WO2024050829A1

WO2024050829A1 - Anti-shake system and image stabilization method

Info

Publication number: WO2024050829A1
Application number: PCT/CN2022/118188
Authority: WO
Inventors: Atushi MATSUTANI
Original assignee: Guangdong Oppo Mobile Telecommunications Corp., Ltd.
Priority date: 2022-09-09
Filing date: 2022-09-09
Publication date: 2024-03-14

Abstract

An object is to reduce a time according to the movement of an OIS unit (5) between frames. An anti-shake system (3) includes 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 a position of an optical system. The vibration suppressor is configured to remove or reduce a signal with a specific frequency from a signal of a target value indicating a reference position of the optical system. The OIS controller (6) is configured to perform feedback control of controlling the position of the optical system. The OIS controller (6) is configured to move the optical system up to the reference position between frames based on the signal indicating the target value for which the specific frequency has been removed or reduced.

Description

ANTI-SHAKE SYSTEM AND IMAGE STABILIZATION METHOD

TECHNICAL FIELD

An embodiment of the present disclosure relates to an anti-shake system and an image stabilization method.

BACKGROUND

Conventionally, there has been known an imaging apparatus with an anti-shake system, such as a video camera and a still camera, equipped with an optical image stabilization (OIS) unit configured to optically correct an image blur of a captured image caused by a camera shake etc. during imaging.

When an exposure time becomes long and an movement amount of the OIS unit increases, for example, by shooting a video by a smartphone (imaging apparatus) while walking at night, there may be a possibility that the movement of the OIS unit exceeds its movable range to hit a mechanical end and thus the OIS unit could not move. As a result, there is a problem that an image quality decreases such that a point light source flows or an image looks double.

For this problem, the conventional arts disclose that the OIS unit is returned to the center position during the non-exposure period between frames of the video, and the OIS unit does not come to hit the mechanical end by absorbing the misalignment of the returned amount by electronic image stabilization (EIS) .

SUMMARY

[Problem to be Solved by the Invention]

There is a demand that a user wants to take a long exposure time during shooting in a dark place. However, when the OIS unit is moved between the frames, there is a problem that a long exposure time cannot be taken due to a time according to the movement of the OIS unit. The time according to the movement includes a time in which the OIS unit moves and a time until the vibrations of the OIS unit and the AF unit mounted on the OIS unit after moving are damped sufficiently.

An object of the present disclosure is to reduce a time according to the movement of an OIS unit between frames.

[Means for Solving Problem]

An anti-shake system according to an aspect of an embodiment includes an optical image stabilization (OIS) unit, a vibration suppressor, and an OIS controller. The OIS unit is configured to be able to change a position of an optical system. The vibration suppressor is configured to remove or reduce a signal with a specific frequency from a signal of a target value indicating a reference position of the optical system. The OIS controller is configured to perform feedback control of controlling the position of the optical system. The OIS controller is configured to move the optical system up to the reference position between frames based on the signal indicating the target value for which the specific frequency has been removed or reduced.

An image stabilization method according to another aspect of the embodiment includes: in optical image stabilization (OIS) of changing a position of an optical system , removing or reducing a signal with a specific frequency from a signal of a target value indicating a reference position of the optical system; performing feedback control of controlling the position of the optical system; and moving the optical system up to the reference position between frames based on the signal indicating the target value for which the specific frequency has been removed or reduced.

[Effect of the Invention]

According to an embodiment of the present disclosure, it is possible to reduce a time according to the movement of the OIS unit between frames.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a configuration of an imaging apparatus equipped with an anti-shake system according to an embodiment;

FIG. 2 is a diagram explaining a movement process of an OIS unit between frames;

FIG. 3 is a diagram illustrating an example of a configuration of the anti-shake system according to the embodiment;

FIG. 4 is a diagram explaining convergence of vibration of the OIS unit accompanied with the movement; and

FIG. 5 is a diagram explaining convergence of vibration of the OIS unit accompanied with the movement.

DETAILED DESCRIPTION

Hereinafter, an anti-shake system, an imaging apparatus, and an image stabilization method according to an embodiment will be described in detail with reference to the present drawings. Note that the present invention is not limited to the embodiment.

In the description of the present embodiment, components having the same or substantially the same functions as the previously described components for the previous drawing have the same reference numbers, and their descriptions may be omitted as appropriate. Moreover, even if the same or substantially the same part is illustrated, the dimension and ratio of the part may be different depending on a drawing. Moreover, from the viewpoint of ensuring visibility of drawings, for example, reference numbers may be assigned to only main components for description of each drawing, and components having the same or substantially the same functions as the previously described components for the previous drawing may not have reference numbers.

Note that, in the description of the present embodiment, "a, b" are added to the ends of the reference numbers and components having the same or substantially the same functions may be distinguished from each other. Moreover, in the description of the present embodiment, adding "a, b" to the ends of the reference numbers is omitted and a plurality of components having the same or substantially the same functions may be collectively referred to.

In recent years, a rolling shutter time is being shortened by the performance enhancement of an image sensor. Herein, the non-exposure time between frames includes a rolling shutter time to start sequential reading from each row of the image sensor and a time according to the movement of the OIS unit.

Therefore, the following embodiment exemplifies an anti-shake system, an imaging apparatus, and an image stabilization method, which can reduce a time according to the movement of an OIS unit between frames. Optionally, the following embodiment exemplifies: an anti-shake system configured to be able to execute control (image stabilization method) of moving an OIS unit at high speed while suppressing a vibration of an AF unit mounted on the OIS unit; and an imaging apparatus equipped with the anti-shake system.

As an example, the imaging apparatus equipped with the anti-shake system according to the embodiment is used in a state where the imaging apparatus is gripped by a user. The user may move the imaging apparatus or change its direction while gripping the imaging apparatus. As another example, the imaging apparatus is used in a state where the imaging apparatus is mounted on various movable bodies such as a bicycle, a motorcycle, and an automobile.

FIG. 1 is a diagram illustrating an example of a configuration of an imaging apparatus 1 equipped with an anti-shake system 3 according to the embodiment. The imaging apparatus 1 is configured to image a subject field to generate image data. As illustrated in FIG. 1, the imaging apparatus 1 includes a lens barrel assembly 11, an image sensor 13, an AF unit 7, and an AF controller 8.

The lens barrel assembly 11 includes an optical system. The optical system includes an optical element configured to form an image of a light beam from a subject on an imaging surface of the image sensor 13. The optical system includes at least one imaging lens 11a. The optical system may have desired imaging performance by at least one optical element having power, and thus may be composed of a compound lens that includes at least one single lens, or may be composed of a combination of a lens system and a reflection system.

Note that, in the present embodiment, it is assumed that a position of the imaging lens 11a in the lens barrel assembly 11 is fixed. In other words, it is assumed that the imaging apparatus 1 according to the present embodiment is configured to be able to change its focus position by an extension operation or a retraction operation of the lens barrel assembly 11 by the AF unit 7. More specifically, the imaging apparatus 1 is configured to be able to change its focus position by changing the position of the lens barrel assembly 11 with respect to the image sensor 13 in an optical axis direction (dashed-dotted line) of the imaging lens 11a. Herein, a change of the optical-axis-direction position of the lens barrel assembly 11 with respect to the image sensor 13 can be represented as a change of the position of the imaging lens 11a (focusing lens) with respect to the image sensor 13 in the optical axis direction. In the example illustrated in FIG. 1, the optical axis direction (dashed-dotted line) of the optical system is the Z direction.

Herein, "to be able to change a focus position" means that an image formed on the imaging surface of the image sensor 13 can be made smaller than a diameter of a permissible circle of confusion for each of at least two object points that exist at different positions in the optical axis direction. A diameter of a permissible circle of confusion is defined depending on a pixel pitch of the image sensor 13 or imaging performance of the optical system, for example. In other words, the imaging apparatus 1 is configured to be able to focus or blur (bokeh) an arbitrary subject.

Note that at least the one imaging lens 11a may be configured to be movable with reference to the lens barrel assembly 11 in the optical axis direction. In other words, the imaging apparatus 1 may be configured to be able to change its focus position by changing the position of at least the one imaging lens 11a (focusing lens) with respect to the lens barrel assembly 11 in the optical axis direction.

Note that the lens barrel assembly 11 may have at least one zoom lens. In this case, the imaging apparatus 1 may be configured to be able to change a zooming magnification by moving the zoom lens or the lens barrel assembly 11 in the optical axis direction.

The image sensor 13 is arranged on an optical axis of the optical system of the lens barrel assembly 11. The image sensor 13 is arranged at a position at which the image of the light beam from the subject is formed by the optical system. The image sensor 13 can appropriately employ a solid-state imaging apparatus such as CCD (Charge Coupled Device) and CMOS (Complementary Metal-Oxide Semiconductor) .

The image sensor 13 is configured to generate an image signal corresponding to the light beam from the subject. Note that the imaging apparatus 1 includes, in back of the image sensor 13, an analog processing circuitry, an A/D converter, and an image processing circuit that are not illustrated. The analog processing circuitry is configured to perform analog processing such as amplification processing with respect to an image signal read from the image sensor 13. The A/D converter is configured to convert an image signal output from the analog processing circuitry into digital-format image data. The image processing circuit is configured to perform various image processing required for displaying and recording an image with respect to the digital-format image data. The image processing includes, for example, an optical black (OB) subtraction process, a white balance (WB) correction process, a demosaic process, a color conversion process, a gamma conversion process, a noise reduction process, an enlargement/reduction process, a compression process, and the like.

Note that the imaging apparatus 1 may be configured to be able to move the imaging surface of the image sensor 13 in the optical axis direction of the optical system, without being limited to the image-side focus position and the object-side focus position of the optical system. In other words, the imaging apparatus 1 may be configured to be able to change its focus position by changing the optical-axis-direction position of at least one of the image-side focus position, the object-side focus position, and the imaging surface.

Note that, when the image sensor 13 is configured to be movable, a peak frequency in closed loop characteristics of the feedback control for an OIS unit to be described later may be determined based on the position of the image sensor 13. Moreover, the peak frequency may be determined based on the position of the lens barrel assembly 11. In these cases, a notch filter 4 to be described later may be configured to perform removal or reduction on a plurality of frequencies, or may be configured to include a plurality of switchable notch filters having different frequencies for removal or reduction.

The AF unit 7 is configured to adjust a focus position of the imaging apparatus 1. Moreover, the AF unit 7 is configured to measure the present position of the lens barrel assembly 11 (focusing lens) and to output the measurement result. Optionally, the AF unit 7 includes an AF/OIS magnet 33, a lens holder 71, AF coils (driving coils) 73, AF springs 75, AF hall elements 77, and an AF controller 8.

The AF unit 7 is supported by the AF spring 75 to be attached to a movable part of an OIS unit 5. Optionally, the AF springs 75 movably support 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 an OIS case 51, and another end is fixed to the lens holder 71. Moreover, the lens holder 71 is fixed to the lens barrel assembly 11 and the AF coils 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.

The AF springs 75 on the Z+ side and the Z-side bias the lens holder 71 to respectively move it in the Z-direction and the Z+ direction. In the AF springs 75 on the Z+ side and the Z-side, forces biasing the lens holder 71 are balanced when the lens barrel assembly 11 is located at a reference position in the optical axis direction. Herein, the AF springs 75 are an example of a flexible member. The flexible member may be a spring, or may be an elastic body such as rubber.

The AF/OIS magnet 33 is provided at positions (X+ side and X-side in FIG. 1) facing the AF coils 73 in a direction (X direction in FIG. 1) orthogonal to the optical axis direction of the lens barrel assembly 11. The AF/OIS magnet 33 has a configuration that a magnet 33a whose magnetic pole is a south pole and a magnet 33b whose magnetic pole is a north pole are arranged in the moving direction of the lens barrel assembly 11, that is, in the optical axis direction (Z direction in FIG. 1) , on a side facing the AF coil 73 and the AF hall element 77. The AF coil 73 and the AF hall element 77 are provided on sides (X+ side and X-side in FIG. 1) facing the AF/OIS magnet 33 of the lens holder 71. Optionally, the AF/OIS magnet 33 and the AF coil 73 are arranged so that a middle position between the

magnets

33a and 33b arranged in the optical axis direction becomes a middle position of the AF coil 73, in a state where the lens barrel assembly 11 is set at a reference position. The AF hall element 77 is provided inside the AF coil 73, for example.

Note that the AF/OIS magnet 33 may be further provided at positions (Y+ side and Y-side in FIG. 1) facing the AF coils 73 in another direction (Y direction in FIG. 1) orthogonal to the optical axis direction of the lens barrel assembly 11.

Note that, in the imaging apparatus 1 according to the present embodiment, the AF/OIS magnet 33 is shared by the OIS unit 5 and the AF unit 7. A relationship between the AF/OIS magnet 33 and the OIS unit 5 will be described later.

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

As an example, the AF/OIS magnet 33 and the AF hole elements 77 constitute a focus lens position detector. The focus lens position detector is configured to output a detection signal corresponding to the present position of the lens barrel assembly 11. Optionally, the AF hall elements 77 are configured to detect the magnetic field generated by the AF/OIS magnet 33 or the change in the magnetic field and to output the detection signal according to the detected magnetic field intensity or change amount.

The AF controller 8 controls each component of the AF unit 7. The AF controller 30 includes a processor and a 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) . Moreover, the memory can appropriately employ various memories such as ROM (Read Only Memory) , a flash memory, and RAM (Random Access Memory) . Note that the AF controller 8 may employ a microcomputer. As an example, the AF controller 8 is provided in the lens holder 71 as illustrated in FIG. 1.

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

As an example, the AF controller 8 is configured to acquire focus information based on the image data etc. The focus information is, for example, an AF evaluation value (contrast value) calculated from the image data. Moreover, when the image sensor 13 is configured to have a focus detection pixel, the focus information may be a defocusing amount calculated from the output of the focus detection pixel. As an example, the AF controller 8 is configured to calculate a target position of the lens barrel assembly 11 based on the focus information. As an example, by the feedback control based on the target position and the present position of the lens barrel assembly 11, the AF controller 8 is configured to output a control signal (electric current) for moving the lens barrel assembly 11 from the present position to the target position to the AF coil 73.

As illustrated in FIG. 1, the anti-shake system 3 includes an AF/OIS case 31, the OIS unit 5, and an OIS controller 6.

A part of the AF/OIS case 31 is configured to be able to transmit light including a wavelength that can be detected by the image sensor 13. This part is a position facing the imaging lens 11a that moves inside a moving area 905 (see FIG. 2) , that is, a portion corresponding to the moving area 905. As an example, the portion corresponding to the moving area 905 of the AF/OIS case 31 may be provided with nothing. As an example, the portion corresponding to the moving area 905 of the AF/OIS case 31 may be provided with an optical window formed of resin, glass, or the like.

The OIS unit 5 is configured to be able to change the position of the optical system of the lens barrel assembly 11 with respect to the image sensor 13. The OIS unit 5 realizes optical image stabilization (OIS) in accordance with the control of the OIS controller 6. As illustrated in FIG. 1, the OIS unit 5 includes the OIS case 51, an OIS base 53, OIS coils (driving coils) 55, OIS springs 57, and OIS hall elements 59.

The OIS unit 5 includes a movable part and a fixed part. For example, the OIS case 51 and each component held by the OIS case 51 constitute the movable part of the OIS unit 5. For example, the OIS base 53 and each component held by the OIS base 53 constitute the fixed part. The movable part of the OIS unit 5 is attached to the fixed part to be movable relative to the fixed part in at least one direction different from the optical axis direction (Z direction) . Herein, at least one direction different from the optical axis direction is, for example, at least one of two direction orthogonal to the optical axis direction. In the present embodiment, "orthogonal" includes substantially orthogonal without being limited to strictly orthogonal. In the example of FIG. 1, the movable part of the OIS unit 5 is attached to the fixed part to be movable relative to the fixed part in directions orthogonal to the optical axis direction, that is, in the X and Y directions. In other words, the fixed part of the OIS unit 5 movably supports the movable part in the X and Y directions. Note that the fixed part of the OIS unit 5 may further movably support the movable part in the Z direction without being limited to the X and Y directions.

The movable part of the OIS unit 5 is supported by the OIS springs 57 to be attached to the fixed part of the OIS unit. Optionally, the OIS springs 57 movably support the fixed part in a plane (biaxial direction of X and Y directions in FIG. 1) orthogonal to the optical axis. In the example of FIG. 1, one end of the OIS spring 57 is fixed to the OIS case 51, and another end is fixed to the OIS base 53.

The OIS springs 57 on the X+ side and the X-side bias the OIS case 51 to respectively move it in the X-direction and the X+ direction. Moreover, the OIS springs 57 on the Y+ side and the Y-side bias the OIS case 51 to respectively move it in the Y-direction and the Y+direction. In the OIS springs 57 on the X+ side and the X-side, forces biasing the OIS case 51 are balanced when the OIS case 51 is located at a reference position in the XY plane. Moreover, in the OIS springs 57 on the Y+ side and the Y-side, forces biasing the OIS case 51 are balanced when the OIS case 51 is located at the reference position in the XY plane. Herein, the OIS spring 57 is an example of a flexible member. The flexible member may be a spring, or may be an elastic body such as rubber.

The reference position of the OIS case 51 is, for example, a middle position of the AF/OIS case 31 in the X and Y directions. In the example illustrated in FIG. 1, the reference position of the OIS case 51 in the X direction is a middle position of a movable range 903 in the X direction. Note that, when the OIS case 51 is located at the reference position, the sizes of a gap 901 between the AF/OIS case 31 and the OIS case 51 in the X and Y directions are equal to each other, for example. Moreover, when the OIS case 51 is located at 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, for example. In other words, when the OIS case 51 is located at the reference position, the imaging lens 11a is located at the center (see FIG. 2) of the moving area 905 in the XY plane. Note that the reference position of the OIS case 51 may be a position different from the middle position of the AF/OIS case 31 in the X and Y directions, or may be different between arbitrary two frames. For example, in frames when a smartphone (imaging apparatus) is moving to one direction, the reference position may be changed to a closer position to the moving direction than the middle position.

A part of the OIS case 51 is configured to be able to transmit light including a wavelength that can be detected by the image sensor 13. This part is a portion corresponding to the moving area 905. As an example, the portion corresponding to the moving area 905 of the OIS case 51 may be provided with nothing. As an example, the portion corresponding to the moving area 905 of the OIS case 51 may be provided with an optical window formed of resin, glass, or the like.

The AF/OIS magnet 33 is provided at positions facing the OIS coils 55 in directions (X and Y directions in FIG. 1) orthogonal to the optical axis direction of the lens barrel assembly 11. The AF/OIS magnet 33 has a configuration that the magnet 33a whose magnetic pole is a south pole and the magnet 33b whose magnetic pole is a north pole are arranged in the moving direction of the OIS case 51, that is, in the X direction or the Y direction, at a side facing the OIS coil 55 and the OIS hall element 59. As an example, the AF/OIS magnet 33 provided on the X+side and the X-side of the OIS case 51 has a configuration that the

magnets

33a and 33b are arranged in the X direction. As an example, the AF/OIS magnet 33 provided on the Y+ side and the Y-side of the OIS case 51 has a configuration that the

magnets

33a and 33b are arranged in the Y direction. The OIS coil 55 and the OIS hall element 59 are provided on a side (Z+ side in FIG. 1) facing the AF/OIS magnet 33 of the OIS base 53 in directions (X and Y directions in FIG. 1) orthogonal to the optical axis direction of the lens barrel assembly 11. Optionally, the AF/OIS magnet 33 and the OIS coil 55 are arranged in a state where the OIS case 51 is at the reference position so that a middle position between the

magnets

33a and 33b arranged in the X direction or the Y direction becomes a middle position of the corresponding OIS coil 55. The OIS hall element 59 is provided inside the OIS coil 55, for example.

As an example, the AF/OIS magnet 33 and the OIS coil 55 constitutes an OIS drive unit. The OIS drive unit is configured to move the movable part of the OIS unit 5 in the X direction and/or the Y direction in accordance with the control signal from the OIS controller 6. Optionally, the OIS coil 55 generates a magnetic field according to the control signal (electric current) from the OIS controller 6. The AF/OIS magnet 33 generates the driving force in the X direction and/or the Y direction depending on the magnetic field generated by the OIS coil 55.

Note that the OIS drive unit of the OIS unit 5 and/or the lens drive unit of the AF unit 7 may be realized by another actuator such as an SMA (shape memory alloy) actuator configured to generate a driving force by sending an electric current to a shape memory alloy to heat it, without being limited to a case of being configured of a voice coil motor (VCM) that generates a driving force depending on electromagnetic force using a magnet and a coil.

As an example, the AF/OIS magnet 33 and the OIS hall element 59 constitute a posture detector. The posture detector is configured to output a detection signal corresponding to the present position of the OIS case 51 (the movable part of the OIS unit 5) . Optionally, the OIS hall element 59 is configured to detect a magnetic field generated by the AF/OIS magnet 33 or a change in the magnetic field and to output a detection signal according to the detected magnetic field intensity or change amount.

The fixed part of the OIS unit 5 further includes an acceleration sensor and a gyro sensor, in addition to the image sensor 13, the analog processing circuitry, the A/D converter, the image processing circuit, the OIS coils 55, the OIS springs 57, and the OIS hall elements 59 described above. These components are mounted on the OIS base 53, for example. The acceleration sensor and the gyro sensor are an example of a sensor configured to detect a shake added to the fixed part.

The OIS controller 6 is configured to control each component of the OIS unit 5. The OIS controller 6 includes a processor and a memory as hardware resources. The processor can appropriately employ various processors such as CPU, DSP, ASIC, and FPGA. Moreover, the memory can appropriately employ various memories such as ROM, a flash memory, and RAM. Note that the OIS controller 6 may employ a microcomputer. As an example, as illustrated in FIG. 1, the OIS controller 6 is provided on the OIS base 53 (fixed part) .

The OIS controller 6 is configured to perform feedback control of controlling positions (positions in X and Y directions) of the optical system of the lens barrel assembly 11, for example in accordance with a blur amount. Optionally, by feedback control based on the target posture and the present posture of the movable part of the OIS unit 5, the OIS controller 6 is configured to control a position of the movable part in the XY plane and to perform a correction process of correcting an image shake of a captured image accompanied with a vibration generated in the imaging apparatus 1.

As an example, based on the detection signal from the acceleration sensor and/or the gyro sensor, the OIS controller 6 is configured to calculate the target posture of the OIS unit 5. As an example, based on the present posture and the target posture of the OIS case 51, the OIS controller 6 is configured to output a control signal (electric current) for moving the OIS case 51 from the present posture to the target posture to the OIS coil 55. Note that the target posture and the present posture of the OIS unit 5 can be respectively represented as the target position and the present position of the OIS case 51 in moving directions (X and Y directions) .

FIG. 2 is a diagram explaining a movement process of the OIS unit 5 between the frames. FIG. 2 illustrates continuous three frames. As described above, in an exposure period T1 of a frame 1, the OIS case 51 moves inside the movable range 903 (see FIG. 1) in accordance with the image stabilization. At this time, as illustrated in FIG. 2, the imaging lens 11a mounted on the movable part of the OIS unit 5 moves inside the moving area 905 in accordance with the image stabilization, in the exposure period T1 of the frame 1.

In shooting with a long exposure time such as shooting in a dark place, a movement amount of the imaging lens 11a in the exposure period T1 of each frame is large. In other words, in the shooting with a long exposure time, when exposure is started in a state where the imaging lens 11a is located in the peripheral portion of the moving area 905, for example, the OIS case 51 hits the AF/OIS case 31 (mechanical end) and thus the OIS might not be executed.

Therefore, the OIS controller 6 is configured to move, between the frames (in the non-exposure period) , the optical system of the lens barrel assembly 11 up to a reference position based on a signal indicating a target value for which 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 the frames while suppressing a vibration of the AF unit 7 mounted on the movable part of the OIS unit 5. As an example, when the read out of the last row of each frame has been completed, that is, when a non-exposure period T2 is started, the OIS controller 6 executes the movement process.

Note that, only when the OIS case 51 contacts the mechanical end, when the gap 901 between the AF/OIS case 31 and the OIS case 51 is not more than a predetermined threshold, or when the end of the moving area 905 is detected from a captured image, the OIS controller 6 may be configured to execute the movement process between the next frames.

As illustrated in FIG. 2, the non-exposure period T2 is a time excluding a rolling shutter time T3 from the period between the frames. Therefore, the movement process of returning the movable part of the OIS unit 5 to the reference position can be executed in the non-exposure period T2 within the period between the frames. For this reason, the shooting with a long exposure time is requested to reduce a time required for the movement process and to shorten the non-exposure period T2.

Herein, the time required for the movement process includes a moving time of moving the movable part of the OIS unit 5 by the control of the OIS controller 6. Moreover, the time required for the movement process further includes a damping time in which vibrations occurring on the movable part of the OIS unit 5 and the AF unit 7 due to this movement are damped up to a predetermined range.

As an example, the OIS controller 6 is configured to output a control signal (electric current) for moving the OIS case 51 from the present posture to the target posture to the OIS coil 55, by feedback control with the reference position as the target position in the movement process.

A method of setting a target value by the OIS unit 5 in the feedback control includes a method of setting a target value in a step shape, a method of setting a target value in a slope shape, and the like. For example, the method of setting the target value in a slope shape has high stability and short damping time but has long moving time, because the movement speed of the movable part of the OIS unit 5 is small. For example, the method of setting the target value in a step shape has short moving time but has low stability and long damping time, because the movement speed of the movable part of the OIS unit 5 is large. Moreover, for example, in a method of dividing and setting the target value into a plurality of steps, the moving time becomes longer as the number of divisions (numbers of steps) increases more.

Therefore, the anti-shake system 3 according to the present embodiment includes a vibration suppressor configured to set a target value of one step in a step shape to make a movement speed larger and also reduce a damping time. The vibration suppressor is configured to remove or reduce a signal with a specific frequency from a signal of a target value indicating the reference position of the optical system of the lens barrel assembly 11. In other words, the vibration suppressor performs filter processing of removing or reducing a signal with a specific frequency from an input signal 907 indicating a step-shaped target value to be input into the OIS controller 6. Note that the vibration suppressor may set target values of a plurality of steps in a step shape.

FIG. 3 is a diagram illustrating an example of a configuration of the anti-shake system 3 according to the embodiment. FIG. 3 illustrates the notch filter 4 as the vibration suppressor according to the embodiment. As illustrated in the block diagram of FIG. 3, the notch filter 4 is provided in front of the OIS controller 6. In other words, the notch filter 4 is provided in front of a control loop (feedback loop) of the OIS unit 5 formed as a closed loop.

The notch filter 4 is a filter configured to remove or reduce a signal with a specific frequency. The notch filter 4 may be referred to as a band elimination filter (BEF) , a band rejection filter (BRF) , or a band stop filter (BSF) .

As described above, the AF unit 7 is supported by the OIS unit 5 via the AF springs 75. For this reason, a movement of the movable part of the OIS unit 5 is not identical with a movement of the AF unit 7. For example, when the movable part of the OIS unit 5 is reciprocated in the X direction or the Y direction, the AF unit 7 moves in amplitude and phase different from those of the movable part of the OIS unit 5. In other words, the optical system of the lens barrel assembly 11 movable in the optical axis direction in the AF unit 7 may be also moved in a direction different from the optical axis direction in accordance with the deformation of the AF springs 75 accompanied with the movement of the movable part of the OIS unit 5. Based on these factors, the control loop of the OIS unit 5 is hard to damp a vibration with a specific frequency due to a nested structure of the OIS unit 5 and the AF unit 7. Optionally, a specific frequency (peak frequency) taking a positive value in a gain diagram for the control loop of the OIS unit 5 is easy to cause a vibration to remain.

For this reason, the notch filter 4 is configured to remove or reduce a peak frequency in the closed loop characteristics. As a result, it is possible to expedite vibration damping in the control loop (feedback loop) of the OIS unit 5 and shorten a time according to the movement process.

FIGS. 4 and 5 are diagrams explaining convergence of vibration of the OIS unit 5 accompanied with the movement. FIG. 4 illustrates the behaviors of the OIS unit 5 (solid line) and the AF unit 7 (broken line) when the notch filter 4 acting as the vibration suppressor is not provided, unlike the anti-shake system 3 according to the present embodiment. FIG. 5 illustrates the behaviors of the OIS unit 5 (solid line) and the AF unit 7 (broken line) by the anti-shake system 3 equipped with the notch filter 4 according to the embodiment. In the graphs of FIGS. 4 and 5, the vertical axis and the horizontal axis respectively indicate an X-direction position [μm] and a time [s] .

Note that FIGS. 4 and 5 illustrate the behaviors of the OIS unit 5 and the AF unit 7 when the target value is changed in one step in a step shape in the X direction. FIG. 5 illustrates a case of providing the notch filter 4 configured to remove or reduce the signal with the specific frequency of 200Hz in accordance with the peak frequency of the closed loop characteristics.

As illustrated in FIG. 4, when the notch filter 4 is not provided, for example, the vibrations of the OIS unit 5 and the AF unit 7 at the time indicated by an arrow in FIG. 4 are not damped sufficiently.

On the other hand, in the case of the anti-shake system 3 according to the present embodiment in which the notch filter 4 is provided, for example, the vibrations of the OIS unit 5 and the AF unit 7 at the time indicated by an arrow in FIG. 5 have about 1/2 amplitudes of the amplitudes at the same time (the time indicated by the arrow in FIG. 4) when the notch filter 4 is not provided.

As described above, according to the image stabilization method, the anti-shake system 3 to realize the image stabilization, and the imaging apparatus 1 equipped with the anti-shake system 3 according to the present embodiment, it is possible to expedite damping of vibration of the OIS unit 5 and the AF unit 7 accompanied with the movement process. In other words, according to the present embodiment, it is possible to reduce a time according to the movement process between the frames. For this reason, even in the case of shooting with a long exposure time such as shooting in a dark place, the OIS can be appropriately executed.

Moreover, the vibration suppressor is configured to remove or reduce a peak frequency according to a control loop for the OIS unit 5 that supports the AF unit 7 via the AF springs 75. For this reason, it is not required to detect the position of the AF unit 7 in the moving direction of the movable part of the OIS unit 5. Optionally, the AF unit 7 may include a focus lens position detector configured to detect the position of the lens barrel assembly 11 in the optical axis direction (Z direction) , and thus does not require to be provided with a sensor configured to detect the positions in the X and Y directions for the detection of convergence of vibration.

Note that the image stabilization method, the anti-shake system 3 to realize the image stabilization, and the imaging apparatus 1 equipped with the anti-shake system 3 according to the present embodiment can be applied to a moving image as well as continuous shooting and image composition (HDR, night view multi-shot, etc. ) after continuous shooting because the OIS unit 5 can be moved between the frames at high speed.

Note that the vibration suppressor may be configured to be able to switch an operation of removing or reducing a peak frequency between the exposure period and a period between the frames. For example, the vibration suppressor is configured to, in the exposure period, weaken a degree by which the peak frequency is removed or reduced compared to the period between the frames. For example, the vibration suppressor is configured, in the exposure period, not to remove or reduce the peak frequency. Note that the switching may be realized by the switching of a plurality of the notch filters 4 that have different degrees of removing or reducing, may be realized by the switching of the number of steps of the notch filter 4, or may be realized by the switching of use/non-use of the notch filter 4.

Note that the vibration suppressor may be configured of a part of the OIS controller 6. Moreover, the vibration suppressor may be realized by processing of firmware (program) in the OIS controller 6.

Note that processing by the circuits in back of the image sensor 13, the OIS controller 6, and the AF controller 8 may be realized as a function of the OIS controller 6 that is realized by executing a program loaded into a memory by a processor or may be realized as a dedicated circuit.

Note that at least two components of components of the circuits in back of the image sensor 13, the OIS controller 6, and the AF controller 8 may be realized by one circuit. Moreover, at least one component of the components of the circuits in back of the image sensor 13, the OIS controller 6, and the AF controller 8 may be realized by combining two or more circuits.

Note that the image stabilization according to the present embodiment can be realized by an electronic device that includes the imaging apparatus 1 and a circuit board not illustrated. This circuit board is configured to provide electricity to the imaging apparatus 1. This circuit board may be a component of the imaging apparatus 1.

Note that a part or the whole of processing executed by the imaging apparatus 1 and/or the anti-shake system 3 according to the present embodiments may be realized by software.

A program executed by the imaging apparatus 1 and/or the anti-shake system 3 according to the present embodiments is recorded and provided in a flash memory (semiconductor memory) such as a USB (Universal Serial Bus) memory and SSD (Solid State Drive) , and a computer-readable recording medium such as HDD (Hard Disk Drive) , in a file with an installable format or an executable format.

Moreover, a program executed by the imaging apparatus 1 and/or the anti-shake system 3 according to the present embodiments may be configured to be provided by being stored on a computer connected to a network such as the Internet and being downloaded by way of the network. Moreover, a program executed by the imaging apparatus 1 and/or the anti-shake system 3 according to the present embodiments may be configured to be provided or distributed by way of a network such as the Internet.

Moreover, a program executed by the imaging apparatus 1 and/or the anti-shake system 3 according to the present embodiments may be configured to be previously incorporated into ROM etc. and be provided.

According to at least one embodiment described above, it is possible to reduce a time according to the movement of the OIS unit between the frames.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

(Supplementary Notes)

(1) An anti-shake system includes:

an optical image stabilization (OIS) unit configured to be able to change a position of an optical system;

a vibration suppressor configured to remove or reduce a signal with a specific frequency from a signal of a target value indicating a reference position of the optical system; and

an OIS controller configured to perform feedback control of controlling the position of the optical system and to move the optical system up to the reference position between frames based on the signal indicating the target value for which the specific frequency has been removed or reduced.

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

(3) In the imaging apparatus according to (1) or (2) , the vibration suppressor is configured, in an exposure period, to weaken a degree by which the signal with the specific frequency is removed or reduced from the signal indicating the target value compared to a period between the frames.

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

(5) In the anti-shake system according to any one of (1) to (4) , a movable part of the OIS unit is movable in at least one direction different from an optical axis direction of the optical system, and

the movable part supports the optical system movable in an optical axis direction of the optical system via a flexible member to be movable in a moving direction of the movable part.

(6) In the anti-shake system according to (5) , at least the 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.

(7) In the anti-shake system according to any one of (1) to (6) , an optical axis of the optical system at the reference position passes through a center of a moving area of the optical system.

(8) In the anti-shake system according to any one of (1) to (7) , the OIS controller is configured to move the optical system in one step up to the reference position.

(9) An imaging apparatus is equipped with the anti-shake system according to any one of (1) to (8) .

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

the image sensor configured to generate an image signal according to a light beam of a subject field; and

the optical system configured to form an image of the light beam from a subject on the imaging surface of the image sensor.

(11) The imaging apparatus according to (10) , the OIS unit configured to be able to change a position of the optical system relative to an image sensor.

(12) The imaging apparatus according to (10) or (11) , an optical axis of the optical system at the reference position passes through a center of an imaging surface of the image sensor.

(13) An Electronic device is equipped with the imaging apparatus according to claim 8, further includes a circuit board that provides electricity to the imaging apparatus.

(14) An image stabilization method, in optical image stabilization (OIS) of changing a position of an optical system, includes:

removing or reducing a signal with a specific frequency from a signal of a target value indicating a reference position of the optical system;

performing feedback control of controlling the position of the optical system; and

moving the optical system up to the reference position between frames based on the signal indicating the target value for which the specific frequency has been removed or reduced.

(15) In the image stabilization method according to (14) , the removing or reducing the signal with the specific frequency is performed by a notch filter.

(16) In the image stabilization method according to (14) or (15) , the removing or reducing includes, in an exposure period, weakening a degree by which the signal with the specific frequency is removed or reduced from the signal indicating the target value compared to a period between the frames.

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

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

(19) In the image stabilization method according to (18) , at least the 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.

(20) In the image stabilization method according to any one of (14) to (19) , an optical axis of the optical system at the reference position passes through a center of a moving area of the optical system.

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

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

[Explanations of Letters or Numerals]

1: Imaging apparatus

11: Lens barrel assembly

11a: Imaging lens

13: Image sensor

3: Anti-shake system

31: AF/OIS case

33: AF/OIS magnet

5: OIS unit

51: OIS case

53: OIS base

55: OIS coil

57: OIS spring

59: OIS hall element

6: OIS controller

7: AF unit

71: Lens holder

73: AF coil

75: AF spring

77: AF hall element

8: AF controller

901: Gap

903: Movable range

905: Moving area

907: Input signal

Claims

An anti-shake system comprising:

an optical image stabilization (OIS) unit configured to be able to change a position of an optical system;

a vibration suppressor configured to remove or reduce a signal with a specific frequency from a signal of a target value indicating a reference position of the optical system; and

an OIS controller configured to perform feedback control of controlling the position of the optical system and to move the optical system up to the reference position between frames based on the signal indicating the target value for which the specific frequency has been removed or reduced.
The anti-shake system according to claim 1, wherein the vibration suppressor includes a notch filter.
The anti-shake system according to claim 1, wherein the vibration suppressor is configured, in an exposure period, to weaken a degree by which the signal with the specific frequency is removed or reduced from the signal indicating the target value compared to a period between the frames.
The anti-shake system according to claim 1, wherein the specific frequency includes a peak frequency in closed loop characteristics of the feedback control.
The anti-shake system according to claim 1, wherein

a movable part of the OIS unit is movable in at least one direction different from an optical axis direction of the optical system, and

the movable part supports the optical system movable in an optical axis direction of the optical system via a flexible member to be movable in a moving direction of the movable part.
The anti-shake system according to claim 1, wherein an optical axis of the optical system at the reference position passes through a center of a moving area of the optical system.
The anti-shake system according to claim 1, wherein the OIS controller is configured to move the optical system in one step up to the reference position.
An imaging apparatus is equipped with the anti-shake system according to claim 1, further comprising

an image sensor configured to generate an image signal according to a light beam of a subject field; and

the optical system configured to form an image of the light beam from a subject on the imaging surface of the image sensor.
The imaging apparatus according to claim 8, wherein the OIS unit configured to be able to change a position of the optical system relative to an image sensor.
The imaging apparatus according to claim 8, wherein an optical axis of the optical system at the reference position passes through a center of an imaging surface of the image sensor.
An Electronic device is equipped with the imaging apparatus according to claim 8, further comprising

a circuit board that provides electricity to the imaging apparatus.
An image stabilization method in optical image stabilization (OIS) of changing a position of an optical system, the method comprising:

removing or reducing a signal with a specific frequency from a signal of a target value indicating a reference position of the optical system;

performing feedback control of controlling the position of the optical system; and

moving the optical system up to the reference position between frames based on the signal indicating the target value for which the specific frequency has been removed or reduced.