Grating interference displacement measuring device

Abstract

The invention relates to the technical field of grating displacement measurement, in particular to a grating interference displacement measurement device which comprises a light source, a collimating lens, a light splitting unit, a first reflective grating, a wave plate, a diaphragm, a second reflective grating and a grating displacement detection mechanism. The collimating lens, the light splitting unit and the first reflective grating are sequentially located on a propagation light path of the light source; the wave plate and the diaphragm are respectively positioned on two sides of the light splitting unit; the grating displacement detection mechanism is located on a propagation light path of the reflected light beam and used for resolving grating displacement. The grating interference displacement measuring device provided by the invention is compact in structure, good in expansibility and capable of realizing horizontal displacement measurement; multi-time optical subdivision can be realized; the displacement in the Z direction is not sensitive, so that the mounting error in the Z direction has large tolerance in the mounting process; the optical path structure adopts a symmetrical design, so that measurement errors caused by dead-range noise and thermal expansion can be effectively suppressed, and the displacement measurement precision is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of grating displacement measurement, and particularly to a grating interference displacement measurement device. Background Art

[0002] Sub-nanometer displacement measurement is of great significance in fields such as the semiconductor industry, nanolithography technology, advanced manufacturing, and precision displacement measurement, and has very strict requirements for measurement accuracy. With the development of its technology, various principles and forms have emerged accordingly, such as grating interference measurement, laser interference measurement, capacitive measurement, etc. Among them, a grating interferometer measures displacement through the principles of light interference and diffraction, and the measurement reference is the grating pitch. With the development of grating manufacturing technology, the currently achievable minimum pitch can reach the sub-micron level, making the accuracy of the grating interferometer higher. In addition, optical subdivision technology and electronic subdivision technology can be used to achieve higher measurement resolution. The substrate of the grating can be made of materials with better thermal stability, such as special ceramics, glass ceramics, etc., making the grating interference measurement have better stability. Compared with other measurement methods, grating interference measurement has more advantages in the field of sub-nanometer accuracy measurement.

[0003] In the existing technical solutions, there are two ways to improve the resolution of the displacement measurement device. One is to increase optical subdivision, and the other is to increase electronic subdivision through electronic interpolation. Compared with electronic subdivision, the measurement noise brought by optical subdivision is smaller, and the accuracy that its system can achieve is higher. There are still some problems in the existing single-degree-of-freedom grating interferometer, such as being sensitive to vertical movement and having a low measurement resolution due to a small number of optical subdivisions. Summary of the Invention

[0004] The present invention provides a grating interference displacement measurement device to solve the defects in the prior art of being sensitive to vertical movement and having a low measurement resolution due to a small number of optical subdivisions.

[0005] The present invention provides a grating interference displacement measurement device, including: A light source; A collimating lens located on the propagation optical path of the light source; A beam splitting unit located on the propagation optical path of the collimating lens and splitting the collimated beam into a transmitted beam; A first reflective grating located on the propagation optical path of the transmitted beam and forming a first diffracted beam and a second diffracted beam; A wave plate located on one side of the beam splitting unit and on the propagation optical path of the first diffracted beam; A window plate located on the other side of the beam splitting unit and on the propagation optical path of the second diffracted beam; A second reflective grating is respectively located on the propagation optical paths of the wave plate and the window plate, and forms a third diffracted beam in the opposite direction of the first diffracted beam and a fourth diffracted beam in the opposite direction of the second diffracted beam. The third diffracted beam and the fourth diffracted beam enter the first reflective grating and form an interference beam. The interference beam enters the spectroscopic unit in the opposite direction of the transmitted beam and forms a reflected beam; A grating displacement detection mechanism is located on the propagation optical path of the reflected beam and is used for calculating the grating displacement.

[0006] The grating interference displacement measuring device provided by the present invention further includes: A first reflecting mirror is disposed between the first reflective grating and the wave plate and is located on the propagation optical paths of the first diffracted beam and the third diffracted beam.

[0007] The grating interference displacement measuring device provided by the present invention further includes: A second reflecting mirror is disposed between the first reflective grating and the window plate and is located on the propagation optical paths of the second diffracted beam and the fourth diffracted beam.

[0008] For the grating interference displacement measuring device provided by the present invention, the grating displacement detection mechanism includes: A spectroscopic grating is located on the propagation optical path of the reflected beam.

[0009] For the grating interference displacement measuring device provided by the present invention, the grating displacement detection mechanism further includes: A focusing lens is located on the propagation optical path of the spectroscopic grating.

[0010] For the grating interference displacement measuring device provided by the present invention, the grating displacement detection mechanism further includes: A three-way polarizer is located on the propagation optical path of the focusing lens.

[0011] For the grating interference displacement measuring device provided by the present invention, the grating displacement detection mechanism further includes: A photodetector is located on the propagation optical path of the three-way polarizer.

[0012] For the grating interference displacement measuring device provided by the present invention, the wave plate includes a quarter-wave plate.

[0013] For the grating interference displacement measuring device provided by the present invention, the first reflective grating includes a 2048 nm reflective grating; the second reflective grating includes a 1024 nm reflective grating.

[0014] The grating interference displacement measurement device provided by the present invention, the beam splitting unit includes: a flat beam splitting prism or a cube beam splitting prism.

[0015] A grating interference displacement measurement device provided by the present invention includes: a light source, a collimating lens, a beam splitting unit, a first reflective grating, a wave plate, a window plate, a second reflective grating, and a grating displacement detection mechanism. The collimating lens is located on the propagation optical path of the light source; the beam splitting unit is located on the propagation optical path of the collimating lens and divides the collimated light beam into a transmitted light beam; the first reflective grating is located on the propagation optical path of the transmitted light beam and forms a first diffracted light beam and a second diffracted light beam; the wave plate is located on one side of the beam splitting unit and on the propagation optical path of the first diffracted light beam; the window plate is located on the other side of the beam splitting unit and on the propagation optical path of the second diffracted light beam; the second reflective grating is respectively located on the propagation optical paths of the wave plate and the window plate and forms a third diffracted light beam in the opposite direction of the first diffracted light beam and a fourth diffracted light beam in the opposite direction of the second diffracted light beam. The third diffracted light beam and the fourth diffracted light beam are incident on the first reflective grating and form an interference light beam. The interference light beam is incident on the beam splitting unit in the opposite direction of the transmitted light beam and forms a reflected light beam; the grating displacement detection mechanism is located on the propagation optical path of the reflected light beam and is used for solving the grating displacement. The grating interference displacement measurement device provided by the present invention has a compact structure, good scalability, can realize horizontal displacement measurement, can flexibly adjust the arrangement structure and position of the prism according to different scenarios and requirements to meet the actual needs; and can achieve multiple optical subdivisions, further improving the resolution of the displacement measurement device; at the same time, it is not sensitive to the displacement in the Z direction, so that during the installation process, it has a large tolerance for the installation error in the Z direction; the optical path structure adopts a symmetric design, which can effectively suppress the dead path noise and the measurement error caused by thermal expansion, and effectively improve the displacement measurement accuracy. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a schematic structural diagram of the grating interference displacement measurement device provided in one embodiment of the present invention.

[0018] Figure 2 Schematic structural diagram of the grating interference displacement measurement device provided in one embodiment of the present invention.

[0019] Reference Signs: 1: Light source; 2: Collimating lens; 3: Wave plate; 4: Beam splitting unit; 5: Second reflective grating; 6: First reflective grating; 7: Window plate; 8: Beam splitting grating; 9: Focusing lens; 10: Three-way polarizer; 11: Photoelectric detector; 12: First mirror; 13: Second mirror. Detailed implementation mode

[0020] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts fall within the scope of protection of the present invention.

[0021] In the description of this embodiment, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing this embodiment and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to this embodiment.

[0022] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of this embodiment, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0023] In this embodiment, unless otherwise clearly specified and limited, terms such as "set", "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in this embodiment can be understood according to specific circumstances.

[0024] In the embodiments of the present invention, unless otherwise clearly specified or limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or simply means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply means that the horizontal height of the first feature is less than that of the second feature.

[0025] The following combines Figure 1 and Figure 2 (In the figure, the dashed line represents the optical path, and the arrow represents the propagation direction of the optical path) to describe a grating interference displacement measurement device of the present invention. The grating interference displacement measurement device includes: a light source 1, a collimating lens 2, a beam splitting unit 4, a first reflective grating 6, a wave plate 3, a window plate 7, a second reflective grating 5, and a grating displacement detection mechanism.

[0026] Among them, the collimating lens 2 is located on the propagation optical path of the light source 1; the beam splitting unit 4 is located on the propagation optical path of the collimating lens 2 and splits the collimated light beam into a transmitted light beam; the first reflective grating 6 is located on the propagation optical path of the transmitted light beam and forms a first diffracted light beam and a second diffracted light beam; the wave plate 3 is located on one side of the beam splitting unit 4 and on the propagation optical path of the first diffracted light beam; the window plate 7 is located on the other side of the beam splitting unit 4 and on the propagation optical path of the second diffracted light beam; the second reflective grating 5 is respectively located on the propagation optical paths of the wave plate 3 and the window plate 7 and forms a third diffracted light beam in the opposite direction of the first diffracted light beam and a fourth diffracted light beam in the opposite direction of the second diffracted light beam. The third diffracted light beam and the fourth diffracted light beam enter the first reflective grating 6 and form an interference light beam. The interference light beam enters the beam splitting unit 4 in the opposite direction of the transmitted light beam and forms a reflected light beam; the grating displacement detection mechanism is located on the propagation optical path of the reflected light beam and is used for calculating the grating displacement.

[0027] Specifically, the wave plate 3 and the window plate 7 are symmetrically arranged on the left and right sides of the beam splitting unit 4 respectively, and the optical path structure adopts a symmetric design, which can effectively suppress the dead path noise and the measurement error caused by thermal expansion, and effectively improve the displacement measurement accuracy.

[0028] Specifically, in the Figure 1 shown structure, it is stipulated that the upward direction is the positive direction of the Z axis, the rightward direction is the positive direction of the X axis, the downward direction is the negative direction of the Z axis, and the leftward direction is the negative direction of the X axis. The light source 1 is a laser with coherence and a wavelength. A beam of light emitted by it passes through the collimating lens 2 along the negative direction of the Z axis and then becomes a collimated Gaussian light beam, and the light intensity distribution of the cross section is Gaussian distribution. Optionally, a wave plate 3 is also provided between the collimating lens 2 and the beam splitting unit 4.

[0029] After the collimated beam first passes through the beam splitting unit 4, it is divided into two beams of light. One is the transmitted beam, and the other is the reflected light (this application does not utilize this reflected light, so the optical path of this reflected light is not marked in the figure. The absorbent material can be used to suppress the influence of stray light on the measurement accuracy). The reflected light exits along the positive X-axis direction.

[0030] The transmitted beam then first passes through the first reflection grating 6, generating diffracted light with diffraction orders of ±1 (i.e., the first diffracted beam and the second diffracted beam).

[0031] Among them, the +1 diffraction order light (i.e., the first diffracted beam) propagates in the upper right direction. After passing through the wave plate 3, it is incident on the second reflection grating 5 at the Littrow angle. The formed third diffracted beam will return along the incident light direction (i.e., the opposite direction of the first diffracted beam) along the original path, and passes through the first reflection grating 6 for the second time. The third diffracted beam passing through the first reflection grating 6 is incident on the beam splitting unit 4 along the positive Z-axis direction for the second time.

[0032] Among them, the -1 diffraction order light (i.e., the second diffracted beam) propagates in the upper left direction. After passing through the window plate 7, it is incident on the second reflection grating 5 at the Littrow angle. The formed fourth diffracted beam will return along the incident light direction (i.e., the opposite direction of the second diffracted beam) along the original path, and passes through the first reflection grating 6 for the second time. The fourth diffracted beam passing through the first reflection grating 6 is incident on the beam splitting unit 4 along the positive Z-axis direction for the second time.

[0033] The propagation paths of the laser E1 and the laser E2 after the second diffraction by the first reflection grating 6 coincide, and an interference beam is generated. The interference beam passes through the beam splitting unit 4 for the second time, and the formed reflected light is used by the grating displacement detection mechanism to calculate the displacement of the grating.

[0034] Preferably, the wave plate 3 includes a quarter-wave plate. It should be understood that other forms of wave plates 3 can also be used.

[0035] Preferably, the first reflection grating 6 includes a 2048 nm reflection grating; Preferably, the second reflection grating 5 includes a 1024 nm reflection grating.

[0036] It should be understood that the reflection gratings used in the present invention are not limited to the above pitch specifications. The 2048 nm reflection grating and the 1024 nm reflection grating are only for display and explanation, and the parameter design can be carried out according to the actual situation. The pitch of the two gratings differs by 2 times, and the same purpose can be achieved.

[0037] Preferably, the beam splitting unit 4 includes a plane beam splitting prism or a cube beam splitting prism. It should be understood that the beam splitting unit 4 can also adopt an alternative beam splitting device.

[0038] The specific principle of the present invention can be understood by the following model.

[0039] Phase change caused by grating displacement: In the formula, is the translational displacement between the reading head and the grating; is the resulting phase shift; is the diffraction order; and are the grating pitches in two directions respectively; is the laser wavelength; is the air refractive index; and are the polar angles of the incident light and the diffracted light of the

[0040] The wave equation of the incident light can be expressed as: where A represents the amplitude value of the laser, f represents the frequency of the laser, represents the initial phase of the laser, represents time. Since it passes through a quarter-wave plate 3, its phase should increase by . When the laser first passes through the 2048nm reflective grating, the +1 order diffracted light will pass through a quarter-wave plate 3 and the 1024nm reflective grating, and then will be reflected back to the 2048nm reflective grating for the second diffraction. At this time, the wave equation of the laser E1 can be expressed as; where, can be expressed as: Similarly, when the laser first passes through the 2048nm reflective grating, the -1 order diffracted light will pass through a window plate 7 and the 1024nm reflective grating, and then will be reflected back to the 2048nm reflective grating for the second diffraction. At this time, the wave equation of the laser E2 can be expressed as; where, can be expressed as: After the laser E1 and the laser E2 are combined, the resulting interference signal can be expressed as: Among them, E1 represents the wave equation of the first laser beam, E2 represents the wave equation of the second laser beam, I represents the light intensity of the interference signal generated after the combination of the first laser beam and the second laser beam, and the right side of the equation is expressed as the product of the complex conjugate of E1 + E2 and E1 + E2, where is expressed as the complex conjugate of E1 + E2; where Idc represents the DC component of the interference signal, and Iac represents the AC component of the interference signal; after the interference signal passes through the diffraction grating 8, the focusing lens 9, and the three-way polarizer 10, three interference signals with a phase difference of 120 degrees are formed, which are represented by I1, I2, and I3. Subsequently, the phase calculation of the interference signals of I1, I2, and I3 is realized through an electronic circuit, and the relationship between displacement and phase is utilized to realize the detection of the grating displacement. The subsequent signal processing is prior art and has nothing to do with the present invention, so it will not be elaborated in detail here.

[0041] This displacement measurement device can achieve 4-fold optical subdivision; at the same time, it is insensitive to the displacement in the Z direction, so that during the installation process, it has a large tolerance for the installation error in the Z direction. Moreover, when passing through the 1024nm reflective grating, its incident angle is the Littrow angle, so that the diffracted return light is retroreflected along the incident light. Therefore, a slight movement in the Z direction does not affect the optical path structure and has no influence on the horizontal measurement. In addition, the device adopts a symmetric design, which can greatly reduce the dead path error and the influence of the error caused by thermal expansion on the detection result.

[0042] In addition, in this device, the diffracted light beam can be reflected by setting a mirror above the 2048nm reflective grating, so as to be further expanded in the transverse direction, and more than eight-fold optical subdivision can be achieved to realize a grating interferometer with higher resolution.

[0043] A grating interference displacement measuring device provided by the present invention includes: a light source 1, a collimating lens 2, a beam splitting unit 4, a first reflective grating 6, a wave plate 3, a window plate 7, a second reflective grating 5, and a grating displacement detection mechanism. The collimating lens 2 is located on the propagation optical path of the light source 1; the beam splitting unit 4 is located on the propagation optical path of the collimating lens 2 and divides the collimated light beam into a transmitted light beam; the first reflective grating 6 is located on the propagation optical path of the transmitted light beam and forms a first diffracted light beam and a second diffracted light beam; the wave plate 3 is located on one side of the beam splitting unit 4 and on the propagation optical path of the first diffracted light beam; the window plate 7 is located on the other side of the beam splitting unit 4 and on the propagation optical path of the second diffracted light beam; the second reflective grating 5 is respectively located on the propagation optical paths of the wave plate 3 and the window plate 7 and forms a third diffracted light beam in the opposite direction of the first diffracted light beam and a fourth diffracted light beam in the opposite direction of the second diffracted light beam. The third diffracted light beam and the fourth diffracted light beam are incident on the first reflective grating 6 and form an interference light beam. The interference light beam is incident on the beam splitting unit 4 in the opposite direction of the transmitted light beam and forms a reflected light beam; the grating displacement detection mechanism is located on the propagation optical path of the reflected light beam and is used to calculate the grating displacement. The grating interference displacement measuring device provided by the present invention has a compact structure, good scalability, can realize horizontal displacement measurement, can flexibly adjust the arrangement structure and position of the prism according to different scenarios and requirements to meet the actual needs; and can achieve multiple optical subdivisions, further improving the resolution of the displacement measuring device; at the same time, it is insensitive to the displacement in the Z direction, so that during the installation process, it has a large tolerance for the installation error in the Z direction; the optical path structure adopts a symmetric design, which can effectively suppress the dead path noise and the measurement error caused by thermal expansion, and effectively improve the displacement measurement accuracy.

[0044] In one embodiment of the present invention, the grating interference displacement measuring device further includes: a first reflecting mirror 12 and a second reflecting mirror 13. The first reflecting mirror 12 is disposed between the first reflective grating 6 and the wave plate 3 and is located on the propagation optical paths of the first diffracted light beam and the third diffracted light beam; the second reflecting mirror 13 is disposed between the first reflective grating 6 and the window plate 7 and is located on the propagation optical paths of the second diffracted light beam and the fourth diffracted light beam.

[0045] In the above embodiment, its structure is as Figure 2 shown. Reflecting mirrors are respectively arranged on the left and right sides of the beam splitting unit 4. The light beam is reflected by the reflecting mirrors and further expanded in the transverse direction, and eight-fold optical subdivision can be realized to achieve a grating interferometer with higher resolution. It should be understood that the number of reflecting mirrors can be adjusted, so as to further expand in the transverse direction, and it has good scalability.

[0046] In one embodiment of the present invention, the grating displacement detection mechanism includes: a spectroscopic grating 8, which is located on the propagation optical path of the reflected light beam. The grating displacement detection mechanism further includes: a focusing lens 9, which is located on the propagation optical path of the spectroscopic grating 8. The grating displacement detection mechanism further includes: a three-way polarizer 10, which is located on the propagation optical path of the focusing lens 9. The grating displacement detection mechanism further includes: a photodetector 11, which is located on the propagation optical path of the three-way polarizer 10.

[0047] Specifically, in the structure shown in Figure 1 and Figure 2 , the reflected light formed after passing through the spectroscopic unit 4 for the second time passes through a spectroscopic grating 8, generating ±1st order and 0th order diffracted lights respectively; each order of diffracted light then passes through a focusing lens 9 to focus the light spot; then it passes through a three-way polarizer 10, whose polarization directions are 120 degrees different from each other pairwise, causing a 120-degree phase difference between the diffracted lights of each order. The interference signals with a 120-degree phase difference are then incident on the photodetector 11 to convert the interference optical signal into an electrical signal; subsequently, by detecting the phase of the electrical signal, the displacement of the grating is calculated.

[0048] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative labor.

[0049] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments or equivalently replace some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A grating interference displacement measuring device, characterized in that Comprising: A light source (1); A collimating lens (2), located on the propagation optical path of the light source (1); A beam splitting unit (4), located on the propagation optical path of the collimating lens (2), and splitting the collimated beam into a transmitted beam; A first reflective grating (6), located on the propagation optical path of the transmitted beam, and forming a first diffracted beam and a second diffracted beam; A wave plate (3), located on one side of the beam splitting unit (4) and on the propagation optical path of the first diffracted beam; A window plate (7), located on the other side of the beam splitting unit (4) and on the propagation optical path of the second diffracted beam; A second reflective grating (5), respectively located on the propagation optical paths of the wave plate (3) and the window plate (7), and forming a third diffracted beam in the opposite direction of the first diffracted beam and a fourth diffracted beam in the opposite direction of the second diffracted beam, the third diffracted beam and the fourth diffracted beam are incident on the first reflective grating (6), and form an interference beam, the interference beam is incident on the beam splitting unit (4) in the opposite direction of the transmitted beam and forms a reflected beam; A grating displacement detection mechanism, located on the propagation optical path of the reflected beam, for calculating the grating displacement.

2. The grating interference displacement measuring device according to claim 1, wherein Further comprising: A first reflector (12), provided between the first reflective grating (6) and the wave plate (3), and located on the propagation optical paths of the first diffracted beam and the third diffracted beam.

3. The grating interference displacement measurement device according to claim 1, characterized in that, Further comprising: A second reflector (13), provided between the first reflective grating (6) and the window plate (7), and located on the propagation optical paths of the second diffracted beam and the fourth diffracted beam.

4. The grating interference displacement measuring device according to claim 1, characterized in that, The grating displacement detection mechanism comprises: A spectroscopic grating (8), located on the propagation optical path of the reflected beam.

5. The grating interference displacement measuring device according to claim 4, characterized in that, The grating displacement detection mechanism further comprises: A focusing lens (9), located on the propagation optical path of the spectroscopic grating (8).

6. The grating interference displacement measuring device according to claim 5, wherein The grating displacement detection mechanism further comprises: A three-way polarizer (10), located on the propagation optical path of the focusing lens (9).

7. The grating interference displacement measuring device according to claim 6, characterized in that, The grating displacement detection mechanism further comprises: A photodetector (11), located on the propagation optical path of the three-way polarizer (10).

8. The grating interference displacement measuring device according to any one of claims 1 to 7, characterized in that The wave plate (3) comprises a quarter-wave plate.

9. The grating interference displacement measurement device according to any one of claims 1 to 7, wherein The first reflective grating (6) comprises: a 2048nm reflective grating; The second reflective grating (5) comprises: a 1024nm reflective grating.

10. The grating interference displacement measuring device according to any one of claims 1 to 7, characterized in that, The beam splitting unit (4) comprises: a planar beam splitting prism or a cube beam splitting prism.

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