JP2016086202A - Imaging apparatus and control method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of suppressing image deterioration due to dust correction by accurately detecting only foreign matters stuck to an optical filter etc. on the front face of an imaging device in acquisition of dust correction data.SOLUTION: The imaging apparatus comprises a first imaging device, a second imaging device, foreign matter detection means for the respective imaging devices, and foreign matter information determination means which determines the final shape and position of a foreign matter. The foreign matter information is determined in accordance with the results of foreign matter detection by the first imaging device and the second imaging device.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image pickup apparatus using an image pickup device such as a CCD or a CMOS sensor, and more particularly to a technique for suppressing image quality deterioration due to foreign matters attached to the surface of an optical element such as an optical low-pass filter disposed in front of the image pickup device.

  In an imaging device such as a digital camera that captures a subject image by converting it into an electrical signal, the imaging light beam is received by the imaging device, a photoelectric conversion signal output from the imaging device is converted into image data, and a memory card, etc. Record on a recording medium. A CCD (Charge Coupled Device), a CMOS sensor (Complementary Metal Oxide Semiconductor), or the like is used as the imaging device.

  In recent years, in addition to an image sensor for generating a main image to be stored on a recording medium, an image sensor has been used for an electronic viewfinder used for composition confirmation before actual shooting or for photometry for measuring the luminance of a subject. There is an imaging device.

  In such an image pickup apparatus, an optical low-pass filter and an infrared absorption filter are arranged on the subject side of the image pickup element. When foreign matter such as dust adheres to the surface of these filters, the attached portion becomes a black dot. The image appears in the photographed image, and the image looks poor.

  Especially in digital SLR cameras with interchangeable lenses, mechanical operation parts such as shutters and quick return mirrors are arranged in the vicinity of the image sensor, and foreign matters such as dust generated from these operation parts are captured by the image sensor and filter. May adhere to the surface. In addition, when the lens is replaced, foreign matter such as dust may enter the camera body from the opening of the lens mount and adhere to it.

  In order to avoid such a phenomenon, in Patent Document 1, a dust-proof filter that transmits a photographic light beam is provided on the subject side of the image sensor, and the dust is adhered to the surface of the dust-proof filter by vibrating this with a piezoelectric element. Techniques for removing foreign substances such as these have been proposed.

  Moreover, there are some foreign substances that cannot be removed even if the foreign substance removing function is used. Thus, in Patent Document 2, dust correction data, which is information on the position and size of a foreign substance in the optical system, is created from an image of a subject having a uniform brightness, and an actual image is taken using the created dust correction data. A technique for improving the quality of image quality by performing the correction process is disclosed.

JP 07-151946 A JP 2004-222231 A

  However, in the prior art disclosed in Patent Document 2 described above, shooting for acquiring dust correction data must be performed by the user, and it is difficult to capture a subject with uniform and uniform brightness. .

  For example, when a user shoots a white wall or the like as a uniform subject, if the wall is dirty, that portion is also erroneously recognized as a foreign object attached to the optical filter or the like on the front surface of the image sensor. For this reason, there is a possibility that an unnecessary correction process is performed even on a portion that does not need to be corrected, and the image quality is deteriorated.

  An object of the present invention is to provide an imaging apparatus capable of accurately detecting only foreign matter attached to an optical filter or the like on the front surface of an imaging element when acquiring dust correction data and suppressing image deterioration due to dust correction. is there.

  To achieve the above object, the present invention provides a first image sensor that photoelectrically changes a subject image to generate image data, and at least one second image sensor that is different from the first image sensor. A first foreign object detecting means for detecting a shape and position of a foreign object existing in the first imaging element or an optical system disposed in front of the first imaging element; and the second imaging element or in front of the second imaging element. A second foreign matter detecting means for detecting the shape and position of the foreign matter existing in the optical system; and a foreign matter information determining means for determining the final shape and position of the foreign matter. Foreign matter information is determined according to the foreign matter detection results of the one foreign matter detection means and the second foreign matter detection means.

  According to the present invention, it is possible to provide an imaging apparatus capable of accurately detecting only foreign matter attached to an optical filter or the like on the front surface of an imaging element when acquiring dust correction data and suppressing image deterioration due to dust correction. it can.

1 is a block diagram of a digital single-lens reflex camera according to an embodiment of the present invention. 1 is an external perspective view of a digital single-lens reflex camera according to an embodiment of the present invention. 1 is a vertical sectional view of a digital single-lens reflex camera according to an embodiment of the present invention. An image of the subject image and the image sensor pixels superimposed Flowchart explaining dust detection processing of individual image sensor Flow chart for explaining a method for improving accuracy of dust information detection

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  A lens interchangeable single-lens reflex digital camera according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a circuit configuration of a lens interchangeable digital single-lens reflex camera as an imaging apparatus according to an embodiment of the present invention.

  In FIG. 1, the microcomputer 402 controls the operation of the entire camera, including the processing of the conformation data output from the image sensor 418 that photoelectrically converts the subject image and the display control of the LCD monitor device 417.

  The switch (SW1) 405 is turned on when the release button (imaging instruction member) 114 (see FIG. 2) is half-pressed, and when the switch (SW1) 405 is turned on, the digital camera of this embodiment is in a shooting preparation state. The switch (SW2) 406 is turned on when the release button 114 is fully pressed (fully pressed), and when the switch (SW2) 406 is turned on, the digital camera according to the present embodiment starts a photographing operation.

  The lens control circuit 407 performs communication with the photographing lens 200 (see FIG. 3) and drive control and aperture control of the photographing lens 200 during autofocus.

  In FIG. 1, an external display control circuit 408 controls an external display device 409 and a display device (not shown) in the viewfinder. The switch sense circuit 410 transmits to the microcomputer 402 signals from a number of switches including an electronic dial 411 and a narrow-down button 429 provided on the camera.

  The strobe light emission dimming control circuit 412 is grounded via the X contact 412a and controls the external strobe. The distance measuring circuit 413 detects the defocus amount with respect to the subject for autofocus. The photometry circuit 414 measures the luminance of the subject.

  A shutter control circuit 415 controls the shutter so that the image sensor 418 is exposed appropriately.

  The LCD monitor device 417 and the backlight illumination device 416 constitute an image display device. The recording device 419 is, for example, a hard disk or a semiconductor memory card that can be attached to and detached from the camera body.

  Further, the microcomputer 402 includes an A / D conversion circuit 423, an image buffer memory 424, an image processing circuit 425 including a DSP, and a pixel defect position memory that records that a predetermined pixel in the image sensor itself is defective. 426 is connected. Also connected is a dust position memory 427 that stores the pixel position in the image pickup device causing the image defect due to dust. Note that the pixel defect position memory 426 and the dust position memory 427 are preferably non-volatile memories. Further, the defective pixel position memory 426 and the dust position memory 427 may be stored using different addresses in the same memory space.

  The memory 428 is a non-volatile memory that stores programs executed by the microcomputer 402.

  The image sensor 430 for live view is used to generate an image for the user to check the composition and subject on the LCD monitor 417 before shooting.

  FIG. 2 is a perspective view showing the appearance of the interchangeable lens single-lens reflex digital camera according to the present embodiment, and FIG. 3 is a vertical sectional view of the interchangeable lens single-lens reflex digital camera according to the present embodiment of FIG.

  In FIG. 2, an eyepiece window 111 for finder observation, an exposure lock button 112, an autofocus distance measuring point selection button 113, and a release button 114 for performing a photographing operation are provided on the upper part of the camera body 100. The electronic dial 411 is another function signal input device for changing the setting value of the camera body in combination with other operation buttons or for switching the shooting mode. The external display device 409 is composed of a liquid crystal display device, and displays shooting conditions such as shutter speed, aperture, and shooting mode, and other information.

  Also, on the back of the camera main body 100, an LCD monitor device 417 for displaying captured images and various setting screens, a monitor switch 121 for turning on / off the LCD monitor device 417, a cross switch 116, and a menu button 124 is provided.

  The cross placement switch 116 has four buttons arranged vertically and horizontally, and a set button arranged in the center. The user instructs the camera to select and execute a menu item displayed on the LCD monitor device 417. Used for

  The menu button 124 is a button for causing the LCD monitor device 417 to display a menu screen for performing various camera settings. For example, when selecting and setting the shooting mode, after pressing this menu button, the user selects the desired mode by operating the up / down / left / right buttons of the cross switch 116, and sets the desired mode in the selected state. The setting is completed by pressing the button.

  The menu button 124 and the cross placement switch 116 are also used when acquiring dust information.

  The live view selection switch 125 is a switch for selecting whether to perform live view display or use an optical viewfinder.

  Since the LCD monitor device 417 of the present embodiment is a transmissive type, an image cannot be visually recognized only by driving the LCD monitor device, and a backlight illumination device 416 is disposed on the back surface thereof. The LCD monitor device 417 and the backlight illumination device 416 constitute an image display device.

  A photographic lens 200 that is an imaging optical system can be attached to and detached from the camera body 100 via a lens mount 202. In FIG. 3, 201 denotes a photographing optical axis, and 203 denotes a quick return mirror.

  The quick return mirror 203 is disposed in the photographic optical path, and is movable between a position for guiding subject light from the photographic lens 200 to the finder optical system (position shown in FIG. 3) and a position for retracting out of the photographic optical path.

  The subject light guided from the quick return mirror 203 to the finder optical system is imaged on the focus plate 204. Reference numeral 205 denotes a condenser lens for improving the visibility of the finder, and 206 denotes a pentagonal roof prism. The object light passing through the focus plate 204 and the condenser lens 205 is used as an eyepiece lens 208 for finder observation and a photometric sensor 207 or a live view. To the image pickup device 430 for use.

  The 206 pentagonal roof prism is provided with a movable mirror 218 that is partially movable, and is movable between a position for guiding subject light to the viewfinder optical system and a position for guiding the image sensor 430 for live view. When the live view display is selected by the live view selection switch 125, the display is moved to a position leading to the live view image sensor 430.

  The signal photoelectrically converted by the live view imaging device is subjected to image generation through an image processing circuit 425 including an A / D conversion circuit 423, an image buffer memory 424, and a DSP, and is displayed on the LCD monitor device 417.

  Reference numerals 209 and 210 respectively denote a rear curtain and a front curtain that constitute a shutter, and an image sensor 418 that is a solid-state image sensor disposed behind the rear curtain 209 and the front curtain 210 is exposed for a necessary time. A captured image converted into an electrical signal for each pixel by the image sensor 418 is processed by the A / D converter 423, the image processing circuit 425, and the like, and is recorded in the recording device 419 as image data. An optical element 418a such as an optical low-pass filter is disposed in front of the image sensor 418, and foreign matter attached to the surface of the optical element 418a is reflected in an image generated by the image sensor 418.

  The image sensor 418 is held on the printed circuit board 211. A display board 215 is disposed behind the printed board 211. An LCD monitor device 417 and a backlight illumination device 416 are disposed on the opposite surface of the display substrate 215.

  Reference numeral 419 denotes a recording device for recording image data, and 217 denotes a battery. The recording device 419 and the battery 217 are detachable from the camera body.

(Dust detection process)
The dust detection process of the image sensor will be described with reference to FIGS. 4, 5, and 6. FIG. 4 is an image diagram in which the subject image and dust are superimposed on the image sensor.

  In FIG. 4A, 418 ′ is a cutout of a part of the image sensor 418 that is 20 × 20 pixels. In the actual image pickup device, pixels of three colors of R, G, and B are arranged in a regular combination. However, in this embodiment, the color components of the pixels are not questioned for simplification of description.

Here, each pixel represents a position below.
(R [x], c [y]) x = 1, 2, 3,... 20, y = 1, 2, 3,.
In FIG. 4A, reference numeral 501 denotes a foreign substance attached to the surface of the optical element 418a. Pixel region 502 ((r8, c15) (r8, c16) (r8, c17) (r9, c15) (r9, c16) (r9, c17) (r10, c15) (r10, c15) ( r10, c16) (r10, c17) (r11, c15) (r11, c16) (r11, c17) (r12, c15) (r12, c16) (r12, c17)) have a luminance because the subject light is blocked. descend.

  Reference numeral 503 denotes a black pattern (scratch) existing on the white wall as a subject. Originally, it is desirable that the subject is uniform, but in practice it is difficult to photograph such a subject, and a pattern such as 503 may appear. Therefore, the pixel region 504 corresponding to the wall pattern 503 ((r3, c6) (r3, c7) (r4, c6) (r4, c7) (r5, c6) (r5, c7) (r6, c6) (r6) , C7)), the luminance is reduced similarly to the pixel region 502 in which the luminance is reduced due to the foreign matter.

  FIG. 4B is an image diagram in which some 20 × 20 pixels of the live view imaging device 430 are cut out and superimposed on the same subject as in FIG. .

  Here, for simplification of description, the pixel size and the corresponding angle of view of the image generation image sensor 418 and the live view image sensor 430 to be recorded are the same. That is, the pixel (r1, c1) of the image sensor 418 and the pixel (r1 ', c1') of the image sensor 430 are in the same place with respect to the subject image.

  In FIG. 4B, since the pattern 503 present on the subject exists on the image sensor 430 as well as the image sensor 418, the luminance of the pixel region 510 decreases.

  However, dust 501 adhering to the optical element 418 ′ does not appear in the pixels of the image sensor 430. Accordingly, the luminance of the pixel region 511 corresponding to the pixel region 502 does not decrease.

  In other words, it is possible to improve the accuracy of the dust position information by determining that dust reflected in both the image sensor 418 and the image sensor 430 is present in the subject and excluding it from the dust position information.

  FIG. 5 is a flowchart for explaining dust detection processing of individual image sensors of the digital camera according to this embodiment.

  When the user operates the menu button 124, various setting screens for the camera are displayed on the LCD monitor 417. Therefore, when the acquisition of dust information is selected by the cross placement switch 116, the mode shifts to the dust acquisition mode.

  (S601) The user performs shooting as a uniform subject such as a white wall. When the release button 114 is turned on by the user, a predetermined photographing operation is performed, and image data obtained from the image sensor 418 is acquired.

  (S602) The foreign matter detection means is realized by the microcomputer 402, and calculates the average luminance of each pixel from the obtained image data.

  (S603) A dust determination threshold is determined from the calculated average luminance.

  (S604) The luminance of each pixel is compared with the dust determination threshold value, and if it is equal to or less than the threshold value, the process proceeds to S605.

  (S605) The pixel determined to be equal to or less than the dust determination threshold is checked against information in the defective pixel position memory 426, and if it is not a defective pixel, it is determined that dust is attached, and the process proceeds to S606. In the case of a defective pixel, it is determined that it is not dust, and the process proceeds to S607.

  (S606) The pixel information determined to have dust attached is recorded in the dust position memory 427.

  (S607) If dust detection processing has not been completed for all pixels of the image sensor, the process returns to S604 and is repeated until all pixels are processed. If all pixel dust detection processing has been completed, the dust information acquisition mode is terminated.

  In this embodiment, for simplification of explanation, the color component of the pixel is not questioned, but the dust detection threshold may be varied for each pixel color, or dust detection is performed based on the color information. May be. Furthermore, in this embodiment, for simplification of description, dust detection of individual image sensors is performed only from luminance information for each pixel. However, the present invention is not limited to this.

  FIG. 6 is a dust detection flowchart for improving dust detection accuracy of the digital camera according to this embodiment.

  When the user operates the menu button 124, various setting screens for the camera are displayed on the LCD monitor 417. Therefore, when the acquisition of dust information is selected by the cross placement switch 116, the mode shifts to the dust information acquisition mode.

  (S701) When the dust information acquisition mode is entered, the movable mirror 218 is moved to a position for guiding the subject light to the live view imaging device 430.

  (S702) The user performs shooting as a uniform subject such as a white wall. The camera enters a standby state in which the release button 114 can be operated by the user. When the release button 114 is turned on by the user, the process proceeds to S704.

  (S703) At this time, if an operation for canceling the dust information acquisition mode is input by the user, the dust information acquisition mode is terminated.

  (S704) The foreign matter detection means (microcomputer) 402 acquires image data of the image sensor 430.

  (S705) The microcomputer 402 drives the photographing lens 200 with a predetermined aperture and moves the quick return mirror 203 to the retracted position. Further, the rear curtain 209 and the front curtain 210 of the shutter are driven to expose the image sensor 418 for a predetermined time.

  (S706) The foreign matter detection means (microcomputer) 402 acquires image data obtained from the image sensor 418.

  (S707) The foreign object detection means (microcomputer) 402 performs the processing from S601 to S605 described in the flowchart of FIG. 5 on the image data acquired from the image sensor 418 and the image sensor 430, respectively.

  (S708) The foreign matter information determination means is realized by the microcomputer 402, and compares the detected dust position of the image sensor 418 with the dust position of the image sensor 430. If it exists at the same position, it is determined that the pattern is present on the subject, and the target is deleted from the dust position memory 427 (S709).

  As a result of the comparison, if they do not exist at the same position, it is determined that the dust has adhered to the optical element 418, and is stored in the dust position memory 427 as dust information (S710).

  (S711) If the foreign matter information determination means for all dust information has not been judged whether or not it is dust attached to the optical element 418, the process returns to S708 and repeats until all dust information is finished. If the processing has been completed for all dust information, the dust position information acquisition operation is terminated.

  As described above, according to the present embodiment, the final dust position information is generated from the dust information acquisition results of a plurality of image sensors, so that scratches and patterns existing in the subject can be erroneously detected as dust information. Therefore, it is possible to suppress deterioration in image quality due to unnecessary correction processing.

  For simplification of description, the pixel sizes of the first image sensor and the second image sensor are the same, but the present invention is not limited to this. For example, if the pixels of the second image sensor are larger than the pixels of the first image sensor, the ratio may be calculated to change the dust position detection threshold. Further, when the angle of view with respect to the subject is different, it may be applied only to overlapping pixels.

  In the present embodiment, the live-view image sensor has been described as the second image sensor. However, the present invention is not limited to this, and a photometric sensor or other image sensor may be used.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

100 camera body, 402 microcomputer, 418 image sensor,
427 Garbage position memory, 430 Live view image sensor

Claims (7)

A first image sensor 418 that photoelectrically changes a subject image and generates image data;
At least one second image sensor 430 different from the first image sensor;
First foreign matter detection means 402 for detecting the shape and position of the foreign matter existing in the first imaging element 418 or the optical system 418a disposed in front of the first imaging device 418;
Second foreign matter detection means 402 for detecting the shape and position of the foreign matter present in the second imaging element 430 or an optical system disposed in front of the second imaging device 430;
Foreign matter information determining means 402 for determining the final shape and position of the foreign matter,
The imaging apparatus according to claim 1, wherein the foreign matter information determination unit 402 determines foreign matter information according to the foreign matter detection results of the first foreign matter detection unit and the second foreign matter detection unit.   The foreign matter information determination means 402 compares the foreign matter detection results of the first foreign matter detection means and the second foreign matter detection means, and the first foreign matter detection result and the second foreign matter detection result are the same. If it is determined that the target foreign matter information is deleted from the first foreign matter detection result, and if it is determined that the first foreign matter detection result and the second foreign matter detection result are not the same, The imaging apparatus according to claim 1, wherein the target foreign matter information is left as it is from the first foreign matter detection result.   The foreign object information determining unit 402 converts the size and the number of pixels of the second image sensor 430 according to the size and the number of pixels of the first image sensor 418, and then converts the first foreign object detector 418. The imaging apparatus according to claim 2, wherein a foreign object detection result of the second foreign object detection means is compared.   If the effective range of the subject of the second image sensor 430 is different from the effective range of the subject of the first image sensor 418, a different area is a foreign object detection result by each of the first foreign object detectors. The imaging apparatus according to any one of claims 1 to 3, wherein a foreign object detection result obtained by the second foreign object detection unit is used.   The foreign matter information determination means 402 compares the foreign matter detection results of the first foreign matter detection means and the second foreign matter detection means, and determines that they are the same if they are within a certain threshold range. The imaging apparatus according to any one of claims 1 to 4, wherein the imaging device is determined to be not identical if not within a range, and the threshold is set for each pixel.   The imaging apparatus according to claim 1, wherein the second imaging element 430 is an image generation element for generating an image for an electronic viewfinder.   The imaging apparatus according to any one of claims 1 to 5, wherein the second imaging element 430 is an imaging element for a photometric sensor for measuring subject luminance of a subject image.