Nanometer displacement measuring device and method based on far-field high-frequency waves

Abstract

The invention relates to an optical precision measurement technology, in particular to a nanometer displacement measurement device and method based on far-field high-frequency waves. The measuring device comprises a spatial light modulator and a sharp edge diffractometer. The spatial light modulator is used for loading a phase diagram and generating a light field with non-uniformly distributed phases; the sharp-edge diffractometer is provided with sharp-edge diffraction structures which are geometrically distributed in an axial symmetry manner and is used for inducing far-field high-frequency diffraction waves; the sharp edge diffractor carries out binary modulation on a light field incident on the sharp edge diffractor, high-frequency diffracted waves in axisymmetric geometric distribution are induced, and the high-frequency diffracted waves are coherently stacked in a far field to form interference fringes of a sub-wavelength period; a light field incident to the sharp-edge diffractometer forms light fields with phase difference in regions on two sides of a symmetry axis of the sharp-edge diffraction structure; the phase difference change is modulated through the spatial light modulator to regulate and control the propagation behavior of the high-frequency diffracted waves, so that the interference fringes are displaced. According to the invention, the interference fringes are used as scale lines to measure the to-be-measured target, and nanometer displacement measurement is realized.

Description

Technical Field

[0001] The present invention relates to optical precision measurement technology, and specifically to a nano-displacement measurement device and method based on far-field high-frequency waves. Background Art

[0002] Precision displacement measurement technology is the most important part of precision measurement technology. With the development of science and technology, in many application scenarios in the fields of information technology, precision machining, biomedicine, etc., high-precision precision displacement measurement technology is required, especially in the field of precision machining and manufacturing. Traditional contact measurement tools, such as ordinary rulers, vernier calipers, etc., will cause unpredictable damage to the measured object and have low measurement accuracy, and can no longer meet the requirements of modern measurement.

[0003] Driven by strong demands, precision displacement measurement technology has also undergone repeated innovations, and the measurement accuracy has been continuously improved. In recent years, researchers have proposed a variety of nano-measurement technologies. Among them, optical nano-displacement measurement technology is widely favored due to its advantages of non-contact, high precision, fast response, etc. For example, when a tightly focused broadband light source irradiates different positions of a nano-antenna, the surface plasmon polariton spectrum excited will change violently, and based on this, precise displacement measurement of the nano-antenna can be realized; based on the spin splitting scattering behavior of nanoparticles in a tightly focused radially polarized light beam, a sensor for measuring the displacement of nanoparticles is realized; the polarization characteristics of the light field are very sensitive to the position of the liquid crystal wave plate. By mapping the lateral displacement of the wave plate to the polarization rotation of the light beam, nano-scale measurement of the lateral displacement of the wave plate can be realized.

[0004] However, current optical nano-displacement measurement technologies are mostly realized based on the dependence relationship between a certain optical phenomenon (such as the change characteristics of the scattered light field mode, the polarization and phase change characteristics of optical parameters, the plasma resonance effect, etc.) and the displacement information of the measured target. These nano-displacement measurement technologies are an indirect measurement method, which cannot directly measure the target to be measured, and the measurement range and accuracy cannot be flexibly adjusted; in addition, their principles and operations are complex, which seriously limits the development of optical precision measurement technology. Summary of the Invention

[0005] To solve the technical problems existing in the prior art, the present invention provides a nano-displacement measurement device and method based on far-field high-frequency waves. Specifically, a large number of high-frequency waves are induced by sharp-edge diffraction, and coherent superposition occurs in the far-field region to generate interference fringes with sub-wavelength periods. Then, by controlling the propagation behavior of the far-field high-frequency waves, nano-scale displacement of the interference fringes can be realized. Taking the interference fringes as a kind of scale line to measure the target to be measured, nano-displacement measurement is realized.

[0006] The present invention is implemented by the following technical solutions: A nano-displacement measurement device based on far-field high-frequency waves, comprising a spatial light modulator and a sharp-edge diffractor; The spatial light modulator is used to load a phase diagram and generate a light field with a non-uniform phase distribution; The sharp-edge diffractor, having a sharp-edge diffraction structure with an axially symmetric geometric distribution, is used to induce far-field high-frequency diffraction waves; The sharp-edge diffractor performs binary modulation on the incident light field, inducing high-frequency diffraction waves with an axially symmetric geometric distribution, and the high-frequency diffraction waves coherently superpose in the far field to form interference fringes with a sub-wavelength period; The light field modulated by the spatial modulator is incident on the sharp-edge diffractor, forming a first light field and a second light field in the regions on both sides of the symmetry axis of the sharp-edge diffraction structure, and the first light field and the second light field have a phase difference; By modulating the change of the phase difference through the spatial light modulator, the propagation behavior of the high-frequency diffraction wave is further regulated, causing the interference fringes to shift.

[0007] Further, the sharp-edge diffractor includes a transparent substrate and a thin film fabricated on the transparent substrate, and the thickness of the thin film is in the order of hundreds of nanometers or dozens of nanometers; The part of the thin film completely blocks the incident light field, and the part of the transparent substrate without the thin film completely transmits the light field, then a sharp-edge diffraction effect is generated at the edge of the thin film, inducing far-field high-frequency diffraction waves.

[0008] Preferably, the phase difference of the light field is greater than 0 or less than 0, and changes in an arithmetic progression in an increasing or decreasing manner; Different phase differences correspond to different displacement amounts, and the phase difference is modulated by the spatial light modulator.

[0009] The nano-displacement measurement method based on far-field high-frequency waves of the present invention is implemented by the above nano-displacement measurement device, and specifically includes the following steps: Induce the coherent superposition of far-field high-frequency diffraction waves through the sharp-edge diffractor to generate interference fringes; Through the spatial light modulator, discretize the phase of 0 - 2π into 256 gray levels, load different phase diagrams, make the first light field and the second light field incident on the regions on both sides of the symmetry axis of the sharp-edge diffraction structure have a phase difference, make the high-frequency diffraction waves induced by the sharp-edge diffractor have different initial phases, and further regulate their propagation behavior to achieve nano-scale movement of the interference fringes; Use the interference fringes as measurement scale lines to measure the nano-displacement of an object.

[0010] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The precise displacement measurement technology implemented by the present invention is different from other indirect measurement technologies. It does not rely on a certain optical phenomenon, but can measure the displacement of the target to be measured by regulating the interference fringes, and can actively measure the target to be measured like a physical ruler, which is a direct measurement technology.

[0011] (2) The precise displacement measurement technology of the present invention is realized by interference fringes with a sub-wavelength period formed by the coherent superposition of far-field high-frequency waves. Different from the near-field displacement measurement technology based on evanescent waves, this technology occurs in the far field, and its physical principle is clear, the experimental system is simple, the operation is convenient, and it has strong scalability.

[0012] (3) The present invention can achieve multi-directional, non-contact, and high-precision measurement of nano-displacements. The present invention is expected to provide novel and effective ideas and methods for breaking through the limits of current precision measurement systems, and has broad application prospects in the fields of precision measurement and micro-nano processing. Description of the Drawings

[0013] Figure 1 It is a schematic structural diagram of a nano-displacement measurement device based on far-field high-frequency waves in an embodiment of the present invention.

[0014] Figure 2 It is a schematic diagram of an edge diffractor involved in an embodiment of the present invention, where (a) shows an edge diffractor with a pair of rectangular slits, (b) shows an edge diffractor with a pair of crescent-shaped slits, and (c) shows an edge diffractor with a pair of bow-shaped slits.

[0015] Figure 3 It is a result diagram of an interference fringe field under incident light fields with different phase differences obtained at a propagation distance of 8.1 μm in an embodiment of the present invention, where (a) shows the interference fringes when Δ ϕ = 0, (b) shows the interference fringes when Δ ϕ = π / 2, (c) shows the interference fringes when Δ ϕ = π, (d) shows the interference fringes when Δ ϕ = 3π / 2, (e) shows the interference fringes when Δ ϕ = 2π; (f)-(j) respectively show the simulation results when the phase difference of the light field Δ ϕ = 0, Δ ϕ = π / 2, Δ ϕ = π, Δ ϕ = 3π / 2, Δ ϕ = 2π; (k)-(o) are respectively the transverse intensity distribution curves corresponding to (a)-(e).

[0016] Figure 4 Among them, (a) is a relationship diagram between the phase difference of the incident light field gradually increasing at intervals of 0.05π within one period and the displacement amount of the interference fringes in an embodiment of the present invention; (b) is a relationship diagram of the displacement amount of interference fringes corresponding to phase differences at intervals of 0.05π including 40 intervals within one period in an embodiment of the present invention.

[0017] Figure 5 Among them, (a) is a relationship diagram between the phase difference of the incident light field gradually increasing at intervals of 0.02π within one period in the embodiment of the present invention and the displacement amount of the interference fringes; (b) is a relationship diagram of the interference fringe displacement increment corresponding to the phase difference at intervals of 100 0.02π within one period in the embodiment of the present invention. Specific Embodiments

[0018] The present invention will be further described in detail below in conjunction with embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto. Embodiment

[0019] This embodiment provides a nano-displacement measurement device based on far-field high-frequency waves, which uses a spatial light modulator and an edge diffraction device to achieve nano-displacement measurement. Refer to Figure 1 , specifically including: A laser light source 1 for generating linearly polarized laser light; An expanding and collimating lens 2 for expanding and collimating the laser light emitted by the light source; A spatial light modulator 3 for loading a phase diagram, such as phase diagram 9, to generate a light field with a non-uniform phase distribution, including but not limited to a plane light field, a Gaussian light field, a Bessel light field, a vortex light field, etc.; A beam splitting prism 4 for separating the beam output by the expanding and collimating lens, using one of the beams to be incident on the spatial light modulator. The beam with a non-uniform phase modulated by the spatial light modulator is then incident on the edge diffraction device through the beam splitting prism, and an initial light field with different phase differences is formed in the edge diffraction device.

[0020] An edge diffraction device 5 having an axially symmetric geometric edge diffraction structure for inducing far-field high-frequency diffraction waves (also simply referred to as high-frequency waves in this embodiment); the edge diffraction device can perform binary modulation on the incident light field, inducing a large number of high-frequency diffraction waves with an axially symmetric geometric distribution. The high-frequency waves coherently superpose in the far field to form interference fringes with a sub-wavelength period; A light field detection component: including a high-power objective lens 6, a tube lens 7, and a camera 8, for detecting (specifically including magnifying, collecting, and recording) the information of the interference fringe field with a sub-wavelength period generated by the edge diffraction device 5.

[0021] Among them, the light field modulated by the spatial modulator is incident on the edge diffraction device, and a first light field and a second light field are formed in the regions on both sides of the axis of symmetry of the edge diffraction structure, and the first light field and the second light field have a phase difference; by modulating the phase difference change of the first light field and the second light field through the spatial light modulator, the propagation behavior of the high-frequency diffraction waves is further regulated, causing the interference fringes to shift.

[0022] In this embodiment, the laser light source 1 is a monochromatic laser light source with vertical polarization, and preferably a helium-neon laser. The spatial light modulator 3 is a pure-phase modulation spatial light modulator, with the model number Holoeye LETOII, pixels of 1920×1080, and pixel size of 6.4 μm. It can discretize the phase of 0-2π into 256 gray levels, so the minimum phase change that can be modulated is about 0.008π, meeting the modulation requirements of the present invention.

[0023] In this embodiment, the sharp-edge diffractor 5 includes a transparent substrate and a metal thin film made on the transparent substrate. The thickness of the metal thin film is in the order of hundreds of nanometers or dozens of nanometers. The metal thin film part of the sharp-edge diffractor 5 completely blocks the incident light field, while the transparent substrate part without metal completely transmits the light field, thus forming a binary modulation. Sufficiently strong sharp-edge diffraction effects can be generated at the edge of the metal thin film, inducing a large number of far-field high-frequency waves.

[0024] More specifically, the sharp-edge diffractor 5 has an axisymmetric distribution. The transparent substrate is a glass substrate, and the metal thin film is a pair of slits with a thickness of 60 nm, an outer diameter of 15 μm, and a maximum light-transmitting width of 0.7 μm plated on the glass substrate, as shown in Figure 2 (b). The shape of the slit can be rectangular, crescent-shaped, or bow-shaped, as shown in (a), (b), and (c) of Figure 2 . For such a metal thin film, the high-frequency waves induced at its edge have an axisymmetric distribution and can coherently superpose to form periodic interference fringes.

[0025] That is to say, in the measurement device of this embodiment, it is required that the thickness of the sharp-edge diffractor is very thin, that is, negligible relative to the overall size of the sharp-edge diffractor, so as to perform binary modulation on the incident light field and ensure that a large number of high-frequency waves that can propagate to the far field can be induced; the sharp-edge diffractor needs to have axisymmetry, such as two linearly-shaped slits with axisymmetric distribution or two crescent-shaped slits with axisymmetric distribution, so that the induced high-frequency waves are symmetrically distributed, and then interference fringes with a far-field sub-wavelength periodic distribution are formed.

[0026] In the light field detection component, the magnification of the high-power objective lens 6 is 100 times or greater, which is used to magnify the light field information generated by the sharp-edge diffractor. For example, a Nikon objective lens with a magnification of 150 times and a numerical aperture of 0.9 can be used; the tube lens 7 is a sleeve lens with an effective focal length of 200 mm for imaging, which is used to image the light field information collected by the high-power objective lens; the pixel size of the camera 8 is 1.4 μm, which is used to record the light field information imaged by the tube lens 7.

[0027] In this embodiment, it is set that the light field generated by the spatial light modulator 3 is approximately a plane light field with unequal phase distributions, and the plane light field is incident on Figure 2The optical field phase difference between the first optical field and the second optical field on both sides of the vertical symmetry axis of the pair of crescent-shaped slit structures shown is Δ ϕ , that is, the initial phases of the high-frequency waves induced by the left and right crescent-shaped slit structures in Figure 2 are inconsistent. Let Δ ϕ = ϕ r - ϕ l , where ϕ l represents the phase of the first optical field incident on the left crescent-shaped slit structure in Figure 2 , and ϕ r represents the phase of the second optical field incident on the right crescent-shaped slit structure.

[0028] When the optical field phase difference in the initial state is Δ ϕ = 0, that is, when the initial phases of the high-frequency waves induced by the sharp-edge diffractor are the same, at a propagation distance of 8.1 μm after being modulated by the sharp-edge diffractor, the optical field distribution diagram shown in Figure 3 (a) is obtained. It can be seen that it is some periodic interference fringes in the far field. From the intensity curve corresponding to y = 0 in the horizontal direction, the period of the interference fringes is D = 512 nm.

[0029] However, if the optical field phase difference Δ ϕ is not 0, the interference fringes will shift, and the measurement of the target displacement can be achieved. Based on this, the change of the interference fringes when the optical field phase difference Δ ϕ is inconsistent is analyzed. Specifically, the phase of the first optical field ϕ l is set to be unchanged and ϕ l = 0, and the phase of the second optical field ϕ r is continuously changed. When the optical field phase difference Δ ϕ = π / 2, at a propagation distance z = 8.1 μm, the experimental results shown in Figure 3 (b) are obtained. Compared with (a), it can be seen that the interference fringes have shifted to the right. According to the corresponding transverse intensity distribution curve shown in Figure 3 (l), the shifted distance is 128 nm; continue to increase the phase difference between the first optical field and the second optical field, such as Δ ϕ = π, Δ ϕ = 3π / 2, the interference fringes will continue to shift to the right, and the corresponding interference fringe distributions are shown in Figure 3 (c) and (d). Taking the black dashed lines in Figure 3 (k)-(o) as the reference, the movement process of the interference fringes can also be seen; when Δ ϕWhen φ = 2π, the phase difference is exactly one period different, and the interference fringes are the same as those when Δφ = 0, that is, the interference fringes just move one period and return to the initial state, as shown in (e) and (o) of ϕ Figure 1. And Figure 3 (f)-(j) of Figure 3 are the relevant simulation results of different optical field phase differences, and it can be seen that the experimental results are in good agreement with the simulation results.

[0030] Figure 3 The results are obtained by gradually increasing the phase difference at intervals of π / 2. The average displacement of the interference fringes corresponding to each change of the phase difference of π / 2 is 128 nm. When the change amount of the phase difference is further refined, that is, the phase of the first optical field ϕ l remains unchanged, and the phase of the second optical field is gradually changed at smaller phase difference intervals ϕ r When φ2 changes, the interference fringes will move slightly, so as to realize precise measurement of smaller displacements or even nanometer displacements.

[0031] For example, when the phase of the second optical field ϕ r changes and gradually increases at intervals of 0.05π, that is, the phase of the second optical field changes with a phase difference Δφ ϕ n - Δφ ϕ n-1 = 0.05π (n represents the nth change of the phase difference) at intervals, at the same propagation distance, the results shown in (a) of Figure 4 Figure 2 are obtained, which shows the displacement of the interference fringes corresponding to different phase differences Δφ ϕ , showing a linear increase relationship. Until the phase difference changes for the 40th time, Δφ ϕ = 2π, the interference fringes move one period D (at the propagation distance z = 8.1 μm, D = 512 nm). At this time, the increment ΔD of the interference fringes corresponding to each change of the phase difference interval of 0.05π is shown in (b) of Figure 4 Figure 2, and the corresponding average increment ΔD = 12.8 nm, that is, the minimum displacement that can be measured at this time is 12.8 nm.

[0032] Similarly, further refining the change amount of the phase difference Δφ ϕ , let Δφ ϕ increase at intervals of 0.02π, that is, the phase difference changes 100 times, and the results shown in Figure 5The results shown, where (a) illustrates the linear relationship between the phase difference of the incident light field gradually increasing at intervals of 0.02π within one period and the corresponding displacement of the interference fringes, and (b) illustrates the increment of the displacement of the interference fringes corresponding to the phase difference with 100 intervals of 0.02π within one period. It can be seen that the present invention has experimentally achieved a precise displacement of the interference fringes of approximately 5.1 nm, that is, the minimum measurable target displacement is 5.1 nm. Further, if the first light field phase incident on the Figure 2 the first light field in the left crescent slit structure in is greater than the second light field phase of the right crescent slit structure, that is, the light field phase difference Δ ϕ <0, the interference fringes will move to the left, thereby realizing displacement measurements in different directions.

[0033] That is, the light field phase difference can be greater than 0 or less than 0. When the light field phase difference changes at intervals of an absolute value of 0.02π (increasing or decreasing arithmetically, and the tolerance value of the phase difference change is 0.02π), displacement measurements to the left or right with a minimum displacement of 5.1 nm will be achieved.

[0034] It can be seen that specifically by using a spatial light modulator, the phase of 0 - 2π can be discretized into 256 gray levels, and different phase diagrams are loaded to make the first light field and the second light field in the regions on both sides of the symmetry axis of the sharp-edge diffraction structure have a phase difference, that is, to make the high-frequency waves induced by the sharp-edge diffractor have different initial phases, thereby regulating their propagation behavior. In this embodiment, the smaller the initial phase difference, the smaller the translation amount of the interference fringes, which can reach the nanometer level. In addition, the positive or negative of the light field phase difference in the regions on both sides of the symmetry axis of the sharp-edge diffractor determines the translation direction of the interference fringes, that is, the present invention can achieve nanoscale displacement and flexible regulation of the interference fringes or scale lines.

[0035] The measurement device in this embodiment can achieve precise displacement measurement at the nanoscale. Its working principle is: by inducing the coherent superposition of far-field high-frequency waves through a sharp-edge diffractor to generate fine interference fringes, thereby forming a super-diffraction-limited interference fringe field; through a spatial light modulator, the propagation behavior of the high-frequency waves is regulated, and precise displacement of the interference fringes can be achieved, that is, by regulating the high-frequency waves, nanoscale movement of the interference fringes is realized, and then nanoscale displacement measurement is achieved. Regarding these interference fringes as the measurement scale lines of a general physical ruler, a far-field precision optical ruler with scale lines that can be displaced at the nanoscale will be obtained, which can be directly used for nanoscale displacement measurement of some objects.

[0036] Therefore, based on the nanoscale displacement measurement device in this embodiment, a nanoscale displacement measurement method is realized, including the following steps: Induce the coherent superposition of far-field high-frequency diffraction waves through a sharp-edge diffractor to generate interference fringes; By using a spatial light modulator, the phase from 0 to 2π is discretized into 256 gray levels, and different phase diagrams are loaded, so that a phase difference exists between the first light field and the second light field incident on the regions on both sides of the symmetry axis of the sharp-edge diffraction structure, enabling the high-frequency diffraction waves induced by the sharp-edge diffractor to have different initial phases, thereby regulating their propagation behaviors and realizing the nano-scale movement of interference fringes; Taking the interference fringes as measurement scale lines, the nano-displacement of an object is measured.

[0037] In summary, this embodiment proposes a nano-displacement measurement device and method based on far-field high-frequency waves, and the physical principle of its measurement technology is clear. Different from other indirect measurement technologies that rely on the association between the target displacement and a certain optical phenomenon, this embodiment can directly measure the target to be measured like a physical ruler, is flexibly adjustable, and the relevant experimental structure is simple and the operation is flexible, having practical value and broad application prospects in the fields of precision measurement and micro-nano processing.

[0038] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A nanometer displacement measurement device based on far-field high-frequency waves, characterized in that, It includes a spatial light modulator and a sharp-edge diffractor; The spatial light modulator is used to load a phase diagram and generate a light field with a non-uniform phase distribution; The sharp-edge diffractor has a sharp-edge diffraction structure with an axially symmetric geometric distribution and is used to induce far-field high-frequency diffraction waves; the sharp-edge diffractor performs binary modulation on the incident light field to induce high-frequency diffraction waves with an axially symmetric geometric distribution, and the high-frequency diffraction waves coherently superpose in the far field to form interference fringes with a sub-wavelength period; The light field modulated by the spatial modulator is incident on the sharp-edge diffractor, and a first light field and a second light field are formed in the regions on both sides of the symmetry axis of the sharp-edge diffraction structure, and the first light field and the second light field have a phase difference; by modulating the change of the phase difference through the spatial light modulator, the propagation behavior of the high-frequency diffraction waves is further regulated, so that the interference fringes are displaced.

2. The nano-displacement measurement device according to claim 1, characterized in that, The sharp-edge diffractor includes a transparent substrate and a thin film fabricated on the transparent substrate, and the thickness of the thin film is in the order of hundreds of nanometers or dozens of nanometers; The part of the thin film completely blocks the incident light field, and the part of the transparent substrate without the thin film completely transmits the light field, so that a sharp-edge diffraction effect is generated at the edge of the thin film, inducing far-field high-frequency diffraction waves.

3. The nano-displacement measurement device according to claim 2, wherein The thin film is a pair of slits with a thickness of 60 nm, an outer diameter of 15 μm, and a maximum light-transmitting width of 0.7 μm plated on the transparent substrate.

4. The nano-displacement measurement device according to claim 3, wherein, The shape of the slit is rectangular, bow-shaped or crescent-shaped.

5. The nano-displacement measurement device according to claim 2, characterized in that The thin film is a metal thin film.

6. The nano-displacement measurement device according to claim 1, wherein, The phase difference of the light field is greater than 0 or less than 0 and changes in an arithmetic progression or an arithmetic decrement; different phase differences correspond to different displacement amounts, and the phase difference is modulated by the spatial light modulator.

7. The nano-displacement measuring device according to claim 6, characterized in that, The tolerance value of the change in the phase difference of the light field is 0.05π or 0.02π.

8. The nano-displacement measurement device according to claim 1, characterized in that, The nano-displacement measurement device further includes: A light source for generating linearly polarized laser light; A beam expander-collimator for expanding and collimating the laser light emitted by the light source; A beam splitting prism for separating the light beam output by the beam expander-collimator; A light field detection component for amplifying, collecting and recording the information of the sub-wavelength period interference fringe field generated by the sharp-edge diffractor.

9. The nano-displacement measurement device according to claim 8, wherein, The light field detection component includes a high-power objective lens, a tube lens and a camera. The high-power objective lens is used to amplify the light field information generated by the sharp-edge diffractor, the tube lens is used to image the light field information collected by the high-power objective lens, and the camera is used to record the light field information imaged by the tube lens.

10. A nano-displacement measurement method based on far-field high-frequency waves, characterized in that, It is realized by the nano-displacement measurement device according to any one of claims 1-9, and the measurement method includes the following steps: Inducing the coherent superposition of far-field high-frequency diffraction waves through the sharp-edge diffractor to generate interference fringes; By means of the spatial light modulator, discretizing the phase of 0-2π into 256 gray levels, loading different phase diagrams, making the first light field and the second light field incident on the regions on both sides of the symmetry axis of the sharp-edge diffraction structure have a phase difference, so that the high-frequency diffraction waves induced by the sharp-edge diffractor have different initial phases, and further regulating their propagation behavior to realize the nano-scale movement of the interference fringes; Taking the interference fringes as measurement scale lines to measure the nano-displacement of an object.

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