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Lighting: Sources and Packaging
by Rich Handley
Significant changes have advanced the LED lighting field in the last two years, coupling LEDs with ceramic for heat dissipation and high output. In addition, white LEDs now have five to ten times the life of standard LEDs. "The vision industry has really been a pioneer in LED lighting," Matt Pinter, a design engineer with DVT partner Spectrum Illumination (Muskegon, MI), told AI, "The high-output LEDs, along with new packages and different lenses, have opened the door for LEDs to compete and even outperform fluorescent and halogen lights. We can even use them at long distances, as in robot pick-and-place applications, or in lighting a very large area."
Since optimal lighting is one of the most important aspects of machine vision, spending time on the front end of a project when setting up software for the application can have big payoffs. According to Phil Heil, DVT's Director of Information Technology, "Optimal lighting can be a moving target so there are some features in our FrameWork software that can accommodate modest changes in light. These features include the field-of-view balance function, which lets a user calibrate the workspace with the application lighting and a white sheet of paper." In addition, he said, the application offers several thresholding options ranging from simple contrast-based techniques to a sophisticated adaptive threshold that recalibrates itself while scanning the image.
Pinter believes the future is wide open for high-power LEDs, and that continued innovations in dissipating heat will achieve even higher powers. As power increases, so will efficiency, with five-watt LEDs (five times the current power) available in the third quarter of 2003. What's more, LED color will continue advancing as LEDs replace halogen and fluorescent lighting. For now, though, the following products should meet your lighting needs.
Advanced Illumination (Rochester, VT) manufactures a family of backlight
solutions suited for simple but essential applications. These
backlights are designed to provide an even field of illumination
against which parts can be viewed in silhouette. They are available
in a range of sizes and wavelengths-from the spotlight-shaped
BL5420 with optional 4 mm or 20 mm illuminated area, to the 200
mm x 200 mm BL47192-including infrared. They can be used for inspection
and a variety of other machine vision applications, including
measuring, sorting and determining part orientation.