MOMES accelerometer based on light intensity modulation

Abstract

The application discloses a MOMES accelerometer based on light intensity modulation and belongs to the technical field of micro-electro-mechanical systems and inertial measurement. The MOMES accelerometer comprises a silicon base, a mass block, fixed anchor points, an elastic beam assembly and double photodetectors. The mass block is suspended on the silicon base through the elastic beam assembly and the fixed anchor points, the fixed anchor points are fixed on the surface of the silicon base, and the fixed anchor points are connected with the elastic beam assembly. The center of the mass block is provided with a light-transmitting hole penetrating through the thickness direction. The double photodetectors are fixed on the surface of the silicon base and located in the light projection area of the light-transmitting hole. When the accelerometer is subjected to external acceleration along the Y-axis direction, the rectangular mass block generates displacement relative to the silicon base, so that the light intensity distribution of the light spot projected by the light-transmitting hole on the double photodetectors is differentially changed. The accelerometer has the advantages of high sensitivity, strong anti-interference capability and good process compatibility and is suitable for high-precision inertial measurement.

Description

Technical Field

[0001] This invention relates to the field of microelectromechanical systems and inertial measurement technology, and particularly to a MOMES accelerometer based on light intensity modulation. Background Technology

[0002] Accelerometers, as core sensors in inertial navigation systems and motion detection devices, are widely used in aerospace, automotive electronics, smart wearables, and robotics. Traditional microelectromechanical systems (MEMS) accelerometers primarily employ capacitive or piezoresistive sensing methods, reflecting acceleration signals by measuring the displacement or strain changes of a rectangular mass. Capacitive accelerometers are simple in structure and low in power consumption, making them suitable for large-scale integration. However, their sensitivity is easily affected by parasitic capacitance and environmental electromagnetic interference, and they are also sensitive to temperature changes, leading to insufficient measurement stability. Piezoresistive accelerometers have fast response times, making them suitable for dynamic measurement scenarios, but they suffer from drawbacks such as large zero-point drift and complex temperature compensation, limiting their accuracy improvement.

[0003] In recent years, optical detection technology has gradually become a research hotspot in the field of MEMS accelerometers due to its high sensitivity, strong resistance to electromagnetic interference, and good environmental adaptability. Based on the principle of light intensity modulation, converting the mechanical displacement caused by acceleration into changes in light intensity can effectively improve the detection performance of accelerometers, especially in the measurement of small signals. However, current optical accelerometers generally suffer from problems such as complex optical structures, large size, and difficulties in optical signal demodulation, which limit their widespread application in portable and miniaturized devices.

[0004] Therefore, developing a micro-opto-mechanical-electro system (MOMES) accelerometer with a simple structure, easy optical signal processing, and high sensitivity is of great technical significance and has broad application prospects. Summary of the Invention

[0005] Purpose of the invention: In view of the above problems, the purpose of this invention is to provide a MOMES accelerometer based on light intensity modulation.

[0006] Technical solution: The MOMES accelerometer based on light intensity modulation of the present invention includes a silicon-based base, a mass block, a fixed anchor point, an elastic beam assembly, and dual photodetectors;

[0007] The mass block is suspended on the silicon-based base by a flexible beam assembly and fixed anchor points. The fixed anchor points are fixed to the surface of the silicon-based base and connected to the flexible beam assembly.

[0008] The center of the mass block has a light-transmitting hole that extends completely through the thickness direction;

[0009] The dual photodetectors are fixed on the surface of the silicon-based base and located in the light projection area of ​​the light-transmitting aperture.

[0010] Furthermore, the elastic beam assembly includes a first-direction elastic beam, a second-direction elastic beam, a third-direction elastic beam, and a fourth-direction elastic beam, and the first-direction elastic beam, the second-direction elastic beam, the third-direction elastic beam, and the fourth-direction elastic beam have the same structure. One end of the first-direction elastic beam, one end of the second-direction elastic beam, one end of the third-direction elastic beam, and one end of the fourth-direction elastic beam are connected to a mass block, and the other ends of the first-direction elastic beam, the second end of the second-direction elastic beam, the third end of the third-direction elastic beam, and the fourth-direction elastic beam are connected to a fixed anchor point.

[0011] Furthermore, the fixed anchor points include a first-direction fixed anchor point, a second-direction fixed anchor point, a third-direction fixed anchor point, and a fourth-direction fixed anchor point. The first-direction fixed anchor point, the second-direction fixed anchor point, the third-direction fixed anchor point, and the fourth-direction fixed anchor point have the same structure and are fixed at the top corner of the silicon-based base, respectively.

[0012] Furthermore, the dual photodetector includes a first photodetector and a second photodetector, which are sequentially fixed on the surface of the silicon-based base along the moving direction of the mass block, and are connected to a differential circuit.

[0013] Furthermore, the MOMES accelerometer also includes a light source, which is fixedly arranged outside the plane of the silicon base. The light source emits a parallel beam of light in a direction perpendicular to the plane of the silicon base, which is perpendicular to the light-transmitting area of ​​the mass block. The light signal is received by the first photodetector and the second photodetector.

[0014] Beneficial effects: Compared with the prior art, the significant advantages of this invention are:

[0015] 1. This invention achieves complementary changes in the light intensity received by the upper and lower photodetectors by arranging dual photodetectors symmetrically along the acceleration-sensitive direction and combining the optical modulation effect of the light-transmitting hole in the center of the rectangular mass block. It utilizes differential signal detection to achieve high-sensitivity acceleration measurement with sub-micron resolution. Differential detection effectively suppresses background light, temperature drift, and electromagnetic interference, significantly improving detection stability and signal-to-noise ratio, making it particularly suitable for applications such as high-precision inertial navigation, attitude sensing, and vibration measurement.

[0016] 2. This invention adopts a suspended rectangular mass block combined with an elastic beam structure, along with a vertically incident light source and fixedly installed dual photodetectors. The mechanical displacement directly corresponds to the change in light intensity, avoiding the high-voltage excitation and complex circuit design of traditional capacitive detection. The system has a fast response and high repeatability, reducing system complexity and improving detection stability.

[0017] 3. The dual photodetector differential structure of the present invention has equal light intensity received by the two photodetectors in the absence of acceleration, and the differential signal output is close to zero; under the action of acceleration, the light intensity produces complementary differences, forming a stable differential electrical signal output. This structure has excellent common-mode interference suppression capability, effectively resists ambient light changes, temperature drift and stray light interference, and enhances the anti-interference performance of the system.

[0018] 4. This invention uses light intensity modulation to replace the traditional capacitance detection method, which greatly reduces system power consumption. At the same time, the micro-suspended structure and photoelectric detection components based on MEMS technology can be integrated at the chip level, which is convenient for miniaturization and low-cost manufacturing. It is suitable for the application and promotion of mobile terminals, wearable devices and highly integrated sensors, and has good industrialization prospects. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the accelerometer of the present invention;

[0020] Figure 2 This is a schematic diagram of the silicon micromechanical structure of the present invention;

[0021] Figure 3 This is a schematic diagram of the first-direction elastic beam of the present invention;

[0022] Figure 4 This is a schematic diagram of the silicon-based substrate and photodetector of the present invention;

[0023] Figure 5 This is a schematic diagram of the light signal emitted by the light source of the present invention.

[0024] In the diagram: 1-1 is the fixed anchor point in the first direction; 1-2 is the elastic beam in the first direction; 2-1 is the fixed anchor point in the second direction; 2-2 is the elastic beam in the second direction; 3-1 is the fixed anchor point in the third direction; 3-2 is the elastic beam in the third direction; 4-1 is the fixed anchor point in the fourth direction; 4-2 is the elastic beam in the fourth direction; 5-1 is the first photodetector; 5-2 is the second photodetector; 6 is the mass block; 7 is the silicon-based base; 8 is the light source. Detailed Implementation

[0025] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the embodiments of the present invention, and not all structures.

[0026] In the following description, specific details such as target system architecture and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of this application with unnecessary detail.

[0027] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0028] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0029] Furthermore, in the description of this application and the appended claims, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0030] References to "one embodiment" or "some embodiments" in this specification mean that one or more embodiments of this application include the target features, structures, or characteristics described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized.

[0031] Combination Figure 1 As shown, the MOMES accelerometer based on light intensity modulation described in this embodiment includes a silicon-based base 7, a mass block 6, a fixed anchor point, an elastic beam assembly, and dual photodetectors.

[0032] Mass block 6 is suspended on silicon base 7 by elastic beam assembly and fixed anchor point. The fixed anchor point is fixed to the surface of silicon base 7 and is connected to elastic beam assembly.

[0033] The center of mass block 6 has a light-transmitting hole that completely penetrates the thickness direction;

[0034] The dual photodetectors are fixed on the surface of the silicon-based base 7 and located in the light projection area of ​​the light-transmitting hole.

[0035] In one example, mass block 6 is a rectangular mass block.

[0036] Furthermore, combined Figure 2 As shown, the elastic beam assembly includes a first-direction elastic beam 1-2, a second-direction elastic beam 2-2, a third-direction elastic beam 3-2, and a fourth-direction elastic beam 4-2, and the first-direction elastic beam 1-2, the second-direction elastic beam 2-2, the third-direction elastic beam 3-2, and the fourth-direction elastic beam 4-2 have the same structure. The fixed anchor points include a first-direction fixed anchor point 1-1, a second-direction fixed anchor point 2-1, a third-direction fixed anchor point 3-1, and a fourth-direction fixed anchor point 4-1, and the first-direction fixed anchor point 1-1, the second-direction fixed anchor point 2-1, the third-direction fixed anchor point 3-1, and the fourth-direction fixed anchor point 4-1 have the same structure. One end of the first-direction elastic beam 1-2, one end of the second-direction elastic beam 2-2, one end of the third-direction elastic beam 3-2, and one end of the fourth-direction elastic beam 4-2 are connected to the mass block 6. The other ends of the first-direction elastic beam 1-2, the second-direction elastic beam 2-2, the third-direction elastic beam 3-2, and the fourth-direction elastic beam 4-2 are connected to fixed anchor points. This allows the mass block 6 to elastically shift along the Y-axis under acceleration, while also providing mechanical restoring force. The mass block 6 is uniformly supported by the elastic beam assembly and the corresponding fixed anchor points, forming a suspended mass system for sensing acceleration in the horizontal plane.

[0037] like Figure 3 As shown, taking the first-direction elastic beam 1-2 as an example, the first-direction elastic beam 1-2 adopts a slender strip design in structure, and is bent at a point in the middle of the beam. After bending, the elastic beam is approximately U-shaped, and the two halves of the beam are parallel to each other. The entire structure is in the same plane. One end of the first-direction elastic beam 1-2 is connected to the mass block 6, and the other end is connected to the first-direction fixed anchor point 1-1. The elastic connection structure of the first-direction elastic beam 1-2 not only has good restoring force characteristics, but also has high compliance, which can effectively restrict the degree of freedom of the mass block 6 in the non-working direction, ensuring that it has the desired dynamic response performance in the working direction.

[0038] The first-direction fixed anchor point 1-1, the second-direction fixed anchor point 2-1, the third-direction fixed anchor point 3-1, and the fourth-direction fixed anchor point 4-1 have the same structure. They are fixed at or near the apex of the silicon-based base 7, and distributed outside the four vertices of the rectangular mass block 6. The first-direction fixed anchor point 1-1 and the second-direction fixed anchor point 2-1 are symmetrically arranged, as are the third-direction fixed anchor point 3-1 and the fourth-direction fixed anchor point 4-1.

[0039] Combination Figure 4 As shown, the dual photodetector includes a first photodetector 5-1 and a second photodetector 5-2. The first photodetector 5-1 and the second photodetector 5-2 are sequentially fixed to the surface of the silicon-based base 7 along the moving direction of the mass block 6, both located within the light projection area. The first photodetector 5-1 and the second photodetector 5-2 are connected to a differential circuit. The mounting positions of the silicon-based base 7 and the dual photodetectors are precisely aligned, ensuring that the light beam emitted by the light source 8 coincides with the optical axis of the sensitive surface of the dual photodetectors at the center of the light-transmitting aperture, thereby reducing measurement errors caused by optical path offset. As the mass block 6 moves along the Y-axis, the light intensity received by the first photodetector 5-1 and the second photodetector 5-2 undergoes complementary changes, thus achieving highly sensitive acceleration measurement. Initially, the two photodetectors are uniformly illuminated by the light source 8, and the illuminated areas are the same (because the two photodetectors are identical). When the mass block 6 is subjected to acceleration, it is displaced in the Y direction, which causes the illuminated area of ​​one photodetector to increase and the other to decrease. This results in the output of a differential electrical signal. The light source 8 remains fixed in one place. Due to the constraint of the elastic beam, there are no areas where the mass block is displaced too much and the light cannot reach.

[0040] The MOMES accelerometer also includes a light source 8, which is fixedly arranged outside the plane of the silicon base 7. The light source 8 emits a parallel beam of light in a direction perpendicular to the plane of the silicon base 7, which shines vertically into the light-transmitting area of ​​the mass block 6. The light signal passing through the light-transmitting hole is received by the first photodetector 5-1 and the second photodetector 5-2, realizing the intensity modulation of light caused by displacement and outputting a differential electrical signal, thereby converting the acceleration signal into an electrical signal that is easy to identify and process.

[0041] In one example, the light-transmitting aperture of the rectangular mass block is a circular structure, and the aperture size matches the diameter of the parallel beam emitted by the light source 8, so as to ensure that the beam can uniformly illuminate the dual photodetectors when the rectangular mass block is stationary, and produce a stable light intensity change when the rectangular mass block is displaced.

[0042] The MOMES accelerometer described in this example consists of an upper rectangular mass block and a lower silicon-based base. The upper rectangular mass block, with a circular light-transmitting aperture, is connected to fixed anchor points via an elastic beam assembly, enabling sensitive movement of the rectangular mass block in the Y-axis direction. The rectangular mass block is fabricated using silicon-based micromachining technology and can displace under acceleration. The lower silicon-based base serves as the optical signal output module, fixed inside the base and integrating dual photodetectors arranged along the Y-axis. The lower silicon-based base is formed into structural layers using a wet etching process, and electrodes and a light source are fabricated using a metal sputtering process.

[0043] When a rectangular mass block is displaced under external acceleration, the relative position of the two photodetectors causes the light intensity received by the first photodetector 5-1 and the second photodetector 5-2 to change complementaryly with the displacement. Then, a differential photoelectric detection architecture is used to convert the mechanical displacement into a measurable change in light intensity. The electrical signal is differentially amplified to achieve a precise response to minute accelerations, thereby achieving highly sensitive position detection.

[0044] The working principle of a photodetector is based on the photoelectric effect. When a photodetector receives a light signal, it generates a photocurrent, the magnitude of which is proportional to the intensity of the received light. Assume the photocurrent of the first photodetector is... The photocurrent of the second photodetector is The changes in light intensity caused by the displacement of the rectangular mass block affect both of them, satisfying the following equation:

[0045] , ,

[0046] in, The reference photocurrent under no-acceleration conditions. This represents the difference in light intensity caused by the displacement of the rectangular mass block. It is processed by a differential circuit to output a voltage signal. for:

[0047] ,

[0048] in, This represents the gain coefficient of the differential amplifier circuit. This differential structure can effectively resist background light variations and temperature drift interference, improving the signal-to-noise ratio and system stability.

[0049] Furthermore, assuming photocurrent difference Displacement of rectangular mass block A linear relationship exists, that is:

[0050] ,

[0051] in, Let be the light intensity-displacement conversion coefficient, then the displacement of the rectangular mass block... It can be expressed by the differential output voltage as:

[0052] ,

[0053] Neglecting system damping, the motion of the rectangular mass block can be simplified to a single-degree-of-freedom vibration system, with the following dynamic model:

[0054] ,

[0055] in, Let be the mass of the rectangular mass, K be the equivalent spring stiffness, and y be the displacement of the rectangular mass along the Y-axis. Let be the function of external acceleration as a function of time.

[0056] Therefore, the quantitative relationship between the minute displacement of the rectangular mass block and the external acceleration can be expressed as follows:

[0057] .

[0058] In this invention, the geometric parameters such as the length, width, and thickness of the elastic beam can be optimized according to performance indicators such as the target acceleration range, resonant frequency, and system damping. For example, the beam length can be set to 1200 mm. The beam width is 10 The beam thickness is 80. This flexible support structure is designed to meet the sensitivity and frequency response requirements of the sensor while ensuring the structural stability and manufacturing feasibility of the device under micro-nano fabrication conditions. It is a fundamental support element for achieving high-intensity modulated detection accuracy and reliability.

[0059] like Figure 5 As shown, the light source 8 is preferably a vertical cavity surface-emitting laser (VCSEL), whose emitting end is fixedly mounted outside the plane of the silicon substrate 7 and aligned with the center of the light-transmitting aperture via the optical axis. The light source 8 can emit a stable single-mode narrowband beam, and the beam diameter matches the size of the light-transmitting aperture on the rectangular mass block to ensure that the light energy is effectively transmitted to the sensitive surfaces of the first photodetector 5-1 and the second photodetector 5-2.

[0060] The emission direction of the light source 8 is perpendicular to the plane of the silicon-based base 7, and the optical axis is precisely aligned with the photosensitive surface of the dual photodetectors through micro-positioning technology, thereby reducing detection errors caused by optical path misalignment. The light source 8 provides stable light intensity during operation, and its output power remains within a preset range, avoiding any impact on acceleration measurement accuracy due to light intensity fluctuations.

[0061] In one embodiment, the output optical power of the light source 8 is controlled within the range of 100 μW to 2 mW to ensure that the photodetector operates within its linear response range, thereby avoiding nonlinear distortion caused by oversaturation and preventing a decrease in signal-to-noise ratio caused by excessively low light intensity.

[0062] Furthermore, the light source 8 structurally includes a light source body, a package housing, and electrode pins. The light beam generated by the light source body is emitted along a direction perpendicular to the mass block 6, and after passing through the light-transmitting hole, it is distributed to the first photodetector 5-1 and the second photodetector 5-2. Through the stable illumination of the light source 8, the mechanical displacement signal is efficiently converted into a change in light intensity, providing a high signal-to-noise ratio input for subsequent differential photoelectric detection.

[0063] In the operation of the MOMES accelerometer based on light intensity modulation provided by the present invention, when the mass block 6 is subjected to acceleration in the Y-axis direction, it will be displaced along the Y-axis direction and move relative to the silicon base 7, so that the light intensity received by the first photodetector 5-1 and the second photodetector 5-2 will produce complementary changes; by performing differential operation on the output signals of the dual photodetectors, high-precision demodulation of the displacement direction and magnitude of the mass block 6 can be achieved.

[0064] This invention provides a MOMES accelerometer based on light intensity modulation. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A MOMES accelerometer based on light intensity modulation, characterized in that, The device comprises a silicon base, a mass, a fixed anchor point, an elastic beam assembly and a dual photodetector. The mass is suspended on the silicon base through the elastic beam assembly and the fixed anchor point, the fixed anchor point is fixed on the surface of the silicon base, and the fixed anchor point is connected with the elastic beam assembly. The center of the mass is provided with a light-transmitting hole penetrating through the thickness direction. The dual photodetector is fixed on the surface of the silicon base and located in the light projection area of the light-transmitting hole. The elastic beam assembly comprises a first direction elastic beam, a second direction elastic beam, a third direction elastic beam and a fourth direction elastic beam, the first direction elastic beam, the second direction elastic beam, the third direction elastic beam and the fourth direction elastic beam have the same structure, one end of the first direction elastic beam, one end of the second direction elastic beam, one end of the third direction elastic beam and one end of the fourth direction elastic beam are connected with the mass, and the other end of the first direction elastic beam, the other end of the second direction elastic beam, the other end of the third direction elastic beam and the other end of the fourth direction elastic beam are connected with the fixed anchor point. The fixed anchor point comprises a first direction fixed anchor point, a second direction fixed anchor point, a third direction fixed anchor point and a fourth direction fixed anchor point, the first direction fixed anchor point, the second direction fixed anchor point, the third direction fixed anchor point and the fourth direction fixed anchor point have the same structure, and are respectively fixed at the top corners of the silicon base. The dual photodetector comprises a first photodetector and a second photodetector, the first photodetector and the second photodetector are fixed on the surface of the silicon base in sequence along the moving direction of the mass, and the first photodetector and the second photodetector are connected with a differential circuit.

2. The MOMES accelerometer based on light intensity modulation according to claim 1, characterized in that, The device further comprises a light source, the light source is fixedly arranged outside the plane of the silicon base, the light source emits parallel light beams in a direction perpendicular to the plane of the silicon base, and the light beams are vertically irradiated to the light-transmitting hole area of the mass, and the light signals are received by the first photodetector and the second photodetector.

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