(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2004/0239771 A1
`(43) Pub. Date:
`Dec. 2, 2004
`Habe
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`US 2004O239771A1
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`DIGITAL STILL CAMERA
`
`Publication Classification
`
`(54)
`(75)
`
`(73)
`
`Inventor: Masaru Habe, Chiyoda-ku (JP)
`Correspondence Address:
`OLIFF & BERRIDGE, PLC
`P.O. BOX 19928
`ALEXANDRIA, VA 22320 (US)
`Assignee: NIKON CORPORATION, Chiyoda-ku
`(JP)
`Appl. No.:
`
`10/855,480
`May 28, 2004
`Foreign Application Priority Data
`
`(51) Int. Cl." ........................... G03B 17/00; H04N 5/235
`(52) U.S. Cl. .................... 348/208.12; 348/229.1; 396/54
`
`(57)
`
`ABSTRACT
`
`Prior to a photographing operation, an image blur quantity
`indicating the extent to which the image becomes blurred
`during the photographing operation is calculated based upon
`an image-capturing Sensitivity having been Set, and a deci
`Sion is made as to whether or not the image-capturing
`Sensitivity needs to be adjusted based upon the calculated
`image blur quantity. If it is decided that the Sensitivity level
`needs to be adjusted, the image-capturing Sensitivity is
`adjusted and the photographing operation is executed at the
`Shutter Speed calculated based upon the adjusted image
`capturing Sensitivity.
`
`Filed:
`
`(21)
`(22)
`(30)
`Jun. 2, 2003
`
`(JP)...................................... 2003-15681.1
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`2A
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`2
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`1
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`PHOTOMETERING
`ELEMENT
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`PHOTOMETERING
`CIRCUIT
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`WIBRATION
`SENSOR
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`3
`WBRATION
`DETECTION CRCUT
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`3A
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`4
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`FOCAL LENGTH
`DETECTION CIRCUIT
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`CPU
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`SHUTTER RELEASE
`SWITCH
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`BLUR PREVENTING MODE
`SWITCH
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`EXPOSURE CONTROL
`CIRCUIT
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`5
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`MAGE CAPTURNG
`ELEMENT
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`6
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`SIGNAL PROCESSING
`CRCUIT
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`7
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`RECORDING
`CIRCUIT
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`8
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`Patent Application Publication Dec. 2, 2004 Sheet 1 of 4
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`US 2004/0239771 A1
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`Patent Application Publication Dec. 2, 2004 Sheet 2 of 4
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`US 2004/0239771 A1
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`FIG.2
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`EXECUTE
`PHOTOMETERING|s
`OPERATION
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`CALCULATE APERTURE
`WALUE AND SHUTTER
`SPEED
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`S2
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`S3 (
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`BLUR
`PREVENTING
`MODE ON?
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`N
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`INPUT CAMERA
`WIBRATION QUANITY
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`INPUT FOCAL LENGTH
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`CALCULATE MAGE
`BLUR QUANTITY
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`Y
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`MAGE BLUR
`QUANTITY > LIMIT
`WALUE
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`EXECUTE
`EXPOSURE
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`S11
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`CALCULATE ISO
`s SENSYTY SHIFT
`QUANTITY
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`s s
`S9 SENS
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`T SO
`TY LEVEL
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`S10
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`RECALCULATE
`SHUTTER SPEED
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`Patent Application Publication Dec. 2, 2004 Sheet 3 of 4
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`US 2004/0239771 A1
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`FG.3
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`Patent Application Publication
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`Dec. 2, 2004 Sheet 4 of 4
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`US 2004/0239771 A1
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`Dec. 2, 2004
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`DIGITAL STILL CAMERA
`0001. The disclosure of the following priority application
`is herein incorporated by reference: Japanese Patent Appli
`cation No. 2003-156811 filed Jun. 2, 2003
`
`BACKGROUND OF INVENTION
`0002) 1. Field of the Invention
`0003. The present invention relates to a digital still cam
`era, and more Specifically, it relates to a technology for
`reducing the extent to which an image becomes blurred.
`0004 2. Description of the Related Art
`0005. An image blur caused by an unsteady hand move
`ment or the like during a photographing operation greatly
`detracts from the appearance of the resulting picture and
`thus greatly lowers the value of the photograph. The extent
`of Such an image blur increases as the shutter Speed
`decreases. Generally, a significant extent of image blur is
`Said to manifest in a photograph taken by holding a 35 mm
`camera mounted with a photographic lens with a focal
`length offmm, if the shutter speed becomes lower than 1/f
`Sec. Accordingly, various attempts have been made in the
`related art to reduce the extent of image blur.
`0006 Japanese Laid Open Patent Publication No. H
`11-215432 discloses a digital Still camera designed to reduce
`the image blur without having to detect any camera vibra
`tion. By taking advantage of a digital Still camera feature
`which allows the ISO speed to be adjusted for each frame,
`the ISO speed level is raised if the calculated shutter speed
`is lower than a hand movement limit value So as to Sustain
`a high shutter speed in this digital still camera. While the
`Shutter Speed can be Sustained at a high level by raising the
`ISO Speed, this method has a problem in that the image
`quality becomes poor due to noise.
`
`SUMMARY OF THE INVENTION
`0007. A digital still camera according to the present
`invention comprises: a Sensitivity Setting device that Sets an
`image-capturing Sensitivity; a photographing device having
`an image-capturing element that receives a light flux trans
`mitted through a photographic lens and executeS photoelec
`tric conversion on the received light flux, a control device
`that engages the photographing device in operation at a
`Shutter Speed corresponding to the image-capturing Sensi
`tivity Set by the Sensitivity Setting device, an image blur
`calculation device that calculates an image blur quantity
`indicating an extent to which an image becomes blurred
`during a photographing operation based upon the image
`capturing Sensitivity having been Set prior to the photo
`graphing operation; and a determination device that makes
`a decision as to whether the image-capturing Sensitivity
`needs to be adjusted based upon the image blur quantity
`calculated by the image blur calculation device, wherein: the
`Sensitivity Setting device adjusts the image-capturing Sensi
`tivity if the determination device determines that the image
`capturing Sensitivity needs to be adjusted; and if the image
`capturing Sensitivity is adjusted, the control device engages
`the photographing device in operation at a shutter Speed
`corresponding to the adjusted image-capturing Sensitivity.
`0008. It is preferable if the calculated image blur quantity
`exceeds a predetermined limit value, the Sensitivity Setting
`
`device shifts the image-capturing Sensitivity to a higher level
`So as to lower the image blur quantity to a value equal to or
`less than the limit value.
`0009. It is preferable that the image blur calculation
`device includes a vibration detection Sensor that detects an
`extent of vibration to which the digital camera is Subjected,
`and calculates the image blur quantity indicating the extent
`to which the image becomes blurred during the photograph
`ing operation based upon detection results provided by the
`Vibration detection Sensor and the Shutter Speed determined
`in conformance to photometering results obtained by pho
`tometering a photographic field and the image-capturing
`Sensitivity having been Set. An optical image blur correction
`mechanism that reduces the extent of image blur based upon
`an output from the vibration detection Sensor may be further
`comprised and it is preferable that the determination device
`determines that the image-capturing Sensitivity needs to be
`adjusted if the image blur quantity cannot be lowered to a
`value equal to or less than a predetermined limit value
`through an image blur correction alone executed by the
`optical image blur correction mechanism.
`0010. The sensitivity setting device may set the image
`capturing Sensitivity to a lowest possible Sensitivity level
`within a range over which the calculated image blur quantity
`does not exceed a predetermined limit value.
`0011. An image blur correction apparatus according to
`the present invention comprises: a Sensitivity Setting device
`that Sets an image-capturing Sensitivity, an image capturing
`command output device that outputs a signal for engaging an
`image-capturing element in photoelectric conversion at a
`Shutter Speed corresponding to the image-capturing Sensi
`tivity Set by the Sensitivity Setting device, an image blur
`calculation device that calculates an image blur quantity
`indicating an extent to which an image becomes blurred
`during a photographing operation based upon the image
`capturing Sensitivity having been Set, prior to the photo
`graphing operation; and a determination device that makes
`a decision as to whether the image-capturing Sensitivity
`needs to be adjusted based upon the image blur quantity
`calculated by the image blur calculation device, wherein: the
`Sensitivity Setting device adjusts the image-capturing Sensi
`tivity if the determination device determines that the image
`capturing Sensitivity needs to be adjusted; and when the
`image-capturing Sensitivity is adjusted, the image capturing
`command output device outputs the Signal to the image
`capturing element to engage the image-capturing element in
`photoelectric conversion at the Shutter Speed corresponding
`to the adjusted image-capturing Sensitivity. It is preferable to
`further comprise a blur preventing mode Switch operated to
`Set/clear a blur preventing mode in which control is imple
`mented to reduce the extent of image blur by adjusting the
`image-capturing Sensitivity.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0012 FIG. 1 is a block diagram of a control system of a
`digital Still camera achieved in an embodiment of the present
`invention;
`0013 FIG.2 presents a flowchart of control implemented
`during image blur correction processing in the camera
`achieved in the embodiment;
`0014 FIG. 3 presents an external view of the digital still
`camera achieved in the embodiment; and
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`US 2004/0239771 A1
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`Dec. 2, 2004
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`FIG. 4 is a block diagram of a control system of a
`0.015
`digital Still camera achieved as a variation of the embodi
`ment of the present invention.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`0016. The following is an explanation of an embodiment
`of the present invention, given in reference to drawings.
`0017 FIG. 1 is a block diagram of a control system of a
`digital still camera 10 achieved in the embodiment. FIG. 3
`is a schematic external view of the digital still camera 10
`having the control system shown in FIG. 1.
`0.018. A photometering circuit 2, a vibration detection
`circuit 3, a focal length detection circuit 4, an exposure
`control circuit 5, an image-capturing element 6 and a signal
`processing circuit 7 are connected to a CPU 1. The pho
`tometering circuit 2 detects the brightness level of a Subject
`by using a photometering Sensor 2A and inputs the detected
`brightness level to the CPU 1. The vibration detection circuit
`3 detects the extent of vibration to which the camera is
`Subjected by using a vibration Sensor 3A constituted of an
`angular Speed Sensor or the like and inputs the detected
`vibration quantity to the CPU 1. The focal length detection
`circuit 4 detects the focal length of a photographic lens 20
`and inputs the detected focal length to the CPU 1.
`0019. The exposure control circuit 5 executes a photo
`graphing operation (exposure) by driving a shutter and an
`aperture (not shown). The image-capturing element 6
`receives a light flux transmitted through the photographic
`lens 20, generates image capturing Signals from the light flux
`thus received and provides the image capturing Signals to the
`Signal processing circuit 7. The Signal processing circuit 7
`generates image data by executing various types of proceSS
`ing on the image capturing Signals and provides the image
`data to a recording circuit 8. The recording circuit 8 records
`the image data into a recording medium Such as a memory
`card. The exposure control circuit 5, the image-capturing
`element 6, the Signal processing circuit 7 and the like
`constitute a photographing device.
`0020. In addition, a shutter release switch SW1, which is
`turned on in response to an operation of a shutter release
`button 30, and a blur preventing mode switch SW2 operated
`to set/clear a blur preventing mode are connected to the CPU
`1.
`0021. Under normal circumstances, the CPU 1 sets the
`ISO Speed in conformance to a photographer operation and
`calculates an exposure value (an aperture value and a shutter
`speed) based upon the ISO speed that has been set and the
`photometering output from the photometering circuit 2.
`However, if the blur preventing mode has been set, it
`calculates the exposure value by automatically adjusting the
`ISO Speed Setting as appropriate for the circumstances as
`detailed later.
`0022. The “ISO speed” was originally a term used in
`international standards to refer to the sensitivity of silver
`halide film to light. The term “ISO speed” used in reference
`to digital still cameras is actually the Sensitivity (image
`capturing Sensitivity) of the image-capturing element 6
`converted to an ISO speed. However, the term “ISO speed”
`is often used in a general way to refer to the image-capturing
`Sensitivity of a digital camera and the term is also used in
`
`this general Sense in this specification. It is to be noted that
`the term "image-capturing Sensitivity” refers to a control
`target quantity to be achieved by adjusting one of the
`Sensitivity level with which the Signal charges at the output
`unit of the image-capturing element 6 are detected, the
`amplification gain of a variable gain amplifying circuit (not
`shown) that amplifies the output from the image-capturing
`element 6 and the exposure quantity which is varied by
`altering the duty of the operational timing of the image
`capturing element 6.
`0023. In the camera 10 adopting the structure described
`above, the CPU 1 sets the blur preventing mode as the blur
`preventing mode Switch SW2 is turned on. In the blur
`preventing mode, the vibration detection circuit 3 is engaged
`prior to a photographing operation So as to detect a camera
`Vibration quantity indicating the extent of Vibration to which
`the camera is Subjected due to an unsteady hand movement
`or the like and to calculate an image blur quantity based
`upon the vibration quantity. The image blur quantity repre
`Sents the extent to which the Subject image vibrates and
`becomes blurred at an image forming plane, i.e., at a light
`receiving Surface of the image-capturing element 6, during
`the exposure. Other parameterS Such as the Shutter Speed and
`the focal length of the photographic lens 20 are needed in
`addition to the camera Vibration quantity to calculate the
`image blur quantity. The Shutter Speed to be used as a
`parameter can be calculated based upon the photometering
`results and the ISO Speed Setting.
`0024.
`It is to be noted that in a camera having a mechani
`cal shutter used to control the length of time over which the
`light flux enters the image-capturing element 6, the length of
`time over which the shutter remains open is equivalent to the
`Shutter Speed. In a camera having an electronic shutter used
`to control the length of time over which charges are Stored
`at the image-capturing element 6, the length of time over
`which the electrical charges are Stored at the image-captur
`ing element 6 is equivalent to the shutter Speed.
`0025 If the image blur quantity having been calculated
`exceeds a predetermined blur limit value, the extent of the
`image blur is judged to be significant and accordingly, the
`ISO speed is automatically shifted toward the higher sensi
`tivity side. The extent to which the ISO speed is shifted (the
`number of stages over which the ISO speed is shifted) can
`be calculated as,
`(1)
`n=log (image blur quantity/blur limit value)
`0026. By raising the sensitivity by n stages, the shutter
`Speed can be shifted toward the higher side by n Stages
`without further opening the aperture, i.e., without affecting
`the field depth. It is to be noted that if n is calculated to be
`a decimal value, n should be rounded up to the higher integer
`to be on the Safe Side. For instance, if the calculated value
`of n is a numerical value between 1 and 2, it should be
`rounded up to 2. By adopting this method, it becomes
`possible to ensure that the image blur quantity never exceeds
`the limit value and thus to ensure that the image blur does
`not become conspicuous in the image.
`0027. It is to be noted that the blur limit value set with
`regard to the image blur quantity is a threshold value used
`to judge as to whether or not the extent of an image blur
`occurring in an image is within an allowable range.
`0028. In more specific terms, let us consider a situation in
`which the ISO speed setting is ISO 100 in a camera that
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`Dec. 2, 2004
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`allows the ISO speed to be set to ISO 100, ISO 200, ISO
`400, ISO 800 or ISO 1600 and the image blur quantity
`having been calculated is 60 lum. It is generally accepted that
`as long as the image blur quantity of a given image blur at
`the image forming plane does not exceed 30 um, the blur
`does not manifest a discernible image blur in a regular
`photographic image. Since the calculated image blur quan
`tity is 60 lum, a rather conspicuous image blur will manifest
`in the photographic image. Accordingly, the shift quantity in
`is calculated by Substituting 30 um for the blur limit value
`in expression (1);
`n=log (60/30)=1
`0029 Namely, by raising the ISO speed by one stage, i.e.,
`from ISO 100 to ISO 200, the shutter speed can be shifted
`to the higher Sidebyone state (e.g., 1/60 sec->1/125 Sec). Asa
`result, the image blur quantity can be reduced from 60 um
`to 30 lim. Likewise, if n=2, the image blur quantity can be
`reduced to 30 um by shifting the ISO speed by two stages
`from ISO 100 to ISO 400, and if n=5, the image blur quantity
`can be reduced to 30 um by shifting the ISO speed by five
`stages from ISO 100 to ISO 1600.
`0.030. When the calculated shutter speed is low, the
`Shutter Speed can be raised by increasing the ISO Speed, but,
`at the Same time, the image quantity is bound to become
`poorer due to noise. Most experienced photographers are
`likely to know how to hold and operate cameras by mini
`mizing an unsteady hand movement which results in an
`image blur and are thus likely to be capable of photograph
`ing pictures without blurring the images even when the
`Shutter Speed is fairly low. For this reason, experienced
`photographers will not often want the Sensitivity to be raised
`Simply because the Shutter Speed is low, Since it will only
`lower the image quality unnecessarily. However, if the
`shutter speed threshold value at which the sensitivity is
`raised is Set to a lower value, inexperienced photographers
`will end up with blurred images.
`0031. In the embodiment, instead of raising the ISO
`Speed based upon the Shutter Speed, the image blur quantity
`representing the extent to which the image becomes blurred
`during the exposure is estimated through an arithmetic
`operation and the ISO Speed is raised based upon this image
`blur quantity. As a result, the extent of image blur can be
`effectively reduced by increasing the Sensitivity for an
`inexperienced photographer who is not likely to be able to
`handle his camera with a steady hand. At the same time, if
`an experienced photographer is handling the camera with a
`Steady hand, the Sensitivity is not raised unnecessarily and
`thus, the image quality is Sustained at a desired level. In
`addition, the extent of image blur can be effectively reduced
`by increasing the Sensitivity even for an experienced pho
`tographer when, for instance, he is forced to photograph
`pictures in a Situation in which Some unsteady movement is
`unavoidable.
`0.032 The extent of image blur may be reduced by
`detecting vibration of the camera caused by a hand move
`ment and photographing a picture with the timing with
`which the image blur is minimized, or by emitting light with
`a flash unit to reduce the extent of the image blur if the
`photographer is forced to take a picture in a fairly Shaky
`State. When photographing a picture with the timing that will
`minimize image blur, the Shutter release timing is not
`constant, and thus, the photographer may miss a good photo
`
`opportunity. When the extent of the image blur is reduced by
`using a flash unit, the image blur in an image which the
`photographer wishes to photograph without using the flash
`unit cannot be reduced.
`0033. By adopting the embodiment, it is ensured that the
`photographer does not miss a good photo opportunity Since
`the shutter release timing does not change in correspondence
`to the degree of vibration and also, the photographer is
`allowed to take blur-free pictures without having to emit
`light with the flash unit. Furthermore, as the camera does not
`need to be equipped with any expensive device Such as an
`optical image blur correction mechanism, the increase in the
`production cost can be minimized.
`0034 FIG. 2 presents a flowchart of the processing
`executed by the CPU 1 in conformance with the blur
`preventing control program described above.
`0035) The CPU 1 starts up this program as the shutter
`release Switch SW1 is turned on, and it engages the pho
`tometering circuit 2 in a photometering operation in Step S1.
`In step S2, the CPU 1 calculates the aperture value and the
`Shutter Speed based upon the photometering results and the
`ISO speed setting.
`0036). In step S3, a decision is made as to whether or not
`the blur preventing mode is currently Set based upon a signal
`provided by the blur preventing mode switch SW2. If it is
`determined that the blur preventing mode is currently Set, the
`operation proceeds to step S4 to engage the vibration
`detection circuit 3 in operation and to read the detection
`output indicating the camera vibration quantity from the
`vibration detection circuit 3. In addition, the focal length of
`the photographic lens 20 detected and output by the focal
`length detection circuit 4 is read in step S5. In step S6, the
`image blur quantity indicating the extent of image blur that
`occurs during the exposure is calculated based upon the
`camera vibration quantity and the focal length respectively
`detected in steps S4 and S5.
`0037. The operation then proceeds to step S7 to compare
`the image blur quantity calculated in step S6 with the blur
`limit value (e.g., 30 um). If the image blur quantity exceeds
`the blur limit value, the operation proceeds to step S8 to
`calculate the number of stages n over which the ISO speed
`is to be shifted by using expression (1) presented earlier. In
`the following step S9, the ISO speed is shifted toward the
`higher side by n stages calculated in step S8. In step S10, a
`new shutter Speed is calculated based upon the photometer
`ing results obtained in step S1 and the ISO speed adjusted in
`step S9. By shifting the ISO speed, the shutter speed can be
`shifted toward the higher Side by n Stages.
`0038. It is to be noted that if the ISO speed is already set
`at the highest limit, the Sensitivity cannot be increased any
`further and accordingly, an image blur warning should be
`issued.
`0039. In step S11, the exposure control circuit 5 is
`engaged to execute exposure by driving the aperture and the
`Shutter based upon the aperture value calculated in Step S2
`and the most recently calculated Shutter Speed. It is to be
`noted that image Signals obtained through the exposure are
`processed and the like through another routine.
`0040) If, on the other hand, it is determined in step S7 that
`the image blur quantity is equal to or lower than the blur
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`limit value, the shutter Speed does not need to be raised, i.e.,
`it is not necessary to increase the ISO Speed. Accordingly,
`the operation simply proceeds to Step S11. In addition, if the
`blur preventing mode is not set currently, the operation
`proceeds directly to step S11 from step S3. In these situa
`tions, the photographing operation is executed at the initial
`ISO Speed Setting and the aperture value and the Shutter
`Speed calculated in Step S2.
`0041. It is to be noted that certain restrictions may be
`imposed with regard to the adjustment of the ISO speed
`Setting. For instance, even when the highest ISO Speed level
`in the camera is ISO 3200, ISO 800 may be set as the upper
`limit to which the sensitivity can be shifted upward in
`correspondence to the image blur quantity So as to prevent
`the image quality from becoming markedly poorer. In addi
`tion in a mode in which the shutter speed is set by the
`photographer, e.g., a shutter Speed priority mode or a manual
`mode, any increase in the Sensitivity that will result in a
`change in the Shutter Speed may be disallowed to give
`precedence to the photographer's intent.
`0042. While the sensitivity is raised when the calculated
`image blur quantity exceeds the blur limit value in the
`explanation given above, the ISO Speed may instead be
`shifted toward the lower Side to improve the image quality
`when the calculated image blur quantity is Small. For
`instance, if the current initial ISO speed setting is ISO 400
`and the calculated image blur quantity is 10 tim, the ISO
`Speed Setting may be adjusted to ISO 200. By lowering the
`ISO Speed by one Stage in this manner, the shutter Speed is
`also lowered by one stage to result in an increase in the
`image blur quantity to 20 lim. However, Since 20 um is still
`less than the blur limit value 30 um explained earlier, it is not
`likely to manifest as a discernible image blur. If, on the hand,
`the ISO speed is lowered to ISO 100, the image blur quantity
`will increase to 40 tim, well over the blur limit value.
`Accordingly, the ISO speed is not lowered any further than
`ISO 200 in such a situation. By adjusting the ISO speed to
`the lowest level at which the calculated image blur quantity
`does not exceed the blur limit value, the image quality can
`be improved while, at the same time, preventing a discern
`ible image blur.
`0043. The image blur limit value does not need to be set
`to 30 lim. In addition, while an explanation is given above
`on an example in which the ISO Speed is adjusted in an
`increment of a single Stage, it may instead be adjusted in
`units of 1/2 stages, 1/3 stages or even finer increments.
`Furthermore, while the camera vibration is detected with the
`Vibration Sensor 3A Such as an angular Speed Sensor, the
`Vibration may be detected with another type of Sensor.
`Alternatively, instead of utilizing the vibration Sensor 3A,
`the extent of image blur may be detected based upon the
`detection results (a so-called through image that is displayed
`on a monitor of the digital still camera 10 in real time before
`or after the shutter release button 30 is pressed) output from
`the image-capturing element 6 in real time.
`0044 As shown in FIG. 4, an optical image blur correc
`tion mechanism 40 may be employed in conjunction with
`the ISO Speed adjustment executed based upon the image
`blur quantity as explained above. The optical image blur
`correction mechanism 40 includes a blur correction lens (not
`shown) disposed within a photographing optical System,
`which is allowed to move along a direction perpendicular to
`
`the optical axis. The extent of image blur is reduced by
`driving a blur correction optical System that includes the blur
`correction lens based upon the extent of vibration to which
`the camera (lens) is subjected detected by the vibration
`sensor 3A. It is to be noted that the optical image blur
`correction mechanism 40 is controlled by a CPU 1A.
`0045 By employing such an optical image blur correc
`tion mechanism 40 to optically correct the image blur, it
`becomes possible to reduce the extent of image blur even
`when the focal length of the photographic lens 20 is fmm
`and the shutter speed is lower than 1/f sec by two to three
`Stages. Accordingly, the image blur correction is executed by
`utilizing the optical image blur correction mechanism 40
`alone under normal circumstances, but if the Shutter Speed is
`lower than 1/f Sec by more than two or three stages, the
`Sensitivity is raised in correspondence to the image blur
`quantity as well. Consequently, the image blur quantity can
`be kept under the limit value by preventing the shutter Speed
`from becoming low, the effect of which can be further
`enhanced with the optical image blur correction. Namely,
`the ISO Speed is adjusted in correspondence to the image
`blur quantity if the image blur quantity cannot be reduced to
`a value under the limit value Simply by executing the optical
`image blur correction. Through this method, the image blur
`can be corrected even more effectively.
`0046 AS explained above, prior to the photographing
`operation, the image blur quantity representing the extent of
`image blur to manifest in the photograph is calculated based
`upon the image-capturing Sensitivity Setting, and a decision
`is made as to whether or not the image-capturing Sensitivity
`needs to be adjusted based upon the calculated image blur
`quantity in the embodiment of the present invention. Since
`the image-capturing Sensitivity is adjusted only if necessary,
`the photographing operation can always be executed at the
`optimal Sensitivity level in correspondence to the Skill level
`of the photographer or the photographing conditions and, as
`a result, the extent of image blur can be highly effectively
`reduced without raising the Sensitivity unnecessarily.
`0047. It is to be noted that the present invention may be
`adopted in a Single lens refleX digital Still camera instead of
`the digital Still camera 10 achieved as a compact camera
`shown in FIG. 3 as in the embodiment.
`0048. The above described embodiment is an example,
`and various modifications can be made without departing
`from the Spirit and Scope of the invention.
`What is claimed is:
`1. A digital Still camera comprising:
`a Sensitivity Setting device that Sets an image-capturing
`Sensitivity;
`a photographing device having an image-capturing ele
`ment that receives a light flux transmitted through a
`photographic lens and executeS photoelectric conver
`Sion on the received light flux,
`a control device that engages the photographing device in
`operation at a shutter Speed corresponding to the
`image-capturing Sensitivity Set by the Sensitivity Setting
`device;
`an image blur calculation device that calculates an image
`blur quantity indicating an extent to which an image
`becomes blurred during a photographing operation
`
`Ex.1013 / Page 9 of 10Ex.1013 / Page 9 of 10
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`TESLA, INC.TESLA, INC.
`
`

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`US 2004/0239771 A1
`
`Dec. 2, 2004
`
`based upon the image-capturing Sensitivity having been
`Set prior to the photographing operation; and
`a determination device that makes a decision as to
`whether the image-capturing Sensitivity needs to be
`adjusted based upon the image blur quantity calculated
`by the image blur calculation device, wherein:
`the Sensitivity Setting device adjusts the image-capturing
`Sensitivity if the determination device determines that
`the image-capturing Sensitivity needs to be adjusted;
`and
`if the image-capturing Sensitivity is adjusted, the control
`device engages the photographing device in operation
`at a Shutter Speed corresponding to the adjusted image
`capturing Sensitivity.
`2. A digital Still camera according to claim 1, wherein:
`if the calculated image blur quantity exceeds a predeter
`mined limit value, the Sensitivity Setting device shifts
`the image-capturing Sensitivity to a higher level So as to
`lower the image blur quantity to a value equal to or leSS
`than the limit value.
`3. A digital Still camera according to claim 1, wherein:
`the image blur calculation device includes a vibration
`detection Sensor that detects an extent of vibration to
`which the digital camera is Subjected, and calculates
`the image blur quantity indicating the extent to which
`the image becomes blurred during the photographing
`operation based upon detection results provided by the
`Vibration detection Sensor and the Shutter Speed deter
`mined in conformance to photometering results
`obtained by photometering a photographic field and the
`image-capturing Sensitivity having been Set.
`4. A digital Still camera according to claim 3, furth