JP2008164928A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the highest image blur correction in first control combined with PID control and in second control combined with PD control. <P>SOLUTION: The imaging apparatus includes: a control switching means that performs a step S(106) of switching so as to preform the first control by which until a first condition is satisfied, an image blur correction function is performed by a combination of proportional control, integral control, and differential control, and a step S(110) of performing second control by which until a second condition is satisfied after the first condition is satisfied, the image blur correction function is performed by a combination of proportional control and differential control; a parameter switching means that performs a step S(113) of switching a blur correction parameter to a first control blur correction parameter during the first control, or a step S(109) of switching the blur correction parameter to a second control blur correction parameter during the second control; and an offset correction means that performs a step (S110) of correcting offset displacement, arising as a result from switching between the first control and the second control. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus having an image blur correction function.

  Conventionally, an angular velocity sensor is often used to detect a shake amount in an image pickup apparatus having a shake correction function that detects shake of an image pickup apparatus and drives an optically movable shift lens to correct image shake. In this angular velocity sensor, a vibrating material such as a piezoelectric element is vibrated at a constant frequency, and the force due to the Coriolis force generated by the rotational motion component is converted into a voltage to obtain angular velocity information. Then, the obtained angular velocity is integrated to calculate a shake amount, a correction position control signal is output based on this shake amount, and the shift lens is driven in a direction to cancel the image shake amount, thereby causing the image shake. Correction is performed.

  In this shift lens drive, the current position of the shift lens is detected as a shift lens position signal, and this is fed back and feedback control is performed to reflect it in the corrected position control signal. In general, feedback control uses a control method called PID control.

  The D control (differential control) is used to improve the decrease in the gain margin GM and the phase margin PM due to the overcompensation of the P control (proportional control) and to improve the stability of the feedback control. I control (integral control) is used to improve the offset characteristics of feedback control. Feedback control in which these P control, I control, and D control are selected and combined as necessary is called PID control.

As a conventional imaging device in which image blur correction control is performed, for example, there is one disclosed in Patent Document 1. That is, when PID control is used for feedback control, high frequency components of noise are emphasized in the feedback loop by D control (differential control), and vibration noise is generated due to this. In the image blur correction technique described above, the combination of PID control is changed before and after the exposure is started in order to reduce the vibration noise. Further, the presence / absence of use of the feedforward function is switched before and after the start of exposure.
Japanese Patent Laid-Open No. 11-218795

  In the above conventional example, only the PID control is changed. However, since the offset is generated when the control method for executing the image blur correction function is changed from the PID control to the PD control, the shift lens position signal is changed with respect to the same command value. There is a difference in output. In addition, the frequency characteristics are different, for example, a phase delay is caused by the input of I control (integral control). For this reason, if the shift lens is driven and controlled by switching the control method without considering the difference in output offset and the frequency characteristic, there is a problem that the image stabilization performance deteriorates.

(Object of invention)
An object of the present invention is to provide an imaging apparatus capable of realizing the highest image blur correction in each of the first control combining PID control and the second control combining PD control.

  In order to achieve the above object, the present invention provides an image pickup apparatus having an image shake correction function for correcting an image shake by driving a shake correction means, and driving the shake correction means according to the shake applied to the image pickup apparatus. Determination means for determining a target position, feedback control means for performing feedback control so that the actual position of the shake correction means converges to the drive target position, and until the first condition is satisfied, the feedback control means includes: The feedback control means executes the first control that operates the image blur correction function by combining proportional control, integral control, and derivative control, and until the second condition is satisfied after the first condition is satisfied, Control switching means for switching to execute the second control that makes the image shake correction function work by combining the proportional control and the differential control, and when the first control is executed, the shake correction parameter is set. Switching to one control shake correction parameter, and when executing the second control, the parameter switching means for switching the shake correction parameter to the second control shake correction parameter, and the switching generated between the first control and the second control The imaging apparatus includes an offset correction unit that corrects an offset deviation of the output of the feedback control unit.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device which can implement | achieve the highest image blur correction in each of 1st control which combined PID control, and 2nd control which combined PD control can be provided.

  The best mode for carrying out the present invention is as shown in Examples 1 and 2 below.

  FIG. 1 is a block diagram illustrating the configuration of the imaging apparatus according to the first embodiment of the present invention. This imaging device is a digital camera mainly for taking still images.

  In FIG. 1, reference numeral 101 denotes a zoom unit, which includes a zoom lens that performs zooming. Reference numeral 102 denotes a zoom drive control unit that controls the drive of the zoom unit 101. Reference numeral 103 denotes a cyst lens (unit) as a shake correction unit capable of changing a position on a plane perpendicular to the optical axis. Reference numeral 104 denotes a shift lens drive control unit, which drives and controls the cyst lens 103. Reference numeral 105 denotes an aperture / shutter unit. Reference numeral 106 denotes an aperture / shutter drive control unit, which controls the drive of the aperture / shutter unit 105. A focus unit 107 includes a lens that performs focus adjustment. A focus drive control unit 108 controls the drive of the focus unit 107. Reference numeral 109 denotes an image pickup unit in which an image pickup element is used, and converts an optical image that has passed through each lens group into an electric signal.

  Reference numeral 110 denotes an imaging signal processing unit that converts an electrical signal output from the imaging unit 109 into a video signal. A video signal processing unit 111 processes the video signal output from the imaging signal processing unit 110 according to the application. Reference numeral 112 denotes a display unit, which displays an image as necessary based on a signal output from the video signal processing unit 111. Reference numeral 113 denotes a power supply unit that supplies power to the entire system according to the application. An external input / output terminal unit 114 inputs / outputs communication signals and video signals to / from the outside. Reference numeral 115 denotes an operation unit for operating the system. Reference numeral 116 denotes a storage unit that stores various data such as video information. Reference numeral 117 denotes a control unit that controls the entire system.

  Next, the operation of the imaging apparatus having the above configuration will be described.

  The operation unit 115 has a shutter release button configured so that the first switch (SW1) and the second switch (SW2) are sequentially turned on according to the amount of pressing. The first switch is turned on when the shutter release button is depressed approximately halfway, and the second switch is turned on when the shutter release button is depressed to the end. When the first switch of the operation unit 115 is turned on, the focus drive control unit 108 drives the focus unit 107 to perform focus adjustment, and the aperture / shutter drive control unit 106 drives the aperture / shutter unit 105 to perform proper adjustment. Set an appropriate exposure amount. Further, when the second switch is turned on, the image data obtained from the light image exposed to the imaging unit 109 is stored in the storage unit 116.

  At this time, if there is an instruction to turn on the image stabilization from the operation unit 115, the control unit 117 instructs the shift lens drive control unit 104 to perform the image stabilization operation. Anti-vibration operation is performed until instructed.

  Further, in this imaging apparatus, one of the still image shooting mode and the moving image shooting mode can be selected from the operation unit 115, and the operating condition of each actuator can be changed in each mode.

  If there is an instruction for zooming with the zoom lens to the operation unit 115, the zoom drive control unit 102 that has received the instruction via the control unit 117 drives the zoom unit 101 to zoom to the instructed zoom position. Move the lens. At the same time, based on the image information processed by the signal processing units 110 and 111 sent from the image capturing unit 109, the focus drive control unit 108 drives the focus unit 107 to perform focus adjustment.

  FIG. 2 is a block diagram showing an internal configuration of the shift lens drive control unit 104 shown in FIG.

  In FIG. 2, reference numeral 201 denotes a pitch direction gyro unit, which detects a shake in the vertical direction (pitch direction) of the imaging apparatus in a normal posture (an posture in which the length direction of the image frame substantially coincides with the horizontal direction). Reference numeral 202 denotes a yaw direction gyro unit that detects a shake in the horizontal direction (yaw direction) of an imaging apparatus in a normal posture. Reference numerals 203 and 204 denote anti-vibration control units as determining means for determining drive target positions in the pitch direction and the yaw direction, and perform anti-vibration control and shift lens position control according to the situation. Reference numerals 205 and 206 denote PID sections as feedback control means, which obtain control amounts from deviations between the correction position control signals in the pitch direction and the yaw direction and the position signal indicating the position of the cyst lens 103, and output position command signals. To do. Reference numerals 207 and 208 respectively denote drive units that drive the cyst lens 103 based on position command signals sent from the PID units 205 and 206. Reference numerals 209 and 210 denote Hall elements, which detect the positions of the cyst lens 103 in the pitch direction and the yaw direction.

  Next, position control of the cyst lens 103 by the shift lens drive control unit 104 will be described.

  In the position control of the cyst lens 103, based on shake information signals (angular velocity signals) representing the shake in the pitch direction and yaw direction of the imaging device from the pitch direction gyro unit 201 and the yaw direction gyro unit 202, the cyst lens 103 in each direction. 103 is driven. A magnet is attached to the cyst lens 103, the magnetic field of the magnet is detected by the Hall elements 209 and 210, and position signals indicating the actual position of the cyst lens 103 are sent to the PID units 205 and 206, respectively. The PID units 205 and 206 perform feedback control such that these position signals converge on the corrected position control signals sent from the image stabilization control units 203 and 204, respectively. Since the position signals output from the Hall elements 209 and 210 have individual variations, the Hall elements 209 and 210 of the Hall elements 209 and 210 are moved so that the cyst lens 103 moves to a predetermined position with respect to a predetermined correction position control signal. It is necessary to adjust the output. At this time, the PID units 205 and 206 perform PID control in which proportional control, integral control, and differential control are selectively combined.

  The image stabilization controllers 203 and 204 are configured to move the position of the cyst lens 103 in a direction in which image shake due to shake of the imaging device is corrected based on shake information signals from the pitch direction gyro unit 201 and the yaw direction gyro unit 202. To do. For this purpose, the image stabilization controllers 203 and 204 each output a corrected position control signal (representing the drive target position). Thus, even if camera shake or the like occurs in the imaging apparatus, image blur can be prevented.

  FIG. 3 is a block diagram showing an internal configuration of the image stabilization control unit 203 shown in FIG. Note that the image stabilization control unit 204 also has the same internal configuration as the image stabilization control unit 203, and the description of the image stabilization control unit 204 is omitted.

  In FIG. 3, reference numeral 301 denotes an A / D converter, which converts a shake information signal (angular velocity signal) from the pitch direction gyro section 201 into a digital signal. Reference numeral 302 denotes a gain adjuster that amplifies the converted digital signal. Reference numeral 303 denotes a high-pass filter (HPF), which is a filter capable of changing a cutoff frequency for cutting a DC component. 304 is also a high pass filter (HPF). Reference numeral 305 denotes a low-pass filter (LPF) capable of changing a cutoff frequency, and is a filter for converting an angular velocity signal into an angular signal. A gain switching unit 306 as a parameter switching unit changes the gain of the gain adjuster 302.

  The shake information signal (angular velocity signal) input to the image stabilization control unit 203 is subjected to the above-described series of filter processing and input to the PID unit 205 as a corrected position control signal.

  FIG. 4 is a block diagram showing an internal configuration of the PID unit 205 shown in FIGS. Note that the PID unit 206 also has the same internal configuration as the PID unit 205, and a description of the PID unit 206 is omitted.

  In FIG. 4, 401 is an integral compensation unit (Ki), 402 is a proportional compensation unit (Kp), and 403 is a differential compensation unit (Kd). 404 is a switch (SW) detector, 405 is a PID switch, 406 and 408 are switches, and 407 is an integral compensation value holder. Reference numeral 409 denotes a shake correction parameter switch as parameter switching means. A cutoff switch 410 changes the cutoff frequency of the PLF 411, PDF 412, and LPF 413, which are digital filter arithmetic units. Reference numeral 414 denotes an offset correction unit that corrects an offset shift by advancing the phase of the position command signal.

  In the PID unit 205, the PID switch 405 operates the switches 406 and 408 and the shake correction parameter switch 409 according to the detection signal of the switch detector 404 to selectively execute PID control or PD control. The shake correction parameter switching unit 409 switches the magnification of the gain adjuster 302 of the image stabilization control unit 203 and corrects the offset of the output offset with respect to the offset correction unit 414. Then, it instructs the cutoff switching unit 410 to switch the cutoff frequency of each digital filter.

  The switch detector 404 detects the ON state of the second switch of the shutter release button and the end of storing the image data in the storage unit 116 (end of exposure). During PID control, the changeover switch 406 is closed, the changeover switch 408 is opened, and an integral compensation value that is an output value of the integral compensation unit (Ki) 401 is input to the integral compensation value holder 407. Retained. During PD control, the changeover switch 406 is opened, the changeover switch 408 is closed, and the integral compensation value stored immediately before switching to PD control is read from the integral compensation value holder 407.

  An image shake correction operation performed in the imaging apparatus configured as described above will be described with reference to the flowchart of FIG.

  First, when the power of the imaging apparatus is turned on in step S101, PID control is executed in the next step S102. That is, the PID switch 405 in FIG. 4 closes the changeover switch 406 and opens the changeover switch 408. Then, in the next step S103, it is determined whether or not the image blur correction mode is set to ON by the user on the operation unit 115. As a result, if the image blur correction mode is set to ON, the process proceeds to step S106, and if the image blur correction mode is set to OFF, the process proceeds to step S104.

  If the image blur correction mode is set to OFF and the process proceeds to step S104, the shift lens 103 is fixed at the optical axis center position by PID control. As a result, center fixing without offset becomes possible. Thereafter, in step S105, it is determined whether or not the power of the imaging apparatus is on. If it is on, the process returns to step S102, and if it is off, the image blur correction operation is terminated.

  On the other hand, if the image blur correction mode is set to ON and the process proceeds from step S103 to step S106, image stabilization control by PID control is performed until the second switch (SW2) of the shutter release button is turned ON. That is, PID control is performed until a still image shooting start command is received. In the image stabilization control based on the PID control, the image stabilization performance is slightly inferior to that in the PD control. However, during this period, the image data is not actually stored in the storage unit 116, but only the image is displayed on the display unit 112. ,No problem. In the next step S107, it is determined whether or not the second switch of the shutter release button is turned on. If turned on, the process proceeds to step S108, and if it remains off, the process proceeds to step S105.

  If the second switch of the shutter release button is turned on and the process proceeds to step S108, the integral compensation value holder 407 in FIG. 4 holds the integral compensation value in the PID control. In the next step S109, when switching to PD control, the following processing is performed by the shake correction control parameter switch 409. That is, PD control shake correction parameters are set for the gain switching unit 306 of the image stabilization control units 203 and 204 and the PLF 411, PDF 412, and LPF 413 of the PID units 205 and 206. In the subsequent step S110, the PID switch 405 that has received the detection signal from the switch detector 404 opens the switch 406 and closes the switch 408. As a result, PD control is executed with the proportional compensation value Ki fixed. That is, image stabilization control by PD control is started using the integral compensation value before PD control execution held in the integral compensation value holder 407 and the shake correction parameter for PD control.

  In the next step S111, the exposure sequence is executed, and in the subsequent step S112, storage of image data (still image shooting) is terminated in the storage unit 116. Then, the PD control shake correction parameters such as the gain switching unit 306, HPFs 303 and 304, and LPF 305 set earlier are returned to the PID control shake correction parameters.

  Thereafter, the process returns to step S102, and PID control is performed again. That is, the PID switch 405 that has received the detection signal from the switch detector 404 closes the switch 406, opens the switch 408, and performs PID control using the PID control shake correction parameter.

  In the first embodiment described above, when the image blur correction mode is set to OFF, the shift lens 103 is fixed at the optical axis center position from which the offset is removed by PID control. That is, the processing of steps S103 → S104 in FIG. 5 is executed. In addition, when the image blur correction mode is set to ON, the image stabilization operation by the PID control having slightly inferior image stabilization performance from when the first switch of the shutter release button is turned on until the second switch is turned on. I do. That is, the process of steps S103 → S106 → S107 → S105 → S102 → S103... In FIG. Then, while the second switch is turned on and the exposure sequence is actually executed, the image stabilization operation by the PD control is performed (step S110). At that time, a PD control shake correction parameter is used to correct the offset deviation and the difference in frequency characteristics (step S109).

  As a result, when checking a captured image, the image stabilization effect is slightly inferior, but image blur correction is performed by PID control with good followability, so that the captured image can be confirmed accurately. At the time of image recording, image blur correction is performed by PD control having a high image stabilization effect, so that image data with a small shake amount (image blur) is stored in the storage unit 116. That is, the highest image stabilization operation can be performed in the control method (PID control method, PD control method) for executing each image blur correction.

  Next, a second embodiment of the present invention will be described. The configuration of the imaging apparatus according to the second embodiment is basically the same as the configuration of the first embodiment. Therefore, in the second embodiment, the description of the same parts as those of the first embodiment is omitted, and only different parts will be described.

  FIG. 6 is a block diagram illustrating a configuration of the PID unit 500 according to the second embodiment of the present invention.

  The PID unit 500 according to the second embodiment corresponds to the PID unit 205 and the PID unit 206 in the first embodiment (FIG. 2), and the drive unit 516 is the same as the drive unit 207 and the drive unit in the first embodiment (FIG. 2). This corresponds to 208.

  In FIG. 6, 501 is an integral compensation unit (Ki), 502 is a proportional compensation unit (Kp), and 503 is a differential compensation unit (Kd). Reference numeral 504 denotes a switch detector, and 505 denotes a PID switch. Reference numeral 507 denotes an integral compensation value holder, and 509 denotes an attitude detector. Reference numeral 510 denotes a shake correction parameter switch.

  In the PID unit 500, the posture detector 509 detects the posture of the imaging device based on the value of the integral compensation value holder 507. The shake correction parameter switching unit 510 selects the shake correction parameter optimal for the state from the information of the attitude detector 509, and the image stabilization control unit 203 performs the image stabilization of the PD control method using the parameter.

  An image blur correction operation performed in the imaging apparatus according to the second embodiment configured as described above will be described with reference to the flowchart of FIG.

  In step S201, when the power of the imaging apparatus is turned on, the process proceeds to step S202, and PID control is executed. That is, the PID switch 505 closes the switch 506 and opens the switch 508. In the next step S203, it is determined whether or not the image blur correction mode is set to ON by the user on the operation unit 115. As a result, if the image blur correction mode is set to ON, the process proceeds to step S206, and if the image blur correction mode is set to OFF, the process proceeds to step S204.

  If the image blur correction mode is set to OFF and the process proceeds to step S204, the shift lens 103 is fixed at the optical axis center position by PID control. As a result, center fixing without offset becomes possible. Thereafter, in step S205, it is determined whether or not the power of the imaging apparatus is on. If it is on, the process returns to step S202, and if it is off, the image blur correction operation is terminated.

  On the other hand, if the image blur correction mode is set to ON and the process proceeds from step S203 to step S206, image stabilization control by PID control is performed until the second switch of the shutter release button is turned ON. Then, in the next step S207, it is determined whether or not the second switch of the shutter release button is turned on. If turned on, the process proceeds to step S208, and if it remains off, the process proceeds to step S205.

  When the process proceeds to step S208 assuming that the second switch is turned on, the integral compensation value holder 507 in FIG. 6 holds the integral compensation value in the PID control. In steps S209, S210, and S211, the orientation of the imaging apparatus is detected from the integral compensation value held by the integral compensation value holder 507. Then, in steps S212, S213, and S214, PD control shake correction parameters suitable for the respective postures are set based on the detected posture information of the imaging device.

  Thereafter, in either case, the process proceeds to step S215, and the PID switch 505 having received the detection signal from the switch detector 504 opens the switch 506 and closes the switch 508. Thereby, PD control is started using the set PD control shake correction parameter. In the next step S216, the exposure sequence is executed, and in the subsequent step S217, the storage of image data (still image shooting) in the storage unit 116 is terminated. In step S218, the shake correction parameter is returned to that for the PID control method.

  Thereafter, the process returns to step S202, and PID control is performed again. That is, the switch 506 is closed by the PID switch 505 that has received the detection signal from the switch detector 504, the switch 508 is opened, and PID control is performed using the PID control shake correction parameter.

  By performing the operation as described above, when switching from the PID control method to the PD control method at the time of imaging, not only the parameter correction due to the difference in the control method but also the correction due to the attitude difference can be performed.

  In the first and second embodiments described above, the degree of shake applied to the imaging apparatus is detected by the pitch direction gyro unit 201 and the yaw direction gyro unit 202. The PID units 205 and 208 perform PID control according to the degree of shake until the first condition for receiving a still image shooting start instruction is satisfied after exposure adjustment and focus adjustment are completed when the image shake correction function is executed. This is performed using the control shake correction parameter. Thereafter, PD control is performed according to the degree of shake until the second condition that the still image shooting is completed after the first condition is satisfied. At this time, since a difference occurs in the output offset due to the switching of the control method, offset correction is performed to correct it. In each control, since the shift amount of the shift lens 103 with respect to the command position is different, the output gain in the detection signal processing in the process of determining the drive target position is adjusted to correct it. Furthermore, since the frequency characteristics are different in each control, the cut-off frequency of the digital filter calculator in the process of calculating the command position is also switched.

  That is, the shake correction parameter is switched in consideration of the shift lens shift amount with respect to the command position that occurs when switching from the PID control method to the PD control method and the difference in frequency characteristics in each control method. Further, by correcting the difference in offset that occurs when the control method is switched, a screen display shift is eliminated at the time of switching. By these corrections, the control method is smoothly switched, and the imaging apparatus is designed to realize the highest image blur correction in each control.

  In the above description, the shift lens is used as the shake correction unit. However, the present invention can also be applied to a variable apex angle prism or an image sensor that performs shake correction by moving on a plane perpendicular to the optical axis.

1 is a block diagram illustrating a configuration of an imaging apparatus according to Embodiment 1 of the present invention. It is a block diagram which shows the internal structure of the shift lens drive control part of FIG. It is a block diagram which shows the internal structure of the image stabilization control part of FIG. It is a block diagram explaining the internal structure of the PID part of FIG. 3 is a flowchart illustrating a procedure of shake correction operation performed in the imaging apparatus according to the first embodiment of the present invention. It is a block diagram which shows the internal structure of the PID part concerning Example 2 of this invention. 10 is a flowchart illustrating a procedure of shake correction operation performed in the imaging apparatus according to the second embodiment of the present invention.

Explanation of symbols

103 cyst lens 104 shift lens drive control unit 115 operation unit 201 pitch direction gyro unit 202 yaw direction gyro unit 203 anti-vibration control unit 204 anti-vibration control unit 205 PID unit 206 PID unit 209 hall element 210 hall element 306 gain switching unit 401, 501, integral compensation unit 402, 502 proportional compensation unit 403, 503 differential compensation unit 405, 505 PID switch 406, 506 switch 407, 507 integral compensation value holder 408, 508 switch 409, 509 shake correction parameter switch 410, 510 Cut-off switch 414, 515 Offset correction unit 509 Attitude detection unit

Claims (5)

In an image pickup apparatus having an image shake correction function for correcting image shake by driving shake correction means,
Determining means for determining a drive target position of the shake correction means in accordance with shake applied to the imaging apparatus;
Feedback control means for performing feedback control so that the actual position of the shake correction means converges to the drive target position;
Until the first condition is satisfied, the feedback control unit executes the first control that works the image blur correction function by combining the proportional control, the integral control, and the derivative control, and after the first condition is satisfied. Until the second condition is satisfied, the feedback control means switches so as to execute the second control for combining the proportional control and the differential control to activate the image blur correction function; and
Parameter switching means for switching the shake correction parameter to the first control shake correction parameter when executing the first control, and for switching the shake correction parameter to the second control shake correction parameter when executing the second control;
An image pickup apparatus comprising: an offset correction unit that corrects an offset deviation of an output of the feedback control unit that occurs when the first control and the second control are switched.   The imaging apparatus according to claim 1, wherein the first condition is a condition that an instruction to start capturing a still image is received, and the second condition is a condition that the still image capturing ends.   The imaging apparatus according to claim 1, wherein the parameter switching unit switches a gain in the determination unit.   The imaging apparatus according to claim 1, wherein the parameter switching unit switches a cutoff frequency of a digital filter arithmetic unit in the feedback control unit.   The imaging apparatus according to claim 1, wherein the parameter switching unit further switches the shake correction parameter in accordance with the posture.

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