endoscopic diagnostic use of blue/green wavelengths enhance detail of surface of mucosa.
Narrow-band imaging is an imaging technique for endoscopic diagnostic medical tests, where light of specific blue and green wavelengths is used to enhance the detail of certain aspects of the surface of the mucosa. A special filter is electronically activated by a switch in the endoscope leading to the use of ambient light of wavelengths of 415 nm (blue) and 540 nm (green).[1][2] Because the peak light absorption of hemoglobin occurs at these wavelengths, blood vessels will appear very dark, allowing for their improved visibility and in the improved identification of other surface structures.[3]
^Tanaka, S.; Sano, Y. (2011). "Aim to Unify the Narrow Band Imaging (Nbi) Magnifying Classification for Colorectal Tumors: Current Status in Japan from a Summary of the Consensus Symposium in the 79th Annual Meeting of the Japan Gastroenterological Endoscopy Society". Digestive Endoscopy. 23: 131–139. doi:10.1111/j.1443-1661.2011.01106.x. PMID21535219. S2CID3218474.