Scanning actuator and optical fiber scanner

Abstract

The scanning actuator comprises an actuator body which is integrally formed through sintering, and the actuator body comprises a lower electrode layer, a lower piezoelectric plate, a middle electrode layer, an upper piezoelectric plate and an upper electrode layer which are sequentially arranged from bottom to top. An optical fiber mounting hole penetrating through the actuator body in the front-back direction is machined in the center of the front end face of the actuator body, and under driving of a driving signal, the upper piezoelectric plate and the lower piezoelectric plate synchronously and reversely stretch out and draw back so as to drive the free vibration end to vibrate in the vertical direction. The left sides of the upper piezoelectric plate and the lower piezoelectric plate and the right sides of the upper piezoelectric plate and the lower piezoelectric plate synchronously and reversely stretch out and draw back to drive the free vibration end to vibrate left and right in the horizontal direction. The piezoelectric sensor is formed by sintering the two piezoelectric patches and the three electrode layers, no adhesive or other additional materials exist, the production process is simplified, mass production is facilitated, only one procedure of machining the through optical fiber mounting hole is needed after sintering is completed, machining is easy, and the consistency of product specifications, performance and parameters is easy to guarantee in mass production.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber scanning display, and in particular to a scanning actuator and an optical fiber scanner. Background Art

[0002] Fiber optic scanner is a display technology that uses a scanning actuator to control the swing of an optical fiber to emit a pattern. The pattern illuminated by this technology has sharp and saturated colors, high contrast, high brightness, and a very small structure volume.

[0003] The actuator of the grid-type optical fiber scanner mainly includes a second actuator as a fast axis and a first actuator as a slow axis. The second actuator and the first actuator have a fixed end and a free end respectively. The fixed end of the second actuator is fixedly connected to the free end of the first actuator. In order to obtain a stable scanning range and accurately control the scanning trajectory, the scanning trajectory of the end of the actuator needs to be precisely consistent with the scanning trajectory of the first actuator and the scanning trajectory of the second actuator. Any machining error of the actuator will make the vibration of the actuator difficult to control or produce a chaotic vibration component.

[0004] Traditional scanner actuators are generally tubular or sheet-shaped. In order to make the actuator part in the slow axis direction meet the slow axis scanning frequency and the actuator part in the fast axis direction meet the fast axis scanning frequency, the shape and size of the actuator must be designed accordingly, which causes the actuator to become irregularly shaped.

[0005] For example, a scanning actuator disclosed in Chinese patent CN111830702A generally adopts a tubular piezoelectric actuator, but due to the above factors, it is designed to be a special-shaped structure, which is quite disadvantageous for mass production of actuators, difficult to process, and the processing consistency cannot be guaranteed. Another example is a scanning actuator disclosed in Chinese patent CN209784655U, which generally adopts a sheet-shaped piezoelectric actuator. For the same performance consideration, the actuator is also set to a special-shaped structure, and the above-mentioned technical problems of difficulty in precise processing and poor processing consistency also exist.

[0006] Therefore, how to make the actuator easy to process and mass produce with good consistency in mass production under the premise that each actuating part meets the performance parameters is a technical problem that needs to be solved. Summary of the invention

[0007] The embodiments of the present invention provide a scanning actuator and an optical fiber scanner, which are used to at least solve the technical problems that actuators are difficult to mass produce and mass produce with poor consistency.

[0008] To achieve the above-mentioned invention object, a first aspect of the present invention provides a scanning actuator, which includes an actuator body integrally formed by sintering. The actuator body includes a lower electrode layer, a lower piezoelectric sheet, a middle electrode layer, an upper piezoelectric sheet, and an upper electrode layer that are sequentially arranged in the up-down direction. Taking the extending direction of the piezoelectric sheet as the horizontal plane direction and the front end of the actuator body as the free vibration end, a fiber optic mounting hole penetrating the actuator body in the front-back direction is machined at the center position of the front end face of the actuator body. The fiber optic mounting hole divides the middle electrode layer into an independent left electrode layer and right electrode layer. Both the upper piezoelectric sheet and the lower piezoelectric sheet are polarized in the vertical direction. Under the drive of a drive signal, the upper piezoelectric sheet and the lower piezoelectric sheet synchronously and reversely expand and contract to drive the free vibration end to vibrate in the vertical direction. At the same time, the left side and the right side of the upper piezoelectric sheet and the lower piezoelectric sheet synchronously and reversely expand and contract to drive the free vibration end to vibrate left and right in the horizontal direction.

[0009] The present invention is sintered from two piezoelectric sheets and three electrode layers, without additional materials such as adhesives, which simplifies the production process and is convenient for mass production. After sintering, only one process of machining a penetrating fiber optic mounting hole is required, which is easy to process, and it is easy to ensure the consistency of product specifications, performance, and parameters in mass production.

[0010] Preferably, the upper piezoelectric sheet and the lower piezoelectric sheet have exactly the same shape and size and completely overlap. The lower electrode layer, the middle electrode layer (before machining the fiber optic mounting hole), and the upper electrode layer all completely cover the corresponding surfaces of the piezoelectric sheet, so as to facilitate the scanning actuator to obtain good precise symmetry and ensure that both vertical vibration and horizontal vibration are linear vibrations.

[0011] Due to the independence of the left electrode layer and the right electrode layer, correspondingly, a symmetrically arranged first left driving region and first right driving region are formed on the left side and the right side of the body of the upper piezoelectric sheet, and a symmetrically arranged second left driving region and second right driving region are formed on the left side and the right side of the body of the lower piezoelectric sheet. The first left driving region and the second left driving region are symmetric up and down, and the first right driving region and the second right driving region are symmetric up and down.

[0012] Preferably, under the drive of a drive signal: the first left driving region and the first right driving region perform a first synchronous and equal-length expansion and contraction action, the second left driving region and the second right driving region perform a second synchronous and equal-length expansion and contraction action, and the first synchronous expansion and contraction action and the second synchronous expansion and contraction action are synchronous, equal-length, and reverse; at the same time, the first left driving region and the second left driving region perform a third synchronous and equal-length expansion and contraction action, the first right driving region and the second right driving region perform a fourth synchronous and equal-length expansion and contraction action, and the third synchronous expansion and contraction action and the fourth synchronous expansion and contraction action are synchronous, equal-length, and reverse.

[0013] Preferably, the polarization directions of the upper piezoelectric sheet and the lower piezoelectric sheet are the same. The upper electrode layer is connected to a first power signal, the lower electrode layer is connected to a second power signal, the left electrode layer is connected to a first driving signal, and the right electrode layer is connected to a second driving signal. Both the first power signal and the second power signal can be positive power signals or negative power signals, and the polarities of the first power signal and the second power signal are opposite.

[0014] Furthermore, both the first driving signal and the second driving signal adopt a mixed-frequency driving method, so that the bimorph vibrates in the vertical direction and the horizontal direction at different frequencies respectively.

[0015] Specifically, the first driving signal is:

[0016] SIgL = Fy(2πωyt + ΦyL) + Axcsin(2πωxt + ΦxcL) + Axsin(2πωxt + ΦxL),

[0017] The second driving signal is:

[0018] SIgR = Fy(2πωyt + ΦyR) + Axcsin(2πωxt + ΦxcR) + Axsin(2πωxt + ΦxR).

[0019] Axsin(2πωxt + ΦxL) / Axsin(2πωxt + ΦxR) is a high-frequency driving signal in the left-right direction (X direction), which can be a sine wave or other waveforms according to application requirements. Among them, the difference between ΦxL and ΦxR is 180° in the ideal case. In actual applications, due to processing accuracy, there are slight differences in the response characteristics on the left and right sides of the bimorph. Appropriately adjust the difference between ΦxL and ΦxR so that the deformations on the left and right sides are strictly out of phase, in order to achieve the maximum deformation amount and the minimum vertical direction component. Ax is the voltage amplitude of the control signals Axsin(2πωxt + ΦxL) and Axsin(2πωxt + ΦxR), ΦxL is the initial phase of the control signal Axsin(2πωxt + ΦxL), and ΦxR is the initial phase of the control signal Axsin(2πωxt + ΦxR);

[0020] Fy(2πωyt + ΦyL) / Fy(2πωyt + ΦyR) is the low-frequency driving signal in the vertical direction (Y direction), which can be a sine wave or other waveforms according to application requirements. Ideally, in the SIgL / SIgR signal, the components of this signal are exactly the same, i.e., ΦyR = ΦyR. In actual applications, due to processing accuracy, there are slight differences in the response characteristics on the upper and lower sides of the bimorph. Appropriately adjusting the difference between ΦyL and ΦyR makes the deformations on the upper and lower sides strictly out of phase, so as to achieve the maximum deformation and the minimum vertical direction component. Fy is the voltage amplitude of the control signals Fy(2πωyt + ΦyL) and Fy(2πωyt + ΦyR), ΦyL is the initial phase of the control signal Fy(2πωyt + ΦyL), and ΦyR is the initial phase of the control signal Fy(2πωyt + ΦyR).

[0021] Axcsin(2πωxt + ΦxcL) / Axcsin(2πωxt + ΦxcR) is the correction signal in the X direction, which is used to correct the Y-direction component of the fast-axis trajectory to zero so that its trajectory is a closed trajectory. Ideally, in the SIgL / SIgR signal, the components of this signal are exactly the same, i.e., ΦxcL = ΦxcR. Axc is the voltage amplitude of the control signals Axcsin(2πωxt + ΦxcL) and Axcsin(2πωxt + ΦxcR), ΦxcL is the initial phase of the control signal Axcsin(2πωxt + ΦxcL), and ΦxcR is the initial phase of the control signal Axcsin(2πωxt + ΦxcR).

[0022] In the second aspect of the embodiments of the present invention, an optical fiber scanning actuator is provided, which includes the scanning actuator and the optical fiber described above. The optical fiber is fixedly passed through the optical fiber mounting hole, and the light-emitting end of the optical fiber passes through the free vibration end of the scanning actuator to form an optical fiber cantilever. The part of the optical fiber located behind the optical fiber cantilever is fixedly connected to the scanning actuator.

[0023] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0024] The present invention is sintered from two piezoelectric wafers and three electrode layers, without additional materials such as adhesives, which simplifies the production process and facilitates mass production. After sintering, only one process of processing the through optical fiber mounting hole is required, which is easy to process. In mass production, it is easy to ensure the consistency of product specifications, performance, and parameters. For the optical fiber scanning imaging technology, the good consistency of the actuator is one of the key factors for the mass production of the optical fiber scanner. At the same time, the sheet structure makes the difference in the characteristic frequency values of the actuator in the horizontal and vertical directions very large. When the scanning actuator is used in the raster scanning mode, the vibration coupling of the actuator in the two vibration directions can be greatly reduced.

[0025] The manufacturing process of machining a center hole at the center after integral sintering ensures the symmetry of the overall structure (left - right symmetry, up - down symmetry). The upper and lower double - wafers share an electrode, which can maximize the consistency of the two piezoelectric ceramic wafers on the same side (left or right), ensuring that when it is used for horizontal - direction driving, there is no vertical - direction component.

[0026] Meanwhile, the existence of the optical - fiber installation hole can effectively reduce the equivalent stiffness of the left - right divided area of the actuator body, thereby reducing the stress concentration in the divided area, appropriately increasing the horizontal bending amplitude of the double - wafer, and reducing power consumption. The optical - fiber installation hole can play a positioning role during optical - fiber assembly and ensure that the optical fiber is strictly centered on the double - wafer, effectively avoiding large - amplitude bending of the double - wafer when the optical fiber is adhesively bonded on the outside, and interference caused by the mismatch between the modulus of the optical fiber and the ceramic wafer, resulting in non - linear vibration response. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic structural diagram of the optical - fiber scanner of the present invention;

[0028] Figure 2 is a schematic end - face structural diagram of the scanning actuator;

[0029] Figure 3 is a schematic structural diagram of the driving - area distribution of the scanning actuator;

[0030] Figure 4 is a schematic diagram of the driving - signal access of the scanning actuator. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0032] Such as Figure 1 、 Figure 2As shown in the figure, the first aspect of the present invention provides a scanning actuator, which includes an actuator body 100 formed by sintering integrally. The actuator body 100 includes a lower electrode layer 101, a lower piezoelectric sheet 102, a middle electrode layer, an upper piezoelectric sheet 103, and an upper electrode layer 104 arranged in sequence along the direction from bottom to top. Taking the extension direction of the piezoelectric sheet as the horizontal plane direction and the front end of the actuator body 100 as the free vibration end, a fiber installation hole 107 penetrating the actuator body 100 in the front-back direction is processed at the center position of the front end face of the actuator body 100. The fiber installation hole 107 divides the middle electrode layer into independent left electrode layer 105 and right electrode layer 106. Both the upper piezoelectric sheet 103 and the lower piezoelectric sheet 102 are polarized in the vertical direction. Under the drive of a drive signal, the upper piezoelectric sheet 103 and the lower piezoelectric sheet 102 synchronously expand and contract in the opposite direction to drive the free vibration end to vibrate in the vertical direction. At the same time, the left side and the right side of the upper piezoelectric sheet 103 and the lower piezoelectric sheet 102 synchronously expand and contract in the opposite direction to drive the free vibration end to vibrate left and right in the horizontal direction.

[0033] The present invention is sintered from two piezoelectric sheets and three electrode layers, without additional materials such as adhesives, which simplifies the production process and is convenient for mass production. After sintering, only one process of processing the through fiber installation hole 107 is required, which is easy to process. In mass production, it is easy to ensure the consistency of product specifications, performance, and parameters. For fiber scanning imaging technology, the good consistency of the actuator is one of the key factors for the mass production of fiber scanners. At the same time, the sheet structure makes the difference in the characteristic frequency values of the actuator in the horizontal and vertical directions very large. When the scanning actuator is used in the raster scanning mode, the vibration coupling of the actuator in the two vibration directions can be greatly reduced.

[0034] The manufacturing process of processing the center hole at the center after integral sintering ensures the symmetry of the overall structure (left-right symmetry, up-down symmetry). The upper and lower double wafers share the electrode, which can maximize the consistency of the upper and lower piezoelectric ceramic sheets on the same side (left or right), ensuring that there is no vertical direction component when it is used for horizontal direction drive.

[0035] At the same time, the existence of the fiber installation hole can effectively reduce the equivalent stiffness of the left and right divided areas of the actuator body, thereby reducing the stress concentration in the divided area, appropriately increasing the horizontal bending amplitude of the double wafer, and reducing power consumption. The fiber installation hole can play a positioning role during fiber assembly and ensure that the fiber is strictly located at the center of the double wafer, effectively avoiding large bending of the double wafer when the fiber is adhesively bonded on the outside, and interference caused by the mismatch of the modulus between the fiber and the ceramic sheet, resulting in non-linear vibration response.

[0036] The electrode layer is an ultra-thin metal conductive layer, generally with a thickness less than 10um.

[0037] Preferably, the upper piezoelectric sheet 103 and the lower piezoelectric sheet 102 are exactly the same in shape and size and completely overlap. The lower electrode layer 101, the middle electrode layer (before processing the optical fiber mounting hole 107), and the upper electrode layer 104 all completely cover the corresponding surfaces of the piezoelectric sheets, so that the scanning actuator can obtain good precise symmetry and ensure that both vertical vibration and horizontal vibration vibrate in a straight line.

[0038] Due to the mutual independence of the left electrode layer and the right electrode layer, correspondingly, as Figure 3 shown, a symmetrically arranged first left driving region 301 and a first right driving region 302 are formed on the left and right sides of the body of the upper piezoelectric sheet 103, and a symmetrically arranged second left driving region 303 and a second right driving region 304 are formed on the left and right sides of the body of the lower piezoelectric sheet 102. The first left driving region and the second left driving region 303 are symmetric up and down, and the first right driving region 302 and the second right driving region 304 are symmetric up and down.

[0039] Preferably, under the drive of the drive signal: the first left driving region 301 and the first right driving region 302 perform a first synchronous and equal-length telescopic action, the second left driving region 303 and the second right driving region 304 perform a second synchronous and equal-length telescopic action, and the first synchronous telescopic action and the second synchronous telescopic action are synchronous, equal-length, and opposite; at the same time, the first left driving region 301 and the second left driving region 303 perform a third synchronous and equal-length telescopic action, the first right driving region 302 and the second right driving region 304 perform a fourth synchronous and equal-length telescopic action, and the third synchronous telescopic action and the fourth synchronous telescopic action are synchronous, equal-length, and opposite.

[0040] Specifically, when the first left driving region 301 and the first right driving region 302 synchronously extend, the second left driving region 303 and the second right driving region 304 synchronously contract, and the above-mentioned extension and contraction amounts are the same, so that the free vibration end moves downward in the vertical direction; conversely, the free vibration end moves upward in the vertical direction; thus, the free vibration end vibrates in the vertical direction. At the same time, when the first left driving region 301 and the second left driving region 303 synchronously extend, the first right driving region 302 and the second right driving region 304 synchronously contract, and the above-mentioned extension and contraction amounts are the same, so that the free vibration end moves to the right in the horizontal direction; conversely, the free vibration end moves to the left in the horizontal direction; thus, the free vibration end vibrates left and right in the horizontal direction. The synthesis of the vibrations in the above two directions realizes the two-dimensional scanning of the free vibration end. When the scanning actuator is used in the raster scanning mode, the vibration in the vertical direction is a low-frequency vibration, and the vibration in the horizontal direction is a high-frequency vibration.

[0041] That is, for the above four driving regions, the movement of each driving region includes two components. One component cooperates with the driving region of the same piezoelectric sheet (the same piezoelectric sheet and on the opposite side), and one component cooperates with the driving region on the same side (the same left side or the same right side and different piezoelectric sheets). Its overall telescopic movement is synthesized by these two components.

[0042] When installing the scanning actuator, it can be installed in a way of fixing the rear end face, or in a way of supporting the rear side. There is no restriction on this.

[0043] As a preferred embodiment, the polarization directions of the upper piezoelectric sheet 103 and the lower piezoelectric sheet 102 are the same. The first left driving region 301 and the first right driving region 302 share the upper electrode layer 104. The second left driving region 303 and the second right driving region 304 share the lower electrode layer 101. The first left driving region 301 and the second left driving region 303 share the left electrode layer. The first right driving region 302 and the second right driving region 304 share the right electrode layer. Further, its driving method is as follows: As Figure 4 shown, the upper electrode layer 104 is connected to the first power signal, the lower electrode layer 101 is connected to the second power signal, the left electrode layer is connected to the first driving signal, and the right electrode layer is connected to the second driving signal. Both the first power signal and the second power signal can be positive power signals or negative power signals, and the first power signal and the second power signal have opposite polarities, which are specifically set according to the polarization directions of the upper piezoelectric sheet 103 and the lower piezoelectric sheet 102. Of course, the above is only a preferred embodiment, and the polarization direction and the corresponding driving signal can be specifically selected according to specific working conditions.

[0044] The driving method of the actuator in the above embodiment will be further described below in combination with the driving signal: When the first driving signal and the second driving signal are the same, the up and down deformation directions of the bimorph structure are opposite, generating bending in the vertical direction to achieve vibration in the vertical direction; when the first driving signal and the second driving signal are out of phase, the left and right deformation directions of the bimorph structure are opposite, generating bending in the horizontal direction to achieve vibration in the horizontal direction. Therefore, both the first driving signal and the second driving signal can adopt a mixed-frequency driving method, so that the double wafer vibrates in the vertical direction and the horizontal direction at different frequencies respectively.

[0045] As an optional specific embodiment, the first driving signal is:

[0046] SIgL = Fy(2πωyt + ΦyL) + Axcsin(2πωxt + ΦxcL) + Axsin(2πωxt + ΦxL),

[0047] The second driving signal is:

[0048] SIgR = Fy(2πωyt + ΦyR) + Axcsin(2πωxt + ΦxcR) + Axsin(2πωxt + ΦxR).

[0049] Axsin(2πωxt + ΦxL) / Axsin(2πωxt + ΦxR) is the high-frequency drive signal in the left-right direction (X direction), which can be a sine wave or other waveforms according to application requirements. Among them, in the ideal case, the difference between ΦxL and ΦxR is 180°. In actual applications, due to processing accuracy, there are slight differences in the response characteristics on the left and right sides of the double wafer. Appropriately adjusting the difference between ΦxL and ΦxR makes the deformations on the left and right sides strictly out of phase, so as to achieve the maximum deformation and the minimum vertical direction component. Ax is the voltage amplitude of the control signals Axsin(2πωxt + ΦxL) and Axsin(2πωxt + ΦxR), ΦxL is the initial phase of the control signal Axsin(2πωxt + ΦxL), and ΦxR is the initial phase of the control signal Axsin(2πωxt + ΦxR).

[0050] Fy(2πωyt + ΦyL) / Fy(2πωyt + ΦyR) is the low-frequency drive signal in the vertical direction (Y direction), which can be a sine wave or other waveforms according to application requirements. In the ideal case, in the SIgL / SIgR signal, this signal component is exactly the same, that is, ΦyR = vyR. In actual applications, due to processing accuracy, there are slight differences in the response characteristics on the upper and lower sides of the double wafer. Appropriately adjusting the difference between ΦyL and ΦyR makes the deformations on the upper and lower sides strictly out of phase, so as to achieve the maximum deformation and the minimum vertical direction component. Fy is the voltage amplitude of the control signals Fy(2πωyt + ΦyL) and Fy(2πωyt + ΦyR), ΦyL is the initial phase of the control signal Fy(2πωyt + ΦyL), and ΦyR is the initial phase of the control signal Fy(2πωyt + ΦyR).

[0051] Axcsin(2πωxt + ΦxcL) / Axcsin(2πωxt + ΦxcR) is the correction signal in the X direction, which is used to correct the Y direction component of the fast axis trajectory to zero so that its trajectory is a closed trajectory. In the ideal case, in the SIgL / SIgR signal, this signal component is exactly the same, that is, ΦxcL = ΦxcR. Axc is the voltage amplitude of the control signals Axcsin(2πωxt + ΦxcL) and Axcsin(2πωxt + ΦxcR), ΦxcL is the initial phase of the control signal Axcsin(2πωxt + ΦxcL), and ΦxcR is the initial phase of the control signal Axcsin(2πωxt + ΦxcR).

[0052] In a second aspect of the embodiments of the present invention, an optical fiber scanning actuator is provided, which includes the scanning actuator as described above and an optical fiber. The optical fiber is fixedly disposed through the optical fiber mounting hole 107, and the light-emitting end of the optical fiber passes through the free vibration end of the scanning actuator to form an optical fiber cantilever 200. The portion of the optical fiber located at the rear side of the optical fiber cantilever 200 is fixedly connected to the scanning actuator.

[0053] It should be noted that the above embodiments illustrate the present invention rather than limit the present invention, and those skilled in the art can design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" or "including" does not exclude the presence of elements or steps not listed in the claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The use of the words first, second, and third, etc. does not denote any order and these words can be interpreted as names.

[0054] All features disclosed in this specification, except for mutually exclusive features, can be combined in any manner.

[0055] Any feature disclosed in this specification (including any additional claims, abstract, and drawings), unless specifically recited, can be replaced by other equivalent or similar-purpose alternative features. That is, unless specifically recited, each feature is only an example of a series of equivalent or similar features.

[0056] The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, as well as any new combination of steps of any new method or process disclosed.

Claims

1. A scanning actuator, characterized in that, it includes an actuator body formed by sintering integrally. The actuator body includes a lower electrode layer, a lower piezoelectric sheet, a middle electrode layer, an upper piezoelectric sheet, and an upper electrode layer arranged in sequence from bottom to top. Taking the extending direction of the piezoelectric sheet as the horizontal plane direction and the front end of the actuator body as the free vibration end, a fiber optic mounting hole penetrating the actuator body in the front-back direction is machined at the center position of the front end face of the actuator body. The fiber optic mounting hole divides the middle electrode layer into independent left and right electrode layers. Both the upper piezoelectric sheet and the lower piezoelectric sheet are polarized in the vertical direction. Driven by a driving signal, the upper piezoelectric sheet and the lower piezoelectric sheet synchronously expand and contract in opposite directions to drive the free vibration end to vibrate in the vertical direction. At the same time, the left side and the right side of the upper piezoelectric sheet and the lower piezoelectric sheet synchronously expand and contract in opposite directions to drive the free vibration end to vibrate left and right in the horizontal direction.

2. A scanning actuator according to claim 1, characterized in that, the upper piezoelectric sheet and the lower piezoelectric sheet have exactly the same shape and size and completely overlap, and the lower electrode layer, the middle electrode layer before the fiber optic mounting hole is machined, and the upper electrode layer all completely cover the corresponding surfaces of the piezoelectric sheets.

3. A scanning actuator according to claim 1 or 2, characterized in that, due to the independence of the left and right electrode layers, a symmetrically arranged first left driving region and a first right driving region are formed on the left and right sides of the body of the upper piezoelectric sheet, and a symmetrically arranged second left driving region and a second right driving region are formed on the left and right sides of the body of the lower piezoelectric sheet. The first left driving region and the second left driving region are symmetrically arranged up and down, and the first right driving region and the second right driving region are symmetrically arranged up and down.

4. A scanning actuator according to claim 3, characterized in that, the first left driving region and the first right driving region perform a first synchronous and equal-length expansion and contraction action, the second left driving region and the second right driving region perform a second synchronous and equal-length expansion and contraction action, and the first synchronous expansion and contraction action and the second synchronous expansion and contraction action are synchronous, equal-length, and in opposite directions; at the same time, the first left driving region and the second left driving region perform a third synchronous and equal-length expansion and contraction action, the first right driving region and the second right driving region perform a fourth synchronous and equal-length expansion and contraction action, and the third synchronous expansion and contraction action and the fourth synchronous expansion and contraction action are synchronous, equal-length, and in opposite directions.

5. A scanning actuator according to claim 4, characterized in that, when the first left driving region and the first right driving region synchronously elongate, the second left driving region and the second right driving region synchronously contract, and the above-mentioned elongation and contraction amounts are the same, so that the free vibration end moves downward in the vertical direction; conversely, the free vibration end moves upward in the vertical direction; thus, the free vibration end vibrates in the vertical direction; at the same time, when the first left driving region and the second left driving region synchronously elongate, the first right driving region and the second right driving region synchronously contract, and the above-mentioned elongation and contraction amounts are the same, so that the free vibration end moves to the right in the horizontal direction; conversely, the free vibration end moves to the left in the horizontal direction; thus, the free vibration end vibrates left and right in the horizontal direction.

6. A scanning actuator as claimed in claim 4 or 5, characterized in that the polarization directions of the upper piezoelectric sheet and the lower piezoelectric sheet are the same, the upper electrode layer is connected to a first power signal, the lower electrode layer is connected to a second power signal, the left electrode layer is connected to a first drive signal, the right electrode layer is connected to a second drive signal, the first power signal and the second power signal can both be a positive power signal or a negative power signal, and the first power signal and the second power signal have opposite polarities.

7. A scanning actuator as claimed in claim 5, characterized in that both the first drive signal and the second drive signal can adopt a mixed-frequency drive mode, so that the bimorph vibrates in the vertical direction and the horizontal direction at different frequencies respectively.

8. A scanning actuator as claimed in claim 7, characterized in that the first drive signal is: SIgL = Fy(2πωyt + ΦyL) + Axcsin(2πωxt + ΦxcL) + Axsin(2πωxt + ΦxL), the second drive signal is: SIgR = Fy(2πωyt + ΦyR) + Axcsin(2πωxt + ΦxcR) + Axsin(2πωxt + ΦxR); Axsin(2πωxt + ΦxL) and Axsin(2πωxt + ΦxR) are high-frequency drive signals in the left-right direction (X direction), Ax is the voltage amplitude of the control signals Axsin(2πωxt + ΦxL) and Axsin(2πωxt + ΦxR), φxL is the initial phase of the control signal Axsin(2πωxt + φxL), ΦxR is the initial phase of the control signal Axsin(2πωxt + ΦxR), where the difference between ΦxL and ΦxR is 180° in the ideal case; in practical applications, due to processing accuracy, there are slight differences in the response characteristics on the left and right sides of the bimorph, and the difference between ΦxL and ΦxR is appropriately adjusted so that the deformations on the left and right sides are strictly out of phase, so as to achieve the maximum deformation amount and the minimum vertical direction component; Fy(2πωyt + ΦyL) and Fy(2πωyt + ΦyR) are low-frequency drive signals in the vertical direction (Y direction), Fy is the voltage amplitude of the control signals Fy(2πωyt + ΦyL) and Fy(2πωyt + ΦyR), φyL is the initial phase of the control signal Fy(2πωyt + ΦyL), ΦyR is the initial phase of the control signal Fy(2πωyt + ΦyR), in the ideal case, in the SigL and SIgR signals, this signal component is exactly the same, that is, ΦyR = ΦyR; in practical applications, due to processing accuracy, there are slight differences in the response characteristics on the upper and lower sides of the bimorph, and the difference between ΦyL and ΦyR is appropriately adjusted so that the deformations on the upper and lower sides are strictly out of phase, so as to achieve the maximum deformation amount and the minimum vertical direction component. Axcsin(2πωxt + ΦxcL) and Axcsin(2πωxt + ΦxcR) are X-direction correction signals, which are used to correct the Y-direction component of the fast-axis trajectory to zero so that its trajectory is a closed trajectory. Axc is the voltage amplitude of the control signals Axcsin(2πωxt + ΦxcL) and Axcsin(2πωxt + ΦxcR). ΦxcL is the initial phase of the control signal Axcsin(2πωxt + ΦxcL), and ΦxcR is the initial phase of the control signal Axcsin(2πωxt + ΦxcR). Ideally, in the SIgL / SIgR signal, this signal component is exactly the same, that is ΦxcL = ΦxcR.

9. An optical fiber scanning actuator, characterized in that, it includes the scanning actuator as described in any one of claims 1-8 and an optical fiber. The optical fiber is fixedly inserted into the optical fiber mounting hole, and the light-emitting end of the optical fiber passes through the free vibration end of the scanning actuator to form an optical fiber cantilever. The part of the optical fiber located behind the optical fiber cantilever is fixedly connected to the scanning actuator.

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