Abstract:
In one embodiment there is shown a method for capturing data, the method comprising sensing a first signal, capturing an auto exposure (AE) image in response to a sensed first signal, the auto exposure image captured with settings based upon preestablished criterion, and upon the AE image being captured, determining if a second signal has been sensed, and if the second signal has been sensed, capturing a speculative full exposure image, and if the captured speculative full exposure is determined to be acceptable, reading the remainder of the captured speculative image.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to establishing electronic data capture and more particularly to a system and method for image capture with respect to an electronic capture device.  
       DESCRIPTION OF RELATED ART  
       [0002]     It has become common practice with respect to image capturing devices to first focus the target image and then, when the focus is acceptable to the viewer, (either by looking through the main lens or through an auto-focus lens) capture the picture. In some systems, an auto focus system is employed to aid the user. Auto-focus systems typically begin with an out-of-focus image and the lens is adjusted by software control until the image is deemed “in-focus”.  
         [0003]     With digital cameras, focusing is performed automatically when the user pushes the camera&#39;s shutter control button. This button (as it is starting its operational trajectory) passes through a stage called the S1 stage. In the S1 stage, the camera, or other imaging device, begins to generate a test sequence of images, some or all of which are at different focus positions with respect to each other. The system then uses auto-focusing software to determine which one of the precaptured images is the “best” image, i.e. which image is the sharpest. In many situations, this focusing process takes between half second and one second, thus preventing the rapid capture of a fleeting event, or of a series of pictures.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     In one embodiment there is shown a method for capturing data, the method comprising sensing a first signal, capturing an auto exposure (AE) image in response to a sensed first signal, the auto exposure image captured with settings based upon preestablished criterion, and upon the AE image being captured, determining if a second signal has been sensed, and if the second signal has been sensed, capturing a speculative full exposure image, and if the captured speculative full exposure is determined to be acceptable, reading the remainder of the captured speculative image.  
         [0005]     In another embodiment there is shown a digital camera comprising; a shutter control, an adjustable focus lens, an image sensor for electronically capturing images based upon the focus position of the lens, a single image analysis routine for determining whether or not a captured image has acceptable focal quality, a multi-image analysis routine for determining the best focal quality from a series of images, and a selector for accepting an image based upon the single image routine when the focal quality of the image is acceptable and for accepting an image based upon the multi-imaging routine when the focal quality based upon the single image metric is not acceptable. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  shows a flow chart of one embodiment of a process for controlling image capturing;  
         [0007]      FIG. 2  shows an image chart of a multi-image auto-focusing system; and  
         [0008]      FIGS. 3 and 4  show an embodiment of an electronic image capturing device using the control process shown in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION  
       [0009]     Turning now to  FIG. 1 , there is shown flow chart  10  of one embodiment of a process for controlling image capturing. Some digital devices, such as digital camera  30 , ( FIG. 3 ) have two-position in-line shutter button  31 . The two positions are called the S1 and S2 positions. The first or S1 position is entered when the shutter button is pushed approximately half-way down. The second or S2 position is entered when the shutter button is pushed beyond the half-way point and usually to its fully stopped position.  
         [0010]     The S1 position allows the camera to focus and, if desired, to adjust for proper light exposure. The user, when satisfied that the target image is properly framed and/or focused, then pushes the shutter button to the S2 position to capture and store the desired image.  
         [0011]     In process  101 ,  FIG. 1 , the system determines if the shutter button has reached the S1 (first) position. When the shutter button reaches the S1 position, the image capture device, under control of process  102 , captures an auto exposure (AE) image. This AE image is taken either at the same focus position as was the most recent prior picture or at the hyperfocal length. For this discussion, the hyperfocal length is defined as a position somewhere between infinity and full close up. The AE image is typically every 5 th  or 7 th  row and is thus smaller and takes less time to read than it does to read a full field. On a typically 3-field interfaced CCD, each field contains every third row of exposure data and the fields must be read out one at a time. With CMOS sensors, the read out is randomly addressable and thus quicker to access. The AE resolution is sufficient for setting the exposure for subsequent AF or full exposures, but may not be of sufficient resolution for good focus measurement.  
         [0012]     The capture device should perform one or more AE exposures to know what apertures and exposure times will be needed for any later exposures, including the auto focus (AF) exposures. Short exposures will be “down in the noise”, while long exposures will saturate the sensor, yielding “blown out” data. The camera typically needs to operate over 20 stops of scene brightness, which is 2ˆ20 th , which is 1,000,000 to 1.  
         [0013]     So, AE is required before either (the speculative exposure) or the AF exposures. In this context, the speculative exposure is one field of the 3-field CCD. The invention describes taking the speculative exposure if the user has pressed from S1 to S2 by the time the AE exposure(s) are done, and before the normal AF exposures have started.  
         [0014]     Process  103  determines whether or not the shutter has been pressed to the S2 position. One reason for the S2 position not being sensed is because the user has paused at the S1 position. If S2 has not been sensed, then the system takes the AF exposure under control of process  110 . An AF exposure must have decent resolution for calculating a focus metric, but only for a center autofocus zone of the CCD or CMOS sensors. Since a CCD must clock out all its rows sequentially (whereas a CMOS sensor can be randomly read), a CCD camera exposes the CCD array and then begins the readout of the first field. The electronics quickly shifts and throws away the unneeded rows above and below the AF zone, but clocks out the rows containing the AF zone. So, AF uses one CCD field and uses special clocking to obtain just the AF zone read out, as quickly as possible.  
         [0015]     Process  111  uses a focus metric to determine if the autofocus exposure is sufficient. One system and method for achieving auto-focus using the S1 position is shown in  FIG. 2  where a series of images  1 - 12  are captured at different focus positions, starting, as shown, at infinity or at the hyperfocal point. The focus contrast metric is used to compare adjacent images against each other. So long as the metric is going up, as shown by line  201 , the next highest valued image is used. When the image value starts down, as shown with image  12 , the system determines that image  11  is the “best” in terms of focus. Note that false peaks, such as shown at image  8 , are taken into consideration, in a typical auto-focus process. These processes are now well-known, and can include, by way of example, creating a moving threshold underneath the focus metric curve. The metric must cross below the threshold to determine that the peak has been passed.  
         [0016]     Process  112  ( FIG. 1 ) determines whether the focus has peaked (as discussed above). If it has not peaked, then the lens is stepped (or otherwise refocused) under control of process  113  and new AF exposures are taken until processes  111  and  112  determine acceptability. Process  114  then returns the lens to the position of best focus.  
         [0017]     Process  115  waits for the shutter control to reach the S2 position. When the S2 position is reached, a full exposure is taken under control of process  116 . The AF process determines the settings that will capture the “best” image and it is these settings that are used for the full image capture.  
         [0018]     Branch  120  of the flow chart shows the processes in a traditional image capture device where there is a relatively long period of time between the detection of the S1 shutter position and the S2 shutter position.  
         [0019]     Returning to Process  103 , if the S2 shutter position is reached relatively quickly after the S1 shutter position is sensed, then process  104  controls the taking of a speculative full exposure.  
         [0020]     Process  105  reads out the AF field/region of the speculative exposure. Process  106  performs an analysis of focus, for example, using an edge analysis to determine if the image is in focus. The speculative exposure analysis is absolute, for example; by looking for any occurrence of edges. This is in contrast to the AF analysis (process  111 ) which is a relative process looking for the maximum of a contrast metric between a series of AF images, as discussed above. Process  107  determines if the image is in focus. If it is, the rest of the speculative exposure, the other fields (fields 2 and 3 in a 3 field system) are read out via process  108  and the image is captured. If, in process  107 , the focus is not acceptable, then branch  120  of flow chart  10  is followed as discussed above.  
         [0021]      FIG. 3  shows the front view of one embodiment of image capture device  30 . In this situation, the device is a digital camera having shutter control button  31 , lens  32 , alternate viewer  33 , and memory card  34  inserted in slot  301 . The image capture device could be a video camera, a PDA, cell phone or any device that determines good data (image data or otherwise) from poorer data. While the systems and methods discussed herein are presented with respect to image capturing, the same concepts can be used for the capture of other types of data where both fast and slower data capture modes are preset.  
         [0022]      FIG. 4  shows the back view of camera  30  having display  42  for showing captured (or about to be captured) images to the user. Inside the camera there is at least one sensor  44  that can be a CCD or other type of sensor for capturing the image. There is also shown the back portion  43  of the auxiliary window, as well as processor  41  and memory  45 . Memory  45  could, if desired, be separate from memory card  34 , and processor  41  could be used, if desired, to run the processes discussed above with respect to  FIG. 1 , as well as many other image control processes. Power for camera  30 , such as a battery, is not shown.