Abstract:
Methods and systems for a video surveillance system are provided. The system includes a video camera assembly including a base, a first pan/tilt mechanism, and a second pan/tilt mechanism. The first pan/tilt mechanism is removably coupled to the base. The second pan/tilt mechanism is configured to be coupled to the base in replacement of the first pan/tilt mechanism. The system also includes a memory configured to store pan/tilt mechanism positional calibration information, and a controller communicatively coupled to the first pan/tilt mechanism configured to receive positional calibration information for the first pan/tilt mechanism, store the positional calibration information to the memory, retrieve the positional calibration information from the memory when the first pan/tilt mechanism is removed and replaced with the second pan/tilt mechanism, and download the retrieved positional calibration information for use by the second pan/tilt mechanism.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to video surveillance systems and, more particularly, to assembling and disassembling camera pan, tilt, and zoom assemblies.  
         [0002]     At least some known video surveillance systems include one or more video cameras mounted in a housing along with a pan, tilt, and zoom (PTZ) assembly. The PTZ permits controlling a movement of the camera to align a viewing area of the camera with an object of interest or location of interest. The zoom portion of the mechanism may be used to adjust a field of view of the camera. The housing protects the camera from the environment in the location where the camera and PTZ assembly are mounted.  
         [0003]     At least some known video camera assemblies are equipped with “preset” controls, for example, servo mechanisms to position the camera to internally stored pan, tilt, zoom, focus, and iris positions. Using the position data, a plurality of “preset” views for each camera is stored and used to direct the respective camera to one, or a sequence of these preset views in response to operating a key on the keypad or from logic in a system control that automatically determines a desired view or sequence.  
         [0004]     During initial installation and periodically thereafter, the camera and/or PTZ assembly may need to be removed from its mounted location. For example, over time, the camera and/or PTZ assembly may require maintenance to restore a damaged or worn camera or PTZ assembly to an operable condition. However, mechanical inaccuracies in the pan/tilt assemblies typically necessitate the presets being reprogrammed after the video camera assemblies are replaced.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0005]     In one embodiment, a video surveillance system includes a video camera assembly including a base, a first pan/tilt mechanism, and a second pan/tilt mechanism. The first pan/tilt mechanism is removably coupled to the base. The second pan/tilt mechanism is configured to be coupled to the base in replacement of the first pan/tilt mechanism. The system also includes a memory configured to store pan/tilt mechanism positional calibration information, and a controller communicatively coupled to the first pan/tilt mechanism configured to receive positional calibration information for the first pan/tilt mechanism, store the positional calibration information to the memory, retrieve the positional calibration information from the memory when the first pan/tilt mechanism is removed and replaced with the second pan/tilt mechanism, and download the retrieved positional calibration information for use by the second pan/tilt mechanism.  
         [0006]     In another embodiment, a method of operating a video camera assembly includes storing position calibration information for a first pan/tilt mechanism, replacing the first pan/tilt mechanism with a second pan/tilt mechanism, and downloading the stored position calibration information for use by the second pan/tilt mechanism.  
         [0007]     In yet another embodiment, a method of maintaining a video camera assembly includes determining position calibration information for a first pan/tilt mechanism associated with the assembly, and storing the position calibration information. The method also includes replacing the first pan/tilt mechanism with a second pan/tilt mechanism, commanding the second pan/tilt mechanism to a predetermined preset address, acquiring an image at the predetermined preset address, processing the image to determine primitive geometries of the image, comparing the determined primitive geometries to primitive geometries stored in the position calibration information to determine a positional calibration information correction, and applying the correction to the positional calibration information associated with the second pan/tilt assembly.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a schematic view of an exemplary video surveillance system in accordance with an embodiment of the present invention;  
         [0009]      FIG. 2  is a perspective view of an exemplary video camera pan, tilt, and zoom (PTZ) assembly that may be used with the system shown in  FIG. 1 ; and  
         [0010]      FIG. 3  is a flowchart of an exemplary method  300  of storing and transferring preset information from a camera being removed from operation to a replacement camera. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]     As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.  
         [0012]      FIG. 1  is a schematic view of an exemplary video surveillance system  100  in accordance with an embodiment of the present invention. Video surveillance system  100  includes a control panel  102 , a display monitor  104 , and a pan, tilt, and zoom (PTZ) assembly  105 . Typically, a camera  106  is housed in an enclosure  108  having a dome  110  for protecting camera  106  from the environment where camera  106  is located. In one embodiment, dome  110  is tinted to allow camera  106  to acquire images of the environment outside of enclosure  108  and simultaneously prevent individuals in the environment being observed by camera  106  from determining the orientation of camera  106 . In various alternative embodiments, dome  110  is not tinted. In the exemplary embodiment, camera  106  includes capabilities to pan about a vertical axis  112 , tilt about a horizontal axis  114 , and control a lens assembly  116  to cause camera  106  to zoom. For example, PTZ assembly  105  includes a pan motor and encoder  113  and tilt motor and encoder  115 . The encoders determine an angular position of the pan and tilt motor and generate position signals that are used with a zoom setting to determine an area in the field of view. Panning movement of camera  106  is represented by an arrow  118 , tilting movement of camera  106  is represented by arrow  120  and the changing of the focal length of lens assembly  116  of camera  106 , i.e., zooming, is represented by arrow  122 . As shown with reference to a coordinate system  124 , panning motion may track movement along the x-axis, titling motion may track movement along the y-axis and focal length adjustment may be used to track movement along the z-axis. Signals representing commands to control such capabilities are transmitted from control panel  102  through a control data line  126 . Image data signals are transmitted from camera  106  to display monitor  104  and a storage device  128  through a video data line  130 .  
         [0013]     Lens assembly  116  views an area of a location  132 , which may be remote from control panel  102  and is in a field of view  134  and along a viewing axis  136  of lens assembly  116 . Images of location  132  are converted by camera  106  into an electrical video signal, which is transmitted to display monitor  104 .  
         [0014]     In the exemplary embodiment, control panel  102  includes an X-Y control joystick  140  that is used to generate pan and tilt commands. A plurality of rocker-type switches  142  are used to control a zoom  144 , a focus  146 , and an iris  148  of lens assembly  116 . In an alternative embodiment, joystick  140  includes a twist actuation that is used to control the zoom of camera  106 . Joystick  140  may also incorporate triggers and/or buttons to facilitate operating various controls associated with system  100 . Control panel  102  also includes a numeric keypad  150  for entering numbers and values. In an alternative embodiment, control panel  102  may include an alpha or alphanumeric keypad (not shown) for entering text as well as numbers. Control panel  102  further includes a plurality of preset switches  152  that may be programmed to execute macros that automatically control the actions of camera  106  and/or lens assembly  116 . A plurality of buttons  154  may be used, for example, for predetermined control functions and/or user-defined functions, for example, a camera selection in a multi-camera video surveillance system. A display  156  may be used to display a status of video surveillance system  100  or may be used to display parameters associated with a selected camera.  
         [0015]     A processor  158  receives programmed instructions, from software, firmware, and data from memory  160  and performs various operations using the data and instructions. Processor  158  may include an arithmetic logic unit (ALU) that performs arithmetic and logical operations and a control unit that extracts instructions from memory  160  and decodes and executes them, calling on the ALU when necessary. Memory  160  generally includes a random-access memory (RAM) and a read-only memory (ROM), however, there may be other types of memory such as programmable read-only memory (PROM), erasable programmable read-only memory (EPROM) and electrically erasable programmable read-only memory (EEPROM). In addition, memory  160  may include an operating system, which executes on processor  158 . The operating system performs basic tasks that include recognizing input, sending output to output devices, keeping track of files and directories and controlling various peripheral devices.  
         [0016]     The term processor, as used herein, refers to central processing units, microprocessors, microcontrollers, reduced instruction set circuits (RISC), application specific integrated circuits (ASIC), logic circuits, and any other circuit or processor capable of executing the functions described herein. Memory  160  may include storage locations for the preset macro instructions that may be accessible using one of the plurality of preset switches  142 .  
         [0017]     As used herein, the terms “software” and “firmware” are interchangeable, and include any computer program stored in memory for execution by processor  158 , including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are exemplary only, and are thus not limiting as to the types of memory usable for storage of a computer program.  
         [0018]     In various embodiments, processor  158  and memory  160  are located external to camera  106  such as in control panel  102  or in a PC or other standalone or mainframe computer system capable of performing the functions described herein.  
         [0019]     In the exemplary embodiment, video surveillance system  100  is a single camera application, however, various embodiments of the present invention may be used within a larger surveillance system having additional cameras which may be either stationary or moveable cameras or some combination thereof to provide coverage of a larger or more complex surveillance area. In an alternative embodiment, one or more video recorders (not shown) are connected to control panel  32  to provide for recording of video images captured by camera  13  and other cameras in system  100 .  
         [0020]      FIG. 2  is a perspective view of an exemplary video camera pan, tilt, and zoom (PTZ) assembly  200  that may be used with system  100  (shown in  FIG. 1 ). PTZ assembly  200  includes an upper bracket or base  202  coupled to an interior portion of a housing. The housing is configured to be fixedly coupled to a structure such as a ceiling, stanchion, post, or other suitable mount able to support the weight of PTZ assembly  200  and is a stable platform to facilitate reducing jitter. Jitter may be apparent in the camera image due to vibration or swaying of PTZ assembly  200 .  
         [0021]     Base  202  includes one or more locating rounds  204  that are complementary to locating slots  206  in a lower bracket  208  of a removable unit  210 . Locating rounds and locating slots  206  are used to align removable unit  210  and base prior to coupling removable unit  210  to base  202 . Base  202  also includes one or more guides  212  configured to receive a pawl  214  coupled to a ring latch  216  on removable unit  210 . In the exemplary embodiment, a second pawl (not shown) is oriented similarly to pawl  214  and spaced approximately 180° from pawl  214 . In an alternative embodiment, a different number of pawls are used. A distal end  218  of guide  212  includes a pin  220  extending away from guide  212  in a radial direction with respect to a longitudinal axis  222  of PTZ assembly  200 . Pawl  214  and pin  220  are configured to engage to transfer the weight of removable unit  210  to base  202  to support removable unit  210 . In various embodiments of the present invention pin  220  is configured as a rotatable wheel.  
         [0022]     Ring latch  216  is rotatably coupled to lower bracket  208 . The amount of rotation ring latch  216  is capable of is limited by a plurality of stops  223  and complementary grooves  224  that engage to limit the rotational travel of ring latch  216  with respect to lower bracket  208 . A stationary member  228  of pan motor  226  is fixedly coupled to lower bracket  208 . When pan motor  226  rotates, removable unit  210  rotates with the rotatable member and with respect to base  202 . A slip ring  230  permits removable unit  210  to rotate continuously in a first rotational direction  232  or a second opposite direction  234 .  
         [0023]     Removable unit  210  includes a shroud  236  that is slidably coupled to a chassis  237 . Shroud  236  is configured to maintain a relaxed position (shown in  FIG. 1 ) and an engaged position. In the engaged position, a plurality of teeth  238  arranged circumferentially about an outer periphery  240  of shroud  236  and extending axially toward ring latch  216  are configured to mesh with a complementary plurality of teeth  242  arranged circumferentially about an outer periphery  244  of ring latch  216  and extending axially toward teeth  238 . Shroud  236  is translated from the relaxed position to the engaged position by applying an upward axial force to a bottom side  246  of shroud  236 . The movement associated with positioning shroud  236  from the relaxed position to the engaged position compresses or tensions a plurality of bias members  248  coupled between shroud  236  and chassis  237 . A plurality of travel limiters  247  limit the upward movement of ring latch  216  with respect to lower bracket  208 . Bias members  248  are configured to return shroud  236  to the relaxed position when the axial force applied to shroud  236  is removed.  
         [0024]     Ring latch  216  is configured to rotate at least partially about axis  222  and shroud  236  is configured to rotate freely about axis  222  with chassis  237  and the rotatable member of pan motor  228 . Accordingly, with teeth  238  and  242  engaged by an axial force applied to shroud  236 , an additional rotational force may be applied to shroud  236  to cause ring latch to rotate. Pawl  214  rotates with ring latch  216  toward or away from pin  220 . If pawl  214  rotates away from pin  220 , the weight of removable unit  210  will no longer be supported by the engagement of pawl  214  and pin  220  and removable unit  210  will be released from base  202  by its own weight. In an alternative embodiment, one or more ejection springs are configured to apply a bias force to removable unit  210  to assist in disengaging removable unit  200  from base  202 .  
         [0025]      FIG. 3  is a flowchart of an exemplary method  300  of storing and transferring preset information from a camera being removed from operation to a replacement camera. Method  300  includes storing  302  primitive geometries associated with a preset reference image. The primitive geometries are extracted from the reference image associated with a respective preset address or plurality of addresses. For example, a preset may be able to be addressed using a single address or in the case of a camera that can tilt 180° or greater a preset location may be addressable using more than one address. As used herein, primitive geometries describe relatively simple shapes and combinations of shapes that are extracted from images that are characteristic of the image and are able to be used to differentiate the image from other images the camera is able to acquire. The set of primitive geometries typically take up less memory resources than a full image. The preset addresses, respective primitive geometries, and associated encoder position information are stored in a memory in a base associated with the camera to facilitate maintaining preset accuracy.  
         [0026]     When a camera is replaced, positional calibration data including, for example, the preset addresses, respective primitive geometries, and associated encoder position information are automatically downloaded into a memory associated with the camera. The accuracy and repeatability is limited by two factors; one, current camera calibration, and two, the mechanical installation tolerances of the camera and the camera bracket. Removing and reinstalling a replacement camera, which inherits the presets determined by the previous camera, can also cause drifts, particularly on high zoom presets due to the calibration variation between the cameras. When a replacement camera is first installed the presets are tested for accuracy.  
         [0027]     The replacement camera is commanded  304  to a preset address using the positional calibration data. In the exemplary embodiment, the replacement camera automatically initiates and executes a script, macro, or program to command the replacement camera to point to the view addressed by the downloaded encoder position information. An image is then acquired  306  at the preset address indicated by the downloaded encoder position information. The acquired image is reduced  308  to primitive geometries in the same manner as the primitive geometries were extracted from the preset reference image. The primitive geometries extracted from the acquired image are compared  310  to the primitive geometries from the reference image previously stored for this preset. From the comparison a pan, tilt, and/or zoom correction is determined  312 , and then the correction is applied  314  to the preset addresses and their conjugates for the replacement camera. The replacement camera may selectably perform the same calibration for all the presets associated with the replacement camera or may only perform the calibration for a selectable number of presets less than all of the presets. When less than all of the presets are calibrated using the method described herein, corrections for the non-calibrated presets are inferred from the calibrations performed. For example, calibrations for non-calibrated cameras may be simple interpolations of the performed calibrations. In an alternative embodiment, the correction factor is determined by searching for a systematic drift of the presets that are calibrated. The determined correction factor would be a value that minimized the preset error over the calibration set. The accuracy using this technique removes the two major uncertainties in the system, namely the encoder calibration variance and the mechanical coupling of the camera into the installation bracket.  
         [0028]     The above-described embodiments of a video surveillance system provide a cost-effective and reliable means for enabling an operator to transfer preset information from one camera to a replacement camera without substantial loss in accuracy of the preset data.  
         [0029]     Exemplary embodiments of video surveillance systems and apparatus are described above in detail. The video surveillance system components illustrated are not limited to the specific embodiments described herein, but rather, components of each system may be utilized independently and separately from other components described herein. For example, the video surveillance system components described above may also be used in combination with different video surveillance system components.  
         [0030]     A technical effect of the various embodiments of the systems and methods described herein include facilitating operation of the video surveillance system by transferring preset information from one camera to another without substantial loss in accuracy of the preset data to facilitate replacement of the camera assembly in with a minimum of time.  
         [0031]     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.