Start With the Video Interface
“Easier-to-use, scalable, and retain as much existing equipment as possible.” For image system integrators, these explicit or implied requirements are key considerations when preparing a quote for an upgrade or retrofit project. While cameras, lenses, lighting, and processing options are often top of mind, choosing the right video interface may be one of the first steps towards a successful project.
The video interface—the hardware and software that formats the imaging data, sends it over a cable or wirelessly, and receives it at a computer or display—plays a significant role in the usability, scalability, and cost-effectiveness of the final system. In this article, we’ll discuss how GigE and USB 3.0 video interfaces can help a system integrator meet customer requirements.
As imaging technologies become increasingly prevalent across the factory floor, more employees are setting up and tearing down systems, monitoring output, and accessing analytics to evaluate performance and track efficiencies. With technical support at a premium, and often an outside expense for many operators, there’s an increasing emphasis on delivering imaging systems that provide more sophisticated analysis while being easier to use.
When machine vision initially moved from research labs to the factory floor in the late 1980s and early ‘90s, designers often relied on interface standards from the broadcast, telecom, and consumer markets to connect imaging sources and analysis platforms. Camera Link, introduced in 2000, was the first purpose built standard for machine vision. As end-users seek easy-to-use imaging systems, the limitations posed by these standards become more apparent.
With each approach, dedicated cabling is required between the image source and endpoint. In applications where images are distributed and displayed across multiple endpoints, cabling becomes costly and complex. More significantly, these interfaces require a PCIe frame grabber at each endpoint to capture data. This limits the types of computers that can be used, drives up component costs, and increases technical complexity.
In comparison, GigE and USB 3.0 interfaces make it easier to install and maintain imaging systems by transmitting full-resolution uncompressed video with low, consistent latency over off-the-shelf cabling directly to existing ports on a computing platform. By eliminating the need for a PCIe frame grabber, any type of computer can be used for processing and analysis, including laptops and single-board systems.
GigE and USB 3.0 interfaces each bring unique advantages in terms of cabling, networking, and installation and maintenance.
With the long-reach cabling of GigE—up to 100 meters over standard Cat5/6 copper cabling, versus 10 meters for Camera Link—processing equipment can be moved to easier to access locations for maintenance, or centralized in an operations center. Ethernet’s inherent networking flexibility allows the design of real-time switched video networks connecting image sources, processors, displays, and storage devices. End-users can switch between image sources, without changing cabling or software.
USB is the backbone for connectivity in a wide range of computing and consumer electronics applications, thanks primarily to its ease-of-use. USB3 Vision interfaces bring the same “plug-and-play” advantages to real-time imaging applications, allowing users to easily set up and tear down work cells for different products and short production runs.
Technology innovation consistently drives a new wave of products that deliver performance and cost-advantages, while sending older products on the fast path to obsolescence. Standards-based solutions are a key way for integrators to ensure both backwards compatibility and future-proof capabilities during imaging system design.
The ongoing evolution of GigE and USB 3.0 interfaces is guided by open global standards that help ensure easier-to-install, upgrade and maintain imaging systems.
The GigE Vision standard allows Ethernet-based imaging products from different vendors to interoperate seamlessly, without time-consuming and costly integration issues. The standard is tightly integrated with numerous international standards, including IEEE 802.3 (Ethernet), IEEE 1588 (time synchronization), and IETF RFC2026 (jumbo frames). This makes it easier to leverage the native performance attributes of the Ethernet platform, such as its long-distance reach, networking flexibility, scalability, high throughput, and full-duplex connections. Thanks to Ethernet’s universal deployment across consumer and telecom networks, off-the-shelf equipment is readily available, affordable, and easy to maintain and install.
Compared with other interface standards, Ethernet’s inherent support for meshed network configurations means it can easily accommodate different data rates and the addition of new processing nodes, displays, and sensors. Because each GigE Vision interface uses its own IP address, there’s no limit to how many endpoints can operate on the same network.
Building on the concepts developed for GigE Vision, the USB3 Vision standard makes it simpler to implement applications using the affordable and widely available USB 3.0 ports. Standards-based cameras and other imaging products from various vendors can interoperate seamlessly, without time-consuming integration issues. Both integrators and end-users also benefit from the technology innovation and cost-advantages driven from the highly competitive consumer electronics market, including off-the-shelf USB 3.0 hubs that provide a straightforward way to scale systems into multi-camera installations.
Both GigE Vision and USB3 Vision, along with other interface standards, also incorporate GenICam; a global standard that defines a generic interface for the computer control of digital cameras and other imaging products that transmit video.
GenICam cost-reduces the design, deployment, and maintenance of high-performance video applications by allowing the same design framework to be used for different types of cameras and imaging products. It also simplifies the integration of new cameras into larger systems by employing an XML-based computer-readable datasheet and defining a Standard Features Naming Convention (SFNC). By standardizing software terms, such as “gain” instead of “brightness,” end-users can use the same interface to program applications for any compliant camera or imaging transmission product, regardless of its vendor.
Designing systems based on well-defined, widely adopted standards is a clear path towards ensuring future scalability.
Investment Protection and Operating Costs
Rarely will a system integrator have the opportunity to quote on a complete “rip and replace” project. More often, a customer has made significant investments in cameras and lenses, and an integrator is asked to retrofit the system to help enhance productivity and efficiencies.
In these situations, external frame grabbers are a straightforward solution that enable an integrator to deliver the advantages of GigE Vision or USB3 Vision. External frame grabbers are available that convert almost any legacy interface (Camera Link, Analog, LVDS, HD-SDI, etc.) into vision standard video that is transmitted directly to a port on a small form factor and low-power computing platform.
Integrators can also increase the value of their system by implementing other solutions that reduce costs or introduce new efficiencies for end-customers. For example, in applications with automated inspection and viewing, monitoring, and recording requirements, integrators can propose designs that eliminate the need for multiple video systems.
With a plug-in transcoder gateway appliance, vision standard video used for processing and analysis can be converted into the more accessible H.264 format. While maintaining the high-bandwidth video required for real-time processing and analysis, end-users with less strict viewing demands can access the video on smartphones and tablets. The lower bandwidth video is also better suited for archiving and recording. Previously, operators would require separate video systems for real-time automated applications and viewing, monitoring, and archiving requirements.
Preparing the Quote
Standard-based GigE and USB 3.0 interfaces provide a solid foundation for a system upgrade or retrofit proposal. In a web inspection upgrade (diagram 2), for example, a solution based on GigE video interfaces helps an integrator meet usability, scalability, and investment protection requirements.
In this application, existing Camera Link Medium cameras are converted to 10 GigE by external frame grabbers. Ethernet’s long cable reach allows the integrator to move the processing computers off the gantry, away from the harsh climate of the inspection floor, and into a central operations center. The flexible, lighter, field-terminated cabling is less expensive and easier to install than most other interface cabling to help reduce costs and simplify maintenance. Thanks to the networking flexibility of Ethernet, new cameras, image sources, and processing platforms can be easily and seamlessly integrated into the system.
To enhance reliability, the external frame grabbers multicast image data to multiple computing platforms simultaneously using an inexpensive off-the-shelf GigE switch. Individual PCs can then be optimized for different types of defects, rather than mating a PC to each individual camera. Moreover, if a primary PC is taken offline for maintenance or live testing of new image processing algorithms, inspection functions can be assumed by backup PCs, without the need to switch cables or change software settings.
To further reduce costs and complexity, external frame grabbers contain a sophisticated programmable logic controller (PLC). This PLC can accept triggers from laser sensors or rotary encoders, and accurately synchronize both the camera’s sensor and the strobe light. In addition, video can be streamed to playback devices for observation or recording units for archiving using a transcoder gateway.
The end result: an imaging system that is easier-to-use and maintain, delivers higher performance, and is scalable for future technologies while retaining existing equipment.