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Network camera technology


The New York Times
on Axis' network camera technology 

Online, All the Time, an All-Seeing Surveillance System
(pdf file) April 24, 2003

A network camera can be described as a camera and computer combined into one unit. It connects directly to the network as any other network device. A network camera has its own IP address and built-in computing functions to handle network communication.

Everything needed for viewing images over the network is built into the unit. A network camera has built-in software for a Web server, FTP server, FTP client and e-mail client. Other features include alarm input and relay output functions. More advanced network cameras can also be equipped with many other value-added options such as motion detection and an analog video output.

The components

The network camera's camera component captures the image -- which can be described as light of different wavelengths -- and transforms it into electrical signals. These signals are then are converted from analog to digital format and transferred into the computer function where the image is compressed and sent out over the network.

The lens of the camera focuses the image onto the image sensor (CCD/CMOS). Before reaching the image sensor, the images pass through the optical filter, which removes any infrared (IR) light so that the "correct" colors will be displayed. (In day/night cameras, this IR-cut filter is removable to provide high quality black & white video during nighttime conditions.) The image sensor converts the image, which is composed of light information, into electrical signals. These electrical, digital signals are now in a format that can be compressed and transferred over networks.

Axis' in-house developed ARTPEC (Axis Real Time Picture EnCoder) chip with associated software performs such camera controller functions as managing the exposure (light level of image), white balance (adjusts the color levels), image sharpness and other aspects of image quality. ARTPEC also includes a video compression component, which compresses the digital image into an image containing less data for efficient transfer over the network.

The camera's Ethernet connection is enabled by Axis' ETRAX chip -- an optimized system-on-chip solution for connecting peripherals to the network. The ETRAX includes a 32-bit CPU, 10/100 MBit Ethernet connectivity, advanced Direct Memory Access (DMA) functionality and a wide range of I/O interfaces. 

The CPU, Flash memory and DRAM memory represent the "brains" or computing functions of the camera and are designed specifically for network applications. Together, they handle the communication with the network and the Web server.

Via the Ethernet port, a high-end network camera can send images directly to 10 or more computers simultaneously. If the images are first sent to an external Web server (instead of directly to the viewers), real-time video can be seen by an unlimited number of viewers.

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