Imaging of hemoglobin oxygen saturation ratio in the face by spectral camera and its application to evaluate dark circles

Background Contact‐type spectrophotometers have been widely used to measure skin color to determine the color values and melanin and hemoglobin contents. Recently, a spectral camera was introduced to evaluate two‐dimensional color distribution. However, its application to skin color measurement has been limited. Methods The original spectral imaging system developed for facial skin consisted of a spectral camera and an original lighting unit for uniform irradiation of the face. The distribution of skin chromophores in the face, including melanin and oxy‐ and deoxyhemoglobin, was calculated from the reflectance data for each pixel of the spectral images. In addition, to create a mean spectral image of the group, a face morphing technology for spectral data was proposed. Using the system, we determined the characteristics of the dark circles around the eyes and also evaluated the effects of an anti‐dark circle cosmetic. Results This system enabled the sensitive detection of skin chromophores in the face. Melanin content increased and hemoglobin oxygen saturation ratio decreased locally in the infraorbital areas of women with dark circles compared with those of women without dark circles. In addition, we were able to detect improvement in the dark circles after 6 weeks' use of anti‐dark circle cosmetic products by visualizing the distribution of the relative concentrations of melanin and hemoglobin oxygen saturation ratio. Conclusion Using a spectral camera, we developed a non‐contact image‐processing system that was capable of capturing a wide area of the face to visualize the distribution of the relative concentrations of skin chromophores in the face.