one-dimensional grating displacement measurement device provided in an embodiment of the present invention includes: the single-frequency laser 1, the first polarization beam splitter prism 2, the first plane mirror 301, the second plane mirror 302, the third plane mirror 303, the fourth plane mirror 304, the fifth plane mirror 305, the sixth plane mirror 306, the first 1/4 wave plate 4, the beam splitter prism 5, the first signal receiving unit 6, the second signal receiving unit 7 and the signal processing system, wherein the first polarization beam splitter prism 2 is arranged in the outgoing direction of the single-frequency laser 1, the first plane mirror 301 and the fourth plane mirror 304 are symmetrically arranged in the reflection direction and the transmission direction of the first polarization beam splitter prism 2, the first 1/4 wave plate 4 is arranged in the reflection direction of the first plane mirror 301 and the fourth plane mirror 304, the first signal receiving unit 6 and the second signal receiving unit 7 are symmetrically arranged in the reflection direction and the transmission direction of the beam splitter prism 5, the first signal receiving unit 6 and the second signal receiving unit 7 ensure the consistency of displacement measurement on the same horizontal plane.
A single-frequency laser 1 sends out a beam of linearly polarized light f with fixed frequency to enter a first beam splitter prism 2 for splitting; one beam is reflected to the first plane mirror 301, vertically transmitted to the diffraction grating 801 through the first plane mirror 301 and the first 1/4 wave plate 4, diffracted by the diffraction grating 801 to generate a first diffraction light, the first diffraction light comprises a + -1 order diffraction light, the other beam is transmitted to the fourth plane mirror 304, vertically transmitted to the diffraction grating 801 through the fourth plane mirror 304 and the first 1/4 wave plate 4, and diffracted by the diffraction grating 801 to generate a second diffraction light, the second diffraction light comprises a + -1 order diffraction light, the + -1 order diffraction light of the first diffraction light and the + -1 order diffraction light of the second diffraction light are respectively reflected by the second plane mirror 302, the third plane mirror 303, the fifth plane mirror 305 and the sixth plane mirror 306 and incident to the first polarization beam splitter prism 2 at 90 degrees, the +1 order diffraction light of the first diffraction light and the-1 order diffraction light of the second diffraction light are interfered to form an interference light, the-1 st order diffraction light of the first diffraction light and the +1 st order diffraction light of the second diffraction light are interfered to form interference light, the two interference light beams are respectively split by the beam splitter prism 5 and enter the first signal receiving unit 6 and the second signal receiving unit 7, the signal processing system carries out differential processing on the interference signals received by the first signal receiving unit 6 and the second signal receiving unit 7, and displacement measurement of four times of single diffraction optical subdivision of the diffraction grating is achieved.
Fig. 2 illustrates the principle of the optical path for generating a first interference signal according to one embodiment of the present invention.
As shown in fig. 2, linearly polarized light emitted by the single-frequency laser 1 enters the first polarization beam splitter prism 2 for splitting, light emitted along the reflection direction of the first polarization beam splitter prism 2 is reflected by the first plane mirror 301 to vertically enter the first 1/4 wave plate 4, then vertically enter the diffraction grating 801, and first diffracted light is generated by the diffraction grating 801, wherein the first diffracted light includes ± 1-order diffracted light; the +1 st order diffraction light of the first diffraction light is reflected by the second plane mirror 302, vertically enters the first 1/4 wave plate 4 and the first plane mirror 301, is reflected to the first polarization beam splitter prism 2 by the first plane mirror 301, and then is transmitted to the beam splitter prism 5.
Light emitted along the transmission direction of the first polarization splitting prism 2 is reflected by the fourth plane mirror 304 to vertically enter the first 1/4 wave plate 4, then vertically enter the diffraction grating 801, and generate second diffraction light through the diffraction grating 801, wherein the second diffraction light comprises +/-1 order diffraction light; the-1 st order diffraction light of the second diffraction light is reflected by the fifth plane mirror 305, vertically enters the first 1/4 wave plate 4, is reflected to the first polarization beam splitter prism 2 by the fourth plane mirror 304, and then is transmitted to the beam splitter prism 5.
The +1 st order diffraction light of the first diffraction light and the-1 st order diffraction light of the second diffraction light interfere to form first interference light, the first interference light is split by the beam splitting prism 5, one beam is reflected to enter the first signal receiving unit 6, and the other beam is transmitted to enter the second signal receiving unit 7.
The first signal receiving unit 6 includes: 1/2 wave plate 601, second polarization splitting prism 602, first photodetector 603, second photodetector 604, third photodetector 605, and fourth photodetector 606.
The second signal receiving unit 7 includes: a second 1/4 wave plate 701, a third polarization beam splitter prism 702, a fifth photodetector 703, a sixth photodetector 704, a seventh photodetector 705, and an eighth photodetector 706.
The first interference light is divided into two interference lights by the beam splitter prism 5, one interference light is reflected to the 1/2 wave plate 601, split by the second polarization beam splitter prism 602, and respectively enters the first photodetector 603 and the second photodetector 604; the other beam is transmitted to the second 1/4 wave plate 701, split by the third polarization beam splitter 702, and respectively enter the fifth photodetector 703 and the sixth photodetector 704.
FIG. 3 is a diagram of the optical path principle for generating a second interference signal according to one embodiment of the present invention.
As shown in fig. 3, the-1 st order diffracted light of the first diffracted light is reflected by the third plane mirror 303, vertically enters the first 1/4 wave plate 4 and the first plane mirror 301, is reflected by the first plane mirror 301 to the first polarization beam splitter prism 2, and is transmitted to the beam splitter prism 5.
The +1 st order diffraction light of the second diffraction light is reflected by the sixth plane mirror 306, vertically enters the first 1/4 wave plate 4 and the fourth plane mirror 304, is reflected by the fourth plane mirror 304 to the first polarization beam splitter prism 2, and then is transmitted to the beam splitter prism 5.
The-1 st order diffraction light of the first diffraction light and the +1 st order diffraction light of the second diffraction light interfere to form second interference light, the second interference light is split by the beam splitter prism 5, one interference light is reflected to the 1/2 wave plate 601, split by the second polarization beam splitter prism 602 and respectively enters the third photodetector 605 and the fourth photodetector 606; the other beam is transmitted to the second 1/4 wave plate 701, split by the third polarization splitting prism 702, and respectively incident to the seventh photodetector 705 and the eighth photodetector 706.
Eight beams of interference light respectively enter the photoelectric detector at an angle of-90 degrees, 0 degrees, 90 degrees and 180 degrees, wherein the 1/2 wave plate 601 enables the first interference light and the second interference light to be distributed at an angle of 90 degrees and form a four-step phase shift structure through the second polarization beam splitter 602, and the angle is 0 degree and 180 degrees respectively; the second 1/4 wave plate 701 makes the first interference light and the second interference light form 45 ° distribution, and forms a four-step phase shift structure through the third polarization beam splitter 702, which is 90 ° and-90 ° respectively.
When the diffraction grating 801 moves along the grating vector direction, according to the Doppler shift, the +1 st order diffraction light of the first diffraction light and the-1 st order diffraction light of the second diffraction light can generate a frequency shift amount of 2 delta f; the-1 st order diffraction light of the first diffraction light and the +1 st order diffraction light of the second diffraction light generate a frequency shift of-2 deltaf. The first interference light forms an interference signal with a frequency shift of 2 Δ f as a fixed frequency; the second interference light forms an interference signal with a frequency shift of-2 Δ f as a fixed frequency. After the first interference light and the second interference light are split by the splitting prism 5, four interference signals are formed and enter the first signal receiving unit 6 and the second signal receiving unit 7 respectively.
The signal processing system performs differential processing on the four paths of interference signals according to the zero-difference type four-step phase shift structure, and displacement measurement of single-diffraction quadruple optical subdivision can be realized.
While satisfying the measurement scheme, the diffraction grating 801 can be separated into two diffraction gratings, one as a measurement grating and one as a reference grating, and the displacement measurement of the single-diffraction quadruple optical subdivision can also be realized.
Figure 4 illustrates the principle of separate homodyne one-dimensional grating displacement measurement according to one embodiment of the present invention.
As shown in fig. 4, the reference grating 803 is located inside the reading head, no doppler shift is generated, two beams of light split by the first polarization splitting prism are incident perpendicularly to the reference grating 803, the other beam of light is incident perpendicularly to the measurement grating 802, and the two beams of light are diffracted by the reference grating 803 and the measurement grating 802 and interfere with each other to measure the displacement.
The +1 st order diffraction light of the first diffraction light interferes with the-1 st order diffraction light of the second diffraction light, and a frequency shift quantity of delta f is generated according to the frequency shift theory; the-1 st order diffracted light of the first diffracted light interferes with the +1 st order diffracted light of the second diffracted light, and the-1 st order diffracted light of the first diffracted light and the +1 st order diffracted light of the second diffracted light generate a frequency shift of- Δ f.
The signal processing system performs differential processing on the four paths of interference signals according to the zero-difference type four-step phase shift structure, and displacement measurement of single-diffraction quadruple optical subdivision can be realized.
The invention can realize quadruple optical subdivision in single measurement, and can also introduce a right-angle prism or introduce one path of symmetrical light to realize eight times of homodyne one-dimensional grating displacement measurement of optical subdivision.
Fig. 5 illustrates the principle of achieving eight-fold optical subdivision according to one embodiment of the present invention.
As shown in fig. 5, the second plane mirror 302, the third plane mirror 303, the fifth plane mirror 305, and the sixth plane mirror 306 are respectively replaced by a right-angle prism 9 (or a pyramid prism), so that diffracted light is diffracted twice, and eight-fold optical subdivision displacement measurement of the diffraction grating 801 can be realized.
The +1 st order diffraction light of the first diffraction light interferes with the-1 st order diffraction light of the second diffraction light, and a frequency shift amount of 4 delta f is generated according to the frequency shift theory; the-1 st order diffraction light of the first diffraction light and the +1 st order diffraction light of the second diffraction light can generate a frequency shift amount of-4 delta f; two beams of different interference light, one beam of which forms an interference signal by taking a frequency shift quantity of 4 delta f as a fixed frequency; the other beam forms an interference signal by taking the frequency shift quantity of minus 4 delta f as a fixed frequency; the signal processing system performs differential processing on the four paths of signals according to the zero-difference type four-step phase shift structure, and displacement measurement of single-diffraction eight-time optical subdivision can be achieved.
In summary, the invention provides a symmetric type homodyne one-dimensional grating displacement measurement device with 4 times optical subdivision, compared with the existing traditional four-step phase shift measurement system, the measurement device can not only realize large-stroke linearity measurement, but also realize displacement measurement of single-time diffraction quadruple optical subdivision, wherein the displacement measurement along the grating motion direction adopts interference measurement of +/-1-order diffraction light; while meeting the measurement scheme, the four-time optical subdivision displacement measurement device can be separated into a fixed structure, one is a measurement grating and the other is a reference grating, and the four-time optical subdivision displacement measurement of single diffraction can also be realized; and the displacement measurement of eight-time optical subdivision can be realized by adopting a right-angle prism or a pyramid prism to replace a plane reflector.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
The above embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.
Claims (9)
1. A homodyne one-dimensional grating displacement measuring device is characterized by comprising: a single-frequency laser, a first polarization beam splitter prism, a first plane reflector, a second plane reflector, a third plane reflector, a fourth plane reflector, a fifth plane reflector, a sixth plane reflector, a first 1/4 wave plate, a first signal receiving unit, a second signal receiving unit and a signal processing system, wherein the first polarization beam splitter prism is arranged in the emergent direction of the single-frequency laser, the first plane reflector and the fourth plane reflector are symmetrically arranged in the reflecting direction and the transmitting direction of the first polarization beam splitter prism, the first 1/4 wave plate is arranged in the reflection direction of the first and fourth plane mirrors, the first signal receiving unit and the second signal receiving unit are symmetrically arranged in the reflection direction and the transmission direction of the beam splitter prism; and the number of the first and second groups,
the single-frequency laser emits a beam of linearly polarized light with fixed frequency f to enter the first polarization splitting prism for splitting, one beam of linearly polarized light is reflected to the first plane reflector, is vertically reflected to the first 1/4 wave plate through the first plane reflector, is vertically incident to the diffraction grating, is diffracted by the diffraction grating to generate first diffracted light comprising +/-1-order diffracted light, is vertically reflected to the first 1/4 wave plate through the second plane reflector and the third plane reflector respectively, is reflected to the first polarization splitting prism through the first plane reflector, and is transmitted to the splitting prism; the other beam is transmitted to the fourth plane mirror, is vertically reflected to the first 1/4 wave plate through the fourth plane mirror, is vertically incident to the diffraction grating, is diffracted by the diffraction grating to generate second diffraction light including +/-1 order diffraction light, is vertically reflected to the first 1/4 wave plate through the fifth plane mirror and the sixth plane mirror respectively, is reflected to the first polarization beam splitter prism through the second plane mirror, and is reflected to the beam splitter prism;
the +1 st order diffraction light of the first diffraction light and the-1 st order diffraction light of the second diffraction light are interfered to form first interference light, the first interference light is divided into two beams by the light splitting prism, one beam is reflected to enter the first signal receiving unit, and the other beam is transmitted to enter the second signal receiving unit;
the-1 st order diffraction light of the first diffraction light interferes with the +1 st order diffraction light of the second diffraction light to form second interference light, the second interference light is divided into two beams by the light splitting prism, one beam is reflected to enter the first signal receiving unit, and the other beam is transmitted to enter the second signal receiving unit;
the signal processing system is used for carrying out differential processing on interference signals received by the first signal receiving unit and the second signal receiving unit, and displacement measurement of single-diffraction quadruple optical subdivision of the diffraction grating is achieved.
2. The homodyne one-dimensional grating displacement measuring device of claim 1, wherein the first signal receiving unit comprises an 1/2 wave plate, a second polarization splitting prism, a first photodetector, a second photodetector, a third photodetector and a fourth photodetector; wherein the content of the first and second substances,
the first interference light and the second interference light which are incident to the 1/2 wave plate are respectively incident to the first photodetector, the second photodetector, the third photodetector and the fourth photodetector after being split by the second polarization splitting prism.
3. The homodyne one-dimensional grating displacement measuring device of claim 1, wherein the second signal receiving unit comprises a second 1/4 wave plate, a third polarization splitting prism, a fifth photodetector, a sixth photodetector, a seventh photodetector and an eighth photodetector; wherein the content of the first and second substances,
the first interference light and the second interference light which are incident to the second 1/4 wave plate are respectively incident to the fifth photodetector, the sixth photodetector, the seventh photodetector and the eighth photodetector after being split by the third polarization splitting prism.
4. The homodyne one-dimensional grating displacement measuring device of claim 2, wherein the 1/2 wave plate makes the first interference light and the second interference light distributed at 90 ° and forms a four-step phase shift structure through the second polarization splitting prism at 0 ° and 180 °, respectively.
5. The homodyne one-dimensional grating displacement measuring device of claim 3, wherein the second 1/4 wave plate makes the first interference light and the second interference light form a 45 ° elliptical or circular distribution, and forms a four-step phase shift structure through the third polarization splitting prism, which is 90 ° and-90 ° respectively.
6. The homodyne one-dimensional grating displacement measuring device according to claim 1, wherein when said diffraction grating is moved in the grating vector direction, the amount of frequency shift between +1 st order diffracted light of first diffracted light and-1 st order diffracted light of said second diffracted light is 2 Δ f, and the amount of frequency shift between-1 st order diffracted light of said first diffracted light and +1 st order diffracted light of said second diffracted light is-2 Δ f.
7. The homodyne one-dimensional grating displacement measuring device according to claim 6, wherein the first interference light forms an interference signal with a frequency shift amount of 2 Δ f as a fixed frequency, and the second interference light forms an interference signal with a frequency shift amount of-2 Δ f as a fixed frequency.
8. The homodyne one-dimensional grating displacement measuring device according to claim 1, wherein the second plane mirror, the third plane mirror, the fifth plane mirror and the sixth plane mirror are respectively replaced by a right-angle prism or a pyramid prism, and diffracted light generated by the diffraction grating is respectively diffracted twice by the right-angle prism or the pyramid prism, so that eight-fold optical subdivision is realized.
9. The homodyne one-dimensional grating displacement measuring device according to claim 1, wherein the diffraction grating is replaced with a reference grating and a measurement grating, linearly polarized light reflected by the first plane mirror is incident to the reference grating, and linearly polarized light reflected by the second plane mirror is incident to the measurement grating.
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| CN113465514B (en) * | 2021-06-28 | 2022-08-16 | 中国科学院长春光学精密机械与物理研究所 | Six-dimensional measuring device and method |
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