|Thursday, 07 September 2006|
In a security system, one or more video cameras are placed so as to provide a field of view of the area under surveillance. These video cameras convert a visual image into an electronic form suitable for transmission. A control station, either co-located within the surveillance area or remote from the area, receives the signals from these cameras and displays the video image at a console, for security assessment and recording. A security monitoring system includes a number of video cameras that are connected via cables to a main monitor installed in the security guard room. By conventional technology, each of the video cameras is connected via a dedicated cable to the central control room. These CCD cameras monitor for 24 hours day after day and the related video camera recorders are also recording continuously. Security guards can quickly switch from viewing one area under video surveillance to another area without ever having to leave their main security office. Video surveillance equipment can be fixed positioned camera and zoom lenses. Fixed positioned cameras are useful for wide angle shots or limited view applications such as entrances and exits. The cameras can be made to pan and zoom so as to modify the field of view. Zoom lenses are used to increase a quality of captured video by allowing security personnel to zoom in on a small portion of a screen in order to evaluate and/or distinguish elements of the scene in greater detail. Cameras having zoom lenses are generally mounted on a pan and tilt mechanisms. Such pan and tilt mechanisms are typically controlled via the control command center by the security personnel. Infrared (IR) imagers extend surveillance beyond starlight into no-light conditions. Visible light is not required for IR imaging because the self-emission of objects in the infrared suffices for their operation. In the infrared, the scenery at nighttime appears the same as the scenery in the daytime.
Security systems may include cameras that obtain the facial image of a person in order to ascertain identification. For example, when facial thermograms are used as part of a security system, a camera is required to obtain the original image of the person and to obtain subsequent images of the person that are compared to the original image. The self contained image data analysis security camera contains logic circuits to capture an initial image and a processor to compare subsequent images. The images are transmitted to a central station allowing the field of view to be displayed on a monitor and recorded by a VCR or other suitable recording device. When in security mode the processor in the camera continually compares incoming subsequent images with the initial captured image stored in the memory until a discrepancy between the two images is detected and initiates an alarm mode. A discrepancy between the initial captured image and an incoming subsequent image initiates an alarm mode and an audible and/or visual alarm is activated at the central station and/or other desired location. This type of security cameras usually includes an alarm sensitivity adjustment means to the processor to allow the operator to determine how much of a discrepancy between the captured image and the stored image is required to initiate the alarm mode. Many self-checkout stations have a security camera mounted on a pole located within the viewing area of a single security camera.
The security camera has been used in CCTV systems (closed-circuit television systems) for surveillance allowing the security guards to visually observe remote sites for detection of potential criminal actions. A central command center is provided for selecting, displaying and recording of an output of any given video camera of the installed cameras. Thus, a small number of security personnel stationed at a central command center can officially monitor an entire facility by selecting, displaying and recording the output of any given camera. In video surveillance systems, a person monitors the images from the cameras on a video screen and initiates security measures if the received image indicates unauthorized activities. Often the monitoring person is responsible for monitoring the images from multiple cameras simultaneously, and means are provided to assist in this process. Automated motion detection systems are employed to alert the monitor of the presence of activity within the view of a camera. These motion detection systems operate by detecting changes in the sequential electronic images of the same scene. A change in the scene implies the entry or exit of an item from that scene. When a change is detected, an alarm is sent to the monitor for a security assessment. The monitor will view the sequence of images which caused the alarm to determine whether the alarm requires the initiation of security measures such as notifying the police or activating a warning signal. These motion detection systems are highly effective in areas within which little or no activity is expected to take place.
There is a large number of different security camera mounting schemes used in the security camera industry. Image sensors are the core components for these optical imaging systems. Image sensors are typically comprised of pixel arrays of a large number of very small light detectors, together called "pixel arrays". These sensors typically generate electronic signals that have amplitudes that are proportional to the intensity of the light received by each of the detectors in the array. Security cameras comprise imaging components to produce an optical image of a scene onto the pixel array. The electronic image sensors convert the optical image into a set of electronic signals. Various types of semiconductor devices can be used image sensors. These include charge couple devices (CCDs), photodiode arrays and charge injection devices. Among them the charge coupled devices are most popular electronic image sensors. Charge coupled device stores and displays image data by converting each pixel (picture element) into an electrical charge. Another currently available type of image sensors is based on metal oxide semiconductor (MOS) technology or complementary metal oxide semi-conductor (CMOS) technology. These sensors are commonly referred to as CMOS sensors. A CMOS image sensor senses an image using a photodiode and a MOS transistor in each pixel for detecting light signals in a switching mode. The CMOS image sensor has several advantages such as a simple operation process, low fabrication costs and low power consumption.
In a surveillance/security system, a lens, a charge coupled device (CCD) camera, and other electronic components (such as an amplifier, an image processor, etc.) are all disposed within the same camera housing. Other portions of the imaging system (e.g., image storage and/or display) may also be included in the camera housing, or may be disposed in a remote location that is connected to the camera housing via cables. Composite cameras have both camera and camera swivel base integrated in a doomed housing respectively. This type of cameras can be adjusted in both panning (horizontal rotation) and tilting (vertical rotation) directions in accordance with the rotation of the swivel base. A protective housing often encloses a surveillance camera to protect the camera from damage by the elements, to prevent vandalism, to conceal the camera, and/or for aesthetic purposes. Such housings can be domed, shaped to generally match the camera contours, or otherwise configured. Dome housings for mounting video cameras employed in security systems typically include a metal housing portion and a plastic dome portion in which the housing portion is mountable through a hole in a ceiling and the dome portion is attached to the housing portion.