Accelerometer device and method applying two-dimensional acceleration measurement

Abstract

The invention relates to the technical field of sensor acceleration measurement, in particular to an accelerometer device and method applying two-dimensional acceleration measurement, and the device is formed by sequentially overlapping a fixed grating layer, an MEMS structural layer and a detector layer. The fixed grating layer is integrated with a two-dimensional grating structure to realize double-axis acceleration synchronous detection; a two-dimensional grating is arranged on the MEMS structure layer, and the diffraction efficiency of the grating is adjusted through mechanical displacement caused by acceleration; the detector layer and the MEMS layer cooperate to form an electromagnetic force adjusting module, a differential output sub-module is arranged in the electromagnetic force adjusting module, and accurate measurement of biaxial acceleration is completed through photoelectric conversion and signal processing. The device realizes high-precision double-shaft synchronous detection through a linear transmission light path, improves the measurement stability in combination with an electromagnetic force feedback mechanism, and is suitable for real-time monitoring scenes of multi-dimensional motion parameters.

Description

Technical Field

[0001] This invention relates to the field of sensor acceleration measurement technology, and specifically to an accelerometer device and method for applying two-dimensional acceleration measurement. Background Technology

[0002] MEMS sensors have become a popular development direction due to their advantages such as small size, light weight and high integration. Micro-nano measurement determines its accuracy, and the development of high-resolution, small-volume precision measurement sensors is of great significance. Grating displacement sensing technology has significant advantages. Its diffraction effect was discovered in the late 18th century. The first engineering prototype of the moiré fringe grating was born in the 1950s, which opened up the application of grating measurement.

[0003] Improving the resolution and integration of micro-displacement measurements is key to the development of MEMS accelerometers. At the same time, the demand for sensor resolution, size, structural simplification, and anti-interference capabilities is becoming increasingly strong.

[0004] The mainstream displacement detection technologies for MEMS accelerometers include laser interferometry, capacitive, electromagnetic, piezoelectric, grating, and fiber Bragg grating sensor technologies. Grating sensors are often used in high-precision fields due to their high resolution and resistance to electromagnetic interference. Fiber Bragg grating technology has a compact optical path, high precision, and is more advantageous in miniaturization and integration.

[0005] While silicon capacitor technology is sensitive and stable, it has a small dynamic range and is susceptible to electromagnetic interference and parasitic capacitance. Electromagnetic devices have high precision but are difficult to manufacture, have low yield, and poor low-frequency response. Piezoelectric devices have simple processes but low resolution and severe temperature effects. Fiber grating technology has problems such as difficulty in manufacturing, low resonant frequency, and high cost of lasers and demodulation systems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an accelerometer device and method for applying two-dimensional acceleration measurement, which addresses the shortcomings of the prior art and solves the technical problems of complex structure, difficulty in miniaturization, and low integration of high-resolution detection devices.

[0007] The objective of this invention is achieved through the following technical solutions: In a first aspect, the present invention provides an accelerometer device for two-dimensional acceleration measurement, which adopts a linear transmission optical path structure, including a fixed grating layer, a MEMS structure layer and a detector layer arranged sequentially. The fixed grating layer has a two-dimensional grating structure for realizing synchronous detection of dual-axis acceleration; The MEMS structure layer is provided with a two-dimensional grating structure, which is used to adjust the relative displacement of the two-dimensional grating structures according to the acceleration. The detector layer and the MEMS structure layer work together to form an electromagnetic force adjustment module. The electromagnetic force adjustment module is equipped with a differential output submodule for measuring dual-axis acceleration.

[0008] As a further improvement of the present invention, the fixed grating layer includes a glass substrate and a first metal grating disposed on the glass substrate; the first metal grating is divided into four grating regions; the grating distribution periods along the X and Y axes of the four grating regions are the same.

[0009] As a further improvement of the present invention, the MEMS structure layer includes a silicon MEMS structure and a second metal grating disposed on the silicon MEMS structure; the silicon MEMS structure includes an X-axis adjustment wire, a Y-axis adjustment wire, a fixed anchor point, and a vibration support beam. The second metal grating has the same period as the first metal grating and is not misaligned; the fixed anchor points are fixedly connected to the fixed grating layer and the detector layer respectively; the vibration support beam is used to drive the second metal grating to move along the X-axis, Y-axis or obliquely with acceleration.

[0010] As a further improvement of the present invention, the detector layer includes a four-quadrant detection module and a permanent magnet module; the four-quadrant detection module is divided into four detection areas, which correspond to the four grating areas of the fixed grating layer respectively; the permanent magnet module includes two permanent magnets corresponding to the X-axis adjustment wire and two permanent magnets corresponding to the Y-axis adjustment wire, which are used to provide a magnetic field for the adjustment wire.

[0011] As a further improvement of the present invention, the electromagnetic force adjustment module operates as follows: when the acceleration causes the silicon MEMS structure of the MEMS structure layer to shift, the X-axis adjustment wire and the Y-axis adjustment wire cut the magnetic field lines generated by the permanent magnet to generate a voltage signal. When the voltage signal indicates that the acceleration exceeds the detection range, the X-axis and Y-axis adjustment wires are energized, thereby generating an electromagnetic force in the permanent magnet's magnetic field, which restricts the displacement of the silicon MEMS structure within the detection range, thus achieving range adjustment.

[0012] Secondly, the present invention provides a measurement method for an accelerometer device using two-dimensional acceleration measurement, comprising: A laser beam is incident perpendicularly onto a fixed grating layer, and after passing through the fixed grating layer, the laser beam forms a periodic light field. When there is X-axis, Y-axis or dual-axis acceleration, the second metal grating of the MEMS structure layer is displaced with the silicon MEMS structure, causing a phase shift in the light field signal passing through the second metal grating of the MEMS structure layer; The four-quadrant detection module of the detector layer detects the transmitted light intensity in each region and converts the light signal into an electrical signal. The differential output module performs differential operations on the electrical signal to obtain the X-axis and Y-axis displacements of the second metal grating relative to the fixed grating layer, thereby obtaining the dual-axis acceleration. The electromagnetic force adjustment module monitors in real time whether the acceleration exceeds the limit. If it does, an electromagnetic force is generated to limit the displacement of the MEMS structure, thereby achieving range adjustment.

[0013] As a further improvement of the present invention, the second metal grating of the MEMS structure layer is disposed at a Talbot distance z1 below the fixed grating layer, and the four-quadrant detection module of the detector layer is disposed at a Talbot distance z2 below the second metal grating; the Talbot distance satisfies:

[0014] Where k is a positive integer, d is the grating period, and λ is the laser wavelength.

[0015] As a further improvement of the present invention, the calculation formula for the difference operation is as follows:

[0016] In the formula, This represents the relative displacement along the X-axis. This represents the relative displacement along the Y-axis. , , , These are the light intensity signals corresponding to the four detection areas in the four-quadrant detection module.

[0017] As a further improvement of the present invention, the light intensity signals of the four detection regions corresponding to the four quadrant detection module are respectively represented as follows:

[0018] In the formula, To fix the light transmittance function of the grating layer, Let be the light transmittance function of the movable grating in the MEMS structure layer. The grating period is in the X-axis direction. The grating period is in the Y-axis direction. , , , These are the light intensity signals corresponding to the four detection areas in the four-quadrant detection module. This represents the relative displacement along the X-axis. This represents the relative displacement along the Y-axis.

[0019] As a further improvement of the present invention, the triggering condition of the electromagnetic force adjustment module is as follows: When the voltage signal generated by any X-axis adjustment wire and Y-axis adjustment wire exceeds the preset threshold, it is determined that the acceleration exceeds the detection range, triggering the energization operation of the other X-axis adjustment wire and the other Y-axis adjustment wire.

[0020] The beneficial effects of this invention are as follows: This invention provides an accelerometer device for two-dimensional acceleration measurement. By adopting a linear transmission optical path structure, it eliminates auxiliary optical components such as glass slides and mirrors in traditional optical paths, simplifying the structural design. A fixed grating layer with a two-dimensional grating structure, a MEMS structure layer with a two-dimensional grating structure that can adjust its displacement according to acceleration, and a detector layer are sequentially arranged. The two-dimensional grating structure of the fixed grating layer is used to construct the optical field foundation required for synchronous detection of dual-axis acceleration. The displacement of the two-dimensional grating structure in the MEMS structure layer with acceleration realizes the conversion of acceleration into optical signal changes, which are then transmitted through the detector layer. The electromagnetic force adjustment module, formed in conjunction with the MEMS structure layer, processes the electrical signal converted from the optical signal using the differential output submodule within this module, ultimately achieving dual-axis acceleration measurement. The resulting technical advantages are: the linear transmission optical path structure effectively avoids the structural complexity issues caused by auxiliary optical components; the sequentially arranged three-layer structure and the functional adaptation of each layer's two-dimensional grating structure improve device integration and facilitate miniaturization; simultaneously, the cooperation between the electromagnetic force adjustment module and the differential output submodule ensures the realization of dual-axis acceleration measurement, thus specifically addressing the current technical problems of complex structures, difficulty in miniaturization, and low integration in high-resolution detection devices. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the accelerometer device using two-dimensional acceleration measurement in an embodiment of the present invention; Figure 2 This is a top view of the fixed grating layer in an embodiment of the present invention; Figure 3 This is a schematic diagram of the MEMS structure layer in an embodiment of the present invention; Figure 4 This is a top view of the MEMS structure layer in an embodiment of the present invention; Figure 5 This is a top view of the detector structure layer in an embodiment of the present invention; Figure 6This is a simulation result of MATLAB modeling this process in an embodiment of the present invention; Figure 7 This is a simulation model of the MEMS structure in an embodiment of the present invention with the X-direction applied as an example. Figure 8 This is a simulation model of the MEMS structure in an embodiment of the present invention with the result of applying the Y-direction. Figure 9 This is a displacement diagram of the MEMS structure in an embodiment of the present invention; Figure 10 This is a graph showing the relationship between applied voltage and structural displacement in an embodiment of the present invention.

[0023] In the figure, 1. Laser source; 2. First metal grating; 3. Glass substrate; 4. Second metal grating; 5. X-axis adjustment guide wire; 6. Y-axis adjustment guide wire; 7. Silicon MEMS structure; 8. Fixed anchor point; 9. Detection area; 10. First permanent magnet structure; 11. Second permanent magnet structure; 12. Substrate; 2a. First grating region; 2b. Second grating region; 2c. Third grating region; 2d. Fourth grating region; 4a. Fifth grating region; 4b. Sixth grating region; 4c. Seventh grating region; 4d. Eighth grating region; 5a. First X-axis adjustment guide; 5b. Second X-axis adjustment guide; 6a. First Y-axis adjustment guide; 6b. Second Y-axis adjustment guide; 8a. First fixed anchor point; 8b. Second fixed anchor point; 8c. Third fixed anchor point; 8d. Fourth fixed anchor point; 9a. First detection region; 9b. Second detection region; 9c. Third detection region; 9d. Fourth detection region; 10a. First permanent magnet structure; 10b. Second permanent magnet structure; 11a. Third permanent magnet structure; 11b. Fourth permanent magnet structure. Detailed Implementation

[0024] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. The described embodiments are only some embodiments of the present invention, and not all embodiments.

[0026] Example 1 This embodiment provides an accelerometer device for two-dimensional acceleration measurement. The device employs a linear transmission optical path structure. For example... Figure 1As shown, the system includes a laser source 1, a fixed grating layer, a MEMS structure layer, and a detector layer arranged sequentially. By designing a staggered grating array in the fixed grating layer, a specific light field distribution is formed beneath it. When acceleration is input, the MEMS structure drives the movable grating to shift, resulting in a corresponding phase shift in the transmitted light intensity detected in the four detector regions. By differentially analyzing the signals in the corresponding regions, the corresponding components of the X and Y axes can be calculated, thus achieving simultaneous measurement of dual-axis acceleration. The displacement of the MEMS structure is limited to a linear range by adjusting the electromagnetic force of the current-carrying wire in the magnetic field, ensuring high resolution while increasing the sensor's measurement range.

[0027] The fixed grating layer features a two-dimensional grating structure for simultaneous detection of dual-axis acceleration. The fixed grating layer includes a glass substrate 3 and a first metal grating 2 disposed on the glass substrate. The first metal grating 4 is divided into four grating regions: a first grating region 2a, a second grating region 2b, a third grating region 2c, and a fourth grating region 2d. The grating distribution periods along the X and Y axes of the four grating regions are identical, denoted as dx and dy, respectively. Specifically, the grating distribution along the Y axis in region 2b is identical to that in region 2a, but the grating along the X axis is offset by half a period (dx / 2). The grating distribution along both the X and Y axes in region 2c is offset by half a period (dx / 2) and dy / 2, respectively, compared to region 2a. The grating distribution along the X axis in region 2d is identical to that in region 2a, but the grating along the Y axis is offset by half a period (dy / 2).

[0028] When a plane wave is incident perpendicularly onto the grating plane, an image of the grating will appear in the optical self-imaging diffraction field below the grating. By designing grating distributions with different periods along the X and Y directions, and introducing half-period misalignment in four regions, a specific distribution of light field is formed below the fixed grating layer.

[0029] The MEMS structure layer is placed below the fixed grating layer. The structure diagram and top view are shown below. Figure 3 , Figure 4 As shown, the MEMS structure layer has a two-dimensional grating structure, which is used to adjust the displacement of the two-dimensional grating structure according to acceleration. The MEMS structure layer includes a silicon MEMS structure 7 and a second metal grating 4 disposed on the silicon MEMS structure; the silicon MEMS structure includes an X-axis adjustment guide 5, a Y-axis adjustment guide 6, a fixed anchor point 8, and a vibration support beam.

[0030] The second metal grating 4 has the same period as the first metal grating 2 and is not misaligned; the fixed anchor point 8 is fixedly connected to the fixed grating layer and the detector layer respectively; the vibration support beam is used to drive the second metal grating to move along the X-axis, Y-axis or oblique direction with acceleration.

[0031] Specifically, in this embodiment, the second metal grating 4 includes four grating regions: a fifth grating region 4a, a sixth grating region 4b, a seventh grating region 4c, and an eighth grating region 4d. These grating regions are movable gratings. The grating structure 4 and the grating structure 2 on the fixed grating have the same periods dx and dy, and the grating distribution within the corresponding 4a, 4b, 4c, and 4d regions is not misaligned. The X-axis adjustment guide in the MEMS structure 7 includes a first X-axis adjustment guide 5a and a second X-axis adjustment guide 5b; the Y-axis adjustment guide includes a first Y-axis adjustment guide 6a and a second Y-axis adjustment guide 6b; and the fixed anchor points include a first fixed anchor point 8a, a second fixed anchor point 8b, a third fixed anchor point 8c, a fourth fixed anchor point 8d, and several vibration support beams.

[0032] A top view of the MEMS structure layers is shown below. Figure 4 As shown, during structural operation, fixed anchor points 8a, 8b, 8c, and 8d are fixed to the upper fixed grating layer and the lower detector layer. When there is X-axis acceleration, the metal grating 4 moves along the mass block along the X-axis under the action of the support beam; when there is Y-axis acceleration, the metal grating 4 moves along the mass block along the Y-axis under the action of the support beam; when there are both X-axis and Y-axis accelerations simultaneously, the metal grating 4 moves obliquely along the mass block under the action of the support beam. The X-axis adjustment wires 5a and 5b, and the Y-axis adjustment wires 6a and 6b, placed on the structure, apply current under the influence of a magnetic field, thus limiting the displacement of the mass block. This protects the sensor while simultaneously increasing the sensor's range through the correlation between acceleration and electromagnetic force, achieving large acceleration detection through electromagnetic force and fine acceleration resolution through the grating.

[0033] A grating layer is placed on the MEMS structure. This grating layer has the same grating period in both the X and Y directions as the fixed grating layer, but without misalignment. It can move along with the MEMS structure. A 1550nm wavelength laser can pass through the silicon MEMS structure and reach the detector layer, enabling the detection of transmitted light intensity. When the MEMS structure moves due to acceleration, causing the grating structure to shift, the signal detected in the corresponding area will undergo a 180° phase shift. Simultaneously, a current-carrying wire placed on the structure generates an electromagnetic force in the magnetic field, which is used to increase the range of the accelerometer.

[0034] The detector layer and the MEMS structure layer work together to form an electromagnetic force adjustment module. The electromagnetic force adjustment module has a differential output sub-module for measuring dual-axis acceleration.

[0035] The detector layer includes a four-quadrant detection module and a permanent magnet module; the four-quadrant detection module is divided into four detection regions, corresponding to the four grating regions of the fixed grating layer; the permanent magnet module includes two permanent magnets corresponding to the X-axis adjustment conductor and two permanent magnets corresponding to the Y-axis adjustment conductor, used to provide a magnetic field for the adjustment conductor. Figure 5 As shown, corresponding to the four regions 2a, 2b, 2c, and 2d of the fixed grating layer, four detection regions 9a, 9b, 9c, and 9d are designed. Permanent magnet structures 10a, 10b and 11a, 11b are provided to provide the magnetic field for the X-axis adjustment wires 5a and 5b and the Y-axis adjustment wires 6a and 6b.

[0036] The electromagnetic force adjustment module works as follows: when acceleration causes displacement of the silicon MEMS structure in the MEMS structure layer, the X-axis and Y-axis adjustment wires cut the magnetic field lines generated by the permanent magnet to generate a voltage signal; when the voltage signal indicates that the acceleration exceeds the detection range, the X-axis and Y-axis adjustment wires are energized, thereby generating an electromagnetic force in the magnetic field of the permanent magnet, which restricts the displacement of the silicon MEMS structure within the detection range, thus achieving range adjustment.

[0037] Therefore, the signals from the four detection regions (9a, 9b, 9c, and 9d) are differentially analyzed and superimposed to achieve separation of the dual-axis signals and elimination of common-mode interference such as laser power jitter. By finally calculating the output signal, the signal components of the X and Y axes can be obtained separately, achieving separation of the dual-axis signals and enabling simultaneous measurement of dual-axis acceleration. During sensor operation, when the mass block displaces due to acceleration, the metal wires 5b and 6b placed on the MEMS structure cut magnetic field lines under the influence of a magnetic field, generating a voltage. By detecting this voltage signal, it is determined whether the input acceleration exceeds the designed detection range. If it does, energizing 5a and 6a generates an electromagnetic force in the magnetic field, controlling the displacement of the structure within the designed detection range. This method improves the range of the designed MEMS accelerometer, achieving high-precision, large-range dual-axis measurement.

[0038] Example 2 The following detailed description of the accelerometer device measurement method using two-dimensional acceleration measurement described in this application is based on specific embodiments.

[0039] The measurement method in this embodiment is based on an accelerometer device consisting of a fixed grating layer, a MEMS structure layer and a detector layer arranged sequentially. The fixed grating layer is provided with a first two-dimensional grating structure. The MEMS structure layer is provided with a second metal grating (movable grating) and a silicon MEMS structure with the same period as the first two-dimensional grating structure. The detector layer is provided with a four-quadrant detection module, a differential output module and an electromagnetic force adjustment module (including an X-axis adjustment wire, a Y-axis adjustment wire and a corresponding permanent magnet).

[0040] The specific steps for measurement are as follows: A laser with a wavelength of λ (e.g., 1550 nm) is incident perpendicularly onto a fixed grating layer. After passing through the first two-dimensional grating structure of the fixed grating layer, the laser forms a periodic light field below it. The second metal grating of the MEMS structure layer is positioned at a Talbot distance z1 below the fixed grating layer, and the four-quadrant detection module of the detector layer is positioned at a Talbot distance z2 below the second metal grating. The Talbot distances satisfy the formula:

[0041] Where k is a positive integer, d is the grating period, and λ is the laser wavelength. This setting ensures that the periodic light field, after being transmitted through the second metal grating, forms a stable and measurable light intensity distribution at the four-quadrant detection module, avoiding additional optical path calibration and improving integration. In this embodiment, d includes the period in the X-axis direction. and Y-axis period .

[0042] When a monochromatic plane wave incident perpendicularly on a periodic object, an image of the object will appear at a periodic distance behind it. Assume the complex amplitude (wavefront) of the incident light is... The transmittance function of the grating is The complex amplitude function of the light wave distribution immediately behind the grating is equal to the product of the transmittance function and the complex amplitude of the input light.

[0043] The diffraction transfer function to the surface of the movable grating can then be expressed as:

[0044] The Fourier transform of the complex amplitude of the light wave at a distance z1 after the grating is fixed is:

[0045] The complex amplitude function of the light at position z1 is:

[0046] The transmittance function of the movable grating is The complex amplitude function of the light wave immediately behind the grating for:

[0047] Similarly, if a detector is placed at a Tuber distance z2 behind the movable grating, the complex amplitude function of the detector surface can be expressed as:

[0048] In the formula, Let be the complex amplitude function of the detector surface.

[0049] When the device is subjected to acceleration along the X-axis, Y-axis, or both axes, the silicon MEMS structure in the MEMS structure layer is displaced under the action of inertial force, causing the second metal grating to be displaced in the X-axis direction relative to the fixed grating layer. and / or displacement in the Y-axis direction Because of the relative displacement between the second metal grating and the first two-dimensional grating structure with the fixed grating layer, the periodic optical field signal passing through the second metal grating undergoes a phase shift due to the change in grating overlap, thus realizing the conversion of acceleration into optical signal variation.

[0050] The four-quadrant detection module of the detector layer (divided into four detection areas) corresponds to the four grating areas of the fixed grating layer (misaligned design: relative to the reference area, misaligned along the X-axis). / 2, Y-axis misalignment ( / 2 or dual-axis misalignment), receives the light intensity signal transmitted through the second metal grating and converts it into an electrical signal. The light intensity signal of each detection area satisfies the following expression:

[0051] In the formula, To fix the light transmittance function of the grating layer, Let be the light transmittance function of the movable grating in the MEMS structure layer. The grating period is in the X-axis direction. The grating period is in the Y-axis direction. , , , These are the light intensity signals corresponding to the four detection areas in the four-quadrant detection module. This represents the relative displacement along the X-axis. This represents the relative displacement along the Y-axis.

[0052] The electrical signal is differentially processed by the differential output module to obtain the X-axis and Y-axis displacements of the second metal grating relative to the fixed grating layer, thereby obtaining the dual-axis acceleration. The calculation formula for the differential operation is as follows:

[0053] In the formula, This represents the relative displacement along the X-axis. This represents the relative displacement along the Y-axis. , , , These represent the light intensity signals corresponding to the four detection regions in the four-quadrant detection module. Combined with parameters such as the stiffness coefficient of the silicon MEMS structure, the displacement... , This is converted into corresponding X-axis and Y-axis accelerations, enabling synchronous measurement of dual-axis acceleration. This differential calculation can effectively cancel common-mode interference such as laser power fluctuations, improving detection accuracy.

[0054] The electromagnetic force adjustment module monitors the acceleration in real time to ensure it does not exceed the limit. If it does, an electromagnetic force is generated to restrict the displacement of the MEMS structure, thus adjusting the measurement range. Specifically, the module monitors the acceleration in real time to ensure it does not exceed the preset detection range: when the voltage signal generated by either the X-axis or Y-axis adjustment wire cutting the permanent magnet's magnetic field (caused by the displacement of the silicon MEMS structure), exceeds a preset threshold, the current acceleration is considered to be exceeding the limit. At this point, the module energizes another set of X-axis and Y-axis adjustment wires, causing them to generate a reverse electromagnetic force in the permanent magnet's magnetic field. This restricts the displacement of the silicon MEMS structure within the detection range, thereby dynamically adjusting the device's measurement range to meet both high-resolution detection and wide-range requirements.

[0055] The measurement method in this embodiment achieves high-precision measurement of dual-axis acceleration through steps such as linear transmission optical path design (no auxiliary optical components required), combination of grating misalignment and differential operation, and dynamic adjustment of electromagnetic force. It simplifies the detection process, adapts to integrated and miniaturized device structures, and effectively solves the problems of complex structure and low integration of traditional high-resolution detection devices.

[0056] Example 3 The two-dimensional acceleration measurement device consists of a fixed grating layer, a MEMS structure layer, a detector layer, etc., and their functions and working processes are described below.

[0057] 1. Fixed grating layer: When a plane wave is incident perpendicularly on the grating plane, an image of the grating will appear in the optical self-imaging diffraction light field below the grating. By designing grating distributions with different periods along the X and Y directions, and introducing half-period misalignment in the four regions, a specific distribution of light field is formed below the fixed grating layer after the light passes through it.

[0058] 2. MEMS Structure Layer: A grating layer is placed on the MEMS structure. This grating layer has the same grating period in both the X and Y directions as the fixed grating layer, but there is no misalignment. It can move along with the MEMS structure. A 1550nm wavelength laser can pass through the silicon MEMS structure and reach the detector layer, enabling the detection of transmitted light intensity. When the MEMS structure moves due to acceleration, causing the grating structure to shift, the signal detected in the corresponding area will undergo a 180° phase shift. Simultaneously, the current-carrying wires placed on the structure generate electromagnetic force in the magnetic field, which is used to increase the range of the accelerometer.

[0059] 3. Detector layer: This layer detects the intensity of transmitted light and converts the light signal into an electrical signal. Simultaneously, permanent magnets placed in this layer provide a magnetic field for the current-carrying conductors.

[0060] A schematic diagram of the core device is shown below. Figure 1 As shown, the overall structure is divided into three parts: a fixed grating layer, a MEMS structure layer, and a detector layer. The fixed grating layer consists of a metal grating 2 and a glass substrate 3. A top view of the fixed grating layer is shown below. Figure 2 As shown, a two-dimensional grating structure is designed to realize four grating regions: 2a, 2b, 2c, and 2d. The grating distribution periods along the X and Y axes are the same, dx and dy, respectively. Specifically, the grating distribution in region 2b is the same as that in region 2a along the Y axis, but the grating along the X axis is offset by half a period, dx / 2. The grating in region 2c is offset from that in region 2a along both the X and Y axes by half a period, dx / 2 and dy / 2, respectively. The grating in region 2d is the same as that in region 2a along the X axis, but the grating along the Y axis is offset by half a period, dy / 2.

[0061] MEMS structural layers such as Figure 3 As shown, the MEMS structure layer consists of a metal grating 4 and a silicon MEMS structure 7. The grating structure 4 has the same dx and dy as the grating structure 2 on the fixed grating, and the grating distribution in the corresponding regions 4a, 4b, 4c, and 4d is not misaligned. The MEMS structure 7 consists of X-axis adjustment guides 5a and 5b, Y-axis adjustment guides 6a and 6b, fixed anchor points 8a, 8b, 8c, and 8d, and several vibration support beams. A top view of the MEMS structure layer is shown below. Figure 4 As shown, during structural operation, fixed anchor points 8a, 8b, 8c, and 8d are fixed to the upper fixed grating layer and the lower detector layer. When there is X-axis acceleration, the metal grating 4 moves along the mass block along the X-axis under the action of the support beam; when there is Y-axis acceleration, the metal grating 4 moves along the mass block along the Y-axis under the action of the support beam; when there are both X-axis and Y-axis accelerations simultaneously, the metal grating 4 moves obliquely along the mass block under the action of the support beam. The X-axis adjustment wires 5a and 5b, and the Y-axis adjustment wires 6a and 6b, placed on the structure, apply current under the influence of a magnetic field, thus limiting the displacement of the mass block. This protects the sensor while simultaneously increasing the sensor's range through the correlation between acceleration and electromagnetic force, achieving large acceleration detection through electromagnetic force and fine acceleration resolution through the grating.

[0062] Top view of the detector structure layer as shown Figure 5 As shown, corresponding to the four regions 2a, 2b, 2c, and 2d of the fixed grating layer, four detection regions 9a, 9b, 9c, and 9d are designed. Permanent magnet structures 10a, 10b and 11a, 11b are provided to provide the magnetic field for the X-axis adjustment wires 5a and 5b and the Y-axis adjustment wires 6a and 6b.

[0063] The Talbot effect refers to the phenomenon where, when a monochromatic plane wave is incident perpendicularly on a periodic object, an image of the object appears at periodic distances behind it. Assume the complex amplitude (wavefront) of the incident light is... The transmittance function of the grating is The complex amplitude function of the light wave distribution immediately behind the grating is equal to the product of the transmittance function and the complex amplitude of the input light.

[0064] In this invention, after a plane wave passes through a fixed grating layer, it forms a periodic image behind it. The movable grating layer is placed at its Tuber distance z1, i.e. The diffraction transfer function to the surface of the movable grating can then be expressed as:

[0065] The Fourier transform of the complex amplitude of the light wave at a distance z1 after the grating is fixed is:

[0066] The complex amplitude function of the light at position z1 is:

[0067] The transmittance function of the movable grating is The complex amplitude function of the light wave immediately behind the grating is:

[0068] Similarly, if a detector is placed at a Tuber distance z2 behind the movable grating, the complex amplitude function of the detector surface can be expressed as:

[0069] Therefore, the light intensity received by the four-quadrant detector can be expressed as:

[0070] in It is the displacement of the movable grating relative to the fixed grating. These are the periods of the grating in the x and y directions, respectively. Based on the transmission function properties of a two-dimensional rectangular grating, we can obtain:

[0071] Therefore, the signals from the four detection regions (9a, 9b, 9c, and 9d) are differentially analyzed and superimposed to achieve separation of the dual-axis signals and elimination of common-mode interference such as laser power jitter. By finally calculating the output signal, the signal components of the X and Y axes can be obtained separately, achieving separation of the dual-axis signals and enabling simultaneous measurement of dual-axis acceleration. During sensor operation, when the mass block displaces due to acceleration, the metal wires 5b and 6b placed on the MEMS structure cut magnetic field lines under the influence of a magnetic field, generating a voltage. By detecting this voltage signal, it is determined whether the input acceleration exceeds the designed detection range. If it does, energizing 5a and 6a generates an electromagnetic force in the magnetic field, controlling the displacement of the structure within the designed detection range. This method improves the range of the designed MEMS accelerometer, achieving high-precision, large-range dual-axis measurement.

[0072] A schematic diagram of the core device is shown below. Figure 1 As shown, the metal grating 2 is disposed on the glass substrate 3, forming a fixed grating layer. The top view of the fixed grating layer is shown below. Figure 2 As shown, four grating regions, 2a, 2b, 2c, and 2d, are realized by designing a two-dimensional grating structure. The grating distribution periods along the X and Y axes are the same, dx and dy, respectively. Specifically, the grating distribution in region 2b is the same as that in region 2a along the Y axis, but the grating along the X axis is offset by half a period dx / 2; the grating in region 2c is offset by half a period dx / 2 and dy / 2 along both the X and Y axes from region 2a; and the grating distribution in region 2d is the same as that in region 1a along the X axis, but the grating along the Y axis is offset by half a period dy / 2.

[0073] The MEMS structure layer is placed below the fixed grating layer. The structure diagram and top view are shown below. Figure 3 , Figure 4 As shown, it consists of a metal grating 4 and a silicon MEMS structure 7. The grating structure 4 has the same period dx and dy as the grating structure 2 on the fixed grating, and the grating distribution in the corresponding regions 4a, 4b, 4c, and 4d is not misaligned. The MEMS structure 7 consists of X-axis adjustment guides 5a and 5b, Y-axis adjustment guides 6a and 6b, fixed anchor points 8a, 8b, 8c, and 8d, and several vibration support beams.

[0074] like Figure 5 As shown, corresponding to the four regions 2a, 2b, 2c, and 2d of the fixed grating layer, four detection regions 9a, 9b, 9c, and 9d are designed. Permanent magnet structures 10a, 10b and 11a, 11b are provided to provide the magnetic field for the X-axis adjustment wires 5a and 5b and the Y-axis adjustment wires 6a and 6b.

[0075] When the sensor is working, a laser beam is incident perpendicularly through the fixed grating plane, forming a specifically distributed light field below it. As the movable grating shifts, the light signal passing through it also changes accordingly. Due to a specific misalignment in the grating on the fixed grating, the light intensity signals received by the four detection areas of the detection layer will differ during the displacement of the movable grating, resulting in a corresponding phase shift in the generated electrical signal. Differential output of the signals enables decoupling, noise reduction, amplification, and readout of the X-axis and Y-axis signals. By adjusting the electromagnetic force of the current-carrying wire in the magnetic field, the displacement of the MEMS structure is limited to a linear range, ensuring high resolution while increasing the sensor's measurement range.

[0076] This process was modeled and simulated using MATLAB. Taking dx=10μm and dy=10μm as an example, to illustrate how this method decouples the X and Y axis signals, the movable grating layer in the model was moved from its initial position (0μm, 0μm) to (80μm, 40μm). The results are as follows. Figure 6 As shown, Figure 6 (a) For this process, the four outputs of the four-quadrant detector, Figure 6 (b) is the output after differential decoupling. Based on the period dx=10μm in the X direction and the period dy=10μm in the Y direction, the displacement in the X direction is 80μm and the displacement in the Y direction is 40μm, which proves that this method has achieved the separation of the X and Y axis signals.

[0077] Create a simulation model of the MEMS structure in COMSOL. Figure 7 , Figure 8 These represent the mode shapes of the MEMS structure when accelerations are applied in the X and Y directions, respectively. Parameter scans were performed on the input acceleration values ​​in both directions, increasing the input acceleration from 1g to 5g (g = 9.8 m / s²). 2 Extract the resulting displacement of the MEMS structure, such as... Figure 9 As shown, within a certain range, the structural displacement is linearly related to the input acceleration in that direction, and due to the high symmetry of the structure, the responses of the structural displacement in the X and Y directions to the acceleration in their respective directions are also very similar.

[0078] The wires 5a, 5b, 6a, and 6b on the MEMS structure can detect and regulate the structural state, controlling the displacement within a linear range. In the COMSOL model, when an acceleration of 5g is applied, the displacement of the structure in both directions is close to 20μm. Under this condition, applying a voltage to the wires 5a and 6a on the MEMS structure generates a current, which, under the influence of a magnetic field, produces a regulating force. The relationship between the applied voltage and the structural displacement is shown in the figure below. Figure 10As shown, with the increase of the applied voltage, the displacement of the structure due to the adjustment force decreases. This method can be used to limit the displacement of the MEMS structure within the linear range. The feasibility of this scheme is demonstrated, ensuring high resolution while increasing the sensor's measurement range.

Claims

1. An accelerometer device applying two-dimensional acceleration measurement, characterized by, The linear transmission type light path structure comprises a fixed grating layer, a MEMS structure layer and a detector layer arranged in sequence; The fixed grating layer is provided with a two-dimensional grating structure for realizing synchronous detection of double-axis acceleration; The MEMS structure layer is provided with a two-dimensional grating structure for adjusting the relative displacement of the two two-dimensional grating structures according to acceleration; The detector layer cooperates with the MEMS structure layer to form an electromagnetic force adjusting module, and the electromagnetic force adjusting module is provided with a differential output submodule for realizing measurement of double-axis acceleration.

2. The accelerometer device using two-dimensional acceleration measurement according to claim 1, wherein, The fixed grating layer comprises a glass substrate and a first metal grating arranged on the glass substrate; the first metal grating is divided into four grating regions; the X-axis and Y-axis grating distribution periods of the four grating regions are the same.

3. The accelerometer device using two-dimensional acceleration measurement according to claim 1, wherein, The MEMS structure layer comprises a silicon MEMS structure and a second metal grating arranged on the silicon MEMS structure; the silicon MEMS structure comprises X-axis adjusting wires, Y-axis adjusting wires, fixed anchor points, a mass block and a vibration support beam; The second metal grating is consistent with the first metal grating in period and has no misalignment; the fixed anchor points are fixedly connected with the fixed grating layer and the detector layer respectively; and the vibration support beam is used for driving the second metal grating to move along the X-axis, Y-axis or at an oblique direction with acceleration.

4. The accelerometer device using two-dimensional acceleration measurement according to claim 1, wherein, The detector layer comprises a four-quadrant detection module and a permanent magnet module; the four-quadrant detection module is divided into four detection regions corresponding to the four grating regions of the fixed grating layer; and the permanent magnet module comprises two permanent magnets corresponding to the X-axis adjusting wires and two permanent magnets corresponding to the Y-axis adjusting wires for providing a magnetic field for the adjusting wires.

5. The accelerometer device using two-dimensional acceleration measurement according to claim 4, wherein The working mode of the electromagnetic force adjusting module is as follows: when the acceleration causes displacement of the silicon MEMS structure of the MEMS structure layer, the X-axis adjusting wires and the Y-axis adjusting wires cut the magnetic induction lines generated by the permanent magnets to generate a voltage signal; When the voltage signal indicates that the acceleration exceeds the detection interval, the X-axis adjusting wires and the Y-axis adjusting wires are electrified, and then electromagnetic force is generated in the magnetic field of the permanent magnet, so that the displacement of the silicon MEMS structure is limited in the detection interval, and range adjustment is realized.

6. A method of measuring an acceleration device using two-dimensional acceleration measurement, characterized by, The method comprises the following steps: laser is vertically incident to the fixed grating layer, and a periodic light field is formed after the laser passes through the fixed grating layer; when there is X-axis, Y-axis or double-axis acceleration, the second metal grating of the MEMS structure layer is displaced with the silicon MEMS structure, so that the light field signal passing through the second metal grating of the MEMS structure layer is phase-shifted; the four-quadrant detection module of the detector layer detects the transmitted light intensity of each region, and converts the light signal into an electric signal; the electric signal is differentially operated through the differential output module, so that the X-axis and Y-axis displacement of the second metal grating relative to the fixed grating layer is obtained, and then the double-axis acceleration is obtained; the electromagnetic force adjusting module is used for monitoring whether the acceleration is out of limit in real time, and if the acceleration is out of limit, electromagnetic force is generated to limit the displacement of the MEMS structure, so that range adjustment is realized.

7. The method according to claim 6, wherein the acceleration measurement by the two-dimensional acceleration measurement accelerometer device is measured by a method comprising: The second metal grating of the MEMS structure layer is arranged at a Talbot distance z1 below the fixed grating layer, and the four-quadrant detection module of the detector layer is arranged at a Talbot distance z2 below the second metal grating; the Talbot distance satisfies: Wherein, k is a positive integer, d is a grating period, and λ is a laser wavelength.

8. The method according to claim 6, wherein the acceleration measurement by the two-dimensional acceleration measurement accelerometer device is measured by a method comprising: The calculation formula of the difference operation is: In the formula, is the relative displacement in the X-axis direction, is the relative displacement in the Y-axis direction, , , , are light intensity signals of the four detection regions in the four-quadrant detection module, respectively.

9. The method according to claim 8, wherein the two-dimensional acceleration measurement accelerometer device is used. The light intensity signals of the four detection regions corresponding to the four-quadrant detection module are respectively represented as: In the formula, is the light transmittance function of the fixed grating layer, is the light transmittance function of the movable grating of the MEMS structure layer, is the grating period in the X-axis direction, is the grating period in the Y-axis direction, , , , are light intensity signals of the four detection regions in the four-quadrant detection module respectively, is the relative displacement in the X-axis direction, is the relative displacement in the Y-axis direction.

10. The method according to claim 6, wherein the two-dimensional acceleration measurement accelerometer device is used. The triggering condition of the electromagnetic force adjusting module is: When the voltage signals generated by any X-axis adjusting wire and Y-axis adjusting wire are greater than a preset threshold, it is determined that the acceleration exceeds the detection interval, and the energization operation on another X-axis adjusting wire and another Y-axis adjusting wire is triggered.

Images