Abstract:
Digital cameras and methods that provide for a rapid camera power-on sequence. A warm-sleep state is defined in which the camera and nearly all of its internal components are shut down, yet just enough information is retained within high speed volatile storage and processing units to rapidly return the camera to full operating state. The warm-sleep state is managed to consume a minimum amount of power to keep the vital information intact. Upon receipt of a power-on indication, the camera then transitions from the warm-sleep state to full operation by simply activating the processing units, and continuing operation from the state it was in immediately prior to the power-off request.

Description:
TECHNICAL FIELD 
   The present invention relates generally to digital camera systems and related methods. 
   BACKGROUND 
   The power-on sequence for a conventional digital camera typically requires numerous time-consuming operations that classically take many seconds to complete. This sequence of operations must be completed before the camera is ready to begin operations to take a picture. Most cameras on the market today have a power-on time that is greater than 3 seconds, and often is longer than that. Customers are often dissatisfied with the relatively slow power-on time of digital cameras. It would be desirable to have a method that dramatically reduces the length of time between the time when a user turns the camera on and the time when the first picture may be taken. 
   The power-on lag is very frustrating to camera users because they want to be able to recognize a photo opportunity, turn the camera on, and take the picture immediately. Often the power-on lag is long enough that the moment is lost and they have missed the opportunity to take the picture because the scene or something within it has changed. 
   In prior solutions, when a camera power-down indication is given by the power switch, the camera retracts the lens, then terminates all operation in internal processing systems. Power is shut off to all of the camera processing systems with the exception of a power switch monitoring component. This brings the camera to the lowest possible power consumption state. 
   A number of patents have issued that relate to waking-up computers and digital cameras from a low power state. For example, U.S. Pat. No. 6,308,278 discloses “Supplying standby voltage to memory and wakeup circuitry to wake a computer from a low power mode.” 
   U.S. Pat. No. 6,002,436 discloses a “Method and system for auto wake-up for time lapse image capture in an image capture unit.” It is stated in U.S. Pat. No. 6,002,436 that “A system and method for time-lapse capture according to the present invention comprises capturing a first image automatically; initiating a sleep mode after capturing the first image; and transitioning from the sleep mode into a wake mode prior to capturing a second image.” 
   U.S. Pat. No. 5,920,726 discloses a “System and method for managing power conditions within a digital camera device.” U.S. Pat. No. 5,920,726 discusses powering up a digital camera. 
   U.S. Pat. No. 6,031,964 discloses a “System and method for using a unified memory architecture to implement a digital camera device” and discusses “method steps for performing a power-up sequence” for the digital camera. 
   U.S. Pat. No. 6,282,665 discloses a “Method and apparatus to reduce power consumption on a bus” by “placing a node in a standby state.” 
   However, none of these patents specifically address apparatus or methods for use with a digital camera that reduces the time between camera power-on and the time when the first picture may be taken. 
   SUMMARY OF THE INVENTION 
   The present invention comprises digital cameras and methods that provide for a rapid camera power-on sequence. The present invention reduces the time between camera power-on and the time when the first picture may be taken. 
   In accordance with an embodiment of the present invention, a warm-sleep state is defined in which the camera and nearly all of its internal components are shut down, yet just enough information is retained within high speed volatile storage and processing units to rapidly return the camera to full operating state. The warm-sleep state is managed to consume a minimum amount of power to keep the vital information intact. Upon receipt of a power-on indication, the camera then transitions from the warm-sleep state to full operation by simply activating the processing units, and continuing operation from the state it was in immediately prior to the power-off request. 

   
     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 embodiment of a digital camera in accordance with the principles of the present invention; 
       FIG. 2  is a flow diagram that illustrates a conventional power-up sequence employed in a digital camera; 
       FIG. 3  is a flow diagram that illustrates steps in an exemplary embodiment of a power-down sequence or method in accordance with the principles of the present invention; and 
       FIG. 4  is a flow diagram that illustrates steps in an exemplary embodiment of a warm-boot sequence or 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 embodiment of a digital camera  10  in accordance with the principles of the present invention. The exemplary digital camera  10  will also be discussed in conjunction with a conventional power-up sequence  50  illustrated in  FIG. 2 . 
   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  45 , 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 an 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) 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 CPU  12  is coupled to a nonvolatile (NV) storage device  14 , a temporary (TEMP) removable storage device  15 , such as a secure digital (SD) card  15 , a memory stick, an multimedia card, a compact flash card or other removable non-volatile storage  15 , and a high speed (volatile) storage device  16 , such as synchronous dynamic random access memory (SDRAM)  16 . 
   As is shown in  FIG. 1   b,  a power switch monitoring component (PMC)  17  is provided that is used to monitor depression of the power switch. The power switch monitoring component (PMC)  17  may be provided by the processing circuitry  12  (μC or CPU), or may be a separate component as is illustrated in  FIG. 1   b.    
   In the conventional digital camera  10 , the processing circuitry  12  (microcontroller (μC)  12  or CPU  12 ) embodies a processing algorithm  13  that implements the conventional power-up sequence  50 . This will be discussed in more detail with reference to  FIG. 2 . 
   In the present digital camera  10 , the processing circuitry  12  (microcontroller μC)  12  or CPU  12 ) embodies a processing algorithm  13  that is used to implement power-down and warm-boot sequences in accordance with the principles of the present invention. These will be discussed in more detail with reference to  FIGS. 3 and 4 . 
   Referring to  FIG. 2 , it is a flow diagram that illustrates the conventional power-up sequence  50  employed in a conventional digital camera  10 . When the camera power-down indication is given by the power switch  21 , the camera  10  retracts the zoom lens  41 , then terminates all operation in internal processing systems. Power is shut off to all of the camera processing systems with the exception of the power switch monitoring component (PMC)  17  (or the processing circuitry  12 ). This brings the camera  10  to the lowest possible power consumption state, which is a cold power down state  51 . 
   Turning the conventional digital camera  10  on requires the following steps: 
   1. Power busses are activated  53  and power is applied to the CPU  12  when depression of the power switch  21  is detected  52  by the (μC or CPU  12 ). 
   2. The CPU  12  is reset  54  by performing a cold boot  55 . 
   3. The CPU begins executing firmware  56  stored in a nonvolatile (NV) storage device  14 . The first firmware to execute is commonly referred to as a bootloader. 
   4. The bootloader evaluates criteria to (a) determine if it should update  57  the firmware, and if so, download  58  new firmware into the nonvolatile storage device  14  from the temporary removable storage device  15  and returns to the cold power down state  51 , and (b) determine  61  whether or not to load firmware from the temporary (TEMP) removable storage device  15  (SD card  15 ), wherein it loads  62  (copies  62 ) operational firmware from the nonvolatile storage device  14  into the SDRAM  16 , or loads  63  (copies  63 ) operational firmware from the temporary (TEMP) removable storage device  15  (SD card  15 ) into the SDRAM  16 . 
   5. The bootloader loads  62  (copies  62 ) firmware stored in the nonvolatile storage device  14  into a high speed storage device  16 , such as the synchronous dynamic random access memory (SDRAM)  16 , or loads  63  (copies  63 ) firmware stored in the temporary removable storage device  15  into a high speed storage device  16 . 
   6. The bootloader jumps  64  the CPU  12  to the start point of the firmware. 
   7. The firmware initiates  65  the operating environment including copying initialized variable values from the nonvolatile storage device  14  into the high speed storage device  16 , clearing all zeroed variable values in the high speed storage device  16 , setting all initial operating values in the CPU  12  such as stack pointers, and initializing the operating system. 
   8. The operating system initializes  66  all of operating firmware including: establishing each of the initial tasks for operation including their individual stacks, establishing the heap, and initializing system services. 
   9. Tasks begin operating to accomplish normal operation  76  such as ASIC configuration,  67 , wakeup  68  for dock operation  77 , lens extension  71 , base zoom and focus  72 , startup  73  of liveview, startup  74  of the imaging system and the LCD  32 , and startup  75  of a user interface displayed on the LCD  32 . Normal operation  76  then commences. Liveview is a presentation of the scene the camera views as a continuous live display on the LCD  32 , which is an electronic representation of the view through the viewfmder  45 . 
   As was mentioned previously and as should be clear from the above discussion, completion of these numerous operations requires many seconds causing the power-on lag time that is experienced using the digital camera  10 . In order to overcome this limitation, the present invention reduces the time between camera power-on and the time when the first picture may be taken. 
   The present digital camera  10  and processing sequences  90 ,  100  that implement a method  80  in accordance with the principles of the present invention are illustrated in  FIGS. 3 and 4 .  FIG. 3  is a flow diagram that illustrates steps in an exemplary embodiment of a power-down sequence  90 , (or warm-sleep sequence  90 ) or method  90  in accordance with the principles of the present invention, and  FIG. 4  is a flow diagram that illustrates steps in an exemplary embodiment of a warm-boot sequence  100  or method  100  in accordance with the principles of the present invention. 
   Referring to  FIG. 3 , the digital camera  10  starts in normal operation  76 . When a power down indication is given by the power switch  21  where activation of the power switch  21  is detected  91  by the power switch monitoring component  17 , or the CPU  12 , for example, the camera  10  (via the CPU  12  and processing algorithm  13 ) initiates the warm-sleep sequence  90  instead of a full power-down sequence. The warm-sleep sequence  90  may be implemented as a specific task within the operating environment, for example. 
   For the purposes of the present description, the power switch monitoring component  17  comprises the microcontroller (μC)  12 , which is only for purposes of illustration. The power switch monitoring component  17  may also be a separate circuit that interfaces the power switch  21  to the microcontroller (μC)  12  or CPU  12  that performs the desired monitoring function. 
   In implementing the warm-sleep sequence  90 , the zoom lens  41  is retracted  92 , and images located in image buffers of the SDRAM  16  are processed  93  to completion. The volatile storage device  16  is placed  95  into a low-power self-sustaining state. This may be accomplished, for example, by placing  95  the SDRAM  16  into a self refresh mode. The power supplies for all components except the SDRAM, CPU, and power switch monitoring component  17  are turned off  96 . The CPU is then instructed  97  to go into a low power consumption halt state, which puts the camera  10  in a warm-sleep state  98 . The power switch monitoring component  17  may optionally be pre-configured to wake  94  the CPU  12  after a specified length of time has elapsed. 
   Referring to  FIG. 4 , the digital camera  10  is in the warm-sleep state  98 . Upon detection  101  of activation of the power switch  21  or reaching the pre-configured timeout  102  of the wakeup monitor, the power switch monitoring component  17  wakes  103  the CPU  12  and brings it out of the halt state. The CPU  12  automatically continues operation  104  of its firmware at the next instruction in the warm-sleep sequence  90 . The warm-sleep sequence  90  determines or evaluates  105  the cause of wakeup. If the cause is a result of the preconfigured timeout, the firmware executes a full power-down sequence and shuts down  106  all power supplies except the CPU  12  and enters a cold power down state  51 . If the wakeup cause is a result of power switch activation, the firmware executes a shortened power-up sequence in accordance with the present invention. This sequence is shorter than the full power-up sequence discussed above, because steps 1 through 8 discussed with reference to  FIG. 2  do not need to be accomplished. 
   Thus, if the wakeup cause is a result of power switch activation, the SDRAM  16  is configured  108  to refresh the CPU  12 . Then the power busses are activated  109  to fully power the CPU  12  and other necessary components. 
   Once the power busses are activated  109 , the warm boot sequence running on the CPU  12  determines  57  if the firmware should be updated. If it does (YES), a cold boot  55  is performed and the firmware is updated. If the firmware does not have to be updated (NO), the warm boot sequence determines  61  whether or not to load firmware from the temporary (TEMP) removable storage device  15  (SD card  15 ). If it does (YES), a cold boot  55  is performed and the firmware is loaded from the SD card  15 . If the firmware does not have to load firmware from the SD card  15 , (NO), it is determined if the camera  10  must wakeup  68  for dock operation. If it does (YES), a cold boot  55  is performed and dock operation is commenced. If dock operation is not required (NO), then lens extension  71 , base zoom and focus  72 , startup  73  of liveview and imaging system, startup  74  of the and the LCD  32 , and startup  75  of a user interface displayed on the LCD  32 . Normal operation  76  of the digital camera  10  then commences. 
   Since the CPU  12  never totally shuts down, it&#39;s registers are intact with their values from prior to the warm-sleep state  98 , the contents of the firmware in the SDRAM  16  and the contents of the stack, heap, and other values are intact in the SDRAM  16 . The CPU  12  continues from the next instruction after the halt  97 , effectively the same as if it had never gone to sleep. Therefore, the warm-sleep sequence  90  only needs to perform the operations in step  9  discussed with reference to  FIG. 2 . 
   Additional logic may be implemented as part of the method  80  to make intelligent decisions regarding the warm-sleep timeout based on the situation. For example, if the camera  10  is plugged into a power supply, the warm-sleep timeout may be indefinite since power savings is not a concern. This provides instant-on functionality on a retail store shelf, for example, providing a demonstration of maximum performance. 
   Furthermore, the warm boot sequence  100  described with reference to  FIG. 4  includes checks for firmware update  57  and dock connection  68 . It is to be understood that these checks are not absolutely required to implement the present invention, but are clearly beneficial to a complete power management solution and can easily be incorporated into the invention as depicted in  FIG. 4 . 
   Using the present invention, the camera  10  may remain in the warm-sleep state almost indefinitely or for a predetermined period of time, then transition into the full powered down state. This timeout can be specified by a user, may be pre-defined using well-understood common camera use procedures, or can be learned by the camera  10  by monitoring a user&#39;s common use patterns. 
   The present invention thus provides a digital camera  10  embodying a method  80  that enables reduced power-on time, which is typically less than a second, limited primarily by the length of time necessary to extend the lens  41 . For a digital camera  10  that has a very fast lens  41 , for example, by using the present invention, the camera  10  can be turned on and be ready to take a picture in approximately ¾ of a second. 
   Using the present invention, digital cameras  10  have a power-on time that is shorter than the time necessary to move the camera  10  from a hand position when it deflects the power switch up to a photo-taking position. Thus, the camera  10  turns on nearly instantaneously for use, enabling the user to immediately capture a picture, thereby addressing this significant source of user dissatisfaction. 
   Thus, it should be clear that the present invention significantly reduces camera  10  power-on time so that the user can rapidly take a picture after power-on without having to wait numerous seconds and miss the photo opportunity. The present invention implements this power-on time reduction without the loss of any secondary power-on states. 
   The present invention accomplishes the power-on time reduction, yet can easily transition into a cold power-down state after a designated period of time if the user has not used the camera  10  during that period of time. This saves battery power when the camera  10  is no longer in use. 
   Thus, digital cameras and methods that provide for rapid power-on to first picture 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.