JP2007184787A - Digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital camera capable of obtaining a less-blur image through smooth photography. <P>SOLUTION: A control section 32 drives a moving mechanism 54 based upon a camera shake detection signal outputted from a vibration detection sensor 56 to move a CCD 42 so as to cancel a camera shake, and thus prevents an image blur due to the camera shake. Further, the control section 32 detects a blur quantity of an image acquired by a shutter releasing operation by an image blur detection section 82 and records the image on a memory card 24 only when the image blur quantity is less than a recording limiting threshold. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a digital camera that records an image captured by an image sensor in an external memory.

  The subject image formed by the taking lens is picked up by an image sensor such as a CCD image sensor or a CMOS image sensor, and the image pickup signal obtained thereby is converted into digital image data and recorded in an external memory such as a memory card. Digital cameras are widely used.

Some digital cameras detect camera shake and move part of the imaging unit, such as the shooting lens and image sensor, in a plane perpendicular to the shooting optical axis to cancel the camera shake. Some images can be obtained with less image quality (see Patent Documents 1 and 2 below). In addition, there is a camera that can obtain an image with less blur by continuously capturing images until the camera shake amount becomes a predetermined amount or less (see Patent Document 3 below).
JP-A-5-14801 JP-A-11-225284 JP 2000-347236 A

  However, the apparatuses described in Patent Documents 1 and 2 have a problem in that, for example, if the camera shake amount is increased to a certain extent, it becomes impossible to cope with the movement speed and movement amount of the member to be moved. In addition, the apparatus described in Patent Document 3 has a problem in that it takes time to obtain an image with less blur because imaging is repeated until the camera blur amount becomes a predetermined amount or less.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a digital camera that can obtain an image with less blurring by smooth shooting.

  In order to achieve the above goal, the digital camera of the present invention records an imaged image in an external memory, and an imaging unit that performs imaging by subjecting a subject image formed by the imaging optical system to photoelectric conversion by an image sensor. In a digital camera provided with a release operation member operated at the time, camera shake detection means for detecting the direction and amount of camera shake generated in the camera body, and the imaging so as to cancel the camera shake based on the direction and amount of camera shake A camera shake correction unit that moves a part of the image, an image blur detection unit that detects a blur amount of the image by comparing at least two images captured in succession, and an image that is captured along with the release operation. Recording control for recording this image in the external memory only when the amount of blur is less than a preset first threshold value It is characterized in that a stage.

  An informing means for informing this may be provided when the blur amount of the captured image exceeds a preset first threshold.

  Further, an imaging condition control unit that increases the shutter speed at the time of imaging may be provided when the blurring amount of the captured image exceeds a preset second threshold value.

  Furthermore, the imaging condition control means may increase the sensitivity at the time of imaging by increasing the amplification rate of the image signal output from the imaging unit as the shutter speed increases.

  The recording control unit includes a continuous shooting mode in which imaging is performed a plurality of times by one release operation, and the recording control unit has a blur amount of the first image taken by the release operation in the continuous shooting mode. Only images that are below the threshold may be recorded in the external memory.

  Further, the recording control means obtains tag information indicating this for an image with the smallest amount of blur among images recorded in the external memory, which is obtained by one release operation in the continuous shooting mode. It may be added.

  In addition, image analysis means for recognizing the face of the subject included in the image by analyzing the captured image, the recording control means is an image obtained by imaging by a single release operation under the continuous shooting mode. Among them, an image in which the amount of blur is less than the first threshold value and includes the face of the subject may be recorded in the external memory.

  Further, the image blur detection means may detect a blur amount of an image based on a difference in contrast between two images obtained by continuous imaging.

  The image blur detection means calculates an image shift amount generated between the two images from a frame difference between the two images obtained by continuous imaging, and based on the image shift amount, the image blur amount is calculated. May be detected.

  Further, the image blur detecting means examines a shift direction and a shift amount of an image generated between the two images from a frame difference between the two images obtained by continuous imaging, and based on the shift direction and the shift amount of the image. The camera shake detecting means may function by detecting the direction and amount of camera shake.

  The digital camera of the present invention detects camera shake, moves a part of the imaging unit in a plane perpendicular to the photographing optical axis so as to cancel the camera shake, and reduces the amount of image blur based on the image acquired by the image sensor. Since detection is performed and recording as a storage image is performed only when the amount of image blur is smaller than a predetermined value, an image with less blur can be obtained with smooth shooting.

  In FIG. 1, a camera body 12 of a digital camera 10 is formed in a thin, substantially rectangular parallelepiped shape, a flash light emitting unit 14 is provided on the front surface thereof, and a photographing lens constituting an imaging unit 16 (see FIG. 3) described later. 18 is exposed. On the upper surface of the camera body 12, an operation dial 20 that is operated when the power is turned on / off and the shooting mode / playback mode / setting mode is switched, and a release button 22 that is operated when a release operation is performed. Is provided. The operation dial 20 is rotated and operated at four positions for selecting power-off, shooting mode, playback mode, and setting mode, respectively.

  When the operation dial 20 is rotated from the power-off position to any of the shooting mode, the playback mode, and the setting mode, the digital camera 10 is turned on. The shooting mode includes a normal shooting mode and a continuous shooting mode. In the normal shooting mode, one shooting operation can be performed by pressing the release button 22 (pressing the release button 22). Imaging can be performed continuously (while the release button 22 is pressed). In the playback mode, an image recorded on the memory card 24 that is detachable from the digital camera 10 can be displayed. In the setting mode, various settings such as on / off switching of the automatic flash function, white balance adjustment, and switching between the normal shooting mode and the continuous shooting mode in the shooting mode can be performed.

  In FIG. 2, a liquid crystal display (LCD) 26 is provided on the back surface of the camera body 12. The LCD 26 functions as an electronic viewfinder in the shooting mode, and displays a captured live view image. In the playback mode, an image recorded on the memory card 24 is displayed. A zoom button 28 is provided on the upper right side of the LCD 26. The zoom button 28 includes a zoom-in button and a zoom-out button, and is operated when the optical photographing magnification is changed by designating the zoom magnification of the photographing lens 18. A cursor button 30 provided below the zoom button 28 is mainly used in the setting mode, and is operated when performing various settings.

  In FIG. 3, a control unit 32 is provided inside the digital camera 10 and is connected to each unit of the digital camera 10. The control unit 32 reads out the sequence program stored in the ROM 34 to the RAM 36 and drives and controls each connected unit. Control by the control unit 32 is performed based on operation signals generated by operation of the operation unit 38 (the operation dial 20, the release button 22, the zoom button 28, and the cursor button 30).

  The imaging unit 16 includes a photographic optical system including a photographic lens 18 and a diaphragm 40, and a CCD image sensor (CCD) 42, which are arranged along the photographic optical axis A1. The photographing lens 18 includes a zoom lens for changing the magnification of optical photographing and a focus lens for performing focus adjustment, and is driven by a lens driving mechanism 44 including a motor. The aperture 40 is driven by an aperture drive mechanism 46 including a motor to switch the aperture diameter. The lens driving mechanism 44 and the aperture driving mechanism 46 are driven by motor drivers 48 and 50 controlled by the control unit 32.

  The CCD 42 is disposed behind the photographing optical system. As is well known, the CCD 42 includes a photoelectric conversion element that accumulates charges corresponding to the amount of received light for each pixel, and is synchronized with a vertical transfer clock and a horizontal transfer clock supplied from a timing generator (TG) 52. Imaging is performed by outputting the charge accumulated in each pixel as a serial imaging signal line by line. The charge accumulation time (exposure time) of each pixel is determined by an electronic shutter drive signal given from the TG 52.

  The CCD 42 is held movably in a plane perpendicular to the photographing optical axis A1 by a moving mechanism 54 having an actuator composed of a piezoelectric element that expands and contracts according to an applied voltage. The moving mechanism 54 is driven and controlled by the control unit 32 based on a signal from a vibration detection sensor 56 that detects a shake (camera shake) of the camera body 12. The vibration detection sensor 56 inputs a camera shake detection signal indicating the direction and amount of camera shake to the control unit 32 when camera shake occurs. The control unit 32 drives the moving mechanism 54 based on the camera shake detection signal, and moves the CCD 42 so as to cancel the camera shake. By doing so, image blur caused by camera shake is prevented.

  When the shooting mode is selected, the control unit 32 drives the CCD 42 to start capturing a through image. The through image is captured, for example, at a frame rate of about 30 frames per second. Further, the control unit 32 interrupts the through image capturing in response to the release operation, and performs the recording main image capturing. When the capturing of the main image is completed, the capturing of the through image is resumed.

  The imaging signal output from the CCD 42 is input to the analog signal processing circuit 58. The analog signal processing circuit 58 includes a correlated double sampling circuit (CDS) 60, an amplifier circuit (AMP) 62, and an AD converter (A / D) 64. The CDS 60 removes noise from the analog signal, the AMP 62 amplifies the analog signal, and the A / D 64 digitally converts the analog signal to generate image data.

  In the digital camera 10, the sensitivity at the time of shooting is determined according to the amplification factor (gain factor) by the AMP 62. As the sensitivity, a plurality of types such as ISO 200, ISO 400, and ISO 800 are prepared (see FIG. 5). The type of sensitivity used at the time of shooting can be set in the setting mode, and can be switched according to the shooting condition adjustment process described later.

  The image data generated by the analog signal processing circuit 58 is written into the frame memory 68 via the data bus 66. The frame memory 68 is a working memory for the DSP (Digital Signal Processor) 70 and the control unit 32 to perform various signal processing on the image data, and temporarily stores image data obtained by imaging. .

  The frame memory 68 is provided with a plurality of storage areas, and images are recorded in order in each storage area. By doing so, it is possible to efficiently process a plurality of images obtained by continuous imaging. As the frame memory 68, for example, an SDRAM (Synchronous Dynamic Random Access Memory) that performs data transfer in synchronization with a bus clock signal having a fixed period is used.

  The DSP 70 is an IC chip including an AF circuit 72, an AE / AWB circuit 74, an image processing circuit 76, a compression / decompression circuit 78, and a media controller 80. Various signal processing is performed on image data recorded in the frame memory 68. In addition, the image is displayed on the LCD 26 and the memory card 24 is accessed to read and write the image file.

  The AF circuit 72 detects the focal position based on the image captured by the CCD 42 and performs focusing. The AE / AWB circuit 74 measures the subject brightness and adjusts exposure and white balance during shooting. The image processing circuit 76 performs image correction processing such as gamma correction, sharpness correction, and contrast correction on the image data. In addition, the image processing circuit 76 converts the captured image data into Y data that is a luminance signal and Cb data that is a blue color difference signal. And YC conversion processing for converting into YC data composed of Cr data which is a red color difference signal.

  The compression / decompression circuit 78 performs compression processing on the main image that has been subjected to various types of image processing by the image processing circuit 76, and then generates an image file that stores the compressed main image. The media controller 80 accesses the memory card 24 to record and read an image file. In the reproduction mode, the main image recorded on the memory card 24 is subjected to expansion processing by the compression / expansion circuit 78, and then the main image is output to the LCD 26.

  As described above, in the digital camera 10, the image blur is prevented by moving the CCD 42 so as to cancel the camera shake. However, if the camera shake is large and the camera shake cannot be canceled by the movement of the CCD 42, image blur will occur. Therefore, in the digital camera 10, an image blur detection unit 82, a shooting condition adjustment unit 84, and a recording control unit 86 are provided in the control unit 32.

  The image blur detection unit 82 detects the blur amount of the image based on the image captured by the CCD 42. The image blur detection unit 82 has a principle that two images obtained by continuous imaging can be regarded as images of the same subject, and when the same subject is imaged, the lower the contrast of the captured images, Based on the principle that the blur amount is large, the blur amount of the image is detected.

  As shown in FIG. 4, every time a new image is recorded in the frame memory 68, the image blur detection unit 82 analyzes this image to check the contrast of the image, and records the contrast change history in the RAM 36. Subsequently, the image blur detection unit 82 calculates a difference in contrast between an image (detection target image) for detecting the blur amount and an image (comparison target image) captured immediately before this detection target image.

  The image blur detection unit 82 detects the blur amount of the detection target image based on the calculated contrast difference. When the contrast of the detection target image is lower than that of the comparison target image, the blur amount of the detection target image is detected as a larger value as the contrast difference between the two images increases. On the contrary, when the contrast of the detection target image is higher than that of the comparison target image, the blur amount of the detection target image is detected as a smaller value as the contrast difference between the two images is larger.

  Although an example in which the image blur amount is detected from the difference in contrast between the detection target image and the comparison target image has been described, the image blur amount may be detected based on the frame difference between the detection target image and the comparison target image. . In this case, the detection target image and the comparison target image are compared on a pixel-by-pixel basis, and an image shift amount generated between these two images is examined. A larger value is detected as the blur amount of the detection target image as the shift amount is larger, and a smaller value is detected as the blur amount of the detection target image as the shift amount is smaller.

  Further, although an example in which an image captured immediately before the detection target image is used as the comparison target image has been described, an image captured immediately after the detection target image may be used as the comparison target image. Furthermore, the present invention is not limited to the case where the image blur amount is detected by a single comparison, and the image blur amount may be detected by performing a plurality of comparisons. In this case, for example, the detection target image is compared with an image captured immediately before the detection target image and an image captured immediately after the detection target image, and the comparison result of these two times is averaged to obtain a final result. What is necessary is just to detect the amount of image blur.

  Note that in a digital camera in which the number of captured pixels is different between the through image and the main image, the number of pixels of the detection target image may be different from that of the images captured before and after the detection target image. In this case, for example, in accordance with an image with few pixels, a new image is generated by thinning out pixels from an image with many pixels, and the image blurring amount is reduced by comparing the generated new image with an image with few pixels. It may be detected. Further, after the detection target image is captured, the image may be captured again under the same conditions, and the image blur amount may be detected by comparing the image obtained by the imaging with the detection target image.

  Based on the amount of image blur detected by the image blur detection unit 82, a shooting condition adjustment process by the shooting condition adjustment unit 84 and a recording control process by the recording control unit 86 are performed. The ROM 34 records a shooting condition change threshold value and a recording limit threshold value set larger than this as a guideline for determining the amount of image blurring. The shooting condition adjustment is performed using these threshold values. Processing and recording control processing are performed.

  In the shooting condition adjustment process, the shooting condition adjustment unit 84 determines the shutter speed of the electronic shutter (the charge accumulation time for each pixel of the CCD 42) and the sensitivity at the time of shooting (the gain rate of the AMP 62) based on the image blur amount. Adjust. As combinations of shutter speed and sensitivity, for example, combinations as shown in FIG. 5 are prepared. As shown in FIG. 6, when the image blur amount exceeds the shooting condition change threshold, the shooting condition adjustment unit 84 increases the sensitivity and the shutter speed at the time of shooting from the currently selected value by one step. If the amount of image blur is less than the shooting condition change threshold, imaging is performed with the currently selected value.

  By increasing the shutter speed, the charge accumulation time in each pixel of the CCD 42 is shortened, so that image blurring can be prevented. Further, by increasing the sensitivity together with the shutter speed, there is no possibility of underexposure. The combination of shutter speed and sensitivity is not limited to the above-described example, and can be changed as appropriate. In addition, the shutter speed and the rate of increase in sensitivity may be controlled independently.

  Further, although an example in which image blurring is prevented by increasing the shutter speed of the electronic shutter has been described, a mechanical shutter having shutter blades that open and close the photographing optical axis is provided, and the shutter speed of this mechanical shutter is increased. The image blur may be prevented. Moreover, although the example which raises a sensitivity in order to prevent an underexposure was demonstrated, you may prevent an underexposure by enlarging an aperture diameter. Of course, an increase in sensitivity and an increase in aperture diameter may be combined to prevent underexposure.

  Next, the recording control process by the recording control unit 86 will be described separately for the normal shooting mode and the continuous shooting mode. In the normal shooting mode, as shown in FIG. 7, the recording control unit 86 invalidates the release operation when the blur amount of the main image captured by the release operation exceeds the recording limit threshold, that is, the main image. Recording to the memory card 24 is prohibited. At this time, the recording control unit 86 displays a notification screen 88 as shown in FIG. 8 on the LCD 26 to notify that the release operation has been invalidated. When the blur amount of the main image captured by the release operation is below the recording limit threshold, the main image is recorded on the memory card 24.

  Although an example has been described in which the release operation is notified when the release operation is invalidated, the release operation is performed in this state when the amount of image blur exceeds the recording limit threshold regardless of the presence or absence of the release operation. However, it may be notified that the operation is invalidated. In addition, the example in which the notification is performed by displaying the notification screen 88 on the LCD 26 has been described, but it is also conceivable that a speaker is provided and the notification is performed by emitting sound from the speaker.

  On the other hand, in the continuous shooting mode, as shown in FIG. 9, the recording control unit 86 records, in the memory card 24, main images acquired during the release operation whose image blur amount is below the recording limit threshold. To do. In addition, when recording on the memory card 24, the recording control unit 86 adds tag information indicating this to the image with the smallest image blur amount recorded. As shown in FIG. 10, a mark 90 indicating that the amount of image blur is small when reproduced in the reproduction mode is displayed on the main image to which tag information is added.

  The operation of the present invention having the above configuration will be described below. When the digital camera 10 is set to the shooting mode, imaging by the CCD 42 is started. When the imaging is started, the control unit 32 drives the moving mechanism 54 based on the camera shake detection signal input from the vibration detection sensor 56 and moves the CCD 42 so as to cancel the camera shake.

  Further, when imaging is started, the blur amount of the captured image is detected by the image blur detection unit 82. When the image blur amount exceeds the shooting condition adjustment threshold value, the shooting condition adjustment process is performed by the shooting condition adjustment unit 84, and the shutter speed and sensitivity during imaging are increased by one level.

  Further, when the image blur amount exceeds the recording condition control threshold value, the recording condition control unit 32 performs the recording control process, and the recording of the image on the memory card 24 is restricted. In the recording control process, only images whose image blur amount is below the recording condition control threshold are recorded on the memory card 24. Further, in the recording control process, tag information indicating this is added to an image with the least image blur among images acquired by a series of imaging under the continuous shooting mode. A mark 90 indicating that the amount of image blur is small when reproduced in the reproduction mode is displayed on the image to which the tag information is added.

  As described above, according to the present invention, image blur can be prevented by detecting camera shake and moving the CCD 42 so as to cancel it. Further, when the amount of image blur is detected based on the captured image and the amount of image blur exceeds the shooting condition adjustment threshold, the shutter speed and sensitivity at the time of imaging are increased by one step, thereby preventing the image from being exposed underexposure. Blur can be prevented. Furthermore, since only the image whose blur amount is lower than the recording condition control threshold value is recorded on the memory card 24, a good image with little image blur can be recorded.

  In addition, when tag information indicating this is added to an image with the smallest image blur amount among images obtained during one release operation in the continuous shooting mode, and the image with the tag information added is reproduced. The mark 90 is displayed on the screen. As a result, an image with less image blur can be easily found from a plurality of reproduced and displayed images. In addition, image blur prevention by moving the CCD and adjusting the shooting conditions and recording restriction when the amount of image blur is large are performed in parallel. Can be obtained.

  In the above embodiment, the example in which the camera shake amount and direction are detected by the vibration detection sensor has been described. However, the camera shake amount and direction may be detected by the image shake detection unit. In this case, the image blur detection unit may detect camera shake based on the frame difference between the detection target image and the comparison target image. That is, the detection target image and the comparison target image are compared in units of pixels, and the direction and amount of image shift that occurs between the two images are examined. Then, camera shake may be detected based on the direction and amount of image shift. By doing so, the vibration detection sensor can be abolished, which can contribute to reduction in size, weight and cost.

  Further, the example of determining whether or not the image can be recorded on the memory card according to whether or not the image blur amount exceeds the recording condition control threshold has been described. However, as in the digital camera 100 shown in FIG. Whether or not the image can be recorded on the memory card may be determined depending on whether or not the amount exceeds the recording condition control threshold and whether or not the captured image includes the face of the subject. In addition, in FIG. 11, the same code | symbol is attached | subjected about the member similar to embodiment mentioned above, and description is abbreviate | omitted.

  In the digital camera 100, an image analysis unit 104 is provided in the control unit 102. When the release operation is performed and the main image is recorded in the frame memory 68, the image analysis unit 104 analyzes the main image to check whether or not the face of the subject is included in the image. The recording control unit 106 records the main image on the memory card 24 only when the amount of image blur of the main image is below the recording condition control threshold and the main image includes the face of the subject. In this way, a better recorded image can be obtained.

It is a front perspective view of a digital camera. It is a rear perspective view of a digital camera. It is a block diagram of a digital camera. It is a flowchart showing the detection procedure of an image blur amount. It is explanatory drawing showing the example of the combination of a sensitivity and shutter speed. It is a flowchart showing the procedure of imaging condition adjustment processing. It is a flowchart showing the procedure of the recording control process in normal imaging | photography mode. It is explanatory drawing showing an alerting | reporting screen. It is a flowchart showing the procedure of the recording control process in continuous shooting mode. It is explanatory drawing showing a mode that a mark is displayed on the image with the smallest blurring amount in the image continuously taken. It is a block diagram of a digital camera.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,100 Digital camera 12 Camera main body 16 Image pick-up part 18 Shooting lens 22 Release button 24 Memory card 26 LCD
32, 102 Control unit 40 Aperture 42 CCD
54 moving mechanism 56 vibration detection sensor 62 AMP
68 Frame memory 82 Image blur detection unit 84 Shooting condition adjustment unit 86, 106 Recording control unit 88 Notification screen 90 Mark 104 Image analysis unit

Claims (10)

A digital camera comprising an imaging unit that performs imaging by subjecting a subject image formed by a photographing optical system to photoelectric conversion by an image sensor, and a release operation member that is operated when recording the captured image in an external memory In
Camera shake detection means for detecting the direction and amount of camera shake generated in the camera body;
Based on the direction and amount of camera shake, camera shake correction means for moving a part of the imaging unit so as to cancel camera shake,
Image blur detection means for detecting a blur amount of the image by comparing at least two images captured in succession;
And a recording control means for recording the image in the external memory only when the amount of blur of the image taken with the release operation is less than a preset first threshold value. camera.   The digital camera according to claim 1, further comprising an informing means for informing when the amount of blur of the captured image exceeds a preset first threshold.   3. The digital camera according to claim 1, further comprising photographing condition control means for increasing a shutter speed at the time of photographing when a blur amount of the picked up image exceeds a preset second threshold value. camera.   4. The digital camera according to claim 3, wherein the photographing condition control means increases the gain of the image signal output from the image pickup unit and increases the sensitivity at the time of image pickup along with an increase in shutter speed.   A continuous shooting mode in which imaging is performed a plurality of times by one release operation, and the recording control unit has a blur amount that exceeds the first threshold value among images captured by a single release operation in the continuous shooting mode; 5. The digital camera according to claim 1, wherein only a lower image is recorded in the external memory.   The recording control means adds tag information indicating this to an image with the smallest amount of blur among images recorded in the external memory, which is obtained by a single release operation in the continuous shooting mode. The digital camera according to claim 5.   Image analysis means for recognizing the face of the subject included in the image by analyzing the captured image, and the recording control means is an image obtained by imaging by one release operation under continuous shooting mode. The digital camera according to claim 5, wherein an image including a blur amount lower than the first threshold and including a face of a subject is recorded in the external memory.   The digital camera according to claim 1, wherein the image blur detection unit detects a blur amount of an image based on a difference in contrast between two images obtained by continuous imaging.   The image blur detecting means calculates an image shift amount generated between two images from a frame difference between two images obtained by continuous imaging, and detects the image blur amount based on the image shift amount. The digital camera according to claim 1, wherein the digital camera is a digital camera.   The image blur detecting means examines a shift direction and a shift amount of an image generated between two images from a frame difference between two images obtained by continuous imaging, and determines a camera blur based on the shift direction and the shift amount of the image. The digital camera according to claim 1, wherein the digital camera functions as the camera shake detection means by detecting the direction and amount of the camera.

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