JP5442159B2 - IMAGING DEVICE AND IMAGING DEVICE CONTROL METHOD - Google Patents

Description

  The present invention relates to a shake correction apparatus, an imaging apparatus, and a control method for the shake correction apparatus.

  There is known an imaging apparatus that corrects a shift (optical axis deviation) of the center of an imaging element from an optical axis of an imaging optical system by moving a lens for shake correction (Patent Document 1).

JP 2006-191181 A

  If the lens for shake correction moves and the center thereof deviates from the optical axis of the imaging optical system, the optical performance (MTF: Modulation Transfer Function) of the imaging optical system deteriorates. However, since Patent Document 1 does not consider a decrease in optical performance, there is a possibility that the optical performance may be greatly deteriorated when a large optical axis shift is corrected.

  The present invention has been made in view of such a situation, and an object thereof is to provide a technique for suppressing a decrease in optical performance when correcting an optical axis shift.

In order to solve the above-described problems, a first aspect of the present invention is an imaging device that detects a subject image that has passed through a photographing optical system, a detection unit that detects shake, and a correction unit that reduces image shake caused by the shake. Determining means for determining a reference position; driving means for driving the correcting means with the reference position as a control center position of a driving range of the correcting means so as to correct image shake caused by shake detected by the detecting means; The center of the imaging device is shifted from the optical axis of the photographing optical system, and the determining means corrects the optical characteristic of the photographing optical system within a range that satisfies a predetermined condition. There is provided an imaging apparatus characterized in that the reference position is determined so that means corrects a deviation of the optical axis of the imaging optical system from the center of the imaging element .

  Other features of the present invention will become more apparent from the accompanying drawings and the following description of the preferred embodiments.

  With the above configuration, according to the present invention, it is possible to suppress a decrease in optical performance when correcting the optical axis deviation.

1 is a block diagram illustrating a configuration of an imaging apparatus 100 including a shake correction apparatus according to the present invention. The block diagram which shows the detailed structure of a target position calculation circuit. The figure which shows the relationship between the control center position of the correction lens 2, and optical performance. The flowchart which shows the flow of the determination process of the reference position of a control center position.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The technical scope of the present invention is determined by the scope of the claims, and is not limited by the following individual embodiments. In addition, all combinations of features described in the embodiments are not necessarily essential to the present invention.

  FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus 100 including a shake correction apparatus according to the present invention. In FIG. 1, the imaging optical system 10 includes an imaging lens 1 and a correction lens 2 for correcting shake applied to the imaging device 100. The correction lens 2 is movable in a direction orthogonal to the optical axis of the imaging optical system 10. The imaging element 3 photoelectrically converts incident light from the imaging optical system 10. The signal processing circuit 4 processes an electrical signal obtained by photoelectric conversion in the image sensor 3 and converts it into, for example, a standard video signal. The output terminal 5 outputs a standard video signal obtained from the signal processing circuit 4. With the above configuration, the imaging apparatus 100 outputs the captured image as a standard video signal.

  The gyro Y11 and the gyro P12 are angular velocity sensors that detect angular velocities in the yaw direction and the pitch direction, respectively, among shakes applied to the imaging apparatus 100. In the present embodiment, the gyro Y11 and the gyro P12 are arranged on one plane orthogonal to the optical axis of the imaging optical system 10 so as to detect the angular velocity of the rotational component of the shake at the rotation axes orthogonal to each other.

  The target position calculation circuit 21 determines the target position of the correction lens 2 based on the angular velocity detected by the gyro Y11 and the gyro P12 and the deviation (optical axis deviation) of the center of the image sensor 3 from the optical axis of the imaging optical system 10. (Details will be described later with reference to FIG. 2). The drive circuit Y31 and the drive circuit P32 drive the correction lens 2 so as to move to the target position calculated by the target position calculation circuit 21.

  The shake correction control circuit 6 controls the target position calculation circuit 21 in accordance with a user instruction regarding whether or not to execute shake correction (details will be described later with reference to FIG. 2). The user can instruct whether or not to perform shake correction via a switch (not shown) or a menu screen.

  The imaging apparatus 100 includes a computer, and the function of each block described above can be realized by the computer executing a program.

  Next, with reference to FIG. 2, the details of the target position calculation processing by the target position calculation circuit 21 will be described. The amplifier Y22 and the amplifier P23 amplify the angular velocity signals detected by the gyro Y11 and the gyro P12, respectively. HPF_Y24 and HPF_P25 are high-pass filters with variable frequency characteristics, and block the low frequency components included in the angular velocity signals amplified by the amplifiers Y22 and P23 and output the remaining components. The integrator Y26 and the integrator P27 obtain the angular displacement amount by integrating the angular velocity signals output from the HPF_Y24 and the HPF_P25, respectively. The angular displacement amount is a correction amount for correcting the shake of the imaging apparatus 100 and corresponds to the target position of the correction lens 2.

  The pan / tilt determination circuit 28 determines panning and tilting based on the angular displacement amount output from the integrator Y26 and the integrator P27. Then, panning control and tilting control are performed by changing the frequency characteristics of HPF_Y24 and HPF_P25 according to the determination of panning and tilting.

  The center position calculation circuit 29 calculates the control center position of the correction lens 2 based on information indicating whether or not to perform shake correction from the shake correction control circuit 6. The control center position is a correction lens that corrects the correction lens 2 in a direction to eliminate the deviation of the center of the optical axis, and when the shake correction amount is zero as the center position of the drive range in the correction lens control when shake correction is executed. 2 is a fixed position. The calculation result of the center position calculation circuit 29 is added to the angular displacement amount output from the integrator Y26 and the integrator P27, and a drive signal indicating the final target position is generated.

  Although not shown, when the shake correction is stopped by a user instruction to the shake correction control circuit 6 and the correction amount is zero, the calculation result of the center position calculation circuit 29 becomes the drive signal as it is (that is, the integrator Y26). And the angular displacement output from the integrator P27 is not used).

  The drive signal thus obtained is input to the drive circuit Y31 and the drive circuit P32. Then, the drive circuit Y31 and the drive circuit P32 drive the correction lens 2 around the control center position according to the drive signal. When shake correction is stopped by a user instruction to the shake correction control circuit 6, the correction amount is zero, and the correction lens 2 is driven to the control center position, but is fixed at that position.

  The target position calculation circuit 21 may further include an automatic shake detection circuit 30. In this case, the automatic shake detection circuit 30 determines whether or not shake has occurred in the imaging apparatus 100 based on the outputs from the amplifier Y22 and the amplifier P23 and the outputs from the integrator Y26 and the integrator P27. The automatic shake detection circuit 30 notifies the center position calculation circuit 29 of the determination result. The center position calculation circuit 29 calculates the control center position based on the information indicating whether or not to perform shake correction from the shake correction control circuit 6 and the determination result of the occurrence of shake from the automatic shake detection circuit 30 (details). Is described later with reference to FIG.

  Next, the relationship between the control center position of the correction lens 2 and the optical performance (MTF) will be described with reference to FIG. The optical performance (MTF) here is a characteristic indicating both contrast and resolution. The driving range of the correction lens 2 is on a plane orthogonal to the optical axis. However, in FIG. 3, the description will be limited to only one axis on the plane of the driving range in order to simplify the description. The horizontal axis in FIG. 3 is an axis obtained by taking out one axis on the drive plane that passes through the optical axis center of the imaging optical system 10, and indicates the coordinate position of the center position of the correction lens 2. The middle of the horizontal axis is the design optical center 331.

  Referring to the change in Modulation Transfer Function (MTF) at the bottom of FIG. 3, the MTF 341 at the center position of the image sensor decreases as the correction lens 2 moves away from the design optical center 331. Assuming that the threshold value for optical performance compensation by MTF is 342, if the correction lens 2 is located within the range 304 between the optical performance (MTF) compensation points 343, the MTF is equal to or greater than the threshold value. Becomes less than the threshold value, and the image quality deterioration becomes large.

  3 are the limit positions 333 of the center position of the correction lens 2 that can maintain the entire screen within the effective image circle. If the center position of the correction lens 2 is within the range of the limit position, the entire screen can be accommodated in the optical image circle. If the limit is exceeded, the range exceeding the effective image circle is captured in the image. As a result, vignetting of the screen occurs.

  When there is no optical axis deviation (when the optical axis center coincides with the design optical center), the control center position of the correction lens 2 is the position 301 and the drive range is the range 311.

  The change in the light amount drop is shown at the bottom of FIG. If there is no optical axis deviation, the screen light amount at the left end of the drive shaft of the correction lens 2 becomes a solid line 321, and the screen light amount at the right end of the drive shaft of the correction lens 2 becomes a solid line 322. As indicated by solid lines 321 and 322, a light amount drop occurs in a symmetrical manner with respect to the design optical center 331. However, when the optical axis shift occurs, the screen light quantity at the left end of the drive shaft of the correction lens 2 becomes a dotted line 323, and the screen light quantity at the right end of the drive axis of the correction lens 2 becomes a dotted line 324. At this time, as indicated by dotted lines 323 and 324, a light amount drop occurs around a position deviated from the design optical center 331. Therefore, when the correction lens 2 is driven in accordance with the design optical center 331 as shown in the range 311, the amount of light decreases at the right end and the left end of the driving range, and an imbalance of the peripheral light amount occurs. Therefore, in order to correct the optical axis deviation, it is necessary to correct the control center position and the driving range of the correction lens 2 (shift the position according to the optical axis deviation).

  When the optical axis deviation is corrected in accordance with the dotted lines 323 and 324, the control center position of the correction lens 2 becomes the position 302, and the drive range becomes the range 312. As a result, the driving range is balanced against the change in the light amount indicated by the dotted lines 323 and 324.

  However, position 302 is outside range 304 and the MTF is below the threshold. When shake correction is performed and the correction lens 2 is driven within the range 312, even if the MTF decreases, it is difficult to recognize the apparent image degradation from the viewpoint of dynamic resolution. However, when the imaging apparatus 100 is stationary and the correction lens 2 is stationary at the position 302, image degradation due to a decrease in MTF is noticeable.

  Therefore, when shake correction is not executed, the control center position of the correction lens 2 is determined with priority on optical performance. Specifically, the position 303 that is the limit of the range in which the condition that the optical performance (MTF) is equal to or higher than the threshold is satisfied is set as the control center position of the correction lens 2, and the range 313 is set as the driving range. Thereby, a decrease in optical characteristics when correcting the optical axis deviation is suppressed, and image quality deterioration is suppressed.

  Next, with reference to FIG. 4, the process for determining the reference position of the control center position will be described. Here, the “reference position” is the final target position of the control center position. Normally, the control center position matches the reference position, but if the control center position changes suddenly, the image quality may deteriorate. Therefore, the center position calculation circuit 29 first determines the reference position, and then moves the control center position to the reference position stepwise. Therefore, when the reference position changes (that is, when the center position calculation circuit 29 determines a new reference position), the center position calculation circuit 29 steps the control center position from the original reference position to the new reference position. Change. However, when image quality deterioration due to abrupt movement of the correction lens 2 is allowed, the center position calculation circuit 29 may immediately move the control center position to the reference position.

  The processing of this flowchart is repeatedly executed at a predetermined cycle (for example, the generation cycle of the vertical synchronization signal). Prior to the processing of this flowchart, the center position calculation circuit 29 determines a “temporary reference position”. The “temporary reference position” is the control center position of the correction lens 2 when correcting the optical axis shift without considering the decrease in MTF, and corresponds to the position 302 in the example of FIG.

  In S401, the center position calculation circuit 29 determines whether or not the MTF of the temporary reference position is equal to or greater than the threshold (that is, whether or not the temporary reference position is within the range 304). If the determination result is “Yes”, the process proceeds to S402, and if “No”, the process proceeds to S403.

  In S402, the center position calculation circuit 29 determines the temporary reference position as the reference position. Then, the control center position is moved stepwise to the reference position.

  In step S <b> 403, the center position calculation circuit 29 determines whether the execution of shake correction is instructed according to the input from the shake correction control circuit 6. If the determination result is “Yes”, the process proceeds to S404, and if “No”, the process proceeds to S406. Note that the process of S404 is optional, and if “Yes” is determined in S403, the process may proceed to S405.

  In step S <b> 404, the center position calculation circuit 29 determines whether or not shake has occurred in the imaging apparatus 100 based on the input from the automatic shake detection circuit 30. If the determination result is “Yes”, the process proceeds to S405, and if “No”, the process proceeds to S406.

  In S405, the center position calculation circuit 29 determines the temporary reference position (in the example of FIG. 3, position 302) as the reference position. Then, the control center position is moved stepwise to the reference position. On the other hand, in S406, the center position calculation circuit 29 determines the position where the MTF is a threshold value (the position 303 in the example of FIG. 3) as the reference position. Then, the control center position is moved stepwise to the reference position.

  The process of S405 means that correction of the optical axis deviation and cancellation of the imbalance of the peripheral light amount are prioritized over the optical performance. Specifically, when shake correction is performed (“Yes” in S403), the image quality deterioration due to the reduction in optical performance is not recognized by the user so much, and in the example of FIG. It does not move to the position 303. However, even if the execution of shake correction is instructed, if the shake correction is not actually executed because the imaging apparatus 100 is not shaken (“No” in S404), the process proceeds from S404 to S406 to change the optical A decrease in performance is suppressed.

  Also, in the above flow, the control center position is moved stepwise to the reference position because the image pickup apparatus moves separately from the detected shake by changing the shake correction position rapidly by moving the center position suddenly. This is to prevent moving images. Therefore, the correction method for slowly changing the control center position may be a level at which the movement of the correction lens 2 is not visually recognizable along with this correction operation. For example, a change amount of 1 pixel or less per cycle may be set for the vertical synchronization signal.

  As described above, according to the present embodiment, the center position calculation circuit 29 of the correction lens 2 is configured to correct the optical axis deviation within a range in which the condition that the optical characteristic (MTF) is equal to or greater than the threshold value is satisfied. The reference position of the control center position is determined. Thereby, the fall of the optical performance at the time of correct | amending an optical axis shift is suppressed.

[Other Examples]
The components and processes described in each of the above embodiments may be implemented by hardware, software, or a combination thereof. Software (program) that implements some or all of these components and processes, and a storage medium storing the software are also included in the scope of the present invention.

Claims (6)

An imaging device for detecting an object image passed through the photographic optical system, detection means for detecting a shake, and determining means for determining a reference position of the correction means of reducing the image blur caused by the shake, before Symbol detection means detects an imaging apparatus having a driving means for driving said correcting means as the control center position of the driving range of the correction means before Symbol reference position so as to correct the image blur caused by the shake,
The center of the image sensor and the optical axis of the photographing optical system are shifted,
It said determining means, to the extent that the optical characteristics of the imaging optical system a predetermined condition is satisfied, so that the correction means to correct the deviation from the center of the image sensor of the optical axis of the photographing optical system, the reference position the image pickup apparatus, wherein the benzalkonium be determined.   When the image blur correction by the driving unit is not performed, the determination unit is configured to capture the image of the optical axis of the imaging optical system so that the optical characteristic of the imaging optical system satisfies a predetermined condition. The reference position is determined so as to correct a deviation from the center of the element,
  When the image blur correction is performed by the driving unit, the determining unit does not consider that the optical characteristic of the photographing optical system satisfies a predetermined condition, and the correcting unit is configured to use the optical axis of the photographing optical system. The imaging apparatus according to claim 1, wherein the reference position is determined so as to correct a deviation from a center of the imaging element. An imaging device for detecting an object image having passed through the photographing optical system having a correcting lens to move in a direction different from the optical axis in order to reduce the image blur caused by the shake, and detecting means for detecting the deflection, pre SL correction determining means for determining a reference position of the lens, the front Symbol control center position and to pre SL correction lens driving range of the correction lens in front Symbol reference position so that the detection means to correct image blur caused by the shake detected An imaging device having driving means for driving,
The center of the image sensor and the optical axis of the photographing optical system are shifted,
The determination unit is configured to correct the deviation of the optical axis of the imaging optical system from the center of the imaging element so that the optical characteristics of the imaging optical system satisfy a predetermined condition. position the image pickup apparatus, wherein the benzalkonium be determined.   When the image blur correction is not performed by the driving unit, the determination unit is configured to capture the image of the optical axis of the photographing optical system so that the correction lens satisfies the predetermined condition of the optical characteristics of the photographing optical system. The reference position is determined so as to correct a deviation from the center of the element,
  When the image blur correction is performed by the driving unit, the determining unit does not consider that the optical characteristics of the photographing optical system satisfy a predetermined condition, and the correction lens is configured so that the optical axis of the photographing optical system is The imaging apparatus according to claim 3, wherein the reference position is determined so as to correct a deviation from a center of the imaging element. An imaging device for detecting an object image passed through the photographic optical system, detection means for detecting a shake, and determining means for determining a reference position of the correction means of reducing the image blur caused by the shake, before Symbol detection means detects a method for controlling an imaging apparatus having a driving means for driving said correcting means as the control center position of the driving range of the correction means before Symbol reference position so as to correct the image blur caused by the shake,
The center of the image sensor and the optical axis of the photographing optical system are shifted,
It said determining means, to the extent that the optical characteristics of the imaging optical system a predetermined condition is satisfied, so that the correction means to correct the deviation from the center of the image sensor of the optical axis of the photographing optical system, the reference A method for controlling an imaging apparatus , comprising a step of determining a position. An image sensor that detects a subject image that has passed through a photographing optical system that includes a correction lens that moves in a direction different from the optical axis in order to reduce image blur caused by the shake, a detection unit that detects the shake, and the correction lens driving determining means for determining a reference position, a pre-SL control center position and to pre SL correction lens driving range of the correction lens in front Symbol reference position so that the detection means to correct image blur caused by the shake detected in And a driving means for controlling the imaging device ,
The center of the image sensor and the optical axis of the photographing optical system are shifted,
The reference means so that the correction lens corrects a deviation of the optical axis of the photographing optical system from the center of the imaging element in a range where the optical characteristic of the photographing optical system satisfies a predetermined condition. A method for controlling an imaging apparatus , comprising a step of determining a position.

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