Patent Publication Number: US-2003234863-A1

Title: Environmental change auto-detection digital camera

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates in general to a digital camera. In particular, the present invention relates to an environmental change auto-detection digital camera.  
       [0003] 2. Description of the Related Art  
       [0004] Generally, in a conventional security system, a video recorder is used to continuously record an image of a scanned region and store the recorded video even if the images are changeless. Therefore, the conventional security system needs to provide power to the video recorder continuously, so the power consumption is substantial. Furthermore, most of the recorded video shows the same images repeatedly.  
       [0005] Typically, conventional digital cameras have a self-timer mode. For example, the camera will wait three or ten seconds after the shutter-release button is pressed before taking a picture. However, the memory in a conventional camera may fill quickly if the camera takes a picture every three or ten seconds without determining the images are the same. The camera will stop taking pictures when the memory is full, at which the camera will not record changes in the environment anymore. Furthermore, many identical pictures may be stored into the memory. In addition, the camera must be kept in a stand by mode if the camera takes a picture every one hour or more, such that power consumption also very large. If the camera is operating on battery power, the camera will stop taking pictures when power runs out. In this case, the camera cannot record changes in the environment anymore.  
       SUMMARY OF THE INVENTION  
       [0006] It is an object of this invention to provide an environmental change auto-detection digital camera and a method to detect environmental change.  
       [0007] In the present invention, the control unit stores the current image in the storage unit and replaces the reference image in the register with the current image for comparison in the next time only if the correlation the current image and the reference image does not exceed the predetermined a mount, and then turns off the digital image acquisition device. Therefore, the present invention can decrease power consumption and avoid repeatedly storing the same images into the memory. In this way, the present invention can record environmental change for a longer time.  
       [0008] The present invention is comprised of a timer unit, a digital image acquisition device, a control unit and a storage unit. The timer unit outputs an enable signal every predetermined interval. The digital image acquisition device acquires a current image. The storage unit stores image data, and the control unit enables the digital image acquisition device to acquire the current image when receiving the enable signal. Further the control unit then detects the correlation between the current image and a reference image in a register. The control unit stores the current image in the storage unit and replaces the reference image in the register with the current image if the correlation does not exceed the predetermined mount. Alternately, the control unit only replaces the reference image in the register with the current image if the correlation exceeds a predetermined amount.  
       [0009] In the method of the present invention, a current image is acquired every predetermined interval. Next, the correlation between the current image and a reference image in register is detected. The current image is stored in the storage unit and the reference image in the register is replaced with the current image if the correlation does not exceed a predetermined mount. Alternately, the reference image is replaced with the current image if the correlation exceeds the predetermined amount. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010]FIG. 1 is a schematic diagram illustrating the environmental change auto-detection digital camera of the present invention.  
     [0011]FIG. 2 shows a process flow of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0012]FIG. 1 is a schematic diagram illustrating the environmental change auto-detection digital camera of the present invention. The environmental change auto-detection digital camera  100  of the present invention is comprised of a timer unit  10 , a digital image acquisition device  20 , a control unit  40  and a storage unit  30 . The timer unit  10  outputs an enable signal En 1  every predetermined interval. The digital image acquisition device  20  acquires a current image. The storage unit  30  stores image data, and the control unit  40  enables the digital image acquisition device  20  to acquire the current image when receiving the enable signal En 1 . Further the control unit  40  then detects the correlation between the current image and a reference image. The control unit  40  stores the current image into the storage unit  30  and replaces the reference image with the current image if the correlation does not exceed the predetermined mount. Alternately, the control unit  40  only replaces the reference image with the current image if the correlation exceeds the predetermined mount.  
     [0013] The timer unit  10  outputs an enable signal every predetermined interval T. For example, the predetermined interval T can be  5 ,  10 ,  30 ,.  60  or  90  seconds, and the predetermined interval is adjusted by the timer unit according to the user&#39;s requirement.  
     [0014] The digital image acquisition device  20 , for example, is a digital camera that has image capture device such as a CMOS sensor and the like. The digital image acquisition device  20  wakes up to acquire a current image after the control unit  40  receives the enable signal En 1 . The storage unit  30  can be any type of memory for storing image data. In this case of the present, the storage unit  30  is a static random access memory.  
     [0015] In this embodiment, the control unit is a microprocessor coupled to the timer unit  10 , digital image acquisition device  20  and the storage unit  30 . In additional, the control unit  40  further comprises a register  50  for storing the reference image.  
     [0016] The control unit  40  enables the digital image acquisition device to wake up for acquiring a current image after receiving the enable signal En 1 . Next, the control unit  40  detects the correlation between the current image and the reference image. The control unit  40  stores the current image into the storage unit  30  and replaces the reference image in the register  50  with the current image for comparison in the next time if the correlation does not exceed a predetermined a mount. Alternately, the control unit  40  only replaces the reference image with the current image for comparison in the next time if the correlation exceeds the predetermined mount.  
     [0017] The control unit  40  further outputs an alarm signal and turns off the digital image acquiring device  20  when the storage unit  30  is full. Moreover, the environmental change auto-detection digital camera  100  of the current image also comprises a voice unit (not shown), for example, a speaker to broadcast an audio signal, for example a voice message.  
     [0018] If the correlation between the current image and the reference image exceeds predetermined a mount, then the frame difference between the current image and the reference image is small. In this case, most of the pixel data in the current image is the same as the pixel data in the reference image, e.g., the current image is similar to the reference image. Alternately, if the correlation between the current image and the reference image does not exceed the predetermined mount, then frame difference between the current image and the reference image is large. In this case, most of the pixel data in the current image is different from the pixel data in the reference image, e.g., the current image is different from the reference image. According to the present invention, the control unit  40  stores the current image into the storage unit  30  and replaces the reference image in the register  50  with the current image for comparison in the next cycle if the correlation does not exceed the predetermined mount. Alternately, the control unit  40  only replaces the reference image with the current image for comparison in the next cycle if the correlation exceeds the predetermined mount. Therefore, different images may are stored into the memory, but identical or nearly-identical are not. Of course the correlation between two images can be adjusted according to different applications. In this case, the current image and the reference image are both digital image data.  
     [0019] Turning to FIG. 2, FIG. 2 shows a process flow of the present invention. In this case of the present invention, the predetermined interval is 15 seconds. The timer unit  10  outputs an enable signal every 15 seconds to wake up the digital image acquisition device  20 . In step  11 , the digital image acquisition device  20  acquires a current image immediately after receiving the enable signal. Next, in step  12 , the control unit  40  detects the relation between the current image and a reference image. In the step  13 , the reference image in the register is replaced with the current image if the correlation exceeds a predetermined amount. Alternately, the current image is stored in the storage unit and is replaced the reference image in the register with the current image if the correlation does not exceed the predetermined mount. The control unit  40  then enables the digital image acquisition device  20  to turn off to wait next 15 seconds. Wherein, the control unit  40  outputs an alarm signal to a voice unit to broadcast a voice message when the current image cannot be stored in the storage unit  30 , for example, the storage unit is full, and then turns off the digital image acquiring device  20 .  
     [0020] Therefore, the present invention only stores different images into the memory, thereby avoiding the memory being filled quickly. Further, the present invention turns off after replacing the reference image parameter by the current image parameter such that the present invention does not stay in the stand by mode all the time, thereby decreasing power consumption.  
     [0021] Finally, while the invention has been described by way of example and in terms of the preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.