A nano displacement measurement device and method based on far-field high-frequency waves

Abstract

The present application relates to optical precision measurement technology, and is a kind of nanometer displacement measurement device and method based on far-field high-frequency wave.The measurement device comprises a spatial light modulator and a sharp edge diffraction device;the spatial light modulator is used to load a phase diagram and generate a light field with non-uniform phase distribution;the sharp edge diffraction device has an axisymmetric geometric distribution of sharp edge diffraction structure and is used to induce far-field high-frequency diffraction wave;the sharp edge diffraction device performs binary modulation on the light field incident thereon to induce high-frequency diffraction wave with axisymmetric geometric distribution, and the high-frequency diffraction wave is superimposed in far field to form subwavelength period interference fringes;the light field incident on the sharp edge diffraction device forms light fields with phase difference on both sides of the symmetry axis of the sharp edge diffraction structure;the spatial light modulator is used to modulate the phase difference change to regulate the propagation behavior of the high-frequency diffraction wave, so that the interference fringes are displaced.The present application uses the interference fringes as a kind of scale line to measure the target to be measured, and realizes nanometer displacement measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to optical precision measurement technology, in particular to a kind of nanometer displacement measurement device and method based on far-field high frequency wave. BACKGROUND

[0002] Precise displacement measurement technology is the most important part of precision measurement technology. With the development of science and technology, many application scenarios in the field of information technology, precision machining, biomedicine and other fields require high-precision precision displacement measurement technology, especially in the field of precision machining and manufacturing. Traditional contact measurement tools, such as ordinary ruler, vernier caliper, etc., will cause unpredictable damage to the measured object, and the measurement precision is low, which cannot meet the requirements of modern measurement.

[0003] Under the strong demand, precision displacement measurement technology has also undergone a revolution, and the measurement accuracy has been continuously improved. In recent years, researchers have proposed a variety of nanometer measurement technologies. Among them, the optical nanometer displacement measurement technology is widely favored due to its non-contact, high precision, fast response and other advantages. For example, when a tightly focused broadband light source irradiates different positions of a nano antenna, the excited surface plasmon spectrum will change dramatically, based on which the precise displacement measurement of the nano antenna can be realized. Based on the spin-splitting scattering behavior of nanoparticles in a tightly focused radial polarization 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 transverse displacement of the wave plate to the polarization rotation of the light beam, nanoscale measurement of the transverse displacement of the wave plate can be realized.

[0004] However, current optical nanometer displacement measurement technology is based on the dependence relationship between certain optical phenomena (such as scattering light field mode change characteristics, optical parameter polarization and phase change characteristics, plasmonic resonance effect, etc.) and the displacement information of the measured target. These nanometer displacement measurement technologies are an indirect measurement method, which cannot directly measure the target to be measured, and the measurement range and precision cannot be flexibly controlled. In addition, the principle and operation are complex, which seriously limits the development of optical precision measurement technology. SUMMARY

[0005] To solve the technical problems existing in the prior art, the present application provides a kind of nanometer displacement measurement device and method based on far-field high frequency wave. Specifically, a large number of high-frequency waves are induced by sharp edge diffraction, and subwavelength period interference fringes are generated by coherent superposition in the far-field region. By regulating the propagation behavior of the far-field high-frequency wave, nanoscale displacement of the interference fringes can be realized. The interference fringes are used as a kind of scale line to measure the target to be measured, and nanometer displacement measurement is realized.

[0006] The application adopts the following technical scheme to realize the same: a nano displacement measurement device based on far-field high-frequency waves, comprising a spatial light modulator and a sharp-edge diffraction device;

[0007] The spatial light modulator is used for loading a phase map to generate a light field with a non-uniform phase distribution;

[0008] The sharp-edge diffraction device has a sharp-edge diffraction structure with an axisymmetric geometric distribution and is used for inducing far-field high-frequency diffraction waves; the sharp-edge diffraction device performs binary modulation on the light field incident thereon to induce high-frequency diffraction waves with an axisymmetric geometric distribution, and the high-frequency diffraction waves are superimposed in a far field to form subwavelength period interference fringes;

[0009] The light field modulated by the spatial light modulator is incident on the sharp-edge diffraction device to form a first light field and a second light field 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; the spatial light modulator is used for modulating the phase difference change to further regulate the propagation behavior of the high-frequency diffraction waves to cause displacement of the interference fringes.

[0010] Further, the sharp-edge diffraction device comprises a transparent substrate and a thin film formed on the transparent substrate, and the thickness of the thin film is in the order of hundreds of nanometers or tens of nanometers;

[0011] The thin film completely blocks the incident light field, and the transparent substrate part 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 to induce far-field high-frequency diffraction waves.

[0012] Preferably, the light field phase difference is greater than 0 or less than 0, and changes in an equal-difference increasing or equal-difference decreasing manner; different phase differences correspond to different displacement amounts, and the phase difference is modulated by the spatial light modulator.

[0013] The nano displacement measurement method based on far-field high-frequency waves is realized by the above-mentioned nano displacement measurement device and specifically comprises the following steps:

[0014] The sharp-edge diffraction device induces far-field high-frequency diffraction wave superposition to generate interference fringes;

[0015] The spatial light modulator discretizes the phase of 0-2π into 256 gray scales, loads different phase maps, and makes the first light field and the second light field incident 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 diffraction device have different initial phases to further regulate the propagation behavior and realize nano-level movement of the interference fringes;

[0016] The interference fringes are used as measurement scale lines to measure the nano displacement of an object.

[0017] Compared with the prior art, the application has the following advantages and beneficial effects:

[0018] (1) The precision displacement measurement technology realized by the present application is different from other indirect measurement technologies, and does not rely on certain optical phenomena, but can measure the displacement of a target to be measured by regulating and controlling interference fringes, can actively measure the target to be measured like a physical ruler, and is a direct measurement technology.

[0019] (2) The precision displacement measurement technology of the present application is realized by sub-wavelength period interference fringes formed by far-field high-frequency wave coherence superposition, unlike the near-field displacement measurement technology based on evanescent waves. The technology occurs in the far field, and its physical principle is clear, the experimental system is simple, the operation is convenient, and the generalizability is strong.

[0020] (3) The present application can realize multi-directional, non-contact and high-precision measurement of nanometer displacement. The present application is expected to break through the current limit of the precision measurement system, provide novel and effective ideas and methods, and has broad application prospects in the fields of precision measurement and micro-nano machining. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a structure schematic diagram of a nanometer displacement measurement device based on a far-field high-frequency wave in an embodiment of the present application.

[0022] Figure 2 is a schematic diagram of a sharp-edge diffraction device involved in an embodiment of the present application, wherein (a) illustrates a sharp-edge diffraction device with a pair of rectangular slits, (b) illustrates a sharp-edge diffraction device with a pair of crescent slits, and (c) illustrates a sharp-edge diffraction device with a pair of arc slits.

[0023] Figure 3 is a result diagram of interference fringes under incident light fields with different phase differences at a propagation distance of 8.1 μm in an embodiment of the present application, wherein (a) illustrates interference fringes when Δ Figure 4 =0, (b) illustrates interference fringes when Δ Figure 5 =π / 2, (c) illustrates interference fringes when Δ Figure 6 =π, (d) illustrates interference fringes when Δ Figure 7 =3π / 2, (e) illustrates interference fringes when Δ Figure 8 =2π; (f)-(j) respectively illustrate simulation results when the phase difference of the light field is Δ Figure 9 =0, Δ Figure 10 =π / 2, Δ Figure 11 =π, Δ Figure 12 =3π / 2, and Δ Figure 13 =2π; (k)-(o) are respectively the transverse intensity distribution curves corresponding to (a)-(e).

[0024] Figure 14In the figure, (a) is a graph showing the relationship between the phase difference of the incident light field and the displacement of the interference fringes in one period in the embodiment of the present application, which gradually increases at intervals of 0.05π;

[0025] (b) is a graph showing the relationship between the phase difference of the incident light field and the displacement of the interference fringes in one period in the embodiment of the present application, which gradually increases at intervals of 0.05π.

[0026] Figure 15 In the figure, (a) is a graph showing the relationship between the phase difference of the incident light field and the displacement of the interference fringes in one period in the embodiment of the present application, which gradually increases at intervals of 0.05π;

[0027] (b) is a graph showing the relationship between the phase difference of the incident light field and the displacement of the interference fringes in one period in the embodiment of the present application, which gradually increases at intervals of 0.05π. DETAILED DESCRIPTION

[0028] The present application will be further described in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present application are not limited thereto. EMBODIMENT

[0029] The present embodiment provides a nanometer displacement measurement device based on far-field high-frequency waves, which utilizes a spatial light modulator and a sharp-edge diffraction device to realize the measurement of nanometer displacement, as shown in Figure 16 , and specifically includes:

[0030] A laser light source 1 is used to generate linearly polarized laser light.

[0031] A beam expander and collimator 2 is used to expand and collimate the laser light emitted by the light source.

[0032] A spatial light modulator 3 is used to load a phase pattern, such as phase pattern 9, to generate a light field with a non-uniform phase distribution, including but not limited to a planar light field, a Gaussian light field, a Bessel light field, a vortex light field, etc.

[0033] A beam splitter prism 4 is used to separate the light beams output by the beam expander and collimator, and one of the light beams is incident on the spatial light modulator. The light beam with a non-uniform phase after being modulated by the spatial light modulator is then incident on the sharp-edge diffraction device through the beam splitter prism, to form an initial light field with different phase differences in the sharp-edge diffraction device.

[0034] The sharp-edge diffraction device 5 has a sharp-edge diffraction structure with an axially symmetric geometric distribution, which is used to induce far-field high-frequency diffraction waves (also referred to as high-frequency waves in the present embodiment). The sharp-edge diffraction device can perform binary modulation on the light field incident thereon, to induce a large number of high-frequency diffraction waves with an axially symmetric geometric distribution. The high-frequency waves are coherently superimposed in the far field to form subwavelength period interference fringes.

[0035] Light field detection assembly: including high-power objective 6, barrel lens 7, camera 8, for detecting (including amplifying, collecting and recording) sub-wavelength period interference fringe field information generated by sharp edge diffraction.

[0036] Wherein the spatial modulator modulated light field is incident to the sharp edge diffraction, the first light field and the second light field are formed in the region 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; the phase difference change of the first light field and the second light field is modulated by the spatial light modulator, and then the propagation behavior of the high-frequency diffraction wave is controlled, so that the interference fringes are displaced.

[0037] In the embodiment, the laser light source 1 is a monochromatic laser light source with vertical direction polarization, which can be further preferably a helium-neon laser. The spatial light modulator 3 adopts a pure phase modulation spatial light modulator, the model of which is Holoeye LETOII, the pixel is 1920x1080, the pixel size is 6.4 μm, the phase of 0-2π can be discretized into 256 gray scales, so the minimum phase change that can be modulated is about 0.008π, which meets the modulation requirements of the application.

[0038] In the embodiment, the sharp edge diffraction 5 includes a transparent substrate and a metal thin film made on the transparent substrate, and the thickness of the metal thin film is in the order of hundreds of nanometers or tens of nanometers. The metal thin film part of the sharp edge diffraction 5 completely blocks the incident light field, and the transparent substrate part without metal completely transmits the light field, so that a binary modulation is formed, and a strong sharp edge diffraction effect can be generated at the edge of the metal thin film to induce a large number of far-field high-frequency waves.

[0039] More specifically, the sharp edge diffraction 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 transmission width of 0.7 μm, which are plated on the glass substrate, as shown in Figure 17 (b). Wherein the shape of the slit can be rectangular, crescent or arcuate, as shown in Figure 18 (a), (b) and (c). Such a metal thin film, the high-frequency waves induced at the edge of which have an axisymmetric distribution, can be coherently superimposed to form periodic interference fringes.

[0040] That is, in the measuring device of the embodiment, the thickness of the sharp edge diffraction is required to be very thin, i.e. negligible relative to the overall size of the sharp edge diffraction, so that binary modulation can be performed on the incident light field to ensure that a large number of high-frequency waves that can propagate to the far field can be induced; the sharp edge diffraction needs to have axisymmetry, such as two straight line type slits with axisymmetric distribution or two crescent slits with axisymmetric distribution, so that the induced high-frequency waves are symmetrically distributed, and then the far-field sub-wavelength periodic distribution interference fringes are formed.

[0041] In the light field detection assembly, the high-magnification objective lens 6 has a magnification of 100x or greater and is used to amplify the light field information generated by the sharp-edge diffractor. For example, a Nikon objective lens with a magnification of 150x and a numerical aperture of 0.9 can be used. The tube lens 7 is a telescopic lens with an effective focal length of 200 mm, used for imaging, and is used to image the light field information collected by the high-magnification objective lens. The camera 8 has a pixel size of 1.4 μm and is used to record the light field information imaged by the tube lens 7.

[0042] In this embodiment, the light field generated by the spatial light modulator 3 is set to approximately be a planar light field with unequal phase distribution, and the planar light field is incident on... Figure 19 The phase difference between the first and second optical fields on either side of the vertical axis of symmetry of the pair of crescent-shaped slit structures shown is Δ. Figure 20 That is, through Figure 21 The initial phases of the high-frequency waves induced by the two crescent-shaped slit structures on the left and right sides are inconsistent. Let Δ Figure 22 = Figure 23 r - Figure 24 l ,in, Figure 25 l Indicates incident on Figure 26 The first optical field phase of the crescent-shaped slit structure on the left side of the middle, Figure 27 r This represents the phase of the second light field incident on the right crescent-shaped slit structure.

[0043] When the initial phase difference of the light field is Δ Figure 28 When the initial phase of the high-frequency wave induced by the sharp-edge diffractor is 0, i.e., when the initial phases are consistent, the experiment yielded the following at a propagation distance of 8.1 μm after modulation by the sharp-edge diffractor: Figure 29 The light field distribution diagram shown in (a) shows that it consists of some far-field periodic interference fringes. The period of the interference fringes can be obtained from the intensity curve at y=0 in the horizontal direction as D=512 nm.

[0044] However, if the phase difference of the light field Δ Figure 30 If the value is not zero, the interference fringes will shift, allowing for the measurement of the target displacement. Based on this, the phase difference Δ of the optical field can be used to... Figure 31 The analysis focuses on the changes in interference fringes when there is inconsistency. Specifically, the phase of the first optical field is set. Figure 32 l Unchanging and Figure 33 l =0, and continuously change the phase of the second light field Figure 34 r When the phase difference of the light field Δ Figure 35 When π / 2, at a propagation distance z = 8.1 μm, the following was obtained: Figure 36The experimental results shown in (b) show that, compared to (a), the interference fringes have shifted to the right to some extent. According to... Figure 37 The transverse intensity distribution curve shown in (l) indicates a shift distance of 128 nm; further increasing the phase difference between the first and second light fields, such as Δ... Figure 38 =π、Δ Figure 39 When = 3π / 2, the interference fringes will continue to shift to the right, and the corresponding interference fringes distribution is as follows: Figure 40 As shown in (c) and (d), and with Figure 41 Using the black dashed line (k)-(o) as a reference, the movement of the interference fringes can also be observed; when Δ Figure 42 When = 2π, the phase difference is exactly one period, and the interference fringes are parallel to Δ. Figure 43 The consistency at =0 means that the interference fringes have just completed one cycle and returned to the initial state, such as Figure 44 As shown in (e) and (o). Figure 45 (f)-(j) represent the correlation simulation results for different optical field phase differences, and it can be seen that the experimental results are in good agreement with the simulation results.

[0045] Figure 46 This is the result obtained by gradually increasing the phase difference in increments of π / 2, with an average shift of 128 nm corresponding to each change in the phase difference of π / 2. When the change in phase difference is further refined, i.e., the phase of the first optical field... Figure 47 l The phase of the second optical field remains unchanged, but is gradually changed at smaller phase difference intervals. Figure 48 r When this happens, the interference fringes will shift slightly, thus enabling precise measurement of even smaller displacements, or even nanometer-sized displacements.

[0046] For example, when the second optical field phase Figure 49 r When the phase of the second optical field changes at intervals of 0.05π and gradually increases, the phase difference Δ... Figure 50 n - Δ Figure 51 n-1 When the interval of 0.05π (where n represents the nth phase difference change) gradually increases, under the same propagation distance, the following results are obtained: Figure 52 The results shown in (a) illustrate different phase differences Δ Figure 53 The corresponding shift in interference fringes increases linearly. This continues until the 40th phase difference change, at which point Δ... Figure 54 =2π, the interference fringes have moved for one cycle D (at a propagation distance z=8.1 μm, D=512 nm). The result of the increment ΔD of the interference fringes movement corresponding to each phase difference interval of 0.05π is as follows: Figure 55As shown in (b), the corresponding average increment ΔD = 12.8 nm, which means that the minimum measurable displacement is 12.8 nm.

[0047] Similarly, further refine the phase difference Δ Figure 56 Let Δ be the change in . Figure 57 Increasing the phase difference by 0.02π increments, i.e., changing the phase difference 100 times, yields the following: Figure 58 The results shown illustrate the linear relationship between (a) the incident light field phase difference that gradually increases in 0.02π intervals within a period and the corresponding interference fringe displacement, and (b) the interference fringe displacement increment corresponding to 100 0.02π interval phase differences within a period. It can be seen that this invention experimentally achieves a precise displacement of approximately 5.1 nm in the interference fringes, meaning the minimum measurable target displacement is 5.1 nm. Furthermore, if the incident light... Figure 59 The first optical field phase of the crescent-shaped slit structure on the left is greater than the second optical field phase of the crescent-shaped slit structure on the right, i.e., the optical field phase difference Δ Figure 60 Figure 61 Figure 62 Figure 63 Figure 64 Figure 65 Figure 66 Figure 67 Figure 68 Figure 69 Figure 70 Figure 71 Figure 72 Figure 73 Figure 74 Figure 75 Figure 76 Figure 77 Figure 78 Figure 79 Figure 80 Figure 81 Figure 82 Figure 83 Figure 84 Figure 85 Figure 86 Figure 87 Figure 88 Figure 89 Figure 90 Figure If the value is less than 0, the interference fringes will shift to the left, thus enabling displacement measurement in different directions.

[0048] That is, the phase difference of the optical field can be greater than 0 or less than 0. When the phase difference of the optical field changes at intervals of 0.02π (increasing or decreasing at equal intervals, with a tolerance of 0.02π for the phase difference change), a leftward or rightward displacement measurement with a minimum displacement of 5.1 nm will be achieved.

[0049] As can be seen, by specifically utilizing a spatial light modulator, the phase from 0 to 2π can be discretized into 256 gray levels. By loading different phase diagrams, a phase difference can be created between the first and second light fields incident on both sides of the symmetry axis of the sharp-edge diffraction structure. This allows the high-frequency waves induced by the sharp-edge diffractor to have different initial phases, thereby modulating their propagation behavior. In this embodiment, the smaller the initial phase difference, the smaller the interference fringe translation, reaching the nanometer scale. Furthermore, the sign of the phase difference between the light fields on both sides of the symmetry axis of the sharp-edge diffractor determines the direction of the interference fringe translation. That is, this invention can achieve nanometer-level displacement and flexible control of interference fringes or scale lines.

[0050] The measuring device in this embodiment can achieve precise displacement measurement at the nanoscale. Its working principle is as follows: A sharp-edge diffractometer induces the coherent superposition of far-field high-frequency waves, generating fine interference fringes, thus forming a super-diffraction-limited interference fringe field. By controlling the propagation behavior of the high-frequency waves through a spatial light modulator, precise displacement of the interference fringes can be achieved; that is, nanoscale movement of the interference fringes is achieved by controlling the high-frequency waves, thereby realizing nanoscale displacement measurement. Treating these interference fringes as the measuring scale lines of a general physical ruler yields a far-field precision optical ruler with nanoscale displacement of the scale lines, which can be directly used for nanoscale displacement measurement of some objects.

[0051] Therefore, based on the nanometer displacement measuring device of the embodiment, the nanometer displacement measuring method realized comprises the following steps:

[0052] The interference fringes are generated by inducing the coherent superposition of the far-field high-frequency diffraction waves through the sharp-edge diffraction device.

[0053] The phase of 0-2pi is discretized into 256 gray scales through the spatial light modulator, different phase patterns are loaded, the first light field and the second light field incident to the regions on both sides of the symmetry axis of the sharp-edge diffraction structure have a phase difference, the high-frequency diffraction waves induced by the sharp-edge diffraction device have different initial phases, and then the propagation behavior thereof is regulated, and the nanometer-level movement of the interference fringes is realized.

[0054] The interference fringes are taken as the measurement scale lines to measure the nanometer displacement of the object.

[0055] In summary, the embodiment proposes a nanometer displacement measuring device and method based on the far-field high-frequency waves, and the physical principle of the measurement technology is clear. Unlike other indirect measurement technologies which depend on the correlation between the target displacement and certain optical phenomena, the embodiment can directly measure the target to be measured like a physical ruler, is flexible and adjustable, and has a simple experimental structure, flexible operation, practical value, and wide application prospects in the fields of precision measurement and micro-nano processing.

[0056] The above embodiment is a preferred embodiment of the present application, but the embodiment of the present application is not limited by the above embodiment, and any change, modification, substitution, combination, simplification made without departing from the spirit and principle of the present application should be an equivalent replacement mode, and all are included in the protection scope of the present application.

Claims

1. A nano-displacement measurement device based on a far-field high-frequency wave, characterized by, The spatial light modulator and the sharp-edge diffraction device are included. The spatial light modulator is used to load a phase pattern to generate a light field with a non-uniform phase distribution. The sharp-edge diffraction device has a sharp-edge diffraction structure with an axisymmetric geometric distribution and is used to induce high-frequency diffraction waves in a far field. The sharp-edge diffraction device performs binary modulation on the light field incident thereon to induce high-frequency diffraction waves with an axisymmetric geometric distribution, and the high-frequency diffraction waves are coherently superimposed in the far field to form interference fringes with a subwavelength period. The light field modulated by the spatial light modulator is incident on the sharp-edge diffraction device to form a first light field and a second light field 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. The sharp-edge diffraction device includes a transparent substrate and a thin film formed on the transparent substrate, and the thickness of the thin film is on the order of 100 nanometers or 10 nanometers. The thin film completely blocks the incident light field, and the transparent substrate part 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 to induce high-frequency diffraction waves in the far field. The thin film is a pair of slits with a thickness of 60 nm, an outer diameter of 15 μm, and a maximum light transmission width of 0.7 μm.

2. The nanometer displacement measuring device according to claim 1, wherein The shape of the slit is rectangular, arcuate, or crescent.

3. The nanometer displacement measuring device of claim 1, wherein, The thin film is a metal film.

4. The nanometer displacement measuring device of claim 3, wherein, The phase difference of the light field is greater than 0 or less than 0 and changes in an arithmetic progression or a geometric progression.

5. The nanometer displacement measuring device of claim 1, wherein, The tolerance of the phase difference is 0.05π or 0.02π. The nanometer displacement measurement device further includes: a light source for generating linearly polarized laser light; a beam expander and collimator for expanding and collimating the laser light emitted by the light source; a beam splitter prism for separating the light beam output by the beam expander and collimator; 6. The nanometer displacement measuring device of claim 5, wherein, a light field detection assembly for amplifying, collecting, and recording the subwavelength period interference fringe field information generated by the sharp-edge diffraction device.

7. A nano-displacement measurement method based on a far-field high-frequency wave, characterized by, The light field detection assembly includes a high-power objective lens, a barrel lens, and a camera, the high-power objective lens is used to amplify the light field information generated by the sharp-edge diffraction device, the barrel 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 barrel lens. The measurement method is implemented by the nanometer displacement measurement device of any one of claims 1-6 and includes the following steps: inducing coherent superposition of high-frequency diffraction waves in a far field by a sharp-edge diffraction device to generate interference fringes; discretizing the phase of 0-2π into 256 gray scales by a spatial light modulator, loading different phase patterns, making the first light field and the second light field incident on both sides of the symmetry axis of the sharp-edge diffraction structure have a phase difference, making the high-frequency diffraction waves induced by the sharp-edge diffraction device have different initial phases, and then regulating the propagation behavior to realize nanometer-level movement of the interference fringes; taking the interference fringes as a measurement scale line to measure the nanometer displacement of an object.

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