JP5169240B2 - Imaging apparatus and image shake correction apparatus - Google Patents

Description

  The present invention relates to an improvement in an image pickup apparatus and an image shake correction apparatus that detect an image shake and detect an image shake by using an angular velocity sensor and a high-pass filter.

  2. Description of the Related Art Conventionally, an imaging apparatus having an image shake correction apparatus that corrects image shake is known. The image blur correction apparatus detects angular velocity based on camera shake using an angular velocity sensor and a high-pass filter (see, for example, Patent Document 1). The angular velocity sensor detects a shake due to camera vibration and outputs a shake signal.

The high-pass filter includes a capacitor and a resistor, and is used to remove an offset (DC component) of a shake signal caused by a drift of the angular velocity sensor. The shake signal after passing through the high-pass filter (AC component due to the shake) is used as an angular velocity signal. Image blur correction is performed based on the angular velocity signal.
JP 2004-215189 A

  By the way, the frequency of a shake signal caused by camera shake is generally about 1 Hz to about 10 Hz. Therefore, unless the cut-off frequency of the high-pass filter is sufficiently lower than 1 Hz, it is not possible to accurately correct image blur due to camera shake. Therefore, the cutoff frequency of the high pass filter is set to about 0.1 Hz.

  Therefore, the time constant of the high-pass filter is about τ = 1 / (2π × 0.1) = 1.6 seconds. However, if such a time constant is set, it takes about 6 × τ = about 10 seconds for the angular velocity signal to settle when there is a large fluctuation in the angular velocity signal.

  Therefore, for example, as shown in FIG. 1, during panning shooting in which the camera body 1 is moved while moving left and right, the phenomenon described below occurs along with the change in the direction of the camera 1.

  In FIG. 1, reference numeral A1 denotes a rotation operation start period for quickly turning the camera body 1 in a stationary state toward a subject, and reference numeral A2 denotes a rotation shooting period in which the camera body 1 is rotated at a constant angular velocity for panning shooting. Reference numeral A3 denotes a rotation operation end period in which the camera body 1 stops rotating after panning photographing is completed, and reference numeral A4 denotes a still state period in which the camera body 1 is kept stationary after the camera body 1 stops rotating. Is shown.

  A change curve Q of the actual angular velocity (true angular velocity) of the camera body 1 during the panning photographing is shown by a solid line in FIG. 2, and a change curve Q 'of the angular velocity signal is shown by a broken line. In FIG. 2, the unit of the horizontal axis is time, and the unit of the vertical axis is a scale value corresponding to angular velocity or voltage.

  In the rotation operation start period A1, the actual angular velocity of the camera body 1 rises from zero as indicated by the symbol Q1 due to the quick rotation operation of the camera body 1 for preparation for panning photography. In the rotational shooting period A2, the actual angular velocity of the camera body 1 is constant as indicated by the symbol Q2. In the rotation operation end period A3, the actual angular velocity of the camera body 1 is lowered as indicated by the symbol Q3 in order to stop the rotation of the camera body 1. In the stationary state period A4, the actual angular velocity of the camera body 1 is zero as indicated by the symbol Q4.

  Note that the change in angular velocity of the camera body 1 when tilting shooting is performed with the camera body 1 tilted so that the camera body 1 faces the subject is similar to the actual change in angular velocity of the camera body 1 during panning shooting. Showing change.

  On the other hand, the angular velocity signal Q ′ output from the angular velocity sensor is charged in the capacitor of the high-pass filter because the camera body 1 is rotated in a fixed direction from the stationary state during the rotation operation start period A1. Is charged and rises as indicated by the symbol Q1 ′. In the rotational shooting period A2, the charge accumulated in the capacitor of the high-pass filter is discharged in accordance with the time constant of the high-pass filter, so that the angular velocity signal Q 'decreases as indicated by the symbol Q2'. Since the angular velocity Q of the camera body 1 is decelerated during the rotation operation end period A3 (because the camera body 1 is accelerated in the reverse direction), the charge of the capacitor of the high-pass filter is suddenly discharged, and the angular velocity signal Q ′ is encoded. As indicated by Q3 ′, the capacitor decreases rapidly and the capacitor is charged in the reverse direction. In the stationary state period A4, the actual angular velocity Q of the camera body 1 becomes zero as indicated by reference numeral Q4. Therefore, the charge accumulated in the capacitor of the high-pass filter is discharged according to the time constant of the high-pass filter, and the angular velocity signal Q ′ Rises as indicated by the symbol Q4 '.

  That is, in the rotation operation start period A1 and the rotation operation end period A3, the actual change in the angular velocity Q of the camera body 1 corresponds to the change in the angular velocity signal Q ′, but it should be a constant angular velocity. In the rotational imaging period A2, it is observed that the angular velocity signal Q ′ is decelerated because the angular velocity signal Q ′ decreases due to the discharge of charges based on the time constant τ of the high-pass filter.

  On the other hand, in the stationary state period A4 in which the camera body 1 should be stationary, the angular velocity signal Q ′ is accelerated until the angular velocity signal Q ′ is settled by discharge of charge based on the time constant τ of the high-pass filter. Observed as if

  Therefore, for example, if shooting is performed immediately after the transition to the stationary state period A4, the camera body 1 is not moving, although the camera body 1 is actually stationary, and the camera body 1 moves greatly. Therefore, if camera shake correction is performed based on the angular velocity signal Q ′, a greatly blurred photo is obtained.

  Therefore, the conventional image pickup apparatus is provided with a camera shake / pan tilt determination means. When the hand shake / pan tilt discriminating means discriminates the pan / tilt, the electric charge accumulated in the high pass filter is abruptly discharged, and the angular velocity signal Q ′ output from the high pass filter waits for the time constant to settle. So that you can shoot without

  This hand shake / pan tilt determination means determines that panning or tilting photography is being performed when the angular velocity signal has a value greater than a predetermined threshold for a predetermined time.

  However, with this camera shake / pan tilt discrimination means, it is discriminated that panning photography (or tilting photography) is performed only by the magnitude of the angular velocity signal, regardless of whether the actual angular velocity of the camera body 1 is accelerating or decelerating. Therefore, the timing at which the actual acceleration of the camera body 1 ends and the transition to the constant velocity motion is completed, and the timing at which the deceleration of the camera body 1 ends and the transition to the stationary state cannot be detected correctly. This will interfere with camera shake correction during shooting (panning shot) or shooting immediately after the camera body 1 is stationary.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an imaging device and an image blur correction device that can accurately perform tilting shake correction immediately after panning or panning shooting. .

The imaging apparatus according to claim 1 , wherein an angular velocity sensor that detects a vibration of the camera body and outputs a shake signal, and a reference voltage by cutting a DC component included in the shake signal based on a first time constant. The high-pass filter that outputs the fluctuation amount with respect to the angular velocity signal, the analog switch that discharges the electric charge accumulated in the high-pass filter in accordance with the second time constant smaller than the first time constant, and the angular velocity signal are input. A calculation unit for performing a calculation for correcting image blur based on the angular velocity signal, and sampling the angular velocity signal at regular intervals to detect temporal changes in angular acceleration of the camera body, and the angular velocity signal A detection unit that obtains a differential value based on a sampling value of the signal and detects a temporal change in the magnitude, and the analog based on a detection result of the detection unit A switching unit that switches a time constant of the high-pass filter between the first time constant and the second time constant by controlling on / off of the switch; A first absolute threshold value and a second absolute threshold value are provided, and the detection unit is a time point when the absolute value of the magnitude of the differential value is smaller than the first absolute threshold value from a time point when the absolute value is greater than or equal to the first absolute threshold value. To determine whether the duration is greater than a predetermined threshold time and whether the absolute value of the output of the high-pass filter is greater than the second absolute threshold And the switching unit determines that the absolute value of the magnitude of the differential value is smaller than the first absolute threshold and the duration is larger than the threshold time and a high pass Absolute value of the filter output And wherein the turning on the analog switch the second the charge accumulated in the high-pass filter is greater than the absolute threshold to discharge in accordance with the second time constant.
The imaging apparatus according to claim 2 , wherein the switching unit switches the time constant of the high-pass filter to the second time constant and then is shorter than the first time constant and longer than the second time constant. The first time constant is restored within a set period.
According to a third aspect of the present invention, the calculation unit prohibits a change in the time constant of the high-pass filter during exposure.
The imaging apparatus according to claim 4 , wherein the arithmetic unit receives the exposure start request during the setting period in which the high-pass filter is set to the second time constant. The exposure is started immediately after.
An image blur correction apparatus according to claim 5 is an angular velocity sensor that detects vibration of a camera body and outputs a blur signal, and cuts a DC component included in the blur signal based on a first time constant. A high-pass filter that outputs a variation with respect to a reference voltage as an angular velocity signal; an analog switch that discharges charges accumulated in the high-pass filter according to a second time constant smaller than the first time constant; and the angular velocity signal An arithmetic unit that performs an operation for correcting image blur based on the input angular velocity signal, and samples the angular velocity signal at regular intervals to detect temporal changes in angular acceleration of the camera body. A detection unit that obtains a differential value based on a sampling value of the angular velocity signal and detects a temporal change in the magnitude, and based on the detection result of the detection unit A switching unit that switches a time constant of the high-pass filter between the first time constant and the second time constant by controlling on / off of a analog switch; The first absolute threshold and the second absolute threshold are provided, and the detection unit is smaller than the first absolute threshold from the time when the absolute value of the differential value is equal to or greater than the first absolute threshold. Calculate the duration up to the time point to determine whether the duration is greater than a predetermined threshold time and determine whether the absolute value of the output of the high-pass filter is greater than the second absolute threshold A determination unit, wherein the switching unit determines that the absolute value of the magnitude of the differential value is smaller than the first absolute threshold and the duration is greater than the threshold time; Of the output of the high-pass filter And wherein the turning on the analog switch to discharge the charge-to-value is accumulated in the high-pass filter is larger than the second absolute threshold in accordance with a second time constant.

According to the imaging device according to any one of claims 1 to 4 and the image blur correcting device according to claim 5 , the determination of panning photography or tilting photography is performed in consideration of the magnitude of the angular velocity signal. Therefore, it is possible to detect the end of acceleration and deceleration of the camera body more accurately than those described in claims 1 to 9 and more reliably perform shake correction immediately after panning or panning. it can.

  Embodiments of a digital camera as an image pickup apparatus according to the present invention will be described below with reference to the drawings.

Example 1
FIG. 3 is a control block diagram of a camera shake correction circuit of the imaging apparatus according to the present invention. In FIG. 3, 11 is an angular velocity sensor, 12 is a high-pass filter circuit unit, 13 and 13 'are amplification circuit units, 14 and 14' are A / D conversion circuits, 15 is a digital operation unit, 16 is a shake correction device, 17 Is an imaging unit, and 18 is an imaging control unit. The angular velocity sensor 11 includes, for example, a gyro sensor S1 that detects camera shake in the yaw direction and a gyro sensor S2 that detects camera shake in the pitch direction.

  Here, the high-pass filter circuit unit 12 includes high-pass filter units HPF1 and HPF2 for removing an offset voltage. The high-pass filter part HPF1 includes a capacitor C11, a resistor R11, a resistor R12, and an analog switch ASW1. The high-pass filter part HPF2 includes a capacitor C21, a resistor R21, a resistor R22, and an analog switch ASW2.

  The first terminal S1a of the gyro sensor S1 is connected to the + side of the power supply capacitor C13, and the-side of the capacitor C13 is grounded. A predetermined voltage is applied to the + side of the capacitor C13. The second terminal S2a of the gyro sensor S2 is connected to the + side of the power supply capacitor C23, and the-side of the capacitor C23 is grounded. A predetermined voltage is applied to the + side of the capacitor C23.

  The second terminal (output terminal) S1b of the gyro sensor S1 is connected to one side of the capacitor C11. The third terminal S1c of the gyro sensor S1 is grounded. The fourth terminal S 1 d of the gyro sensor S 1 is connected to the reference voltage application line 19. The other side of the capacitor C11 is connected to one side of the resistor R11 and to one side of the resistor R12.

  The other side of the resistor R11 is connected to the reference voltage application line 19. The other side of the resistor R12 is connected to the reference voltage application line 19 through an ASW1 switch. The capacitor C11 and the resistor R11 constitute a high pass filter. The resistor R12 and the analog switch ASW1 constitute a discharge circuit. The analog switch ASW1 is turned on / off by a switching signal described later. The resistance value of the resistor R12 is much smaller than the resistance value of the resistor R11. The capacitor C11 and the resistor R11 set a first time constant of the high pass filter HPF1, and the capacitor C11, the resistor R11, the resistor R12, and the analog switch ASW1 set a second time constant of the high pass filter HPF1.

  The second terminal (output terminal) S2b of the gyro sensor S2 is connected to one side of the capacitor C21. The third terminal S2c of the gyro sensor S2 is grounded. The fourth terminal S2d of the gyro sensor S2 is connected to the reference voltage application line 19 '. The other side of the capacitor C21 is connected to one side of the resistor R21, and is connected to one side of the resistor R22 via the analog switch ASW2. The other sides of the resistors R21 and R22 are connected to a reference voltage application line 19 '.

  The capacitor C21 and the resistor R21 constitute a high pass filter, and the resistor R22 and the analog switch ASW2 constitute a discharge circuit. The analog switch ASW2 is turned on / off by a switching signal described later. The resistance value of the resistor R21 is much smaller than the resistance value of the resistor R22. The capacitor C21 and the resistor R21 set a first time constant of the high-pass filter HPF2, and the capacitor C21, the resistor R21, the resistor R22, and the analog switch ASW2 set a second time constant of the high-pass filter HPF2. Here, the resistors R12 and R22 indicate equivalent resistances of the analog switches ASW1 and ASW2. The value of the equivalent resistance is several tens to several hundreds Ω.

  The amplifier circuit unit 13 includes an operational amplifier OP11 and a resistor R13. The amplifier circuit unit 13 'is composed of an operational amplifier OP21 and a resistor R23. The + terminal of the operational amplifier OP11 is connected to one side of the resistor R12. The negative terminal of the operational amplifier OP11 is connected to one side of the resistor R13. The other side of the resistor R13 is connected to the reference voltage application line 19. The output terminal of the operational amplifier OP11 is connected to the negative terminal of the operational amplifier OP11 and one side of the resistor R13.

  The + terminal of the operational amplifier OP21 is connected to one side of the resistor R21 and one side of the resistor R22 via the analog switch ASW2. The negative terminal of the operational amplifier OP21 is connected to one side of the resistor R23. The other side of the resistor R23 is connected to the reference voltage application line 19 '. The output terminal of the operational amplifier OP21 is connected to the negative terminal of the operational amplifier OP21 and one side of the resistor R23.

  The angular velocity signal output from the operation amplifier OP11 and the angular velocity signal output from the operation amplifier OP21 are input to the digital calculation unit 15 via the A / D conversion circuits 14 and 14 '. The detailed configuration of the digital calculation unit 15 will be described later.

  The imaging unit 17 is generally composed of, for example, a lens barrel unit and an imaging element. For example, a CCD or CMOS sensor is used as the image sensor. The lens barrel unit is generally composed of an imaging lens, a shutter mechanism, a diaphragm mechanism, a zoom mechanism, a focusing mechanism, and the like. Since these configurations are known, detailed description thereof will be omitted.

  Information such as exposure timing is exchanged between the imaging unit control unit 18 and the digital calculation unit 15. The imaging unit control unit 18 drives and controls the lens barrel unit based on a command from the digital calculation unit 15, and controls zoom operation, focusing operation, exposure adjustment, exposure operation, transfer of a captured image to the image processing unit 20, and the like. Done. The imaging data of the imaging unit 17 is input to the image processing unit 20. The image processing unit 20 outputs image processing data to a memory or a display unit based on a command from the digital calculation unit 15.

   The digital calculation unit 15 includes an integration circuit 15A, a control unit 15B, a low-pass filter unit 15C, and a detection circuit unit 15D. The low-pass filter unit 15C is provided in front of the detection circuit unit 15D. The fluctuation component of the digitally converted angular velocity signal is input to the integrating circuit 15A and integrated to be converted into an angular signal. The angle signal is input to the control unit 15B. The control unit 15B generates a camera shake correction control signal based on the angle signal.

  For example, the shake correction device 16 is mainly configured by a mounting stage that supports the imaging element, an imaging element holding mechanism 16B including an actuator such as a voice coil motor, and a drive circuit 16A that drives the actuator. The drive circuit 16A drives and controls the mounting stage in a direction in which image blur is corrected based on a camera shake correction control signal from the control unit 15B. Thereby, the mounting stage is moved in a direction in which image blur is canceled. Note that, here, a description is given of a configuration in which the image pickup device is moved to correct image blur, but a configuration in which the image pickup device is fixed and the image pickup lens is moved to cancel image blur may be employed.

  An angular velocity signal from which the high-frequency fluctuation component has been removed is input to the detection circuit unit 15D via the low-pass filter unit 15C. The detection circuit unit 15D includes a detection unit 15D1 and a switching unit 15D2. The detection unit 15D1 samples the angular velocity signal at regular intervals to detect a temporal change in the angular velocity of the camera body 1, and obtains a differential value based on the sampling value of the angular velocity signal to detect a temporal change in the magnitude. It has a function.

  The switching unit 15D2 switches the time constants of the high-pass filters HPF1 and HPF2 between the first time constant and the second time constant by performing on / off control of the analog switches ASW1 and ASW2 based on the detection result of the detection unit 15D1. It has a function.

  The detection unit 15D1 has a predetermined absolute threshold L1, and calculates a duration from the time when the absolute value of the differential value becomes equal to or greater than the absolute threshold L1 to the time when the absolute value becomes smaller than the absolute threshold L1. The counter includes a determination unit that determines whether or not the duration time is longer than a predetermined threshold time T1. The absolute threshold L1 is determined in consideration of the change in the actual angular acceleration of the camera body 1. Here, the absolute threshold L1 is set to be slightly larger in order to avoid determining that camera shake is panning shooting or tilting shooting. The threshold time T1 is determined in consideration of an acceleration / deceleration curve of angular velocity at the time of actual panning photographing of the camera body 1.

  When the analog switches ASW1 and ASW2 are turned on, the other side of the capacitor C11 and the reference voltage application line 19 and the other side of the capacitor C21 and the reference voltage application line 19 ′ are connected via the analog switches ASW1 and ASW2. Since it is short-circuited and switched from the first time constant τ to the second time constant τ ′, the charges accumulated in the capacitors C11 and C21 are rapidly discharged, and the DC components of the HPF1 and HPF2 are removed quickly. The angular velocity signals of the high pass filters HPF1 and HPF2 are set to the reference voltage. The high-pass filters HPF1 and HPF2 are switched from the first time constant τ to the second time constant τ ′ and then switched again to the first time constant τ after the set time T2.

  The set time T2 is desirably a time that is sufficient to sufficiently discharge the charges charged in the high-pass filters HPF1 and HPF2. The set time T2 is set shorter than the first time constant τ and longer than the second time constant τ '. Preferably, the set time T2 is about 6 times the second time constant τ ′.

  The first time constants of the high-pass filters HPF1 and HPF2 are τ = R11 × C11 = R21 × C21. When the resistance values R12 and R22 of the analog switches ASW1 and ASW2 are 1/200 of the resistance values R11 and R21, the combined resistance of the resistors R11 and R12 (the combined resistance of the resistors R21 and R22) is R12 << R11 (R22 << R21) is substantially equal to R12 (R22), so the second time constant τ ′ when the analog switches ASW1 and ASW2 are turned on is the first time constant when the analog switches ASW1 and ASW2 are turned off. 1/200 of τ.

  Therefore, when the first time constant τ when the analog switches ASW1 and ASW2 are OFF is 1.55 s (cutoff frequency f = 1 / (2π * τ) = 0.1 Hz), the second time constant τ ′ is 0.008 s. Accordingly, it is desirable that the set time T2 for turning on the analog switches ASW1 and ASW2 is 0.048 s or more and shorter than the threshold time T1.

  Hereinafter, an example of the operation of the imaging apparatus and the image shake correction apparatus according to the present invention will be described with reference to FIGS. 4 to 6.

  FIG. 4 is a flowchart for explaining the relationship between the posture changing operation of the camera body 1 and the time constant switching operation of the high-pass filter according to the present invention. Here, it is assumed that the camera shake correction switch is turned on.

  When performing panning photography (tilting photography) in which the orientation of the camera body 1 is changed, a blur signal is output from the angular velocity sensor 11. The blur signal is input to the high-pass filter circuit unit 12. An angular velocity signal based on the shake signal is amplified by the amplification circuit units 13 and 13 'and then input to the A / D conversion circuits 14 and 14'. The angular velocity signal is A / D converted by the A / D conversion circuits 14 and 14 '(S.1). The angular velocity data after the A / D conversion is input to the digital calculation unit 15.

  The angular velocity data is input to the integration circuit 15A and is input to the low-pass filter 15C. The low-pass filter 15C performs a low-pass filter (LPS) process to remove high-frequency noise (S.2). The angular velocity data from which the high frequency noise has been removed is input to the detection circuit unit 15D.

  The detector 15D1 calculates the difference between the angular velocity data value at the previous sampling and the angular velocity data value at the current sampling, that is, the differential value (angular acceleration) of the angular velocity signal. Next, it is determined whether or not the absolute value of the differential value is larger than the absolute threshold value L1 (S.3).

  When the absolute value of the differential value is larger than the absolute threshold L1, the detection unit 15D1 increments the counter (S.4). Then S. 5 and after waiting for a sampling process for a predetermined time, Returning to S.1. 1 to S.M. Process 3 is performed. When the absolute value of the differential value is larger than the absolute threshold L1, S.M. 1 to S.M. 5 is continued, and the count value of the counter is incremented by “1”.

  When the absolute value of the differential value is smaller than the absolute threshold value L1, the detection unit 15D1 determines whether the count value of the counter is larger than the threshold time T1 (S.6). That is, it is determined whether or not the absolute value of the differential value is equal to or less than the absolute threshold value L1 after the duration time in which the absolute value of the differential value is equal to or greater than the absolute threshold value L1 continues for the threshold time T1 or longer.

  S. 6, if the count value of the counter is smaller than the threshold time T 1, S.I. 11 and reset the count value of the counter to zero. 5 and wait for the sampling process. 1 and again S.I. 1 and subsequent processes are performed. This is a processing loop corresponding to the vibration of the camera body 1 other than panning photography (tilting photography).

  When the count value of the counter is larger than the threshold time T1, that is, the absolute value of the differential value becomes equal to or less than the absolute threshold value L1 after the duration time in which the absolute value of the differential value is greater than the absolute threshold value L1 continues for the threshold time T1 In this case, it is determined whether or not exposure is being performed by operating the release button RL shown in FIG. If it is determined that exposure is in progress, S. 8 to S.M. 10 without performing the processing of 10. 11 and the counter count value is reset to zero. 5 and waits for the sampling process. 1 to return to S.I. 1 and subsequent processes are repeated. Therefore, as shown in FIG. 5, the analog switches ASW1 and ASW2 are not turned on, and the time constant of the high-pass filters HPF1 and HPF2 is not changed from the first time constant τ to the second time constant τ ′ during exposure. Further, it is possible to avoid the occurrence of a blurred photographed image due to a sudden change in the angular velocity signal. That is, during exposure, the change of the time constant of the high-pass filter circuit unit 12 is prohibited.

  S. If it is determined in step S7 that the exposure is not in progress, the analog switches ASW1 and ASW2 are turned on (S.8). When the analog switches ASW1 and ASW2 are turned on, the charges accumulated in the high-pass filters HPF1 and HPF2 are rapidly discharged.

  Then S. 9 and after waiting for the discharge process for the set time T2, the analog switches ASW1 and ASW2 are turned off (S.10). Next, the count value of the counter is reset to zero (S.11). After the transition to S.5, S. Returning to 1, the camera shake correction process is continued.

  FIG. 6 shows a relationship among an actual angular velocity curve, an angular velocity signal curve, and a differential curve based on a posture change at the time of panning photographing of the camera body 1 when the discharge process shown in FIG. 4 is performed. In FIG. 6, symbol K1 is an actual angular velocity curve or angular velocity (indicated by a solid line) of the camera body 1, and symbol K2 is an angular velocity signal curve or angular velocity signal (indicated by a broken line) output from the high-pass filter circuit unit 12. Yes, symbol K3 is a differential curve (indicated by a one-dot chain line) obtained by differential processing based on sampling. The horizontal axis indicates the time until the end of panning imaging with the panning imaging start time as 0 seconds, and the unit is seconds.

  The vertical axis represents a voltage value depending on the sensitivity of the angular velocity sensor 11, and zero corresponds to the reference voltage Vref. In FIG. 6, in order to facilitate understanding of the invention, the maximum voltage value at the time of panning photographing is represented as “1”. The differential value is displayed as a voltage value that is 100 times the difference of each sampling value, assuming that the sampling period of the angular velocity data is 1 ms.

  When the absolute value of the differential value becomes equal to or less than the absolute threshold value L1 after the duration time that the absolute value of the differential value is equal to or greater than the absolute threshold value L1 continues for the threshold time T1 or more at the time X1 when panning imaging starts (end of acceleration of angular velocity). When judged, the analog switches ASW1 and ASW2 are turned on.

  As a result, the time constant of the high-pass filter circuit unit 12 is switched from the first time constant τ to the second time constant τ ′, so that the charge accumulated in the high-pass filter circuit unit 12 is indicated by the symbol K2 ′. As a result of the discharge, the angular velocity signal K2 rapidly decreases and settles to Vref. As the angular velocity signal K2 rapidly decreases, the differential value rapidly increases / decreases as indicated by symbol K3 '. Since the set time T2 is set to be larger than the second time constant τ ', the charges accumulated in the high pass filter circuit unit 12 are sufficiently discharged.

  Further, at the time point X2, which is the end of panning imaging (end of angular velocity deceleration), the absolute value of the differential value continues again for the threshold time T1 or more after the absolute value of the differential value is the absolute threshold L1 or more. If it is determined that the analog switches ASW1, ASW2 are turned on in the same manner.

  As a result, the time constant of the high-pass filter circuit unit 12 is switched from the first time constant τ to the second time constant τ ′, so that the charge accumulated in the high-pass filter circuit unit 12 is indicated by a symbol K2 ″. As a result of the discharge, the angular velocity signal K2 rises rapidly and is set to Vref. As the angular velocity signal K2 rises rapidly, its differential value rapidly increases and decreases as indicated by the symbol K3 ″. Also in this case, since the set time T2 is set to be larger than the second time constant, the charge accumulated in the high-pass filter circuit unit 12 is sufficiently discharged.

The time X1 corresponds to the change start time of the camera body 1, the time X2 corresponds to the change end time of the camera body 1, and the detection unit 15D1 detects the temporal change in the angular acceleration of the camera body 1 to detect the camera. The switching unit 15D2 functions as a detection unit that detects the direction change start and the direction change end of the main body 1, and when the detection unit 15D1 detects the direction change start or the direction change end of the camera main body 1, the analog switch ASW1, Functions as a switching unit that switches the time constant of the high-pass filter circuit unit 12 from the first time constant τ to the second time constant τ ′ and then returns to the first time constant τ by controlling on / off of the ASW 2 To do.
(Example 2)
FIG. 7 is a flowchart for explaining a second embodiment of the image pickup apparatus according to the present invention. In the second embodiment, the time constant of the high-pass filter is changed to the second time constant τ ′. In addition, when a request to start exposure is received, it is possible to avoid occurrence of a blurred photographed image due to a sudden change in the angular velocity signal.

  In the second embodiment, the detection circuit unit 15D performs S.D. after the analog switches ASW1 and ASW2 are turned on (S.8). Then, the process proceeds to 12, and it is determined whether or not the release switch RL shown in FIG. If the release switch RL is not pressed, The process proceeds to 9, and the same processing as in the first embodiment is performed. If the release switch RL has been pressed, it is determined that an exposure request command has been issued. 13, after the exposure prohibiting signal is output to the other processing circuit unit of the digital arithmetic unit 15, Move to 9.

  Next, after the set time T2 has elapsed, the detection circuit unit 15D determines whether or not an exposure inhibition signal has been output (S.14). When the exposure start signal is not output, the detection circuit unit 15D performs the S.D. The process proceeds to 10 and the same processing as in the first embodiment is performed. When the exposure start signal is output, the detection circuit unit 15D turns off the analog switches ASW1 and ASW2 (S.15), and then outputs an exposure prohibition release signal to the other processing circuit units of the digital calculation unit 15 ( S.16), S.M. 11 and the same processing as in the first embodiment is performed.

  As a result, as shown in FIG. 8, exposure is prohibited when the release switch RL shown in FIG. 1 is pressed during the on period of the analog switches ASW1 and ASW2, that is, within the set time T2, and there is an exposure request command. Then, the exposure is started immediately after the analog switches ASW1 and ASW2 are turned off.

According to the second embodiment, when the exposure start request is received during the setting period in which the time constant of the high-pass filter is changed to the second time constant τ ′, the exposure is performed immediately after the setting period T2. Therefore, it is possible to avoid the occurrence of a blurred photographed image due to a sudden change in the angular velocity signal during exposure.
(Example 3)
9 to 12 are explanatory views for explaining a third embodiment of the imaging apparatus according to the present invention. FIG. 9 is an enlarged view for explaining the malfunction of the imaging apparatus according to the first embodiment, and is a graph schematically showing the relationship between the angular velocity signal curve K2 and the differential curve K3.
In the first embodiment, the absolute threshold value L1 of the differential value is determined in consideration of a change in the magnitude of the actual angular acceleration Q of the camera body 1, but the magnitude of the absolute threshold value L1 is determined by panning photography due to camera shake. In order not to determine (tilting shooting), it is set slightly larger as described in the first embodiment.
Accordingly, it may be determined that the acceleration or deceleration has ended when the acceleration period Q1 of the true angular velocity Q or the deceleration period Q3 of the true angular velocity Q of the camera body 1 has not ended.
That is, as shown in FIG. 9, when only the absolute threshold value L1 of the differential value is determined, the acceleration of the camera body 1 is accelerated at a time Z1 (X1) considerably before the acceleration period of the true angular velocity Q of the camera body 1 ends. At this time Z1 (X1), the analog switches ASW1 and ASW2 are turned on, and the electric charge accumulated in the capacitor of the high-pass filter circuit unit 12 is once discharged according to the second time constant τ ′. However, since the camera body 1 is accelerated, a detection timing shift Δt occurs, and an offset voltage offs is generated in accordance with the detection timing shift Δt. Further, it is determined that the deceleration of the camera body 1 is completed at a time Z2 (X2) that is considerably before the end of the deceleration period Q3 of the true acceleration Q of the camera body 1, and the analog switch ASW1 is determined at this time Z2 (X2). Since the camera body 1 is decelerated even after the ASW 2 is turned on and the electric charge accumulated in the capacitor of the high-pass filter circuit unit 12 is discharged according to the second time constant τ ′, the detection timing deviation Δt is the same. The offset voltage offs is generated along with the detection timing shift Δt.
For this reason, the time constant of the high-pass filter circuit unit 12 cannot be substantially reduced, and it is difficult to speed up the settling of the angular velocity signal K2 beyond that described in the first embodiment.
In Example 3, camera shake correction immediately after panning shooting or panning shooting is detected by more accurately detecting the start of panning shooting (end of acceleration of camera body 1) and the end of panning shot (end of deceleration of camera body 1). Provided is an imaging device that can be more reliably performed.
The details will be described below with reference to FIGS. 3 and 10 to 12.
Here, the detection unit 15D1 has a first absolute threshold L1 and a second absolute threshold L2 that are determined in advance. Here, the first absolute threshold L1 is set at a time point Z1 (X1) immediately before the end of the acceleration period of the true angular velocity Q of the camera body 1 and a time point Z2 (X2) immediately before the end of the deceleration period of the true angular velocity Q of the camera body 1. ) Is set to a very small value in order to accurately determine. The second absolute threshold L2 is used for comparison with the absolute value of the output of the angular velocity signal K2. The second absolute threshold L2 is used to detect whether panning shooting or tilting shooting is performed.
When performing panning photography (tilting photography) in which the orientation of the camera body 1 is changed, a blur signal is output from the angular velocity sensor 11. The blur signal is input to the high-pass filter circuit unit 12. An angular velocity signal based on the shake signal is amplified by the amplification circuit units 13 and 13 ′ and then input to the A / D conversion circuits 14 and 14 ′. The angular velocity signal is A / D converted by the A / D conversion circuits 14 and 14 '(S.1). The angular velocity data after the A / D conversion is input to the digital calculation unit 15.
The angular velocity data is input to the integration circuit 15A and also input to the low-pass filter unit 15C. The low-pass filter unit 15C performs a low-pass filter (LPS) process to remove high-frequency noise (S.2). The angular velocity data from which the high frequency noise has been removed is input to the detection circuit unit 15D.
The detector 15D1 calculates the difference between the angular velocity data value at the previous sampling and the angular velocity data value at the current sampling, that is, the differential value (angular acceleration) of the angular velocity signal. Next, as shown in FIGS. 11 and 12, it is determined whether or not the absolute value of the differential value is larger than the first absolute threshold L1 (S.3). When the absolute value of the differential value is larger than the first absolute threshold L1, the detection unit 15D1 increments the counter (S.4). Then S. 5 and after waiting for a sampling process for a predetermined time, Returning to S.1. 1 to S.M. Process 3 is performed. When the absolute value of the differential value is larger than the first absolute threshold L1, S.I. 1 to S.M. 5 is continued, and the count value of the counter is incremented by “1”.
When the absolute value of the differential value is smaller than the first absolute threshold L1, the detection unit 15D1 determines whether or not the counter value is larger than the threshold time T1 (S.6). That is, it is determined whether or not the absolute value of the differential value has become equal to or less than the first absolute threshold value L1 after the duration time in which the absolute value of the differential value is equal to or greater than the first absolute threshold value L1 continues for the threshold time T1 or longer.
S. 6, if the count value of the counter is smaller than the threshold time T 1, S.I. 11 and reset the count value of the counter to zero. 5 and wait for the sampling process. 1 and again S.I. 1 and subsequent processes are performed. This is a processing loop corresponding to the vibration of the camera body 1 other than panning photography (tilting photography).
When the count value of the counter is larger than the threshold time T1, that is, the absolute value of the differential value is equal to or greater than the first absolute threshold value L1 after the duration time in which the absolute value of the differential value is greater than the first absolute threshold value L1 continues for the threshold time T1. In the following case, the detection circuit unit 15D1 determines whether or not the absolute value of the output of the angular velocity signal K2 output from the high-pass filter circuit unit 12 is larger than the second absolute threshold L2 (S.6 ′).
When the absolute value of the output of the angular velocity signal K2 is smaller than the second absolute threshold L2, S.I. 11 and reset the count value of the counter to zero. 5 and wait for the sampling process. 1 and again S.I. 1 and subsequent processes are performed. Therefore, as shown in FIG. 11, when the count value of the counter is larger than the threshold time T1, and when the second absolute threshold L2 is larger than the absolute value of the output of the angular velocity signal K2, the analog switch ASW1, The ASW2 is not turned on, and as a result, the time constants of the high-pass filters HPF1 and HPF2 are not changed from the first time constant τ to the second time constant τ ′, and the detection unit 15D1 is not panning shooting but panning shooting. Can be avoided.
In FIG. 11, the symbol K2 is an angular velocity signal curve (shown by a broken line) output from the high-pass filter circuit unit 12 as in FIG. 9, and the symbol K3 is a differential curve (determined by a differentiation process based on sampling). (Shown by a one-dot chain line). The horizontal axis indicates the time until the end of panning imaging with the panning imaging start time as 0 seconds, and the unit is seconds.
The vertical axis represents a voltage value depending on the sensitivity of the angular velocity sensor 11, and zero corresponds to the reference voltage Vref.
When the absolute value of the output of the angular velocity signal K2 is larger than the second absolute threshold L2, the detection unit 15D1 determines whether exposure is being performed by operating the release button RL shown in FIG. 1 (S.7). If it is determined that exposure is in progress, S. 8 to S.M. 10 without performing the processing of 10. 11 and the counter count value is reset to zero. 5 and waits for the sampling process. 1 to return to S.I. 1 and subsequent processes are repeated. Accordingly, as in the first embodiment, the analog switches ASW1 and ASW2 are not turned on, and the time constant of the high-pass filters HPF1 and HPF2 is changed from the first time constant τ to the second time constant τ ′ during exposure. Therefore, it is possible to avoid the occurrence of a blurred photographed image due to a sudden change in the angular velocity signal.
S. If it is determined in step S7 that the exposure is not in progress, the analog switches ASW1 and ASW2 are turned on (S.8). When the analog switches ASW1 and ASW2 are turned on, the charges accumulated in the high-pass filters HPF1 and HPF2 are rapidly discharged.
Then S. 9 and after waiting for the discharge process for the set time T2, the analog switches ASW1 and ASW2 are turned off (S.10). Next, the count value of the counter is reset to zero (S.11). After the transition to S.5, S. Returning to 1, the camera shake correction process is continued.
FIG. 12 shows the relationship between the angular velocity signal curve K2 and the differential curve K3 based on the posture change at the time of panning photographing of the camera body 1 when the discharge process is performed.
At the time of Z1 (X1) when panning imaging is started (end of acceleration of angular velocity), the duration time during which the absolute value of the differential value is less than or equal to the first absolute threshold value L1 and the absolute value of the differential value is greater than or equal to the first absolute threshold value L1 If it is determined that the threshold time T1 or more has continued, and if the absolute value of the angular velocity signal K2 is greater than the second absolute threshold L2 and it is determined that exposure is not in progress, the analog switches ASW1 and ASW2 are turned on.
As a result, the time constant of the high-pass filter circuit unit 12 is switched from the first time constant τ to the second time constant τ ′, so that the charge accumulated in the high-pass filter circuit unit 12 is indicated by the symbol K2 ′. As a result of the discharge, the angular velocity signal K2 rapidly decreases and quickly settles to Vref. As the angular velocity signal K2 rapidly decreases, its differential value rapidly increases / decreases (not shown). Since the set time T2 is set to be larger than the second time constant τ ′, the charge accumulated in the high-pass filter circuit unit 12 is sufficiently discharged.
Further, the absolute value of the differential value is less than or equal to the first absolute threshold L1 at the time of Z2 (X2), which is the end of panning imaging (end of deceleration of the angular velocity), and the absolute value of the differential value is continued beyond the first absolute threshold L1. If it is determined that the time has continued for the threshold time T1 or more and the output of the angular velocity signal K2 is greater than the second absolute threshold L2 and it is determined that the exposure is not being performed, the analog switches ASW1 and ASW2 are similarly turned on. .
As a result, the time constant of the high-pass filter circuit unit 12 is switched from the first time constant τ to the second time constant τ ′, so that the charge accumulated in the high-pass filter circuit unit 12 is indicated by a symbol K2 ″. As a result of the discharge, the angular velocity signal K2 rapidly rises and quickly settles to Vref, and as the angular velocity signal K2 rises rapidly, its differential value rapidly increases / decreases (not shown). However, since the set time T2 is set larger than the second time constant, the charge accumulated in the high-pass filter circuit unit 12 is sufficiently discharged.
As is apparent from FIG. 12, by reducing the absolute threshold L1, the detection timing deviation Δt can be reduced, and the residual offset voltage offs can be reduced. Therefore, compared to the first embodiment, it is possible to accurately detect the start of panning shooting and the end of panning shooting of the camera body 1 and more reliably perform shake shooting and camera shake correction immediately after panning shooting.
In the third embodiment, it is determined whether or not the exposure is being performed, and it is determined whether or not the first time constant τ is switched to the second time constant τ ′. However, the present invention is not limited to this.
In the third embodiment, the change of the time constant of the high-pass filter is prohibited during exposure. In the third embodiment, when the exposure start request is received during the set period in which the high-pass filter is set to the second time constant τ ′, the exposure is started immediately after the set period has elapsed. You can also

  As described above, in the embodiments, the configuration for correcting the image blur by mechanically correcting the positional deviation between the image and the image sensor has been described, but the present invention is not limited to this, and the blur information of the angular velocity sensor is used. The present invention can also be applied to a configuration in which image blur is corrected by image processing.

It is a conceptual diagram for demonstrating panning imaging | photography. It is a graph for demonstrating the relationship between the angular velocity change of the camera main body at the time of the conventional panning imaging | photography, and an angular velocity signal. It is a block circuit diagram concerning the Example of the imaging device concerning this invention. It is a flowchart for demonstrating the effect | action of the imaging device concerning Example 1 of this invention. FIG. 3 is an operation timing chart of the imaging apparatus according to the first embodiment of the present invention. It is a graph for demonstrating the relationship between the angular velocity curve of the imaging device concerning Example 1 of this invention, an angular velocity signal, and a differential curve. It is a flowchart for demonstrating the effect | action of the imaging device concerning Example 2 of this invention. It is an operation | movement timing chart figure of the imaging device concerning Example 2 of this invention. It is an enlarged view for demonstrating the malfunction of the imaging device concerning Example 1 of this invention, Comprising: It is a graph which shows typically the relationship between an angular velocity curve and a differential curve. It is a flowchart figure for demonstrating the effect | action of the imaging device concerning Example 3 of this invention. FIG. 6 is a graph schematically showing a relationship among an angular velocity curve, an angular velocity signal, and a differential curve of an imaging apparatus according to Embodiment 3 of the present invention, and an enlarged explanatory diagram when an output value output from a high-pass filter is smaller than a threshold value. It is. FIG. 6 is a graph schematically showing a relationship among an angular velocity curve, an angular velocity signal, and a differential curve of an imaging apparatus according to Embodiment 3 of the present invention, and an enlarged explanation when an output value output from a high-pass filter exceeds a threshold value. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Angular velocity sensor 12 ... High pass filter circuit part 15 ... Digital operation part 15D ... Detection circuit part ASW1 ... Analog switch

Claims (5)

An angular velocity sensor that detects vibration of the camera body and outputs a shake signal;
A high-pass filter that cuts a direct current component included in the shake signal based on a first time constant and outputs a variation with respect to a reference voltage as an angular velocity signal;
An analog switch for discharging the electric charge accumulated in the high-pass filter according to a second time constant smaller than the first time constant;
A calculation unit that receives the angular velocity signal and performs a calculation for correcting image blur based on the angular velocity signal;
Detection in which the angular velocity signal is sampled at regular intervals to detect a temporal change in angular acceleration of the camera body, and a differential value is obtained based on a sampling value of the angular velocity signal to detect a temporal change in the magnitude. And
A switching unit that switches a time constant of the high-pass filter between the first time constant and the second time constant by performing on / off control of the analog switch based on a detection result of the detection unit; ,
The detection unit is provided with a first absolute threshold value and a second absolute threshold value that are determined in advance, and the detection unit is configured to perform the detection from the time when the absolute value of the magnitude of the differential value becomes equal to or greater than the first absolute threshold value. The duration until the point when it becomes smaller than the first absolute threshold is calculated to determine whether the duration is greater than a predetermined threshold time, and the absolute value of the output of the high-pass filter is the second absolute threshold A determination unit for determining whether or not the
The switching unit is the absolute value of the output of the high-pass filter when the determination unit determines that the absolute value of the magnitude of the differential value is smaller than the first absolute threshold and the duration is longer than the threshold time. An image pickup apparatus, wherein when the value is larger than the second absolute threshold, the analog switch is turned on in order to discharge the charge accumulated in the high-pass filter according to a second time constant. The switching unit switches the time constant of the high-pass filter to the second time constant and then sets the first time constant within a set period shorter than the first time constant and longer than the second time constant. The imaging apparatus according to claim 1 , wherein the imaging apparatus is returned to a constant. The imaging apparatus according to claim 2 , wherein the arithmetic unit prohibits a change in a time constant of the high-pass filter during exposure. The arithmetic unit starts exposure immediately after the set period elapses when an exposure start request is received during the set period in which the high-pass filter is set to the second time constant. The imaging device according to claim 2 . An angular velocity sensor that detects vibration of the camera body and outputs a shake signal;
A high-pass filter that cuts a direct current component included in the shake signal based on a first time constant and outputs a variation with respect to a reference voltage as an angular velocity signal;
An analog switch for discharging the electric charge accumulated in the high-pass filter according to a second time constant smaller than the first time constant;
A calculation unit that receives the angular velocity signal and performs a calculation for correcting image blur based on the angular velocity signal;
Detection in which the angular velocity signal is sampled at regular intervals to detect a temporal change in angular acceleration of the camera body, and a differential value is obtained based on a sampling value of the angular velocity signal to detect a temporal change in the magnitude. And
A switching unit that switches a time constant of the high-pass filter between the first time constant and the second time constant by performing on / off control of the analog switch based on a detection result of the detection unit; ,
The detection unit is provided with a first absolute threshold value and a second absolute threshold value that are determined in advance, and the detection unit is configured to perform the detection from the time when the absolute value of the magnitude of the differential value becomes equal to or greater than the first absolute threshold value. The duration until the point when it becomes smaller than the first absolute threshold is calculated to determine whether the duration is greater than a predetermined threshold time, and the absolute value of the output of the high-pass filter is the second absolute threshold A determination unit for determining whether or not the
The switching unit is the absolute value of the output of the high-pass filter when the determination unit determines that the absolute value of the magnitude of the differential value is smaller than the first absolute threshold and the duration is longer than the threshold time. An image blur correction apparatus, wherein when the value is larger than the second absolute threshold, the analog switch is turned on to discharge the charge accumulated in the high-pass filter in accordance with a second time constant.

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