Patent Publication Number: US-8970713-B2

Title: Automatic engagement of image stabilization

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 12/943,328, by Noah J. Stupak, et al., entitled “Automatic Engagement of Image Stabilization,” filed Nov. 10, 2010, which is incorporated by reference herein in its entirety. 
     Reference is made to commonly-assigned, U.S. patent application Ser. No. 12/943,357, by Keith S. Karn et al., entitled “Imaging System with Automatically Engaging Image Stabilization,” filed Nov. 10, 2010, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention pertains to the field of digital cameras and more particularly capturing a digital image of a scene using a selectively engaged image stabilization system. 
     BACKGROUND OF THE INVENTION 
     An electronic imaging system depends on a lens system to form an image on an image sensor to create an electronic representation of a visual image. Examples of such image sensors include charge coupled device (CCD) image sensors and active pixel sensor (APS) devices. (APS devices are often referred to as CMOS sensors because of the ability to fabricate them in a Complementary Metal Oxide Semiconductor process.) A sensor includes a two-dimensional array of individual picture element sensors, or “pixels.” For color imaging systems, each pixel is typically provided with either a red, green, or blue filter, as for example described by Bayer in U.S. Pat. No. 3,971,065 so that a full color image can be produced. Regardless of the type of image sensor employed (e.g., CCD or CMOS), the pixel acts as a bucket in which photo-generated charge is accumulated in direct proportion to the amount of light that strikes the pixel during the capture of an image by the electronic imaging system. 
     The image sensor gathers light for an interval of time called the exposure time or integration time to make a correct exposure during image capture. Based on brightness measurements of the scene, an exposure control system is used to determine a suitable exposure time that will yield an image with effective brightness and an effective signal to noise ratio. The exposure control system may also determine other settings such as a lens aperture setting and an exposure index setting. Generally, the dimmer the scene, the larger the amount of time the electronic imaging system must use to gather light to make a correct exposure. 
       FIG. 1  shows a flow chart of a typical exposure control system  200  for a digital camera. In assess scene brightness step  210 , the camera assesses the scene brightness either with a scene brightness sensor or with an analysis of a preview image. In the typical camera control system shown in  FIG. 1 , motion is not measured nor taken into account. In determine capture mode step  220 , a capture mode setting  225  is determined based on the measured scene brightness and any operator-selected user interface settings. In determine exposure index step  230 , an exposure index setting  235  (S) is determined in accordance with the measured scene brightness and the capture mode setting  225 . In determine aperture step  240 , an aperture setting  245  is determined to control the F/# of the camera lens in accordance with the measured scene brightness, the capture mode setting  225  and the exposure index setting  235 . An exposure time setting  255  (T E ) is then determined in determine exposure time step  250  in accordance with the measured scene brightness, the capture mode setting  225 , the exposure index setting  235  and the aperture setting  245 . It should be noted that these steps are not necessarily performed in the order shown in  FIG. 1 . After the various settings have been determined, a capture digital image step  260  is used to capture and store a digital image  265 . 
     If motion of the image capture device or the scene occurs during image capture, motion blur can result in the captured image as the magnitude of the motion increases relative to the exposure time. There are two types of motion blur: global motion blur and local motion blur. Global motion blur is produced when the image capture device is moving relative to the scene during capture, resulting in the entire image being blurred. Local motion blur is produced when the image capture device is stationary, but one or more objects in the scene are moving. In this case, only the moving object is blurred. Motion blur problems are generally more severe in low light level photography environments due to the fact that longer exposure times are typically required. 
     A number of methods to reduce global motion blur are known to those in the field. One method is to use an image stabilization system. Such methods typically use an inertial measurement device (e.g., a gyroscope or an accelerometer) to measure the motion of the image capture device during capture and then use a special lens with a lens element that can be moved laterally to cause the image formed by the lens on the image sensor to move in a direction that compensates for the image capture device motion. In other embodiments, the image sensor itself can be moved laterally to compensate for the image capture device motion. 
     A method that can be used to correct for motion during the capture of video image is described in U.S. Patent Application Publication. 2006/0274156, to Rabbani et al., entitled “Image sequence stabilization method and camera having dual path image sequence stabilization.” This approach is based on a digital shifting of individual frames in a captured video sequence to compensate for movement of the digital camera. While this method cannot reduce motion blur in a single frame, it is effective to stabilize a sequence of captured video images to reduce the effect of camera shake. 
     None of the above-described methods are effective to reduce the effects of local motion blur. One method to reduce local motion blur is to shorten the exposure time to a setting which is shorter than the value determined by the exposure control system. The resulting images will be darker and have a lower signal-to-noise ratio. An analog or digital gain can then be applied to the pixel values in the image to brighten the darker images, but those skilled in the art will recognize that this will result in noisier images. 
     Another method to reduce motion blur is to gather more light by using either a lens with a larger aperture or an image sensor with larger pixels, thereby enabling the use of a shorter exposure time. This approach can produce images with reduced motion blur and acceptable noise levels. However, the current industry trend in electronic imaging systems is to make image capture devices more compact and less expensive. High-grade optical elements with large apertures and image sensors with larger pixels are substantially more expensive, and are therefore not practical for many applications. 
     Another method to reduce motion blur is to supplement the available light with a photographic flash in order to reduce the effective exposure time. A photographic flash produces a strong light flux that is sustained for a small fraction of a second. The actual exposure time can be set to a short value which is marginally longer than the flash duration. Generally, the flash will be the dominant light source, and therefore the flash duration will define the effective exposure time. Therefore, the motion blur caused by either global or local motion during the exposure can be significantly reduced. However, flash photography is typically only useful if the distance between the flash and the scene being photographed is relatively small. Flash photography also tends to produce artifacts such as red eyes, shadows, and very bright areas or dark areas, which many people find objectionable. 
     U.S. Patent Application Publication 2007/0237514 to Pillman, entitled “Varying camera self-determination based on subject motion,” teaches a method for capturing digital images where motion in the scene is measured prior to image capture. The camera settings are adjusted responsive to the determined scene motion. 
     In U.S. Patent Application Publication 2007/0237506 to Minema et al., entitled “Image blurring reduction,” a camera is described wherein an image is captured at a slower shutter speed if no camera motion is detected. If camera motion is detected, then an image is captured at a faster shutter speed. While this method does reduce motion blur in images, it does not address the combined effects of motion blur and noise in the image on the perceived image quality of the image in selecting capture conditions including exposure time and ISO. 
     U.S. Patent Application Publication 2009/0040364 to Rubner, entitled “Adaptive Exposure Control,” teaches using a multiple image capture process to reduce image quality artifacts including motion blur. With this method, a first image is captured using exposure conditions defined by the a conventional exposure control system. The first image is then analyzed for aspects of image quality such as overexposure or underexposure, motion blur, dynamic range or depth of field to determine which aspects have been met and where deficiencies remain. If deficiencies are identified in aspects of image quality, the process determines new exposure parameters and captures an additional image. This process repeats until all the aspects of image quality have been met amongst the multiple images that have been captured. A final image is then constructed by combining portions of the multiple images. This method does not address motion related image quality issues in applications which require capturing only a single digital image. 
     U.S. Pat. No. 5,598,237 to McIntyre, entitled “Image capture apparatus,” describes an image capture apparatus operable in a handheld condition and in a stabilized non-hand-held condition. Different exposure parameters are selected depending on whether the camera is being used in the hand-held condition. 
     U.S. Pat. No. 6,384,976 to Ishijima et al., entitled “Image stabilizing apparatus,” and related U.S. Patent Application Publication 2002/0093739 to Ishijima et al., entitled “Image stabilizing apparatus,” disclose an image stabilization apparatus in which a vibration reduction mode and a panning/tilting mode are selected automatically. 
     U.S. Pat. No. 7,164,531 to Yamamoto, entitled “Image stabilization apparatus,” describes an image stabilization apparatus comprising an optical system where a portion of the optical elements are controlled to stabilize the optical image while the remaining optical elements are held in a predetermined position. 
     While image stabilization systems that adjust the position of optical elements or the sensor can substantially reduce the level of global motion blur in a digital image, their use has a number of disadvantages. One disadvantage is that the image stabilization system uses power and therefore drains the battery faster than non-stabilized lens systems. Another disadvantage is that the image stabilization systems have moving parts that can wear out over time, thereby decreasing the lifetime of the camera. Some cameras have a switch that can be used to turn the image stabilization system off when it is not needed, but this requires a manual user action and requires the user to understand what photography conditions would benefit from the use of the image stabilization system. It also makes it likely that the user will forget to engage the image stabilization system during some situations where it would be beneficial and will capture some images with significant image quality degradations. 
     There remains a need for a digital camera having reduced susceptibility to motion blur that does not have the disadvantages of cameras having image stabilization systems that are constantly operating or must be manually activated. 
     SUMMARY OF THE INVENTION 
     The present invention represents an image stabilized digital image capture device, comprising: 
     an image sensor for capturing a digital image; 
     an optical system for imaging a scene onto the image sensor; 
     an image stabilization system; 
     an exposure control system; 
     a memory system; and 
     a processor for performing the steps of:
         determining exposure settings using the exposure control system;   selectively engaging the image stabilization system responsive to whether the determined exposure settings satisfy a predefined condition;   capturing a digital image of a scene using the image sensor and the selectively engaged image stabilization system; and   storing the captured digital image in the memory system.       

     An advantage of the present invention is that the power consumption of the digital image capture device is reduced when the image stabilization system is disengaged, thereby extending battery life and reducing wasted energy. 
     An additional advantage of the present invention is that mechanical wear of mechanical components in the image stabilization system is reduced when the image stabilization system is disengaged, thereby extending the useful life of the imaging system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flow chart for a prior art exposure control system; 
         FIG. 2  is a high-level diagram showing the components of a digital camera system; 
         FIG. 3  is a flow diagram depicting typical image processing operations used to process digital images in a digital camera; 
         FIG. 4  is a flowchart illustrating a method for controlling an image stabilized digital image capture device according to an embodiment of the present invention; and 
         FIG. 5  is a flowchart illustrating a method for controlling an image stabilized imaging according to an alternate embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, a preferred embodiment of the present invention will be described in terms that would ordinarily be implemented as a software program. Those skilled in the art will readily recognize that the equivalent of such software can also be constructed in firmware or hardware. Because image manipulation algorithms and systems are well known, the present description will be directed in particular to algorithms and systems forming part of, or cooperating more directly with, the system and method in accordance with the present invention. Other aspects of such algorithms and systems, and hardware or software for producing and otherwise processing the image signals involved therewith, not specifically shown or described herein, can be selected from such systems, algorithms, components and elements known in the art. Given the system as described according to the invention in the following materials, software not specifically shown, suggested or described herein that is useful for implementation of the invention is conventional and within the ordinary skill in such arts. 
     Still further, as used herein, a computer program for performing the method of the present invention can be stored in a computer readable storage medium, which can include, for example; magnetic storage media such as a magnetic disk (such as a hard drive or a floppy disk) or magnetic tape; optical storage media such as an optical disc, optical tape, or machine readable bar code; solid state electronic storage devices such as random access memory (RAM), or read only memory (ROM); or any other physical device or medium employed to store a computer program having instructions for controlling one or more computers to practice the method according to the present invention. 
     The invention is inclusive of combinations of the embodiments described herein. References to “a particular embodiment” and the like refer to features that are present in at least one embodiment of the invention. Separate references to “an embodiment” or “particular embodiments” or the like do not necessarily refer to the same embodiment or embodiments; however, such embodiments are not mutually exclusive, unless so indicated or as are readily apparent to one of skill in the art. The use of singular or plural in referring to the “method” or “methods” and the like is not limiting. It should be noted that, unless otherwise explicitly noted or required by context, the word “or” is used in this disclosure in a non-exclusive sense. 
     Because digital cameras employing imaging devices and related circuitry for signal capture and processing, and display are well known, the present description will be directed in particular to elements forming part of, or cooperating more directly with, the method and apparatus in accordance with the present invention. Elements not specifically shown or described herein are selected from those known in the art. Certain aspects of the embodiments to be described are provided in software. Given the system as shown and described according to the invention in the following materials, software not specifically shown, described or suggested herein that is useful for implementation of the invention is conventional and within the ordinary skill in such arts. 
     The following description of a digital camera will be familiar to one skilled in the art. It will be obvious that there are many variations of this embodiment that are possible and are selected to reduce the cost, add features or improve the performance of the camera. 
       FIG. 2  depicts a block diagram of a digital photography system, including a digital camera  10  in accordance with the present invention. Preferably, the digital camera  10  is a portable battery operated device, small enough to be easily handheld by a user when capturing and reviewing images. The digital camera  10  produces digital images that are stored as digital image files using image memory  30 . The phrase “digital image” or “digital image file”, as used herein, refers to any digital image file, such as a digital still image or a digital video file. 
     In some embodiments, the digital camera  10  captures both motion video images and still images. The digital camera  10  can also include other functions, including, but not limited to, the functions of a digital music player (e.g. an MP3 player), a mobile telephone, a GPS receiver, or a programmable digital assistant (PDA). 
     The digital camera  10  includes a lens  4  having an adjustable aperture and adjustable shutter  6 . In a preferred embodiment, the lens  4  is a zoom lens and is controlled by zoom and focus motor drives  8 . The lens  4  focuses light from a scene (not shown) onto an image sensor  14 , for example, a single-chip color CCD or CMOS image sensor. The lens  4  is one type optical system for forming an image of the scene on the image sensor  14 . In other embodiments, the optical system may use a fixed focal length lens with either variable or fixed focus. 
     The output of the image sensor  14  is converted to digital form by Analog Signal Processor (ASP) and Analog-to-Digital (A/D) converter  16 , and temporarily stored in buffer memory  18 . The image data stored in buffer memory  18  is subsequently manipulated by a processor  20 , using embedded software programs (e.g. firmware) stored in firmware memory  28 . In some embodiments, the software program is permanently stored in firmware memory  28  using a read only memory (ROM). In other embodiments, the firmware memory  28  can be modified by using, for example, Flash EPROM memory. In such embodiments, an external device can update the software programs stored in firmware memory  28  using the wired interface  38  or the wireless modem  50 . In such embodiments, the firmware memory  28  can also be used to store image sensor calibration data, user setting selections and other data which must be preserved when the camera is turned off. In some embodiments, the processor  20  includes a program memory (not shown), and the software programs stored in the firmware memory  28  are copied into the program memory before being executed by the processor  20 . 
     It will be understood that the functions of processor  20  can be provided using a single programmable processor or by using multiple programmable processors, including one or more digital signal processor (DSP) devices. Alternatively, the processor  20  can be provided by custom circuitry (e.g., by one or more custom integrated circuits (ICs) designed specifically for use in digital cameras), or by a combination of programmable processor(s) and custom circuits. It will be understood that connectors between the processor  20  from some or all of the various components shown in  FIG. 2  can be made using a common data bus. For example, in some embodiments the connection between the processor  20 , the buffer memory  18 , the image memory  30 , and the firmware memory  28  can be made using a common data bus. 
     The processed images are then stored using the image memory  30 . It is understood that the image memory  30  can be any form of memory known to those skilled in the art including, but not limited to, a removable Flash memory card, internal Flash memory chips, magnetic memory, or optical memory. In some embodiments, the image memory  30  can include both internal Flash memory chips and a standard interface to a removable Flash memory card, such as a Secure Digital (SD) card. Alternatively, a different memory card format can be used, such as a micro SD card, Compact Flash (CF) card, MultiMedia Card (MMC), xD card or Memory Stick. 
     The image sensor  14  is controlled by a timing generator  12 , which produces various clocking signals to select rows and pixels and synchronizes the operation of the ASP and A/D converter  16 . The image sensor  14  can have, for example, 12.4 megapixels (4088×3040 pixels) in order to provide a still image file of approximately 4000×3000 pixels. To provide a color image, the image sensor is generally overlaid with a color filter array, which provides an image sensor having an array of pixels that include different colored pixels. The different color pixels can be arranged in many different patterns. As one example, the different color pixels can be arranged using the well-known Bayer color filter array, as described in U.S. Pat. No. 3,971,065, “Color imaging array” to Bayer, the disclosure of which is incorporated herein by reference. As a second example, the different color pixels can be arranged as described in U.S. Patent Application Publication 2005/191729, filed on Jul. 28, 2007 and titled “Image sensor with improved light sensitivity” to Compton and Hamilton, the disclosure of which is incorporated herein by reference. These examples are not limiting, and many other color patterns may be used. 
     It will be understood that the image sensor  14 , timing generator  12 , and ASP and A/D converter  16  can be separately fabricated integrated circuits, or they can be fabricated as a single integrated circuit as is commonly done with CMOS image sensors. In some embodiments, this single integrated circuit can perform some of the other functions shown in  FIG. 2 , including some of the functions provided by processor  20 . 
     The image sensor  14  is effective when actuated in a first mode by timing generator  12  for providing a motion sequence of lower resolution sensor image data, which is used when capturing video images and also when previewing a still image to be captured, in order to compose the image. This preview mode sensor image data can be provided as HD resolution image data, for example, with 1280×720 pixels, or as VGA resolution image data, for example, with 640×480 pixels, or using other resolutions which have significantly fewer columns and rows of data, compared to the resolution of the image sensor. 
     The preview mode sensor image data can be provided by combining values of adjacent pixels having the same color, or by eliminating some of the pixel values, or by combining some color pixel values while eliminating other color pixel values. The preview mode image data can be processed as described in U.S. Pat. No. 6,292,218 to Parulski, et al., entitled “Electronic camera for initiating capture of still images while previewing motion images,” which is incorporated herein by reference. 
     The image sensor  14  is also effective when actuated in a second mode by timing generator  12  for providing high resolution still image data. This final mode sensor image data is provided as high resolution output image data, which for scenes having a high illumination level includes all of the pixels of the image sensor, and can be, for example, a 12 megapixel final image data having 4000×3000 pixels. At lower illumination levels, the final sensor image data can be provided by “binning” some number of like-colored pixels on the image sensor, in order to increase the signal level and thus the “ISO speed” of the sensor. 
     The zoom and focus motor drivers  8  are controlled by control signals supplied by the processor  20 , to provide the appropriate focal length setting and to focus the scene onto the image sensor  14 . The exposure level of the image sensor  14  is controlled by controlling the f/number and exposure time of the adjustable aperture and adjustable shutter  6 , the exposure period of the image sensor  14  via the timing generator  12 , and the gain (i.e., ISO speed) setting of the ASP and A/D converter  16 . The processor  20  also controls a flash  2  which can illuminate the scene. 
     The lens  4  of the digital camera  10  can be focused in the first mode by using “through-the-lens” autofocus, as described in U.S. Pat. No. 5,668,597, entitled “Electronic Camera with Rapid Automatic Focus of an Image upon a Progressive Scan Image Sensor” to Parulski et al., which is incorporated herein by reference. This is accomplished by using the zoom and focus motor drivers  8  to adjust the focus position of the lens  4  to a number of positions ranging between a near focus position to an infinity focus position, while the processor  20  determines the closest focus position which provides a peak sharpness value for a central portion of the image captured by the image sensor  14 . The focus distance which corresponds to the closest focus position can then be utilized for several purposes, such as automatically setting an appropriate scene mode, and can be stored as metadata in the image file, along with other lens and camera settings. 
     The digital camera  10  in the present invention includes an image stabilization system  80 , which is used to reduce the effects of motion blur in captured digital images. In a preferred embodiment, the lens  4  includes one or more lens elements that can be moved laterally to cause the image formed by the lens  4  on the image sensor  14  to move in a direction that compensates for the motion of the digital camera  10 . The image stabilization system  80  will typically include an inertial measurement device (e.g., a gyroscope or an accelerometer) to measure the motion of the digital camera  10  in order to determine the required motions of the lens elements. In some embodiments, the digital camera  10  can include inertial measurement devices that are used for other purposes. In this case the image stabilization system  80  can use the signals from those inertial measurement devices rather than duplicating those components. It some embodiments, the image stabilization system  80  can move the image sensor  14  to compensate for the motion of the digital camera  10 , rather than moving one or more of the lens elements. 
     The processor  20  produces menus and low resolution color images that are temporarily stored in display memory  36  and are displayed on the image display  32 . The image display  32  is typically an active matrix color liquid crystal display (LCD), although other types of displays, such as organic light emitting diode (OLED) displays, can be used. A video interface  44  provides a video output signal from the digital camera  10  to a video display  46 , such as a flat panel HDTV display. In preview mode, or video mode, the digital image data from buffer memory  18  is manipulated by processor  20  to form a series of motion preview images that are displayed, typically as color images, on the image display  32 . In review mode, the images displayed on the image display  32  are produced using the image data from the digital image files stored in image memory  30 . 
     The graphical user interface displayed on the image display  32  is controlled in response to user input provided by user controls  34 . The user controls  34  are used to select various camera modes, such as video capture mode, still capture mode, and review mode, and to initiate capture of still images, recording of motion images. The user controls  34  are also used to set user processing preferences, and to choose between various photography modes based on scene type and taking conditions. In some embodiments, various camera settings may be set automatically in response to analysis of preview image data, audio signals, or external signals such as GPS, weather broadcasts, or other available signals. 
     In some embodiments, when the digital camera is in a still photography mode the above-described preview mode is initiated when the user partially depresses a shutter button, which is one of the user controls  34 , and the still image capture mode is initiated when the user fully depresses the shutter button. The user controls  34  are also used to turn on the camera, control the lens  4 , and initiate the picture taking process. User controls  34  typically include some combination of buttons, rocker switches, joysticks, or rotary dials. In some embodiments, some of the user controls  34  are provided by using a touch screen overlay on the image display  32 . In other embodiments, the user controls  34  can include a means to receive input from the user or an external device via a tethered, wireless, voice activated, visual or other interface. In other embodiments, additional status displays or images displays can be used. 
     The camera modes that can be selected using the user controls  34  include a “timer” mode. When the “timer” mode is selected, a short delay (e.g., 10 seconds) occurs after the user fully presses the shutter button, before the processor  20  initiates the capture of a still image. 
     An audio codec  22  connected to the processor  20  receives an audio signal from a microphone  24  and provides an audio signal to a speaker  26 . These components can be used to record and playback an audio track, along with a video sequence or still image. If the digital camera  10  is a multi-function device such as a combination camera and mobile phone, the microphone  24  and the speaker  26  can be used for telephone conversation. 
     In some embodiments, the speaker  26  can be used as part of the user interface, for example to provide various audible signals which indicate that a user control has been depressed, or that a particular mode has been selected. In some embodiments, the microphone  24 , the audio codec  22 , and the processor  20  can be used to provide voice recognition, so that the user can provide a user input to the processor  20  by using voice commands, rather than user controls  34 . The speaker  26  can also be used to inform the user of an incoming phone call. This can be done using a standard ring tone stored in firmware memory  28 , or by using a custom ring-tone downloaded from a wireless network  58  and stored in the image memory  30 . In addition, a vibration device (not shown) can be used to provide a silent (e.g., non audible) notification of an incoming phone call. 
     The processor  20  also provides additional processing of the image data from the image sensor  14 , in order to produce rendered sRGB image data which is compressed and stored within a “finished” image file, such as a well-known Exif-JPEG image file, in the image memory  30 . 
     The digital camera  10  can be connected via the wired interface  38  to an interface/recharger  48 , which is connected to a computer  40 , which can be a desktop computer or portable computer located in a home or office. The wired interface  38  can conform to, for example, the well-known USB 2.0 interface specification. The interface/recharger  48  can provide power via the wired interface  38  to a set of rechargeable batteries (not shown) in the digital camera  10 . 
     The digital camera  10  can include a wireless modem  50 , which interfaces over a radio frequency band  52  with the wireless network  58 . The wireless modem  50  can use various wireless interface protocols, such as the well-known Bluetooth wireless interface or the well-known 802.11 wireless interface. The computer  40  can upload images via the Internet  70  to a photo service provider  72 , such as the Kodak EasyShare Gallery. Other devices (not shown) can access the images stored by the photo service provider  72 . 
     In alternative embodiments, the wireless modem  50  communicates over a radio frequency (e.g. wireless) link with a mobile phone network (not shown), such as a 3GSM network, which connects with the Internet  70  in order to upload digital image files from the digital camera  10 . These digital image files can be provided to the computer  40  or the photo service provider  72 . 
       FIG. 3  is a flow diagram depicting image processing operations that can be performed by the processor  20  in the digital camera  10  ( FIG. 2 ) in order to process color sensor data  100  from the image sensor  14  output by the ASP and A/D converter  16 . In some embodiments, the processing parameters used by the processor  20  to manipulate the color sensor data  100  for a particular digital image are determined by various photography mode settings  175 , which are typically associated with photography modes that can be selected via the user controls  34 , which enable the user to adjust various camera settings  185  in response to menus displayed on the image display  32 . 
     The color sensor data  100  which has been digitally converted by the ASP and A/D converter  16  is manipulated by a white balance step  95 . In some embodiments, this processing can be performed using the methods described in U.S. Pat. No. 7,542,077 to Miki, entitled “White balance adjustment device and color identification device”, the disclosure of which is herein incorporated by reference. The white balance can be adjusted in response to a white balance setting  90 , which can be manually set by a user, or which can be automatically set by the camera. 
     The color image data is then manipulated by a noise reduction step  105  in order to reduce noise from the image sensor  14 . In some embodiments, this processing can be performed using the methods described in U.S. Pat. No. 6,934,056 to Gindele et al., entitled “Noise cleaning and interpolating sparsely populated color digital image using a variable noise cleaning kernel,” the disclosure of which is herein incorporated by reference. The level of noise reduction can be adjusted in response to an ISO setting  110 , so that more filtering is performed at higher ISO exposure index setting. 
     The color image data is then manipulated by a demosaicing step  115 , in order to provide red, green and blue (RGB) image data values at each pixel location. Algorithms for performing the demosaicing step  115  are commonly known as color filter array (CFA) interpolation algorithms or “deBayering” algorithms. In one embodiment of the present invention, the demosaicing step  115  can use the luminance CFA interpolation method described in U.S. Pat. No. 5,652,621, entitled “Adaptive color plane interpolation in single sensor color electronic camera,” to Adams et al., the disclosure of which is incorporated herein by reference. The demosaicing step  115  can also use the chrominance CFA interpolation method described in U.S. Pat. No. 4,642,678, entitled “Signal processing method and apparatus for producing interpolated chrominance values in a sampled color image signal”, to Cok, the disclosure of which is herein incorporated by reference. 
     In some embodiments, the user can select between different pixel resolution modes, so that the digital camera can produce a smaller size image file. Multiple pixel resolutions can be provided as described in U.S. Pat. No. 5,493,335, entitled “Single sensor color camera with user selectable image record size,” to Parulski et al., the disclosure of which is herein incorporated by reference. In some embodiments, a resolution mode setting  120  can be selected by the user to be full size (e.g. 3,000×2,000 pixels), medium size (e.g. 1,500×1000 pixels) or small size (750×500 pixels). 
     The color image data is color corrected in color correction step  125 . In some embodiments, the color correction is provided using a 3×3 linear space color correction matrix, as described in U.S. Pat. No. 5,189,511, entitled “Method and apparatus for improving the color rendition of hardcopy images from electronic cameras” to Parulski, et al., the disclosure of which is incorporated herein by reference. In some embodiments, different user-selectable color modes can be provided by storing different color matrix coefficients in firmware memory  28  of the digital camera  10 . For example, four different color modes can be provided, so that the color mode setting  130  is used to select one of the following color correction matrices: 
     
       
         
           
             
               
                 
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                             1.80 
                           
                           
                             
                               - 
                               0.40 
                             
                           
                         
                         
                           
                             
                               - 
                               0.20 
                             
                           
                           
                             
                               - 
                               0.20 
                             
                           
                           
                             1.40 
                           
                         
                       
                       ] 
                     
                     ⁡ 
                     
                       [ 
                       
                         
                           
                             
                               R 
                               in 
                             
                           
                         
                         
                           
                             
                               G 
                               in 
                             
                           
                         
                         
                           
                             
                               B 
                               in 
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
             
               
                 
                   Setting 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   2 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     
                       saturated 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       color 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       reproduction 
                     
                     ) 
                   
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             R 
                             out 
                           
                         
                       
                       
                         
                           
                             G 
                             out 
                           
                         
                       
                       
                         
                           
                             B 
                             out 
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             2.00 
                           
                           
                             
                               - 
                               0.60 
                             
                           
                           
                             
                               - 
                               0.40 
                             
                           
                         
                         
                           
                             
                               - 
                               0.80 
                             
                           
                           
                             2.60 
                           
                           
                             
                               - 
                               0.80 
                             
                           
                         
                         
                           
                             
                               - 
                               0.40 
                             
                           
                           
                             
                               - 
                               0.40 
                             
                           
                           
                             1.80 
                           
                         
                       
                       ] 
                     
                     ⁡ 
                     
                       [ 
                       
                         
                           
                             
                               R 
                               in 
                             
                           
                         
                         
                           
                             
                               G 
                               in 
                             
                           
                         
                         
                           
                             
                               B 
                               in 
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
             
               
                 
                   Setting 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   3 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     
                       de 
                       ⁢ 
                       
                         - 
                       
                       ⁢ 
                       saturated 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       color 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       reproduction 
                     
                     ) 
                   
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             R 
                             out 
                           
                         
                       
                       
                         
                           
                             G 
                             out 
                           
                         
                       
                       
                         
                           
                             B 
                             out 
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             1.25 
                           
                           
                             
                               - 
                               0.15 
                             
                           
                           
                             
                               - 
                               0.10 
                             
                           
                         
                         
                           
                             
                               - 
                               0.20 
                             
                           
                           
                             1.40 
                           
                           
                             
                               - 
                               0.20 
                             
                           
                         
                         
                           
                             
                               - 
                               0.10 
                             
                           
                           
                             
                               - 
                               0.10 
                             
                           
                           
                             1.20 
                           
                         
                       
                       ] 
                     
                     ⁡ 
                     
                       [ 
                       
                         
                           
                             
                               R 
                               in 
                             
                           
                         
                         
                           
                             
                               G 
                               in 
                             
                           
                         
                         
                           
                             
                               B 
                               in 
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
             
               
                 
                   Setting 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   4 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     monochrome 
                     ) 
                   
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             R 
                             out 
                           
                         
                       
                       
                         
                           
                             G 
                             out 
                           
                         
                       
                       
                         
                           
                             B 
                             out 
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             0.30 
                           
                           
                             0.60 
                           
                           
                             0.10 
                           
                         
                         
                           
                             0.30 
                           
                           
                             0.60 
                           
                           
                             0.10 
                           
                         
                         
                           
                             0.30 
                           
                           
                             0.60 
                           
                           
                             0.10 
                           
                         
                       
                       ] 
                     
                     ⁡ 
                     
                       [ 
                       
                         
                           
                             
                               R 
                               in 
                             
                           
                         
                         
                           
                             
                               G 
                               in 
                             
                           
                         
                         
                           
                             
                               B 
                               in 
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
     In other embodiments, a three-dimensional lookup table can be used to perform the color correction step  125 . 
     The color image data is also manipulated by a tone scale correction step  135 . In some embodiments, the tone scale correction step  135  can be performed using a one-dimensional look-up table as described in U.S. Pat. No. 5,189,511, cited earlier. In some embodiments, a plurality of tone scale correction look-up tables is stored in the firmware memory  28  in the digital camera  10 . These can include look-up tables which provide a “normal” tone scale correction curve, a “high contrast” tone scale correction curve, and a “low contrast” tone scale correction curve. A user selected contrast setting  140  is used by the processor  20  to determine which of the tone scale correction look-up tables to use when performing the tone scale correction step  135 . 
     The color image data is also manipulated by an image sharpening step  145 . In some embodiments, this can be provided using the methods described in U.S. Pat. No. 6,192,162 entitled “Edge enhancing colored digital images” to Hamilton, et al., the disclosure of which is incorporated herein by reference. In some embodiments, the user can select between various sharpening settings, including a “normal sharpness” setting, a “high sharpness” setting, and a “low sharpness” setting. In this example, the processor  20  uses one of three different edge boost multiplier values, for example 2.0 for “high sharpness”, 1.0 for “normal sharpness”, and 0.5 for “low sharpness” levels, responsive to a sharpening setting  150  selected by the user of the digital camera  10 . 
     The color image data is also manipulated by an image compression step  155 . In some embodiments, the image compression step  155  can be provided using the methods described in U.S. Pat. No. 4,774,574, entitled “Adaptive block transform image coding method and apparatus” to Daly et al., the disclosure of which is incorporated herein by reference. In some embodiments, the user can select between various compression settings. This can be implemented by storing a plurality of quantization tables, for example, three different tables, in the firmware memory  28  of the digital camera  10 . These tables provide different quality levels and average file sizes for the compressed digital image file  180  to be stored in the image memory  30  of the digital camera  10 . A user selected compression mode setting  160  is used by the processor  20  to select the particular quantization table to be used for the image compression step  155  for a particular image. 
     The compressed color image data is stored in a digital image file  180  using a file formatting step  165 . The image file can include various metadata  170 . Metadata  170  is any type of information that relates to the digital image, such as the model of the camera that captured the image, the size of the image, the date and time the image was captured, and various camera settings, such as the lens focal length, the exposure time and f-number of the lens, and whether or not the camera flash fired. In a preferred embodiment, all of this metadata  170  is stored using standardized tags within the well-known Exif-JPEG still image file format. In a preferred embodiment of the present invention, the metadata  170  includes information about various camera settings  185 , including the photography mode settings  175 . 
     The present invention will now be described with reference to  FIG. 4 , which is a flowchart of illustrating a method for an image stabilized digital image capture device according to an embodiment of the present invention. First a power on device step  300 , powers on the digital image capture device. In a preferred embodiment, the digital image capture device is a digital camera  10  as described with reference to  FIGS. 2 and 3 . The digital camera  10  can be a digital still camera or a digital video camera, for example. In the  FIG. 4  embodiment, it will be assumed that the digital image capture device include a zoom lens, although this is not a requirement. 
     A set zoom position step  310  is used to set a focal length  315  (F) for the lens  4  ( FIG. 2 ). Generally, the set zoom position step  310  will involve a user adjusting various user interface controls on the digital image capture device. Any method known in the art for adjusting the focal length of a lens  4  can be used in accordance with the present invention. For example, some digital image capture devices include “zoom in” and “zoom out” buttons which are used to control the focal length of the lens  4 . Other digital image capture device configurations include a lens  4  where the focal length can be adjusted by grasping a ring on the exterior of the lens barrel and twisting in a clockwise or counter-clockwise direction to adjust the focal length. The selected focal length  315  can be automatically reported to the processor  20  ( FIG. 2 ) in the digital image capture device so that it can be used in the process of determining whether or not to engage the image stabilization system  80  ( FIG. 2 ) as will be described below. Methods for determining a digital representation of the selected focal length  315  of a zoom lens are well-known in the art. 
     Next, a determine exposure time step  320  is used to determine an exposure time setting  325  (T E ). In a preferred embodiment, the determine exposure time step  320  is included as part of an exposure control system, such as the prior art exposure control system  200  described with reference to  FIG. 1 . In general, the exposure control system will also determine other exposure settings such as a capture mode setting, an exposure index setting, a lens aperture setting or a flash setting. Typically, the process of determining the exposure settings will be initiated by a user action such as initiating an image capture or by pressing an image capture button down halfway. 
     An exposure time test  330  is used to evaluate the exposure time  325  to determine whether the image stabilization system  80  should be engaged. In the embodiment shown in  FIG. 4 , the exposure time test  330  involves a comparison of the calculated exposure time setting  325  with a threshold exposure time computed from the focal length  315 . If the exposure time is greater than the threshold exposure time then the image stabilization system  70  is engaged, otherwise it is not engaged. In the  FIG. 4  embodiment, the threshold exposure time, T t  is given by
 
 T   t   =K/F   (5)
 
where K is a predefined constant. A reasonable value of the constant that can be used in many cases is K=1.0, although those skilled in the art will recognize that other values may be appropriate depending on the application. In other embodiments, the threshold exposure time T t  can be a fixed constant, or can be calculated using other appropriate relationships
 
     If the exposure time test  330  determines that the exposure time setting  325  is greater than the threshold exposure time, T t , then an engage image stabilization step  340  is called to engage the image stabilization system  80  ( FIG. 2 ) before a capture digital image step  350  is used to capture a digital image  360 . Otherwise, the image stabilization system  80  is left in a disengaged state and execution proceeds directly to the capture digital image step  350 . 
     In some embodiments, the decision of whether to engage the image stabilization system  80  is initiated when the user presses an image capture button down halfway. The capture digital image step  350  is then initiated with the user fully depresses the image capture button. In other embodiments, the process of deciding whether to engage the image stabilization system  80  is not tied to the image capture button, but occurs automatically anytime the exposure control system  200  determines new exposure settings. 
     In some embodiments, the decision to engage the image stabilization system  80  can be based on other exposure settings in addition to, or instead of, the exposure time setting  325 . Examples of other exposure settings that could be used would include the capture mode setting, the exposure index setting, the lens aperture setting or the flash setting. Some of these exposure settings may be determined automatically using the exposure control system, while others may be fixed, or may be manually user selected using a user interface control. For example, many digital image capture devices allow a user to manually select a capture mode such as “sports, “portrait,” or “landscape.” One or more predefined conditions can be defined which can be evaluated to determine whether the image stabilization system should be engaged. For example, a condition could be defined according to the following logic: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                   
                 if (Flash =“ ON”) 
                 (6) 
               
            
           
           
               
               
            
               
                   
                 Disengage Image Stabilization 
               
            
           
           
               
               
            
               
                   
                 else if ((CaptureMode =“ SPORTS”) AND (T E  &gt; 0.5/F)) 
               
            
           
           
               
               
            
               
                   
                 Engage Image Stabilization 
               
            
           
           
               
               
            
               
                   
                 else if (T E  &gt; 1/F) 
               
            
           
           
               
               
            
               
                   
                 Engage Image Stabilization 
               
            
           
           
               
               
            
               
                   
                 else 
               
            
           
           
               
               
            
               
                   
                 Disengage Image Stabilization 
               
               
                   
               
            
           
         
       
     
     With this condition, the image stabilization system is never engaged if the electronic flash is used. Furthermore a different exposure time test is used depending on whether the capture mode is set to a “sports” mode. In the sports mode, the image stabilization system is engaged at a shorter exposure time than for other capture modes. 
     In some embodiments, the decision to engage the image stabilization system  80  can also be based on other factors in addition to (or instead of) the exposure settings. For example, the motion of the digital image capture device can be evaluated by analyzing the signal from an accelerometer or a gyroscope. If it is determined that the digital image capture device is relatively still (e.g., if it is mounted on a tripod), then a different criteria can be applied to determine whether to engage the image stabilization system than is applied when the motion of the digital image capture device exceeds some threshold. 
     In some embodiments, a time sequence of preview images of the scene can be captured in a preview mode and can be analyzed to detect motion in the scene. Any method known in the art can be used to detect motion in the scene. An example of a method for detecting motion in a scene by analyzing a time sequence of preview images is taught in U.S. patent application Ser. No. 12/701,659 to Pillman et al., entitled “Capture condition selection from brightness and motion.” which is incorporated herein by reference. This method involves analyzing differences between the captured preview images to detect motion in the scene. The image stabilization system  80  can then be selectively engaged responsive to the detected motion characteristics. For example, if motion is detected that exceeds a predefined threshold, then the image stabilization system  80  can be engaged, otherwise it can remain in an unengaged state. The detected motion can be global motion corresponding to a motion of the digital image capture device, or it can be local motion corresponding to motion of an important object in the scene. 
     The principles described herein with respect to the use of image stabilization systems with digital image capture devices can also be applied to other types of imaging systems such as binoculars and telescopes which produce images intended for observation by a human observer rather than for the purpose of capturing a digital image. Many such imaging systems have a zoom capability provided by variable focal length optics. The use of image stabilization systems in such imaging systems are well-known in the art. However, the image stabilization systems are manually activated, typically using some sort of power switch. The advantages provided by the use of image stabilization systems are most significant when the imaging systems are being used at magnification levels where small variations in the orientation of the imaging system can produce large changes in the viewed image. 
     When an imaging system having a zoom capability is used at low-magnification levels, engaging the image stabilization system provides very little value, but continues to consume power. Additionally, various mechanical components of the image stabilization system continue to experience unnecessary wear. However, in conventional imaging systems the user must decide when it is appropriate to engage the image stabilization system. Often the user will forget to engage the image stabilization system when it would be beneficial to do so, or will forget to disengage the image stabilization system when it is not providing any significant benefit. 
       FIG. 5  shows an embodiment of the present invention where an image stabilization system in an imaging system is selectively engaged responsive to adjustable optical system settings. In particular, the image stabilization system can be selectively engaged responsive to a magnification setting for the imaging system. Typically, the magnification setting is controlled by a user-selectable variable focal length setting for the imaging system. In one embodiment, the image stabilization system is selectively engaged responsive to the selected focal length. If the selected focal length is larger than a prespecified threshold focal length, the image stabilization system is automatically engaged. Otherwise, the image stabilization system is automatically disengaged, thus providing the benefits of reduced power consumption and reduced mechanical component wear. 
     According to the flow chart of  FIG. 5 , a power on device step  400 , powers on the imaging device. In one embodiment, the imaging device is a set of binoculars having a zoom capability. In other embodiments, the imaging device can be a telescope, or some other type of imaging device for forming an optical imaging having a variable magnification capability. 
     A set zoom position step  410  is used to set a focal length  420  (F) for the imaging system. Generally, the set zoom position step  410  will involve a user adjusting a zoom position control on the imaging system. Any method known in the art for adjusting the zoom position can be used in accordance with the present invention. For example, the zoom position for some imaging systems can be adjusted by grasping a ring on the exterior of the lens barrel and twisting in a clockwise or counter-clockwise direction to adjust the focal length. In other configurations, an adjustment wheel or lever can be provided to adjust the focal length. Other types of imaging systems include electronic controls for adjusting the magnification. For example, “zoom in” and “zoom out” buttons can be provided to control the focal length of the imaging system. 
     The selected focal length  420  can be automatically reported to a processor in the imaging device for use in the process of determining whether or not to engage the image stabilization system. Methods for determining a digital representation of the selected focal length  420  of a zoom lens are well-known in the art. 
     A focal length test  430  is used to compare the selected focal length  420  to a threshold focal length, F T . If the focal length  420  is greater than the threshold focal length, then an engage image stabilization step  440  is executed to automatically engage the image stabilization system. Otherwise, a disengage image stabilization step  450  is executed to automatically disengage the image stabilization system. 
     In some embodiments, the selective engagement of the image stabilization system is also responsive to a sensed light level. This enables the image stabilization system to be automatically disengaged when the imaging system is not being used (e.g., if the user has placed lens caps on the optical components or if the imaging system is stored in a case). In this configuration, if the user forgets to power off the device, then the image stabilization system will not continue to be drain power from the battery. In this case, the engage image stabilization step  440  will only be executed if the focal length test  430  indicates that the focal length  420  is greater than the threshold focal length and the sensed light level is simultaneously determined to be larger than a threshold light level. In addition to disengaging the image stabilization system when the imaging system is not being used. The imaging system can be automatically fully powered down if it remains in this state for more than a predetermined length of time. 
     In some embodiments, the imaging system further includes a means for detecting motion in the scene, and the selective engagement of the image stabilization system is also responsive to the detected motion in the scene. In this configuration the image stabilization system can be disengaged when no scene motion is detected, even if the imaging system is being used at a high imagination level. For example, if the imaging system is being used in a tripod mounted configuration, the image of the scene may be very stable so that no motion will be detected. As a result, there would be no need to engage the image stabilization system. The same means for detecting motion in the scene described above with respect to the digital camera configuration can be used in used to detect the scene motion in this case. For example, an image sensor can be used to capture a time sequence of images and the captured images can be analyzed to detect motion of the image scene. 
     In some embodiments, the imaging system further includes a means for detecting motion of the imaging device, and the selective engagement of the image stabilization system is also responsive to the detected motion of the imaging device. In this configuration the image stabilization system can be disengaged when the imaging device is stationary, even if the imaging system is being used at a high imagination level. For example, if the imaging system is being used in a tripod mounted configuration, there may be no need to engage the image stabilization system. Any means for detecting motion of the imaging device known in the art can be used for this purpose. For example, an inertial measurement device including a gyroscope or an accelerometer can be used to detect any motion of the image capture device. 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
     PARTS LIST 
     
         
           2  flash 
           4  lens 
           6  adjustable aperture and adjustable shutter 
           8  zoom and focus motor drives 
           10  digital camera 
           12  timing generator 
           14  image sensor 
           16  ASP and A/D Converter 
           18  buffer memory 
           20  processor 
           22  audio codec 
           24  microphone 
           26  speaker 
           28  firmware memory 
           30  image memory 
           32  image display 
           34  user controls 
           36  display memory 
           38  wired interface 
           40  computer 
           44  video interface 
           46  video display 
           48  interface/recharger 
           50  wireless modem 
           52  radio frequency band 
           58  wireless network 
           70  Internet 
           72  photo service provider 
           80  image stabilization system 
           90  white balance setting 
           95  white balance step 
           100  color sensor data 
           105  noise reduction step 
           110  ISO setting 
           115  demosaicing step 
           120  resolution mode setting 
           125  color correction step 
           130  color mode setting 
           135  tone scale correction step 
           140  contrast setting 
           145  image sharpening step 
           150  sharpening setting 
           155  image compression step 
           160  compression mode setting 
           165  file formatting step 
           170  metadata 
           175  photography mode settings 
           180  digital image file 
           185  camera settings 
           200  exposure control system 
           210  assess scene brightness step 
           220  determine capture mode step 
           225  capture mode setting 
           230  determine exposure index step 
           235  exposure index setting 
           240  determine aperture step 
           245  aperture setting 
           250  determine exposure time step 
           255  exposure time setting 
           260  capture digital image step 
           265  digital image 
           300  power on device step 
           310  set zoom position step 
           315  focal length setting 
           320  determine exposure time step 
           325  exposure time setting 
           330  exposure time test 
           340  engage image stabilization step 
           350  capture digital image step 
           360  digital image 
           400  power on device step 
           410  set zoom position step 
           420  focal length setting 
           430  focal length test 
           440  engage image stabilization step 
           450  disengage image stabilization step