| abstract |
In a special mode, a first frame image including a blue signal B 1, a green signal G 1, and a red signal R 1 is captured in a first frame period. In a second frame period, a second frame image including a blue signal B 2, a green signal G 2, and a red signal R 2 is captured. An oxygen saturation level calculator calculates an oxygen saturation level of each pixel based on signal ratios B 1 /G 2 and R 2 /G 2, and sequentially outputs obtained special images on a monitor. Whenever the special image is produced, a signal ratio R 2 /R 1 is calculated. When the signal ratio R 2 /R 1 exceeds a threshold value, a warning sign “!!” is displayed. When the signal ratio R 2 /R 1 is larger than a predetermined range S, a warning sign “HIGH StO 2 ” is displayed. When the signal ratio R 2 /R 1 is smaller than the range S, a warning sign “LOW StO 2 ” is displayed. |