Nanometer grating interference type three-axis MOEMS acceleration sensing device

Abstract

The invention belongs to the technical field of grating MOEMS acceleration sensing, and particularly relates to a nano grating interference type triaxial MOEMS acceleration sensing device, which comprises an upper grating, a sensitive structure layer, a driving magnet and a base, the upper grating is arranged above the sensitive structure layer, the sensitive structure layer is arranged above the driving magnet, the upper grating, the sensitive structure layer and the driving magnet are all arranged in the base, and an x-axis accelerometer, a y-axis accelerometer and a z-axis accelerometer which are orthogonally distributed are integrated in the sensitive structure layer. The acceleration sensors are respectively used for measuring accelerations in X-axis, Y-axis and Z-axis directions; the upper grating and the sensitive structure layer are arranged in parallel at an interval, and a grating interference detection area is formed between the two. The device has the advantages of being compact in structure, high in response speed, high in measurement precision, high in environmental adaptability and the like, and an integrated and miniaturized advanced solution is provided for multi-dimensional dynamic parameter measurement.

Description

Technical Field

[0001] The present invention belongs to the technical field of grating MOEMS acceleration sensing, and in particular relates to a nano-grating interferometric three-axis MOEMS acceleration sensing device. Background Art

[0002] A microelectromechanical (MEMS) accelerometer is a sensing device that measures the acceleration of an object. As a key component of an inertial navigation system, it is widely used in many military and civilian fields, including automotive safety, earthquake monitoring, gravity detection, heading indication, attitude reference motion tracking, and health testing. According to its detection effect classification, it includes capacitive, piezoelectric, piezoresistive, grating, etc. In comparison, the grating detection effect stands out with its significant advantages such as high precision, anti-electromagnetic interference and fast response, while other detection methods are often limited by factors such as parasitic capacitance, external electromagnetic interference and temperature effects, making it difficult to further improve measurement accuracy. From a technical perspective, grating displacement detection technology can be divided into interferometric, subwavelength evanescent field coupling effect, Talbot effect and moiré fringe type. Among them, the moiré fringe type is mostly used in the field of surface morphology measurement due to its low displacement resolution; the subwavelength evanescent field coupling effect refers to the situation where when the distance between two or more subwavelength structures is very close (usually at the nanometer scale), the evanescent fields overlap and couple with each other, thereby significantly changing the propagation characteristics of light. However, this technology is limited by stringent processing accuracy requirements and short working distance, making it difficult to be widely used in MEMS devices; although the grating Talbot effect has advantages such as high integration and large measurement range, the grating detection sensitivity is lower than that of the other types; compared with the first three, the grating interferometry type is the most commonly used choice for achieving high-sensitivity detection. It detects the magnitude of acceleration by the change in interference intensity after the combined beams of diffracted photosynthesis at different orders of the grating. Although it has the advantage of high precision, it is difficult to achieve integrated measurement due to the complexity of multi-optical path devices. Currently, three-axis measurement is still mainly based on discrete integration, which has problems such as large volume and large orthogonality error. Summary of the Invention

[0003] To address the technical issues mentioned above, where three-axis measurement is currently still primarily based on discrete integration, resulting in large size and large orthogonality errors, the present invention provides a nano-grating interferometric three-axis MOEMS acceleration sensor device. Based on the interference effect of the nano-grating, by measuring the changes in the intensity of the interfering light, the micro-displacement changes under the action of acceleration are obtained, thereby improving the measurement accuracy and sensitivity of acceleration.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: A nano-grating interferometric three-axis MOEMS acceleration sensing device comprises an upper grating, a sensitive structural layer, a driving magnet, and a base. The upper grating is disposed above the sensitive structural layer, which is disposed above the driving magnet. The upper grating, the sensitive structural layer, and the driving magnet are all disposed within the base. The sensitive structural layer integrates orthogonally distributed x-axis, y-axis, and z-axis accelerometers for measuring acceleration in the x-axis, y-axis, and z-axis directions, respectively. The upper grating and the sensitive structural layer are disposed parallel and spaced apart, forming a grating interference detection region therebetween.

[0005] The x-axis accelerometer and the y-axis accelerometer are both in-plane detection structures. The x-axis accelerometer and the y-axis accelerometer both include a cantilever beam, a first lower movable grating, a first sensitive mass block, a first outer frame and a support beam. The first outer frame is connected to the eight cantilever beams through four support beams, the first sensitive mass block is connected to the eight cantilever beams, and the first lower movable grating is arranged at the center of the first sensitive mass block.

[0006] The z-axis accelerometer is an off-plane detection structure, comprising an L-shaped cantilever beam, a second lower movable grating, a second sensitive mass block, and a second outer frame. The second outer frame is connected to the second sensitive mass block via the L-shaped cantilever beam, and the second lower movable grating is arranged at the center of the second sensitive mass block.

[0007] The grating direction of the upper grating and the first lower movable grating of the X-axis accelerometer is the X-axis direction, and the grating direction of the first lower movable grating of the Y-axis accelerometer is the Y-axis direction.

[0008] The grating direction of the second lower movable grating of the z-axis accelerometer is the Z-axis direction.

[0009] A method for measuring a nano-grating interferometric three-axis MOEMS acceleration sensor device comprises the following steps: S1. When acceleration is applied in the X-axis or Y-axis direction, the cantilever beam of the in-plane detection accelerometer bends and deforms, driving the first sensitive mass to translate. This causes the first lower movable grating and the upper grating to produce relative displacement, resulting in the movement of the (+1,0) and (0,+1) levels or (-1,0) and (0,-1) levels of diffracted light interference fringes. The detector detects the periodic change in light intensity and calculates the magnitude of the in-plane acceleration based on the corresponding relationship between the grating pitch d and the interference fringe period. S2. When acceleration is applied in the Z-axis direction, the L-shaped cantilever beam of the out-of-plane detection accelerometer deforms, driving the second sensitive mass to rise and fall, changing the vertical spacing between the second lower movable grating and the upper grating. This causes an optical path difference between the direct diffracted light and the reflected diffracted light. The detector detects the sinusoidal change in the interference light intensity, and the out-of-plane acceleration is calculated based on the relationship between the optical path difference and the displacement. S3. By synchronously collecting three-axis interference signals and processing them through a 90-degree phase shift circuit, a DC bias circuit, and a subdivision interpolation circuit, phase, amplitude, and bias errors are eliminated to achieve full-range high-precision linear measurement.

[0010] The method for calculating the magnitude of the in-plane acceleration in S1 is: According to the grating diffraction theorem, when a light beam is incident on a diffraction grating at an angle θ with the grating normal, diffraction occurs, and the diffraction angle satisfies the following relationship: Where θ is the angle of incidence, is the diffraction angle, m is the diffraction order, λ is the wavelength of the incident light, is the grating pitch; When a collimated light beam is incident perpendicularly on the upper grating, the incident angle θ is 0. In this case, after passing through the upper grating, the light beam generates three orders of diffraction light. The diffraction angle of the 0th order diffraction light is also 0, which means that the direction of the light beam does not change after diffraction. The +1st and -1st order diffraction lights are diffracted outward at angles of +φ and −φ, respectively. Their diffraction angles are calculated using the following formula: When these diffracted lights are transmitted to the first lower movable grating, they will also produce their own diffracted lights; the +1-order diffracted light will produce three diffracted lights (+1, +1), (+1, 0), and (+1, -1) after passing through the first lower movable grating; similarly, the -1-order diffracted light will be diffracted twice into three lights (-1, +1), (-1, 0), and (-1, -1), and the 0-order diffracted light will be diffracted twice into three lights (0, +1), (0, 0), and (0, -1); because the working surface of the first lower movable grating is parallel to the working surface of the upper grating, the incident angle of the +1-order diffracted light on the first lower movable grating is −φ +1 According to the grating diffraction principle, the diffraction angle of the 0th order diffracted light (+1,0) is φ +1 Similarly, the incident angle of the 0th order diffracted light on the first lower movable grating is 0, and the diffraction angle of the +1st order diffracted light (0, +1) is also φ +1 ; From this we can see that the (+1,0) order diffraction light and the (0,+1) order diffraction light are parallel to each other; their lateral misalignment is: Therefore, when the distance L between the grating working surfaces is small enough, the two beams of light will have a large overlapping area, thus interfering with each other. According to the principle of Doppler effect, the Doppler frequency shift of the diffraction grating is With its movement speed Proportional to the diffraction order m: When an acceleration is applied to the in-plane accelerometer, the first lower movable grating moves at a speed v in a direction perpendicular to the scribed lines. Different Doppler shifts will appear in the (0, +1) and (+1, 0) order diffraction gratings, which are: Therefore, the frequency shift difference between the (0, +1) order and the (+1, 0) order diffracted light is expressed as: Based on the above formula, it can be inferred that when the first lower movable grating moves by one grating distance d compared to the upper grating, the phase at each position in the interference field will change by 2π, causing the light intensity to fluctuate through a complete cycle. Therefore, based on the periodic counting of the light intensity changes in the interference field, the relative displacement between the upper grating and the first lower movable grating can be accurately determined, and thus the magnitude of the acceleration can be determined.

[0011] The method for calculating the magnitude of the off-plane acceleration in S2 is: When a light beam is incident perpendicularly on the upper grating, part of the light is directly reflected by the grating, while the other part passes through the grating and incident on the second lower movable grating. When there is acceleration in the direction of the sensitive axis, the second lower movable grating is displaced relative to the upper grating, and the diffracted light at the grating's reflection end interferes with the diffracted light of the same order reflected by the upper grating, resulting in a change in the intensity of the interference light. According to the Fraunhofer diffraction formula, the normalized complex amplitude distribution of the first diffracted light beam formed by the upper grating relative to the incident light is expressed as: The electric field expression of the incident light that is reflected by the second lower movable grating and passes through the grating again is: The total electric field of the first diffracted light and the second diffracted light is The intensity of the diffracted field is expressed as: According to the multi-slit Fraunhofer diffraction theory, when the optical path difference δ = 0 and δ = 2π, it corresponds to the 0th and 1st order diffraction light intensities respectively; for the 0th order diffraction beam, its intensity is: For ±1 order diffraction beams, the intensity is: From the expressions of 0th and 1st order light intensity, we can see that and Proportional, and proportional; The light intensity is correlated with the distance between the upper grating and the second, lower movable grating. Each movement of λ / 2 causes a change in the waveform. By detecting changes in the interference light intensity, the change in micro-displacement can be measured, and the magnitude of the acceleration can be inferred.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The proposed nanograting triaxial MOEMS acceleration sensor device leverages the nanograting interferometry effect and optimizes the accelerometer and grating structural parameters to achieve high-precision acceleration measurement in three orthogonal directions: X, Y, and Z. The device integrates the triaxial acceleration measurement modules into a monolithic structure. By orthogonally distributing in-plane (X / Y-axis) and out-of-plane (Z-axis) accelerometers within the sensitive structural layer, and utilizing the interference detection area formed by the upper grating and the lower movable grating, the device accurately reflects the displacement through the movement of diffracted light interference fringes during in-plane acceleration measurement and through the change in optical path difference during out-of-plane acceleration measurement. By combining the quantitative relationships between grating pitch and interference period, and optical path difference and displacement, the device significantly improves the sensitivity and resolution of acceleration detection. This monolithic design effectively reduces system size and weight, improves integration and reliability, avoids assembly errors associated with discrete multi-axis components, and reduces orthogonality errors. Furthermore, the miniaturized manufacturing process based on the MOEMS process further enhances structural stability. Furthermore, the nanograting interferometry principle endows the device with electromagnetic interference resistance. The device simultaneously collects three-axis interference signals and processes them through a 90-degree phase shift, DC bias, and interpolation circuit, eliminating phase, amplitude, and offset errors and achieving high-precision linear measurement across the full range. The device boasts a compact structure, fast response, high measurement accuracy, and strong environmental adaptability. It is suitable for complex scenarios sensitive to three-axis acceleration, such as high-precision inertial navigation, vibration monitoring, and industrial automation. It provides an integrated, miniaturized, and advanced solution for multi-dimensional dynamic parameter measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0014] The structures, proportions, sizes, etc. illustrated in this specification are intended solely to complement the contents disclosed herein and to facilitate understanding and reading by persons skilled in the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, without affecting the efficacy and objectives of the present invention, shall remain within the scope of the technical contents disclosed herein.

[0015] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 An exploded view of the present invention; Figure 3 Schematic diagram of the structure of the sensitive structural layer of the present invention; Figure 4 Schematic diagram of the structure of the x-axis accelerometer and the y-axis accelerometer of the present invention; Figure 5 Schematic diagram of the structure of the z-axis accelerometer of the present invention; Figure 6 This is the schematic diagram of the nano-grating off-plane accelerometer; Figure 7 Schematic diagram of the nanograting in-plane accelerometer.

[0016] Among them: 1 is the upper grating, 2 is the sensitive structure layer, 3 is the driving magnet, 4 is the base, 5 is the x-axis accelerometer, 6 is the y-axis accelerometer, 7 is the z-axis accelerometer, 8 is the cantilever beam, 9 is the first lower movable grating, 10 is the first sensitive mass block, 11 is the first outer frame, 12 is the supporting beam, 13 is the L-shaped cantilever beam, 14 is the second lower movable grating, 15 is the second sensitive mass block, and 16 is the second outer frame. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of this application, not all the embodiments. These descriptions are only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0018] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following embodiments are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0019] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. Throughout this application, unless otherwise specified, "plurality" means two or more.

[0020] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0021] This embodiment provides a nano-grating interferometric three-axis MOEMS acceleration sensor device, such as Figure 1 、 Figure 2 As shown, it includes an upper grating 1, a sensitive structure layer 2, a driving magnet 3 and a base 4. The upper grating 1 is arranged above the sensitive structure layer 2, the sensitive structure layer 2 is arranged above the driving magnet 3, and the upper grating 1, the sensitive structure layer 2 and the driving magnet 3 are all arranged inside the base 4. Figure 3 As shown, the sensitive structure layer 2 is internally integrated with an orthogonally distributed x-axis accelerometer 5, a y-axis accelerometer 6, and a z-axis accelerometer 7, which are used to measure the acceleration in the X-axis, Y-axis, and Z-axis directions, respectively; the upper grating 1 is arranged parallel to the sensitive structure layer 2 and spaced apart, forming a grating interference detection area between the two.

[0022] Further, if Figure 4 As shown, both the x-axis accelerometer 5 and the y-axis accelerometer 6 employ in-plane detection structures. Each comprises a cantilever beam 8, a first lower movable grating 9, a first sensitive mass 10, a first outer frame 11, and support beams 12. The first outer frame 11 is connected to the eight cantilever beams 8 via four support beams 12, and the first sensitive mass 10 is connected to the eight cantilever beams 8. The first lower movable grating 9 is positioned at the center of the first sensitive mass 10. The x-axis accelerometer operates according to the following principle: under the action of external x-direction acceleration, the cantilever beam undergoes elastic deformation in the x-axis direction. This deformation causes the first lower movable grating 9 on the surface of the first sensitive mass 10 to change position relative to the upper fixed grating. This displacement changes the interference light intensity signal. A detector detects this change in interference light intensity, thereby detecting the displacement change and ultimately determining the magnitude of the external sensitive acceleration. The y-axis accelerometer operates on the same principle as the x-axis accelerometer.

[0023] Further, if Figure 5 As shown, the z-axis accelerometer 7 employs an out-of-plane detection structure and comprises an L-shaped cantilever beam 13, a second lower movable grating 14, a second sensitive mass 15, and a second outer frame 16. The second outer frame 16 is connected to the second sensitive mass 15 via the L-shaped cantilever beam 13, and the second lower movable grating 14 is positioned at the center of the second sensitive mass 15. The z-axis accelerometer operates by applying acceleration in the z-axis direction, causing the second sensitive mass 15 to move along the z-axis. The second sensitive mass 15 is connected to the L-shaped cantilever beam 13. During this movement, the L-shaped cantilever beam 13 undergoes elastic deformation, causing the position of the second lower movable grating 14 on the surface of the second sensitive mass 15 to change relative to the upper grating 1. This change in the relative position of the gratings in turn alters the interference light intensity of the gratings. Through a series of signal processing steps, the magnitude of the acceleration in the z-axis direction can also be accurately determined.

[0024] Furthermore, the grating direction of the upper grating 1 and the first lower movable grating 9 of the X-axis accelerometer 5 is the X-axis direction, the grating direction of the first lower movable grating 9 of the Y-axis accelerometer 6 is the Y-axis direction, and the grating direction of the second lower movable grating 14 of the Z-axis accelerometer 7 is the Z-axis direction.

[0025] The working principle of the in-plane detection accelerometer is based on the nano-interference effect. Figure 6 、 Figure 7 As shown, the accelerometer consists of two layers of gratings, optical elements formed by alternating equally spaced translucent and opaque regions. When a light beam is projected perpendicularly onto the parallel upper fixed grating and lower movable grating, the laser beam is first diffracted by the upper fixed grating into multiple diffraction orders based on the grating's diffraction properties. The +1, 0, and -1 orders are the most pronounced. These diffracted beams are then further diffracted by the lower movable grating into even more orders, such as (+1,+1), (+1,0), (+1,-1), (0,+1), (0,0), (0,-1), (-1,+1), (-1,0), and (-1,-1). Among these diffracted beams, some orders (such as (+1,0) and (0,+1), and (-1,0) and (0,-1)) overlap, causing interference and forming interference fringes. When subjected to in-plane acceleration, the lower grating shifts transversely, perpendicular to the lines of the upper, fixed grating. The interference fringes shift accordingly. Each time the grating moves one pitch, the period of the interference fringes changes accordingly. By collecting and analyzing these fringe signals with a photodetector, the magnitude of the acceleration can be accurately measured.

[0026] According to the grating diffraction theorem, when a light beam is incident on a diffraction grating at an angle θ with the grating normal, diffraction occurs, and the diffraction angle satisfies the following relationship: Where θ is the angle of incidence, is the diffraction angle, m is the diffraction order, λ is the wavelength of the incident light, is the grating pitch; When a collimated light beam is incident vertically on the upper grating 1, the incident angle θ is 0. In this case, after the light beam passes through the upper grating 1, three orders of diffraction light are generated. The diffraction angle of the 0th order diffraction light is also 0, which means that the direction of the light beam does not change after diffraction. The +1st order and -1st order diffraction lights are diffracted outward at angles of +φ and −φ, respectively. Their diffraction angles are calculated using the following formula: When these diffracted lights are transmitted to the first lower movable grating 9, they will also produce their own diffracted lights; the +1-order diffracted light will produce three diffracted lights (+1, +1), (+1, 0), and (+1, -1) after passing through the first lower movable grating 9; similarly, the -1-order diffracted light will be diffracted twice into three lights (-1, +1), (-1, 0), and (-1, -1), and the 0-order diffracted light will be diffracted twice into three lights (0, +1), (0, 0), and (0, -1); because the working surface of the first lower movable grating 9 is parallel to the working surface of the upper grating 1, the incident angle of the +1-order diffracted light on the first lower movable grating 9 is −φ +1 According to the grating diffraction principle, the diffraction angle of the 0th order diffracted light (+1,0) is φ +1 Similarly, the incident angle of the 0th order diffracted light on the first lower movable grating 9 is 0, and the diffraction angle of the +1st order diffracted light (0, +1) is also φ +1 ; From this we can see that the (+1,0) order diffraction light and the (0,+1) order diffraction light are parallel to each other; their lateral misalignment is: Therefore, when the distance L between the grating working surfaces is small enough, the two beams of light will have a large overlapping area, thus interfering with each other. According to the principle of Doppler effect, the Doppler frequency shift of the diffraction grating is With its movement speed Proportional to the diffraction order m: When an acceleration is applied to the in-plane accelerometer, the first lower movable grating 9 moves at a speed v in a direction perpendicular to the scribed lines. Different Doppler shifts will appear in the (0, +1) and (+1, 0) order diffraction gratings, which are: Therefore, the frequency shift difference between the (0, +1) order and the (+1, 0) order diffracted light is expressed as: Based on the above formula, it can be inferred that when the first lower movable grating 9 moves by one grating distance d compared to the upper grating 1, the phase of each position in the interference field will change by 2π, causing the light intensity to fluctuate through a complete cycle. Therefore, based on the periodic counting of the light intensity changes in the interference field, the relative displacement between the upper grating 1 and the first lower movable grating 9 can be accurately obtained, and thus the magnitude of the acceleration can be obtained.

[0027] When a light beam is incident perpendicularly on the upper grating 1, part of the light is directly reflected by the grating, while the remaining part passes through the grating and impinges on the second lower movable grating 14. When acceleration occurs in the direction of the sensitive axis, the second lower movable grating 14 displaces relative to the upper grating 1. The diffracted light at the grating's reflective end interferes with the diffracted light of the same order reflected by the upper grating 1, resulting in a change in the intensity of the interference light. According to the Fraunhofer diffraction formula, the normalized complex amplitude distribution of the first diffracted light beam formed by the upper grating 1 relative to the incident light is expressed as: The electric field expression of the incident light reflected by the second lower movable grating 14 and passing through the grating again is: The total electric field of the first diffracted light and the second diffracted light is The intensity of the diffracted field is expressed as: According to the multi-slit Fraunhofer diffraction theory, when the optical path difference δ = 0 and δ = 2π, it corresponds to the 0th and 1st order diffraction light intensities respectively; for the 0th order diffraction beam, its intensity is: For ±1 order diffraction beams, the intensity is: From the expressions of 0th and 1st order light intensity, we can see that and Proportional, and proportional; The light intensity is related to the distance between the upper grating 1 and the second lower movable grating 14. Each time it moves a distance of λ / 2, the waveform changes. Based on this, by detecting the change in the interference light intensity, the change in micro-displacement can be measured, and the magnitude of the acceleration can be calculated.

[0028] The above only describes in detail the preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the purpose of the present invention, and various changes should be included in the scope of protection of the present invention.

Claims

1. A nano-grating interferometric three-axis MOEMS acceleration sensor device, characterized by: The invention comprises an upper grating (1), a sensitive structural layer (2), a driving magnet (3) and a base (4); the upper grating (1) is arranged above the sensitive structural layer (2), the sensitive structural layer (2) is arranged above the driving magnet (3), the upper grating (1), the sensitive structural layer (2) and the driving magnet (3) are all arranged inside the base (4), and an orthogonally distributed x-axis accelerometer (5), y-axis accelerometer (6) and z-axis accelerometer (7) are integrated inside the sensitive structural layer (2), which are used to measure acceleration in the directions of the x-axis, y-axis and z-axis respectively; the upper grating (1) and the sensitive structural layer (2) are arranged in parallel and spaced apart, and a grating interference detection area is formed between the two.

2. The nano-grating interferometric three-axis MOEMS acceleration sensor device according to claim 1, characterized in that: The x-axis accelerometer (5) and the y-axis accelerometer (6) are both in-plane detection structures. The x-axis accelerometer (5) and the y-axis accelerometer (6) both include a cantilever beam (8), a first lower movable grating (9), a first sensitive mass block (10), a first outer frame (11) and a support beam (12). The first outer frame (11) is respectively connected to the eight cantilever beams (8) through four support beams (12). The first sensitive mass block (10) is respectively connected to the eight cantilever beams (8). The first lower movable grating (9) is arranged at the center of the first sensitive mass block (10).

3. The nano-grating interferometric three-axis MOEMS acceleration sensor device according to claim 1, characterized in that: The z-axis accelerometer (7) is an off-plane detection structure, comprising an L-shaped cantilever beam (13), a second lower movable grating (14), a second sensitive mass block (15), and a second outer frame (16), wherein the second outer frame (16) is connected to the second sensitive mass block (15) via the L-shaped cantilever beam (13), and the second lower movable grating (14) is arranged at the center of the second sensitive mass block (15).

4. The nano-grating interferometric three-axis MOEMS acceleration sensor device according to claim 2, characterized in that: The grating direction of the upper grating (1) and the first lower movable grating (9) of the X-axis accelerometer (5) is the X-axis direction, and the grating direction of the first lower movable grating (9) of the Y-axis accelerometer (6) is the Y-axis direction.

5. The nano-grating interferometric three-axis MOEMS acceleration sensor device according to claim 1, characterized in that: The grating direction of the second lower movable grating (14) of the z-axis accelerometer (7) is the Z-axis direction.

6. The method for measuring a nano-grating interferometric three-axis MOEMS acceleration sensor device according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. When acceleration is applied in the X-axis or Y-axis direction, the cantilever beam (8) of the in-plane detection accelerometer bends and deforms, driving the first sensitive mass block (10) to translate, causing the first lower movable grating (9) and the upper grating (1) to produce relative displacement, resulting in the movement of the (+1,0) and (0,+1) level or (-1,0) and (0,-1) level diffraction light interference fringes. The detector detects the periodic change in light intensity, and the magnitude of the in-plane acceleration is calculated based on the corresponding relationship between the grating pitch d and the interference fringes period. S2. When acceleration is applied in the Z-axis direction, the L-shaped cantilever beam (13) of the off-plane detection accelerometer is deformed, driving the second sensitive mass block (15) to rise and fall, changing the vertical spacing between the second lower movable grating (14) and the upper grating (1), resulting in an optical path difference between the direct diffracted light and the reflected diffracted light. The detector detects the sinusoidal change in the interference light intensity, and the off-plane acceleration is calculated based on the relationship between the optical path difference and the displacement; S3. By synchronously collecting three-axis interference signals and processing them through a 90-degree phase shift circuit, a DC bias circuit, and a subdivision interpolation circuit, phase, amplitude, and bias errors are eliminated to achieve full-range high-precision linear measurement.

7. The method for measuring a nano-grating interferometric three-axis MOEMS acceleration sensor device according to claim 6, characterized in that: The method for calculating the magnitude of the in-plane acceleration in S1 is: According to the grating diffraction theorem, when a light beam is incident on a diffraction grating at an angle θ with the grating normal, diffraction occurs, and the diffraction angle satisfies the following relationship: Where θ is the angle of incidence, is the diffraction angle, m is the diffraction order, λ is the wavelength of the incident light, is the grating pitch; When the collimated light beam is incident vertically on the upper grating (1), the incident angle θ is 0. In this case, after the light beam passes through the upper grating (1), three diffraction lights will be generated. Among them, the diffraction angle of the 0th order diffraction light is also 0, which means that the direction of the light beam does not change after diffraction. The +1st order and -1st order diffraction lights will be diffracted outward at angles of +φ and −φ respectively. The diffraction angles are calculated by the following formula: When these diffracted lights are transmitted to the first lower movable grating (9), they will also produce their own diffracted lights; the +1-order diffracted light will produce three diffracted lights (+1, +1), (+1, 0), and (+1, -1) after passing through the first lower movable grating (9); similarly, the -1-order diffracted light will be diffracted twice into three lights (-1, +1), (-1, 0), and (-1, -1), and the 0-order diffracted light will be diffracted twice into three lights (0, +1), (0, 0), and (0, -1); because the working surface of the first lower movable grating (9) is parallel to the working surface of the upper grating (1), the incident angle of the +1-order diffracted light on the first lower movable grating (9) is −φ +1 According to the grating diffraction principle, the diffraction angle of the 0th order diffracted light (+1,0) is φ +1 Similarly, the incident angle of the 0th order diffracted light on the first lower movable grating (9) is 0, and the diffraction angle of the +1st order diffracted light (0, +1) is also φ +1 ; From this we can see that the (+1,0) order diffraction light and the (0,+1) order diffraction light are parallel to each other; their lateral misalignment is: Therefore, when the distance L between the grating working surfaces is small enough, the two beams of light will have a large overlapping area, thus interfering with each other. According to the principle of Doppler effect, the Doppler frequency shift of the diffraction grating is With its movement speed Proportional to the diffraction order m: When an acceleration is applied to the in-plane accelerometer, the first lower movable grating (9) moves at a speed v in a direction perpendicular to the scribed lines. Different Doppler shifts will appear in the (0, +1) and (+1, 0) order diffraction gratings, which are: Therefore, the frequency shift difference between the (0, +1) order and the (+1, 0) order diffracted light is expressed as: According to the above formula, it can be inferred that when the first lower movable grating (9) moves a grating distance d compared with the upper grating (1), the phase of each position in the interference field will change by 2π, thereby causing the light intensity to fluctuate in a complete cycle; therefore, based on the periodic counting of the light intensity change in the interference field, the relative displacement between the upper grating (1) and the first lower movable grating (9) can be accurately obtained, thereby obtaining the magnitude of the acceleration.

8. The method for measuring a nano-grating interferometric three-axis MOEMS acceleration sensor device according to claim 6, characterized in that: The method for calculating the magnitude of the off-plane acceleration in S2 is: When the light beam is vertically irradiated onto the upper grating (1), part of the light is directly reflected by the grating, and the other part of the light passes through the grating and irradiates the second lower movable grating (14). When there is acceleration in the direction of the sensitive axis, the second lower movable grating (14) is displaced relative to the upper grating (1), and the diffracted light at the grating reflection end interferes with the diffracted light of the same order reflected by the upper grating (1), thereby causing a change in the intensity of the interference light. According to the Fraunhofer diffraction formula, the normalized complex amplitude distribution of the first beam of diffracted light formed by the upper grating (1) relative to the incident light is expressed as follows: The electric field expression of the incident light that is reflected by the second lower movable grating (14) and passes through the grating again is: The total electric field of the first diffracted light and the second diffracted light is The intensity of the diffracted field is expressed as: According to the multi-slit Fraunhofer diffraction theory, when the optical path difference δ = 0 and δ = 2π, it corresponds to the 0th and 1st order diffraction light intensities respectively; for the 0th order diffraction beam, its intensity is: For ±1 order diffraction beams, the intensity is: From the expressions of 0th and 1st order light intensity, we can see that and Proportional, and proportional; The light intensity is related to the distance between the upper grating (1) and the second lower movable grating (14). Each time the distance is moved by λ / 2, the waveform changes. Based on this, by detecting the change in the interference light intensity, the change in micro-displacement can be measured, and the magnitude of the acceleration can be calculated.

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