Iridescence and its applications in thin-film conformal uniformity

Iridescence is structural color, as opposed to pigment, in which the color is a result of constructive or destructive interference of light traveling through periodic structures, where the thickness of each layer plays a critical role in the color observed. Bragg fibers are man-made cylindrical structures with periodic layer coatings, modeled after the atomic lattice structure found in naturally occurring crystals. Bragg layers with even a slight deviation of micrometers in its thickness can result in a non-uniform color, which is the basis of our study. A non-invasive approach was taken to best approximate the dominant wavelength of the reflected hues through the use of microscopic imaging. The RGB values present in the images were extracted, and transformed into new coordinates using matrix operations, from which we were able to estimate the dominant wavelengths present in the Bragg fiber.