Why we removed the Red light but only use Blue and Green light for the NBI observation? What will happen if the Red light included?
The whole image will be very dark because red blood cells absorb all the red light.
The penetration of the light will be too deep that made the light difficult to reflect back to CCD.
The red light with long wavelength will cover the blue/green light with shorter wavelength then the blue/green light can’t be projected on the mucosa.
The reflection of the light from deeper layer will blur the contour of the blood vessel image in the surface layer, the information in deeper layer also masked the information in the surface layer, and eventually the contrast of blood vessel will be decreased.