A high-precision displacement measurement system and method based on ultrasonic grating

Abstract

The present invention relates to the field of grating measurement technology, and specifically provides a high-precision displacement measurement system and method based on ultrasonic grating, comprising: a light source, an ultrasonic grating unit and an optical signal processing unit, wherein an ultrasonic grating is formed by injecting ultrasonic waves into an acousto-optic material, and a detection light provided by the light source is injected into the ultrasonic grating at a specific angle, and the optical signal processing unit comprises: a reflector for changing the propagation path of multi-order diffracted light, a beam combining prism for beam combining interference of the multi-order diffracted light, and a detector for collecting interference information, and the displacement of a target to be measured is obtained by collecting interference information of multi-order diffracted light formed by the detection light passing through the acousto-optic material. The present invention uses ultrasonic grating to replace traditional physical gratings, and is designed and applied to displacement measurement, thereby overcoming the disadvantages of traditional physical gratings and greatly improving the displacement measurement accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of grating measurement, and in particular relates to a high-precision displacement measurement system and method based on ultrasonic grating. Background Art

[0002] At present, high-precision displacement measurement technologies mainly include laser interferometry and grating interferometry. Among them, the measurement basis of laser interferometry is the laser wavelength. Its disadvantage is that it is sensitive to the refractive index of air and has strict requirements on external environmental conditions. It is easy to obtain high precision under short strokes, but as the measurement stroke gradually increases, slight changes in the measurement environment such as temperature, humidity and air pressure will seriously affect the accuracy of the measurement results. The measurement error of strokes above the meter level can even be as high as hundreds of nanometers. A high-level environmental control system is required to achieve high-precision measurement with a laser interferometer. The measurement basis of grating interferometry is the grating pitch, and the grating substrate can be made of zero expansion material. Compared with the wavelength, the external environment has little effect on the groove, and its measurement accuracy is almost unaffected by the increase in stroke. It does not require strict environmental control such as constant temperature, constant pressure, and constant humidity, which greatly reduces the requirements for the measurement environment. In view of the above advantages, grating interferometry displacement measurement equipment has an urgent application demand in high-end CNC machine tools and aerospace fields.

[0003] The range expansion of existing grating interferometers relies on large-size gratings, but the manufacturing cost of large-size gratings is high, and there will be line errors and surface errors during the manufacturing process, which will seriously affect the accuracy of displacement measurement. On the other hand, dust and oil in the working environment adhere to the grating surface, which will reduce the grating diffraction efficiency and shorten the grating service life. The above reasons limit the further development of traditional grating measurement systems. Summary of the invention

[0004] In view of this, the invention aims to provide a high-precision displacement measurement system and method based on ultrasonic grating, using ultrasonic grating to replace traditional physical grating, and by collecting the interference information of multi-order diffracted light after the light beam passes through the ultrasonic grating, a mathematical relationship between the displacement and the change in the frequency shift of the diffracted light is established, and then the displacement of the target to be measured is calculated. The present invention is the first to design a scheme for applying ultrasonic grating to displacement measurement in detail, avoiding the shortcomings of traditional physical gratings through ultrasonic gratings, and greatly improving the displacement measurement accuracy.

[0005] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0006] The invention provides a high-precision displacement measurement system based on ultrasonic grating, comprising: a light source, an ultrasonic grating unit and an optical signal processing unit;

[0007] The ultrasonic grating unit includes an electroacoustic transducer for providing ultrasonic waves, and an acousto-optic material modulated by the ultrasonic waves provided by the electroacoustic transducer;

[0008] The light source is used to provide a probe light that passes through the acousto-optic material;

[0009] The optical signal processing unit is used to receive and combine the multi-order diffracted light formed after the detection light passes through the acousto-optic material, and obtain the detection result according to the interference information of the multi-order diffracted light.

[0010] Preferably, the acousto-optic material is an elastic medium.

[0011] Preferably, the electroacoustic transducer is arranged on the side of the acousto-optic material, and the ultrasonic wave provided by the electroacoustic transducer is vertically incident on the acousto-optic material.

[0012] Preferably, the detection light provided by the light source is incident on the acousto-optic material vertically, or the detection light provided by the light source is incident on the acousto-optic material at a Bragg angle.

[0013] Preferably, the optical signal processing unit includes: a reflector for changing the propagation path of the multi-order diffracted light, a beam combining prism for combining and interfering the multi-order diffracted light, and a detector for collecting interference information.

[0014] Another aspect of the present invention provides a high-precision displacement measurement method based on ultrasonic grating, which uses a high-precision displacement measurement system based on ultrasonic grating to perform displacement measurement, including:

[0015] The ultrasonic grating unit and the target to be measured are relatively fixed;

[0016] The electroacoustic transducer provides ultrasonic waves to be injected into the acousto-optic material;

[0017] Controlling the light source to provide detection light, the detection light is incident on the acousto-optic material at a preset angle;

[0018] The Doppler frequency shift variation of the multi-order diffracted light is calculated according to the interference information collected by the optical signal processing unit, and the displacement of the target to be measured is calculated according to the Doppler frequency shift variation.

[0019] Preferably, when the detection light provided by the light source is vertically incident on the acousto-optic material, the optical signal processing unit collects The order diffracted light and The interference signal of the diffracted light is:

[0020] ;

[0021] represents the strength of the interference signal, Indicates that the target displacement The complex amplitude of the diffracted light, Indicates that the target displacement The complex amplitude of the diffracted light, Indicates time, It indicates the frequency of ultrasonic waves provided by the electroacoustic transducer; Indicates that the target displacement The Doppler frequency shift change of the diffracted light is Indicates that the target displacement The change of Doppler frequency shift of the first-order diffraction light;

[0022] Displacement of the target to be measured for:

[0023] ;

[0024] in, Indicates the wavelength of ultrasound provided by the electroacoustic transducer.

[0025] Preferably, when the detection light provided by the light source enters the acousto-optic material at the Bragg angle, the optical signal processing unit collects the 0th order diffraction light and The diffracted light of order 1, or the diffracted light of order 0 and Interference signal of the diffracted light.

[0026] Preferably, the optical signal processing unit collects the 0th order diffracted light and When the 0th order diffraction light is generated, the optical signal processing unit collects the 0th order diffraction light and The interference signal of the diffracted light is:

[0027] ;

[0028] in, represents the strength of the interference signal, It represents the complex amplitude of the 0th order diffracted light after the target is displaced. Indicates that the target displacement The complex amplitude of the diffracted light, Indicates time, It indicates the frequency of ultrasonic waves provided by the electroacoustic transducer; Indicates that the target displacement The change of Doppler frequency shift of the first-order diffraction light;

[0029] Displacement of the target to be measured for:

[0030] ;

[0031] in, Indicates the wavelength of ultrasound provided by the electroacoustic transducer.

[0032] Preferably, the optical signal processing unit collects the 0th order diffracted light and When the 0th order diffraction light is generated, the optical signal processing unit collects the 0th order diffraction light and The interference signal of the diffracted light is:

[0033] ;

[0034] in, represents the strength of the interference signal, It represents the complex amplitude of the 0th order diffracted light after the target is displaced. Indicates that the target displacement The complex amplitude of the diffracted light, Indicates time, It indicates the frequency of ultrasonic waves provided by the electroacoustic transducer; Indicates that the target displacement The change of Doppler frequency shift of the first-order diffraction light;

[0035] Displacement of the target to be measured for:

[0036] ;

[0037] in, Indicates the wavelength of ultrasound provided by the electroacoustic transducer.

[0038] Compared with the prior art, the invention can achieve the following beneficial effects:

[0039] The present invention has designed in detail a scheme for applying ultrasonic grating to displacement measurement. Since the movement of ultrasonic grating will cause the diffracted light to undergo Doppler frequency shift, high-precision displacement measurement is achieved by establishing a mathematical relationship between the frequency shift change and the displacement. By replacing the traditional grating with an ultrasonic grating, since the ultrasonic grating has no physical grating lines, there is no need to worry about stains causing the grating diffraction efficiency to decrease. In theory, it has complete anti-fouling ability, and the equivalent grating pitch of the ultrasonic grating is the wavelength of the ultrasonic wave. The wavelength of the ultrasonic wave in the acousto-optic material is constant. Therefore, the ultrasonic grating has no line error and surface error, which can eliminate the system error caused by grating manufacturing and greatly improve the displacement measurement accuracy.

[0040] In addition, the essence of ultrasonic grating is uniform acousto-optic material, which is easy to obtain and has low production cost. Moreover, the grating lines of ultrasonic grating are erasable, and the ultrasonic wavelength can be adjusted according to needs, thereby replacing the grating pitch, which improves the flexibility of displacement measurement while avoiding the problem of size limitation of traditional gratings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0042] Figure 1 A high-precision displacement measurement system based on ultrasonic grating provided according to Embodiment 1 of the present invention;

[0043] Figure 2 It is a high-precision displacement measurement system based on ultrasonic grating provided according to Example 2 of the present invention.

[0044] Reference numerals include:

[0045] Ultrasonic grating unit A, optical signal processing unit B, light source 1, acousto-optic material 2, electroacoustic transducer 3, first reflector 4, second reflector 5, beam combining prism 6, detector 7. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical scheme and advantages of the invention clearer, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the invention and do not constitute a limitation to the invention. Similar components in different embodiments use associated similar component numbers. In the following embodiments, many detailed descriptions are to enable the invention to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other components, materials, and methods. In some cases, some operations related to the invention are not shown or described in the specification, in order to avoid the core part of the invention being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0047] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to form various implementation methods. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a necessary sequence, unless otherwise specified that a certain sequence must be followed.

[0048] In the description of the invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the invention 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 therefore cannot be understood as a limitation on the invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0049] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0050] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0051] See also Figure 1In one embodiment 1 of the present invention, a high-precision displacement measurement system based on ultrasonic grating is provided, comprising: an ultrasonic grating unit A, an optical signal processing unit B and a light source 1, wherein the ultrasonic grating unit A is used to replace the physical grating in the traditional displacement measurement system, and is mainly composed of an acousto-optic material 2 and an electroacoustic transducer 3, and the acousto-optic material 2 is an elastic medium. The electroacoustic transducer 3 is arranged on the side of the acousto-optic material 2, and is a device that can convert an electrical signal into an acoustic signal or convert an acoustic signal into an electrical signal. In the embodiment of the present invention, the electroacoustic transducer 3 is used to generate an ultrasonic wave of a certain frequency, and the ultrasonic wave is incident perpendicular to the side of the acousto-optic material 2, and the wavelength and frequency of the ultrasonic wave generated by the electroacoustic transducer 3 can be customized. Since ultrasound is an elastic wave, when entering the acousto-optic material 2 and propagating in the acousto-optic material 2, the elastic wave will cause the acousto-optic material 2 to produce elastic stress or strain, resulting in elastic strains that change periodically with time and space at each point in the acousto-optic material 2. Due to the elasto-optic effect, the refractive index of each point in the acousto-optic material 2 will also undergo corresponding periodic changes. This change makes the acousto-optic material 2 present a periodic refractive index distribution under the action of ultrasound, which is similar to a phase grating in function. When a light beam passes through the acousto-optic material 2 with periodic refractive index changes, the phase of the light beam will be modulated, resulting in a diffraction phenomenon, similar to the effect of passing through a diffraction grating, and the equivalent grating pitch is equal to the wavelength of the ultrasound wave that causes the elasto-optic effect. Therefore, the embodiment of the present invention modulates the acousto-optic material 2 by the electroacoustic transducer 3 to obtain an ultrasonic grating with adjustable size and adjustable grating pitch. Compared with the traditional physical grating, the ultrasonic grating formed by the ultrasonic grating unit A has no physical grating lines, and there is no difficulty in grating preparation, especially when a large-size grating is required. Since the wavelength of the ultrasonic wave in the acousto-optic material 2 is constant, there is no line error and surface error, and the acousto-optic material 2 is easy to obtain and does not require complex processing, so the ultrasonic grating is far superior to the physical grating in terms of production cost and preparation accuracy. In addition, the grating lines and grating pitch of the ultrasonic grating can be controlled by the electroacoustic transducer 3. When facing different measurement requirements, it can be modulated by the electroacoustic transducer 3 without the need for replacement, disassembly, assembly, etc., and the cost and reliability of displacement detection are higher.

[0052] The optical signal processing unit B is used to receive and collect interference information of multi-order diffraction light emitted by the light source 1 and formed after passing through the ultrasonic grating unit A. Specifically, the light source 1 is used to provide detection light, and the detection light is incident on the ultrasonically modulated acousto-optic material 2 at a specific angle.

[0053] When the detection light provided by the light source 1 needs to be vertically injected into the acousto-optic material 2, the phase of the detection light will be modulated when passing through the acousto-optic material 2 with ultrasonic action, generating The order diffracted light and The optical signal processing unit B is provided with a first reflector 4, a second reflector 5, a beam combining prism 6 and a detector 7. The first reflector 4 is arranged The propagation path of the diffracted light is changed by the first reflector 4. The propagation direction of the first-order diffracted light is adjusted so that it is directed toward the beam combining prism 6. Similarly, the second reflector 5 is arranged at The propagation path of the diffracted light is changed by the second reflector 5. The propagation direction of the first-order diffraction light is changed so that it also irradiates the beam-combining prism 6. The order diffracted light and The multi-order diffracted light is combined by the beam combining prism 6 and enters the detector 7, where a stable interference is formed on the target surface of the detector 7. The interference information of the multi-order diffracted light after diffraction by the acousto-optic material 2 can be obtained through the detector 7. The interference information is The order diffracted light and Interference light intensity pattern of the first order diffraction light.

[0054] The displacement can be further calculated by the interference light intensity information. Specifically, the method for displacement measurement using the high-precision displacement measurement system based on ultrasonic grating includes the following steps:

[0055] S1: The ultrasonic grating unit A and the target to be measured are relatively fixed, that is, during the movement of the target to be measured, the ultrasonic grating unit A and the target to be measured are relatively stationary, so that the displacement of the target to be measured can be determined according to the displacement of the ultrasonic grating unit A later.

[0056] S2: Start the electroacoustic transducer 3 and modulate the ultrasonic wave emitted by the electroacoustic transducer 3. The propagation speed of the ultrasonic wave generated by the electroacoustic transducer 3 in the acousto-optic material 2 is V, and the frequency of the ultrasonic wave is f 1, the wavelength of the ultrasonic wave is Λ. The ultrasonic wave is incident vertically from the side of the acousto-optic material 2, and the acousto-optic material 2 forms an ultrasonic grating based on the photoelastic effect.

[0057] S3: Start the light source 1. Usually, the light source 1 can be a laser. The frequency of the detection light provided by the light source 1 is expressed as f , whose wavelength is λ , then the complex amplitude of the detection light It can be expressed as:

[0058] ;

[0059] in, Represents the complex amplitude of the detection light, which is a complex number that contains the amplitude and phase information of the detection light wave. represents the amplitude of the detection light, which is a real number and represents the maximum intensity of the detection light wave. e represents the base of natural logarithms,i represents the imaginary unit, Indicates time, φ 0 indicates the initial phase.

[0060] According to the wavelength of the ultrasonic wave emitted by the electroacoustic transducer 3 and the wavelength of the detection light, The order diffracted light and The diffraction angle equation of the first-order diffraction light is:

[0061] ;

[0062] Where θ represents the diffraction angle, m Represents the diffraction order of the diffracted light, which can be a positive or negative integer, here is and , Indicates the wavelength of the ultrasonic wave provided by the electroacoustic transducer 3.

[0063] When the target to be measured is stationary, the ultrasonic grating unit A has no movement. Since the ultrasonic wave is an elastic traveling wave, the refractive index change inside the acousto-optic material 2 is a traveling change, and the change direction and frequency are consistent with the movement direction and frequency of the ultrasonic wave generated by the electroacoustic transducer 3. The order diffracted light and The complex amplitude of the order diffraction light can be expressed as:

[0064] ;

[0065] In the above formula Indicates that the target to be measured is stationary The complex amplitude of the diffracted light, Indicates that the target to be measured is stationary The complex amplitude of the diffracted light, express The order diffracted light and The amplitude of the diffracted light is a constant, which represents the intensity of the diffracted light. It represents the frequency of the ultrasonic wave provided by the electroacoustic transducer 3.

[0066] When the target to be measured is stationary, The order diffracted light and From the formula of the complex amplitude of the diffracted light, we can know that the traveling wave characteristics of ultrasonic waves will lead to The order diffracted light and The frequency of the diffracted light will change. Therefore, when the target moves a certain distance, The order diffracted light and The order diffraction light brings additional grating Doppler frequency shift change, and the expression of Doppler frequency shift change is:

[0067] ;

[0068] in, Indicates that the target displacement The Doppler frequency shift change of the diffracted light is Indicates that the target displacement The Doppler frequency shift change of the diffracted light is Indicates the moving distance of the target to be measured, that is, moving in the direction perpendicular to the incident direction of the detection light .

[0069] When the target moves along the X direction S x back, The order diffracted light and The complex amplitude of the order diffracted light can be updated as:

[0070] .

[0071] Depend on The order diffracted light and The complex amplitude of the diffracted light is known to be: The order diffracted light and The first and second order diffraction lights are respectively reflected by the second reflector 5 and the first reflector 4 toward the beam combining prism 6. The order diffracted light and After the diffracted light is combined by the beam combining prism 6, a stable interference is formed on the target surface of the detector 7. The detector 7 collects The order diffracted light and The interference signal of the diffracted light is:

[0072] ;

[0073] In the above formula, represents the strength of the interference signal, Indicates that the target displacement The complex amplitude of the diffracted light, Indicates that the target displacement The complex amplitude of the diffracted light.

[0074] Furthermore, the displacement of the target to be measured It can be expressed as:

[0075] .

[0076] Through the above process, high-precision displacement measurement of the target can be achieved.

[0077] In addition, based on the high-precision displacement measurement system based on ultrasonic grating given in Example 1 of the present invention, it can also be used for ultrasonic measurement. Assuming that the frequency, wave velocity, wavelength and other parameters of a certain ultrasonic wave are unknown, the high-precision displacement measurement system based on ultrasonic grating can be used to measure the parameters. At this time, the ultrasonic wave injected into the acousto-optic material 2 is the unknown ultrasonic wave to be measured.

[0078] When the ultrasonic grating unit A is stationary, the detector 7 collects The order diffracted light and Interference signal of diffracted light for:

[0079] .

[0080] Interference signal at rest Expanding the spectrum analysis can obtain the frequency of the interference signal f 1.

[0081] At this time, the ultrasonic grating unit A is driven to move a known displacement along the X-axis direction. , then according to the displacement of the target to be measured derived in the previous article The calculation formula is:

[0082] ;

[0083] It can be transformed to obtain, when the displacement is known Under the premise of , the wavelength of the unknown ultrasonic wave inside the acousto-optic material 2 is solved as:

[0084] ;

[0085] In the above formula, represents the wavelength of the unknown ultrasonic wave, Indicates the displacement of the target to be measured back The Doppler frequency shift change of the diffracted light is Indicates the displacement of the target to be measured back The change in Doppler frequency shift of the diffracted light.

[0086] Further, based on the mathematical relationship between wavelength, frequency and wave speed, the unknown ultrasonic wave speed can be solved as:

[0087] .

[0088] The high-precision displacement measurement system based on ultrasonic grating proposed in the embodiment of the present invention can realize the accurate measurement of the sound wave frequency, wave velocity and wavelength of unknown ultrasonic waves.

[0089] Embodiment 1 of the present invention details the situation where the detection light needs to be incident vertically into the acousto-optic material 2. In Embodiment 2 of the present invention, a method for high-precision displacement measurement of the target to be measured is provided when the detection light provided by the light source 1 is incident into the acousto-optic material 2 at a Bragg angle. For details, please refer to Figure 2 , which is different from the vertical injection of the detection light into the acousto-optic material 2, in that the detection light is injected into the acousto-optic material 2 at the Bragg angle, the ultrasonic wave frequency provided by the electroacoustic transducer 3 is relatively high, and the wavelength of the ultrasonic wave propagating in the acousto-optic material 2 is relatively short, which can satisfy the requirement that the distance of the acousto-optic effect is greater than the characteristic length of the acousto-optic diffraction, so that the acousto-optic material 2 has the characteristic of "volume grating". At this time, when the detection light passes through the acousto-optic material 2 with ultrasonic effect, Bragg diffraction will occur, and only the 0th order diffraction light and order diffracted light, or produce 0th order diffracted light and The angle between the two diffracted lights is twice the Bragg angle, that is, .

[0090] Accordingly, the first reflector 4 in the optical signal processing unit B is arranged The diffracted light or The second reflector 5 is arranged on the propagation optical path of the 0th order diffraction light, and makes it project to the beam combining prism 6, and enters the detector 7 after the beam combining process of the beam combining prism 6, and forms a stable interference on the target surface of the detector 7, and obtains the interference through the detector 7. The interference information of the 1st-order diffracted light and the 0th-order diffracted light, or Interference information between the 1st-order diffraction light and the 0th-order diffraction light.

[0091] The above-mentioned The interference information of the 1st-order diffracted light and the 0th-order diffracted light, or The process of displacement measurement based on the interference information of the first-order diffracted light and the 0th-order diffracted light is exactly the same. Take the first-order diffraction light and the 0th-order diffraction light as examples to illustrate:

[0092] The complex amplitude of the probe light provided by light source 1 Still expressed as:

[0093] .

[0094] When the target is stationary, The complex amplitudes of the first-order diffracted light and the 0th-order diffracted light can be expressed as:

[0095] ;

[0096] In the above formula It represents the complex amplitude of the 0th order diffracted light when the target is stationary. Indicates that the target to be measured is stationary The complex amplitude of the diffracted light, represents the amplitude of the 0th order diffracted light, is a constant, represents the intensity of the diffracted light, Indicates when Bragg diffraction occurs The amplitude of the first-order diffraction light is a constant, which represents the intensity of the diffracted light.

[0097] According to the traveling wave characteristics of ultrasonic waves, the frequency of the −1-order diffracted light will change. When the target moves, it will bring additional grating Doppler frequency shift changes to the −1-order diffracted light, while the 0-order diffracted light has no additional Doppler frequency shift changes. Therefore, when the target moves, The expression of the Doppler frequency shift change of the first-order diffraction light and the 0th-order diffraction light is:

[0098] ;

[0099] in, It indicates the change in Doppler frequency shift of the 0th order diffracted light after the target is displaced. Indicates that the target displacement The change of Doppler frequency shift of the diffracted light.

[0100] When the target moves along the X direction S x After that, the 0th order diffracted light and The complex amplitude of the order diffracted light can be updated as:

[0101] ;

[0102] In the above formula Indicates that the target to be measured moves The complex amplitude of the diffracted light.

[0103] After the 0th order diffracted light and the −1st order diffracted light are processed by the first reflector 4, the second reflector 5 and the beam combining prism 6, interference is formed at the detector 7. The interference signal received by the detector 7 is It is expressed as:

[0104] .

[0105] Then the displacement of the target to be measured along the X-axis direction is obtained The calculation formula is:

[0106] .

[0107] Similarly, diffraction obtains When the 0th-order diffracted light and the 0th-order diffracted light are collected, the only difference is the specific expression form of the calculation formula. The calculation process and results are exactly the same. The optical signal processing unit B collects the 0th-order diffracted light and When the 0th order diffraction light is detected, the detector 7 collects the 0th order diffraction light and Interference signal of diffracted light for:

[0108] ;

[0109] The displacement of the target along the X-axis The calculation formula is:

[0110] .

[0111] In short, the above description is only a preferred embodiment of this specification and is not intended to limit the protection scope of this specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this specification shall be included in the protection scope of this specification.

[0112] The systems, devices, modules or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, the computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0113] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0114] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0115] The above is a description of a specific embodiment of the specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A high-precision displacement measurement system based on ultrasonic grating, characterized in that: include: A light source, an ultrasonic grating unit and an optical signal processing unit; Wherein, the ultrasonic grating unit includes an electroacoustic transducer for providing ultrasonic waves, and an acousto-optic material modulated by the ultrasonic waves provided by the electroacoustic transducer; The light source is used to provide a detection light that passes through the acousto-optic material; The optical signal processing unit is used to receive the multi-order diffracted light formed after the combined detection light passes through the acousto-optic material, and obtain the detection result according to the interference information of the multi-order diffracted light; calculate the Doppler frequency shift change of the multi-order diffracted light according to the interference information collected by the optical signal processing unit, and calculate the displacement of the target to be measured according to the Doppler frequency shift change; When the detection light provided by the light source vertically enters the acousto-optic material, the optical signal processing unit collects The order diffracted light and The interference signal of the diffracted light is: ； in, represents the strength of the interference signal, Indicates that the target displacement The complex amplitude of the diffracted light, Indicates that the target displacement The complex amplitude of the diffracted light, Indicates time, Indicates the frequency of the ultrasonic wave provided by the electroacoustic transducer; Indicates that the target displacement The Doppler frequency shift change of the diffracted light is Indicates that the target displacement The change of Doppler frequency shift of the first-order diffraction light; Displacement of the target to be measured for: ； in, Indicates the wavelength of the ultrasonic wave provided by the electroacoustic transducer; When the detection light provided by the light source enters the acousto-optic material at a Bragg angle, the optical signal processing unit collects the 0th order diffraction light and The diffracted light of order 1, or the diffracted light of order 0 and Interference signal of the diffracted light of order; The optical signal processing unit collects the 0th order diffracted light and When the 0th order diffraction light is generated, the optical signal processing unit collects the 0th order diffraction light and The interference signal of the diffracted light is: ； in, represents the strength of the interference signal, It represents the complex amplitude of the 0th order diffracted light after the target is displaced. Indicates that the target displacement The complex amplitude of the diffracted light, Indicates time, Indicates the frequency of the ultrasonic wave provided by the electroacoustic transducer; Indicates that the target displacement The change of Doppler frequency shift of the first-order diffraction light; Displacement of the target to be measured for: ； The optical signal processing unit collects the 0th order diffracted light and When the 0th order diffraction light is generated, the optical signal processing unit collects the 0th order diffraction light and The interference signal of the diffracted light is: ； in, represents the strength of the interference signal, It represents the complex amplitude of the 0th order diffracted light after the target is displaced. Indicates that the target displacement The complex amplitude of the diffracted light, Indicates time, Indicates the frequency of the ultrasonic wave provided by the electroacoustic transducer; Indicates that the target displacement The change of Doppler frequency shift of the first-order diffraction light; Displacement of the target to be measured for: ； in, It indicates the wavelength of ultrasonic wave provided by the electroacoustic transducer.

2. The high-precision displacement measurement system based on ultrasonic grating according to claim 1, characterized in that: The acousto-optic material is an elastic medium.

3. The high-precision displacement measurement system based on ultrasonic grating according to claim 1, characterized in that: The electroacoustic transducer is arranged on the side of the acousto-optic material, and the ultrasonic wave provided by the electroacoustic transducer is vertically incident on the acousto-optic material.

4. The high-precision displacement measurement system based on ultrasonic grating according to claim 1, characterized in that: The detection light provided by the light source is incident on the acousto-optic material vertically, or the detection light provided by the light source is incident on the acousto-optic material at a Bragg angle.

5. The high-precision displacement measurement system based on ultrasonic grating according to claim 1, characterized in that: The optical signal processing unit comprises: a reflector for changing the propagation path of the multi-order diffracted light, a beam combining prism for combining and interfering the multi-order diffracted light, and a detector for collecting interference information.

6. A high-precision displacement measurement method based on ultrasonic grating, characterized in that: The method of performing displacement measurement using the high-precision displacement measurement system based on ultrasonic grating as claimed in any one of claims 1 to 5 comprises: The ultrasonic grating unit is relatively fixed to the target to be measured; The electroacoustic transducer provides ultrasonic waves to be injected into the acousto-optic material; Controlling the light source to provide detection light, wherein the detection light enters the acousto-optic material at a preset angle; The Doppler frequency shift variation of the multi-order diffracted light is calculated according to the interference information collected by the optical signal processing unit, and the displacement of the target to be measured is calculated according to the Doppler frequency shift variation.

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