The nail bed is located under the finger nail. The arched portions of the nail bed, which contain a large number of capillary loops, are separated by the valley of the nail bed. The valley of the nail bed does not contain capillary loops. Light is scattered when it propagates through the dermis of skin, and human blood strongly absorbs the light with proper wavelength. By use of the optical properties of the nail bed, we propose an optical technique which extracts the nail bed image of the finger nail. After achieving nail bed images of each individual, we correlated between them. The correlation outputs show that we can identify individuals by comparing the peak heights of the correlation outputs.