Focus motor, closed-loop control method for a focus motor, and imaging device

Abstract

Embodiments of the present application relate to the technical field of imaging, and disclose a focus motor, a closed-loop control method for a focus motor, and an imaging device. 【Solution means】The focus motor includes a first pole plate (10), a second pole plate (20), a hovering conductor plate (30), a mover holder (40), and a processing unit. The first pole plate (10) and the second pole plate (20) are fixedly installed and arranged perpendicular to the focusing direction. The hovering conductor plate (30) is installed opposite to the first pole plate (10) and the second pole plate (20) respectively. The hovering conductor plate (30) is provided on the mover holder (40). The mover holder (40) is movable in the focusing direction. The projection area between the hovering conductor plate (30) and the first pole plate (10), and the projection area between the hovering conductor plate (30) and the second pole plate (20) both change according to the movement of the mover holder (40). A reference capacitance is formed between the first pole plate (10) and the second pole plate (20). The processing unit controls the movement of the mover holder (40) in the focusing direction based on the reference capacitance.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application is filed based on a Chinese patent application with application number CN202410131895.6 and filing date January 30, 2024, and claims the priority of this Chinese patent application. The entire disclosure of this Chinese patent application is hereby incorporated by reference into this application.

[0002] (Field of the Invention) Embodiments of the present application relate to the technical field of imaging, and particularly to a focus motor, a closed - loop control method for a focus motor, and an imaging device.

Background Art

[0003] Currently, in an imaging device, a camera module usually detects the real - time position of a mover holder in a focus motor during focusing, and adjusts the drive current for driving a lens based on the detected position of the mover holder, so as to adopt a closed - loop control method that enables the mover holder to quickly reach an accurate focus position. In related technologies, a method in which a transmitting electrode plate and a receiving electrode plate are arranged opposite to each other is used. The transmitting electrode plate serves as a mover electrode plate, and its position relative to the receiving electrode plate changes, thereby causing a change in the capacitance between the transmitting electrode plate and the receiving electrode plate, and realizing the position detection of an optical focus motor by the change in capacitance.

[0004] However, in related technologies, it is necessary to reserve sufficient space in advance for designing the transmitting electrode plate and the receiving electrode plate in the focus motor. The requirement for space is high, which is disadvantageous for further reducing the size of the focus motor. Also, it is necessary to install connection wires to realize capacitance detection, and although the mover electrode plate moves constantly to realize the closed - loop control of the focus motor, the connection wires of the mover electrode plate are disadvantageous for the movement of the mover electrode plate, restricting the movement of the mover electrode plate and affecting the accuracy of the closed - loop control of the focus motor.

Summary of the Invention

[0005] The present embodiment aims to provide a focus motor, a closed-loop control method for a focus motor, and an imaging device that can further reduce the dimensions of the focus motor and improve the accuracy of closed-loop control of the focus motor. [Means for solving the problem]

[0006] To solve the above technical problems, an embodiment of the present invention provides a focus motor comprising a first electrode plate, a second electrode plate, a hovering conductor plate, a movable element holder, and a processing unit, wherein the first electrode plate and the second electrode plate are fixedly installed, the first electrode plate and the second electrode plate are arranged perpendicular to the focusing direction, the hovering conductor plate is installed opposite the first electrode plate and the second electrode plate, the hovering conductor plate is provided on the movable element holder, the movable element holder is movable in the focusing direction, the projection region between the hovering conductor plate and the first electrode plate and the projection region between the hovering conductor plate and the second electrode plate both change according to the movement of the movable element holder, a reference capacitance is formed on the first electrode plate and the second electrode plate, and the processing unit controls the movement of the movable element holder in the focusing direction based on the reference capacitance.

[0007] Embodiments of the present invention further provide a closed-loop control method for a focus motor applied to the processing unit of the focus motor described above, the method comprising: obtaining the reference capacitance after the movable element holder has moved in the focusing direction; determining whether the position of the movable element holder coincides with the target position based on the capacitance value of the reference capacitance; and, if they do not coincide, controlling the movable element holder to move again in the focusing direction until it is determined that the position of the movable element holder coincides with the target position.

[0008] The present embodiment further provides an imaging device comprising a lens and the above-described focus motor for driving the lens.

[0009] In some embodiments, the focus motor further comprises a base, magnets, and coils, the base comprising a bottom plate and two side walls along the focusing direction, the coils provided on the two side walls of the base, the magnets provided on both sides of the movable element holder in the focusing direction, each coil provided opposite each magnet, and the movable element holder is driven in the focusing direction by the electromagnetic force between the magnets and the coils.

[0010] In some embodiments, the first electrode plate and the second electrode plate are fixedly installed on the bottom plate, and the hovering conductor plate is provided on the surface of the movable element holder closest to the bottom plate.

[0011] In some embodiments, the first electrode plate is fixedly installed on the bottom plate, the second electrode plate is fixedly installed on one of the side walls, and the hovering conductor plate comprises a first conductor plate and a second conductor plate connected to the first conductor plate, the first conductor plate being provided on the surface of the movable element holder near the bottom plate, and the second conductor plate being provided on the surface of the movable element holder near the second electrode plate.

[0012] In some embodiments, the first electrode plate and the second electrode plate are integrally molded with the base by insert injection molding, and the hovering conductor plate is integrally molded with the movable element holder by insert injection molding.

[0013] In some embodiments, the number of second plates is two, and the two second plates are arranged along the focusing direction.

[0014] In some embodiments, the material of the hovering conductor plate is stainless steel. [Effects of the Invention]

[0015] The technical solution according to the embodiment of the present invention has at least the following advantages.

[0016] In this embodiment, by installing the first and second electrode plates in a fixed arrangement, the problem of the large dimensions of the focus motor caused by the first and second electrode plates being installed facing each other is resolved. In this embodiment, the capacitance between the first and second electrode plates is changed by the jump bridge connection characteristics of the hovering conductor plate with respect to the capacitance signal. Since the distance between the hovering conductor plate and the first and second electrode plates is smaller than the distance between the first and second electrode plates in related technologies, the impact of the installation of the hovering conductor plate on the dimensions of the focus motor is small, which is advantageous for further reduction of the dimensions of the focus motor. Furthermore, the jump bridge connection characteristics of the hovering conductor plate can be realized without providing connection wires, resolving the complexity of the focus motor assembly process and the problem of localized signal linearity degradation caused by connection wires of the movable electrode plates, and improving the accuracy of closed-loop control of the focus motor. [Brief explanation of the drawing]

[0017] One or more embodiments are illustrated by corresponding figures in the drawings, and these illustrative descriptions are not limiting to the embodiments. Elements with the same reference numerals in the drawings are shown as similar elements, and unless otherwise specified, the figures in the drawings do not constitute a limitation on scale. [Figure 1] Figure 1 shows the structure of a focus motor in related technologies. [Figure 2] Figure 2 shows the structure of a focus motor according to one embodiment of the present invention. [Figure 3] Figure 3 shows the principle of the jump bridge connection characteristics of a hovering conductor plate according to one embodiment of the present invention. [Figure 4] Figure 4 shows graphs illustrating the trend of changes in two reference volumes according to one embodiment of the present invention. [Figure 5] Figure 5 shows the structure of a focus motor according to one embodiment of the present invention. [Figure 6]FIG. 6 is a diagram showing the structure of a focus motor according to an embodiment of the present application. [Figure 7] FIG. 7 is a flowchart of a closed-loop control method for a focus motor according to an embodiment of the present application. [Figure 8] FIG. 8 is a flowchart showing a process of determining whether it matches a target position according to an embodiment of the present application.

Embodiments for Carrying Out the Invention

[0018] In order to make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, each embodiment of the present application will be described in detail below with reference to the drawings. However, those skilled in the art can understand that in each embodiment of the present application, many technical details are proposed to enable readers to better understand the present application. However, even if there are no such technical details or various changes and modifications based on the following embodiments, it is still possible to implement the technical solution that the present application intends to protect. The classification of the following embodiments is for convenience and does not constitute any limitation to the specific embodiments of the present application. Each embodiment can be combined and referred to each other on the premise that there is no contradiction.

[0019] As shown in FIG. 1, it is a diagram showing the structure of a focus motor in the related art. In the related art, pole plates 1 and 2 are used as receiving pole plates, pole plate 3 is used as a transmitting pole plate, the transmitting pole plate and the receiving pole plates are installed opposite to each other, and the transmitting pole plate 3 moves along with the mover holder as a mover pole plate to realize the position detection of the optical focus motor. However, in order to realize accurate detection of the position of the focus motor, not only is it necessary to provide a dedicated space in the focus motor for installing the transmitting pole plate 3 and the receiving pole plates 1 and 2 so that the transmitting pole plate 3 has sufficient movement space, but also a sufficient interval is required between the transmitting pole plate 3 and the receiving pole plates 1 and 2, and the requirement for space is high. For this reason, it is necessary to reserve sufficient space in advance for designing the transmitting and receiving pole plates in the focus motor, and it becomes impossible to further reduce the size of the focus motor.

[0020] In the related art, it is necessary to install connection lines to realize the detection of capacitance. In order to realize the closed-loop control of the focus motor, the mover pole plate moves constantly. However, due to the connection lines of the mover pole plate, not only is the assembly process complicated, but the linearity of local signals may deteriorate depending on the position of the connection lines, which affects the accuracy of the closed-loop control of the focus motor.

[0021] To solve the technical problems existing in the related art, such as the large size of the focus motor and the low accuracy of the closed-loop control of the focus motor, an embodiment of the present application relates to a focus motor. This focus motor includes a first pole plate, a second pole plate, a hovering conductor plate, a mover holder, and a processing unit. The first pole plate and the second pole plate are fixedly installed, and the first pole plate and the second pole plate are arranged perpendicular to the focusing direction. The hovering conductor plates are respectively installed opposite to the first pole plate and the second pole plate. The hovering conductor plates are provided on the mover holder, and the mover holder is movable in the focusing direction. The projection area between the hovering conductor plate and the first pole plate, and the projection area between the hovering conductor plate and the second pole plate both change according to the movement of the mover holder. A reference capacitance is formed by the first pole plate and the second pole plate. The processing unit controls the movement of the mover holder in the focusing direction based on the reference capacitance.

[0022] In this embodiment, a first electrode plate and a second electrode plate are fixedly installed and arranged perpendicular to the focusing direction, and a hovering conductor plate is installed opposite the first electrode plate and the second electrode plate. The hovering conductor plate is movable in the focusing direction in accordance with the movable element holder, so that the projected area between the hovering conductor plate and the first electrode plate and the projected area between the hovering conductor plate and the second electrode plate changes, and the capacitance between the projected area of ​​the first electrode plate and the projected area of ​​the second electrode plate changes under the influence of the jump bridge connection characteristics of the hovering conductor plate. As a result, as the hovering conductor plate moves along the movable element holder, the capacitance between the first electrode plate and the second electrode plate tends to change linearly, and the processing unit can determine the position of the movable element holder based on the capacitance between the first electrode plate and the second electrode plate, and control the movement of the movable element holder in the focusing direction to move the movable element holder to the target position.

[0023] In this embodiment, by installing the first and second electrode plates in a fixed arrangement, the problem of the large dimensions of the focus motor caused by the first and second electrode plates being installed facing each other is resolved. In this embodiment, the capacitance between the first and second electrode plates is changed by the jump bridge connection characteristics of the hovering conductor plate with respect to the capacitance signal. Since the distance between the hovering conductor plate and the first and second electrode plates is smaller than the distance between the first and second electrode plates in related technologies, the impact of the installation of the hovering conductor plate on the dimensions of the focus motor is small, which is advantageous for further reduction of the dimensions of the focus motor. In addition, the jump bridge connection characteristics of the hovering conductor plate can be realized without providing connection wires, which resolves the complexity of the focus motor assembly process and the problem of localized signal linearity degradation caused by connection wires of the movable electrode plates, and improves the accuracy of closed-loop control of the focus motor.

[0024] To clarify the purpose, technical concept, and advantages of the embodiments of this application, each embodiment will be described in detail below with reference to the drawings. However, those skilled in the art will understand that many technical details are proposed in each embodiment of this application to help the reader better understand the application. However, even without these technical details and the various changes and modifications based on the embodiments below, it is possible to realize the technical concept that this application seeks to protect.

[0025] One embodiment of the present invention relates to a focus motor, the specific structure of which is shown in Figure 2, and the focus motor includes a first pole plate 10, a second pole plate 20, a hovering conductor plate 30, a movable element holder (not shown), and a processing unit (not shown).

[0026] Specifically, the first electrode plate 10 and the second electrode plate 20 are fixedly installed, the first electrode plate 10 and the second electrode plate 20 are arranged perpendicular to the focusing direction, the hovering conductor plate 30 is installed opposite the first electrode plate 10 and the second electrode plate 20 respectively, the hovering conductor plate 30 is provided on a movable element holder, the movable element holder is movable in the focusing direction, the projection area between the hovering conductor plate 30 and the first electrode plate 10 and the projection area between the hovering conductor plate 30 and the second electrode plate both change according to the movement of the movable element holder, a reference capacitance is formed on the first electrode plate 10 and the second electrode plate 20, and the processing unit controls the movement of the movable element holder in the focusing direction based on the reference capacitance.

[0027] Note that in Figure 2, the number of second electrode plates 20 is set to two, but in actual applications, it may be set to one or more, and is specifically set according to the actual needs. In this embodiment, it is not specifically limited, and in the figure, only two second electrode plates 20 are used as an example for explanation.

[0028] In one embodiment, the first electrode plate 10 is a transmitting electrode plate, and the second electrode plate 20 is a receiving electrode plate. In another embodiment, the first electrode plate 10 is a receiving electrode plate, and the second electrode plate 20 is a transmitting electrode plate. In the following description, the first electrode plate 10 is used as a transmitting electrode plate and the second electrode plate 20 as a receiving electrode plate for illustrative purposes, but this does not limit the scope of protection of the present application.

[0029] Specifically, as the hovering conductor plate 30 moves in the focusing direction following the movable element holder, the projection region between the hovering conductor plate 30 and the first electrode plate 10, and the projection region between the hovering conductor plate 30 and the second electrode plate 20 change, and the capacitance between the projection region of the first electrode plate 10 and the projection region of the second electrode plate 20 changes under the influence of the jump bridge connection characteristics of the hovering conductor plate 30. Figure 3 is a diagram showing the principle of the jump bridge connection characteristics of the hovering conductor plate 30 according to this embodiment. Here, when detecting the reference capacitance between the first electrode plate 10 and the second electrode plate 20, the first electrode plate 10 and the second electrode plate 20 are connected to a peripheral circuit, and the reference capacitance between the first electrode plate 10 and the second electrode plate 20 is measured by charge transfer on that circuit. When a positive voltage signal is applied to the first electrode plate 10, a large amount of positive charge accumulates on the surface of the first electrode plate 10, and negative charge accumulates on the surface of the hovering conductor plate 30 corresponding to the first electrode plate 10. Since the hovering conductor plate 30 has no external circuitry, charge is not transferred, and the charge of one hovering conductor plate 30 itself is conserved at a constant level. As a result, positive charge accumulates on the other surface, i.e., the surface closer to the second electrode plate 20. Consequently, the surface on the second electrode plate 20 side is affected by the positive charge of the hovering conductor plate 30, and negative charge accumulates on its surface, thus achieving a capacitive effect between the two electrodes.

[0030] Therefore, the presence of the hovering conductor plate 30 is equivalent to eliminating the dielectric in the space occupied by the hovering conductor plate 30 between the first electrode plate 10 and the second electrode plate 20, and is equivalent to reducing the distance between the first electrode plate 10 and the second electrode plate 20. As can be seen from the capacitance calculation formula C = εS / 4πkd, where C is capacitance, ε is the dielectric constant of the dielectric, k is the electrostatic force constant, S is the overlapping area of ​​the two electrodes, and d is the perpendicular distance between the two electrodes, the presence of the hovering conductor plate 30 is equivalent to reducing the distance d between the first electrode plate 10 and the second electrode plate 20, and the hovering conductor The capacitance of the plate 30 and a portion of the first electrode plate 10 and a portion of the second electrode plate 20 in the projection area becomes larger. As a result, during the process in which the hovering conductor plate 30 moves along with the movable element holder, the capacitance between the first electrode plate 10 and the second electrode plate 20 exhibits a tendency to change linearly. This allows the processing unit to more easily determine the position of the movable element holder based on the linear change in capacitance between the first electrode plate 10 and the second electrode plate 20, control the movement of the movable element holder in the focusing direction, move the movable element holder to the target position, and improve the accuracy of the closed-loop control of the focus motor.

[0031] Continuing to refer to Figure 2, when the number of second pole plates 20 is set to two, the length of the first pole plate 10 is greater than or equal to the length of the two second pole plates 20, and when there is a gap between the two second pole plates 20, the length of the first pole plate 10 is greater than or equal to the sum of the lengths of the two second pole plates 20 and the gap. Here, the length of the first pole plate 10 and the length of the second pole plates 20 are both lengths in the focusing direction, the width of the first pole plate 10 and the width of the second pole plates 20 are the same, and the shape and size of the two second pole plates 20 are the same. In this case, during the process of moving in the focusing direction following the movable element holder, the area of ​​the projection region between the hovering conductor plate 30 and one of the second pole plates 20 gradually decreases, and the area of ​​the projection region between the hovering conductor plate 30 and the other second pole plate 20 gradually increases, but the area of ​​the projection region between the hovering conductor plate 30 and the first pole plate 10 does not change during movement.

[0032] Therefore, as the hovering conductor plate 30 moves in the focusing direction following the movable element holder, the reference capacitance between the first electrode plate 10 and one of the second electrode plates 20 gradually increases, and the reference capacitance between the first electrode plate 10 and the other second electrode plate 20 gradually decreases. The changing trends of the two reference capacitances are shown in Figure 4, where the horizontal axis is the distance the movable element holder moves in the focusing direction, and the vertical axis is the capacitance value of the reference capacitance. Curve A shows a linear decreasing trend, and curve B shows a linear increasing trend. In this embodiment, two second electrode plates 20 are provided, and the linearly changing capacitance between the first electrode plate 10 and the two second electrode plates 20 enhances the robustness of the capacitance signal and further improves the accuracy of the closed-loop control of the focus motor. At the same time, in this embodiment, by controlling the movable element holder to move to the target position using the two formed reference capacitances, the influence of environmental factors on the acquired capacitance signal is more easily offset, the position of the movable element holder can be controlled more precisely, and the accuracy of the closed-loop control of the focus motor can be improved.

[0033] The focus motor described above may be an electromagnetic motor, a piezoelectric motor, or a shape memory alloy motor, but is not limited to these three types of motors. An electromagnetic motor is a motor that uses the electromagnetic force of a coil and a magnet as the driving force, a piezoelectric motor is a motor that uses the piezoelectric effect of ultrasonic piezoelectric ceramics as the driving force, and a shape memory alloy motor is a motor that uses the deformation characteristics of a memory metal as the driving force.

[0034] In this embodiment, the first electrode plate 10 and the second electrode plate 20 are fixedly arranged, and the capacitance between the first electrode plate 10 and the second electrode plate 20 is changed by the jump bridge connection characteristics of the hovering conductor plate 30 with respect to the capacitance signal. Since the distance between the hovering conductor plate and the first and second electrode plates is smaller than the distance between the first and second electrode plates in related technologies, the impact of the installation of the hovering conductor plate 30 on the dimensions of the focus motor is small, which is advantageous for further reduction of the dimensions of the focus motor. In addition, the jump bridge connection characteristics of the hovering conductor plate 30 can be realized without providing connection wires, eliminating the complexity of the focus motor assembly process and the problem of localized signal linearity degradation caused by connection wires for the movable electrode plates, and improving the accuracy of closed-loop control of the focus motor.

[0035] In one embodiment, the focus motor further comprises a base, a magnet, and a coil. As shown in Figure 5, which illustrates the structure of the focus motor according to this embodiment, the focus motor includes a first pole plate 10, a second pole plate 20, a hovering conductor plate 30, a movable element holder 40, a processing unit (not shown), a base 50, a magnet 60, and a coil 70.

[0036] Specifically, the base 50 comprises a bottom plate 501 and two side walls 502 aligned with the focusing direction, the coils 70 are provided on the two side walls 502 of the base 50, the magnets 60 are provided on both sides of the movable element holder 40 in the focusing direction, each coil 70 is provided opposite each magnet 60, and the movable element holder 40 is driven in the focusing direction by the electromagnetic force between the magnets 60 and the coils 70.

[0037] In this embodiment, the specific connection method between the movable element holder 40 and the base 50 is limited. In this embodiment, the movable element holder 40 is driven in the focusing direction by the electromagnetic force between the magnet 60 and the coil 70. The movable element holder 40 has a large movable stroke, and in this embodiment, it can also function as a motor with a large stroke.

[0038] In one embodiment, the first electrode plate 10 and the second electrode plate 20 are fixedly installed on the base plate 501, and the hovering conductor plate 30 is provided on the surface of the movable element holder 40 that is close to the base plate 501.

[0039] Specifically, regarding the placement of the first electrode plate 10 and the second electrode plate 20 on the base 50, the first electrode plate 10 and the second electrode plate 20 can be directly attached to the corresponding areas on the base 50 and connected to the connection wires inside the motor to enable conductivity. Alternatively, insert injection molding, which incorporates metal parts into plastic parts, can be used to directly injection mold them, saving on the motor assembly process. Alternatively, laser direct molding technology can be used to activate electroplating on a portion of the surface of a plastic part using laser engraving, giving conductivity to the electroplated area and enabling the processing of electrode plates in the corresponding areas of the base 50.

[0040] In one embodiment, the first electrode plate 10 and the second electrode plate 20 are integrally molded with the base 50 by insert injection molding, and the hovering conductor plate 30 is integrally molded with the movable element holder 40 by insert injection molding.

[0041] In related technologies, for a motor with a large stroke, in order to achieve stable motion control, the movable element holder does not use a conductive metal elastic sheet, but always uses non-conductive balls or rail bars to achieve sliding connection between the movable element holder and the housing. In related technologies, the movable element plates are installed on the movable element holder, and as the movable element holder moves, the movable element plates require connecting wires to supply electricity. Therefore, in related technologies, supplying electricity to the movable element plates of a large-stroke motor with balls or rail bars is extremely difficult. Accordingly, in this embodiment, the transmitting and receiving plates can be installed on a fixed base 50 where electrical connection can be easily realized, and the corresponding hovering conductor plate 30 can be installed on the movable element holder 40. The hovering conductor plate 30 can detect the position of the movable element with respect to capacitance without requiring an electrical connection structure, enabling focused closed-loop control, and can be applied to large-stroke motors with balls or rail bars. Accordingly, the movable element holder 40 of this embodiment can be slidably connected to the housing using balls or rail bars to achieve stable motion control. In this embodiment, the housing is a metal housing, installed outside the base, and a ball or rail bar is installed on the metal housing to achieve a sliding connection between the movable element holder 40 and the metal housing.

[0042] In one embodiment, the first pole plate 10 is fixedly installed on the bottom plate 501, and the second pole plate 20 is fixedly installed on one side wall 502. The hovering conductor plate 30 comprises a first conductor plate and a second conductor plate connected to the first conductor plate, the first conductor plate being provided on the surface of the movable element holder 40 closest to the bottom plate 501, and the second conductor plate being provided on the surface of the movable element holder 40 closest to the second pole plate 20. As shown in Figure 6, this figure shows the structure of the focus motor of this embodiment, where the first pole plate 10 and the second pole plate 20 are perpendicular to each other and are provided on the bottom plate 501 and one side wall 502, respectively. On the other hand, the hovering conductor plate 30 has an L-shaped structure and comprises a first conductor plate and a second conductor plate connected to the first conductor plate. The first conductor plate is installed facing the first electrode plate 10, and the second conductor plate is installed facing the second electrode plate 20. Accordingly, the first conductor plate is installed on the surface of the movable element holder 40 closest to the bottom plate 501, and the second conductor plate is installed on the surface of the movable element holder 40 closest to the second electrode plate 20.

[0043] In this embodiment, an alternative method is provided for installing the first electrode plate 10 and the second electrode plate 20 on the base 50, and the same position detection function is achieved by installing the first electrode plate 10 and the second electrode plate 20 on two adjacent curved surfaces.

[0044] In one embodiment, the material of the hovering conductor plate 30 is stainless steel. In other embodiments, the hovering conductor plate 30 may be made of other metals, such as copper, aluminum, and other materials capable of providing conductive properties.

[0045] The above classifications of the components are for illustrative purposes only; in practice, they can be integrated into a single component or divided into several components, and as long as they contain the same logical relationship, they are all within the scope of protection of this patent.

[0046] Another embodiment of the present invention relates to a closed-loop control method for a focus motor applied to the focus motor described above, and as shown in Figure 7, the closed-loop control method for a focus motor includes the following steps.

[0047] Step 101: After the movable element holder moves in the focusing direction, the reference capacitance is obtained.

[0048] Step 102: Based on the capacity value of the reference capacity, determine whether the position of the movable element holder coincides with the target position.

[0049] If they do not match, the process proceeds to step 103, where the output drive current or drive voltage is increased or decreased to control the movement of the movable element holder, and then returns to step 101, where the reference capacitance between the first and second plates is obtained after the movable element holder has moved in the focusing direction, and the determination in step 102 is repeated until it is determined that the position of the movable element holder matches the target position, and then the process proceeds to step 104 to complete the movement of the movable element holder.

[0050] Step 103: Control the movable holder to continue moving by increasing or decreasing the output drive current or drive voltage.

[0051] Step 104: Complete the movement of the movable holder.

[0052] In one embodiment, step 102, which involves determining whether the position of the movable element holder coincides with the target position based on the capacity value of the reference capacity, has specific substeps shown in Figure 8 and specifically includes the following substeps.

[0053] Step 201: Receive the target position required for movement of the movable element holder, which has been transmitted from the host.

[0054] Step 202: Based on the correspondence between previously stored positions and capacity values, the capacity value corresponding to the target position is determined as the target capacity value.

[0055] Step 203: Based on the reference capacity value and the target capacity value, determine whether the position of the movable element holder coincides with the target position.

[0056] Specifically, when there are two second plates, the movement of the movable element holder in the focusing direction can be controlled using the reference capacitances of the first and second plates, and it can be determined whether the movable element holder coincides with the target position using the following methods. In the first method, if the two acquired reference capacitances are the same as the two capacitances between the first plate and the two second plates acquired when the focus motor is in the target position during the pre-adjustment process, the movable element holder coincides with the target position. In the second method, a difference calculation is performed on the two acquired reference capacitances, and if the calculated difference value is the same as the difference value between the two capacitances between the first plate and the two second plates acquired when the focus motor is in the target position during the pre-adjustment process, the movable element holder coincides with the target position. After performing the difference calculation, the difference value can be amplified to increase the robustness of the capacitance signal and make the control of the focus motor more sensitive. In the third method, a calibration value is calculated from the two reference capacitances mentioned above and the two capacitance values ​​between the first pole plate and the two second pole plates when the movable element holder is positioned at the bottom of the focus motor. To offset the influence of environmental factors on the two reference capacitances, the difference between the two reference capacitances is calibrated based on this calibration value. The difference after calibration is then compared with the difference between the two reference capacitances when the focus motor is in the target position during the pre-adjustment process. If the two values ​​are the same, the movable element holder coincides with the target position.

[0057] Specifically, closed-loop control is implemented by a processing unit, which includes a capacitance detection circuit, an analysis and calculation circuit, and a control output circuit. Here, the capacitance detection circuit is used to detect a reference capacitance between the first and second plates, the analysis and calculation circuit is used to determine whether or not to move the movable element based on the acquired reference capacitance, and to determine the drive current or drive voltage required for the movement, and the control output circuit is used to output the calculated drive current or drive voltage to the motor in order to control the movement of the motor's movable element holder.

[0058] Specifically, after controlling the motor's movable element holder to move, the moved movable element holder again changes the reference capacitance between the first and second electrode plates. The processing unit then performs analysis and calculations based on the changed capacitance signal until the current position of the movable element holder matches the target position, and completes the motor control.

[0059] Specifically, in step 202, the correspondence between the pre-stored position and capacity value can be established by the following method. First, the movable element holder is moved to the bottom of the focus motor, and then the movable element holder is moved step by step at a predetermined interval, and the capacity value of the reference capacity after each step and the distance between the movable element holder and the bottom plate of the focus motor after each step are recorded, and the correspondence between the distance between the movable element holder and the bottom plate after each step and the capacity value of the reference capacity is defined as the correspondence between the position and capacity value.

[0060] The division of the steps in each of the above methods is for illustrative purposes only and can be integrated into a single step or divided into several steps in practice, as long as they contain the same logical relationships, and are all within the scope of this patent. In both algorithms and processes, non-essential modifications may be added or non-essential designs may be introduced, but core designs that do not change the algorithm or process are all within the scope of this patent.

[0061] Another embodiment of the present invention relates to an imaging device comprising a lens and the aforementioned focus motor for driving the lens.

[0062] The imaging device according to this embodiment is equipped with the focus motor according to the above embodiment, compared to related technologies, and can similarly achieve the technical effects of the above embodiment, so a detailed explanation is omitted here.

[0063] Those skilled in the art will understand that while the above embodiments are specific examples for realizing the present invention, various modifications can be made to the form and details in actual applications without departing from the spirit and scope of the present application.

Claims

1. It is a focus motor, It includes a first electrode plate, a second electrode plate, a hovering conductor plate, a movable element holder, and a processing unit. The first and second plates are fixedly installed, and the first and second plates are arranged perpendicular to the focusing direction. The hovering conductor plates are installed facing the first electrode plate and the second electrode plate, respectively, and the hovering conductor plates are provided on the movable element holder, the movable element holder is movable in the focusing direction, and the projection area between the hovering conductor plate and the first electrode plate, and the projection area between the hovering conductor plate and the second electrode plate, both change according to the movement of the movable element holder. A reference capacitance is formed in the first electrode plate and the second electrode plate, and the processing unit controls the movement of the movable element holder in the focusing direction based on the reference capacitance. The number of the second plates is two, and the two second plates are arranged along the focusing direction. As the hovering conductor plate moves in the focusing direction in accordance with the movable element holder, the area of ​​the projection region between the hovering conductor plate and one of the second electrodes gradually decreases, and the area of ​​the projection region between the hovering conductor plate and the other of the second electrodes gradually increases, but the area of ​​the projection region between the hovering conductor plate and the first electrode plate remains unchanged. The focus motor further comprises a base, the base comprising a bottom plate and two side walls aligned with the focusing direction, The first electrode plate and the second electrode plate are fixedly installed on the bottom plate, and the hovering conductor plate is provided on the surface of the movable element holder near the bottom plate, or the first electrode plate is fixedly installed on the bottom plate and the second electrode plate is fixedly installed on one of the side walls. The hovering conductor plate comprises a first conductor plate and a second conductor plate connected to the first conductor plate, wherein the first conductor plate is provided on the surface of the movable element holder near the bottom plate, and the second conductor plate is provided on the surface of the movable element holder near the second electrode plate. Neither the first plate nor the second plate is grounded. A focus motor characterized by the following features.

2. The focus motor further comprises a magnet and a coil, The coils are provided on the two side walls of the base, the magnets are provided on both sides of the movable element holder in the focusing direction, and each coil is provided opposite each of the magnets. The movable element holder is driven in the focusing direction by the electromagnetic force between the magnet and the coil. The focus motor according to feature 1.

3. The first electrode plate and the second electrode plate are integrally molded with the base by insert injection molding, and the hovering conductor plate is integrally molded with the movable element holder by insert injection molding. The focus motor according to feature 1.

4. The material of the hovering conductor plate is stainless steel. The focus motor according to feature 1.

5. A closed-loop control method for a focus motor applied to the processing unit of a focus motor according to any one of claims 1 to 4, After the movable element holder moves in the focusing direction, the reference capacitance is acquired. Based on the capacity value of the aforementioned reference capacity, it is determined whether the position of the movable element holder coincides with the target position. If they do not match, the control includes moving the movable element holder again in the focusing direction until it is determined that the position of the movable element holder and the target position match, A closed-loop control method for a focus motor, characterized by the above.

6. Determining whether the position of the movable element holder coincides with the target position based on the capacity value of the aforementioned reference capacity is: Based on the correspondence between pre-stored positions and capacity values, the capacity value corresponding to the target position is determined as the target capacity value. This includes determining whether the position of the movable element holder coincides with the target position based on the capacity value of the reference capacity and the target capacity value, The closed-loop control method for a focus motor according to feature 5.

7. The device comprises a lens and a focus motor according to any one of claims 1 to 4 for driving the lens. An imaging device characterized by the following features.

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