JP4740074B2 - Imaging apparatus and imaging method - Google Patents

Description

  The present invention relates to an imaging apparatus and an imaging method that perform automatic focus detection (hereinafter referred to as “AF”).

  Generally, an electronic imaging device such as a digital still camera is equipped with an AF device that automatically focuses on a subject. As an AF control method in the AF apparatus, a contrast detection method is widely used (see, for example, Patent Document 1).

  In this contrast detection method, an integral value of a luminance difference of a high-frequency component or a neighboring pixel in a video signal obtained for each field (or one frame) is obtained, and this integral value of the luminance difference is used to indicate an in-focus level. This is an evaluation value. When the subject is in focus, the AF portion of the subject is clear and the AF evaluation value is large. Conversely, when the subject is not in focus, the portion of the subject is unclear and the AF evaluation value is small.

  When the AF operation is performed, the AF evaluation values are sequentially acquired while moving the focus lens in the optical axis direction, and the point where the AF evaluation value is maximized (hereinafter referred to as “peak position”) is focused. Stop the lens as Generally, an apparatus that captures a still image such as a digital still camera requires strict focusing as compared with an apparatus that captures a moving image such as a video camera. The focusing operation is always repeated in the mode.

  However, if there is a background with a strong contrast or if the distance between the target subject and the surrounding subjects is close in close-up shooting, the background may be in focus and the desired focus may not be achieved. There was a problem. In addition, when shooting with a tripod fixed, if the target subject does not exist in the center of the desired angle, the focal point must be locked to the target subject and then the tripod must be fixed again. there were.

With respect to this point, a method has been proposed for solving the above-described problem by displaying an AF range on a liquid crystal display and moving the range by an operation input (see, for example, Patent Document 2).
Japanese Examined Sho 39-5265 JP 2003-121732 A

  However, an area for AF (hereinafter referred to as “AF area”) is simply obtained by cutting out a part of a video signal and performing AF shooting within the range as in the electronic zoom function installed in recent digital still cameras. ) Is not always the desired result. In other words, the AF area cannot be smaller than a certain size for the accuracy of focus detection, and the AF area occupied on the liquid crystal display becomes large at the time of electronic zoom at a high magnification, and even if the AF area is moved, the focus is achieved. There may be a problem that the result does not change or the focus position is not desired. Further, even if the AF area is moved by pressing the up / down / left / right movement button, the amount of movement of the AF area by one operation becomes smaller as the electronic zoom magnification becomes higher, and the focus operability is lowered.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an imaging apparatus and an imaging method that improve the operability of focusing even when electronic zooming of a display image is performed.

In order to solve the above-mentioned problem, the invention according to claim 1 is directed to an automatic focus detection unit that automatically detects a focus, an image display unit that displays an image on a display screen, and an enlargement or display of a display image on the display screen. Electronic zoom means for performing reduction, focus detection area display means for displaying a focus detection area on the display screen, focus detection area moving means for moving the position of the focus detection area with respect to the display image in response to an operation input, an imaging apparatus having an operation unit for moving the focus detection area, the focus detection area moving means, the amount of the movement of the focus detecting area according to an operation input, to change in response to the electron beam magnification together, it is characterized in that it comprises a focus detection area moving amount changing means for increasing an amount of the movement in accordance with the increase of the electronic zoom magnification

According to a second aspect of the present invention, in the imaging apparatus according to the first aspect, the focus detection area moving amount changing unit moves the position of the focus detection area on the display screen , and is based on one operation input. The amount of movement is changed in accordance with the electronic zoom magnification, and the amount of movement is increased in accordance with the increase in the electronic zoom magnification .

According to a third aspect of the present invention, in the imaging apparatus according to the first aspect, the focus detection area moving amount changing unit moves the display area of the display image on the display screen , and the one-input is used. The amount of movement is changed according to the electronic zoom magnification, and the amount of movement is increased as the electronic zoom magnification increases .

According to a fourth aspect of the present invention, in the imaging apparatus according to any one of the first to third aspects, the focus detection area display means determines an occupancy ratio of the focus detection area with respect to the display screen. A focus detection area occupancy rate changing unit that changes according to a zoom magnification is provided , and the focus detection area occupancy rate changing unit reduces the occupancy rate of the focus detection area according to an increase in the electron beam magnification. To do.

According to a fifth aspect of the present invention, there is provided an automatic focus detection means for automatically detecting a focus, an image display means for displaying an image on a display screen, and an electronic zoom for enlarging or reducing the display image on the display screen. Means, focus detection area display means for displaying a focus detection area on the display screen, focus detection area moving means for moving the position of the focus detection area with respect to the display image in response to an operation input, and the focus detection area. An imaging method in an imaging apparatus comprising: an operation unit to be moved, wherein the amount of movement of the focus detection area by one operation input is changed according to an electronic zoom magnification, and according to an increase in the electron beam magnification Thus, the amount of movement is increased .

The invention according to claim 6, in the imaging method according to claim 5, to move the position of the focus detection area on the display screen, according to the amount of the movement according to an operation input to the electronic zoom magnification And the amount of movement is increased in accordance with the increase in the electron beam magnification .

Further, an invention according to claim 7, in the imaging method according to claim 5, wherein the moving the display area of the display image on the display screen, in accordance with the amount of the movement according to an operation input to the electronic zoom magnification In addition, the amount of movement is increased in accordance with an increase in the electron beam magnification .

The invention according to claim 8 is the imaging method according to any one of claims 5 to 7 , wherein the occupation ratio of the focus detection area with respect to the display screen is reduced according to an increase in the electronic zoom magnification. It is characterized by doing.

  According to the present invention, when the display image is enlarged or reduced by the electronic zoom function, the movement amount by one operation input of the focus detection area can be changed in accordance with the enlargement or reduction ratio. Is improved.

  Embodiments of an imaging apparatus and an imaging method according to the present invention will be described below with reference to the drawings.

  First, each part of the block diagram of the digital camera will be described. The lens group 10 (zoom lens and focus lens) in the lens unit is driven by a motor driver 20. The motor driver 20 is controlled by a microcomputer (hereinafter referred to as “microcomputer”) 71 included in the signal processing IC 70.

  The imaging unit 50 includes a CCD 40, a timing signal generator (TG) 51 that drives the CCD 40, a CDS 52 that removes noise from the CCD, an analog gain controller (AGC) 53, and an output electrical signal (analog image data) of the CCD 40. It comprises an A / D converter 54 that converts it into a digital signal.

  Digital data input from the imaging unit 50 is temporarily stored as RGB data 82 in the SDRAM 80 serving as an image storage unit via the CCD I / F unit 72.

  The signal processing IC 70 includes a microcomputer 71 that performs system control, a CCD I / F unit 72, an image processing unit 73, a resizing unit 74, a JPEG codec unit 75, a display I / F unit 76, an audio codec unit 77, a card controller unit 78, And a memory controller 79.

  The CCD I / F unit 72 outputs a screen horizontal synchronization signal (HD) and a screen vertical synchronization signal (VD), and takes in a digital RGB signal input from the A / D converter 54 in accordance with the synchronization signal. Then, the RGB data 82 is written into the SDRAM 80 via the memory controller 79.

  The image processing unit 73 performs conversion processing into YUV data 83 temporarily stored as RGB data 82 in the SDRAM 80 based on image processing parameters set by the microcomputer 71 serving as a control unit.

  The resizing unit 74 reads the YUV data 83 and performs size conversion for recording, thumbnail images, and display.

  The display I / F unit 76 sends the display data written in the SDRAM 80 to the display device 90 to display the captured image. In addition to displaying on the LCD 203 (see FIG. 2A) incorporated in the camera, the display device 90 can also output and display a TV video signal on a television as the display device 90.

  The JPEG codec unit 75 compresses the YUV data 83 written in the SDRAM 80 during recording and outputs JPEG-encoded data, and decompresses the JPEG-encoded data read from the card into YUV data 83 during reproduction. Output.

  The card controller unit 78 reads data in the memory card 110 to the SDRAM 80 and writes data on the SDRAM 80 to the memory card 110 according to instructions from the microcomputer 71.

  The microcomputer 71 serving as a control unit loads a program and control data stored in the ROM 120 into the SDRAM 80 at the time of activation, and controls the whole based on the program 81. The microcomputer 71 follows an instruction from a button (hereinafter referred to as “button”) of the operation unit 60, an external operation instruction from a remote controller (not shown), or a communication operation instruction by communication from an external terminal such as a personal computer. , Imaging operation control, setting of image processing parameters in the image processing apparatus, memory control, and various display controls.

  The operation unit 60 is used by the photographer to instruct operation of the imaging apparatus, and is used to perform various settings from the outside, such as a release button for instructing photographing, a zoom button for setting the magnification of the optical zoom and electronic zoom, and the like. Button is provided.

  Next, the photographing operation during electronic zoom will be described.

  When the shooting / playback switching dial 212 of FIG. 2 is set to shooting and the camera is activated by the power button 201, the lens is set at a predetermined focal length position, and a live view image is displayed on the LCD 203 which is an electronic viewfinder.

  When a zoom telephoto button (hereinafter referred to as “zoom T button”) 207 is pressed from the activated state, the trimming portion of the display image is enlarged and displayed. Further, when a zoom wide-angle button (hereinafter referred to as “zoom W button”) 208 is pressed, the trimming portion of the display image is reduced and displayed.

  FIG. 3A shows a state before electronic zoom, and FIG. 3B shows a state after electronic zoom. When the release button 202 is pressed, shooting preparation processing such as AF operation and exposure time setting is performed, followed by recording exposure processing. After the shutter 30 is closed, the RGB data 82 for all the CCD pixels is once taken into the SDRAM 80.

  Here, the image data of the currently displayed portion (see FIG. 3) is sent to the image processing unit 73 and converted into YUV data 83. The YUV data 83 is converted into a size corresponding to the number of recording pixels by the resizing unit 74, and then JPEG compression processing is performed, header information is added, and the data is stored in the memory card 110 as a JPEG file.

  Next, the AF method in this digital camera will be described. When the release button 202 is pressed, an AF evaluation value indicating the degree of focus on the screen and an AE evaluation value indicating the exposure state are calculated from the digital RGB signals captured in the CCD I / F unit 72 of the signal processing IC 70. The The AF evaluation value data is read as feature data to the microcomputer 71 and used for AF processing. The integral value of adjacent pixels has the highest high-frequency component because the edge of the subject is clear when in focus. For this reason, AF is performed by acquiring the AF evaluation value at each focus lens position and detecting the peak position of the AF evaluation value. In addition, when there are a plurality of AF evaluation value peak positions in focus detection by AF, the magnitude of the AF evaluation value at each peak position and the difference from the surrounding AF evaluation values are judged, and the most reliable AF is executed with a certain point as the in-focus position.

  The AF evaluation value can be calculated from a specific range in the digital RGB signal. FIG. 3 shows a frame near the center shown in FIG. 3B in a state where a live view image is displayed before electronic zoom (FIG. 3A) and after electronic zoom (FIG. 3B). The inside is an AF area 301 of this digital camera. As shown in FIG. 4, the AF area 301 here is centered on the AF evaluation value target 401 and is 40% horizontal and 30% vertical in the RGB signal.

  The default position of the AF evaluation value target 401 is the center position of the AF area 301, but can be moved. For example, in the case of a subject as shown in FIG. By pressing 209, the center of the subject (the center of the face) can be adjusted as shown in FIG. This makes it possible to focus on the subject without changing the position or angle of the digital camera.

  Next, operations that characterize the present invention will be described.

  As the AF operation when the release button 202 is pressed in this image pickup apparatus, first, as shown in FIG. 5, before the AF operation is performed, the up / down / left / right movement button 209 is pressed to press the AF area 301, that is, the AF evaluation value target 401. Is moved to match the subject. At this time, for example, the amount by which the AF evaluation value target 401 moves is set as shown in FIG. 6 by one press (hereinafter referred to as “one operation input”) of the up / down / left / right movement button 209 before the electronic zoom. The AF evaluation value target 401 moves the grid-like coordinates 501 in the display screen one by one every time the up / down / left / right movement button 209 is pressed. In this example, the AF evaluation value target 401 can be moved to 8 × 8 positions on the display screen. When the position of the AF evaluation value target 401 is determined, it is determined by pressing the Enter button 210. At this time, coordinate information where the AF evaluation value target is currently located is sent to the microcomputer 71 side. When electronic zoom is performed here, the AF evaluation value target 401 is enlarged so as to be positioned at the center of the LCD 203 as a display screen (FIG. 7). This is possible by specifying the AF evaluation value target position in the RGB signal from the coordinate information sent to the microcomputer 71 side. Display images with electronic zoom magnifications of 2.0 times and 4.0 times are as shown in FIGS. 7 and 8, respectively.

  Here, when the AF operation is executed by pressing the release button 202, the AF area 301 also increases with the electronic zoom magnification, which causes a problem that a desired focus cannot be obtained. Therefore, the AF area 301 is reduced in inverse proportion to the electronic zoom magnification so as to be smaller than the horizontal 40% vertical 30% of the RGB signal before the electronic zoom (FIG. 9). However, since there is a concern that the focusing accuracy may drop when the AF area 301 becomes 20% horizontal or 20% vertical or less, when the AF area 301 becomes 20% horizontal or 20% vertical or less of the RGB signal as a result of the reduction. Cease further reduction to 20% horizontal and 20% vertical.

  When the position of the AF evaluation value target 401 is further moved after the electronic zoom, the operation is different from the movement before the electronic zoom. That is, when moving the position of the focus detection area on the display screen, the amount of movement by one operation input is increased in accordance with the increase in the electronic zoom magnification (FIG. 11). That is, the amount of movement of the AF evaluation value target 401 by one operation input is increased as shown in FIG. 11 by setting the grid-like coordinates (FIG. 10). This is because when the electronic zoom magnification is close to 4.0 times, the movement amount of the AF evaluation value target by one operation input is considerably smaller than that before the electronic zoom (FIG. 6). This is because it does not make sense to move the target.

  Here, the movable position of the AF evaluation value target 401 in the normal area is 8 × 8, but is not limited thereto. Further, the reduction ratio of the AF area 301 is set to 20% horizontal and 20% vertical due to the limitation of focusing accuracy. However, since a higher resolution CCD 40 can guarantee sufficient focusing accuracy, it is possible to enlarge the reduction range. This is possible and is not limited to this reduction rate. Furthermore, in the present embodiment, the method of changing the movement amount of the AF area when the electronic zoom magnification is increased has been described, but the same method can be applied even when the electronic zoom magnification is decreased.

  According to the present embodiment, when the display image is enlarged or reduced by the electronic zoom function, the movement amount by one operation input of the AF area can be changed according to the enlargement or reduction ratio. Is improved. Furthermore, since the AF area can be enlarged or reduced according to the electronic zoom magnification, for example, if the display image is enlarged, the AF target can be specified in detail, and a desired focus can be obtained. it can.

  Next, a second embodiment is shown. For the same reason as described in the first embodiment, when the position of the AF evaluation value target 401 is moved after the electronic zoom, the AF evaluation value target 401 is moved by an operation different from the movement before the electronic zoom. .

  In the present embodiment, the grid size of the grid-like coordinates remains the same as in FIG. 6, but the display area of the display image is moved simultaneously with the movement of the AF evaluation value target 401 as shown in FIG. I have to. That is, the movement amount of the AF evaluation value target is increased by moving the display area of the display image in the direction opposite to the movement direction of the AF evaluation value target 401 together with the movement of the AF evaluation value target. The movement amount of the display area of the display image is such that the movement amount of the AF area by one operation input is effective when the AF area is most reduced (for example, horizontal 20% vertical 20% of the RGB signal). Set to. For example, the amount of movement of the display area of the display image is set so that the horizontal or vertical size of the AF area is moved relative to the display image when the AF evaluation value target moves a part of the grid-like coordinates. That's fine. During the AF operation, the display area of the display image changes, but the actual shooting area is performed in the display area before the AF evaluation value target is moved (see FIG. 13).

  Also in this case, as in the first embodiment, the movable position of the AF evaluation value target 401 and the enlargement or reduction range of the AF area 301 are not limited to a certain range. In this embodiment, the method of changing the movement amount of the AF area when the electronic zoom magnification is increased has been described. However, the same method can be applied even when the electronic zoom magnification is decreased. Furthermore, it is naturally possible to move only the display area of the display image with the AF evaluation value target fixed at a fixed position, and to change the amount of movement according to the electronic zoom magnification.

  According to the present invention, when the display image is enlarged or reduced by the electronic zoom function, the movement amount by one operation input of the AF area can be changed according to the enlargement or reduction ratio. Improvement is achieved. In addition, it is possible to obtain a desired focus without changing the position or angle of the imaging device. Furthermore, since the AF area can be enlarged or reduced according to the electronic zoom magnification, for example, if the display image is enlarged, the AF target can be specified in detail, and a desired focus can be obtained. it can.

It is a block diagram which shows the outline | summary of the system configuration inside the digital camera as an imaging device which concerns on the Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic of the digital camera as an imaging device based on the Example of this invention, (a) is a front view, (b) is a rear view, (c) is a top view. The state of the change of the subject by electronic zoom is shown, (a) is before electronic zoom, (b) is a figure after electronic zoom. It is the schematic of a live view video display screen. It is the figure which showed the example of a movement of AF evaluation value target. It is the figure which showed the movable position of the focus detection area before electronic zoom (normal state), and the AF area movable width by one operation input. The state of electronic zoom 2.0 times is shown, (a) before electronic zoom, (b) after electronic zoom. The state of electronic zoom 4.0 times is shown, (a) before electronic zoom and (b) after electronic zoom. It is the figure which showed the example of the size change of AF area according to an electronic zoom magnification. It is the figure which showed the AF area movable position after electronic zoom, and the AF area movable width by one operation input. It is the figure which showed the mode of the movement of AF evaluation value target which concerns on Example 1 of this invention. It is the figure which showed the mode of the movement of AF evaluation value target which concerns on Example 2 of this invention. It is the figure which showed the image actually image | photographed after the movement of the AF evaluation value target which concerns on Example 2 of this invention (FIG. 12).

Explanation of symbols

71 Microcomputer (control unit)
76 Display IF
203 LCD 203
301 AF area 401 AF evaluation value target 501 AF area movable width by one operation input before electronic zoom 502 AF area movable width by one operation input after electronic zoom

Claims (8)

Automatic focus detection means for automatically detecting the focus;
Image display means for displaying an image on the display screen;
Electronic zoom means for enlarging or reducing the display image on the display screen;
Focus detection area display means for displaying a focus detection area on the display screen;
A focus detection area moving means for moving the position of the focus detection area with respect to the display image in response to an operation input;
An operation unit that moves the focus detection area;
The focus detection area moves Dote stage, the amount of the movement of the focus detecting area according to an operation input, as well as changes in response to the electron beam magnification to increase the amount of the movement in accordance with the increase of the electronic zoom magnification An imaging apparatus comprising a focus detection area moving amount changing means . The focus detection area movement amount changing means moves the position of the focus detection area on the display screen, changes the movement amount by one operation input according to the electronic zoom magnification, and increases the electronic zoom magnification. The imaging apparatus according to claim 1, wherein the amount of movement is increased in accordance with the frequency . The focus detection area movement amount changing means moves the display area of the display image on the display screen, changes the movement amount by one operation input according to the electronic zoom magnification, and increases the electronic zoom magnification. The imaging apparatus according to claim 1, wherein the amount of movement is increased accordingly . The focus detection area display means includes a focus detection area occupancy rate changing means for changing an occupancy ratio of the focus detection area with respect to the display screen according to an electronic zoom magnification,
The focus detection area occupancy changing means, the imaging apparatus according to any one of claims 1 to 3, characterized in that to reduce the occupancy of the focus detection area in response to an increase of the electron beam magnification. Automatic focus detection means for automatically detecting the focus, image display means for displaying an image on the display screen, electronic zoom means for enlarging or reducing the display image on the display screen, and a focus detection area on the display screen An imaging apparatus comprising: a focus detection area display means for displaying; a focus detection area moving means for moving the position of the focus detection area with respect to the display image in response to an operation input; and an operation unit for moving the focus detection area. An imaging method in
The amount of the movement of the focus detecting area according to an operation input, as well as changes in accordance with the electronic zoom magnification, imaging method characterized by increasing the amount of the movement in accordance with the increase of the electron beam magnification. The position of the focus detection area on the display screen is moved, the amount of movement by one operation input is changed according to the electronic zoom magnification, and the amount of movement is increased according to the increase of the electron beam magnification. The imaging method according to claim 5 . The display area of the display image on the display screen is moved, the amount of movement by one operation input is changed according to the electronic zoom magnification, and the amount of movement is increased according to the increase of the electron beam magnification. The imaging method according to claim 5 . The imaging method according to claim 5 , wherein an occupation ratio of the focus detection area with respect to the display screen is reduced according to an increase in the electronic zoom magnification .