New fiber-optic light source for food inspection

Published 23 March 2007

Princeton Lightwave and OFS Labs team up to improve imaging capabilities of live-scan cameras; fiber grating creates a perfect rectangular beam of light

Let there be light. Two New Jersey-based companies, Princeton Lightwave and OFS Labs, have developed a fiber-optics-based system that promises to improve the inspection of food, produce, paper, currency, recyclables, and other inspection-worthy products — the idea being to improve on the line-scan cameras often used in industrial processes for quality control. Such live scan cameras typically record images of manufactured products one at a time, while rapid electronic processors look to identify any problems. The problem, the two companies realized, is that current systems lack ideal light sources to image objects properly. Currently, the most popular methods are tungsten halogen lamps and arrays of light-emitting diodes, but both have their drawbacks.

The Princeton Lightwav-OFS Labs approach solves the issues by transmitting laser light through an optical fiber. That sounds simple enough, but the rest is more complicated. Along the length of the fiber is an ultraviolet-light-treated region called a “fiber grating” that deflects the light so that it exits perpendicularly to the length of the fiber as a long, expanding rectangle of light. This optical rectangle is then collimated by a cylindrical lens, such that the rectangle illuminates objects of interest for the line scan cameras. Among the various advantages suggested by the two companies are: uniform illumination, energy savings, and a “cool” source that does not heat up the objects to be imaged. According to the researchers, the system can be customized for a specific inspection application within four to six weeks, then manufactured for that application in sixteen to twenty weeks.