The Edge of Light (EOL) scanner is unique in its ability to convert changes in surface slope into light intensity variation in an image. The technique is relatively quick, with scanning speeds in the order of 2 to 20 linear cm/sec and line widths of 10 cm or more. EOL inspection results are easily interpreted, as they closely resemble the actual subject. The technology is proven in principle, in detecting corrosion in surfaces and joints, and in inspecting gas turbine components, such as turbine disks. For many applications, EOL performs better than inspections using liquid penetrant, magnetic particle, ultrasonic inspections, or optical microscopy. Development work is under way to incorporate EOL with eddy current inspection in a single device, as the technologies are complementary in many ways. Figure 10: Top - Lap splice joint from a Boeing 727, as seen by the unaided eye. Bottom - EOL image of the same lap splice joint clearly showing corrosion pillowing.

Published in:
October 1998 NASA M&P Update Newsletter Vol. 2, No. 1
NASA MATERIALS & PROCESSES UPDATE (NMPU) NEWSLETTER
Published by NMPWG and NASA HQ, Code AE
Editors: Yoseph Bar-Cohen and Cheng Hsieh, JPL
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