JP2009168938A - Photographing equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To change responsiveness of compensation for blurring in response to a shutter speed. <P>SOLUTION: The shutter speed is determined from a calculated exposure value (step S81). A gain calculating part 74 determines a gain of feedback control of a correcting lens 12 in response to the shutter speed (steps S82, S85, S86). In other words, if the shutter speed is faster than 1/125 seconds, the gain is doubled, and if the shutter speed is slower than 1/10 seconds, the gain is changed to half. By determining the gain in such way, the correcting lens 12 can be controlled at a favorable responsiveness responding to the shutter speed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photographing apparatus using a device that detects vibration caused by hand shake or the like.

  In Patent Document 1, when the photographing apparatus is in a posture other than the upright posture, the gain is increased.

  In Patent Document 2, when the end of the panning operation is detected, the gain of the shake signal is changed.

In Patent Document 3, when it is expected from the occurrence of impact vibration from the start of operation of an operation member such as a release button, the time constant of the vibration detecting means is changed.
JP 2007-57998 A JP-A-10-213832 JP-A-6-230447

  Especially when the shutter speed is slow, if the responsiveness to the shake of the shake correction unit is low, appropriate shake correction cannot be performed.

  An object of the present invention is to enable accurate shake detection during shooting.

  The present invention detects a vibration state of an imaging device and outputs a detection signal indicating the detected vibration state of the imaging device, and via a shooting lens according to the detection signal from the vibration detection unit. A shake correction unit that optically reduces shake of a received subject image, a position detection unit that detects a position of the shake correction unit, and outputs a position detection signal indicating the detected position, and a detection signal from the vibration detection unit A target position calculation unit that calculates a target position of the shake correction unit based on the image, and a drive control unit that controls to drive the shake correction unit to the target position based on the position detection signal from the position detection unit. The apparatus includes a feedback gain control unit that controls the gain of the feedback path from the position detection unit to the drive control unit in accordance with the shutter speed of the photographing unit.

  According to the present invention, since the gain of the feedback path from the position detection unit to the drive control unit is controlled according to the shutter speed of the photographing unit, the gain of the feedback path is increased when shake at a slow shutter speed becomes a problem. In addition, it is possible to perform shake correction with high accuracy.

  The feedback gain control unit sets the gain to a high level when the shutter speed of the shooting unit is high, and sets the gain to a medium level when the shutter speed of the shooting unit is medium, and sets the gain to the shutter speed of the shooting unit. If is slow, the gain should be set to a low level.

  According to the present invention, since the gain of the feedback path from the position detection unit to the drive control unit is controlled according to the shutter speed of the photographing unit, the gain of the feedback path is increased when shake at a slow shutter speed becomes a problem. In addition, it is possible to perform shake correction with high accuracy.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

<Imaging unit>
FIG. 1 is a block diagram showing an electrical configuration of a digital camera 1 to which the present invention is applied.

  As shown in the figure, the digital camera 1 of the present embodiment includes a CPU 111, an operation unit 112, a zoom lens motor driver 114, a zoom lens 10, a focus lens motor driver 115, a focus lens 11, and a camera shake correction control unit 117. , Camera shake correction unit 118, timing generator 119, CCD driver 120, CCD 13, analog signal processing unit 122, A / D converter 123, image input controller 124, image signal processing circuit 125, compression processing circuit 126, video encoder 127, image The display device 128 includes a bus 129, a media controller 130, a recording medium 131, a memory (SDRAM) 132, an AF detection circuit 133, an AE detection circuit 134, and the like.

  Each unit operates under the control of the CPU 111, and the CPU 111 controls each unit of the digital camera 1 by executing a predetermined control program based on an input from the operation unit 112.

  The CPU 111 has a built-in program ROM in which various data necessary for control are recorded in addition to the control program executed by the CPU 111. The CPU 111 controls each unit of the digital camera 1 by reading the control program recorded in the program ROM into the memory 132 and sequentially executing the program.

  The memory 132 is used as a program execution processing area, a temporary storage area for image data, and various work areas.

  The operation unit 112 includes general camera operation means such as a power switch, a shooting mode dial, and a camera shake correction switch in addition to the release button 113, and outputs a signal corresponding to the operation to the CPU 111. The release button 113 includes a switch S1 that is turned on when half-pressed to prepare for photographing such as focus lock and photometry, and a switch S2 that is turned on when fully pressed to capture an image.

  The focus lens 11 is driven by the focus motor driver 115 to move back and forth on the optical axis of the zoom lens 10. The CPU 111 controls the movement of the focus lens 11 via the focus motor driver 115 to perform focusing.

  The zoom lens 10 is driven by the zoom lens motor driver 114 and moves back and forth on the optical axis of the focus lens 11. The CPU 111 controls the movement of the zoom lens 10 via the zoom lens motor driver 114 to perform zooming.

  The camera shake correction unit 118 includes the correction lens 12 and is controlled by the camera shake correction control unit 117 to correct camera shake of a subject image via the zoom lens 10 and the focus lens 11. Details of the camera shake correction control unit 117 and the camera shake correction unit 118 will be described later.

  The CCD 13 is disposed after the camera shake correction unit 118 and receives subject light transmitted through the correction lens 12. As is well known, the CCD 13 includes a light receiving surface on which a large number of light receiving elements are arranged in a matrix. The subject light that has passed through the correction lens 12 forms an image on the light receiving surface of the CCD 13 and is converted into an electric signal by each light receiving element.

  The CCD 13 outputs the charge accumulated in each pixel as a serial image signal line by line in synchronization with the vertical transfer clock and horizontal transfer clock supplied from the timing generator 119 via the CCD driver 120. The CPU 111 controls the timing generator 119 to control the driving of the CCD 13.

  Note that the charge accumulation time (exposure time) of each pixel is determined by an electronic shutter drive signal given from the timing generator 119. The CPU 111 instructs the timing generator 119 about the charge accumulation time.

  The output of the image signal is started when the digital camera 1 is set to the shooting mode. That is, when the digital camera 1 is set to the photographing mode, output of an image signal is started to display a through image on the image display device 128. The output of the image signal for the through image is temporarily stopped when the instruction for the main photographing is given, and is started again when the main photographing is finished.

  The image signal output from the CCD 13 is an analog signal, and this analog image signal is taken into the analog signal processing unit 122.

The analog signal processing unit 122 includes a correlated double sampling circuit (CDS) and an automatic gain control circuit (AGC). The CDS removes noise contained in the image signal, and the AGC amplifies the noise-removed image signal with a predetermined gain. The analog image signal subjected to the required signal processing by the analog signal processing unit 122 is captured by the A / D converter 123. The A / D converter 123 converts the captured analog image signal into a predetermined gradation width. Is converted into a digital image signal. This image signal is so-called RAW data, and has a gradation value indicating the density of R, G, and B for each pixel.

  The image input controller 124 has a built-in line buffer having a predetermined capacity, and stores the image signal for one frame output from the A / D converter 123. The image signal for one frame accumulated in the image input controller 124 is stored in the memory 132 via the bus 129.

  In addition to the CPU 111, the memory 132, and the image input controller 124, the image signal processing circuit 125, the compression processing circuit 126, the video encoder 127, the media controller 130, the AF detection circuit 133, the AE detection circuit 134, and the like are connected to the bus 129. These are configured to be able to transmit / receive information to / from each other via a bus 129.

  The image signal for one frame stored in the memory 132 is taken into the image signal processing circuit 125 in dot order (pixel order).

  The image signal processing circuit 125 performs predetermined signal processing on the image signals of R, G, and B colors captured in a dot-sequential manner, and generates an image signal (Y / C) composed of a luminance signal Y and color difference signals Cr and Cb. Signal).

  The AF detection circuit 133 fetches R, G, and B image signals stored in the memory 132 via the image input controller 124 in accordance with a command from the CPU 111, and calculates a focus evaluation value necessary for AF (Automatic Focus) control. . The AF detection circuit 133 includes a high-pass filter that passes only high-frequency components of the G signal, an absolute value processing unit, a focus region extraction unit that extracts a signal within a predetermined focus region set on the screen, and a focus region An integration unit for integrating the absolute value data is included, and the absolute value data in the focus area integrated by the integration unit is output to the CPU 111 as a focus evaluation value. During the AF control, the CPU 111 searches for a position where the focus evaluation value output from the AF detection circuit 133 is maximized, and moves the focus lens 11 to that position, thereby performing focusing on the main subject.

  The AE detection circuit 134 takes in R, G, and B image signals stored in the memory 132 via the image input controller 124 in accordance with a command from the CPU 111, and calculates an integrated value necessary for AE control. The CPU 111 calculates a luminance value from the integrated value and obtains an exposure value from the luminance value. Further, the aperture value and the shutter speed are determined from the exposure value according to a predetermined program diagram.

  The compression processing circuit 126 performs compression processing of a predetermined format (for example, JPEG) on the image signal (Y / C signal) composed of the input luminance signal Y and color difference signals Cr and Cb in accordance with a compression command from the CPU 111. Generate compressed image data. Further, in accordance with a decompression command from the CPU 111, the input compressed image data is subjected to decompression processing in a predetermined format to generate uncompressed image data.

  The video encoder 127 controls display on the image display device 128 in accordance with a command from the CPU 111.

  The media controller 130 controls reading / writing of data with respect to the recording medium 131 in accordance with a command from the CPU 111. The recording medium 131 may be detachable from the camera body, such as a memory card, or may be built in the camera body. In the case of detachable, a card slot is provided in the camera body, and the card slot is used by being loaded.

<Lens movement mechanism for image stabilization>
Next, the camera shake correction control unit 117 and the camera shake correction unit 118 will be described.

  The digital camera 1 can be switched between a camera shake ON mode and a camera shake OFF mode by the operation unit 112. In the camera shake ON mode, the movement of the correction lens 12 is controlled so that camera shake is canceled. In the camera shake OFF mode, the correction lens 12 is controlled to stop.

  FIG. 2 is a diagram showing an optical system of the digital camera 1. The optical system of the digital camera 1 includes a zoom lens 10, a focus lens 11, and a correction lens 12. A CCD 13 is disposed on the optical axis 14 of the optical system, and the CCD 13 converts an image of a subject into an electrical signal as described above.

  When camera shake occurs, the image of the subject moves on the CCD 13 within one frame, so that an electrical signal of a blurred image is generated from the CCD 13. In order to detect the occurrence of camera shake, an X direction gyro sensor 50 (see FIG. 6) and a Y direction gyro sensor (not shown) are provided in the camera body or the lens assembly. These gyro sensors output a signal representing the angular velocity. Alternatively, a gyro sensor that outputs a signal representing angular acceleration may be used.

  When camera shake does not occur, the optical axis of the correction lens 12 coincides with the optical axis 14 of the optical system. When camera shake is detected by the X gyro sensor 50 and / or the Y gyro sensor, the correction lens 12 moves in the X direction and / or the Y direction according to the size and direction of the camera shake. As a result, the image formed on the CCD 13 is almost stopped, and a signal representing a sharp image is output from the CCD 13.

  Next, the lens movement mechanism of the camera shake correction control unit 117 and the camera shake correction unit 118 will be described. FIG. 3 is an exploded perspective view showing the lens moving mechanism, and FIG. 4 is a front view of the lens moving mechanism with the cover removed. FIG. 5 is a cross-sectional view showing a part of the lens moving mechanism.

  3 and 4, the zoom lens 10 and the focus lens 11 are attached to the lens barrel 15. The lens barrel 15 is fixed to the lens assembly. The lens barrel 15 is provided with a main guide shaft 16 extending in the X direction and a main guide shaft 17 extending in the Y direction, and an X slider 18 movable in the X direction, A Y slider 19 that is movable in the direction is housed. The X slider 18 and the Y slider 19 are substantially L-shaped when viewed from the plane.

  A pair of shaft holes 18 a are formed in the X slider 18, and these shaft holes 18 a are fitted to the main guide shaft 16 in a slider bullet. Similarly, the pair of shaft holes 19 a of the Y slider 19 are fitted to the main guide shaft 17 in the slider bullet.

  The X slider 18 has a pair of shaft holes 18b. The shaft hole 18b is fitted in the slider bullet on the sub guide shaft 20 extending in the Y direction. The pair of shaft holes 19b of the Y slider 19 are fitted in the slider bullet on the sub guide shaft 21 extending in the X direction.

  A flat ring-shaped coil 22 is attached to the X slider 18. Similarly, a coil 23 is attached to the Y slider 19. A yoke 25 having a permanent magnet 26 attached inside is attached to the lens barrel 15 in order to generate an X-direction electromagnetic force between the coil 22 and the coil 22. Note that the yoke and the permanent magnet for generating the electromagnetic force in the Y direction between the coil 23 are omitted in the drawing.

  The lens holder 30 holds the correction lens 12. The lens holder 30 is formed with a pair of holes 30a. Both ends of the sub guide shaft 21 extending in the X direction are fitted into these holes, and fixed with an adhesive or the like so that the sub guide shaft 21 does not move. Has been. Similarly, the sub guide shaft 20 is firmly held in the pair of holes 30b.

  A cover 32 is disposed on the lens holder 30 so as to hide the sliders 18 and 19. The cover 32 is placed on the step 15 a of the lens barrel 15. Two permanent magnets 33 and 34 are attached to the inner surface of the cover 32. The permanent magnet 33 faces the yoke 25, and the permanent magnet 34 faces another yoke (not shown).

  As shown in FIG. 5, permanent magnets 26 and 33 are located on both sides of the coil 22, and a bent piece 25 a of the yoke 25 enters the coil 22. When the coil 22 is energized, an electromagnetic force is generated by the magnetic field generated in the coil 22 and the magnetic fields of the permanent magnets 26 and 33. This electromagnetic force acts in the + X direction or the −X direction according to the direction of the current of the coil 22 and moves the X slider 18 in the + X direction or the −X direction. Similarly, when the coil 23 is energized, the Y slider 19 is moved in the + Y direction or the −Y direction by the magnetic field generated in the coil 23 and the electromagnetic force generated from the magnetic field of the permanent magnet 34 and the permanent magnet 34 (not shown).

  In addition, the X Hall element 40 and the Y Hall element 41 are accommodated in the holes 15 b and 15 c of the lens barrel 15. The X Hall element 40 generates a voltage in response to a magnetic field of a small magnet 42 embedded in the lower surface of the X slider 18. This voltage corresponds to the position of the X slider 18 in the X direction. The Y Hall element 41 also generates a voltage in response to the magnetic field of the magnet 43 embedded in the lower surface of the Y slider 19, and this voltage corresponds to the position of the Y slider 19 in the Y direction. Each Hall element 40 and 41 generates a signal in a voltage range of 0 to 5 V, for example, according to the position of the correction lens 12. When the output signals of the Hall elements 40 and 41 are 2.5 V (reference voltage), the X slider 18 is located at the X reference position, and the Y slider 19 is located at the Y reference position. In this state, the optical axis of the correction lens 12 coincides with the optical axis 14 of the optical system.

  Next, the operation of the lens movement mechanism of the camera shake correction control unit 117 and the camera shake correction unit 118 will be described. When the power of the digital camera is turned on to prepare for shooting, the control circuit (see FIG. 6) uses the reference voltage (2.5 V) as the target lens position signal. Then, the control circuit performs feedback control on the direction and magnitude of the current supplied to the coils 22 and 23 so that the output signals of the Hall elements 40 and 41 reach the reference voltage that is the target lens position signal. By this feedback control, the X slider 18 is moved toward the X reference position, and the Y slider 19 is moved toward the Y reference position. When the sliders 18 and 19 are set at the reference position, the optical axis of the correction lens 12 coincides with the optical axis 14 of the optical system. In the camera shake OFF mode, the target lens position signal is kept at the reference voltage even if there is camera shake. As a result, the lens holder 30 remains stopped even if camera shake occurs.

  In the camera shake ON mode, the correction lens 12 moves together with the lens holder 30 in accordance with camera shake. Camera shake in the X direction is detected by the X gyro sensor 50, and camera shake in the Y direction is detected by the Y gyro sensor. When camera shake occurs, each gyro sensor generates an angular velocity signal. The angular velocity signals of each gyro sensor are individually integrated and converted into angle signals in the X direction and the Y direction, respectively. This angle signal is converted into a lens displacement amount signal corresponding to the linear movement of the correction lens 12. The obtained lens displacement amount signal is added to the reference voltage (2.5 V) to become a target lens position signal. Here, since the lens displacement amount signal has a positive or negative sign depending on the direction of camera shake, the target lens position signal changes around the reference voltage (2.5 V).

  For example, when camera shake occurs in the + X direction, a negative lens displacement amount signal is added to the reference voltage, and a target lens position signal is calculated. Next, the direction and magnitude of the current of the coil 22 are determined so that the output signal of the X Hall element 40 becomes the target lens position signal. The electromagnetic force in the −X direction acts on the coil 22 by the magnetic field generated by energizing the coil 22 and the magnetic field of the permanent magnets 26 and 33. With this electromagnetic force, the X slider 18 moves in the −X direction along the main guide shaft 16. Further, since the X slider 18 is connected to the lens holder 30 via the sub guide shaft 20, the X slider 18 pushes the lens holder 30 in the -X direction.

  Here, the sub guide shaft 21 fixed to the lens holder 30 is guided in the shaft hole 19 b of the Y slider 19. As a result, the X slider 18 and the lens holder 30 move together while being guided by the pair of shaft holes 19 a of the main guide shaft 16 and the Y slider 19.

  When the X slider 18 moves to the lens position corresponding to the target lens position signal, the output signal of the X Hall element 40 matches the target lens position signal. As a result, the lens holder 30 moves in the X direction by a distance corresponding to the stroke of camera shake, so that the image formed on the CCD 13 hardly moves. Accordingly, a clear image electrical signal is generated from the CCD 13.

  When the camera shake is stopped, the lens displacement amount signal becomes 0, so that the target lens position signal becomes the reference voltage (2.5 V). The direction and magnitude of the current of the coil 22 are determined so that the output signal of the X Hall element 40 returns to the reference voltage. As a result, the X slider 18 gradually moves toward the X reference position. After the X slider 18 returns to the X reference position, the direction and magnitude of the current in the coil 22 are controlled so that the X reference position is maintained. Since the lens holder 30 returns together with the X slider 18, the optical axis of the correction lens 12 coincides with the optical axis 14 of the optical system.

  When camera shake in the −X direction occurs, a plus lens displacement signal having a value corresponding to the magnitude of camera shake is added to the reference voltage, and a target lens position signal is calculated. The direction and magnitude of the current of the coil 22 are determined so that the output signal of the X Hall element 40 becomes the target lens position signal. When the coil 22 is energized, the X slider 18 moves in the + X direction along the main guide shaft 16. When there is no camera shake in the −X direction, the X slider 18 gradually returns to the X reference position and maintains the X slider 18 at the X reference position. At this time, the optical axis of the correction lens 12 coincides with the optical axis 14 of the optical system.

  The same applies to camera shake in the Y direction. For the camera shake in the Y direction, the coil 23 moves the Y slider 19 in the Y direction. At this time, the lens holder 30 is pushed in the Y direction via the sub guide shaft 21. The Y slider 19 is guided by the main guide shaft 17, and the sub guide shaft 20 of the lens holder 30 is guided by the shaft hole 18 b of the X slider 18. When the lens holder 30 moves in the Y direction together with the Y slider 19, the movement of the image due to camera shake in the Y direction is prevented, and the image formed on the CCD 13 almost stops. When there is no camera shake in the Y direction, the Y slider 19 is gradually returned to the Y reference position.

  Since actual camera shake occurs in both the X direction and the Y direction, the lens holder 30 moves simultaneously in both the X direction and the Y direction.

<Lens movement control circuit for image stabilization>
Next, control circuits of the camera shake correction control unit 117 and the camera shake correction unit 118 will be described. Two control circuits are provided in the X direction and the Y direction. FIG. 6 is a block diagram illustrating a configuration of a control circuit for suppressing camera shake in the X direction of the camera shake correction control unit 117 and the camera shake correction unit 118. The X gyro sensor 50 generates an angular velocity signal when camera shake in the X direction occurs. This angular velocity signal is sent to the high-pass filter 51, and a high frequency angular velocity signal is extracted and then amplified by the amplifier 52. Thereby, the angular velocity signal generated when the digital camera 1 is moved slowly is removed, and only the angular velocity signal generated when the digital camera 1 is moved suddenly is amplified and sent to the CPU 80.

  The CPU 80 includes an A / D converter 53 and converts an analog angular velocity signal from the amplifier 52 into a digital angular velocity signal. The A / D converter 53 samples an analog angular velocity signal with a sampling pulse of 16 kHz and converts it into a 10-bit digital angular velocity signal. The 10-bit angular velocity signal is sent to the averaging circuit 54, where the average value of the 16 angular velocity signals is calculated. Thereby, one angular velocity signal is obtained every 1 ms. This represents that the transfer rate of the angular velocity signal is 1 kHz.

  The averaged angular velocity signal is sent to the subtractor 55 and the long-time integrator 56. The long-time integrator 56 calculates the drift component of the angular velocity signal by cyclically integrating the angular velocity signal. In the cyclic integration, specifically, a difference (positive / negative) between the current signal and the previous signal is obtained and integrated. The obtained drift component is sent to the subtractor 55 and subtracted from the angular velocity signal being input.

  The drift-corrected angular velocity signal is input to the coring circuit 57. The coring circuit 57 converts the angular velocity output from the subtractor 55 to 0 when the angular velocity is equal to or lower than the threshold level. As a result, since the suppression operation is not performed for fine camera shake, the correction lens 12 can be prevented from wobbling.

The angular velocity signal subjected to the coring process is sent to the integration circuit 60. The integration circuit 60 first integrates the input angular velocity signal A1 and converts it into an angle signal _{An + 1} . The following equation is used for this integration.

[Equation 1]
A _{n + 1} = (A ₁ −A _n ) × α + A _n
Here, α is a coefficient, and _An is the previous integrated value read from the register.

By the above integration, the tilt angle of the optical system caused by camera shake is calculated. The obtained angle signal _{An + 1} is sent to the limiter. When the inclination angle exceeds a limit angle (for example, 2 degrees), the limiter is cut off. Therefore, the maximum value of the angle signal _{An + 1} is the limit angle. The limit angle is a constant value regardless of the focal length of the optical system. This angle-processed angle signal _{An + 1} is sent to the phase compensator 61 as an output signal of the integration circuit 60. At the same time, the angle signal A _{n + 1} is stored in the register is used as the integral value A _n in the next integration operation.

  The phase compensator 61 adjusts the phase of the angle signal. The angular velocity signal input to the phase compensator 61 has a time delay until the signal output from the X gyro sensor 50 with respect to the shake of the digital camera 1 or the phase of the integration processing time in the integration circuit 60 occurs. The device 61 compensates for the transfer delay obtained by adding these times.

  The angle signal subjected to the phase compensation process is input to the multiplier 63. The multiplier 63 multiplies the mechanical coefficient γ read from the memory 64 and the angle signal to calculate the displacement amount of the lens. The mechanical coefficient γ is a value corresponding to the focal length of the optical system, and the mechanical coefficient γ increases as the focal length increases. Actually, the mechanical coefficient γ is determined in consideration of the conversion efficiency of the coils 22 and 23 in addition to the focal length. As the mechanical coefficient γ at each focal length, for example, a numerical value shown in FIG. 7 is used. Due to this mechanical coefficient γ, even when the camera shake is the same, the amount of movement of the correction lens 12 is larger when the focal length is long than when the focal length is short.

  The lens displacement amount signal output from the multiplier 63 is added to the reference voltage (2.5 V) by the adder 65, and a target lens position signal is calculated. As described above, the target lens position signal has a value that changes around the reference voltage in accordance with the magnitude and direction of the blur angle of the optical system. This target lens position signal is sent to the subtractor 70 as an output signal of the CPU 80.

  The amplifier / constant current circuit 71 supplies a constant current to the X Hall element 40. The X Hall element 40 detects the position of the X slider 18 in response to the magnetic field of the magnet 42. The amplifier / constant current circuit 71 amplifies the output signal of the X Hall element 40 with a predetermined amplification factor. The output signal of the amplifier / constant current circuit 71 is converted into a digital signal by the A / D converter 73 and input to the subtractor 70.

  The subtractor 70 sends a signal corresponding to the difference between the two signals input from the multiplier 66 and the A / D converter 73 to the driver 72. The driver 72 causes a current having a magnitude obtained by amplifying the output signal of the subtractor 70 in accordance with the gain calculated by the gain calculation unit 74 to flow in the coil 22 in a direction corresponding to the sign of the output signal of the computing unit 70. The correction lens 12 is moved in the + X direction or the −X direction.

  The CPU 111 sets the threshold level of the coring circuit 57, the coefficient α and limiter value of the integrating circuit 60, the addition coefficient β of the memory 62, the mechanical coefficient γ of the memory 64, the reference voltage of the adder 65, and the like.

  Next, the operation of the control circuits of the camera shake correction control unit 117 and the camera shake correction unit 118 will be described. For example, when camera shake occurs in the + X direction, the X gyro sensor 50 generates an angular velocity signal having a minus sign and a value corresponding to the magnitude of the angular velocity. When camera shake is reduced, an angular velocity signal having a value corresponding to the magnitude of the convergence angular velocity is generated with a plus sign. This angular velocity signal is extracted at a predetermined frequency or higher by the high-pass filter 51, amplified by the amplifier 52, and then sent to the CPU 80.

  The A / D converter 53 of the CPU 80 converts the angular velocity signal into a digital signal, and the averaging circuit 54 calculates the average value of the 16 angular velocity signals. The drift component is removed from the averaged angular velocity signal by the subtractor 55.

  The coring circuit 57 replaces the angular velocity signal with 0 when the angular velocity signal is equal to or less than a predetermined value. The angular velocity signal that has been subjected to the coring process is integrated by the integrating circuit 60 and converted into an angle signal, and an angle signal that is equal to or greater than a predetermined value is replaced with a limit value. The value of the angle signal increases from 0 when camera shake occurs, and decreases toward 0 when camera shake converges. Therefore, the angle signal is 0 when there is no camera shake. Further, the angle signal has a plus or minus sign depending on the direction of camera shake.

  The angle signal subjected to the limit processing is sent to the phase compensator 61 and subjected to phase compensation processing. The phase signal subjected to the phase compensation processing is multiplied by a mechanical coefficient by a multiplier 63 and converted into a lens displacement amount signal. The adder 65 adds a reference voltage to the lens displacement amount signal and converts it into a target lens position signal. This target lens position signal is input to the subtractor 70.

  The subtractor 70 calculates the difference between the output signal of the X Hall element 40 and the target lens position signal, and controls the direction and magnitude of the current flowing through the coil 22 via the driver 72.

  As described above, the CPU 80 outputs the reference voltage (2.5 V) as the target lens position signal when the camera shake is not generated, and only the voltage corresponding to the lens displacement amount when the camera shake is generated. A voltage larger or smaller than the reference voltage is output as the target lens position signal. The driver 72 controls the direction and magnitude of the current flowing through the coil 22 so that the output signal of the X Hall element 40 matches the target lens position signal. Thereby, the correction lens 12 moves via the X slider 18 to suppress camera shake. When the camera shake is reduced, the target lens position signal becomes the reference voltage, so that the X slider 18 returns to the reference position. The movement of the correction lens 12 can change the responsiveness according to the gain calculated by the gain calculation unit 74.

<Gain calculation for correction lens feedback control>
Next, gain calculation of the gain calculation unit 74 will be described. In the digital camera 1 of the present invention, the gain calculation unit 74 calculates the gain according to the shutter speed at the time of actual photographing. FIG. 8 is a flowchart showing the gain calculation operation in the gain calculation unit 74.

  As described above, the CPU 111 calculates a luminance value from the integrated value calculated by the AE detection circuit 134 and obtains an exposure value from the luminance value. Further, the aperture value and the shutter speed are determined from the exposure value (step S81).

  Next, it is determined whether or not the determined shutter speed is faster than 1/125 second (step S82). When the shutter speed is faster than 1/125 second, the gain calculation unit 74 determines the gain to be twice the standard (step S83). If the shutter speed is slower than 1/125 second, it is determined whether it is slower than 1/10 second (step S84). When the shutter speed is slower than one tenth of a second, the gain calculation unit 74 determines the gain to be a half of the standard (step S85). If the shutter speed is faster than 1/10 second, the standard gain is determined (step S86).

  Based on the gain thus determined, the correction lens 12 is controlled to perform camera shake correction (step S87). The X driver 72 includes a PWM control unit, determines a pulse width corresponding to the output signal of the subtractor 70, and determines a voltage value of the output pulse based on the gain calculated by the gain calculation unit 74. This output pulse causes a current to flow through the coil 22 to drive the correction lens 12. The same applies to the Y direction. Thereafter, photographing is performed based on the photographing instruction (step S88).

  In general, a high-speed shutter is less affected by blurring in a low-frequency component, and a low-speed shutter is less affected by blurring in a high-frequency component. Therefore, it is effective to prevent blur in the high frequency component when the shutter speed is fast, and to prevent blur in the low frequency component when the shutter speed is slow. According to the present invention, when the shutter speed is fast, by increasing the feedback control gain, it is possible to improve the high frequency response and effectively prevent the blur of the high frequency component. Also, when the shutter speed is slow, the feedback control gain is lowered to reduce overshoot and effectively prevent low-frequency component blurring.

  Note that the threshold value for determining the shutter speed and the gain control magnification are not limited to the numerical values in the present embodiment. Further, in the present embodiment, the current value flowing through the coil 22 is controlled based on the gain calculated by the gain calculation unit 74, but the amplification factor of the amplifier / constant current circuit 71 may be controlled, The constant current supplied to the X Hall element 40 may be controlled.

  In the embodiment of the present invention, the camera shake correction is performed by controlling the correction lens in accordance with the camera shake. However, the camera shake correction method is not limited to this. For example, the position of the image sensor is controlled. It may be applied to a camera that has undergone image stabilization. In this case, gain control of feedback control for controlling the position of the image sensor is performed. In addition, a method of correcting camera shake by controlling the bending angle of the bending optical system, or a method of correcting camera shake by controlling the entire imaging lens and the image sensor can also be applied. It can also be applied to camera shake correction of an analog camera using a film.

FIG. 1 is a block diagram showing an electrical configuration of a digital camera 1 to which the present invention is applied. FIG. 2 is a diagram showing an optical system of the digital camera 1. FIG. 3 is an exploded perspective view showing the lens moving mechanism. FIG. 4 is a front view of the lens moving mechanism with the cover removed. FIG. 5 is a cross-sectional view showing a part of the lens moving mechanism. FIG. 6 is a block diagram illustrating a configuration of a control circuit for suppressing camera shake in the X direction. FIG. 7 is a diagram showing the mechanical coefficient γ at each focal length for calculating the displacement amount of the lens. FIG. 8 is a flowchart illustrating gain calculation in feedback control of the correction lens 12 of the digital camera 1 according to the first embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Digital camera, 10 ... Zoom lens, 11 ... Focus lens, 12 ... Correction lens, 13 ... CCD, 15 ... Lens barrel, 18 ... X slider, 19 ... Y slider, 22 ... Coil, 25 ... Yoke, 26 ... Permanent magnet, 33 ... Permanent magnet, 40 ... X Hall element, 41 ... Y Hall element, 50 ... X gyro sensor, 70 ... Subtractor, 71 ... Amplifier / constant current circuit, 72 ... X driver, 73 ... A / D conversion , 74... Gain calculation unit, 111... CPU, 112 .. operation unit, 117... Camera shake correction control unit, 118.

Claims (2)

A vibration detection unit that detects a vibration state of the photographing device and outputs a detection signal indicating the detected vibration state of the photographing device, and a subject that is received via the photographing lens according to the detection signal from the vibration detection unit A shake correction unit that optically reduces shake of an image, a position detection unit that detects a position of the shake correction unit, outputs a position detection signal indicating the detected position, and a detection signal from the vibration detection unit A target position calculation unit that calculates a target position of the shake correction unit based on a drive control unit that controls to drive the shake correction unit to the target position based on a position detection signal from the position detection unit; A photographic device comprising:
An imaging apparatus including a feedback gain control unit that controls a gain of a feedback path from the position detection unit to the drive control unit in accordance with a shutter speed of the imaging unit.   The feedback gain control unit sets the gain to a high level when the shutter speed of the imaging unit is high, and sets the gain to a medium level when the shutter speed of the imaging unit is medium, The imaging device according to claim 1, wherein when the shutter speed of the imaging unit is low, the gain is set to a low level.

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