Camera components that provide optical image stabilization

Abstract

The present application relates to a camera assembly that provides optical image stabilization. A camera assembly includes a support structure and an image sensor mounted on a bracket. The bracket is suspended from the support structure by at least one sliding bearing that allows the bracket and image sensor to move relative to the support structure in any direction lateral to a photosensitive area of ​​the image sensor. An actuator arrangement comprising a plurality of shape memory alloy wires is arranged to move the bracket and image sensor relative to the support structure to provide optical image stabilization of images captured by the image sensor.

Description

[0001] This application is a divisional application of an application filed on October 28, 2016, with application number 201680060899.3 and invention name “Camera assembly providing optical image stabilization”.

[0002] The present invention relates to a camera assembly providing optical image stabilization (OIS).

[0003] In cameras, the purpose of optical isolation (OIS) is to compensate for camera shake—vibration in the camera, typically caused by the user's hand movements, which degrades the quality of the image captured by the image sensor. Mechanical OIS typically involves detecting vibrations via a vibration sensor, such as a gyroscope, and, based on the detected vibrations, controlling an actuator device that adjusts the camera to compensate for the vibrations. Several techniques are known for adjusting camera devices. While OIS performed by processing the captured image is, in principle, possible, it requires significant processing power. Consequently, mechanical OIS has been developed, in which the camera's optical system is mechanically adjusted.

[0004] Many actuator devices using mechanical OIS technology are known and have been successfully implemented in relatively large camera devices such as digital cameras, but miniaturization has been difficult. Cameras have become very common in various portable electronic devices, such as mobile phones and tablets, and miniaturization is important in many of these applications. However, the very tight packaging of components in miniature camera devices makes it difficult to incorporate an OIS actuator into the desired package.

[0005] In one type of mechanical OIS, a camera unit, including an image sensor and a lens system for focusing an image on the image sensor, is tilted relative to the camera assembly's support structure about two imaginary axes that are perpendicular to each other and to the photosensitive area of ​​the image sensor. This type of OIS will be referred to herein as "OIS-tilt." WO-2010 / 029316 and WO-2010 / 089529 each disclose camera assemblies of this type, in which a plurality of shape memory alloy (SMA) actuator wires are arranged to drive the tilt of the camera unit. In such cameras, sufficient clearance needs to be provided to allow tilting of the entire camera unit.

[0006] In another type of mechanical OIS, the lens assembly moves orthogonally to the optical axis of at least one lens. This type of OIS will be referred to herein as "OIS-lens translation". Compared to OIS-tilt, OIS-lens translation has the potential to reduce the overall package size of the camera because only the lens assembly moves and the clearance required for its lateral movement is smaller than the clearance required to tilt the entire camera. WO-2013 / 175197 and WO-2014 / 083318 each disclose a camera assembly of this type, in which a plurality of SMA actuator wires are arranged to drive the movement of the lens arrangement. WO-2013 / 175197 and WO-2014 / 083318 use different suspension systems for the lens assembly, which utilize beams and ball bearings respectively.

[0007] A first aspect of the present invention relates to an alternative camera assembly that can provide OIS using SMA actuator wires.

[0008] According to a first aspect of the present invention, there is provided a camera assembly comprising: a support structure; an image sensor having a photosensitive area, the image sensor being suspended on the support structure in a manner allowing the image sensor to move relative to the support structure in any direction lateral to the photosensitive area of ​​the image sensor; and a plurality of shape memory alloy actuator wires arranged to enable the image sensor to move relative to the support structure in any direction lateral to the photosensitive area of ​​the image sensor when they are selectively actuated.

[0009] Thus, a first aspect of the present invention provides relative movement between an image sensor and a lens assembly disposed in a camera (in which the camera assembly may be included). This relative movement provides OIS in a manner similar to OIS-lens translation. Because the movement is driven by multiple SMA actuator wires, this achieves advantages similar to those described in WO-2013 / 175197 and WO-2014 / 083318. For example, the use of SMA actuator wires facilitates miniaturization compared to other types of actuators and can reduce dimensions along the optical axis compared to OIS-tilt arrangements.

[0010] However, the first aspect of the present invention differs from OIS-lens shift in that the image sensor (rather than the lens assembly) is moved sideways. This provides a number of advantages as follows.

[0011] Moving the image sensor is often more convenient because it is a smaller component than the lens assembly. This facilitates the miniaturization of cameras.

[0012] Furthermore, providing OIS by moving the image sensor can improve the performance of OIS compared to OIS-lens translation. Although the main component of image blur caused by jitter lies in the plane perpendicular to the optical axis, rotation about the optical axis can also cause rotational blur. Since the lens assembly is generally rotationally symmetric about the optical axis, reverse rotation of the lens assembly will not affect this rotation-induced blur. However, the first aspect of the present invention also allows for rotational image stabilization to be provided. That is, the image sensor can be supported on the support structure in a manner that further allows the image sensor to be rotated about an axis orthogonal to the photosensitive area, and a plurality of shape memory alloy actuator wires can be provided in an arrangement that, when selectively driven, can cause the image sensor to rotate about the axis.

[0013] A second aspect of the invention relates to an alternative camera assembly that can provide OIS.

[0014] According to a second aspect of the present invention, a camera assembly is provided, comprising: a support structure; an image sensor mounted on a bracket, the image sensor having a photosensitive area; at least one sliding bearing comprising a bearing surface on each of the bracket and the support structure, the bearing surfaces supporting each other so as to suspend the bracket on the support structure and allow the image sensor to move relative to the support structure in any direction lateral to the photosensitive area of ​​the image sensor; an actuator device arranged to move the image sensor relative to the support structure in any direction lateral to the photosensitive area of ​​the image sensor.

[0015] Thus, a second aspect of the present invention provides relative movement between an image sensor and a lens assembly disposed within a camera (in which the camera assembly may be included). This relative movement provides OIS in a manner similar to OIS-lens shifting. However, the second aspect of the present invention differs from OIS-lens shifting in that the image sensor (rather than the lens assembly) is moved laterally relative to the photosensitive area of ​​the image sensor. This provides a number of advantages, as follows.

[0016] Moving the image sensor is often more convenient because it is a smaller component than the lens assembly. This facilitates the miniaturization of cameras.

[0017] Furthermore, providing OIS by moving the image sensor can improve the performance of OIS compared to OIS-lens translation. Although the main component of image blur caused by jitter lies in the plane perpendicular to the optical axis, rotation about the optical axis can also cause blur. Since one or more lenses of a lens assembly are typically rotationally symmetric about the optical axis, reverse rotation of the lens assembly will not have an effect on such rotation-induced blur. However, the second aspect of the present invention also allows for rotational image stabilization to be provided. That is, the image sensor can be supported on the support structure in a manner that further allows the image sensor to rotate about an axis orthogonal to the photosensitive area, and a plurality of shape memory alloy actuator wires can be provided in an arrangement that, when selectively driven, enables the image sensor to rotate about the axis.

[0018] To suspend the carriage from the support structure and allow movement of the image sensor relative to the support structure in any direction lateral to the photosensitive area of ​​the image sensor, a second aspect of the present invention utilizes at least one sliding bearing. The at least one sliding bearing comprises bearing surfaces on each of the carriage and the support structure, the bearing surfaces supporting each other. A sliding bearing is a bearing comprising two bearing surfaces supporting each other, allowing relative sliding motion. While sliding bearings are a simple type of bearing known for other applications, friction within the bearing inevitably negatively impacts performance, particularly in micro-devices.

[0019] Surprisingly, however, it is actually possible to provide good performance using plain bearings, where friction is low enough to allow lateral movement. Particular advantages are achieved where the actuator arrangement comprises multiple SMA actuator wires, as SMAs provide high actuation forces compared to other forms of actuators, which helps to overcome the friction in plain bearings.

[0020] Furthermore, this type of suspension of the at least one plain bearing in the second aspect of the invention offers the following specific advantages.

[0021] Firstly, the plain bearing can be formed to have inherently small dimensions along the height of the bearing (i.e. along the optical axis), particularly compared to suspension systems employing balls. Compared to the use of ball bearings, such as disclosed in WO-2014 / 083318, the plain bearing allows the dimensions of the suspension to be reduced along the optical axis.

[0022] Secondly, image sensors generate a significant amount of heat. Therefore, it is desirable to attach the image sensor to other components that act as heat sinks to allow this heat to be dissipated. This reduces the temperature rise of the image sensor and the thermal degradation caused by self-heating of the image sensor.

[0023] One way to dissipate the generated heat is to attach a heat sink to the image sensor and move both the image sensor and the heat sink. However, this is undesirable, particularly in miniature cameras, because it requires moving both the heat sink and the image sensor, which can increase the size and / or power consumption of the camera assembly.

[0024] At least one plain bearing not only suspends the image sensor and allows it to move, but also facilitates heat transfer from the image sensor to the support structure. This is because the bearing surfaces on each of the bracket and support structure support each other, thus providing a continuous area of ​​thermally conductive material without air gaps. This provides a path with good thermal conductivity to dissipate heat from the image sensor and provides the necessary suspension.

[0025] Each bearing surface may be planar. This improves the thermal conductivity of planar bearings by providing a relatively large area of ​​contact.

[0026] A fluid (such as grease) can be placed between the bearing surfaces. This can improve the thermal conductivity of the flat bearing, especially if the fluid is chosen to have a high thermal conductivity.

[0027] The two aspects of the present invention can be used in combination. In this case, the preferred features of these two aspects can be applied together in any combination.

[0028] Both aspects of the invention offer particular advantages when applied to camera assemblies for miniature cameras, for example where the light-sensitive area of ​​the image sensor has a diagonal length of at most 12 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] For a better understanding, embodiments of the invention will now be described by way of non-limiting examples with reference to the accompanying drawings, in which:

[0030] Figure 1 is a schematic cross-sectional view of a camera device including a camera assembly;

[0031] Figure 2 is a cross-sectional view of the camera assembly;

[0032] Figure 3 is a perspective view of a moving plate of a bracket of a camera assembly;

[0033] Figure 4 is a top plan view of the camera assembly;

[0034] Figures 5 to 7 is a cross-sectional view of an alternative plain bearing that may be used in camera assemblies; and

[0035] Figures 8 to 11It is a plan view of the contact area of ​​the sliding bearing of the camera assembly.

[0036] exist Figure 1 FIG. 1 shows a camera device 1 including an OIS sensor translation camera assembly 2 according to the present invention, Figure 1 is a cross-sectional view taken along the optical axis O. The camera device 1 is to be incorporated into a portable electronic device such as a mobile phone or a tablet computer. Therefore, miniaturization is an important design criterion.

[0037] exist Figures 2 to 4 The camera assembly 2 is shown in detail in FIG. Figure 2 is a side view of the camera assembly 2, Figure 3 is a perspective view of the moving plate 9 of the bracket 8 of the camera assembly 2; and Figure 4 is a plan view of the camera assembly 2. For clarity, Figure 2 and Figure 4 The bending piece 67 described below is omitted. The camera assembly 2 can be manufactured first and then assembled with the other components of the camera device 1.

[0038] The camera assembly 2 includes a support structure 4 on which is supported an image sensor 6 having a photosensitive area 7. An optical axis O is orthogonal to the photosensitive area 7. The image sensor 6 captures images and can be of any suitable type, such as a CCD (charge coupled device) or a CMOS (complementary metal oxide semiconductor) device. Conventionally, the image sensor 6 has a rectangular photosensitive area 7. Without limiting the present invention, in this example, the camera device 1 is a miniature camera, in which the photosensitive area 7 of the image sensor 6 has a diagonal length of at most 12 mm.

[0039] The image sensor 6 is mounted on a bracket 8 including a moving plate 9. The moving plate 9 may be formed of a sheet material, which may be a metal, for example steel, such as stainless steel. Figure 3 6, which is shown separately and includes a bend 67 described in more detail below.

[0040] Although the carriage 8 includes a single moving plate 9 in this example, the carriage 8 may alternatively include other layers that may be attached or laminated with the moving plate 9 .

[0041] The support structure 4 comprises a support plate 5 which may be formed from a sheet material, which may be a metal, for example steel, such as stainless steel.

[0042] Although the support structure 4 comprises a single support plate 5 in this example, the support structure 4 may alternatively comprise further layers that may be attached or laminated with the support plate 5 .

[0043] The support structure 4 further comprises an edge portion 10 fixed to the front side of the support plate 5 and extending around the support plate 5. The edge portion 10 has a central aperture 11.

[0044] The support structure 4 further comprises an IC (Integrated Circuit) chip 30 and a gyro sensor 31 fixed on the rear side of the support plate 5. In the IC chip 30 a control circuit is implemented which is described further below.

[0045] The moving plate 9 is suspended together with the image sensor 6 on the support structure 4 in such a way that the image sensor 6 is allowed to move in any direction lateral to the photosensitive area 7 of the image sensor 6 (i.e. lateral to the optical axis O and parallel to the plane in which the photosensitive area 7 extends) and also to rotate about the optical axis O. In the example shown, the moving plate 9 is suspended on the support structure 4 by a suspension system in the form of a sliding bearing 100 arranged between the support plate 5 and the moving plate 9, which will now be described.

[0046] In this example, the sliding bearing 100 includes a first bearing surface 101 on the carriage 8 (specifically, the lower surface of the moving plate 9) and a second bearing surface 102 on the support structure 4 (specifically, the upper surface of the support plate 5). In this example, the bearing surfaces 101 and 102 are each planar. The bearing surfaces 101 and 102 support each other and thereby suspend the carriage 8 on the support structure 4. Because the bearing surfaces 101 and 102 can slide relative to each other, they allow the image sensor 6 to move in any direction lateral to the photosensitive area 7 of the image sensor 6 and also allow the image sensor to rotate about the optical axis O.

[0047] Sliding bearing 100 not only suspends image sensor 6 but also facilitates heat transfer from image sensor 6 to support structure 4. This is because bearing surfaces 101 and 102 provide a continuous area of ​​thermally conductive material without air gaps. This provides a path with good thermal conductivity to dissipate heat from image sensor 6 and provides the necessary suspension. This allows support structure 4 to act as a heat sink for image sensor 6.

[0048] By forming the moving plate 9 and the support plate 5 from a material having a high thermal conductivity, such as metal, heat transfer from the image sensor 6 is further facilitated.

[0049] Figures 5 to 7 Some alternative configurations of the sliding bearing 100 are shown, in which a bearing member is used which provides at least one of the bearing surfaces 101 and 102 , instead of the bearing surfaces 101 and 102 being the surfaces of the moving plate 9 and the support plate 5 .

[0050] exist Figure 5In an alternative embodiment, the bearing 100 comprises a bearing member 104 fixed to the moving plate 9 . Thus, the first bearing surface 101 is the lower surface of the bearing member 104 and the second bearing surface 102 is the upper surface of the support plate 5 .

[0051] exist Figure 6 In an alternative embodiment, the bearing 100 comprises a bearing member 105 fixed to the support plate 5 . Thus, the first bearing surface 101 is the lower surface of the moving plate 9 and the second bearing surface 102 is the upper surface of the bearing member 105 .

[0052] exist Figure 7 In an alternative embodiment, the bearing 100 includes a bearing member 106 fixed to the moving plate 9 and a bearing member 107 fixed to the support plate 5. Therefore, the first bearing surface 101 is the lower surface of the bearing member 106, and the second bearing surface 102 is the upper surface of the bearing member 107.

[0053] In the case of using one or more bearing members, the one or more bearing members may be fixed to the moving plate 9 or the support plate 5 by an adhesive.

[0054] Where one or more bearing members 104 to 107 are used, the or each bearing member 104 to 107 separates the moving plate 9 and the support plate 5 and the thickness of the or each bearing member 104 to 107 is selected accordingly.

[0055] An advantage of using one or more bearing members 104 to 107 is that the material of the bearing members may be selected to improve bearing performance, such as having reduced wear and / or a reduced coefficient of friction.

[0056] In the example shown, a single sliding bearing 100 is provided between the support plate 4 and the bracket 8. In this example, the sliding bearing 100 has the same Figure 8 A rectangular contact area 110 between the bearing surfaces 101 and 102 is shown in FIG together with the bracket 8. In general, however, the contact area may vary and / or a plurality of plain bearings 100 may be provided.

[0057] Figures 9 to 11 The contact area 110 is shown in some alternative, non-limiting, alternative arrangements of the sliding bearing 100 .

[0058] In the case of providing a single sliding bearing 100, the contact area 110 of the sliding bearing 100 may have a shape other than a rectangle. For example, the contact area 110 may have a shape such as Figure 9 A rounded shape is shown, which may be easier to manufacture and / or help provide balanced bearing contact.

[0059] The alternative of providing multiple plain bearings 100 may aid in manufacturing and / or help provide a balanced bearing contact. Typically, at least three plain bearings may be used to provide a stable contact. Figure 10 An example is shown comprising four plain bearings 100 having rounded contact areas 110 located in the corners of the bracket 8 .

[0060] Advantageously, each is composed of one or more bearing members 104 to 107 (as in the above Figures 5 to 7 A plurality of plain bearings 100 formed in any of the examples of FIG. 10A and FIG. 10B may be provided with channels between the bearing members 104 to 107. These channels may collect wear particles. Figure 11 An example of this type is shown comprising six sliding bearings 100 having rectangular contact areas 110 in a regular rectangular array with channels 111 provided between them.

[0061] The total contact area of ​​the bearing surfaces 101 and 102 of the sliding bearing 100 (or the total area of ​​all sliding bearings 100 if more than one sliding bearing is provided) is selected to control friction and thermal conductivity. Generally, there is a balance between reducing friction by minimizing the total area and increasing thermal conductivity by maximizing the total area.

[0062] Surprisingly, the use of one or more plain bearings 100 as bearings with sufficiently low friction to allow movement perpendicular to the optical axis O can actually provide good performance, taking into account the forces applied by the SMA actuator wire 40. When the plain bearings 100 maintain a relatively high total contact area on the bearing surfaces 101 and 102, the effects of wear over time are reduced compared to bearings with point or line contact.

[0063] Regarding thermal conductivity, the total contact area of ​​bearing surfaces 101 and 102 of sliding bearing 100 is selected to be sufficiently large relative to the size of image sensor 6 so that the heat generated thereby can be removed by thermal conductivity. Typically, the total contact area may be at least 0.2 times, and preferably at least 0.5 times, the area of ​​photosensitive area 7 of image sensor 6. The total contact area may even be larger than photosensitive area 7 of image sensor 6 or larger than the overall size of image sensor 6. To achieve this, bracket 8 may be arranged to have a larger overall size than image sensor 6.

[0064] The material properties of the bearing surfaces 101 and 102 are selected to provide a low friction and low wear plain bearing.

[0065] With regard to reducing friction, bearing surfaces 101 and 102 may be designed to have a coefficient of friction of 0.2 or less.

[0066] Each bearing surface 101 and 102 may be made of the same material as the element on which it is formed, such as the support plate 5, the moving plate 9 or the bearing members 104 to 107. The material may be selected to provide suitable properties.

[0067] Where bearing members 104 to 107 are provided, their material may be selected to provide suitable properties. As non-limiting examples, where used, bearing members 104 to 107 may be made of a polymer such as nylon, polytetrafluoroethylene (PTFE) (e.g., Teflon), acetal (e.g., Delrin), or ultra-high molecular weight polyethylene (UHMWPE).

[0068] Alternatively, the bearing surfaces 101 and 102 may be coated with a material selected to provide suitable properties. Where a coating is used, the coating may have lower friction and / or lower wear than the material of the element being coated (e.g., the support plate 5, the moving plate 9, or the bearing members 104 to 107). As non-limiting examples, where used, the coating may be made of a polymer such as nylon, polytetrafluoroethylene (PTFE) (e.g., Teflon), acetal (e.g., Delrin), or ultra-high molecular weight polyethylene (UHMWPE).

[0069] As shown in the illustrated example, fluid 103 may be disposed between bearing surfaces 101 and 102. The material properties of fluid 103 (if provided) are selected to provide lubrication between bearing surfaces 101 and 102, such that the coefficient of friction between bearing surfaces 101 and 102 is reduced and / or to have a thermal conductivity that improves thermal contact between bearing surfaces 102 and 103. For example, fluid 103 may be grease.

[0070] However, fluid 103 is optional. As an alternative to providing fluid 103, bearing surfaces 101 and 102 may be in direct contact. Depending on the material properties of bearing surfaces 101 and 102 and / or the coatings thereon, direct contact may provide sufficient thermal contact and friction coefficient.

[0071] In addition, the camera assembly 2 includes two flexures 67 connected between the support structure 4 and the bracket 8 to act as biasing devices that bias the bearing surfaces 101 and 102 together and provide electrical connection to the image sensor 6. In this example, the flexures 67 are integrally formed with the moving plate 9 at one end 68 thereof and are mounted to the support plate 5 of the support structure 4 at the other end 69 thereof. Alternatively, the flexures 67 can be integrally formed with the plate of the support structure 4 and mounted to the bracket, or can be separate elements mounted to each of the support structure 4 and the bracket 8. In any of these examples, the mounting of the flexures 67 can be achieved by welding, which provides both mechanical and electrical connections.

[0072] The flexures 67 are arranged as follows to provide their mechanical function. Each flexure 67 is an elongated beam connecting the support structure 4 and the bracket 8. Due to their inherent elasticity, the flexures 67 bias the support structure 4 and the bracket 8 together, with the biasing force applied parallel to the optical axis O. This maintains contact between the bearing surfaces 101 and 102 of the sliding bearing 100. At the same time, the flexures 67 can deflect laterally to allow lateral movement and rotation of the image sensor 6 relative to the support structure 4, thereby enabling OIS functionality.

[0073] Also due to its inherent resiliency, the flexure 67 also provides a lateral biasing force that biases the image sensor 6 toward a central position aligned with the optical axis O of the lens assembly 20 from any direction about that central position. As a result, the image sensor 6 will tend toward the central position in the absence of actuation of the SMA actuator wires 40. This ensures that the camera device 1 functions to capture images even in the absence of actuation of the SMA actuator wires 40.

[0074] The flexures 67 are designed as follows to provide suitable retention force for the sliding bearing 100 along the optical axis O while also allowing lateral movement using a lateral biasing force. The magnitude of the lateral biasing force is kept low enough so as not to interfere with the OIS, while being high enough to center the image sensor 6 without actuation. Each flexure 67 has a cross-section having an average width perpendicular to the optical axis O that is greater than its average thickness parallel to the optical axis O. Each flexure 67 extends in an L-shape about the optical axis O, and it is generally desirable that the angular range measured between the ends of the flexure 67 is at least 90°.

[0075] In the assembled state of the camera assembly 2 , the flexure 67 is deflected from its relaxed state to provide a preload force that biases the support structure 4 and bracket 8 together.

[0076] The bending piece 67 is made of a suitable material that provides the desired mechanical properties and is electrically conductive. Typically, the material is a metal with a relatively high yield, such as steel, such as stainless steel.

[0077] In addition, flexure 67 supports electrical traces connected to at least image sensor 6. In this way, flexure 67 provides an electrical function as well as a mechanical function. This avoids the need for a separate electrical connection to image sensor 6, which would otherwise hinder the movement of image sensor 6 during OIS.

[0078] Although in this example the mobile plate 9 is suspended from the support structure 4 by a suspension system in the form of sliding bearings 100, any other type of suspension system may be provided according to the first aspect of the present invention. For example, a suspension system employing a plurality of beams extending parallel to the optical axis O, such as the suspension system for suspending a lens assembly disclosed in WO-2013 / 175197, or a suspension system employing ball bearings, such as the suspension system for suspending a lens assembly disclosed in WO-2014 / 083318.

[0079] The movement of the image sensor 6 relative to the support structure 4 is arranged as follows and is Figure 4 The actuator device, which is most easily seen in the figure, is driven. The actuator device is formed by a total of four SMA actuator wires 40 connected between the support structure 4 and the bracket 8. To attach the SMA actuator wires 40, the bracket 8 includes a crimping portion 41 fixed to the moving plate 9, and the support structure 4 includes a crimping portion 42 fixed to the edge portion 10. The crimping portions 41 and 42 crimp the four SMA actuator wires 40 to connect them to the support structure 4 and the bracket 8. The crimping portion 41 fixed to the moving plate 9 is integrally formed from a metal sheet to electrically connect the SMA actuator wires 40 together at the bracket 8.

[0080] Although the crimping portions 41 and 42 are separate elements fixed to the moving plate 9 and the edge portion 10 in this example, the crimping portion 41 may alternatively be formed integrally with the moving plate 9 and / or the crimping portion 42 may be formed integrally with the support plate 5 .

[0081] The SMA actuator wires 40 are arranged such that when selectively actuated they can move the image sensor 6 relative to the support structure 4 in any direction lateral to the photosensitive area 7 of the image sensor 6 and can also rotate the image sensor 6 about the optical axis O.

[0082] Each of the SMA actuator wires 40 is held in tension, thereby exerting a force between the support structure 4 and the bracket 8 .

[0083] The SMA actuator wires 40 may be perpendicular to the optical axis O such that the force applied to the bracket 8 is lateral to the photosensitive area 7 of the image sensor 6. Alternatively, the SMA actuator wires 40 may be tilted at a small angle relative to the photosensitive area 7 of the image sensor 6 such that the force applied to the bracket 8 includes a component lateral to the photosensitive area 7 of the image sensor 6 and a component along the optical axis O that acts as a biasing force that biases the bearing surfaces 101 and 102 of the sliding bearing 100 together.

[0084] The overall arrangement of SMA actuator wires 40 will now be described, which are similar to those described in WO-2014 / 083318 except that they are connected to the bracket 8 for moving the image sensor 6 rather than to the lens assembly 20 .

[0085] SMA materials have the property of undergoing a solid-state phase transition when heated, which causes the SMA material to contract. At low temperatures, the SMA material enters the martensite phase. At high temperatures, the SMA enters the austenite phase, inducing deformation that causes the SMA material to contract. Due to the statistical distribution of transition temperatures in the SMA crystal structure, phase transitions occur within a certain temperature range. Therefore, heating the SMA actuator wires 40 causes them to decrease in length.

[0086] The SMA actuator wire 40 can be made of any suitable SMA material, such as Nitinol or another titanium alloy SMA material. Advantageously, the material composition and pre-treatment of the SMA actuator wire 40 are selected to provide a phase change within a temperature range that is above the expected ambient temperature during normal operation and is as wide as possible to maximize the degree of position control.

[0087] When one of the SMA actuator wires 40 is heated, the stress in that wire increases and it contracts, causing the image sensor 6 to move. This movement occurs as the temperature of the SMA increases within the temperature range where the SMA material undergoes a phase transition from martensite to austenite. Conversely, when one of the SMA actuator wires 40 is cooled to reduce the stress therein, the wire expands under the force of the opposing SMA actuator wire 40. This causes the image sensor 6 to move in the opposite direction.

[0088] The bracket 8 and the image sensor 6 are axially positioned within an aperture 11 of an edge portion 10 of the support structure 4. Four SMA actuator wires 40 are arranged on four sides of the image sensor 6. The SMA actuator wires 40 have the same length and have a rotationally symmetric arrangement.

[0089] When viewed in the axial direction, the first pair of SMA actuator wires 40 are parallel to the first axis ( Figure 4 The first axis extends in a vertical direction in the image sensor 6, the first axis being lateral to the photosensitive area 7 of the image sensor 6. However, the first pair of SMA actuator wires 40 are oppositely connected to the support structure 4 and the bracket 8 so that the first pair of SMA actuator wires 40 are in opposite directions along the first axis (in the vertical direction in the image sensor 6). Figure 4 In the case of equal tension in each SMA actuator wire 40, the forces applied by the first pair of SMA actuator wires 40 are balanced. This means that the first pair of SMA actuator wires 40 applies a first torque ( Figure 4 counterclockwise in ).

[0090] When viewed in the axial direction, the second pair of SMA actuator wires 40 are parallel to the second axis ( Figure 4 The second axis extends in a horizontal direction in the image sensor 6, which is lateral to the photosensitive area 7 of the image sensor 6. However, the second pair of SMA actuator wires 40 are oppositely connected to the support structure 4 and the bracket 8 so that the second pair of SMA actuator wires 40 are in the opposite direction (in the horizontal direction in the image sensor 6) along the second axis. Figure 4 With equal tension in each SMA actuator wire 40, the forces applied by the second pair of SMA actuator wires 40 balance. This means that the second pair of SMA actuator wires 40 applies a second torque ( Figure 3 The second torque is arranged to be opposite to the first torque. Therefore, if the tension in each SMA actuator wire 40 is the same, the first torque and the second torque are balanced.

[0091] As a result, the SMA actuator wires 40 can be selectively driven to move the image sensor 6 laterally in any direction and to rotate the image sensor 6 about the optical axis O. That is:

[0092] Movement of the image sensor 6 in either direction along the first axis may be achieved by driving the first pair of SMA actuator wires 40 to contract differentially (as they apply forces in opposite directions);

[0093] • Movement of the image sensor 6 in either direction along the second axis may be achieved by driving the second pair of SMA actuator wires 40 to contract differentially (as they apply forces in opposite directions); and

[0094] • Rotation of the image sensor 6 may be achieved by driving the first pair of SMA actuator wires 40 and the second pair of SMA actuator wires 40 to contract differentially (because the first torque and the second torque are opposite).

[0095] The amount of movement and rotation range depends on the geometry and the range of contraction of the SMA actuator wire 40 within its normal operating parameters.

[0096] This particular arrangement of the SMA actuator wires 40 is advantageous because it allows the desired lateral movement and rotation to be driven with a minimum number of SMA actuator wires. However, other arrangements of the SMA actuator wires 40 may be employed. To provide three degrees of motion (two lateral degrees of motion and one degree of rotational motion), a minimum of four SMA actuator wires 40 are provided. Other arrangements may employ different numbers of SMA actuator wires 40. Fewer SMA actuator wires 40 may be provided to provide lateral movement but not rotation. Arrangements with more than four SMA actuator wires 40 are also possible and may have the advantage of allowing control of additional parameters besides motion, such as the degree of stress in the SMA actuator wires 40.

[0097] The lateral position and orientation of the image sensor 6 relative to the support structure 4 is controlled by selectively varying the temperature of the SMA actuator wire 40. Such actuation of the SMA actuator wire 40 is achieved by passing a selective drive signal through the SMA actuator wire 40 to provide resistive heating. Heating is provided directly by the current of the drive signal. Cooling is provided by reducing or stopping the current of the drive signal to allow the SMA actuator wire 40 to cool by conduction, convection, and radiation from its surroundings.

[0098] The camera device 1 comprises a lens assembly 20 which is assembled with the camera assembly 2 by being mounted to the support structure 4 , in particular the edge portion 10 .

[0099] The lens assembly 20 includes a lens holder 21 in the form of a cylinder mounted to the edge portion 10 of the support structure 4. The lens holder supports at least one lens 22 arranged along the optical axis O. Generally, any number of one or more lenses 22 may be provided. Without limiting the present invention, in this example, the camera device 1 is a miniature camera, wherein the at least one lens 22 (i.e., each lens 22, if multiple lenses are provided) typically has a diameter of at most 10 mm. The at least one lens 22 of the lens assembly 20 is arranged to focus an image onto the image sensor 6.

[0100] In this example, at least one lens 22 is supported on the lens holder 21 in such a manner that the at least one lens 22 is movable relative to the lens holder 21 along the optical axis O, for example, to provide focusing or zooming, but this is not required. Specifically, the at least one lens 22 is fixed to a lens holder 23 that is movable relative to the lens holder 21 along the optical axis O. In the event that there are multiple lenses 22, any or all of the lenses 22 may be fixed to the lens holder 23, and / or one or more of the lenses 22 may be fixed to the lens holder 21 and thus unable to move relative to the lens holder 21 along the optical axis O.

[0101] An axial actuator arrangement 24, provided between the lens holder 21 and the lens holder 23, is arranged to drive movement of the lens holder 21 and the lens 22 relative to the lens holder 21 along the optical axis O. The axial actuator arrangement 24 may be any suitable type of arrangement, for example a voice coil motor (VCM) or an SMA actuator wire, such as described in WO-2007 / 113478, which is incorporated herein by reference.

[0102] Furthermore, the camera apparatus 1 comprises a can 15 which is fixed to the support structure 4 and projects forward from the support structure 4 to enclose and protect other components of the camera apparatus 1 .

[0103] As described above, in operation, the SMA actuator wires 40 are selectively driven to move the image sensor 6 laterally in any direction and to rotate the image sensor 6 about the optical axis O. This serves to provide OIS, compensating the camera apparatus 1 for image movement due to, for example, hand shake.

[0104] Relative movement of image sensor 6 relative to support structure 4, and therefore also relative to lens assembly 20, can be used to stabilize the image against tilt of camera device 1, i.e., rotation about an axis extending laterally from photosensitive area 7 of image sensor 6. This occurs in a similar manner to camera devices that provide OIS-lens translation of the type disclosed in WO-2013 / 175197 and WO-2014 / 083318, which also involve relative lateral movement of image sensor 6 and lens assembly 20. Furthermore, rotation of image sensor 6 can be used to stabilize the image against rotation of camera device 1 about optical axis O. This type of stabilization is not achieved by camera devices that provide OIS-lens translation of the type disclosed in WO-2013 / 175197 and WO-2014 / 083318.

[0105] The SMA actuator wires 40 are driven by a control circuit implemented in the IC chip 30. Specifically, the control circuit generates a drive signal for each of the SMA actuator wires 40 and supplies the drive signal to the SMA actuator wires 40.

[0106] Control circuit 30 receives output signals from gyro sensor 31, which acts as a vibration sensor. Gyro sensor 31 detects vibrations experienced by camera device 1, and the output signals of gyro sensor 31 represent those vibrations, specifically the angular velocity of camera lens element 20 in three dimensions. Gyro sensor 31 is typically a pair of miniature gyroscopes that detect vibrations about three axes: two axes lateral to photosensitive area 7 of image sensor 6 and optical axis O. More generally, a larger number of gyroscopes or other types of vibration sensors may be used.

[0107] The drive signal is generated by the control circuit in response to the output signal of the gyro sensor 31, thereby driving the camera lens element 20 to move to stabilize the image focused by the camera lens element 20 on the image sensor 6, thereby providing OIS. The drive signal can be generated using, for example, the resistive feedback control technology disclosed in any of International Patent Application Nos. PCT / GB2013 / 051325, PCT / GB2013 / 052959, WO-2012 / 066285, WO-2012 / 020212, WO-2011 / 104518, WO-2012 / 038703, WO-2010 / 089529, or WO-2010029316, each of which is incorporated herein by reference.

[0108] The content described in the following numbered clauses is also disclosed:

[0109] Clause 1. A camera assembly comprising:

[0110] Support structure;

[0111] an image sensor having a photosensitive area, the image sensor being suspended from the support structure in a manner permitting movement of the image sensor relative to the support structure in any direction lateral to the photosensitive area of ​​the image sensor; and

[0112] A plurality of shape memory alloy actuator wires are arranged to enable movement of the image sensor relative to the support structure in any direction lateral to the photosensitive area of ​​the image sensor when selectively actuated.

[0113] Item 2. A camera assembly according to Item 1, wherein the image sensor is supported on the support structure in a manner further allowing the image sensor to rotate about an axis orthogonal to the photosensitive area, and the plurality of shape memory alloy actuator wires are arranged to enable the image sensor to rotate about the axis when selectively driven.

[0114] Clause 3. The camera assembly of Clause 1 or 2, wherein the plurality of shape memory alloy actuator wires comprises a total of four shape memory alloy actuator wires.

[0115] Clause 4. The camera assembly of Clause 3, wherein the four shape memory alloy actuator wires are arranged on four sides of the image sensor.

[0116] Item 5. A camera assembly according to Item 3 or 4, wherein the four shape memory alloy actuator wires include: a first pair of shape memory alloy actuator wires, the first pair of shape memory alloy actuator wires being arranged to apply forces to the image sensor in opposite directions along a first axis lateral to the photosensitive area of ​​the image sensor and to apply a first torque to the image sensor; and a second pair of shape memory alloy actuator wires being arranged to apply forces to the image sensor in opposite directions along a second axis lateral to the photosensitive area of ​​the image sensor and perpendicular to the first axis, and to apply a second torque to the image sensor that is opposite to the first torque.

[0117] Clause 6. The camera assembly of any one of clauses 1 to 5, wherein the image sensor is mounted on a bracket and the plurality of shape memory alloy actuator wires are connected between the support structure and the bracket.

[0118] Clause 7. The camera assembly of any one of clauses 1 to 6, further comprising a lens assembly comprising at least one lens arranged to focus an image on the photosensitive area of ​​the image sensor, the lens assembly being mounted to the support structure.

[0119] Clause 8. The camera assembly of clause 7, wherein the photosensitive area of ​​the image sensor has a diagonal length of at most 12 mm.

[0120] Clause 9. The camera assembly of any one of clauses 1 to 8, further comprising at least one sliding bearing supporting the movable element on the support structure, thereby allowing the movable element to move orthogonally to the optical axis relative to the support structure.

[0121] Clause 10. The camera assembly of any one of Clauses 1 to 9, further comprising a control circuit arranged to drive the shape memory alloy actuator wire.

[0122] Item 11. The camera assembly according to Item 10 further includes a vibration sensor, which is arranged to generate an output signal representing the vibration of the camera assembly, and the control circuit is arranged to drive the shape memory alloy wire in response to the output signal of the vibration sensor so as to drive the movement of the image sensor, thereby stabilizing the image captured by the image sensor.

[0123] Clause 12. A camera assembly comprising:

[0124] Support structure;

[0125] an image sensor mounted on the bracket, the image sensor having a light-sensitive area;

[0126] at least one plain bearing comprising bearing surfaces on each of the bracket and the support structure, the bearing surfaces bearing against each other to suspend the bracket from the support structure and to permit movement of the image sensor relative to the support structure in any direction lateral to the photosensitive area of ​​the image sensor;

[0127] An actuator arrangement is arranged to move the image sensor relative to the support structure in any direction laterally to the light-sensitive area of ​​the image sensor.

[0128] Clause 13. The camera assembly of clause 12, wherein each of the bearing surfaces is planar.

[0129] Clause 14. The camera assembly of clause 12 or 13, wherein the bearing surface has a coefficient of friction of 0.2 or less.

[0130] Clause 15. The camera assembly of any of Clauses 12 to 14, further comprising a fluid disposed between the bearing surfaces.

[0131] Clause 16. The camera assembly of clause 15, wherein the fluid is grease.

[0132] Clause 17. The camera assembly of clause 15 or 16, wherein the fluid reduces the coefficient of friction between the bearing surfaces and / or improves thermal contact between the bearing surfaces.

[0133] Clause 18. The camera assembly of any one of clauses 12 to 17, further comprising biasing means for biasing the bearing surfaces together.

[0134] Clause 19. The camera assembly of Clause 18, wherein the biasing means comprises at least one bend.

[0135] Clause 20. The camera assembly of clause 19, wherein the flexure supports electrical traces connected to at least the image sensor.

[0136] Clause 21. The camera assembly of any one of clauses 12 to 20, wherein the SMA actuator wire is tilted relative to the photosensitive area of ​​the image sensor so as to apply a biasing force that biases the bearing surfaces together.

[0137] Clause 22. A camera assembly according to any one of clauses 12 to 21, wherein the support structure includes a support plate formed from a sheet material, and the bracket includes a moving plate formed from a sheet material, and the sliding bearing is disposed between the support plate and the moving plate.

[0138] Clause 23. The camera assembly of Clause 22, wherein one or both of the support plate and the moving plate are made of metal.

[0139] Clause 24. The camera assembly of clause 22 or 23, wherein the bearing surfaces are a surface of the support plate and a surface of the moving plate.

[0140] Clause 25. A camera assembly according to clause 22 or 23, wherein the sliding bearing includes a bearing member fixed to one of the support plate and the movable plate, one of the bearing surfaces of the sliding bearing is a surface of the bearing member, and the other of the bearing surfaces of the sliding bearing is a surface of the other of the support plate and the movable plate.

[0141] Clause 26. The camera assembly of Clause 22 or 23, wherein the sliding bearing comprises bearing members fixed to both the support plate and the moving plate, the bearing surface of the sliding bearing being a surface of each bearing member.

[0142] Clause 27. A camera assembly according to clause 25 or 26, wherein the or each bearing member is made from a polymer.

[0143] Clause 28. The camera assembly of any of Clauses 12 to 15, wherein at least one of the bearing surfaces has a coating having lower friction and / or lower wear than the material of the coated conforming surface.

[0144] Clause 29. The camera assembly of any one of clauses 12 to 28, wherein the at least one sliding bearing comprises a plurality of sliding bearings.

[0145] Clause 30. The camera assembly of any one of clauses 1 to 17, wherein the at least one sliding bearing has a total contact area that is at least 0.2 times the area of ​​the photosensitive region of the image sensor.

[0146] Clause 31. A camera assembly according to any one of clauses 12 to 30, wherein the actuator device includes a plurality of shape memory alloy actuator wires connected between the support structure and the bracket, and the plurality of shape memory alloy actuator wires are arranged to enable the image sensor to move relative to the support structure in any direction lateral to the photosensitive area of ​​the image sensor when they are selectively driven.

[0147] Clause 32. A camera assembly according to any one of clauses 12 to 31, wherein the at least one sliding bearing further allows the image sensor to rotate about an axis orthogonal to the photosensitive area, and the actuator device is also arranged to rotate the image sensor about the axis.

[0148] Clause 33. A camera assembly according to any one of clauses 12 to 32, further comprising a lens assembly comprising at least one lens arranged to focus an image on the photosensitive area of ​​the image sensor, the lens assembly being mounted to the support structure.

[0149] Clause 34. The camera assembly of clause 33, wherein the photosensitive area of ​​the image sensor has a diagonal length of at most 12 mm.

[0150] Clause 35. The camera assembly of any one of clauses 12 to 34, further comprising a control circuit arranged to drive the actuator arrangement.

[0151] Item 36. The camera assembly according to Item 35 further includes a vibration sensor, which is arranged to generate an output signal representing the vibration of the camera assembly, and the control circuit is arranged to drive the actuator device in response to the output signal of the vibration sensor so as to drive the movement of the image sensor, thereby stabilizing the image captured by the image sensor.

Claims

1. A camera assembly comprising: Support structure; an image sensor mounted on the bracket and having a light-sensitive area; at least one plain bearing comprising bearing surfaces on each of the bracket and the support structure, the bearing surfaces bearing against each other to suspend the bracket from the support structure and to permit movement of the image sensor relative to the support structure in any direction lateral to the photosensitive area of ​​the image sensor and in a manner permitting rotation of the image sensor about an axis orthogonal to the photosensitive area; a plurality of shape memory alloy actuator wires arranged to, upon selective actuation thereof, enable movement of the image sensor relative to the support structure in any direction lateral to the photosensitive area of ​​the image sensor and rotation of the image sensor about the axis; and A biasing device biases the bearing surfaces together, the biasing device including at least one flexure that supports electrical traces connected to the image sensor.

2. The camera assembly according to claim 1, wherein: The plurality of shape memory alloy actuator wires are connected between the support structure and the bracket.

3. The camera assembly of claim 1 , further comprising a lens assembly comprising at least one lens arranged to focus an image on the photosensitive area of ​​the image sensor, the lens assembly being mounted to the support structure.

4. The camera assembly of claim 2 , further comprising a lens assembly comprising at least one lens arranged to focus an image on the photosensitive area of ​​the image sensor, the lens assembly being mounted to the support structure.

5. The camera assembly of claim 3, wherein: The photosensitive area of ​​the image sensor has a diagonal length of at most 12 mm.

6. The camera assembly of claim 4, wherein: The photosensitive area of ​​the image sensor has a diagonal length of at most 12 mm.

7. The camera assembly of any one of claims 1-6, further comprising a control circuit arranged to drive the shape memory alloy actuator wire.

8. The camera assembly of claim 7 , further comprising a vibration sensor arranged to generate an output signal representative of vibration of the camera assembly, the control circuit being arranged to drive the shape memory alloy actuator wire in response to the output signal of the vibration sensor so as to drive movement of the image sensor, thereby stabilizing an image captured by the image sensor.

9. The camera assembly according to any one of claims 1 to 6 and 8, wherein: The plurality of shape memory alloy actuator wires include a total of four shape memory alloy actuator wires arranged on four sides of the image sensor.

10. The camera assembly of claim 7, wherein: The plurality of shape memory alloy actuator wires include a total of four shape memory alloy actuator wires arranged on four sides of the image sensor.

11. The camera assembly of claim 9 , wherein the four shape memory alloy actuator wires include a first pair of shape memory alloy actuator wires and a second pair of shape memory alloy actuator wires, the first pair of shape memory alloy actuator wires being arranged to apply forces to the image sensor in opposite directions along a first axis lateral to the photosensitive area of ​​the image sensor and to apply a first torque to the image sensor, and the second pair of shape memory alloy actuator wires being arranged to apply forces to the image sensor in opposite directions along a second axis lateral to the photosensitive area of ​​the image sensor and perpendicular to the first axis, and to apply a second torque to the image sensor that is opposite to the first torque.

12. The camera assembly of claim 10 , wherein the four shape memory alloy actuator wires include a first pair of shape memory alloy actuator wires and a second pair of shape memory alloy actuator wires, the first pair of shape memory alloy actuator wires being arranged to apply forces to the image sensor in opposite directions along a first axis lateral to the photosensitive area of ​​the image sensor and to apply a first torque to the image sensor, and the second pair of shape memory alloy actuator wires being arranged to apply forces to the image sensor in opposite directions along a second axis lateral to the photosensitive area of ​​the image sensor and perpendicular to the first axis, and to apply a second torque to the image sensor that is opposite to the first torque.

Images