Figure 1

The principle of autofluorescence observation. Normal tissue: In response to blue excitation rays of approximately 400–450 nm, green autofluorescence of approximately 520 nm is observed. Malignant Lesion: Autofluorescence is reduced due to thickening of the mucosal epithelium, decrease in autofluorescent substances, an increase in fluorescence absorbing substances, etc., causing the color spectrum of emitted fluorescence to shift.