A MEMS optical microphone

Abstract

The application discloses a MEMS optical microphone, comprising: a shell, the shell having an inner cavity and a sound inlet for connecting the inner cavity with the outside; a diaphragm, the diaphragm being suspended in the inner cavity and closing the sound inlet; a waveguide sheet, the waveguide sheet having a through hole, the waveguide sheet being provided with an input waveguide and an output waveguide on opposite sides of the through hole; a variable light wave piece, the second end of the variable light wave piece extending into the through hole, the variable light wave piece being capable of reciprocating along a first direction with the vibration and deformation of the diaphragm; a photoelectric module, comprising an electromagnetic radiation source and a sensing piece, the variable light wave piece being used for converting the input polarization state of a first light path into an output polarization state, the output polarization state presenting different forms with the change of the moving distance of the variable light wave piece along the first direction; and an integrated circuit module, electrically connected with the diaphragm and the photoelectric module. Compared with the prior art, the application has the advantages of high sensitivity, flat frequency response and the like, and provides potential for further improving the performance of the device.

Description

Technical Field

[0001] This invention relates to the field of microphone technology, and in particular to a MEMS optical microphone. Background Technology

[0002] Traditional microphones are based on capacitors. The diaphragm vibrates with the sound waves, and the voltage changes by changing the spacing between the capacitor substrates, thereby achieving sound-to-electric conversion.

[0003] An optical microphone is a relatively new type of microphone. It generally consists of three main modules: an optoelectronic module, an integrated circuit module (ASIC), and a microelectromechanical system (MEMS). The optoelectronic module emits light toward the MEMS module and receives the light reflected by the MEMS module. When sound waves actuate the diaphragm of the MEMS module, the diaphragm vibrates slightly and changes the intensity and phase of the light reflected back to the optoelectronic module. The optoelectronic module converts the intensity and phase signals of the reflected light into electrical signals and sends them to the integrated circuit module, thus realizing the conversion from sound signal to light signal and then to electrical signal.

[0004] With consumers demanding increasingly higher levels of experience, it is necessary to develop a MEMS optical microphone with superior performance. Summary of the Invention

[0005] The purpose of this invention is to provide a MEMS optical microphone to solve the technical problems in the prior art.

[0006] This invention provides a MEMS optical microphone, comprising:

[0007] A housing having an inner cavity and a sound inlet that connects the inner cavity to the outside;

[0008] A diaphragm, which is suspended in the inner cavity and seals the sound inlet;

[0009] A waveguide sheet is suspended in the inner cavity and located on the side of the diaphragm away from the sound inlet. A through hole is provided on the waveguide sheet, and an input waveguide and an output waveguide are provided on opposite sides of the through hole.

[0010] A variable optical wave element is disposed between the diaphragm and the waveguide plate. The first end of the variable optical wave element is connected to the surface of the diaphragm opposite to the sound inlet, and the second end of the variable optical wave element extends into the through hole. As the diaphragm vibrates and deforms, the variable optical wave element can reciprocate along a first direction.

[0011] An optoelectronic module includes an electromagnetic radiation source and a sensing element. The electromagnetic radiation source and the sensing element are respectively disposed on opposite sides of a waveguide sheet. A first optical path emitted by the electromagnetic radiation source is coupled into the waveguide sheet. The first optical path passes sequentially through the input waveguide, the variable optical waveguide, and the output waveguide before entering the sensing element. The variable optical waveguide is used to convert the input polarization state of the first optical path into an output polarization state. The output polarization state exhibits different forms as the variable optical waveguide moves a distance along the first direction.

[0012] An integrated circuit module is electrically connected to the diaphragm and the optoelectronic module.

[0013] In the MEMS optical microphone described above, preferably, the variable optical element comprises a birefringent crystal with different refractive indices in different directions.

[0014] In the MEMS optical microphone described above, preferably, the birefringent crystal has a wedge-shaped or cone-shaped structure.

[0015] In a MEMS optical microphone as described above, preferably, the birefringent crystal comprises mesoporous or porous silicon or a compound thereof formed by etching.

[0016] In the MEMS optical microphone described above, preferably, the output polarization state includes linear polarization, elliptical polarization, and circular polarization.

[0017] In the MEMS optical microphone described above, preferably, a reference waveguide is provided on the waveguide sheet, and the second optical path emitted by the electromagnetic radiation source enters the sensing element through the reference waveguide.

[0018] In the MEMS optical microphone described above, preferably, a light beam emitted by the electromagnetic radiation source is split into a first optical path and a second optical path, and two sensing elements are provided, with the first optical path and the second optical path respectively entering an independent sensing element.

[0019] In the MEMS optical microphone described above, preferably, the sensing element includes a polarizer and a photodiode, with the photodiode located on the side of the polarizer opposite to the electromagnetic radiation source.

[0020] In the MEMS optical microphone described above, preferably, lenses are provided on the side of both the input waveguide and the output waveguide near the through-hole.

[0021] In a MEMS optical microphone as described above, preferably, the diaphragm shape comprises a centrally symmetrical pattern, and the variable optical element is located at the geometric center of the diaphragm.

[0022] Compared with the prior art, the present invention provides a variable optical waveplate on the surface of the diaphragm. When pressure or sound signals are applied to the diaphragm and it vibrates, the variable optical waveplate attached to the diaphragm will also be displaced from its original position along a first direction. The first optical path emitted by the electromagnetic radiation source enters the variable optical waveplate through the input waveguide. After leaving the variable optical waveplate, the input polarization state of the first optical path is converted into a new output polarization state. The shape of the output polarization state changes with the displacement of the variable optical waveplate. The first optical paths with different output polarization states are coupled into the output waveguide and transmitted to the sensing element to generate corresponding optical signals. Finally, the level of the applied pressure or sound signal is determined on the integrated circuit module. It has the advantages of high sensitivity and flat frequency response, and provides potential for further improving device performance. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the MEMS optical microphone in its initial state according to Embodiment 1 of the present invention;

[0024] Figure 2 This is a schematic diagram of the interaction between the variable optical wavelet and the waveguide sheet in the initial state of the MEMS optical microphone according to Embodiment 1 of the present invention. Figure 1 ;

[0025] Figure 3 This is a schematic diagram of the interaction between the variable optical wavelet and the waveguide sheet in the initial state of the MEMS optical microphone according to Embodiment 1 of the present invention. Figure 2 ;

[0026] Figure 4 This is a schematic diagram of the MEMS optical microphone in the working state according to Embodiment 1 of the present invention;

[0027] Figure 5 This is a schematic diagram illustrating the interaction between the variable optical wavelet and the waveguide sheet in the working state of the MEMS optical microphone of Embodiment 1 provided by the present invention. Figure 1 ;

[0028] Figure 6 This is a schematic diagram illustrating the interaction between the variable optical wavelet and the waveguide sheet in the working state of the MEMS optical microphone of Embodiment 1 provided by the present invention. Figure 2 ;

[0029] Figure 7 This is a top view of the MEMS optical microphone of Embodiment 1 provided by the present invention;

[0030] Figure 8 This is a top view of the MEMS optical microphone of Embodiment 2 provided by the present invention;

[0031] Figure 9 This is an isometric view of the variable optical waveguide provided by the present invention;

[0032] Figure 10 This is a side view of the variable optical waveguide provided by the present invention;

[0033] Figure 11 This is a top view of the diaphragm provided by the present invention;

[0034] Figure 12 This is a schematic diagram of the cooperation between the lens and the waveguide sheet provided by the present invention;

[0035] Figure 13 This is a schematic diagram showing the correspondence between light intensity and applied sound or pressure signals;

[0036] Figure 14 This is a schematic diagram showing the correspondence between light intensity and the output polarization state of the first optical path.

[0037] Explanation of reference numerals in the attached figures:

[0038] 10-Shell, 11-Sound inlet, 12-First shell wall, 13-Second shell wall, 14-Side shell wall, 15-Inner cavity;

[0039] 20 - Diaphragm;

[0040] 30-Waveguide plate, 31-Through hole, 32-Input waveguide, 33-Output waveguide, 34-Reference waveguide, 35-Lens;

[0041] 40 - Variable optical waveguide;

[0042] 50 - Electromagnetic radiation source, 51 - Polarizer, 52 - Photodiode, 53 - First optical path, 54 - Second optical path;

[0043] 60 - Integrated Circuit Module;

[0044] 70 - Input polarization state;

[0045] 80 - Output polarization state. Detailed Implementation

[0046] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0047] Reference Figures 1 to 14 As shown, this application provides a MEMS optical microphone, including a housing 10, a diaphragm 20, a waveguide 30, a variable optical element 40, and an optoelectronic module, wherein:

[0048] The housing 10 has an inner cavity 15 and a sound inlet 11 that connects the inner cavity 15 to the outside. In the embodiment provided by the present invention, the inner cavity 15 includes a first housing wall 12, a second housing wall 13, and a side housing wall 14 that connects the first housing wall 12 and the second housing wall 13. The first housing wall 12 and the second housing wall 13 are opposite to each other. The first housing wall 12 is a PCB substrate. The diaphragm 20, the optoelectronic module, the integrated circuit module 60, and the sound inlet 11 are all disposed on the first housing wall 12. It should be noted that the side housing wall 14 can be integrally formed as part of the first housing wall 12 or the second housing wall 13, or it can be an independent part.

[0049] The diaphragm 20 is suspended in the inner cavity 15 and closes the sound inlet 11. Sound waves enter the housing 10 through the sound inlet 11 and actuate the diaphragm 20. When the diaphragm 20 vibrates, it moves upward (or downward, depending on the type of microphone) and downward (or upward, depending on the type of microphone), just like a standard oscillating structure, with a specific frequency and displacement. The frequency depends on the frequency of the sound wave, and the displacement depends on the pressure of the sound wave.

[0050] The waveguide 30 is suspended in the inner cavity 15 and located on the side of the diaphragm 20 away from the sound inlet 11. In one feasible embodiment, a support arm is also provided, with the opposite ends of the support arm connected to the waveguide 30 and the first shell wall 12, respectively, to suspend the waveguide 30 in the inner cavity 15. It is a flat plate that includes the optical path for transmitting light and is placed parallel to the MEMS film. A through hole 31 is provided on the waveguide 30 to allow the variable optical waveplate to pass through. The waveguide 30 is a polarization-maintaining waveguide that does not affect the polarization state of light during transmission. The waveguide 30 has an input waveguide 32 and an output waveguide 33 on opposite sides of the through hole 31.

[0051] A variable light wave element 40 is disposed between the diaphragm 20 and the waveguide plate 30. The first end of the variable light wave element 40 is connected to the surface of the diaphragm 20 away from the sound inlet 11, and the second end of the variable light wave element 40 extends into the through hole 31. As the diaphragm 20 vibrates and deforms, the variable light wave element 40 can reciprocate along the first direction. In the embodiment provided in this application, the first direction is the direction parallel to the Z-axis in the coordinate system shown in the figure. When the diaphragm 20 vibrates in the Z-axis or vertical direction due to external sound signals, the variable light wave element 40 also moves accordingly. The displacement of the movement is proportional to the amplitude of the diaphragm 20.

[0052] The variable optical waveguide 40 is an optical element that can change the polarization state of light passing through it. To convert a given input polarization state 70 of light into an arbitrary output polarization state 80, this can be achieved by providing a material or structure with variable delay, which involves the birefringence of the material and the optical path length or thickness of the optical structure. The optical material used in the variable optical waveguide 40 adds a phase delay between the orthogonal components of the electric field of light at a fixed wavelength. For example, a quarter-wave plate converts a linear input polarization state 70 to a circular polarization state, and vice versa.

[0053] The optoelectronic module includes an electromagnetic radiation source 50 and a sensing element. The electromagnetic radiation source 50 and the sensing element are respectively disposed on opposite sides of the waveguide plate 30. The electromagnetic radiation source 50 includes, for example, an infrared (IR), visible light, or UV source, which can be a laser or a light-emitting diode. The sensing element includes a polarizer 51 and a photodiode 52. The photodiode 52 is located on the side of the polarizer 51 away from the electromagnetic radiation source 50.

[0054] The first optical path 53 emitted by the electromagnetic radiation source 50 is coupled into the waveguide plate 30. Optical coupling can be achieved in various ways, such as using an optical fiber to directly couple or dock the first optical path 53 to the edge of the input waveguide 32, or using a grating coupler to transmit light to the input waveguide 32. The first optical path 53 passes sequentially through the input waveguide 32, the variable optical wavelet 40, and the output waveguide 33 before entering the sensing element. Since the input waveguide 32 is a polarization-maintaining waveguide, the input polarization state 70 of the first optical path 53 maintains its polarization shape when passing through it. The first optical path 53 leaves the input waveguide 32 at the through-hole 31 and is transmitted through the variable optical wavelet 40, then coupled again to the output waveguide 33, and finally transmitted to the photodiode 52 through the polarizer 51.

[0055] The variable optical wave element 40 is used to convert the fixed input polarization state 70 of the first optical path 53 into various output polarization states 80. The output polarization state 80 exhibits different forms as the variable optical wave element 40 moves a distance along the first direction. When the first optical path 53 passes through the polarizer 51, the intensity level of the light changes, and the light intensity depends on the specific form of the output polarization state 80. The intensity of the output polarized light is converted into an electrical signal on the photodiode 52, which is processed on the integrated circuit module 60 to determine the level of the applied sound signal.

[0056] The integrated circuit module 60 is electrically connected to the diaphragm 20 and the optoelectronic module. The integrated circuit module 60 (ASIC) includes electronic circuits that constitute a control or central processing unit and drive, control and take necessary actions on the relevant electronic and optoelectronic components in the system.

[0057] Based on the above embodiments, the working principle of the present invention is as follows:

[0058] Reference Figures 1 to 3 As shown, Figure 1 This is a schematic diagram of the MEMS optical microphone in its initial state according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the interaction between the variable optical wavelet 40 and the waveguide plate 30 in the initial state of the MEMS optical microphone of Embodiment 1 provided by the present invention. Figure 1 ; Figure 3 This is a schematic diagram of the interaction between the variable optical wavelet 40 and the waveguide plate 30 in the initial state of the MEMS optical microphone of Embodiment 1 provided by the present invention. Figure 2 When there is no sound signal, the diaphragm 20 and the variable optical waveguide 40 attached thereto are in a balanced position. The first optical path 53 emitted by the electromagnetic radiation source 50 is coupled into the input waveguide 32. The light from the input waveguide 32 is transmitted through a position near the vertex on the variable optical waveguide 40, where the variable optical waveguide 40 has no thickness or minimum thickness of birefringent material so as not to affect the polarization state of the first optical path 53. After passing through such a position in the variable optical waveguide 40, the light is coupled to the output waveguide 33 before being guided to the sensing element. This means that when no pressure or sound is applied, the input polarization state 70 (e.g., linear polarization state) of the first optical path 53 remains unchanged after passing through the variable optical waveguide 40.

[0059] Reference Figures 4 to 6 As shown, Figure 4 This is a schematic diagram of the MEMS optical microphone in the working state according to Embodiment 1 of the present invention; Figure 5 This is a schematic diagram illustrating the interaction between the variable optical wavelet 40 and the waveguide plate 30 in the working state of the MEMS optical microphone of Embodiment 1 provided by the present invention. Figure 1 ; Figure 6 This is a schematic diagram illustrating the interaction between the variable optical wavelet 40 and the waveguide plate 30 in the working state of the MEMS optical microphone of Embodiment 1 provided by the present invention. Figure 2 When pressure or sound signals are applied to the diaphragm 20 and cause it to vibrate, the variable optical waveguide 40 attached to the diaphragm 20 also shifts from its original position. Therefore, the first optical path 53 emitted from the electromagnetic radiation source 50 couples into the input waveguide 32, and the light from the input waveguide 32 is transmitted through a new position on the variable optical waveguide 40. Due to the varying delay of the variable optical waveguide 40, one of the orthogonal components of the light experiences a certain delay after passing through the new position on the variable optical waveguide 40, resulting in a phase delay. After leaving the variable optical waveguide 40, these components generate a new output polarization state 80. Then, the first optical path 53 with the new output polarization state 80 is coupled into the output waveguide 33 and transmitted to the sensing element (polarizer 51 followed by photodiode 52). The optical axis of the polarizer 51 is set relative to the direction of the input polarized light, meaning that the morphology of the new output polarization state 80 is detected at a certain light intensity level on the photodiode 52. (Refer to...) Figure 13 As shown, Figure 13 The diagram shows the relationship between light intensity and applied sound or pressure signal. The stronger the sound or pressure signal applied to the diaphragm 20, the stronger the light intensity detected in the first optical path 53.

[0060] In summary, a given sound or pressure signal actuates the diaphragm 20 and the variable light wave element 40. This alters the polarization state of the first optical path 53 transmitted through the variable light wave element 40, resulting in a different output polarization state 80 for the given sound signal. The specific shape of the output polarization state 80 determines the light intensity. The intensity of the output polarized light is converted into an electrical signal at the photodiode 52, processed at the integrated circuit module 60, and the level of the applied pressure or sound signal is determined, thereby allowing the determination of the applied sound level.

[0061] In one feasible embodiment, the variable optical wave element 40 includes a birefringent crystal with different refractive indices in different directions. The birefringent crystal has a variable thickness, and the variation in the thickness of the variable optical wave element 40 results in a variable delay. The structure of the birefringent crystal includes a wedge shape or a cone shape, see reference. Figure 9 as well as Figure 10 As shown, Figure 9 This is an isometric view of the variable optical wave element 40 provided by the present invention; Figure 10 This is a side view of the variable optical wave element 40 provided by the present invention; the cross-section of the variable optical wave element 40 is a triangular structure, specifically, the refractive index of the birefringent crystal is... and Among them, ordinary is and It features an unusual refractive index, and a triangular structure is created to alter the thickness of an optically anisotropic material with fixed birefringence. ; The varying thickness of the triangular structure at different locations results in different delays. When the first optical path 53 passes through this structure at a certain position, a certain level of phase delay is added between the two orthogonal electric field components of the first optical path 53. (Refer to...) Figure 10 As shown, the thicknesses at positions 1, 2, and 3 are respectively The resulting phase delays are respectively , , .

[0062] The output polarization state 80 includes linear polarization, elliptical polarization, and circular polarization. It is determined by the delay in the position of the incident light as it passes through the wedge. (Refer to...) Figure 10As shown, position 3 corresponds to linear polarization, position 2 to elliptic polarization, and position 1 to circular polarization. For example, when the first optical path 53 in linear polarization falls at position 1 with a delay, a quarter-wave plate is formed at position 1 on the variable optical wavelet 40, and a phase delay of π / 2 is added between the two orthogonal components of the electric field of the first optical path 53; therefore, the first optical path 53 changes to a circular polarization state after passing through position 1. Figure 10 It also illustrates other examples of polarization manipulation, such as linear or elliptical polarization states at different positions on the wedge.

[0063] When a first optical path 53 with a certain degree of polarization passes through polarizer 51, the intensity level of the light after passing through polarizer 51 will change. Under given conditions, the amplitude of the light intensity depends on the output polarization state 80 of the first optical path 53 and the orientation of the optical axis in that case. For example, if the linearly polarized first optical path 53 is transmitted through polarizer 51, the amplitude of the transmitted light intensity changes from maximum to minimum.

[0064] Reference Figure 10 as well as Figure 14 As shown:

[0065] (1) In When the electric field of the first optical path 53 in the linear polarization state is oriented along the optical axis of the polarizer, it will completely pass through the polarizer and reach the maximum light intensity level.

[0066] (2) In At the point where the direction of the electric field vector of the first optical path 53 of the circularly polarized state is in the same position as the optical axis of the rotating polarizer, no light passes through, and a minimum or no light intensity is observed.

[0067] (3) For the first optical path 53 in other positions with elliptic polarization, the light intensity of the photodiode 52 will vary between the maximum and minimum values.

[0068] For an ideal linear polarization state, the modulation level is maximum, while in an ideal circular polarization state, the modulation of light is zero because the electric field vector of circularly polarized light always passes through polarizer 51 during rotation. For an elliptically polarized state, the modulation intensity of light will vary between maximum modulation (linear polarization) and zero modulation (circular polarization). The modulation level will determine the ellipticity of the polarization state, which means that different polarization states are produced at a given sound level determined by the modulation level in the light intensity signal.

[0069] The variable optical element 40 can be a wedge-shaped or cone-shaped birefringent crystal with variable delay, fixed to the diaphragm 20. It can also be an in-situ fabricated optical anisotropic structure, formed with a semiconductor material such as silicon or its compounds to provide variable delay in certain crystallographic directions. Examples of such structures include mesoporous or porous silicon or its compounds formed by etching, such as pillars or trenches in silicon that change their effective optical anisotropy in different directions along a specific orientation, or anisotropic nanowires based on semiconductors.

[0070] Reference Figure 8 As shown, Figure 8 This is a top view of the MEMS optical microphone according to Embodiment 2 of the present invention. Embodiment 2 differs from Embodiment 1 in that a reference waveguide 34 is provided on the waveguide sheet 30. The second optical path 54 emitted from the electromagnetic radiation source 50 enters the sensing element (polarizer 51 followed by photodiode 52) via the reference waveguide 34. The reference waveguide 34 serves as a reference and is used to compare and extract the polarization state of the first optical path 53 passing through the input waveguide 32 and the output waveguide 33. The input waveguide 32 carries the same polarization as the reference waveguide 34, while the output waveguide 33 has a changed polarization state after the first optical path 53 passes through the optical structure.

[0071] In one feasible implementation, refer to Figure 8 As shown, there is only one electromagnetic radiation source 50. The light beam emitted by the electromagnetic radiation source 50 is split into a first optical path 53 and a second optical path 54. There are two sensing elements. The first optical path 53 and the second optical path 54 enter independent sensing elements (polarizer 51 is connected to photodiode 52).

[0072] In principle, the first optical path 53 from a certain input polarization state 70 (e.g., linear polarization state) is transmitted into the waveguide 30. It then splits into a first optical path 53 and a second optical path 54 at the junction forming the interference arrangement. The first optical path 53 enters the input waveguide 32, and the second optical path 54 enters the reference waveguide 34. Since the waveguide 30 is a polarization-maintaining waveguide, the polarization state of the light passing through it is not affected. For example, the second optical path 54, with a linear polarization state from the electromagnetic radiation source 50, will remain linear at the end of the reference waveguide 34, where it is transmitted to the photodiode 52 via the polarizer 51. On the other hand, when the first optical path 53 with a linear polarization state leaves the input waveguide 32, it encounters a certain phase delay as it passes through the variable optical element 40. After leaving the variable optical element 40, the first optical path 53 will have a different polarization state than the second optical path 54; the change in the output polarization state 80 of the first optical path 53 will be elliptical, circular, or linear polarization. The first optical path 53 with a new polarization state is guided to the output waveguide 33 and transmitted to the photodiode 52 via the polarizer 51, where it is extracted by comparing its polarization state with that of the second optical path 54.

[0073] Reference Figure 12 As shown, Figure 12 This is a schematic diagram of the interaction between the lens 35 and the waveguide plate 30 provided by the present invention. Micro / nano lenses 35 are provided on the side of the input waveguide 32 and the output waveguide 33 near the through-hole 31. The micro / nano lenses 35 can couple light from the input waveguide 32 to the variable optical wavelet 40 and the output waveguide 33. The lens 35 on the input waveguide 32 focuses the first optical path 53 onto a small area on the variable optical wavelet 40. After passing through the variable optical wavelet 40, the first optical path 53 is collected by another lens 35 created in the output waveguide 33. The focal length and numerical aperture of the lens 35 are selected to produce a minimum spot size. The small spot size allows light to be focused onto a smaller area where the effective delay of the birefringent material remains unchanged, so that when the applied sound level changes, it can correctly manipulate the input polarization state 70 to other output polarization states 80.

[0074] Reference Figure 11 As shown, Figure 11 This is a top view of the diaphragm 20 provided by the present invention; the diaphragm 20 is a micromachined thin film, sheet, or membrane made of silicon or its compounds. The diaphragm 20 can be made of a single material or multiple materials. It can be monocrystalline silicon, silicon nitride, silicon oxide, polycrystalline silicon, polyimide, or a combination thereof; the shape of the diaphragm 20 includes a centrally symmetrical figure, and the shape of the diaphragm 20 is not limited to a circle, but can also be a square or other centrally symmetrical figure.

[0075] The variable optical wave element 40 is located at the geometric center of the diaphragm 20. The amplitude is the largest at the center of the diaphragm 20. Even a small vibration can cause the variable optical wave element 40 to shift, thereby improving the sensing accuracy.

[0076] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A MEMS optical microphone, characterized by, The application relates to a sound transducer, comprising: a housing having an inner cavity and a sound inlet opening; a diaphragm suspended in the inner cavity and closing the sound inlet opening; a waveguide suspended in the inner cavity and located on a side of the diaphragm away from the sound inlet opening, the waveguide having a through hole, and the waveguide being provided with an input waveguide and an output waveguide on opposite sides of the through hole; a variable optical wave element arranged between the diaphragm and the waveguide, a first end of the variable optical wave element being connected to a surface of the diaphragm away from the sound inlet opening, and a second end of the variable optical wave element extending into the through hole, the variable optical wave element being capable of reciprocating along a first direction with vibration and deformation of the diaphragm; a photoelectric module comprising an electromagnetic radiation source and a sensing element, the electromagnetic radiation source and the sensing element being arranged on opposite sides of the waveguide respectively, a first light path emitted by the electromagnetic radiation source being coupled into the waveguide, the first light path entering the sensing element in sequence via the input waveguide, the variable optical wave element and the output waveguide, the variable optical wave element being used for converting an input polarization state of the first light path into an output polarization state, the output polarization state presenting different states with a change in a moving distance of the variable optical wave element along the first direction; an integrated circuit module electrically connected to the diaphragm and the photoelectric module; the variable optical wave element comprising a birefringent crystal having different refractive indexes in different directions.

2. The MEMS optical microphone of claim 1, wherein: The structure of the birefringent crystal comprises a wedge shape or a taper shape.

3. The MEMS optical microphone of claim 1, wherein: The birefringent crystal comprises mesoporous or porous silicon or a compound thereof formed by etching.

4. The MEMS optical microphone of claim 1, wherein: The states of the output polarization state comprise linear polarization, elliptical polarization and circular polarization.

5. The MEMS optical microphone of claim 1, wherein: The waveguide is provided with a reference waveguide, and a second light path emitted by the electromagnetic radiation source enters the sensing element via the reference waveguide.

6. The MEMS optical microphone of claim 5, wherein: A light beam emitted by the electromagnetic radiation source is split into the first light path and the second light path, and the sensing element is provided with two sensing elements, and the first light path and the second light path enter the independent sensing elements respectively.

7. The MEMS optical microphone of claim 1, wherein: The sensing element comprises a polarizer and a photodiode, and the photodiode is located on a side of the polarizer away from the electromagnetic radiation source.

8. The MEMS optical microphone of claim 1, wherein: The input waveguide and the output waveguide are each provided with a lens on a side close to the through hole.

9. The MEMS optical microphone of claim 1, wherein: The shape of the diaphragm comprises a figure about a central symmetry, and the variable optical wave element is arranged at a geometric center of the diaphragm.

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