Standards
@imveurope
www.imveurope.com
‘Performance includes, cost, response time latency and variance, error handling capability, and flexibility to support low- and high- bandwidth system needs to reduce system bring-up and support costs. ‘CLHS is the transport technology of choice
when needing to trigger the camera from the frame grabber card with trigger rates of megahertz possible,’ he added. ‘Systems that can’t afford to miss data choose CLHS due to its error immunity and the minimal latencies resulting from hardware-based resend or forward error correction. CLHS is also chosen when there is a need to split the data to multiple image processing systems because of the protocol’s support for multiple frame grabber synchronisation.’
The latest interface
standards are designed with high bandwidth in mind, as new CMOS sensors, such as Sony’s IMX174 found in Point Grey’s Grasshopper3 cameras, are released
Te function will mean the application or frame grabber can command the camera to change ROI frame by frame with confirmation returned in the video channel. Tis enables tracking applications and the full use of CMOS sensor technology, according to Miethig. At the moment, the standard uses both
copper and fibre optic cables, although Miethig believes that there will be a transition to fibre cabling as cost for fibre optics declines. In addition to cost considerations, fibre optics provides improved distances compared to copper, higher EMI susceptibility performance, and better cable size, bend radius, flex life cycles and ease of installation. ‘Cost versus performance is how most
vision integrators determine which camera or transport layer to use,’ Miethig commented.
Lighting for machine vision
Vision interface standards are targeted at the camera, software, cabling and connector side of vision systems, but what about the lighting side of the equation? The North American AIA and the European Machine Vision Association (EMVA) are working with the Japan Industrial Imaging Association (JIIA) to establish working groups to help JIIA extend its existing lighting standard. Lighting is a very complex
technology, especially relating to its use in machine vision systems. Bob McCurrach, director of standards development at AIA, commented: ‘To promote the [lighting] technology, both within the industry and to end users, it is helpful to have a go-to reference targeting the physics of light to machine vision applications, as well as some industry norms that help drive common practices and protocols. The existing
28 Imaging and Machine Vision Europe • Yearbook 2014/2015
JIIA standard does a good job of the former, but not so much of the latter. AIA was approached by a number of lighting companies to extend the standard beyond the theoretical to more of practical application.’ There are five initial
working groups that have been established based on interest from lighting companies. The working groups aim to add value to the ‘usability’ aspect of lighting for machine vision,
according to McCurrach. The working groups
will provide a mechanism to classify the lighting according to the application, and to specify the features and performance of the product, according to Hiroshi Totsuka, chair of the Lighting Group at JIIA. The standard will also cover photobiological safety of the light, which is particularly pertinent for laser diodes. Totsuka noted that
there is a need to remotely
control illuminators, other than simply for on/off. The working groups plan to advance the maintenance of control functions for lighting. In August 2014,
McCurrach stated: ‘AIA and EMVA have put an invitation letter out to solicit any companies who would be interested in participating in the enhancements to the lighting standard. These are just being collected by JIIA, who will work with AIA and EMVA to develop this plan.’
Ease of use Speed is not the only factor though – USB3 Vision, for instance, is plug-and-play and doesn’t require a frame grabber, while still providing reasonably high bandwidth, which makes it appealing for many applications. Eric Gross, senior soſtware engineer at
National Instruments and chair of the USB3 Vision committee, commented that, in addition to higher sensor resolution and speed, the vision industry is recognising the value of using off-the-shelf technology. Tis is leading to more cost-effective solutions and additional options available to meet application needs, he said. FireWire was the first interface adapted from
a consumer interface technology (in this case from Apple) for machine vision, and which meant that frame grabbers were no longer
Point Grey
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