JP2010226395A - Imaging apparatus, control method thereof, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove a foreign substance in a short period of time with reduced power consumption, the foreign substance affecting focusing using the outputs of focus-detecting pixels of an imaging element. <P>SOLUTION: An imaging apparatus includes an optical member which transmits light from an imaging optical system to the imaging plane of an imaging element and covers the imaging plane to prevent a foreign substance from being adhered to the imaging plane. When removing the foreign substance adhered to the optical member, the foreign substance affecting a focus-detecting pixel couple, the imaging apparatus controls the vibration of the optical member so that the node position of a standing wave of the optical member generated by vibrating the optical member and the position of the optical member transmitting light to the focus-detecting pixel couple do not overlap each other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, a control method thereof, and a program.

  In an imaging apparatus such as a digital still camera that captures an object image by converting it into an electrical signal, the imaging light beam is received by the imaging device, and a photoelectric conversion signal output from the imaging device is converted into image data, and a memory card or the like. Is recorded on the recording medium. As the image sensor, a charge coupled device (CCD), a complementary metal oxide semiconductor (CMOS) image sensor, or the like is used.

  In such an imaging apparatus, an optical member such as an optical low-pass filter or an infrared absorption filter is disposed on the subject side of the imaging element. When foreign matter such as dust (hereinafter referred to as dust) adheres to the surface of these optical members, the photographing light flux that has passed through the lens is blocked by the dust, and a shadow is formed on the image sensor. As a result, the appearance of the image is degraded.

  Particularly in a single-lens reflex digital still camera with interchangeable lenses, mechanical operating parts such as shutters and quick return mirrors are arranged near the image sensor, and dust generated from these operating parts adheres to the surface of the optical member. There are things to do. In addition, when the lens is exchanged, dust may enter the main body from the opening of the lens mount and adhere to it.

  In order to avoid such adhesion of dust, Patent Document 1 is provided with a dustproof filter that transmits a photographic light beam on the subject side of the image sensor, and is vibrated by a piezoelectric element to adhere to the surface of the dustproof filter. A technique for removing the dust that has been removed has been proposed. Specifically, a piezoelectric element for applying vibration to a peripheral portion of a circular dustproof filter (a dustproof optical member) is disposed. Then, the dust attached to the surface of the optical member is removed by switching the primary vibration mode and the secondary vibration mode having point-symmetric nodes on the optical member to resonate the dustproof filter.

  Further, as an automatic focus detection (AF) method for a digital still camera, a phase difference detection method (referred to as a shift method) is generally employed. In the phase difference detection method, the light beam that has passed through the exit pupil of the imaging optical system is divided into two, and the two divided light beams are received by a set of focus detection sensors. Then, the amount of shift in the focus direction of the imaging optical system is directly obtained by detecting the amount of shift in the signal output according to the amount of received light, that is, the amount of relative positional shift in the beam splitting direction. Therefore, once the accumulation operation is performed by the focus detection sensor, the amount and direction of the focus shift can be obtained, and a high-speed focus adjustment operation is possible.

  In recent years, an image sensor having a function of the above-described phase difference detection method has been developed (Patent Document 2). In the imaging device of Patent Document 2, a pupil division function is provided by dividing a light receiving portion of some pixels into two in the left-right direction or the up-down direction. These pixels are used as focus detection pixels (AF sensors), and phase difference type focus detection is performed by arranging the pixels at a predetermined interval between the imaging pixel groups.

JP 2003-338916 A JP 2000-292686 A

  In the imaging device described in Patent Document 2, when a shadow of dust adhering to the surface of an optical member such as an optical low-pass filter or an infrared absorption filter overlaps a focus detection pixel, focus detection accuracy (defocus detection accuracy) There is a problem that decreases.

  This state will be described with reference to FIGS. 18 (a) and 18 (b). Normally, a plurality of focus detection pixels are used in combination as a line sensor. Images obtained by receiving the light beams from the exit pupil of the imaging optical system divided into two by a pair of line sensors are referred to as an A image and a B image, respectively. FIG. 18A is a diagram for explaining the correlation calculation between the A image and the B image for focus detection when the line sensor for obtaining the A image is not affected by dust.

  As shown in FIG. 18A, after plotting the A and B images by a set of line sensors and shaping the waveform, the prediction value is calculated by correlation calculation, and the defocus amount D1 is based on the result. Is obtained. In this correlation calculation, the line sensor that obtains the A image is not affected by dust, so the shapes of the A and B images are substantially the same, and the focus detection accuracy is high.

  On the other hand, FIG. 18B is a diagram for explaining the correlation calculation of the A image and the B image for focus detection when the influence of dust is generated on the Nth pixel of the line sensor that obtains the A image. . As shown in FIG. 18B, a defocus amount D2 is obtained by plotting the A and B images by a pair of line sensors and performing correlation calculation. However, since the output of the Nth pixel in the A image is reduced by dust, the defocus amount D2 is different from the defocus amount D1 when there is no influence of dust. Specifically, a deviation of D2-D1 occurs. Accordingly, the focus detection causes an error of D2-D1 and the focus detection accuracy is lowered.

  Here, when the dust on the optical member is removed using the dust removing method described in Patent Document 1, it takes time to remove the dust because it tries to remove all the dust on the entire optical member. If dust is removed from the entire optical member every time AF processing is performed, the AF processing takes time, which is inconvenient for the user. Further, only dust that has overlapped with the focus detection pixels needs to be removed. However, since the entire optical member is intended to be completely removed, power consumption is increased accordingly.

  The present invention has been made for the purpose of solving at least one of the problems of the prior art. An object of the present invention is to provide an imaging apparatus capable of removing dust that affects focus adjustment using the output of the focus detection pixel of the imaging element in a short time with low power consumption, a control method thereof, and a program With the goal.

  The object is to have a plurality of pixels for photoelectric conversion of a subject image arranged on an imaging surface, and a part of the plurality of pixels includes an imaging element that forms a focus detection pixel pair, and outputs the focus detection pixels. An imaging device that performs focus detection based on the optical member, disposed in front of the imaging device, transmits light reaching the imaging surface, vibration means that vibrates the optical member, and the optical by the vibration means Control means for controlling the vibration of the member, and when the control means removes the foreign matter adhering to the optical member affecting the focus detection pixels, the optical member is generated by the vibration of the optical member. The vibration of the optical member is controlled so as not to overlap the node position of the standing wave and the position of the optical member that transmits the light to the focus detection pixels. It is.

  In addition, the object is that a plurality of pixels that photoelectrically convert a subject image are arranged on the imaging surface, a part of the plurality of pixels is arranged in front of the imaging element, an imaging element that constitutes a focus detection pixel, An imaging apparatus control method comprising: an optical member that transmits light reaching the imaging surface; and a vibration unit that vibrates the optical member, and performs focus detection based on an output of the focus detection pixel pair, A control step of controlling the vibration of the optical member by the vibration means, and when the control step removes foreign matter attached to the optical member affecting the focus detection pixels, the optical member vibrates. According to the present invention, the vibration of the optical member is controlled so that the node position of the generated standing wave of the optical member does not overlap the position of the optical member that transmits the light to the focus detection pixels. Imaging Also achieved by a control method of the location.

  According to the present invention, it is possible to remove foreign matter that affects the focus adjustment using the output of the focus detection pixel of the image sensor in a short time with less power consumption.

It is a front side perspective view of the image pick-up device main part concerning this embodiment. It is a back side perspective view of the image pick-up device main part concerning this embodiment. It is a block diagram which shows the electric constitution of the imaging device which concerns on this embodiment. It is a disassembled perspective view which shows schematic structure inside the imaging device main body for showing the holding structure around the imaging unit concerning this embodiment. It is a disassembled perspective view which shows the structure of the imaging unit which concerns on this embodiment. (A) is a figure which shows the surface (F surface), back surface (B surface), and side surface of the piezoelectric element which concerns on this embodiment, (b) is a perspective view at the time of seeing a piezoelectric element from the F surface side. It is. It is a figure for demonstrating arrangement | positioning of an electrode. It is a figure showing signs that the vibration shape of the optical low pass filter by the piezoelectric element concerning this embodiment is shown in the front and the side, and the wave front of vibration occurred in the lengthwise direction. (A) is a top view of the imaging pixel of the imaging device which concerns on this embodiment, (b) is sectional drawing of the imaging pixel of the imaging device which concerns on this embodiment. (A) is a top view of the focus detection pixel of the image sensor according to the present embodiment, and (b) is a cross-sectional view of the focus detection pixel of the image sensor according to the present embodiment. It is a top view of the pixel for focus detection of the image sensor concerning this embodiment, and (b) is a sectional view of the pixel for focus detection of the image sensor concerning this embodiment. It is a figure for demonstrating the arrangement | positioning rule of the minimum unit of the image pick-up element which concerns on this embodiment. It is a figure for demonstrating the arrangement | positioning rule of the cluster in the whole area | region of the image pick-up element based on this embodiment. (A) is a figure explaining the pixel group at the time of performing the focus detection of the lateral shift according to the present embodiment, and (b) illustrates the pixel group at the time of performing the focus detection of the vertical shift according to the present embodiment. It is a figure to do. It is a figure which illustrates a mode that the shadow of dust is reflected in the pixel for focus detection which concerns on this embodiment. It is a figure showing the position of the dust adhering on the pixel for imaging in the imaging region which concerns on this embodiment, the pixel for focus detection, and an optical low-pass filter, (a) is a figure showing the state before removing dust. (b) is a figure showing the state after removing dust, (c) is a figure showing the state after removing dust, and (d) is a figure showing the state after removing dust. 6 is a flowchart of an AF cleaning mode according to the present embodiment. It is a modification of the flowchart of AF cleaning mode which concerns on this embodiment. (A) is the schematic for demonstrating the correlation calculation for focus detection, (b) is the schematic for demonstrating the correlation calculation for focus detection.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments. Further, the embodiment of the present invention shows the most preferable mode of the invention, and does not limit the scope of the invention.

<Configuration of imaging device>
First, an imaging apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2 are external views of the imaging apparatus according to the present embodiment. FIG. 1 is a perspective view of the imaging apparatus main body 1 viewed from the front side (subject side), and shows a state where an imaging lens unit (details will be described later) is removed.

  FIG. 2 is a perspective view of the imaging apparatus main body 1 viewed from the back side (user side). As shown in FIGS. 1 and 2, the imaging apparatus according to the present embodiment is a single-lens reflex digital still camera that is used by mounting an imaging lens unit on the imaging apparatus body 1.

  As shown in FIG. 1, the imaging apparatus main body 1 is provided with a grip portion 1 a that protrudes toward the subject side so that the user can easily grip it stably during imaging. An imaging lens unit is detachably fixed to the mount portion 2 of the imaging apparatus body 1. The mount contact 21 enables control signals, status signals, data signals, and the like to be communicated between the imaging apparatus body 1 and the imaging lens unit, and supplies power from the imaging apparatus body 1 to the imaging lens unit side.

  The mount contact 21 may be configured not only to perform electrical communication but also to optical communication, voice communication, and the like. Next to the mount portion 2 of the imaging apparatus main body 1, a lens lock release button for releasing the lock for fixing the imaging lens unit to the imaging apparatus main body 1 by pushing in when removing the imaging lens unit from the imaging apparatus main body 1. 4 is arranged.

  A mirror box 5 that guides an imaging light beam that has passed through the imaging lens is provided in the imaging apparatus body 1, and a main mirror 6 (quick return mirror) is provided in the mirror box 5. The main mirror 6 is held at a 45 ° angle with respect to the imaging optical axis to guide the imaging light beam in the direction of the penta roof mirror, and held at a position retracted from the imaging light beam to guide it in the direction of the imaging element. The state to be taken can be taken. Details of the penta roof mirror and the image sensor will be described later.

  A release button 7, a main operation dial 8, and an operation mode setting button 10 are arranged on the grip unit 1 a side of the upper part of the imaging apparatus main body. The release button 7 is an activation switch for starting imaging. The main operation dial 8 is a dial for the user to set the shutter speed and the lens aperture value according to the operation mode at the time of imaging. The operation mode setting button 10 is a button for the user to set the operation mode of the imaging system. Some of the operation results of these operation members are displayed on the LCD display panel 9.

  The release button 7 is configured such that the first switch 7a is turned on in the first stroke (half-pressed state) and the second switch 7b is turned on in the second stroke (full-pressed state) (first switch 7a, first switch). (See FIG. 3 for the 2 switch 7b). In addition, the operation mode setting button 10 is used for setting an operation mode, such as whether continuous shooting or only one frame is captured when the release button 7 is pressed once, setting a self-imaging mode, and the like. It is a button. The setting status of the operation mode setting button 10 is displayed on the LCD display panel 9.

  A strobe unit 11 that hops up with respect to the imaging apparatus main body 1, a shoe groove 12 for attaching an external flash, and a flash contact 13 are provided at the center of the upper part of the imaging apparatus main body. An imaging mode setting dial 14 for a user to set an imaging mode is arranged on the right side of the upper part of the imaging apparatus main body.

  An external terminal lid 15 that can be opened and closed is provided on the side surface opposite to the grip portion 1 a of the imaging apparatus main body 1. Inside the external terminal lid 15, a video signal output jack 16 and a USB output connector 17 are housed as external interfaces.

  As shown in FIG. 2, a finder eyepiece window 18 is provided above the back surface of the imaging apparatus main body 1. Further, a color liquid crystal monitor 19 capable of displaying an image is provided near the center of the back surface of the imaging apparatus main body 1.

  A sub operation dial 20 is arranged next to the color liquid crystal monitor 19. The sub operation dial 20 plays an auxiliary role of the function of the main operation dial 8 and is a dial for the user to make settings related to the auxiliary role. For example, the sub operation dial 20 is used in the AE mode of the imaging apparatus to set an exposure correction amount with respect to an appropriate exposure value calculated by automatic exposure.

  In the manual mode in which the user sets the shutter speed and the lens aperture value, the shutter speed is set with the main operation dial 8 and the lens aperture value is set with the sub operation dial 20. The sub operation dial 20 is also used when selecting a captured image to be displayed on the color liquid crystal monitor 19.

  Further, a main switch 43 for starting or stopping the operation of the image pickup apparatus and a cleaning instruction operation member 44 for operating the cleaning mode are disposed on the back surface of the image pickup apparatus main body 1. The cleaning instruction operation member 44 is for a user to give an instruction to operate a cleaning mode in which foreign matters such as dust adhered to the surface of the optical low-pass filter 410 (details will be described later) are removed.

  The cleaning mode may be arbitrarily operated using the cleaning instruction operation member 44, or may be automatically operated when the main switch 43 is turned on, when it is turned off, or at both timings.

  FIG. 3 is a block diagram illustrating a main electrical configuration of the imaging apparatus according to the present embodiment. In addition, the same code | symbol is attached | subjected to the part which is common in FIG. 1, FIG. As shown in FIG. 3, the imaging apparatus main body 1 includes a central processing unit (hereinafter referred to as “MPU”) MPU 100 including a microcomputer.

  The MPU 100 controls operation of the imaging apparatus, and executes various processes and instructions for each element. The MPU 100 incorporates an EEPROM 100a (Electrically Erasable and Programmable Read Only Memory). The EEPROM 100a stores time information of the time measuring circuit 109 and other information.

  Connected to the MPU 100 are a mirror drive circuit 101, a focus detection circuit 102, a shutter drive circuit 103, a video signal processing circuit 104, a switch sense circuit 105, and a photometric circuit 106. The MPU 100 is connected to an LCD drive circuit 107, a battery check circuit 108, a time measurement circuit 109, a power supply circuit 110, and a piezoelectric element drive circuit 111. These circuits operate under the control of the MPU 100.

  The MPU 100 communicates with the lens control circuit 201 in the imaging lens unit 200 a via the mount contact 21. The lens control circuit 201 has a function of transmitting a signal to the MPU 100 via the mount contact 21 when the imaging lens unit 200a is connected. Thereby, the lens control circuit 201 communicates with the MPU 100 and drives the imaging lens 200 and the diaphragm 204 in the imaging lens unit 200a via the AF driving circuit 202 and the diaphragm driving circuit 203. For convenience, FIG. 3 illustrates only one imaging lens 200, but the imaging lens unit 200a is actually composed of a large number of lens groups.

  The AF drive circuit 202 is configured by, for example, a stepping motor, and changes the position of the focus lens in the imaging lens 200 under the control of the lens control circuit 201 so as to adjust the imaging light beam to focus on the imaging element 33. The aperture driving circuit 203 is configured by, for example, an auto iris or the like, and changes the aperture 204 under the control of the lens control circuit 201 to obtain an optical aperture value.

  The main mirror 6 guides the imaging light beam passing through the imaging lens 200 to the penta roof mirror 22 and transmits a part thereof while being held at an angle of 45 ° with respect to the imaging optical axis shown in FIG. Guide to submirror 30. The sub mirror 30 guides the imaging light beam transmitted through the main mirror 6 to the focus detection sensor unit 31.

  The mirror drive circuit 101 is composed of, for example, a DC motor and a gear train, and moves the main mirror 6 to either a position where the subject image can be observed by the finder or a position where the subject image is retracted from the imaging light beam. When the main mirror 6 moves, the sub mirror 30 simultaneously moves to either the position for guiding the imaging light beam to the focus detection sensor unit 31 or the position for retracting from the imaging light beam. Specifically, the mirror drive circuit 101 retracts the main mirror 6 and the sub mirror 30 when performing imaging with the imaging device 33 so that the imaging light flux from the imaging lens unit 200 a reaches the imaging device 33.

  The focus detection sensor unit 31 includes a field lens, a reflection mirror, a secondary imaging lens, a diaphragm, a line sensor composed of a plurality of CCDs (all not shown) arranged near the imaging surface, and a phase difference method. Focus detection is performed. A signal output from the focus detection sensor unit 31 is supplied to the focus detection circuit 102, converted into a subject image signal, and then transmitted to the MPU 100.

  The MPU 100 performs focus detection calculation by the phase difference detection method based on the subject image signal. By this focus detection calculation, the MPU 100 obtains the defocus amount and the defocus direction, and moves the focus lens in the imaging lens 200 to the in-focus position via the lens control circuit 201 and the AF drive circuit 202.

  The penta roof mirror 22 converts the imaging light beam reflected by the main mirror 6 into an erect image by reflection. The user can observe the subject image from the viewfinder eyepiece window 18 via the viewfinder optical system including the imaging lens 200, the main mirror 6, and the penta roof mirror 22.

  The penta roof mirror 22 also guides part of the imaging light flux to a photometric sensor 23 such as a photoelectric conversion element. The photometric circuit 106 obtains the output of the photometric sensor 23, converts it into a luminance signal for each area on the observation surface, and outputs it to the MPU 100. The MPU 100 calculates an exposure value based on the luminance signal.

  The shutter unit 32 (mechanical focal plane shutter) has a shutter front curtain (not shown) in the light shielding position and a shutter rear curtain (not shown) in the exposure position when the user observes the subject image with the viewfinder. Next, at the time of image capturing, the shutter front curtain performs an exposure run in which the shutter curtain moves from the light shielding position to the exposure position, and allows light from the subject to pass through, thereby exposing the image sensor 33.

  After the elapse of a desired shutter speed, the shutter rear curtain moves from the exposure position to the light shielding position to perform light shielding travel, thereby completing the imaging. In the shutter unit 32, the travel of the shutter front curtain and the shutter rear curtain described above is controlled by the shutter drive circuit 103 that has received an instruction from the MPU 100.

  The imaging unit 400 is a unit in which an optical low-pass filter 410, a piezoelectric element 430 that is a piezoelectric member, and an imaging element 33 are combined with other components described later. The image sensor 33 photoelectrically converts a subject image, and a CMOS image sensor is used in this embodiment.

  Although details will be described later, the imaging element 33 is provided with a phase difference detection function in addition to the imaging function. Since the phase difference detection function on the image sensor is mainly used in the live view imaging mode, the use condition is different from that of the focus detection sensor unit 31 mainly used in the normal imaging mode. In addition to the CMOS image sensor in the present embodiment, the image pickup element 33 has various forms such as a CCD type, a CMOS type, and a CID type, and any form of image pickup device may be adopted.

  The optical low-pass filter 410 disposed in front of the image sensor 33 is a single birefringent plate made of quartz and has a rectangular shape. The optical low-pass filter 410 is an optical member that transmits light from the imaging optical system to the imaging surface of the imaging device 33 and covers the imaging surface of the imaging device 33 to prevent dust from adhering to the imaging surface. The piezoelectric element 430 is a single-plate piezoelectric element (piezo element), and is configured to vibrate according to the drive voltage by the piezoelectric element drive circuit 111 that receives an instruction from the MPU 100 and to transmit the vibration to the optical low-pass filter 410. ing.

  The clamp / CDS circuit 34 performs basic analog processing before A / D conversion, and can also change CDS (correlated double sampling) and the clamp level. The AGC 35 (automatic gain adjustment) performs basic analog processing before A / D conversion, and can change the AGC basic level. The A / D converter 36 converts the analog output signal of the image sensor 33 into a digital signal.

  The video signal processing circuit 104 performs overall image processing by hardware such as gamma / knee processing, filter processing, and information composition processing for monitor display on the digitized image data. The monitor display image data from the video signal processing circuit 104 is displayed on the color liquid crystal monitor 19 via the distance measuring circuit 112.

  The video signal processing circuit 104 can also store image data in the buffer memory 37 through the memory controller 38 in accordance with an instruction from the MPU 100. Furthermore, the video signal processing circuit 104 can also perform image data compression processing such as JPEG (Joint Photographic Experts Group). When continuous imaging is performed, such as continuous shooting, image data can be temporarily stored in the buffer memory 37 and unprocessed image data can be sequentially read out through the memory controller 38. As a result, the video signal processing circuit 104 can sequentially perform image processing and compression processing regardless of the transfer speed of the image data input from the A / D converter 36.

  The memory controller 38 has a function of storing the image data input from the external interface 40 in the memory 39 and outputting the image data stored in the memory 39 from the external interface 40. The memory controller 38 stores the image data after the image processing by the video signal processing circuit 104 in the memory 39, and displays the image data stored in the memory 39 on the color liquid crystal monitor 19. It may have a function to output to. The external interface 40 corresponds to the video signal output jack 16 and the USB output connector 17 in FIG. As the memory 39, a flash memory that can be attached to and detached from the imaging apparatus main body 1 is used.

  The switch sense circuit 105 transmits an input signal to the MPU 100 according to the operation state of each switch. The first switch 7a is turned on by the first stroke (half press) of the release button 7. The second switch 7b is turned on by the second stroke (full press) of the release button 7. When the second switch 7b is turned on, an instruction to start imaging is transmitted to the MPU 100.

  The switch sense circuit 105 is connected to the main operation dial 8, the sub operation dial 20, the imaging mode setting dial 14, the main switch 43, and the cleaning instruction operation member 44, and transmits each input signal to the MPU 100. For example, the MPU 100 operates as follows when the user performs a predetermined operation with the imaging mode setting dial 14 or the like and selects the live view imaging mode. The MPU 100 displays the image data sequentially obtained from the image sensor 33 on the color liquid crystal monitor 19 in real time in the valve state where both the shutter front curtain and the rear curtain are in the exposure position.

  The LCD drive circuit 107 drives the LCD display panel 9 and the in-finder liquid crystal display device 41 in accordance with instructions from the MPU 100. The battery check circuit 108 performs a battery check of the power source 42 in accordance with an instruction from the MPU 100 and transmits the result to the MPU 100. The power supply circuit 110 adjusts the amount of power that the power supply 42 supplies to each element in accordance with an instruction from the MPU 100. The power source 42 is a commercial power source, a primary battery, a secondary battery, or the like, and supplies power to each element of the imaging device.

  The time measuring circuit 109 is a circuit that realizes an RTC (Real Time Clock) function. The time measuring circuit 109 measures the time and time from when the main switch 43 is turned off to when it is turned on, and transmits the measurement result to the MPU 100 in accordance with an instruction from the MPU 100. Note that the time measuring circuit 109 may hold an internal power supply separately from the power supply 42 and be able to measure time even when the power supply 42 is not energized.

  The distance measuring circuit 112 is a phase difference type focus detection sensor disposed on the image sensor 33, which is mainly used in the live view imaging mode (details will be described later). The MPU 100 drives the distance measuring circuit 112 and calculates the defocus of the subject from the subject image signal of the distance measuring circuit 112. Based on this calculation result, the MPU 100 moves the focus lens in the imaging lens 200 to the in-focus position via the lens control circuit 201 and the AF drive circuit 202.

<Dust removal structure>
Next, a dust removal structure that vibrates the optical low-pass filter 410 will be described with reference to FIGS. 4 and 5. FIG. 4 is an exploded perspective view showing a schematic configuration inside the imaging apparatus main body 1 for showing a holding structure around the imaging unit 400. FIG. 5 is an exploded perspective view showing the configuration of the imaging unit 400.

  As shown in FIG. 4, the mirror box 5 and the shutter unit 32 are arranged in this order from the subject side on the subject side of the main body chassis 300 that is a skeleton of the imaging device main body 1. An imaging unit 400 is disposed on the user side of the main body chassis 300 opposite to the subject side. The image pickup unit 400 is adjusted and fixed so that the image pickup surface of the image pickup element 33 is parallel to the attachment surface of the mount portion 2 which is a reference to which the image pickup lens unit 200a is attached with a predetermined distance.

  As shown in FIG. 5, the optical low-pass filter 410 is a single birefringent plate made of quartz, and its shape is rectangular. The optical low-pass filter 410 is a vibrating member and corresponds to an optical member disposed in front of the image sensor 33. The optical low-pass filter 410 has a peripheral portion 410b in which the piezoelectric element 430 is disposed in one way of the effective photographing area 410a, and is asymmetric in a direction orthogonal to the imaging optical axis center (camera left-right direction).

  In this way, by setting so that the effective imaging area 410a and the peripheral edge 410b do not overlap, it is ensured that the piezoelectric element 430 does not enter the effective luminous flux of the subject image. Further, the surface of the optical low-pass filter 410 is provided with a conductive coating for providing conductivity and an optical coating such as an antireflection film.

  The piezoelectric element 430 is integrally formed with a plurality of electrodes and has a strip-shaped outer shape. The piezoelectric element 430 is bonded at the peripheral portion 410 b of the optical low-pass filter 410 so that the long side of the piezoelectric element 430 is parallel to the short side (side measurement) of the optical low-pass filter 410. That is, the piezoelectric element 430 is bonded in parallel to the side in the vicinity of one side of the four sides of the optical low-pass filter 410.

  By bonding the piezoelectric element 430 and the optical low-pass filter 410 in this way, the vibration of the piezoelectric element 430 in the vibration mode corresponding to the driving voltage by the piezoelectric element driving circuit 111 is transmitted to the optical low-pass filter 410. Due to the vibration transmitted from the piezoelectric element 430, a standing wave vibration is generated in the optical low-pass filter 410. Details of the standing wave vibration of the optical low-pass filter 410 will be described later.

  The optical low-pass filter holding member 420 is a resin or metal member that holds the optical low-pass filter 410 and is screw-fixed to the holding member 510. The flexible printed circuit board 470 is connected to each electrode of the piezoelectric element 430 and applies a voltage to the piezoelectric element 430. The urging member 440 abuts at four locations outside the imaging effective area 410 a of the optical low-pass filter 410 to urge the optical low-pass filter 410 toward the image sensor 33 and is locked to the optical low-pass filter holding member 420.

  The urging member 440 is grounded (0 [V]), and the surface of the optical low-pass filter 410 (surface on which the conductive coating and the optical coating are applied) in contact with the urging member 440 is grounded (0 [V]). ) Therefore, electrostatic adhesion of dust to the surface of the optical low-pass filter 410 can be suppressed.

  The elastic member 450 has a frame shape with a substantially circular cross section, and is tightly held between the optical low-pass filter 410 and the optical low-pass filter holding member 420. This adhesion force is determined by the urging force of the urging member 440 in the direction of the image sensor 33. The elastic member 450 may be rubber, or a polymer such as poron or plastic may be used as long as it is an elastic body.

  The optical member 460 is obtained by bonding a phase plate (depolarization plate) made of quartz, an infrared cut filter, and a birefringent plate having a birefringence direction different from that of the optical lowpass filter 410 by 90 °. The filter holding member 420 is adhesively fixed.

  The holding member 510 is a plate-like member for holding the image sensor 33 and has a rectangular opening. The image sensor 33 is fixed to the opening so as to expose the image sensor 33. Around the holding member 510, fixing portions for fixing screws to the mirror box 5 at, for example, three positions are provided.

  The mask 520 is sandwiched and held between the optical low-pass filter holding member 420 and the image sensor 33, and prevents extra light from outside the imaging optical path from entering the image sensor 33. The biasing member 530 is a pair of left and right leaf springs, is screw-fixed to the holding member 510, and presses the image sensor 33 against the holding member 510.

  With the above-described configuration, the optical low-pass filter 410 is sandwiched between the biasing member 440 and the elastic member 450 and is supported so as to freely vibrate.

<Electrode arrangement of piezoelectric element>
FIG. 6A and FIG. 6B are diagrams for explaining the details of the piezoelectric element 430. FIG. 6A is a view showing the front surface (first surface side, here F surface), the back surface (second surface side, here B surface), and the side surface of the piezoelectric element 430. FIG. 6B is a perspective view when the piezoelectric element 430 is viewed from the F-plane side.

  As shown in FIGS. 6A and 6B, the piezoelectric element 430 includes a piezoelectric member 430a that is a single piezoelectric element, and two electrodes AF and AB that are provided on the piezoelectric member 430a. Composed. The electrode AF and the electrode AB are drive electrodes (first drive electrode and second drive electrode) that are disposed to face each other with the piezoelectric member 430a interposed therebetween and that excite the standing wave vibration in the optical low-pass filter 410. Each electrode is independently connected to the flexible printed circuit board 470. Then, the electrode AF and the electrode AB are connected to the piezoelectric element driving circuit 111 through the wiring of the flexible printed circuit board 470.

  The piezoelectric element 430 configured as described above is fixed by bonding the B surface or the F surface at the peripheral portion 410b of the optical low-pass filter 410 described above. In the region where the piezoelectric element 430 is bonded to the optical low-pass filter 410, that is, the region used for bonding in the peripheral portion 410b of the optical low-pass filter 410, the optical low-pass filter 410 and the piezoelectric element 430 are preferably bonded directly. . That is, it is desirable not to apply conductive coating or optical coating in the region used for adhesion in the peripheral portion 410b. This is to prevent the driving force of the piezoelectric element 430 from being lost.

  The piezoelectric element drive circuit 111 serving as a control means alternately applies voltages to these electrodes to vibrate the piezoelectric member 430a in a vibration mode of a predetermined frequency, thereby causing a plurality of nodes and antinodes parallel to the arrow Y direction to be generated. The standing low-frequency vibration is generated in the optical low-pass filter 410. Similarly, the piezoelectric element driving circuit 111 serving as a control unit vibrates the piezoelectric member 430a in a vibration mode having a predetermined frequency, so that standing wave vibration having a plurality of nodes and antinodes parallel to the arrow X direction is optically low-pass filtered. 410.

<Description of vibration>
Next, with reference to FIG. 7, a state of vibration as an operation of removing dust of the optical low-pass filter 410 will be described. FIG. 7 is a diagram illustrating the front and side surfaces of the imaging unit 400, in which only the optical low-pass filter 410 and the piezoelectric element 430 that is integrally bonded to the optical low-pass filter 410 are taken out. FIG. 7 shows the vibration shapes of the optical low-pass filter 410 and the piezoelectric element 430 when a drive voltage is applied to the piezoelectric element 430.

  FIG. 7 is a diagram illustrating a state in which a wavefront of vibration is generated in the vertical direction (vertical direction orthogonal to the long side direction of the optical low-pass filter 410).

  The piezoelectric element 430 applies a positive voltage to the electrode AF through the flexible printed circuit board 470 and sets the electrode AB to the ground (0 [V]), and applies a positive voltage to the electrode AB to connect the electrode AF to the ground (0 [V]) is periodically and alternately switched. By this switching, the piezoelectric element 430 performs a periodic contraction motion. By making this period coincide with the resonance frequency of the natural mode of the optical low-pass filter 410, the optical low-pass filter 410 can be resonated by standing wave vibration.

  The vibration mentioned above is a vibration which repeats the state of a continuous line and the state of a broken line alternately, as shown on the side surface of FIG. The merit of resonance is that a large amplitude can be obtained even with a small applied voltage, and the efficiency is good.

  In addition, there are a plurality of resonance frequencies of the optical low-pass filter 410. When a voltage is periodically applied to the piezoelectric element 430 at each resonance frequency, it is possible to oscillate standing waves in vibration modes of different orders. FIG. 7 shows an eighth vibration mode in which eight antinodes occur in the vertical direction. In the optical low-pass filter 410, by switching the resonance frequency for vibrating the piezoelectric element 430, standing wave vibration as shown in FIG. 7 occurs.

  As shown in FIG. 7, in standing wave vibration, vibration node positions (d1, d2,...) And antinode positions are alternately generated. The vibration node position is a position where the amplitude is substantially zero, and the vibration antinode position is a position where the amplitude is maximum between adjacent node positions. Note that the dotted line on the front of FIG. 7 represents the vibration node position.

  There are the following two cases when foreign matter such as dust attached to the surface of the optical low-pass filter 410 is screened out by vibration of the piezoelectric element 430. First, one is a case where dust is removed in the imaging effective area 410a. This is hereinafter defined as “normal cleaning mode”.

  In order to remove dust adhering to the surface of the optical low-pass filter 410, acceleration that generates a force greater than the adhesion force of dust must be applied to the dust. However, since the amplitude is almost zero at the vibration node position, the acceleration generated is almost zero, and the dust cannot be removed against the adhesion force. Therefore, when the optical low-pass filter 410 is vibrated only in one vibration mode, dust remains on the vibration node position. Therefore, in the normal cleaning mode, after the optical low-pass filter 410 is vibrated in a predetermined vibration mode, the piezoelectric element 430 is controlled to vibrate the optical low-pass filter 410 in a vibration mode different from that.

  By controlling the piezoelectric element 430 in this way, dust remaining on the node position in the first vibration mode can be removed in another vibration mode thereafter. In this case, if a node position in a predetermined vibration mode and a node position in another vibration mode overlap, dust at the overlapped node position cannot be removed. Therefore, for the two vibration modes, it is necessary to select a combination of vibration modes so that the node positions do not overlap each other. In general, even-order and odd-order vibration modes are combined. Note that any combination of vibration modes may be used as long as there are two or more.

  The other is a case where dust that affects the focus detection pixels on the image sensor 33 is mainly removed, as will be described in detail later. This is hereinafter defined as “AF cleaning mode”. In this AF cleaning mode, only one specific vibration mode is required. Therefore, in the AF cleaning mode, specific dust that needs to be removed can be removed in a short time while suppressing power consumption, compared to the normal cleaning mode in which dust is removed using a plurality of vibration modes.

  The AF cleaning mode includes a cleaning mode related to the horizontal eye that removes dust affecting the focus detection pixels arranged in the horizontal direction, and a cleaning mode related to the vertical eye that removes dust affecting the focus detection pixels arranged in the vertical direction. is there. In the cleaning mode for the horizontal eye, a standing wave vibration as shown in FIG. 7 is generated in the optical low-pass filter 410 so that the position of the optical low-pass filter 410 corresponding to the horizontal focus detection pixel does not become a node position of the standing wave. Remove. Similarly, in the cleaning mode for vertical eyes, standing wave vibration as shown in FIG. 7 is applied to the optical low-pass filter 410 so that the position of the optical low-pass filter 410 corresponding to the vertical focus detection pixel does not become a node position of the standing wave. Create and remove dust.

  The resonance frequency of the optical low-pass filter 410 varies depending on the shape, plate thickness, material, etc. of the optical low-pass filter 410, but a resonance frequency that is outside the audible range is selected in order to suppress the generation of unpleasant sound. Is preferred.

  In the present embodiment, the optical member for protecting the imaging surface of the imaging device 33 from dust is not limited to the optical low-pass filter 410. For example, in the present embodiment, the quartz birefringent plate is configured to excite standing wave vibration. However, the birefringent plate may be made of another material such as lithium niobate instead of quartz. Further, an optical low-pass filter configured by bonding a birefringent plate, a phase plate, and an infrared absorption filter, or a configuration in which standing wave vibration is excited in a single infrared absorption filter may be used. Further, a configuration in which standing wave vibration is excited in a single glass plate arranged in front of the birefringent plate may be employed.

<Configuration of focus detection pixel>
8 to 10 are diagrams for explaining the structure of the imaging pixels and the focus detection pixels in the imaging device 33. FIG. In this embodiment, out of 4 pixels of 2 rows × 2 columns, pixels having a spectral sensitivity of G (green) are arranged in 2 diagonal pixels, and R (red) and B (blue) are arranged in the other 2 pixels. A Bayer arrangement in which one pixel each having spectral sensitivity is arranged is employed. Between the Bayer array, a plurality of pairs of focus detection pixels having a configuration described later are arranged in a distributed manner according to a predetermined rule.

  8A and 8B show the arrangement and configuration of the imaging pixels. FIG. 8A is a plan view of 2 × 2 imaging pixels. As shown in FIG. 8A, in the Bayer array, G pixels are arranged diagonally, and R and B pixels are arranged in the other two pixels. On the image sensor 33, the above-described 2 rows × 2 columns structure is repeatedly arranged.

  FIG. 8B is a cross-sectional view taken along line AA in FIG. As shown in FIG. 8B, the on-chip microlens ML is disposed on the forefront of each pixel. The color filter CFR is an R (red) color filter, and the color filter CFG is a G (green) color filter. The photoelectric conversion element PD schematically shows a photodiode in the imaging element 33. The wiring layer CL is a CL (Contact Layer) for forming signal lines for transmitting various signals in the image sensor 33 that is a CMOS image sensor. The imaging optical system TL schematically shows a TL (Taking Lens) of the imaging lens unit 200a.

  Here, the on-chip microlens ML and the photoelectric conversion element PD of the imaging pixel are configured to capture the light beam that has passed through the imaging optical system TL as effectively as possible. In other words, the exit pupil EP (Exit Pupil) of the imaging optical system TL and the photoelectric conversion element PD are conjugated with each other by the on-chip microlens ML, and the effective area of the photoelectric conversion element PD is designed to be large.

  8B illustrates the incident light beam of the R pixel, the G pixel and the B (blue) color pixel have the same configuration. Therefore, the exit pupil EP corresponding to each RGB pixel for imaging has a large diameter, and the S / N of the image signal is improved by efficiently capturing the light flux from the subject.

  FIGS. 9A and 9B show the arrangement and configuration of focus detection pixels that perform pupil division in the horizontal direction (lateral direction) of the imaging optical system. Here, the horizontal direction (lateral direction) is orthogonal to the optical axis when the imaging apparatus is held so that the optical axis of the imaging optical system and the long side of the imaging screen are parallel to the ground, and the horizontal direction. The direction along the straight line extending to

  FIG. 9A is a plan view of pixels of 2 rows × 2 columns including focus detection pixels. When an image signal for recording or viewing is obtained from the image sensor 33, the main component of luminance information is acquired by G pixels. Human image recognition characteristics are sensitive to luminance information. Therefore, when the G pixel is lost, image quality deterioration is easily recognized.

  On the other hand, the R pixel or the B pixel is a pixel for obtaining color information (color difference information). Since human visual characteristics are insensitive to color information, it is difficult to perceive image quality degradation even if some pixels are missing from the color information acquisition pixel.

  Therefore, in the present embodiment, in a part of the pixels of 2 rows × 2 columns, as shown in FIG. 9A, the G pixel is left as the imaging pixel, and the R pixel and the B pixel are the focus detection pixels SHA, Replace with SHB.

  FIG. 9B is a cross-sectional view taken along the line AA in FIG. As illustrated in FIG. 9B, the on-chip microlens ML and the photoelectric conversion element PD in the focus detection pixel have the same structure as the imaging pixel illustrated in FIG. 8B. In the present embodiment, focus detection pixel signals are not used for image generation. Accordingly, in the focus detection pixel, the transparent film CFW (white) is disposed instead of the color separation color filter.

  Further, in the focus detection pixel, since the pupil division is performed by the image sensor 33, the opening of the wiring layer CL is in one direction with respect to the center line of the on-chip microlens ML (FIGS. 9A and 9B). ) In the horizontal direction in the focus detection pixels shown in FIG.

  Specifically, the focus detection pixel SHA receives the light beam that has passed through the left exit pupil EPHA of the imaging optical system TL because the opening OPHA is biased to the right in the horizontal direction. Similarly, the focus detection pixel SHB receives the light beam that has passed through the right exit pupil EPHB of the imaging optical system TL because the opening OPHB is biased to the left in the horizontal direction.

  In the image sensor 33, a plurality of focus detection pixels SHA are regularly arranged in the horizontal direction, and a plurality of focus detection pixels SHB paired with the focus detection pixels SHA are also regularly arranged in the horizontal direction. That is, a plurality of focus detection pixel pairs (first focus detection pixel pairs) for detecting defocus in the horizontal direction are arranged on the imaging surface.

  The imaging device uses the subject image acquired by the pixel group of the focus detection pixel SHA of the image sensor 33 as the A image, the subject image acquired by the pixel group of the focus detection pixel SHB as the B image, and the A image and the B image. The relative position (phase difference) is detected. By this phase difference detection, the imaging apparatus can detect the defocus amount (defocus amount) of the subject image in the image sensor 33.

  In the above-described focus detection pixels SHA and SHB, focus detection is possible for an object having a luminance distribution in the horizontal direction of the imaging screen, for example, a vertical line, but a horizontal line having a luminance distribution in the vertical direction, etc. Cannot detect the focus. Therefore, in the present embodiment, a focus detection pixel pair (second focus) that performs pupil division also in the vertical direction (vertical direction of the imaging optical system) different from the horizontal direction so that focus detection is possible for the latter. It may be configured to include a detection pixel pair).

  FIGS. 10A and 10B show the arrangement and configuration of focus detection pixels that perform pupil division in the vertical direction (vertical direction or vertical direction) of the imaging optical system. Here, the vertical direction (vertical direction or vertical direction) is orthogonal to the optical axis when the imaging apparatus is held so that the optical axis of the imaging optical system and the long side of the imaging screen are parallel to the ground, The direction along a straight line extending in the vertical direction.

  FIG. 10A is a plan view of pixels of 2 rows × 2 columns including focus detection pixels. As in FIG. 9A, in some of the pixels of 2 rows × 2 columns, as shown in FIG. 10A, the G pixel is left as an imaging pixel, and the R pixel and the B pixel are focus detection pixels SVC. , SVD.

  FIG. 10B is a cross-sectional view taken along the line AA in FIG. The focus detection pixel shown in FIG. 9B has a structure in which the pupil is divided in the horizontal direction, whereas the focus detection pixel shown in FIG. 10B has a vertical direction in the pupil division direction. Other structures are the same as those in the horizontal direction.

  As shown in FIG. 10B, the focus detection pixel SVC receives the light beam that has passed through the upper exit pupil EPVC of the imaging optical system TL because the opening OPVC is biased downward. Similarly, the focus detection pixel SVD receives the light beam that has passed through the lower exit pupil EPVD of the imaging optical system TL because the opening OPVD is biased upward.

  In the image sensor 33, a plurality of focus detection pixels SVC are regularly arranged in the vertical direction, and a plurality of focus detection pixels SHB paired with the focus detection pixels SVC are also regularly arranged in the vertical direction. The imaging device uses a subject image acquired by the pixel group of the focus detection pixels SVC of the image sensor 33 as a C image, a subject image acquired by the pixel group of the focus detection pixel SVD as a D image, and the C image and the D image. The relative position (phase difference) is detected. By this phase difference detection, the imaging apparatus can detect the amount of defocus (defocus amount) of the subject image in the imaging device 33.

<Arrangement of focus detection pixels>
11 and 12 are diagrams illustrating the arrangement of the imaging pixels and focus detection pixels illustrated in FIGS. 8 to 10. FIG. 11 is a diagram for explaining a minimum unit arrangement rule when the focus detection pixels are distributed and arranged between the imaging pixels.

  As shown in FIG. 11, in the image sensor, focus detection pixels are discretely distributed between the image pickup pixels. In FIG. 11, a square area of 10 rows × 10 columns = 100 pixels is defined as one block.

  In the upper left block BLKh (1, 1), a set of focus detection pixels (first focus detection unit) SHA that divides the lower left R pixel and B pixel in the horizontal direction (first direction). Replace with SHB. In the block BLKv (1, 2) on the right side, a pair of focus detection pixels (second focus) that similarly perform pupil division in the vertical direction (second direction) on the lower left R pixel and B pixel. Detection unit) Replace with SVC or SVD.

  The pixel arrangement of the block BLKv (2, 1) adjacent below the first block BLKh (1, 1) is the same as that of the block BLKv (1, 2). The pixel arrangement of the block BLKh (2, 2) on the right side of the block BLKv (2, 1) is the same as that of the leading block BLKh (1, 1).

  When this arrangement rule is generalized, the block BLK (i, j) is a block BLKh (i, j) in which focus detection pixels for pupil division in the horizontal direction are arranged if i + j is an even number. Similarly, the block BLK (i, j) is a block BLKv (i, j) in which focus detection pixels for vertical pupil division are arranged if i + j is an odd number.

  That is, 2 × 2 = 4 blocks in FIG. 11 is the minimum unit of the arrangement rule described above. In the following, the area of the four blocks (20 rows × 20 columns = 400 pixels) is defined as a cluster as an upper array unit of the block.

  FIG. 12 is a diagram for explaining an arrangement rule with the above cluster as a unit. In FIG. 12, the upper left cluster composed of 20 rows × 20 columns = 400 pixels is assumed to be CST (u, w) = CST (1,1). In the present embodiment, all the clusters CST (u, w) have the same arrangement as the top cluster CST (1, 1).

  Therefore, in the imaging device, CST (1, 1), CST (1, 2)... In the horizontal direction, CST (1, 1), CST (2, 1). Arrange the clusters. By arranging clusters in this way, focus detection pixels can be uniformly distributed over the entire imaging region.

  Next, a pixel group at the time of focus detection will be described with reference to FIGS. 13 (a) and 13 (b). When performing focus detection in the lateral shift direction (horizontal direction) of the subject image formed by the imaging optical system, as shown in FIG. 13A, in the present embodiment, one block in the vertical direction and 30 in the horizontal direction. One focus detection area (line sensor) is configured by the block.

  This one focus detection region includes 15 focus detection pixels SHA that perform one pupil division in the horizontal direction and 15 focus detection pixels SHB that perform the other pupil division. A phase difference detection A image signal formed by connecting the image signals from the focus detection pixel SHA pixel group and a phase difference detection image formed by connecting the image signal from the focus detection pixel SHB pixel group. A lateral shift amount relative to the B image signal is calculated by a known correlation calculation. By this correlation calculation, the defocus amount (defocus amount) of the subject can be obtained.

  On the other hand, when performing focus detection in the vertical deviation direction (vertical direction) of the subject image formed by the imaging optical system, as shown in FIG. One focus detection area (line sensor) is composed of 30 blocks.

  This one focus detection region includes 15 focus detection pixels SVC that perform one pupil division in the vertical direction and 15 focus detection pixels SVD that perform the other pupil division. A phase difference detection C image signal formed by connecting image signals from the focus detection pixel SVC pixel group and a phase difference detection image formed by connecting the focus detection pixel SVD image signal. The amount of vertical deviation relative to the D image signal is calculated by a known correlation calculation. By this correlation calculation, the defocus amount (defocus amount) of the subject can be obtained.

  Then, two defocus amounts detected by the lateral shift and vertical shift focus detection areas are compared, and a highly reliable value may be adopted. In addition, since the focus detection area can be set at an arbitrary position on the screen, focus detection can be performed in the entire imaging area.

<Description of AF cleaning mode>
FIG. 14 is a diagram illustrating a state in which a shadow of dust is reflected on the focus detection pixels. Specifically, FIG. 14 is a diagram in which an optical low-pass filter 410 to which dust, dust, has adhered is added to the configuration illustrated in FIG. 9B.

  As shown in FIG. 14, when dust adheres to the optical low-pass filter 410, the shadow may overlap the focus detection pixels. In other words, the light beam from one of the divided pupils is blocked, and the light reception amount of the focus detection pixel may be smaller than the light reception amount that should be originally obtained. In such a case, the defocus amount derived from the A image signal and the B image signal for phase difference detection is different from the ideal defocus amount when there is no dust (see FIG. 18B).

  FIGS. 15A to 15D are views of the image sensor 33 viewed from the optical low-pass filter 410 side. FIGS. 15A to 15D schematically illustrate the positions of the imaging pixels, the focus detection pixels, and the dust (black circles in the drawing) attached to the optical low-pass filter 410 in a certain imaging region. . FIG. 15A shows a state before dust is removed, and FIGS. 15B to 15D show states after dust is removed.

  As shown in FIG. 15A, there is a portion where the dust and the focus detection pixel overlap before the dust is removed. Therefore, standing wave vibration is generated in the optical low-pass filter 410 to mainly remove dust that overlaps the focus detection pixels.

  FIG. 15B is an example in which dust that overlaps with the focus detection pixels is removed. A dotted line in the figure represents a node position of standing wave vibration in a vibration mode in which a wavefront of vibration is generated in the vertical direction of the optical low-pass filter. As shown in FIG. 15B, when the optical low-pass filter is vibrated in a vibration mode in which a wavefront of vibration is generated in the vertical direction, dust remains only at the node position of the stationary wave generated by vibration, and dust other than the node position Is removed.

  As described above, standing wave vibration has a vibration node position (amplitude is substantially zero) and an antinode position (amplitude is maximum). Due to this standing wave vibration, the dust adhering to the antinode position and its immediate vicinity is removed from the optical low-pass filter, and the dust adhering to the vicinity of the antinode position is moved to the node position. As a result, dust remains only at the node position of the standing wave vibration.

  In addition, the standing wave generated in the optical low-pass filter has a well-defined node position and anti-node position, and the vibration frequency of any wavelength is generated in the optical low-pass filter by setting the resonance frequency input to the piezoelectric element to a predetermined value. Can be made. The distance between adjacent nodes (or adjacent antinodes) (hereinafter defined as the node pitch) corresponds to a half wavelength (λ / 2).

  Therefore, the node pitch is the same as the pitch between the focus detection pixels arranged in a dispersed manner (here, one block = 10 pixels), and between two focus detection pixels that are not adjacent in the horizontal direction. The optical low-pass filter is vibrated in a vibration mode in which nodes are generated. At least, if standing wave vibration is generated in a vibration mode in which no node is generated on the focus detection pixel and the position of the focus detection pixel and the node position in the standing wave do not overlap, dust overlapping with the focus detection pixel can be removed.

  By vibrating the optical low-pass filter in this way, dust that overlaps the focus detection pixels can be mainly removed. In other words, the focus detection pixel is generated by generating standing wave vibration in a vibration mode in which the antinode pitch (corresponding to the node pitch) and the pitch between the focus detection pixels are the same and the antinode is generated on the focus detection pixels. It is possible to mainly remove dust that overlaps. When the antinode position of the standing wave having the maximum amplitude overlaps with the focus detection pixel, dust can be more efficiently removed.

  Note that the vibration mode used in the AF cleaning mode is only one specific vibration mode. That is, unlike the above-described normal cleaning mode, this is different from the case where dust is removed in the imaging effective area 410a using a plurality of vibration modes. This is because the purpose of the AF cleaning mode is to intensively remove dust that overlaps the focus detection pixels. Furthermore, it is preferable to make the time for vibrating the optical low-pass filter as short as possible, and it is preferable to make the voltage inputted to the piezoelectric element 430 as small as possible for vibrating.

  As described above, when the normal cleaning mode and the AF cleaning mode are compared, the AF cleaning mode overlaps with the focus detection pixel while reducing the vibration time to ½ or less and suppressing the power consumption to ½ or less. Dust can be removed.

  In the example described with reference to FIG. 15B, the configuration for removing dust that overlaps all the focus detection pixels is illustrated, but it overlaps with the focus detection pixels for detecting the lateral defocus. It may be a vibration mode that removes only dust. Specifically, the standing wave vibration may be generated in a vibration mode in which no node is generated on the focus detection pixel for detecting the defocus in the horizontal direction, and the position of the focus detection pixel and the node position in the standing wave It is good if there is no overlap.

  Similarly, a vibration mode may be used in which only dust that overlaps with focus detection pixels for detecting vertical defocus is removed. Specifically, it is only necessary to generate standing wave vibration in a vibration mode in which no node is generated on the focus detection pixel for detecting the defocus in the vertical direction, and the position of the focus detection pixel and the node position in the standing wave It is good if there is no overlap.

  With reference to FIGS. 15C and 15D, another example of removing dust that overlaps the focus detection pixels will be introduced. A dotted line in the figure represents a node position of standing wave vibration in a vibration mode in which a wavefront of vibration is generated in the vertical direction of the optical low-pass filter.

  As shown in FIG. 15 (c), when the optical low-pass filter is vibrated in a vibration mode in which a vibration wavefront is generated in the vertical direction, dust remains only on the node position, and dust other than the node position is removed. The difference from FIG. 15B is that the node pitch is changed.

  That is, in the example shown in FIG. 15C, the node pitch is twice the pitch between focus detection pixels (here, one block = 10 pixels), and two focus detections that are not adjacent in the horizontal direction. The optical low-pass filter is vibrated in a vibration mode in which a node is generated between pixels.

  By vibrating the optical low-pass filter in this way, dust that overlaps the focus detection pixels can be mainly removed. In the example shown in FIG. 15C, the node pitch is twice the pitch between focus detection pixels, but it may be three times or more. That is, the resonance frequency may be determined so that the node pitch is a natural number multiple of the pitch between the focus detection pixels (natural number n = 1, 2, 3,...).

  FIG. 15D shows dust generated by vibrating the optical low-pass filter in a vibration mode in which a node is generated at a node pitch having a width (horizontal distance) larger than that of the focus detection region RA and outside the focus detection region RA in the horizontal direction. It is a figure showing the state after removing. The focus detection area RA is set by automatic selection from a plurality of ranging areas (multi-point AF) or by arbitrary selection by a user via an operation unit (not shown) under the control of the MPU 100 as setting means. It is an area. The focus detection area RA is an area in which focus detection is performed on the imaging surface of the imaging element 33 when the focus of the imaging lens 200 is adjusted under the control of the MPU 100. That is, the MPU 100 adjusts the focus of the imaging lens 200 based on the output of the focus detection pixels included in the focus detection area RA.

  In order to vibrate the optical low-pass filter in this vibration mode, an appropriate resonance frequency may be determined in accordance with the width (horizontal distance) and position of the focus detection area RA corresponding to the selected distance measurement area. As described above, it is possible to mainly remove dust that overlaps the focus detection area RA by vibrating the optical low-pass filter in the vibration mode corresponding to the set focus detection area RA.

<Flow chart of AF cleaning mode>
FIG. 16 is a flowchart of an AF cleaning mode executed by the imaging apparatus according to the present embodiment. The AF cleaning mode is executed in a live view imaging mode in which image data sequentially obtained from the image sensor 33 is displayed on the color liquid crystal monitor 19 in real time.

  As shown in FIG. 16, in S101, the MPU 100 starts the live view imaging mode when the user operates the imaging mode setting dial 14. By starting the live view imaging mode, image data sequentially obtained from the imaging device 33 is displayed on the color liquid crystal monitor 19 in real time.

  Next, in S102, the MPU 100 determines whether or not the first switch 7a of the release button 7 is ON. The MPU 100 advances the process to S103 when the first switch 7a is ON.

  In S103, the MPU 100 executes the AF cleaning mode. Specifically, the MPU 100 controls the following processing.

  When the AF cleaning mode is executed, the power supply circuit 110 supplies power necessary for the AF cleaning mode to each part of the imaging apparatus main body 1. In parallel with this, the remaining battery level of the power source 42 is detected, and the result is transmitted to the MPU 100. When the MPU 100 receives the result of the remaining battery level detected by the power supply circuit 110, the MPU 100 sends a drive signal to the piezoelectric element drive circuit 111 when the remaining battery level is sufficient for the operation in the AF cleaning mode.

  When the piezoelectric element driving circuit 111 receives the driving signal from the MPU 100, the piezoelectric element driving circuit 111 generates a periodic voltage that excites the standing wave vibration of the optical low-pass filter 410, and applies the generated periodic voltage to the piezoelectric element 430. The piezoelectric element 430 expands and contracts according to the applied periodic voltage, and causes the optical low-pass filter 410 to generate standing wave vibration. The generated standing wave vibration is determined in advance as one vibration mode in consideration of the pitch between the focus detection pixels and the size of the focus detection area. When this AF cleaning mode ends, the MPU 100 advances the process to S104.

  The determination of the vibration mode in consideration of the pitch between focus detection pixels and the size of the focus detection area is performed by the MPU 100 based on setting information regarding the image sensor 33 stored in advance in the EEPROM 100a. The EEPROM 100a stores in advance setting information related to a vibration mode based on a simulation result at the design stage of the image sensor 33 and a test result obtained when the image sensor 33 is combined with an image pickup apparatus. This setting information includes the periodic voltage applied to the piezoelectric element 430 to vibrate the optical low-pass filter 410 in the vibration mode exemplified in FIGS. 15B and 15C, and the vibration mode based on the periodic voltage. It is information such as wavelength and node position of standing wave. The MPU 100 can vibrate the optical low-pass filter 410 as illustrated in FIGS. 15B and 15C by controlling the piezoelectric element driving circuit 111 with reference to the setting information.

  When the focus detection area RA illustrated in FIG. 15D is set, the MPU 100 calculates based on the setting information stored in the EEPROM 100a to determine the vibration mode. Specifically, a vibration mode in which no node position exists in the focus detection area RA is calculated based on the information on the wavelength and standing wave node position included in the setting information.

  In S <b> 104, the MPU 100 reads out the focus detection pixels included in the focus detection area of the image sensor 33. Next, in S105, the MPU 100 obtains a first concatenated signal by concatenating the output signals from the first focus detection pixels over a plurality of blocks assigned to the focus detection area. Similarly, the MPU 100 concatenates output signals from the second focus detection pixels to obtain a second concatenated signal. These first and second connection signals correspond to two image signals (A image signal and B image signal, or C image signal and D image signal) for correlation calculation.

  Next, in S106, the MPU 100 performs correlation calculation of the obtained two image signals, and calculates a relative positional deviation amount of the two image signals. Next, in S107, the MPU 100 determines the reliability of the correlation calculation result in S106.

  Here, the reliability refers to the degree of coincidence (correlation degree) of the signals of the two images. When the degree of coincidence of the signals of the two images is good, the reliability of the focus detection result is generally high. Therefore, when a plurality of focus detection areas are selected, highly reliable information is preferentially used for the calculation of the defocus amount.

  Next, in S108, the MPU 100 calculates a defocus amount (defocus amount) from the highly reliable correlation calculation result. Next, in S109, the MPU 100 determines whether or not the defocus amount calculated in S108 is less than an allowable value, and determines whether or not it is in a focused state.

  If the defocus amount is greater than or equal to the allowable value, it is determined that the in-focus state is present, and the MPU 100 drives the focus lens in S110, and then returns to S104. Therefore, when it is in the out-of-focus state, the processes of S104 to S109 are repeatedly executed.

  If the defocus amount is less than the allowable value, it is determined that the in-focus state is reached, and the MPU 100 advances the process to S111, ends the AF process, and returns to the main process in the live view imaging mode.

  As described above, in the present embodiment, dust overlapping with the focus detection pixels is intensively removed while reducing power consumption in a short time compared to dust removal (normal cleaning mode) on a normal imaging effective area. (AF cleaning mode). Therefore, even if AF is performed while removing dust during the live view imaging mode, only a short time is required, and a decrease in focus detection accuracy due to dust shadows can be prevented without adversely affecting the number of shots. Further, by performing the AF cleaning mode prior to reading out the focus detection pixels related to the focus adjustment, it is possible to improve the accuracy of the focus adjustment.

<Modification of Flowchart in AF Cleaning Mode>
FIG. 17 is a modification of the flowchart of the AF cleaning mode executed by the imaging apparatus according to the present embodiment. In the following description, steps that perform the same processing as in FIG. 16 are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 17, following S102, the MPU 100 executes the AF cleaning mode for the horizontal eye in S103a. Specifically, the MPU 100 performs substantially the same processing as S103 described above, and causes the optical low-pass filter 410 to generate standing wave vibration as illustrated in FIG. The standing wave vibration in S103a removes dust that affects the focus detection pixels arranged in the horizontal direction.

  Next, in S104a, the MPU 100 reads out the focus detection pixels related to the horizontal eye included in the focus detection area of the image sensor 33. Reading of the focus detection pixels regarding the horizontal eye is performed based on the pixel positions (addresses) of the focus detection pixels stored in the memory in advance.

  Subsequent to S107, the MPU 100 determines in S107a whether the degree of coincidence (correlation degree) of the two image signals in the correlation calculation result is equal to or higher than a preset threshold and whether the reliability is sufficiently high. If dust that affects the focus detection pixels arranged in the horizontal direction in S103a is removed, but the determination result in S107a is not sufficiently reliable, the focus detection pixels related to the vertical eye are affected by dust. It shall be. Accordingly, after execution of the AF cleaning mode for the vertical eye, which will be described later, the process proceeds to S108 without performing the process of S107a.

  If the determination result in S107a is not sufficiently reliable, the MPU 100 executes the AF cleaning mode for the vertical eye in S103b. Specifically, the MPU 100 performs substantially the same processing as S103 described above, and causes the optical low-pass filter 410 to generate a standing wave vibration as illustrated in FIG. Due to the standing wave vibration in S103b, dust affecting the focus detection pixels arranged in the vertical direction is removed. Next, in S104b, the MPU 100 reads focus detection pixels regarding the vertical eye included in the focus detection area of the image sensor 33 in the same manner as in the case of the horizontal eye.

  As described above, in the modified example, dust that affects the focus detection pixels of the horizontal eye is removed, and when the correlation calculation result is highly reliable, the focusing operation is performed as it is, and the power consumption is reduced in a shorter time. The dust related to AF can be removed while suppressing. Further, even when dust removal affecting the horizontal focus detection pixels is performed, if the reliability of the correlation calculation result is low, dust removal affecting the vertical focus detection pixels is performed. Therefore, highly accurate focus adjustment can be realized. In this case as well, only dust removal that affects the focus detection pixels for the horizontal and vertical eyes is performed, and power consumption can be reduced in a shorter time compared to dust removal on a normal imaging effective area.

  Note that the description in the above-described embodiment shows an example, and the present invention is not limited to this. The configuration and operation in the embodiment described above can be changed as appropriate.

(Other embodiments)
The above-described embodiment can also be realized in software by a computer of a system or apparatus (or CPU, MPU, etc.). Therefore, the computer program itself supplied to the computer in order to implement the above-described embodiment by the computer also realizes the present invention. That is, the computer program itself for realizing the functions of the above-described embodiments is also one aspect of the present invention.

  The computer program for realizing the above-described embodiment may be in any form as long as it can be read by a computer. For example, it can be composed of object code, a program executed by an interpreter, script data supplied to the OS, but is not limited thereto. A computer program for realizing the above-described embodiment is supplied to a computer via a storage medium or wired / wireless communication. Examples of the storage medium for supplying the program include a magnetic storage medium such as a flexible disk, a hard disk, and a magnetic tape, an optical / magneto-optical storage medium such as an MO, CD, and DVD, and a nonvolatile semiconductor memory.

  As a computer program supply method using wired / wireless communication, there is a method of using a server on a computer network. In this case, a data file (program file) that can be a computer program forming the present invention is stored in the server. The program file may be an executable format or a source code. The program file is supplied by downloading to a client computer that has accessed the server. In this case, the program file can be divided into a plurality of segment files, and the segment files can be distributed and arranged on different servers. That is, a server apparatus that provides a client computer with a program file for realizing the above-described embodiment is also one aspect of the present invention.

  In addition, a storage medium in which the computer program for realizing the above-described embodiment is encrypted and distributed is distributed, and key information for decrypting is supplied to a user who satisfies a predetermined condition, and the user's computer Installation may be allowed. The key information can be supplied by being downloaded from a homepage via the Internet, for example. Further, the computer program for realizing the above-described embodiment may use an OS function already running on the computer. Further, a part of the computer program for realizing the above-described embodiment may be configured by firmware such as an expansion board attached to the computer, or may be executed by a CPU provided in the expansion board. Good.

Claims (8)

An imaging apparatus in which a plurality of pixels are arranged on an imaging surface, a part of the plurality of pixels includes an imaging element that forms a focus detection pixel, and performs focus detection based on an output of the focus detection pixel. ,
An optical member that is disposed in front of the imaging element and transmits light reaching the imaging surface;
Vibration means for vibrating the optical member;
Control means for controlling the vibration of the optical member by the vibration means;
With
When the control means removes foreign matter adhering to the optical member that affects the focus detection pixel, the node position of the standing wave of the optical member generated by the vibration of the optical member, and the focus detection pixel The vibration of the optical member is controlled so that the position of the optical member that transmits the light does not overlap.   The control means vibrates the optical member such that the antinode position of the standing wave of the optical member generated by the vibration of the optical member overlaps the position of the optical member that transmits the light to the focus detection pixels. The imaging apparatus according to claim 1, wherein the imaging apparatus is controlled. A plurality of the focus detection pixels are distributed and arranged on the imaging surface at a predetermined pitch,
The said control means controls the vibration of the said optical member, and removes a foreign material so that the pitch of the adjacent antinode or node in the said standing wave may become the natural number multiple of the said predetermined pitch. Or the imaging device of 2. A first focus detection pixel for detecting a horizontal defocus in the imaging plane; a second focus detection pixel for detecting a vertical defocus in the imaging plane; Have
When the controller removes the foreign matter attached to the optical member that affects either the first focus detection pixel or the second focus detection pixel, the node position of the standing wave, and 4. The vibration of the optical member is controlled so as not to overlap with a position of the optical member that transmits the light to any one of the focus detection pixels. 5. The imaging device described. Correlation between outputs of the first focus detection pixel pair and the second focus detection pixel after the removal of the foreign matter attached to the optical member affecting one of the focus detection pixels is performed. A determination means for determining whether or not to remove the foreign matter adhering to the optical member affecting the other focus detection pixel based on the degree;
In accordance with the determination result of the determination unit, the optical member prevents the node position of the standing wave from overlapping the position of the optical member that transmits the light to the other focus detection pixel. The imaging apparatus according to claim 4, wherein the vibration of the imaging apparatus is controlled. Further comprising setting means for setting a focus detection area on the imaging surface;
When the control means removes foreign matter adhering to the optical member affecting the focus detection pixels included in the set focus detection area, the light is applied to the node position of the standing wave and the focus detection area. The imaging apparatus according to claim 1, wherein the vibration of the optical member is controlled so that the position of the optical member that transmits light does not overlap. An imaging element in which a plurality of pixels are arranged on an imaging surface, and a part of the plurality of pixels constitutes a focus detection pixel; an optical member that is arranged in front of the imaging element and transmits light that reaches the imaging surface; And a control method of an imaging apparatus that has a vibration means for vibrating the optical member, and performs focus detection based on an output of the focus detection pixel,
A control step of controlling the vibration of the optical member by the vibration means;
When the control step removes the foreign matter attached to the optical member that affects the focus detection pixel, the node position of the standing wave of the optical member generated by the vibration of the optical member and the focus detection pixel A method of controlling an imaging apparatus, comprising: controlling vibration of the optical member so that the position of the optical member that transmits the light does not overlap.   The program for making a computer perform each process of the control method of the imaging device of Claim 7.

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