JP6656589B2 - Imaging device and imaging control program - Google Patents

Description

  The present invention relates to a function of suppressing image noise in an imaging device.

  Various techniques for suppressing image noise in an imaging device such as a digital camera have been proposed. As an example, in Patent Document 1, as a method of correcting image noise, a dark image corresponding to an image obtained by shading an image sensor is acquired in advance, and the dark image is subtracted from an image sensor output at the time of shooting. The method is described. Specifically, in the imaging device of Patent Document 1, a dark image obtained in advance at a specific temperature is multiplied by a gain obtained from an exposure time and a temperature at the time of shooting, and then a dark image is output from an imaging device output at the time of shooting. It is configured to subtract.

  Patent Document 2 discloses a configuration in which the magnitude of vibration generated at the time of shooting by a camera is sensed and converted into an output signal, and the output signal is used to suppress image noise caused by the vibration.

JP-A-63-263883 JP 2011-114543 A

  On the other hand, the present inventors have noticed that the image noise included in the output of the image sensor changes depending on the attitude of the image capturing apparatus. This change in image noise is considered to be due to a change in the noise source in the imaging device due to a change in the attitude of the imaging device. A main noise source of this type of image noise is considered to be an operating unit that causes a change in a magnetic field in accordance with a change in the attitude of the imaging device, thereby affecting the image sensor.

  In Patent Literature 1, a configuration is adopted in which a gain is applied to a dark image to perform correction, but image noise that changes depending on the attitude of the imaging device cannot be corrected. Further, the camera described in Patent Literature 2 corrects noise when vibration occurs, and does not have a configuration for correcting image noise that changes depending on the posture of the camera.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an imaging device that can appropriately correct image noise that changes depending on the attitude of the imaging device.

  According to one aspect of the present invention, there is provided an imaging device, which acquires an image sensor that generates an image signal, an actuator having a magnetic field effect, and information on a magnetic field (state of a magnetic field) in the actuator. Magnetic field information acquisition means, reference information holding means for holding reference information representing a reference of image noise caused by a magnetic field, and information acquired by the image sensor based on the reference information and information on the magnetic field acquired by the magnetic field information acquisition means Correction means for correcting the image noise of the photographed image to be obtained.

  Here, the actuation device having a magnetic field effect is typically a device having an electromagnetic actuator such as a shake correction mechanism, and changes the magnetic field in accordance with a change in the attitude of the imaging device. Therefore, according to the imaging device having the above configuration, it is possible to suitably correct image noise that changes depending on the attitude of the imaging device.

  The magnetic field information acquisition means may acquire information on a magnetic field from a drive signal of the actuator.

  The imaging device may further include a posture information acquisition unit for acquiring information on the posture of the imaging device. In this case, the magnetic field information acquisition unit can acquire information on the attitude of the imaging device as information on the magnetic field.

  The reference information holding means holds reference information representing a reference of image noise for each component of each coordinate axis of a coordinate system fixed to the imaging device, and the magnetic field information obtaining means obtains information about a magnetic field for each coordinate axis. Is also good. In this case, the correction means generates a corrected image by multiplying the reference information held for each component of each coordinate axis by information about the magnetic field acquired for each coordinate axis as a coefficient, and synthesizing them, thereby correcting the captured image. Do.

  The reference information may be acquired in a posture where the magnetic field in the imaging device is maximized.

  The reference information may be acquired in a posture in which the magnetic field in the imaging device has a minimum influence on other than the target axis.

  Also provided by another aspect of the present invention is an imaging device, an imaging element that generates an image signal, a posture information acquisition unit for acquiring information on the posture of the imaging device, and an imaging device. A reference information holding unit that holds reference information representing a reference of image noise due to a change in posture, the reference information, and information acquired by the image sensor based on information about the posture of the imaging device acquired by the posture information acquisition unit. Correction means for correcting image noise of the captured image to be captured.

  According to such a configuration, image noise that changes depending on the attitude of the imaging device can be suitably corrected.

  According to another aspect of the present invention, a computer has a magnetic field information obtaining procedure for obtaining information on a magnetic field in an operating device having a magnetic field effect, and reference information holding reference information representing a standard of image noise caused by the magnetic field. An imaging control program for executing a holding procedure, a reference procedure, and a correction procedure for correcting image noise of a captured image acquired by an imaging device based on information on a magnetic field acquired by a magnetic field information acquisition procedure. Is provided.

  Further, according to another aspect of the present invention, a computer holds a posture information acquisition procedure for acquiring information on the posture of the imaging device and reference information indicating a reference of image noise due to a change in the posture of the imaging device. A reference information holding procedure, and a correction procedure for correcting image noise of a captured image acquired by the imaging device based on the reference information and the information on the orientation of the imaging device acquired by the orientation information acquisition procedure. An imaging control program for causing the imaging control program is provided.

  As described above, according to the present invention, there is provided an imaging apparatus capable of suitably correcting image noise that changes depending on the attitude of the imaging apparatus.

FIG. 1 is an external view of the imaging device of the present embodiment. FIG. 2 is a block diagram illustrating a configuration of the imaging device according to the present embodiment. FIG. 3 is a diagram for explaining the correspondence between the output from the acceleration sensor and the attitude of the imaging device with respect to rotation about the Z axis. FIG. 4 is a diagram for explaining the correspondence between the output from the acceleration sensor and the attitude of the imaging device with respect to rotation about the X axis. FIG. 5 is a diagram illustrating a configuration of a shake correction mechanism in the imaging apparatus. FIG. 6 is a flowchart illustrating a photographing process including image noise correction according to the present embodiment.

  Hereinafter, an imaging device according to an embodiment of the present invention will be described with reference to the drawings. As described in detail below, the imaging device of the present embodiment is configured to appropriately correct image noise that changes depending on the attitude of the imaging device. In the following, a compact digital camera will be described as an example of an imaging device. However, the imaging device is not limited to a compact digital camera. For example, a digital single-lens reflex camera, a mirrorless single-lens camera, a smartphone, a feature phone, a portable game machine For example, another type of device having a photographing function may be used.

[Overall Configuration of Imaging Device]
FIG. 1 is an external view of an imaging device 1 of the present embodiment. As shown in FIG. 1, the imaging device 1 includes a lens unit 11 and a flash window 12 on the front side of a housing 10 and a release button 13 on an upper part.

  FIG. 2 is a block diagram illustrating a configuration of the imaging device 1 according to the present embodiment. As shown in FIG. 2, a CPU (Central Processing Unit) 100, an operation unit 102, a drive circuit 104, an aperture / shutter 110, an image sensor 112, a shake correction mechanism 140, a signal Processing circuit 114, image processing engine 116, buffer memory 118, card interface 120, LCD (Liquid Crystal Display) control circuit 122, LCD 124, ROM (Read Only Memory) 126, flash drive circuit 127, flash 128, acceleration sensor 130, A gyro sensor 131 is provided. A focus lens 106 and a lens driving mechanism 107 are provided in the lens unit 11 of the imaging device 1.

  The shake correction mechanism 140 is configured as a so-called sensor shift type shake correction mechanism. In the imaging device 1, the acceleration sensor 130 and the gyro sensor 131 output signals corresponding to the vibration and the rotational motion (pitch, yaw) of the imaging device 1. The CPU 100 includes a function as a shake correction controller, calculates a drive amount of the image sensor 112 based on signals from the acceleration sensor 130 and the gyro sensor 131, and controls the shake correction mechanism 140 to set the image sensor 112 to a predetermined value. The blur correction is performed by shifting in the plane of. The configuration of the shake correction mechanism 140 will be described later. Note that a control method known in the art can be used as the shake correction control of the sensor shift method, and a detailed description of the shake correction control will be omitted.

  The operation unit 102 includes various switches or buttons necessary for the user to operate the imaging apparatus 1, such as a power switch, a release button 13, and a shooting mode switch. When a power switch is pressed by a user, power is supplied from a battery (not shown) to various circuits of the imaging apparatus 1 through a power supply line. After the power is supplied, the CPU 100 accesses the ROM 126 to read the control program, load the control program into a work area (not shown), and execute the loaded control program to control the entire imaging apparatus 1.

  When the release button 13 is operated, the CPU 100 operates the drive circuit 104 so that an appropriate exposure is obtained based on a photometric value measured by a TTL (Through The Lens) exposure meter (not shown) built in the imaging apparatus 1. The drive and control of the aperture / shutter 110 is controlled via the. Here, the aperture and shutter 110 has a function as a shutter and a function as an aperture for adjusting an aperture value. The drive circuit 104 drives the aperture / shutter 110 and adjusts the aperture value so that an appropriate exposure is obtained. The adjustment of the aperture value is performed based on an AE function designated by a shooting mode switch, such as a program AE (Automatic Exposure) or a shutter speed priority AE. Since the configuration and control of these AEs are well known, a detailed description thereof will be omitted.

  Further, the CPU 100 performs AF (Auto Focus) control together with AE control. In the AF control, the driving of the lens driving mechanism 107 is controlled via the driving circuit 104, and the positions and positional relationships of a plurality of lenses provided in the focus lens 106 are adjusted. Thereby, the focal length of the focus lens 106 changes. In the AF control, the focus of the focus lens 106 is automatically adjusted to the subject by changing the focal length of the focus lens 106.

  A light beam from the subject is received by the image sensor 112 via the focus lens 106 and the aperture / shutter 110. The image sensor 112 is, for example, a CCD (Charged Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The time during which the image sensor 112 is exposed to the light beam of the subject is adjusted by the aperture / shutter 110. The imaging element 112 converts a light beam received by each pixel on the imaging surface into an electric signal according to the amount of light, and outputs the converted electric signal to the signal processing circuit 114. The signal processing circuit 114 performs predetermined signal processing on the electric signal input from the image sensor 112 and outputs the signal to the image processing engine 116.

  The image processing engine 116 performs predetermined signal processing such as color interpolation, matrix operation, and Y / C separation on the signal input from the signal processing circuit 114 to generate a luminance signal Y and color difference signals Cb and Cr. Compression is performed in a predetermined format such as JPEG (Joint Photographic Experts Group). The buffer memory 118 is used as a temporary storage for processing data when the image processing engine 116 executes processing.

  The image processing engine 116 can communicate with the memory card 200 via the card interface 120. The image processing engine 116 stores the generated compressed image signal (captured image data) in the memory card 200 or a built-in memory (not shown) provided in the imaging device.

  Further, the image processing engine 116 performs predetermined signal processing on the signal after the Y / C separation, and buffers the signal in a frame memory (not shown) for each frame. The image processing engine 116 sweeps out the buffered signal from each frame memory at a predetermined timing, converts the signal into a video signal of a predetermined format, and outputs the video signal to the LCD control circuit 122. The LCD control circuit 122 controls the modulation of the liquid crystal of the LCD 124 based on the image signal input from the image processing engine 116. As a result, the captured image of the subject is displayed on the display screen of the LCD 124. The user can visually recognize a photographed image photographed with appropriate luminance and focus on the display screen of the LCD 124 based on the AE control and the AF control.

  When a user inputs a reproduction operation of a photographed image, the image processing engine 116 reads the photographed image data designated by the user operation from the memory card 200 or the built-in memory, converts the data into an image signal of a predetermined format, and Output to the control circuit 122. The LCD control circuit 122 controls the modulation of the liquid crystal based on the image signal input from the image processing engine 116, so that the captured image of the subject is displayed on the display screen of the LCD 124.

  The flash drive circuit 127 applies a drive voltage to the flash 128 when a user inputs an operation for instructing flash photography to the operation unit 102 by the user. The flash 128 emits irradiation light (flash light) according to the drive voltage, and irradiates the subject through the flash window 12. Whether the imaging device 1 performs flash photography using flash or photography without flash is set automatically or manually.

  The acceleration sensor 130 is a three-axis acceleration sensor capable of detecting accelerations in three directions orthogonal to each other, and is used for detecting the acceleration of the imaging device 1. The acceleration sensor 130 outputs three acceleration values based on accelerations in three directions. CPU 100 calculates the magnitude of the acceleration and the direction of the acceleration based on the output acceleration value. The state of the imaging device 1 can be determined using the calculated magnitude and direction of the acceleration. For example, the direction of gravity applied to the imaging device 1 is calculated using the direction of acceleration. By using the direction of gravity, the attitude of the imaging device 1 is calculated.

[Configuration for Image Noise Correction]
Hereinafter, a configuration for image noise correction in the imaging apparatus 1 will be described. The imaging device 1 previously acquires a dark image corresponding to an image acquired by shielding the image sensor 112 from light, and corrects image noise generated in the image sensor 112 by subtracting the dark image from the image sensor output at the time of shooting. It has a function to do. The inventors of the present invention paid attention to the fact that in an apparatus having a shake correction mechanism like the imaging apparatus 1 of the present embodiment, image noise changes depending on the attitude of the imaging apparatus 1. It is considered that this is because the magnetic flux leaking from the electromagnetic actuator in the shake correction mechanism 140 (that is, the magnetic flux affecting the image sensor 112) changes depending on the attitude of the image capturing apparatus 1. In view of such a phenomenon, the imaging device 1 corrects the dark image by applying a coefficient to the dark image according to the attitude of the imaging device 1, and then subtracts the corrected dark image from the output of the imaging device at the time of shooting. Thus, the image noise that changes depending on the attitude of the imaging device 1 is appropriately corrected.

[Camera posture information]
In the imaging device 1, the attitude of the imaging device 1 is detected based on the output from the three-axis acceleration sensor 130. 3 and 4 are diagrams for explaining the correspondence between the output from the acceleration sensor 130 and the attitude of the imaging device 1. FIG. Here, the optical axis direction of the imaging apparatus 1 is defined as the Z-axis direction (the direction from the subject side toward the imaging apparatus is defined as positive), and the horizontal and vertical directions in the normal posture are defined as the X-axis direction, respectively. (The direction from the right side (grip side) to the left side is defined as positive when the imaging device in the normal posture is viewed from the back side as shown in FIG. 3A), and the Y-axis direction (vertical upward in the normal posture is defined as positive). ). In detail, FIG. 3 shows a correspondence relationship between a change in posture due to rotation of the imaging device 1 around the Z axis and a corresponding acceleration detection value, and FIG. 3 shows a correspondence relationship between a change in posture due to rotation in FIG. In the tables of FIGS. 3B and 4B and in the following description, the detection value of the acceleration sensor 130 indicates the magnitude of the acceleration K [m / s ² ] when the reference noise image is obtained. It is normalized and expressed as 1.

  In the state of the normal posture (Z-axis rotation of 0 degree) of the imaging apparatus 1 schematically shown in FIG. 3A, the gravitational acceleration g acts on the lower side of the Y-axis. It is detected that the Y-axis acceleration and the Z-axis acceleration are 0, −1, and 0, respectively. The state in which the imaging device 1 is rotated 90 degrees around the Z axis so that the grip portion is located upward (Z axis rotation 90 degrees) is when the X axis acceleration, the Y axis acceleration, and the Z axis acceleration are 1, 0, 0, respectively. Is detected. The state in which the normal posture and the upside-down state are reversed (Z-axis rotation 180 degrees) is detected as the states where the X-axis acceleration, the Y-axis acceleration, and the Z-axis acceleration are 0, 1, and 0, respectively. When the imaging apparatus 1 is rotated 270 degrees around the Z axis (hereinafter, also referred to as a vertical posture), the X-axis acceleration, the Y-axis acceleration, and the Z-axis acceleration are −1, 0, 0, respectively. Detected as a state.

  Regarding the rotation around the X axis shown in FIG. 4A, the state of the normal posture (X axis rotation of 0 degree) indicates that the X axis acceleration, the Y axis acceleration, and the Z axis acceleration are 0, −1, and 0, respectively. Detected as a state. The state in which the imaging apparatus 1 is rotated by 90 degrees around the X axis (hereinafter, this state is also referred to as an upward posture) is such that the X axis acceleration, the Y axis acceleration, and the Z axis acceleration are 0, 0, 1 respectively. Detected as a state. A state in which the normal posture and the upside-down state are reversed (X-axis rotation 180 degrees) is detected as a state in which the X-axis acceleration, the Y-axis acceleration, and the Z-axis acceleration are 0, 1, and 0, respectively. The state in which the imaging apparatus 1 is rotated by 270 degrees around the X axis (hereinafter, this state is also referred to as a downward attitude) is when the X-axis acceleration, the Y-axis acceleration, and the Z-axis acceleration are 0, 0, and −1, respectively. Detected as a state.

  As described above, the attitude of the imaging device 1 can be detected based on the output of the acceleration sensor 130.

[Configuration of blur correction mechanism]
Hereinafter, the configuration of the shake correction mechanism 140 will be described in detail. FIG. 5 is a diagram illustrating a configuration of the shake correction mechanism 140. Specifically, FIG. 5A is a plan view of the movable portion of the shake correction mechanism 140 viewed from the surface on which the image sensor 112 is mounted. FIG. 5B is a cross-sectional view taken along line BB in FIG. 5A. FIG. 5 (b) also shows the fixed part. As described above, the blur correction mechanism is configured to perform the blur correction by driving the movable unit including the image sensor 140 and the imaging element 112 in a predetermined plane (in the XY plane in the present embodiment).

  As shown in FIG. 5A, the movable part of the shake correction mechanism 140 includes a slide plate 13, an image sensor substrate 12, an image sensor 112 held by the slide plate 13, and four drive coils 14. ing. As shown in FIG. 5B, the fixing portion includes a front yoke 16, a rear yoke 15, and a magnet 17. The fixing portion is arranged so as to sandwich the drive coil 14 between the magnet 17 and the rear yoke 15.

  Since there is a magnetic flux at the position of the drive coil 14 as shown by a broken line arrow in FIG. 5B, when a drive current flows through the drive coil 14, Lorentz force is generated, and the movable portion can be driven. The magnitude and direction of the Lorentz force generated at this time are determined by the magnitude and direction of the drive current flowing through the drive coil 14. Therefore, by controlling the magnitude and direction of the drive current flowing through the drive coil 14, the movable section can be driven in a desired direction. For the drive coil 14, drive current control by, for example, PWM (pulse width modulation) is performed.

[Principle of image noise correction by posture]
In the blur correction mechanism 140, if there is a magnetic flux leaking from the drive coil 14, a magnetic field is applied to the image sensor 112, and this phenomenon appears as image noise. As described above with reference to FIGS. 3 and 4, the direction of gravity with respect to the imaging device 1 (the state of the detection value detected by the three-axis acceleration sensor) changes depending on the attitude of the imaging device 1. Therefore, the magnitude and direction of the drive current flowing through the drive coil 14 for holding the image sensor 112 change with the posture of the image pickup apparatus 1 (that is, change in the direction of gravity). That is, the state of driving the drive coil 14 and the state of the detection value of the acceleration sensor 130 are correlated with each other. For example, the driving force (the magnitude and direction of the driving current) for holding the position of the image sensor 112 is the same in the normal posture and the upside-down posture of the imaging device 1, but the driving amount is the same but the driving direction is opposite. . In this case, regarding the amount of magnetic field covering the image sensor 112, if the image noise in the normal posture is set to +1, it can be considered that the image noise of -1 is generated in the upside down posture.

  In the imaging device 1, a dark image (DARKy) in a normal posture (a state in which gravity is applied only in the Y-axis direction) and a dark image (DARKx) in a vertical posture (a state in which gravity is applied only in the X-axis direction) are set in advance. Are stored in, for example, a non-volatile memory (not shown) in the imaging device 1. The dark image in the X-axis direction (DARKx) and the dark image in the Y-axis direction (DARKy) are multiplied by the X-axis direction acceleration and the Y-axis direction acceleration acquired from the acceleration sensor 130 at the time of shooting as coefficients, and are synthesized and corrected. Get the data.

  Here, DARKx is a dark image acquired in a state where gravity is applied only in the X-axis direction, and is an image noise component corresponding to X-axis direction acceleration minus K (see FIGS. 3 and 4). That is, DARKx is a reference image representing the reference value of the X-axis direction component of the image noise caused by the change in the attitude of the imaging device 1. DARKy is a dark image acquired in a state where gravity is applied only in the Y-axis direction, and is an image noise component corresponding to the Y-axis direction acceleration minus K (see FIGS. 3 and 4). That is, DARKy is a reference image representing a reference value of a Y-axis direction component of image noise caused by a change in the attitude of the imaging device 1. Therefore, the above description of the correction data generation is based on the data obtained by multiplying the reference image of the X-axis direction component of the image noise caused by the change in the attitude of the imaging device 1 by the X-axis direction acceleration as a coefficient, and the This corresponds to generating correction data by synthesizing a reference image of a Y-axis component of image noise caused by a change with data obtained by multiplying a Y-axis acceleration as a coefficient.

  Then, by subtracting the correction data from the photographed image data at the time of photographing, image noise due to the attitude of the imaging device 1 is corrected. The above is the principle of the correction of the image noise due to the posture change.

  In the above description, when the reference image of the X-axis direction component of the image noise and the reference image of the Y-axis direction component of the image noise are acquired, the vertical posture of the X-axis direction acceleration minus K and the Y-axis direction acceleration, respectively. The positive attitude of minus K is intended to use, as a reference, data having the maximum amount of noise in the direction in which the reference image is obtained. Specifically, the reference image of the X-axis direction component of the image noise is acquired in a state where the X-axis direction acceleration is the maximum (minus K) and the Y-axis direction acceleration is the minimum (zero). The reference image of the Y-axis direction component of the image noise is acquired in a state where the acceleration in the Y-axis direction is maximum (minus K) and the acceleration in the X-axis direction is minimum (zero). This makes it possible to avoid an operation of enlarging the absolute value of the value of the reference image of the image noise in the calculation of the image noise correction, thereby improving the accuracy of the image noise correction. Here, the maximum acceleration means the maximum that can be assumed in a normal use state (the stationary state of the imaging device 1). Therefore, for example, in a situation where the rising acceleration is applied to the imaging device 1, the acceleration at the time of acquiring the reference image becomes larger than the maximum that can be assumed in a normal use state (the stationary state of the imaging device 1). There are cases.

  In the above description, the reason why the noise components are synthesized only in the X-axis direction and the Y-axis direction when the correction data is obtained is that the drive control of the drive coil 14 is performed only in the X-axis direction and the Y-axis direction. (I.e., no driving coil for driving the movable portion in the Z-axis direction), the basic idea is to change the image noise with the change in the attitude of the imaging device 1 in the Z-axis direction. It is not necessary to consider the acceleration component of.

  Therefore, in the case where the shake correction mechanism 140 is configured to drive the image sensor 112 also in the Z-axis direction (when further provided with a drive coil for driving in the Z-axis direction), a method similar to that described above in the Z-axis direction is used. The noise component acquired in step (1) is further combined to generate correction data.

[Shooting processing including image noise correction]
FIG. 6 is a flowchart illustrating a photographing process including image noise correction according to the present embodiment. The photographing process in FIG. 6 is a process executed by cooperation of various components (such as the image processing engine 116) under the control of the CPU 100. This photographing process is started when the release button 13 is pressed. Prior to the execution of the photographing process, a dark image in the X-axis direction and the Y-axis direction is prepared at the stage of acquiring adjustment data at the time of shipping or the like.

(Step S11 (exposure))
When the photographing process is started in response to the depression of the release button 13, the exposure with the AE control and the AF control described above is performed (step S11).

(Step S12 (posture information acquisition))
Next, the acceleration of each axis is obtained from the acceleration sensor 130 at the timing of reading the image signal from the image sensor 112 (Step S12. The output of the acceleration sensor 130 is obtained at the timing immediately before the reading of the image signal, thereby obtaining the image. It is possible to acquire posture information that more appropriately represents the influence of a magnetic field on the element 112. Note that the processes in steps S11 and S12 are described in detail, such as mirror up (in the case of a configuration having a mirror), aperture control, Processing is executed in the order of reset (sensor reset), shutter opening, exposure, shutter closing, posture information acquisition, and image signal reading (sensor reading) from the image sensor in the image sensor 112. More strict posture information If the position information is acquired, the posture information is continuously acquired during the period of the sensor reading, and the average is calculated. It may also be averaged to obtain the attitude information before and after the sensor reading.

(Step S13 (correction data creation))
Next, in step S13, correction data is generated based on the above-described principle of generation of correction data, using the previously acquired dark image and the posture information obtained in step S12.

  In step S13, correction data may be generated by further applying the exposure condition and other various factors as coefficients to the dark image.

(Step S14 (noise correction of photographed image))
Next, in step S14, noise correction of the captured image is performed by subtracting the correction data from the image data (photographed image) read with the exposure in step S11.

(Step S15 (normal image processing))
In step S15, various generally known image processes are performed on the image data corrected in step S14.

  According to the above-described photographing processing, image noise caused by a change in the posture of the imaging device 1 is appropriately corrected.

[Example of creating correction data]
Hereinafter, an example of creating correction data corresponding to the above-described principle of generating correction data will be described.

In this example, first, in the adjustment data acquisition stage at the time of manufacturing or the like, a dark image in a normal posture, a vertical posture, and an upward posture is acquired in advance (see FIGS. 3 and 4). The correspondence between these attitudes and the detected acceleration values of the respective axes will be described below again.

Normal posture: X-axis acceleration 0, Y-axis acceleration -1, Z-axis acceleration 0
Vertical posture: X-axis acceleration-1, Y-axis acceleration 0, Z-axis acceleration 0
Upward posture: X-axis acceleration 0, Y-axis acceleration 0, Z-axis acceleration 1

In the shake correction mechanism 140, the state in which acceleration is applied only in the Z-axis direction, which is a direction in which the imaging element 112 is not driven (upward posture), is increased or decreased when acceleration in the X-axis direction is applied to the imaging apparatus 1. An axial noise component and a Y-axis noise component that increases or decreases when acceleration in the Y-axis direction is applied to the imaging device 1 are acquired as reference data.

Reference data = A
A: Upward attitude data

Then, a change amount of the dark image data acquired in the normal posture (normal posture data) with respect to the reference data and a change amount of the dark image data acquired in the vertical posture with respect to the reference data (vertical posture data) are as follows. So get it.

(Normal posture data) = DS-(reference data)
DS: Dark image data acquired in normal posture

(Vertical attitude data) = DT-(reference data)
DT: Dark image data acquired in vertical orientation

The normal posture data corresponds to the reference image of the Y-axis component of the image noise caused by the change in the posture of the imaging device 1, and the vertical posture data corresponds to the X-axis of the image noise caused by the change in the posture of the imaging device 1 This corresponds to the reference image of the direction component. Then, a value obtained by multiplying the vertical posture data by the acceleration in the X-axis direction at the time of photographing and a value obtained by multiplying the normal posture data by the acceleration in the Y-axis direction at the time of photographing are combined, so that the image noise due to the posture of the imaging device 1 is obtained. The correction amount is calculated in advance, and the correction data is generated by the following equation in consideration of the above-described reference data.

(Correction data) = (reference data)-{(vertical attitude data) gx + (normal attitude data) gy}
gx: acceleration in the X-axis direction (the acceleration obtained at the time of shooting divided by the acceleration at the time of adjustment)
gy: acceleration in the Y-axis direction (the acceleration obtained during shooting divided by the acceleration during adjustment)

  Note that the reference data in the first item on the right side of the above mathematical expression corresponds to image noise independent of gx and gy in the imaging device 1.

  According to the above example of creating correction data, image noise due to a change in posture in the imaging device 1 can be suitably corrected.

Further, a configuration may be adopted in which a correction offset amount, which is a DC component noise amount, is defined as the image noise due to the attitude of the imaging device 1 by the following formula, and this correction offset amount is added to the above-described correction data calculation. In the calculation of the offset correction amount described below, the detection value gz of the Z-axis direction acceleration is considered in consideration of the fact that the imaging apparatus 1 is driven with respect to the shake correction mechanism 140 even when acceleration is applied in the Z-axis direction. Is added.

Correction offset amount = (reference data offset) gz-(vertical attitude data offset) gx-(normal attitude data offset) gy
gz: acceleration in the Z-axis direction

  The above is the description of the exemplary embodiment of the present invention. The embodiments of the present invention are not limited to those described above, and various modifications are possible within the scope of the technical idea of the present invention. For example, the embodiments of the present invention also include embodiments exemplarily illustrated in the specification or contents obtained by appropriately combining obvious embodiments and the like.

  In the above-described embodiment, the acceleration detection value is used as the information correlated with the driving state (ie, the noise source) of the shake correction mechanism 140 (the driving coil 14). However, the present invention is not limited to this. . For example, information relating to the drive amount of the drive coil 14 that is PWM-controlled may be used as information correlated with the state of the noise source, for example. Alternatively, a method of directly measuring the amount of a magnetic field, such as a Hall sensor, may be used.

  In the above-described embodiment, the shake correction mechanism has been described as an operating unit that changes the magnetic field according to the attitude of the imaging apparatus 1 in the imaging apparatus 1. However, the operation that changes the magnetic field according to the attitude of the imaging apparatus 1 in the imaging apparatus 1 has been described. The means is not limited to this. For example, when the imaging device 1 has an electromagnetic actuator such as a motor that drives a component such as a lens or a mirror, these also change the magnetic field in the imaging device 1 according to the attitude of the imaging device 1, thereby reducing image noise. It can be the actuation means that causes it.

  Further, as a factor that changes the magnetic field that affects the image pickup device depending on the attitude of the image pickup device 1, a magnetic field outside the image pickup device 1 can be considered in addition to the components inside the image pickup device 1. For example, there is an influence when the imaging device is used in a terrestrial magnetic field or a strong magnetic field environment. Regarding these external magnetic fields as well, it is considered that the orientation of the imaging device and the attitude in the use environment have a correlation with image noise. Therefore, when correcting image noise due to the influence of the earth's magnetic field, an azimuth magnetic needle sensor and a GPS (Global Positioning System) sensor are provided in the imaging device, and the azimuth and position of the imaging device are detected based on the outputs of these sensors. Based on the detected azimuth and position, the correction can be performed according to the principle of the image noise correction described in the above embodiment. When the imaging device is used in an environment with a strong magnetic field, a magnetic sensor such as a Hall sensor is provided in the imaging device, an external magnetic field is detected in the imaging device, and the above-described operation is performed based on the detected magnetic field. The correction can be performed according to the principle of the image noise correction described in the embodiment.

DESCRIPTION OF SYMBOLS 1 Imaging device 10 Housing 11 Lens unit 12 Flash window 13 Release button 100 CPU
102 Operation unit 104 Drive circuit 106 Focus lens 107 Lens drive mechanism 110 Aperture and shutter 112 Image sensor 114 Signal processing circuit 116 Image processing engine 118 Buffer memory 120 Card interface 122 LCD control circuit 124 LCD
126 ROM
127 Flash drive circuit 128 Flash 130 Acceleration sensor 131 Gyro sensor 140 Image stabilizer 200 Memory card

Claims (6)

An image sensor that generates an image signal;
An actuator with a magnetic field effect;
Magnetic field information acquisition means for acquiring information on a magnetic field in the actuator,
Reference information holding means for holding reference information representing a reference of image noise due to the magnetic field,
A correction unit that corrects image noise of a captured image obtained by the imaging device based on the reference information and information on the magnetic field obtained by the magnetic field information obtaining unit;
Attitude information obtaining means for obtaining information on the attitude of the imaging device,
Equipped with a,
The magnetic field information acquisition means,
Information relating to the posture of the imaging device, obtained as information on the magnetic field,
Imaging device. The reference information holding means,
Reference information representing the reference of the image noise is held for each component of each coordinate axis of a coordinate system fixed to the imaging device,
The magnetic field information acquisition means,
Acquiring information on the magnetic field for each of the coordinate axes,
The correction means,
Reference information held for each component of each of the coordinate axes is multiplied by multiplying information on the magnetic field obtained for each of the coordinate axes as a coefficient to generate a corrected image, and the captured image is corrected.
The imaging device according to claim 1 . The reference information is obtained in a posture in which the magnetic field in the imaging device is maximized,
The imaging device according to claim 1 . The reference information, the magnetic field in the imaging device is acquired in a posture in which the influence other than the target axis is minimized,
The imaging device according to claim 1 . An image sensor that generates an image signal;
Attitude information acquisition means for acquiring information on the orientation of the imaging device ,
Reference information holding means for holding reference information representing a reference of image noise due to a change in the attitude of the imaging device,
A correction unit configured to correct image noise of a captured image obtained by the imaging device, based on the reference information and information on a posture of the imaging device obtained by the posture information obtaining unit;
An imaging device comprising: On the computer,
A posture information acquisition procedure for acquiring information on the posture of the imaging device,
A reference information holding procedure for holding reference information representing a reference of image noise due to a change in the attitude of the imaging device,
A correction procedure for correcting image noise of a captured image acquired by an imaging device, based on the reference information and information on the orientation of the imaging device acquired by the orientation information acquisition procedure;
An imaging control program for executing the program.

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