ScienceDaily (Mar. 16, 2007) — A new light source based on fiber-optic technology promises to improve the inspection of food, produce, paper, currency, recyclables and other products. 

Currently, industrial processes for inspecting foodstuffs and other items often use "line-scan" cameras, which record images of objects one line at a time, just as fax machines scan documents on a line-by-line basis.  Rapid electronic processors then detect whether there are any problems with the items and instruct mechanical actuators (such as air jets) to separate out unsatisfactory items. The problem is current line-scan cameras lack ideal light sources to image objects properly.

Now, Princeton Lightwave of Cranbury, N.J. and OFS Labs (a Somerset, N.J.-based division of Furukawa Electric) have introduced a fiber-optics-based solution, which they will describe in their OFC/NFOEC paper. In their design, a bright light source such as a laser sends light through an optical fiber. Along the length of the fiber is an ultraviolet-light-treated region called a "fiber grating." The grating 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 at various distances from the source. The bright rectangle allows line scan cameras to sort products at higher speeds with improved accuracy. 

The new fiber-based light source combines all the ideal features necessary for accurate and efficient scanning: uniform, intense illumination over a rectangular region; a directional beam that avoids wasting unused light by only illuminating the rectangle; and a "cool" source that does not heat up the objects to be imaged. Currently employed light sources such as tungsten halogen lamps or arrays of light-emitting diodes lack at least one of these features.

According to the researchers, this fiber-based device can be customized for a specific inspection application within four to six weeks, then manufactured for that application in 16 to 20 weeks.

New research revealing this technology will be presented at the Optical Fiber Communication Conference and Exposition/National Fiber Optic Engineers Conference (OFC/NFOEC), being held March 25-29 in Anaheim, Calif.

Meeting Paper: G.E. Carver, K.S. Feder, P.S. Westbrook, "FBG Based Distributed Lighting for Sensing Applications."

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