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Camera Interfaces

This Tech Tip is designed to re-visit the camera interfaces and transmission standards available for vision systems. Since the last Tech tip on this subject, over four years ago, there have been a number of new developments.

C ameraLink CameraLink is a method of serialising parallel data that made it straightforward for manufacturers of digital cameras and framegrabbers to add a ChannelLink chip to existing LVDS devices to make them Cam eraLink devices. The CameraLink standard defines three levels of bandwidth:

  • Base – which uses a single ChannelLink chip to give 225M B /s over a single cable

  • Medium – which uses two chips to make 450MB /s over two cables

  • Full – three ChannelLink chips giving upto 675M B /s over two cables In addition to the image data the cables also carry serial data, CameraLink framegrabbers emulating a serial port on the PC in which they are installed.

The cables themselves are somewhat bulky by modern standards and are terminated on both ends by an MDR26 connector. The original standard came out in 2000. In 2007 there were developments to create Mini - CameraLink using an SDR 26 connect or and als o Power over CameraLink (PoCL). The transmission distance is limited by the nominal 10m cable limit, although it is possible to extend this in some cases. Good quali ty cables and low pixel clock values can take this fu rther (as far as 18m) but larger increases can be made with CEI ’ s Bit M axx cables that add pre - emphasis and equalisation to give up to 25m for base C ameraLink .

Much longer distances can be achieved using either a repeater such as the Phrontier CLEVER or a fibre - optic converter such as the Phrontier PHOX , see Figure 1.