What is Camera Link?
Soon after PULNiX released
information regarding the TMC-6700 and TMC-1000 cameras, other camera
and frame-grabber manufacturers expressed interest in Channel Link™,
the digital data transmission method used in these cameras. It became
apparent that the Channel Link technology lent itself well to a
standard that could be adopted industry-wide. An ad-hoc committee,
chaired by PULNiX America, Inc., was formed to discuss the creation of
a standard for Channel Link communications specific to the vision
industry.
The result is Camera Link. Camera Link is defined as a camera-to-frame-grabber cable specification. It defines a single connector for both the frame grabber and camera end, and ensures that all Camera Link products are interchangeable with one another.
Configurations
A
single Camera Link connection provides the following information on an
MDR-26 pin connector:
| Image data and timing | 4 pairs |
| 1 pair transmission clock | |
| Serial communication | 1 pair transmit |
| 1 pair receive | |
| Camera Control | 4 signal pairs |
This configuration will transfer up to 28 bits of image data, along
with the serial communications and camera control signals.
The heart of Camera Link is Channel Link™, a data transmission method by National Semiconductor. Channel Link is made up of a receiver chip and a transmitter chip. This chipset is used to transmit digital data. This technology offers many advantages to machine-vision applications over the previous method, namely, RS-644 (LVDS format of RS-422).
LVDS (Low Voltage Differential Signaling) has become the most common means to transmit digital data in recent years. This method, however, has several major drawbacks. LVDS requires a pair of wires for transmission of each data bit, creating bulky cables prone to breakage if stressed. Also, the maximum data transmission rate of LVDS is 400 MB/s, fast enough for today's applications, but limiting for tomorrow's requirements. Channel Link takes LVDS to the next level.
Channel Link uses LVDS standards to transmit data. Far fewer wires, however, are needed to transmit the data. A Channel Link transmitter will convert 28 bits of data into a format that can be transmitted over 4 parallel lines. A transmit clock over a fifth line finishes the requirements for Channel Link transmission. The diagram below shows how just five pairs of wire are able to transmit data that would require 56 wires using standard LVDS methods.
Channel Link™ is a registered trademark of National Semiconductor, Inc.
Last Updated Thursday February 02, 2006