JP2010032669A - Digital still camera, and control method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To comparatively accurately determine the focusing position of a focus lens. <P>SOLUTION: An imaging scene is discriminated. When a landscape imaging scene is selected, an aperture value is determined by using a program diagram for a wide-open aperture priority landscape imaging scene, so as to be an aperture value larger than that determined by a program diagram for a normal landscape imaging scene. An object is repeatedly imaged in such a manner that the focus lens is moved, with the determined aperture value. A focus lens position for applying the peak position of the contrast data of the obtained image data is used as the focusing position. Since the contrast data is obtained by using an open side aperture, it is easy to find the peak position and the focusing position of the focus lens can be comparatively accurately determined. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a digital still camera and a control method thereof.

The camera is equipped with an automatic focusing control function so that even a user unfamiliar with camera operation can perform focusing control relatively easily. In addition to this automatic focus control, the distance to the subject is calculated, compared with the depth of field, and shooting outside the depth of field is prohibited (Patent Document 1), and distance information on the focus position is used. And an appropriate aperture value is calculated (Patent Document 2).
Japanese Patent Laid-Open No. 5-308567 JP 2000-292680 A

  When automatic focusing control is performed using contrast data of image data obtained by imaging, the subject is imaged, and the aperture value used for imaging in the automatic focusing control is obtained from the obtained image data. It is determined. The position of the peak value of the contrast data of the image data obtained by repeatedly moving the subject with the aperture value while moving the imaging lens is set as the imaging lens position. A subject is imaged at the determined imaging lens position, and an aperture value used for imaging for recording is determined again from the obtained image data. Imaging for recording is performed with the determined aperture value.

  When the aperture value is small (F value is small), the peak value of the contrast data is also known because the depth of field is shallow and the blurred and clear parts of the subject image are clear. Cheap. On the other hand, when the aperture value is large (the F value is large), the depth of field is so deep that the blurred portion of the subject image and the clear portion are not clear, so the contrast data. The peak value is difficult to understand. If the aperture value determined during the automatic focusing control is large, the imaging lens position determined during the automatic focusing control may not be very accurate.

  An object of the present invention is to determine an imaging lens position relatively accurately.

  The digital still camera according to the present invention repeatedly captures an image of a subject in accordance with the setting of the two-stroke type shutter release button and the imaging mode, and captures image data representing the image of the subject at a constant cycle. In response to depression of the first stage of the shutter release button, first imaging scene discrimination means for discriminating the imaging scene of the subject image represented by the image data output from the imaging means, An exposure amount calculating means for calculating an exposure amount using image data output from the imaging means, and a program line for a landscape imaging scene in response to the fact that the first imaging scene determination means determines that the scene is a landscape imaging scene. Using the open aperture priority program diagram that is closer to the open aperture than the aperture determined by the figure, the exposure amount calculation means A focus value for the focus control corresponding to the calculated exposure amount is determined, and the program line for the imaged scene determined in accordance with the fact that the first imaged scene discriminating means has not discriminated from the landscape scene. Referring to the drawing, the focus control diaphragm value determining means for determining the focus control diaphragm value corresponding to the exposure amount calculated by the exposure amount calculation means, the focus control diaphragm while moving the imaging lens position. Focusing to position the imaging lens at a position where the contrast data of the image data output from the imaging unit becomes a peak value by repeatedly imaging the subject with the focus control aperture value determined by the value determining unit Imaged by the image data output from the imaging means by imaging the subject at the imaging lens position positioned by the control means and the focusing control means. Exposure calculated by the exposure amount calculation means using a second imaging scene discrimination means for discriminating the imaging scene of the subject image to be captured, and a program diagram for the imaging scene determined by the second imaging scene discrimination means A recording imaging aperture value determining means for determining a recording imaging aperture value corresponding to the amount, and an imaging lens position positioned by the focusing control means in response to a second step of pressing the shutter release button. And a recording control means for recording the image data output from the imaging means on a recording medium when the subject is imaged with the aperture value determined by the recording imaging aperture value determining means. Features.

  The present invention also provides a control method suitable for the digital still camera. That is, according to this method, the imaging unit repeatedly captures an image of the subject in response to the setting of the imaging mode, outputs image data representing the subject image at a constant period, and the first imaging scene determination unit The imaging scene of the subject image represented by the image data output from the imaging means is determined, and the exposure amount calculating means is output from the imaging means in response to the first release of the shutter release button. The exposure amount is calculated using the image data, and the program diagram for the landscape imaging scene is obtained in response to the fact that the focus control aperture value determination means is determined as the landscape imaging scene by the first imaging scene determination means. The aperture control program corresponding to the exposure amount calculated by the exposure amount calculation means using the open aperture priority program diagram that is closer to the open aperture side than the aperture determined by the The exposure calculated by the exposure amount calculating means is determined using a program diagram for the determined imaging scene in response to determining a value and not being determined as a landscape scene by the first imaging scene determining means. The focus control aperture value corresponding to the amount is determined, and the focus control means repeatedly moves the subject with the focus control aperture value determined by the focus control aperture value determination means while moving the imaging lens position. The image pickup lens is positioned at a position where the contrast data of the image data output from the image pickup means reaches a peak value, and the second image pickup scene determination means is positioned by the focus control means. By imaging the subject at the imaging lens position, the imaging scene of the subject image represented by the image data output from the imaging means is discriminated and recorded. The aperture value determining means determines the recorded imaging aperture value corresponding to the exposure amount calculated by the exposure amount calculating means, using the program diagram for the imaging scene determined by the second imaging scene determining means. And the recording control means is the imaging lens position positioned by the focusing control means in response to the second release of the shutter release button, and the recording imaging aperture value determining means When the subject is imaged with the determined aperture value, the image data output from the imaging means is recorded on a recording medium.

  According to this invention, a subject is imaged, and a first imaging scene determination process for determining an imaging scene of the captured subject image is performed. When it is determined that the scene is a landscape imaging scene in the first imaging scene determination process, an open aperture priority program diagram that is closer to the open aperture than the aperture determined in the program diagram for a normal landscape imaging scene is used. , A focus control aperture value is determined. If it is determined that the scene is not a scene shooting scene, a focus control aperture value is determined using a program diagram for the determined shooting scene. The subject is repeatedly imaged while moving the imaging lens using the determined focus control aperture value. The position where the contrast data of the image data obtained by repeated imaging is at the peak value is determined as the in-focus position, and the imaging lens is positioned. Thereafter, the imaging scene determination is performed again (second imaging scene determination), and an imaging aperture value for recording is determined using the determined imaging scene program diagram. The subject is imaged with the determined aperture value, and image data representing the subject image is recorded on the recording medium.

  A normal program diagram used for a landscape imaging scene is defined so that the aperture value becomes small. Contrast data of image data obtained by repeatedly imaging the subject while moving the imaging lens with the aperture value determined in this way makes it difficult to find the peak value and to find the in-focus position accurately. . According to the present invention, in the case of a landscape image capturing scene, an open aperture priority program diagram is used so that the aperture value on the open side is larger than the aperture value determined in the program diagram for a normal landscape image capturing scene. Since the focus control aperture value is determined, it becomes easy to find the peak value of the contrast data of the image data obtained by repeatedly imaging the subject using the focus control aperture value. The imaging lens position can be determined relatively accurately and focusing control can be performed without performing focusing control again at the time of imaging for recording.

  FIG. 1 shows an embodiment of the present invention and is a block diagram showing an electrical configuration of a digital still camera.

  The overall operation of the digital still camera is controlled by the CPU 30.

  The digital still camera is provided with a mode setting switch 1 for setting an imaging mode, a reproduction mode, and other modes. The mode setting signal output from the mode setting switch 1 is input to the CPU 30. The digital still camera is also provided with a two-stroke type shutter release button 2. A signal S1 indicating the first-stage depression of the shutter release button 2 and a signal S2 indicating the second-stage depression are also input to the CPU 30.

  A zoom lens 3 and a focus lens 4 are provided in front of the CCD 5 so as to be movable in the optical axis direction. A zoom position of the zoom lens 3 is determined by a zoom motor 6 controlled by a motor driver 7. Further, the position of the focus lens 4 is determined by the focus motor 8 controlled by the motor driver 9.

  When the imaging mode is set by the mode setting switch 1, the subject is repeatedly imaged by the CCD 5, and a video signal representing the subject image is repeatedly output at a constant period. A video signal representing a subject image is input to the analog / digital conversion circuit 10 and converted into digital image data by the analog / digital conversion circuit 10. The converted digital image data is input to the image signal processing circuit 12 via the image input controller 11. In the image signal processing circuit 12, predetermined signal processing such as gamma correction and white balance adjustment is performed.

  The image data output from the image signal processing circuit 12 is input to an AE (automatic exposure) / AF (automatic focus) detection circuit 16. In the AE / AF detection circuit 16, subject brightness is measured from the input image data, and a photometric value (BV value) is calculated. In the AE / AF detection circuit 16, an exposure amount (EV value) is calculated from the photometric value. Data representing the calculated exposure amount is input to the aperture / shutter speed determination circuit 17. The aperture / shutter speed determination circuit 17 stores data representing a plurality of program diagrams suitable for the imaging scene, as will be described later, and the aperture value and shutter speed of the aperture (not shown) based on the program diagrams. (So-called electronic shutter) is determined. The AE / AF detection circuit 16 determines the lens position of the focus lens 4 based on the contrast of the input image data. The imaging of the subject is repeated with the determined exposure amount and lens position. Further, the AE / AF detection circuit 16 calculates the distance to the subject based on the determined lens position of the focus lens 4.

  The digital still camera is provided with a scene discrimination circuit 18. The scene discrimination circuit 18 discriminates an imaging scene. Examples of imaging scenes that can be identified include a person imaging scene, a macro imaging scene, a landscape imaging scene, and a night scene imaging scene.

  The scene discrimination circuit 18 also has a face detection function. The image data output from the image signal processing circuit 12 is also input to the scene discrimination circuit 18. It is detected whether or not a face image is included in the subject image represented by the input image data. When it is detected that a face image is included in the captured subject image, it is determined as a human image capturing scene.

  The scene discrimination circuit 18 is also input with data representing the photometric value detected by the AE / AF detection circuit 16 and the distance to the subject. If it is not a person image capturing scene and the distance to the subject is several tens of centimeters, it is determined as a macro image capturing scene. When the exposure amount is ten or more Ev or more, it is determined as a landscape imaging scene. When the exposure amount is 3 to 4 Ev or less, it is determined as a night scene imaging scene. When none of the person imaging scene, macro imaging scene, landscape imaging scene, and night scene imaging scene can be determined, it is determined as a normal imaging scene.

  The digital still camera includes the aperture / shutter speed determination circuit 17 as described above. An aperture value and a shutter speed are determined based on the exposure amount using a program diagram corresponding to the determined imaging scene from a plurality of program diagrams.

  The image data output from the image signal processing circuit 12 passes through the compression processing circuit 13 and is given to the display control circuit 14. When the image display device 15 is controlled by the display control circuit 14, a subject image that is repeatedly captured is displayed on the display screen of the image display device 15.

  If the shutter release button 2 is depressed in the second stage when the imaging mode is set, the image data obtained by imaging is compressed in the compression processing circuit 13 and temporarily stored in the memory 19. The The image data is read from the memory 19 and recorded by a media controller 20 on a recording medium 21 such as a memory card.

  FIG. 2 shows the relationship between the imaging lens position and contrast data.

  Contrast data is extracted in the above-described AE / AF detection circuit 16 from image data obtained by repeatedly imaging the subject while moving the position of the focus lens 2. Then, the graph G1 or G2 is obtained.

  The graph G1 is obtained when the aperture is on the open side (open aperture, small aperture value). The graph G2 is obtained when the aperture is narrowed (small aperture, large aperture value). When the aperture is on the open side, the depth of field is shallow, so you can clearly see where the subject image is blurred and where it is clear. For this reason, the peak value of the graph G1 becomes easy to understand. For example, if the peak value of the contrast data of the graph G1 obtained at the full aperture is P1, the position of the focus lens 4 that provides the peak value P1 is known as L1. The focus lens 4 is positioned with the position of L1 as the in-focus position.

  On the other hand, if the aperture is a small aperture, the depth of field is deep, so the portion where the subject image is blurred and the clear portion are not clearly separated. For this reason, the peak value of the graph G2 becomes difficult to understand. For example, if the peak value of the contrast data of the graph G2 obtained when the aperture is small is P2, the position of the focus lens 4 that gives the peak value P2 is L2. However, since the graph G2 is gentle, it is difficult to detect the peak value P2 itself and to detect the position L2 of the focus lens 4 from the peak value P2, and the obtained position L2 accurately represents the in-focus position. There may not be. For this reason, in this embodiment, when detecting the in-focus position, a program diagram that provides an aperture value on the open side is used.

  3 and 4 are examples of a program diagram for calculating an aperture value and a shutter speed when obtaining image data used for focusing control in the case of a landscape imaging scene. FIG. 3 is a program diagram used in a normal case, and FIG. 4 is a program diagram used in this embodiment.

  In a normal landscape imaging scene, it is preferable to capture clearly from a near view to a distant view. Therefore, the aperture is determined so that the depth of field is deep. For this reason, referring to FIG. 3, in the normal case, a program diagram is defined such that the aperture value is small (the aperture value is large). For example, when the exposure amount is 12 EV, the shutter speed is 7 TV or 8 TV, and the aperture value is determined to be F5.6 or F8.0. These shutter speeds and aperture values are determined depending on whether shutter speed priority or aperture priority.

  On the other hand, in the program diagram used in this embodiment, referring to FIG. 4, the aperture is determined so that the depth of field becomes shallower in the focus control even in the landscape imaging scene. . For this reason, a program diagram is defined such that the aperture value is on the open side (the aperture value is small). For example, when the exposure amount is 12 EV, the shutter speed is 10 TV and the aperture value is determined to be F2.8. The aperture value is determined on the basis of a program diagram in which the aperture value is on the open side, and as described above, the subject is imaged while moving the focus lens 4 with the determined aperture value to obtain contrast data. It is done. The obtained contrast data graph is relatively easy to detect the peak value. The in-focus position can be detected relatively accurately.

  In this embodiment, the program diagram shown in FIG. 3 is used to determine the aperture value used for imaging for automatic focusing control when it is determined that the mode is the human imaging mode, night scene imaging mode, or macro imaging mode. Is also used.

  FIG. 5 is an example of a program diagram used to determine a diaphragm when taking an image for recording in a landscape imaging scene.

  In the landscape imaging scene, as described above, a program diagram is defined such that a small aperture (large aperture value) is set so as to focus from a near view to a distant view. A subject is imaged with an aperture value determined based on such a program diagram. Then, a subject image that is in focus from near view to distant view is recorded.

  FIG. 6 is an example of a program diagram used for determining an aperture used for imaging at the time of recording a human imaging scene or a macro imaging scene.

  The depth of field is reduced so that a person is captured clearly in the case of a person imaging scene, and the subject that is close-up is also clearly imaged in the case of a macro imaging scene. For this purpose, as shown in FIG. 6, a program diagram is defined so as to provide an aperture on the open side.

  FIG. 7 is an example of a program diagram used for determining an aperture used for imaging at the time of recording a night scene imaging scene.

  In the case of a night scene shooting scene, the subject is dark. For this reason, a program diagram is defined in which the aperture is set to the open side and can be determined even with a low exposure amount (EV value) so that the aperture value can be determined even for a dark subject.

  8 and 9 are flowcharts showing the processing procedure of the digital still camera.

  When the imaging mode is set (YES in step 41), the subject is repeatedly imaged, and image data representing the subject image is output at a constant cycle (step 42). As described above, photometric value calculation and exposure setting are performed for each imaging cycle using image data for one frame output for each imaging (step 43), and the displayed subject image is the imaging cycle. Switch. Further, as described above, the first imaging scene discrimination is performed using the image data obtained by imaging (step 44). The imaging scene determination may be repeated according to the imaging cycle if possible, or may be repeatedly performed at a cycle slower than the imaging cycle. Steps 42 to 44 are repeated until the first release of the shutter release button 2 is pressed (step 45). Even after the shutter release button 2 is pressed in the first stage, the subject is repeatedly imaged.

  When the shutter release button 2 is pressed in the first stage (YES in step 45), a photometric value (BV value) is calculated using image data obtained by imaging the subject (step 46). . An exposure amount (EV value) is calculated from the obtained photometric value (exposure amount calculation) (step 47).

  If it is determined that the scene is a landscape imaging scene in the first imaging scene determination (YES in step 48), as described above, an open priority landscape imaging scene program diagram (see FIG. 4) that provides an aperture value on the open side. Is used to determine the aperture value (focusing aperture value for focus control) used for automatic focusing control imaging (step 49). If it is not discriminated as a landscape imaging scene in the first imaging scene discrimination (NO in step 48), it is a program diagram for the discriminated imaging scene for determining an aperture value used for automatic focusing control Using the program diagram (FIG. 6, FIG. 8, or FIG. 10), an aperture value (a focus control aperture value) used for imaging of the automatic focus control is determined (step 50).

  When the aperture value used for the automatic focusing control is determined, the subject is repeatedly imaged while the position of the focus lens 4 is moved with the determined aperture value. Contrast data is extracted from the image data obtained by imaging. By this repeated imaging, a graph showing the relationship between the position of the focus lens 4 and the contrast data is obtained as shown in FIG. The position of the focus lens 4 that gives the peak value of the obtained graph is determined as the focus position (focus control) (step 51).

  The focus lens 4 is positioned at the determined in-focus position, and the subject is imaged. Second imaging scene discrimination is performed from the image data obtained by imaging (step 52). When an imaging scene is determined by the second imaging scene determination, an aperture value (recording value) corresponding to the exposure amount calculated in step 47, using the recorded imaging scene, is determined. Imaging aperture value) and shutter speed are determined. The ISO sensitivity may be determined.

  If the shutter release button 2 is pressed in the second stage (YES in step 54), the subject is imaged at the determined aperture value, shutter speed, and focus lens position (step 55). Image data obtained by imaging is recorded on the recording medium 21 (step 56).

  In the above-described embodiment, imaging for automatic focusing control (step 51) and imaging for second imaging scene discrimination (step 52) are performed separately, but imaging for automatic focusing control is performed. The second imaging scene determination may be performed using the image data obtained by the above.

  In the above-described embodiment, the program diagram used for focusing control imaging and the program diagram used for recording imaging are different, but a common program diagram is used for each imaging scene. You may make it use.

It is a block diagram which shows the electric constitution of a digital still camera. The relationship between contrast data and focus lens position is shown. It is an example of a program diagram for normal landscape imaging scene AF. It is an example of a program diagram for an open aperture priority landscape imaging scene AF. It is an example of a program chart for landscape imaging scene recording imaging. It is an example of a program diagram for person / macro imaging scene recording imaging. It is an example of a program diagram for night scene imaging scene recording imaging. It is an example of the processing procedure of a digital still camera. It is an example of the processing procedure of a digital still camera.

Explanation of symbols

2 Shutter release button 5 CCD
16 AE / AF detection circuit
17 Aperture / shutter speed decision circuit
18 Scene discrimination circuit
19 memory

Claims (2)

Two-stroke type shutter release button,
An imaging unit that repeatedly captures an image of a subject in response to setting of an imaging mode and outputs image data representing the image of the subject at a constant period;
First imaging scene determination means for determining an imaging scene of a subject image represented by image data output from the imaging means;
Exposure amount calculating means for calculating an exposure amount using image data output from the imaging means in response to a first-stage depression of the shutter release button;
An open aperture priority program diagram that is closer to the open aperture than the aperture determined by the program diagram for the landscape imaging scene in response to the scene imaging scene being determined by the first imaging scene determining means. And determining a focus control aperture value corresponding to the exposure amount calculated by the exposure amount calculation unit, and determining the scene according to the fact that the first imaging scene determination unit has not determined the scene scene. A focus control aperture value determination means for determining a focus control aperture value corresponding to the exposure amount calculated by the exposure amount calculation means, using a program diagram for the captured scene;
The contrast data of the image data output from the imaging unit is peaked by repeatedly imaging the subject with the focusing control aperture value determined by the focusing control aperture value determining unit while moving the imaging lens position. A focusing control means for positioning the imaging lens at a position to be a value;
Second imaging scene discrimination means for discriminating an imaging scene of a subject image represented by image data output from the imaging means by imaging a subject at an imaging lens position positioned by the focusing control means;
The recorded imaging aperture value for determining the recorded imaging aperture value corresponding to the exposure amount calculated by the exposure amount calculation means using the imaging scene program diagram determined by the second imaging scene determination means And an aperture determined by the recording imaging aperture value determining unit, the imaging lens position positioned by the focus control unit in response to a second step of pressing the shutter release button. Recording control means for recording image data output from the imaging means on a recording medium by imaging a subject with values;
Digital still camera equipped with The imaging means repeatedly captures the subject according to the setting of the imaging mode, and outputs image data representing the subject image at a constant cycle,
A first imaging scene determination unit for determining a shooting scene of a subject image represented by the image data output from the imaging unit;
The exposure amount calculating means calculates the exposure amount using the image data output from the imaging means in response to the first release of the shutter release button.
In response to the fact that the focus control aperture value determining means is determined to be a landscape imaging scene by the first imaging scene determination means, the aperture value is set to a position closer to the open aperture than the aperture determined by the program diagram for the landscape imaging scene. An aperture value for focusing control corresponding to the exposure amount calculated by the exposure amount calculation means is determined using the open aperture priority program diagram as described above, and is determined as a landscape scene by the first imaging scene determination means. And determining a focus control aperture value corresponding to the exposure amount calculated by the exposure amount calculating means, using the program diagram for the determined imaging scene in response to the failure.
Image data output from the imaging unit when the focusing control unit repeatedly images the subject with the focusing control aperture value determined by the focusing control aperture value determining unit while moving the imaging lens position. Position the imaging lens at the position where the contrast data of
A second imaging scene determination unit that determines an imaging scene of a subject image represented by image data output from the imaging unit by imaging the subject at an imaging lens position positioned by the focusing control unit;
The recording and imaging aperture value determination means uses the imaging scene program diagram determined by the second imaging scene determination means and uses the recording and imaging aperture corresponding to the exposure amount calculated by the exposure amount calculation means. Determine the value,
The recording control means is the imaging lens position positioned by the focusing control means in response to the second release of the shutter release button, and is determined by the recording imaging aperture value determining means. Recording the image data output from the imaging means on the recording medium by imaging the subject with the aperture value;
Control method of digital still camera.

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