| 摘要 |
PROBLEM TO BE SOLVED: To reliably distinguish a plurality of types of blood vessels at different depths even if a ratio between a blue component of illuminating light and a green component of the illuminating light has changed.SOLUTION: A subject is simultaneously exposed to white light BB and narrowband blue light BN. A light quantity ratio between the white light BB and the narrowband blue light BN is set by a light quantity-ratio setting unit 37a. The subject is imaged using a color CCD 44, yielding a blue signal B, a green signal G and a red signal R. A base image is generated from the three signals B, G and R, and a B/G image is generated from a B/G ratio, i.e. the ratio of the blue signal B to the green signal G. Pixels representing B/G ratios less than or equal to a mucous-membrane/superficial-blood-vessel boundary value Ls are extracted from the B/G image, yielding an image containing extracted superficial blood vessels, and pixels representing B/G ratios greater than or equal to a mucous-membrane/mid-depth-blood-vessel boundary value Ld are extracted, yielding an image containing extracted mid-depth blood vessels. The boundary values Ls and Ld differ depending on the light quantity ratio set by the light quantity-ratio setting unit 37a. |
