JP2004056368A - Electronic imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic imaging apparatus capable of vibrating dust-proofing glass in an optimum state without making the configuration of a drive circuit for a piezoelectric element complicated. <P>SOLUTION: The electronic imaging apparatus provided with a dust-proofing mechanism includes: a photoelectric conversion element (imaging element 27) for converting an optical image of a subject into an electric signal; a dust-proofing member (dust-proofing filter 21) placed on the front face of the photoelectric conversion element (imaging element 27); an exciting means (piezoelectric element 22) for vibrating the dust-proofing member (dust-proofing filter 21) to perform dust elimination; and a body controlling microcomputer 150 for sequentially changing the vibration frequency of the dust-proofing member (dust-proofing filter 21) vibrated by the exciting means (piezoelectric element 22), monitoring the amplitude of the vibration when the dust-proofing member (dust-proofing filter 21) is vibrated, and controlling the dust elimination operation depending on the monitored amplitude. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electronic imaging device such as a digital camera.
[0002]
[Prior art]
In an electronic imaging device such as a digital camera, various mechanisms that operate mechanically are arranged in the main body, so that dust and the like generated from the mechanisms adhere to the photoelectric conversion surface of the imaging element and deteriorate a captured image. There was a problem of letting it.
[0003]
Therefore, as an example of a technique relating to a dustproof function of an electronic imaging device, a technique has been proposed in which a protective glass (dustproof glass) for protecting an image sensor is vibrated to remove dust and the like attached to the glass.
[0004]
Specifically, for example, there is a device disclosed in Japanese Patent Application No. 2000-401291, in which a piezoelectric element is provided as means for vibrating a glass plate, and the piezoelectric element expands and contracts in response to an applied periodic voltage. By applying the method, the attached glass plate is vibrated at a predetermined cycle.
[0005]
More specifically, a dust-proof glass (filter) is arranged on the front side of the image sensor as a dust-proof member, and a piezoelectric element is provided as a vibrating means so as to be integrated with the periphery of the dust-proof glass. Then, the piezoelectric element is vibrated by applying a periodic voltage to the piezoelectric element, and a predetermined vibration is applied to the dustproof glass by the vibration.
[0006]
[Problems to be solved by the invention]
In the above-described prior art, the amount of displacement of the piezoelectric element itself is small, so that dust cannot be efficiently removed even if the dustproof glass is vibrated with the amount of displacement of the piezoelectric element. Therefore, in order to increase the amplitude of the vibration of the dust-proof glass, it is necessary to vibrate at the inherent resonance frequency of the dust-proof glass itself. Further, when a high voltage is applied to the piezoelectric element, the displacement amount becomes large, and a vibration having a large amplitude can be generated in the dustproof glass.
[0007]
On the other hand, when the amplitude of the dust-proof glass is too large, the dust-proof glass itself may be broken. In particular, in the case of an imaging apparatus using a battery as a driving power source, a difference occurs in the amplitude of the dust-proof glass according to the battery voltage. In the case of a new battery, the above-described accident may occur.
[0008]
The present invention has been made in view of such a problem, and provides an electronic imaging apparatus that can vibrate a dustproof member in an optimal state without complicating the configuration of a driving circuit of a piezoelectric element. It is in.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a first invention is an electronic imaging device provided with a dustproof mechanism, comprising: a photoelectric conversion element for converting an optical image of a subject into an electric signal; and a front face of the photoelectric conversion element. A dustproof member, a vibrating means for vibrating the dustproof member to perform a dust removing operation, a frequency varying means for sequentially changing a vibration frequency of the dustproof member vibrated by the vibrating means, and the dustproof member Monitoring means for monitoring the amplitude value when the vibration is occurring, and controlling the dust removal operation in accordance with the monitored amplitude value.
[0010]
According to a second aspect, in the electronic imaging device according to the first aspect, the vibration unit vibrates the dustproof member according to a frequency signal supplied from the frequency variable unit.
[0011]
According to a third aspect, in the electronic imaging apparatus according to the second aspect, the vibration unit is configured to control the dustproof member in accordance with a plurality of frequency signals in a predetermined frequency range sequentially supplied from the frequency variable unit. Vibrate.
[0012]
In a fourth aspect based on the electronic imaging device according to the third aspect, the predetermined frequency range is a range including a resonance frequency of the dustproof member.
[0013]
According to a fifth aspect, in the electronic imaging device according to the first aspect, the monitor unit monitors an amplitude value at which the dust-proof member may be broken, and when the amplitude value exceeds the amplitude value, Stop the dust removal operation.
[0014]
According to a sixth aspect of the present invention, there is provided an imaging optical system that forms an optical image of a subject, a photoelectric conversion element that converts the optical image into an electric signal, and an optical system that is disposed between the imaging optical system and the photoelectric conversion element. A dust filter, a piezoelectric element integrally provided in a part of the dust filter, a drive circuit for applying a voltage signal to the piezoelectric element to drive the piezoelectric element, and vibrating the piezoelectric element. A control circuit that supplies a drive signal to the drive circuit so as to vibrate the dustproof filter, and a monitor circuit that monitors a vibration state of the piezoelectric element and outputs a monitor signal to the control circuit. In the electronic imaging apparatus, the control circuit sequentially changes the drive signal supplied to the drive circuit so that the vibration frequency of the dustproof filter sequentially changes, and during the time, the control circuit determines whether the monitor circuit is in operation. If the level of the supplied monitor signal exceeds a predetermined value and stops the supply of the drive signal.
[0015]
In a seventh aspect based on the electronic imaging device according to the sixth aspect, the control circuit supplies the drive signal after a predetermined time after a level of the monitor signal from the monitor circuit exceeds a predetermined value. Stop.
[0016]
In an eighth aspect based on the electronic imaging device according to the sixth aspect, the drive circuit changes a frequency of a voltage signal applied to the piezoelectric element according to a drive signal from the control circuit.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, a case where the present invention is applied to a digital camera will be described. FIG. 1 is a perspective view in which a part of a digital camera according to a first embodiment of the present invention is cut and an internal configuration thereof is schematically illustrated.
[0018]
The camera 1 of the present embodiment includes a camera body 11 and a lens barrel 12 which are separately formed, and the camera body 11 and the lens barrel 12 are configured to be detachable from each other. It is.
[0019]
The lens barrel 12 is configured to internally hold a photographing optical system 12a including a plurality of lenses and a driving mechanism thereof. The photographing optical system 12a transmits, for example, a plurality of light beams from a subject so that an image of the subject formed by the subject light beams is formed at a predetermined position (on a photoelectric conversion surface of an image sensor described later). And the like. The lens barrel 12 is provided so as to protrude toward the front of the camera body 11.
[0020]
The camera body 11 is provided with various constituent members and the like, and is a photographing optical system which is a connecting member for detachably mounting a lens barrel 12 holding a photographing optical system 12a. This is a so-called single-lens reflex camera having a mounting portion 11a provided on the front surface thereof.
[0021]
That is, an exposure opening having a predetermined diameter capable of guiding a subject light beam into the camera body 11 is formed at a substantially central portion on the front side of the camera body 11, and the periphery of the exposure opening is formed. A photographing optical system mounting section 11a is formed in the section.
[0022]
On the outer surface side of the camera main body 11, the above-described photographing optical system mounting portion 11a is provided on the front surface thereof, and various kinds of components for operating the camera main body 11 at predetermined positions such as an upper surface portion and a rear surface portion are provided. Are provided, for example, a release button 17 for generating an instruction signal or the like for starting a photographing operation.
[0023]
Inside the camera body 11, various constituent members, for example, a finder device 13 constituting a so-called observation optical system, and a subject light flux to a photoelectric conversion surface of an image sensor (not shown) fixed by an image sensor fixing plate 28. A shutter unit 14 having a shutter mechanism or the like for controlling the irradiation time and the like, an image sensor (not shown) for obtaining an image signal corresponding to a subject image, and a predetermined position on the front side of a photoelectric conversion surface of the image sensor The image pickup unit 15 including a dustproof filter (also referred to as dustproof glass) 21 which is a dustproof member for preventing dust and the like from adhering to the photoelectric conversion surface, and various electric members constituting an electric circuit are mainly mounted. A plurality of circuit boards including the circuit board 16 (only the main circuit board 16 is shown) and the like are disposed at predetermined positions.
[0024]
The finder device 13 receives a light beam emitted from the reflecting mirror 13b, and a reflecting mirror 13b configured to bend the optical axis of the subject light beam transmitted through the photographing optical system 12a and guide the light beam toward the observation optical system. It is composed of a pentaprism 13a for forming an erect image and an eyepiece 13c for forming an image in an optimal form for magnifying and observing the image formed by the pentaprism 13a.
[0025]
The reflecting mirror 13b is configured to be movable between a position retracted from the optical axis of the imaging optical system 12a and a predetermined position on the optical axis. In a normal state, the reflecting mirror 13b is located on the optical axis of the imaging optical system 12a. They are arranged at a predetermined angle with respect to the optical axis, for example, at an angle of 45 degrees. Thus, when the camera 1 is in the normal state, the optical axis of the subject light beam transmitted through the imaging optical system 12a is bent by the reflecting mirror 13b, and the luminous flux of the pentaprism 13a disposed above the reflecting mirror 13b is changed. It is reflected to the side.
[0026]
On the other hand, while the camera 1 is performing the photographing operation, the reflecting mirror 13b moves to a predetermined position retracted from the optical axis of the photographing optical system 12a. As a result, the subject light flux is guided toward the image sensor.
[0027]
As the shutter unit 14, for example, a shutter mechanism of a focal plane system, a driving circuit thereof, or the like that is generally used in a conventional camera or the like is applied.
[0028]
FIG. 2 is a block diagram of the digital camera system according to the first embodiment of the present invention.
[0029]
This camera system mainly includes a camera body 11 and a lens barrel 12 as an interchangeable lens, and a desired lens barrel 12 is detachably mounted on the front surface of the camera body 11. .
[0030]
The lens barrel 12 is controlled by a lens control microcomputer (hereinafter referred to as “Lucom”) 205. The control of the camera body 11 is performed by a body control microcomputer (hereinafter referred to as “Bucom”) 150. The Lucom 205 and the Bucom 150 are electrically connected via the communication connector 206 so that they can communicate with each other at the time of synthesis. Then, as a camera system, the Lucom 205 operates in cooperation with the Bucom 150 in a dependent manner.
[0031]
In the lens barrel 12, a photographing optical system 12a and an aperture 203 are provided. The photographing optical system 12a is driven by a DC motor (not shown) provided in the lens driving mechanism 202. The aperture 203 is driven by a stepping motor (not shown) in the aperture drive mechanism 204. The Lucom 205 controls each of these motors according to a command from the Bucom 150.
[0032]
The following components are arranged in the camera body 11 as shown. For example, components of a single-lens reflex system as an optical system (a pentaprism 13a, a reflecting mirror 13b, an eyepiece 13c, and a sub-mirror 114), a focal plane shutter 14 on the optical axis, and a reflected light beam from the sub-mirror 114 An AF sensor unit 116 for automatically measuring a distance in response to the signal is provided.
[0033]
Further, an AF sensor driving circuit 117 for driving and controlling the AF sensor unit 116, a mirror driving mechanism 118 for driving and controlling the reflecting mirror 13b, and a shutter for charging a spring for driving a front curtain and a rear curtain of the shutter unit 14. A charging mechanism 119, a shutter control circuit 120 for controlling the movement of the front curtain and the rear curtain, and a photometry circuit 121 for performing photometry processing based on the light beam from the pentaprism 13a are provided.
[0034]
On the optical axis, an image sensor 27 for photoelectrically converting a subject image passing through the optical system is provided as a photoelectric conversion element. Further, the image pickup device 27 is protected by a dustproof filter 21 as an optical element disposed between the image pickup device 27 and the shutter unit 14. For example, a piezoelectric element 22 is attached to the periphery of the dustproof filter 21 as a part of the vibration means for vibrating the dustproof filter 21 at a predetermined frequency.
[0035]
The piezoelectric element 22 had two electrodes, and the piezoelectric element 22 was driven by a dust-proof filter drive circuit 140 as a part of the vibrating means to vibrate the dust-proof filter 21 and adhere to the glass surface. It is configured to remove dust.
[0036]
Note that a temperature measurement circuit 133 is provided near the dustproof filter 21 to measure the temperature around the image sensor 27.
[0037]
The camera system further includes an image processing controller 128 via an interface circuit 123 connected to the image sensor 27. The image processing controller 128 performs image processing using a liquid crystal monitor 124, an SDRAM 125 as a storage medium, a flash ROM (FlashROM) 126, a recording medium 127, and the like, thereby providing an electronic recording function as well as an electronic imaging function. It is configured as follows.
[0038]
As another storage medium, a non-volatile memory 129 composed of, for example, an EEPROM is provided so as to be accessible from the Bucom 150 as a non-volatile storage means for storing predetermined control parameters required for camera control.
[0039]
Further, the Bucom 150 is provided with an operation display LCD 151 for notifying the user of the operation state of the camera by a display output, and a camera operation SW 152. The camera operation SW 152 is a group of switches including operation buttons required for operating the camera, such as a release SW, a mode change SW, and a power SW.
[0040]
Further, a battery 154 as a power supply and a power supply circuit 153 for converting the voltage of the power supply to a voltage required by each circuit unit constituting the camera system and supplying the converted voltage are provided.
[0041]
In the camera system configured as described above, each unit operates as follows.
[0042]
The image processing controller 128 controls the interface circuit 123 in accordance with a command from the Bucom 150 to capture image data from the image sensor 27. This image data is converted into a video signal by the image processing controller 128 and output and displayed on the liquid crystal monitor 124. The user can check the captured image from the display image on the liquid crystal monitor 124.
[0043]
The SDRAM 125 is a memory for temporarily storing image data, and is used as a work area when the image data is converted. The image data is set to be stored in the recording medium 127 after being converted into JPEG data.
[0044]
It is more preferable that the imaging element 27 and the piezoelectric element 22 are integrally housed in a case that has the dustproof filter 21 on one side and is surrounded by a frame as shown by a broken line.
[0045]
Normally, temperature affects the elastic modulus of a glass material and is one of the factors that change its natural frequency. Therefore, it is necessary to measure the temperature during operation and consider the change in the natural frequency. No. It is better to measure the temperature change of the dustproof filter 21 provided to protect the front surface of the image sensor 27 whose temperature rises sharply during operation, and to estimate the natural frequency at that time.
[0046]
Therefore, in the case of this example, a sensor (not shown) connected to the temperature measurement circuit 133 is provided to measure the temperature around the image sensor 27. It is preferable that the temperature measurement point of the sensor is set very close to the vibration surface of the dustproof filter 21.
[0047]
The mirror driving mechanism 118 is a mechanism for driving the reflecting mirror 13b to the UP position and the DOWN position. When the reflecting mirror 13b is at the DOWN position, the light flux from the photographing optical system 12a is transmitted to the AF sensor unit 116 The light is divided and guided to the prism 13a side.
[0048]
The output from the AF sensor in the AF sensor unit 116 is transmitted to the Bucom 150 via the AF sensor drive circuit 117, and a known distance measurement process is performed.
[0049]
Further, while the user can view the subject from the eyepiece 13c adjacent to the pentaprism 13a, a part of the light beam passing through the pentaprism 13a is guided to a photosensor (not shown) in the photometric circuit 121, where it is detected. A well-known photometric process is performed based on the light amount thus obtained.
[0050]
Next, details of the imaging unit 15 in the camera 1 of the present embodiment will be described below.
[0051]
FIGS. 3, 4, and 5 are views showing a part of the imaging unit 15 in the camera 1 of the present embodiment, and FIG. 3 is an exploded perspective view of a main part of the imaging unit in an exploded manner. is there. FIG. 4 is a perspective view showing a part of the image pickup unit in an assembled state. FIG. 5 is a cross-sectional view along the cut surface of FIG.
[0052]
Note that the imaging unit 15 of the camera 1 of the present embodiment is a unit configured by a plurality of members including the shutter unit 14 as described above, but in FIGS. The illustration of the shutter section 14 is omitted. In addition, in order to show the positional relationship between the constituent members, in FIGS. FIG. 2 also shows a main circuit board 16 on which an electric circuit of an imaging system is mounted. It should be noted that the details of the main circuit board 16 itself are applied to those generally used in conventional cameras and the like, and the description thereof is omitted.
[0053]
The imaging unit 15 is composed of a CCD or the like, and transmits an image signal corresponding to the light irradiated on its own photoelectric conversion surface through the imaging optical system 12a, and a thin plate-shaped fixedly supporting the imaging element 27. An image sensor fixing plate 28 made of a member and an optical element arranged on the side of the photoelectric conversion surface of the image sensor 27 and formed to remove high frequency components from a subject light beam transmitted through the imaging optical system 12a and irradiated. An optical low-pass filter (hereinafter, referred to as an optical LPF) 25, and a low-pass filter receiving member disposed at a peripheral portion between the optical LPF 25 and the image sensor 27 and formed by a substantially frame-shaped elastic member or the like 26, and the image pickup device 27 are housed and fixedly held, and the optical LPF 25 is closely adhered to a peripheral portion thereof or a portion in the vicinity thereof. And an image pickup device housing case member 24 (hereinafter referred to as a CCD case 24) disposed so as to make close contact with a dust-proof filter receiving member 23 described later, and a dust-proof filter 21 disposed on the front side of the CCD case 24. And a dust-proof filter receiving member 23 which is in close contact with a peripheral portion thereof or a portion in the vicinity thereof, and is supported by the dust-proof filter receiving member 23 on the side of the photoelectric conversion surface of the image sensor 27 and on the front side of the optical LPF 25. A dustproof filter 21 which is a dustproof member disposed opposite to a predetermined position having a predetermined distance from the optical LPF 25; and a predetermined vibration is arranged on the periphery of the dustproof filter 21 to cause the dustproof filter 21 to vibrate. The piezoelectric element 22 is a vibrating member for applying, for example, an electromechanical transducer or the like, and the dustproof filter 21 is prevented. It is composed of a pressing member 20 and the like made of an elastic body that is airtightly joined to and fixedly held to the dust filter receiving member 23.
[0054]
The imaging element 27 receives the subject light beam transmitted through the imaging optical system 12a on its own photoelectric conversion surface and performs a photoelectric conversion process to obtain an image signal corresponding to the subject image formed on the photoelectric conversion surface. For example, a charge coupled device (CCD; Charge Coupled Device) is applied.
[0055]
The image sensor 27 is mounted at a predetermined position on the main circuit board 16 via an image sensor fixing plate 28. The image signal processing circuit, the work memory, and the like are mounted on the main circuit board 16 as described above, and the signal output from the image sensor 27 is processed by these circuits.
[0056]
On the front side of the image sensor 27, an optical LPF 25 is disposed with a low-pass filter receiving member 26 interposed therebetween. Then, a CCD case 24 is provided so as to cover this.
[0057]
That is, the CCD case 24 is provided with an opening 24c having a rectangular shape at a substantially central portion, and the optical LPF 25 and the image sensor 27 are arranged in the opening 24c from the rear side. . A step portion 24a having a substantially L-shaped cross section is formed on the inner peripheral edge portion on the rear side of the opening 24c, as shown in FIGS.
[0058]
As described above, the low-pass filter receiving member 26 made of an elastic member or the like is provided between the optical LPF 25 and the image sensor 27. The low-pass filter receiving member 26 is disposed at a position on the front edge of the imaging device 27 that avoids the effective range of the photoelectric conversion surface, and comes into contact with the vicinity of the rear edge of the optical LPF 25. I have. The airtightness between the optical LPF 25 and the image sensor 27 is maintained. As a result, an elastic force is exerted on the optical LPF 25 by the low-pass filter receiving member 26 in the optical axis direction.
[0059]
Therefore, by arranging the peripheral portion on the front side of the optical LPF 25 so as to be substantially airtightly contacted with the step portion 24a of the CCD case 24, a low-pass device for displacing the optical LPF 25 in the optical axis direction is provided. The position of the optical LPF 25 in the optical axis direction is regulated against the elastic force of the filter receiving member 26.
[0060]
In other words, the position of the optical LPF 25 inserted from the rear side into the opening 24c of the CCD case 24 is regulated in the optical axis direction by the step portion 24a. Thus, the optical LPF 25 does not escape from the inside of the CCD case 24 toward the front side.
[0061]
After the optical LPF 25 is inserted into the opening 24c of the CCD case 24 from the rear side in this way, the imaging element 27 is disposed on the rear side of the optical LPF 25. In this case, a low-pass filter receiving member 26 is sandwiched between the optical LPF 25 and the image sensor 27 at the peripheral edge.
[0062]
The image sensor 27 is mounted on the main circuit board 16 with the image sensor fixing plate 28 interposed therebetween as described above. The image sensor fixing plate 28 is fixed to the screw hole 24e from the rear side of the CCD case 24 by a screw 28b via a spacer 28a. The main circuit board 16 is fixed to the image sensor fixing plate 28 by screws 16d via spacers 16c.
[0063]
On the front side of the CCD case 24, a dust filter receiving member 23 is fixed to a screw hole 24b of the CCD case 24 by a screw 23b. In this case, a peripheral groove 24d is formed in a substantially annular shape at a predetermined position on the peripheral side and the front side of the CCD case 24, as shown in detail in FIGS. On the other hand, an annular convex portion 23d (not shown in FIG. 3) corresponding to the peripheral groove 24d of the CCD case 24 is entirely provided at a predetermined position on the peripheral side and the rear side of the dustproof filter receiving member 23. It is formed in a substantially annular shape over the circumference. Therefore, the CCD case 24 and the dust-proof filter receiving member 23 are connected to each other in the annular region, that is, in the region where the peripheral groove 24d and the annular convex portion 23d are formed by fitting the annular convex portion 23d and the peripheral groove 24d. Are fitted substantially airtightly.
[0064]
The dustproof filter 21 has a circular or polygonal plate shape as a whole, and at least a region having a predetermined spread in the radial direction from its own center forms a transparent portion, and this transparent portion is provided on the front side of the optical LPF 25. Are arranged facing each other with an interval of.
[0065]
A predetermined vibration member for applying vibration to the dustproof filter 21 is formed on the peripheral portion of one surface (the rear side in the present embodiment) of the dustproof filter 21 and is formed by an electromechanical transducer or the like. The piezoelectric elements 22 to be integrated are arranged by, for example, means such as sticking with an adhesive. The piezoelectric element 22 is configured to generate a predetermined vibration in the dust filter 21 by applying a predetermined driving voltage from the outside.
[0066]
The dust filter 21 is fixed and held by a pressing member 20 made of an elastic body such as a leaf spring so as to be airtightly joined to the dust filter receiving member 23.
[0067]
An opening 23f having a circular or polygonal shape is provided in the vicinity of a substantially central portion of the dustproof filter receiving member 23. The opening 23f is set to have a size large enough to allow a subject light beam transmitted through the photographing optical system 12a to pass therethrough and to irradiate the photoelectric conversion surface of the image sensor 27 disposed behind the subject light beam. .
[0068]
A wall portion 23e (see FIGS. 4 and 5) protruding toward the front side is formed in a substantially annular shape at a peripheral portion of the opening 23f, and the front end side of the wall portion 23e further faces the front side. A receiving portion 23c is formed so as to protrude.
[0069]
On the other hand, in the vicinity of the outer peripheral edge on the front side of the dust-proof filter receiving member 23, a plurality of (three in this embodiment) projections 23a are formed at predetermined positions so as to protrude toward the front side. . The protruding portion 23a is a portion formed to fix the pressing member 20 for fixing and holding the dustproof filter 21, and the pressing member 20 is formed with a screw 20a or the like with respect to the tip of the protruding portion 23a. It is fixed by fastening means.
[0070]
The pressing member 20 is a member formed of an elastic body such as a leaf spring as described above, and has a base end fixed to the protruding portion 23 a and a free end abutting against the outer peripheral edge of the dustproof filter 21. By being in contact, the dust filter 21 is pressed toward the dust filter receiving member 23, that is, in the optical axis direction.
[0071]
In this case, a predetermined portion of the piezoelectric element 22 disposed on the outer peripheral edge on the back side of the dustproof filter 21 abuts on the receiving portion 23c, and thereby the position of the dustproof filter 21 and the piezoelectric element 22 in the optical axis direction. Are being regulated. Accordingly, the dustproof filter 21 is thereby fixed and held so as to be airtightly joined to the dustproof filter receiving member 23 via the piezoelectric element 22.
[0072]
In other words, the dust-proof filter receiving member 23 is configured to be airtightly joined to the dust-proof filter 21 via the piezoelectric element 22 by the urging force of the pressing member 20.
[0073]
By the way, as described above, the circumferential groove 24d and the annular convex portion 23d (see FIGS. 4 and 5) of the dust-proof filter receiving member 23 and the CCD case 24 are substantially airtightly fitted to each other. At the same time, the dust-proof filter receiving member 23 and the dust-proof filter 21 are hermetically joined via the piezoelectric element 22 by the urging force of the pressing member 20. The optical LPF 25 disposed in the CCD case 24 is disposed so as to be substantially airtight between the peripheral edge on the front side of the optical LPF 25 and the step portion 24 a of the CCD case 24. Further, on the rear side of the optical LPF 25, an image sensor 27 is disposed via a low-pass filter receiving member 26, so that substantially airtightness is maintained between the optical LPF 25 and the image sensor 27. ing.
[0074]
Accordingly, a predetermined gap 51a is formed in the space between the optical LPF 25 and the dustproof filter 21 facing each other. Further, a space 51b is formed by the periphery of the optical LPF 25, that is, the CCD case 24, the dust filter receiving member 23, and the dust filter 21. The space 51b is a sealed space formed so as to protrude outside the optical LPF 25 (see FIGS. 4 and 5). The space 51b is set to be a space wider than the space 51a. The space formed by the gap 51a and the space 51b is a sealed space 51 which is substantially airtightly sealed by the CCD case 24, the dust filter receiving member 23, the dust filter 21, and the optical LPF 25 as described above. ing.
[0075]
As described above, in the imaging unit 15 of the camera according to the present embodiment, the sealing structure that forms the substantially sealed space 51 that is formed around the optical LPF 25 and the dustproof filter 21 and that includes the void 51a is configured. I have. The sealing structure is provided at a position outside the periphery of the optical LPF 25 or its vicinity.
[0076]
Further, in the present embodiment, the dustproof filter receiving member 23, which is the first member that supports the dustproof filter 21 in close contact with the peripheral portion or in the vicinity thereof, and the optical LPF 25 in close contact with the peripheral portion or in the vicinity thereof. The sealing structure is constituted by the CCD case 24 and the like, which is a second member disposed so as to be in close contact with the dust-proof filter receiving member 23 at a predetermined portion of the device.
[0077]
In the camera according to the present embodiment configured as described above, the dustproof filter 21 is disposed at a predetermined position on the front side of the image sensor 27 so as to be formed on the periphery of the photoelectric conversion surface of the image sensor 27 and the dustproof filter 21. The sealing space 51 to be sealed is sealed, thereby preventing dust and the like from adhering to the photoelectric conversion surface of the image sensor 27.
[0078]
In this case, a periodic voltage is applied to the piezoelectric element 22 disposed integrally with the periphery of the dust-proof filter 21 for dust and the like adhering to the exposed surface on the front side of the dust-proof filter 21. By applying a predetermined vibration to the dustproof filter 21, the dustproof filter 21 can be removed.
[0079]
FIG. 6 is a front view showing only the dustproof filter 21 and the piezoelectric element 22 provided integrally with the dustproof filter 21 of the imaging unit 15 of the camera 1. 7 and 8 show the state change of the dustproof filter 21 and the piezoelectric element 22 when a driving voltage is applied to the piezoelectric element 22 of FIG. 6, and FIG. 7 is along the line AA of FIG. FIG. 8 is a sectional view taken along line BB of FIG.
[0080]
Here, for example, when a negative (minus;-) voltage is applied to the piezoelectric element 22, the dustproof filter 21 is deformed as shown by a solid line in FIGS. +) When a voltage is applied, the dustproof filter 21 is deformed as shown by a dotted line in FIG.
[0081]
In this case, the amplitude is substantially zero at the position of the node of vibration as indicated by the reference numeral 21a in FIGS. 6 to 8, so that the receiving portion 23c of the dustproof filter receiving member 23 is provided at a portion corresponding to the node 21a. Is set to abut. Thereby, the dustproof filter 21 can be efficiently supported without hindering the vibration.
[0082]
In this state, by controlling the dustproof filter driving circuit 140 at a predetermined time and applying a periodic voltage to the piezoelectric element 22, the dustproof filter 21 vibrates and adheres to the surface of the dustproof filter 21. Dust and the like are removed.
[0083]
The resonance frequency at this time is determined by the shape, plate thickness, material and the like of the dustproof filter 21. In the examples shown in FIGS. 6 to 8 described above, the case where the primary vibration is generated is shown. However, the present invention is not limited to this, and a higher-order vibration may be generated.
[0084]
Next, the driving of the dust filter 21 of the digital camera according to the first embodiment and the operation and control thereof will be described based on the circuit diagram of the dust filter driving circuit 140 shown in FIG. 9 and the time chart of FIG.
[0085]
The dustproof filter driving circuit 140 exemplified here has a circuit configuration as shown in FIG. 9, and waveform signals (Sig1 to Sig6) represented by the time chart of FIG. Is controlled as follows. That is, as shown in FIG. 9, the dust filter drive circuit 140 includes an N-ary counter 41, a 1/2 frequency divider 42, an inverter 43, a plurality of MOS transistors (Q00, Q01, Q02) 44a, 44b, 44c, and a transformer 45. , A resistor (R00) 46, an A / D converter 60, a first electrode A of the piezoelectric element 22 and a second electrode B61 arranged in parallel therewith, a diode (D00) 62, resistors (R01, R02) 63 and 64, and a capacitor ( C00) 65.
[0086]
By the ON / OFF switching operation of the transistor (Q01) 44b and the transistor (Q02) 44c connected to the primary side of the transformer 45, a signal (Sig4) of a predetermined cycle is generated on the secondary side of the transformer 45. While driving the piezoelectric element 22 having the two electrodes A and B variously based on the signal of the predetermined cycle, an efficient resonance frequency is searched for and the dust filter 21 is effectively resonated. Has become. Details will be described later.
[0087]
The Bucom 150 controls the dust filter drive circuit 140 via two IO ports P_PwCont and IO port D_NCnt provided as control ports and the clock generator 55 existing inside the Bucom 150 as follows. The clock generator 55 outputs a pulse signal (basic clock signal) to the N-ary counter 41 at a frequency sufficiently faster than the signal frequency applied to the piezoelectric element 22. This output signal is signal Sig1 having a waveform represented by the time chart in FIG. The basic clock signal is input to the N-ary counter 41.
[0088]
The N-ary counter 41 counts the pulse signal and outputs a count end pulse signal each time the pulse signal reaches a predetermined value “N”. That is, the basic clock signal is divided by 1 / N. This output signal is signal Sig2 having a waveform shown in the time chart of FIG.
[0089]
In the frequency-divided pulse signal, the duty ratio between High and Low is not 1: 1. Therefore, the duty ratio is converted to 1: 1 through the 1/2 frequency dividing circuit 42.
[0090]
The converted pulse signal corresponds to signal Sig3 having a waveform represented by the time chart in FIG.
[0091]
In the High state of the converted pulse signal, the MOS transistor (Q01) 44b to which this signal has been input is turned on. On the other hand, the pulse signal is applied to the transistor (Q02) 44c via the inverter 43. Therefore, in the low state of the pulse signal, the transistor (Q02) 44c to which this signal has been input is turned on. When the transistor (Q01) 44b and the transistor (Q02) 44c connected to the primary side of the transformer 45 are turned on alternately, a signal having a cycle like the signal Sig4 in FIG. 10 is generated on the secondary side.
[0092]
The winding ratio of the transformer 45 is determined from the output voltage of the unit of the power supply circuit 153 and the voltage required for driving the piezoelectric element 22. Note that the resistor (R00) 46 is provided to restrict an excessive current from flowing through the transformer 45.
[0093]
To drive the piezoelectric element 22, the transistor (Q00) 44a must be in the ON state, and a voltage must be applied from the unit of the power supply circuit 153 to the center tap of the transformer 45. In the figure, ON / OFF control of the transistor (Q00) 44a is performed via P_PwCont of the IO port. The set value “N” of the N-ary counter 41 can be set from the IO port D_NCnt. Therefore, the Bucom 150 can arbitrarily change the drive frequency of the piezoelectric element 22 by appropriately controlling the set value “N”.
[0094]
At this time, the frequency can be calculated by the following equation.
[0095]
N: Set value to counter,
fpls: frequency of the output pulse of the clock generator,
fdrv: frequency of a signal applied to the piezoelectric element,
fdrv = fpls / 2N (1 equation)
The calculation based on this equation is performed by the CPU (control means) of the Bucom 150.
[0096]
The electrode B61 is an electrode of a piezoelectric element for detecting a vibration state of the glass plate. An AC voltage (monitor signal) is generated from the electrode B61 according to the vibration state of the glass plate. This is Sig5 on the time chart of FIG.
[0097]
A diode (D00) 62 connected to the electrode B61 is provided for half-wave rectification of the monitor signal. The resistors (R01, R02) 63, 64 and the capacitor (C00) 65 following the diode (D00) 62 form an envelope of the monitor signal. The optimum value of the time constant determined by the detection circuit including the resistors (R01, R02) 63 and 64 and the capacitor (C00) 65 differs depending on the vibration frequency of the glass. The monitor signals are reduced by the resistors (R01, R02) 63, 64 to a level that can be input to the A / D converter 60. This signal is Sig6 on the time chart of FIG.
[0098]
This signal is converted to digital data by the A / D converter 60 and read from the IO port D_DACin of the Bucom 150. The Bucom 150 may determine the value to be set in the N-ary counter 41 so that the monitor signal has the maximum level. When the glass is driven with the value (resonance frequency) of the N-ary counter 41 indicating the maximum level, dust can be efficiently removed.
[0099]
The control performed by the camera body control microcomputer (Bucom) 150 will be specifically described.
[0100]
FIG. 11 illustrates a main routine of a control program operating on the Bucom 150. First, when the power switch (not shown) of the camera is turned on, the Bucom 150 starts operating, and in step # 001, a process for activating the camera system is executed. The power supply circuit 153 is controlled to supply power to each circuit unit constituting the camera system. In addition, initialization of each circuit is performed.
[0101]
In step # 002, a subroutine "dust removal operation" is called and executed. In this subroutine, the dust filter 21 is vibrated while the drive frequency is changed near the resonance frequency, and the dust adhered to the glass surface is shaken off. The attached dust can be removed.
[0102]
Step # 003 is a step that is periodically executed, and is an operation step for detecting a detached state of the lens barrel 12 by performing a communication operation with the Lucom 205. Then, in step # 004, it is determined whether or not the lens barrel 12 is mounted on the camera body 11, and if YES, the process proceeds to step # 007, and if NO, the process proceeds to step # 005. In step # 005, it is determined whether or not the lens barrel 12 has been removed from the camera body 11. If YES here, the process proceeds to step # 006 to reset the control flag F_Lens, and then proceeds to step # 010. If the determination in step # 005 is NO, the process immediately proceeds to step # 010.
[0103]
On the other hand, in step # 007, the control flag F_Lens is set. This control flag indicates “1” while the lens barrel 12 is mounted on the camera body 11, and indicates “0” while the lens barrel 12 is removed.
[0104]
Then, in step # 008, a subroutine "dust removal operation" for removing dust from the dustproof filter 21 is called and executed. Thereafter, the process proceeds to step # 010.
[0105]
In step # 010, the state of the camera operation SW 152 is detected. Then, in step # 011, it is determined whether or not the CleanUP-SW (not shown), which is one of the camera operation SWs 152, has been operated, based on whether or not a change in the state has been detected. The process proceeds to step # 012, and if NO, proceeds to step # 014.
[0106]
In step # 012, an operation for removing dust from the dust filter 21 is performed. In conjunction with the operation of step # 012, an operation of taking in pixel defect information of a CCD (imaging device) is executed in step # 013. The information on the defective pixel is stored in the FlashROM 126 and used for correcting the image data. If dust adheres, defect information cannot be obtained accurately. Therefore, before the operation of step # 013, the operation of step # 012 is executed in the same manner as described above.
[0107]
On the other hand, in step # 014, 1st. It is determined whether or not a release SW (not shown) has been operated. If 1st. If the release SW is ON, the process proceeds to step # 015. If the release SW is OFF, the process returns to step # 003.
[0108]
In step # 015, the luminance information of the subject is obtained from the photometry circuit 121. The exposure time (Tv value) of the image sensor 27 and the aperture setting value (Av value) of the photographic lens 1 are calculated from this information.
[0109]
In step # 016, detection data of the AF sensor unit 116 is obtained via the AF sensor drive circuit 117. The amount of defocus is calculated based on this data.
[0110]
Next, in step # 017, the state of F_Lens is determined. If “0”, it means that the lens barrel 12 does not exist, so that the photographing operation after the next step # 018 cannot be executed. Therefore, in this case, the process returns to step # 003. If the state of F_Lens is "1", the flow shifts to step # 018. In step # 018, the focus shift amount is transmitted to the Lucom 205, and the driving of the photographing optical system 12a based on the shift amount is commanded.
[0111]
In step # 019, one of the camera operation SWs 152, 2nd. It is determined whether or not a release SW (not shown) has been operated. This 2nd. When the release SW is ON, the process proceeds to step # 0190 to perform a predetermined photographing operation. When the release SW is OFF, the process returns to step # 003.
[0112]
In step # 0190, a "dust removal operation" routine is executed to remove dust prior to the photographing operation.
[0113]
In the next step # 020, the Av value is transmitted to the Lucom 205, and the drive of the aperture 203 is commanded. In step # 021, the reflecting mirror (mirror) 13b is moved to the UP position. In step # 022, the front curtain of the shutter 14 starts running, and in step # 023, the image processing controller 128 is instructed to execute an imaging operation. When the exposure to the image sensor 27 is completed for the time indicated by the Tv value, the rear curtain running of the shutter 14 is started in step # 024, and the reflecting mirror 13b is driven to the Down position in step # 025.
[0114]
At the same time, the shutter 14 is charged.
[0115]
In step # 026, the Lucom 205 is instructed to return the aperture 203 to the open position. In step # 027, the image processing controller 128 is instructed to record the photographed image data on the recording medium 127. I do. When the recording of the image data is completed, the process returns to step # 003.
[0116]
FIG. 12 is a flowchart of a subroutine for performing the dust removing operation. Before that, a characteristic portion of the present invention will be described.
[0117]
As in the electronic imaging device according to the first embodiment, in an electronic imaging device having a dustproof mechanism that removes dust adhering to the surface of the dustproof filter by vibrating a dustproof filter disposed in front of the image sensor, It is necessary to vibrate at the resonance frequency inherent to the dust filter in order to increase the amplitude of the dust filter. However, the approximate value of the resonance frequency can be obtained by design, but is not actually constant due to various factors such as variation of the dustproof filter, aging, and ambient temperature.
[0118]
Therefore, in the first embodiment, the frequency at which the dust filter is vibrated is sequentially changed (scanning the frequency) in a predetermined frequency range including the designed resonance frequency. Thereby, even if the resonance point deviates from the design value, the vibration at the resonance frequency can always be performed within the range.
[0119]
FIG. 13 is a diagram showing the relationship between the preset value set in the N-ary counter 41 and the drive frequency applied to the piezoelectric element 22 when scanning the vibration frequency from F1 to F15. In this case, for example, the design resonance frequency is 40 Hz, and even if the resonance frequency is shifted for some reason, vibration at the resonance frequency is possible within a range of about ± 0.5 Hz.
[0120]
FIG. 14 is a diagram showing a change in monitor output with respect to the frequency scan operation. The frequency Fk at which the monitor output becomes maximum corresponds to the resonance frequency at this time.
[0121]
By the way, the amplitude of the vibration of the dustproof filter also changes according to the power supply voltage. For example, when a battery is used as a drive power source, the amplitude is large in the case of a new battery, and the amplitude is reduced as the remaining capacity decreases. Therefore, unless a large amplitude is obtained even at a relatively low voltage, a sufficient dust removal function cannot be obtained.However, in the case of a new battery, the amplitude of the dust filter becomes too large, and the dust filter itself becomes It may be damaged. In order to prevent such an accident, a circuit such as a voltage regulator may be provided. However, it is not a good idea because the overall circuit configuration becomes complicated and the size and cost of the camera are increased.
[0122]
Therefore, in the first embodiment of the present invention, as shown in FIG. 15, a monitor output value that “if the vibration continues for a long time at an amplitude exceeding the current amplitude, the probability that the dust filter will be damaged increases”, that is, The upper limit value at which the vibration can be safely performed is defined as Mmax, and the frequency range (Fh1 to Fh2) and the frequency range (F1 to Fh1 and Fh2 to F15) where there is a risk of damage depending on the frequency at that time are defined to remove dust. During the operation, the vibration state is controlled depending on whether or not the monitor output exceeds the above-mentioned Mmax.
[0123]
Hereinafter, the details will be described with reference to FIG.
[0124]
In step # 031, a preset value corresponding to F1 in FIG. In step # 032, the dustproof filter drive circuit 140 is controlled to start the vibration operation. In step # 033, it is determined whether or not the monitor output has exceeded Mmax. If not, the process proceeds to step # 034, and if it has, the process proceeds to step # 035.
[0125]
In step # 034, it is determined whether the frequency scan has been completed, that is, whether the frequency has been changed in order from the initial frequency F1 and has reached the final frequency F15. If the frequency has not reached the final frequency F15, the process proceeds to step # 036. If the frequency has reached, the process proceeds to step # 035.
[0126]
In step # 036, a frequency next to the current set frequency is set based on FIG. 13, and the process returns to step # 033.
[0127]
In step # 035, when it is determined in step # 033 that the monitor output has exceeded Mmax, or when it is determined in step # 034 that it has reached the final frequency F15, the vibration operation is terminated (stopped). And return.
[0128]
As described above, in the first embodiment, when the monitor output exceeds Mmax, the vibrating operation is immediately stopped. Therefore, an accident that the amplitude of the dustproof filter becomes too large and breaks occurs. Absent.
[0129]
By the way, if the battery voltage is very high, the monitor output may exceed Mmax immediately after the start of the vibration operation. Since a certain amount of vibration continuation time is required to reliably remove dust and the like adhering to the dustproof filter, the vibration operation is stopped immediately after the monitor output exceeds Mmax as in the first embodiment. If this occurs, the dust removal operation may be insufficient.
[0130]
Accordingly, in the second embodiment of the present invention, as shown in FIG. 16, even if the monitor output exceeds Mmax, the vibration is not stopped immediately, and the standby is performed for 100 mS as shown in step # 047. I have to. As a result, dust can be reliably removed.
[0131]
The time of 100 mS is a value determined by the characteristics of the dust removing mechanism including the dust filter, and is not specified.
[0132]
Steps # 041 to # 046 are the same as steps # 031 to # 036 in FIG. 12, and a description thereof will be omitted.
[0133]
【The invention's effect】
According to the present invention, there is provided an electronic imaging apparatus which can vibrate dustproof glass in an optimal state without complicating the configuration of a driving circuit of a piezoelectric element.
[Brief description of the drawings]
FIG. 1 is a perspective view of a part of a digital camera according to a first embodiment of the present invention, schematically showing an internal configuration thereof.
FIG. 2 is a block configuration diagram of the digital camera system according to the first embodiment of the present invention.
FIG. 3 is an exploded perspective view of a main part of the camera 1 according to the embodiment, in which a part of the image pickup unit 15 is taken out and shown.
FIG. 4 is a perspective view showing a part of the imaging unit 15 in the camera 1 of the present embodiment, which is taken out and partially cut away in an assembled state.
FIG. 5 is a cross-sectional view taken along the section plane of FIG. 4;
FIG. 6 is a front view showing only a dustproof filter 21 and a piezoelectric element 22 provided integrally with the dustproof filter 21 of the imaging unit 15 of the camera 1;
7 is a cross-sectional view taken along the line AA of FIG. 6, showing a state change of the dust filter 21 and the piezoelectric element 22 when a driving voltage is applied to the piezoelectric element 22 of FIG.
8 is a cross-sectional view taken along the line BB of FIG. 6, showing a state change of the dust filter 21 and the piezoelectric element 22 when a driving voltage is applied to the piezoelectric element 22 of FIG.
FIG. 9 is a circuit diagram of a dust filter driving circuit 140.
FIG. 10 is a time chart for explaining the driving of the dustproof filter 21 of the digital camera according to the first embodiment and the operation and control thereof.
FIG. 11 is a diagram showing a main routine of a control program operating on the Bucom 150.
FIG. 12 is a flowchart of a subroutine for performing a dust removing operation.
FIG. 13 is a diagram illustrating a relationship between a preset value set in an N-ary counter 41 and a drive frequency applied to a piezoelectric element 22 when scanning the vibration frequency from F1 to F15.
FIG. 14 is a diagram showing a change in monitor output with respect to a frequency scan operation.
FIG. 15 is a diagram illustrating a method of controlling a vibration state according to whether or not a monitor output has exceeded Mmax during a dust removal operation.
FIG. 16 is a flowchart for explaining a method according to the second embodiment of the present invention in which the vibration operation is not stopped immediately even when the monitor output exceeds Mmax.
[Explanation of symbols]
1 camera
11 Camera body
11a Mounting unit for photographing optical system
12 lens barrel
12a Imaging optical system
13 Finder device
13a Penta prism
13b reflector
13c eyepiece
14 Shutter section
15 Imaging unit
16 Main circuit board
17 Release button
21 Dustproof filter (dustproof member)
22 Piezoelectric element (vibration means)
27 Image sensor (photoelectric conversion device)
28 Image sensor fixing plate
114 Submirror
116 AF sensor unit
117 AF sensor drive circuit
118 Mirror drive mechanism
119 Shutter charge mechanism
120 Shutter control circuit
121 Photometric circuit
123 Interface Circuit
124 LCD monitor
125 SDRAM
126 Flash ROM
127 Recording media
128 Image processing controller
129 Non-volatile memory
133 Temperature measurement circuit
140 Dustproof filter drive circuit
150 Body control microcomputer (Bucom)
151 LCD for operation display
152 Camera operation switch
153 Power supply circuit
154 batteries
202 Lens drive mechanism
203 aperture
204 Aperture drive mechanism
205 Lens control microcomputer (Lucom)
206 communication connector

Claims (8)

An electronic imaging device having a dustproof mechanism,
A photoelectric conversion element that converts an optical image of a subject into an electric signal,
A dustproof member arranged on the front surface of the photoelectric conversion element,
Vibrating means for vibrating the dustproof member to perform a dust removing operation,
Frequency varying means for sequentially changing the vibration frequency of the dustproof member vibrated by the vibration means,
Monitoring means for monitoring an amplitude value when the dustproof member is vibrating, and controlling the dust removal operation according to the monitored amplitude value;
An electronic imaging device comprising: 2. The electronic imaging apparatus according to claim 1, wherein the vibration unit vibrates the dustproof member according to a frequency signal supplied from the frequency variable unit. 3. The electronic imaging apparatus according to claim 2, wherein the vibration unit vibrates the dustproof member in accordance with a plurality of frequency signals in a predetermined frequency range sequentially supplied from the frequency variable unit. . The electronic imaging device according to claim 3, wherein the predetermined frequency range is a range including a resonance frequency of the dustproof member. 2. The electronic imaging apparatus according to claim 1, wherein the monitoring unit monitors an amplitude value at which the dust-proof member may be damaged, and stops the dust removal operation when the amplitude value exceeds the amplitude value. 3. apparatus. An imaging optical system that forms an optical image of a subject;
A photoelectric conversion element that converts the optical image into an electric signal,
A dustproof filter disposed between the imaging optical system and the photoelectric conversion element,
A piezoelectric element integrally disposed on a part of the dustproof filter,
A drive circuit that applies a voltage signal to the piezoelectric element to drive the piezoelectric element;
A control circuit that supplies a drive signal to the drive circuit so as to vibrate the dust filter by vibrating the piezoelectric element,
A monitor circuit that monitors a vibration state of the piezoelectric element and outputs a monitor signal to the control circuit;
An electronic imaging device comprising:
The control circuit sequentially changes the drive signal supplied to the drive circuit so that the vibration frequency of the dustproof filter sequentially changes, and when the level of the monitor signal supplied from the monitor circuit exceeds a predetermined value during that time. Wherein the supply of the drive signal is stopped. 7. The electronic imaging apparatus according to claim 6, wherein the control circuit stops supplying the drive signal after a predetermined time after a level of the monitor signal from the monitor circuit exceeds a predetermined value. . The electronic imaging apparatus according to claim 6, wherein the drive circuit changes a frequency of a voltage signal applied to the piezoelectric element according to a drive signal from the control circuit.

Images