JP4556560B2 - Blur correction device and camera system - Google Patents

Description

  The present invention relates to a camera shake correction apparatus and a camera system that optically corrects image plane blur of a subject image on an imaging surface.

2. Description of the Related Art Conventionally, a technique for optically correcting image plane blurring of a subject image due to camera shake using a blur correction optical system in a photographing lens is known.
In this type of prior art, first, vibration of a camera (including a photographing lens) is detected by an angular velocity sensor. Based on this angular velocity, the camera determines the position of the blur correction optical system (hereinafter referred to as “target drive position”) necessary to cancel the image movement of the subject image, and follows the blur correction optical system to this target drive position. Let

Patent Documents 1 and 2 listed below disclose techniques for suppressing image plane blur in a video camera. This video camera detects an image motion signal from a captured image. Next, the video camera interpolates this image motion signal to increase the sampling rate. The video camera improves the image stabilization performance of the blur correction by feeding back the interpolated image motion signal to the target drive position.
Japanese Patent Laid-Open No. 10-322585 (FIG. 1) Japanese Patent Laid-Open No. 10-145562 (FIGS. 1 and 3)

[Problems of conventional technology]
By the way, in the shake correction, DC offset and drift included in the sensor output of the angular velocity sensor become a problem. In order to accurately track the image plane blur of the subject image, these extra components must be removed from the sensor output of the angular velocity sensor.
However, these components fluctuate sensitively under the influence of the temperature of the angular velocity sensor and use conditions. Therefore, offset and drift during use cannot be canceled based on actual measurement data when the sensor is stationary at the time of factory shipment.

Therefore, a method of separating and extracting DC offset and drift from the output when using the angular velocity sensor has been conventionally performed.
That is, human hand shake is dominated by frequency components of about 2 to 7 Hz. On the other hand, the frequency component of less than about 1 Hz is dominant in the stationary output of the angular velocity sensor. Therefore, the DC offset and drift can be estimated by using a low-pass filter to extract a low frequency component of less than 1 Hz from the sensor output of the angular velocity sensor.
The true vibration component can be obtained by removing (subtracting) the estimated DC offset and drift from the sensor output as the reference value of the sensor output.

  However, in this conventional method, various errors are included in the extraction of the low frequency component. For example, in order to extract a low frequency component of less than 1 Hz from the sensor output, it is necessary to average the past sensor output over a considerably long period, and a large time delay occurs in the low frequency component. Therefore, it is difficult to detect the current DC offset and drift in real time.

  In the extracted low frequency component, a vibration component that cannot be completely removed remains as an error. When a low frequency component including such an error is subtracted from the sensor output as a reference value of the sensor output, the error is mixed into the obtained true vibration component.

When blur correction is performed so as to cancel out the vibration component in which the error is mixed, the image plane drifts or vibrates due to accumulation of the error.
For the reasons described above, the image stabilization performance of blur correction depends on how accurately the reference value of the sensor output is obtained.

[Problems of Patent Document 1 and Patent Document 2]
By the way, in the related art disclosed in Patent Document 1 and Patent Document 2, the image motion signal is fed back to the target drive position of the optical system (this is based on the present invention in which the image motion signal is fed back to the reference value). Is greatly different in the configuration of the feedback path).
When such control methods of Patent Document 1 and Patent Document 2 are applied to an electronic still camera, the following problems [1] and [2] specifically occur.

[1] First, in an electronic still camera, an image motion signal is obtained from a captured image for monitor display during a period before release. In this case, the average imaging interval (for example, 30 frames / second) is several times to several tens of times longer than the imaging interval of a general video camera (for example, 60 fields / second in NTSC). That is, in the electronic still camera, the sample interval of the image motion signal is often coarser than that of the video camera. In the conventional method of feeding back the rough image motion signal to the target drive position, the dead time generated in the feedback path cannot be ignored, the follow-up performance of the target drive position and the control stability are remarkably lowered, and in the worst case, oscillation occurs. .

[2] Furthermore, in Patent Document 1 and Patent Document 2, in order to match the update interval of the target drive position, an interpolation value is generated by predicting the extension of the image motion signal.
Since an electronic still camera handles an image motion signal having a rough sample interval, a discontinuous interpolation error is larger in this type of extension prediction than in a video camera. Since this interpolation error is directly reflected in the control error of the target drive position, the image stabilization performance is significantly lowered.
As a supplement, in Patent Document 1 and Patent Document 2, a high-pass filter is provided in the feedback path of the image motion signal. Therefore, the low-pass component corresponding to drift and offset is cut by this high-pass filter. Therefore, in Patent Document 1 and Patent Document 2, it is impossible to realistically correct the low-frequency drift and offset.

[Problems related to image motion signals]
By the way, in a state where no blur correction is applied, the captured image is greatly shaken due to the influence of camera shake. In this state, the amplitude of the image motion signal increases. On the other hand, when the blur correction starts to be applied, the shake of the captured image is suddenly reduced. For this reason, the amplitude of the image motion signal largely changes before and after driving the blur correction.

For example, in a system in which a margin of three shutter speeds is provided by blur correction, an abrupt amplitude change of about 1 / (2 3), that is, about 18 dB, occurs in the image motion signal before and after blur correction.
Due to the sudden amplitude change in the image motion signal, there is a problem that the image stabilization performance of the blur correction is deteriorated or the oscillation occurs in the worst case.

  In view of the above, an object of the present invention is to devise the feedback timing of the image motion signal to improve the vibration-proof performance of the blur correction.

A blur correction device according to a first aspect of the present invention is a blur correction device that corrects image plane blur of a subject image in an imaging unit of a camera, and includes a blur correction mechanism, a vibration detection unit, a reference value generation unit, a target drive position calculation unit, And a drive unit.
The blur correction mechanism changes the relative position between the imaging unit and the light beam forming the subject image.
The vibration detection unit detects the vibration of the camera and outputs a vibration detection signal.
Reference value generation unit, based on the vibration detection signal, estimates a reference value which is the output of the vibration detection unit in the still state with no vibration.
The target drive position calculation unit obtains a vibration component that causes image plane blur from the difference between the vibration detection signal and the estimated reference value, and obtains a target drive position of the shake correction mechanism based on the vibration component.
The drive unit controls the shake correction mechanism to follow the target drive position.
In particular, the reference value generation unit includes a feedback path and a feedback suppression unit.
The feedback path acquires an image motion signal obtained by analyzing a captured image of the camera, feeds back the image motion signal to a reference value, and corrects the reference value.
Feedback suppression unit, when driving the start of the drive unit to suppress the amount of feedback of the image motion signal to the reference value.

In a second aspect based on the first aspect, the feedback suppression unit releases the suppression of the feedback amount after an acquisition point of an image motion signal analyzed based on a captured image captured after the start of driving.
According to a third aspect, in the first or second aspect, the feedback suppression unit suppresses the feedback amount for a period of at least (DLY + 2 / FR) from the driving start time of the driving unit. However, DLY is a waiting time from when a captured image is captured until an image motion signal is obtained. FR is the frame rate of the captured image. When the frame rate is not constant, 2 / FR corresponds to two imaging intervals immediately after the start of driving.

In a fourth aspect based on the second aspect, the feedback suppression unit suppresses the feedback amount for a period of at least (T1 + DLY + 1 / FR) from the driving start time of the driving unit. However, T1 is a time lag from the drive start time of the said drive part to obtaining the picked-up image imaged first after the drive start. FR is the frame rate of the captured image. DLY is a waiting time from when a captured image is captured until an image motion signal is obtained. When the frame rate is not constant, 1 / FR corresponds to one imaging interval after the start of driving.

According to a fifth invention, in any of the first to fourth invention, the feedback suppression unit, control of the feedback amount to zero, control of lowering the off I over-back gain, limit the image motion signal to and feedback The feedback amount is suppressed by performing at least one of the limiting controls .

According to a sixth aspect of the present invention, there is provided a camera system including any one of the first to fifth aspects of the shake correction apparatus and a camera that performs the shake correction using the shake correction apparatus.

[1]
In the present invention, the reference value of the vibration detection signal is corrected using an image motion signal obtained by analyzing a captured image of the camera.
In general, if there is an error in this reference value, it becomes a vibration component detection error and causes a residual blur in the captured image. In the present invention, the residual blur of the captured image is detected by the image motion signal, and the reference value is corrected. By such a feedback action, an error in the reference value can be suppressed.
Since the reference value becomes accurate in this way, it is possible to accurately obtain the value of the vibration component from the vibration detection unit, and it is possible to further improve the anti-shake performance of shake correction.
In particular, the reference value selected as the feedback destination by the present invention is a signal that is much lower centered than the target drive position with a short update interval. For this reason, even if an image motion signal with a rough sampling interval is fed back, there is little possibility of excessive overshooting in the control system, and a stable and appropriate control response can be realized.

(Effect of feedback suppression)
The inventor of the present application has noticed that if the image motion signal is immediately fed back at the start of driving of the drive unit, the pull-in time of the blur correction operation takes a long time.
The image motion signal at the start of driving is a signal obtained by analyzing the motion of the captured image before the blur correction. Therefore, a large image plane shake before blur correction appears in the image motion signal at the start of driving. Therefore, if the image motion signal at the start of driving is directly fed back to the reference value as it is, the reference value itself is greatly disturbed rather than the residual blur of the reference value cannot be removed. As a result, an unexpected value is temporarily output as the reference value, and the vibration component calculated based on the reference value and further the target drive position are greatly disturbed. In this state, the shake correction does not function normally, and the shake correction operation is confused until the reference value once disturbed is drawn to a correct value.

Therefore, in the present invention, the feedback amount of the image motion signal with respect to the reference value is suppressed at the start of driving of the driving unit. The time point at which the suppression is released is after the time point when the captured image is captured after the driving of the driving unit is started and the image motion signal analyzed based on the captured image is acquired.
By this operation, the feedback amount is suppressed for a period until the image motion signal shows a fine residual blur reflecting the reference value error. As a result, the disturbance of the reference value that occurs immediately after the start of driving can be prevented, and the blur correction pull-in time can be shortened.

[2]
Next, a specific suppression period is considered on the premise that an image motion signal is obtained from image comparison of captured images of two frames.
First, it is necessary to obtain captured images for two frames after the drive unit starts driving and the image stabilization operation starts. First, considering the case where a captured image is output immediately before the driving of the drive unit is started, the maximum required time required to output the captured image of the first frame is “1 / FR” when the frame rate is FR. It becomes. Subsequently, in order to output the captured image of the second frame, a time of “1 / FR” is further required. Therefore, the maximum required time from the start of driving of the driving unit to obtaining a captured image for two frames is “2 / FR”.
Next, a waiting time “DLY” for calculation processing is required from the acquisition of captured images for these two frames to the creation of an image motion signal.
That is, by waiting for a period of (DLY + 2 / FR) from the drive start time of the drive unit, it is possible to reliably obtain an image motion signal reflecting residual blur due to a reference value error. Therefore, in the present invention, it is preferable to suppress the feedback amount at least during a period of (DLY + 2 / FR) from the driving start time of the driving unit.
By such an operation in consideration of the maximum required time, it is possible to reliably prevent the reference value from being disturbed even if the captured image acquisition timing changes.

[3]
Next, consider the possibility of shortening the suppression period described above.
First, the time “T1” from when the drive unit starts driving to the start of the image stabilization operation until the captured image of the first frame is output can be acquired from the camera side. Subsequently, in order to output the captured image of the second frame, a time of “1 / FR” is further required. Therefore, the required time from the start of driving of the driving unit to obtaining a captured image for two frames is “T1 + 1 / FR”.
Next, a waiting time “DLY” for calculation processing is required from the acquisition of captured images for these two frames to the creation of an image motion signal.
That is, if a period of (T1 + DLY + 1 / FR) is accurately waited from the driving start time of the driving unit, it is possible to obtain an image motion signal that reflects residual blur due to a reference value error. Therefore, in the present invention, it is preferable to suppress the feedback amount at least for a period of (T1 + DLY + 1 / FR) from the driving start time of the driving unit.
By such an operation in consideration of the exact required time, it becomes possible to release the suppression of the feedback amount as soon as possible.

[4]
In the present invention, it is preferable to suppress the feedback amount by any of the following means.
1: “Set the feedback amount to (substantially) zero”,
2: “Lower the feedback gain”
3: “Limit the image motion signal to be fed back”
Such suppression means can reliably prevent the reference value from being disturbed.

[5]
The camera system of the present invention includes the above-described blur correction device. Since this blur correction apparatus can prevent the disturbance of the reference value that occurs immediately after the start of driving, a camera system that exhibits a good blur correction effect is realized.

[Description of Embodiment Configuration]
FIG. 1 is a diagram showing a camera system 190 (including a shake correction device) having a shake correction mechanism. Note that the actual camera system 190 corrects image plane blurring in two horizontal and vertical directions. However, in FIG. 1, only one axis of the shake correction mechanism is shown for the sake of simplicity.

Hereinafter, the configuration of each unit will be described with reference to FIG.
The angular velocity sensor 10 detects the vibration of the camera system 190 as an angular velocity by Coriolis force or the like. The amplifying unit 20 amplifies the output of the angular velocity sensor 10. The A / D converter 30 converts the output of the amplifier 20 into digital angular velocity data.
The reference value calculation unit 40 extracts a low frequency component from the angular velocity data output from the A / D conversion unit 30, and estimates a reference value of angular velocity (angular velocity data in a stationary state without vibration). Further, the reference value calculation unit 40 corrects the reference value using a feedback path of an image motion vector described later.

  The target drive position calculation unit 50 subtracts the reference value from the angular velocity data to obtain a true angular velocity that causes image plane blurring. The target drive position calculation unit 50 obtains the optical axis angle of the photographing lens 190a by integrating the true angular velocity. The target drive position calculation unit 50 determines the target drive position based on this optical axis angle. The target drive position is the position of the blur correction optical system 100 that cancels the image plane displacement of the subject image due to the optical axis angle.

  The target drive position calculation unit 50 uses the focal length information 120, the shooting magnification information 130, and the optical information 140 of the shake correction optical system 100 for determining the target drive position. The focal length information 120 is information obtained from time to time from the encoder output of the zoom ring of the photographing lens 190a. The photographing magnification information 130 is information obtained at any time from the lens position of the photographing lens 190a and the AF driving mechanism. The optical information 140 of the blur correction optical system 100 is a blur correction coefficient (blur correction coefficient = image movement amount with respect to lens movement amount / lens movement amount), and is data stored in advance in the photographing lens 190a.

  Further, the photographing lens 190 a is provided with a position detection unit 90 for detecting the position of the blur correction optical system 100. The position detection unit 90 includes an infrared LED 92, a PSD (position detection element) 98, and a slit plate 94. The light from the infrared LED 92 passes through the slit hole 96 of the slit plate 94 provided in the lens barrel 102 of the blur correction optical system 100 to become a thin light beam. This light beam reaches the PSD 98. The PSD 98 outputs the light receiving position of this light beam as a signal. By converting this signal output digitally via the A / D converter 110, position data of the blur correction optical system 100 can be obtained.

The drive signal calculation unit 60 calculates a deviation between the position data and the target drive position, and calculates a drive signal according to the deviation. For example, in the calculation of the drive signal, PID control is performed in which the proportional term, the integral term, and the derivative term of the deviation are added at a predetermined ratio.
The driver 70 causes a drive current to flow through the drive mechanism 80 in accordance with the obtained drive signal (digital signal).

  The drive mechanism 80 includes a yoke 82, a magnet 84, and a coil 86. The coil 86 is disposed in a magnetic circuit formed by the yoke 82 and the magnet 84 while being fixed to the lens barrel 102 of the shake correction optical system 100. By passing the driving current of the driver 70 through the coil 86, the blur correction optical system 100 can be moved in a direction orthogonal to the optical axis.

The blur correction optical system 100 is a part of the imaging optical system of the photographing lens 190a. By moving the blur correction optical system 100 to the target drive position and shifting the imaging position of the subject image, it is possible to suppress image plane blurring of the subject image.
On the other hand, an image pickup surface of the image pickup device 150 is provided in the image space of the photographing lens 190a. The image sensor 150 captures a subject image formed on the imaging surface. In addition to being displayed on a monitor screen (not shown), the captured image is output to the motion vector detection unit 160.

The motion vector detection unit 160 detects an image motion vector including residual blur by detecting the motion of the captured image in the time axis direction. The motion vector conversion unit 170 converts the image motion vector into the same scale as the reference value using the focal length information 120 and the shooting magnification information 130. The image motion vector is fed back to the reference value of the reference value calculation unit 40 described above via the feedback suppression unit 220.
The camera system 190 is provided with a control unit 320. The control unit 320 controls operations of the image sensor 150, the feedback suppression unit 220, and the like.
Note that the calculation function and control function related to blur correction in the present embodiment are mainly realized by the microprocessor 500 indicated by a dotted line in FIG.

[Correspondence with Invention]
The correspondence relationship between the invention and this embodiment will be described below. Note that the correspondence relationship here illustrates one interpretation for reference, and does not limit the present invention.
The shake correction mechanism described in the claims corresponds to the shake correction optical system 100.
The vibration detection unit described in the claims corresponds to the angular velocity sensor 10.
The reference value generation unit described in the claims corresponds to the reference value calculation unit 40, the feedback suppression unit 220, and the motion vector conversion unit 170.
The target drive position calculation unit described in the claims corresponds to the target drive position calculation unit 50.
The drive unit described in the claims corresponds to the drive signal calculation unit 60, the driver 70, the drive mechanism 80, and the position detection unit 90.
The feedback path described in the claims corresponds to a path that feeds back an image motion vector to a reference value via the motion vector detection unit 160, the motion vector conversion unit 170, and the feedback suppression unit 220.
The feedback suppression unit described in the claims corresponds to the feedback suppression unit 220.
The camera system described in the claims corresponds to the camera system 190.
The image motion signal described in the claims corresponds to an image motion vector component.

[Description of operation of this embodiment]
FIG. 2 is a flowchart showing the blur correction control operation.
FIG. 3 is a diagram for explaining the timing of the image motion vector feedback operation.
Hereinafter, the blur correction operation will be described in the order of the step numbers shown in FIG.

Step S1: The control unit 320 determines the state of the main switch (not shown) of the camera system 190.
If it is in the off state, the control unit 320 shifts the operation to step S2.
If in the on state, the control unit 320 shifts the operation to step S3.

Step S2: The control unit 320 stops driving the blur correction system in the following order.
(1) Stop driving the blur correction lens.
(2) Stop driving signal calculation.
(3) Stop the calculation of the target drive position.
(4) The calculation for correcting the angular velocity data with the reference value is stopped.
(5) Stop calculating and updating the image motion vector.
(6) Stop generating the reference value.
(7) The power supply to the angular velocity sensor 10 is stopped.
After stopping driving through such an order, the control unit 320 returns the operation to step S1.

Step S3: When the control unit 320 detects the ON operation of the main switch, the control unit 320 starts supplying power to the angular velocity sensor 10 and the like. The angular velocity signal of the angular velocity sensor 10 is digitized by the A / D converter 30 at a predetermined sampling interval.

Step S4: The controller 320 determines the state of a half-press switch (not shown) of the camera system 190.
If it is in the off state, the control unit 320 shifts the operation to step S1.
If it is in the on state, the control unit 320 shifts the operation to step S5.

Step S5: The reference value calculation unit 40 performs a moving average or a low-pass filter process on the angular velocity data after A / D conversion, and estimates a reference value Wo of the angular velocity data.

Step S6: Here, every time the motion vector detection unit 160 calculates a new image motion vector, an interrupt is generated and the value of the image motion vector is updated.

Note that the motion vector detection unit 160 calculates an image motion vector in the following procedure.
(1) The image sensor 150 reads out the captured image repeatedly by thinning out the number of readout lines. These captured images are used for purposes such as monitor display, exposure and focus control, white balance adjustment control, and moving image recording.
(2) The motion vector detection unit 160 detects an image correlation or the like for the previous and next frames of the captured image, and calculates an image motion vector. Such image motion vector detection methods include a spatiotemporal gradient method and a block matching method.
(3) The motion vector conversion unit 170 acquires information on the focal length information 120 and the photographing magnification information 130 of the photographing lens 190a. Using these pieces of information, the motion vector conversion unit 170 converts the image motion vector, which is the unit of displacement on the screen, into the same angular velocity unit as the reference value.

Step S7: The controller 320 determines whether the blur correction is being driven or paused.
When blur correction is temporarily stopped due to panning determination, which will be described later, the control unit 320 shifts the operation to step S11.
On the other hand, if the blur correction is being driven, the control unit 320 shifts the operation to step S8.

Step S8: The control unit 320 measures the passage of time from the start of blur correction driving, and determines whether or not a predetermined suppression period has elapsed.
Here, in the suppression period, the control unit 320 shifts the operation to Step S9.
On the other hand, when the suppression period has already elapsed, the control unit 320 shifts the operation to step S10.
In addition, in this “blur correction drive start”, in addition to the drive start by turning on the half-press switch (time point t1 shown in FIG. 3), the drive restart from the shake correction paused state (panning determination or the like) ( It is also preferable to include the time point t4) shown in FIG.

Moreover, as this suppression period, it is preferable to employ the following periods.
(Case 1) A period from when a captured image that has started photoelectric accumulation after the start of blur correction driving begins to be output from the image sensor 150 until an image motion vector based on the captured image can be acquired.
(Case 2) A period (see FIG. 4) until at least (DLY + 2 / FR) elapses from the start of blur correction driving. However, FR corresponds to the frame rate of the image sensor 150. DLY corresponds to a waiting time from the capture of the captured image until the calculation of the image motion vector is completed.
(Case 3) A period until at least (T1 + DLY + 2 / FR) elapses from the start of blur correction driving. However, T1 corresponds to a time lag until the first captured image in which photoelectric accumulation is started after the start of blur correction driving is output (see FIG. 4).

Step S9: The control unit 320 suppresses the feedback amount of the image motion vector during the suppression period.

As a suppression method here, for example, any of the following treatments 1 to 3 is preferable.
(Processing 1) The feedback amount is made substantially zero.
(Process 2) The feedback gain is lowered to such an extent that the disturbance of the reference value does not become a problem (including the case where the number of feedbacks per unit time is reduced).
(Process 3) Limit the image motion signal to be fed back to such an extent that disturbance of the reference value does not become a problem

Step S10: The reference value calculation unit 40 feeds back the image motion vector B that has passed through the feedback suppression unit 220 to the reference value Wo.
For example, feedback is performed according to the following formula.
Wo ′ = Wo−b (2)
However, b is a vector component coinciding with the blur correction direction of the image motion vector B.

Step S11: The target drive position calculation unit 50 subtracts the corrected reference value Wo ′ from the angular velocity data output from the A / D conversion unit 30 to obtain true angular velocity data that causes image blurring.

Step S12: Here, the target drive position calculation unit 50 performs panning determination. In this panning determination, it is determined whether the camera system 190 is continuously moving in a certain direction based on the angular velocity data. Note that, not limited to this determination method, for example, panning may be determined from an image motion vector or the like.
If panning is determined, the operation proceeds to step S13.
On the other hand, if it is not panning, the operation proceeds to step S14.

Step S13: In this step, the camera system 190 is panning. Therefore, the target drive position calculation unit 50 stops driving the blur correction optical system in the panning direction by keeping the target drive position at a constant value. With this stopped state, the operation proceeds to step S16.

Step S14: In this step, since the camera system 190 is not in the panning state, the following blur correction operation is executed.
First, the target drive position calculation unit 50 obtains the inclination of the optical axis angle of the photographing lens 190a by integrating the true angular velocity data. The target drive position calculation unit 50 obtains the position (so-called target drive position) of the blur correction optical system 100 necessary for canceling the displacement of the imaging position of the subject image from the optical axis angle.

Step S15: The drive signal calculation unit 60 acquires the target drive position from the target drive position calculation unit 50, and obtains the deviation from the current position of the shake correction optical system 100 obtained from the position detection unit 90. The drive signal calculation unit 60 outputs a drive signal for eliminating this deviation. The driver 70 generates a drive current from this drive signal and passes it to the drive mechanism 80. By this drive control, the blur correction optical system 100 moves following the target drive position.

Step S16: Here, the control unit 320 determines the state of the full push switch (not shown) of the camera system 190.
If it is in the off state, the controller 320 returns the operation to step S1.
If it is in the on state, the control unit 320 shifts the operation to step S17.

Step S17: The control unit 320 drives the image sensor 150 and captures a still image while continuing the above-described blur correction. After completion of this imaging operation, control unit 320 returns the operation to step S1.

[Effects of this embodiment, etc.]
FIG. 4 is a timing chart showing the relationship between the suppression period and the image motion vector.
The image sensor 150 sequentially outputs captured images Im1 to Im8 at an imaging interval 1 / FR. The motion vector detection unit 160 takes in the two immediately preceding captured images, and sequentially outputs the image motion vectors V1 to V7 through the arithmetic processing waiting time DLY. By the way, in the example of FIG. 4, the blur correction starts to be driven after the captured image Im <b> 2 is output. By passing a time T1 from the start of driving the blur correction, a captured image Im3 after the blur correction is output.

In this case, since the image motion vector V1 is calculated from the captured images Im1 and Im2 before the blur correction, the image motion vector V1 is an image motion vector reflecting a camera shake before the blur correction is performed.
Further, since the image motion vector V2 is calculated from the captured image Im2 before the blur correction and the captured image Im3 after the blur correction, the image motion vector V2 is an image motion vector that reflects a transitional blur change from the stop of the blur correction to the driving. .

On the other hand, after the image motion vector V3, since it is calculated from the captured images Im3 and Im4 after blur correction, the image motion vector reflects the residual blur in the blur correction state.
A period from the time t1 (t4) when the blur correction driving is started until the image motion vector V3 reflecting the remaining blur is obtained is equal to (T1 + DLY + 1 / FR).
Therefore, at least for this period (T1 + DLY + 1 / FR), by suppressing the feedback amount of the image motion vector, large image motion before blur correction is not mixed in the reference value, and disturbance of the reference value is suppressed. Can do.
Furthermore, after the elapse of this period (T1 + DLY + 1 / FR), the reference value can be corrected correctly using the image motion vector reflecting the remaining blur by releasing the suppression.

  The time T1 changes every time depending on the drive timing of blur correction. Therefore, instead of the time T1, the maximum value 1 / FR that the time T1 can take may be used as a safety value. In this case, by waiting for the elapse of a certain period (DLY + 2 / FR), it is possible to reliably obtain the image motion vector V4 reflecting the remaining blur.

FIGS. 5A to 5C are diagrams in which the state of the reference value pull-in operation is obtained by computer simulation. The specific effect of the suppression period will be described with reference to FIGS.
FIG. 5A shows a case where no suppression period is provided. That is, the feedback of the image motion vector is started immediately after the start of blur correction driving. In this case, the value of the reference value momentarily deviates greatly due to the image motion vector before blur correction. Therefore, it takes a period of time to pull in the reference value. During the period required for pulling in the reference value, the blur correction effect cannot be obtained, and the blur is worsened.

  Further, in FIG. 5B, the feedback amount is suppressed for the period from the start of blur correction driving until the waiting time DLY elapses. At the end of the waiting time DLY, the image motion vector shows a transitional change before and after blur correction. Therefore, also in this case, the reference value is shifted, and it takes time to pull the reference value. During this pull-in period, the blur correction effect is not obtained, and the blur is worsened.

  On the other hand, FIG. 5C is a case where the suppression period is set to (DLY + 2 / FR). At the end of this suppression period, the image motion vector is a small value reflecting the residual blur after blur correction. As a result, the reference value does not deviate greatly, and the time required for drawing in the reference value can be remarkably shortened. As a result, the effect of blur correction can be obtained quickly.

[Supplementary items of the embodiment]
In the embodiment described above, the photographic lens 190a and the camera system 190 may be configured integrally. Further, the photographic lens 190a and the camera system 190 may be detachable. Note that when the photographic lens 190 a and the camera system 190 are attached and detached, the block that generates the image motion signal may be installed in either the photographic lens 190 a or the camera system 190. For example, a mode in which a block that generates an image motion signal is installed on the camera system 190 side, and a block that converts the image motion signal into the same scale as the reference value is installed on the photographing lens 190a side.

  In the above-described embodiment, the angular velocity is detected as the vibration detection signal. However, the present invention is not limited to the detection of the angular velocity, and it is sufficient to detect a vibration component that can estimate the displacement of the imaging position of the subject image. For example, an acceleration acting on the camera system, an angular acceleration, a centrifugal force, an inertial force, or the like may be detected as a vibration detection signal.

  In the above-described embodiment, blur correction is performed by shifting or tilting the optical image of the photographing lens 190a. However, the present invention is not limited to this. For example, blur correction may be performed by moving the image sensor.

  In the above-described embodiment, when the suppression period has elapsed, the suppression of the feedback amount may be released at any time. However, in order to correct the reference value as soon as possible, it is preferable to immediately cancel suppression of the feedback amount immediately after the suppression period ends.

  In the embodiment described above, an image motion vector is detected from two frames of the captured image. However, the present invention is not limited to this. An image motion vector may be detected from an image stream of one frame. Further, an image motion vector may be detected by comparing captured images of three frames or more.

  As described above, the present invention is a technique that can be used for an optical apparatus having an optical blur correction function.

It is a figure which shows the camera system 190 (including a blurring correction apparatus) which has a blurring correction mechanism. It is a flowchart which shows the control operation | movement of blur correction. It is a figure explaining the timing of the feedback operation | movement of an image motion vector. It is a timing chart which shows the relationship between a suppression period and an image motion vector. It is a figure which shows the effect of the drawing-in speed of a reference value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Angular velocity sensor 20 Amplification part 30 A / D conversion part 40 Reference value calculation part 50 Target drive position calculation part 60 Drive signal calculation part 70 Driver 80 Drive mechanism 82 Yoke 84 Magnet 86 Coil 90 Position detection part 92 Infrared LED
94 Slit plate 98 PSD (position detection element)
DESCRIPTION OF SYMBOLS 100 Blur correction optical system 102 Lens barrel 120 Focal length information 130 Shooting magnification information 140 Optical information 150 Image sensor 160 Motion vector detection part 170 Motion vector conversion part 190 Camera system 190a Shooting lens 220 Feedback suppression part 320 Control part

Claims (6)

A blur correction device that corrects image plane blur of a subject image in an imaging unit of a camera,
A blur correction mechanism that changes a relative position between the imaging unit and a light beam forming the subject image;
A vibration detection unit that detects vibration of the camera and outputs a vibration detection signal;
A reference value generation unit that estimates a reference value that is an output of the vibration detection unit in a stationary state without the vibration based on the vibration detection signal;
Target drive position calculation for obtaining a vibration component that causes image blurring from the difference between the vibration detection signal and the estimated reference value, and for obtaining a target drive position of the shake correction mechanism based on the vibration component And
A drive unit that controls the blur correction mechanism to follow the target drive position;
The reference value generator is
A feedback path to get the image motion signal obtained by analyzing a captured image of the camera, by feeding back the image motion signal to the reference value, correcting the reference value,
A blur correction apparatus comprising: a feedback suppression unit that suppresses a feedback amount of the image motion signal with respect to the reference value at the start of driving of the driving unit. The blur correction device according to claim 1,
The feedback suppression unit is
The blur correction device , wherein the suppression of the feedback amount is canceled after an acquisition point of an image motion signal analyzed based on a captured image captured after the start of driving . The blur correction device according to claim 1 or 2 ,
The feedback suppression unit is
The frame rate of the captured image is FR,
DLY is the waiting time from the capture of the captured image until the image motion signal is obtained,
The blur correction apparatus that suppresses the feedback amount for at least a period of (DLY + 2 / FR) from the driving start time of the driving unit. The blur correction device according to claim 2 ,
The feedback suppression unit is
The time lag from the start of driving of the driving unit to the acquisition of the first captured image after the start of driving is T1,
The frame rate of the captured image is FR,
DLY is the waiting time from the capture of the captured image until the image motion signal is obtained,
The blur correction device , wherein the feedback amount is suppressed for at least a period of (T1 + DLY + 1 / FR) from a driving start time of the driving unit. The blur correction device according to any one of claims 1 to 4 ,
The feedback suppression unit is
The feedback amount is suppressed by performing at least one of a control to reduce the feedback amount to zero, a control to lower the feedback gain, and a control to limit the image motion signal to be fed back.
The blur correction device characterized by the above. The blur correction device according to any one of claims 1 to 5,
A camera that performs shake correction using the shake correction device;
A camera system comprising:

Images