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`
`US 2()[)301936(K)A1
`
`(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2003/0193600 A1
`
` Kitamnra et al. (43) Pub. Date: Oct. 16, 2003
`
`
`(54)
`
`IMAGE CAPTURINC: APP/\RA'I‘US
`
`Publication Classification
`
`(75)
`
`Inventors: Masahim Kitamura, t')saka—shi (JP);
`Noriyuki Okisu, Osakasayamirshi (J P);
`Keiji 'l‘nmni, Suita-shi (JP); Motohim
`Nnkanishi, Kobe-shi (JP); 'I'osltihiro
`Hnmamurn, Osaka-shi (JP); Shinichl
`Fujii, Osaka-ski (J P); 'l‘sutomu Hundn,
`Sakai-slit (JP)
`
`(forrcspondcnco Address:
`SII)LI£Y AUSTIN BROWN 8; WOOD LLP
`
`151:1?gill; HARWOOD
`DAI 1A9 TX 75201 (US)
`‘
`L 5
`'
`L
`n
`..-,
`..
`-
`1
`.
`(73) N51511:“ MINOLIA L0" L”)
`(3|) Appl. No:
`1039;407
`
`(32)
`
`Filed:
`
`Mar. 19, 2003
`
`(30)
`
`Foreign Application Priority Data
`
`...... P20()2-(19(l735
`(JP)..
`(JP) .................................... l’2fl02~156987
`
`Mar. 38, 2002
`May 30, 2002
`
`Int. Cl.7 ..................................................... H04N 5122.2
`(51)
`(52) U.S. Cl.
`........................................................ 348,833.01
`
`(57)
`
`ABSTRACT
`
`A digital camera obtains image data of a subject by a (SCI).
`'I'lte CC!) ltas, as image data output modes, a "normal mode"
`01 outputting all 01 pixels ofthu Imago data at 60 [p5 and art
`"area-limited mode" of outputting an area including 3 lim-
`itcd focus area in the ima 10 data at 180 fps. Thc output mode
`of the (TCD is sot
`to 1111:: "normal mode" in a live-view
`operation. At the time of an auto—focus control, the output
`mode is switched at the intervals of Win second between the
`
`“arcmlimitcrl modo” and the "normal mode". White the
`output mode ol’ the CCD is set to tho ”area—limited mode".
`the state of a display scrocn of a liquid crystal monitor is
`hold. Consequently, while performing auto-focus promptly,
`a subject
`image can be appropriately displayed on the
`display screen of the liquid crystal monitor.
`
`24
`
`25
`
`27
`
`Elf—2‘1
`
`oo
`
`298 29b 29c 29d
`\——Y,_____—_J
`29
`
`1
`
`APPLE 1012
`
`APPLE 1012
`
`1
`
`

`

`Patent Application Publication Oct. 16, 2003 Sheet 1 0f 26
`
`US 2003/0193600 A1
`
`- ¢
`
`52
`
`3¢
`
`293 29b 290 29d
`%__V_._._._J
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`
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`
`

`

`Patent Application Publication
`
`Oct. 16, 2003 Sheet 2 0f 26
`
`US 2003/0193600 A1
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`Patent Application Publication Oct. 16, 2003 Sheet 3 0f 26
`
`US 2003/0193600 A1
`
`FIG..4
`
`60
`
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`
`61
`
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`
`

`

`Patent Application Publication Oct. 16, 2003 Sheet 4 0f 26
`
`US 2003/0193600 A1
`
`EVALUATION-.
`
`VALUE
`
`LENS POSITION
`
`5
`
`

`

`Patent Application Publication Oct. 16, 2003 Sheet 5 0f 26
`
`US 2003/0193600 A1
`
`FIG.T
`
`IMAGE CAPTURING
`MODE
`
`000 NORMAL MODE
`
`ST“
`
`
`
`/ST1T
`
`I S
`
`T18
`No
`
`S 1 ?
`
`Yes
`AUTO—FOCUS CONTROL
`
`I
`
`82?
`
`Yes
`
`RECORD IMAGE DATA FOR RECORDING
`
`
`
`6
`
`

`

`Patent Application Publication Oct. 16, 2003 Sheet 6 0f 26
`
`US 2003/0193600 Al
`
`F
`
`|
`
`(3
`
`.
`
`8
`
`AUTO-FOCUS CONTROL
`
`STEM
`
`LUMINANCE VALUE OF SUBJECT
`
`VALUE?
`
`EQUAL TO OR HTGHER THAN
`
`PREDETERMINED REFERENCE
`
`0
`
`Yes
`
`ST32
`
`LIQUID CRYSTAL MONTTOR IS
`
`IN DISPLAY STATE?
`
`N0 0
`
`Yes
`
`STBS
`
`INITIALIZE INTERNAL COUNTER C
`
`ST34
`
`ST40
`
`ST41
`
`ST42
`
`UPDATE LIVE-VIEW IMAGE
`
`DFRWE FOCUS EVALUATION 1ITALUE
`
`ST43
`
`ST44
`
`
`
`
`
`LENS DRIVE CONTROL
`
`8T45
`
`LENS FOCUS POSITiON?
`
`Yes
`
`7
`
`

`

`Patent Application Publication Oct. 16, 2003 Sheet 7 0f 26
`
`US 20030193600 Al
`
`FIG.9
`
`CCD NORMAL MODE
`
`EXPOSURE
`
`OUTPUT NORMAL IMAGE
`
`UPDATE LIVE‘VIEW IMAGE
`
`
`
`
`
`
`
`
`STBI
`
`ST52
`
`STBS
`
`ST54
`
`ST55
`
`ST56
`
`-
`
`STBT
`
`_
`
`DERIVE FOCUS EVALUATION VALUE
`
`LENS DRIVE CONTROL
`
`LENS FOCUS POSITION?
`
`Yes
`
`RETURN
`
`8
`
`

`

`Patent Application Publication Oct. 16, 2003 Sheet 8 0f 26
`
`US 2003/0193600 A1
`
`FIG.10
`
`ST61
`
`
` ST62
`
`CCD AREA-LIMITED MODE
`
`
`
`
`
`
`ST68
`
`ST64
`
`ST65
`
`ST66
`
`EXPOSURE
`
`OUTPUT AREA-LIMITED IMAGE
`
`OERIVE FOCUS EVALUATION VALUE
`
`LENS DRIVE CONTROL
`
`LENS IN-FOCUS POSITION?
`
`Yes
`
`'
`
`
`
`9
`
`

`

`Patent Application Publication
`
`Oct. 16, 2003 Sheet 9 0f 26
`
`US 2003/0193600 A1
`
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`Patent Application Publication Oct. 16, 2003 Sheet 10 0f 26
`
`US 2003/0193600 A1
`
`FIG.12
`
`AUTO-FOCUS CONTROL
`
`STT‘I
`
`
`
`
`
`LUMINANCE VALUE OF SUBJECT
`IS EOUAL TO OR HIGHER THAN
`PREDETERMINED REFERENCE
`VALUE?
`
`N“ 0
`
`Yes
`
`.
`
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`
`IN DISPLAY STATE?
`
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`Yes
`
`N0 0
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`
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`
`EXPOSURE
`
`OUTPUT NORMAL IMAGE
`
`UPDATE LIVE-VIE‘Al
`
`IMAGE
`
`DERIVE FOCUS EVALUATION VALUE
`
`LENS DRIVE CONTROL
`
`STT4
`
`STTS
`
`STTS
`
`STTT
`
`STTB
`
`STTQ
`
`
`
`
`
`
`
`LENS POSITION IS IN THE VICINITY
`OF IN-FOCUS POSITION?
`
`Yes
`
`ST33
`
`11
`
`11
`
`

`

`Patent Application Publication
`
`Oct. 16, 2003 Sheet 11 0f 26
`
`US 2003/0193600 A1
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`Patent Application Publication
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`Oct. 16, 2003 Sheet 12 0f 26
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`Patent Application Publication
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`Patent Application Publication Oct. 16, 2003 Sheet 16 0f 26
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`US 2003/0193600 A1
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`
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`
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`
`
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`
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`

`US 2003/0193600 A1
`
`Oct. 16, 2003
`
`IMAGE CAPTURING APPARATUS
`
`[0001] This application is based on application Nos. 2002‘
`090735 and 2002-15698";t filed in Japan. the contents of
`which are hereby incorporated by reference.
`
`BACKGROUND or THE INVENTION
`
`[0002]
`
`1. Field of the Invention
`
`[0003] The present invention relates to a focus control
`technique of an image capturing apparatus.
`
`[0004]
`
`3. Description of the Background Art
`
`in an image capturing apparatus
`[0005] Conventionally,
`for obtaining image data by using an image capturing device
`such as a CCD like a digital still camera (hereinafter, simply
`referred to as a “digital camera”) or a video camera, a
`technique called a contrast method (or hill climbing method)
`is applied to an auto-focus control. The contrast method is a
`method of obtaining, as an evaluation value, contrast of
`image data obtained at each of driving stages while driving
`a focusing lens, to determine a position of the lens at which
`the evaluation value is the highest as a focus position.
`
`In an image capturing apparatus having a display
`[0006]
`such as a liquid crystal monitor, live-view display is per-
`formed by obtaining image data every predetermined time in
`an image capturing standby state and displaying a subject
`image on the display on the basis of the obtained image data.
`By such live-viewr display, a user can perform framing while
`recognizing a subject image having no parallax.
`
`In recent years, improvement in operation speed of
`[0007]
`auto—focus control
`is demanded in the image capturing
`apparatus. Generally, an evaluation value is obtained from a
`predetermined focus area as a limited area where an image
`of a main subject is very likely to exist in image data, so that
`it is sufficient to obtain image data including the predeter-
`mined focus area in order to perform the auto-focus control.
`In the case where an area of image data outputted from an
`image capturing device is
`limited,
`image data can be
`obtained at a relatively high frame rate. Consequently, by
`outputting a limited image data including at least a focus
`area, improvement in Speed of the auto-focus control opera-
`tion is expected.
`
`[0008] However, in the case of outputting a limited image
`data from the image capturing device, a problem occurs such
`that the whole image of the subject cannot be displayed on
`a display such as a liquid crystal monitor.
`
`[0009] Conventionally, in order to obtain image data at a
`relatively high frame rate, image data is read while being
`compressed by skipping at a predetermined ratio and the
`compressed image data is outputted from image capturing
`device. When the ratio of skipping at the time of reading
`image data is increased, the frame rate can be increased, and
`further improvement in speed of the auto-focus control can
`be expected.
`
`[0010] However, at the time of auto-focus control, in order
`to also display a livevview on the display, the resolution of
`image data outputted from the image capturing device has to
`be equal to or higher than resolution of the display. Specifi-
`cally, the amount of image data outputted from the image
`capturing device is constrained to the amount of data nec-
`essary to display a subject image on the display. Conse-
`
`quently, the frame rate cannot be increased and a problem
`such that
`the speed of the auto-focus control cannot be
`further increased occurs.
`
`SUMMARY OF THE INVEN'I‘ION
`
`invention is directed to an image
`[0011] The present
`capturing apparatus for obtaining an image of a subject.
`
`[0012] According to the present invention, an image cap-
`turing apparatus comprises: an image capturing part for
`obtaining an image of a subject via an optical system, the
`image capturing part having a first output mode of output-
`ting first image data expressing a whole area of the image
`and a second output mode of outputting second image data
`including at
`least a focusing area of the image at higher
`speed as compared with the first output mode, a focus
`controller for performing a focus control of the optical
`system by referring to the focusing area; a display for
`displaying the image of the subject on a display screen on
`the basis of the first image data; an image capturing con—
`troller for enabling the second output mode in performing
`the focus control; and a display controller for holding a state
`of the image of the subject on the display screen in the
`second output mode.
`
`[0013] Since the slate of the image of the subject on the
`display screen is held in the second output mode, while
`performing the focus control promptly,
`the image of the
`subject can be displayed on the display.
`
`[0014] According to an aspect of the present invention, the
`image capturing controller alternately enables the first out~
`put mode and the second output mode at predetermined
`intervals in performing the focus control.
`
`[0015] Since the first image data expressing the whole area
`of an image is outputted at the predetermined intervals, the
`image of the subject on the display screen can be updated at
`the predetermined intervals, at the time of performing the
`focus control.
`
`[0016] According to another aspect of the present inven—
`tion, an image capturing apparatus comprises: an image
`capturing part for obtaining an image of a subject via an
`optical system; a focus controller for performing a focus
`control of the optical system; and an image display. The
`image capturing part has a first output mode of outputting
`first image data which is sufficient for both performing the
`focus control and displaying the image of the subject, and a
`second output mode of outputting second image data which
`is sufficient for performing the focus control but is insuffia
`cient for displaying the image of the subject. The image
`capturing apparatus further comprises a screen image gen~
`erator for generating a screen image of the subject on the
`basis of the second image data, and the screen image is
`displayed on the image display in the second output mode.
`
`[0017] Since the screen image is generated on the basis of
`the second image data when the image capturing part
`outputs the second image data which is insufficient for
`displaying an image of a subject, an image of a subject can
`be displayed on the image display.
`
`[0018] Therefore, an object of the present invention is to
`provide an image capturing apparatus capable of appropri-
`ately displaying an image of a subject on a display while
`promptly performing a focus control.
`
`28
`
`28
`
`

`

`US 2003/0193600 A1
`
`Oct. 16, 2003
`
`features, aspects and
`[0019] These and other objects,
`advantages of the present
`invention will become more
`apparent from the following detailed description of the
`present
`invention when taken in conjunction with the
`accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0020] FIG. 1 is a perspective view of a digital camera as
`an image capturing apparatus in preferred embodiments;
`
`[0021] FIG. 2 is a diagram showing a configuration of a
`rear side of the digital camera;
`
`[0022] FIG. 3 is a block diagram showing main internal
`components of a digital camera of a first preferred embodi-
`merit;
`
`[0023] FIG. 4 is a diagram showing image data obtained
`by a CCD and a normal image;
`
`[0024] FIG. 5 is a diagram showing image data obtained
`by the CCD and an area-limited image;
`
`[0025] FIG. 6 is a diagram showing an example of the
`relation between a lens position and a focus evaluation
`value;
`
`[0026] FIG. 7 is a diagram schematically showing opera-
`tions in an image capturing mode of the digital camera of the
`first preferred embodiment;
`
`FIGS. 8 to 10 are diagrams showing the flow of
`[0027]
`auto-focus control operation in the first preferred embodi-
`ment;
`
`[0028] FIG. 11 is a time chart showing processes of the
`auto—focus control in the first preferred embodiment;
`
`[0029] FIG. 12 is a diagram showing the flow of auto-
`focus control operation in a second preferred embodiment;
`
`[0030] FIG. 13 is a time chart showing processes of the
`auto-focus control in the second preferred embodiment;
`
`[0031] FIG. 14 is a block diagram showing main internal
`components ofa digital camera ofa third preferred embodi—
`ment;
`
`[0032] FIG. 15 is a diagram showing an example of a
`pixel array of a photosensitive part of a CCD;
`
`[0033] FIG. 16 is a diagram showing image data outputted
`from the CCD of the third preferred embodiment;
`
`[0034] FIG. 17 is a diagram for describing a read line of
`obtained image data;
`
`[0035] FIG. 18 is a diagram schematically showing the
`operation in an image capturing mode in the digital camera
`of the third preferred embodiment;
`
`[0036] FIG. 19 is a diagram for describing a method of
`generating a live-view image from a first compressed image;
`
`[0037] FIG. 20 is a diagram showing the flow of a process
`of selecting either a normal control or a highuspced control;
`
`[0038] FIG. 21 is a diagram showing an auto-focus con-
`trol operation in the normal control;
`
`[0039] FIG. 22 is a diagram showing an auto-focus con-
`trol operation in a high-speed control of the third preferred
`embodiment;
`
`[0040] FIG. 23 is a diagram for describing a method of
`generating a live-view image from a second compressed
`image;
`
`[0041] FIG. 24 is a diagram showing image data outputted
`from a (.‘CD of a fourth preferred embodiment;
`
`[0042] FIG. 25 is a diagram showing an auto-focus con-
`trol operation in high-speed control of the fourth preferred
`embodiment;
`
`[0043] FIG. 26 is a diagram for describing a method of
`generating a live-view image on the basis of the first
`compressed image and the area-limited image;
`
`[0044] FIG. 27 is a diagram showing an example of a
`live-view image generated in the fourth preferred embodi-
`ment; and
`
`[0045] FIG. 28 is a diagram showing an auto-focus con—
`trol operation in high-speed control of a fifth preferred
`embodiment.
`
`DESCRIP'I'IUN OF THE. PREFERRED
`EMBODIMENTS
`
`[0046] Hereinafter, embodiments of the present invention
`will be described in detail with reference to the drawings. In
`the following, a digital camera will be described as an
`example of an image capturing apparatus.
`
`[0047]
`
`I. First Preferred Embodiment
`
`[0048]
`
`1—1. Configuration of Digital Camera
`
`First; the configuration ofa digital camera 1 will be
`[0049]
`described. FIG. I is a perspective view showing the digital
`camera 1. FIG. 2 is a diagram showing the configuration on
`a rear face side of the digital camera 1.
`
`[0050] As shown in FIG. 1, at taking lens 3, an electronic
`[lash 23 and an objective window of an optical viewfinder 22
`are provided. The taking lens 3 has therein a unit of a
`plurality of lenses including a focusing lens 31 (see FIG. 3)
`which determines a focus state of a subject
`image.
`In a
`proper position on the rear side of the taking lens 3 in the
`digital camera 1, a CCD 21 as an image capturing device for
`obtaining image data (hereinafter, also simply referred to as
`“image") of a subject via the lens unit is provided.
`
`()n the top face side of the digital camera 1; a
`[005]]
`shutter release button 25 and a main switch 24 for switching
`onioli' states of a power source are disposed. The shutter
`release button 25 is a button of receiving an instruction of
`start of the auto-focus control or an instruction of taking a
`picture from the user and is a two-stage switch capable of
`detecting a half—pressed state (SI state) and a full—pressed
`state (82 state). In a side face ofthe digital camera 1, a card
`slot 26 into which a memory card 9 as a recording medium
`for recording image data and the like is removably inserted
`is formed.
`
`[0052] As shown in FIG. 2, on the rear face side of the
`digital camera I, an eyevpiecc window of the optical view-
`finder 22, a mode switching lever 27 for switching the
`operation mode, a liquid crystal monitor 28 for displaying
`various images, and a button group 29 for performing
`various operations are provided.
`
`[0053] The digital camera I has operations modes of an
`"image capturing mode“ for obtaining image data of the
`
`29
`
`29
`
`

`

`US 2003/0193600 A1
`
`Oct. 16, 2003
`
`La.)
`
`subject and a “reproduction mode" of reproducing and
`displaying recorded image data. The operation modes are
`switched by operation of the mode switching lever 27.
`
`[0054] The liquid crystal monitor 28 displays obtained
`image data, image data recorded on the memory card 9, and
`a menu screen for making various settings of the digital
`camera 1.
`
`[0055] On the liquid crystal monitor 28 in an image
`capturing standby state, live-view display is performed in
`which image data obtained by the CCD 21 every predeter-
`mined time is displayed continuously with respect to time,
`and the user can perform framing while recognizing a
`displayed subject’s image. At
`the time of the live-view
`display, a frame 28:: indicative of a predetermined focusing
`area is displayed. The user performs framing so that a
`desired subject’s image is disposed in the frame 28a, thereby
`setting a desired subject image into an in-focus state.
`
`[0056] The button group 29 includes a display switching
`button 29a, a left button 291’), a right button 29c and a menu
`button 294. The display switching button 29:: is a button for
`setting whether an image is displayed on the liquid crystal
`monitor 28 in the image capturing standby state or not. Each
`ti me the display switching button 29a is depressed, the state
`of the liquid crystal monitor 28 is switched between display
`and undisplay.
`
`[0057] The left button 2%, right button 29c and menu
`button 29d arc buttons for mainly making various settings of
`the digital camera I. By depressing the menu button 29d, a
`menu screen is displayed on the liquid crystal monitor 28.
`By operating the left button 2% and the right button 29c
`while recognizing the menu screen, various settings can be
`made.
`
`[0058]
`
`1-2. tnterna] Configuration of Digital Camera
`
`[0059] The internal configuration of the digital camera 1
`will now be described. FIG. 3 is a functional block diagram
`showing main internal componean of the digital camera 1.
`
`[0060] The CCD 21 is constructed by a photosensitive part
`for accumulating signal charges by exposure, a vertical
`transfer part and a horizontal transfer part for transferring the
`signal charge, an output part and the like. The photosensitive
`part is constructed by a plurality of pixels to each of which
`a color filter of one of R (red), G (green) and B (blue) is
`adhered. The photosensitive part photoelectrically converts
`a light image of the subject formed by the lens unit of the
`taking lens 3 into signal charges (image data). The signal
`charges accu mulated in the photosensitive part are once
`transferred to the vertical transfer part and, after that, to the
`horizontal transfer part every pixel line (hereinafter, referred
`to as “line“) in the lateral direction (horizontal direction),
`and sequentially outputted from the output part. Alternately,
`as the color filters adhered to the photosensitive part, color
`filters of complementary colors of a combination of (.1
`(cyan). M (magenta) and Y (yellow) may be employed.
`
`[0061] The CCD 21 has, as image data output modes, a
`"normal mode” of outputting all of pixels of image data and
`an "area-limited mode“ of outputting only a limited area
`including at least a focusing area in the image data.
`
`[0062] FIGS. 4 and 5 are diagrams showing image data
`60 obtained by the CCD 21. An image of a main subject in
`the image data 60 is very likely to exist in an almost center
`
`portion. Thus, as shown in the diagrams, the almost center
`portion is assigned to a focusing area FA as an area on which
`focus is achiever].
`
`[0063] When the CCD 21 is set in the normal mode, as
`shown in FIG. 4, all of pixels. of the image data 60 are
`outputted as a normal image 61. On the other hand, when the
`CCD 21 is set in the area-limited mode, signal charges in
`areas 63 in the upper and lower parts in the image data 60
`are discharged as unnecessary charges and an area-limited
`image 62 only in an area around the focusing area is
`outputtcd as shown in FIG. 5. The number of lines trans—
`ferred and output of the area-limited image 62 is smaller
`than that of the normal image 61. Consequently, when the
`CCD 21 is set in the area-limited mode, as compared with
`the case where the CCD 21 is set in the normal mode, one
`frame of image data can be outputted at higher speed, and
`the number of frames of image data outputted per unit time,
`that is, a frame rate (unit: fps) can be increased.
`
`[0064] When a period {inverse number of the frame rate)
`of outputting the normal image 61 from the CC!) 21 in the
`normal mode is T1 and a period of outputting the area—
`limited image 62 in the area-limited mode is T2,
`it
`is
`preferable that the periods '1‘1 and T2 have the following
`relation:
`
`Tl=n‘1l'2(where n is a natural number of 3 or larger)
`
`(1,1.
`
`[0065] That is, preferably, the period T1 is longer than the
`period T2 by a multiple of a natural number. In the preferred
`embodiment, the period TI is set
`to 1/50 second, and the
`period '1? is set to Vita; second (13:3). That is, the CCD 21
`outputs the normal image 61 at the frame rate of 60 fps in
`the normal mode and outputs the area—limited image 62 at
`the frame rate of 180 fps in the area-limited mode.
`[0066] Referring again to FIG. 3, a timing generator 201
`transmits various drive control signals to the CCD 21 on the
`basis ofa signal inputted from an overall control unit 40. For
`example, the timing generator 201 transmits a vertical sync
`signal for transferring signals charges accumulated in the
`pixels in the CCD 21 to the vertical transfer part, a horizontal
`sync signal for transferring signal charges in one line from
`the vertical transfer part to the horizontal transfer part, an
`unnecessary charge discharging signal
`for discharging
`unnecessary charges in the pixels, an output mode switching
`signal of switching the output mode to the normal mode or
`the area-limited mode, and the like. Therefore, the output
`mode of the CCD 21 is switched by the timing generator
`201.
`
`[0067] A signal processing circuit 202 performs a prede-
`termined analog signal process on image data (analog sig-
`nal) outputtcd from the CCD 21. The signal processing
`circuit 202 has therein a CDS (Correlated Double Sampling)
`circuit and an AGC (Auto Gain Control) circuit, for reducing
`noises in image data by the CDS circuit and adjusts the level
`of image data by the AGC circuit.
`
`[0068] An MD converter 203 converts image data of an
`analog signal outputtcd from the signal processing circuit
`202 to a digital signal. The value of each pixel outputtcd
`from the AID converter 20."! is expressed as a color compofi
`nent value of any of the color components of R, G and B.
`[0069] An image memory 204 is. a memory for storing
`image data outputtcd from the All) converter 203 and has a
`storage capacity of at least one frame of the normal image
`61.
`
`30
`
`30
`
`

`

`US 2003/0193600 A1
`
`Oct. 16, 2003
`
`[0070] An image processing unit 205 performs predeter-
`mined image processes of white balance correction, 7 cor-
`rection, resolution conversion, and compressing process on
`image data stored in the image memory 204.
`
`[0071] A VRAM 210 is a buffer memory for storing screen
`image data to be displayed on the display screen of the liquid
`crystal monitor 28.
`
`In the image capturing standby state, image data
`[0072]
`(normal image 61) outputted from the OCT) 21 in the period
`'l‘l (1/60 second) is subjected to predetermined signal pro
`cesses in the signal processing circuit 202 and the ND
`converter 203, and the processed image data is stored in the
`image memory 204. The pixels are skipped at predetermined
`intervals in the image processing unit 205, thereby obtaining
`a live-view image (screen image data used for live-view
`display), and the live-view image is stored in the VRAM
`210. The live-view image stored in the VRAM 210 is read
`at predetermined intervals by the overall control unit 40 and
`converted into a video signal, and the video signal
`is
`transmitted to the liquid crystal monitor 28. As a result, a
`subject image is displayed on the display screen of the liquid
`crystal monitor 28 (live-view display). A refresh rate (the
`number of times of rewriting the display screen per unit
`time) of the liquid crystal monitor 28 is set to 60 fps so as
`to coincide with the frame rate of outputting the normal
`image 6] from the CCD 21.A live-view image stored in the
`VRAM 210 is transmitted to the liquid crystal monitor 28
`every loo second. Image data obtained by the CCD 21 is
`sequentially smoothly displayed on the display screen of the
`liquid crystal monitor 28. Since the area-limited image 62 is
`not image data indicative of the whole area of the subject
`image, it cannot be used for such live-view display.
`
`[0073] On the other hand, after the instmction of photo-
`graphing by the shutter release button 25, image data (nor—
`mal image 61) outputted from the (.‘CD 21 as image data to
`be recorded is similarly subjected to the predetermined
`signal processes in the signal processing circuit 202 and the
`ND converter 203, and the processed image is stored in the
`image memory 204. The image is subjected to a compress-
`ing process conformed with the .1 PEG method in the image
`processing unit 205, thereby obtaining a compressed image.
`The compressed image is recorded on the memory card 9 via
`a card UP 206.
`
`Image data outputted from the CCD 21 in the
`[0074]
`image capturing standby state is also inputted to an AF
`computing unit 207 and a luminance computing unit 208 and
`used for an exposure control and a focusing control.
`
`[0075] The AP computing unit 207 derives a focus evalu—
`ation value used for the auto-focus control by using image
`data of both the normal image 61 and the area~limited image
`62. Concretely, pixels in the focusing area in image data are
`used for computation and a contrast value is obtained from
`the pixels in the focusing area and used as a focus evaluation
`value. The computed focus evaluation value is inputted to
`the overall control unit 40.
`
`[0076] The luminance computing unit 208 derives a lumi~
`nance value of the subject used for exposu rc control by using
`the normal image 61. Concretely, a luminance component
`value of a pixel in the input image data is obtained and an
`average value in all of pixels of obtained luminance com-
`ponent values is computed as a luminance value of the
`
`subject. The computed luminance value of the subject
`inputted to the overall control unit 40.
`
`is
`
`[0077] A lens driving unit 209 drives the focusing lens 31
`in the taking lens 3, an aperture in the taking lens 3 for
`determining an incident light amount, and the like. The lens
`driving unit 209 is electrically connected to the overall
`control unit 40 and drives the focusing lens 31 in the taking
`lens 3 and the like on the basis of a signal inputted from the
`overall control unit 40.
`
`[0078] An operation input unit 20 is an operation member
`shown as one function block including the shutter release
`button 25, main switch 24, mode switching lever 27, button
`group 29 and the like. The operation of the operation input
`unit 20 is inputted as a signal to the overall control unit 40.
`
`[0079] The overall control unit 40 is to control operations
`of the above-described members of the digital camera 1 in
`a centralized manner, and includes a CPU 41 for performing
`various computing processes, a RAM 42 as a work area for
`computation, and a ROM 43 in which a control program and
`the like is stored.
`
`[00