CN118010147A - Optical fiber microphone and microphone system based on microstructure cantilever beam - Google Patents
Optical fiber microphone and microphone system based on microstructure cantilever beam Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
- G01H9/006—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors the vibrations causing a variation in the relative position of the end of a fibre and another element
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R23/00—Transducers other than those covered by groups H04R9/00 - H04R21/00
- H04R23/008—Transducers other than those covered by groups H04R9/00 - H04R21/00 using optical signals for detecting or generating sound
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Abstract
The invention discloses an optical fiber microphone and a sound transmission system based on a microstructure cantilever beam, comprising: a rectangular through hole is formed in the middle of the vibrating diaphragm; the micro-structure cantilever beam is arranged in the rectangular through hole, is connected with the wide edge of the rectangular through hole and is arranged to swing along the direction perpendicular to the surface of the vibrating diaphragm under the action of sound waves; the micro-structure cantilever beam comprises a first beam arm and a second beam arm which are connected with each other, wherein the end part of the first beam arm is connected with the broadside of the rectangular through hole, and the second beam arm is a free end; the width of the second beam arm is larger than that of the first beam arm, the length of the second beam arm is smaller than that of the first beam arm, and the geometric center of the second beam arm is overlapped with the geometric center of the vibrating diaphragm. The optical fiber microphone based on the microstructure cantilever beam disclosed by the embodiment of the invention can keep the effective light reflection area while reducing the size of the cantilever beam, can improve the sensitivity by reducing the equivalent spring coefficient of the cantilever beam, and can improve the frequency response bandwidth by reducing the equivalent quality.
Description
Technical Field
The invention belongs to the technical field of sound wave signal perception, and particularly relates to an optical fiber microphone based on a microstructure cantilever beam and a sound transmission system.
Background
The microphone is a transducer capable of converting sound energy into electric energy, commonly called as a microphone, and is widely applied to the fields of mobile communication, hearing assistance, ultrasonic medical treatment and the like. Traditional electronic microphones such as capacitive microphones and electret microphones represent the current latest technology, but the traditional electronic microphones have the defects of insufficient sensitivity, high electric noise, easiness in electromagnetic field interference and the like, and are difficult to be suitable for complex industrial sites. Therefore, it is urgent to develop a new microphone based on a new principle and a new structure.
The fiber microphone has attracted a lot of attention by virtue of compact structure, high sensitivity, easy processing and the like. The optical fiber microphone utilizes the Fabry-Perot (F-P) interference principle to establish an energy conversion mechanism of 'acoustic signal-optical signal-electric signal'. The main structure of the fiber comprises a ceramic ferrule at the tail end of the fiber and a rigid vibrating diaphragm, incident light is injected by an optical fiber, and is reflected for multiple times on the end face of the ceramic ferrule and the inner side of the rigid vibrating diaphragm to form F-P interference; when external sound wave signals act on the rigid diaphragm, the surface of the rigid diaphragm is elastically deformed to cause the phase change of interference light, and the interference light with the phase change is received by the high-sensitivity photoelectric detector and converted into voltage signals to be output.
In the current F-P microphone diaphragm design, the introduction of a cantilever structure can further improve the sensitivity of the microphone. The bending deformation amount of the cantilever beam is 10 times larger than that of the common circular vibrating diaphragm, and the response is more sensitive and linear. At present, a common rectangular cantilever beam generally adopts a method for improving the length, reducing the width and the thickness of the cantilever beam, so that the cantilever beam can generate larger deformation under the same sound pressure, and the sensitivity of the cantilever beam is improved. But this optimization suffers from two limitations: firstly, the cantilever beam needs to keep a certain reflective area, so that the cantilever beam can reflect light rays to form F-P interference, and therefore, the size cannot be infinitely reduced to improve the sensitivity; second, performance trade-offs exist when the sensitivity and frequency response of the cantilever beam are optimized, and the improvement of the length, the reduction of the width and the thickness improves the sensitivity, but the resonance frequency of the cantilever beam is obviously reduced, so that the frequency response bandwidth of the microphone is obviously reduced.
Disclosure of Invention
In view of this, some embodiments disclose a micro-structured cantilever based fiber microphone comprising:
A rectangular through hole is formed in the middle of the vibrating diaphragm;
the micro-structure cantilever beam is arranged in the rectangular through hole, is connected with the wide edge of the rectangular through hole and is arranged to swing along the direction perpendicular to the surface of the vibrating diaphragm under the action of sound waves;
The micro-structure cantilever beam comprises a first beam arm and a second beam arm which are connected with each other, wherein the end part of the first beam arm is connected with the broadside of the rectangular through hole, and the second beam arm is a free end;
The width of the second beam arm is larger than that of the first beam arm, the length of the second beam arm is smaller than that of the first beam arm, and the geometric center of the second beam arm is overlapped with the geometric center of the vibrating diaphragm.
Some embodiments disclose a microstructured cantilever-based fiber microphone having a ratio of lengths of a first beam arm to a second beam arm of greater than or equal to 3:1, a step of; the ratio of the widths of the first beam arm to the second beam arm is less than or equal to 1:2.
Some embodiments disclose a fiber microphone based on a micro-structural cantilever beam, wherein the micro-structural cantilever beam is of a symmetrical structure; the first beam arm is of an elongated symmetrical structure, and the second beam arm is of a short-wide symmetrical structure.
Some embodiments disclose a fiber microphone based on a micro-structural cantilever, and the resonance frequency f 0 of the micro-structural cantilever is expressed as:
In the formula, k eff is the equivalent spring coefficient of the micro-structure cantilever beam, and m eff is the equivalent mass of the micro-structure cantilever beam;
wherein, the equivalent spring coefficient k eff of the microstructure cantilever beam is expressed as:
In the above formula, E is the Young's modulus of the micro-structure cantilever, W is the equivalent width of the micro-structure cantilever, and L is the equivalent length of the micro-structure cantilever.
Some embodiments disclose a fiber microphone based on a micro-structured cantilever, and the sensitivity S m of the micro-structured cantilever is expressed as:
Sm＝Δz/ΔP
In the above description, Δz is the displacement generated by the free end of the micro-structure cantilever when the external sound pressure P uniformly acts on the surface of the micro-structure cantilever;
Wherein Δz is expressed as:
In the above formula, I is the moment of inertia of the micro-structure cantilever, i=h 3 W/12, and h is the thickness of the micro-structure cantilever.
Some embodiments disclose a micro-structured cantilever-based fiber microphone further comprising:
the middle position of the base is provided with a first through cavity;
The bracket is arranged above the base and is used for supporting the vibrating diaphragm; a second through cavity is formed in the middle of the bracket, and the first through cavity is communicated with the second through cavity; when the vibrating diaphragm is arranged on the bracket in an adapting way, the micro-structure cantilever beam corresponds to the second through cavity;
the fixing piece is arranged above the bracket and is used for fixing the vibrating diaphragm in a matched manner with the bracket; a third through cavity is formed in the middle of the fixing piece and corresponds to the second through cavity;
The optical fiber and the ceramic ferrule are adaptively arranged in the first through cavity; an F-P interference cavity is formed between the optical fiber and the ceramic ferrule and the micro-structure cantilever beam.
Some embodiments disclose a micro-structure cantilever-based fiber microphone, wherein an air pressure balance hole is formed in a side wall of the base and used for communicating the first through cavity with the outside of the base.
Some embodiments disclose a micro-structured cantilever-based fiber microphone, wherein the diameters of the first through cavity, the second through cavity and the third through cavity are the same.
Some embodiments disclose a micro-structured cantilever-based fiber microphone, whose optical sensitivity S i is expressed as:
In the formula, R 1 is the reflectivity of the optical fiber and the ceramic ferrule, and R 2 is the reflectivity of the microstructure cantilever beam; i i is the intensity of the incident light; lambda is the wavelength of incident light; lc is the static cavity length of the F-P interferometric cavity.
Some embodiments disclose a micro-structured cantilever-based fiber-optic microphone system, including the above-described fiber-optic microphone.
According to the optical fiber microphone and the microphone system based on the micro-structure cantilever beam, disclosed by the embodiment of the invention, the first beam arm of the micro-structure cantilever beam is of an elongated structure, so that the equivalent spring coefficient of the cantilever beam is reduced, the micro-structure cantilever beam is easy to deform under sound waves, and the micro-structure cantilever beam has excellent sensitivity; the second beam arm of the micro-structure cantilever beam reduces the size on the basis of guaranteeing the reflecting surface, reduces the equivalent mass of the micro-structure cantilever beam, and improves the problem of resonance frequency reduction caused by the shape of the first beam arm, thereby improving the frequency response bandwidth of the optical fiber microphone. The optical fiber microphone based on the microstructure cantilever beam disclosed by the embodiment of the invention can keep the effective light reflection area while reducing the size of the cantilever beam, can improve the sensitivity by reducing the equivalent spring coefficient of the cantilever beam, and can improve the frequency response bandwidth by reducing the equivalent quality. The optical fiber microphone based on the micro-structure cantilever beam disclosed by the embodiment of the invention can be suitable for detecting weak acoustic signals and can also be used in an industrial environment with strong electromagnetic interference. The optical sound transmission system based on the microstructure cantilever beam disclosed by the embodiment of the invention has the advantages of simple structure, low manufacturing cost, electromagnetic interference resistance, long detection distance and good application prospect in the field of sound wave detection.
Drawings
FIG. 1 is a schematic structural diagram of a micro-structural cantilever according to example 1;
FIG. 2 is a mechanical deformation schematic diagram of a microstructured cantilever according to example 1;
FIG. 3 is a schematic illustration of the microstructure cantilever of example 2;
FIG. 4 is a schematic illustration of the microstructure cantilever of example 3;
fig. 5 embodiment 4 is a schematic structural diagram of a micro-structural cantilever-based fiber microphone;
Fig. 6 is a schematic diagram of the working principle of a micro-structure cantilever-based fiber microphone according to embodiment 4;
FIG. 7 is a schematic diagram of a microstructure cantilever-based fiber optic microphone system according to example 5;
FIG. 8 is a graph of the frequency response of a cantilever beam of different configuration according to example 6;
FIG. 9 is a graph of the frequency response of a cantilever beam of different configuration according to example 7;
FIG. 10 is a graph of the frequency response of a cantilever beam of different configurations of example 8;
FIG. 11 example 9 real-time output voltage graphs for micro-structured cantilever-based fiber microphones at different acoustic pressures;
FIG. 12 example 10 a graph of output voltage fit for a microstructured cantilever-based fiber microphone at different acoustic pressures;
fig. 13 example 11 frequency response plot of a microstructured cantilever-based fiber microphone.
Reference numerals
1. Rectangular through hole of vibrating diaphragm 11
2. First beam arm of microstructure cantilever beam 21
22. Second beam arm 3 fixing piece
31. Third three-way cavity 4 bracket
41. Second through cavity 5 base
51. First through cavity 6 optical fiber and ceramic ferrule
7. Gasket
Detailed Description
The word "embodiment" as used herein does not necessarily mean that any embodiment described as "exemplary" is preferred or advantageous over other embodiments. Performance index testing in the examples of the present application, unless otherwise specified, was performed using conventional testing methods in the art. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure.
Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; other test methods and techniques not specifically mentioned in the present application are those commonly used by those skilled in the art.
The terms "substantially" and "about" are used herein to describe small fluctuations. For example, they may refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Numerical data presented or represented herein in a range format is used only for convenience and brevity and should therefore be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range. For example, a numerical range of "1 to 5%" should be interpreted to include not only the explicitly recited values of 1% to 5%, but also include individual values and sub-ranges within the indicated range. Thus, individual values, such as 2%, 3.5% and 4%, and subranges, such as 1% to 3%, 2% to 4% and 3% to 5%, etc., are included in this numerical range. The same principle applies to ranges reciting only one numerical value. Moreover, such an interpretation applies regardless of the breadth of the range or the characteristics being described.
In this document, including the claims, conjunctions such as "comprising," including, "" carrying, "" having, "" containing, "" involving, "" containing, "and the like are to be construed as open-ended, i.e., to mean" including, but not limited to. Only the conjunctions "consisting of … …" and "consisting of … …" are closed conjunctions.
Numerous specific details are set forth in the following examples in order to provide a better understanding of the present application. It will be understood by those skilled in the art that the present application may be practiced without some of these specific details. In the examples, some methods, means, instruments, devices, etc. well known to those skilled in the art are not described in detail in order to highlight the gist of the present application.
On the premise of no conflict, the technical features disclosed by the embodiment of the application can be combined at will, and the obtained technical scheme belongs to the disclosure of the embodiment of the application. It should be noted that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like refer to the directions or positional relationships based on the directions or positional relationships shown in the drawings, and are merely for convenience of description and to simplify description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application unless otherwise in conflict with the context. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance unless otherwise conflicting with context.
In some embodiments, a micro-structured cantilever-based fiber microphone includes:
a rectangular through hole is formed in the middle of the vibrating diaphragm; typically, the diaphragm has a suitable thickness and size to produce vibrations perpendicular to its surface under acoustic wave action; typically, the diaphragm has a symmetrical structure, such as a rectangle, square, polygon, circle, etc.; typically, the diameter of the diaphragm is in millimeter level, the thickness is in micron level, and the width of the rectangular through hole is in micron level; the rectangular through hole is arranged at the middle position of the vibrating diaphragm, so that the influence on the detection result caused by the obstruction of surrounding environment on the swing of the micro-structure cantilever beam arranged in the rectangular through hole can be effectively prevented;
The micro-structure cantilever beam is arranged in the rectangular through hole, is connected with the wide edge of the rectangular through hole and is arranged to swing along the direction perpendicular to the surface of the vibrating diaphragm under the action of sound waves; in general, a vibrating diaphragm is fixed on a support, so that a micro-structure cantilever beam is in a free state, an external sound field is applied to the micro-structure cantilever beam, the micro-structure cantilever beam positioned at the middle position of the vibrating diaphragm continuously deforms under the action of sound pressure, and the micro-structure cantilever beam swings in the direction perpendicular to the surface of the vibrating diaphragm, so that a sound wave signal is converted into a mechanical vibration signal, and the conversion from sound wave energy to mechanical vibration energy is realized; in some embodiments, the microstructured cantilever beam has a suitable thickness, shape, and size; in some embodiments, the microstructured cantilever has a length of 2mm and a width of 0.5mm;
The micro-structure cantilever beam comprises a first beam arm and a second beam arm which are connected with each other, the end part of the first beam arm is connected with the wide edge of the rectangular through hole, the second beam arm is a free end, and the center of the second beam arm coincides with the center of the vibrating diaphragm; in some embodiments, the first beam arm, the second beam arm, and the diaphragm are integrally formed;
The width of the second beam arm is larger than that of the first beam arm, the length of the second beam arm is smaller than that of the first beam arm, and the geometric center of the second beam arm is overlapped with the geometric center of the vibrating diaphragm.
In some embodiments, the microstructured cantilever beam is a symmetrical structure; generally, the symmetrical structure is favorable for generating regular deformation under the action of the rebirth sound wave, so that regular swing is generated, and the response stability to the sound wave signal is improved; the first beam arm is of a slender symmetrical structure, the second beam arm is of a short and wide symmetrical structure, the first beam arm is of a slender symmetrical structure, the equivalent spring coefficient of the micro-structure cantilever beam can be reduced, the sensitivity of the micro-structure cantilever beam is improved, the second beam arm is of a short and wide symmetrical structure, the equivalent quality of the micro-structure cantilever beam can be reduced on the basis of guaranteeing the light reflecting area of the micro-structure cantilever beam, and therefore the resonance frequency of the micro-structure cantilever beam is improved.
In some embodiments, on the basis of guaranteeing the reflective area of the micro-structure cantilever beam, the size of the second beam arm is gradually reduced, so that the equivalent mass of the micro-structure cantilever beam can be reduced, the resonance frequency of the micro-structure cantilever beam is improved, the bandwidth of the optical fiber microphone is improved, and the sensitivity of the micro-structure cantilever beam is not affected.
In some embodiments, the first beam arm is configured to be rectangular in shape.
In some embodiments, the second beam arm is shaped as a rectangle, square, circle, trapezoid, triangle, or oval.
In some embodiments, the ratio of the length of the first beam arm to the second beam arm of the microstructured cantilever is greater than or equal to 3:1, a step of; the ratio of the widths of the first beam arm to the second beam arm is less than or equal to 1:2. the length of the first beam arm is far greater than that of the second beam arm, the second beam arm can be equivalent to a counterweight added at the free end of the first beam arm, the size of the first beam arm mainly influences the equivalent spring coefficient of the micro-structure cantilever beam, the size of the second beam arm mainly influences the equivalent quality of the micro-structure cantilever beam, and the equivalent spring coefficient influence is small.
In some embodiments, the microstructured cantilever is fabricated from a metallic material, a high molecular polymer, or a semiconductor material. Such as stainless steel, gold, silver, aluminum, silicon, etc.
In some embodiments, the resonant frequency f 0 of the microstructured cantilever is expressed as:
In the formula, k eff is the equivalent spring coefficient of the micro-structure cantilever beam, and m eff is the equivalent mass of the micro-structure cantilever beam;
wherein, the equivalent spring coefficient k eff of the microstructure cantilever beam is expressed as:
In the above formula, E is Young's modulus of the micro-structure cantilever beam, W is equivalent width of the micro-structure cantilever beam, L is equivalent length of the micro-structure cantilever beam, generally, the equivalent width of the micro-structure cantilever beam is the width of the second beam arm, and the equivalent length of the micro-structure cantilever beam is the sum of the lengths of the first beam arm and the second beam arm; from the above formula, it can be seen that increasing the length of the micro-structure cantilever beam, decreasing the width of the micro-structure cantilever beam, decreasing the equivalent spring coefficient of the micro-structure cantilever beam, making the micro-structure cantilever beam more easily deform under the action of external sound waves, and optimizing the structure of the cantilever beam should make the cantilever beam as slender as possible, however, decreasing the equivalent spring coefficient of the cantilever beam will result in decreasing the resonant frequency, thereby resulting in decreasing the bandwidth of the frequency response of the optical fiber microphone.
In some embodiments, the sensitivity S m of the microstructured cantilever is expressed as:
Sm＝Δz/ΔP
In the above description, Δz is the displacement generated by the free end of the micro-structure cantilever when the external sound pressure P uniformly acts on the surface of the micro-structure cantilever;
Wherein Δz is expressed as:
In the formula, I is the rotational inertia of the micro-structure cantilever, I=h 3 W/12, and h is the thickness of the micro-structure cantilever; from the above equation, the longer the length, the smaller the thickness, and the smaller the width of the microstructure cantilever, the larger the deformation amount at the same acoustic pressure, and the higher the sensitivity.
In order to improve the sensitivity of the micro-structure cantilever beam, the first beam arm is made to be as slender as possible, and the size of the second beam arm is reduced on the basis of guaranteeing the reflecting surface, so that the quality of the micro-structure cantilever beam is reduced, the resonance frequency of the micro-structure cantilever beam is improved, and the problem of reduced frequency response bandwidth caused by the improvement of the sensitivity is solved.
In some embodiments, the micro-structured cantilever-based fiber microphone further comprises:
the middle position of the base is provided with a first through cavity;
The bracket is arranged above the base and is used for supporting the vibrating diaphragm; a second through cavity is formed in the middle of the bracket, and the first through cavity is communicated with the second through cavity; when the vibrating diaphragm is arranged on the bracket in an adapting way, the micro-structure cantilever beam corresponds to the second through cavity;
the fixing piece is arranged above the bracket and is used for fixing the vibrating diaphragm in a matched manner with the bracket; a third through cavity is formed in the middle of the fixing piece and corresponds to the second through cavity; when the optical fiber microphone works, external sound waves act on the micro-structure cantilever through the third through cavity, so that the micro-structure cantilever vibrates between the second through cavity and the third through cavity;
The optical fiber and the ceramic ferrule are adaptively arranged in the first through cavity; the end surfaces of the optical fiber and the ceramic ferrule are parallel to the micro-structure cantilever beam to form an F-P interference cavity. In the F-P interference cavity, a light ray parallel to the axis of the resonant cavity is reflected by the parallel micro-structure cantilever beam, the end face of the optical fiber and the ceramic ferrule, and the propagation direction is still parallel to the axis, so that the light ray can not escape from the cavity all the time. Typically, the optical fiber is made of glass, and the ceramic ferrule is made of ceramic.
In general, a vibrating diaphragm is fixed on a support, so that a micro-structure cantilever beam is in a free state, then an external sound field is applied, the micro-structure cantilever beam positioned in the middle area of the vibrating diaphragm deforms under the action of sound wave pressure, and swings perpendicular to the surface direction of the vibrating diaphragm, so that the cavity length of an F-P interference cavity is changed, the phase of interference light is changed, and the conversion from sound energy to light energy is realized.
In some embodiments, the base, the bracket and the fixing piece can be made of polyester fibers through 3D printing, and the sizes of the base, the bracket and the fixing piece can be adjusted according to the sizes of the micro-structure cantilever beams.
In some embodiments, the side wall of the base is provided with an air pressure balance hole for communicating the first through cavity with the outside of the base, so as to maintain the balance of internal and external air pressure and avoid the obstruction to the movement of the micro-structure cantilever beam caused by the compression of air in the F-P interference cavity.
In some embodiments, the components of the microstructured cantilever fiber microphone are secured by screws or photo-curable adhesive.
In some embodiments, the first through cavity, the second through cavity, and the third through cavity are the same diameter.
In some embodiments, the optical sensitivity S i of the fiber-optic microphone is expressed as:
In the formula, R 1 is the reflectivity of the optical fiber and the ceramic ferrule, and R 2 is the reflectivity of the microstructure cantilever beam; i i is the intensity of the incident light; lambda is the wavelength of incident light; lc is the static cavity length of the F-P interferometric cavity. When the cavity length of the F-P interference cavity and the wavelength of incident light satisfy L c = (2n+1) λ/8, the optical sensitivity of the optical fiber microphone is maximum, where n is a natural number.
In some embodiments, a micro-structured cantilever based fiber optic microphone system includes the above-described fiber optic microphone. The optical fiber microphone based on the micro-structure cantilever beam is used as an acoustic wave sensing device, responds to acoustic waves, and converts acoustic wave signals into mechanical vibration signals.
In some embodiments, the optical transmission system of the microstructured cantilever further comprises:
a laser for providing a detection laser; typically the laser includes a temperature controller and a current controller; the temperature controller and the current controller are used for controlling the wavelength of the laser; generally, a DFB laser is selected as the laser;
a photodetector for detecting the interference light;
the optical fiber circulator is used for transmitting detection laser emitted by the laser to the optical fiber microphone and transmitting interference light emitted by the optical fiber microphone to the photoelectric detector;
The data acquisition processing component is used for acquiring and processing the photoelectric detector signals and generally comprises a data acquisition card and a computer, wherein the data acquisition card is used for receiving the photoelectric detector signals and inputting the photoelectric detector signals into the computer, and the computer demodulates the voltage signals into sound wave signals.
When the system works, the laser emits detection laser, the detection laser enters the optical fiber microphone through the optical fiber circulator, the detection laser is reflected between the micro-structure cantilever beam and the end faces of the optical fiber and the ceramic ferrule to form interference light, the interference light enters the photoelectric detector through the optical fiber circulator and is converted into a voltage signal, the voltage signal is output to the data acquisition and processing assembly, and the data acquisition and processing assembly demodulates the voltage signal into an acoustic wave signal. When an external sound field acts on the optical fiber microphone, the micro-structure cantilever beam at the middle position of the vibrating diaphragm deforms under the action of sound pressure to cause the phase change of interference light, so that the voltage signal output by the microphone changes.
Further exemplary details are described below in connection with the embodiments.
Example 1
FIG. 1 is a schematic structural diagram of a microstructured cantilever disclosed in example 1; fig. 2 is a mechanical deformation schematic diagram of the microstructure cantilever disclosed in example 1.
As shown in fig. 1, the micro-structure cantilever beam 2 is disposed in a rectangular through hole 11 formed in the middle of the diaphragm 1, where the micro-structure cantilever beam 2 includes a first beam arm 21 in a strip shape and a second beam arm 22 in a square shape, which are connected to each other, an end of the first beam arm 21 is connected to a broadside on the lower side of the rectangular through hole 11, the second beam arm 22 is a free end, a geometric center of the second beam arm 22 overlaps with a geometric center of the diaphragm 1, and the micro-structure cantilever beam 2 swings along a direction perpendicular to the surface of the diaphragm 1 under the action of sound waves.
As shown in fig. 2, the micro-structure cantilever beam 2 connected with the diaphragm 1 includes a first beam arm 21 and a second beam arm 22, wherein the length of the first beam arm 21 is 3/4L, the width of the first beam arm 21 is 1/2W, the length of the second beam arm 22 is 1/4L, the width of the second beam arm 22 is W, and the micro-structure cantilever beam 2 can be equivalently added with a counterweight on the free end of a rectangular cantilever beam with the length L, the width W and the thickness h.
Since the length of the first beam arm 21 is greater than that of the second beam arm 22, the width of the first beam arm 21 is smaller than that of the second beam arm 22, and under the action of the external sound pressure P, the first beam arm 21 is elastically deformed to provide sensitivity, and the second beam arm 22 is used for changing the equivalent mass of the micro-structure cantilever beam, so that the resonance frequency is changed.
When external sound pressure P uniformly acts on the surface of the micro-structure cantilever, the displacement Δz generated by the free end of the micro-structure cantilever is expressed as formula (1):
In the formula (1), E is the Young's modulus of the micro-cantilever, and I is the rotational inertia of the micro-cantilever, wherein the rotational inertia I=h 3 W/12; the sensitivity S m = Δz/Δp of the microstructured cantilever beam, so that the thinner, longer, thinner microstructured cantilever beam is easier to deform under the same acoustic pressure and the sensitivity is higher.
The resonant frequency f 0 of the microstructured cantilever is represented by formula (2):
In the formula (2), k eff is an equivalent spring coefficient, and m eff is an equivalent mass; wherein the expression of k eff is formula (3):
According to the formula (3), the first beam arm 21 of the microstructure cantilever beam is optimized to be longer and thinner, so that the equivalent spring coefficient of the cantilever beam can be reduced, and the sensitivity is effectively improved; however, this optimization also causes a significant drop in the resonant frequency in equation (2), reducing the frequency response bandwidth of the fiber microphone. In order to compensate for the problem of resonance frequency drop caused by sensitivity improvement, the second beam arm 12 of the micro-cantilever beam can be optimized from square to round and triangular, and the size of the second beam arm can be reduced on the premise of ensuring the light reflection area. The shape optimization of the second beam arm has small influence on the equivalent spring coefficient of the micro-structure cantilever beam, and can reduce the equivalent mass of the micro-structure cantilever beam, thereby improving the resonant frequency in the formula (2) and improving the frequency response bandwidth of the optical fiber microphone.
Example 2
Fig. 3 is a schematic structural diagram of the microstructure cantilever disclosed in example 2.
As shown in fig. 3, the micro-structure cantilever beam 2 is disposed in a rectangular through hole 11 formed in the middle of the diaphragm 1, where the micro-structure cantilever beam 2 includes a first beam arm 21 in a strip shape and a second beam arm 22 in a round shape, which are connected to each other, an end of the first beam arm 21 is connected to a broadside on the lower side of the rectangular through hole 11, the second beam arm 22 is a free end, a geometric center of the second beam arm 22 overlaps with a geometric center of the diaphragm 1, and the micro-structure cantilever beam 2 swings along a direction perpendicular to the surface of the diaphragm 1 under the action of sound waves.
Example 3
Fig. 4 is a schematic structural diagram of the microstructure cantilever disclosed in example 3.
As shown in fig. 1, the micro-structure cantilever beam 2 is disposed in a rectangular through hole 11 formed in the middle of the diaphragm 1, where the micro-structure cantilever beam 2 includes a first beam arm 21 in a strip shape and a second beam arm 22 in a triangle shape, which are connected to each other, an end of the first beam arm 21 is connected to a broadside on the lower side of the rectangular through hole 11, the second beam arm 22 is a free end, a geometric center of the second beam arm 22 overlaps with a geometric center of the diaphragm 1, and the micro-structure cantilever beam 2 swings along a direction perpendicular to the surface of the diaphragm 1 under the action of sound waves.
Example 4
Fig. 5 is a schematic structural diagram of a micro-structure cantilever-based fiber microphone disclosed in example 4; fig. 6 is a schematic diagram of the working principle of the micro-structure cantilever-based fiber microphone disclosed in embodiment 4.
As shown in fig. 5, the optical fiber microphone based on the microstructure cantilever beam comprises a fixing piece 3, a bracket 4 and a base 5 which are sequentially arranged from left to right, wherein a first through cavity 51 is formed in the middle position of the base 5, a second through cavity 41 communicated with the first through cavity 51 is formed in the middle position of the bracket 4, and a third through cavity 31 communicated with the second through cavity 41 is formed in the middle position of the fixing piece 3; the vibrating diaphragm 1 is disposed in the third through cavity 31, the micro-structure cantilever beam 2 is disposed at a middle position of the vibrating diaphragm 1, and the optical fiber and the ceramic ferrule 6 are adaptively disposed in the first through cavity 51 through the gasket 7, so that an F-P interference cavity is formed between a left end face of the optical fiber and the ceramic ferrule 6 and a right side face of the micro-structure cantilever beam 2.
As shown in fig. 6, when the optical fiber microphone works, incident light enters from the optical fiber and the ceramic ferrule 6, passes through the air medium, is reflected by the lower surface of the micro-structure cantilever beam 2, returns to the air medium, and emits reflected light from the ceramic ferrule, and when the reflectivity of the lower surface of the micro-structure cantilever beam 2 and the upper surfaces of the optical fiber and the ceramic ferrule is low, the optical fiber microphone can be simplified into a double-beam interference model, and the reflected light and the incident light form interference light.
When the outside silence field acts, the intensity I r of the interference light in the fiber microphone is expressed as formula (4):
In the formula (4), I i is the intensity of incident light; r 1 is the reflectivity of the optical fiber and the ceramic ferrule, R 2 is the reflectivity of the micro-structure cantilever, Is the phase difference of the incident light and the reflected light;
In this embodiment, when stable interference is formed, phi=4pi L c/lambda, where lambda is the wavelength of incident light and Lc is the F-P static cavity length; the optical sensitivity S i of the fiber microphone is expressed as formula (5):
In the formula (5), when the wavelength of the incident light and the cavity length of the F-P interference cavity satisfy L c = (2n+1) lambda/8, the optical sensitivity of the F-P interference cavity is maximum, wherein n is a natural number.
As can be seen from the expression of the optical sensitivity S i of the optical fiber microphone, the optical sensitivity can be optimized by adjusting the F-P cavity length of the assembled optical fiber microphone to a specific corresponding relation with the wavelength of the detected light under the same optical fiber microphone structure.
Example 5
Fig. 7 is a schematic structural diagram of a microstructure cantilever-based fiber optic microphone system disclosed in example 5.
As shown in fig. 7, the micro-structural cantilever-based fiber-optic sound transmission system includes:
The optical fiber microphone is based on a microstructure cantilever beam;
a laser for providing a detection laser; the laser comprises a temperature controller and a current controller; the temperature controller and the current controller are used for controlling the wavelength of the laser;
the optical fiber circulator is connected with the laser and is used for transmitting detection laser emitted by the laser to the optical fiber microphone and transmitting interference light emitted by the optical fiber microphone to the photoelectric detector;
the photoelectric detector is connected with the optical fiber circulator and used for detecting interference light, and a photodiode in the photoelectric detector converts an optical signal into an electric signal and outputs the electric signal;
the data acquisition processing assembly is used for acquiring and processing the photoelectric detector signals and comprises a data acquisition card and a computer, wherein the data acquisition card is connected with the photoelectric detector and used for receiving the photoelectric detector signals, and the computer is connected with the data acquisition card and used for processing the information acquired by the data acquisition card and demodulating the voltage signals into sound wave signals.
When the system works, the laser emits detection laser, the detection laser enters the optical fiber microphone through the optical fiber circulator, the detection laser is reflected between the micro-structure cantilever beam and the end faces of the optical fiber and the ceramic ferrule to form interference light, the interference light enters the photoelectric detector through the optical fiber circulator and is converted into voltage signals, the voltage signals are output to the data acquisition card, the data acquisition card transmits the acquired voltage signals to the computer, and the computer demodulates the voltage signals into sound wave signals.
When an external sound field acts on the optical fiber microphone, the micro-structure cantilever beam at the middle position of the vibrating diaphragm deforms under the action of sound pressure to cause the phase change of interference light, so that the voltage signal output by the microphone changes.
Example 6
Fig. 8 is a graph of the frequency response of the different configurations of cantilever beams disclosed in example 6.
Example 6 studied the sensitivity of a general rectangular cantilever beam of length L, the sensitivity of a micro-structured cantilever beam of length 1/2L of the first beam arm, and the sensitivity of a micro-structured cantilever beam of length 3/4L of the first beam arm, as shown in fig. 8, the sensitivity of a micro-structured cantilever beam of length 1/2L of the first beam arm was increased, the resonance frequency was not greatly changed, the sensitivity of a micro-structured cantilever beam of length 3/4L of the first beam arm was increased, and the resonance frequency was decreased, as compared to the general rectangular cantilever beam; compared with the micro-structure cantilever beam with the length of the first beam arm being 1/2L, the micro-structure cantilever beam with the length of the first beam arm being 3/4L has the advantages of increased sensitivity and reduced resonance frequency.
Example 7
Fig. 9 is a graph of the frequency response of the different configurations of cantilever beams disclosed in example 7.
Example 7 studied the sensitivity of a general rectangular cantilever beam having a width W, the sensitivity of a micro-structural cantilever beam having a first beam arm width of 1/2W, and the sensitivity of a micro-structural cantilever beam having a first beam arm width of 1/4W, as shown in fig. 9, the sensitivity of a micro-structural cantilever beam having a first beam arm width of 1/2W was increased, the resonance frequency was decreased, the sensitivity of a micro-structural cantilever beam having a first beam arm width of 1/4W was increased, and the resonance frequency was decreased, as compared to the general rectangular cantilever beam; compared with the micro-structure cantilever beam with the width of the first beam arm being 1/2W, the micro-structure cantilever beam with the width of the first beam arm being 1/4W has the advantages that the sensitivity is increased, and the resonance frequency is reduced.
Example 8
Fig. 10 is a graph of the frequency response of the different configurations of cantilever beams disclosed in example 8.
Embodiment 8 studied the sensitivity of a general rectangular cantilever, a microstructure cantilever with a square second beam arm, a microstructure cantilever with a round second beam arm, and a microstructure cantilever with a triangle second beam arm, wherein the lengths of the first beam arms of the microstructure cantilever with a square second beam arm, the microstructure cantilever with a round second beam arm, and the microstructure cantilever with a triangle second beam arm are 3/4L, and the widths of the first beam arms are 1/2W.
In fig. 10, the curve with the square pattern is the curve of the microstructure cantilever with the square second beam arm, the curve with the circular pattern is the curve of the microstructure cantilever with the circular second beam arm, and the curve with the triangular pattern is the curve of the microstructure cantilever with the triangular second beam arm.
As shown in fig. 10, the sensitivity of the square micro-structure cantilever beam of the second beam arm, the circular micro-structure cantilever beam of the second beam arm and the triangular micro-structure cantilever beam of the second beam arm is higher than that of the common rectangular cantilever beam, the resonance frequency of the square micro-structure cantilever beam of the second beam arm, the circular micro-structure cantilever beam of the second beam arm and the triangular micro-structure cantilever beam of the second beam arm is gradually raised, and the resonance frequency of the triangular micro-structure cantilever beam of the second beam arm exceeds that of the common rectangular cantilever beam.
Example 9
Fig. 11 is a graph of real-time output voltage at various acoustic pressures for a microstructured cantilever-based fiber microphone as disclosed in example 9.
In example 9, sound pressures of 5mPa, 10mPa, and 20mPa were applied to a fiber microphone having a square second beam arm, a fiber microphone having a circular second beam arm, and a fiber microphone having a triangular second beam arm, respectively, with an acoustic wave signal of 1 kHz.
In fig. 11, the curve with the square pattern is the curve of the fiber microphone with the second beam arm being square, the curve with the circular pattern is the curve of the fiber microphone with the second beam arm being circular, and the curve with the triangle pattern is the curve of the fiber microphone with the second beam arm being triangle.
As shown in fig. 11, the output voltages of the optical fiber microphones with square, round and triangle second beam arms are all increased synchronously, which indicates that the optical fiber microphone based on the micro-structure cantilever disclosed in the embodiment has good energy conversion efficiency.
Example 10
Fig. 12 is a graph showing the output voltage fit of the microstructure cantilever-based fiber microphone disclosed in example 10 at different acoustic pressures.
In fig. 12, the curve with the square pattern is the curve of the fiber microphone with the second beam arm being square, the curve with the circular pattern is the curve of the fiber microphone with the second beam arm being circular, and the curve with the triangle pattern is the curve of the fiber microphone with the second beam arm being triangle. The hatched area represents the standard deviation of the multiple measurements, indicating that the fiber microphone output signal is stable.
As shown in fig. 12, under a 1kHz acoustic signal, the output voltage of the micro-structure cantilever-based optical fiber microphone increases with the increase of acoustic pressure, and the fitted curve of the output voltage has good linearity. The sensitivity of the optical fiber microphone with the second beam arm being square, round and triangular is higher than that of the optical fiber microphone with the common rectangular cantilever beam, wherein the sensitivity of the optical fiber microphone with the second beam arm being round is 302.8mV/Pa which is far higher than that of the optical fiber microphone with the common rectangular cantilever beam.
In this embodiment, the sensitivity of the fiber microphone with the second beam arm being round is 302.8mV/Pa, the sensitivity of the fiber microphone with the second beam arm being triangular is 144.3mV/Pa, the sensitivity of the fiber microphone with the second beam arm being square is 71.7mV/Pa, which is higher than that of the electronic commercial microphone manufactured by Denmark B & K company, and the sensitivity is 50mV/Pa.
Example 11
Fig. 13 is a frequency response plot of a microstructured cantilever-based fiber microphone disclosed in example 11.
In this example 11, 100Hz to 3kHz acoustic signals were applied to three different-shaped fiber microphones including a microstructured cantilever beam, respectively, and the sensitivity of the fiber microphones at different acoustic frequencies was tested and plotted as a frequency response curve.
In fig. 13, the curve with the square pattern is the curve of the fiber microphone with the second beam arm being square, the curve with the circular pattern is the curve of the fiber microphone with the second beam arm being circular, and the curve with the triangle pattern is the curve of the fiber microphone with the second beam arm being triangle.
As shown in fig. 13, the frequency response curves of the optical fiber microphones with the microstructure cantilever beam second beam arm in three different shapes are far higher than those of the common cantilever beam. The fiber microphone based on the microstructure cantilever beam disclosed by the embodiment of the invention not only optimizes the sensitivity, but also improves the frequency response bandwidth of the fiber microphone.
According to the optical fiber microphone and the microphone system based on the micro-structure cantilever beam, disclosed by the embodiment of the invention, the first beam arm of the micro-structure cantilever beam is of an elongated structure, so that the equivalent spring coefficient of the cantilever beam is reduced, the micro-structure cantilever beam is easy to deform under sound waves, and the micro-structure cantilever beam has excellent sensitivity; the second beam arm of the micro-structure cantilever beam reduces the size on the basis of guaranteeing the reflecting surface, reduces the equivalent mass of the micro-structure cantilever beam, and improves the problem of resonance frequency reduction caused by the shape of the first beam arm, thereby improving the frequency response bandwidth of the optical fiber microphone. The optical fiber microphone based on the microstructure cantilever beam disclosed by the embodiment of the invention can keep the effective light reflection area while reducing the size of the cantilever beam, can improve the sensitivity by reducing the equivalent spring coefficient of the cantilever beam, and can improve the frequency response bandwidth by reducing the equivalent quality. The optical fiber microphone based on the micro-structure cantilever beam disclosed by the embodiment of the invention can be suitable for detecting weak acoustic signals and can also be used in an industrial environment with strong electromagnetic interference. The optical sound transmission system based on the microstructure cantilever beam disclosed by the embodiment of the invention has the advantages of simple structure, low manufacturing cost, electromagnetic interference resistance, long detection distance and good application prospect in the field of sound wave detection.
The technical details disclosed in the technical scheme and the embodiment of the invention are only illustrative of the inventive concept of the invention and are not limiting to the technical scheme of the invention, and all conventional changes, substitutions or combinations of the technical details disclosed in the embodiment of the invention have the same inventive concept as the invention and are within the scope of the claims of the invention.
Claims (10)
1. Optical fiber microphone based on micro-structure cantilever beam, characterized by comprising:
A rectangular through hole is formed in the middle of the vibrating diaphragm;
the micro-structure cantilever beam is arranged in the rectangular through hole, is connected with the wide edge of the rectangular through hole and is arranged to swing along the direction perpendicular to the surface of the vibrating diaphragm under the action of sound waves;
The micro-structure cantilever comprises a first beam arm and a second beam arm which are connected with each other, wherein the end part of the first beam arm is connected with the broadside of the rectangular through hole, and the second beam arm is a free end;
The width of the second beam arm is larger than that of the first beam arm, the length of the second beam arm is smaller than that of the first beam arm, and the geometric center of the second beam arm is overlapped with the geometric center of the vibrating diaphragm.
2. The micro-structured cantilever-based fiber optic microphone according to claim 1, wherein the ratio of the lengths of the first and second beam arms is greater than or equal to 3:1, a step of; the ratio of the widths of the first beam arm to the second beam arm is less than or equal to 1:2.
3. The micro-structured cantilever-based fiber microphone of claim 1, wherein the micro-structured cantilever is a symmetrical structure; the first beam arm is of an elongated symmetrical structure, and the second beam arm is of a short-wide symmetrical structure.
4. The micro-cantilever based fiber microphone according to claim 1, wherein the resonance frequency f 0 of the micro-cantilever is expressed as:
In the formula, k eff is the equivalent spring coefficient of the micro-structure cantilever beam, and m eff is the equivalent mass of the micro-structure cantilever beam;
Wherein, the equivalent spring coefficient k eff of the micro-structure cantilever beam is expressed as:
In the above formula, E is the Young's modulus of the micro-structure cantilever, W is the equivalent width of the micro-structure cantilever, and L is the equivalent length of the micro-structure cantilever.
5. The micro-cantilever based fiber microphone according to claim 4, wherein the sensitivity S m of the micro-cantilever is expressed as:
Sm＝Δz/ΔP
In the above description, Δz is the displacement generated by the free end of the micro-structure cantilever when the external sound pressure P uniformly acts on the surface of the micro-structure cantilever;
Wherein Δz is expressed as:
In the above formula, I is the moment of inertia of the micro-structure cantilever, i=h 3 W/12, and h is the thickness of the micro-structure cantilever.
6. The micro-structured cantilever-based fiber optic microphone of claim 1, further comprising:
the base is provided with a first through cavity at the middle position;
The bracket is arranged above the base and is used for supporting the vibrating diaphragm; a second through cavity is formed in the middle of the bracket, and the first through cavity is communicated with the second through cavity; when the vibrating diaphragm is arranged on the support in an adapting mode, the micro-structure cantilever beam corresponds to the second through cavity;
The fixing piece is arranged above the bracket and is used for fixing the vibrating diaphragm in a matched manner with the bracket; a third through cavity is formed in the middle of the fixing piece, and the third through cavity corresponds to the second through cavity;
the optical fiber and the ceramic ferrule are adaptively arranged in the first through cavity; and an F-P interference cavity is formed between the optical fiber and the ceramic ferrule and the microstructure cantilever beam.
7. The micro-cantilever based fiber microphone according to claim 6, wherein an air pressure balance hole is provided on a sidewall of the base for communicating the first through cavity with the outside of the base.
8. The micro-cantilever based fiber microphone according to claim 6, wherein the first, second and third through cavities have the same diameter.
9. The micro-structured cantilever-based fiber microphone according to claim 6, wherein the optical sensitivity S i of the fiber microphone is expressed as:
In the formula, R 1 is the reflectivity of the optical fiber and the ceramic ferrule, and R 2 is the reflectivity of the microstructure cantilever beam; i i is the intensity of the incident light; lambda is the wavelength of incident light; lc is the static cavity length of the F-P interferometric cavity.
10. A micro-structured cantilever based fiber optic microphone system comprising the fiber optic microphone of any of claims 1-9.
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