383Camera Basics
© 2010 Thorlabs
NOTE
The maximum bandwidth of 480Mbit/s per USB2.0-Host cannot be exceeded.
Therefore the maximum possible bandwidth per camera might be reduced if image
data of several USB cameras is transferred at the same time.
The available bandwidth might also be decreased by hubs and repeaters. By
lowering the frame-rate or image size the bandwidth required for each camera can
be reduced.
9.13.4
Data transmission and bandwidth
The USB2.0 standard specifies an overall bandwidth of 480 MBit/s shared between different
transmission modes. DCU cameras use the USB2.0 Bulk-mode for transmitting images. This mode
uses error correction and retry on error to guarantee correct delivery of the image data. There is no
guaranteed bandwidth or latency. To ensure error free communication with all devices, the maximum
bandwidth for data payload is limited to 416 MBit/s.
Theoretically, up to 50 MB/s of data payload can be transmitted via USB2.0. In practice a high-
performance desktop-PC can transmit about 40 MB/s, most notebooks or embedded systems even
less than 40 MB/s.
The overall bandwidth can be increased by the use of USB2.0 expansion cards. These cards are
available for PCI and PCIe bus and provide an own host controller chip. To achieve maximum USB
bandwidth it is important to use high-performance mainboards and chipsets.
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