Anti-shake system and image stabilization method

Abstract

The object of the invention is to reduce the time required for the OIS (5) unit to move between frames. An anti-shake system (3) comprises an optical image stabilization (OIS) unit (5), a vibration suppressor, and an OIS controller (6). The OIS unit (5) is configured to be able to change the position of an optical system. The vibration suppressor is configured to remove or reduce signals having a certain frequency from a signal indicating a target value of a reference position of the optical system. The OIS controller (6) is configured to perform feedback control that controls the position of the optical system. The OIS controller (6) is configured to move the optical system to the reference position between frames based on a signal indicating a target value in which the certain frequency has been removed or reduced.

Description

Image stabilization systems and image stabilization methods Technical Field

[0001] Embodiments of this disclosure relate to an image stabilization system and an image stabilization method. Background Technology

[0002] Imaging devices known to have image stabilization systems, such as cameras and camcorders, are typically equipped with an optical image stabilization (OIS) unit, which is configured to optically correct image blur caused by camera shake or other factors during imaging.

[0003] When exposure time increases and the movement of the OIS unit increases, such as when shooting video with a smartphone (imaging device) while walking at night, the OIS unit may move beyond its movable range and collide with the mechanical end, causing the OIS unit to become immobile. This results in a decrease in image quality, such as point light source trailing or image ghosting.

[0004] To address this issue, conventional techniques disclose returning the OIS unit to the center position during the non-exposure period between video frames and absorbing the deviation in the amount of return through electronic image stabilization (EIS) to prevent the OIS unit from hitting the mechanical end. Summary of the Invention

[0005] [The problem this invention aims to solve]

[0006] Users require long exposure times when shooting in dark environments. However, when the OIS unit moves between frames, there is a problem of not being able to obtain long exposure times because the movement of the OIS unit takes time. The time required for movement includes the time it takes for the OIS unit to move, as well as the time it takes for the vibrations of the moved OIS unit and the AF (Automatic Focus) unit mounted on the OIS unit to be sufficiently attenuated.

[0007] The purpose of this disclosure is to reduce the time required for OIS units to move between frames.

[0008] [Solutions to the problem]

[0009] According to one aspect of an embodiment, a stabilization system includes an optical image stabilization (OIS) unit, a vibration suppressor, and an OIS controller. The OIS unit is configured to change the position of the optical system. The vibration suppressor is configured to remove or reduce signals having a specific frequency from a signal indicating a target value that indicates a reference position of the optical system. The OIS controller is configured to perform feedback control to control the position of the optical system. The OIS controller is configured to move the optical system to the reference position between frames based on the signal indicating the target value that has been removed or reduced for the specific frequency.

[0010] According to another aspect of the embodiments, an image stabilization method includes: in optical image stabilization (OIS) of changing the position of an optical system, removing or reducing a signal having a specific frequency from a signal indicating a target value of a reference position of the optical system; performing feedback control to control the position of the optical system; and moving the optical system to the reference position between frames based on the signal indicating that the target value of the specific frequency has been removed or reduced.

[0011] [Effects of the Invention]

[0012] According to embodiments of this disclosure, the time required for OIS units to move between frames can be reduced. Attached Figure Description

[0013] Figure 1 is a schematic diagram illustrating an example configuration of an imaging device equipped with an image stabilization system according to an embodiment;

[0014] Figure 2 is a schematic diagram illustrating the movement process of OIS units between frames;

[0015] Figure 3 is a schematic diagram illustrating a configuration example of the image stabilization system according to an embodiment;

[0016] Figure 4 is a schematic diagram illustrating the convergence of vibration of the OIS element with movement; and

[0017] Figure 5 is a schematic diagram illustrating the convergence of the vibration of the OIS element with movement. Detailed Implementation

[0018] The image stabilization system, imaging apparatus, and image stabilization method according to embodiments will be described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to this embodiment.

[0019] In the description of this embodiment, components that have the same or substantially the same function as those previously described in the earlier figures have the same reference numerals, and their descriptions may be appropriately omitted. Furthermore, even if the same or substantially the same parts are shown, the size and scale of those parts may differ depending on the figures. Moreover, from the perspective of ensuring the visibility of the figures, for example, reference numerals may be assigned only to the main components used to describe each figure, while components that have the same or substantially the same function as those previously described in the earlier figures may not have reference numerals.

[0020] It should be noted that in the description of this embodiment, "a" and "b" are added to the end of the reference numerals to distinguish different components having the same or substantially the same function. Furthermore, in the description of this embodiment, the addition of "a" and "b" to the end of the reference numerals is omitted, and multiple components having the same or substantially the same function can be collectively referred to.

[0021] Imaging devices known to have image stabilization systems, such as cameras and camcorders, are typically equipped with an optical image stabilization (OIS) unit, which is configured to optically correct image blur caused by camera shake or other factors during imaging.

[0022] When exposure time increases and the movement of the OIS unit increases, such as when shooting video with a smartphone (imaging device) while walking at night, the OIS unit may move beyond its movable range and collide with the mechanical end, causing the OIS unit to become immobile. This results in a decrease in image quality, such as point light source trailing or image ghosting.

[0023] To address this issue, conventional techniques disclose returning the OIS unit to the center position during the non-exposure period between video frames and preventing the OIS unit from hitting the mechanical end by absorbing the deviation in the amount of return through electronic image stabilization (EIS).

[0024] Users require long exposure times when shooting in dark environments. However, when the OIS unit moves between frames, there is a problem that long exposure times cannot be achieved because the movement of the OIS unit takes time. The time required for movement includes the time it takes for the OIS unit to move, and the time until the vibrations of the moved OIS unit and the AF unit mounted on the OIS unit are sufficiently attenuated.

[0025] In recent years, with the improvement of image sensor performance, rolling shutter time has been shortened. In this paper, the non-exposure time between frames includes the rolling shutter time read sequentially from the beginning of each row of the image sensor, as well as the time required for the OIS unit to move.

[0026] Therefore, the following embodiments illustrate an image stabilization system, imaging apparatus, and image stabilization method that can reduce the time required for the OIS unit to move between frames. Optionally, the following embodiments also illustrate an image stabilization system and an imaging apparatus equipped with the image stabilization system, which is configured to perform high-speed movement control of the OIS unit (image stabilization method) while suppressing vibration of the AF unit mounted on the OIS unit.

[0027] As an example, the imaging device equipped with an image stabilization system according to the embodiment is used when the user holds the imaging device in their hand. While holding the imaging device, the user can move the imaging device or change its orientation. As another example, the imaging device is used when it is mounted on various movable objects (such as bicycles, motorcycles, and cars).

[0028] Figure 1 is a schematic diagram illustrating an example configuration of an imaging device 1 equipped with an image stabilization system 3 according to an embodiment. The imaging device 1 is configured to image a shooting scene to generate image data. As shown in Figure 1, the imaging device 1 includes a lens barrel assembly 11, an image sensor 13, an AF unit 7, and an AF controller 8.

[0029] The lens barrel assembly 11 includes an optical system. This optical system includes optical elements configured to form an image of a light beam from the subject onto the imaging surface of the image sensor 13. The optical system includes at least one imaging lens 11a. The optical system can achieve the desired imaging performance using at least one optical element with optical power, and therefore can consist of a compound lens including at least one single lens, or a combination of a lens system and a reflection system.

[0030] It should be noted that in this embodiment, it is assumed that the position of the imaging lens 11a within the lens barrel assembly 11 is fixed. In other words, it is assumed that the imaging device 1 in this embodiment is configured to change its focal position by performing an expansion or contraction operation of the lens barrel assembly 11 through the AF unit 7. More specifically, the imaging device 1 is configured to change its focal position by changing the position of the lens barrel assembly 11 relative to the image sensor 13 in the optical axis direction (shown by the dotted line) of the imaging lens 11a. In this document, the change in position of the lens barrel assembly 11 relative to the image sensor 13 in the optical axis direction can be expressed as the change in position of the imaging lens 11a (focusing lens) relative to the image sensor 13 in the optical axis direction. In the example shown in FIG1, the optical axis direction of the optical system (shown by the dotted line) is the Z direction.

[0031] In this text, "able to change the focus position" means that the image formed on the imaging surface of the image sensor 13 can be smaller than the circle of confusion diameter allowed for each of at least two object points located at different positions along the optical axis. For example, the allowed circle of confusion diameter is defined based on the pixel pitch of the image sensor 13 or the imaging performance of the optical system. In other words, the imaging device 1 is configured to focus or blur (bokeh) any photographed object.

[0032] It should be noted that at least one imaging lens 11a may be configured to be movable relative to the lens barrel assembly 11 in the optical axis direction. In other words, the imaging device 1 is configured to change its focal position by changing the position of at least one imaging lens 11a (focusing lens) relative to the lens barrel assembly 11 in the optical axis direction.

[0033] It should be noted that the lens barrel assembly 11 may include at least one zoom lens. In this case, the imaging device 1 may be configured to change the zoom magnification by moving the zoom lens or the lens barrel assembly 11 in the optical axis direction.

[0034] Image sensor 13 is disposed on the optical axis of the optical system of lens barrel assembly 11. Image sensor 13 is disposed at the position where the optical system forms an image of the beam of light from the object being photographed. Image sensor 13 may suitably employ a solid-state imaging device such as CCD (Charge Coupled Device) and CMOS (Complementary Metal-Oxide Semiconductor).

[0035] Image sensor 13 is configured to generate an image signal corresponding to the light beam from the object being photographed. It should be noted that the imaging device 1 also includes, but is not shown, analog processing circuitry, an A / D converter, and image processing circuitry behind image sensor 13. The analog processing circuitry is configured to perform analog processing, such as magnification, on the image signal read from image sensor 13. The A / D converter is configured to convert the image signal output from the analog processing circuitry into digital image data. The image processing circuitry is configured to perform various image processing operations required for displaying and recording images associated with the digital image data. These image processing operations include, for example, optical black level (OB) subtraction, white balance (WB) correction, de-mosaicing, color conversion, gamma conversion, noise reduction, magnification / reduction, and compression.

[0036] It should be noted that the imaging device 1 can be configured to move the imaging surface of the image sensor 13 in the optical axis direction of the optical system, and is not limited to the image-side focal position and the object-side focal position of the optical system. In other words, the imaging device 1 can be configured to change its focal position by changing the optical axis direction position of at least one of the image-side focal position, the object-side focal position, and the imaging surface.

[0037] It should be noted that when the image sensor 13 is configured to be movable, the peak frequency in the closed-loop characteristics of the feedback control of the OIS unit, which will be described below, can be determined based on the position of the image sensor 13. Furthermore, this peak frequency can also be determined based on the position of the lens barrel assembly 11. In these cases, the notch filter 4, which will be described below, can be configured to remove or reduce multiple frequencies, or can be configured to include multiple switchable notch filters with different removal or reduction frequencies.

[0038] The AF unit 7 is configured to adjust the focal position of the imaging device 1. Furthermore, the AF unit 7 is also configured to measure the current position of the lens barrel assembly 11 (focusing lens) and output the measurement result. Optionally, the AF unit 7 includes an AF / OIS magnet 33, a lens support 71, an AF coil (drive coil) 73, an AF spring 75, an AF Hall element 77, and an AF controller 8.

[0039] The AF unit 7 is supported by an AF spring 75 and attached to a movable portion of the OIS unit 5. Optionally, the AF spring 75 movably supports the lens holder 71 in the optical axis direction (Z direction in FIG. 1). The lens holder 71 supports the lens barrel assembly 11. In the example of FIG. 1, one end of the AF spring 75 is fixed to the OIS housing 51, and the other end is fixed to the lens holder 71. Furthermore, the lens holder 71 is fixed to the lens barrel assembly 11 and the AF coil 73. As described above, the optical system of the lens barrel assembly 11 is movably supported by the OIS unit 5 in the optical axis direction.

[0040] The AF springs 75 on the Z+ and Z- sides exert forces on the lens mount 71, causing the lens mount to move in the Z- and Z+ directions, respectively. When the lens barrel assembly 11 is in a reference position along the optical axis, the biasing forces exerted by the AF springs 75 on the Z+ and Z- sides on the lens mount 71 are balanced. Here, the AF spring 75 is an example of a flexible component. The flexible component can be a spring or an elastomer such as rubber.

[0041] The AF / OIS magnet 33 is positioned facing the AF coil 73 in a direction orthogonal to the optical axis of the lens barrel assembly 11 (X direction in FIG1), at a position (X+ side and X- side in FIG1). The AF / OIS magnet 33 has the following configuration: a magnet 33a with its magnetic pole at the south pole and a magnet 33b with its magnetic pole at the north pole are positioned in the direction of movement of the lens barrel assembly 11, i.e., the optical axis direction (Z direction in FIG1), on one side facing the AF coil 73 and the AF Hall element 77. The AF coil 73 and the AF Hall element 77 are positioned on both sides of the lens holder 71 facing the AF / OIS magnet 33 (X+ side and X- side in FIG1). Optionally, with the lens barrel assembly 11 in the reference position, the AF / OIS magnet 33 and the AF coil 73 are arranged such that the intermediate position between the magnets 33a and 33b arranged along the optical axis direction becomes the intermediate position of the AF coil 73. For example, the AF Hall element 77 is disposed inside the AF coil 73.

[0042] It should be noted that the AF / OIS magnet 33 can also be positioned on the other direction (Y direction in Figure 1) orthogonal to the optical axis of the lens assembly 11, facing the AF coil 73 (Y+ side and Y- side in Figure 1).

[0043] It should be noted that in the imaging apparatus 1 according to this embodiment, the AF / OIS magnet 33 is shared by the OIS unit 5 and the AF unit 7. The relationship between the AF / OIS magnet 33 and the OIS unit 5 will be described below.

[0044] As an example, the AF / OIS magnet 33 and the AF coil 73 constitute a lens driving unit. This lens driving unit is configured to move the lens barrel assembly 11 in the optical axis direction according to a control signal from the AF controller 8. Optionally, the AF coil 73 generates a magnetic field according to the control signal (current) from the AF controller 8. The AF / OIS magnet 33 then generates a driving force in the optical axis direction according to the magnetic field generated by the AF coil 73.

[0045] As an example, the AF / OIS magnet 33 and the AF Hall element 77 constitute a focusing lens position detector. This focusing lens position detector is configured to output a detection signal corresponding to the current position of the lens barrel assembly 11. Optionally, the AF Hall element 77 is configured to detect the magnetic field or changes in the magnetic field generated by the AF / OIS magnet 33, and output a detection signal based on the detected magnetic field strength or change.

[0046] The AF controller 8 controls the various components of the AF unit 7. The AF controller 30 includes a processor and memory as hardware resources. The processor can appropriately employ various processors, such as CPU (Central Processing Unit), DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit), and FPGA (Field-Programmable Gate Array). Furthermore, the memory can appropriately employ various types of memory, such as ROM (Read Only Memory), flash memory, and RAM (Random Access Memory). It should be noted that the AF controller 8 can be a microcomputer. As an example, as shown in Figure 1, the AF controller 8 is housed within the lens holder 71.

[0047] The AF controller 8 is configured to perform an autofocus adjustment (AF) process for controlling the drive of the AF unit 7 based on focus information acquired from image data, etc. Optionally, the AF controller 8 is configured to control the position of the lens barrel assembly 11 in the optical axis direction through feedback control based on the current position and target position of the lens barrel assembly 11.

[0048] As an example, the AF controller 8 is configured to acquire focus information based on image data, etc. The focus information may be, for example, an AF evaluation value (contrast value) calculated from the image data. Furthermore, when the image sensor 13 is equipped with focus detection pixels, the focus information may be the defocus amount calculated from the output of the focus detection pixels. As an example, the AF controller 8 is configured to calculate the target position of the lens barrel assembly 11 based on the focus information. As an example, through feedback control based on the current position and target position of the lens barrel assembly 11, the AF controller 8 is configured to output a control signal (current) to the AF coil 73 for moving the lens barrel assembly 11 from the current position to the target position.

[0049] As shown in Figure 1, the image stabilization system 3 includes an AF / OIS housing 31, an OIS unit 5, and an OIS controller 6.

[0050] A portion of the AF / OIS housing 31 is configured to transmit light, including wavelengths detectable by the image sensor 13. This portion is the location facing the imaging lens 11a, which moves within the moving region 905 (see FIG. 2), i.e., the portion corresponding to the moving region 905. As an example, the portion of the AF / OIS housing 31 corresponding to the moving region 905 may be free of any objects. As an example, the portion of the AF / OIS housing 31 corresponding to the moving region 905 may be provided with an optical window made of resin, glass, or the like.

[0051] The OIS unit 5 is configured to change the position of the optical system of the lens barrel assembly 11 relative to the image sensor 13. The OIS unit 5 achieves optical image stabilization (OIS) under the control of the OIS controller 6. As shown in FIG1, the OIS unit 5 includes an OIS housing 51, an OIS base 53, an OIS coil (drive coil) 55, an OIS spring 57, and an OIS Hall element 59.

[0052] OIS unit 5 includes a movable portion and a fixed portion. For example, OIS housing 51 and various components held by OIS housing 51 constitute the movable portion of OIS unit 5. For example, OIS base 53 and various components held by OIS base 53 constitute the fixed portion. The movable portion of OIS unit 5 is attached to the fixed portion to be movable relative to the fixed portion in at least one direction different from the optical axis direction (Z direction). Here, at least one direction different from the optical axis direction is, for example, at least one of two directions orthogonal to the optical axis direction. In this embodiment, "orthogonal" includes substantially orthogonal, but is not limited to strictly orthogonal. In the example of FIG1, the movable portion of OIS unit 5 is attached to the fixed portion to move relative to the fixed portion in a direction orthogonal to the optical axis direction, i.e., in the X and Y directions. In other words, the fixed portion of OIS unit 5 movably supports the movable portion in the X and Y directions. It should be noted that the fixed part of OIS unit 5 is not limited to movably supporting the movable part in the X and Y directions, but can also movably support the movable part in the Z direction.

[0053] The movable portion of OIS unit 5 is supported by OIS spring 57 for attachment to the fixed portion of OIS unit. Optionally, OIS spring 57 movably supports the fixed portion in a plane orthogonal to the optical axis (the dual-axis direction of X and Y in FIG1). In the example of FIG1, one end of OIS spring 57 is fixed to OIS housing 51, and the other end is fixed to OIS base 53.

[0054] The OIS springs 57 on the X+ and X- sides exert forces on the OIS housing 51, causing the OIS housing 51 to move in the X- and X+ directions, respectively. Similarly, the OIS springs 57 on the Y+ and Y- sides exert forces on the OIS housing 51, causing the OIS housing 51 to move in the Y- and Y+ directions, respectively. When the OIS housing 51 is located at a reference position in the XY plane, the biasing forces exerted by the OIS springs 57 on the OIS housing 51 on the X+ and X- sides are balanced. Furthermore, when the OIS housing 51 is located at a reference position in the XY plane, the biasing forces exerted by the OIS springs 57 on the OIS housing 57 on the OIS housing 51 on the Y+ and Y- sides are also balanced. Here, the OIS spring 57 is an example of a flexible member. The flexible member can be a spring or an elastomer such as rubber.

[0055] The reference position of the OIS housing 51 is, for example, the midpoint of the AF / OIS housing 31 in the X and Y directions. In the example shown in FIG1, the reference position of the OIS housing 51 in the X direction is the midpoint of the movable range 903 in the X direction. It should be noted that, for example, when the OIS housing 51 is in the reference position, the gap 901 between the AF / OIS housing 31 and the OIS housing 51 is equal in size in the X and Y directions. Furthermore, for example, when the OIS housing 51 is in the reference position, the optical axis of the lens barrel assembly 11 passes through the center of the imaging surface of the image sensor 13. In other words, when the OIS housing 51 is in the reference position, the imaging lens 11a is located at the center of the movable region 905 in the XY plane (see FIG2). It should be noted that the reference position of the OIS housing 51 may be different from the midpoint of the AF / OIS housing 31 in the X and Y directions, or may be different between any two frames. For example, in a frame where the smartphone (imaging device) is moving in one direction, the reference position may change to a position closer to the direction of movement than the midpoint position.

[0056] A portion of the OIS housing 51 is configured to transmit light, including wavelengths detectable by the image sensor 13. This portion corresponds to the moving area 905. As an example, the portion of the OIS housing 51 corresponding to the moving area 905 may be free of any objects. As an example, the portion of the OIS housing 51 corresponding to the moving area 905 may be provided with an optical window made of materials such as resin or glass.

[0057] The AF / OIS magnet 33 is positioned facing the OIS coil 55 in a direction orthogonal to the optical axis of the lens assembly 11 (the X and Y directions in FIG. 1). The AF / OIS magnet 33 is configured such that magnet 33a, with its magnetic pole at the south pole, and magnet 33b, with its magnetic pole at the north pole, are positioned in the direction of movement of the OIS housing 51, i.e., in the X or Y direction, on the side facing the OIS coil 55 and the OIS Hall element 59. As an example, the AF / OIS magnets 33 positioned on the X+ and X- sides of the OIS housing 51 are configured such that magnets 33a and 33b are arranged in the X direction. As an example, the AF / OIS magnets 33 positioned on the Y+ and Y- sides of the OIS housing 51 are configured such that magnets 33a and 33b are arranged in the Y direction. The OIS coil 55 and OIS Hall element 59 are disposed in a direction orthogonal to the optical axis of the lens assembly 11 (X and Y directions in FIG. 1), on the side of the OIS base 53 facing the AF / OIS magnet 33 (Z+ side in FIG. 1). Optionally, with the OIS housing 51 in the reference position, the AF / OIS magnet 33 and OIS coil 55 are arranged such that the midpoint between magnets 33a and 33b arranged in the X or Y direction becomes the midpoint of the corresponding OIS coil 55. For example, the OIS Hall element 59 is disposed inside the OIS coil 55.

[0058] As an example, the AF / OIS magnet 33 and the OIS coil 55 constitute an OIS drive unit. This OIS drive unit is configured to move a movable portion of the OIS unit 5 in the X and / or Y directions according to a control signal from the OIS controller 6. Optionally, the OIS coil 55 generates a magnetic field according to a control signal (current) from the OIS controller 6. The AF / OIS magnet 33 then generates a driving force in the X and / or Y directions according to the magnetic field generated by the OIS coil 55.

[0059] It should be noted that the OIS drive unit of OIS unit 5 and / or the lens drive unit of AF unit 7 can be implemented by other actuators such as shape memory alloy (SMA) actuators, which are configured to generate driving force by sending current to the shape memory alloy to heat it, and are not limited to the case of a voice coil motor (VCM) that uses magnets and coils to generate driving force according to electromagnetic force.

[0060] As an example, the AF / OIS magnet 33 and the OIS Hall element 59 constitute an attitude detector. This attitude detector is configured to output a detection signal corresponding to the current position of the OIS housing 51 (the movable portion of the OIS unit 5). Optionally, the OIS Hall element 59 is configured to detect the magnetic field or changes in the magnetic field generated by the AF / OIS magnet 33, and output a detection signal based on the detected magnetic field strength or change.

[0061] In addition to the image sensor 13, analog processing circuit, A / D converter, image processing circuit, OIS coil 55, OIS spring 57, and OIS Hall element 59 described above, the fixed part of OIS unit 5 also includes an accelerometer and a gyroscope sensor. These components are mounted on the OIS base 53, for example. The accelerometer and gyroscope sensor are examples of sensors configured to detect jitter applied to the fixed part.

[0062] The OIS controller 6 is configured to control each component of the OIS unit 5. The OIS controller 6 includes a processor and memory as hardware resources. The processor may appropriately employ various processors, such as CPUs, DSPs, ASICs, and FPGAs. Furthermore, the memory may appropriately employ various types of memory, such as ROM, flash memory, and RAM. It should be noted that the OIS controller 6 may employ a microcomputer. As an example, as shown in Figure 1, the OIS controller 6 is mounted on the OIS base 53 (fixed portion).

[0063] The OIS controller 6 is configured to perform feedback control, for example, based on the amount of blur, of the position (position in the X and Y directions) of the optical system of the lens barrel assembly 11. Optionally, through feedback control based on the current attitude and target attitude of the movable part of the OIS unit 5, the OIS controller 6 is configured to control the position of the movable part in the XY plane and perform a correction process to correct image jitter in the captured image caused by vibrations generated in the imaging device 1.

[0064] As an example, the OIS controller 6 is configured to calculate the target attitude of the OIS unit 5 based on detection signals from the accelerometer and / or gyroscope sensor. As an example, based on the current attitude and target attitude of the OIS housing 51, the OIS controller 6 is configured to output a control signal (current) to the OIS coil 55 to move the OIS housing 51 from the current attitude to the target attitude. It should be noted that the target attitude and current attitude of the OIS unit 5 can be represented as the target position and current position of the OIS housing 51 in the movement directions (X and Y directions), respectively.

[0065] Figure 2 is a schematic diagram illustrating the movement process of the OIS unit 5 between frames. Figure 2 shows three consecutive frames. As described above, during the exposure period T1 of frame 1, the OIS housing 51 moves within the movable range 903 (see Figure 1) according to the image stabilization. At this time, as shown in Figure 2, during the exposure period T1 of frame 1, the imaging lens 11a mounted on the movable part of the OIS unit 5 moves within the movable area 905 according to the image stabilization.

[0066] When shooting with a long exposure time, such as when shooting in low light, the imaging lens 11a moves a large amount during the exposure period T1 of each frame. In other words, when shooting with a long exposure time, if the exposure begins when the imaging lens 11a is located at the edge of the moving area 905, for example, the OIS housing 51 hits the AF / OIS housing 31 (mechanical end), the OIS may fail to function.

[0067] Therefore, the OIS controller 6 is configured to move the optical system of the lens barrel assembly 11 to a reference position between frames (non-exposure periods) based on a signal indicating that a target value of a specific frequency has been removed or reduced. In other words, the OIS controller 6 is configured to perform a movement process of moving the movable part to the reference position between frames while suppressing vibrations of the AF unit 7 mounted on the movable part of the OIS unit 5. For example, the OIS controller 6 performs the movement process when the last line of each frame is read, i.e., at the start of the non-exposure period T2.

[0068] It should be noted that the OIS controller 6 can be configured to perform the movement process between the next frame only when the OIS housing 51 contacts the mechanical end, when the gap 901 between the AF / OIS housing 31 and the OIS housing 51 is not greater than a predetermined threshold, or when the end of the moving area 905 is detected from the captured image.

[0069] As shown in Figure 2, the non-exposure period T2 is the time after removing the rolling shutter time T3 from the inter-frame time period. Therefore, the movement process of the movable part of OIS unit 5 returning to the reference position can be performed within the non-exposure period T2 of the inter-frame time period. Therefore, it is required to shoot with a long exposure time to reduce the time required for the movement process and shorten the non-exposure period T2.

[0070] The time required for the movement process includes the movement time of the movable part of the OIS unit 5 controlled by the OIS controller 6. In addition, the time required for the movement process also includes the damping time, during which the vibrations generated on the movable part of the OIS unit 5 and the AF unit 7 due to the movement are damped to a predetermined range.

[0071] As an example, the OIS controller 6 is configured to output a control signal (current) to the OIS coil 55 during movement by means of feedback control with the reference position as the target position, so as to move the OIS housing 51 from the current attitude to the target attitude.

[0072] The OIS unit 5 sets the target value in feedback control using methods such as step-like setting and ramp-like setting. For example, the ramp-like setting method offers higher stability and a shorter decay time, but has a longer settling time due to the lower movement speed of the movable part of the OIS unit 5. Conversely, the step-like setting method offers a shorter settling time, but has lower stability and a longer decay time due to the higher movement speed of the movable part of the OIS unit 5. Furthermore, in methods that divide and set the target value into multiple steps, the settling time increases with the number of divisions (steps).

[0073] Therefore, the image stabilization system 3 according to this embodiment includes a vibration suppressor configured to set a target value in a stepped manner to increase the movement speed and reduce the decay time. The vibration suppressor is configured to remove or reduce signals with specific frequencies from the target value signal indicating the reference position of the optical system of the lens barrel assembly 11. In other words, the vibration suppressor performs filtering to remove or reduce signals with specific frequencies from the input signal 907 indicating the stepped target value to be input to the OIS controller 6. It should be noted that the vibration suppressor may also set multiple target values ​​in a stepped manner.

[0074] Figure 3 is a schematic diagram illustrating a configuration example of the image stabilization system 3 according to an embodiment. Figure 3 shows a notch filter 4 as a vibration suppressor in the embodiment. As shown in the block diagram of Figure 3, the notch filter 4 is disposed before the OIS controller 6. In other words, the notch filter 4 is disposed before the control loop (feedback loop) of the OIS unit 5 forming a closed loop.

[0075] A notch filter is a filter used to remove or reduce signals with a specific frequency. It can also be called a band-stop filter (BEF), band rejection filter (BRF), or band stop filter (BSF).

[0076] As described above, the AF unit 7 is supported by the OIS unit 5 via the AF spring 75. Therefore, the movement of the movable portion of the OIS unit 5 differs from the movement of the AF unit 7. For example, when the movable portion of the OIS unit 5 reciprocates in the X or Y direction, the amplitude and phase of the movement of the AF unit 7 differ from those of the movable portion of the OIS unit 5. In other words, the optical system of the lens barrel assembly 11 can move along the optical axis in the AF unit 7, or it can move in a direction different from the optical axis due to the deformation of the AF spring 75 that occurs with the movement of the movable portion of the OIS unit 5. Based on these factors, due to the nested structure of the OIS unit 5 and the AF unit 7, the control loop of the OIS unit 5 has difficulty suppressing vibrations with a specific frequency. Optionally, in the gain diagram of the control loop of the OIS unit 5, a specific frequency (peak frequency) that takes a positive value can easily lead to residual vibration.

[0077] Therefore, notch filter 4 is configured to remove or reduce the peak frequency in the closed-loop characteristics. This can accelerate vibration attenuation in the control loop (feedback loop) of OIS unit 5 and shorten the movement time.

[0078] Figures 4 and 5 are schematic diagrams illustrating the convergence of vibration of OIS unit 5 with movement. Figure 4 shows the behavior of OIS unit 5 (solid line) and AF unit 7 (dashed line) without notch filter 4 as a vibration suppressor, in a different image stabilization system 3 according to this embodiment. Figure 5 shows the behavior of OIS unit 5 (solid line) and AF unit 7 (dashed line) in image stabilization system 3 with notch filter 4 according to the embodiment. In the graphs of Figures 4 and 5, the vertical axis and horizontal axis represent position [μm] and time [s] in the X direction, respectively.

[0079] It should be noted that Figures 4 and 5 illustrate the behavior of OIS unit 5 and AF unit 7 when the target value is changed stepwise in the X direction. Figure 5 shows the case where notch filter 4 is configured to remove or reduce signals with a specific frequency of 200Hz based on the peak frequency of the closed-loop characteristics.

[0080] As shown in Figure 4, when the notch filter 4 is not set, for example, at the time point indicated by the arrow in Figure 4, the vibration of OIS unit 5 and AF unit 7 is not sufficiently attenuated.

[0081] On the other hand, in the case of the anti-shake system 3 provided with notch filter 4 according to this embodiment, for example, at the time point indicated by the arrow in FIG5, the vibration amplitude of OIS unit 5 and AF unit 7 is about half of the vibration amplitude at the same time point (the time point indicated by the arrow in FIG4) when notch filter 4 is not provided.

[0082] As described above, the image stabilization method, the image stabilization system 3, and the imaging device 1 equipped with the image stabilization system 3 according to this embodiment can accelerate the attenuation of vibrations generated by the OIS unit 5 and the AF unit 7 during movement. In other words, according to this embodiment, the time spent on the movement process between frames can be reduced. Therefore, even when shooting with a long exposure time, such as when shooting in low light, OIS can be performed appropriately.

[0083] Furthermore, the vibration suppressor is configured to remove or reduce peak frequencies according to the control loop of the OIS unit 5, which supports the AF unit 7 via the AF spring 75. Therefore, it is unnecessary to detect the position of the AF unit 7 in the direction of movement of the movable portion of the OIS unit 5. Optionally, the AF unit 7 may include a focusing lens position detector configured to detect the position of the lens barrel assembly 11 in the optical axis direction (Z direction), thus eliminating the need for sensors to detect vibration convergence by detecting positions in the X and Y directions.

[0084] It should be noted that since the OIS unit 5 can move at high speed between frames, the image stabilization method, the image stabilization system 3, and the imaging device 1 equipped with the image stabilization system 3 according to this embodiment can be applied to moving images and continuous shooting, as well as image synthesis after continuous shooting (HDR, night scene multi-shot, etc.).

[0085] It is important to note that the vibration suppressor can be configured to switch between removing or reducing peak frequencies during the exposure period and the inter-frame period. For example, the vibration suppressor can be configured to reduce the degree of peak frequency removal or reduction during the exposure period compared to the inter-frame period. Alternatively, the vibration suppressor can be configured not to remove or reduce peak frequencies during the exposure period. This switching can be achieved by switching between multiple notch filters 4 with different degrees of removal or reduction, by switching the number of steps in the notch filters 4, or by switching between using / not using the notch filters 4.

[0086] It should be noted that the vibration suppressor can be configured as part of the OIS controller 6. Furthermore, the vibration suppressor can also be implemented through firmware (program) processing within the OIS controller 6.

[0087] It should be noted that the processing performed by the circuitry behind the image sensor 13, the OIS controller 6, and the AF controller 8 can be implemented as a function of the OIS controller 6, which is achieved by the processor executing a program loaded into memory, or it can be implemented as a dedicated circuit.

[0088] It should be noted that at least two components of the circuitry behind the image sensor 13, the OIS controller 6, and the AF controller 8 can be implemented by a single circuit. Furthermore, at least one component of the circuitry behind the image sensor 13, the OIS controller 6, and the AF controller 8 can be implemented by combining two or more circuits.

[0089] It should be noted that image stabilization according to this embodiment can be achieved by an electronic device including imaging device 1 and a circuit board (not shown). The circuit board is configured to supply power to imaging device 1. The circuit board can be a component of imaging device 1.

[0090] It should be noted that some or all of the processing performed by the imaging device 1 and / or the image stabilization system 3 according to this embodiment can be implemented by software.

[0091] The program executed by the imaging device 1 and / or the image stabilization system 3 according to this embodiment is recorded as a file in an installable or executable format and stored in a computer-readable recording medium such as a USB (Universal Serial Bus) memory, a flash memory (semiconductor memory) such as an SSD (Solid State Drive), or a computer-readable recording medium such as a HDD (Hard Disk Drive).

[0092] Furthermore, the program executed by the imaging device 1 and / or the image stabilization system 3 according to this embodiment can be configured to be provided via a computer stored on a network connected to a network such as the Internet and downloaded over the network. Additionally, the program executed by the imaging device 1 and / or the image stabilization system 3 according to this embodiment can also be configured to be provided or distributed via a network such as the Internet.

[0093] Furthermore, the program executed by the imaging device 1 and / or the image stabilization system 3 according to this embodiment can be configured to be pre-embedded in ROM or the like and provided.

[0094] According to at least one embodiment described above, the time required for OIS units to move between frames can be reduced.

[0095] Although certain embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. In fact, the novel embodiments described herein may be embodied in many other forms; furthermore, various omissions, substitutions, and modifications may be made to the forms of the embodiments described herein without departing from the spirit of the invention. The appended claims and their equivalents are intended to cover such forms or modifications that fall within the scope and spirit of the invention.

[0096] (Supplementary Explanation)

[0097] (1) A stabilization system includes:

[0098] An optical image stabilization (OIS) unit is configured to change the position of the optical system;

[0099] A vibration suppressor, configured to remove or reduce a signal of a specific frequency from a signal indicating a target value of a reference position of an optical system; and

[0100] The OIS controller is configured to perform feedback control of the position of the optical system and move the optical system to a reference position between frames based on a signal indicating that a target value of a specific frequency has been removed or reduced.

[0101] (2) In the anti-shake system according to (1), the vibration suppressor includes a notch filter.

[0102] (3) In the image stabilization system according to (1) or (2), the vibration suppressor is configured to reduce the degree to which a signal with a specific frequency is removed or reduced from the signal indicating the target value during the exposure period, compared to the time period between frames.

[0103] (4) In any one of (1) to (3) of the anti-shake system, the specific frequency includes the peak frequency in the closed-loop characteristics of the feedback control.

[0104] (5) In the image stabilization system according to any one of (1) to (4), the movable portion of the OIS unit is movable in at least one direction different from the optical axis direction of the optical system, and

[0105] The movable part is supported by a flexible component, which allows the optical system to move in the direction of the optical axis.

[0106] (6) In the image stabilization system according to (5), at least one direction that is different from the optical axis direction of the optical system includes at least one of two directions orthogonal to the optical axis direction.

[0107] (7) In any one of (1) to (6) of the image stabilization system, the optical axis of the optical system at the reference position passes through the center of the moving area of ​​the optical system.

[0108] (8) In any one of (1) to (7) the image stabilization system, the OIS controller is configured to move the optical system to a reference position in one step.

[0109] (9) An imaging device is equipped with a stabilization system according to any one of (1) to (8).

[0110] (10) The imaging apparatus according to (9) further includes:

[0111] An image sensor configured to generate an image signal based on the light beams in the shooting scene; and

[0112] An optical system configured to form an image of a beam of light from the object being photographed on the imaging surface of an image sensor.

[0113] (11) According to the imaging apparatus of (10), the OIS unit is configured to change the position of the optical system relative to the image sensor.

[0114] (12) In the imaging apparatus according to (10) or (11), the optical axis of the optical system at the reference position passes through the center of the imaging surface of the image sensor.

[0115] (13) An electronic device equipped with an imaging device according to (9), the electronic device further comprising a circuit board for supplying power to the imaging device.

[0116] (14) An image stabilization method, in optical image stabilization (OIS) involving changing the position of an optical system, includes:

[0117] Remove or reduce signals with specific frequencies from the target value that indicates the reference position of the optical system;

[0118] Feedback control is used to control the position of the optical system; and

[0119] Based on signals indicating that target values ​​at specific frequencies have been removed or reduced, the optical system is moved to a reference position between frames.

[0120] (15) In the image stabilization method according to (14), the removal or reduction of signals with a specific frequency is performed by a notch filter.

[0121] (16) In the image stabilization method according to (14) or (15), removal or reduction includes reducing the degree of removal or reduction of a signal with a specific frequency from the signal indicating the target value during the exposure period compared to the time period between frames.

[0122] (17) In the image stabilization method according to any one of (14) to (16), the specific frequency includes the peak frequency in the closed-loop characteristics of the feedback control.

[0123] (18) In the image stabilization method according to any one of (14) to (17), the OIS includes controlling the position of an OIS unit in at least one direction different from the optical axis direction, the OIS unit having a movable portion configured to support the optical system moving in the optical axis direction of the optical system via a flexible member in the moving direction of the movable portion.

[0124] (19) In the image stabilization method according to (18), at least one direction different from the optical axis direction of the optical system includes at least one of two directions orthogonal to the optical axis direction.

[0125] (20) In the image stabilization method according to any one of (14) to (19), the optical axis of the optical system at the reference position passes through the center of the moving region of the optical system.

[0126] (21) In the image stabilization method according to any one of (14) to (19), the optical axis of the optical system at the reference position passes through the center of the imaging surface of the image sensor.

[0127] (22) In the image stabilization method according to any one of (14) to (21), the movement includes moving the optical system to a reference position in one step.

[0128] [Explanation of letters or numbers]

[0129] 1: Imaging device

[0130] 11: Lens tube assembly

[0131] 11a: Imaging lens

[0132] 13: Image Sensor

[0133] 3: Image stabilization system

[0134] 31: AF / OIS housing

[0135] 33: AF / OIS magnet

[0136] 5: OIS unit

[0137] 51: OIS casing

[0138] 53: OIS base

[0139] 55: OIS coil

[0140] 57: OIS spring

[0141] 59: OIS Hall element

[0142] 6: OIS controller

[0143] 7: AF unit

[0144] 71: Lens bracket

[0145] 73: AF coil

[0146] 75: AF spring

[0147] 77: AF Hall element

[0148] 8: AF controller

[0149] 901: Gap

[0150] 903: Movable Range

[0151] 905: Movement Area

[0152] 907: Input signal

Claims

1. A stabilization system, the stabilization system comprising: An optical image stabilization (OIS) unit is configured to change the position of the optical system. A vibration suppressor is configured to remove or reduce a signal having a specific frequency from a target value indicating a reference position of the optical system. And an OIS controller configured to perform feedback control to control the position of the optical system, and to move the optical system to the reference position between frames based on the signal indicating that the target value of the specific frequency has been removed or reduced; wherein the specific frequency includes the peak frequency in the closed-loop characteristics of the feedback control.

2. The image stabilization system according to claim 1, wherein, The vibration suppressor includes a notch filter.

3. The image stabilization system according to claim 1, wherein, The vibration suppressor is configured to reduce the degree to which signals with the specific frequency are removed from the signal indicating the target value during the exposure period, compared to the time interval between the frames.

4. The image stabilization system according to claim 1, wherein: The movable portion of the OIS unit is movable in at least one direction different from the optical axis direction of the optical system, and the movable portion is supported by a flexible member to move the optical system in the direction of movement of the movable portion.

5. The image stabilization system according to claim 1, wherein, The optical axis of the optical system at the reference position passes through the center of the moving region of the optical system.

6. The image stabilization system according to claim 1, wherein, The OIS controller is configured to move the optical system to the reference position in one step.

7. An imaging device, the imaging device being equipped with the image stabilization system according to claim 1, the imaging device further comprising: An image sensor configured to generate image signals based on the light beams in the shooting scene; And an optical system configured to form an image of a beam of light from the object being photographed on the imaging surface of the image sensor.

8. The imaging apparatus according to claim 7, wherein, The OIS unit is configured to change the position of the optical system relative to the image sensor.

9. The imaging apparatus according to claim 7, wherein, The optical axis of the optical system at the reference position passes through the center of the imaging surface of the image sensor.

10. An electronic device equipped with the imaging apparatus according to claim 7, the electronic device further comprising: A circuit board that supplies power to the imaging device.

11. An image stabilization method in optical image stabilization (OIS) involving changing the position of an optical system, the method comprising: Remove or reduce signals with specific frequencies from the target value indicating the reference position of the optical system; Perform feedback control to control the position of the optical system; And based on the signal indicating that the target value of the specific frequency has been removed or reduced, the optical system is moved to the reference position between frames; wherein the specific frequency includes the peak frequency in the closed-loop characteristics of the feedback control.

Images