USOO77334-14B2
`
`(12) United States Patent
`Kobayashi
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,733,414 B2
`Jun. 8, 2010
`
`(54) PHOTOGRAPHIC DEVICE AND CONTROL
`METHOD THEREFOR
`
`(75) Inventor: Koji Kobayashi, Saitama (JP)
`
`(73) Assignee: Fujifilm Corporation, Tokyo (JP)
`
`(*) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 1490 days.
`
`(21) Appl. No.: 11/075.937
`1-1.
`(22) Filed:
`
`Mar 10, 2005
`
`(65)
`
`Prior Publication Data
`US 2005/02OO744 A1
`Sep. 15, 2005
`
`(30)
`Foreign Application Priority Data
`Mar. 12, 2004 (JP)
`............................. 2004-071516
`(51) Int. Cl.
`(2006.01)
`H04N 5/235
`(2006.01)
`H04N 3/4
`348/362. 348/2211: 348/296
`(52) U.S. Cl
`58 Fi ld f c - - - - - .ficatior Search s
`348f221.1
`(58) Field of Classification Searc
`348/296 297. 23 i 6
`S
`lication file f
`let
`h hi t
`s
`ee application ille Ior complete Search n1Story.
`References Cited
`U.S. PATENT DOCUMENTS
`4,837.628 A
`6, 1989 Sasaki ..................... 348,220.1
`
`(56)
`
`1/1991 Kokubo
`4,984,002 A
`6,667,770 B1* 12/2003 Higuchi et al. .............. 348,362
`9.
`6,888,570 B1* 5/2005 Yoshida ...................... 348,296
`7,408,574 B2* 8/2008 Miyazaki - - - - - - - - - -
`... 348,231.1
`2002/00851 12 A1* 7/2002 Hiramatsu et al. .......... 348,362
`2004/0212723 A1 * 10/2004 Lin ............................ 348,362
`
`FOREIGN PATENT DOCUMENTS
`2-185173 A
`7, 1990
`JP
`* cited by examiner
`Primary Examiner—Luong T Nguyen
`(74) Attorney, Agent, or Firm—Birch, Stewart, Kolasch &
`Birch, LLP
`
`(57)
`
`ABSTRACT
`
`There is disclosed a photographic device that uses an image
`sensor and an electronic viewfinder. When a release button is
`pressed halfway, an aperture value, an electronic shutter
`speed and a photosensitivity are decided based on the present
`Subject brightness to provide a proper exposure value for
`photographing a still image. So long as the release button is
`kept being pressed halfway, a timing generator drives the
`image sensor to shoot video images at a frame rate of 20 Hz,
`and the aperture value decided for still image photography is
`fixed, whereas the electronic shutter speed and the photosen
`sitivity are adjusted according to the subject brightness by use
`of an aperture-priority type video program. When the release
`button is pressed to the full, an exposure for a still image is
`done with the fixed aperture value.
`
`2 Claims, 17 Drawing Sheets
`
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`CONTROLLER
`
`33
`
`34
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`t
`
`35
`
`36
`
`37
`
`IMAGE
`PROCESSOR
`
`DATA
`COMPRESSOR
`
`AF
`DETECTOR
`
`AE/AWB
`DETECTOR
`
`
`
`
`
`
`
`
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`to c T
`16
`
`- - - - -
`
`TIMER
`
`41
`
`15a
`RAM RAM 5b
`
`
`
`MEDIA
`CONTROLLER
`38
`40
`
`MEMORY
`CARD
`
`INTERNAL
`39 MEMORY
`
`LCD
`DRIVER
`
`LCD
`
`
`Ex.1011 / Page 1 of 29Ex.1011 / Page 1 of 29
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`U.S. Patent
`
`Jun. 8, 2010
`
`Sheet 1 of 17
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`US 7,733.414 B2
`
`FIG.1
`
`
`
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`U.S. Patent
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`Jun. 8, 2010
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`Sheet 2 of 17
`
`US 7,733.414 B2
`
`(IOT
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`88
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`U.S. Patent
`
`Jun. 8, 2010
`
`Sheet 3 of 17
`
`US 7,733.414 B2
`
`FIG.4
`
`RELATIVE ADDRESS
`00000
`
`
`
`MEMORY AREA M1
`(640x480)
`
`MEMORY AREA M2
`(640x480)
`
`MEMORY AREA M3
`(640x480)
`
`96000
`
`12COOO
`
`1C2000
`
`
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`U.S. Patent
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`Jun. 8, 2010
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`Sheet 4 of 17
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`US 7,733.414 B2
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`:EW DOWN
`
`:EVUP
`
`FIG.5A 12
`
`11
`
`SHUTTER 10
`SPEED
`(TV)
`9
`
`
`
`FIG5B
`
`|
`
`|
`
`|
`
`|
`
`12
`
`13
`
`14
`
`15
`
`16
`
`17
`
`| SUBJECT BRIGHTNESS (EV)
`
`INCREASE IN
`PHOTO-
`SENSITIVITY
`
`(ASV)
`
`l
`
`'
`
`
`
`FIG5C
`(a)
`6(f8)
`APERTURE
`(FNUMBER) 5(f5.6)
`(AV)
`4(f4)
`3 (f2.8)
`
`Y
`Ya
`
`Y
`Ya
`
`I
`
`Y.
`Ya
`
`8
`
`|
`
`|
`
`|
`
`|
`
`|
`
`17
`6
`15
`14
`SUBJECT BRIGHTNESS (EV)
`
`H
`SHUTTERSPEED
`H- 1/50 SEC.
`-
`:SHUTTER SPEED
`1/100 SEC.
`
`
`
`17
`16
`15
`14
`13
`0.6 11 6 SUBJECT BRIGHTNESS (EV)
`
`
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`U.S. Patent
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`Jun. 8, 2010
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`Sheet 5 of 17
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`US 7,733.414 B2
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`FIG.6
`
`
`
`
`
`TVe-EW-AWS
`
`
`
`
`
`
`
`
`
`
`
`TVe-TV min
`
`ASWe TV min-AWS-EW
`
`
`
`TWe-TVmin
`
`ASV-TVmini-AVs-EVmin
`
`
`
`
`
`
`
`TVe-EWmin-AWS
`
`
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`U.S. Patent
`
`Jun. 8, 2010
`
`Sheet 6 of 17
`
`US 7,733.414 B2
`
`f8
`
`f5, 6 f
`
`f2.8
`
`11
`
`17
`16
`15
`14
`13
`12
`SUBJECT BRIGHTNESS (EV)
`
`FIG.7A
`12
`
`11
`
`10
`
`SHUTTER
`SPEED 8
`(TY)
`
`6
`
`PHOTO
`SENSITIVITY
`(ASV)
`
`7.6 8.6 9. 6 10.6
`
`17
`16
`15
`14
`13
`12
`SUBJECT BRIGHTNESS (EV)
`
`
`
`
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`
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`“DIS“ONAS‘TIVOLLYSA
`
`U.S. Patent
`
`Jun. 8, 2010
`
`Sheet 7 of 17
`
`US 7,733,414 B2
`
`TA‘SIS“ONAS
`
`IWOLLYAA
`
`JINONLOITA
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`U.S. Patent
`
`Jun. 8, 2010
`
`Sheet 8 of 17
`
`US 7,733.414 B2
`
`FIG.9A
`
`VERTICAL
`SYNC, SIG. VI
`
`MECHANICAL
`SHUTTER
`
`ELECTRONIC
`SHUTTER PULSE
`
`VERTICAL
`SYNC, SIG. VI
`
`MECHANICAL
`SHUTTER
`
`ELECTRONIC
`SHUTTER PULSE
`
`OPEN YCLOSE
`
`OUTPUT
`STILL IMAGE
`SIGNAL
`
`S2ON
`
`STILL IMAGE
`EXPOSURE
`
`SECOND PREPARATION PROCESS
`
`FIG.9B
`
`Ta
`
`OPEN N CLOSE
`
`;
`
`:
`
`OUTPUT
`STILLIMAGE
`SIGNAL
`
`S2ON
`
`STILLIMAGE
`EXPOSURE
`SECOND PREPARATION PROCESS
`
`
`Ex.1011 / Page 9 of 29Ex.1011 / Page 9 of 29
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`U.S. Patent
`
`Jun. 8, 2010
`
`Sheet 9 of 17
`
`US 7,733.414 B2
`
`FIG.10
`
`SET TO FIRST WIDEO EXPOSURE MODE
`(FRAMERATE e-3OHz)
`
`SETUPAPERTURE WALUE, ELECTRONIC SHUTTERSPEED &
`PHOTOSENSITIVITY BASED ON FIRST WIDEO PROGRAM
`
`AE PROCESS (SETUPELECTRONIC SHUTTERSPEED,
`APAERTURE WALUE &
`PHOTOSENSITIVITY BASED ON STILLIMAGE PROGRAM)
`
`AF PROCESS
`
`
`
`FOCUS LOCK
`
`SET TO APERTURE WALUE
`
`
`
`SET TO SECOND WIDEO EXPOSURE MODE
`(FRAMERATE -2OHz)
`
`SETUPELECTRONIC SHUTTERSPEED & PHOTOSENSITIVITY
`BASED ON SECOND WIDEO PROGRAM
`
`RELEASE SWS2 ON?
`
`SECOND PREPARATION PROCESS
`
`NO
`
`
`
`STILLIMAGE EXPOSURE
`
`OUTPUT STILLIMAGE SIGNAL
`
`
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`U.S. Patent
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`Jun. 8, 2010
`
`Sheet 10 of 17
`
`US 7,733.414 B2
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`FIG.11
`
`SECOND PREPARATION PROCESS
`
`GET TIMER WALUE
`
`BLACK-OUT PROCESS
`
`TIMERVALUEkTa 2 NO
`YES
`SET TO STILLIMAGE EXPOSURE MODE
`& SETUPELECTRONIC SHUTTERSPEED, YES
`APERTURE WALUE &
`MECHANICAL SHUTTER
`
`
`
`
`
`
`
`TRALING EDGE
`OF
`VERTICAL SYNC,
`SIG, WI?
`NO
`
`SETUP PHOTOSENSITIVITY
`
`RETURN
`
`
`Ex.1011 / Page 11 of 29Ex.1011 / Page 11 of 29
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`U.S. Patent
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`Jun. 8, 2010
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`Sheet 11 of 17
`
`US 7,733.414 B2
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`FIG. 12
`
`SECOND PREPARATION PROCESS
`
`BLACK-OUT PROCESS
`
`STOP SYNCHRONIZED OPERATION
`
`SET TO STILLIMAGE EXPOSURE MODE
`SETUPELECRONIC SHUTTERSPEED,
`APERTURE WALUE & MECHANICAL SHUTTER
`
`INITIALIZE SYNCHRONIZED OPERATION
`
`SETUP PHOTOSENSITIVITY
`
`RESTART SYNCHRONIZED OPERATION
`
`RETURN
`
`
`Ex.1011 / Page 12 of 29Ex.1011 / Page 12 of 29
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`U.S. Patent
`
`Jun. 8, 2010
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`Sheet 12 of 17
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`US 7,733.414 B2
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`FIG.13
`
`VERTICAL
`SYNC, SIG. VI
`
`S2ON
`
`STILL IMAGE EXPOSURE
`
`SECOND PREPARATION PROCESS
`
`
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`U.S. Patent
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`Jun. 8, 2010
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`Sheet 13 of 17
`
`US 7,733.414 B2
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`FIG.14
`
`SECOND PREPARATION PROCESS
`
`STOP SYNCHRONIZING OPERATION
`
`BLACK-OUT PROCESS
`
`TOTAL EXPOSURE TIME FOR
`STILLIMAGE PHOTOGRAPHY 2T4?
`YES
`SELECT LONG FRAME PERIOD FOR STILLIMAGE EXPOSURE
`
`NO
`
`
`
`
`
`SELECT SHORT FRAME PERIOD
`FOR STILLIMAGE EXPOSURE
`
`CALCULATE TIMING OF STOPPING INPUTTING
`ELECTRONIC SHUTTER PULSE FOR SELECTED FRAME PERIOD
`
`SET TO STILLIMAGE EXPOSURE MODE &
`SETUPELECTRONIC SHUTTER SPEED, APERTURE VALUE &
`MECHANICAL SHUTTER
`
`SETUP FRAMERATE CORRESPONDING TO
`SELECTED FRAME PERIOD
`
`SETUP FOR INITIALIZING SYNCHRONIZING OPERATION
`
`SETUP PHOTOSENSITIVITY
`
`RESTART SYNCHRONIZING OPERATION
`
`RETURN
`
`
`Ex.1011 / Page 14 of 29Ex.1011 / Page 14 of 29
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`U.S. Patent
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`Jun. 8, 2010
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`Sheet 14 of 17
`
`US 7,733.414 B2
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`FIG.15A
`
`VERTICAL
`
`se's v.
`
`MECHANICAL
`
`VERTICAL
`SYNC, SIG. VI
`
`MECHANICAL
`SHUTTER
`
`ELECTRONIC
`SHUTTER PULSE
`
`SECOND PREPARATION PROCESS
`
`FIG.15B
`
`:
`OPEN \
`
`CLOSE
`
`OUTPUT
`STILL IMAGE
`SIGNAL
`
`S2ONN STILLIMAGE EXPOSURE
`SECOND PREPARATION PROCESS
`
`
`Ex.1011 / Page 15 of 29Ex.1011 / Page 15 of 29
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`U.S. Patent
`
`Jun. 8, 2010
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`Sheet 15 Of 17
`
`US 7,733,414 B2
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`FIG.16
`
`
`
`
`
`
`
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`U.S. Patent
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`Jun. 8, 2010
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`Sheet 16 of 17
`
`US 7,733.414 B2
`
`FIG.17
`SECOND PREPARATION PROCESS
`
`STOP SYNCHRONIZING OPERATION
`
`BLACK-OUT PROCESS
`
`TOTAL EXPOSURE TIME FOR
`STILL IMAGE PHOTOGRAPHY >T4?
`YES
`SELECT LONG FRAME PERIOD FOR STILLIMAGE EXPOSURE
`
`NO
`
`
`
`SELECT SHORT FRAME PERIOD
`FOR STILLIMAGE EXPOSURE
`
`CALCULATE TIMING OF DRIVING MECHANICAL SHUTTER
`FOR SELECTED FRAME PERIOD
`
`SET TO STILLIMAGE EXPOSURE MODE &
`SETUPELECTRONIC SHUTTERSPEED, APERTURE WALUE &
`MECHANICAL SHUTTER
`
`SET UP FRAME RATE CORRESPONDING TO
`SELECTED FRAME PERIOD
`
`SETUPELECTRONIC SHUTTER PULSE TO
`COME ONCE AT THE START OF FRAME PERIOD
`
`SETUP FOR INITIALIZING SYNCHRONIZING OPERATION
`
`SETUP PHOTOSENSITIVITY
`
`RESTART SYNCHRONIZING OPERATION
`
`RETURN
`
`
`Ex.1011 / Page 17 of 29Ex.1011 / Page 17 of 29
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`U.S. Patent
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`Jun. 8, 2010
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`Sheet 17 of 17
`
`US 7,733,414 B2
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`FIG.18A
`
`VERTICAL
`
`se's v.
`
`MECHANICAL
`
`ELECTRONIC
`SHUTTER PULSE |
`
`VERTICAL
`SYNC, SIG. VI
`
`MECHANICAL
`
`OUTPUT
`STILL IMAGE
`SIGNAL
`
`ILLIMAGE EXPOSURE
`
`SECOND PREPARATION PROCESS
`
`FIG. 18B
`
`S2ON
`
`STILL IMAGE EXPOSURE
`SECOND PREPARATION PROCESS
`
`
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`US 7,733,414 B2
`
`1.
`PHOTOGRAPHICDEVICE AND CONTROL
`METHOD THEREFOR
`
`FIELD OF THE INVENTION
`
`The present invention relates to a photographic device like
`a digital camera and a control method for this photographic
`device.
`
`BACKGROUND ARTS
`
`10
`
`15
`
`25
`
`30
`
`35
`
`Digital cameras have been widely used, wherein Subjects
`are photographed through an imaging device Such as a CCD
`image sensor. The digital camera shoots video images, and
`displays a slew of video images on a liquid crystal display that
`serves as an electronic viewfinder. In response to a release
`button being pressed, the digital camera photographs a still
`image and records data of the photographed still image on a
`recording medium like a memory card. There are such digital
`cameras that can record video image data.
`In Such a digital camera, the image sensor is exposed and
`read out generally at a frame rate or shooting frequency of 30
`HZ, i.e. 30 frames per second, in synchronism with the record
`ing and displaying of the video images. Meanwhile, there are
`two kinds of frequencies of commercial power source in
`Japan: 60 Hz and 50 Hz. Being powered with the 60 Hz
`commercial power source, a fluorescent light will blink 120
`times per second. With the 50 Hz, commercial power source,
`the fluorescent light will blink 100 times per second. Under
`these periodically blinking fluorescent lights, especially
`those activated with the 50 Hz, commercial power source,
`so-called flicker occur in photography with the digital cam
`era. The flicker is a phenomenon that brings variations in
`photographic lightness, and is caused where the frame rate of
`the image sensor using the 50 HZ commercial power Source
`does not have any common multiple to the blinking cycle of
`the fluorescent lights.
`To prevent the flicker on shooting video images of low
`brightness subjects which are illuminated with fluorescent
`lights, especially the fluorescent lights activated with the 50
`40
`HZ commercial power source, the conventional digital cam
`era uses a charging time of the image sensor, i.e. a shutter
`speed of an electronic shutter, hereinafter called the elec
`tronic shutter speed, that is set at/So Sec. or /100 sec. whenever
`possible, while anaperture value is adjusted to obtain a proper
`exposure value.
`As described above, unless the release button is pressed
`down, the digital camera shoots video images through the
`image sensor so as to display a slew of images of the shot
`subjects on the LCD. The photographer frames a photo
`graphic field while observing the images on the LCD, and
`presses down the release button to photograph a still image.
`When the release button is pressed halfway, the digital camera
`carries out an automatic exposure (AE) process for deciding
`a aperture value and an electronic shutter speed for photo
`graphing a still image, and an automatic focusing (AF) pro
`cess for focusing a taking lens onto the aimed Subject. After
`the AE and AF processes are completed, the digital camera
`shoots video images again through the image sensor, to dis
`play a slew of images on the LCD. Thus, the LCD serves as an
`electronic viewfinder.
`Upon the release button being fully pressed down, the
`digital still camera makes a freeze process to display a still
`image of the currently shot subject on the LCD, and then
`switches over the aperture value to a value predetermined in
`the AE process. Thereafter the digital camera makes a prepa
`ration operation for setting up a timing generator in order to
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`drive the image sensor at a timing and an electronic shutter
`speed, which are determined for still image photography, as
`well as for setting up the timing generator with an actuation
`timing of a mechanical shutter. After the completion of this
`preparation operation, the image sensor is exposed to photo
`graph a still image.
`In some digital camera, a timing generator for outputting a
`variety of drive signals for driving the image sensor is set up
`to raise frequency of vertical synchronizing signals when the
`release button is fully pressed down, wherein the vertical
`synchronizing signals serve as a reference for the operation
`timing. As being loaded with parameters for deciding driving
`timings of the image sensor and other components, the timing
`generator makes the loaded parameters effective when the
`Vertical synchronizing signal is generated first after the load
`ing, and drives the image sensor and other components on the
`basis of these parameters from a frame period after the
`completion of setting. Therefore, raising the frequency of the
`Vertical synchronizing signals reduces the delay from the
`completion of setting with respect to the still image photog
`raphy through the image sensor.
`As described above, since the conventional digital cameras
`starts many processing upon the release button being pressed
`to the full, there is a certain time lag to the actual start of
`exposure. As a known technique for minimizing the release
`time lag, Japanese Laid-open Patent Application No. Hei
`2-185173 Suggests controlling driving the image sensor by a
`timing generatorso as to start charging of the image sensor for
`photographing a frame of still image in Synchronism with an
`external trigger signal, although the charging conventionally
`starts after several electronic shutter pulses are given at the
`start of exposure for the still image photography.
`One of factors that enlarge the release time lag is an opera
`tion to change the aperture value at the moment when the
`release button is fully pressed down. However, in order to
`shoot video images at Such an aperture value that is adapted to
`the still image photography prior to the full press of the
`release button, the shutter speed must be changed in accor
`dance with varying Subject brightness. So it becomes impos
`sible to keep the electronic shutter speed at a value preventive
`against the flicker.
`In addition to that, although the method disclosed in the
`above prior art is effective for reducing the release time lag,
`this prior method needs a specific timing generator, and can
`not be embodied with a general timing generator.
`Since the conventional digital camera validates content set
`in the timing generator in Synchronism with the vertical Syn
`chronizing signal, there is a delay from the shutter release to
`the actual start of an exposure for photographing a still image.
`As described above, the delay, a factor for the release time lag,
`can be reduced by raising the frequency of the vertical Syn
`chronizing signal. But because there is a limit in the available
`range of frequency of the vertical synchronizing signal, this
`method cannot sufficiently reduce the delay and the release
`time lag.
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`SUMMARY OF THE INVENTION
`
`In view of the foregoing, a primary object of the present
`invention is to provide a photographic device and a control
`method therefore, which reduce the release time lag effec
`tively without the need for a specific timing generator.
`To achieve the above and other objects, the present inven
`tion provides a photographic device that comprises a release
`button movable to a half-pressed position and a full-pressed
`position; an image sensor having a function of an electronic
`shutter and converting an optical image of a subject to a still
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`image signal, the image sensor shooting video images while
`the release button is not pressed or is kept in the half-pressed
`position, and photographing a still image when the release
`button is moved to the full-pressed position; a display device
`for displaying images on the basis of still image signals output
`from the image sensor, an exposure control device that sets an
`electronic shutter speed of the image sensor, an aperture value
`and a photosensitivity according to Subject brightness based
`on a first program while the release button is not pressed, the
`first program setting the electronic shutter speed to be a value
`preventive against flicker in a low brightness range, the expo
`Sure control device deciding an aperture value for still image
`photography upon the release button being pressed halfway,
`and so long as the release button is kept in the half-pressed
`position, the exposure control device using an aperture-pri
`ority type second program for setting an electronic shutter
`speed and a photosensitivity according to Subject brightness
`while applying the aperture value for still image photography
`to the second program; and a frame rate setting device that
`sets a first frame rate as a frame rate of the image sensor while
`the release button is not pressed, and sets a second frame rate
`as the photographic frame so long as the release button is kept
`in the half-pressed position, the second frame rate being
`adapted to prevent flicker.
`According to a preferred embodiment, the photographic
`device further comprises a timing generator that drives the
`image sensor based on parameters set therein, and generates
`a vertical synchronizing signal that is synchronized with a
`driving cycle of the image sensor, and a timing control device
`that controls timing of setting parameters for still image pho
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`tography in the timing generator, depending upon when the
`release button is pressed to the full relative to the vertical
`synchronizing signal. Such that the parameters for still image
`photography are set in the timing generator either at a time
`immediately after the release button is pressed to the full, or at
`a time when the vertical synchronizing signal is generated
`first after the release button is pressed to the full.
`According to another present invention, a photographic
`device comprises an image sensor driven either in a video
`exposure mode or in a still image exposure mode, the image
`sensor being switched over from the video exposure mode to
`the still image exposure mode to photograph a still image in
`response to a release signal that is entered through an external
`operation; a timing generator generating a vertical synchro
`nizing signal that is synchronized with a driving cycle of the
`image sensor, and Switching the image sensor to a selected
`one of the exposure modes by validating parameters as set
`therein according to the selected exposure mode, at a time
`when the vertical synchronizing signal is generated first after
`the parameters are completely set in the timing generator; and
`a control device that sets parameters for the still image expo
`Sure mode in the timing generator and initializes synchroniz
`ing operation of the timing generator to restart the synchro
`nizing operation immediately after the entry of the release
`signal, thereby to cause the timing generator to generate the
`Vertical synchronizing signal immediately after the setting of
`the parameters for still image photography.
`According to the present invention, a control method for a
`photographic device that shoots video images through an
`image sensor and displays the shot video images while a
`release button is not pressed or is kept in a half-pressed
`position, and photographs a still image through the image
`sensor upon the release button being pressed fully, the control
`method comprising steps of
`using a first program for setting an electronic shutter speed
`of the image sensor, an aperture value and a photosensitivity
`in accordance with subject brightness while the release button
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`is not pressed, the first program setting the electronic shutter
`speed to a value preventive against flicker in a low brightness
`range.
`deciding an aperture value for still image photography
`upon the release button being pressed halfway; and
`using while the release button is kept in the half-pressed
`position, an aperture-priority type second program for setting
`an electronic shutter speed and a photosensitivity according
`to Subject brightness while applying the aperture value for
`still image photography to the second program and using a
`frame rate adapted to prevent flicker.
`According to another control method of the present inven
`tion, for a photographic device that is provided with a timing
`generator for driving an image sensor, the timing generator
`generating vertical synchronizing signals in Synchronism
`with driving cycle of the image sensor, and validating param
`eters set therein synchronously with the vertical synchroniz
`ing signal being generated after the parameters is completely
`set in the timing generator, the photographic device Switching
`the image sensor from a video exposure mode to a still image
`exposure mode to photograph a still image in response to a
`release signal entered through an external operation, the con
`trol method comprising steps of:
`setting up the timing generator with parameters for driving
`the image sensor in the still image exposure mode immedi
`ately after the entry of the release signal; and immediately
`thereafter
`initializing synchronizing operation of the timing genera
`tor to restart the synchronizing operation, thereby to generate
`the vertical synchronizing signal to drive the image sensor in
`the still image exposure mode.
`The present invention also provides a control method for a
`photographic device using an image sensor having a function
`of an electronic shutter wherein electronic shutter pulses are
`input in the image sensor from the start of each frame period,
`and effective charging in the image sensor starts from when
`the electronic shutter pulses stop being input, the control
`method comprising steps of
`determining an exposure time for still image photography
`according to a subject brightness;
`selecting from among different frame periods the shortest
`one of those frame periods which permit charging during the
`exposure time;
`deciding timing of stopping inputting the electronic shutter
`pulses so as to provide the exposure time; and photographing
`a still image in the selected frame period and the decided
`timing in response to a release signal.
`The present invention further provides a control method for
`a photographic device using an image sensor and a mechani
`cal shutter, the image sensor having a function of an elec
`tronic shutter that gives effect to charging from when elec
`tronic shutter pulses stop being input in the image sensor, the
`control method comprising steps of:
`inputting only a single electronic shutter pulse in the image
`sensor at the start of a frame period for still image photogra
`phy; and
`activating the mechanical shutter to block photographic
`light from the image sensor when an exposure time deter
`mined according to a subject brightness has elapsed since the
`single electronic shutter pulse.
`Since the frame rate preventive against the flicker is used
`for shooting video images while the release button is pressed
`halfway, the flicker will not occur even if the shutter speed is
`changed during this condition. Since the aperture value is
`determined for still image photography up on the release
`button being pressed halfway, and is fixed at this value so long
`as the release button is kept being pressed, it is unnecessary to
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`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
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`5
`change the aperture value in response to the release button
`being pressed to the full. Therefore the release time lag is
`reduced.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`5
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`The above and other objects and advantages of the present
`invention will be more apparent from the following detailed
`description of the preferred embodiments when read in con
`nection with the accompanied drawings, wherein like refer
`ence numerals designate like or corresponding parts through
`out the several views, and wherein:
`FIG. 1 is a schematic front view of a digital camera
`embodying the present invention;
`FIG. 2 is a schematic rear view of the digital camera of FIG.
`1;
`FIG. 3 is a block diagram illustrating an internal structure
`of the digital camera;
`FIG. 4 is an explanatory diagram illustrating an internal
`memory that is virtually divided into a number of memory
`areas in first and second video exposure modes;
`FIGS.5A, 5B and 5C show program diagrams constituting
`a first video program used in the first video exposure mode;
`FIG. 6 is a flowchart illustrating a sequence of deciding
`electronic shutter speed and photosensitivity in the second
`Video exposure mode;
`FIGS. 7A and 7B show program diagrams constituting a
`second video program used in the second video exposure
`mode;
`FIG. 8A shows timing charts in the first video exposure
`mode;
`FIG. 8B shows timing charts in the second video exposure
`move;
`FIGS. 9A and 9B show timing charts illustrating two kinds
`ofoperations done when a release button is pressed to the full;
`FIG. 10 is a flowchart illustrating a sequence of still image
`photography;
`FIG. 11 is a flowchart illustrating a sequence of a second
`preparation process executed in response to the full-pressing
`of the release button;
`FIG. 12 is a flowchart illustrating a sequence of the second
`preparation process according to a second embodiment,
`wherein a still image exposure is done immediately after
`parameters for still image photography are set up;
`FIG. 13 shows timing charts illustrating an operation done
`when a release button is pressed to the full in the second
`embodiment;
`FIG. 14 is a flowchart illustrating a sequence of the second
`preparation process, according to a third embodiment
`wherein a short frame period or a long frame period is
`selected for a still image exposure;
`FIGS. 15A and 15B show timing charts illustrating two
`kinds of operations done when a release button is pressed to
`the full in the third embodiment;
`FIG. 16 is an explanatory diagram illustrating another
`embodiment where there are four kinds of frame periods
`available for a still image exposure;
`FIG. 17 is a flowchart illustrating a sequence of the second
`preparation process, according to a further embodiment that
`controls driving timing of a mechanical shutter for a still
`image exposure; and
`FIGS. 18A and 18B show timing charts illustrating two
`kinds of operations done when a release button is pressed to
`the full in the embodiment of FIG. 17.
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`As shown in FIGS. 1 and 2, a digital camera has a photo
`graphic lens 3 with Zooming function, a release button 4 and
`a flash window 5 on a front side of its camera body 2, and a
`console 7 consisting of control buttons 7a and a cursor key 7a,
`and an LCD 9 on a rear side of the camera body 2.
`The release button 4 can be pressed down in two steps:
`halfway and full. So long as the release button 4 is not pressed
`in a camera mode, still image signals of Subjects are continu
`ally picked up through a CCD image sensor 10 that is located
`behind the photographic lens 3, as shown in FIG. 3, and the
`LCD 9 displays a slew of video images based on the still
`image signals currently picked up through the CCD image
`sensor 10. So the LCD9 functions as an electronic viewfinder.
`Upon the release button 4 being pressed halfway, a first
`preparation process is carried out. The first preparation pro
`cess consists of an AE (automatic exposure) process for
`deciding a shutter speed, an aperture value and a photosensi
`tivity, which are Suitable for photographing a still image, an
`AF (automatic focusing) process for focusing the photo
`graphic lens 3 onto a Subject, an aperture Switching process
`for Switching to the decided aperture value, and a process for
`changing exposure mode of the CCD image sensor 10, as set
`forth in detail later. While the release button 4 is being kept in
`the halfway position, the digital camera shoots video images
`and displays them on the LCD9 like before the release button
`4 being pressed.
`When the release button 4 is pressed to the full, a second
`preparation process is carried out, before the CCD image
`sensor 10 executes a still image exposure, i.e. an exposure for
`photographing a still image. The second preparation process
`consists of a setting process for setting up the shutter speed
`and the photosensitivity as decided for still image photogra
`phy in the first preparation process, a process for changing the
`CCD image sensor 10 to an exposure mode for still image
`photography, and other minor processes. The photographed
`still image is converted into a frame of digital image data, and
`stored in a removable memory card 11, see FIG. 3.
`The flash window 5 projects a flash of light toward a main
`Subject if the main subject has a lower brightness than a
`predetermined level at the still image photography. The con
`sole 7 is operable to turn the power on or off, choose between
`the camera mode and a player mode and, in the camera mode,
`choose between the still image photography mode and a
`Video shooting mode. The console 7 is also used for Zooming
`up or down the photographic lens 3, selecting desirable image
`frames in the player mode, and so on. The LCD9 serves not
`only as the electronic viewfinder that displays a slew of video
`images of the Subjects, but also displays photographed
`images, i.e. recorded images, in the player mode.
`Referring to FIG. 3 illustrating an internal structure of the
`digital camera, the console 7 sends control signals to a CPU
`15 in accordance with operations on the control buttons 7a
`and the cursor key 7b. A switching section 16 consists of first
`and second release switches S1 and S1 that are turned on or
`offin cooperation with the release button 4being pressed. The
`first release switch S1 is turned ON as the release button 4 is
`pressed halfway, whereas the second release switch S2 is
`turned ON as the release button 4 is pressed to the full. The
`switching conditions of the release switches S1 and S2 are
`sent to the CPU 15. That the second release Switch S2 is
`turned ON is regarded as a release signal for starting the still
`image photography.
`The CPU 15 controls respective parts of the digital camera
`on the basis of various signals from the console 7 and the
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`Ex.1011 / Page