Outline of popular interfaces for machine vision

GigE Vision

The gigabit Ethernet interface was introduced to the industrial machine vision world in 2006 as the GigE Vision interface. Since that time, GigE Vision has become highly standardized under the supervision of the Automated Imaging Association (AIA) and has been able to leverage the continued evolution of Ethernet networking technology. The GigE Vision standard unifies various protocols allowing better interconnectivity between hardware devices and software resulting in high speed image transfer using low cost standard cables over very long distances. This has enabled it to grow into one of the most widely used interfaces in the machine vision industry.

Most installed GigE Vision cameras are based on the original 1000BASE-T Ethernet implementation, providing 1 Gbps of total bandwidth. More and more new GigE Vision cameras are now being equipped with faster GigE interfaces including so-called NBASE-T (with 2.5 Gbps or 5.0 Gbps speeds) and 10GBASE-T (also called 10GigE) with the capability of transmitting image data at up to 10 Gbps.

Typical applications with a GigE interface:
• Internet of Things (IoT) and Industry 4.0: A few popular application examples are additive manufacturing and production processes; intelligent robot automation systems; and quality control and monitoring.
• Boxed Vision Systems: A GigE interface may be used in automotive, semiconductor, food sorting & recycling, industrial quality control stations, medical diagnosis, traffic systems & speed enforcement, and calibration & alignment devices, among others.
• Standalone Vision Systems: Typical examples are automotive parts inspection and microscopy.
• Intelligent Vision Systems: Many applications like intelligent farming, food sorting, automotive parts inspection, etc.

 

The SFP+ interface module is derived from the SFP (short form-factor pluggable) module which is mainly used in telecommunications and data transfer. Depending on the application requirement, a very wide variety of SFP+ modules are available ranging from $350 – $2800 . SFP typically supports only 1 Gbps speed. The SFP+ specification was released in 2006 and supports a speed of 10 Gbps. The physical connectivity layer in most of the cases is an optical fiber. SFP+ provides Stable data transfer under rough conditions over long distances hence the use of optical fibers with SFP+ transceivers is advantageous.

Typical applications with a SFP+ interface:
• Long distance outdoor: Many outdoor applications like railway track inspection, container goods inspection, etc. need very long cable distances.
• Long distance indoor: Some industrial applications like paper manufacturing require very large machinery spread across more than 100 meters.
• Electrostatic environments: Applications like battery inspection and inspection of other electronic devices have high electrostatic environments.

 

The CXP standard for machine vision was created to achieve very high data rates over long cable lengths. The development of the CXP standard was first announced in 2008 and the first version of the standard, CXP 1.0, was released in early 2011. Subsequently, the CXP 1.1 standard was released in late 2011 and updated in 2013. It contained some improvements and additional features over the first standard. The latest standard, CXP 2.0, was launched in 2019 and includes even higher speeds and new functions.

The CXP interface offers high throughput. With its latest standard, CXP delivers the highest raw data throughput when it comes to machine vision applications. A 4xCXP-12 connection offers 50 Gbps speed with a per lane speed via CXP-12 of 12.5 Gbps. Furthermore, CXP efficiently supports multiple high-speed cameras and is well-suited to applications with multiple high-speed/high resolution cameras.

Typical applications with a CXP interface
• Defense & Medical: Some typical applications include situational awareness, target positioning systems, border and entry surveillance, surgical live viewing, etc.
• Industrial Machine Vision: Low jitter and latency, real-time triggering at high speeds, robust and flexible cables help CXP to perform well in harsh industrial environments. Typical applications include roll-based inspection of paper, metal and plastic foil, and also semiconductor and PCB inspection.

Released in 2000, Camera Link was the first interface built from the ground up for machine vision applications. Recognizing the limitations of the IIDC-Firewire combination, a committee of industry leaders developed Camera Link to offer a range of speeds, real-time signaling and control, robust connections, and other features that have made it a "gold standard" in the industry, and have made it especially popular for interfacing with line scan cameras.

Camera Link is a point-to-point parallel data interface (not packet-based like the other interfaces) and can be configured over one or two 26-pin connectors. In addition to image transmission, four of the signal pairs are used for control signals providing dedicated camera control with minimal latency. A camera-to-host connection can be configured with a single connector and cable (called Camera Link Base) supporting 2.04 Gbps. Two-cable configurations can include CL Medium at 4.08 Gbps, CL Full at 5.44 Gbps, and CL Deca at 6.8 Gbps (850 Mbytes/s). A "Lite" configuration was also launched in 2009 that offers a "less bulky" one connector/cable interface option, albeit with less than half the bandwidth of a CL Base configuration.

Typical applications with a Camera Link interface
• High speed line scan applications: Being a high-speed interface with very low latency and jitter, Camera Link is popularly used in web applications like print, paper, foil and metal inspection.
• Reliability applications: The high point-to-point reliability of Camera Link operation has also led to its use in critical inspection tasks within electronics and semiconductor industry where network delays or other instabilities cannot be tolerated.

 

The USB3 Vision standard is derived from the USB 3.0 standard with some changes and adjustments to the transport layers defined specifically for machine vision applications. Within the USB3 Vision standard, USB 3.0 and USB 3.1 (Generation 1) support a data rate of 400 MB/s (3.2 Gbps) at a cable length of 5m and the USB 3.1 (Generation 2) supports a bandwidth of 900 MB/s at a cable length of 1m.

USB3 Vision has grown to be one of the most popular machine vision interfaces mainly because of its simplicity. Most PCs are equipped with USB 3 ports. It is most often used in single camera configurations, such as on a microscope or a standalone inspection system that utilizes an integrated processing unit or is connected to a nearby PC located within the interface's 1-5m cabling range. But it can also support multi-camera configurations connected via a USB 3 hub in a star topology.


Typical applications with a USB3 interface
• Plug and play: Known for its table-top, plug and play capabilities, USB3 Vision is a popular interface in microscopy, standalone inspection systems, portable inspection devices, etc.
• Multi-camera environments: USB3 Vision can be used effectively in many types of moderate-speed multi-camera environments, such as 3D vision systems on robot arms, autonomous vehicles, and multi-camera virtual reality "heads" providing 360-degreee views