Patent Publication Number: US-2005122406-A1

Title: Digital camera system and method having autocalibrated playback viewing performance

Description:
TECHNICAL FIELD  
      The present invention relates generally to digital cameras and methods.  
     BACKGROUND  
      Digital cameras certainly have come of age when it comes to capturing and instantly reviewing photographs. More and more however, digital cameras are often used as a sharing device for showing pictures stored in the camera with friends and family. Many times this is done using a video output port of the camera and a conventional television.  
      Shop at any major retailer (Wal-Mart, Circuit City, Best Buy, for example) and it is clear no two televisions are the same. As is clear from looking at the large number of televisions that are on display at these stores, colors can vary dramatically, and contrast often times needs adjustment, for example.  
      In general, conventional televisions vary significantly in terms of color performance, brightness, and contrast, for example. It would be desirable to calibrate out those variances, to the extent possible, when viewing photographs or video stored in a digital camera. There are no know conventional solutions that address this problem.  
     SUMMARY OF THE INVENTION  
      The present invention comprises a system and method having a digital camera that is coupled to a television that cooperate to calibrate and optimize the image displayed on the television. The digital camera comprises a video output port, an image sensor, a display, a lens and processing circuitry. The digital camera stores a television color bar. The digital camera has autocalibration firmware (a software algorithm) comprising a user interface that is used to automatically calibrate the video signal sent from the digital camera to the television so that the television displays the best possible images to a viewer.  
      The firmware, by way of the user interface, prompts the user to point the camera at the television. The digital camera outputs the color bar by way of the output port to the television, which is displayed. Once pointed at the television, the image sensor views the color bar displayed on the television, and the firmware automatically detects the imaged color bar. The firmware automatically adjusts (calibrates) the video signal output to the television until an optimal displayed image has been achieved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The various features and advantages of embodiments of the present invention may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which:  
       FIGS. 1   a  and  1   b  are rear and front views, respectively, of an exemplary digital camera that may be used in a system in accordance with the principles of the present invention;  
       FIG. 2  illustrates an exemplary system in accordance with the principles of the present invention; and  
       FIG. 3  illustrates an exemplary method in accordance with the principles of the present invention. 
    
    
     DETAILED DESCRIPTION  
      Referring to the drawing figures,  FIGS. 1   a  and  1   b  are rear and front views, respectively, of an exemplary digital camera  10  implemented in accordance with the principles of the present invention. As is shown in  FIGS. 1   a  and  1   b , the exemplary digital camera  10  comprises a handgrip section  20  and a body section  30 . The handgrip section  20  includes a power button  21  or switch  21  having a lock latch  22 , a record button  23 , a strap connection  24 , and a battery compartment  26  for housing batteries  27 . The batteries may be inserted into the battery compartment  26  through an opening adjacent a bottom surface  47  of the digital camera  10 .  
      As is shown in  FIG. 1   a , a rear surface  31  of the body section  30  comprises a liquid crystal display (LCD)  32  or viewfinder  32 , a rear microphone  33 , a joystick pad  34 , a zoom control dial  35 , a plurality of buttons  36  for setting functions of the camera  10  and a video output port  37  for downloading images to a computer, for example. As is shown in  FIG. 1   b , a zoom lens  41  extends from a front surface  42  of the digital camera  10 . A metering element  43  and front microphone  44  are disposed on the front surface  42  of the digital camera  10 . A pop-up flash unit  45  is disposed adjacent a top surface  46  of the digital camera  10 .  
      An image sensor  11  is coupled to processing circuitry  12  (illustrated using dashed lines) that are housed within the body section  30 , for example. An exemplary embodiment of the processing circuitry  12  comprises a microcontroller (μC)  12  or central processing unit (CPU)  12 . The (μC  12  or CPU  12  is coupled to a nonvolatile (NV) storage device  14 , and a high speed (volatile) storage device  15 , such as synchronous dynamic random access memory (SDRAM)  15 , for example.  
      The processing circuitry  12  (microcontroller (μC)  12  or CPU  12 ) in the digital camera  10 , embodies firmware  13  comprising an autocalibration algorithm  13  in accordance with the principles of the present invention. This will be discussed in more detail with reference to  FIGS. 2 and 3 .  
       FIG. 2  illustrates an exemplary system  50  in accordance with the principles of the present invention. The exemplary system  50  comprises a digital camera  10 , such as the digital camera  10  discussed with reference to  FIGS. 1   a  and  1   b , for example, that is coupled to a television  51 . The television  51  has a screen  52 . The digital camera  10  is coupled to a television  51  by way of a cable  54 , such as a coaxial cable or composite video cable, for example.  
      In accordance with the present invention, the digital camera  10  includes a user interface  55  implemented using the autocalibration firmware  13  (or software algorithm  13 ) that runs on the processing circuitry  12  (microcontroller (μC)  12  or CPU  12 ). A standard television color bar  53 , which may be a stored image or picture, for example, is stored in the digital camera  10 . The television color bar  53  may be stored in the nonvolatile storage device  14 , for example.  
      The autocalibration firmware  13  is designed to automatically calibrate the video signal sent from the digital camera  10  to the television  51  so that the television  51  displays the best possible images to a viewer.  
      The firmware  13 , by way of the user interface  55 , prompts the user to point the digital camera  10  at the television  51 . The digital camera  10  outputs a color bar  53  by way of the output port  37  to the television  51 , which are displayed on the television screen  52 . Once pointed at the television  51 , the lens  41  and image sensor  11  views the color bar  53  displayed on the television screen  52 , and the firmware  13  automatically detects the imaged color bar  53 .  
      The firmware  13  automatically adjusts the video signal output to the television  51  until an optimal displayed image of the color bar  53  has been achieved. This adjustment is described in the next paragraph. When finished with this autocalibration procedure, a sample image (a selected stored picture, for example), may be displayed to the user on the television screen  52  to verify the change from the image displayed prior to autocalibration.  
      Adjustments in each of the colors is made. Color in the camera  10  is usually stored in an R,G,B pixel value. At some point, this RGB data is converted to TV standard YCbCr data. There are very standard methods for this transformation across the color spaces. During this transformation, data that was obtained from the color-calibration process is used in various ways. For example, if the green color on the TV looks a little to hued, then during the transformation, additional saturation of the green RBG data would be performed before the transformation, or saturation to the green channel would be added while in the YCbCr color space. Doing this directly in YCbCr is a good way to accomplish this because pictures are typically stored in this fashion (a .jpg image is YCbCr). Similarly if the Red color bar appears more yellow or orange than it should, then the same adjustments would be made in the Red channel of every pixel within the image to make each pixel have the value of red that would best be represented on the television  51 .  
      Thus, by using a mechanism such as a color bar  53 , for example, and using the lens  41  and sensor  11  of the digital camera  10 , autocalibration of the system  50 , and in particular, the video signal supplied to the television  51 , is achieved to optimize colors, brightness and provide the best picture and video sharing experience possible.  
      In addition, the video output port  37  of the digital camera  10  causes variances in the displayed image. The present invention calibrates out the television-related variances and also simultaneously calibrates out problems caused by the video output port  37 . Generally, the in-camera variances caused by the video output port  37  are minimal or negligible compared to the television-related variances, but they are there none-the-less.  
      For the purposes of completeness,  FIG. 3  illustrates an exemplary method  60  in accordance with the principles of the present invention. The exemplary method  60  comprises the following steps.  
      A digital camera  10  is provided 61 that comprises a lens  41 , an image sensor  11 , a display  32 , a video output port  37 , and processing circuitry  12 . A television  51  is provided 62. The digital camera  10  is coupled  63  to a television  51 , such as by using its output port  37  and a cable  54 , for example. A standard television color bar  53  is stored  64  in the digital camera  10 .  
      The digital camera  10  is configured  65  with autocalibration firmware  13  that runs on the processing circuitry  12 . When initiated  66 , the autocalibration firmware  13  prompts  67  the user to point the digital camera  10  at the television  51 , displays  68  the color bar  53  on the television  51 , images  69  the color bar  53  displayed on the television  51  onto the image sensor  11 , detects  70  the imaged color bar  53 , and automatically calibrates  71  the video signal sent from the digital camera  10  to the television  51  to display the best possible image on the television  51  to a viewer. Optionally, and in addition, a sample image may be displayed  72  to the user on the television  51 .  
      Thus, by using a mechanism such as a color bar, for example, and using the lens and sensor of the digital camera, autocalibration of the video signal is readily achieved to optimize colors, brightness and provide the best picture and video sharing experience possible.  
      Advantages provided by the present invention are that this solution provides better color reproduction for a given television than any known prior solution that uses the exact same video signal for all televisions.  
      Thus, digital cameras and methods that provide autocalibration for playback viewing and performance have been disclosed. It is to be understood that the above-described embodiments are merely illustrative of some of the many specific embodiments that represent applications of the principles of the present invention. Clearly, numerous and other arrangements can be readily devised by those skilled in the art without departing from the scope of the invention.