<p>(a) The device is designed such that it can be inserted through the accessory channel of a clinical endoscope. As the endoscope is being retracted in the GI tract, the device simultaneously scans the lumen. The collected Raman-scattered light is analyzed, and an image is displayed to the user (also see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123185#pone.0123185.s001" target="_blank">S1 Video</a>). (b) Expanded schematic of the distal end of the device. The schematic illustrates the position of the device relative to the end of the endoscope. A brushless DC motor that rotates a mirror causing the collimated beam to sweep 360 degrees, enabling luminal imaging of the colon wall. The device is not required to be in contact with the tissue, which is enabled through the use of the collimated illumination beam. A custom, miniature, concentrically segmented, air-spaced doublet lens having a non-reciprocal optical path consists of a plano-convex lens and an adjacent plano-concave lens with a central hole. The doublet lens increases collection efficiency at longer, clinically relevant working distances.</p
