Section: Scientific Foundations
Multiple-camera acquisition of visual data
Modern computer vision techniques and applications require the deployment of a large number of cameras linked to a powerful multi-PC computing platform. Therefore, such a system must fulfill the following requirements: The cameras must be synchronized up to the millisecond, the bandwidth associated with image transfer (from the sensor to the computer memory) must be large enough to allow the transmission of uncompressed images at video rates, and the computing units must be able to dynamically store the data and/to process them in real-time.
Until recently, the vast majority of systems were based on hybrid analog-digital camera systems. Current systems are all-digital ones. They are based on network communication protocols such as the IEEE 1394. Current systems deliver 640× 480 grey-level/color images but in the near future 1600× 1200 images will be available at 30 frames/second.
Camera synchronization may be performed in several ways. The most common one is to use special-purpose hardware. Since both cameras and computers are linked through a network, it is possible to synchronize them using network protocols, such as NTP (network time protocol).