Patent Publication Number: US-2005122407-A1

Title: Image-taking apparatus, image-taking system and control method of image-taking apparatus

Description:
This application claims priority from Japanese Patent Application No. 2003-410943 filed on Dec. 9, 2003, which is hereby incorporated by reference herein.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an image-taking apparatus, and more particularly, to an image-taking apparatus provided with a detection circuit which detects movement of an object and an image-taking system having the image-taking apparatus and control method of the image-taking apparatus.  
      2. Description of the Related Art  
      As a conventional monitoring camera system, a technology which changes a compression ratio of communication information generated based on an image taken when abnormality is detected is disclosed (e.g., see Japanese Patent Application Laid-Open No. 2002-245571).  
      However, since an image-pickup device has low resolution comparable to a video level, it is neither possible to obtain an image with high resolution nor possible to decide the object to be monitored correctly.  
      Furthermore, a method of moving a monitoring camera to a monitoring target by driving a pan head which is a driving apparatus of the monitoring camera, etc., and zooming in on the object to take close-ups, etc., is proposed.  
      However, this method identifies a target object, drives a pan head to the target object first, and then zooms in on the target object using a zoom lens, etc., and carries out an image-taking operation, and therefore this method takes time until image-taking is started, which may miss the right moment for image-taking of the target object.  
      Therefore, it is an object of the present invention to provide an image-taking apparatus, an image-taking system and a control method of the image-taking apparatus capable of immediately taking a detailed image when a problem occurs and taking the whole image.  
     SUMMARY OF THE INVENTION  
      One aspect of the image-taking apparatus of the present invention includes an image-pickup device which has a plurality of pixels, a control circuit which controls the driving of the image-pickup device and a detection circuit which detects movement of an object in an image-taking area based on an image signal generated using the image-pickup device. The control circuit controls the driving of the image-pickup device so as to take an image using a first number of pixels when the detection circuit does not detect any movement of the object and take an image using a second number of pixels which is greater than the first number of pixels when some movement of the object is detected.  
      The features of the image-taking apparatus of the invention will become more apparent from the following detailed description of a preferred embodiment of the invention with reference to the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a functional block diagram of an image-taking system; and  
       FIG. 2  is a functional block diagram of a monitoring camera and an image processing apparatus.  
       FIG. 3  is a flow chart which shows the control method of a monitoring camera apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      With reference now to  FIG. 1  and  FIG. 2 , an image-taking system which is an embodiment of the present invention will be explained. Here,  FIG. 1  is a block diagram of an image-taking system of this embodiment and  FIG. 2  is a functional block diagram of a monitoring camera.  
      In these figures, reference numeral  10  denotes a monitoring camera, which performs an image-taking operation based on an output signal from a camera control circuit  104  which will be described later. Reference numeral  11  denotes an image processing apparatus which processes an image-taking signal output from the monitoring camera  10 , details of which will be described later.  
      Reference numeral  13  denotes a control signal decoder section which demodulates a control signal sent from a monitoring terminal apparatus  2  which will be described later, and reference numeral  14  denotes a camera-side transmission/reception apparatus which is an I/F which communicates with a monitoring terminal apparatus which will be described later.  
      A monitoring camera apparatus  1  (image-taking apparatus) is constructed of these monitoring camera  10 , image processing apparatus  11 , control signal decoder section  13  and camera-side transmission/reception apparatus  14 .  
      Reference numeral  20  denotes a host-side transmisslon/reception apparatus which communicates with the camera-side transmission/reception apparatus  14 ,  21  denotes an image expansion section which expands a compressed image signal sent from the monitoring camera apparatus  1 , and  22  denotes a control signal encoder section which sends a control signal which controls the monitoring camera apparatus  1  to the host-side transmission/reception section  20 .  
      Reference numeral  23  denotes a terminal control circuit which controls the entire monitoring terminal apparatus  2 ,  24  denotes an image processing section which converts the image signal expanded by the image expansion section  21  to a displayable signal and  25  denotes a recording apparatus which records a video signal output from the image processing section  24 .  
      Reference numeral  26  denotes an operation panel which operates the terminal control circuit  23  from the outside,  27  denotes a monitor which displays the image signal converted by the image processing section  24  as an image-taking image, and  30  denotes a network line which connects the monitoring camera apparatus  1  and monitoring terminal apparatus  2 .  
      The monitoring terminal apparatus  2  is constructed of the host-side transmission/reception apparatus  20 , image expansion section  21 , control signal encoder section  22 , terminal control circuit  23 , image processing section  24 , recording apparatus  25 , operation panel  26  and monitor  27 .  
      Next, details of the structure of the monitoring camera  10  will be explained.  
      Reference numeral  101  denotes an image-pickup device which converts an optical signal condensed by a lens unit which will be described later to an electric signal. This embodiment uses a CCD as the image-pickup device, but a CMOS image sensor, for example, may also be used.  
      Reference numeral  102  denotes a CCD signal processing section which converts an image-taking signal photoelectrically converted by the CCD  101  to an image signal, and  103  denotes a TG/VD as a timing generator/vertical driver which drives the CCD  101 . Reference numeral  104  denotes a camera control circuit (control means) which controls the entire monitoring camera  10 , and  105  denotes a lens unit which condenses reflected light from the object onto the image-taking surface of the CCD  101 .  
      Next, the structure of the image processing apparatus  11  will be explained.  
      Reference numeral  111  denotes a selector section which selects and outputs an image area, and  112  denotes an image compression section which compresses an image signal output from the selector section  111 .  
      Reference numeral  113  denotes an image coding section which converts the image signal compressed by the image compression section  112  to a signal suitable for communication,  114  denotes a movement detection circuit which causes a memory  115  to store the image signal from the signal processing section  102 , calculates a difference between the image signal read from this memory  115  and a newly input image signal to detect the movement of the object.  
      Reference numeral  115  denotes a memory which stores the image signal outputted from the movement detection circuit  114 , and  116  denotes an area specification section which specifies an area of the image signal compressed based on the signal from the movement detection circuit  114 .  
      In this embodiment, the monitoring camera  10  is separated from the image processing apparatus  11 , but the monitoring camera  10  may also be constructed of the CCD  101 , camera control circuit  104  and image processing apparatus  11 .  
      Next, the operation of the image-taking system will be explained with reference to  FIG. 1 . The image-taking system of the present embodiment is constructed so as to be able to switch between a normal monitoring mode (mode  1 ) and abnormality monitoring mode (mode  2 ) and changes the number of pixels read from the CCD  101  according to each mode.  
      With reference to  FIG. 3 , the operation of the image-taking system in a normal monitoring mode and an abnormality monitoring mode will be explained. Control of the monitoring camera apparatus is performed by the camera control circuit  104 , control of the monitoring terminal apparatus is performed by the terminal control circuit  23 . First, the operation of the image-taking system in a normal monitoring mode will be explained.  
      The signal photoelectrically converted by the CCD  101  is converted to a video signal by the signal processing section  102 . Here, in the normal monitoring mode, the CCD  101  is driven in a high-speed draft mode and in this high-speed draft mode, image-taking pixels are selected from among the image-taking pixels of the CCD  101  by the TG of the TG/VD  103  at predetermined intervals in the vertical direction and a video signal is generated based on color signals (R, G/B, G) output from the selected image-taking pixels (S 102 ).  
      With regard to the video signal generated by the signal processing section  102 , pixels in the horizontal direction are selected by the selector section  111 , while the area is not selected and sent to the image compression section  112 . That is, the image-taking pixels of the CCD  101  in the vertical direction are selected during a CCD read, while image-taking pixels in the horizontal direction are selected by the selection section  111  after the video signal is sent to the image processing apparatus  11 .  
      The image compression section  112  attaches the monitoring image information in a normal mode whose area is not specified to the start of the compressed image and compresses the image (S 103 ), and then the image coding section  113  divides the compressed information into blocks of a predetermined amount of information and outputs the information to the camera-side transmission/reception apparatus  14  (S 104 ).  
      The block-divided compressed information is sent from the camera-side transmission/reception apparatus  14  to the host-side transmission/reception apparatus  20  through a network line  30  and reunited as one piece of compressed image information. The reunited compressed image information is sent to the image expansion section  21 , expanded and demodulated into a displayable video signal (S 105 ).  
      The demodulated video signal is sent to and displayed on the monitor  27  and recorded in the recording apparatus  25  (S 106 ).  
      Next, the operation of the image-taking system in an abnormality monitoring mode will be explained.  
      When the movement detection circuit  114  detects some movement of the object based on the difference between the image information recorded in the memory  115  and newly input image information (S 101 ), a detection signal is output from the movement detection circuit  114  to the camera control circuit  104  (S 110 ).  
      The camera control circuit  104  switches the drive mode of the TG/VD  103  from the normal monitoring mode to the abnormality monitoring mode based on the detection signal output from the movement detection circuit  114  (S 111 ). When the drive mode is changed to the abnormality monitoring mode, the image-taking mode is set to a so-called full pixel read mode and all image-taking signals from the CCD  101  are read and output to the signal processing section  102  (S 112 ).  
      The color array of pixels read in the abnormality monitoring mode is the same as the read array in the normal monitoring mode, and the processing at the signal processing section  102  is carried out in the same way as in the normal monitoring mode.  
      The video signal output from the signal processing section  102  is input to the selector section  111 . The selector section  111  selects the area of the signal based on the signal from the area specification section  116  and outputs the signal to the image compression section  112  (S 113 ).  
      Here, a method of determining an area to be specified will be explained. The location of the movement detected within the image-taking area by the movement detection circuit  114  is specified based on a synchronization signal from the TG and the vertical line number and horizontal pixel number are output to the camera control circuit  104 .  
      The camera control circuit  104  outputs the vertical line number and horizontal pixel number of the pixel at top left of the area selected by the selector section  111  to the area specification section  116  based on the position information sent from the movement detection circuit  114 .  
      The area specification section  116  selects an image signal outputted to the image compression section  112  from the selector section  111  based on the position information from the camera control circuit  104 , the vertical synchronization signal, horizontal synchronization signal and clock signal from the TG.  
      The image compression section  112  attaches image start end information (vertical line number and horizontal pixel number of the pixel at top left of the area) to the start of the image information and creates compressed information (S 113 ). The subsequent processing is the same as that in the normal monitoring mode (S 114 ).  
      The monitoring terminal apparatus  2  expands the image information compressed by the image expansion section  21  (S 115 ), the start end information attached to the start of the compressed image information is converted to a video signal by the image processing section  24  and an expanded image thereof is displayed on the monitor  27  (S 116 ).  
      Furthermore, when some movement is detected at a plurality of positions in the image-taking area, start end information of each image is generated according to the detection target and attached to the compressed information.  
      Furthermore, it is also possible to combine and output a high definition image in the abnormality monitoring mode not to a normal monitor but to a high definition monitor.  
      While preferred embodiments have been described, it is to be understood that modification and variation of the present invention may be made without departing from the scope of the following claims.