Camera Link HS Standard

Camera Link HS® (CLHS) is designed to specifically meet the needs of today’s most challenging high-speed vision and imaging applications. 

The machine vision landscape today involves rapidly progressing technologies evolving to meet new and expanding customer needs. As sensor and camera manufacturers produce imaging products with smaller pixel sizes, increasingly higher pixel counts, and higher frame rates, machine vision interface standards must also advance. Currently in v1.2, CLHS has become a leader in speed, reliability, ease of development, and bandwidth, and it continually expands its capabilities to meet the demands of today and tomorrow.

First introduced in 2012, Camera Link HS delivers high-bandwidth, low-latency, low-jitter, real-time signals between a camera and a frame grabber, carrying both image and configuration data. In addition to high-speed transfer, CLHS provides standardized connectivity with low-cost cables along with support for both copper and fiber cabling and, importantly, intellectual property (IP) cores for ease of product development.

Inexpensive IP Cores Ease Development

Available from A3 for only $1,000 to help promote the technology, CLHS IP cores help camera and frame grabber companies speed CLHS development and implementation. Through an open-source format, end users can also customize IP cores and add features that can be technically reviewed and approved to become a permanent part of the core available to the user for a lifetime. In this way, the user community contributes to meaningful and continual CLHS interface improvements.  

A3’s Very High-Speed Integrated Circuit Hardware Description Language (VHDL) IP cores have been field-proven with Altera, Xilinx, and Microsemi field programmable gate arrays (FPGAs) and are used in industrial cameras and frame grabbers. CLHS implements its protocol in two physical layer encodings:

CLHS M Protocol IP Core: 8b/10b line encoding with single bit error immunity for use in lower-cost, lower-power FPGAs. It supports hardware for copper (C2) cabling with CX4 connections up to 15 m and 2.1 GBps in the CLHS cable. An active plug-on fiber cable can be added externally to reach up to 100 m. Typical bit rates for the M Protocol are up to 5 GBps per lane.

CLHS X Protocol IP Core: 64b/66b line encoding with forward error correction (FEC) is designed for 10 GBps and higher. Due to the line encoding technique, CLHS 10.3 Gbps is equivalent to 12.5 Gbps encoded 8b/10b interfaces. With the FEC, which can correct up to 11 bits of an error burst, the single-bit error immunity requirement is achieved. CLHS supports connector type F2 (SFP+) and F3  (quad small-form-factor pluggable (QSFP+) and multifiber push-on (MPO)) fiber connections at rates up to 25.7 Gbps per lane.

CLHS Features and Benefits

Five message types are available with CLHS: a low-latency (< 1 µs) 0 ns jitter trigger for real-time triggering at 8 MHz or more with seven separate modes, 16 bidirectional general-purpose I/Os with < 1 µs latency, remote DMA video packet, high-speed command uplink-enabling streaming correction coefficients, and revision information used in device discovery. One major benefit of CLHS is that it provides a real-time, reliable, point-to-point interface enabling low-power streaming cameras.

CLHS provides several other key benefits for machine vision and imaging applications. These include:

• Scalable bandwidths from 1200 (single cable with 10 G) to 96,000 MBps (eight cables with 25 G)
• Immunity to single-bit transmission errors
• Bidirectional triggering — low jitter of 6.4 ns pk-pk possible with IP core — which makes Camera Link HS viable for line scan and short exposure area scan applications
• Parallel image processing capabilities
• Video packetization, which enables regions of interest to be transferred easily and precisely
• 300 MBps/1200 MBps uplink, which allows quick camera reconfiguration, such as updated coefficient sets
• 16 bidirectional general purpose I/Os with latencies < 1µs
• Frame-by-frame control of camera supported by the trigger message, and image status returned in the video header, forming a closed-loop system

Camera Link HS supports copper or fiber optic cables from 15 to 300+ m in length. Full cable options include:

• Eight cables maximum
• 1200 to 1850 MBps (X Protocol) F2 fiber optic with 300+ m distance (SFP+ connector)
• 4800 to 12,000 MBps (X Protocol) F3 fiber optic with 300+ m distance (QSFP connector)
• 2100 to 3300 MBps (M Protocol) C2 copper cable with 15 m distance (CX4 connector)
• 8400 to 10,000 MBps (X Protocol) C3 copper cable/active optical cable with 100 m distance (CX4 connector)
• Small, low-cost, lightweight fiber optic cabling, which is long distance–capable, high bandwidth, extreme flex-life rated, and immune to electrical noise

Adding Real-World Value

Path to 50 Gbps and Beyond

Camera Link HS — already a leading high-speed camera interface — will bring significantly expanded capabilities through its inexpensive, open-source IP core. The forthcoming releases are well suited for the future of imaging and machine vision. >>>Read More

COVID-19 Vaccine Development

In research that ultimately helped identify the spike protein of the virus that causes COVID-19, Thermo Fisher Scientific leveraged the CLHS standard in its transmission electron microscopy cameras and detectors. >>>Read More

Unlocking Atomic and Molecular-Level Insights

Researchers at Switzerland’s Paul Scherrer Institute leveraged scientific CMOS cameras and Camera Link HS technology — along with the SwissFEL X-ray free-electron laser — to record numerous biological and chemical processes for the first time. >>>Read More.

Next Steps
 

• Download the CLHS specification here.
• Reach out with any questions by emailing Bob McCurrach here.