Five-DOF MEMS actuators for autofocus, optical image stabilization, and super-resolution imaging in miniature cameras

Abstract

A MEMS electrostatic actuator providing five degrees of freedom (5-DOF) motion is disclosed. The actuator comprises nested inner, intermediate, and outer MEMS structures. Each structure consists of multiple rotors and stators. The rotors also include multiple movable capacitor electrodes that engage with multiple fixed capacitor electrodes in the stator to provide various translational and rotational motions.

Description

Technical Field

[0001] The present invention relates generally to the field of MEMS electrostatic actuators that provide large forces and are capable of translating and rotating large masses, and more particularly to the field of miniature cameras to enable autofocus (AF) and / or optical image stabilization (OIS) to counteract hand shake, and to achieve zoom with super-resolution imaging. Background Art

[0002] Different types of MEMS electrostatic microactuators have been used to implement autofocus (AF) and optical image stabilization (OIS) for miniature cameras. U.S. Patent US9264591B2 discloses a MEMS electrostatic actuator that implements OIS and AF by providing multiple degrees of freedom (DOF) motion to move the image sensor. The actuator also uses mechanical deflection / springs between the drive comb electrode and the load stage to amplify the rotational stroke and reduce the coupling effect between motions along different axes. This structure, i.e., the elastic deflection between the load and the drive electrode, greatly reduces the electrostatic force acting on the load. When a set of springs (i.e., four mechanical springs) is connected to a single load stage and is responsible for moving the load stage along multiple axes, it also introduces mechanical coupling between different motions. When the drive electrode moves the load along one axis of motion by applying a force transmitted to the load through two springs, the other two springs connected to the load transmit the motion to the other immobile electrodes, and vice versa. This mechanical coupling is undesirable in MEMS actuation.

[0003] Another MEMS electrostatic actuator is used to implement OIS in miniature cameras and is proposed in US patent US 9578217B2. The actuator is able to move the image sensor along the 3-DOF plane, i.e. translation along the x and y axes and rotation around the z axis to achieve OIS. This actuator cannot provide translational motion along the optical axis z to achieve autofocus, which makes it used in compact cameras. Therefore, its benefits are limited because it only provides partial functionality to the camera (only OIS and not AF).

[0004] There is a growing demand for a single actuator that can provide large forces and fully decoupled motion along 3 axes (x, y and z) to enable autofocus, optical image stabilization and super-resolution imaging using a single MEMS actuator. Summary of the invention

[0005] The present invention discloses a 5-DOF electrostatic microactuator capable of providing translational motion along the x, y and z axes and two dual-axis tilting motions around the x and y axes. The actuator utilizes a nested MEMS structure so that the translational motion along each axis is completely decoupled from the motion along the other axes.

[0006] The novel 5-DOF electrostatic microactuator consists of 3 nested MEMS structures. These structures are called internal MEMS structure, intermediate MEMS structure and external MEMS structure. The internal MEMS structure provides in-plane translational motion along the x-axis and holds the load stage. The internal MEMS structure is rigidly attached to the rotor of the intermediate MEMS structure and is mechanically separated from the stator of the intermediate MEMS structure by a groove. Therefore, the internal MEMS structure that holds the target load is considered to be a load that must be moved by the rotor of the intermediate MEMS structure that provides translational motion along the y-axis. Similarly, the intermediate MEMS structure is rigidly attached to the rotor of the external MEMS structure and is mechanically separated from the stator of the external MEMS structure. Therefore, the internal MEMS structure and the external MEMS structure are considered to be loads that need to be moved by the rotor of the external MEMS structure with 3-DOF motion (i.e., translation along the z-axis, and biaxial tilt around the x and y axes).

[0007] The actuator is made using two silicon wafers (upper and lower). The lower part is a silicon-on-insulator (SOI) with an insulating layer that can be used for electrical isolation between the various MEMS structures. The upper structure is a standard silicon wafer. Within the thickness of these wafers are formed the different parts of the 3 MEMS structures.

[0008] The inner MEMS structure consists of an inner stator and an inner rotor. The inner stator includes a base, an electrical insulation layer, an electrical connection layer, fixed comb electrodes, fixed comb support columns, and a binding frame that mechanically connects the rotor of the intermediate MEMS structure to the inner MEMS structure. The inner rotor includes a load table, a mobile comb electrode, which is rigidly connected to each other and attached to the inner stator by a plurality of mechanical springs. The mobile comb electrode is horizontally aligned with the fixed comb electrode in the inner stator along the xy plane.

[0009] The mechanical spring of the internal rotor is designed to be compliant / elastic along the in-plane axis x and high stiffness along the other axes of motion (y and z). When a voltage potential is applied to the fixed and moving comb electrodes in the internal MEMS structure, an electrostatic force is generated between the electrodes, which causes the load table and the internal rotor to translate along the x-axis. The fixed comb electrodes can be divided into two or more fixed comb arrays, allowing them to translate bidirectionally along the x-axis.

[0010] The intermediate MEMS structure consists of an intermediate stator and an intermediate rotor. The intermediate stator includes a base, an electrical insulation layer, an electrical connection layer, a fixed comb support column, a fixed comb electrode, and a bonding frame that mechanically connects the rotor of the external MEMS structure to the intermediate MEMS structure. The intermediate rotor holds the internal MEMS structure and consists of mobile comb electrodes rigidly connected to each other and connected to the intermediate stator through multiple mechanical springs. The mobile comb electrodes of the intermediate rotor are horizontally aligned with the fixed comb electrodes of the intermediate stator along the xy plane.

[0011] The mechanical springs of the middle rotor are designed to be compliant / elastic along the in-plane axis y and have high stiffness along the other axes of motion (x and z). When a voltage potential is applied to the fixed and moving comb electrodes in the middle MEMS structure, an electrostatic force is generated between the electrodes, resulting in the translation of the middle rotor, which holds the entire inner MEMS structure in the y-axis. The fixed comb electrodes in the middle stator can be divided into two or more fixed comb arrays, allowing them to translate bidirectionally along the y-axis.

[0012] The external MEMS structure consists of an external stator and an external rotor. The external stator includes a base, an electrical insulation layer, an electrical connection layer, vertically protruding pillars called pistons, and a bonding frame that mechanically connects the external stator to the external fixed peripheral frame. The pistons can be electrically divided into multiple arrays by the insulation layer to provide translational motion along the z-axis and dual-axis tilting around the x and y axes. The external rotor holds both the internal and intermediate MEMS structures and consists of multiple through holes called tubes that are vertically aligned with the pistons in the external rotor and connected to the external fixed peripheral frame of the actuator through multiple mechanical springs.

[0013] The mechanical springs of the outer rotor are designed to be compliant / elastic along the out-of-plane axis (z) and high stiffness along the in-plane axes (x and y). When a voltage potential is applied across all the piston arrays in the outer stator and all the tubes in the outer rotor, an electrostatic force is generated between the walls of the pistons and the tubes, causing the outer rotor holding the inner and intermediate MEMS structures to translate along the z-axis. When a voltage is applied to only a single piston array, resulting in a voltage difference between the walls of these pistons and the corresponding tubes in the outer rotor, an electrostatic torque is generated, which causes the outer rotor to tilt about the x-axis or y-axis.

[0014] The present invention exhibits many advantages, including complete decoupling between translational motions along three axes (x, y, z). Decoupling between the axes of motion is an important feature of an actuator, which allows for better performance when implementing autofocus and optical image stabilization in compact cameras. Autofocus is achieved by translational motion of the optical element (lens or image sensor) along the optical axis (z), while image stabilization is achieved by in-plane translational motion of the optical element along the x and y axes. Such translations must be completely decoupled from each other to achieve better performance in autofocus and optical image stabilization.

[0015] Another advantage of the invention is the high stiffness of the moving part (rotor) of the actuator structure. The rotor combines a comb drive with a tube that gives the rotor a mesh-like structure. Each moving comb is supported at both ends, which leads to an increased stiffness of the rotor that can resist the impact of high accelerations.

[0016] The present invention also utilizes an electrode configuration that enables a large capacitive area within the compact size of the actuator to generate large forces. The number of moving comb drives or tubes can be increased along the xy plane in each rotor since the moving combs can be viewed as through holes with teeth on the sides, thus similar to the tubes used in the outer rotor structure. These holes can be easily increased in the xy plane of each rotor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In the following, various embodiments will be described in conjunction with the accompanying drawings provided for the purpose of illustrating and not limiting the scope of the claims, wherein like reference numerals denote like elements, and wherein:

[0018] Figure 1A A perspective view of a 5-DOF MEMS electrostatic actuator is shown.

[0019] Figure 1B A top view of a 5-DOF MEMS electrostatic actuator is shown, illustrating the three main internal structures of the actuator.

[0020] Figure 1C Shows Figure 1A An exploded view of the two wafers used to fabricate the actuator is shown.

[0021] Figure 1D Shows Figure 1A An exploded view of the main parts of the three MEMS structures of the actuator is shown.

[0022] Figure 1E An exploded cross-sectional view of a 5-DOF MEMS electrostatic actuator is shown, illustrating the different parts of the actuator.

[0023] Figure 2A An exploded view of the internal MEMS structure of the actuator is shown, showing the internal rotor and stator.

[0024] Figure 2B A cross-sectional view of the internal MEMS structure of the actuator is shown, showing various portions of the internal rotor and stator.

[0025] Figure 2C is a top view showing the translational motion of the inner rotor along the x-axis when a voltage is applied between comb drive electrodes in the inner MEMS structure.

[0026] Figure 3A An exploded view of the intermediate MEMS structure of the actuator is shown, showing the intermediate rotor and stator.

[0027] Figure 3B A cross-sectional view of the intermediate MEMS structure of the actuator is shown, showing various parts of the intermediate rotor and stator.

[0028] Figure 3C is a top view showing the translational motion of the middle rotor along the y-axis when a voltage is applied between the comb drive electrodes in the middle MEMS structure.

[0029] Figure 4A An exploded view of the external MEMS structure of the actuator is shown, showing the external rotor and stator.

[0030] Figure 4B A cross-sectional view of the external MEMS structure of the actuator is shown, showing various parts of the external rotor and stator.

[0031] Figure 4C are front and back perspective views showing the translational motion of the outer rotor along the z-axis when a voltage is applied between the piston and the tube in the outer MEMS structure.

[0032] Figure 4D are front and back perspective views showing the tilting motion of the outer rotor about the x-axis when a voltage is applied between a single array of pistons and tubes in the outer MEMS structure.

[0033] Figure 4E are front and back perspective views showing the tilting motion of the external rotor about the y-axis when a voltage is applied between a single array of pistons and tubes in the external MEMS structure.

[0034] Figure 5 is a perspective view of a 5-DOF MEMS electrostatic actuator showing the three translational motions provided by the three MEMS structures along the x, y, and z axes.

[0035] Figure 6 A perspective view of a 5-DOF MEMS electrostatic actuator with an image sensor.

[0036] Figure 7 is a side view of a camera module incorporating the 5-DOF MEMS electrostatic actuator of the present invention to achieve AF, OIS and super-resolution imaging.

[0037] Figure 8 is a side view of an extended stroke camera module that combines the 5-DOF MEMS electrostatic actuator and the 3-DOF MEMS piston-tube electrostatic actuator of the present invention to achieve AF, OIS, super-resolution imaging, and static and dynamic tilt function correction. DETAILED DESCRIPTION

[0038] exist Figures 1A-1EThe 5DOF MEMS electrostatic microactuator 100 of the present invention is shown in FIG. The actuator is mainly composed of three main MEMS structures nested in each other, namely, an inner MEMS structure 200, an intermediate MEMS structure 300 and an outer MEMS structure 400, see FIG. Figure 1B . The inner MEMS structure can bear the load and provide in-plane translational motion along the x-axis. The middle MEMS structure holds the inner MEMS structure and provides in-plane translational motion along the y-axis. The outer MEMS structure holds the middle and inner MEMS structures and provides out-of-plane translational motion along the z-axis, as well as biaxial tilt around the x and y axes. The three MEMS structures can be interchangeable. In one embodiment of the present invention, the inner MEMS structure is responsible for providing y-axis motion or z-axis motion, the middle MEMS structure is responsible for providing x-axis motion or z-axis motion, and finally the outer structure is responsible for x-axis or y-axis motion.

[0039] The actuator is manufactured by bonding two silicon wafers (lower 110 and upper 120). The lower wafer is preferably a silicon-on-insulator (SOI) wafer with an oxide layer within its thickness to provide electrical insulation between the electrodes of the actuator. The top wafer is a standard silicon wafer. The two wafers form the various parts of the actuator, including the moving part and the fixed part. In other embodiments of the present invention, any other metal or semiconductor material can be used to manufacture the actuator.

[0040] Internal MEMS structure 200 Figure 1D -E and Figure 2A -C. It includes an inner stator 230 and an inner rotor 220, see Figure 1D . Figure 2B The internal stator shown in the figure comprises a stator base 231, an electrical insulation layer 122, an electrical connection layer 121, an array of fixed comb electrodes 223, fixed comb support pillars 232, and a bonding frame 240 that mechanically connects the internal MEMS structure to the rotor of the intermediate MEMS structure. The internal rotor 220 comprises a load table 224, a through hole 225, and the through hole 225 has a moving comb tooth 222 protruding from the wall of the through hole along the xy plane. The walls of the through hole are rigidly connected to each other and are connected to the internal stator by a plurality of mechanical springs 221. The moving comb teeth in the internal rotor are aligned with the fixed comb electrodes along the x-axis along the xy plane in the internal stator.

[0041] The fixed comb support posts are used to align the fixed comb with the moving comb in the rotor along the xy plane and provide an electrical path for the fixed comb. The array of fixed comb electrodes in the internal stator can be grouped into one or more electrode sub-arrays, where the fixed comb electrodes in each group are electrically connected by a thin layer of silicon connection layer 121 and together form a single sub-stator. The electrical insulation layer 122 is used to provide electrical insulation between the individual sub-stators. Ideally, the array should be grouped into two sub-arrays of fixed comb electrodes - two sub-stators - to allow bidirectional translational motion along the in-plane axis (x). If only one fixed comb electrode array is formed, the internal rotor will move in a unidirectional motion along the positive or negative direction of the x-axis.

[0042] When the inner stator is divided into only two sub-stators, the fixed comb teeth in one sub-stator will extend in the opposite direction to the fixed comb teeth in the other sub-stator. This is to enable the rotor to move in both directions.

[0043] The insulating layer can be an oxide layer within the thickness of the SOI wafer, and electrical insulation between different silicon regions can be achieved using deep reactive ion etching (DRIE) of the device layer through trenches that will isolate different silicon regions in the stator layer. A thin layer of silicon can be formed using deep reactive ion etching (DRIE) of the device layer so that the thin layer of silicon remains above the oxide layer of the SOI wafer and is electrically connected between the fixed comb support pillars. Electrical wiring of the internal sub-stator to the external circuit can be accomplished by wire bonding directly on electrical pads that can be created on the top side of the fixed comb.

[0044] The internal rotor structure has high stiffness as it contains through holes from the walls of which the moving fingers extend. Such holes / openings make the rotor structure well connected and rigid to absorb any impact forces that the actuator may be subjected to. It also prevents deformation within the rotor structure so that the electrostatic forces are directly applied to any load placed on the load table. The mechanical springs that hold the internal rotor can be of any design - crab legs, snakes, folding springs, etc. - so that they are compliant along the axis of motion (x in this case) and highly stiff along the other axes (y and z).

[0045] When a voltage signal is applied to the inner rotor (common electrode) and one or more inner sub-stators, an electrostatic force is generated between the active comb and the fixed comb teeth, pushing the inner rotor in the direction of the active sub-stator. Figure 2C The inner rotor is shown translating towards the active sub-stator (shown on the left side of the rotor in the figure) 250. During the movement, the comb teeth of the inner rotor and the comb teeth of the active sub-stator engage 251, while the comb teeth of the inner rotor and the comb teeth of the passive sub-stator disengage 252.

[0046] The inner MEMS structure is rigidly connected to the middle rotor of the middle MEMS structure through the inner bonding frame 240, see Figure 3B , and is mechanically isolated from the stator of the intermediate MEMS structure by grooves 341. This mechanical connection / attachment (between the internal MEMS structure and the intermediate rotor) and mechanical isolation (between the internal MEMS structure and the intermediate stator) completely decouples the motion in the internal MEMS structure and the intermediate MEMS structure. This is because the internal MEMS structure (holding the target load) is considered to be a load rigidly attached to the intermediate rotor. Therefore, any motion within the internal MEMS structure will be affected by the motion of the intermediate rotor and vice versa.

[0047] exist Figure 1D -E and Figure 3A -C shows the middle MEMS structure 300. It includes the middle stator 330 and the middle rotor 320, see Figure 3A .exist Figure 3B The intermediate stator clearly shown in the figure includes a stator base 331, an electrical insulation layer 122, an electrical connection layer 121, an array of fixed comb electrodes 323, fixed comb support pillars 332, and a bonding frame 240 that mechanically connects the internal MEMS structure to the rotor of the intermediate MEMS structure. Similar to the internal rotor design, the intermediate rotor 320 includes a plurality of through holes 325, which have movable comb teeth 322 protruding from the walls of the through holes along the xy plane. The walls of the through holes form a body (i.e., formed from the same wafer) and are connected to the intermediate stator by a plurality of mechanical springs 321. The movable comb teeth in the intermediate rotor are aligned along the xy plane with the fixed comb electrodes in the intermediate stator along the y axis.

[0048] The fixed comb support column 332 is used to align the fixed comb in the intermediate stator with the moving comb in the intermediate rotor along the xy plane and provide an electrical route to the fixed comb in the intermediate stator. The array of fixed comb electrodes in the intermediate stator can be grouped into one or more sub-arrays of fixed comb electrodes, wherein the fixed comb electrodes in each group are electrically connected by a thin layer of silicon - the connecting layer 121 - and together form a single sub-stator. The electrical insulating layer 122 is used to provide electrical insulation between the individual sub-stators. Ideally, the array should be grouped into two sub-arrays of fixed comb electrodes - two sub-stators - to allow for bidirectional translational motion along the in-plane axis (y). If only one column of fixed comb electrodes (one stator) is formed, the intermediate rotor will move unidirectionally in the positive or negative direction of the y-axis.

[0049] When the middle stator is divided into two sub-stators, the fixed comb teeth in one sub-stator will extend in the opposite direction to the fixed comb teeth in the other sub-stator. This is to achieve the bidirectional movement of the middle rotor.

[0050] Since the middle of the rotor of the middle MEMS structure bears the entire inner MEMS structure and the load applied to it, as the load size (target load combined with the mass of the inner structure) gets larger, the mechanical springs that secure the middle rotor to the outer MEMS structure must be stiffer than the inner rotor springs along the axis of motion. This is to ensure that both the inner and middle rotors have similar dynamic performance.

[0051] Similar to the inner rotor, the mid-rotor structure has a high degree of rigidity as it contains through holes and the moving fingers extend from the walls of these holes. Such holes / openings make the structure strong and rigid to absorb any impact forces that the actuator may be subjected to. It also prevents deformation within the rotor structure so that the electrostatic force is directly applied to any load placed on the load table.

[0052] When a voltage signal is applied across the intermediate rotor (common electrode, since all three rotors have the same polarity) and one of the intermediate sub-stators, an electrostatic force is generated between the moving and fixed comb teeth, pushing the intermediate rotor in the direction of the active intermediate sub-stator. Figure 3C shows the direction of the existing source stator (in Figure 3C 3 . The middle rotor is shown in the upper half of the middle MEMS structure) in translational motion 350. During the motion, the comb teeth of the middle rotor engage 351 with the comb teeth of the active middle sub-stator, while the comb teeth of the middle rotor disengage 352 with the comb teeth of the passive sub-stator.

[0053] The external MEMS structure 400 is Figure 1D -E and Figure 4A -C. It includes an external stator 430 and an external rotor 420, see Figure 4A .exist Figure 4B The external stator clearly shown in FIG. 4 comprises a stator base 431, an electrical insulating layer 122, an electrical connection layer 121, an array of pistons 432 protruding vertically along the z-axis, and a bonding frame 440 that mechanically connects the external MEMS structure to an external fixed peripheral frame 441 of the actuator. The external rotor 420 comprises a plurality of through holes 422 formed along the axis z and referred to as tubes. The walls of the tubes are rigidly connected to each other and are attached to the external fixed peripheral frame 441 by a plurality of mechanical springs 421. The tubes in the external rotor are vertically aligned with the pistons in the external stator along the z-axis.

[0054] The pistons in the outer stator can be grouped into one or more piston sub-arrays, where the pistons in each sub-array are electrically connected by a thin layer of silicon-connection layer 121 and together form a single sub-stator. An electrical insulation layer 122 is used to provide electrical insulation between the individual sub-stators. Ideally, the piston array should be grouped into four sub-arrays of fixed comb electrodes - four sub-stators - to achieve dual-axis tilting motion around the in-plane axes (x and y).

[0055] Similar to the inner and middle rotors, the outer rotor structure is highly rigid as it contains through holes (tubes) which make the structure strong and rigid to absorb any impact forces that the actuator may be subjected to. It also prevents deformation within the rotor structure so that the electrostatic forces are applied directly to any load placed on the rotor.

[0056] The intermediate MEMS structure is in turn rigidly attached to the outer rotor of the outer MEMS structure via an intermediate bonding frame 340, see Figure 4B , and is mechanically isolated from the stator of the outer MEMS structure by groove 441. This mechanical connection / attachment (between the intermediate MEMS structure and the outer rotor of the outer MEMS structure) and mechanical isolation (between the intermediate MEMS structure and the outer stator) allows for a complete decoupling between the motion in the intermediate and outer MEMS structures. This is because the intermediate MEMS structure (holding the inner MEMS structure and the target load) is considered to be a load rigidly attached to the outer rotor; therefore any motion within the inner and intermediate MEMS structures is not affected by the motion of the outer rotor, and vice versa.

[0057] When voltage is applied to all / some of the outer sub-stators and the outer rotor, an electrostatic force / torque is generated between the inner wall of the tube in the outer rotor and the wall of the piston in the outer stator. This force or torque drives the outer rotor (holding the entire intermediate and inner MEMS structure together with the target load) in 3-DOF motion, that is, translation along the z-axis 450 (see Figure 4C ), tilted about the x-axis 451 (see Figure 4D ) and tilted about the y-axis 452 (see Figure 4E ).

[0058] As a result, the target load on the load platform of the internal MEMS structure experiences 5-DOF motion provided by the actuator, see Figure 5 : Translational motion 501 along the x-axis provided by the inner MEMS structure, translational motion 502 along the y-axis provided by the middle MEMS structure, and 3 motions (translation 503 along the z-axis and dual-axis tilt around the in-plane axes (x and y)) provided by the outer MEMS structure.

[0059] In one embodiment of the present invention, a 5DOF MEMS electrostatic actuator is used to move the image sensor 600 within a camera module with 5-DOF motion (see Figure 6), to compensate for user hand shake (OIS function), to obtain clearer images by translating the image sensor along the x and y axes and moving along the z axis for autofocus. The actuator's other 2 DOF motion (dual-axis tilt around the x and y axes) can be used to correct unwanted lens tilt due to imperfections in camera components or to enable new camera functions. The image sensor is attached to the load stage inside the rotor of the internal MEMS structure using adhesive. The image sensor can be wire-bonded directly to the PCB board without going through the MEMS actuator structure. Figure 7 A camera module incorporating a 5-DOF MEMS electrostatic actuator is shown. The camera is composed of a housing 701, a flexible / PCB board 703, an image sensor 600, a 5-DOF MEMS actuator 100, and a lens barrel 702. The image sensor 600 is attached to the 5-DOF MEMS actuator 100 using an adhesive, and then the actuator is connected to the flexible / PCB board using an adhesive on the back. In another embodiment, the flexible / PCB board is attached to the MEMS from the front side of the MEMS for wire bonding. The housing includes a lens barrel that is fixed to the flexible / PCB board using an adhesive. In such a camera, the lens barrel can be a large design, and the lens can be made of a heavy material such as glass. This is possible because the lens does not need to move for AF and OIS, so the weight of the optical element is very light. In the present invention, both features (AF and OIS) can be achieved by the movement of the image sensor, which has a small weight.

[0060] Super-resolution imaging can also be achieved by in-plane translation of the image sensor within the camera module, where actuators apply sub-micron motion along the x and y axes to the image sensor to capture many sub-pixel / pixel offset images. These images are then superimposed to create a single high-resolution image. However, this is difficult to achieve while the OIS system is operating due to the difficulty in controlling the same rotors (inner and middle) to achieve both functions (OIS and super-resolution) simultaneously. Therefore, dual-axis tilting of the image sensor actuated using the image sensor's outer rotor can be used to achieve super-resolution, as the tilt of the image sensor produces an image shift. However, this approach is not ideal for achieving super-resolution because the image shift produced by the sensor tilt motion is not uniform across the image.

[0061] Figure 8A camera module capable of simultaneously achieving OIS and super-resolution is shown. The camera combines the 5-DOF MEMS electrostatic actuator 100 of the present invention, the 3-DOF MEMS piston-tube actuator 800 proposed in US10122924B2 (which is incorporated herein by reference), a housing 701, a flexible / PCB board 703, and a lens barrel 702. The 5-DOF MEMS actuator translates the image sensor along the optical axis z to achieve AF, and translates the image sensor along the x and y axes to achieve OIS, while the 3-DOF MEMS piston-tube actuator (which consists of a stator 801 and a rotor 802 that fixes the lens) tilts the lens barrel around the in-plane axis (x and y) to move the image on the image sensor plane with sub-micron motion to achieve super-resolution imaging. In this camera system, the functions of OIS and super-resolution imaging can be achieved using two different actuators, which makes control easier.

[0062] It will be apparent to a person having ordinary skill in the art that the present invention can be modified in many ways without departing from the spirit of the invention. For example, the positions of the inner, middle and / or outer MEMS structures can be changed. Thus, all three MEMS structures are interchangeable, where one structure can be moved to the position of another structure.

[0063] It is obvious to a person having ordinary skill in the art that the present actuator invention can be used as a MEMS sensor. Instead of applying voltage to provide motion, the present invention can be used to read the capacitance of the actuator electrodes in response to, for example, force, acceleration, contact, or any other physical property that can be measured by changes in electrode capacitance.

[0064] The foregoing is considered to be only an example of the principles of the present invention. In addition, since many modifications and changes will be readily apparent to those skilled in the art, it is not desirable to limit the present invention to the exact construction and operation shown and described, and therefore, all suitable modifications and equivalents that fall within the scope of the present invention may be adopted.

[0065] With respect to the above description, it should be recognized that the optimal relationships of the components of the present invention in terms of size, shape, form, material, function and mode of operation, assembly and use are considered to be obvious to those skilled in the art, and all equivalent relationships to those shown in the drawings and described in the specification are intended to be covered by the present invention.

Claims

1. A five-degree-of-freedom (5-DOF) MEMS electrostatic microactuator, comprising: a) an internal MEMS structure comprising an internal stator and an internal rotor, the internal rotor defining an xy plane having an x-axis and a y-axis, and the z-axis being perpendicular to the xy plane, wherein the internal rotor is comprised of a load stage for holding a load and a plurality of mobile internal capacitive electrodes, the plurality of mobile internal capacitive electrodes being attached to the internal stator by a plurality of internal mechanical springs, the internal stator being comprised of a plurality of fixed internal capacitive electrodes, wherein the plurality of mobile internal capacitive electrodes and the fixed internal capacitive electrodes in the internal MEMS structure engage in the presence of a voltage potential, thereby causing the internal rotor holding the load to translate along the x-axis or the y-axis; b) an intermediate MEMS structure comprising an intermediate stator and an intermediate rotor, wherein the inner MEMS structure is rigidly attached to the intermediate rotor of the intermediate MEMS structure, the intermediate rotor consisting of a plurality of mobile intermediate capacitor electrodes attached to the intermediate stator via a plurality of intermediate mechanical springs, the intermediate stator consisting of a plurality of fixed intermediate capacitor electrodes, wherein the plurality of mobile intermediate capacitor electrodes and the fixed intermediate capacitor electrodes in the intermediate MEMS structure engage in the presence of a voltage potential, thereby causing the intermediate rotor holding the inner MEMS structure to translate along the y-axis or the x-axis, and c) an outer MEMS structure comprising an outer stator and an outer rotor, wherein the intermediate MEMS structure is rigidly attached to the outer rotor, the outer rotor consisting of a plurality of mobile outer capacitive electrodes attached to the outer stator by a plurality of external mechanical springs, the outer stator consisting of a plurality of fixed outer capacitive electrodes, wherein the plurality of mobile outer capacitive electrodes and the fixed outer capacitive electrodes in the outer MEMS structure engage in the presence of a voltage potential, thereby causing the outer rotor holding the inner MEMS structure and the intermediate MEMS structure to translate along an axis z and / or to tilt the outer rotor biaxially about the x-axis or y-axis, d) the plurality of mobile inner capacitor electrodes and the plurality of mobile middle capacitor electrodes are arrays of through holes or tubes having a plurality of walls, wherein a plurality of mobile comb drive teeth extend from each of the through holes or tube walls along the xy plane, and e) the plurality of fixed inner capacitor electrodes and the plurality of fixed middle capacitor electrodes are arrays of pistons, wherein a plurality of fixed comb drive teeth extend from a side of each piston along the xy plane and interdigitate with the plurality of moving comb drive teeth of the inner rotor and middle rotor.

2. The five-degree-of-freedom (5-DOF) MEMS electrostatic microactuator according to claim 1, wherein: The plurality of moving external capacitive electrodes of the outer rotor are an array of through holes or tubes, and the plurality of fixed external capacitive electrodes of the outer stator are an array of pistons extending vertically along the z-axis.

3. The five-degree-of-freedom (5-DOF) MEMS electrostatic microactuator according to claim 2, wherein: The inner rotor, the middle rotor and the outer rotor form a common electrode and have a single polarity; wherein the plurality of fixed inner capacitor electrodes, the middle capacitor electrodes and the outer capacitor electrodes are grouped into a plurality of piston arrays; wherein the pistons in each piston array are electrically connected to each other to form a plurality of sub-stators, wherein each sub-stator is electrically insulated from the pistons in other sub-stators, wherein the sub-stators in the inner and middle structures provide bidirectional motion, and the sub-stators in the outer rotor provide translation along the z-axis and / or biaxial tilting motion around the x-axis and the y-axis.

4. The five-degree-of-freedom (5-DOF) MEMS electrostatic microactuator according to claim 1, wherein: The inner MEMS structure is mechanically decoupled from the middle stator by back-etching, and the middle MEMS structure is mechanically decoupled from the outer stator by back-etching.

5. The five-degree-of-freedom (5-DOF) MEMS electrostatic microactuator according to claim 3, wherein: The plurality of sub-stators in the inner MEMS structure, the middle MEMS structure, and the outer MEMS structure are electrically insulated from each other by an insulating layer of the SOI wafer.

6. The five-degree-of-freedom (5-DOF) MEMS electrostatic microactuator according to claim 3, wherein: The pistons in each of the plurality of sub-stators in the inner MEMS structure, the middle MEMS structure, and the outer MEMS structure are electrically connected to each other through a conductive layer.

7. The five-degree-of-freedom (5-DOF) MEMS electrostatic microactuator according to claim 1, wherein: A sensor or optical element is attached to the load stage of the microactuator, the optical element having 5 degrees of freedom of motion provided by the microactuator.

8. A camera module, comprising: a) Five-degree-of-freedom (5-DOF) MEMS electrostatic microactuator, including: i) an internal MEMS structure comprising an internal stator and an internal rotor, the internal rotor defining an xy plane having an x-axis and a y-axis, and the z-axis being perpendicular to the xy plane, wherein the internal rotor is comprised of a load stage for holding a load and a plurality of mobile internal capacitive electrodes, the plurality of mobile internal capacitive electrodes being attached to the internal stator by a plurality of internal mechanical springs, the internal stator being comprised of a plurality of fixed internal capacitive electrodes, wherein the plurality of mobile internal capacitive electrodes and the fixed internal capacitive electrodes in the internal MEMS structure engage in the presence of a voltage potential, thereby causing the internal rotor holding the load to translate along the x-axis or the y-axis; ii) an intermediate MEMS structure comprising an intermediate stator and an intermediate rotor, wherein the inner MEMS structure is rigidly attached to the intermediate rotor of the intermediate MEMS structure, the intermediate rotor consisting of a plurality of mobile intermediate capacitor electrodes attached to the intermediate stator via a plurality of intermediate mechanical springs, the intermediate stator consisting of a plurality of fixed intermediate capacitor electrodes, wherein the plurality of mobile intermediate capacitor electrodes and the fixed intermediate capacitor electrodes in the intermediate MEMS structure engage in the presence of a voltage potential, thereby causing the intermediate rotor holding the inner MEMS structure to translate along the y-axis or the x-axis, and iii) an outer MEMS structure comprising an outer stator and an outer rotor, wherein the intermediate MEMS structure is rigidly attached to the outer rotor, the outer rotor consisting of a plurality of mobile outer capacitive electrodes attached to the outer stator by a plurality of external mechanical springs, the outer stator consisting of a plurality of fixed outer capacitive electrodes, wherein the plurality of mobile outer capacitive electrodes and the fixed outer capacitive electrodes in the outer MEMS structure engage in the presence of a voltage potential, thereby causing the outer rotor holding the inner MEMS structure and the intermediate MEMS structure to translate along an axis z and / or to tilt the outer rotor biaxially about the x-axis or y-axis; b) a circuit board attached to the top or bottom side of the microactuator; c) an image sensor attached to the load stage of the microactuator, wherein the image sensor is wire-bonded directly to the circuit board; d) a housing surrounding the microactuator and the image sensor, and e) a set of optical lenses attached to the housing, The microactuator thereby moves the image sensor in the xy plane along the x-axis and the y-axis to achieve optical image stabilization and / or super-resolution imaging, and translates the image sensor along the optical axis (z) to achieve autofocus.

9. The camera module according to claim 8, wherein: The microactuator tilts the image sensor about an in-plane axis to correct for static and dynamic optical tilt and / or to achieve super-resolution imaging.

10. The camera module according to claim 8, wherein: The wire bonding signals of the image sensor are directed through the microactuator structure.

11. A camera module, comprising: a) Five-degree-of-freedom (5-DOF) MEMS electrostatic microactuator, including: i) an internal MEMS structure comprising an internal stator and an internal rotor, the internal rotor defining an xy plane having an x-axis and a y-axis, and the z-axis being perpendicular to the xy plane, wherein the internal rotor is comprised of a load stage for holding a load and a plurality of mobile internal capacitive electrodes, the plurality of mobile internal capacitive electrodes being attached to the internal stator by a plurality of internal mechanical springs, the internal stator being comprised of a plurality of fixed internal capacitive electrodes, wherein the plurality of mobile internal capacitive electrodes and the fixed internal capacitive electrodes in the internal MEMS structure engage in the presence of a voltage potential, thereby causing the internal rotor holding the load to translate along the x-axis or the y-axis; ii) an intermediate MEMS structure comprising an intermediate stator and an intermediate rotor, wherein the inner MEMS structure is rigidly attached to the intermediate rotor of the intermediate MEMS structure, the intermediate rotor consisting of a plurality of mobile intermediate capacitor electrodes attached to the intermediate stator via a plurality of intermediate mechanical springs, the intermediate stator consisting of a plurality of fixed intermediate capacitor electrodes, wherein the plurality of mobile intermediate capacitor electrodes and the fixed intermediate capacitor electrodes in the intermediate MEMS structure engage in the presence of a voltage potential, thereby causing the intermediate rotor holding the inner MEMS structure to translate along the y-axis or the x-axis, and iii) an outer MEMS structure comprising an outer stator and an outer rotor, wherein the intermediate MEMS structure is rigidly attached to the outer rotor, the outer rotor consisting of a plurality of mobile outer capacitive electrodes attached to the outer stator by a plurality of external mechanical springs, the outer stator consisting of a plurality of fixed outer capacitive electrodes, wherein the plurality of mobile outer capacitive electrodes and the fixed outer capacitive electrodes in the outer MEMS structure engage in the presence of a voltage potential, thereby causing the outer rotor holding the inner MEMS structure and the intermediate MEMS structure to translate along an axis z and / or to tilt the outer rotor biaxially about the x-axis or y-axis; b) an image sensor attached to the load stage; c) a circuit board attached to the top side or the bottom side of the five-DOF MEMS electrostatic microactuator; d) a housing surrounding the five-DOF MEMS electrostatic microactuator and the image sensor; e) a set of optical lenses attached to the housing, and f) a 3-DOF MEMS piston-tube electrostatic microactuator placed around the set of optical lenses, The five-DOF MEMS electrostatic microactuator moves the image sensor along the xy plane to achieve optical image stabilization and translates the image sensor along the z axis to achieve auto focus (AF), and the three-DOF MEMS piston-tube electrostatic microactuator tilts the set of optical lenses around the xy plane to achieve super-resolution imaging and expand the AF range of the camera module.

12. The camera module according to claim 11, wherein: The five-DOF MEMS electrostatic microactuator tilts the image sensor about the xy plane to correct for static and dynamic optical tilt and / or achieve super-resolution imaging.

13. The camera module according to claim 11, wherein: A set of wire bonding signals of the image sensor is directed through the inner MEMS structure, the middle MEMS structure, and the outer MEMS structure of the five-degree-of-freedom MEMS electrostatic microactuator.

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