How do you think the new GigE standards will influence the machine vision industry?
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LED lighting is the fastest growing because there's been such a huge increase in intensity, especially white, says Muyskens. "It has doubled in intensity from a year ago. The home market is trying to replace standard incandescent bulbs, and that's why white is advancing so much. You won't see it that fast with other colors. It's gone from 45 lumens to 90 lumens just that fast, but you can drive it to over 200 lumens per LED.
"Advances in LED [combine with] the disadvantages of halogen or fluorescent or xenon strobes, [which] have such a short lifespan. LEDs have made huge advances; they're getting closer and closer to where they can compete with the brightest. I have some projects switching from xenon strobe to LED because the brightness is getting so close."
Most LED users require a driver, or controller around each light source. LED current controllers typically provide a digitally controlled, repeatable constant current output, along with accurate pulse timing with variable delay and pulse width and selectable intensity. Current and pulse timing are set manually or dynamically from software and are stored in the controller, explains Peter Bhagat of Gardasoft Vision in the U.K.
The pulses are triggered on an opto-isolated digital input, usually from a PLC, frame grabber or camera. The pulse width and the delay before it fires can be controlled. "Often two or more views of an object are taken using different lights at different intensities," Bhagat says. "With an LED lighting current controller it is possible to switch lights on and off and to switch between several preset intensities."