Use of a spectrally tunable source to explore improvement in chromatic contrast for illumination of tissues

Human vision by a clinical practitioner is often the first disease detection tool. Illumination for such procedures as endoscopy use broadband white light, with luminance level being the only control available. The use of staining dyes for contrast improvement have shown limited adoption due to the additional steps needed and small number of approved dyes for in vivo use. Here we explore the control of the illuminant spectral distribution to improve chromatic contrast without the use of dyes. The computational steps used in converting spectral data to RGB and use of the CIELAB chromatic and luminance contrast metric as criteria in determining the appropriate lighting spectral distribution will be discussed. The skin on the back of the hand and the skin section over a vein are used as examples of tissue features to be contrasted. A 3-wavelelength LED lamp and an incandescent lamp with the yellow spectral region filtered out are shown as examples that spectrally-shaped illumination can enhance visual contrast.