JP2008283443A - Imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging device which can perform suitable blur correction by carrying out suitable processing according to an exposure time. <P>SOLUTION: The device integrates output signals from a gyroscope sensor 201 in an integration unit 209, and calculates blur angle data. Afterward, it establishes whether HPF (High Pass Filter) processing is done or not by a HPF 213 according to the exposure time. It prevents deterioration of camera shake correction effect by influence of an offset temperature drift, etc. of the gyroscope sensor 201 by carrying out the HPF processing in a case that the exposure time is long. Inversely, it prevents deterioration of the camera shake correction effect by influence of a phase difference by the HPF processing by not carrying out the HPF processing in a case that the exposure time is short. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus that can prevent image degradation due to blurring of the imaging apparatus.

  2. Description of the Related Art There is known a blur correction device that detects vibrations such as camera shake in an imaging device or the like and moves the image sensor based on the detected vibrations to perform blur correction. In such a shake correction device, an angular velocity sensor such as a gyro sensor detects a camera shake signal as an angular velocity signal, amplifies the angular velocity signal so that it can be easily handled, and then converts the angular velocity information into angular information. The angular velocity signal is integrated. A correction amount necessary for blur correction is calculated based on the integration result (angle information), and the image sensor is driven based on the calculation result.

  Here, the angular velocity sensor is used to detect a camera shake signal, but it is known that the blur correction accuracy deteriorates due to the exposure time due to the influence of a drift due to a temperature change or the like.

Therefore, in order to eliminate the influence of drift due to this temperature change, a dynamic range using a technique in which a high-pass filter (HPF) process is performed after the output of the angular velocity sensor or a DA converter (DAC) as in Patent Document 1 is used. The technique etc. which ensure are taken.
Japanese Patent Laid-Open No. 10-228043

  Here, in the method of performing the HPF process after the output of the angular velocity sensor, the correction accuracy can be maintained during long exposure because it follows the temperature change of the detection system circuit, but when the exposure time is short, the HPF process is performed. There is a risk that the correction accuracy will deteriorate due to the influence of the constants. On the other hand, in the method of Patent Document 1, the use of the DAC eliminates the influence of the HPF time constant, but it cannot follow the temperature change during long-time exposure, and the correction accuracy may deteriorate.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an imaging apparatus capable of performing appropriate blur correction by performing appropriate processing according to the exposure time.

  In order to achieve the above object, an imaging apparatus according to a first aspect of the present invention includes an imaging unit that acquires image data of a subject, a detection unit that detects blur, and a high-pass filter process on the output of the detection unit. High-pass filter processing means to perform, correction means for performing blur correction operation to prevent image data deterioration of the subject due to blur, exposure control means to control the exposure operation of the imaging means, and during the exposure operation of the imaging means Control means for executing the blur correction operation by the correction means, the control means of the detection means via the high-pass filter processing means according to the exposure time set prior to the exposure operation. One of the output and the output of the detection means that does not pass through the high-pass filter processing means is selected, and the correction means is added to the correction means based on the selected output. Characterized in that to perform the motion compensation operation.

  In order to achieve the above object, an imaging apparatus according to a second aspect of the present invention includes an imaging means for acquiring image data of a subject, a detection means for detecting blur, and a high-pass filter at the output of the detection means. A high-pass filter processing unit that performs processing, a correction unit that performs a blur correction operation that prevents deterioration of image data of the subject due to blurring, an exposure control unit that controls an exposure operation of the imaging unit, and an exposure operation of the imaging unit Control means for executing the blur correction operation by the correction means, and the control means performs high-pass filter processing of the high-pass filter processing means according to an exposure time set prior to the exposure operation. The correction means is changed based on the output of the high-pass filter processing means that changes the cutoff frequency and changes the cutoff frequency. Characterized in that to execute the serial motion compensation operation.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device which can perform suitable blurring correction by performing a suitable process according to exposure time can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus including a shake correction apparatus according to the first embodiment of the present invention. An imaging apparatus 1 illustrated in FIG. 1 is assumed to be, for example, an interchangeable lens camera, and includes a lens unit 10 and a main body unit 50. The lens unit 10 is configured to be detachable from the main body unit 50. When the lens unit 10 is attached to the main body unit 50, the lens unit 10 and the main body unit 50 are in a communicable state.

  The lens unit 10 includes a photographing lens 11, a lens frame 12, a lens driving mechanism 13, a lens driving circuit 14, a shutter 15, a shutter driving mechanism 16, and a shutter driving circuit 17.

  The taking lens 11 is held by the lens frame 12 and makes light from a subject (not shown) incident in the direction of the main body 50. The lens driving mechanism 13 is configured by a motor or the like, receives the output from the lens driving circuit 14, drives the photographing lens 11 held by the lens frame 12, and performs zoom and focus driving of the photographing lens 11. The shutter 15 brings the imaging surface of the CCD unit 20 of the main body 50 into an exposed state or a light shielding state. The shutter drive mechanism 16 is composed of a motor or the like and receives the output from the shutter drive circuit 17 to drive the shutter 15.

  The main unit 50 includes a camera control microcomputer (Mucom) 18, an optical low-pass filter 19, a CCD unit 20, a CCD interface circuit 21, an image processing controller 22, an SDRAM 23, a FlashRom 24, a recording medium 25, A nonvolatile memory 26, a strobe 27, a strobe control circuit 28, a camera operation switch (SW) 29, a liquid crystal monitor 30, a battery 31, a power supply circuit 32, and a camera shake correction unit 40 are provided. .

  The Mucom 18 having a function as a control unit performs overall control of the main body unit 50, and also controls the lens driving circuit 14 and the shutter driving circuit 17 of the lens unit 10 when the lens unit 10 is mounted. The overall control of the imaging device 1 is performed.

  The optical low-pass filter 19 is provided on the optical axis of the photographing lens 11, removes a predetermined frequency component (for example, infrared component) of light incident from the photographing lens 11, and protects the imaging surface of the CCD unit 20. . The CCD unit 20 having a function as an imaging unit is a photoelectric conversion unit provided on the optical axis of the photographing lens 11 and converts an image of a subject incident through the photographing lens 11 into an electric signal by photoelectric conversion. At the time of shooting, the shutter 15 is driven by the shutter drive circuit 17 under the control of the Mucom 18 so that the light passing through the shooting lens 11 forms an image on the imaging surface of the CCD unit 20.

  The CCD interface circuit 21 is an interface circuit that reads an electrical signal obtained in the CCD unit 20. The image processing controller 22 performs various image processing in accordance with instructions from the Mucom 18. The SDRAM 23 and the FlashRom 24 are storage areas for storing various data processed by the image processing controller 22 or the like. The recording medium 25 records image data compressed by the image processing controller 22 according to a predetermined compression method such as the JPEG method.

  The nonvolatile memory 26 is composed of, for example, an EEPROM and stores predetermined control parameters necessary for camera control. The nonvolatile memory 26 is provided so as to be accessible from the Mucom 18.

  The strobe 27 radiates auxiliary light toward the subject. The strobe control circuit 28 drives the strobe 27. The Mucom 18 irradiates the subject with auxiliary light via the strobe control circuit 28 when the subject is dark at the time of shooting.

  The camera operation SW 29 is a switch group that responds to operation of operation buttons necessary for the user to operate the imaging apparatus 1 such as a release SW, a mode change SW, and a power SW. Here, the release SW is a switch for giving an instruction to start shooting, and the mode change SW is a switch for switching various modes such as switching the mode of the imaging apparatus 1 between, for example, a shooting mode and a playback mode. It is. The power SW is a switch for turning on or off the power supply of the imaging apparatus 1.

  The liquid crystal monitor 30 displays an image based on a video signal obtained by converting image data in the image processing controller 22. The user can confirm an image taken from the display image on the liquid crystal monitor 30.

  The battery 31 is a power source for the imaging device 1. Further, the power supply circuit 32 converts the voltage of the battery 31 into a voltage required by each circuit constituting the imaging device 1 and supplies the converted voltage.

  The camera shake correction unit 40 having a function as a shake correction unit moves the CCD unit 20 based on an instruction from the Mucom 30 and corrects the shake in the imaging apparatus 1. Hereinafter, the camera shake correction unit 40 will be described in more detail. FIG. 2 is a block diagram illustrating a schematic configuration of the camera shake correction unit 40. 2, the camera shake correction unit 40 includes a camera shake correction control microcomputer (Tucom) 100, a camera shake detection unit 101, a camera shake correction drive circuit 102, a camera shake correction drive mechanism 103, and a position detection sensor. 104.

  The Tucom 100 performs overall control of the camera shake correction unit 40. Tucom 100 and Mucom 18 are electrically connected, and Tucom 100 operates in accordance with instructions from Mucom 18.

  The shake detection unit 101 detects vibration of the imaging device 1. Based on this vibration, the Tucom 100 calculates a shake correction amount and outputs a signal corresponding to the shake correction amount to the shake correction drive circuit 102. The shake correction drive circuit 102 drives the CCD unit 20 via the shake correction drive mechanism 103 including a motor or the like according to a signal from the Tucom 100 to perform shake correction. The position detection sensor 104 detects the drive position of the CCD unit 20 and outputs a signal based on this drive position to the Tucom 100. The Tucom 100 performs feedback control on the shake correction signal according to the signal of the driving position.

  Hereinafter, the camera shake correction unit 40 shown in FIG. 2 will be described in more detail. FIG. 3 is a diagram illustrating a detailed configuration of the camera shake correction unit 40. In FIG. 3, a gyro sensor 201 is an angular velocity sensor for detecting a vibration (hand shake) amount of the imaging device 1. The gyro sensor 201 detects the vibration of the imaging device 1 and outputs a shake angular velocity signal corresponding to the detected vibration to the amplifier circuit 202. The amplifier circuit 202 amplifies the output of the gyro sensor 201 having a small amplitude. The offset removal circuit 205 removes a predetermined offset amount from the output signal of the amplification circuit 202 so that the output of the amplification circuit 202 falls within the dynamic range of the AD converter (ADC) 203 at the subsequent stage. Note that the offset amount to be removed by the offset removal circuit 205 is determined by the offset amount calculation unit 204.

  The ADC 203 digitizes the input signal and outputs angular velocity data obtained thereby to the offset adding unit 206. The offset adding unit 206 adds the offset amount removed by the offset removing circuit 205 to the output of the AD converter 203. The angular velocity data output from the offset adding unit 206 includes a reference value (zero point) component, which will be described later. In the shake correction operation, angular velocity data from which this zero point component has been removed is necessary. Hereinafter, the angular velocity data including the zero point component is defined as the first angular velocity data, and the angular velocity data from which the zero point component is removed is defined as the second angular velocity data.

  Here, the amplifier circuit 202 and the offset removal circuit 205 will be described in detail. FIG. 4 is a circuit diagram of the amplifier circuit 202, the offset removal circuit 205, and the periphery thereof.

The amplifier circuit 202 and the offset removal circuit 205 are as shown in FIG. That is, the amplifier circuit 202 includes an operational amplifier 301 and an inverting amplifier circuit using resistors R1, R3, and R4. The offset removal circuit 205 is provided with, for example, an 8-bit DA converter (DAC) 302. The output of the DAC 302 is connected to the inverting input terminal of the operational amplifier 301 via the resistor R2. The non-inverting input terminal of the operational amplifier 301 is connected to the Vref terminal (eg, 1.35 V) of the gyro sensor 201. With the circuit configuration shown in FIG. 4, the input signal to the ADC 203 is

It becomes. Note that the second term on the right side of equation (1) corresponds to the portion of the amplifier circuit 202, and the third term on the right side corresponds to the portion of the offset removal circuit 205.

  Note that if the power supply voltage of the ADC 203 and the DAC 302 is 3.3 V, for example, and the number of bits is 8 bits, if the output of the DAC 302 is increased by 1 LSB in the case of an ideal ADC and DAC, the AD conversion is performed according to the equation (1). It can be seen that the input is reduced by (R3 / R2) LSB. Note that the waveform of the AD conversion input of equation (1) is shown as a waveform 401 in FIG. This waveform 401 is obtained by subtracting the DAC 302 output × DAC 302 gain indicated by the waveform 402 in FIG. 5 from the output of the amplifier circuit 202. By inputting such a signal to the ADC 203, the output signal of the amplifier circuit 202 falls within the dynamic range of the ADC 203.

In order to reproduce the original angular velocity signal from such a waveform 401,

What should I do? The second term on the right side of the equation (2) is a value calculated by the offset amount calculation unit 204. In this way, digital data (first angular velocity data) corresponding to the angular velocity signal as shown by the waveform 403 is reproduced.

  In this way, the dynamic range can be secured wider than the dynamic range of the AD converter 203, and the blur angle range that can be detected in the subsequent calculation can be expanded.

  After the first angular velocity data is obtained in the offset adding unit 206, the offset adding unit 206 outputs the first angular velocity data to the averaging unit 207 and the zero point subtracting unit 208. The averaging unit 207 calculates an average value of the first angular velocity data.

  The zero point subtracting unit 208 subtracts the zero point component from the first angular velocity data to obtain the second angular velocity data in order to calculate the second angular velocity data from which the reference value (zero point) is removed. The integrating unit 209 integrates the second angular velocity data output from the zero point subtracting unit 208 to convert the angular velocity data into angle data (blur angle data). The blur angle data obtained by the conversion is divided into the high-pass and the divider unit 210. Output to the filter (HPF) 213. The division unit 210 divides the output of the integration unit 209 by the integration time (that is, calculates the average value of the second angular velocity data).

  The zero point update determination unit 211 determines whether or not the imaging device 1 is in a stationary state, and whether or not to update the zero point based on the result, and how to update the zero point. Determine whether. The zero point update unit 212 updates the zero point based on the determination result of the zero point update determination unit 211, and outputs the updated zero point (the already calculated zero point) to the zero point subtraction unit 208.

  Here, the zero point of the gyro sensor 201 which is an angular velocity sensor fluctuates due to variation in solids, temperature drift, and aging. This fluctuation range is larger than the blur signal to be detected. For example, the accuracy of the shake angular velocity signal sufficient for practical use is 0.01 deg / s (corresponding to the output voltage of the gyro sensor 201 of 20 μV), but the variation range of the zero point is ± 600 mV. That is, since the fluctuation range of the zero point is more than 30,000 times larger than the shake angle signal to be detected, it is necessary to calculate a precise zero point in order to detect an accurate shake angle.

In the first embodiment, the zero point is
1. Averaging unit 207 averages the first angular velocity data
2. Average the second angular velocity data, which is the difference between the first angular velocity data and the already calculated zero point (the second angular velocity data is integrated by the integrating unit 209 and then divided by the dividing unit 210).
It calculates | requires by either.

  Here, the zero point update determination unit 211 determines whether the zero point is obtained by any of the methods 1 and 2 described above. Further, when the imaging device 1 is in a stationary state and the difference between the already calculated zero point and the newly calculated zero point is equal to or smaller than a predetermined value, it is considered that the accuracy of the calculated zero point is good. In this case, the zero point update determination unit 211 notifies the user that the blur correction effect is expected and the display unit 105 is turned on to perform the blur correction, and the drive determination unit 215 permits the blur correction. Send instructions.

  The HPF 213 removes a low frequency component in the blur angle data prior to blur correction at the time of shooting. In this case, for example, in the case of long-time exposure such as bulb photography, the zero point is shifted due to drift due to temperature fluctuations, so that the drift component of low frequency (for example, less than 1 Hz) is cut. On the other hand, it is preferable not to use the HPF 213 because the accuracy of angle detection is reduced if the HPF 213 is used in the case of short-time exposure.

Here, the part related to the HPF process in the HPF 213 will be further described.
The input waveform to the integration unit 209 has a certain slope as shown in FIG. 6A due to the influence of the temperature drift of the offset of the gyro sensor 201 and the like. In this case, the output waveform of the integrating unit 209 also has a certain slope. For accurate blur detection, it is ideal that the input waveform to the correction amount calculation unit 214 has no inclination as shown in FIG. For this purpose, zero point update and HPF processing are performed.

  Here, in HPF processing, in principle, a phase difference (more specifically, the phase of the output is delayed with respect to the input) occurs between the input and the output. Further, if the HPF 213 does not perform HPF processing, even if the zero point update unit 212 updates the zero point, the deviation of the zero point due to the offset temperature drift or the like is accumulated over time, so that FIG. Again, the output from the integrator 209 has a slope with respect to the ideal waveform indicated by the broken line. The error of the output waveform from the ideal waveform is as shown in FIG. Even when HPF processing is performed, the followability to low-frequency blur differs depending on the cutoff frequency. In general, when the cutoff frequency in the HPF process is increased, the convergence time (the time required for the output of the HPF 213 to be stabilized) is shortened, but the low-frequency phase difference is increased, and the followability to the low-frequency blur is deteriorated. On the other hand, when the cut-off frequency is lowered, the convergence time is lengthened, but the phase difference of the low frequency is reduced, and the followability to the low frequency blur is also improved.

  Therefore, by dividing the exposure time at an arbitrary interval and assigning no HPF process and having an HPF process to each divided section, a constant camera shake correction effect can be obtained regardless of the exposure time. In order to switch the HPF process according to the exposure time, a changeover switch 216, a cut-off frequency switching unit 217, and an exposure time determination processing unit 218 are provided.

  For example, when the HPF process is performed when the exposure time is short, the influence of the phase difference of the HPF process is increased, and the camera shake correction effect is deteriorated. Therefore, the exposure time determination processing unit 218 receives the exposure time from the Mucom 18, and sends an instruction to switch the changeover switch 216 to the correction amount calculation unit 214 side when the exposure time is shorter than the predetermined time. Instead of switching the changeover switch 216, the cutoff frequency set in the HPF 213 by the cutoff frequency switching unit 217 may be set to 0 Hz. In practice, the cutoff frequency is made zero by not performing the HPF processing by the HPF 213. On the other hand, if the HPF process is not performed when the exposure time is long, the influence of temperature drift or the like becomes dominant and the camera shake correction effect is deteriorated. Therefore, the exposure time determination processing unit 218 receives the exposure time from the Mucom 18, and sends an instruction to switch the changeover switch 216 to the HPF 213 side when the exposure time is longer than the predetermined time. Note that the cutoff frequency set in the HPF 213 by the cutoff frequency switching unit 217 may be set to a frequency exceeding 0 Hz, that is, the HPF process by the HPF 213 may be performed.

  The correction amount calculation unit 214 is a drive amount (blur correction amount) for driving the motor that constitutes the blur correction drive mechanism 103 based on the output value of the HPF 213 and the position of the CCD unit 20 detected by the position detection sensor 104. Is calculated. The drive determination unit 215 sets whether to perform shake correction driving in accordance with an instruction from the zero point update determination unit 211.

  Hereinafter, the operation of the imaging apparatus 1 including the shake correction apparatus of the first embodiment will be further described. FIG. 7 is a flowchart showing the operation of the Tucom 100. Here, FIG. 7A is a diagram illustrating processing performed by the Tucom 100 when the imaging device 1 is in a state before still image shooting, and FIG. 7B is a diagram illustrating the Tucom 100 during still image shooting of the imaging device 1. It is a figure shown about the process performed.

  When the power SW is turned on by the user and the main power supply of the imaging apparatus 1 is turned on, the zero point is calculated every predetermined time (for example, 250 μs). First, the Tucom 100 takes the output of the amplifier circuit 202 by performing AD conversion in the ADC 203, and then adds the offset amount calculated based on the equation (2) to the output of the ADC 203 by the offset adder 206 to obtain the first angular velocity. Data is obtained (step S101). Next, the Tucom 100 calculates an offset amount based on the output of the ADC, and sends an instruction to change the offset amount to be removed by the offset removal circuit 205, that is, the voltage value of the DAC 302, as necessary (step S102). This DAC voltage changing process will be described later.

  Subsequently, Tucom 100 calculates a difference between the first angular velocity data and the zero point in the zero point subtracting unit 208 to obtain second angular velocity data. Thereafter, the second angular velocity data is integrated by the integrating unit 209 (step S103). Subsequently, Tucom 100 performs a zero point calculation process and sets a drive permission flag in the zero point update determination unit 211 (step S104). This zero point calculation process will be described later.

  Next, the zero point update determination unit 211 determines whether the drive permission flag set as a result of the zero point calculation process in step S104 is 0 or 1 (step S105). If the drive permission flag is 1 in the determination in step S105, the zero point update determination unit 211 turns on the display unit 105 (step S106). On the other hand, if it is determined in step S105 that the drive permission flag is 0, the zero point update determination unit 211 turns off the display unit 105 (step S107).

  Next, the Tucom 100 determines whether 250 μs has elapsed (step S108) and waits until 250 μs has elapsed. If 250 μs has elapsed in the determination in step S108, the Tucom 100 determines whether or not a shooting start instruction has been issued from the Mucom 18 (step S109). If it is determined in step S109 that a shooting start instruction has been issued, the process returns to step S101, and the zero point is calculated again. Here, the “shooting start instruction” is a command that the Mucom 18 transmits to the Tucom 100 when the imaging apparatus 1 starts an exposure operation. By receiving this command, the Tucom 100 can detect that the imaging apparatus 1 has entered the exposure operation.

  On the other hand, if the Mucom 18 gives an instruction to start shooting in the determination in step S109, the Tucom 100 performs AD conversion on the output of the amplifier circuit 202 in the ADC 203, and then inputs (2) to the output of the ADC 203 by the offset adder 206. ) To obtain the first angular velocity data by adding the offset amount calculated based on the equation (step S110). Next, Tucom 100 performs a DAC voltage change process similar to step S102 (step S111).

  Thereafter, the Tucom 100 calculates a difference between the first angular velocity data and the zero point in the zero point subtracting unit 208 to obtain second angular velocity data. Thereafter, the second angular velocity data is integrated by the integrating unit 209 (step S112). Thereafter, the Tucom 100 determines, in the exposure time determination processing unit 218, whether or not the exposure time notified from the Mucom 18 is longer than a predetermined time (step S113). If the exposure time is longer than the predetermined time in the determination in step S113, the exposure time determination process 218 permits the HPF process by switching the changeover switch 216 or the cutoff frequency switching unit 217. (Step S114). Thereafter, without performing zero point calculation processing, the blur angle data obtained in the integration unit 209 is subjected to HPF (a high-pass filter is formed by digital filter processing) processing (step S115). On the other hand, if it is determined in step S113 that the exposure time is equal to or shorter than the predetermined time, the exposure time determination process 218 prohibits the HPF process by switching the changeover switch 216 or the cut-off frequency switching unit 217 (step S116).

  Next, Tucom 100 calculates the shake correction amount in the correction amount calculation unit 214 (step S117). Subsequently, the drive determination unit 215 of the Tucom 100 determines whether the drive permission flag is 0 or 1 (step S118). If it is determined in step S118 that the drive permission flag is 1, the drive determination unit 215 drives the shake correction drive mechanism (motor) 103 via the shake correction drive circuit 102 to perform shake correction (step S119). . Thereafter, the process proceeds to step S120. On the other hand, if it is determined in step S118 that the drive permission flag is 0, the process proceeds to step S120 without performing blur correction.

  Thereafter, Tucom 100 determines whether or not 400 μs has elapsed (step S120), and waits until 400 μs has elapsed. If 400 μs has elapsed in the determination in step S120, Tucom 100 determines whether or not an instruction to end shooting has been issued from Mucom 18 (step S121). If it is determined in step S121 that no shooting end instruction has been issued, the process returns to step S110, and shooting (exposure) is continued. On the other hand, if it is determined in step S121 that a shooting end instruction has been issued, the process returns to step S101. Here, the “shooting end instruction” is a command that the Mucom 18 transmits to the Tucom 100 when the exposure operation of the imaging apparatus 1 is ended. By receiving this command, Tucom 100 can detect the end of the exposure operation.

  Next, the DAC voltage changing process in step 102 and step S108 in FIG. 7 will be further described. FIG. 8 is a flowchart showing the DAC voltage changing process. 8 is performed in the offset amount calculation unit 204.

  The offset amount calculation unit 204 first sets the variable ad to the AD conversion input value from the ADC 203 (step S201). Next, the offset amount calculation unit 204 determines whether or not the variable ad exceeds a predetermined value, for example, 2.0 V (step S202). When the variable ad is 2.0 V or less in the determination in step S202, the offset amount calculation unit 204 determines whether or not the variable ad is less than a predetermined value, for example, 1.0 V (step S203). In the determination of step S203, when the variable ad is 1.0 V or more, the offset amount calculation unit 204 determines that the offset removal amount is appropriate and the DAC voltage does not need to be changed, and the process of FIG. And return to FIG.

  On the other hand, if it is determined in step S202 that the variable ad exceeds 2.0V, the offset amount calculation unit 204 determines that the offset removal amount is insufficient and increases the output of the DAC 302 by αV so as to increase by αV. An instruction is sent to (step S204). If the variable ad is less than 1.0 V in the determination in step S203, the offset amount calculation unit 204 determines that the offset removal amount is excessive and outputs the output of the DAC 302 of the offset removal circuit 205 to αV. An instruction is sent to the DAC 302 so as to reduce only by (step S205). After adjusting the voltage of the DAC 302 as described above, the processing of FIG. 8 is terminated and the processing returns to FIG.

  Next, the zero point calculation process in step S104 of FIG. 7 will be further described. FIG. 9 is a flowchart showing the zero point calculation process.

  First, the zero point update determination unit 211 determines whether or not a predetermined averaging time β seconds has elapsed (step S301). If β seconds have not elapsed, the process of FIG. 9 is terminated and the process returns to the process of FIG. On the other hand, in the determination in step S301, when β seconds have elapsed, the zero point update determination unit 211 determines whether or not the output of the integration unit 209 exceeds a predetermined value (step S302). Normally, a new zero point is calculated by the method of calculating the average value of the second angular velocity data described above. However, if the output of the integrating unit 209 exceeds a predetermined value in the determination of step S302, A zero point is calculated by a method of calculating an average value of the first angular velocity data. That is, in this case, the zero point update determination unit 211 calculates the zero point using the output of the averaging unit 207 (step S303).

  On the other hand, if it is determined in step S302 that the output of the integrating unit 209 does not exceed the predetermined value, the zero point is calculated by the above-described method 2. However, prior to the calculation of the zero point, the zero point update determination unit 211 determines whether or not the imaging apparatus 1 is in a stationary state depending on whether or not the slope of the integration data output from the integration unit 209 is constant. Determination is made (step S308). If the slope of the integral data is not constant in the determination in step S308, the zero point update determination unit 211 ends the process of FIG. 9 without updating the zero point update unit 212. On the other hand, when the slope of the integral data is constant in the determination in step S308, the zero point update determination unit 211 calculates the zero point using the output of the integration unit 209 (step S304).

Here, the reason why the determinations in steps S302 and S308 are performed will be described with reference to FIGS.
When the imaging apparatus 1 is in a stationary state, the first angular velocity data is substantially constant with the actual zero point (the zero point to be calculated from now) as the center, as shown in FIG. The integral data from the integration unit 209 is obtained by integrating the difference (zero point error) between the actual zero point and the already calculated zero point (zero point before update). In this case, the integral data is It can be approximated by a straight line as shown in FIG. In FIG. 10B, it can be seen that the amount of change (slope) of the integral data at each point y1, y2,... Y5 is constant. Further, the straight line shown in FIG. 10B has a smaller slope as the zero point error is smaller, and the slope is larger as the zero point error is larger.

  Here, the averaging unit 207 is provided with a buffer for storing the addition result of the first angular velocity data, and the division unit 210 has a buffer for storing the integration result of the integration unit 209. Is provided. Normally, the buffer overflows in a shorter time in the method 1 described above, but if the zero point error is large, the buffer overflows in a time shorter in the method 2 described above. Since the accuracy of zero point calculation increases as the averaging time increases, in the first embodiment, the determination in step S302 is performed, and the output of the integrating unit 209 exceeds a predetermined value that causes the buffer to overflow. In such a case, the zero point is calculated by the method 1 described above, and the zero point is calculated by the method 2 described above when the output of the integrating unit 209 is equal to or less than a predetermined value.

  Further, when the imaging device 1 is not in a stationary state, the first angular velocity data is not constant as shown in FIG. 11A, and therefore the slope of the integrated data is not constant as shown in FIG. That is, it can be determined whether or not the imaging apparatus 1 is stationary by determining whether or not the slope of the integral data is constant. Then, by calculating the zero point only when the slope of the integral data is constant, that is, when the imaging apparatus 1 is stationary, it is possible to increase the accuracy of the zero point calculation.

  Whether or not the slope of the integral data in step S304 is constant is determined according to the flowchart of FIG. First, the zero point update determination unit 211 calculates the overall slope “dave” by calculation of yn ÷ n (step S401). Here, n is the number of samplings, and yn is the nth integration data.

  Next, the zero point update determination unit 211 calculates a difference d1 between the first integration data y1 and the initial value y0 of the integration data (step S402). Then, the zero point update determination unit 211 determines whether or not d1 is between “dave−γ” and “dave + γ” (step S403). The zero point update determination unit 211 repeats the operations of step S402 to step S403 from i = 1 to n, and determines that the slope is constant when all of d1 to dn are between dave−γ and dave + γ. .

  Here, it returns to description of FIG. 9 again. When the zero point is calculated in either step S303 or step S304, the zero point update determination unit 211 determines that the difference (zero point error) between the newly calculated zero point and the already calculated zero point is a predetermined value δ. It is determined whether or not the following is true (step S305). If the zero point error is equal to or less than δ in the determination in step S305, the zero point update determination unit 211 sets the drive permission flag to 1 (step S306), assuming that the effect of the shake correction operation is high (step S306), and the process of FIG. Exit. On the other hand, if the zero point error exceeds δ in the determination in step S305, the zero point update determination unit 211 sets the drive permission flag to 0, assuming that the effect of the blur correction operation is low (step S307). The process of FIG. 9 is terminated.

Here, the reason why the effect of the blur correction operation is low when the zero point error is large will be described with reference to FIG.
As described above, assuming that a blur angular velocity signal such as that shown in FIG. 13A occurs during exposure of a still image, the blur correction amount is integrated after subtracting the zero point component Δω ₀ from the blur angular velocity signal. To obtain a shake angle signal, and obtain it based on this shake angle signal. Therefore, when the error of the zero point is large, the integration is performed in a state where the zero point component is included, so that the blur angle signal has a waveform as shown in FIG. 13B, and a correct blur angle signal cannot be obtained. . On the other hand, when the error at the zero point is small, the zero point component is not integrated, so that a correct blur angle signal can be obtained as shown in FIG.

  As described above, according to the first embodiment, by setting whether or not the HPF process is performed on the output of the integration unit 209 according to the exposure time, a constant camera shake correction is performed regardless of the exposure time. An effect can be obtained.

  Here, in the first embodiment, the blur correction in still image shooting is described as an example, but the method of the first embodiment can also be applied to moving image shooting.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. The second embodiment is an example in which blur correction is performed not only during still image shooting but also during live view display prior to still image shooting. Here, the through image display is to display the image from the CCD unit 20 on the liquid crystal monitor 30 in real time with the shutter 15 opened prior to still image shooting. The configurations of the imaging apparatus and the camera shake correction unit are the same as those shown in FIGS.

  FIG. 14 is a flowchart illustrating the operation of the Tucom 100 according to the second embodiment. When the power SW is turned on by the user and the main power supply of the imaging apparatus 1 is turned on, the Tucom 100 first takes the output of the amplifier circuit 202 by AD conversion in the ADC 203, and then converts the output to the ADC 203 by the offset adder 206. The first angular velocity data is obtained by adding the offset amount calculated based on the equation (2) (step S501). Next, the Tucom 100 performs the DAC voltage changing process described with reference to FIG. 8 (step S502).

  Subsequently, Tucom 100 calculates a difference between the first angular velocity data and the zero point in the zero point subtracting unit 208 to obtain second angular velocity data. Thereafter, the second angular velocity data is integrated by the integrating unit 209 (step S503). Next, the Tucom 100 determines whether the current operation state of the imaging apparatus 1 is displaying a through image or shooting (exposure) (step S504). If the through image is being displayed in the determination in step S504, the Tucom 100 performs the zero point calculation process described with reference to FIG. 9 (step S505), and then proceeds to step S506. On the other hand, if it is determined in step S504 that exposure is being performed, the process proceeds to step S506 without performing zero point calculation processing.

  Next, HPF processing is performed on the shake angle data obtained in the integration unit 209 (step S506). Next, Tucom 100 calculates the shake correction amount in the correction amount calculation unit 214 (step S507).

  Subsequently, the drive determination unit 215 of the Tucom 100 determines whether the drive permission flag is 0 or 1 (step S508). If it is determined in step S508 that the drive permission flag is 1, the drive determination unit 215 drives the shake correction drive mechanism 103 via the shake correction drive circuit 102 to perform shake correction (step S509). Thereafter, the process proceeds to step S510. On the other hand, if it is determined in step S508 that the drive permission flag is 0, the process proceeds to step S510 without performing blur correction. The drive permission flag is set in the zero point calculation process in step S505.

  Thereafter, the Tucom 100 determines whether 400 μs has elapsed (step S510) and waits until 400 μs has elapsed. In step S510, when 400 μs has elapsed, the Tucom 100 determines whether or not a shooting start instruction has been issued from the Mucom 18 (step S511). Here, the “shooting start instruction” is a command that the Mucom 18 transmits to the Tucom 100 when the imaging apparatus 1 starts an exposure operation. By receiving this command, the Tucom 100 can detect the exposure start timing. In the determination in step S511, when an instruction to start photographing is given, Tucom 100 sets the presence or absence of HPF processing or the constant (cutoff frequency) of HPF 213 according to the exposure time. This setting is performed as follows. That is, the Tucom 100 determines in the exposure time determination processing unit 218 whether or not the exposure time notified from the Mucom 18 is equal to or shorter than a first predetermined time (for example, 1 s) (step S512). If it is determined in step S512 that the exposure time is 1 s or less, the exposure time determination process 218 switches the changeover switch 216 to the correction amount HPF213 side or switches the changeover switch 216 to the HPF213 side and sets the cutoff frequency to 0 Hz. Set (step S513). In effect, the cutoff frequency is made zero by not performing the HPF process. In this case, the HPF process is not performed. On the other hand, if it is determined in step S512 that the exposure time exceeds 1 s, the exposure time determination processing 218 performs the exposure time not longer than a second predetermined time (for example, 4 s) that is longer than the first predetermined time. It is determined whether or not there is (step S514). If it is determined in step S514 that the exposure time is 4 s or less, the exposure time determination process 218 switches the changeover switch 216 to the HPF 213 side and sets the cutoff frequency to a first predetermined value (for example, 0.5 Hz). (Step S515). If it is determined in step S514 that the exposure time exceeds 4 s, the exposure time determination process 218 switches the changeover switch 216 to the HPF 213 side and sets the cutoff frequency to a second predetermined value lower than the first predetermined value. (For example, 0.05 Hz) is set (step S516).

  Such a correspondence relationship between the exposure time and the cut-off frequency is preferably stored as table data in a FlashRom (not shown) of the Tucom 100, and a configuration that can be changed as necessary is desirable.

  In the determination in step S511, if no shooting start instruction is issued, the Tucom 100 determines whether a shooting end instruction is issued from the Mucom 18 (step S517). Here, the “shooting end instruction” is a command that the Mucom 18 transmits to the Tucom 100 when the exposure operation of the imaging apparatus 1 is ended. By receiving this command, Tucom 100 can detect the end of the exposure operation. If it is determined in step S517 that an instruction to end shooting is given, the constant of HPF 213 is set to a constant for displaying a through image, and the position of CCD unit 20 is returned to the initial position (for example, the center position) (step S517). S518), the process returns to step S501. On the other hand, if it is determined in step S517 that no shooting end instruction has been issued, the process returns to step S501.

  According to the second embodiment as described above, not only switching whether to perform the HPF process according to the exposure time but also the cutoff frequency when performing the HPF process according to the length of the exposure time. By setting, it is possible to perform more appropriate blur correction than in the first embodiment.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention.

  Further, the above-described embodiments include various stages of the invention, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some configuration requirements are deleted from all the configuration requirements shown in the embodiment, the above-described problem can be solved, and this configuration requirement is deleted when the above-described effects can be obtained. The configuration can also be extracted as an invention.

1 is a block diagram illustrating a configuration of an imaging apparatus including a shake correction apparatus according to a first embodiment of the present invention. It is a block diagram which shows the schematic structure of a camera shake correction unit. It is a figure shown about the detailed structure of a camera-shake correction unit. It is an amplifier circuit, an offset removal circuit, and its periphery circuit diagram. It is the figure shown about the waveform reproduced from the input waveform of ADC, the output waveform of DAC, and the input of ADC, and the output of DAC. 6A is a diagram showing a shift in the gyro sensor output due to the influence of temperature drift or the like, and FIG. 6B is a diagram showing an input waveform to an ideal correction amount calculation unit. (C) is a diagram showing the deviation of the integration unit output due to the influence of temperature drift or the like, and FIG. 6 (d) is a diagram showing the error between the integration unit output where the deviation has occurred and the ideal waveform. It is a flowchart shown about operation | movement of Tucom in the 1st Embodiment of this invention. It is a flowchart shown about a DAC voltage change process. It is a flowchart shown about a zero point calculation process. FIG. 10A is a diagram illustrating an example of the first angular velocity data in a state where the imaging device is stationary, and FIG. 10B is a diagram illustrating a result of integrating FIG. 10A. FIG. 11A is a diagram illustrating an example of the first angular velocity data in a state where the imaging apparatus is not stationary, and FIG. 11B is a diagram illustrating a result of integrating FIG. 11A. It is a flowchart shown about the process for determining whether an inclination is constant. FIG. 13A is a diagram showing a blur angular velocity signal when there is a zero point error, FIG. 13B is a diagram showing a result of integrating FIG. 13A, and FIG. 13C is zero. It is a figure which shows the result of having integrated the blurring angular velocity signal when there is no point error. It is a flowchart shown about operation | movement of Tucom in the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Imaging device, 18 ... Microcomputer for camera control (Mucom), 20 ... CCD unit, 21 ... CCD interface circuit, 22 ... Image processing controller, 40 ... Camera shake correction unit, 100 ... Microcomputer for camera shake correction control ( Tucom), 101 ... blur detection unit, 102 ... blur correction drive circuit, 103 ... blur correction drive mechanism, 104 ... position detection sensor, 105 ... display unit, 201 ... gyro sensor, 202 ... amplifier circuit, 203 ... AD converter ( ADC), 203 ... offset removing circuit, 204 ... offset amount calculating unit, 205 ... offset removing circuit, 206 ... offset adding unit, 207 ... averaging unit, 208 ... zero point subtracting unit, 209 ... integrating unit, 210 ... dividing unit 211 ... Zero point update determination unit, 212 ... Zero point update unit, 213 ... Hyper Filter (HPF), 214 ... Correction amount calculation unit, 215 ... Drive determination unit, 216 ... Changeover switch, 217 ... Cut-off frequency switching unit, 218 ... Exposure time determination processing unit, 301 ... Operational amplifier, 302 ... DA converter (DAC) )

Claims (6)

Imaging means for acquiring image data of a subject;
Detection means for detecting blur;
High-pass filter processing means for performing high-pass filter processing on the output of the detection means;
Correction means for performing a shake correction operation for preventing deterioration of the image data of the subject due to shake;
Exposure control means for controlling the exposure operation of the imaging means;
Control means for executing the blur correction operation by the correction means during the exposure operation of the imaging means;
Comprising
The control means is either an output of the detection means via the high-pass filter processing means or an output of the detection means not via the high-pass filter processing means according to an exposure time set prior to the exposure operation. An imaging apparatus, wherein one is selected, and the correction means is caused to execute the blur correction operation based on the selected output.   The control means selects the output of the detection means via the high-pass filter processing means when the exposure time is longer than a predetermined time, and the high-pass filter processing means when the exposure time is shorter than the predetermined time. The image pickup apparatus according to claim 1, wherein an output of the detection unit that does not pass through is selected. Imaging means for acquiring image data of a subject;
Detection means for detecting blur;
High-pass filter processing means for performing high-pass filter processing on the output of the detection means;
Correction means for performing a shake correction operation for preventing deterioration of the image data of the subject due to shake;
Exposure control means for controlling the exposure operation of the imaging means;
Control means for executing the blur correction operation by the correction means during the exposure operation of the imaging means;
Comprising
The control means changes the cutoff frequency used for the high-pass filter processing of the high-pass filter processing means according to the exposure time set prior to the exposure operation, and the high-pass filter processing means changes the cutoff frequency. An image pickup apparatus that causes the correction means to perform the shake correction operation based on the output of the image.   According to the exposure time set prior to the exposure operation, the control means may output either the output of the detection means via the high-pass filter processing means or the output of the detection means not via the high-pass filter processing means. The imaging apparatus according to claim 3, further comprising a switching unit that selects one of them and causes the correction unit to execute the shake correction operation based on the selected output.   The switching means selects the output of the detection means via the high-pass filter processing means when the exposure time is longer than a predetermined time, and the high-pass filter processing means when the exposure time is shorter than the predetermined time. The image pickup apparatus according to claim 4, wherein an output of the detection unit that does not pass through is selected.   4. The imaging apparatus according to claim 3, wherein the control unit changes the cutoff frequency when the exposure time is long to be lower than the cutoff frequency when the exposure time is short.

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