LEDs: Not Just Another Light Bulb

Often viewed as commodities, LED light manufacturers are using intelligence, standards, and new materials to once again revolutionize the machine vision illumination industry.

It’s not very often that a light is nominated for a machine vision industry award. This year, it happened three times. And the lights won twice.

Gardasoft Vision Limited’s (Cambridge, UK) Triniti intelligent LED light controller was nominated for the Vision Award at the Vision trade fair in Stuttgart last fall before taking a silver product innovation award during AIA’s Automate trade show in Chicago this past March. Metaphase Technologies, Inc. (Bristol, Pennsylvania) followed, grabbing a bronze award for its high-speed LED illumination system HISLED-1003, which allows ultra-short light pulses for imaging objects traveling at high speeds without blur. This past year, the bulb has burned very bright indeed!

That might be the end of the story if LEDs were just another light, and machine vision just another automation technology. Instead, the drive for intelligent automation systems, new industry standards, and new optical materials may keep LEDs in the awards circle for several more years to come.

Standard Intelligence

The aptly named Triniti LED light controller garnered a lot of attention this year by bringing control, operational monitoring, and network compatibility to machine vision lighting. Other LED light manufacturers have introduced Ethernet-compatible light controllers to the market in the past so that users could change light settings from the host computer. It’s only recently that Triniti technology has fully enabled an intelligent, networked lighting system compliant with GenICam and GigE Vision standards that allows the light programming and control directly from the vision platform API for machine vision, traffic, and related applications, according to John Merva, vice president, North America at Gardasoft.

“A few companies such as Advanced illumination and Spectrum illumination have had Ethernet-connectable controllers, but their functionality is different than Gardasoft’s,” Merva says. He also notes that light controllers have typically been the second-class citizens in the lighting industry as lighting companies must focus resources on their lighting products first. “But at Gardasoft, lighting controllers have been our primary product for 15 years,” he says. “We see a wider range of applications [for lighting controllers] than other lighting companies, and that puts us in a good position to develop a controller with APIs for major machine vision camera and software suppliers and an SDK for expert users and OEMs that want to build Triniti into their own machines. If we just had one or the other, Triniti wouldn’t have seen the market acceptance that it has since the launch last November.”

The development of the IEEE’s 1588’s Precision Time Protocol (PTP) — which provides for sub-microsecond clock accuracy across a local area network, making it suitable for industrial control systems — has a lot of people excited, Merva says. “And there’s a reason for that: the non-deterministic nature of Ethernet. But now with GigE Vision, GenICam, and the new IEEE 1588 timing standard that allows a single network clock to be synchronized among all devices on a network, full network control is now possible.”

Steve Kinney, general manager of business development at CCS America Inc. (Burlington, Massachusetts), says that when a CCS Triniti-compatible light is plugged into a Gardasoft controller, “it does a GenICam-style handshake just like a camera and PC would on a GigE Vision network.”

As AIA’s lighting committee continues to make progress, Kinney notes, “it’s not hard to see a time when the command and control segment of the lighting standard might also extend to intelligent optics. I know of applications right now that would like to have the control system talk to the lens, telling it to zoom in here, autofocus there, track this target. You can see this conversation expanding to include all components on a machine vision system, allowing them to self-configure, time to each other, and give users seamless control of all components. Companies that move first to support this smart system approach will have the advantage.”

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Whether the machine vision market is ready for the additional costs of this intelligence remains to be seen, however. "Personally, I think the technology is really interesting but I’m not yet convinced that the intelligent controllers model is what customers want,” says Jason Baechler, President of MORITEX North America, Inc. (formerly SCHOTT North America Inc., San Jose, California). “LED costs are dropping so quickly that I’m not sure small- to mid-level users or large automation companies want this cost added to the LED or system.”

Will a new lighting standard help drive the market’s appetite for more intelligent lights and optics? That remains to be seen. According to Smart Vision Lights’ (Muskegon, Michigan) co-founder and head of engineering, Matt Pinter, the lighting committee has made some progress thanks to the Japanese Industrial Imaging Association (JIIA). However, more remains to be done before companies and customers have a generally accepted way to compare the performance of different lights. Work on control and command and connectors is likely further away than the “performance” part of the standard. The fourth part of the lighting standard under development covers safety, much of which is already laid out by IEC and other standards groups for lasers and LED lights.

New LED Optics Light the Way

LED optics may soon have a new “standard” thanks to the optical properties of Dow Corning’s silicone product, says Smart Vision Lights’ Pinter.

“Dow’s silicone can be injection-molded into multi-element optics for LEDs with better thermal and optical properties, as well as improved vibration resistance, over today’s standard plastic lenses used to shape LED light output,” he explains. “With the help of a local optical engineering company, we’ve developed a family of LED lenses out of silicone that perform closer to glass than plastic. You can have multi-cavity molds, which you can’t do well and consistently with plastic optics. We expect to release a new line of lenses to both our customers and other LED light manufacturers in the near future.”

Pinter’s company has a provisional patent on both the optic-forming process using the silicone and a method of using surface-mount technology (SMT) to automatically place a clip, similar to a watch battery clip, for holding the silicone optic.

"One of the biggest problems that LED light makers face is how to attach plastic lenses to the light,” Pinter adds. “Some use glue or tape. It’s usually done manually, and that can lead to output variations between die and light assemblies. This approach is going to be important for industries beyond just machine vision, including automotive lights. And the spongy silicone is more resistant to vibrations too, especially when you combine it with a clip holder applied in a fraction of a second by an SMT machine instead of glued on by hand.”

MORITEX also aims to improve its LED optics. “But we’re focused on line scan applications, no pun intended,” says Baechler. “Optimizing LED illumination with our lens products continues to be a differentiator for us. Line scan is a growing area, mostly in the visible or NIR wavelengths. During the last year, we have also had a large influx of UV LED applications where customers are imaging the visible range response of a sample that reacts to certain UV wavelengths, such as 365 nm to 385 nm.

“Also, new densely packaged multi-die light engines coupled with focusing optics are breathing new life into our fiber optic lighting products,” he continues. “The efficiency of these light engines is allowing us to package halogen-equivalent-output LED light sources and beyond with much smaller footprints, due mostly to the ability to use smaller cooling fans.”

While these advances in LED lighting may not be as significant as the first solid-state emitter, there can be little doubt that the everyday machine vision illuminator is due for a major facelift as new standards, intelligent lights, and new optical materials and designs come online.