JP2015081950A - Imaging device and control method of the same - Google Patents

Abstract

In an imaging apparatus that changes the control mode and corrects the image blur by the correction means, when changing the pulse width modulation frequency, the control mode can be switched while suppressing the positional deviation and unnatural behavior of the correction means. To do. An image pickup apparatus that performs image shake correction in a plurality of control modes includes a shake detection unit that detects shake and a position detection unit of a correction lens, and calculates a movement target position of the correction lens according to the shake detection signal. Then, control is performed so that the position of the correction lens converges to the movement target position. The PWM frequency determination unit 101 determines the PWM frequency according to the control mode. The duty ratio determining unit 103 determines the duty ratio using a correction coefficient corresponding to the PWM frequency according to the control mode. The PWM signal generation unit 104 generates a PWM signal and outputs it to the drive units 507 and 508. The drive units 507 and 508 are configured by an H bridge circuit, and the drive signal is output to the actuator of the correction lens via a filter. [Selection] Figure 1

Description

  The present invention relates to a technique for correcting image blur caused by camera shake or the like.

  In an imaging apparatus equipped with an image sensor such as a CMOS (complementary metal oxide semiconductor) sensor, when driving a lens, horizontal stripe noise may occur in an image captured from the image sensor due to the influence of magnetic field noise generated from the actuator. There is. This is due to the influence of the magnetic field generated when the actuator coil is energized. In particular, in the case of PWM (pulse width modulation) control, a pulsating current is generated by repeating energization and regeneration of the coil, or repeating energization in the forward direction and the reverse direction. Imaging noise is generated with a change in the magnetic field generated by the coil. As a countermeasure, a method is known in which the ripple width is reduced by using the output current of the driver as a current obtained via a filter with respect to the drive current of the coil of the actuator. That is, the influence on the image sensor can be suppressed by reducing the change in the magnetic field generated by the coil. However, the loss of power consumed by the filter increases. Therefore, if the PWM frequency is increased and the setting is changed so as to be away from the resonance frequency of the LC circuit constituting the filter, the gain of the current lost in the filter can be reduced to prevent an increase in power consumption.

On the other hand, in the drive control of the image blur correction lens, a PWM signal for driving is generated by setting a PWM cycle and a duty ratio. Increasing the PWM frequency (decreasing the PWM cycle) results in coarse duty ratio resolution. That is, the drive resolution of the image blur correction lens also becomes rough. Therefore, although the power consumption can be reduced by increasing the PWM frequency, the control performance of the image blur correction lens is lowered. Conversely, lowering the PWM frequency increases power consumption, but improves the control performance of the image blur correction lens.
Patent Document 1 discloses a method for avoiding the influence of noise received by an image sensor. When a lens unit with an actuator driving frequency f is mounted, the imaging driving frequency is such that the time difference ΔT ′ between the noise component (dark image) reading timing and the signal component reading timing is an integral multiple of the reciprocal of the driving frequency f. Is changed. Alternatively, the actuator driving frequency is changed based on a frequency having a period of time difference ΔT between the noise reading timing and the signal reading timing.

JP 2010-50636 A

In the conventional actuator control method, when the PWM frequency is changed, there is a problem that the position of the lens shifts or instantaneous vibration (so-called “picking”) occurs. This is because, due to the response speed and dead time of the H bridge driver that drives the actuator, even if the duty ratio is the same, a difference occurs in the output current of the H bridge circuit due to the difference in PWM frequency. For example, when the lens position shifts and the operation is performed discretely, the larger the frequency change width, the more likely the instantaneous vibration of the lens becomes conspicuous.
An object of the present invention is to provide an image pickup apparatus that corrects image blur by a correction unit by changing a control mode, and controls the control mode while suppressing the positional deviation and unnatural behavior of the correction unit when changing the pulse width modulation frequency. Switching.

  In order to solve the above-described problems, an apparatus according to the present invention is an imaging apparatus that performs image shake correction by a correction unit by changing a control mode, and includes a shake detection unit that detects shake of the imaging apparatus, and the correction Position detection means for detecting the position of the means; control means for obtaining a shake detection signal by the shake detection means and a position detection signal by the position detection means, calculating a control amount, and generating a control signal by pulse width modulation; And a drive means for driving the correction means in accordance with a control signal from the control means. The control means determines the control mode and determines a duty ratio of the control signal using a correction coefficient corresponding to a pulse width modulation frequency, and the driving means drives the duty ratio determined by the control means. The signal is output to the correction means via the filter means.

  According to the present invention, in an imaging apparatus that changes the control mode and corrects the image blur by the correction unit, when changing the pulse width modulation frequency, the control mode is suppressed while suppressing misalignment and unnatural behavior of the correction unit. Can be switched.

It is a block diagram which shows the structure of the control part which concerns on embodiment of this invention. It is a block diagram of a lens barrel having an image blur correction function. FIG. 4 is a perspective view illustrating a configuration example of an image shake correction unit. It is a figure which shows the structural example of the whole imaging device which concerns on embodiment of this invention. FIG. 3 is a block diagram illustrating an internal configuration example of a drive control unit of an image blur correction lens. It is a figure which shows the structural example of an image shake correction unit drive part. It is a figure which shows the applied voltage (A), inductor current (B), capacitor | condenser current (C), and drive current (D) to an image shake correction unit drive part. It is a figure which shows the current-frequency characteristic of an image shake correction unit drive part. It is a flowchart explaining the camera-shake correction process in 1st Embodiment of this invention. 10 is a flowchart illustrating a duty ratio determination process S115 in FIG. 9. It is a flowchart explaining the duty ratio determination process in 2nd Embodiment of this invention. 12 is a flowchart illustrating PWM sweep processing S203 of FIG. It is a figure which shows the change of PWM duty ratio and PWM period which are changed by PWM sweep process S203 of FIG.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. As for an imaging apparatus that performs image blur correction by changing the control mode, a mode in which drive control is performed using a lens constituting the image blur correction optical system as a correction unit is illustrated.

[First Embodiment]
With respect to the imaging apparatus according to the first embodiment of the present invention, the configuration of the entire apparatus will be described with reference to FIG.
The zoom unit 401 constituting the imaging optical system includes a zoom lens. The zoom drive control unit 402 performs a scaling operation by driving control of the zoom unit 401. The aperture / shutter unit 405 includes an aperture device that adjusts the amount of light and a shutter device, and is driven and controlled by an aperture / shutter drive control unit 406.

The correction lens unit 403 includes a correction lens as an optical member that can change the position on a plane perpendicular to the optical axis of the imaging optical system. The correction lens constitutes an image blur correction optical system and corrects image blur due to vibration such as camera shake. In the present embodiment, the correction lens unit 403 for reducing the blur of the subject image formed on the imaging surface of the imaging device by the imaging optical system is used. However, the image blur may be reduced by changing the position of the image sensor on a plane perpendicular to the optical axis. The correction lens drive control unit 404 controls driving of the correction lens unit 403, and performs stop control of the driving power supply in accordance with the state of the imaging apparatus. For example, during power saving control, power is saved by stopping the drive power supply so that unnecessary power is not consumed.
The focus unit 407 includes a focus lens that performs focus adjustment. A focus drive control unit 408 controls drive of the focus unit 407. Each drive control part controls the drive of the movable member which each takes charge according to the control command from the below-mentioned control part 417.

  The imaging unit 409 uses an imaging element to convert an optical image formed through each lens group into an electrical signal by photoelectric conversion. The imaging signal processing unit 410 converts the output signal of the imaging unit 409 into a video signal. The video signal processing unit 411 performs image processing to process the output signal of the imaging signal processing unit 410 according to the application. The display unit 412 displays an image according to the output signal of the video signal processing unit 411. Processing and operation of the imaging signal processing unit 410, the video signal processing unit 411, and the display unit 412 are controlled by a control unit 417 described later.

The power supply unit 413 supplies a power supply voltage corresponding to the application to each unit constituting the camera system. The external input / output terminal unit 414 is used for input / output processing of signals and video signals communicated with an external device. The operation unit 415 is used when the user operates the camera, and outputs an operation instruction signal to the control unit 417. The operation unit 415 includes an operation member used for photographing operation and an operation member used for control setting. The storage unit 416 stores various data such as video information and control information.
A control unit 417 that controls the entire system includes a CPU (Central Processing Unit), and performs a process described later by executing a program read from the storage unit 416.

Next, the operation of the imaging apparatus having the above configuration will be described.
The operation unit 415 is a two-stage type in which a first switch (hereinafter abbreviated as SW1) and a second switch (hereinafter abbreviated as SW2) are sequentially turned on in accordance with the pressing amount of a shutter release button (not shown). Has a switch. The first switch SW1 is turned on by the first stroke (half press) of the shutter release button, and the second switch SW2 is turned on by the second stroke (full press). When the first switch SW1 is turned on, the control unit 417 sends a control instruction to the focus drive control unit 408 and drives the focus unit 407 to perform focus adjustment. Along with this control, the control unit 417 sends a control instruction to the aperture / shutter drive control unit 406 and drives the aperture / shutter unit 405 to set the exposure amount to an appropriate value. Thereafter, when the second switch SW2 is turned on, the control unit 417 causes the storage unit 416 to store image data obtained from the light image exposed by the imaging unit 409. When the control unit 417 receives an operation instruction to set the image blur correction control to the ON state from the operation unit 415, the control unit 417 instructs the correction lens drive control unit 404 to control the image blur correction operation. Upon receiving this control instruction, the correction lens drive control unit 404 drives the correction lens unit 403 to perform image blur correction control until an instruction to turn the control off is given.

Further, when the operation unit 415 is not operated for a certain time or more, the control unit 417 cuts off the power supply of the display of the display unit 412 for power saving control. In the imaging apparatus according to the present embodiment, the user can select camera modes such as a still image shooting mode, a moving image shooting mode, and a playback mode with the operation unit 415, and the operating conditions of each actuator can be changed for each mode. .
When an instruction for a zooming operation using the zoom lens is made in accordance with a user operation using the operation unit 415, the control unit 417 instructs the zoom drive control unit 402 to drive the zoom unit 401, thereby instructing the designated zoom position. Move the zoom lens to. At that time, the control unit 417 controls the focus adjustment operation based on the image information obtained by processing the output signal of the imaging unit 409 by the signal processing units 410 and 411. The control unit 417 calculates a focus control drive control amount using the focus adjustment state detection signal generated by processing the imaging signal, and transmits the focus control drive control amount to the focus drive control unit 408. The focus drive control unit 408 performs focus adjustment by driving the focus unit 407 in accordance with an instruction from the control unit 417.

  FIG. 2 schematically shows the configuration of a lens barrel 201 having a shake correction function. A first lens group 202 is fixed to the lens barrel 201. The second lens group 203 performs a zooming operation. The diaphragm 204 adjusts the amount of light, and the third lens group (shift lens) 205 corrects image blur caused by camera shake or the like. The fourth lens group 206 has both a focus surface correction and a focus adjustment function by the second lens group 203. The light passing through each lens group is imaged on the light receiving surface of the image sensor 207, and the image sensor 207 outputs an electrical signal by photoelectric conversion.

FIG. 3 is an exploded perspective view showing a configuration example of an image blur correction unit that holds a correction lens 301 for image blur correction so as to be movable in a direction orthogonal to the optical axis of the imaging optical system.
The drive coils 302 and 303 provided in the holder generate a magnetic field when energized by a drive unit (not shown). A correction lens unit (shift lens) 301 and driving magnets 304 and 305 are integrally provided in the correction lens unit. The magnets 304 and 305 together with the drive coils 302 and 303 constitute a voice coil motor as an actuator. In order to detect the magnetic field, Hall elements 306 and 307 are arranged with respect to the magnets 304 and 305, respectively, and detect the position of the correction lens unit in a plane orthogonal to the optical axis.

Next, position control of the correction lens unit 403 by the correction lens drive control unit 404 will be described.
FIG. 5 is a block diagram showing the internal configuration of the correction lens drive controller 404 and the main part of the correction lens unit 403 shown in FIG. Note that the posture detection and shake detection of the imaging device are performed in the pitch direction and the yaw direction with reference to a normal posture, that is, a posture in which the longitudinal direction of the image frame of the image frame substantially coincides with the horizontal direction. The pitch direction is the tilting direction with respect to the horizontal plane in the vertical direction of the imaging device, and the yaw direction is the tilting direction with respect to the vertical plane in the horizontal direction of the imaging device, and are directions orthogonal to each other. FIG. 5 shows an example in which shake detection of the imaging apparatus is performed. The gyro sensor units 501 and 502 constitute a two-way shake detection unit, respectively.

  A gyro sensor unit (hereinafter referred to as a pitch direction gyro unit) 501 that detects a shake of the imaging apparatus in the pitch direction outputs a shake detection signal to the image shake correction control unit 503. A gyro sensor unit (hereinafter referred to as a yaw direction gyro unit) 502 that detects a shake of the imaging apparatus in the yaw direction outputs a shake detection signal to the image shake correction control unit 504. Although the pitch direction gyro part 501 and the yaw direction gyro part 502 are provided in the present embodiment, an acceleration sensor or the like may be provided. The image blur correction control units 503 and 504 receive the shake detection signals of the gyro units 501 and 502, respectively, and generate control signals for controlling the position of the correction lens 301. The image blur correction control unit 503 outputs a control signal to the PID unit 505, and the image blur correction control unit 504 outputs a control signal to the PID unit 506.

  PID units 505 and 506 are feedback control means, and perform feedback control of the correction lens 301 by P (proportional) I (integral) D (differential) control. The PID unit 505 calculates a control amount by obtaining a deviation from the control signal of the correction position in the pitch direction and the position detection signal of the Hall element 509 that detects the position of the correction lens 301 in the pitch direction. The PID unit 505 outputs a position command signal corresponding to the calculated control amount to the drive unit 507. Similarly, the PID unit 506 calculates a control amount by obtaining a deviation from the control signal for the correction position in the yaw direction and the position detection signal for the Hall element 510 that detects the position of the correction lens 301 in the yaw direction. The PID unit 506 outputs a position command signal corresponding to the calculated control amount to the drive unit 508. The drive units 507 and 508 drive the correction lens 301 by outputting a drive signal to the actuator based on the position command signals sent from the PID units 505 and 506, respectively.

FIG. 1 shows a configuration example of the PID units 505 and 506 shown in FIG.
The PWM frequency determination unit 101 determines the pulse width modulation frequency according to the control mode signal output from the control unit 417. For example, in the case of the first control mode, which is a mode in which the control performance of the correction lens 301 is prioritized, a first PWM cycle (hereinafter referred to as the first cycle) corresponding to the first PWM frequency (hereinafter referred to as the first frequency) is determined. . In the case of the second control mode, which is a mode that prioritizes reduction of power consumption, a second PWM cycle (hereinafter referred to as a second cycle) corresponding to a second PWM frequency (hereinafter referred to as a second frequency) is determined. The PWM frequency determination unit 101 outputs the determined PWM cycle to the PWM signal generation unit 104.

The control calculation unit 102 obtains the target position signal generated by the image blur correction control units 503 and 504 and the position detection signal by the Hall elements 509 and 510, calculates the position deviation, and performs the PID control calculation. It is assumed that the PID calculation corresponding to the first frequency is executed.
The duty ratio determination unit 103 multiplies the calculation result of the control calculation unit 102 by a correction coefficient in accordance with the control mode signal from the control unit 417. Thereby, a duty ratio corresponding to the PWM frequency is determined and output to the PWM signal generation unit 104. As the correction coefficient, a value determined by one or more of a dead time, a rise time, and a fall time of an H bridge circuit described later that constitutes the drive unit is used.
The PWM signal generation unit 104 generates a PWM signal based on the PWM cycle set by the PWM frequency determination unit 101 and the duty ratio set by the duty ratio determination unit 103, and outputs them to the drive units 507 and 508, respectively. .

FIG. 6 is a configuration diagram of the drive unit 507.
The H bridge driver 601 controls the current supplied to the actuator coil of the correction lens unit 403. The inductor 602 and the capacitor 603 constitute a filter that smoothes the current flowing through the coil of the actuator. When the current flowing through the drive coils 302 and 303 (see FIG. 3) varies greatly, the generated magnetic field variation also increases. When the imaging signal of the imaging device 207 varies due to the variation of the magnetic field generated by the drive coils 302 and 303, the image output from the video signal processing unit 411 may be affected (occurrence of horizontal stripes or the like). Therefore, a filter is formed by the inductor 602 and the capacitor 603, and the current flowing through the coil of the actuator is smoothed to reduce the current fluctuation. For example, the waveform diagram of FIG. 7A shows the output of the H bridge driver 601. The H bridge driver 601 outputs a rectangular wave PWM voltage having a predetermined frequency from each output terminal. In the figure, VH indicates a high level and VL indicates a low level.

  By applying the rectangular wave PWM voltage, a triangular wave current shown in FIG. 7B flows in the inductor 602, and a triangular wave current shown in FIG. 7C flows in the capacitor 603. The inductor current has an offset with respect to the capacitor current. A substantially direct current, which is smoothed as shown in FIG. 7D, flows through the coil of the actuator.

FIG. 8 shows frequency characteristics of the image blur correction unit including the inductor 602 and the capacitor 603. The horizontal axis indicates the frequency, and the vertical axis indicates the current gain. For a current change at a frequency higher than the resonance frequency, the current change is attenuated. The PWM output frequency of the output signal of the H bridge driver 601 is set by the drive frequency setting unit 604 in FIG. As the PWM output frequency of the output signal of the H-bridge driver 601 becomes higher than the resonance frequency of FIG. 8, the change in the output current of the H-bridge driver 601 is also attenuated, so that the power consumption is reduced. However, since the clock signal for generating the PWM output of the H-bridge driver 601 is constant, increasing the PWM output frequency decreases the resolution of energization control of the image blur correction unit. That is, when the PWM output frequency of the H-bridge driver 601 is increased, the accuracy of the correction lens position control is lowered. Therefore, when there is no need to increase the accuracy of position control of the correction lens, the power consumption can be reduced by changing the PWM output frequency.
The drive unit 508 has the same configuration as the drive unit 507, and a description thereof is omitted.

Next, the operation of the image blur correction apparatus in the present embodiment will be described with reference to the flowchart of FIG.
First, in S101, the control unit 417 initializes various variable values necessary for the camera shake correction process. When the timing signal for determining the correction lens control period is output from the control unit 417 in S105, the process proceeds to S107. If the timing signal is not output, the determination process in S105 is repeated to enter a waiting state.

  In step S107, the gyro units 501 and 502 detect camera shake amounts. The image blur correction control units 503 and 504 calculate the target position by calculation (S109). Further, the position detection signal of the correction lens 301 is acquired from the outputs of the Hall elements 509 and 510 (S111), and the control calculation unit 102 calculates a control amount for PID control (denoted as PID_O) (S113). In the control calculation unit 102, the PID control parameter is adjusted so that the control amount when driving at the first frequency is optimal, and the output control amount is the control when driving at the first frequency. It corresponds to the quantity. After the duty ratio determination process is executed in S115 and the duty ratio corresponding to the PWM frequency is determined, the process returns to S105.

Next, the duty ratio determination process S115 performed by the duty ratio determination unit 103 will be described with reference to FIG.
In S121, the current control mode is determined. If the current control mode is the first control mode that prioritizes the control performance of the correction lens, the process proceeds to S123. If the current control mode is the second control mode that reduces power consumption, the process proceeds to S125. Proceed with the process.
In S123, a process of determining the control amount PID_O calculated by the control calculation unit 102 as it is as the next PWM duty ratio (denoted as DUTY_N) is performed. In S125, the control amount PID_O calculated by the control calculation unit 102 is multiplied by the frequency conversion coefficient α and the duty correction coefficient β. The frequency conversion coefficient α is a ratio of the second period to the first period (that is, a result of dividing the second period PWM_2 by the first period PWM_1). The duty correction coefficient β is a correction coefficient for correcting a difference in current output characteristics caused by a difference in PWM frequency. The value of the duty correction coefficient β is determined by the switching characteristics of the H bridge driver 601 and is a value of 1 or less when the first period is represented as 1.

In S125, the next PWM duty ratio DUTY_N is determined by “PID_O × α × β”. By multiplying the calculation result of the control calculation unit 102 by the correction coefficient, it is possible to correct the difference between the PWM duty ratio and the energization current to the actuator due to the difference in PWM frequency.
Further, in order to suppress a decrease in current linearity (linearity) in the vicinity of 0% and 100% of the PWM duty ratio, a lower limit threshold and an upper limit threshold of the PWM duty ratio are set. Thereby, the fall of a control characteristic can be suppressed.

  According to the present embodiment, the control mode for reducing the power consumption of the correction optical system (including the correction lens) and the control mode in which the control performance of the correction optical system is emphasized are switched according to the control mode of the imaging apparatus. Thus, both power consumption and control performance can be achieved. The discontinuous movement of the correction lens can be suppressed when the control mode is switched.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals as those used in the first embodiment, and detailed descriptions thereof are omitted, and differences are mainly described.
In the present embodiment, the content of the duty ratio determination process in S115 is different in the flowchart of FIG. In the present embodiment, a process of continuously changing the PWM frequency (hereinafter referred to as a PWM sweep process) is executed. In the initialization process of S101 of FIG. 9, when the PWM frequency is continuously changed in the PWM sweep process, the value of the count variable (denoted by n) for counting the number of changes is set to zero. The initialization process is executed.

Hereinafter, the duty ratio determination process in the present embodiment will be described with reference to FIG.
S201 is a flag value determination process instructing to change the control mode. When the value of the flag for instructing the change of the control mode is 1, the process proceeds to S203, and the PWM sweep process is executed. The PWM sweep process S203 will be described later with reference to FIG. In S201 of FIG. 11, if the value of the flag for instructing the change of the control mode is zero, the process proceeds to S205.

  In S205, the current control mode is determined. If the current control mode is the first control mode, the process proceeds to S207. If the current control mode is the second control mode, the process proceeds to S211. In S207, a process of setting the control amount PID_O, which is the calculation result of the control calculation unit 102, as the next PWM duty ratio DUTY_N is executed. In S211, processing for setting the value obtained by multiplying the control amount PID_O, which is the calculation result of the control calculation unit 102, by the PWM frequency conversion coefficient α as the next PWM duty ratio DUTY_N is executed. When the processes in S203, S207, and S211 are completed, the process proceeds to a return process, the duty ratio determination process S115 in FIG. 9 is terminated, and the process returns to S105.

Next, the PWM sweep process S203 of FIG. 11 will be described with reference to the flowchart of FIG.
First, in S401, the value of the count variable n is incremented (n = n + 1), and an operation for determining the PWM output in the next sampling is executed. In S403, it is determined whether the flag value for instructing the change of the control mode is changed. When the imaging apparatus is in the first control mode in which priority is given to the controllability of the correction lens 301, if a signal instructing the second control mode in which priority is given to reducing power consumption is output, the process proceeds to S405. For example, when exposure to the image sensor is completed, the first control mode is changed to the second control mode, and switching from the first frequency to the second frequency is performed during the blanking period.

  In S405, the PWM frequency determination unit 101 calculates a difference between the first period PWM_1 corresponding to the first frequency and the second period PWM_2 corresponding to the second frequency. A value obtained by dividing the difference “PWM_1−PWM_2” into n equal parts by the count variable is subtracted from the current PWM cycle PWM_C, and this is set to the PWM signal generation unit 104 as the next PWM cycle PWM_N.

  On the other hand, in S403, when the signal indicating the first control mode is output in the second control mode, the process proceeds to S407. For example, when the release button of the camera is operated and a shooting preparation signal (ON signal of SW1) is output, the second control mode is changed to the first control mode. The PWM frequency determination unit 101 calculates a difference between the first period PWM_1 corresponding to the first frequency and the second period PWM_2 corresponding to the second frequency. A value obtained by dividing the difference “PWM_1−PWM_2” into n equal parts by the count variable is added to the current PWM cycle PWM_C, and a process of setting this as the next PWM cycle PWM_N to the PWM signal generation unit 104 is performed.

  After S405 and S407, the process proceeds to S409, where the duty ratio determination unit 103 multiplies the control amount PID_O output from the control calculation unit 102 by a predetermined ratio. The predetermined ratio is a ratio of the period after the change to the first period, that is, a value (PWM_N / PWM_1) obtained by dividing the next PWM period PWM_N by the first period PWM_1. The multiplication result is output to the PWM signal generation unit 104 as the next PWM duty ratio DUTY_N. It is assumed that the control calculation unit 102 has been tuned for PID control parameters that are optimal when driving at the first frequency.

  In the next S411, a process of substituting the next PWM cycle determined in S405 and S407 for PWM_C which is the current PWM cycle is performed, and the process proceeds to S413. The value of the count variable n is compared with the number of times (denoted as N) that determines how many times PWM switching is performed in the PWM sweep process. If the value of n matches the number N, that is, if the PWM frequency set immediately before has reached the second frequency or has reached the first frequency, the process proceeds to S415. In S415, the flag instructing to change the control mode is canceled. After S415, the PWM sweep process is terminated and the process proceeds to a return process.

On the other hand, if the value of n does not match the number N in S413, that is, if the PWM frequency set immediately before has not reached the second frequency or has not reached the first frequency, The PWM sweep process is terminated without releasing the flag, and the process proceeds to the return process.
When the PWM sweep process ends, the duty ratio determination process S115 of FIG. 9 is subsequently ended, and the process returns to S105.

  If the flag is not released in S415, the PWM sweep process is executed again when the next control timing signal during the image blur correction process arrives. That is, the frequency switching is performed for the set number of times until the flag for instructing the change of the control mode is released, and the PWM sweep process is repeated until the desired PWM frequency is reached. The update cycle of the PWM frequency is a constant cycle, and is set to a cycle that is sufficiently longer than the PWM cycle.

  With reference to FIG. 13, how the cycle is gradually switched from the first cycle to the second cycle by repeating the PWM sweep processing during the duty ratio determination processing will be specifically described. Sn shown in FIG. 13 represents a state in which the PWM cycle changes step by step, and the value of the count variable n is n = 0, 1-6. “PWM duty n” in FIG. 13 indicates a change in duty ratio, and “PWMn” indicates a change in cycle. In this case, the first period corresponding to the first frequency is “PWM0”, and the first duty ratio is “PWM duty 0”. The second period corresponding to the second frequency is “PWM6”, and the second duty ratio is “PWM duty6”.

  S0 represents a state immediately before the PWM sweep process is executed, and a PWM signal having a duty ratio determined by the first period and the control amount PID_O output from the control calculation unit 102 is output. It is. S1 shows a state immediately after the first PWM sweep process is executed. S2 shows a state immediately after the second PWM sweep process is executed. Depending on the value of the number of times n when the PWM sweep process S203 is repeated, the state progresses sequentially as S3, S4,. In this example, the sixth PWM sweep process S203 is executed, resulting in the state of S6. This state is a state in which a PWM signal having a second period and a second duty ratio corresponding thereto is output. Note that the change from the second period to the first period and the change from the second duty ratio to the first duty ratio are performed according to the reverse process to that described above, and thus description thereof is omitted.

  In the present embodiment, when switching from the first frequency to the second frequency or switching from the second frequency to the first frequency, the frequency can be gradually changed. Further, if the number N is increased, the number of switching stages is increased, so that the frequency can be changed more smoothly.

DESCRIPTION OF SYMBOLS 101 PWM frequency determination part 102 Control calculating part 103 Duty ratio determination part 104 PWM signal generation part 507,508 Drive part 509,510 Hall element

Claims (13)

An imaging apparatus that performs image blur correction by a correction unit by changing a control mode,
Shake detection means for detecting shake of the imaging device;
Position detecting means for detecting the position of the correcting means;
Control means for obtaining a shake detection signal by the shake detection means and a position detection signal by the position detection means, calculating a control amount, and generating a control signal by pulse width modulation;
Drive means for driving the correction means in accordance with a control signal from the control means;
The control means determines the control mode and determines a duty ratio of the control signal using a correction coefficient corresponding to a pulse width modulation frequency;
The image pickup apparatus, wherein the drive means outputs a drive signal having a duty ratio determined by the control means to the correction means via a filter means. The control means includes
A calculation means for acquiring a shake detection signal from the shake detection means and calculating a target position of the correction means;
Frequency determining means for determining a different pulse width modulation frequency for each control mode;
Duty ratio determining means for determining the duty ratio from the output of the calculating means;
The signal generation means for generating the control signal having the pulse width modulation frequency determined by the frequency determination means and the duty ratio determined by the duty ratio determination means and outputting the control signal to the drive means. The imaging apparatus according to 1.   The duty ratio determining means determines the duty ratio from the control amount in the first control mode, and determines the duty ratio by multiplying the control amount by the correction coefficient in the second control mode. The imaging device according to claim 2.   4. The image pickup apparatus according to claim 2, wherein the driving unit is configured by an H-bridge circuit, and the filter unit is configured by an inductor and a capacitor.   The duty ratio determining means determines the duty ratio by multiplying the control amount by a correction coefficient determined by one or more of a dead time, a rise time, and a fall time of the H bridge circuit. The imaging device according to claim 4.   When changing the pulse width modulation frequency between the first control mode and the second control mode, the frequency determining means changes from the first frequency in the first control mode to the second frequency in the second control mode. 3. The imaging according to claim 2, wherein the transition is performed by changing the frequency, or the transition is performed by changing the frequency from the second frequency in the second control mode to the first frequency in the first control mode. apparatus.   The duty ratio determining means changes the duty ratio from the first duty ratio in the first control mode to the second duty ratio in the second control mode, or shifts the second duty ratio in the second control mode. The imaging apparatus according to claim 2, wherein the shift is performed by changing the duty ratio from the first duty ratio to the first duty ratio in the first control mode. When changing from the first control mode to the second control mode,
The frequency determining means calculates a difference between a first period corresponding to the first frequency and a second period corresponding to the second frequency, and subtracts a value obtained by dividing the difference by a set number of times from the current period. The imaging apparatus according to claim 6, wherein the process of changing the pulse width modulation frequency is repeated. When changing from the second control mode to the first control mode,
The frequency determining means calculates a difference between a first period corresponding to the first frequency and a second period corresponding to the second frequency, and adds a value obtained by dividing the difference by a set number of times to the current period. The imaging apparatus according to claim 6, wherein the process of changing the pulse width modulation frequency is repeated.   The duty ratio determining means determines the duty ratio by multiplying the control amount by the ratio of the period after the change to the first period every time processing for changing the pulse width modulation frequency is performed. The imaging device according to claim 8 or 9.   11. The control unit according to claim 8, wherein the control unit determines a change between a first control mode that prioritizes controllability of the correction unit and a second control mode that prioritizes reduction of power consumption. The imaging apparatus according to item 1. When a shooting preparation signal is output and a change from the second control mode to the first control mode is determined, the control means changes the pulse width modulation frequency from the second frequency to the first frequency,
When exposure to the image sensor is completed and a change from the first control mode to the second control mode is determined, the control means changes the pulse width modulation frequency from the first frequency to the second frequency during the blanking period. The imaging apparatus according to claim 11, wherein the imaging apparatus is changed. An imaging method executed by an imaging device that changes a control mode and performs image blur correction by a correction unit,
A shake detection step of detecting shake of the imaging device by shake detection means;
A position detecting step of detecting the position of the correcting means by a position detecting means;
A control step in which a control unit obtains a shake detection signal from the shake detection unit and a position detection signal from the position detection unit, calculates a control amount, and generates a control signal by pulse width modulation;
The driving means drives the correction means in accordance with a control signal from the control means;
In the control step, the control means determines the control mode, determines a duty ratio of the control signal using a correction coefficient corresponding to a pulse width modulation frequency,
In the driving step, the driving unit outputs a driving signal having a duty ratio determined by the control unit to the correcting unit via a filter unit.

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